JPS5935573A - Constant margin angle control system for multistage cascade thyristor converter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a constant margin angle control method for a power converter in an AC electric vehicle when a power converter for driving a main motor is operated by a separately excited inverter to perform regenerative operation.

If a thyristor uniform bridge is used as this type of electric converter, a regenerative brake capable of separately excited inverter operation can be realized. Adopting this AC regenerative braking has major advantages over the dynamic braking method from the viewpoint of energy saving, such as a smaller brake device, lighter weight, and more effective use of electric power through secondary regenerative power.

Figure 1 (α) shows the DC output voltage waveform during operation of a separately excited inverter with a Sirisk uniform bridge, and generally the power factor and DC output voltage are lower than during forward conversion operation due to the minimum control advance angle βm. , the harmonic current on the AC side increases. In addition, in the same figure, if the time corresponding to the commutation margin angle δ obtained by subtracting the commutation type angle U from the minimum control advance angle βm exceeds the turn-off time of the side risk, commutation failure occurs and a DC short circuit occurs. Therefore, the magnitude of the commutation margin angle δ is
It is necessary to control so that the turn-off time of Cyrisk is always exceeded. On the other hand, in the case of AC electric vehicles, the magnitude of the reactance on the power supply side changes depending on the length of the feeder wire, and the percent impedance can reach as much as 20 factors at the farthest point from the substation. The angle becomes very large.

In the so-called constant minimum control advance angle control method in which the minimum control advance angle βm is always fixed at a constant value, the commutation weight angle U
The minimum control advance angle βm must be set so that the necessary commutation margin angle can be obtained under the operating conditions where
For this reason, as shown in Fig. 1 fbJK, under operating conditions where the commutation margin angle is small, the commutation margin angle δ is larger than necessary and the regenerative power factor becomes extremely poor, resulting in insufficient regenerative power. This causes the inconvenience of not being able to obtain the required amount. In AC electric cars that operate at relatively low speeds, such as those on American lines, if the electric braking force is insufficient during regenerative braking operation, it is supplemented by pneumatic brakes, but in high-speed cars it is supplemented by mechanical brakes. is impractical due to severe wear.

For this reason, especially when putting AC regenerative braking systems into practical use in high-speed vehicles such as Shinkansen trains, it is desirable to always control the margin angle to a constant value in order to obtain sufficient regenerative braking force from high speeds.

Next, such a constant commutation margin angle control method will be explained.

The relational expression between the commutation margin angle δ and the minimum control advance angle β is given by the following equation.

δ = βm −u = c−os−′(c′6sβm
10('2・Xp・Id/E7))・=(+1
However, U2 commutation angle, Ep: AC power supply voltage value,
Id: Direct current (when completely smooth).

Xp: Indicates AC side reactance.

In the minimum control advance angle constant control method, co
If sβm is constant and Xp・Id increases, the margin angle δ
decreases. Therefore, as mentioned above, the value of the minimum control advance angle must be set so that the value of the margin angle δ is greater than the specified value under the condition that the commutation angle U is maximum.Xd-Idl
In a state where the start value is small (such as when passing directly under a substation or in a speed range where Id is small), the value of the margin angle δ becomes unnecessarily large, which may cause a decrease in the output voltage and power factor.

As a countermeasure for this, it is possible to control the value of the minimum control advance angle βm according to changes in Xp・Id/Ep, that is, changes in the commutation weight angle, so that the size of the margin angle δ is always kept at a constant value. A nearly constant power factor can be obtained regardless of the state. In this case, by making the set value of the margin angle δ as small as possible and greater than the turn-off time of the sirisk, a significant improvement in the power factor can be expected, and at the same time, it is possible to reduce the harmonic current of the overhead wire.

On the other hand, to explain the main circuit of an AC electric vehicle with reference to Fig. 2, the secondary windings 21 to 26 are divided to reduce harmonic currents on the power supply side of the main transformer 2 that inputs the AC power supply 1, and the si-risk is uniform. The main converter 6 is constructed by connecting the unit converters 61 to 66 formed of bridges, and cascading the unit converters 61 to 66 to each other. Armatures 51 to 54 of a DC motor are connected to the raw converter 6 via a flat sliding axle 3. In the figure, 41 to 44 indicate field windings of the motor, which are controlled by a field converter (not shown) connected to the secondary winding of the main transformer 2.

The main converter 6 is one unit converter 66 that performs phase control.
The main converter 6 is controlled by a vernier control method.The main converter 6 is controlled by a vernier control method.

When applying the constant margin angle control method to the main converter 6 having a multi-stage cascaded thyristor bridge configuration in such a circuit,
The problem is the influence of the margin angle control system on the current control system.

Figure 3 shows the DC voltage waveform of the converter when the separately excited inverter is operating.If the minimum control advance angle increases by △θ from βm due to the command from the margin angle control system, △E corresponds to the shaded area. decreases. During this period, the voltage generated by the main motor is almost constant, and after half a cycle, the DC current increases by an amount equivalent to △E.The more bridges that are changed at the same time by △θ, the larger the increase becomes. .

If this increase in DC current is large, the value of the margin angle may become smaller, and in this case, the minimum control advance angle is controlled to become even larger, so the margin angle control system diverges and the DC current If the amount continues to increase, there is a risk of commutation failure.

In response to the increase in the DC current, a normal current control system using a vernier control stage works, but the main converter 6 is cascaded in multiple stages as shown in FIG. The amount of change in the DC current generated by the margin angle control system is quite large for the main converter as a whole.When attempting to correct the amount of change in the DC current generated from the margin angle control system using the vernier stage, a problem arises in that sufficient responsiveness cannot be obtained.

The purpose of the present invention is to eliminate the disadvantages of the conventional example, and to minimize the value of the commutation margin angle so that it always remains a certain constant value when operating thyristor converters connected in series in multiple stages with separately excited inverter operation. The normal current control system is not disturbed by the change in DC voltage that occurs because the control advance angle is changed and the minimum control advance angle is controlled, and as a result, the regenerative power factor is 2.
It is an object of the present invention to provide a constant commutation margin angle control method for multi-stage cascade-connected sirisk converters, which improves the regeneration rate and at the same time has the effect of reducing the AC side and the DC side pulsation rate.

According to the present invention, when changing the minimum control advance angle βm for constant margin angle control during separately excited inverter operation of a Sirisk converter in which unit converters are connected in cascade in multiple stages, This is achieved by limiting the number of unit converters that change the optimum control advance angle βm within a cycle to a specified value.

Embodiments of the present invention will be described in detail below with reference to the drawings.

First, to control the minimum control advance angle βm, step advance control is used in which the amount of change in βm is set in advance according to the phase angle of βm.
The cycle was kept within the specified value.

FIG. 4 shows a block diagram of this step progression control, and the margin angle detection circuit 8 is a circuit that detects the value of the commutation margin angle, and detects the value of the margin angle of each bridge. βm calculation unit 2
00 has a function of calculating and outputting the minimum control advance angle β2 of the next cycle, and is a comparison unit io.

It has a function to add or subtract one step from the current value to the voice value of the next cycle by a preset angle △θ, according to the comparison result between the margin angle detection value δ and the margin angle setting value δ0. .

For example, if detected value δ>set value δ0, the amount of change in βm is -
If Δθ, δ<δ0, set it to +Δθ and set the margin angle to the set value δ. control so that it approaches . Here, the smaller the value of △θ, the smaller the amount of voltage change, but on the other hand, the control response becomes slower, so it does not cause disturbance to the normal current control system.
．． /1@, the larger the value of Δθ, the better.

Second, the number of bridges that change βm within the same power supply half cycle is limited to one stage. When the unit converters 61 to 66 are connected in cascade as shown in FIG. 2, when all the bridges change the above-mentioned Δθ in the same direction at the same time,
It is necessary to suppress the amount of change in DC voltage within a specified value, and the value of Δθ must be made smaller as the number of cascaded stages increases.

Therefore, when the number of cascaded bridge stages is large, it is necessary to make the stage advancement step of the stage m considerably small, and a certain level of accuracy is required in terms of control, which is difficult to realize.

In addition, since the commutation angle U of each bridge is significantly affected by the mutual induction between the windings, if the minimum control advance angle βm of the multi-stage bridge is varied independently, There is a risk that the margin angle control system may become unstable due to interference.

Therefore, in the method of the present invention, the comparison section 100 and the βm calculation section 20
The margin angle control system is stabilized by providing a function to select the bridge to be controlled between 0 and 3 to limit the number of bridges to be controlled in one cycle.

For example, when the main converter 6 is configured by cascading four unit converters 61 to 64 as shown in FIG. 5, as shown in FIG. 6, δ1 to δ4 and βm1 to β? ? Z4 is the calculation result of the advance angle of the margin angle detection circuit corresponding to the first to fourth bridges of each unit converter 61 to 64. The margin angle detection values δl to δ4 are compared in magnitude with the set value δ0 in comparisons @101 to 104, respectively, to determine whether the minimum control advance angle of each bridge is increased or decreased in steps. The control stage selection unit 300 selects only one stage of the bridge that controls the minimum control advance angle βm according to the magnitude relationship of the margin angles δl to δ4 of each bridge, and selects the determination result of the comparator corresponding to the selected bridge. βm Notify the step advancement section. The minimum control advance angle values of all other bridges that are not selected are kept the same as in the previous cycle.

Therefore, according to this method, the amount of variation in the DC voltage that occurs in one cycle is the value that occurs when one bridge is changed by βm'il steps.

Next, the control stage selection section 300 will be explained. control stage 30
For example, the method for selecting the βm control stage with 0 is as follows:
If there is a bridge whose margin angle detection value δl to δ4 is equal to or less than the margin angle setting value, that bridge is selectively selected. If there are two or more bridges, the one with the smallest margin angle is selected and controlled every cycle. Conversely, if all the bridges are larger than the set value δ0, the bridges are selected in descending order of margin angle.

In addition, if there is a large difference in the commutation reactance of each bridge and a large difference in commutation weight angle occurs even if firing is performed with the same phase of βm, or if commutation interference between windings is large, id: There is a control method in which the firing order of βm of each bridge is set in advance so as to suppress the influence of pγ on the flow operation as much as possible. FIG. 7 is a diagram showing the current waveform during commutation operation of each bridge in this case, and i1 to $4 indicate the winding current of each bridge. Id is the value of the direct current in the case of complete smoothness. In the figure, the firing order of βm is from the largest to the first. 4th. Third. It is the second bridge.

This figure shows a case where i2 receives interference from the commutation of i3 and the commutation period is extended. In such a case, it is more stable from the viewpoint of the margin angle control system to control βm so as not to disturb the firing order of the voices of each bridge.For example, when the margin angle detection values are all larger than the set value δ0, Step back is performed in the order of 1st to 4th to 6th to 2nd bridges, and conversely, if even one bridge is less than δ0, for example, 2nd to 3rd to 4th to 1st bridges are returned.
If step progression is performed on the bridge's I stage, control can be performed without changing the order of βm. As a specific method for implementing this control stage selection section 300, for example, a microcomputer or the like may be used to determine the magnitude relationship of the detected margin angle values.

Although the above embodiment has been described in the case where the AC power source is single-phase AC, it can be similarly applied to the case where the AC power source is three-phase AC.

As described above, the method of the present invention is capable of keeping the amount of fluctuation in the DC output voltage that occurs due to changing the minimum control advance angle βm within a specified value when operating multi-stage cascade-connected Sylrisk converters with separately excited inverter operation. In order to suppress the margin angle, the margin angle can be controlled to a constant value without disturbing the normal current control system by limiting the number of unit converters that control the minimum control advance angle βm within the same power supply half cycle. The result is a regenerative power factor.

It is possible to improve the rotation tH rate, and at the same time reduce the harmonic current on the AC side and the pulsating current rate on the DC side.

[Brief explanation of the drawing]

Figure 1 is an output voltage waveform diagram of the thyristor uniform bridge converter during separately excited inverter operation, Figure 2 is a circuit diagram showing the main circuit of an AC electric vehicle, and Figure 3 is the separately excited inverter of the converter in Figure 2. Figure 4 is a block diagram showing step advancement control in an embodiment of the method of the present invention, Figure 5 is a block circuit diagram of the main converter section, and Figure 6 is a diagram of the DC voltage waveform during operation. FIG. 7 is a block diagram showing a case in which H7υ unit converters are restricted in the embodiment, and is a current waveform diagram during commutation operation of each unit converter in the method of the present invention. 1... AC power supply 2... Main transformer 21
~26... Secondary winding 3... Smoothing reactor 41-44... Field winding 51-54.
...DC motor armature 6...Main converter 61
~66...Unit converter 8.81~84...
... Margin angle detection circuits 100 to 104 ... Comparators 200 to 204 ... βm calculation section 300 ...
...Control stage selection section Applicant: Fuji Electric Manufacturing Co., Ltd.

Claims (1)

[Claims] When changing the minimum control advance angle βm for constant margin angle control during separately excited inverter operation of a thyristor converter in which unit converters are connected in cascade in multiple stages, the minimum control advance angle βm must be changed within the same power supply half cycle. Change 1 A constant margin angle control method for multi-stage cascaded thyristor converters, characterized by limiting the number of unit converters to a specified value.