JPH114505A - Controller for electric rolling stock - Google Patents

Abstract

PROBLEM TO BE SOLVED: To limit loss generated in a switching element for an inverter constituting a main circuit within a range not made larger than a normal operation state when the special operation mode for a train washing operation is used as an operation mode, and to improve the efficiency of a device and miniaturize the device. SOLUTION: In the controller driving the electric rolling stock by inverters 7-9, a means 1 in which the special operation mode for a train washing operation in the continuity of low-speed operation during the train washing time is set at the time of the washing of the train containing a normal operation mode; a means 2 in which the switching frequency of switching elements 70-73, etc., is set in response to the operation mode; and a frequency-voltage setting means 4 of the inverters having a means in which the current command of a normal operation and a special operation are changed over, and a speed control system; are installed. The switching frequency of the inverters is lowered when the operation is changed over to a special operation from a normal operation, while an inverter frequency command and an output voltage command corresponding to the current command of the special operation mode are outputted through the speed control system.

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 electric vehicle that drives an AC motor, and more particularly to a control device for an electric vehicle that is suitable for downsizing a power conversion device for driving an electric motor of an electric vehicle.

[0002]

2. Description of the Related Art An inverter for converting a direct current into an alternating current to drive an electric motor, and particularly an inverter for driving an induction motor for an electric vehicle using a gate turn-off thyristor (GTO thyristor) having a high breakdown voltage as a switching element for a main circuit. Many have been put to practical use. These inverters generally output a two-level potential to an AC terminal, and the output voltage is controlled by pulse width modulation (PWM) control at a maximum of about 500 Hz. Meanwhile, in recent years,
In addition to the high potential point and the low potential point of the DC power supply, an intermediate potential point between the high potential point and the low potential point is provided. Alternatively, a technique of a three-level inverter (also referred to as a neutral point clamped (NPC) inverter) for selectively leading a three-level potential at an intermediate potential point to an AC terminal is being established. This three-level inverter can increase the apparent switching frequency, so that an AC output with little current ripple can be obtained, and the voltage applied to the switching element can be reduced by dividing the DC voltage source.
It has features such as lowering the breakdown voltage of the switching element. Therefore, a high-frequency switching element such as an insulated gate bipolar transistor (IGBT) can be applied instead of the GTO thyristor.

[0003]

By the way, in applications such as electric vehicles, in order to further improve the reliability of the system, in addition to the operation control for normal traveling, the operation control which occurs irregularly is also used. It is necessary to realize a device that can respond. For example, a propulsion operation to evacuate a train that stuck on the track due to a failure by another train, a unit that separates the failed unit when some of the units being trained fail and operates only with the remaining units In the case of a cut operation or a car wash of a train, a car wash operation in which a low-speed operation is maintained during the car wash time is included. In general, since the loss generated by the switching elements constituting the main circuit greatly affects the size of the device, it is necessary to always set the element current and the switching frequency so as to be within a predetermined value. However, in propulsion operation and unit cut operation, it is necessary to set the output current higher than in normal operation to maintain the same running performance as in normal operation, and therefore, a larger element loss occurs than in normal operation. In addition, during normal operation, since the operation is performed in an unnecessary short time, there are problems that the size of the cooling device and the entire device must be increased, and the operation time must be limited. In addition, in a low-speed car wash operation during car washing, the operation duration is relatively long and the operation is performed at a constant speed at a low speed, so the average loss increases. There was a problem that the size had to be increased. An object of the present invention is to provide a range in which, when the train operation mode is in a special operation state in which low-speed operation is maintained when the train is washed, the loss generated by the switching elements constituting the main circuit is not significantly increased as compared with the normal operation state. It is an object of the present invention to provide a highly efficient and compact electric vehicle control device.

[0004]

The object of the present invention is to provide a means for setting the switching frequency of a switching element to be lower than that in a normal operation mode when the operation mode is a special operation mode of a car wash operation. The problem is solved by providing means for outputting an inverter frequency command and an output voltage command according to the current command in the special operation mode via the speed control system when the current command is switched to the special command in the special operation mode.

The output of the operation mode setting means sets the switching frequency of the switching element in the special operation mode of the car wash operation so as to be lower than that in the steady state, and also provides the output of the frequency / voltage setting means of the inverter. In order to output the inverter frequency command and the output voltage command according to the current command in this special operation mode, the generation loss of the switching element is limited to a range that does not greatly increase compared to the normal operation, and a high-efficiency and small-sized device is provided. Can be realized.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a three-level inverter for an electric vehicle will be described below with reference to FIGS. First, the main circuit configuration and basic operation of the three-level inverter will be described. In FIG. 1, reference numeral 60 denotes a train line which is a DC voltage source;
Capacitors (divided) to create an intermediate point N (hereinafter referred to as a neutral point) from the voltages of
Reference numerals 83, 90 to 93 denote self-extinguishing switching elements having a rectifying element for reflux (in this example, IGBTs are used, but GTO thyristors, transistors, etc. may be used);
Reference numerals 4, 75, 84, 85, 94 and 95 are auxiliary rectifiers for deriving the neutral point potential of the capacitor. Also, a case where the induction motor 10 is connected as a load is shown. Here, since the switching arms 7 to 9 can operate independently for each phase, the basic operation will be described with the switching arm 7 as an example. The voltages ed1 and ed2 of the capacitors 61 and 62 are used as a completely smooth DC voltage source.
= Ed2 = Ed / 2 (Ed: total DC voltage). At this time, the switching elements 70 to 73 are turned on and off as shown in Table 1 to obtain three levels of output voltages e of Ed / 2, 0, and -Ed / 2 at the AC output terminal U. Table 1 {Conduction state of switching element Output voltage 70 71 72 73 e} ────── ON ON OFF OFF Ed / 2 OFF ON ON OFF 0 OFF OFF ON ON ―Ed / 2 ───────────────────── Output voltage e Is a waveform obtained by combining pulse-like voltages having the magnitudes of Ed / 2, 0, and -Ed / 2, and performs PWM control so that the output voltage e approaches a sine wave. The details of the main circuit of the three-level inverter are described in JP-A-51-47848.
And JP-A-56-74088.

Next, the configuration and operation of this embodiment will be described. In FIG. 1, reference numeral 1 denotes an operation mode setting means for outputting an operation mode command according to an operation condition, and outputs a normal operation command or a special operation command. The operation mode setting means 1 is constituted by, for example, a switch provided on a driver's cab or a means for detecting a special operation. Reference numeral 2 denotes a switching frequency setting means for setting the switching frequency Fsw of the inverter main circuit element to be lower than that in the normal operation mode when the operation mode setting means 1 instructs the special operation. As shown in FIG. Operation command is time T1
(When turned on), the switching frequency is reduced from Fsw1 to Fsw2. Reference numeral 4 denotes frequency / voltage setting means for setting the inverter frequency command Fi and the output voltage command E. Reference numeral 3 denotes a gate signal generating means for generating a gate signal of the inverter main circuit element according to the switching frequency command Fsw from the switching frequency setting means 2 and the inverter frequency command Fi and the output voltage command E from the frequency / voltage setting means 4. is there. Here, the gate signal generating means 3 outputs the switching frequency command Fsw,
From the inverter frequency command Fi and the output voltage command E, a gate signal is generated as follows. First, from the inverter frequency command Fi and the output voltage command E, the positive-side and negative-side instantaneous voltage commands ap and an shown in FIGS. 3A and 3B are converted to Asin (2πFit) (when 0 ≦ 2πFit <π). ap = ｛(1) 0 (when π ≦ 2πFit <2π) 0 (when 0 ≦ 2πFit <π) an = ｛(2) -Asin (2πFit) (when π ≦ 2πFit <2π) where A : Amplitude command, t: time (U-phase example) Here, assuming that the output voltage command E = 1 with the 180 ° conduction square wave output as the output voltage reference, the amplitude command A is given by A = (4 / π) E (3) FIG. 4 shows an example of a method of generating a gate signal corresponding to the instantaneous voltage command. In FIG. 4A, a waveform C is a carrier signal. This carrier signal C
And the instantaneous voltage command a, the gate signal can be determined as in the following equation. 1 (when a> C) Gate signal = ｛(4) 0 (when a <C) In this way, the gate signals of FIGS. 3C and 3D are generated, and FIG. ), Ed / 2,
A phase voltage consisting of three levels of voltages 0 and -Ed / 2 is obtained. The setting change of the switching frequency is performed by changing the cycle Tsw (=
1 / Fsw) is changed from Tsw1 to Ts as shown in FIG.
It is realized by adjusting to w2. Similarly, the V phase,
A gate signal is also created for the W phase. As shown in FIG. 5, the three-level inverter can also perform "dipolar modulation" in which voltage pulses are alternately output via a zero voltage as shown in FIG. 5 (FIG. 3 is called "unipolar modulation"). ). The bias B in FIGS. 5A and 5B is for generating a sinusoidal voltage command over positive and negative periods, and thereby adjusts the zero voltage period of the output phase voltage. In this way,
The gate signals shown in FIGS. 5C and 5D are generated, and as shown in FIG. 5E, 3 of Ed / 2, 0, and -Ed / 2 is obtained.
A phase voltage consisting of level voltages is obtained. Since this modulation method can adjust the minute voltage including the zero voltage,
This is a particularly effective method when the inverter frequency is low, such as during startup. In this case, the present invention can be applied similarly to the above-described unipolar modulation method. Incidentally, the output of the operation mode setting means 1 may be divided for each operation mode as shown in FIG. That is, as the output of the operation mode setting means 1, a propulsion operation command, a unit cut operation command, and a car wash operation command, which are special operation commands, are prepared in addition to the normal operation command, and input to the switching frequency setting means 2. Thereby, frequency setting corresponding to a plurality of special operation commands becomes possible.

Next, a method of setting the switching frequency will be described. The internally generated loss of the switching element can be roughly classified into an FVD loss due to a forward voltage drop (FVD) of the element and a switching loss generated at the time of commutation. In the case of a three-level inverter, the FVD loss Pfvd of the main circuit element
And the switching loss Psw can be expressed by the following equation. Pfvd = K1 · Im + K2 · Im ² ５ (5) Psw = K3 · Fsw · Im where Im: output current effective value, Fsw: switching frequency K1, K2: constant determined by modulation factor (A) and load power factor K3 : Constant determined by element constant The element loss Pd is the sum of the FVD loss and the switching loss, and can be expressed as Pd = Pfvd + Psw = (K1 + K3 · Fsw) Im + K2 · Im ² (6) from the relationship of the equation (5). The element cooling device is designed to be able to handle the element loss shown in the expression (6) in the output current and the switching frequency during normal operation, and generally has some allowance. Therefore, the switching frequency setting means 2 determines the switching frequency Fsw for each operation mode as follows, using the switching frequency at the time of the normal operation command as the reference frequency. At the time of the propulsion operation command, the switching frequency Fsw2 is set so as to fall within the range of the element loss during normal operation or within the range of the design margin in order to suppress an increase in element loss due to an increase in the output current command. At the time of a unit cut operation command, the switching frequency Fsw2 is gradually reduced as the number of unit cuts increases. Further, at the time of the car wash operation command, the switching frequency Fsw2 is reduced within a range where the output current ripple does not matter. In the present embodiment, since the switching frequency of the switching element is set to be lower than that in the normal operation by the output of the operation mode setting means 1, even in a mode other than the normal operation, the switching element loss is smaller than that in the normal operation. Is limited to a range that does not greatly increase. As a result, it is not necessary to increase the size of the cooling device for the element, and a highly efficient and compact device can be realized. In the special operation mode, it is possible to reduce the switching frequency after operating for a predetermined time using a normal switching frequency up to the limit of the temperature rise of the device or element. In this case, there is an effect that output current distortion can be minimized.

Next, in particular, when a car wash operation command is issued, a low speed and constant speed operation of about several kilometers per hour is required, so that a large element current continuously flows during the car wash, and element loss is remarkable.
Therefore, when the increase in loss cannot be suppressed only by lowering the switching frequency, the effect is further improved by limiting the output current together with the lowering of the switching frequency. In such a method, it is possible to limit the output current at the same time as the switching frequency is reduced. However, as shown in FIG. 8, the switching frequency is reduced from Fsw1 to Fsw2 at the time T1 when the special operation command is turned on. After a lapse of a predetermined time, the upper limit value of the output current is set to Im at time T2.
It is more desirable to reduce from ax1 to Imax2. In this case, there is an advantage that the same acceleration performance as that during normal operation can be realized without reducing the vehicle performance until time T2. FIG. 7 shows another embodiment of the present invention in a car wash operation command. In the present embodiment, the speed control system is incorporated in the frequency / voltage setting means 4 of FIG.
A low-loss operation is performed by reducing the output current of the inverter. That is, as shown in FIG. 9, when the car wash operation command is turned on at time T1, the switching frequency is reduced from Fsw1 to Fsw2, and at the same time, the operation of switching from the normal operation to the constant speed operation is performed. Here, the car wash operation command is provided with a switch button dedicated to the car wash operation on the operation panel of the cab, and by operating this switch button, the control system in the car wash operation mode is operated. 7, reference numeral 41 denotes current command setting means, 42 denotes speed adjusting means, 43 denotes a changeover switch for switching a current command in accordance with a car wash operation command, 44 denotes current adjusting means, 45 denotes speed calculating means, 46 denotes a coefficient unit, and 47 ~ 4
9 indicates an adding means. In the example of the frequency / voltage setting means, during normal operation, the changeover switch 43 is turned off, and the current adjusting means 4 is set so that the deviation between the current command Im * from the current setting means 41 and the output current detection value Im is eliminated.
4 calculates the slip frequency command Fs * of the induction motor and calculates the sum with the detected value Fr of the motor rotor frequency to create an inverter frequency command Fi. The output voltage command E
Is created by multiplying the inverter frequency command Fi by the coefficient K of the coefficient unit 46 so that the ratio between the frequency and the voltage becomes substantially constant. On the other hand, when the car wash operation command is turned on, the changeover switch 43 is switched to the on side, and the constant speed operation is performed by the speed control system. That is, the vehicle speed Vt is calculated from the motor rotor frequency Fr by the speed calculating means 45, and the speed Vt is made to coincide with the speed command Vt *.
The speed adjusting means 42 calculates and outputs a current command Im *. Other operations are the same as those in the normal operation. in this case,
After a predetermined time has elapsed after the changeover switch 43 has been switched to the ON side, as shown in FIG. 8, at time T2, the upper limit value of the output current decreases from Imax1 to Imax2. As described above, the switching frequency reduction control is performed, and at the same time, constant speed automatic operation in which the low speed for the car wash operation command is set in advance is realized, and the upper limit value of the output current of the inverter is reduced from Imax1 to Imax2. It is possible to operate the vehicle while suppressing the fluctuation.

The method of determining the operation command based on the command from the driver's cab or the like has been described above. However, it is also possible to shift to the special operation by detecting the current operation state as described below. . That is, as shown in FIG. 10, when it is detected at time T1 ′ that the vehicle is in the low-speed operation in which the driving state is maintained, the switching frequency is changed to Fsw.
Immediately drop from 1 to Fsw2. Further, when the low-speed operation continues, after a predetermined time has elapsed, the upper limit value of the current command is switched from Imax1 to Imax2 at time T2 '.
Here, as shown in FIG. 11, when the vehicle speed Vt is equal to or less than the set speed Vset and the duration T is equal to or more than the set value Tset, SWVL = 1 and the low speed detection signal is set to 1, as shown in FIG. In other cases, SWVL = 0 and the low-speed detection signal is set to 0. By treating the low speed detection signal as the special operation command described above, the operation state is automatically detected, and the operation can be performed without greatly increasing the loss.

Although the above embodiment has been described by taking an induction motor as an example of the load, similar effects can be expected with other AC motors and load devices. Although all of the above embodiments have been described with respect to inverters, the output terminals of these inverters are connected to an AC power supply via a reactance element, and operate as a converter for converting AC to DC (operation similar to the regenerative operation of the inverter). ). In this case, the same effect as that of the inverter can be expected.

[0012]

According to the present invention, when the train operation mode is the special operation mode of the car wash operation in which the low speed operation is continued when the train is washed, the switching frequency of the switching element is lower than that in the normal operation. In addition, since the inverter frequency command and the output voltage command corresponding to the current command in the special operation mode are output, the generation loss of the switching element is limited to a range that does not greatly increase compared to the normal operation. An efficient and compact device can be realized. In addition, the present invention is particularly useful when applied to a power converter that uses an AC motor such as an induction motor to drive an electric vehicle and supplies power to the motor.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing an example of a setting method of a switching frequency.

FIG. 3 is a diagram showing an example of a voltage command and an output voltage waveform.

FIG. 4 is a diagram showing an example of a gate signal generation method.

FIG. 5 is a diagram showing an example of a voltage command and an output voltage waveform.

FIG. 6 is a diagram showing an example of an operation mode setting.

FIG. 7 is a configuration diagram showing another embodiment of the present invention.

FIG. 8 is a diagram showing an example of a setting method of a switching frequency and a current command upper limit value.

FIG. 9 is a diagram illustrating an example of a setting method of a switching frequency.

FIG. 10 is a diagram showing an example of a setting method of a switching frequency and a current command upper limit value.

FIG. 11 is a diagram showing one method of low-speed detection.

[Explanation of symbols]

 1 operation mode setting means 2 switching frequency setting means 3 gate signal generation means 4 frequency / voltage setting means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keiji Jimbo 1070 Ma, Katsuta-shi, Ibaraki Pref.Hitachi, Ltd.Mito Plant

Claims (7)

[Claims] 1. An inverter for converting a DC voltage into a variable frequency, variable voltage AC voltage, pulse width modulation control means for controlling on / off of a switching element constituting the inverter, and driving the electric vehicle by the inverter. Means for setting a special operation mode of a car wash operation in which low-speed operation is maintained during a car wash time of a train including a normal operation mode in a control device for an electric car including the device, and switching according to the operation mode. A control device for an electric vehicle, further comprising means for setting a switching frequency of an element, wherein the switching frequency of the inverter is reduced in the special operation mode. 2. An inverter for converting a DC voltage into a variable frequency, variable voltage AC voltage, pulse width modulation control means for controlling on / off of a switching element constituting the inverter, and driving the electric vehicle by the inverter. Means for setting a special operation mode of a car wash operation in which low-speed operation is maintained during a car wash time of a train including a normal operation mode in a control device for an electric car including the device, and switching according to the operation mode. Means for setting the switching frequency of the element, means for switching between the current command in the normal operation mode and the current command in the special operation mode, and frequency / voltage setting means for the inverter including a speed control system are provided. When switching to the special operation mode, while reducing the switching frequency of the inverter, A control device for an electric vehicle, which outputs an inverter frequency command and an output voltage command according to a current command in the special operation mode via a speed control system. 3. An inverter according to claim 2, wherein an induction motor is used as the electric vehicle drive device, and the frequency / voltage setting means of the inverter compares a current command with a detected output current value of the inverter in the normal operation mode. Calculate the slip frequency command, take the sum of the slip frequency command and the detected value of the induction motor rotor frequency, output the inverter frequency command and the output voltage command, and switch to the special operation mode when in the special operation mode. A control device for an electric vehicle, wherein a current command is calculated by comparing a speed command with a detected value of an induction motor rotor frequency. 4. The car wash operation control system according to claim 1, wherein a switch button dedicated to car wash operation is provided on an operation panel of a cab, and when the switch button is operated, the control system of the car wash operation is activated. Electric vehicle control device. 5. An electric vehicle control device according to claim 1, wherein the pulse width modulation control means includes unipolar modulation and dipolar modulation. 6. The switching frequency setting means according to claim 1, wherein the switching frequency setting means operates at a normal switching frequency for a predetermined time in the special operation mode other than the normal operation mode. A control device for an electric vehicle, characterized by lowering the power consumption. 7. The switching frequency setting means according to claim 1, wherein the switching frequency setting means changes the switching frequency of the inverter immediately upon detecting that the normal operation mode is switched to the special operation mode. The control device for an electric vehicle, wherein the frequency / voltage setting means of the inverter detects the special operation mode when the special operation mode has continued for a set time or more, and lowers the upper limit value of the current command.