JPS58130702A - Power converting system for ac electric motor vehicle - Google Patents

Abstract

PURPOSE:To reduce the numbers of the secondary coils of a transformer and of unit converters by forming an intermediate tap at one of the secondary coils of the transformer respectively connected to the unit cnverters, connecting the converters of 6-arm bridge configuration to the coils, and controlling the phases of the converters. CONSTITUTION:An AC power source 1 is connected through a reactance 2 to the primary coil of a transformer 3, the secondary coil of the transformer 3 is divided into three segments, and the coil segments 37-39 are respectively connected to unit converters 47-49 which form a converter 4. The converters 47- 49 are sequentially connected in cascade to each other, and a load 6 is connected to the DC output side. The coils 37 are divided into segments 371, 372, a tap 373 is attached, and the converter 47 is formed in a 6-arm bridge configuration. In this case, the ratio of the secondary coils of the transformer 3 is set to 1:2:3:4, and the converter 47 is controlled in phase, thereby switching the converters 48, 49.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a power conversion system for an AC electric vehicle using a combination of a transformer having a plurality of secondary windings and a semiconductor power converter connected to each of the secondary windings of the transformer. It is related to.

In AC electric vehicles, the voltage applied to the DC drive motor is often controlled by a transformer and a semiconductor converter mounted on the vehicle to perform the cut-off tW node.

Furthermore, some AC electric vehicles are capable of regenerative braking and reversing by using a semiconductor converter capable of road conversion operation.

In either case, it goes without saying that it is desirable to reduce harmonics contained in the current flowing to the power supply side.

FIG. 1 is a circuit diagram showing a conventional example, in which an AC power source 1 is connected to the primary winding of a transformer 3 via a reactance 2, and the transformer 3
In a configuration in which the secondary winding of is connected to a load 6 as a DC drive motor via a transformer 4 and a smoothing reactor 5,
In order to reduce the harmonic current flowing to the power supply l side, the secondary winding of the transformer 3 is divided into multiple parts (into six parts in the figure), and each semiconductor unit converter 41 to 1 constituting the transformer 4 is connected to this. and each unit converter is connected in cascade.

By setting the winding voltage of some of the secondary windings lower than other windings, the phase of only the converter connected to this winding with low voltage is controlled according to the load voltage, and the other windings are controlled in phase. The converter connected to the winding operates as a switch to further reduce the harmonic current generated per power supply due to phase control.

FIG. 112 shows a specific example of the above control, which is generally called vernier control.

In FIG. 1, only the converter 41 connected to the lower voltage winding 31 of the secondary winding 31-860 of the transformer II3 is phase controlled.

FIG. 82 shows the operation during continuous operation, in which the phase of the converter 41 is controlled at operation notch 1, and the other converters perform switching operations, that is, freewheeling operations that bypass the load current. In operation notch 2, the converter 42 connected to the winding 32 having approximately the same voltage as the winding 31 is operated in a diode-like manner (
The converter 4 B-46 is operated in a freewheeling manner, and the converter 43 connected to the winding 33 whose voltage is approximately twice the voltage of the winding 31 is operated in a diode-like manner. Let and convert! 42. 44-46 perform freewheeling motion.

In addition, when switching from operation notch 1 to operation notch 2, the converter 42 is switched to diode-like operation at the time when converter 41 becomes diode-like operation, and at the same time, the output of converter 41 is switched to minimum output operation.

The switching from operating notch 2 to 3 occurs when the output of converter 41 reaches its maximum, and the output of converter 43 changes from free-wheeling operation to diode-like operation, and converter 42 changes from diode-like operation to free-wheeling operation. At the same time, the converter 41 is also switched from diode-like operation to minimum output operation.

Similarly, when switching from operation notch 3 to 4 and from operation notch 4 to 5, the converter is switched as shown in Figure 2. In this case, there is almost no fluctuation in the combined output voltage of the converter at the time of switching. Therefore, the load current is hardly affected. Furthermore, in the conventional method, in order to reduce the equivalent disturbance current JP° of the primary current in the operating range where the output voltage is large, as shown in the example in Fig. 3,
Even if each unit rectifier is commutated at the same time (the figure shows the case of a maximum of 10 notches), the commutation of each unit rectifier 6 is as shown in the figure (
As shown in b), the actances of the secondary windings are made to be different so that the windings are performed in an orderly manner.

In reality, the 1st to 9th notch operation is an acceleration operation notch and the operating time is short, but the 10th notch is a continuous operation notch and the operating time is very long. For this reason, J at 10 knots in particular
, reduction is a major issue, and reduction of Jp at the lO notch is attempted by performing a commutation operation as shown in FIG. 3 (bl).

However, in conventional vernier control, regardless of the magnitude of the converter output voltage, the phase-controlled winding is always the same, and the voltage is the lowest, and the winding voltage for switching operation is Almost the same as the phase control winding or 2
Since the number of secondary windings is doubled, the number of secondary windings required to obtain the necessary secondary voltage is also increased, and the number of unit converters connected in the ξ direction is also increased, resulting in an increase in the overall size of the eccentric arrangement. As is clear from Fig. 4, which shows the relationship between the equivalent disturbance power J, and the operating notch, when the converter output voltage is low, J at notch 9.10,
is much smaller than the notch 1.2, and in this operating range where the converter output is low, the harmonic current is reduced more than necessary.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the conventional example described above, reduce the number of secondary winding divisions of a transformer, and provide a transformer.

The present invention provides a power conversion system for AC electric vehicles that allows the converter to be made smaller and lighter.

According to the present invention, the secondary winding of the transformer is divided into a plurality of parts, each of the divided windings is connected with a unit converter constituting a positive semiconductor converter, and each unit replacer is connected in cascade. In an AC electric vehicle that connects and controls the voltage applied to a DC drive motor, windings that have almost the same commutation operation among the multi-divided windings connected to the switch operation converter are combined into one winding. At the same time, the unit converter connected to this unit uses a semiconductor with high withstand voltage to reduce the number of secondary windings of the transformer and the number of unit converters, and the secondary winding with the lowest voltage has a voltage ratio of 1. :
This is achieved by providing a tap at position No. 2, making the unit converter connected to this winding a six-arm bridge configuration, and operating this converter under phase control. In other words, if the windings perform almost the same commutation operation as shown in Figure 5 (Figure 5), the current will flow to the primary side even if the windings are connected in series and a unit converter is connected to this as shown in Figure (C). The current waveform becomes as shown in (d), which is almost the same as the current waveform in case (a). Therefore, the harmonic current of the -order current is almost the same in both Ic) and (a). However, although the voltage applied to the converter in case (C) is twice that in case (a), the number of elements is half that in case (1) by using a resistor with twice the withstand voltage.

On the other hand, almost the same effect can be obtained by creating a 6-arm bridge by taking out a tap from the middle of the windings connected in series as shown in (.).Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Figure 1116 is a circuit diagram showing an embodiment of the present invention.
is connected to the primary winding of the converter 3 via the reactance 2, the secondary winding of the transformer 3 is divided into three, and each winding 37 to 39 is connected to each unit converter 47 to 49 constituting the converter 4. The position converters 47 to 49 are connected to each other in cascade, and a load 6 is connected to the DC output side thereof via a smoothing reactor 5. Secondary winding 3 is winding 371 and 37
2 and tap 3γ3. The converter 47 connected to the secondary winding @37 has a six-arm bridge configuration.

In this case, the ratio of the secondary winding of the transformer 3 is set as follows, each unit converter 47 performs phase control, and 48
, 49 perform a switch operation. That is, the phase control unit converter 47 and the switch operation converters 48 and 49 perform vernier control.

FIG. 7 shows the operation during the 4-way operation, in which the converter 47 is operated under phase control (1) so that only the voltage of the winding 371 is output at operation notch l, and the other converters 48 and 49 are Through operation, that is, freewheeling operation that bypasses the load current is performed. At operating notch 2.3, the winding is 37!・
The converter 47 is phase controlled (2
), and the transducers 48 and 49 are freewheeling. At operation notch 4, the converter 4B connected to the winding 38 with a voltage approximately three times higher than the voltage of the winding 371 is operated like a diode, and the converter 47 is phase controlled (1) so that the voltage of the winding 371 is output. The converter 49 is caused to perform a freewheeling operation.

Note that FIG. 8 shows the output voltage waveform of the converter 47 during the phase control (1) operation and the phase control (2) operation. Switching from operation notch 3 to 4 involves switching the output of converter 48 from freewheeling operation to diode-like operation when the output of converter 47 reaches the maximum, and at the same time converter 47 also changes from diode-like operation to minimum output. Switch to action.

Thereafter, the converter is similarly switched from operation notch 4 to 5 and from operation notch 5 to 6 as shown in FIG. In this case, since there is no fluctuation in the combined output voltage of the converter during switching, there is also almost no fluctuation in the load current.

The solid line in FIG. 119 indicates J for the operating notch of the embodiment in FIG. 6, and the dotted line in the same figure is for the conventional system. As can be seen from the figure, J at the lO notch, which is the highest operating notch, is almost the same as in the conventional method. In the case of 8.9 notches, the phase control winding voltage is doubled, so J is slightly increased compared to the conventional method. Similarly, with the 5.6 notch and 2.3 notch, J increases slightly compared to the conventional one, but since it is an acceleration notch, there is no practical problem.As described above, according to the power conversion method of the present invention, the output voltage The number of transformer secondary windings and the number of unit converters can be reduced without increasing the harmonic current of the primary current in a high operating range, and the size and weight of transformers and converters can be reduced.

Although the present invention has been explained in the case of power-row operation, regenerative operation is also possible by configuring the unit converter with a thyristor uniform bridge, but it can also be applied to this type of converter, and similar effects can be expected. I can do it.

Although the above embodiment has been described only for the case of a unit converter for an AC electric vehicle, it is also possible to divide the transformer secondary winding into a plurality of parts,
The present invention can be similarly applied to a three-phase converter to which a converter is connected.

[Brief explanation of the drawing]

811 to 5 show conventional examples, FIG. 1 is a circuit diagram showing an example of a conventional power converter, and FIG. 2 is a relationship diagram between the operation notch and the converter showing the control method in case 1-. , Figure 3 and @Figure 5 are the voltage and current waveforms of the primary winding and the current waveform of the secondary winding, respectively, in the case of Figure 1, and Figure 4 is the relationship between the operating notch and the equivalent disturbance current during continuous operation. In the graph showing, on the other hand,
Fig. 6 shows an embodiment of the power conversion method of the present invention, edicts 7 and 8 are relationship diagrams between the operating notch and the converter showing the control method in the case of Fig. 6, and Fig. 9 is a diagram showing the relationship between the operating notch and the converter. It is a graph showing the relationship between the operating notch and the equivalent disturbance current during operation. l... AC power supply 2... Reactance 3... Transformer 4... Converter 37-39... Secondary winding of transformer 47-49... Unit converter 5... Smoothing Reactor 6...Load. T 1 Mouth 1/20 ■ : fll? -F/lff11t'lff30 ■

Claims (1)

[Claims] 1) The secondary winding of the transformer is divided into a plurality of parts, each divided winding is connected to a unit converter composed of a main semiconductor converter, and each unit converter is connected in cascade. In an AC electric vehicle that controls the voltage applied to a DC drive motor by using An AC electric vehicle characterized in that a unit converter having a six-arm bridge configuration is connected, and this converter performs a phase control operation, and the other converters perform a switch operation to perform vernier control of the converters. Power conversion system 0 2, AC electricity characterized in that the number of secondary windings of the transformer is 3 and the voltage ratio of these windings is 1=1:4/3 in claim 1. Car power conversion method. 3) A power conversion system for an AC electric vehicle, characterized in that one of the windings with a voltage ratio of 1 is wound with an intermediate tap in the first or second term of the range of 41111'F. ) 4I The power conversion system for an AC electric vehicle according to claim 1, characterized in that the intermediate tap of the transformer winding comes out from a position at a voltage ratio of 1:2.