JPH04317501A - Controller for ac electric vehicle - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an AC electric vehicle.

0002

BACKGROUND ART FIG. 3 is a block diagram showing a conventional AC electric vehicle control device disclosed in, for example, IEEJ Technical Report (Part II) No. 251 (June 1988), page 26.
In the figure, 1 is an AC overhead wire, 2 is a pantograph in contact with this AC overhead wire 1, 3 is a main transformer electrically connected to this pantograph 2, and 4 is connected to the secondary winding of this main transformer 3. For example, a pulse width modulation control converter (hereinafter referred to as a PWM converter), 5 is the PWM converter.
A smoothing capacitor connected in parallel with the WM converter 4,
6 is an inverter connected in parallel with the smoothing capacitor 5, such as a variable voltage variable frequency inverter (hereinafter referred to as VVV).
It is called F inverter. ), 7 is a motor connected to this VVVF inverter 6, such as an induction motor (IM), 8 is a tertiary winding of the main transformer 3 used as a control power source for auxiliary equipment, etc., and 9 is this tertiary winding 8. 10 is an AC current detector connected to the secondary winding of the main transformer 3, 11 is a DC voltage detector connected in parallel with the smoothing capacitor 5, and 12 is an AC voltage detector. 9, a converter control circuit connected to the AC current detector 10 and the DC voltage detector 11, and for giving a control command 13 to the PWM converter 4; 14, a motor current detector connected to the output side of the VVVF inverter 6; , 15 is a motor rotation speed detector connected to the induction motor 7, and 16 is an inverter control circuit connected to the motor current detector 14 and the motor rotation speed detector 15 for giving a control command 17 to the VVVF inverter 6. .

Next, the operation will be explained. When an AC voltage is applied from the AC overhead line 1 to the main transformer 3 via the pantograph 2, this AC voltage is stepped down by the main transformer 3 and then input to the PWM converter 4. The PWM converter 4 receives tertiary voltages and 2 voltages respectively detected from an AC voltage detector 9, an AC current detector 10, and a DC voltage detector 11.
Converter control circuit 1 based on the next current and output DC voltage
It is controlled by pulse width modulation according to the control command 13 issued by the power source 2, and outputs a constant DC output voltage while keeping the power factor at approximately 1. The VVVF inverter 6 uses a smoothing capacitor 5 connected to the DC output side of the PWM converter 4 as a voltage source, and a motor current detector 14 and a motor rotation speed detector 15.
The induction motor 7 is controlled by a control command 17 issued by an inverter control circuit 16 based on the motor current and motor rotation speed detected from the inverter control circuit 16, and outputs an alternating current voltage with a variable voltage and variable frequency, thereby driving and controlling the induction motor 7.

[0004] Furthermore, the drive control method of the induction motor 7 and the VV
The details of the pulse width modulation control method of the VF inverter 6 are described in, for example, the above-mentioned Institute of Electrical Engineers of Japan Technical Report (Part II) No. 251, pages 38-39, and will therefore be omitted.

Generally, in the low speed range, the number and pulse width of the inverter's output voltage pulses are variably controlled to change the output voltage and output frequency proportionally, and in the high speed range, the output voltage and output frequency are changed proportionally to a constant value determined by the inverter input voltage. Outputs the output voltage,
A control method is adopted that changes only the inverter output frequency.

[0006] The output voltage pulses of the inverter are switched to reduce the number of voltage pulses as the inverter frequency increases due to various constraints. For example, in the output voltage variable control region, the number starts with 27 pulses, then 15 pulses, and then 9 pulses. , 5 pulses, and finally becomes 3 pulses, and may become 1 pulse in a constant output voltage region.

FIG. 4 is a waveform diagram showing a voltage waveform applied to the induction motor during three-pulse control and a voltage waveform during one-pulse control. The minimum off time between voltage pulses is restricted by the minimum on/off time characteristics of the main circuit switching elements used in the inverter, and the minimum time as an absolute value is determined. Therefore, as the inverter frequency increases, this minimum off-time restriction affects the creation of an ideal pulse width modulation waveform, and the fundamental wave effective value of the output voltage that is actually output is calculated within the inverter control device. This may result in a value that is lower than the output voltage target value that is intended to be output.

Furthermore, when switching from 3-pulse control to 1-pulse control, as shown in the waveform diagram of FIG. 5, a jump in motor voltage is unavoidable, resulting in a sudden change in motor current, that is, a sudden change in torque. .

[0009]

[Problem to be Solved by the Invention] Since the conventional control device for an AC electric vehicle is configured as described above, the effective value of the output voltage fundamental wave in the inverter output voltage variable control region is affected by the control target due to the distortion of the output waveform. There was a problem in that the motor torque was lower than the value and the motor torque was reduced. Furthermore, the voltage jump when transitioning from variable inverter output voltage control to constant output voltage control can cause sudden changes in motor current and torque, which can worsen ride comfort and cause unnecessary stoppage of the control device due to overcurrent protection detection. There was a problem.

[0010] The present invention was made to solve these problems, and it prevents reductions in motor torque and sudden changes in motor current, and maintains stable motor torque at all times without activating unnecessary protection detection. The purpose is to obtain a control device for an AC electric vehicle that can be controlled.

[0011]

[Means for Solving the Problems] A control device for an AC electric vehicle according to the present invention includes means for detecting a reduction in the fundamental wave effective value of an output voltage in an output voltage variable control area of an inverter, and The converter is provided with means for controlling the converter DC output voltage so that the inverter output voltage maintains continuity upon transition to the constant voltage control region.

0012

[Operation] The control device for an AC electric vehicle according to the present invention increases the converter output voltage in response to the reduction in the fundamental wave effective value of the inverter output voltage due to waveform distortion.

[0013]

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 an embodiment of a control device for an AC electric vehicle according to the present invention, and in the figure, 1 to 11,
and 13 to 17 are the same as described with respect to FIG. Reference numeral 18 indicates inverter control calculation information output from the inverter control circuit 16, such as the inverter frequency, the number of modulation pulses, and the modulation rate. 19 is a detection circuit for a fundamental wave effective value reduction rate due to inverter output voltage waveform distortion, and 20 is a converter output voltage increase rate command output from this detection circuit 19.

Since the control device for an AC electric vehicle of the present invention is constructed as described above, the reduction rate of the fundamental wave effective value due to waveform distortion of the inverter output voltage is determined by the inverter frequency,
It can be determined from the number of modulation pulses, modulation rate, and minimum off time. For example, in the case of an inverter frequency of 70 Hz, 3-pulse modulation mode, and minimum off time of 250 μs, waveform distortion occurs at a modulation rate of approximately 0.9 or more, and 3 pulses are compared to the fundamental wave effective value in 1-pulse mode at the same frequency. In this mode, the effective value of the fundamental wave is reduced by about 10%.

The fundamental wave reduction rate detection circuit 19 determines the fundamental wave effective value reduction rate from the various inverter control calculation information 18 described above, and if the fundamental wave effective value reduction rate is reduced by 10% as in the above case, for example, the converter control circuit 12A detects the fundamental wave effective value reduction rate. A converter output voltage increase rate command 20 of a 10% increase over a predetermined control target value is output to.

With this control, as shown in FIG. 2, even if waveform distortion occurs in the modulated pulse voltage waveform, the motor voltage increases in inverse proportion to the amount of distortion, so the fundamental wave effective value increases. No longer reduced. In addition, even if the transition to the constant voltage control region, which is the one-pulse mode, the converter output voltage is returned to the predetermined value at the same time as the transition, there is no voltage jump and the output voltage maintains continuity, so the motor current or sudden changes in torque will not occur.

[0017]

As described above, according to the present invention, there is provided a means for detecting a reduction in the effective value of the fundamental wave of the output voltage in the output voltage variable control area of an inverter, and a means for detecting a reduction in the effective value of the fundamental wave of the output voltage in the output voltage variable control area of an inverter, and Since a means for controlling the converter DC output voltage is provided so that the inverter output voltage maintains continuity during transition, there is no fluctuation in motor current or torque, the ride is comfortable, and unnecessary protection detection is not activated. This has the effect of obtaining a control device for an AC electric vehicle with high precision and high reliability.

[Brief explanation of drawings]

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

FIG. 2 is a waveform diagram for explaining the operation of the present invention.

FIG. 3 is a block diagram showing a conventional control device for an AC electric vehicle.

FIG. 4 is a waveform diagram in 3-pulse mode and 1-pulse mode.

FIG. 5 is a waveform diagram for explaining the operation of a conventional device.

[Explanation of symbols]

1 AC overhead wire 3 Main transformer 4 PWM converter 5 Smoothing capacitor 6 VVVF inverter 7 Induction motor 12A Converter control circuit 16 Inverter control circuit 19 Detection circuit

Claims (1)

[Claims] Claim 1: A main transformer whose primary winding is connected to an AC overhead line, a converter which is connected to the secondary winding of the main transformer and outputs a DC output voltage, and a DC output side of the converter. In an AC electric vehicle, the AC electric vehicle includes a smoothing capacitor connected thereto, an inverter using the smoothing capacitor as a voltage source, and an electric motor connected to the AC output side of the inverter. means for detecting a reduction in the fundamental wave effective value of the output voltage due to deformation distortion of the output voltage; and a means for detecting a reduction in the fundamental wave effective value of the output voltage of the inverter; 1. A control device for an AC electric vehicle, comprising: means for controlling the DC output voltage of the converter so as to maintain the DC output voltage of the converter.