JPH09168208A - Electrical system for electric automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent current leakage between a vehicle mounted apparatus and the body frame of a car by a constitution wherein an inner conductor switch is operated by subjecting the output voltage from a resonance circuit to power conversion and an output voltage is obtained by converting an input voltage into a pulse train of half-waves of the resonant voltage. SOLUTION: A charger 416 comprises a power converter 415, an insulating transformer 413, and a rectifying/smoothing circuit 414. The power converter 415 is a single phase inverter for converting the output voltage from a resonance circuit 60 into a pulse train of half-wave of the resonance voltage having a predetermined number of resonance voltage pulses. The insulating transformer 413 insulates the input side from the output side and steps down the output voltage from the power converter 415 to a level suitable for charging an auxiliary battery 410. The rectifying/smoothing circuit 414 comprises a rectifier and a DC output smoothing filter. A resonance voltage is inputted from a single resonance circuit 60 to power converters 400A, 415, 423, 433 this producing a predetermined pulse train of resonance voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric system of an electric vehicle driven by a battery as a power source, and more particularly to an electric system for driving a vehicle driving electric motor or the like by a resonance type power converter.

[0002]

2. Description of the Related Art FIG. 3 shows a typical prior art of an electric system of an electric vehicle driven by a battery as a power source. In the figure, reference numeral 1 denotes a main battery, which is a power source for main equipment and devices of an electric vehicle. 2 is the main switch,
It is used for connecting or disconnecting the main battery 1 and equipment or devices. Reference numeral 3 is a protective fuse, which is used as necessary.

Reference numeral 5 is an electric motor for driving the vehicle, and 4 is a semiconductor power converter for driving the electric motor. When the electric motor 5 is an AC electric motor, an inverter is used for the electric power converter 4.
Reference numeral 410 is an auxiliary battery, which is generally a 12V battery similar to an engine car. 411 is a charger for the auxiliary battery 410, which corresponds to an alternator of an engine vehicle, and charges the auxiliary battery 410 using the main battery 1 as a power source. Reference numeral 412 is a device such as a lighting device or a radio connected to the auxiliary battery 410.

Reference numeral 420 is an air conditioner, 421 is a compressor motor, and 422 is a motor driving inverter. 430 is a power steering device, 431 is a steering motor in the case of electric power steering,
In the case of hydraulic steering, it is a pump drive motor.
Reference numeral 432 is a semiconductor power converter for driving a motor, which is an inverter when the motor is an AC machine.

FIG. 4 illustrates a three-phase voltage source inverter, which is a typical circuit configuration of an inverter as the semiconductor power converter 4, in which 41 and 42 are transistors and 4 respectively.
3 and 44 are diodes, and 45 is a DC input smoothing capacitor. The other inverters 422 and 432 in FIG. 3 have substantially the same configuration.

FIG. 5 shows an example of the charger 411 in FIG. 3, which is generally called a DC-DC converter. In FIG. 5, 411a is a single-phase inverter, 411b is a DC input smoothing capacitor, 411c is an insulating transformer for electrically insulating the main battery 1 and the auxiliary battery 410, 411d is a rectifier, and 411e is a DC output smoothing filter. is there.

In this system, the operating frequency of the inverter 411a is set to several hundred KHz or more in order to miniaturize the insulating transformer 411c. The above-mentioned inverters (power converters) 4, 422, 432 generally perform PWM control operation, and the inverter frequency is several KHz or less and the carrier frequency is several tens KHz or less.

FIG. 6 shows an example of the waveform of the voltage between the output lines of the PWM-controlled voltage source inverter, in which the number of output voltage pulses is 9.
It is shown in the case of. In this case, the output line voltage waveform becomes a rectangular wave voltage pulse train having a peak value of the main battery voltage E _B. In the figure, the broken line shows the voltage waveform of the fundamental wave component of the inverter output frequency. The power converter 4 and the inverters 422 and 432 in FIG. 3 are usually voltage-type PWM control inverters, and the output waveform thereof is as shown in FIG.

FIG. 7 shows an input voltage waveform of the rectifier 411d shown in FIG. Inverter 411a
Is a switching cycle T (switching frequency f of the inverter 411a = 1 / T), conduction time Ton (conduction rate α =
It operates in Ton / T). In addition, n is the insulation transformer 41
It is a winding ratio of 1c. As shown in FIG. 7, the rectifier 411
The input of d is a rectangular wave voltage having a peak value of E _B / n.
Further, as the control of the charger 411, the conduction ratio α is controlled.

[0010]

As described above, in the conventional electric system of the electric vehicle, the AC voltage waveform of the semiconductor power converter for converting the DC voltage of the main battery into the AC voltage is a rectangular wave pulse train. . Thus, when the output voltage waveform of the power converter is a rectangular wave, a leak current flows through the insulator between the vehicle-mounted device and the vehicle body frame, and this current causes a communication problem in electronic devices such as car radios. Cause

FIG. 8 shows the leakage current when an AC motor for driving a vehicle is driven by an inverter, where C _m , C _i and C _b are equivalent electrostatic capacitances with respect to the vehicle body frame. i _cm , i _ci and i _cb respectively indicate the leakage currents. In the case of an electric vehicle, it is necessary to reduce these leakage currents to a level below which communication interference is not a problem in practice, and conventionally, the following measures have been taken as a countermeasure.

(1) As the power converter, a conventional voltage source inverter is used, and as shown in FIG. 9, the AC converter has a zero-phase reactor 101 on the AC side and a zero-phase reactor 102 on the DC side. Is inserted to act as a noise filter. This method is the same for other inverters. (2) The snubber circuit of the switching circuit of the voltage source inverter is strengthened to make the rising voltage of the rectangular wave voltage waveform gentle.

(3) Each of the power converters is a resonant inverter, and the output voltage pulse waveform is changed from a rectangular wave to a sine wave to suppress the generation of noise. FIG. 10 shows a basic circuit of a resonance type inverter, 6 is an LC resonance circuit, 40
Reference numeral 0 is a switch circuit. Here, the figure shows only one arm, and a three-phase inverter has a three-arm configuration.

FIG. 11 shows the operation of FIG.
(A) is a resonance voltage waveform of the resonance circuit 6, that is, an input voltage waveform of the switch circuit 400. In this case, the peak value is twice the main battery voltage E _B. Further, (b) is an output voltage waveform (between lines) of the switch circuit 6, which is shown in correspondence with FIG. The broken line in FIG. 11 (b) corresponds to the broken line in FIG.

The switch circuit 400 operates as if it were a rectifier having a resonance voltage as an input. When the output voltage of the inverter is low, the number of pulses is reduced, and when the output voltage is high, the switch circuit 400 is operated so as to increase the number of pulses (controlling the number of pulses of the resonance voltage waveform in this way , PD for the above PWM
M (Pulse Density Modulation)).

As described above, in the electric system of the conventional electric vehicle, by making each of the plurality of power converters a resonance type inverter, noise reduction can be achieved in each power converter and switching loss of the semiconductor switch. However, (1) the power converter becomes expensive. (2) The power converter becomes large and heavy. And so on. Therefore, the present invention has been made to solve these problems.

[0017]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the fact that the output voltage of all power converters connected to a DC circuit of a conventional electric system is a combination of voltage pulse trains. That is, the invention according to claim 1 is an electric system of an electric vehicle equipped with a plurality of semiconductor power converters using a main battery as a power source, wherein a high-frequency resonance circuit is connected to the main battery, and output from the resonance circuit. The resonant voltage is input to the power converter to operate the internal semiconductor switch, and the input voltage is converted into a pulse train having a half-wave resonant voltage waveform to obtain a desired output voltage.

According to a second aspect of the present invention, in the electric system according to the first aspect, the power converter is for at least driving a vehicle, driving an air conditioner, driving power steering,
It is characterized by including a power converter for charging the auxiliary battery.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment, and the same components as those in FIG. 3 are given the same numbers.

In FIG. 1, a high frequency resonance circuit 60 has the same structure as the resonance circuit 6 of FIG. Also, 4
00A is a semiconductor power converter, which includes the switch circuit 400 of FIG. 10 for three phases. The resonant circuit 60 and the power converter 400A constitute a resonant inverter.

Reference numeral 416 denotes a charger corresponding to the charger 411 shown in FIG. 3, which includes a power converter 415 and an insulation transformer 41.
3 and a rectifying / smoothing circuit 414. Here, the power converter 415 is the single-phase inverter 4 in FIG.
11a, which converts the output voltage of the resonance circuit 60 of FIG. 1 into a pulse train of a half-wave waveform of the resonance voltage waveform of the required number of resonance voltage pulses. Further, the isolation transformer 413 insulates the input / output side and reduces the output voltage of the power converter 415 to a voltage suitable for charging the auxiliary battery 410. Rectifying and smoothing circuit 4
Reference numeral 14 corresponds to the rectifier 411d and the DC output smoothing filter 411e in FIG. 423 and 433 are power converters having the same configuration as the power converter 400A.

FIG. 2 shows the operation waveforms of FIG.
11A shows the resonance voltage waveform of the resonance circuit 60, and its crest value is 2E _B as in FIG. 11A. FIG.
(B) is the output voltage of the power converter 400A (AC motor 5
The output voltage of the resonance circuit 60 is converted into a half-wave pulse train of the resonance voltage waveform of the required number of resonance voltage pulses by the operation of the semiconductor switch inside the power converter 400A.

FIG. 2C shows the waveform of the output voltage (on the side of the insulation transformer 413) of the power converter 415 in the charger 416. Here, the cycle T is controlled by the power converter 415.
The number of pulses in the period is controlled, and the cycle T in this case is selected regardless of the cycle T in FIG.

As described above, in the present embodiment, the resonance voltage output from the single resonance circuit 60 is input to the plurality of power converters 400A, 415, 423, 433, and a required number of power converters are provided. Resonance voltage pulse train is created to obtain a predetermined voltage output waveform. Since each power converter operates in the same way as a conventional resonant inverter, the output voltage waveform should be made almost sinusoidal to reduce communication interference. You can

[0025]

As described above, according to the present invention, the resonance voltage of the resonance circuit is converted into a desired pulse train by each power converter and output, so that the following effects can be expected. .

(1) Since the voltage pulse waveforms of the outputs of all the power converters can be made substantially sinusoidal, the leakage current flowing through the body frame can be reduced, and radio interference and other communication obstacles can be greatly reduced. Can be reduced to (2) Since the resonance circuit is shared by a plurality of power converters, it is possible to reduce the size, weight, and cost of the vehicle-mounted device for the entire electric vehicle. (3) Since each power converter is of the resonance circuit type, the switching loss of the power converter is reduced, and the efficiency of the electric vehicle as a whole can be improved.

As described above, according to the present invention, it is possible to provide an electric system for an electric vehicle that has a small number of communication failures, a small size, a light weight, a low price, and high efficiency.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of FIG. 1;

FIG. 3 is a block diagram showing a configuration of a conventional technique.

FIG. 4 is a configuration diagram of an inverter in FIG.

5 is a configuration diagram of the charger in FIG.

FIG. 6 is an output voltage waveform diagram of the inverter of FIG.

FIG. 7 is an input voltage waveform diagram of the rectifier in FIG.

FIG. 8 is an explanatory diagram of a leakage current of an electric vehicle.

FIG. 9 illustrates a known method for reducing leakage current in an electric vehicle.

FIG. 10 is a configuration diagram of a basic circuit of a resonant inverter.

11 is an explanatory diagram of the operation of the inverter of FIG.

[Explanation of symbols]

 1 Main Battery 2 Main Switch 3 Protection Fuse 5 AC Motor 60 Resonance Circuit 400A, 415, 423, 433 Semiconductor Power Converter 410 Auxiliary Battery 413 Insulation Transformer 414 Rectifying and Smoothing Circuit 416 Charger 421, 431 Motor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location H02P 7/63 302 H02P 7/63 302B 302K

Claims (2)

[Claims] 1. An electric system for an electric vehicle comprising a plurality of semiconductor power converters using a main battery as a power source, wherein a high-frequency resonance circuit is connected to the main battery, and a resonance voltage output from the resonance circuit is converted into the resonance voltage. An electric system for an electric vehicle, comprising: inputting to a power converter to operate an internal semiconductor switch; converting an input voltage into a pulse train of a resonance voltage half-wave waveform to obtain a desired output voltage. 2. The electric system of the electric vehicle according to claim 1, wherein the power converter includes at least a power converter for driving a vehicle, driving an air conditioner, driving power steering, and charging an auxiliary battery. And the electric system of the electric vehicle.