JP2004120866A - Power controller of electric automobile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the reliability of an electric automobile. <P>SOLUTION: An inverter converts the DC current of a battery into an AC current and supplies it to a traction motor. A main contactor electrically connects/disconnects between the battery and the inverter. A precharge contactor is provided parallel to the main contacter and electrically connects/disconnects between the inverter and the battery. A capacitor is put in the inverter and smoothes a voltage supplied from the battery. A controller closes the main contactor if it judges that the precharge contactor is closed to stop precharging. The controller judges that precharging has finished if a change rate of a precharge voltage of a capacitor 23 falls below a prescribed value. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power control device for an electric vehicle including an inverter.
[0002]
[Prior art]
Generally, an electric vehicle (EV) or a hybrid electric vehicle (HEV) includes a battery that stores DC power, an inverter that converts the DC power of the battery into AC power, and a drive motor that is driven by the AC power converted by the inverter. In addition, a main switch is provided between the battery and the inverter for disconnecting and electrically connecting the battery and the inverter. Further, at the input terminal of such an inverter, an electrolytic capacitor for converting the DC power to the AC power after smoothing the input voltage is provided in order to suppress the fluctuation of the voltage supplied from the battery. .
[0003]
However, when a DC current from the battery is input to the inverter via the main switch, a large amount of current flows into the electrolytic capacitor in an extremely short time, so that the main switch interposed between the battery and the capacitor is not used. The contacts may be damaged. Therefore, a precharge switch that bypasses the main switch and supplies a capacitor while suppressing the amount of DC current from the battery by a predetermined amount is provided, and the precharge switch is turned on before the main switch is turned on. In general, a technique is known in which a capacitor is gradually charged, and after the charging is completed, the main switch is turned on to prevent damage to a main switch contact. A series of operations for charging the capacitor of the inverter with the precharge switch turned on before the main switch On is hereinafter simply referred to as precharge.
[0004]
In the above-described technology, it is essential to determine the completion of charging of the capacitor by pre-charging. As a technology for determining the completion of charging, for example, the pre-charging is started when a predetermined time has elapsed since the start of pre-charging. There are known a technology that regards charging as being complete (see Patent Literature 1) and a technology that determines that precharging is completed when the capacitor voltage becomes equal to or higher than a reference value (see Patent Literature 2).
[0005]
[Patent Document 1]
JP-A-4-165901 [Patent Document 2]
US Pat. No. 5,369,540.
[Problems to be solved by the invention]
However, according to the technique disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 4-165901), it is considered that the precharge is completed after a predetermined time elapses, and the main switch is not related to the actual progress of the precharge. Becomes On, and if the precharge is insufficient, a large rush current flows. Therefore, it is difficult to reliably prevent the main switch from being damaged by this technique.
[0007]
Further, according to the technique of Patent Document 2 (US Pat. No. 5,369,540), it is difficult to set a reference voltage for considering precharge completion. For example, when the voltage of a battery is low, Since the capacitor voltage of the inverter also decreases as the voltage of the battery decreases, the precharge completion condition may not actually be satisfied. Further, in order to avoid such a situation, if the reference voltage regarded as the completion of precharge is set lower, if the battery voltage does not decrease so much, the precharge becomes insufficient with respect to the actual battery voltage. Since the main switch is turned on in this state, a large rush current flows through the capacitor, and there is a possibility that the contacts of the main switch may be damaged.
[0008]
The present invention has been made in view of such a problem, and in an electric vehicle including an inverter having a capacitor, it is possible to provide a power control device for an electric vehicle, which can accurately determine completion of precharge. The purpose is.
[0009]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a power control device for an electric vehicle that converts DC power of a battery into AC power and supplies the AC power to a traveling motor, and disconnects an electrical connection between the battery and the inverter. A main contactor in contact with the main contactor, a precharge contactor disposed in parallel with the main contactor to disconnect and connect an electrical connection between the battery and the inverter, and a voltage interposed between the inverter and smoothed from a voltage supplied from the battery. And a controller that closes the pre-charge contactor and closes the main contactor when it is determined that the pre-charge has been completed. The controller is configured to pre-charge when the rate of change of the pre-charge voltage of the capacitor becomes less than a predetermined value. Is determined to have been completed.
[0010]
For this reason, the completion of the precharge of the capacitor of the inverter can be reliably determined with a simple configuration, and the reliability of the electric vehicle is improved.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a power control device for an electric vehicle according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. Note that in this specification, an electric vehicle is treated as including a hybrid electric vehicle.
FIG. 1 is a schematic block diagram showing a power control device for an electric vehicle according to an embodiment of the present invention, FIG. 2 is a time chart showing its operation, and FIG. 3 is an operation flow thereof.
[0012]
First, as shown in FIG. 1, a power control device 1 for an electric vehicle according to the present invention includes a battery 21, a junction box 10, an inverter 22, a motor (running motor) 24, a generator 25, a controller (ECU) 26, and the like. Mainly composed of Hereinafter, these components will be described.
The battery 21 is electrically connected to the inverter 22 by a power supply line via the junction box 10 and stores a high-voltage (for example, about 600 V) DC power in a chargeable / dischargeable manner, and is constituted by a lithium ion battery. ing.
[0013]
The junction box 10 is electrically interposed between the battery 21 and the inverter 22. Inside the junction box 10, a main contactor 11 capable of connecting and disconnecting the electrical connection between the battery 21 and the inverter 22 is provided. And a precharge contactor 12 that can connect and disconnect the battery 21 and the inverter 22 by bypassing the main contactor 11. Further, a resistor R1 for suppressing the amount of DC current supplied from the battery 21 is provided on the positive electrode side of the precharge contactor 12. For this reason, when the precharge contactor 12 is On (closed; connected) and the main contactor 11 is Off (opened / disconnected), the DC current from the battery 21 causes the precharge contactor 12 having the resistor R1 to pass through. When the precharge contactor 12 is turned off (open; disconnected) and the above-mentioned main contactor 11 is turned on (closed; connected), The DC current from the battery 21 is transmitted directly to the inverter 22. Note that the On / Off control of the main contactor 11 and the precharge contactor 12 is performed by the ECU 26.
[0014]
The inverter 22 is connected to the battery 21 via the junction box 10 by a power supply line, and is also electrically connected to each of the motor 24, the generator 25, and the ECU 26. The inverter 22 converts the DC power stored in the battery 21 into AC power and supplies the AC power to the motor 24. Further, the inverter 22 further operates when the regenerative braking system is operated. It also has a function of converting AC power from the DC power into DC power and sending the DC power to the battery 10.
[0015]
Further, in the inverter 22, a capacitor 23 is provided at an input terminal (hereinafter referred to as a primary terminal) to which a power supply line extending from the battery 21 is connected. This capacitor 23 temporarily stores DC power input from the battery 22, smoothes voltage fluctuations, and stabilizes power.
The generator 25 is electrically connected to the inverter 22 and mechanically connected to an engine (not shown), generates AC power by inputting engine driving force, and converts the generated AC power into the inverter. The power is supplied to the battery 21 and the motor 24 via the power supply 22.
[0016]
The ECU 26 is electrically connected to the inverter 22 and the junction box 10 and controls the main conductor 11 and the precharge conductor 12 built in the junction box 10 in accordance with a voltage increase rate at the primary end of the inverter 22 during precharge. Is what you do.
Next, the function of the main part of the present invention will be described with reference to the time chart of FIG. First, when the precharge contactor 12 of the junction box 10 is turned on (closed; connected) by the ECU 26 (see time point A), the voltage of the capacitor (the inverter voltage) at the primary end of the inverter 22 gradually increases. Then, the amount of increase (Δv / Δt) of the voltage per unit time (for example, 0.1 ms) is calculated as the voltage increase rate. During this time, the current flowing into the inverter 22 is substantially constant.
[0017]
When the voltage increase rate is equal to or higher than a predetermined value (hereinafter, sometimes referred to as an “estimated charge completion value”) set in advance, the precharge contactor 12 is continuously turned on (closed; connected) and the battery is turned on. When the DC current from the inverter 21 continues to be input to the inverter 22 while being attenuated by the resistor R1, and when the voltage increase rate at the primary end of the inverter 22 becomes less than the estimated charging completion value (see the time point B), the ECU 26 sets the pre-charging for the capacitor 23. Assuming that the charging is completed, the main contactor 11 is turned on (closed; connected).
[0018]
At this time, if the capacitor 23 is fully charged, the amount of inverter current does not fluctuate. However, even if the precharge completion determination is made, the capacitor 23 actually has a small free capacity. Therefore, if the main contactor 11 is turned on, the inverter current slightly increases momentarily. However, since the capacitor 23 is almost fully charged by pre-charging, the amount of current flowing into the capacitor 23 is not the amount of current that damages the contact of the main contactor 11.
[0019]
Since the power control device for an electric vehicle according to an embodiment of the present invention is configured as described above, the following operation and effect can be obtained.
First, as shown in step A1 in the operation flow of FIG. 3, the precharge contactor 12 in the junction box 10 is turned on (closed; connected) by the ECU 26, and then, as shown in step A2, the inverter 22 is turned on by the ECU 26. The voltage rise rate (Δv / Δt) at the primary end is measured and calculated, and it is determined whether this voltage rise rate is equal to or greater than a set value. Here, if the voltage increase rate is equal to or more than the set value, the process returns to step A1 via the yes route, while if the voltage increase rate is less than the set value, the process proceeds to step A3 via the no route. That is, in step A2, if the voltage increase rate is equal to or higher than the set value, the charging of the capacitor 23 is regarded as incomplete, and the monitoring is continued until the voltage increase rate of the inverter 22 becomes less than the estimated charge completion value. When the voltage increase rate of the inverter 22 decreases to less than the estimated charge completion value, it is determined that the charging of the capacitor 23 has been completed, and the process proceeds to step A3.
[0020]
Then, in step A3, the main contactor 11 is turned ON (closed; connected) by the ECU 26, and the DC current from the battery 21 is directly input to the inverter 22 without being attenuated via the main contactor 11. Thereafter, the process proceeds to step A4, in which the precharge contactor 12 is turned off (open; disconnected), and a series of controls ends.
[0021]
As described above, it is possible to reliably grasp the precharge (charge amount) in the capacitor 23 by a method that focuses on detecting the voltage rise rate of the primary end of the inverter 22 that decreases as the charge amount in the capacitor 23 increases. The control of the main contactor 11 and the pre-charge contactor 12 according to the amount of charge in the capacitor 23 can be performed with a simple configuration.
[0022]
Further, according to the present invention, the controller 23 determines the precharge completion by monitoring the voltage change rate at the primary end of the inverter 22, so that, for example, the output of the motor 24 of the electric vehicle is changed. Therefore, even if the storage capacity of the capacitor 23 is changed due to the above, there is no need to add a device such as a sensor for the precharge completion determination, and further, it is not necessary to change the control content of the ECU 26. Therefore, the present invention can be applied to various kinds of electric vehicles.
[0023]
It should be noted that the present invention is not limited to the above-described embodiment, and can be implemented with various modifications without departing from the spirit of the present invention.
For example, in the above embodiment, the case where the present invention is applied to an electric vehicle has been described. However, a hybrid electric vehicle may be used, and in this case, a series type or a parallel type may be used. .
[0024]
In the above-described embodiment, the ECU 26 is provided separately from the junction box 10 and the inverter 22. However, for example, the ECU 26 may be built in the junction box 10 or may be built in the inverter 22. Good.
Also, the battery 71 has been described as a lithium ion battery, but may be a nickel metal hydride battery, a lead battery, or the like.
[0025]
Further, in the flowchart of FIG. 3, when the inverter voltage rise rate is less than the predetermined value, the main contactor is immediately turned on. However, when the voltage rise rate becomes less than the predetermined value, the main contactor is turned on. For example, the main contactor may be set to On when the continuation is continued for 50 ms or more. According to this, if the voltage rise rate instantaneously falls below a predetermined value due to fluctuations in the inverter voltage rise rate, etc., the precharge of the capacitor is not considered to be completed. It is possible to make a determination.
[0026]
【The invention's effect】
As described in detail above, according to the power control apparatus for a power supply circuit of a series hybrid electric vehicle of the present invention, an inverter that converts DC power of a battery into AC power and supplies the AC power to a traveling motor, A main contactor for connecting / disconnecting electrical connection with the inverter, a precharge contactor disposed in parallel with the main contactor for connecting / disconnecting electrical connection between the battery and the inverter, and a battery interposed in the inverter, And a controller that closes the precharge contactor and performs control to close the main contactor when it is determined that precharge has been completed, and the controller controls the rate of change of the precharge voltage of the capacitor. Is smaller than the predetermined value, it is determined that the precharge is completed. Which is configured, can be advantageously by a simple configuration, it performs reliably precharged completion judgment of the capacitor of the inverter.
[0027]
This can also contribute to improving the reliability of the electric vehicle. Furthermore, since the controller performs the precharge completion determination by monitoring the rate of change of the power input to the capacitor, even if the storage capacity of the capacitor changes due to a change in the capacitor design, etc. Since it is not necessary to add a device necessary for the precharge completion determination or change the control condition, the present invention can be applied to various electric vehicles.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram illustrating a power control device for an electric vehicle according to an embodiment of the present invention.
FIG. 2 is a time chart showing an operation of the electric vehicle power control device according to the embodiment of the present invention.
FIG. 3 is a flowchart illustrating an operation of the electric vehicle power control device according to the embodiment of the present invention.
11 Main Contactor 12 Precharge Contactor 21 Battery 22 Inverter 24 Motor (Running Motor)
23 Capacitor 26 ECU (controller)

Claims (1)

An inverter that converts the DC power of the battery into AC power and supplies the AC power to the traveling motor;
A main contactor that disconnects and connects an electrical connection between the battery and the inverter;
A precharge contactor disposed in parallel with the main contactor to disconnect and connect an electrical connection between the battery and the inverter;
A capacitor interposed in the inverter for smoothing a voltage supplied from the battery;
A controller that closes the main contactor when the precharge contactor is closed and the precharge is determined to be completed,
The controller according to claim 1, wherein the controller determines that the precharge has been completed when the rate of change of the precharge voltage of the capacitor is less than a predetermined value.

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