JP2004357412A - Dc power supply device for inverter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To discharge the charging electric charge of a capacitor without installing an exclusive discharging circuit when a device is stopped. <P>SOLUTION: This DC power supply device for an inverter is constituted as follows: A high-voltage DC power supply is generated by boosting a low-voltage DC power supply BAT by step-up circuits L1, Tr1, R2, and D1. It is supplied to a DC link of the inverter INV. When switches MR1, MR2, and MR3 are open and the supply of the low-voltage DC power supply BAT to the step-up circuits L1, Tr1, R2, and D1 is stopped, a first capacitor C1 and a second capacitor C2 are discharged by flowing only a d-axis current to a motor M by the inverter INV from the first capacitor C1 installed on the low-voltage DC power supply side and the second capacitor C2 installed on the high-voltage DC power supply side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for supplying DC power to a DC link of an inverter.
[0002]
[Prior art]
2. Description of the Related Art There is known a power supply device in which a voltage of a low-voltage battery is boosted by a booster circuit and supplied to a chopper circuit, and a DC motor is driven by the chopper circuit (for example, see Patent Document 1). In this power supply device, capacitors are connected to the input side of the booster circuit, that is, the low-voltage battery side, and the output side, that is, the chopper circuit side.
[0003]
Prior art documents related to the invention of this application include the following.
[Patent Document 1]
JP 2001-268900 A
[Problems to be solved by the invention]
However, in the above-described conventional power supply device, there is a problem that the stored power of the capacitor connected to the input / output side of the booster circuit cannot be discharged when the device is stopped.
[0005]
SUMMARY OF THE INVENTION The present invention provides a DC power supply for an inverter that discharges a charge from a capacitor when the apparatus is stopped.
[0006]
[Means for Solving the Problems]
The present invention relates to a DC power supply device for an inverter, in which a low-voltage DC power supply is boosted by a booster circuit to generate a high-voltage DC power supply and supplied to a DC link of the inverter, wherein a switch is opened to supply the low-voltage DC power supply to the booster circuit When the power supply is stopped, the first capacitor and the second capacitor are supplied from the first condenser installed on the low-voltage DC power supply side and the second condenser installed on the high-voltage DC power supply side by the inverter to flow only the d-axis current to the motor. To discharge.
[0007]
【The invention's effect】
According to the present invention, when the operation of the inverter is stopped, a dedicated discharge circuit such as a discharge resistor is provided to charge the first capacitor on the low-voltage DC power supply side and the charge of the second capacitor on the high-voltage DC power supply side. Discharge can be performed without the need.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
One embodiment in which the present invention is applied to a traveling drive device of an electric vehicle will be described. FIG. 1 shows a configuration of an embodiment. The driving device for an electric vehicle according to one embodiment boosts the DC power of the low-voltage battery BAT and supplies the high-voltage DC power to the inverter INV, and also lowers the high-voltage regenerative power from the inverter INV to charge the low-voltage battery BAT. I do.
[0009]
The relays MR1, MR2, and MR3 are connected between the low-voltage battery BAT and the boost circuits L1, Tr1, R2, and D1, and supply and stop of low-voltage DC power from the low-voltage battery BAT to the boost circuits L1, Tr1, R2, and D1. The MR1 is for starting, the MR2 is for running, and the MR3 is shared.
[0010]
The coil L1, the transistor Tr1, the resistor R2, and the diode D1 constitute a booster circuit, and a voltage generated at both ends of the coil L1 is added to a voltage of the battery BAT by switching operation of the transistor Tr1, thereby generating a high DC voltage. Then, it is supplied to the DC link of the inverter INV via the diode D1. The diode D1 prevents current from flowing back from the DC link capacitor C2 of the inverter INV charged to a high voltage to the battery BAT.
[0011]
On the other hand, the transistor Tr2 forms a step-down circuit, and performs switching operation of the transistor Tr2 to step down the high-voltage regenerative power of the inverter INV and charge the battery BAT.
[0012]
A capacitor C1 is connected between the relays MR1, MR2, MR3 and the booster circuits L1, Tr1, R2, D1, and the step-down circuit Tr2 in parallel with the low-voltage battery BAT. This capacitor C1 prevents the voltage of the low-voltage DC power supply from dropping every time the switching operation is performed by the boosting circuits L1, Tr1, R2, and D1 to boost the low-voltage DC power supply of the low-voltage battery BAT. A low-voltage DC power supply smoothing capacitor for supplying a low-voltage DC power supply having a high voltage to the booster circuits L1, Tr1, R2, and D1.
[0013]
The above-mentioned capacitor C2 is connected to the DC link of the inverter INV. This capacitor C2 prevents the voltage of the high-voltage DC power supply from being lowered at every switching when the high-voltage DC power output from the booster circuits L1, Tr1, R2, D1 is switched by the inverter INV to the AC power. And a high-voltage DC power supply smoothing capacitor for supplying a high-voltage DC power supply having a stable voltage to the inverter INV.
[0014]
The voltage sensor V1 detects the voltage across the capacitor C1, ie, the low-voltage DC power supply voltage, and the voltage sensor V2 detects the voltage across the capacitor C2, ie, the high-voltage DC power supply voltage.
[0015]
The inverter INV converts high-voltage DC power supplied from the booster circuits L1, Tr1, R2, and D1 into AC power, applies the AC power to the AC motor M for driving, and drives the AC motor M. The inverter INV performs vector control, and can control the rotation speed and the torque of the motor M to arbitrary values.
[0016]
The resistor R1 connected in series with the starting relay MR1 prevents a large inrush current from flowing from the low-voltage battery BAT to the capacitor C1 when the relay MR1 is turned on, that is, at the time of starting. The resistor R2 connected to the emitter of the booster circuit transistor Tr1 limits the current flowing through the transistor Tr1 during the boosting operation, turns on the transistor Tr1, short-circuits the capacitor C1, and discharges the charge of the capacitor C1. Limit the discharge current at the time.
[0017]
The control unit CU is composed of a microcomputer and peripheral parts such as a memory, and controls the inverter INV, the transistors Tr1, Tr2, and the relays MR1 to MR3 to control the start-up of the device, the rotation speed of the motor M, and the torque control. While monitoring the low-voltage DC power supply voltage and the high-voltage DC power supply voltage by the voltage sensors V1 and V2, the boosting control of the boosting circuits L1, Tr2, R2 and D2, the step-down control of the voltage lowering circuit Tr2, and the control of the capacitors C1 and C2 after the ignition is turned off. Perform discharge treatment and the like.
[0018]
When the low-voltage DC power of the low-voltage battery BAT is supplied to the capacitor C1 and the booster circuits L1, Tr1, R1, and D1, in order to prevent burnout of circuit devices due to inrush current to the capacitors C1 and C2, a start-up relay MR1 is provided. The common relay MR3 is closed, and the capacitor C1 is charged via the charging resistor R1, and the capacitor C2 is further charged via the coil L1 and the diode D1. When the voltage between both ends of the capacitors C1 and C2 is saturated, or when the charging current to the capacitors C1 and C2 decreases, the starting relay MR1 is opened, and the traveling relay MR2 is closed instead.
[0019]
Next, the voltage of the battery BAT is boosted by switching the transistor Tr1 of the booster circuit, and the high-voltage DC voltage is supplied to the DC link of the inverter INV to charge the capacitor C2 to a high voltage. The inverter INV converts high-voltage DC power supplied by the booster circuits L1, Tr1, R2, and D1 into AC power, applies the AC power to the motor M, and performs a power running operation of the motor M. At this time, a forward current flows through the diode D1. On the other hand, the inverter INV performs the regenerative operation of the motor M by inversely converting the AC power generated by the motor M into the DC power. This regenerative DC power is stepped down by switching the transistor Tr2 of the step-down circuit, and is supplied to the battery BAT to be charged.
[0020]
When the operation of the electric vehicle is completed and the device is stopped, the traveling relay MR2 and the shared relay MR3 are opened. In this state, both capacitors C1 and C2 remain charged and need to be discharged early. In this embodiment, current is supplied from the capacitors C1 and C2 so that torque is not generated in the motor M by performing vector control of the inverter INV, and the capacitors C1 and C2 are discharged.
[0021]
In the vector control type inverter, the current flowing through the motor M can be separated and controlled on the orthogonal dq axes. Therefore, the q-axis current for generating torque in the motor M is set to 0, and the d-axis for generating magnetic flux in the motor M is set to 0. By supplying only the current, the discharge current of the capacitors C1 and C2 can be supplied without generating torque in the motor M.
[0022]
Here, since the capacitor C2 is directly connected to the inverter INV, the charge can be completely discharged. However, since the capacitor C1 is connected to the inverter INV via the coil L1 and the diode D1, the charge cannot be completely discharged due to the voltage-current characteristics of the diode D1.
[0023]
FIG. 2 shows the characteristics of the forward current with respect to the anode-cathode voltage of the diode. As is apparent from this characteristic, the current flowing through the diode depends on the voltage between both ends of the diode. When the voltage decreases, the current stops flowing. For this reason, the electric charge charged in the capacitor C1 cannot be completely discharged.
[0024]
Therefore, in this embodiment, the transistor Tr1 of the booster circuit is turned on, and the charge of the capacitor C1 is discharged through the path of the coil L1, the transistor Tr1, and the resistor R2. That is, the capacitor C1 is short-circuited via the booster circuit L1, Tr1, and R2, and the capacitor C1 is discharged. As a result, the charged charges of the capacitors C1 and C2 can be completely discharged when the apparatus is stopped.
[0025]
FIG. 3 is a flowchart showing a capacitor discharging process according to one embodiment. The operation of the embodiment will be described with reference to this flowchart. The control unit CU executes the capacitor discharging process when the ignition switch IGN is turned off.
[0026]
In step 1, the relays MR2 and MR3 are opened. In the following step 2, the inverter INV is vector-controlled, a current is supplied from the capacitors C1 and C2 to the motor M so that no torque is generated in the motor M, and the discharge of the capacitors C1 and C2 is started.
[0027]
In step 3, the voltage across the capacitor C1 (here, V1 for convenience) is read from the voltage sensor V1, and the voltage across the capacitor C2 (here, V2 for convenience) is read from the voltage sensor V2. Then, it is determined whether or not the voltage V1 across the capacitor C1 is smaller than a predetermined voltage k1, and whether a voltage difference (V1-V2) between the capacitors C1 and C2 is smaller than a predetermined voltage k2.
[0028]
Here, since the resistance value of the coil L1 is small, the voltage drop of the coil L1 due to the current flowing through the coil L1 can be ignored. Therefore, the voltage difference (V1-V2) between the capacitors C1 and C2 can be considered to be substantially equal to the voltage across the diode D1.
[0029]
The voltage V1 across the capacitor C1 becomes lower than the predetermined voltage k1, it is determined that the discharge of the capacitor C1 has been sufficiently performed, and the voltage difference (V1-V2) between the capacitors C1 and C2 is equal to the predetermined voltage k2. If it is determined that the voltage has become smaller and the voltage across the diode D1 has dropped to a voltage at which current does not easily flow, the process proceeds to step 4. If the voltages V1 and V2 across the capacitors C1 and C2 do not satisfy the condition of step 3, the process returns to step 2 and discharge to the motor M is continued.
[0030]
In step 4, the transistor Tr1 is turned on, and the charge remaining in the capacitor C1 is discharged through the path of the coil L1, the transistor Tr1, and the resistor R2. In step 5, it is checked whether the voltage V2 of the capacitor C2 has become lower than a predetermined voltage k3. The voltage k3 is a voltage for determining the completion of discharging of the capacitor C2. When the discharge of the capacitor C2 is completed, the process proceeds to step 6, in which the operation of the inverter INV is stopped to terminate the discharge of the capacitor C2.
[0031]
In the following step 7, it is confirmed whether or not the voltage V1 of the capacitor C1 has become lower than a predetermined voltage k4. Here, the voltage k4 is a voltage lower than the voltage k1 described above, and is a voltage for determining the completion of discharging of the capacitor C1. When the discharge of the capacitor C1 is completed, the process proceeds to step 8, where the transistor Tr1 is turned off to terminate the discharge of the capacitor C1 by the coil L1, the transistor Tr1, and the resistor R2.
[0032]
As described above, in one embodiment, the low-voltage battery BAT and the booster circuits L1, Tr1, R2, and D1 that boost the voltage of the low-voltage battery BAT and output the high-voltage DC power via the backflow prevention diode D1 include: Switches MR1, MR2, MR3 connected between the battery BAT and the boost circuits L1, Tr1, R2, D1 for supplying and stopping low-voltage DC power of the low-voltage battery BAT to the boost circuits L1, Tr1, R2, D1. A vector-controlled inverter INV that converts high-voltage DC power output from the booster circuits L1, Tr1, R2, and D1 into AC power and supplies the AC power to the motor M, switches MR1, MR2, MR3, and booster circuits L1, Tr1 , R2, and D1, a first capacitor C1 connected in parallel with the low-voltage battery BAT, and a DC link of the inverter INV. A second capacitor C2 connected to the first capacitor C1, a first voltage sensor V1 for detecting a voltage V1 across the first capacitor C1, a second voltage sensor V2 for detecting a voltage V2 across the second capacitor C2, and a first voltage sensor V2. A control unit CU that controls discharge of the first capacitor C1 and the second capacitor C2 based on the detection voltage V1 of the voltage sensor V1 and the detection voltage V2 of the second voltage sensor V2, and the control unit CU includes a switch When MR1, MR2 and MR3 are opened and the supply of the low voltage DC power to the booster circuits L1, Tr1, R2 and D1 is stopped, the d-axis from the first capacitor C1 and the second capacitor C2 to the motor M by the inverter INV. Only the current was supplied to discharge the first capacitor C1 and the second capacitor C2.
[0033]
As a result, the low-voltage DC power supply of the low-voltage battery BAT is boosted by the booster circuits L1, Tr1, R2, and D1 to generate a high-voltage DC power supply. When the power supply is stopped, a dedicated discharge circuit such as a discharge resistor is installed to charge the charge of the power supply voltage smoothing capacitor C1 installed on the low voltage DC power supply side and the power supply voltage smoothing capacitor C2 installed on the high voltage DC power supply side. It can be discharged without performing.
[0034]
Further, in one embodiment, the detection voltage V1 of the voltage sensor V1 becomes lower than the predetermined voltage k1, and the voltage difference (V1-V2) between the detection voltage V1 of the voltage sensor V1 and the detection voltage V2 of the voltage sensor V2. When the voltage becomes lower than the predetermined voltage k2, both ends of the capacitor C1 are short-circuited and discharged by the booster circuits L1, Tr1, and R2, so that the charge of the power supply voltage smoothing capacitor C1 installed on the low voltage DC power supply side is discharged. When discharging from the inverter INV via the motor M, even if the discharge current stops flowing due to the characteristic of the backflow prevention diode D1 of the booster circuit, it can be completely discharged via L1, Tr1, R2 of the booster circuit. . Since the discharging of the capacitor C1 by the booster circuits L1, Tr1, R2 is performed after the voltage V1 across the capacitor C1 becomes lower than the predetermined voltage k1, the power consumed by the resistor R2 of the booster circuit (= V1 ² / R2) ) Is small, and the resistor R2 of the booster circuit does not need to be a large-capacity resistor.
[0035]
When the detection voltage V2 of the voltage sensor V2 becomes lower than the predetermined voltage k3 for judging the completion of the discharge, the inverter INV is stopped to terminate the discharge of the capacitor C2. Can be completely discharged. Further, when the detection voltage V1 of the voltage sensor V1 becomes lower than a predetermined voltage k4 (<k1) for judging the discharge completion, the booster circuits L1, Tr1, R2 are stopped to terminate the discharge of the capacitor C1. Therefore, the power supply voltage smoothing capacitor C1 installed on the low voltage DC power supply side can be completely discharged when the apparatus is stopped.
[0036]
Note that each component is not limited to the configuration of the above-described embodiment as long as the characteristic functions of the present invention are not impaired. For example, in the above-described embodiment, the booster circuit including L1, Tr1, R2, and D1 and the step-down circuit including Tr2 have been described as examples. The present invention is not limited to the configuration of the embodiment.
[0037]
In the above-described embodiment, an example is shown in which the DC power supply device of the inverter of the present invention is applied to a traveling drive device of an electric vehicle, and the low-voltage DC power supply is a vehicle-mounted low-voltage battery. Can be applied to
[0038]
In the above-described embodiment, the example in which the completion of the discharge is determined based on the voltages V1 and V2 across the capacitors C1 and C2 has been described. However, the completion of the discharge is determined based on the discharge time of the capacitors C1 and C2. You may. In this case, the discharge time of the capacitors C1 and C2 is measured, and a time slightly longer than the measured time is stored as the required discharge time. Then, it is determined that the discharge has been completed when the required discharge time has elapsed from the start of the discharge.
[0039]
Further, in the above-described embodiment, an example in which the low-voltage battery BAT is used as the low-voltage DC power supply has been described, but the low-voltage DC power supply is not limited to the low-voltage battery.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an embodiment.
FIG. 2 is a diagram showing voltage-current characteristics of a capacitor.
FIG. 3 is a flowchart showing a capacitor discharging process according to one embodiment.
[Explanation of symbols]
BAT Battery MR1 to MR3 Relay V1, V2 Voltage sensor C1, C2 Capacitor R1, R2 Resistor Tr1, Tr2 Transistor D1 Diode INV Inverter M Motor CU Control unit IGN SW Ignition switch

Claims (5)

A low-voltage DC power supply,
A booster circuit that boosts the voltage of the low-voltage DC power supply and outputs high-voltage DC power via a backflow prevention diode,
A switch that is connected between the low-voltage DC power supply and the booster circuit and that supplies and stops the low-voltage DC power supply to the booster circuit;
A vector control inverter that converts high-voltage DC power output from the booster circuit into AC power and supplies the AC power to the motor,
A first capacitor connected in parallel with the low-voltage DC power supply between the switch and the booster circuit;
A second capacitor connected to a DC link of the inverter;
A first voltage sensor for detecting a voltage V1 across the first capacitor;
A second voltage sensor for detecting a voltage V2 across the second capacitor;
A control circuit that controls discharge of the first capacitor and the second capacitor based on a detection voltage V1 of the first voltage sensor and a detection voltage V2 of the second voltage sensor,
The control circuit is configured such that when the switch is opened and the supply of the low-voltage DC power to the booster circuit is stopped, only the d-axis current is supplied from the first capacitor and the second capacitor to the motor by the inverter. And causing the first capacitor and the second capacitor to discharge. The DC power supply for an inverter according to claim 1,
The control circuit determines that the detection voltage V1 of the first voltage sensor is lower than a predetermined voltage k1 and that a voltage difference (V1-V1) between the detection voltage V1 of the first voltage sensor and the detection voltage V2 of the second voltage sensor. A DC power supply for an inverter, wherein when the voltage V2) becomes lower than the predetermined voltage k2, the booster circuit causes the both ends of the first capacitor to be short-circuited and discharged. The DC power supply for an inverter according to claim 2,
Wherein the control circuit stops the inverter and terminates the discharge of the second capacitor when the detection voltage V2 of the second voltage sensor becomes lower than a predetermined voltage k3. . The DC power supply for an inverter according to claim 2 or 3,
The control circuit stops the discharge circuit and terminates the discharge of the first capacitor when the detection voltage V1 of the first voltage sensor becomes lower than a predetermined voltage k4 (<k1). Inverter DC power supply. 5. The DC power supply for an inverter according to claim 1, wherein the DC power supply for an inverter is mounted on an electric vehicle, and a low-voltage battery is used as the low-voltage DC power supply.

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