JP5098565B2 - Induction motor excitation voltage control method for power regeneration device and power regeneration device - Google Patents

Description

  The present invention relates to an induction motor excitation voltage control method and an uninterruptible power supply apparatus for an uninterruptible power supply apparatus using a flywheel and an induction motor.

  Conventionally, a power regeneration device using a flywheel regenerates power by generating power in order to supply power to the load instead of a power supply system that is supplied from a power source to the load. For example, a power regeneration device in which a flywheel is connected to a synchronous generator using a permanent magnet as a rotor is known.

  Moreover, there exists a power generation regeneration apparatus which connected the flywheel to the induction motor always energized and used as described in Patent Document 1 and Patent Document 2 below. For example, Patent Document 1 below proposes a flywheel uninterruptible power supply device using a wound induction machine. In the technology of Patent Document 1, a flywheel is configured by connecting a flywheel to a wound induction machine, the primary winding of the wound induction machine is connected to the load side, and the secondary winding is converted from a power source to a converter. The flywheel type uninterruptible power supply that supplies power to the load by supplying power through the inverter, receiving power supply from the power supply when the power supply is stable, and storing the power in the flywheel when the power supply voltage drops In the power supply device, the winding induction machine is rotated at a speed higher than the synchronous speed, and an excitation current determined by the rotational speed of the flywheel and the frequency of the system is applied to the secondary winding for variable speed control. Moreover, in the following patent document 2, a flywheel uninterruptible power supply device using a cage induction machine is proposed. The technology of Patent Document 2 connects a load to be protected to a squirrel-cage induction motor coupled with a flywheel in parallel, rotates it to stand by, and turns off the backflow prevention switch at the time of a short-time power outage or instantaneous drop. Due to the magnetic excitation phenomenon, it becomes an induction generator and supplies power to the load.

  Patent Document 3 below proposes an operation control method for reducing power consumption of an uninterruptible power supply using an induction machine. The technology of Patent Document 3 supplies electric power to a three-phase induction generator motor having a flywheel-equipped rotor to rotate the flywheel, and at the time of power interruption, converts the rotational energy of the flywheel into electric energy and releases the electric power. After supplying a predetermined drive voltage to the uninterruptible power supply and increasing the rotational speed of the flywheel, the drive voltage is lowered to perform steady operation, and when the power is cut off, the drive voltage is increased to a predetermined value. is there.

Patent Document 4 below proposes a method of reducing friction loss by replacing with helium gas to reduce air windage loss. In the technique of Patent Document 4, the cooling gas in the machine is sealed with a gas having a small windage loss and an electric withstand voltage for the purpose of reducing the loss of a rotating machine such as a vertical generator or a motor generator with a flywheel. To do.
JP 2001-178023 A JP 2003-235179 A JP 2003-111494 A JP 2000-358344 A

  By the way, the power regeneration device using the flywheel and the synchronous generator has a drawback that when the energization to the synchronous generator is stopped, the rotational speed of the flywheel is reduced due to the loss of cogging torque by the permanent magnet in the free rotation state due to inertia. there were.

  FIG. 28 is a configuration diagram of a power regeneration device (uninterruptible power supply) 100 using the synchronous machine 105 and the flywheel 106. For example, a three-phase AC voltage from the power source 101 is converted into a DC voltage by a rectifier (not shown) and supplied to a load inverter (not shown) through the DC bus 103 to generate, for example, an AC voltage with a frequency of 50 Hz and supplied to the load 102. At the time of a power failure, the synchronous machine 105 connected to the flywheel 106 is used as a flywheel generator, and the electric power generated by this generator is converted into a DC voltage by a flywheel inverter 104 along a path 107. This is supplied to the load 102 via the bus 103. However, the synchronous machine 105 has a configuration in which a coil and a permanent magnet are combined. The synchronous magnet 105 uses a permanent magnet as a rotor. When the synchronous machine 105 is idled by being connected to the flywheel 106, the cogging torque is caused by an inquiry with the permanent magnet. Is generated, causing resistance and loss, and the rotational speed of the flywheel 106 decreases.

  In addition, as in Patent Document 1 and Patent Document 2, in the case of an induction motor in which an exciting coil is always excited, the coil is always excited and used, so that a rapid decrease in the rotational speed does not occur. In addition, there is an advantage that the transition to the power generation state can be easily performed, but there is a disadvantage that the power loss due to the excitation current is large.

  FIG. 29 is a configuration diagram of the power regeneration device 110 in which the flywheel 116 is connected to the induction motor 115 that is always exciting the excitation coil. For example, a three-phase AC voltage from the power supply 111 is converted into a DC voltage by a rectifier (not shown) and supplied to a load inverter (not shown) through the DC bus 113, for example, an AC voltage having a frequency of 50 Hz is generated and supplied to the load 112. At the time of a power failure, the induction motor 115 connected to the flywheel 116 is used as a flywheel generator, and the electric power generated by this generator is converted into a DC voltage by a flywheel inverter 114 along a path 117. It is supplied to the load 112 via the bus 113. However, as shown in FIG. 30, a constant excitation voltage is always applied to the induction motor 115 as shown by the broken line even when a power failure occurs and the rotational speed decreases gently as shown in FIG. 30. That is, loss due to the excitation current occurs.

  Moreover, the said patent document 3 (Unexamined-Japanese-Patent No. 2003-11494) has proposed the operation control method which reduces the power consumption of an uninterruptible power supply. This is a method in which the voltage is made lower than the rated voltage in order to prevent loss while maintaining the rotational speed during standby. If the voltage is lowered, it is possible to reduce power consumption because less wasteful current flows. For example, the steady driving voltage is set to 0.4 times the startup driving voltage. If the rated voltage is 100V, it is reduced to 40V on a voltage basis and 0.16 times on a power basis. However, the amount of reduction has a limit and does not become zero.

  Further, Patent Document 4 (Japanese Patent Laid-Open No. 2000-358344) proposes a method of reducing friction loss by replacing with helium gas in order to reduce air windage loss, but the amount of reduction is limited. For this reason, a structure in which the flywheel and the induction generator are installed in a vacuum in order to completely eliminate the windage loss has been considered, but the heat generated by the excitation current is difficult to escape. If air can be air-cooled and put into a vacuum, friction can be reduced, but it becomes difficult to remove the heat, which is an obstacle to realization.

  In view of this, the applicant of the present application disclosed in Japanese Patent Application No. 2006-80979, a power regeneration device capable of de-exciting the induction motor in a free rotation state due to inertia of the flywheel, and performing re-excitation in a short time when necessary, and its excitation A method and its power generation method were proposed. According to this proposal, the loss due to the exciting current can be suppressed by preventing the induction motor from being kept in the excited state at the time of non-power failure.

  By the way, when the induction current is brought into a non-excited state during a non-power failure, a residual voltage due to a residual magnetic field is generated in the induction motor that has stopped applying the excitation voltage. For this reason, if the induction motor is re-excited while the residual voltage is generated, the excitation voltage is added to the residual voltage and applied to the induction motor to increase the value of the inrush current flowing through the inverter. Then, the current exceeding the trip value of the inverter flows through the inverter, and the induction motor cannot be excited by the inverter, and the power source cannot be normally backed up for the load at the time of power failure. Therefore, if a non-excitation period is provided in the induction motor, it is necessary to provide a re-excitation prohibition period until the residual voltage of the induction motor is eliminated.

  Since regeneration of the induction motor cannot be performed during this re-excitation prohibition period, it is necessary to have a large-capacity capacitor as a backup corresponding to the re-excitation prohibition period in order to cope with a power failure during the re-excitation prohibition period. Since a large-capacity capacitor leads to an increase in the size of the device, it is desirable to avoid such a configuration as much as possible. For this reason, the conventional proposal has room for further improvement in terms of the reexcitation prohibition period.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to generate a power regeneration device capable of resuming the application of the excitation voltage to the induction motor as soon as the application of the excitation voltage to the induction motor is stopped. The present invention provides an induction motor excitation voltage control method and a power generation regenerator suitable for use in carrying out this method.

  In order to achieve the above object, an induction motor excitation voltage control method for a power regeneration device according to the present invention described in claim 1 operates as a motor by applying an excitation voltage generated by an inverter using electric power supplied from a power source. The flywheel accelerated to the predetermined rotational speed by the induced induction motor is brought into a free-wheeling state in which inertial energy is accumulated by releasing application of the excitation voltage from the inverter to the induction motor. When receiving a power generation command, the induction motor rotated by the idle flywheel is operated as a generator by applying an excitation voltage generated by the inverter using electric power stored in a capacitor, The regenerative power generated by the induction motor is loaded via the inverter instead of the power from the power failure A method of controlling an excitation voltage of the induction motor in a power generation regenerative device to be supplied, wherein a controller is configured to release the excitation voltage when the excitation voltage is applied from the inverter to the induction motor. Excitation release that reduces the value of the excitation voltage in a ramp shape at a rate corresponding to the rate of decrease of the residual voltage so that the value of the excitation voltage does not fall below the value of the residual voltage of the induction motor due to the residual magnetic field generated in the motor It has a step.

  According to the induction motor excitation voltage control method of the power regeneration device of the present invention described in claim 1, when the application of the excitation voltage from the inverter to the induction motor is canceled, the value of the excitation voltage at a speed corresponding to the decreasing speed of the residual voltage. Is reduced to a ramp, and the excitation voltage that does not fall below the residual voltage value due to the residual magnetic field generated in the induction motor when the excitation voltage is released is reduced until the excitation voltage value becomes zero. Will be applied.

  Thereby, until the value of the excitation voltage becomes zero, the electric energy of the residual voltage generated in the induction motor is converted into heat energy or the like in the inverter electrically connected to the induction motor for applying the excitation voltage. Is consumed. Therefore, the residual voltage can be quickly eliminated and the induction motor can be brought into a state where it can be re-excited early.

According to the induction motor excitation voltage control method of the power regeneration device of the present invention described in claim 1, when the controller starts applying the excitation voltage from the inverter to the induction motor, the inrush current flowing through the inverter is An excitation start step for increasing the value of the excitation voltage in a pattern that always falls below the trip value of the inverter; and when the power generation command is received during a decrease in the value of the excitation voltage, the controller While the value of the excitation voltage is greater than the value of the excitation voltage in the excitation start step, the value of the excitation voltage is decreased by the excitation release step, and the value of the excitation voltage in the excitation release step is After the time point when the value of the excitation voltage coincides with the excitation start step, the excitation voltage And further comprising at an excitation voltage control step magnetic field increases the value remaining.

Further , according to the induction motor excitation voltage control method of the power regeneration device of the present invention described in claim 1 , when a power generation command is received while the excitation voltage of the induction motor is reduced in a ramp shape by the excitation release step, Depending on the excitation voltage value at that time, either the control to decrease the excitation voltage value of the induction motor in the excitation release step or the control to increase the excitation voltage value of the induction motor in the excitation start step This is preferentially executed in the excitation voltage control step.

  That is, while the excitation voltage value of the induction motor in the excitation release step is decreased only to a value exceeding the excitation voltage value of the induction motor in the excitation start step, the excitation voltage value of the induction motor is reduced by the excitation release step. The control to be performed is prioritized and priority is given to eliminating the residual voltage of the induction motor due to the residual magnetic field generated in the induction motor.

  On the other hand, after the excitation voltage value of the induction motor in the excitation release step coincides with the excitation voltage value of the induction motor in the excitation start step, the trip value of the inverter is exceeded even if the excitation voltage value of the induction motor is increased. Assuming that the inrush current does not flow through the inverter, the control for increasing the value of the excitation voltage of the induction motor in the excitation voltage increase control step is preferentially executed.

  As a result, even when the excitation voltage is increased while the value of the excitation voltage is decreasing, the electric energy of the residual voltage generated in the induction motor due to the decrease of the excitation voltage is consumed by the inverter, and the trip value of the inverter Without causing an inrush current exceeding 1 to flow to the inverter, the excitation voltage of the induction motor can be smoothly changed from a decrease to an increase so that the induction motor can quickly generate regenerative power and supply it to the load.

In addition, the said pattern at the time of increasing the value of the said excitation voltage in the said excitation start step is the rated voltage of the said induction motor like the induction motor excitation voltage control method of the electric power regeneration apparatus of this invention described in Claim 2. The excitation voltage value is increased stepwise until the inrush current flowing through the inverter is lower than the inverter trip value, and the value of the excitation voltage from the predetermined value to the rated voltage. The pattern can be increased in a ramp shape.

According to the induction motor excitation voltage control method of the power regeneration device of the present invention described in claim 2 , the excitation motor excitation voltage is set so that the inrush current flowing through the inverter falls within a range below the trip value of the inverter in the excitation start step. When the voltage is increased efficiently, the increase pattern can be simplified and the control or processing can be facilitated.

In order to achieve the above object, a power regeneration device according to a third aspect of the present invention is provided by an induction motor operated as a motor by applying an excitation voltage generated by an inverter using electric power supplied from a power source. When the flywheel accelerated to the rotational speed of the inverter is turned into an idle state in which inertial energy is accumulated by releasing the application of the excitation voltage from the inverter to the induction motor, and when receiving a power generation command from the outside during a power failure, The regenerative power generated by the induction motor is operated by causing the induction motor rotated by the idle flywheel to operate as a generator by applying the excitation voltage generated by the inverter using the electric power stored in the capacitor. In a power regeneration device that supplies power to the load via the inverter instead of power from the power source that has failed. When the excitation voltage is released from the inverter to the induction motor, the value of the excitation voltage does not fall below the value of the residual voltage of the induction motor due to the residual magnetic field generated in the induction motor when the excitation voltage is released. As described above, excitation stop voltage control means is provided for controlling the value of the excitation voltage to decrease in a ramp shape at a rate corresponding to the rate of decrease of the residual voltage.

According to the power regeneration device of the present invention as set forth in claim 3 , when the excitation voltage is released from the inverter to the induction motor, excitation is performed at a speed corresponding to the decreasing speed of the residual voltage by controlling the voltage control means at the time of excitation stop. While the voltage value is reduced in a ramp shape, the excitation voltage that does not fall below the residual voltage value due to the residual magnetic field generated in the induction motor when the excitation voltage is released is reduced until the excitation voltage value becomes zero. It will be applied to the induction motor.

  Thereby, until the value of the excitation voltage becomes zero, the electric energy of the residual voltage generated in the induction motor is converted into heat energy or the like in the inverter electrically connected to the induction motor for applying the excitation voltage. Is consumed. Therefore, the residual voltage can be quickly eliminated and the induction motor can be brought into a state where it can be re-excited early.

Further, in the power regeneration device according to the third aspect of the present invention, the inrush current flowing through the inverter is always less than the trip value of the inverter at the start of application of the excitation voltage from the inverter to the induction motor. An excitation start voltage control means for controlling the excitation voltage value to increase, and the excitation voltage when the power generation command is received while the excitation voltage value is decreasing by the control of the excitation stop voltage control means. And a magnetic field residual voltage control means for controlling the value of the magnetic field, the magnetic field residual voltage control means, wherein the excitation voltage value controlled by the excitation stop voltage control means is the excitation start voltage control While the value exceeds the value of the excitation voltage by the control of the means, priority is given to the control of the excitation stop voltage control means, and the excitation start voltage control means controls the excitation. The excitation value is reduced after the time when the excitation voltage value controlled by the excitation stop voltage control means coincides with the excitation voltage value controlled by the excitation start voltage control means. The control of the hour voltage control means is prioritized, and the value of the excitation voltage is increased by the control of the excitation start time voltage control means.

According to the power regeneration device of the present invention described in claim 3 , when a power generation command is received while the excitation voltage of the induction motor is being reduced in a ramp shape by the excitation stop voltage control means, the excitation at that time Depending on the voltage value, either the control to decrease the excitation voltage value of the induction motor by the excitation stop voltage control means or the control to increase the excitation voltage value of the induction motor by the excitation start voltage control means, It is executed preferentially in the voltage control means when the magnetic field remains.

  That is, while the excitation voltage value of the induction motor by the excitation stop voltage control means is reduced only to a value exceeding the excitation voltage value of the induction motor by the excitation start voltage control means, the excitation stop voltage control means Control that reduces the value of the excitation voltage of the induction motor is preferentially executed, and priority is given to eliminating the residual voltage of the induction motor due to the residual magnetic field generated in the induction motor.

  On the other hand, after the time when the excitation voltage value of the induction motor by the excitation stop voltage control means coincides with the excitation voltage value of the induction motor by the excitation start voltage control means, even if the excitation voltage value of the induction motor is increased. Assuming that an inrush current exceeding the trip value of the inverter does not flow through the inverter, control for increasing the value of the excitation voltage of the induction motor by the excitation start voltage control means is preferentially executed.

  As a result, even when the excitation voltage is increased while the value of the excitation voltage is decreasing, the electric energy of the residual voltage generated in the induction motor due to the decrease of the excitation voltage is consumed by the inverter, and the trip value of the inverter Without causing an inrush current exceeding 1 to flow to the inverter, the excitation voltage of the induction motor can be smoothly changed from a decrease to an increase so that the induction motor can quickly generate regenerative power and supply it to the load.

In addition, at the start of application of the excitation voltage from the inverter to the induction motor, the excitation start voltage control means is based on the rated voltage of the induction motor as in the power regeneration device of the present invention described in claim 4. The excitation voltage value is increased stepwise until the inrush current flowing through the inverter is lower than the inverter trip value, and the excitation voltage is increased from the predetermined value to the rated voltage. The voltage value can be controlled to increase in a ramp shape.

According to the power regeneration device of the present invention as set forth in claim 4 , at the start of excitation for efficiently increasing the excitation voltage of the induction motor so that the inrush current flowing through the inverter falls within the range below the trip value of the inverter. By simplifying the increase pattern of the excitation voltage of the induction motor by the voltage control means, the control or processing of the excitation start voltage control means is made easier, and consequently the configuration of the excitation start voltage control means is simplified. be able to.

  According to the induction motor excitation voltage control method and the power regeneration device according to the present invention, the electric energy of the residual voltage of the induction motor due to the residual magnetic field generated in the induction motor is converted into heat energy or the like by the inverter and consumed. Since the excitation voltage of the induction motor is reduced to zero, the residual voltage must be eliminated quickly so that the induction motor can be re-excited quickly so that the induction motor can be re-excited as soon as the excitation voltage becomes zero. Can do.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 shows an uninterruptible power supply 1 that is an embodiment of a power regeneration device according to the present invention. It is a figure which shows as a structure which connected.

  Although details will be described later, the uninterruptible power supply 1 employs a squirrel-cage induction motor 10 and makes the induction motor 10 coupled to the flywheel 9 non-excited in a rotating state due to inertia, thereby generating an excitation current. Loss was lost, rotation loss was reduced, and the flywheel 9 and the induction motor 10 could be completely idle.

  Since the squirrel-cage induction motor 10 is not excited in the idling state, it is necessary to flow an excitation current in a short time to the induction machine 10 that rotates at a high speed in order to perform a power regeneration operation.

  Therefore, the uninterruptible power supply 1 excites the exciting coil of the induction motor 10 within a short time while preventing the inverter trip due to the inrush current, and starts power generation. The present embodiment can be used not only for high-speed excitation for power regeneration, which will be described later, but also for high-speed excitation for powering.

  In FIG. 1, a normal power supply system (path) 3 converts, for example, a three-phase AC voltage from a power source 2 into a DC voltage by a rectifier 6 and supplies it to a load inverter 7 through a DC bus 4. The load inverter 7 generates an AC voltage having a frequency of 50 Hz, for example, and supplies the AC voltage to the load 8.

  In a power supply system (path) 5 at the time of a power failure, a squirrel-cage induction motor 10 is connected to a flywheel 9 to be used as a flywheel generator, and the electric power generated by this generator is converted into a DC voltage by a flywheel inverter 11. Converted and supplied to the DC bus 4.

  The squirrel-cage induction motor 10 is an electric motor using a wound rotor and a stator, and becomes a motor or a generator. When operating as a motor, the flywheel 9 is accelerated to a predetermined speed. When operating as a generator, power is generated according to the rotational force based on the inertial energy of the flywheel 9.

  The flywheel 9 is a disk having inertia and mass. It rotates on bearings and magnetic bearings. By using a magnetic bearing, contactlessness and loss due to friction can be prevented. When the induction motor 10 operates as a motor, it is rotated at a high speed like a coma. When idling, it retains energy in the form of rotational energy. The rotational speed of the flywheel 9 is measured as a frequency [Hz] by the rotational speed meter 12.

  An ammeter 13 is provided between the squirrel-cage induction motor 10 and the flywheel inverter 11, and measures an excitation current value that flows due to an excitation voltage generated by the flywheel inverter 11.

  The flywheel inverter 11 converts the AC voltage from the induction motor 10 operating as a generator based on the rotational force of the flywheel 9 into a DC voltage and supplies the DC voltage to the DC bus 4. At this time, the DC voltage value is measured by the DC voltmeter 14. The flywheel inverter 11 supplies an excitation voltage and an excitation current to the induction motor 10.

  The capacitor 15 has a minimum power energy for operating the flywheel inverter 11 when the power is cut off due to a power failure or the like, and a period from when the power failure occurs until power generation is started by the squirrel-cage induction motor 10. The power energy required by the load 8 is accumulated. That is, the power supply to the load 8 when a power failure occurs can use the generated energy if power generation is started by the squirrel-cage induction motor 10, but the power from the capacitor 15 is used until power generation. If the load 8 is of a property that allows it to be placed in an instantaneous power failure state, the load inverter 7 is turned on for a short period from the time of the power failure to the time when the cage induction motor 10 is excited to start power generation. It is possible to keep the capacitance of the capacitor 15 to a minimum by stopping and preventing the power of the capacitor 15 from being supplied to the load 8. Note that the DC power converted by the flywheel inverter 11 is not supplied to the capacitor 15.

  In the uninterruptible power supply 1 having such a configuration, the squirrel-cage induction motor 10 in the power supply path 5 normally operates as a motor and accelerates the flywheel 9. When the rotational speed of the flywheel 9 is sufficiently increased, the excitation of the squirrel-cage induction motor 10 is stopped and the flywheel 9 is left idle. Since the flywheel 9 and the squirrel-cage induction motor 10 are connected, the rotor of the squirrel-cage induction motor 10 continues to rotate.

  As described above, the flywheel 9 is in a state where inertia energy is accumulated. In this state, for example, when a power failure occurs, the flywheel inverter 11 operates the squirrel-cage induction motor 10 as a generator based on the rotational force of the flywheel 9 this time. The AC energy generated by the squirrel-cage induction motor 10 is supplied to the flywheel inverter 11. The DC voltage converted from AC to DC by the flywheel inverter 11 is supplied to the DC bus 4 while being measured by the DC voltmeter 14. The load inverter 7 converts the generated electric power supplied to the DC bus 4 into 50 Hz AC as described above and supplies it to the load 8.

  In this way, the uninterruptible power supply 1 supplies the power from the load inverter 7 based on the power from the rectifier 6 in the normal power supply path 3 to the load 8, and the power supply path 5 at the time of a power failure. Then, the electric power generated by the induction motor 10 can be supplied.

  In particular, the uninterruptible power supply 1 operates based on the following principle. First, at normal time, the squirrel-cage induction motor 10 connected to the flywheel 9 is brought into a non-excited state when the flywheel 9 reaches a predetermined speed, and the flywheel 9 is rotated as it is at a high speed. This state, that is, a state in which the cage induction motor 10 is de-energized and the flywheel 9 is idling at a predetermined high speed is referred to as an idle state.

  In this idle state, inertial kinetic energy is accumulated in the flywheel 9. From this state, the squirrel-cage induction motor 10 is excited by the control of the flywheel inverter 11 and the rotational speed (slip) control is performed to generate power by kinetic energy.

  Thus, the present embodiment is an uninterruptible power supply 1 that applies the above-described principle, and a high-speed excitation method from the idle state to the power generation state and a power generation method for generating power generation energy within a short time The standby power is minimized by shortening the power failure time, reducing the capacity of the capacitor, and eliminating the excitation current loss.

  Hereinafter, the excitation method of the induction motor 10 and the power generation method of the induction motor 10 executed by the uninterruptible power supply 1 will be described in detail.

  In the idle state, the squirrel-cage induction motor 10 is not excited and must be brought into a power generation state in order to perform a power regeneration operation. Therefore, first, it is necessary to flow an exciting current from the flywheel inverter 11 to the squirrel-cage induction motor 10 that rotates at high speed in a short time.

  Conventionally, induction motors that are always in an excited state have the following slip amount-torque characteristics, and can be put into a power generation state by putting the slip amount of the horizontal axis in a region (3) described later in a short time. It was. FIG. 2 is a slip amount-torque characteristic diagram. The slip amount referred to here is the difference between the frequency [Hz] of electrical alternating current that flows through the exciting coil of the conventional induction motor and the rotational speed of the mechanical induction motor.

  Usually, when the AC frequency matches the rotational speed of the conventional induction motor and the difference is zero (1), the slip amount is zero. On the other hand, when the rotational speed of the conventional induction motor is slower than the alternating current frequency (2), that is, when “the alternating current frequency> the rotational speed of the induction motor”, the conventional induction motor is Generates power as a motor and generates torque called power running. When the torque, friction, load, etc. are balanced, the rotational speed of the induction motor settles. Further, when the rotational speed of the conventional induction motor is faster than the AC frequency (3), that is, when “AC frequency <the rotational speed of the induction motor”, the conventional induction motor is regenerated. Operates as a generator.

  Thus, when the induction motor is rotated faster than the AC magnetic field, it operates as a generator. The generated energy enters the power system. Normally, when the AC frequency and the rotation speed of the induction motor match (1), power consumption is low. Actually, there is a little friction, so if you keep applying excitation for a long time, it will move around (4) because the friction will be canceled out and rotated at a constant rotation. For example, it is assumed that the induction motor is rotated at a constant rotation and excitation is also supplied. When an instruction to generate electricity due to a power failure or the like comes from a state in which the induction motor is energized, the slip amount s1 is brought toward the region (3). If this is an uninterruptible power supply equipped with a flywheel inverter, it can be easily done by changing the frequency of the inverter. If the number of revolutions of the induction motor exceeds the frequency of the alternating current, the energy of power generation can be obtained. As described above, when the conventional induction motor is used, if the slip amount control as shown in FIG. 2 is performed, the generated energy can be obtained in a short time. However, according to this conventional induction motor, since power is always consumed for excitation even in the standby state, the loss is large.

  Therefore, in the uninterruptible power supply 1 of the present embodiment, in order to eliminate the loss, the induction motor 10 is not excited and is not excited and is idled. When a power failure or the like occurs from that state, the induction motor 10 must be brought into the power generation mode. First, an exciting current must be applied to the induction motor 10 to create a magnetic field. However, in general, it takes time to excite by applying an exciting current from the idling state. Therefore, there is a need for an excitation method that excites in a shorter time than conventional excitation methods.

  However, if the rated voltage is applied at a certain point in the non-excited state, the inrush current of the exciting current becomes large. FIG. 3 is a comparative diagram showing that inrush current flows from the time when no voltage is excited to the time when the rated voltage is obtained at time t1 with time on the horizontal axis and voltage on the vertical axis. The inverter trips.

  Moreover, in FIG. 4, the example which used the star connection and the delta connection properly is shown as a comparative example. In the star connection, the resistance is tripled on the electric circuit, so that even when the rated voltage V1 is obtained at time t1, the exciting current does not flow at once as shown by the broken line. That is, since the resistance is large, the current can be suppressed. After exciting with star connection for a certain time, switch the excitation coil to delta connection. Thereby, inrush current can be suppressed. This was used in a configuration that does not use an inverter.

  FIG. 5 shows the characteristics of a comparative example in which the voltage is freely controlled using an inverter, the excitation voltage is gradually increased at a certain rate, and the inrush current of the excitation current is suppressed. The excitation current shown by the broken line does not become an inrush current from the start of excitation at time t1 until the rated voltage V1 is reached at time t2, but in an example of a general 400V several hundred kW class induction machine, several hundreds It takes more than milliseconds.

  FIG. 6 is a characteristic diagram when the rated voltage V1 is excited at a high speed by the excitation method executed in the uninterruptible power supply 1 of the present embodiment. In this excitation method, first, the value of the excitation voltage is stepped to a predetermined value lower than the rated voltage V1 of the induction motor 10 and the inrush current flowing through the flywheel inverter 11 is lower than the trip value of the flywheel inverter 11. Control to increase the shape. Following this, the value of the excitation voltage is increased in a ramp from the predetermined value to the rated voltage V1 of the induction motor 10. The predetermined value mentioned here can be obtained and set by calculation or experiment according to the characteristics of the induction motor 10 or the flywheel inverter 11.

  FIG. 7 is a characteristic diagram when excitation is performed to the rated voltage V1 at high speed by another excitation method executed in the uninterruptible power supply 1 of the present embodiment. Even in the case of a general 400V several hundred kW class induction machine, it takes about several tens of milliseconds to obtain the rated voltage V1 from the non-excited state.

  As will be described later, this can be achieved by an excitation method that determines the rate of increase of the excitation voltage based on current feedback control or an excitation voltage increase waveform pattern determined in advance through experiments or the like. This can be realized by exciting at high speed.

  And control of the excitation voltage of the induction motor 10 by the flywheel inverter 11 in the uninterruptible power supply 1 of this Embodiment is performed by the controller 16 shown in FIG. In addition to the excitation voltage of the induction motor 10, the controller 16 also controls electrical connection / disconnection of the capacitor 15 to the flywheel inverter 11. The controller 16 can be configured by a microcomputer that performs processing by executing a control program, various drivers including a V / f conversion circuit (voltage-frequency conversion circuit), and the like.

  FIG. 8 is a flowchart showing a procedure of processing performed by the controller 16 of the uninterruptible power supply 1 by executing a control program. With reference to this FIG. 8, the whole process including the excitation method of the induction motor in the electric power regeneration apparatus concerning this invention is demonstrated.

  First, in step S1 (a), the controller 16 drives the cage induction motor 10 connected to the flywheel 9 with the flywheel inverter 11 based on V / f control, and accelerates to the rated rotational speed. To do.

  FIG. 9 is a V / f control characteristic diagram. This figure shows the control characteristics for turning the induction motor. The horizontal axis represents the rotational speed f [Hz] of the induction motor 10 and can be controlled by changing the frequency of the flywheel inverter 11. The vertical axis represents the voltage V [V] of the induction voltage machine. The squirrel-cage induction motor 10 connected to the flywheel 9 is driven by the flywheel inverter 11 and accelerated to the rated rotational speed f0. The voltage can be determined according to the rotational speed. Initially, the rotation speed is 0 and the voltage is 0, but the operation is performed such that the rotation speed is increased by the flywheel inverter 11 and the rated voltage V0 is set at the rated rotation speed f0.

  Further, the V / f control will be described with reference to FIGS. V / f control uses a slip state, which is a characteristic of an inverter. This characteristic is set in the inverter. When the frequency of f1 is applied to the induction motor at a voltage of V1, the induction motor is pulled and rotated. If there is no friction, it completely coincides with f1, but in reality there is a loss, so f1 is not reached, and the balance is slightly ahead.

  The speed of acceleration varies depending on the magnitude of friction, the moment of the flywheel, and the magnitude. In the meantime, it becomes slippery. The rotational speed of the alternating magnetic field remains f1, but the motor slowly rises and balances at some point. When you want to change the rotation speed, change the AC frequency.

  The motor also catches up with a certain slip, although it doesn't match perfectly. It is not completely constant. This is how the voltage V is set with respect to the frequency f at that time.

  When viewed from the generated torque of the motor, as shown in FIG. 11, when the voltage extends with a constant slope with respect to the frequency, the generated torque becomes constant as shown by the broken line. As shown in FIG. 12, when the voltage becomes a constant value with respect to the frequency, the generated torque decreases as shown by a broken line.

  Therefore, in the V / f control characteristic as shown in FIG. 10, the generated torque is constant when the voltage extends with a constant slope with respect to the frequency, but when the voltage becomes a constant value with respect to the frequency. The generated torque decreases.

  The rotational speed is measured by the rotational speed meter 12 shown in FIG. I don't know where the rotation speed is now depending on the flywheel operating condition. Since excitation is not performed, the rotational speed is measured by the rotational speed meter 12 when excitation is to be applied. Then, it can be seen from the characteristics of FIG.

  Based on such V / f control, in step S1 (a), the controller 16 drives the induction motor 10 connected to the flywheel 9 with the flywheel inverter 11 and accelerates it to the rated rotational speed. While increasing the frequency, increase the voltage. Change the voltage while changing the rotation speed. Desired torque characteristics are also obtained.

  Returning to FIG. 8, the controller 16 determines whether or not the rated speed has been reached in step S2. If the rated speed f0 has been reached (YES), the process proceeds to step S3 (A), and the induction motor 10 is de-energized according to the method of the present invention.

  FIGS. 13A and 13B are explanatory diagrams showing an excitation release pattern when excitation of the induction motor 10 is stopped, with time on the horizontal axis and the excitation voltage of the induction motor 10 on the vertical axis. As shown in FIG. 13A, when the excitation voltage is released from the flywheel inverter 11 to the induction motor 10, the residual voltage of the induction motor 10 due to the residual magnetic field generated in the induction motor 10 when the excitation voltage is released. The value of the excitation voltage is reduced in a ramp shape at a rate corresponding to the rate of decrease of the residual voltage so that the value of the excitation voltage does not fall below the value of.

  For example, as shown in FIG. 13B, when the excitation voltage for the induction motor 10 having the rated voltage V1 of the excitation voltage of 400V and several hundreds kW is suddenly released as zero volts stepwise, induction by the residual magnetic field is performed. It takes several seconds until the residual voltage of the electric motor 10 is eliminated.

  On the other hand, when the excitation voltage is reduced in a ramp shape over a time of several hundred milliseconds in the reduction pattern due to the linear characteristic shown in FIG. 13A, the residual voltage due to the residual magnetic field generated in the induction motor 10 is While the excitation voltage is reduced to zero volts, the flywheel inverter 11 converts the heat energy into heat energy and the like, so that when the excitation voltage drops to zero volts, the residual voltage of the induction motor 10 due to the residual magnetic field is already It will be in a canceled state.

  Accordingly, the induction motor 10 can be re-excited by reducing the excitation voltage in the form of a ramp over a period of several hundred milliseconds rather than releasing the excitation voltage suddenly at zero volts stepwise. As a result, the time when the residual voltage is zero can be reached early.

  Since the residual voltage due to the residual magnetic field of the induction motor 10 changes depending on the specifications of the induction motor 10 and the uninterruptible power supply 1 as a whole, the rate of decrease when the excitation voltage of the induction motor 10 is reduced to a ramp shape (FIG. 13 ( The slope of the linear characteristic shown in a) is preferably calculated or experimentally based on those specifications. When the induction motor 10 is de-energized, the flywheel 9 and the induction motor 10 thereafter obtain a free rotation state due to inertia and maintain the inertial energy of the flywheel 9 for a long time.

  FIGS. 14A and 14B are characteristic diagrams of the rotational speed with time on the horizontal axis and rotational speed on the vertical axis, and are diagrams showing changes in the rotational speed on the time axis. As shown in FIG. 14 (a), at step S1 (a), the rotational speed increases like U and is set to the rated rotational speed f0. After that, in step S3 (A), no-excitation was performed, and the spinning state was set. At this time, the number of revolutions decreases as D1. However, the rate of decrease is lower than that of the above-described synchronous machine by the amount that cogging torque is not generated.

  If the excitation is continued, the rotation speed is kept constant, but in this embodiment, since the excitation is not performed, the rotation speed decreases by a minimum amount. However, if the bearing of the flywheel 9 is a magnetic bearing and is in a vacuum state, in the case of 4000 revolutions per minute, it takes only 15 minutes to drop four or five revolutions. Therefore, the rotation loss may be almost zero. Of course, if the bearing of the flywheel 9 is used as a bearing and is rotated in the air, the loss increases a little, but it is still less than the synchronous machine.

  Next, the controller 16 proceeds to step S5 (c) when determining that the power generation command is received from the outside at an arbitrary timing such as shutting off the power source in step S4 of FIG. To perform high-speed re-excitation. At this time, the voltage of the capacitor 15 slightly decreases due to discharge. Further, if electric power is supplied to the load 8 using the electric charge of the capacitor 15, the voltage further decreases. In FIG. 14A, since the excitation state is changed from non-excitation, the rotation speed does not decrease like the N characteristic. This high-speed re-excitation method will be described later with reference to FIG.

  Moreover, when it determines with not receiving the electric power generation instruction | command in step S4 of FIG. 8 (NO), it progresses to step S9 (e), and the flywheel 9 reached some rotation speed D4 by rotation speed fall in an idle state. Determine whether or not. If it is determined that the rotational speed has decreased to D4 (YES), the process returns to step S1, and the flywheel 9 is accelerated again to the rated rotational speed D0, as shown in FIG. 14 (b).

  When the high-speed reexcitation ends in step S5 (c), the controller 16 proceeds to step S6 (d) and performs power regeneration according to the method of the present invention. In the power generation state, power is generated while the rotational speed is reduced to D3. The power generation method in step S6 will also be described later.

  Next, in step S7, the controller 16 is in a power generation state, and the flywheel inverter 11 rotates the number of revolutions of the induction motor 10 in order to maintain the voltage of the DC bus at the same constant value as the voltage value at the start of power generation. The slip amount is controlled while monitoring. Here, the voltage of the DC bus, that is, the voltage of the capacitor 15 is slightly reduced due to the discharge as compared with the standby state before the completion of the charge before the occurrence of the power failure. However, the energy generated by the induction motor 10 is used for recharging the capacitor 15 by keeping the voltage of the capacitor 15 at the same constant value as the voltage value at the start of power generation by the power generation of the induction motor 10. All are supplied to the load 8 without.

  Next, the controller 16 continues the control of the load voltage by the load inverter 7 that receives the regenerative power supplied from the power source 2 or the induction generator 10 through the DC bus and supplies the power to the load 8 in step S8. To do.

  Details of the excitation method in step S5 executed by the controller 16 will be described below with reference to FIGS. FIG. 15 is a flowchart showing the processing procedure of the excitation method, and FIG. 16 is an excitation voltage / current characteristic diagram for explaining the high-speed excitation method.

  In step S51 of FIG. 15, the controller 16 measures the current rotation speed of the induction motor 10 in the non-excited state with the rotation speed meter 12.

  Next, in step S52, the controller 16 determines the excitation frequency f1 for the current rotational speed using the preset initial value s1 of the slip value. Since the power generation state is set, a slip value corresponding to the power generation state is set in advance. As shown in FIG. 2, when generating electricity, the slip value s1 is set in the region (3). For example, if the induction motor 10 is rotating at 50 Hz, power is generated if excitation of 51 Hz is applied. Therefore, the initial value s1 of the slip is set to +1 Hz. Considering this, the excitation frequency f1 is determined from the rotational speed. However, if the initial value s1 of the slip is too large, the inrush current at the time of excitation becomes large. Therefore, the initial value s1 of the slip is determined based on the characteristics of the induction motor 10 or is set to zero.

In step S53, the controller 16 determines the excitation target voltage V corresponding to f1 from the V / f control characteristic shown in FIG. That is, when f1 is determined, the excitation voltage V to be excited is known.

In step S54, the controller 16 starts the excitation by driving the flywheel inverter 11 at the excitation frequency f1. At this time, the excitation voltage starts from 0 or a voltage V2 lower than the rated voltage V1 as shown in FIG. At this time, V2 is desirably set to a maximum value at which the inrush current does not exceed the trip current value of the inverter.

  In step S55, the controller 16 increases the excitation voltage from 0 or V2 toward V1. Also at this time, the rising speed is set so that the increase in current accompanying the increase in excitation voltage does not exceed the trip value of the inverter.

  FIG. 17 is a configuration diagram of a specific example 30 of the excitation voltage control circuit. This is an equivalent circuit realized by a microcomputer and a driver constituting the controller 16. The excitation release pattern memory 36a stores a table showing an excitation release pattern (see FIG. 13) when excitation of the induction motor 10 is stopped.

  FIG. 18 is an explanatory diagram showing this excitation release pattern table. In the excitation release pattern table, the elapsed time T from the excitation release point of the induction motor 10 measured by the timer 37a of FIG. 17 corresponding thereto, the excitation voltage of the induction motor 10 corresponding to the elapsed time T, and its excitation The time required for increasing the excitation voltage of the induction motor 10 from zero volts up to the voltage (the elapsed time T ′ from the excitation start point) is associated with the voltage.

  The excitation voltage of the induction motor 10 corresponding to the elapsed time T from the excitation release time of the induction motor 10 is set as a percentage with respect to the rated voltage V1 of the induction motor 10. Further, the above-described increase required time (elapsed time T ′ from the excitation start time) increases the excitation voltage of the induction motor 10 from zero volts according to the excitation start pattern at the start of excitation of the induction motor 10 shown in FIG. It is the time required for

  In addition, the excitation start pattern memory 36b of the circuit shown in FIG. 17 stores a table indicating an excitation start pattern (see FIG. 6) at the start of excitation of the induction motor 10.

  FIG. 19 is an explanatory diagram showing this excitation start pattern table. In the excitation start pattern table, the elapsed time T ′ from the excitation start time of the induction motor 10 measured by the timer 37b of FIG. 17 corresponding thereto and the excitation voltage of the induction motor 10 corresponding to the elapsed time T ′ are displayed. It is configured in association.

  The excitation voltage of the induction motor 10 corresponding to the elapsed time T ′ from the excitation start time of the induction motor 10 is the rated voltage of the induction motor 10 in the same manner as the excitation voltage of the induction motor 10 in the excitation release pattern table of FIG. It is set as a percentage of V1. In FIG. 19, the excitation voltage of the corresponding induction motor 10 is described for the range of the elapsed time T ′ from 0 to 38 msec, but the percentage of the rated voltage V1 of the induction motor 10 is present at the elapsed time T ′ after 38 msec. Is associated with an excitation voltage of 100%.

  Further, the circuit changeover switch 38 shown in FIG. 17 uses a pattern table used by the controller 16 for controlling the excitation voltage of the induction motor 10 from one of the excitation release pattern table of FIG. 18 and the excitation start pattern table of FIG. To switch to.

  For example, if an external excitation start command is generated while the excitation voltage is decreasing due to excitation cancellation, and the controller 16 switches from the excitation cancellation pattern table of FIG. 18 to the excitation start pattern table of FIG. The increase required time (elapsed time T ′ from the excitation start time) on the excitation release pattern table of FIG. 18 corresponding to the elapsed time T from the excitation release time of the induction motor 10 measured by the timer 37a of FIG. ) Is set in the timer 37b of FIG. Accordingly, the timer 37b measures the elapsed time after the set time T ′ from the excitation start time after the switching from the excitation release pattern table of FIG. 18 to the excitation start pattern table of FIG.

  Further, the low value selection circuit 39 of the circuit shown in FIG. 17 is operated by the switch 38 corresponding to the elapsed times T and T ′ measured by the timers 37a and 37b corresponding to the pattern table selected by the switch 38. The lower one of the excitation voltage of the induction motor 10 defined in the selected pattern table and the rated voltage V1 of the induction motor 10 is selected, and the induction motor 10 of the induction motor 10 is selected with respect to the flywheel inverter 11. It is output as an excitation voltage.

  Therefore, when an excitation start command is generated from the outside while the excitation voltage is being reduced by the excitation release pattern of the excitation release pattern table of FIG. The excitation voltage is increased by the excitation start pattern in the excitation start pattern table of FIG.

  When the excitation start command from the outside is generated, the excitation voltage of the induction motor 10 has already switched the excitation voltage increase pattern from the step shape to the ramp shape in the excitation start pattern of the excitation start pattern table of FIG. When the value is below the predetermined value in the characteristic diagram of FIG. 6, the excitation voltage of the induction motor 10 is increased stepwise to the predetermined value and then increased to the rated voltage V1 when the excitation start command is generated. Will be.

  FIG. 20 is a configuration diagram of another specific example 30A of the excitation voltage control circuit. Similarly to the excitation voltage control circuit of FIG. 17, this is an equivalent circuit realized by a microcomputer and a driver constituting the controller 16. The excitation release pattern memory 36c stores a table indicating an excitation release pattern (see FIG. 13) when excitation of the induction motor 10 is stopped.

  FIG. 21 is an explanatory diagram showing this excitation release pattern table. The excitation release pattern table associates the elapsed time T from the excitation release time of the induction motor 10 measured by the timer 37c of FIG. 20 corresponding thereto with the excitation voltage of the induction motor 10 corresponding to the elapsed time T. Configured.

  The excitation voltage of the induction motor 10 corresponding to the elapsed time T from the excitation release time of the induction motor 10 is set as a percentage with respect to the rated voltage V1 of the induction motor 10 as in the excitation release pattern table of FIG. .

  In addition, the excitation start pattern memory 36d of the circuit shown in FIG. 20 stores a table indicating an excitation start pattern (see FIG. 6) at the start of excitation of the induction motor 10.

  FIG. 22 is an explanatory diagram showing this excitation start pattern table. In the excitation start pattern table, the elapsed time T ′ from the excitation start time of the induction motor 10 measured by the timer 37d of FIG. 20 corresponding thereto and the excitation voltage of the induction motor 10 corresponding to the elapsed time T ′ are displayed. It is configured in association.

  The excitation voltage of the induction motor 10 corresponding to the elapsed time T ′ from the excitation start time of the induction motor 10 is the rated voltage of the induction motor 10 in the same manner as the excitation voltage of the induction motor 10 in the excitation start pattern table of FIG. It is set as a percentage of V1. In FIG. 22, the excitation voltage of the corresponding induction motor 10 is shown for the range of the elapsed time T ′ from 0 to 38 msec, but the percentage of the rated voltage V1 of the induction motor 10 is present at the elapsed time T ′ after 38 msec. Is associated with an excitation voltage of 100%.

  In the circuit shown in FIG. 20, when an excitation release command is generated from the outside, the elapsed time from the excitation release point of the induction motor 10 measured by the timer 37c on the excitation release pattern table of FIG. The excitation voltage corresponding to T is sequentially input from the excitation release pattern memory 36c to the high value selection circuit 39a. At the time when the command for releasing the excitation of the induction motor 10 does not occur and the timer 37c does not measure the elapsed time T, the rated voltage of the induction motor 10 corresponding to the elapsed time T = 0 on the excitation release pattern table of FIG. An excitation voltage whose percentage with respect to V1 is 100% is input from the excitation release pattern memory 36c to the high value selection circuit 39a.

  In the circuit shown in FIG. 20, when an external excitation start command is generated, the controller 16 controls the excitation start pattern table of FIG. 22 to start from the excitation start point of the induction motor 10 measured by the timer 37d. The excitation voltage corresponding to the elapsed time T ′ is sequentially input from the excitation start pattern memory 36d to the high value selection circuit 39a. At the time when the excitation start command for the induction motor 10 is not generated and the timer 37c does not measure the elapsed time T ', the induction motor 10 corresponding to the elapsed time T' = 0 on the excitation start pattern table of FIG. An excitation voltage having a percentage of 0% with respect to the rated voltage V1 is input from the excitation start pattern memory 36d to the high value selection circuit 39a.

  The high value selection circuit 39a selects the higher one of the excitation voltage of the induction motor 10 input from the excitation release pattern memory 36c and the excitation voltage of the induction motor 10 input from the excitation start pattern memory 36d. This is output to the value selection circuit 39b. The low value selection circuit 39b selects the lower one of the excitation voltage having the higher value input from the high value selection circuit 39a and the rated voltage V1 of the induction motor 10, and supplies the flywheel inverter 11 with the lower value selection circuit 39b. The voltage command value indicating the excitation voltage of the induction motor 10 is output.

  Accordingly, when an external excitation release command is generated, the controller 16 inputs the elapsed time T ′ = 0 on the excitation start pattern table of FIG. 22 which is input from the excitation start pattern memory 36d to the high value selection circuit 39a. On the excitation release pattern table of FIG. 21, which is input from the excitation release pattern memory 36c to the high value selection circuit 39a, the value of which is higher than the excitation voltage of 0% of the rated voltage V1 of the induction motor 10 corresponding to The excitation voltage corresponding to the elapsed time T from the excitation release point of the induction motor 10 measured by the timer 37c is applied to the flywheel inverter 11 from the high value selection circuit 39a to the low value selection circuit 39b. As output.

  Then, as shown in FIG. 13 described above, the excitation voltage of the induction motor 10 is reduced in a ramp shape.

  Further, when an external excitation start command is generated, the controller 16 inputs the elapsed time T ′ = 0 on the excitation start pattern table of FIG. 22 input from the excitation release pattern memory 36c to the high value selection circuit 39a. On the excitation start pattern table of FIG. 22, which is input from the excitation start pattern memory 36d to the high value selection circuit 39a, the value of which is higher than the excitation voltage of 0% corresponding to the rated voltage V1 of the induction motor 10. The excitation voltage corresponding to the elapsed time T ′ from the excitation start time of the induction motor 10 measured by the timer 37d is applied to the flywheel inverter 11 from the high value selection circuit 39a to the low value selection circuit 39b. Output as voltage.

  Then, as shown in FIG. 6 described above, the excitation voltage of the induction motor 10 increases in a step shape up to a predetermined value, and increases from the predetermined value to the rated voltage V1 of the induction motor 10 in a ramp shape.

  Further, when an external excitation start command is generated while the excitation voltage is decreasing due to excitation cancellation, the controller 16 is input from the excitation cancellation pattern memory 36c to the high value selection circuit 39a. The excitation voltage corresponding to the elapsed time T from the excitation release time of the induction motor 10 measured by the timer 37c on the pattern table and the excitation start pattern of FIG. 22 inputted from the excitation start pattern memory 36d to the high value selection circuit 39a. Among the excitation voltages corresponding to the elapsed time T ′ from the excitation start time of the induction motor 10 measured by the timer 37d on the table, the higher value is output from the high value selection circuit 39a to the low value selection circuit 39b. Among the excitation voltage having the higher value input from the high value selection circuit 39a and the rated voltage V1 of the induction motor 10, the lower value is set to Against Lee wheel inverter 11 to output as the excitation voltage of the induction motor 10.

  Accordingly, when an excitation start command is generated from the outside while the excitation voltage is being reduced by the excitation release pattern in the excitation release pattern table of FIG. Until the excitation voltage corresponding to the elapsed time T decreases to a value equal to the excitation voltage corresponding to the elapsed time T ′ from the time when the excitation start command is generated, the excitation release pattern in the excitation release pattern table of FIG. The excitation voltage is decreased, and thereafter, the excitation voltage is increased by the excitation start pattern of the excitation start pattern table of FIG.

  FIG. 23 is a configuration diagram of still another specific example 30B of the excitation voltage control circuit. This is also an equivalent circuit realized by a microcomputer and a driver constituting the controller 16 as in the excitation voltage control circuit of FIG. 17 and FIG. The controller 16 uses a function calculator 32 to calculate a function Fx of time with respect to the voltage measured by the timer 31. Further, the controller 16 calculates the difference between the excitation current measured by the ammeter 13 and the maximum current setting value by the delta calculator 33 and then supplies the difference to the compensator 34 such as PID control by feedback to compensate. Then, the controller 16 adds the function Fx and the compensation value in the Σ adder 35. Then, the speed becomes as shown in FIG.

  Next, the controller 16 checks whether or not the excitation voltage has reached V1 in step S56. If it is determined that the excitation voltage has reached, the high-speed excitation is completed.

  Below, the detail of the electric power generation method of step S6 is demonstrated with reference to FIG.24 and FIG.25. FIG. 24 is a flowchart showing a processing procedure of the power generation method, and FIG. 25 is a time-rotation speed characteristic diagram for explaining the power generation method.

  In step S61 of FIG. 24, the controller 16 determines the excitation voltage by V / f control continuously from step S56.

  Next, in step S62, the controller 16 determines the excitation frequency f, with f1 or s1 as an initial value, by a preceding command based on the current rotation speed and feedback control (PID control or the like) of the DC bus voltage.

  Next, in Step S63, the controller 16 appropriately controls the excitation frequency or the slip with respect to the decrease in the rotation speed due to the power generation and the consumption of the load power. Thereby, the regenerative electric power corresponding to the electric power consumption by load is obtained.

  In the characteristic diagram of FIG. 25, the power generation start time t2 is temporally the same as the excitation completion time t2 shown in FIG. Before the start of power generation, the frequency is f1. In FIG. 25, the vertical axis represents the rotation speed or frequency, and the horizontal axis represents time. The solid line is the actual rotational speed of the motor, and the alternate long and short dash line is the excitation frequency Hz. The excitation frequency is set to be slightly lower than the actual motor speed. When power generation starts, power generation is performed while controlling the rotation speed.

  FIG. 26 is a configuration diagram of a specific example 20 of the circuit for controlling the excitation frequency. This is also an equivalent circuit realized by a microcomputer and a driver constituting the controller 16 as in the excitation voltage control circuit of FIG. 17, FIG. 20, and FIG. A function calculator 21 calculates a function Fx from the rotation speed [Hz] of the induction motor measured by the tachometer 12 and supplies it to the Σ adder 24. On the other hand, the DC voltage value measured by the DC voltmeter 14 is compared with the DC voltage set value by the delta calculator 22, and the compensator 23 compensates the voltage value based on the difference, and the Σ adder 24 Supply. The Σ adder 24 calculates the excitation frequency by adding the calculation result of the function Fx to the compensation value.

  FIG. 27 is a diagram for explaining the principle of excitation frequency control. Usually, power is supplied from the power source 2 to the load 8 through the load inverter 7. Assume that the power supply system has a power failure. Then, the uninterruptible power supply 1 regenerates electric power from the flywheel inverter 11.

  If the load is consuming PL (KW), the flywheel generator must generate PL (Kw). That is, a balanced state is obtained if the generated power of PF (Kw) covers the load PL (Kw).

  However, if the power generated by the flywheel generator is larger than that consumed by the load, the power supply becomes excessive. This appears in the DC voltage. That is, PF> PL → DC voltage rises. This is measured by a DC voltmeter 14.

  Also, if the power consumed by the load is greater than the power generated by the flywheel generator, the energy escapes and the DC voltage drops. That is, PF <PL → DC voltage decreases. Further, PF = PL → DC voltage is constant.

  This is because the DC voltage is determined by the integration of the difference between power generation and consumption. It becomes constant when balanced. If the incoming amount is large and the outgoing amount is small, it is accumulated.

  The load side consumes electric power according to the state. The fluctuation appears in the measured value of the DC voltage at the DC voltmeter 14. If the power generation amount PF (Kw) is determined so that the DC voltage is constant, the PF and the power consumption PL are balanced as a result. The voltage from the flywheel generator can be controlled by adjusting the amount of slip.

  If the slip amount is small, the power generation energy is small. If the amount of slip is large, the power generation energy increases. This is the opposite of power running. In power running, if the amount of slip is small, the power is small. The greater the slip, the greater the power. The amount of power generation can be controlled by controlling the slip amount during power generation. Since slip = rotation frequency−rotation speed of the motor, if the rotation speed of the motor is 50 Hz, for example, and the slip is 1 Hz, the rotation frequency is 49 Hz. Then, the output for 1 Hz has come out. When power is generated, the motor speed decreases. If the inverter is not always below 1 Hz, it will not be possible to generate power continuously and stably. When the number of rotations decreases, it is necessary to always control it downward while watching it. Therefore, the excitation frequency is determined based on the rotation speed. Fine adjustment is performed by controlling the frequency while observing the DC voltage.

  As described above, according to the uninterruptible power supply 1 of the present embodiment, when the application of the excitation voltage from the flywheel inverter 11 to the induction motor 10 is canceled, the induction motor 10 is accompanied by the cancellation of the application of the excitation voltage. The value of the excitation voltage is reduced in a ramp shape at a rate corresponding to the rate of decrease of the residual voltage so that the value of the excitation voltage does not fall below the value of the residual voltage of the induction motor 10 due to the residual magnetic field generated in the above.

  For this reason, the time when the residual voltage is zero when the residual voltage of the induction motor 10 due to the residual magnetic field is eliminated and the induction motor 10 can be re-excited in a shorter time than when the excitation voltage for the induction motor 10 is suddenly released as zero volts stepwise. As a result.

  Thereby, the re-excitation prohibition period after canceling the excitation of the induction motor 10 can be shortened. Therefore, when a power failure occurs during the re-excitation prohibition period, until the re-excitation prohibition period elapses and power generation by the induction motor 10 becomes possible, the capacitor 15 is supplied with power for backup to the load 8. It is possible to reduce the capacitance that needs to be secured. That is, the capacitor 15 can be reduced in size, and thus the apparatus can be reduced in size.

It is a block diagram of an uninterruptible power supply. It is a slip amount-torque characteristic diagram. It is a figure for the comparison which shows that an inrush current flows until it obtains rated voltage V1 at time t1 from non-excitation. It is an excitation voltage / excitation current characteristic diagram of an example in which star connection and delta connection are used properly. FIG. 10 is a characteristic diagram of a comparative example in which the voltage is freely controlled using an inverter, the excitation voltage is gradually increased at a certain rate, and the inrush current of the excitation current is suppressed. It is a characteristic view when exciting to the rated voltage V1 at high speed by the excitation method executed in the uninterruptible power supply. It is a characteristic view when exciting to the rated voltage V1 at high speed by the excitation method executed in the uninterruptible power supply. It is a flowchart which shows the procedure of the process performed with an uninterruptible power supply. It is a V / f control characteristic figure. It is a V / f control characteristic figure. In a V / f control characteristic figure, it is a figure which shows that the voltage is extended with the fixed inclination with respect to the frequency. In a V / f control characteristic figure, it is a figure which shows that a voltage is a fixed value with respect to a frequency. It is explanatory drawing which shows the excitation cancellation | release pattern at the time of the excitation stop of the induction motor 10 which took time on the horizontal axis and took the excitation voltage of the induction motor on the vertical axis | shaft. FIG. 6 is a characteristic diagram of the number of rotations with time on the horizontal axis and the number of rotations on the vertical axis, showing changes in the number of rotations on the time axis. It is a flowchart which shows the process sequence of the excitation method. It is an excitation voltage / current characteristic diagram for explaining a high-speed excitation method. It is a figure which shows the example of an excitation voltage control circuit. It is explanatory drawing which shows the content of the excitation cancellation | release pattern table stored in the excitation cancellation | release pattern memory. It is explanatory drawing which shows the content of the excitation start pattern table stored in the excitation start pattern memory. It is a figure which shows the other example of an excitation voltage control circuit. It is explanatory drawing which shows the content of the excitation cancellation | release pattern table stored in the excitation cancellation | release pattern memory. It is explanatory drawing which shows the content of the excitation start pattern table stored in the excitation start pattern memory. It is a figure which shows the further another example of an excitation voltage control circuit. It is a flowchart which shows the process sequence of an electric power generation method. It is a characteristic view for demonstrating the power generation regeneration control method. It is a block diagram of the example of an excitation frequency control circuit. It is a figure for demonstrating the principle of excitation frequency control. It is a block diagram of the electric power regeneration apparatus (uninterruptible power supply device) using a synchronous machine and a flywheel. It is a block diagram of the electric power regeneration apparatus which connected the flywheel to the induction motor which is always exciting the exciting coil. It is a figure for demonstrating the loss which generate | occur | produces with an exciting current.

Explanation of symbols

1 ... Uninterruptible power supply (power regeneration device)
2 ... Power supply 3 ... Power supply path at normal time 4 ... DC bus 5 ... Power supply path at power failure 6 ... Rectifier 7 ... Inverter for load 8 ... Load 9 ... Flywheel 10 ... induction motor 11 ... flywheel inverter 12 ... revolution meter 13 ... ammeter 14 ... DC voltmeter 15 ... capacitor 16 ... controller 20 ... Excitation frequency control circuit 30, 30A, 30B ... Excitation voltage control circuit 36a, 36c ... Excitation release pattern memory 36b, 36d ... Excitation start pattern memory 31, 37a, 37b, 37c, 37d ... Timer 21 , 32 ... function calculator 22, 33 ... delta calculator 23, 34 ... compensator 24, 35 ... Σ adder 38 ... changeover switch 39, 39b ... low Selection circuit 39a ··· high value selector circuit

Claims (4)

The excitation voltage from the inverter to the induction motor is a flywheel accelerated to a predetermined rotational speed by an induction motor operated as a motor by applying an excitation voltage generated by the inverter using power supplied from a power source. When the power application is received from the outside during a power failure, the induction motor rotated by the flywheel in the idle state is accumulated in the capacitor. Operate as a generator by applying an excitation voltage generated by the inverter using electric power, and supply the regenerative power generated by the induction motor to the load via the inverter instead of the power from the power failure In a power regeneration device, a method for controlling the excitation voltage of the induction motor,
When the controller cancels the application of the excitation voltage from the inverter to the induction motor, the value of the excitation voltage indicates the value of the residual voltage of the induction motor due to the residual magnetic field generated in the induction motor when the application of the excitation voltage is canceled. so as not to fall below the excitation releasing steps to reduce the value of the excitation voltage at a speed corresponding to the reduction rate of the residual voltage in a ramp form,
An excitation start step for increasing the value of the excitation voltage in a pattern in which an inrush current flowing through the inverter is always lower than a trip value of the inverter when the controller starts applying the excitation voltage from the inverter to the induction motor;
When the controller receives the power generation command while the excitation voltage value is decreasing, the controller is in a state where the excitation voltage value in the excitation release step is greater than the excitation voltage value in the excitation start step. The excitation voltage value is decreased by the excitation release step, and after the time when the excitation voltage value by the excitation release step coincides with the excitation voltage value by the excitation start step, the excitation start step An excitation voltage control step when the magnetic field remains to increase the voltage value ,
An induction motor excitation voltage control method for a power regeneration device characterized by that. The pattern of the excitation start step increases the value of the excitation voltage stepwise until the inrush current flowing through the inverter is lower than the rated voltage of the induction motor and below a trip value of the inverter. The induction motor excitation voltage control method for a power regeneration device according to claim 1, wherein the excitation voltage value is increased in a ramp shape from the predetermined value to the rated voltage . The excitation voltage from the inverter to the induction motor is a flywheel accelerated to a predetermined rotational speed by an induction motor operated as a motor by applying an excitation voltage generated by the inverter using power supplied from a power source. When the power application is received from the outside during a power failure, the induction motor rotated by the flywheel in the idle state is accumulated in the capacitor. Operate as a generator by applying an excitation voltage generated by the inverter using electric power, and supply the regenerative power generated by the induction motor to the load via the inverter instead of the power from the power failure In the power regeneration device,
When the application of the excitation voltage from the inverter to the induction motor is canceled, the value of the excitation voltage does not fall below the value of the residual voltage of the induction motor due to the residual magnetic field generated in the induction motor due to the cancellation of the application of the excitation voltage. In addition, the excitation stop time voltage control means for controlling the value of the excitation voltage to decrease in a ramp shape at a speed according to the decrease speed of the residual voltage,
Excitation start voltage control for controlling the inrush current flowing through the inverter to increase the value of the excitation voltage in a pattern that always falls below the trip value of the inverter at the start of application of the excitation voltage from the inverter to the induction motor Means,
A magnetic field residual voltage control means for controlling the value of the excitation voltage when the power generation command is received during the decrease of the value of the excitation voltage by the control of the excitation stop voltage control means,
While the magnetic field residual voltage control means is in a state where the value of the excitation voltage controlled by the excitation stop voltage control means exceeds the value of the excitation voltage controlled by the excitation start voltage control means, Prioritize the control of the voltage control means at the time of excitation stop and decrease the value of the excitation voltage by the control of the voltage control means at the time of excitation start, and the value of the excitation voltage by the control of the voltage control means at the time of excitation stop After the time point when the excitation voltage value coincides with the value of the excitation voltage control means, the control of the excitation start voltage control means is prioritized and the excitation voltage value is increased by the control of the excitation start voltage control means. ,
A power regeneration device characterized by that. The excitation start time voltage control means increases the value of the excitation voltage in a stepped manner until the inrush current flowing through the inverter is lower than the rated voltage of the induction motor and falls below a trip value of the inverter. 4. The power regeneration device according to claim 3, wherein control is performed so that the value of the excitation voltage is increased in a ramp shape from the predetermined value to the rated voltage.

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