JPH01144364A - Controlling method for multiple pwm converter - Google Patents

Abstract

PURPOSE:To promote its compact and lightweight design at a low cost by making the operating current (the maximum braking-current) for a power semiconductor equal among unit converters. CONSTITUTION:A controller of a triple-three phase PWM converter is equipped with AC current transformers (ACCT) 71-72, PWM controlling circuits 81-83 and a current operational circuit 104. A command value of the DC intermediate circuit voltage determined by a voltage setting 101 is compared with the output of a DC voltage detector 102 and is controlled by a voltage blind controller 100. The voltage blind controller 100 outputs the converter power Pc to the unit converter current operational circuit 104 so as to keep the voltage of the DC intermediate circuit constant. The operational circuit 104 derives a fundamental wave resultant current command value of a secondary winding from the converter power and the detection voltage ES. In addition, from the command value, a fundamental wave current command of each unit converter 41, 42, 43 is decided respectively. Accordingly, the maximum breaking-current value of each element can be equalized.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides a voltage type P in a transformer secondary winding divided into a plurality of parts.
The present invention relates to a method for controlling multiple PWM converters in which WM (Pulse Width Modulation) converters are connected and operated in multiple ways.

[Conventional technology]

Using a voltage source PWM converter as a power supply side converter,
A technique for increasing the power factor by making the current flowing to the power supply side sinusoidal is already known.

On the other hand, in order to apply this type of converter to AC electric vehicles such as Shinkansen, the AC power source must be an extra high voltage single phase.
In addition, since the converted power is on the order of several MW, due to the capacity of the power semiconductor, the secondary winding of the transformer mounted on the vehicle is divided into multiple parts, and a unit PWM converter is connected to each secondary winding. A multiple PWM co/verter scheme is used.

FIG. 3 is a schematic diagram showing a conventional example in which a triple PWM converter is applied to an AC electric vehicle. In the figure, 1 is a pantograph, 2 is an AC breaker, 3 is a main transformer, and 30
is its primary winding, 31 to 33 are secondary windings, 41 to 43 are unit converters, 51 to 53 are reactors, and 6 is a DC smoothing capacitor. Note that this example shows a case where a reverse conduction GTO is used as the power semiconductor element of the PWM converter. In addition, in the case of this type of multiplex converter, it is common to operate with a phase difference in the carrier signal between each unit PWM converter in order to reduce the harmonic current flowing to the power supply side through the transformer and secondary winding. be.

FIG. 4 shows an example of a 3-phase PWM control method for a 3-multiplex inverter. That is, the carrier signal CA of the unit converter 42 shown in FIG.
carrier signal C of the unit converter 43.
A is delayed by 120 degrees with respect to the carrier signal OA of the unit converter 42, as shown in FIG. In this way, many of the harmonic components contained in the transformer-order current due to PWM control are eliminated by providing a phase difference to each carrier signal, resulting in a primary current with less harmonic current.

In addition, FIG. 4 OCT shows a control signal.

FIG. 5 is a vector diagram showing the relationship between voltage and current of the PWM converter 41 shown in FIG.

In the figure, (a) shows the relationship during forward driving, and (b) shows the relationship during regenerative braking. In addition, l5 (the vector quantity is indicated by adding "r.") is the current of the secondary winding 31, E is the voltage of the secondary winding 31, the inductance of the L beam axle 51, and ω is the angle of the AC power supply. At frequency, EC is the converter input terminal voltage. In other words, ;Parameter input voltage Ec is Es
If the phase and magnitude of K are controlled to satisfy the relationship shown in FIG. 5, E and Is will be in phase, that is, the power factor will be 1. OK control is possible.

FIG. 6 is a schematic configuration diagram showing an example of a triplex three-phase PWM converter. Here, 100 is a voltage regulator, the output of which is a power command with a power factor of "1" for the secondary winding. 103 is a converter voltage calculation circuit which calculates and commands the AC voltage EC of the converter so that the vector relationship as shown in FIG. 5 is established. Based on this command value, PWM control circuits 111 to 113 control converters 41 to 43. FIG. 3 shows a case where a reactor is inserted externally to reduce AC ripple during PWM control, but generally the leakage reactance of the transformer is used and this external reactor is omitted.

Next, the transformer secondary winding is divided into many parts, and the PW
Let us consider the leakage reactance of the transformer when an M converter is connected. FIG. 7 shows each reactance when the secondary side of the transformer is divided into three parts. When the secondary winding is multi-divided, a reactance corresponding to the mutual induction between the windings is generated. In the example of FIG. 7, the reactance of the secondary winding 31 is the winding 1i [31's own leakage reactance Xll and the winding #il! 32 mutual leakage reactance X21% winding ll1133 mutual leakage reactance X31. Furthermore, a mutual leakage reactance Xpl between the second winding and the second winding is added. In other words, the combined reactance of winding 8131 is due to the current flowing through the other windings.
It fluctuates under its influence. Further, when the voltage of the negative winding is particularly high, the mutual leakage reactance between the windings and the leakage reactance of the windings are not equal due to restrictions on the arrangement of the windings. Therefore, the current ripple in each secondary winding will not be the same. FIG. 8 shows an example of this case. In addition, in the same figure, i3□ is the current of winding 1J31, i3□ is the current of winding 32, i
33 indicates the current of winding 'm33, respectively. From the figure, it can be seen that the equivalent actance of the winding 320 is small and the current ripple is the largest.

[Problem that the invention seeks to solve]

From the above, a multiple PWM converter in which a secondary winding is divided, a unit PWM converter is connected to this secondary winding, and these converters are operated in a multiple manner has the following problems.

(1) There is interference between the windings 1s, and the leakage reactance of each winding is not the same.

(2) Due to interference between the windings, the leakage reactance in terms of the secondary winding varies depending on the operating state of other converters.

(3) Due to the reasons in (11 and (2)), the current ripple of each converter is different.

(4) As a result of (3), the fundamental wave current of the converter is constrained by the winding with the largest current ripple,
The performance of the semiconductor element cannot be fully demonstrated, and the converter becomes large and expensive.

(5) (As a result of 31, there is a risk that the maximum operating current will exceed the allowable value of power semiconductor devices such as GTOs, leading to device destruction.

(6) (As a result of 31, the harmonic current of the -order winding increases.

Therefore, the present invention solves the above problems and maximizes the performance of semiconductor elements including GTOs. It is changed according to the magnitude of the winding reactance (or current ripple), and PWM control is performed based on this.

[Effect]

By changing the fundamental wave current value of each converter according to the magnitude of current ripple caused by interference between windings, the maximum cut-off current value of each semiconductor element is made equal, and the performance of the element is maximized. do.

〔Example〕

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

In addition, in the same figure, 71 to 72 are AC current transformers (A(,
"CT), 81 to 83 are PWM control circuits, 104 is a current calculation circuit, and the others are the same as in FIG. 6.

The command value of the DC intermediate circuit voltage determined by the voltage setting device 101 is compared with the output of the DC voltage detector 102 in the voltage regulator 100 and adjusted.

Voltage regulator 100 outputs converter power Pc equal to the power of the DC intermediate circuit to unit converter current calculation circuit 104 so as to keep the voltage of the DC intermediate circuit constant. In the unit converter current calculation circuit 104, this converter power and the secondary winding voltage E detected by the ACPT34,
From this, a predetermined calculation is performed to obtain the fundamental wave composite current command value I of the secondary winding, and further, from this I, the fundamental wave current command value 181 * isz l of each unit converter.
'Determine $3 for each. Here, the relationship between the current command value on the secondary side of each unit converter is as follows:
Use the following formula.

Is = Ist + IS2 + I33" = 3, and 1 t K2 * K3 is set according to the magnitude of each secondary current ripple. In other words, the peak value of the secondary current including the ripple of each winding is Set 1., 2., and 3 so that they are the same.

At this time, the leakage reactance of the secondary winding of the transformer and the composite reactance that takes into account mutual interference with other windings can be known in advance, so the current ripple of each converter corresponding to the control state of the multiple converter can also be calculated. It can be known in advance. That is, since the transformer current actance is known in advance, 1 r K2 pK3 can be set. Each unit converter PWM control circuit 81 to 83 sets the magnitude and phase of the converter input voltage EC in the state shown in the vector diagram shown in FIG.
M control.

The difference between the method according to the present invention and the conventional example is that, conventionally, each unit converter PWM control DOjlK has the same converter input voltage Ec
In contrast, in this invention, a secondary winding current command value is given to each unit, and converter input voltage Ec is determined from that value.
The point is that the secondary winding and ms flow are different for each unit converter in order to determine the magnitude and phase of.

From the above, since we know the current ripple in each winding, we can: Secondary winding current can flow.

FIG. 2 shows the operation of FIG. 1 in correspondence with FIG. 8. In FIG. 2, ImJIX is the maximum current of each unit converter, and each shows the same value. This means that
This indicates that the value of the fundamental wave current differs depending on the value of the ripple current of each unit converter. In addition, although the above explanation mainly concerned the single-phase case,
The same effect can be obtained by applying this invention in exactly the same way to a multiphase case.

〔Effect of the invention〕

By making the operating current of power semiconductors, such as the maximum cut-off current of self-grooved arc elements, the same between unit converters, the performance of the elements can be utilized to the fullest, making the converter smaller, lighter, and more economical. This makes it possible to reduce the price.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an embodiment of the present invention, Fig. 2 is a waveform diagram showing a secondary winding current waveform compatible with a unit converter according to the invention, and Fig. 3 is a 3-multiple single-phase P for AC electric vehicle.
4 is an explanatory diagram for explaining the control method of each converter in FIG. 3; FIG. 5 is a vector diagram showing the relationship between current and voltage of the unit converter; FIG. Figure 6 is a schematic configuration diagram showing a conventional example of a triplex three-phase PWM converter, Figure 7 is an explanatory diagram to explain the winding reactance of a transformer, and Figure 8 is a secondary winding for a conventional unit converter. FIG. 3 is a waveform diagram showing a line current waveform. Code explanation 3...Main transformer, 30...-Next winding stop,
31-33...Secondary winding, 34...AC transformer (CPT), 41-43...Unit converter, 6...Smoothing capacitor , 71~
73...AC current transformer (ACCT), 81~
83---PWM control circuit, 1°O...
Voltage regulator, 101... Voltage setting device, 102.
...DC voltage detector, 104...Current calculation circuit. Agent Patent Attorney Akio Namiki Agent Patent Attorney Kiyoshi Matsuzaki 141 Figure 1E2 Figure 3 Figure 4 Figure 1g5 (A) 15 csM 6 Figure 1 [Jj 100 1f7 Figure 8! l

Claims (1)

[Claims] At least two or more unit PWM (pulse width modulation)
The DC side of the converter is connected in parallel, and the AC side has a common iron core and its secondary winding is divided into multiple parts, each of which is connected to each winding of a transformer with a different equivalent reactance. For the converter, the magnitude of the fundamental wave current command value of each unit PWM converter is changed according to the magnitude of the equivalent reactance,
A method for controlling a multiple PWM converter, characterized in that each unit converter is PWM controlled based on this.