JPS60200703A - Controller of ac electric railcar - Google Patents

Abstract

PURPOSE:To prevent an overvoltage phenomenon at a current interrupting time by inserting a resistor into a rectifier output circuit in a current interrupting range. CONSTITUTION:An AC power is supplied through a rectifier 3, filters 4, 5 and a power controller 6 to a DC series motor. When a filter capacitor voltage Vc becomes larger than a pattern voltage (limiting voltage) Vp at this time, a phase shifter 14 outputs a signal, and a switching unit 10 flows a current to a resistor 11 to suppress the voltage Vc. Thus, the phenomenon that the peak is charged to the capacitor 5 can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a control device for an electric vehicle, and particularly to a speed control device for an electric vehicle running in an AC section.

[Background of the invention]

FIG. 1 is a main circuit configuration diagram of the prior art. In the figure j
is a pantograph that receives power from an AC overhead line; 2 is a transformer; 3
4 is a rectifier, 4 is a filter reactor, 5 is a filter capacitor, 6 is a power control device, and as a typical example, a chopper 61. A freewheeling diode 62 is shown.

7 is a current smoothing reactor, 8 is an armature of a DC series motor, and 9 is a field winding thereof. That is, AC power is converted to DC power by a rectifier 3, and smoothed DC power by filters 4 and 5 is produced. This DC power source is controlled to have a wide range of voltage from 0 volts to the maximum DC voltage by the action of the power control device 6, and is used to control the speed of the DC series motor. FIG. 2 is a characteristic diagram showing the voltage fluctuation rate of FIG. 1. 1. is the direct current flowing through the filter reactor 4, V
c is the filter capacitor voltage. In Figure 2, the characteristic a
-b-C is Vc-Ic1 assuming that the DC current waveform never becomes 0 ampere, that is, there is no intermittent current.
It is a characteristic. However, in reality, when the load is small and the current that the power control device 6 takes in from the filter capacitor 5 becomes small, the current waveform flowing through the filter reactor 4 becomes an intermittent waveform, and the average value of the filter capacitor voltage is rise like. Here, I is the intermittent limit current.

In other words, ■ has a current waveform with a pulsating current rate of 100%.

If the effective value of the main transformer secondary voltage is 02, then o in Figure 2
The magnitude of -d is 5X e 2.

That is, the filter capacitor is charged with the peak voltage value of the AC secondary voltage. Usually, such a phenomenon is sometimes referred to as peak charging.

As can be seen from Figure 2, peak charging causes an apparent increase in the voltage fluctuation rate, which not only causes problems in vehicle performance, but also reduces the withstand voltage of elements used in power control equipment, including the withstand voltage of filter capacitors. leading to an increase in
A hardware problem occurs. As a countermeasure to this problem, it is easy to think of cascading a large number of rectifiers, and using some of them as mixed bridge type rectifiers that can vary the DC output voltage. In this method, peak charging can be avoided since the rectifier output can be throttled when the voltage of the filter capacitor exceeds a certain predetermined value.

However, rectifiers require an additional thyristor arm, which makes the circuit layout large and complicated.Furthermore, phase control increases alternating current distortion, which is undesirable in terms of inductive disturbances and makes the device expensive. be. Another measure against peak charging is to always insert a resistor at the output end of the rectifier or in parallel with the filter capacitor to provide a dummy load to avoid current interruption, but this method requires a large resistor capacity. In addition, there are many drawbacks, such as being an inefficient electric car that is energy-saving.

[Purpose of the invention]

An object of the present invention is to provide a control device that is economical and has no problems even at the peak of efficiency by using resistors only in areas where current is interrupted.

[Summary of the invention]

In the present invention, a resistor is inserted into the rectifier output circuit in the region of intermittent current, and the resistor current is controlled so that overvoltage does not occur.

[Embodiments of the invention]

FIG. 3 shows a circuit groove diagram for explaining the present invention in detail. 1
0 is a switchgear (shown as a chopper in Figure 3);
11 is a resistor, 12 is a voltage detection device, and 13 is a comparator that detects the pattern voltage Vp and the filter capacitor voltage V. Which difference is taken and its deviation AV is given to the phase shifter 14. The output signal (phase angle) of the phase shifter 14 is given to the switchgear jO via the gate control device 15. In other words, the filter capacitor voltage ■6 is the pattern voltage (that is, the limiting voltage) v
When the voltage becomes larger than p, the phase shifter 14 outputs an output, and the switchgear 10 causes current to flow through the resistor 11 under phase control so as to suppress the □ filter capacitor voltage Vc. This avoids peak charging of the filter capacitor 5. The switching device 10 can be made small in size by using a chopper using a G'rO thyristor.

According to the embodiment of the present invention, there is no need to increase the size of the rectifier 3, there is no problem with induction disturbance, and the current flowing through the resistor can be suppressed to the necessary minimum value, so there is no problem with efficiency. This has the effect that the electrical components to be added can be made relatively compact and can be almost ignored.

Although the power control device 6 is described as a chopper in FIGS. 1 and 2, the present invention can also be applied to an inverter device. In the case of an inverter device, the drive motor is not a DC series motor but a commutatorless motor.

〔Effect of the invention〕

According to the present invention, it is possible to prevent an overvoltage phenomenon when the current is interrupted, so it is possible to provide a control device that is economical and has no problems in terms of effectiveness.

[Brief explanation of drawings]

FIG. 1 is a main circuit diagram of a conventional embodiment, FIG. 2 is a characteristic diagram illustrating problems of the conventional technology, and FIG. 3 is a circuit diagram showing an embodiment of the present invention.

Claims (1)

[Claims] 1. Consisting of a transformer, a rectifier connected to the secondary side of the transformer, and a power control device that uses the DC output voltage of the rectifier as input to control the power given to the drive motor. 1. A control device for an AC electric vehicle, characterized in that the output circuit of the wave rectifier is provided with a resistor, and a switching device for controlling a current flowing through the resistor.