JPH0866055A - Power conversion apparatus - Google Patents

Abstract

PURPOSE: To obtain a power conversion apparatus which improves the power factor in the whole regenerative power range of an inverter constituted of a switching element which does not have any self-arc-extinguishing capability. CONSTITUTION: A power conversion apparatus is provided with a converter 3 by an element which is not self-arc-extinguished such as a thrysitor which controls a phase so as to obtain a DC output voltage, with a reactor 4 and with a capacitor 5, and an inverter 8 whose power can be regenerated and a motor 9 are connected as loads. A converter control device 7 sets a target capacitor voltage Ed* so as to be high according to the large input of detected inverter regenerative power Wr, i.e., according to a reduction in the value of regenerative power, when power is regenerated, and the ignition phase of the thyristor is controlled in such a way that the voltage Ed of the capacitor 5 becomes high. Consequently, in the converter constituted of the switching element which does not have any self-arc-extinguishing capability, a power factor can be improved when regenerative power is small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter provided with a converter for converting alternating current to direct current, which converter is composed of switching elements having no self-extinguishing ability,
The present invention relates to a power conversion device in which power regeneration operation is performed.

[0002]

2. Description of the Related Art When an AC power source is used to supply power to an inverter, a converter for converting AC to DC is generally required. As a conventional technique related to a power conversion device having a converter and an inverter of this type, for example, a technique described in Japanese Patent Laid-Open No. 2-307303 is known.

In this prior art, a converter for converting alternating current to direct current by controlling the phase of a thyristor bridge circuit, an inverter connected to the converter via a smoothing reactor and a smoothing capacitor, and an induction motor driven by the inverter. And controlling the output of the converter such that the voltage of the smoothing capacitor becomes a constant voltage, whereby the power running operation and the regenerative operation of the converter are performed.

[0004]

Generally, a converter composed of switching elements that do not self-extinguish is
During the regenerative operation, if the regenerative power increases, the commutation period (the period from the start to the end of commutation) becomes longer, and if the power regeneration does not end before the polarity of the AC voltage reverses, the commutation A failure may occur and it may become impossible to continue the regeneration of electric power. Therefore, the converter
Normally, even if the maximum amount of power regenerated from the induction motor through the inverter is reached, the power of the transformer must be kept constant so that power regeneration can be continued, that is, commutation failure will not occur. Constants such as the next voltage, reactor, and capacitor voltage are set.

As described above, the converter according to the prior art, which is constituted by the switching element which does not self-extinguish, sets the capacitor voltage so that the regeneration of the electric power can be surely continued. However, there is a problem that the power factor of the AC input is remarkably reduced as the regenerative power (equal to the power regenerated from the inverter) regenerated by the converter is reduced.

An object of the present invention is to improve the power factor of an AC input at the time of power regeneration, in a power converter including a converter composed of switching elements that do not self-extinguish, regardless of the magnitude of regenerated power. An object of the present invention is to provide a power conversion device that can continue power regeneration without causing commutation failure.

[0007]

Generally, in a converter composed of switching elements that do not self-extinguish, the power factor of the input AC is improved when the capacitor voltage is set high, so the capacitor voltage should be set high. As a result, it is possible to improve the power factor when the regenerative power is small. However, conversely, if the capacitor voltage is set high, the power that the converter can regenerate without causing commutation (regenerative power) becomes small, and the regenerated power regenerated is higher than the regenerative power of the converter. If it becomes too large, commutation failure will occur and it will become impossible to continue the regeneration of electric power.

According to the present invention, the above object is made based on the relationship between the regenerative power of the converter and the capacitor voltage as described above, and the regenerative power of the converter is reduced during the regenerative operation of the converter. Accordingly, the ignition phase of the converter is adjusted in the direction of increasing the capacitor voltage in a range in which the regenerative power of the converter is larger than the regenerative power regenerated from the induction motor through the inverter. Achieved by

[0009]

According to the present invention, the regenerative power is detected and the set value of the capacitor voltage is changed according to the detected regenerative power, so that the power factor of the converter is always maximized. It is possible to regenerate electric power in the range of all regenerated electric power without causing commutation failure.

That is, according to the present invention, when the regenerative power is large, the capacitor voltage is set low, and the regenerative power can be continuously regenerated without causing commutation failure.
Then, the regeneration of electric power is continued, and the braking force is applied to the induction motor driven through the inverter,
When the rotation speed of the electric motor decreases and the regenerative power gradually decreases, the capacitor voltage is set to be high as the regenerative power decreases.

As described above, the present invention can continue the operation of power regeneration without lowering the power factor of the converter and without causing commutation failure.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a power converter according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a diagram for explaining the characteristics of the power factor with respect to the regenerative power of the converter, and FIG. 3 is a diagram of the target capacitor voltage Ed * with respect to the regenerative power of the converter. FIG. 4 is a diagram for explaining the relationship, and FIG. 4 is a diagram for explaining the characteristics of the power factor with respect to the regenerative power of the converter according to the embodiment of the present invention. In FIG. 1, 1 is an AC power supply, 2 is the inside of the power supply, overhead line and main transformer impedance, 3 is a converter, 4 is a filter reactor, 5 is a filter capacitor, 7 is a converter control device, 8 is an inverter, and 9 is an induction motor. 10 is an inverter control device, 11 is a power running regeneration switch, 12 is a pantograph, 13 is a main transformer, 61 and 62 are voltage detectors, 63,
64 and 67 are current detectors, 65 is an effective motor current calculator, 66 is a pulse generator, 70 is a target capacitor voltage generator, 71 and 73 are subtractors, 72 is a voltage controller,
74 is a current controller, 75 is a multiplier, 78 is a phase generator,
79 is a gate pulse generator.

An embodiment of the present invention shown in FIG. 1 is one in which the present invention is applied to an electric power converter having an inverter for supplying electric power to an induction motor for driving a train and a converter connected to the inverter. Is. In the illustrated embodiment of the present invention, the ratio of the primary winding to the secondary winding, which receives power from the AC power source 1 including a power plant and a substation via the pantograph 12, is n, and the voltage Ep from the pantograph is Transformer 13 for lowering the transformer secondary voltage Es, and this transformer 1
A thyristor T which is a bridge-connected switching element having no self-erasing ability for rectifying the secondary voltage Es of No. 3
The converter 3 configured by h1 to Th4, the inverter 8 to which the DC power from the converter 3 is input through the power running regeneration switch 11, the filter reactor 4, and the filter capacitor 5, and the AC power from the inverter 8 It is composed of an induction motor 9 to be driven, a converter control device 7, and an inverter control device 10.

The converter control unit 7 includes a target capacitor voltage generator 70, subtractors 71 and 73, and a voltage controller 7
2, a current controller 74, a phase generator 78, and a gate pulse generator 79. Then, the target capacitor voltage generator 70 causes the multiplier 75 to detect the capacitor voltage Ed detected by the voltage detector 62 and the inverter DC current Iinv detected by the current detector 67.
A target capacitor voltage Ed * corresponding to the regenerative electric power Wr of the converter calculated by multiplying and is generated as described later. The subtractor 71 uses the target capacitor voltage Ed.
The capacitor voltage Ed is subtracted from *, and the value is input to the voltage controller (AVR) 72. The voltage controller 72 generates a DC current command value id * proportional to the voltage deviation (including not only proportional control but also integral control).

The subtractor 73 receives the direct current command value id *
DC current id is subtracted from the
R) 74. The current controller 74 generates a control delay angle α based on the given current deviation and inputs it to the gate pulse generator 79. In addition, the phase generator 78 detects the primary voltage Ep of the transformer 13 detected by the voltage detector 61.
Is input, and the electrical angle θ, which is the phase of the AC voltage obtained from this, is input to the gate pulse generator 79. The gate pulse generator 79 compares the input control angle α with the electrical angle θ and inputs a predetermined gate signal to the thyristor converter 3 based on the result.

On the other hand, the inverter control device 10 has a target effective current Imr for the induction motor 9 input from the outside.
*, And the effective motor current Imr calculated by the effective motor current calculator 65 based on the input current of the induction motor 9 detected by the current detector 64 (active current component in phase with the motor current), and attached to the induction motor 9. Motor rotation frequency fr detected by the pulse generator 66
Generates a predetermined gate pulse by the inverter 8
Control.

The embodiment of the present invention shown in FIG. 1 is provided with the above-mentioned configuration, and the inverter 8 and the converter 3 control the power running regeneration of the induction motor 9 for driving the electric vehicle.

Next, the capacitor voltage Ed and the regenerative power Wr
And the power factor of the converter will be described.

FIG. 2 shows the power factor characteristic of the thyristor converter with respect to the regenerative electric power Wr with the capacitor voltage Ed as a parameter. It can be seen from FIG. 2 that the power factor of the converter decreases as the regenerative power Wr decreases. FIG. 2 shows that when the capacitor voltage Ed is Ed0, the regenerative power Wr can be regenerated up to W0, and when the capacitor voltage Ed is Ed1, the regenerative power Wr is W1.
Regeneration is possible, and the capacitor voltage Ed is Ed2
In the case of, it is shown that the regenerative electric power Wr can be regenerated up to W2. However, in the above description, Ed0>Ed1>
Ed2 and W0 <W1 <W2.

That is, the capacitor voltage Ed is set to Ed0,
The maximum regenerable electric power W, which is the maximum electric power that the converter can regenerate when set to Ed1 and Ed2, is W0, W1, and W2, respectively, as shown in FIG. 2, and when more electric power is regenerated from the inverter 8, Cannot generate electricity due to commutation failure and continue power regeneration. Now
When the maximum value of the regenerative electric power Wr regenerated from the induction motor 9 via the inverter 8 is Wrmax, the thyristor converter 3 can regenerate the electric power in the range of the entire regenerative electric power without causing commutation failure. Needs to set the capacitor voltage Ed so as to satisfy the following expression (1) W> Wrmax (1).

Further, from FIG. 2, the maximum regenerative electric power Wrmax has a relationship of the following equation (2) W1 <Wrmax <W2 (2), so that the regenerative electric power W of the thyristor converter 3 has a margin, When the capacitor voltage Ed is set to be constant, it is appropriate to set the capacitor voltage Ed to Ed2.

On the other hand, as can be seen from FIG. 2, when the capacitor voltage Ed is set high from Ed2 to Ed1 and Ed0,
The power factor characteristic in the case of regenerating the regenerable power determined by the capacitor voltage can be improved. However, if the set value of the capacitor voltage Ed is increased, the regenerative electric power W of the thyristor converter decreases, so that the above formula (1) cannot be satisfied and the electric power cannot be regenerated up to the maximum regenerative electric power Wrmax. .

That is, in the converter, when the capacitor voltage Ed is set high, the power factor at the time of power regeneration can be improved, but the regenerable power W decreases, so that the power regeneration in the entire regenerative power range is possible. On the other hand, if the capacitor voltage Ed is set low in order to enable regeneration in the entire regenerative power range, the power factor improving effect at the time of power regeneration cannot be obtained.

As described above, in order for the thyristor converter 3 shown in FIG. 1 to continue regenerating electric power in the entire regenerative power region without failing in commutation, as described with reference to FIG. The maximum value of regenerative power is W
When rmax is set, it is necessary to set the capacitor voltage that satisfies the expression (1), that is, the capacitor voltage Ed to Ed2. However, when the regenerative power Wr decreases due to the decrease in the rotation speed of the induction motor 9 and Wr <W1,
When the capacitor voltage Ed is set to Ed1 and the regenerative power Wr is further reduced to Wr <W0, even if the capacitor voltage Ed is set to Ed0, the converter regenerates power without failing commutation. It is possible to continue.

Based on the above consideration, the present invention detects the regenerative power and variably controls the capacitor voltage Ed according to the magnitude of the detected regenerative power, that is, the regenerative power Wr. The capacitor voltage Ed is controlled so as to increase in accordance with the decrease of the power consumption, whereby the power regeneration can be continued without failing commutation in the entire regenerative power region, and the power factor can be improved. It is possible.

In FIG. 3, the capacitor voltage Ed at which the regenerative electric power W of the thyristor converter 3 becomes equal to the regenerative electric power Wr regenerated from the induction motor 9 via the inverter 8.
Value, that is, the limit value of the capacitor voltage Ed that enables the thyristor converter 3 to regenerate the regenerative electric power Wr regenerated from the induction motor 9 without causing commutation failure. However, in FIG. 3, Edmax
Is the maximum value of the capacitor voltage Ed determined by the breakdown voltage of the semiconductor elements forming the thyristor converter 3 and the inverter 8.

As can be seen from FIG. 3, with respect to the regenerative electric power Wr regenerated through the inverter 8, the capacitor voltage Ed
Is set lower than the characteristic curve shown in FIG. 3, the thyristor converter 3 can continue the regeneration of electric power without causing commutation failure. Also, the capacitor voltage Ed
By setting a high value, the power factor of the converter can be improved.

In the embodiment of the present invention, as described above, the capacitor voltage Ed is set with respect to the detected regenerative electric power Wr as shown in FIG.

That is, in the embodiment of the present invention shown in FIG. 1, the target capacitor voltage generator 70 is a multiplier 75.
A target capacitor voltage Ed * is generated according to the characteristic shown in FIG. Then, when the converter 3 is regeneratively operated, the converter control device 7 regenerates the regenerable electric power W of the thyristor converter 3 via the inverter in accordance with the target capacitor voltage Ed * from the target capacitor voltage generator 70. In order to increase the capacitor voltage Ed in a range that becomes larger than the
Thyristor Th1 which is a switching element constituting
Control the firing phase of Th4.

FIG. 4 shows the capacitor voltage Ed as the regenerative power Wr.
According to the power factor characteristics in the converter of one embodiment of the present invention when changed and set as shown in FIG. 3, and in the converter of the prior art when the capacitor voltage is set to Ed2 constant over the entire power range. The power factor characteristics are shown.

As shown by the slant lines in FIG. 4, according to one embodiment of the present invention, the power factor of the converter is greatly improved as compared with the case where the capacitor voltage is set to be constant Ed2 in the range of the entire regenerative power. You can see that That is, FIG.
An embodiment of the present invention shown in is, in the entire regenerative power range,
Electric power can be regenerated by improving the power factor of the converter.

In the above-described embodiment of the present invention, in order to generate the capacitor voltage target value Ed *, the regenerative power Wr of the converter obtained by the product of the capacitor voltage Ed and the inverter current Iinv is obtained and used. , The regenerative power Wr may be any value indicating the power regenerated by the converter. For example, the capacitor voltage Ed and the converter current id
It may be obtained as the product of

The operation of the above-described embodiment of the present invention has been described only when the embodiment of the present invention performs the power regeneration operation. However, during the power running operation, the capacitor voltage is set to the same value as in the prior art. It may be set to a constant value, or the characteristics of the target capacitor voltage generator may be switched so as to generate a target capacitor voltage corresponding to the output power of the converter.

Although the above-described one embodiment of the present invention has been described as the one in which the present invention is applied to the converter used for driving the train, the present invention uses the induction motor shown in FIG. 1 for other purposes. If the converter is used, the converter can be applied even if a three-phase alternating current is input. The present invention can also be applied to the case where a DC motor is connected to the output of the converter via a chopper circuit.

That is, the present invention can be applied to any system as long as the load on the converter has a power regeneration function.

[0037]

As described above, according to the present invention, in the converter constituted by the switching elements having no self-extinguishing ability, the power factor of the converter during power regeneration is reduced in the entire regenerative power range. In other words, the converter can surely continue the regeneration of electric power.

[Brief description of drawings]

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

FIG. 2 is a diagram illustrating power factor characteristics of a converter with respect to regenerative power.

FIG. 3 is a diagram illustrating a relationship between a target capacitor voltage Ed * and regenerative power of a converter.

FIG. 4 is a diagram illustrating a power factor characteristic with respect to regenerative power of a converter according to an embodiment of the present invention.

[Explanation of symbols]

 1 AC power supply 2 Impedance of power supply inside, overhead line and main transformer 3 Converter 4 Filter reactor 5 Filter capacitor 7 Converter controller 8 Inverter 9 Induction motor 10 Inverter controller 11 Power regeneration switch 12 Pantograph 13 Main transformer 61, 62 Voltage Detector 63, 64, 67 Current detector 65 Effective motor current calculator 66 Pulse generator 70 Target capacitor voltage generator 71, 73 Subtractor 72 Voltage controller 74 Current controller 75 Multiplier 78 Phase generator 79 Gate pulse generator

Claims (6)

[Claims] 1. A converter which is composed of a switching element that does not self-extinguish, and which converts an alternating current into a direct current by controlling the ignition phase of the switching element; In a power conversion device configured with a load that generates, a firing phase of a switching element that configures the converter is controlled in a direction in which a voltage of the capacitor increases in accordance with a decrease in regenerative power regenerated from the load. An electric power conversion device comprising: 2. The power conversion according to claim 1, wherein the regenerative power regenerated from the load is calculated based on a detected value of the actual voltage of the capacitor and a detected value of the actual current of the reactor. apparatus. 3. The electric power according to claim 1, wherein the regenerative electric power regenerated from the load is calculated based on a detected value of an actual voltage of the capacitor and a detected value of an actual current from the load. Converter. 4. The converter control means for controlling the ignition phase includes a target capacitor voltage generating means for generating a target capacitor voltage which is a voltage command for a capacitor corresponding to regenerative power regenerated from a load, 4. The power converter according to claim 1, 2 or 3, wherein the ignition phase of the switching element is controlled so that the voltage becomes a value lower than the target capacitor voltage from the target capacitor voltage generating means. 5. The power converter according to claim 1, wherein the load is composed of an inverter and an induction motor connected to the output of the inverter. 6. The power converter according to claim 1, wherein the load is composed of a chopper and a DC motor connected to an output of the chopper.