JP2010130841A - Discharger for inverter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharger discharging a smoothing power storing means while minimizing motor torque. <P>SOLUTION: The discharger includes: a power storing means 5 for smoothing the output of a DC power supply; a plurality of pairs of switching elements Tr1-Tr6 each connected to both ends of the power storing means; rectification elements D1-D6 connected in parallel to the switching elements, respectively; and control means 9, 10 for controlling ON-OFF of the switching elements to convert the DC power of the DC power supply into AC power. The control means control the ON-OFF operation of the switching elements at a frequency in which the ON periods of the paired switching elements do not overlap each other and a dead time not less than a predetermined time is set so that the charges stored in the power storing means flows as a displacement current to the switching elements and the rectification elements. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an inverter discharge device.

  One that drives an AC motor with a DC power supply via an inverter is known (Patent Document 1). In this apparatus, before the inverter or motor is maintained, inspected, or repaired, the electric charge accumulated in the smoothing power storage means (smoothing capacitor) is caused to flow through the winding resistance of the motor to be discharged.

Japanese Patent No. 3289567

  However, in the above conventional discharge device, the torque command current value of the motor is set to zero and the excitation current command value is set to non-zero, so that the detection accuracy of the parts constituting the motor control system such as the rotor position sensor is high. If it is bad, there is a problem that torque is generated in the motor.

The problem to be solved by the present invention is to provide an inverter discharge device capable of discharging the electric charge of the smoothing power storage means while minimizing the torque of the motor.

In the present invention, when the electric charge stored in the power storage means of the inverter flows as a displacement current in the switching element circuit of the inverter, the ON periods of the paired switching elements do not overlap with each other and a dead time of a predetermined time or more is set. The above-described problem is solved by performing ON / OFF control at the frequency thus determined.

  According to the present invention, when a switching element is turned on, a displacement current (recovery current) flows through the switching element circuit, and the charge stored in the storage means can be discharged. However, a dead time longer than a predetermined time is provided. Therefore, even if motor torque is generated during discharging, it can be suppressed.

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

<< First Embodiment >>
FIG. 1 is a block diagram showing a drive power supply device for an electric vehicle according to the embodiment of the present invention. Although detailed illustration is omitted, the electric vehicle of this example is a vehicle that travels using a three-phase AC power permanent magnet motor 4 as a travel drive source, and the motor 4 is coupled to the axle of the electric vehicle.

The electric vehicle of the present example converts the above-described three-phase AC motor 4, the battery 1 (DC power supply) that is a power source of the motor 4, such as a secondary battery, and the DC power of the battery 1 into AC power. An inverter 3 and a capacitor 5 (storage means) for smoothing DC power are provided, and the battery 1 is connected to the inverter 3 via a relay 2 (switch means).

The relay 2 is driven to open and close by the vehicle controller 11 in conjunction with the ON / OFF operation of the key switch 12 of the vehicle. That is, when the key switch 12 is ON, the relay 2 is closed, and when the key switch 12 is OFF, the relay 12 is opened.

The inverter 3 includes a plurality of switching elements (insulated gate bipolar transistors IGBTs) Tr1 to Tr6 and rectifying elements that are connected in parallel to the switching elements Tr1 to Tr6 and in which a current flows in a direction opposite to the current direction of the switching elements Tr1 to Tr6. (Diodes) D <b> 1 to D <b> 6, which converts the DC power of the battery 1 into AC power and supplies it to the motor 4. In this example, three pairs of circuits in which two switching elements are connected in series are connected in parallel to the battery 1, and each pair of switching elements is connected to the three-phase input portion of the motor 4.

  In the example shown in FIG. 1, switching elements Tr1 and Tr2, switching elements Tr3 and Tr4, switching elements Tr5 and Tr6 are connected in series, and between the switching elements Tr1 and Tr2, the U phase of the motor 4, and the switching element Tr3. And Tr4 are connected to the V phase of the motor 4, and the switching elements Tr5 and Tr6 are connected to the W phase of the motor 4. The positions between the switching elements connected to the phases U, V, and W of the motor 4 correspond to the output means according to the invention. Details of the operation of the inverter 4 will be described later.

A capacitor 5 for smoothing DC power is connected in parallel with the battery 1 between the relay 2 and the inverter 3.

The vehicle controller 11 includes a central processing unit CPU, a read only memory ROM, and a random access memory RAM. The vehicle controller 11 calculates a torque command value T ^* based on an accelerator signal, a brake signal, a shift position signal, and the like of the electric vehicle. And a start request command and a stop request command are output to the motor controller 10. Further, the vehicle controller 11 outputs a control signal for opening and closing the relay 2 between the battery 1 and the inverter 3, and simultaneously outputs relay opening / closing information to the motor controller 10.

The motor controller 10 controls the operation of the inverter 3. That is, the motor controller 10 generates a pulse width modulation (PWM) signal based on the torque command value T ^* from the vehicle controller 11 and outputs it to the gate drive circuit 9. The gate drive circuit 9 performs ON / OFF control of the switching elements Tr1 to Tr6 constituting the inverter 3 based on the generated PWM signal at a predetermined timing.

The gate drive circuit 9 has a function of detecting an overheat abnormality or an overcurrent abnormality state of the switching elements Tr1 to TR6 and outputting an IGBT abnormality signal to the motor controller 10.

The gate drive circuit 9 receives a signal from the voltage sensor 8 that detects the voltage of the capacitor 5, converts the signal into a waveform level that can be recognized by the motor controller 10, and outputs the waveform level signal to the motor controller 10 as a capacitor voltage signal.

When performing the control as described above, the motor controller 10 is an output from a rotor position sensor 7 (for example, a resolver, an encoder, etc., a rotational speed detection means) provided in the motor 4, and the rotor position of the motor 4. A position sensor signal indicating θ, a feedback signal from a current sensor 6 (current detection means) for detecting each phase current Iu, Iv, Iw supplied from the inverter 3 to the motor 4, and a terminal between the capacitors 5 are connected. The capacitor voltage signal from the voltage sensor 8 (voltage detection means) is read.

The above gate drive circuit 9 and motor controller 10 correspond to the control means according to the present invention.

FIG. 2 is a block diagram showing a main part of the motor controller 10. The motor controller 10 of this example includes a current command value calculation unit 21, a current control unit 22, a dq / 3 phase conversion unit 23, a PWM signal generation unit 24, and a 3 phase / dq conversion unit 25. , Θ (phase) calculation unit 26, a rotation speed (electrical angular velocity) calculation unit 27, and a discharge control unit 28.

The current command value calculation unit 21 is based on the torque command value T ^* calculated by the vehicle controller 11 and the rotation speed of the motor 4 calculated by the rotation number calculation unit 27, and the d-axis current command value Id ^* and q A shaft current command value Iq ^* is calculated. Here, the d-axis current is an excitation current component of a three-phase current (Iu, Iv, Iw) flowing through the motor 4, and the q-axis current is a torque current component.

The current control unit 23 is based on the d-axis current command value Id ^* and the q-axis current command value Iq ^*, and the d-axis current Id and the q-axis current Iq input from the three-phase / dq conversion unit 25 described later. Then, the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* are calculated. Specifically, the deviation between the current command value and the actual current ^{(Id * -Id), (Iq} * -Iq) is calculated respectively for the calculated deviation by performing PI (proportional-integral) operation The d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* can be calculated.

The dq / 3-phase converter 23 converts the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* calculated by the current controller 22 into a phase calculated by a θ (phase) calculator 26 described later. Based on θ, it is converted into a three-phase AC voltage command value Vu ^* , Vv ^* , Vw ^* . The converted three-phase AC voltage command values Vu ^* , Vv ^* , Vw ^* are output to the PWM signal generator 24.

PWM signal generating unit 24, three-phase AC voltage command values ^{Vu *,} Vv *, and Vw ^*, based on the triangular wave signal (carrier signal), generates a PWM signal for controlling the inverter 3.

The three-phase / dq converter 25 converts the current sensor signal (Iu, Iv, Iw) into a d-axis current Id and a q-axis current Iq.

The θ (position) calculation unit 26 calculates the rotation phase θ based on the signal from the rotor position sensor 7. Further, the rotation speed calculation unit 27 calculates the rotation speed (electrical angular velocity) ω by differentiating the rotation phase θ.

The discharge control unit 28 of this example sets a driving condition of a switching element that discharges the electric charge stored in the capacitor 5 when a stop command signal and relay cut-off information accompanying turning OFF of the relay 2 are input from the vehicle controller 11.

Here, both the q-axis voltage command value Vq ^* , which is a torque voltage component, and the d-axis voltage command value Vd ^* , which is an excitation voltage component, are set to 0 (zero) V.

In this example, the q-axis voltage during normal motor current control for driving and controlling the motor 4 and during discharge control for discharging the stored charge of the capacitor 5 such as during maintenance and inspection of the motor 4 is also shown. The command value Vd ^* and the d-axis voltage command value Vd ^* can be switched and selected by a Vd ^* Vd ^* switching signal.

FIG. 3 shows the gate drive from the gate drive circuit to each of the switching elements Tr1 to Tr6 when the discharge controller 28 sets both the q-axis voltage command value Vq ^* and the d-axis voltage command value Vd ^* to 0V. 4 is a timing chart showing signals GUP, GUN, GVP, GVN, GWP, GWN, inverter output terminal voltages Vu, Vv, Vw, and an output current Icap from a capacitor 5; 3 indicates the ON period of the switching element, and DT is a period (dead time) in which the Hi-side switching elements Tr1, Tr3, Tr5 are OFF and the Lo-side switching elements Tr2, Tr4, Tr6 are OFF. Indicates.

The output current Icap from the capacitor 5 is a displacement current (recovery current) generated when the switching elements Tr1 to Tr6 are turned from OFF to ON, and the junction capacitance Cj of the switching elements Tr1 to Tr6 or the rectifying elements D1 to D6. And the current value is obtained by the product of the voltage change amount dV / dt during switching of the switching elements Tr1 to Tr6 (Icap = Cj × dV / dt).

  The displacement current Icap is generated at a frequency at which the Hi side switching elements Tr1, Tr3, Tr5 and the Lo side switching elements Tr2, Tr4, Tr6 are alternately driven, that is, a frequency 2fsw that is twice the carrier frequency fsw of the triangular wave signal. In particular, the discharge time of the capacitor 5 can be shortened by increasing the drive frequency.

The discharge time Tdischarge at this time can be calculated by the following equation 1 when the capacitance of the capacitor 5 is C, the battery voltage is Vdc, and the switching speed of the switching elements Tr1 to Tr6 is dV / dt.

[Formula 1]
Tdischarge = C × Vdc / (∫Icap dt × 2 fsw)
The gate drive signal during the discharge process in this example has a frequency at which the ON period of the Hi-side switching elements Tr1, Tr3, Tr5 and the ON period of the Lo-side switching elements Tr2, Tr4, Tr6 do not overlap each other. . Also, the ON period between the Hi-side switching elements Tr1, Tr3, Tr5 and the ON period between the Lo-side switching elements Tr2, Tr4, Tr6 are set to frequencies that do not overlap each other.

That is, the dead times DT of the paired switching elements Tr1 and Tr2, switching elements Tr3 and Tr4, and switching elements Tr5 and Tr6 are set to a predetermined time or more. In other words, the ON period of each of the switching elements Tr1 to Tr6 is set to a minimum value or a value approximate to this.

Next, the discharge process of this example will be described.

FIG. 4 is a flowchart showing the contents of processing performed by the motor controller 10 when the electric vehicle finishes running, that is, when the key switch 12 is turned OFF.

  In step S10, based on the signal input from the vehicle controller 11, it is determined whether or not the relay 2 has been disconnected. If it is determined that the relay 2 has not been disconnected, the process waits in step S10. If it is determined that the relay 2 has been disconnected, the process proceeds to step S20.

In step S20, based on the rotational speed (electrical angular velocity) ω, it is determined whether the rotational speed of the rotor of the motor 4 is a predetermined value or less (near zero). If it is determined that the rotor of the motor 4 is not lower than the predetermined rotational speed, the process waits in step S20. If it is determined that the rotor is lower than the predetermined rotational speed, the process proceeds to step S30.

In step S30, it is determined based on the voltage value of the capacitor 5 whether or not the discharge of the electric charge accumulated in the capacitor 5 has been completed. That is, if the capacitor voltage signal detected based on the voltage sensor 8 is lower than the threshold value of the discharge completion voltage, it is determined that the discharge has been completed, and the process proceeds to step S90. Otherwise, the process proceeds to step S40.

Since discharge processing is required when the voltage of the capacitor 5 detected by the voltage sensor 8 is equal to or higher than the discharge completion voltage, the process proceeds to step S40 to stop the PWM signal for driving the switching elements Tr1 to Tr6 of the inverter 3. After canceling the setting, the process proceeds to step S50. The process of step S40 is because a stop command of the PWM drive signal for each of the switching elements Tr1 to Tr6 is output from the vehicle controller 11 to the motor controller 10 by turning off the key switch.

In step S50, the frequency fsw of the triangular wave signal (carrier signal) of the PWM signal generation unit 24 is set higher than in normal current control. For example, when the carrier frequency during normal operation for driving the motor 4 is 5 kHz, this is set to 35 kHz, for example.

Furthermore, in step S50, both the q-axis voltage command value Vq ^* and the d-axis voltage command value Vd ^* output from the discharge control unit 28 are set to 0V. The d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* set to 0 V are converted into a three-phase AC voltage command value Vu ^* based on the rotor phase θ in the dq / 3-phase converter 23. The signals are converted into Vv ^* and Vw ^* , which are output to the PWM signal generator 24. And after starting the output of a PWM signal from the PWM signal generation part 24, it progresses to step S60. By setting both the q-axis voltage command value Vq ^* and the d-axis voltage command value Vd ^* to 0V, the rotation speed of the motor 4 becomes zero, and the motor 4 is prevented from being driven during the discharge process. The

In step S60, the current sensor signals Iu, Iv, Iw from the current sensor 6 are converted into the d-axis current Id and the q-axis current Iq by the three-phase / dq converter 25, and the converted d-axis current Id and Based on the q-axis current Iq, it is determined whether the amount of change of the d-axis current Id and the q-axis current Iq compared to the previous calculation value is equal to or less than a predetermined value (zero or a value near zero). After confirming that the amount of change is zero, that is, the rotor position sensor signal θ, the switching elements Tr1 to Tr6, the rectifying elements D1 to D6, and the gate drive circuit 9 constituting the inverter 3 are not abnormal, the process proceeds to step S70.

In step S60, when the amount of change in the d-axis current Id and the q-axis current Iq is not less than or equal to a predetermined value (zero or near zero), the rotor position sensor signal θ, the switching elements Tr1 to Tr6 constituting the inverter 3, the rectifying element It is determined that an abnormality has occurred in any of D1 to D6 and the gate drive circuit 9, and the process jumps to step S70 and proceeds to step S80, and the discharge process is terminated. Instead of this, when any one of the switching elements Tr1 to Tr6 or the rectifying elements D1 to D6 is determined to be abnormal in operation and the rotational speed of the motor 4 is less than a predetermined value, the abnormal operation is detected. It is also possible to continue the discharge process by driving ON / OFF switching elements other than the switching element determined to be ON.

In step S70, if the discharge duration so far is equal to or longer than a preset discharge specified time, the process proceeds to step S80. If the discharge duration is within the specified discharge time, the process returns to step S60, and the capacitor 5 is continuously discharged until the specified discharge time is exceeded.

In step S80, after stopping the PWM signal that drives each switching element Tr1 to Tr6 of the inverter 3, the process proceeds to step S90. In step S90, the discharging process of the capacitor 5 is terminated.

  In addition, when the relay 2 is short-circuited by welding or the like, there is a possibility that the voltage does not drop below a predetermined voltage (for example, 60 V) even if a certain time (for example, 1 second) elapses after the discharge process is started. Therefore, in step S70 of this example, it is not determined whether or not the discharge has been completed based on the voltage value of the capacitor 5, but it is determined whether or not the discharge duration has exceeded a predetermined specified discharge time. Thereby, even when the relay 2 is short-circuited by welding or the like, the discharge can be stopped. In this case, it is also possible to notify the driver that an abnormality has occurred by a notifying device (not shown).

FIG. 5 is a timing chart showing the state of each component when operating based on the discharge process of FIG. As shown in FIG. 5, when the key switch 12 is turned off, the vehicle controller 11 cuts off the relay 2. After the relay 2 is cut off, by setting the d-axis voltage command value Vd ^* and q-axis voltage command value Vq ^* to zero, the displacement current Icap by the driving occurs in the switching element, the discharge process of the capacitor 5 is performed Is done.

As described above, in the drive power supply device of this example, when discharging the electric charge stored in the smoothing capacitor 5, the d-axis voltage command value Vd ^* and q-axis for the motor 4 are not discharged to the coil of the motor 4. the motor 4 and the non-rotating state by setting the voltage command value Vq ^* to zero, by oN / OFF control of the switching element Tr1~Tr6 of the inverter 3 in this state, the switching element at the moment when the switching element is turned oN The recovery current flowing through Tr1 to Tr6 and the rectifying elements D1 to D6 is used for the discharging process of the smoothing capacitor 5.

As a result, even if the motor 4 is removed or the coil of the motor 4 is disconnected, the charge stored in the smoothing capacitor 5 can be discharged. Further, in the discharge process, the discharge time can be shortened by increasing the frequency of the PWM signal for the switching elements Tr1 to Tr6.

Incidentally, d-axis voltage command value Vd during discharge treatment ^* and q-axis voltage command value Vq ^* is set to PWM signal through a d-q / 3-phase converter 23 and a PWM signal generating unit 24, these d- It is also possible to directly generate a desired PWM signal without going through the q / 3-phase converter 23 and the PWM signal generator 24.

<< Second Embodiment >>
FIG. 6 shows a case where the q-axis voltage command value Vq ^* and the d-axis voltage command value Vd ^* are both set to 0 V in the discharge control unit 28 of the drive power supply device for an electric vehicle according to another embodiment of the present invention. Gate drive signals GUP, GUN, GVP, GVN, GWP, GWN from the gate drive circuit to the switching elements Tr1 to Tr6, inverter output terminal voltages Vu, Vv, Vw, and an output current Icap from the capacitor 5 It is a timing chart which shows.

In this example, the ON period of the Hi-side switching elements Tr3 and Tr5 and the ON period of the Lo-side switching elements Tr4 and Tr6 overlap each other as compared with the timing chart (FIG. 3) of the first embodiment described above. The difference is that the frequency. In other words, the ON period of the Hi-side switching elements Tr1, Tr3, and Tr5 and the ON period of the Lo-side switching elements Tr2, Tr4, and Tr6 are set to frequencies that do not overlap each other.

Of the hardware configuration and software configuration of the other drive power supply devices, the common portions with FIG. 3 are the same as those in the first embodiment, and therefore the description of those portions is incorporated here and the specific description is omitted.

<< Operational effects in the first and second embodiments >>
As described in the background art section, if the detection accuracy of the components constituting the motor control system such as the rotor position sensor 7 is poor, there is a problem that torque is generated in the motor 4 during the discharge process. In order to solve this problem, in the above-described embodiment, a displacement current is generated in the switching elements Tr1 to Tr6 of the inverter 3 with the excitation voltage command value and the torque voltage command value output to the motor 4 set to zero. As a result, the capacitor 5 is discharged.

  However, when the discharge process is performed using the switching element of the inverter 3 and the motor 4 is rotating, the following new problem arises.

  That is, (A) When the output phase voltage of the inverter 3 is zero, the motor wires are short-circuited, so that a negative torque is generated at the same time as a current is generated in the motor 4. Further, (B) the voltage of the capacitor 5 cannot be made smaller than a certain value due to the parasitic operation of the booster circuit configured between the motor 4 and the inverter 3. Further, (C) since there is a limit to supply the gate current to the switching element, the discharge time cannot be shortened when the ON / OFF drive frequency cannot be increased.

  Hereinafter, each of the above problems (A) to (C) will be described in detail.

  First, the problem (A) will be described. The motor torque T can be expressed by the following equation (A-1).

上式において、ｐは極対数、φａは永久磁石の磁束、Ｌｄは回転子のｄ軸インダクタンス、Ｌｑは回転子のｑ軸インダクタンス、ｉｑはトルク電流、ｉｄは励磁電流である。トルク電流ｉｑおよび励磁電流ｉｄには、トルク電圧Ｖｑ、励磁電圧Ｖｄとそれぞれ、次式（Ａ−２）及び（Ａ−３）に示す関係がある。 [Formula A-1]

In the above equation, p is the number of pole pairs, φa is the magnetic flux of the permanent magnet, Ld is the d-axis inductance of the rotor, Lq is the q-axis inductance of the rotor, iq is the torque current, and id is the excitation current. The torque current iq and the excitation current id have a relationship shown in the following expressions (A-2) and (A-3) with the torque voltage Vq and the excitation voltage Vd, respectively.

［式Ａ−３］

インバータ３の相電圧がゼロの場合は、Ｖｄ＝Ｖｑ＝０となるから、式（Ａ−２）および（Ａ−３）はそれぞれ、式（Ａ−４）及び（Ａ−５）のように記述することができる。 If the electrical angular velocity is ωre and the motor armature resistance is Ra,
[Formula A-2]

[Formula A-3]

When the phase voltage of the inverter 3 is zero, Vd = Vq = 0. Therefore, the expressions (A-2) and (A-3) are respectively expressed by the expressions (A-4) and (A-5). Can be described.

［式Ａ−５］

よって、課題（Ａ）については、式（Ａ−１）および式（Ａ−４）、式（Ａ−５）より、Ｌｄ−Ｌｑ＜０であれば必ずトルクＴの符号は負となる。また、式（Ａ−４）及び（Ａ−５）より、励磁電流ｉｄは、電気角速度の２乗に比例するため、モータの回転数とともにｉｄ＞ｉｑとなることがわかる。これと式（Ａ−１）とあわせると、Ｌｄ−Ｌｑ≧０であってもトルクＴの符号は回転数上昇とともに負となることがわかる。 [Formula A-4]

[Formula A-5]

Therefore, regarding the problem (A), the sign of the torque T is always negative if Ld−Lq <0, from the expressions (A-1), (A-4), and (A-5). Also, from the equations (A-4) and (A-5), it can be seen that the excitation current id is proportional to the square of the electrical angular velocity, so that id> iq along with the rotational speed of the motor. When this is combined with equation (A-1), it can be seen that the sign of torque T becomes negative as the rotational speed increases even if Ld−Lq ≧ 0.

  As described above, when the output phase voltage of the inverter 3 is zero, the motor wires are short-circuited, so that a negative torque is generated at the same time as a current is generated in the motor 4.

  Next, the problem (B) will be described.

  FIG. 7 is a circuit diagram showing the inverter 3 and the motor 4 extracted from FIG. 1. In the motor 4 and the inverter 3 shown in FIG. 1, a current as shown in FIG. 8 is generated by the switching operation during rotation. That is, the iL1 current flows into the capacitor 5 when the gate signal GUN is in the ON period ton, and the iL2 current flows into the capacitor 5 through the rectifier element during the OFF period toff. Assuming that the voltage across the capacitor 5 is Vdc and the voltage between the motor lines during motor rotation is Vuv, iL1 and iL2 can be expressed as in equations (B-1) and (B-2).

［式Ｂ−２］

ｉＬ１＝ｉＬ２より、Ｖｄｃは式（Ｂ−３）で表わされる。 [Formula B-1]

[Formula B-2]

From iL1 = iL2, Vdc is expressed by equation (B-3).

スイッチング周期Ｔは、ｔonとｔoffを合わせた時間であり、仮にデューディが５０％であるとすると、直流電圧Ｖｄｃは線間電圧Ｖｕｖの２倍となる。つまり、回転中に発生する線間電圧Ｖｕｖは、昇圧動作により一定値以下にすることができない。 [Formula B-3]

The switching period T is a time obtained by adding ton and toff. If the duty is 50%, the DC voltage Vdc is twice the line voltage Vuv. That is, the line voltage Vuv generated during the rotation cannot be reduced below a certain value by the boosting operation.

  Next, the problem (C) will be described.

  When driving the switching element, assuming that the gate charge amount of the IGBT is Qg and the switching frequency is fsw, the gate charge / discharge average current ig is expressed by the following equation (C-1).

一方、放電時間Ｔdischargeは、次式（Ｃ−２）及び（Ｃ−３）で表すことができる。インバータの直流電圧をＶｄｃ、入力平滑コンデンサ静電容量をＣ、スイッチング時に発生するコンデンサ５を介して流れるリカバリ電流（変位電流）をＩｃａｐ、スイッチ接合用容量をＣｊとすると、
［式Ｃ−２］

［式Ｃ−３］

式（Ｃ−２）より、スイッチング周波数ｆｓｗを高くすることで、放電時間Ｔdischargeを小さくできることがわかる。しかし、スイッチング周波数ｆｓｗを高くすると、式（Ｃ−１）よりゲート充放電平均電流ｉｇが大きくなる。つまり、ゲート駆動用電源能力の理由等で、スイッチング周波数を高くできない場合は、放電時間を短縮することができないという問題が生じる。 [Formula C-1]

On the other hand, the discharge time Tdischarge can be expressed by the following equations (C-2) and (C-3). When the DC voltage of the inverter is Vdc, the input smoothing capacitor electrostatic capacity is C, the recovery current (displacement current) flowing through the capacitor 5 generated during switching is Icap, and the switch junction capacitance is Cj.
[Formula C-2]

[Formula C-3]

From formula (C-2), it can be seen that the discharge time Tdischarge can be reduced by increasing the switching frequency fsw. However, when the switching frequency fsw is increased, the gate charge / discharge average current ig increases from the equation (C-1). That is, there is a problem that the discharge time cannot be shortened when the switching frequency cannot be increased due to the power supply capability for the gate drive.

  In order to solve the above problems (A) to (C), the following means is adopted in this example.

  First, as described in FIG. 3 and FIG. 6, a period from when the Hi-side switching elements Tr1, Tr3, Tr5 are turned off to when the Lo-side switching elements Tr2, Tr4, Tr6 are turned on and the Lo-side switching elements. A dead time DT from when the Tr1, Tr3, Tr5 is turned OFF to when the Hi-side switching elements Tr2, Tr4, Tr6 are turned ON is provided.

式（Ａ−６）において、モータ線間電圧Ｖｕｖは、モータ回転数と比例するため、デッドタイムＤＴを大きくすれば、モータ４が回転している時の負トルクを抑制することができる。 In the discharging operation by the switching operation of the inverter 3 when the motor 4 is rotating, the condition that the negative torque is not generated in the motor 4 is that the motor current iL of FIG. It is shown in 6). When the motor line voltage is Vuv and the forward voltage of the rectifying elements D1 to D6 is Vf,
[Formula A-6]

In the formula (A-6), the motor line voltage Vuv is proportional to the motor rotation speed. Therefore, if the dead time DT is increased, the negative torque when the motor 4 is rotating can be suppressed.

Further, from the equation (B-3), by increasing the switching off time toff, that is, by increasing the dead time DT, the influence of the boosting operation is suppressed, and the motor line voltage Vuv and the inverter DC Vdc are made equal. Is possible.

  In this example, in addition to this, as described with reference to FIG. 3, the frequency is set such that the ON periods of all the switching elements Tr1 to Tr6 do not overlap each other, but this can shorten the discharge time. . This point will be described in comparison with a reference example.

  FIG. 9 is a timing chart of a reference example for the embodiment of FIG. 3, in which the cycle and phase of the Hi-side switching elements Tr1, Tr3, Tr5 are the same, and the Lo-side switching elements Tr2, Tr4, Tr6 are the same. The period and phase are the same.

  Here, when attention is paid to the Hi-side switching elements Tr1, Tr3, Tr5 of this example shown in FIG. 3, the ON operation is performed at a timing different from that of the reference example of FIG. That is, in FIG. 3, only the switching element Tr1 (GUP) is turned on from time t0 to time t1, but in FIG. 9, all the switching elements on the Hi side are turned on from time t0 to time t1. . For this reason, from the formula (C-3), the current Icap from the capacitor 5 is smaller in the embodiment shown in FIG.

  The discharge rate in the embodiment shown in FIG. 3 and the reference example shown in FIG. 9, that is, the voltage drop of the inverter input voltage Vdc per unit period T is compared. FIG. 10 is an equivalent circuit of the inverter 3 of FIG. The capacitor is C1, its initial voltage is Vdc, the Hi-side switching elements are Hsw1, Hsw2, Hsw3, the Lo-side switching elements are Lsw1, Lsw2, and Lsw3, and the junction capacitances of the switching elements are C2, C3, and C4. In the discharge process, for example, when the high-side switching element Hsw1 (GUP) is turned on, the junction capacitance C2 of the switching element connected in parallel to the high-side switching element Hsw1 is charged, and Lo is paired therewith. When the switching element Lsw1 (GUN) on the side is turned on, the junction capacitor C2 is discharged. By repeating this, the electric charge stored in the capacitor C1 of the inverter 3 is discharged.

  Here, in order to explain the operation in the unit period T, the explanation will be made focusing on the switching element on the Hi side. FIG. 11 shows a timing chart of the reference example shown in FIG. 9, and FIG. 12 shows a timing chart of this example shown in FIG.

式（Ｃ−４）をＶａについて解くと、式（Ｃ−５）のように記述できる。 In FIG. 11, the following energy conservation equation (C-4) is established by the operation from time t0 to time t1. Here, the input voltage of the inverter 3 at time t0, that is, the voltage across the capacitor C1 is Vdc, and the voltage across the capacitor C1 at time t1 is Va.
[Formula C-4]

When equation (C-4) is solved for Va, it can be described as equation (C-5).

一方、図１２では、時間ｔ０から時間ｔ１の動作により、次のエネルギー保存式（Ｃ−６）〜（Ｃ−８）が成立する。ここで、時間ｔ０におけるインバータ入力電圧、すなわちコンデンサＣ１の両端電圧をＶｄｃ、時間ｔ１におけるコンデンサ両端電圧をＶｂとする。また、Ｈｉサイドのスイッチング素子Ｈｓｗ１、Ｈｓｗ２、Ｈｓｗ３が順に動作した際のコンデンサの両端電圧をそれぞれＶ１、Ｖ２、Ｖ３とすると、
［式Ｃ−６］

［式Ｃ−７］

［式Ｃ−８］

式（Ｃ−６）〜（Ｃ−８）をＶｂについて解くと、式（Ｃ−９）のように記述できる。 [Formula C-5]

On the other hand, in FIG. 12, the following energy conservation equations (C-6) to (C-8) are established by the operation from time t0 to time t1. Here, the inverter input voltage at time t0, that is, the voltage across capacitor C1 is Vdc, and the voltage across capacitor at time t1 is Vb. Also, assuming that the voltage across the capacitor when the Hi-side switching elements Hsw1, Hsw2, and Hsw3 are operated in sequence is V1, V2, and V3, respectively,
[Formula C-6]

[Formula C-7]

[Formula C-8]

When Expressions (C-6) to (C-8) are solved for Vb, they can be expressed as Expression (C-9).

ここで、式（Ｃ−５）と式（Ｃ−９）の大小関係を確認する。図１０におけるＣ２、Ｃ３、Ｃ４は同じ静電容量と考えることができるので、Ｃ２＝Ｃ３＝Ｃ４＝Ｃ０とすると、式（Ｃ−５）と式（Ｃ−９）はそれぞれ式（Ｃ−１０）と式（Ｃ−１１）に変換することができる。 [Formula C-9]

Here, the magnitude relationship between Expression (C-5) and Expression (C-9) is confirmed. Since C2, C3, and C4 in FIG. 10 can be considered to have the same capacitance, when C2 = C3 = C4 = C0, Expression (C-5) and Expression (C-9) are respectively expressed by Expression (C-10). ) And formula (C-11).

［式Ｃ−１１］

式（Ｃ−１０）及び（Ｃ−１１）より、式（Ｃ−１２）が導出できる。ここでＶａとＶｂの不等号を確認する。 [Formula C-10]

[Formula C-11]

Expression (C-12) can be derived from Expressions (C-10) and (C-11). Here, the inequality sign of Va and Vb is confirmed.

式（Ｃ−１２）の左辺の逆数を右辺に乗算し、整理すると式（Ｃ−１３）を導出できる。 [Formula C-12]

By multiplying the right side by the reciprocal of the left side of Expression (C-12) and rearranging, Expression (C-13) can be derived.

式（Ｃ−１３）より、分子＜分母すなわち、右辺＜１となることがわかる。つまり式（Ｃ−１０）と（Ｃ−１１）のＶａとＶｂの大小関係は、Ｖａ＞Ｖｂである。 [Formula C-13]

From the formula (C-13), it can be seen that the numerator <the denominator, that is, the right side <1. That is, the magnitude relationship between Va and Vb in the expressions (C-10) and (C-11) is Va> Vb.

  As described above, the operation pattern of this example shown in FIG. 12 (FIG. 3) has a faster discharge rate of the capacitor 5 than the operation pattern of the reference example shown in FIG. 11 (FIG. 9).

  13 is a graph showing the results of confirming the discharge characteristics of the present example shown in FIG. 3 and the reference example shown in FIG. 9 when the motor 4 is rotating, and FIG. 14 is a graph showing the results of confirming the torque characteristics. is there. From this figure, it was confirmed that the voltage of this example can be minimized and the discharge time can be minimized as compared with the reference example. It was also confirmed that the torque T can be minimized.

It is a block diagram which shows the drive power supply device of the electric vehicle which concerns on embodiment of invention. It is a block diagram which shows the principal part of the motor controller of FIG. 2 is a timing chart showing an operation of a discharge process of the drive power supply device shown in FIG. It is a flowchart which shows the discharge processing procedure of the drive power supply device shown in FIG. FIG. 5 is a timing chart showing an operation state of each component during the discharge process of FIG. 4. FIG. 6 is a timing chart showing an operation of a discharge process of another example of the drive power supply device shown in FIG. 1. It is an equivalent circuit diagram of an inverter for explaining a problem at the time of executing a discharge process when a motor is rotating. It is a timing chart for demonstrating the problem at the time of performing a discharge process when the motor is rotating. 4 is a timing chart showing an operation of a discharge process showing a reference example of the embodiment shown in FIG. 3. FIG. 4 is an equivalent circuit diagram of an inverter for explaining the effect of the embodiment shown in FIG. 3. It is a timing chart of the reference example for demonstrating the effect of embodiment shown in FIG. It is a timing chart of the embodiment for explaining the effect of the embodiment shown in FIG. It is a graph (discharge time-capacitor voltage) which shows the result of having confirmed the effect of embodiment shown in FIG. It is a graph (discharge time-motor torque) which shows the result of having confirmed the effect of the embodiment shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Battery 2 ... Relay 3 ... Inverter 4 ... Motor 5 ... Capacitor 6 ... Current sensor 7 ... Rotor position sensor 8 ... Voltage sensor 9 ... Gate drive circuit 10 ... Motor controller 11 ... Vehicle controller Tr1-Tr6 ... Switching element D1- D6: Rectifying element

Claims (7)

Power storage means for smoothing the output of the DC power supply;
A plurality of pairs of switching elements respectively connected to both terminals of the power storage means;
A rectifying element connected in parallel to each of the switching elements;
A control means for controlling ON / OFF of the switching element to convert the DC power of the DC power source into AC power;
The control means is configured such that the ON periods of the paired switching elements do not overlap each other and the dead time is equal to or longer than a predetermined time so that the electric charge stored in the power storage means flows as a displacement current to the switching element and the rectifying element. An inverter discharge device that controls the ON / OFF operation of the switching element at a frequency set by. The discharge device for an inverter according to claim 1,
The control means sets the peripheral number so that the ON periods of at least any two switching elements among a plurality of switching elements connected to the same terminal side of the power storage means do not overlap each other. Inverter discharge device. The discharge device for an inverter according to claim 2,
The inverter discharge device according to claim 1, wherein the control means sets the peripheral end number so that the ON periods of all the switching elements connected to the same terminal side of the power storage means do not overlap each other. In the discharge device of the inverter according to any one of claims 1 to 3,
The inverter discharge device according to claim 1, wherein the control means ends the discharge process when a predetermined discharge time has elapsed. In the discharge device of the inverter according to any one of claims 1 to 4,
Switch means for turning on and off the electrical connection between the DC power source and the inverter;
The control means detects whether or not the switch means is connected, and only when the switch means is not connected, the charge stored in the power storage means is displaced to the switching element and the rectifier element. The inverter discharge device controls the ON / OFF operation of the switching element so as to flow as follows. In the inverter discharge device according to any one of claims 1 to 5,
Comprising output means for outputting the AC power converted by the control means to the motor;
The control device sets the excitation voltage command value and torque voltage command value to be output to the motor via the output device to zero, the discharge device for an inverter, The inverter discharge device according to claim 6,
The control means sets the ON / OFF drive frequency for the switching element when discharging the electric charge stored in the power storage means to a frequency higher than the ON / OFF drive frequency for the switching element when driving the motor. A discharge device for an inverter, characterized by being set.

Images