JP5331397B2 - Power control device - Google Patents

Description

  The present invention relates to a power control apparatus that charges a battery from a commercial power source using an inverter that controls current supply to a coil.

  2. Description of the Related Art Conventionally, it has been widely performed to drive an AC motor by converting DC power from a battery into AC current using an inverter. There is also known a power control device in which two inverters are provided, a commercial power source is connected between the two AC motors between neutral points, and power is exchanged between the commercial power source and the battery (Patent Document 1).

  In this patent document 1, the effective value and phase of the voltage of a commercial power source are detected, and based on these and the charging request to the battery, the zero-phase voltage of the inverter is controlled to control the charging of the battery by the commercial power source. In addition, a filter capacitor is connected between the neutral points of the two motors and the power line connected to the commercial power source, thereby removing the influence of ripples based on inverter switching to the commercial power source.

JP 2007-318970 A

  The power control device described in Patent Document 1 has a problem that ripples to the commercial power source cannot be sufficiently removed.

The present invention has two motors driven by AC power obtained by converting DC voltage from a battery by two inverters, and a commercial power source is connected between the neutral points of the two motors via a connection end. A power control device that can generate and output zero-phase voltage with an inverter to control the voltage between neutral points of the motor and transfer power between the commercial power supply and the battery. a filter capacitor that is, have a, a reactor that is disposed between the connection end and the filter capacitor, the inductance of the reactor, the frequency characteristic of the AC filter composed of the said reactor and said filter capacitor Switching in the commercial power source that is generated in response to switching of the two inverters by setting the value independent of the inductance of the commercial power source Characterized by reducing a pull.

  In addition, it is preferable to further have a reactor disposed between the filter capacitor and the neutral point of the motor.

  It is preferable that current measuring means for measuring a current flowing on the connection end side of the filter capacitor is included, and switching of the inverter is controlled in accordance with a measured value of the current measuring means.

In addition, the present invention has a coil driven by AC power obtained by converting a DC voltage from a battery by an inverter, and a commercial power source is connected through the coil, and power is supplied between the commercial power source and the battery by switching the inverter. A power control apparatus capable of transmitting and receiving, comprising: a filter capacitor connected in series with the coil between a pair of outputs of an inverter; and a reactor disposed between the filter capacitor and the connection end. Then, the inductance of the reactor is generated according to the switching of the two inverters by setting the frequency characteristic of the AC filter composed of the filter capacitor and the reactor to a value that does not depend on the inductance of the commercial power supply. The switching ripple in the commercial power supply is reduced .

  According to the present invention, since the reactor is additionally provided on the commercial power supply side of the filter capacitor, even if the inductance of the commercial power supply changes, the current ripple (switching ripple) resulting from the switching of the inverter enters the commercial power supply side. Can be effectively prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

“Embodiment 1”
FIG. 1 is a diagram illustrating a configuration of the first embodiment. The positive electrode of the battery 10 is connected to the boost converter 12, and the negative electrode is connected to the negative bus. The step-up converter includes a coil 12a and switching elements 12b and 12c. One end of the coil 12a is connected to the positive electrode of the battery 10, and the other end of the coil 12a is connected to a connection point of the switching elements 12b and 12c. ing. The reverse end of switching element 12b is connected to the positive bus, and the reverse side of switching element 12c is connected to the negative bus. The switching elements 12b and 12c are composed of transistors such as IGBTs, for example, and are connected in parallel with the transistors to flow current from the negative bus side to the positive bus bar. That is, two transistors are connected in series between the positive bus and the negative bus, and two diodes are connected in series.

  A capacitor 14 is provided between the positive bus and the negative bus. The positive and negative buses are the positive and negative buses of the two inverters 16 and 18.

  The inverters 16 and 18 have the same configuration, and three arms made up of two switching elements connected in series are arranged in parallel between the positive bus and the negative bus. The middle point of each arm is the output end, and the respective coil ends of the three-phase AC motors 20 and 22 are connected to each other. An AC motor 20 is connected to the inverter 16, and an AC motor 22 is connected to the inverter 18. In the hybrid vehicle, one of AC motors 20 and 22 mainly functions as a motor for traveling, and the other functions as a generator that generates power by being driven by an engine.

  Each of the AC motors 20 and 22 is a motor in which coils are star-connected, and a lead wire is drawn out from a neutral point, and an AC filter 24 is connected between the lead wires. The AC filter 24 includes a filter capacitor Cf disposed between the lead wires, a lead wire from the AC motor 20, and a reactor La having one end connected to a connection point of the filter capacitor Cf.

  The other end of the reactor La is connected to the terminal 26, and the lead wire from the neutral point of the AC motor 22 is connected to the terminal 28. A commercial AC power supply 30 is connected between the terminals 26 and 28. In the following, this commercial AC power supply is referred to as a system power supply, and the system power supply side is referred to as the system side. Here, the system power supply 30 includes an inductance Ls, and in the figure, the terminal 26 is described as being connected to the system power supply 30 via the inductance Ls. The system power supply 30 is normally an alternating current of 100 V, but other voltages may be used.

  In such a device, the configuration from the battery 10 to the terminals 26 and 28 is mounted on the vehicle. When the vehicle is traveling, the output of battery 10 is boosted by converter 12 and the input voltages of inverters 16 and 18 are controlled. This voltage is set to an appropriate value according to the output torque command of AC motors 20 and 22. Then, the switching of inverters 16 and 18 is controlled to control the output torque of AC motors 20 and 22 according to the command. Although it is possible to control the neutral point voltage of the motors 20 and 22, both of them are normally set to ½ of the inverter input voltage.

  On the other hand, when charging the battery 10 from the system power supply 30, the system power supply 30 is connected between the terminals 26 and 28 as shown in the figure. Normally, connection is made by inserting a plug having terminals 26 and 28 into the outlet of the system power supply 30.

  In this case, switching of the inverters 16 and 18 is controlled so that the zero-phase current has a magnitude corresponding to the charge / discharge command (see Patent Document 1). For this purpose, the phase of the alternating current from the system power supply 30 is detected to generate an in-phase sine wave. Further, the effective value of the AC voltage from the system power supply 30 is detected, the target ratio is calculated by dividing the charging power command value by this effective value, and this target ratio is multiplied by the sine wave generated as described above. Then, a current command is generated. Based on this current command, the inverters 16 and 18 are controlled so that the battery can be charged by the power of the system power supply 30. Inverters 16 and 18 are controlled based on a zero-phase voltage command calculated based on a current command.

  In addition, by using the charge / discharge force command from the battery 10, the DC power from the battery 10 can be converted into AC power and supplied to the system power supply 30 side. It is also possible to drive AC motors 20 and 22 during charging and discharging.

  Here, the filter capacitor Cf is for preventing the harmonic switching ripple generated due to the switching of the inverters 16 and 18 from flowing out to the system power supply 30 side. However, when the reactor La in FIG. 1 is removed, the frequency characteristics greatly depend on the value of the inductance Ls on the system power supply side.

That is, in the AC filter 24, assuming that the switching ripple is a current source (switching ripple source), an equivalent circuit of the AC filter is expressed as shown in FIG. The transfer function G (s) of the AC filter 24 is
G (s) = ω ₀ ² / (s ² + (ω ₀ / Q) s + ω ₀ ² )
Here, ω ₀ = 1 / √ (Ls * Cf) and Q = (1 / R) √ (Ls / Cf).

  The frequency characteristics of the AC filter 24 are shown in FIG. Here, the set values of Ls of L1 to L4 in FIG. 6 are L1 = 0.01 mH, L2 = 0.03 mH, L3 = 0.06 mH, L4 = 0.2 mH, and the horizontal value of the transfer function G (s). A gain characteristic (upper stage) and a phase characteristic (lower stage) with respect to the axis frequency are shown. From this, it can be seen that both the gain characteristic and the phase characteristic greatly change the frequency characteristic depending on the value of Ls.

  As can be seen from the above equation, since the resonance frequency of the AC filter 24 is determined by the system inductance Ls and the filter capacitor Cf, the frequency characteristic of the AC filter 24 greatly depends on the value of the system inductance Ls. FIG. 7 shows the system switching ripple with respect to the system inductance. If the value of the system inductance is small, the resonance frequency of the filter is increased and the attenuation rate of the switching frequency component is decreased, so that the system switching ripple cannot be sufficiently suppressed.

On the other hand, in this embodiment, as shown in the equivalent circuit of FIG. 8, a reactor La is added in addition to the filter capacitor Cf. FIG. 9 shows the frequency characteristics when the reactor La is 0.19 mH. In this way, the change in system inductance of 0mH to 0.2mH (this is the maximum impedance of 500M from the line impedance of the domestic distribution system, the 50kV low voltage distribution transformer, and the constant voltage distribution transformer The filter frequency characteristic changes little with respect to the line impedance of the indoor wiring. As shown in FIG. 10, the system ripple (switching ripple entering the system side) from the system inductance 0 mH is eliminated. ) Is suppressed. From the above-described filter transfer function, the filter attenuation rate is substantially −40 dB / dc from the resonance frequency. Therefore, in order to attenuate the switching ripple by about 1 / n, the resonance frequency ω 0 is set to 1 / √n of the carrier frequency. Must be: When the filter capacitor Cf = 16.8 μF and the reactor La = 0.19 mH, the switching ripple current can be reduced to about 1/10 at ω ₀ = 2.8 kHz.

“Embodiment 2”
The configuration of the second embodiment is shown in FIG. Thus, in the second embodiment, compared to the first embodiment, the reactor Lb is added between the lead wire from the neutral point of the AC motor 20 and the filter capacitor Cf (motor side).

  In the first embodiment, a motor coil is connected to the inverter. However, with only the leakage inductance of the motor, the switching ripple is large, and it is difficult to suppress the harmonic current flowing out to the system power supply side, or the motor noise There is a problem that occurs.

  Since the filter capacitor Cf has a low impedance with respect to the switching frequency, as shown in FIG. 11, the switching ripples flowing through the inverter and the motor largely depend on the value of the leakage inductance of the motor and the value of the DC voltage of the inverter. Therefore, the switching ripple flowing between the inverter and the motor cannot be sufficiently reduced only by the leakage inductance of the motor, and problems such as increased inverter loss, increased motor noise, and leakage current occur.

  In the present embodiment, the reactor Lb is connected between the filter capacitor Cf and the motor neutral point. As a result, switching ripples flowing through the inverter and the motor can be reduced, and the above problem can be solved. Here, the reactor Lb may have a small capacity relative to the capacity of the motor because a charging current flows only during charging.

“Embodiment 3”
The configuration of the third embodiment is shown in FIG. In the third embodiment, the current flowing in the power line on the system current side of the filter capacitor Cf connected between the neutral points of the motor is detected to control the charging current on the AC side. For this purpose, a voltage detector 34 is provided to measure the voltage across the filter capacitor Cf, that is, the voltage Vs between the neutral points of the two motors 20 and 22. Further, a current sensor 36 for measuring a current i flowing in a line between the filter capacitor Cf and the neutral point of the motor 22 and the terminal 28 is provided. Then, the switching of the inverters 16 and 18 is controlled based on the voltage Vs and the current i to control the charging of the battery 10.

  The voltage Vs of the voltage detector 34 is supplied to the current command generator 40. The current command generation unit 40 generates a current command i * having a power factor of 1 with respect to the voltage Vs from the voltage Vs and the charge / discharge amount command value in the same manner as in Patent Document 1. i * is supplied to the adder 42, where the current i detected by the current sensor 36 is subtracted from i *. The obtained difference is multiplied by the gain Kp by the proportional unit 44 and supplied to the adder 46. The difference obtained by the adder 42 is also supplied to the sine wave internal model compensator 47. The sine wave internal model compensator 47 calculates and outputs a compensation amount for the sine wave internal model used when generating i *, and supplies this to the adder 46.

  The addition results of the compensation amounts from the proportional device 44 and the sine wave internal model compensator 47 obtained by the adder 46 are supplied to the adder 48, and the compensation amount for the disturbance from the disturbance voltage compensator 50 is added. And supplied to the PWM controller 52. The PWM controller 52 controls the switching in the inverters 16 and 18 based on the control amount supplied from the adder 48, so that the detected current i becomes the target current i *. The charge / discharge in the battery 10 is achieved with the target charge / discharge amount.

  Here, FIG. 12 shows a mathematical configuration of the charge control system in such a device. Here, s in this figure is a Laplace operator, and Ts is a sampling time. Thus, the adder 42 calculates the difference between the target current i * (s) and the actual current i (s). The obtained difference e (s) is input to the proportional unit 44 and the sine wave internal model compensator 47, and both outputs are added by the adder 48. The dead time adding unit 60 controls the inverter 62 (inverters 16 and 18) in consideration of the dead time (exp [−s · Ts]) such as the above calculation. The transfer function of the inverter 62 is (1-exp [−s · Ts]), and the inverter input is converted by this transfer function and becomes the output of the inverter 62. The inverter output is added to the system power supply voltage Vs (s) by the adder 64 and converted by the motor, filter, and system impedance (impedance in the system power supply system) to become the current i (s) detected by the current sensor 36. . The circuit from when the deviation output from the adder 42 is input until the switching control signal is output from the PWM controller 52 is referred to as a current controller 38.

The one-cycle pulse transfer function Glp (z) of the control system of such a closed loop digital control system is
Glp (z) = Z {Gc (s)} · Z {Gh (s) · Gp (s)}
It is represented by Z {} is z-transform, Gc (s) is the transfer function of the current controller 38, Gh (s) is the transfer function of the inverter, and Gp (s) is the transfer function on the AC circuit side (motor, filter, system impedance) For the transfer function).

The characteristic equation in this case is
1 + Glp (z) = 0
It is.

  Therefore, the system becomes stable if there is a root of the characteristic equation in the unit circle on the z plane shown in FIG. 13 due to the stability condition of the digital control system.

  The transfer function Gp (s) on the AC circuit side differs with and without the filter capacitor Cf and at the current detection position. This is shown in FIG.

The AC circuit side transfer function Gp (s) without the filter capacitor Cf in FIG.
Gp (s) = 1 / (Rm + Rs + s (Lm + Ls))
It becomes. Here, Rm is the resistance of the motor, Rs is the resistance on the system side, Lm is the inductance of the motor, and Ls is the inductance on the system side.

Further, there is a filter capacitor Cf in FIG. 14B, and the AC circuit side transfer function Gp (s) when the current is detected on the motor side from the filter capacitor Cf is:
Gp (s) = (Cf * Ls * s ² + Cf * Rs * s + 1) / (Lm * Ls * Cf * s ³ + (Rm * Ls * Cf + Lm * Rs * Cf) s ² + (Rm * Rs * Cf + Lm + Ls) s + Rm + Rs)
It becomes.

Further, there is a filter capacitor Cf in FIG. 14C, and the AC circuit side transfer function Gp (s) when the current is detected on the system power supply side from the filter capacitor Cf is:
Gp (s) = 1 / (Lm * Ls * Cf * s ³ + (Rm * Ls * Cf + Lm * Rs * Cf) s ² + (Rm * Rs * Cf + Lm + Ls) s + Rm + Rs)
It becomes.

The transfer function of the inverter is
Gh (s) = (1-exp [-sTs]) / s
The transfer function Gc (s) of the current controller 38 is
Gc (s) = (kp + (ks * s) / (s ² + ω ² )) exp [−sTs]
It is.

  When Glp (z) is obtained using these, the stability limit of the proportional gain with respect to the system inductance Ls in each case is obtained as shown in FIG.

  When the filter capacitor Cf is not present (diamonds), the change in the stability limit of the proportional gain with respect to the system inductance Ls is small, but when the filter capacitor Cf is present, the change is large. In particular, when there is a filter capacitor Cf and current is detected on the motor side (square), the stability limit becomes smaller when the system inductance Ls exceeds a certain value. Further, when there is a filter capacitor Cf and current is detected on the system power supply side with respect to the filter capacitor Cf, there is a region where the stability limit is small in a region where the system inductance Ls is small. From this result, it can be seen that the stability against Ls can be ensured by detecting the current on the system power supply side of the filter capacitor Cf and connecting the reactor La in advance to the system power supply side of Cf.

  That is, a circuit in the case where there is a filter capacitor Cf, a reactor La is added thereto, and current is detected on the system power supply side from the filter capacitor Cf can be expressed as shown in FIG. In this case, the stability limit of the proportional gain with respect to the change in the system inductance Ls is as shown in FIG. In FIG. 17, the change with respect to the system inductance Ls is shifted in the right direction because the reactor La is added compared to FIG. 15.

  Thus, according to the present embodiment, the current i detected by the current sensor 36 is set to the system power supply side from the filter capacitor, and the reactor La is added, so that the stability limit of the proportional gain is largely maintained and the control system is It becomes possible to configure.

“Embodiment 4”
FIG. 4 shows the configuration of the fourth embodiment. Thus, in this embodiment, there is only one inverter 70, and only the inductance Lm is employed as an addition. As in the third embodiment, a reactor La is added, and a current sensor 36 is disposed on the AC power supply side from the filter capacitor Cf.

  In this configuration, the inverter 70 has two arms, and a lead-out line is drawn from the middle point of the two arms, and one of them is connected to one end of the filter capacitor Cf of the AC filter 24 via the inductance Lm. The The other lead line is connected to the other end of the filter capacitor Cf.

  Even in such a configuration, the above-described transfer function and the like are completely the same. Therefore, by adding the reactor La, it is possible to effectively eliminate the influence of the switching ripple on the system power supply side and control the charging / discharging of the battery 10.

  In addition, as the battery 10, an uninterruptible power supply, a solar cell, etc. can be employ | adopted, charging of the uninterruptible power supply by a system power supply, or the electric power supply to the system power supply side by a solar cell can be performed.

  In each of the above-described embodiments, the reactors La and Lb and the current sensor 36 to be added may be arranged on any line to which the terminals 26 and 28 are connected.

1 is a diagram illustrating a configuration of a first embodiment. 6 is a diagram illustrating a configuration of a second embodiment. FIG. FIG. 6 is a diagram illustrating a configuration of a third embodiment. FIG. 6 is a diagram illustrating a configuration of a fourth embodiment. It is a figure which shows the equivalent circuit of the alternating current filter when reactor La is not added. It is a figure which shows the frequency characteristic of the alternating current filter at the time of not adding reactor La. It is a figure which shows the magnitude | size of the system current ripple with respect to the system | strain inductance at the time of not adding the reactor La. It is a figure which shows the equivalent circuit of an alternating current filter at the time of adding reactor La. It is a figure which shows the frequency characteristic of the alternating current filter at the time of adding reactor La. It is a figure which shows the magnitude | size of the system current ripple with respect to the system | strain inductance at the time of adding the reactor La. It is a figure which shows the relationship between the magnitude | size of the ripple which flows into a motor, and the motor leakage inductance Lm. It is a figure which shows the structure of a charge control system. It is a figure which shows z plane by z conversion. It is a figure which shows the equivalent circuit of an alternating current circuit. It is a figure which shows the stability limit of the proportional gain with respect to system | strain inductance. It is a figure which shows the structure which adds reactor La and performs an electric current detection by the system power supply side. It is a figure which shows the stability limit of the proportional gain when adding reactor La and performing electric current detection by the system power supply side.

Explanation of symbols

  10 batteries, 12 boost converters, 12a coils, 12b, 12c switching elements, 14 capacitors, 16, 18, 62, 70 inverters, 20, 22 AC motors, 24 AC filters, 26, 28 terminals, 30 system power supplies, 34 voltage detection 36, current sensor, 38 current controller, 40 current command generator, 42, 46, 48, 64 adder, 44 proportional device, 47 sine wave internal model compensator, 50 disturbance voltage compensator, 52 PWM controller, 60 Dead time adding unit, Cf filter capacitor, La, Lb reactor, Lm, Ls inductance.

Claims (5)

It has two motors that are driven by AC power obtained by converting the DC voltage from the battery by two inverters. A commercial power source is connected between the neutral points of the two motors via a connection end. A power control device capable of generating a phase voltage to control a voltage between neutral points of a motor and transferring power between a commercial power source and a battery,
A filter capacitor connected between the neutral points;
A reactor disposed between the filter capacitor and the connection end;
I have a,
The commercial inductance generated in response to switching of the two inverters by setting the inductance of the reactor to a value in which the frequency characteristic of an AC filter composed of the filter capacitor and the reactor does not depend on the inductance of the commercial power supply. A power control apparatus characterized by reducing switching ripple in a power supply . The power control apparatus according to claim 1,
The power control apparatus further comprising a reactor disposed between the filter capacitor and a neutral point of the motor. The power control apparatus according to claim 1 or 2,
Current measuring means for measuring the current flowing on the connection end side of the filter capacitor;
Have
A power control apparatus that controls switching of the inverter according to a measured value of the current measuring means. It has a coil that is driven by AC power obtained by converting DC voltage from the battery with an inverter, and it is possible to connect a commercial power source through this coil and transfer power between the commercial power source and the battery by switching the inverter. A power control device,
A filter capacitor connected in series with the coil between a pair of outputs of the inverter;
A reactor disposed between the filter capacitor and the connection end;
I have a,
The commercial inductance generated in response to switching of the two inverters by setting the inductance of the reactor to a value in which the frequency characteristic of an AC filter composed of the filter capacitor and the reactor does not depend on the inductance of the commercial power supply. A power control apparatus characterized by reducing switching ripple in a power supply . The power control apparatus according to claim 4,
Current measuring means for measuring the current flowing on the connection end side of the filter capacitor;
Have
A power control apparatus that controls switching of the inverter according to a measured value of the current measuring means.

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