JP2877577B2 - AC electric vehicle control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art FIG. 2 shows a conventional converter for converting an AC power supply into DC power and an AC electric vehicle control device for converting the output of the converter into AC power again to drive and control an induction motor. Configurations are known.

In this conventional AC electric vehicle control device, AC power received from a pantograph 101 is stepped down through a transformer 102 and input to a converter 103 composed of a power semiconductor element such as a thyristor to be converted into DC. Then, smoothing is performed by a capacitor 104 connected in parallel to the output side of the converter 103, and this DC is supplied to a variable voltage variable frequency (VVVF) inverter 105 to be reconverted into a desired AC power, which is used as a load. To the induction motor 106 to control the driving of the electric vehicle.

In FIG. 2, reference numeral 107 denotes a speed detector for detecting the speed of the electric vehicle, and 108 denotes an inverter 10
5, a DC voltage detector for detecting a DC voltage as an input, 109 is a converter control device for performing conversion control of converter 103, and 110 is an inverter 105
Is an inverter control device for performing the control of (1).

[0005] In such a conventional AC electric vehicle control device, the VVVF inverter 105 is generally controlled to maintain the torque of the induction motor 106 constant at a constant slip frequency fs from a low speed range to a middle speed range. The f / V constant control for keeping the ratio between the inverter output frequency f and the induction motor voltage VIM constant is performed.

In the case of the constant f / V control, the GTO thyristor of the VVVF inverter 105 has its maximum shutoff capability,
Due to limitations such as the maximum switching frequency and gate turn-off time, the lower the inverter frequency fINV, the higher the ratio of the carrier frequency used for pulse width modulation to the inverter frequency, and the higher the inverter frequency fINV, the smaller this ratio becomes. Done.

[0007]

However, such a conventional AC electric vehicle control device has the following problems. FIG. 3 shows an example of the relationship between the modulation rate AL and the inverter frequency fINV during power running. In FIG. 3, the straight line falling to the right represents the maximum modulation rate limit NPLIM for each pulse mode. When the modulation rate AL of each pulse mode coincides with the modulation rate maximum limit, the mode is shifted to the next lower pulse mode. This is a control method that takes into account that the same performance can be obtained in the low-speed range even if the power supply voltage fluctuates.It is widely used in electric vehicles that use a DC overhead line as a power supply. In addition, the relationship between the modulation factor AL and the inverter frequency fINV varies, and as a result, the pulse mode switching frequency also varies.

[0008] The DC output voltage of converter 103 includes a pulsating component having twice the frequency of the input AC power supply. When the inverter frequency approaches the pulsation frequency, a beat phenomenon occurs in the motor current or the like due to interference between the pulsation frequency and the inverter frequency. During the occurrence of this beat phenomenon, the state where the motor current peak value has increased continues,
When a disturbance or the like is applied in this state, the possibility of reaching the overcurrent protection threshold becomes higher than when no beat phenomenon occurs.

Therefore, if the pulse mode is switched during the occurrence of the beat phenomenon, the jump of the motor current due to the pulse mode switching is superimposed on the ripple of the motor current due to the beat phenomenon, the peak value of the motor current becomes high, and the overcurrent protection detection is performed. In addition, there is a problem in that the probability of the control becomes unnecessarily high, and an increase in the size of the VVVF inverter due to an increase in the capacity of the GTO thyristor caused by the maximum breaking current is inevitable.

The present invention has been made in view of such a conventional problem, and in order to avoid superposition of the motor current ripple due to the beat phenomenon and the motor current due to the pulse mode switching, the pulse mode switching during the beat phenomenon is performed. In this case, frequent occurrence of overcurrent of the motor current can be prevented, controllability can be improved, and VVV
It is another object of the present invention to provide an AC electric vehicle control device that can reduce the maximum breaking current of a GTO thyristor used in an F inverter and can reduce the size and size of the GTO thyristor.

[0011]

An AC electric vehicle control device according to the present invention includes a converter for converting AC power supplied from an AC power supply via a pantograph and a transformer into DC power having a constant voltage, and an output of the converter. Circuit formed by a capacitor connected to the DC side, and a voltage-type pulse width modulation (P) for converting the DC power input through the DC circuit and converted by the converter into AC power.
WM) type variable voltage variable frequency (VVVF) inverter, an induction motor driven by AC power converted by the VVVF inverter, and a carrier frequency used for pulse width modulation of the VVVF inverter is an integral multiple of the inverter output frequency. A pulse mode switching unit for switching the ratio between the carrier frequency and the inverter output frequency based on the inverter frequency condition, wherein the pulse mode switching unit switches the ratio between the carrier frequency and the inverter output frequency. The frequency is set to a frequency other than an even multiple of the input AC power supply frequency.

[0012]

According to the AC electric vehicle control device of the present invention, the AC power supplied from the AC power supply via the pantograph and the transformer is converted into DC power of a constant voltage by the converter.
The converter output is smoothed by a capacitor connected to the output side of the converter, supplied to a VVVF inverter of the voltage pulse width modulation type, and DC power is converted to AC power to obtain drive power for the induction motor.

The carrier frequency used for the pulse width modulation of the VVVF inverter is set to an integral multiple of the inverter output frequency, and the ratio between the carrier frequency and the inverter output frequency is switched by the pulse mode switching unit based on the inverter frequency condition. But at this time,
By setting the pulse mode switching frequency for switching the ratio between the carrier frequency and the inverter output frequency to a frequency other than an even multiple of the input AC power supply frequency, the pulsation frequency of twice the input AC power supply causes the inverter frequency to change. The pulse mode switching control is not performed during the beat phenomenon that occurs when approaching to prevent frequent occurrence of overcurrent of the motor current, thereby improving the controllability, and the GT used in the VVVF inverter.
The O-thyristor can also reduce the maximum breaking current.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a circuit configuration of an embodiment of the present invention. The AC electric vehicle control device of this embodiment shows a configuration of a control circuit applied to the inverter control device 110 in the circuit of the general AC electric vehicle control device shown in FIG. A speed detector 2 for detecting a speed; a motor rotation speed calculator 3 for obtaining a motor rotation frequency fr from a speed signal of the speed detector 2; a slip frequency pattern calculator 4 for outputting a pattern of a slip frequency fs of an electric vehicle; By adding the motor rotation frequency fr by the rotation speed calculation unit 3 and the slip frequency fs by the slip frequency pattern calculation unit 4, the inverter frequency f
An adder 5 for outputting INV and a pulse mode switching circuit 6 are provided.

The pulse mode switching circuit 6 has a pulse mode selection circuit 7. The pulse mode selection circuit 7 receives the inverter frequency fINV, and sets pulse mode switching frequencies C1, C2, C
Pulse mode selection signal 1P
M, 3PM, 5PM, 9PM, 15M, and outputs a pulse mode switching frequency set value C1, C
2, C3, C4, and the pulse mode switching frequency setting units 8 to 11, and the inverter frequency fINV is set to these pulse mode switching frequency setting values C1, C2,
Compared to C3 and C4, each pulse mode selection signal 1PM,
Comparator 12 that outputs 3PM, 5PM, 9PM, and 15M
And a pulse mode output unit 17 that outputs a pulse mode #NP (# indicates one of 1, 3, 5, 9, and 15) selected and determined by the comparators 12 to 16. .

On the output side of the pulse mode switching circuit 6, a PWM modulating unit 18 and a modulation factor calculating unit 19 are provided, and a pulse mode command matching the current inverter frequency fINV as an output of the pulse mode selecting circuit 7 is provided. The value #NP is received.

Next, the operation of the AC electric vehicle control device having the above configuration will be described.

The speed signal detected by the speed detector 2 attached to the induction motor 1 is input to the motor speed calculation unit 3 in the inverter control device 110, and the motor rotation frequency fr is obtained. This motor rotation frequency fr
Is added in the adder 5 to the slip frequency fs calculated by the slip frequency pattern generator 4 and is input to the pulse mode switching circuit 6 as the inverter frequency fINV. FIG. 1 shows a power running state.
The inverter frequency fINV is obtained by adding the motor rotation speed fr and the slip frequency fs.

In the pulse mode selection circuit 7 of the pulse mode switching circuit 6, the input inverter frequency fINV
Are set in advance in pulse mode switching frequency setting devices 8 to
The pulse mode switching frequency set values C1, C2, C3, and C4 set at 11 and the comparator 12
16 and when the conditions are met, the respective pulse mode selection signals 15PM, 9PM, 5P
Output M, 3PM or 1PM.

Here, the set values C1 to C4 of the pulse mode switching frequency setting units 8 to 11 are set to an even multiple frequency such as twice or four times of the converter input AC power supply in which a beat phenomenon occurs, for example, a 50 Hz power supply. If the frequency is set to a value close to 100 Hz, the ripple of the motor current due to the beat phenomenon and the jump of the motor current due to the pulse mode switching are superimposed as described in the description of the conventional example, and the peak value of the motor current is superimposed. Will cause an overestimation.
Therefore, all of the set values C1 to C4 are set so as not to be an even multiple of the power supply frequency of the AC motor, such as 100 Hz, or a value near the multiple. However, in this case, it is necessary to set the value to be equal to or less than the maximum modulation rate limit of each pulse mode resulting from the limitation of the gate turn-off time of the GTO thyristor of the inverter 105.

Therefore, for example, 105 Hz, 90 Hz, 75 Z, 60 Hz, etc. are set as AL shown in FIG.

The pulse mode switching frequency #NP selected and determined by comparing the pulse mode switching frequency set values C1 to C4 set in this way is PWM.
Modulation unit 18 and modulation ratio calculation unit 19 perform constant motor torque control from a low speed range to a middle speed range.

In this way, the overcurrent detection occurs when the pulse mode switching frequency 3NPT is output during the occurrence of the beat phenomenon that occurs when the pulsation frequency, which is an even multiple of the frequency of the AC power supply, and the inverter frequency approach each other. The possibilities can be reduced.

[0025]

As described above, according to the present invention, the pulse mode switching circuit prevents the inverter frequency for switching the pulse mode from becoming a frequency near an even multiple of the AC power supply frequency. Of the motor current and the overlap of the ripple of the motor current during the beat phenomenon can be avoided, and overcurrent conduction of the motor current can be prevented. In addition, the GTO thyristor used in the VVVF inverter can also keep the maximum breaking current small, so that the GTO thyristor can be downsized.
Circuit size can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a functional block diagram of a general AC electric vehicle control device.

FIG. 3 is an operation explanatory diagram of a conventional example.

[Description of Signs] 1 Induction motor 2 Speed detector 3 Motor rotation speed calculation unit 4 Slip frequency calculation unit 5 Adder 6 Pulse mode switching unit 7 Pulse mode selection circuit 8-11 Pulse mode switching frequency setting unit 12-16 Comparator 17 pulse mode output section 18 PWM modulator 19 modulation rate calculation section

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-119573 (JP, A) JP-A-63-302766 (JP, A) JP-A-63-117606 (JP, A) (58) Investigation Field (Int.Cl. ⁶ , DB name) B60L 9/00-9/32 B60L 15/00-15/38 H02M 7/42-7/98 H02P 5/408-5/412 H02P 7/628-7 / 632

Claims (1)

(57) [Claims] 1. A converter for converting AC power supplied from an AC power supply via a pantograph and a transformer to DC power of a constant voltage, a DC circuit including a capacitor connected to an output side of the converter, A variable voltage variable frequency (VVVF) inverter of a voltage-type pulse width modulation (PWM) type, which is input through this DC circuit and converts DC power converted by the converter into AC power, and converted by the VVVF inverter. An induction motor driven by AC power;
A pulse mode switching unit that sets a carrier frequency used for pulse width modulation of the F inverter to an integral multiple of the inverter output frequency, and switches a ratio between the carrier frequency and the inverter output frequency based on an inverter frequency condition; An AC electric vehicle control device, characterized in that a pulse mode switching frequency for switching the ratio between the carrier frequency and the inverter output frequency is set to a frequency other than an even multiple of the input AC power supply frequency.