JPH04200202A - Driving method for de electric vehicle through voltage type vvvf inverter - Google Patents

Abstract

PURPOSE:To lower fault rate and to enhance reliability by disposing a switch between inverters thereby disconnecting a faulty inverter upon occurrence of fault while furthermore forming a bypass circuit for driving a DC electric vehicle through the remaining inverters connected in series. CONSTITUTION:Upon detection of a fault in an inverter 31, open switches 51, 52 relevant to the inverter 31 function. In other words, contacts thereof switch from side A to side B to disconnect the inverter 31 while at the same time a bypass circuit 61 is formed. Since input current of inverter flows through the bypass circuit 61, a sound inverter 32 can sustain operation. Upon disconnection of the faulty inverter, input voltage to the remaining sound inverters increases to cause increase of their output and thereby output of the entire inverter system is prevented from decreasing after disconnection of the faulty inverter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving a DC electric vehicle using a voltage type VVVF (variable voltage variable frequency) inverter.

[Prior Art] The applicant has previously proposed a voltage source inverter connected in series on the DC input side.

FIG. 4 is a schematic diagram showing such a proposed method. In the figure, 1 is a pantograph, 2 is an inverter input circuit consisting of a switch, an axle, etc., 31 to 34 are voltage type inverter units, and 41 to 44 are electric motors for driving the vehicle. The inverter unit 31 includes, for example, a voltage type unit inverter 311 and an input capacitor 312 as shown in FIG.
, a resistor 313, a semiconductor chopper 314, etc., and the other inverter units 32 to 34 are also similar.

In this way, when voltage source inverters are connected in series, if the load (motor) of each inverter becomes unbalanced, the input voltage of each inverter also becomes unbalanced. For example, the input terminal of a unit inverter with a reduced load may rise, possibly causing the inverter to fail. Therefore, when the load current of a unit inverter decreases, the semiconductor chopper connected to the DC side of the unit inverter is operated to divert the decreased load current to the series circuit of the semiconductor chopper and the resistor. Try to keep the input voltage approximately constant.

[Problem to be Solved by the Invention] However, when multiple inverters are connected in series in this way, if one inverter or the motor connected to it breaks down, the system will fail even if all the remaining inverters are healthy. The overall result is a failure. In other words, there is a problem that the failure rate of the system increases and reliability decreases.

(Means for solving the problem) A plurality of voltage type unit inverters that collect current from a DC overhead contact line and drive an electric car motor are connected in series on each DC input side, and a switch is provided between each of the unit inverters. When a unit inverter fails, the switch disconnects the failed inverter to form a bypass path, and the remaining inverters connected in series drive the electric vehicle.

[Function] When driving a DC electric vehicle, the number of driving electric motors per vehicle is usually four, and the number of inverters connected in series is four accordingly. The contact line voltage of DC electric cars is generally 15
00V, so the input voltage of the 4 series inverter is 375V.
becomes. On the other hand, the input terminal of a transistor inverter used for driving a vehicle can use about 700V. The present invention is based on the performance of such a transistor inverter.
Assuming that the inverter has failed, disconnect this failed inverter and
Even as a stand, the inverter input voltage per groove is 500
Focusing on the fact that V can be used sufficiently, a switch is installed between the inverters.If an inverter fails, it disconnects the faulty inverter, forms a bypass circuit, maintains the current path of the healthy inverter, and connects the inverter in series. By driving the DC electric vehicle with the remaining inverter, the failure rate is reduced and reliability is improved.

(Embodiment) Fig. 1 is a block diagram showing an embodiment of the present invention. In the figure, 51 to 5'8 are inverter open switches;
61 to 64 are bypass circuits.

FIG. 2 is an explanatory diagram for explaining the opening operation of a faulty inverter, and shows a case where inverter 31 is faulty and inverter 32 is healthy.

Therefore, when it is detected by means not shown that a failure has occurred in the inverter 31, the open switches 51 and 52 related to the inverter 31 are operated. The eight contacts are switched to the B side as shown in FIG. 2, and the inverter 31 is disconnected from the circuit, while a bypass circuit 61 is created. Since the inverter input current flows as shown by the broken line in FIG. 2, the healthy inverter 32 can continue operating.

FIG. 3 is an example in which the number of open switches is reduced compared to FIG. 1. Note that 71 to 74 are open switches, and the number thereof is about half that of the one in FIG.

Here, the performance of the inverter will be explained.

In the case of an electric car system with four 1500cm DC electric cars connected in series, if one car breaks down and is released, there will be three cars, and the input voltage per car is 500V, which will not cause any problems such as inverter operation.

Next, the opening operation of the failed inverter will be explained.

-C, failure detection and protection of the inverter itself (including the electric motor connected to the inverter) has been conventionally performed. Upon detection of this failure, a protective circuit breaker in the input circuit 2 is operated to temporarily stop the operation of the inverter system, and then the failed inverter is disconnected by an open switch, and the remaining healthy inverters are operated. At this time, the open switch may be automatically operated in response to a failure signal, or may be operated manually.

Note that a voltage-type PWM inverter or a voltage-type square wave inverter can be used as the voltage-type inverter.

〔Effect of the invention〕

According to the present invention, since an open switch is provided in the input circuit of the inverter, 1) Even if an inverter fails, only the failed inverter can be disconnected and operation can be continued with other healthy inverters, so that the inverter system can be Trajectory is significantly improved.

ii) After the faulty inverter is disconnected, the input voltage of the remaining healthy inverters becomes higher, which not only increases the output of the healthy inverter, but also reduces the decrease in the output of the entire inverter system after the faulty inverter is disconnected. This effect is particularly great in the case of vehicle drive, since there is little deterioration in vehicle performance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining the opening operation of a failed inverter, and FIG.
4 is a block diagram showing an embodiment of the present invention, FIG. 4 is a schematic diagram showing a proposed system, and FIG. 5 is a detailed diagram of the inverter shown in FIG. 4. Code explanation 1...Pantograph, 2...Input circuit, 31-34
... Inverter, 41 to 44 ... Vehicle drive electric motor,
51-58.71-74...Open switch, 61-6
4... Bypass circuit, 311... Voltage type unit inverter, 312... Input capacitor, 313...
Resistor, 314... semiconductor chopper. Agent Patent Attorney Akira Namiki

Claims (1)

[Claims] 1) When a plurality of voltage-type unit inverters that collect current from DC overhead lines and drive motors for electric cars are connected in series on each DC input side, and a switch is provided between each of the unit inverters, when a unit inverter fails. The voltage type VV is characterized in that the switch disconnects the failed inverter to form a bypass path, and the remaining inverters connected in series drive the electric vehicle.
A method of driving a DC electric car using a VF inverter.