JP6658501B2 - Battery charging circuit - Google Patents

Description

  The present invention relates to a battery charging circuit for charging a battery in a motor drive system including a motor driven and controlled by a three-phase inverter using a battery as a power supply.

  A battery charging circuit is disclosed in Patent Literature 1, which is a motor driving system battery charging circuit including a three-phase motor driven and controlled by a three-phase inverter using a battery as a power source. A connection point of one set of switching elements forming one phase is connected to a secondary-side output terminal of a single-phase output. Then, of the three-phase inverters, one set of switching elements constituting one phase connected to the transformer is kept in an off state, and at least one of the other two sets of switching elements is turned on / off. By controlling, the battery can be charged. Here, the battery can also be charged by synchronizing on / off control of two sets of switching elements constituting two phases not connected to the transformer, of the three-phase inverter.

JP 2011-212889 A

  By the way, when two sets of switching elements of a two-phase inverter of a three-phase inverter that are not connected to a transformer are controlled to be turned on / off synchronously, a current sensor may be provided for each phase. However, if only one of the two phases to be turned on and off is provided with a current sensor, the two-phase currents cannot be controlled equally due to inter-phase variations in the dead time of each switching element, etc. An error occurs.

  An object of the present invention is to provide a battery charging circuit that can accurately control a battery charging current.

  According to the first aspect of the present invention, the first switching element for the upper arm of the first phase, the second switching element for the lower arm of the first phase, the third switching element for the upper arm of the second phase, A three-phase inverter having a fourth switching element for the lower arm of the phase, a fifth switching element for the upper arm of the third phase, and a sixth switching element for the lower arm of the third phase is driven and controlled using a battery as a power supply. A battery charging circuit for a motor drive system including a three-phase motor, wherein the three-phase inverter is connected to a single-phase output transformer and one terminal of a secondary-side output of the single-phase output transformer. A rectifier circuit connected in parallel to a battery, and a connection point between the first switching element and the second switching element in the three-phase inverter is connected to the secondary side output. And a wiring connected to the other terminal, the first switching element and the second switching element are kept in an off state during charging, and the third switching element and the fifth switching element are synchronously turned on and off while being charged. A control device for synchronously turning on and off the fourth switching element and the sixth switching element, and a current sensor for detecting a current flowing between the connection point and the three-phase motor; Before starting charging, the device sets the current value by the current sensor in a state where the second switching element is controlled to a specified value, the first duty by the on / off control of the third switching element, and the current value by the current sensor. The second duty by the on / off control of the fifth switching element to make the specified value, and the first switch The third duty by the on / off control of the fourth switching element and the sixth switching element to set the current value by the current sensor to a specified value by controlling the on / off control of the fourth switching element when the switching element is controlled. A fourth duty obtained by on / off control is acquired, and after charging is started, on / off control is performed while correcting the third switching element and the fifth switching element with the first duty and the second duty. The gist is to perform on / off control while correcting the fourth switching element and the sixth switching element with the third duty and the fourth duty.

  According to the first aspect of the present invention, before the start of charging, the control device sets the current value by the current sensor in a state in which the second switching element is controlled to a specified value by the on / off control of the third switching element. A second duty by the on / off control of the fifth switching element for setting the current value of the first duty and the current sensor to the specified value, and a fourth duty for setting the current value of the current sensor in the state where the first switching element is controlled to the specified value. A third duty by the on / off control of the switching element and a fourth duty by the on / off control of the sixth switching element for setting the current value by the current sensor to a specified value are obtained. Then, after the start of charging, the control device performs on / off control while correcting the third switching element and the fifth switching element with the first duty and the second duty, and controls the fourth switching element and the sixth switching element. On / off control is performed while correcting with the third duty and the fourth duty. As a result, it is possible to accurately control the battery charging current.

  As described in claim 2, in the battery charging circuit according to claim 1, the control device is configured to control the current value of the current sensor in a state where the second switching element is controlled before the start of charging by the first value. The fifth duty by the on / off control of the third switching element, which is a prescribed value different from that when acquiring the duty, and the current value by the current sensor, which is a prescribed value different from that when the second duty is acquired, A sixth duty based on on / off control of a fifth switching element, and a second duty that is set to a current value obtained by the current sensor in a state where the first switching element is controlled, which is different from a value obtained when the third duty is acquired. The fourth duty by the on / off control of the four switching elements and the current value by the current sensor are applied to the fourth duty. The eighth duty is obtained by the on / off control of the sixth switching element, which is set to a specified value different from the value obtained when the third switching element is obtained, and after the start of charging, the third switching element and the fifth switching element are On / off control is performed while correcting with the first duty, the second duty, the fifth duty, and the sixth duty, and the fourth switching element and the sixth switching element are controlled by the third duty and the fourth duty. On / off control may be performed while correcting with the seventh duty and the eighth duty.

  According to the present invention, it is possible to accurately control the battery charging current.

FIG. 2 is a circuit diagram of the battery forklift according to the embodiment. FIG. 4 is an explanatory diagram of a current path during charging. FIG. 4 is an explanatory diagram of a current path during charging. FIG. 4 is an explanatory diagram of a current path before the start of charging. FIG. 4 is an explanatory diagram of a current path before the start of charging. FIG. 11 is a characteristic diagram illustrating a relationship between a current command value and a correction value for explaining another example.

  Hereinafter, an embodiment in which the present invention is embodied in a battery forklift will be described with reference to the drawings. The battery forklift is provided with a traveling motor and a cargo handling motor which are controlled by an inverter while using a battery as a power supply, as a motor drive system. The battery charging circuit uses coils of a traveling motor and a cargo handling motor and switching elements of an inverter as components.

  As shown in FIG. 1, the battery forklift includes an in-vehicle device 10. The in-vehicle device 10 includes a traveling motor 11 and a cargo handling motor 17 as a three-phase motor using a battery 30 as a power source. A traveling inverter 12 as a three-phase inverter is provided between the traveling motor 11 and the battery 30, and a loading inverter 18 as a three-phase inverter is provided between the cargo motor 17 and the battery 30. Is provided.

  The in-vehicle device 10 includes a Scott transformer 13 as a single-phase output transformer connected to a three-phase AC power supply 40. The Scott transformer 13 has primary windings 13a and 13b and secondary windings 13c and 13d.

  Inverters 12 and 18 include first switching elements Q1 and Q11 for a V-phase upper arm as a first phase and second switching elements Q2 and Q12 for a V-phase lower arm. Inverters 12 and 18 have third switching elements Q3 and Q13 for the upper arm of the W phase as the second phase and fourth switching elements Q4 and Q14 for the lower arm of the W phase. Inverters 12 and 18 include fifth switching elements Q5 and Q15 for the upper arm of the U phase as the third phase, and sixth switching elements Q6 and Q16 for the lower arm of the U phase as the third phase. A motor drive system battery charging circuit including motors 11 and 17 that are driven and controlled by a battery 30 as a power source by inverters 12 and 18.

  A traveling inverter 12 is connected to a secondary winding 13c which is one single-phase output of the Scott transformer 13 via a rectifier circuit 14, and a traveling motor 11 is connected to the traveling inverter 12. As the traveling motor 11, a three-phase AC motor in which the coils 23, 24, and 25 are delta-connected is used. The loading winding inverter 18 is connected to the secondary winding 13 d, which is the other single-phase output of the Scott transformer 13, via a rectifier circuit 19, and the loading inverter 18 is connected to a loading motor 17. As the cargo handling motor 17, a three-phase AC motor in which coils 26, 27, and 28 are delta-connected is used.

  The rectifier circuit 14 is configured by a series circuit of two diodes D1 and D2, and a terminal 15a of a secondary winding 13c, which is one single-phase output of the Scott transformer 13, is connected to a midpoint between the diodes D1 and D2. ing. The positive side of the rectifier circuit 14 is connected to the positive electrode of the battery 30, and the negative side of the rectifier circuit 14 is connected to the negative electrode of the battery 30.

  The traveling inverter 12 includes a first switching element Q1, a third switching element Q3, and a fifth switching element Q5 as three-phase upper-arm switching elements, and a second switching element Q2 as a lower-arm switching element. , A fourth switching element Q4 and a sixth switching element Q6. A MOSFET is used for each of the switching elements Q1 to Q6. The first switching element Q1 and the second switching element Q2, the third switching element Q3 and the fourth switching element Q4, the fifth switching element Q5 and the sixth switching element Q6 are connected in series, respectively. The drains of switching elements Q1, Q3, and Q5 are each connected to the positive electrode of battery 30, and the sources of switching elements Q2, Q4, and Q6 are each connected to the negative electrode of battery 30. Each of the switching elements Q1 to Q6 has a parasitic diode D connected between the drain and the source in anti-parallel, that is, with the cathode corresponding to the drain and the anode corresponding to the source.

  A connection point A (a connection point between the source of the first switching element Q1 and the drain of the second switching element Q2), which is a middle point between the first switching element Q1 and the second switching element Q2, is connected via the current sensor S1 for traveling. It is connected to a connection point between the coil 23 and the coil 24 of the motor 11. The midpoint between the third switching element Q3 and the fourth switching element Q4 (the connection point between the source of the third switching element Q3 and the drain of the fourth switching element Q4) is connected to the coil 24 of the traveling motor 11 via the current sensor S2. And the connection point of the coil 25.

  The midpoint between the fifth switching element Q5 and the sixth switching element Q6 (the connection point between the source of the fifth switching element Q5 and the drain of the sixth switching element Q6) is the connection between the coil 23 and the coil 25 of the traveling motor 11. Connected to a point. A connection point A between the source of the first switching element Q1 and the drain of the second switching element Q2 is connected to the rectifier circuit 14 in the secondary winding 13c, which is one single-phase output of the Scott transformer 13, by the wiring 20. Connected to the terminal 15b on the opposite side of the terminal 15a.

  The rectifier circuit 19 is composed of a series circuit of two diodes D3 and D4, and the terminal 16a of the secondary winding 13d, which is the other single-phase output of the Scott transformer 13, is connected to the midpoint between the two diodes D3 and D4. ing. The positive side of the rectifier circuit 19 is connected to the positive electrode of the battery 30, and the negative side of the rectifier circuit 19 is connected to the negative electrode of the battery 30.

  The loading inverter 18 includes a first switching element Q11, a third switching element Q13, and a fifth switching element Q15 as three-phase upper-arm switching elements, and a second switching element Q12 as a lower-arm switching element. , A fourth switching element Q14 and a sixth switching element Q16. MOSFETs are used for the switching elements Q11 to Q16. The first switching element Q11 and the second switching element Q12, the third switching element Q13 and the fourth switching element Q14, the fifth switching element Q15 and the sixth switching element Q16 are respectively connected in series. The drains of switching elements Q1, Q3, and Q5 are each connected to the positive electrode of battery 30, and the sources of switching elements Q2, Q4, and Q6 are each connected to the negative electrode of battery 30. Each of the switching elements Q11 to Q16 has a parasitic diode D connected between the drain and the source in anti-parallel, that is, with the cathode corresponding to the drain and the anode corresponding to the source.

  A connection point B (a connection point between the source of the first switching element Q11 and the drain of the second switching element Q12) which is a middle point between the first switching element Q11 and the second switching element Q12 is used for cargo handling via the current sensor S11. It is connected to a connection point between the coil 26 and the coil 27 of the motor 17. The midpoint between the third switching element Q13 and the fourth switching element Q14 (the connection point between the source of the third switching element Q13 and the drain of the fourth switching element Q14) is connected to the coil 27 of the unloading motor 17 via the current sensor S12. And the coil 28. The midpoint between the fifth switching element Q15 and the sixth switching element Q16 (the connection point between the source of the fifth switching element Q15 and the drain of the sixth switching element Q16) is the connection between the coil 26 and the coil 28 of the loading motor 17. Connected to a point. A connection point B between the source of the first switching element Q11 and the drain of the second switching element Q12 is connected to the rectifier circuit 19 in the secondary winding 13d, which is the other single-phase output of the Scott transformer 13, by the wiring 21. Terminal 16b on the opposite side of the terminal 16a.

  The gates of the switching elements Q1 to Q6 and Q11 to Q16 are connected to the control device 22. The control device 22 is connected to current sensors S1 and S2 that detect a current flowing through the traveling motor 11 and current sensors S11 and S12 that detect a current flowing through the cargo handling motor 17. The control device 22 includes a CPU and a memory (not shown), and a control program required to drive the traveling motor 11 and the cargo handling motor 17 is stored in the memory. Further, the memory stores a control program necessary for controlling the switching elements Q1 to Q6 and Q11 to Q16 when charging the battery 30 with the Scott transformer 13 connected to the three-phase AC power supply 40. I have. Further, the control device 22 can detect a secondary current (a charging current of the battery 30) of the Scott transformer 13 by a signal from the current sensors S1, S2, S11, and S12.

  The battery charging circuit of the motor drive system includes a Scott transformer (single-phase output transformer) 13. The rectifier circuits 14 and 19 provided in the battery charging circuit of the motor drive system are connected to one terminal 15a and 16a of the secondary side output of the Scott transformer (single-phase output transformer) 13, and the inverters 12 and 18 and The battery 30 is connected in parallel. Current sensors S1 and S11 provided in the battery charging circuit of the motor drive system detect a current flowing between the connection points A and B and the motors 11 and 17. Wirings 20 and 21 provided in the battery charging circuit of the motor drive system connect the connection points A and B between the first switching elements Q1 and Q11 and the second switching elements Q2 and Q12 in the inverters 12 and 18 on the secondary side. It is connected to the other output terminals 15b and 16b.

Next, the operation of the vehicle-mounted device 10 according to the present embodiment will be described.
The battery forklift is kept disconnected from the three-phase AC power supply 40 except when the battery 30 is charged. The switching elements Q1 to Q6 of the traveling inverter 12 are turned on / off by a command from the control device 22 so that the DC power of the battery 30 is converted into AC power and supplied to the traveling motor 11, and The motor 11 is driven. Further, the switching elements Q11 to Q16 of the cargo handling inverter 18 are turned on / off according to a command from the control device 22, so that DC power of the battery 30 is converted into AC power and supplied to the cargo handling motor 17, and The motor 17 is driven.

  When the in-vehicle device 10 is used as a charging device, the input and the output are electrically insulated by the Scott transformer 13, and the in-vehicle power storage device connected to the output after converting AC power, which is input power, into DC power is connected to the output. The battery 30 is charged.

  At the time of charging, the control device 22 provided in the battery charging circuit of the motor drive system, as shown in FIGS. 2 and 3, uses two sets of switching elements Q3 (W-phase and U-phase) that are not connected to a transformer. , Q4, Q5, Q6, Q13, Q14, Q15, and Q16 are synchronously turned on and off. That is, the first switching elements Q1, Q11 and the second switching elements Q2, Q12 are kept in an off state, and the third switching elements Q3, Q13 and the fifth switching elements Q5, Q15 are controlled to be turned on / off in synchronization with each other. The on / off control of the fourth switching elements Q4, Q14 and the sixth switching elements Q6, Q16 is synchronized.

  Specifically, when charging the battery 30, the Scott transformer 13 is maintained in a state where AC power is supplied from the three-phase AC power supply 40. Specifically, a plug of a charging cable of the three-phase AC power supply 40 is connected to a power outlet provided in the forklift. Then, the control device 22 holds the switching elements Q1, Q2, Q11, Q12 of the traveling inverter 12 and the cargo handling inverter 18 in the off state, and controls the third switching elements Q3, Q13, the fourth switching elements Q4, Q14, The fifth switching element Q5, Q15 and the sixth switching element Q6, Q16 are turned on / off. That is, when the control device 22 charges the battery 30, the upper-arm switching element and the lower-arm switching element for PWM control are the switching elements Q3, Q13, Q4, Q14, Q5, Q15, Q6, and Q16. Become. The switching elements for the upper arm and the switching elements for the lower arm that are not subjected to PWM control when the battery 30 is charged by the control device 22 are the switching elements Q1, Q2, Q11, and Q12.

  Then, the control device 22 switches the third switching element Q3, Q13, the fourth switching element Q4, Q14, the fifth switching element Q5, Q15, and the sixth switching element Q6, Q16 in the traveling inverter 12 and the cargo handling inverter 18. I do. By doing so, the battery 30 is charged using the coils 23 and 24 of the traveling motor 11 and the coils 26 and 27 of the cargo handling motor 17 as charging inductors.

  The path of the current flowing through the in-vehicle device 10 when the battery 30 is charged will be described with reference to FIGS. Although FIGS. 2 and 3 show the current paths when charging the battery 30 by controlling the switching elements Q3, Q4, Q5, and Q6 of the traveling inverter 12, the switching element of the cargo handling inverter 18 is described. A similar route is used when charging the battery 30 by controlling Q13, Q14, Q15, and Q16.

  As shown in FIG. 2, when power is output from terminal 15a of one secondary winding 13c of Scott transformer 13 on traveling inverter 12 side, switching elements Q3 and Q5 are turned on, and switching elements Q4 and Q6 are turned on. Is in the off state, a current flows as shown by a broken line in FIG. That is, the path of the terminal 15a of the secondary winding 13c → the diode D1 → the third switching element Q3 → the coil 24 of the traveling motor → the terminal 15b of the secondary winding 13c, and the terminal 15a of the secondary winding 13c → the diode. A current flows through a path of D1 → fifth switching element Q5 → running motor coil 23 → terminal 15b of secondary winding 13c. At this time, electromagnetic energy is stored in the coils 23 and 24.

  When the switching elements Q4 and Q6 are turned on, the electromagnetic energy stored in the coils 23 and 24 becomes a current flowing through a path shown by a dashed line in FIG. That is, the path of the coil 24 of the traveling motor 11 → the terminal 15b of the secondary winding 13c → the terminal 15a of the single-phase output 13c → the diode D1 → the battery 30 → the fourth switching element Q4 → the path of the coil 24 of the traveling motor 11 And the path of the coil 23 of the traveling motor 11 → the terminal 15b of the secondary winding 13c → the terminal 15a of the single-phase output 13c → the diode D1 → the battery 30 → the sixth switching element Q6 → the coil 23 of the traveling motor 11 It becomes a flowing current. At this time, the battery 30 is charged.

  As shown in FIG. 3, when power is output from terminal 15b of secondary winding 13c and switching elements Q3 and Q5 are off and switching elements Q4 and Q6 are on, dashed arrows in FIG. A current flows as shown by. That is, the path of the terminal 15b of the secondary winding 13c → the coil 24 of the traveling motor 11 → the fourth switching element Q4 → the diode D2 → the terminal 15a of the one secondary winding 13c, and the terminal of the secondary winding 13c. 15b → the coil 23 of the traveling motor 11 → the sixth switching element Q6 → the diode D2 → current flows through the terminal 15a of the one secondary winding 13c. At this time, electromagnetic energy is stored in the coils 23 and 24. When the switching elements Q3 and Q5 are turned on, the electromagnetic energy stored in the coils 23 and 24 becomes a current flowing through a path indicated by an alternate long and short dash line arrow in FIG. That is, the route of the coil 24 of the traveling motor 11 → the third switching element Q3 → the battery 30 → the diode D2 → the terminal 15a of the secondary winding 13c → the terminal 15b of the secondary winding 13c → the coil 24 of the traveling motor 11; And, on the route of the coil 23 of the traveling motor 11 → the fifth switching element Q5 → the battery 30 → the diode D2 → the terminal 15a of the secondary winding 13c → the terminal 15b of the secondary winding 13c → the coil 23 of the traveling motor 11 It becomes a flowing current. At this time, the battery 30 is charged.

  At the time of charging, the current sensors S2 and S12 are used as abnormality detection sensors for detecting an overcurrent or the like. During charging, the current sensors S1 and S11 are also used as abnormality detection sensors for detecting overcurrent and the like.

  Also, charging is performed on the cargo handling inverter 18 side in the same manner as the traveling inverter 12. Specifically, the secondary winding 13c on the traveling inverter 12 side is connected to the secondary winding 13d, the terminals 15a and 15b to the terminals 16a and 16b, the third switching element Q3 to the third switching element Q13, and the fourth If switching element Q4 is replaced with fourth switching element Q14, fifth switching element Q5 is replaced with fifth switching element Q15, sixth switching element Q6 is replaced with sixth switching element Q16, and diodes D1 and D2 are replaced with diodes D3 and D4, respectively. Good.

Rather than providing a current sensor for each phase, only one phase (W-phase) of the two phases (W-phase and U-phase) for on / off control is provided with a current sensor.
The switching elements (MOSFETs) Q1 to Q6 and Q11 to Q16 have dead time, that is, delays (time from turn-on and turn-off) from the command to the actual operation are not uniform. The following control is performed before charging is started in order to correct.

  Before the start of charging, the control device 22 controls the on / off of the third switching element Q3 to set the current value by the current sensor S1 in the state where the second switching element Q2 is controlled as shown in FIGS. And the second duty by the on / off control of the fifth switching element Q5 for setting the current value by the current sensor S1 to a specified value, and the current value by the current sensor S1 in a state where the first switching element Q1 is controlled. The third duty by the on / off control of the fourth switching element Q4 to be the specified value and the fourth duty by the on / off control of the sixth switching element Q6 to make the current value by the current sensor S1 the specified value are acquired.

  The first duty, the second duty, the third duty, and the fourth duty are also acquired on the cargo handling inverter 18 side in the same manner as the traveling inverter 12. Specifically, the first switching element Q1 and the second switching element Q2 on the traveling inverter 12 side are switched to the first switching element Q11, the second switching element Q2 is switched to the second switching element Q12, and the third switching element Q3 is switched to the third switching element Q13. The fourth switching element Q4 is replaced with a fourth switching element Q14, the fifth switching element Q5 is replaced with a fifth switching element Q15, the sixth switching element Q6 is replaced with a sixth switching element Q16, and the current sensor S1 is replaced with a current sensor S11. I just need.

This will be described in detail with reference to FIGS.
Prior to the start of charging, power is supplied in the following patterns (a current path shown by a broken line in FIG. 4, a current path shown by a dashed line in FIG. 4, a current path shown by a broken line in FIG. 5, and a current path shown by a dashed line in FIG. 5). , The duty correction amount of the switching element for equalizing the two-phase currents is obtained.

  As a pattern 1, the switching element Q2 for the V-phase lower arm is fixed in the ON state, and the switching element Q3 for the W-phase upper arm is chopper-controlled. The current path is from the battery 30 → the switching element Q3 → the coil 24 → the switching element Q2 → the battery 30, as shown by the broken line in FIG. At this time, the switching element Q3 for the W-phase upper arm is chopper-controlled so that the current value detected by the V-phase current sensor S1 becomes the specified value + α [A]. Note that + in + α [A] indicates the direction in which current flows. The duty of the switching element Q3 for the W-phase upper arm at this time is defined as a first duty (DutyWαn [%]).

  As a pattern 2, the switching element Q2 for the V-phase lower arm is fixed in the ON state (same as the energizing current in the pattern 1), and the switching element Q5 for the U-phase upper arm is chopper-controlled. The current path is from the battery 30 → the switching element Q5 → the coil 23 → the switching element Q2 → the battery 30 as shown by the dashed line in FIG. At this time, the switching element Q5 for the U-phase upper arm is chopper-controlled so that the current value detected by the V-phase current sensor S1 becomes the specified value + α [A]. At this time, the duty of the switching element Q5 for the U-phase upper arm is a second duty (DutyUαn [%]).

  As a pattern 3, the switching element Q1 for the V-phase upper arm is fixed in the ON state, and the switching element Q4 for the W-phase lower arm is chopper-controlled. The current path is, as shown by the broken line in FIG. 5, the battery 30 → the switching element Q1 → the coil 24 → the switching element Q4 → the battery 30. At this time, the switching element Q4 for the W-phase lower arm is chopper-controlled so that the current value detected by the V-phase current sensor S1 becomes the specified value -α [A]. In addition,-of [alpha] [A] indicates the direction of current flow. At this time, the duty of the switching element Q4 for the W-phase lower arm is a third duty (DutyWαp [%]).

  As a pattern 4, the switching element Q1 for the V-phase upper arm is fixed in the ON state (same as the energizing current in the pattern 3), and the switching element Q6 for the U-phase lower arm is chopper-controlled. The current path is, as shown by the one-dot chain line in FIG. 5, the battery 30 → the switching element Q1 → the coil 23 → the switching element Q6 → the battery 30. At this time, the switching element Q6 for the U-phase lower arm is chopper-controlled so that the current value detected by the V-phase current sensor S1 becomes the specified value -α [A]. The duty of the switching element Q6 for the U-phase lower arm at this time is a fourth duty (DutyUαp [%]).

  In this way, the first, second, third, and fourth duties are obtained in advance, and the control device 22 sets the third switching element Q3 and the fifth switching element Q5 to the first duty and the fourth duty after the start of charging. On / off control is performed while correcting with two duties, and on / off control is performed while correcting the fourth switching element Q4 and the sixth switching element Q6 with third and fourth duties.

Specifically, it is as follows.
During charging, the U-phase switching duty is controlled by adding the following correction amount to the W-phase switching duty.

  When the current is in the + direction shown in FIG. 2, the U-phase duty = W-phase duty + (DutyUαn−DutyWαn). That is, the difference between the second duty (DutyUαn [%]) and the first duty (DutyWαn [%]) is added to the W-phase duty to be the U-phase duty.

  On the other hand, when the current is in the minus direction shown in FIG. 3, the U-phase duty = W-phase duty + (DutyUαp−DutyWαp). That is, the sum of the difference between the fourth duty (DutyUαp [%]) and the third duty (DutyWαp [%]) is added to the W-phase duty to be the U-phase duty.

  By performing the correction in this way, it is possible to acquire and correct the variation between phases without adding an element, a sensor, or the like, by devising a switching pattern and passing a current before starting charging. Become. That is, by acquiring and correcting the inter-phase variation before the start of charging, the battery charging current can be accurately controlled.

  In other words, when two sets of switching elements of a three-phase inverter that are not connected to a transformer are controlled to be turned on and off in synchronization with each other, a current sensor may be provided for each phase. If only one of the two phases to be turned off has a current sensor, the two-phase currents cannot be controlled equally due to inter-phase variations in the dead time of each switching element, and an error occurs in the battery charging current. appear. In the present embodiment, when the same current flows at the time of charging, the correction is performed based on the duty difference of the switching element obtained before the start of charging, so that this can be avoided and the battery charging current can be accurately controlled.

The embodiment is not limited to the above, and may be embodied as follows, for example.
The patterns for obtaining the duty correction amount of the switching element include four patterns (a conduction path indicated by a broken line in FIG. 4, a conduction path indicated by a dashed line in FIG. 4, a conduction path indicated by a broken line in FIG. 5, and a dashed line in FIG. 5). (Electrification path indicated by). The following four patterns (patterns 5, 6, 7, and 8) may be added to the patterns 1, 2, 3, and 4. That is, the following four patterns may be added after the current is applied not in one but in two different magnitudes, that is, in four patterns of ± α [A].

  As pattern 5, the switching element Q2 for the V-phase lower arm is fixed in the ON state as in the current path indicated by the broken line in FIG. 4, so that the current detected by the V-phase current sensor S1 is + β [A]. The chopper control is performed on the switching element Q3 for the W-phase upper arm. At this time, the duty of the switching element Q3 for the W-phase upper arm is set to a fifth duty (DutyWβn [%]).

  As a pattern 6, the switching element Q2 for the V-phase lower arm is fixed in the ON state as in the current path indicated by the alternate long and short dash line in FIG. 4, so that the current value detected by the V-phase current sensor S1 becomes + β [A]. Then, the switching element Q5 for the U-phase upper arm is chopper-controlled. The duty of the switching element Q5 for the U-phase upper arm at this time is defined as a sixth duty (DutyUβn [%]).

  As the pattern 7, the switching element Q1 for the V-phase upper arm is fixed in the ON state as in the current path indicated by the broken line in FIG. 5, so that the current value detected by the V-phase current sensor S1 becomes -β [A]. Then, the switching element Q4 for the W-phase lower arm is chopper-controlled. The duty of the switching element Q4 for the W-phase lower arm at this time is set to a seventh duty (DutyWβp [%]).

  As the pattern 8, the switching element Q1 for the V-phase upper arm is fixed in the ON state as in the current path indicated by the one-dot chain line in FIG. 5, and the current value detected by the V-phase current sensor S1 becomes -β [A]. As described above, the switching element Q6 for the U-phase lower arm is chopper-controlled. At this time, the duty of the switching element Q6 for the U-phase lower arm is set to an eighth duty (DutyUβp [%]).

  In FIG. 6, the horizontal axis indicates the current command value, and the vertical axis indicates the correction value. As shown in FIG. 6, the correction value for the current command value α is (DutyUαp−DutyWαp), that is, the first duty which is the difference between the fourth duty (DutyUαp [%]) and the third duty (DutyWαp [%]). Is obtained as a plot point. As a correction value for the current command value β, (DutyUβp−DutyWβp), that is, a second correction value P2 that is a difference between the eighth duty (DutyUβp [%]) and the seventh duty (DutyWβp [%]) is used. Obtained as plot points.

From the characteristic line L1 connecting these two points (the first correction value P1 and the second correction value P2), the correction amount is interpolated and applied according to the current flowing during charging.
Similarly, as a correction value for the current command value α, (DutyUαn−DutyWαn), that is, a difference between the second duty (DutyUαn [%]) and the first duty (DutyWαn [%]) is obtained as a plot point. Further, as a correction value for the current command value β, (DutyUβn-DutyWβn), that is, a difference between the sixth duty (DutyUβn [%]) and the fifth duty (DutyWβn [%]) is obtained as a plot point. From the characteristic line connecting these two points, the correction amount is given by interpolation according to the current flowing during charging.

  Thus, the first correction value P1 based on patterns 1 to 4 when α is taken as the current command value on the horizontal axis in FIG. 6 and the patterns 5 to 5 when β is taken as the current command value on the horizontal axis in FIG. 8 is obtained. The characteristic line L1 is a straight line passing through the first correction value P1 and the second correction value P2. Then, a correction value is calculated by linearly interpolating the target current value using the characteristic line L1.

  By doing so, the current at the time of obtaining the correction amount can be made large and small, so that the variation in the load (motor coil) can be corrected together. The same applies to the cargo handling inverter 18 side.

  In this way, the control device 22 sets the current values of the current sensors S1 and S11 in a state where the second switching elements Q2 and Q12 are controlled to a specified value different from the value obtained when the first duty is obtained before the charging is started. The fifth duty by the on / off control of the third switching elements Q3, Q13 and the current value by the current sensors S1, S11 are set to a specified value different from the value obtained when the second duty is acquired. The sixth duty by the OFF control, and the fourth switching element Q4 that sets the current value of the current sensors S1 and S11 in a state where the first switching elements Q1 and Q11 are controlled to a specified value different from the value obtained when the third duty is obtained. The seventh duty by the on / off control of Q14 and the current value by the current sensors S1 and S11 An eighth duty is obtained by on / off control of the sixth switching elements Q6 and Q16, which is set to a specified value different from that obtained when the duty is obtained, and after the start of charging, the third switching elements Q3 and Q13 and the fifth switching are switched. The on / off control is performed while correcting the elements Q5 and Q15 by the first duty, the second duty, the fifth duty, and the sixth duty, and the fourth switching elements Q4 and Q14 and the sixth switching elements Q6 and Q16 are controlled by the third duty. On / off control may be performed while correcting with the fourth, seventh, and eighth duties.

  When acquiring the switching duty correction amount, in the patterns 1 to 4 or the patterns 1 to 8, the V-phase upper arm first switching elements Q1 and Q11 to the lower arm second switching elements Q2 and Q2 are used. Switching may be performed at a certain duty without fixing Q12 to ON. That is, since the input voltage is adjusted to reduce the conduction current, the on-time of the duty becomes longer, so that an error can be detected with high accuracy. As described above, the duty of the V-phase switching elements Q1, Q2, Q11, and Q12 at the time of acquiring the correction amount is not fixed to 100% ON, but is controlled to a constant amount, so that the variation is obtained for the U-phase and W-phase. Of the switching elements Q3 to Q6 and Q13 to Q16 are relatively long, and the accuracy of obtaining the correction amount is improved.

The battery 30 may be charged using either the traveling inverter 12 or the cargo handling inverter 18.
○ A transformer other than the Scott transformer 13 may be used.

  Although the in-vehicle device including the three-phase motor (the traveling motor 11 and the cargo handling motor 17), such as a battery forklift, is used as the charging device, it may be applied to a general electric vehicle charging device.

  ○ Although applied to forklifts, it may be applied to other industrial vehicles. Moreover, you may apply to vehicles other than an industrial vehicle, for example, a passenger car and a bus.

  11: traveling motor (three-phase motor), 12: traveling inverter (three-phase inverter), 13: Scott transformer, 14: rectifier circuit, 15a: terminal, 15b: terminal, 16a: terminal, 16b: terminal, 17 ... Cargo handling motor (three-phase motor), 18 ... Cargo handling inverter (three-phase inverter), 19 ... Rectifier circuit, 20 ... Wiring, 21 ... Wiring, 22 ... Control device, 30 ... Battery, A ... Connection point, B ... Connection Points, S1, S11: current sensor, Q1, Q11: first switching element, Q2, Q12: second switching element, Q3, Q13: third switching element, Q4, Q14: fourth switching element, Q5, Q15 ... Fifth switching element, Q6, Q16 ... Sixth switching element.

Claims (2)

A first switching element for the upper arm of the first phase, a second switching element for the lower arm of the first phase, a third switching element for the upper arm of the second phase, and a fourth switching for the lower arm of the second phase Motor drive provided with a three-phase motor driven and controlled by a battery as a power source by a three-phase inverter having an element, a fifth switching element for the upper arm of the third phase, and a sixth switching element for the lower arm of the third phase System battery charging circuit,
A single-phase output transformer,
A rectifier circuit connected to one terminal of the secondary side output of the single-phase output transformer and connected in parallel to the three-phase inverter and the battery;
A wiring connecting a connection point between the first switching element and the second switching element in the three-phase inverter to the other terminal of the secondary output;
At the time of charging, the first switching element and the second switching element are kept in an off state, the third switching element and the fifth switching element are synchronously turned on and off, and the fourth switching element and the sixth switching element are synchronized. A control device for synchronously turning on and off the switching element;
A current sensor for detecting a current flowing between the connection point and the three-phase motor,
With
The control device includes:
Before the start of charging, the first duty by the on / off control of the third switching element and the current value by the current sensor are set to a specified value by setting the current value by the current sensor in a state where the second switching element is controlled to a specified value. The second duty by the on / off control of the fifth switching element, and the on / off control of the fourth switching element to set a current value by the current sensor in a state where the first switching element is controlled to a specified value. And a fourth duty by ON / OFF control of the sixth switching element for setting the current value by the current sensor to a specified value, and
After charging is started, the third switching element and the fifth switching element are turned on / off while being corrected by the first duty and the second duty, and the fourth switching element and the sixth switching element are A battery charging circuit that performs on / off control while correcting with a third duty and a fourth duty. The control device includes:
Before the start of charging, the current value obtained by the current sensor in a state where the second switching element is controlled is set to a specified value different from the value obtained when the first duty is acquired. A sixth duty by the on / off control of the fifth switching element and a state in which the first switching element is controlled, wherein the duty and the current value obtained by the current sensor are set to different specified values than when the second duty is obtained. The current value obtained by the current sensor is set to a specified value different from the value obtained when the third duty is obtained. The seventh duty by the on / off control of the fourth switching element and the current value obtained by the current sensor are set to the fourth duty. For the on / off control of the sixth switching element, which is a specified value different from the one obtained Eighth in advance to get the duty that,
After charging is started, the third switching element and the fifth switching element are turned on / off while correcting the third switching element and the fifth switching element with the first duty, the second duty, the fifth duty, and the sixth duty. The battery charging according to claim 1, wherein on / off control is performed while correcting the switching element and the sixth switching element with the third duty, the fourth duty, the seventh duty, and the eighth duty. circuit.

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