JPS627376A - Controller for dc substation - Google Patents

Abstract

PURPOSE:To reduce power loss and change power running to regenerative running speedily, by stopping circulating current between a converter and an inverter, only on changing the power running to the regenerative running, and by limiting the circulating current. CONSTITUTION:The AC output of a power source is rectified by a converter 1, and DC power is fed to a load, and regenerative DC power generated by the load is converted to AC by an inverter 2 and is returned to the power source. By a current control amplifier 4, the input of deviation quantity between signal in proportion with the current of the converter 1 and a converter current set value is provided, and by a voltage control amplifier 5, the input of deviation quantity between signal in proportion with the voltage of the inverter 2, and the output signal of an inverter voltage set value and the current control amplifier 4 is provided. So far as an electronic switch SW having hysteresis characteristic is concerned, when the current of the inverter 2 comes to a value larger than a specified value, then the control system is switched to constant voltage control with the voltage control amplifier 5.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a control device for a DC substation for electric railways, etc., and in particular, a system in which regenerative power generated in a load is reverse-converted by an inverter and returned to the power source. As a control device for a DC substation, it prevents excessive circulating current from the converter to the inverter.
The present invention also relates to a control device that can avoid abnormal voltage increases during regeneration.

(Prior Art) Recently, there has been an increase in the number of DC substations for electric railways that use an inverter to inversely convert regenerated power from electric cars and return it to a power source. FIG. 3 shows an example of a conventional substation of this type, in which 21 is a power transformer, 22 is a converter consisting of a tie motor, 23 is an electric vehicle with direct load as L load,
24 is an inverter made of a thyristor, 25 is a regenerative transformer, and 26 is a reactor for suppressing circulating current from the conohator to the inverter.

In the above configuration, the AC output of the power source is rectified by the converter 22 via the power transformer 21 during power generation, and is supplied to the electric car 23 via the overhead wire T, and during regeneration, the AC output of the power source is
The regenerative DC power generated in step 3 is reversely converted to AC by an inverter 24, and is returned to the power source via a regenerative transformer 25.

In the DC substation configured as shown in Figure 4, only the converter 22 is in operation when the line is in line T, and the voltage-current characteristics of the overhead wire T are as shown in the area in line T in FIG. Next, the overhead line voltage rises during regeneration, and when this exceeds the regeneration set voltage VS, a control circuit (not shown) operates and the operation of the inverter 24 is started, and the inverter 24 enters the regeneration region shown in FIG. As shown, constant voltage; 11 control is performed to keep the rack Vj tonnage pressure at the voltage S at the start of regeneration.

(Problems to be Solved by the Invention) In the DC substation configured as described in 4-, the maximum overhead line voltage (no-load voltage) Edo and the regeneration setting voltage V
When s are brought closer to each other, converter 22 and inverter 2
In order to avoid this, it is necessary to make the regeneration setting voltage Vs considerably higher than the no-load voltage Edo when the vehicle is running. However, in this case, the inverter 24 remains inactive until the overhead wire voltage reaches the regeneration setting voltage Vs from the no-load voltage Edo when the electric car is running, and the regenerative power generated by the electric car 23 is effectively used. Not only is it impossible to use the regenerative current, but if the start of operation of the inverter 24 is delayed as described above, especially when the rise of the regenerative current is fast, the overhead wire voltage will rise abnormally, which will have a negative impact on the electric car 23'$. It turns out.

Therefore, the present invention eliminates the above-mentioned drawbacks of the conventional control device for a DC substation in which the regenerative DC power generated at the load is reversely converted by the inverter and returned to the power supply, and the circulating current is transferred from the converter to the inverter. It is an object of the present invention to provide a control device that can prevent the generation of excessive circulating current by stopping the flow only when switching between power and regeneration.

Furthermore, the present invention achieves the above-mentioned objectives, and
An object of the present invention is to provide a control device for a DC substation that can prevent abnormal voltage increases during regeneration.

Furthermore, the present invention provides a DC substation that can switch the control system to constant voltage control when the inverter current is larger than a predetermined value during regeneration, and maintain this state regardless of fluctuations in the inverter current within a predetermined range. The purpose is to provide a control device.

(Means for Solving the Problems) In order to achieve the above object, the DC substation control device of the present invention rectifies the AC output of the power source and supplies DC power to the load. an inverter that converts regenerative DC power generated in the load into alternating current and returns it to the power source; current control means that receives as input the amount of deviation between a signal proportional to the current of the converter and a set value of the converter current; Voltage control means receives as input the amount of deviation between a signal proportional to the voltage of the inverter and the output signal of the inverter voltage set value and current control stage F, and when the current of the inverter is larger than a predetermined value, A switch means for switching to constant voltage control by the voltage control means and having a hysteresis characteristic is provided.

(Function) Based on the above configuration, the control device for a DC power plant of the present invention substantially reduces the circulating current between the converter and the inverter when the converter current exceeds its set value during continuous operation. When the inverter current is about to drop below its set value, it is possible to maintain the sum of the load current and the above-mentioned circulating current substantially constant, especially when the inverter is in regenerative operation. When the current exceeds a predetermined value, the control system is switched to constant voltage control using only the voltage control means, and hunting of the sinch means is prevented regardless of fluctuations within the predetermined range of the inverter current, and is maintained under constant voltage control.

(Embodiment) Referring to FIG. 1 and FIG. 2, an embodiment of the control device for a DC substation according to the present invention will be described in detail in the order of its structure and operation.

(Configuration of embodiment of control device for DC substation of this invention) (
(Fig. 1) Fig. 1 shows the main parts of an embodiment of the control device for a DC substation according to the present invention. The output side is connected to an overhead wire T that supplies power to an electric car as a load, and its internal configuration is, for example, a circuit shown at 22 in FIG. 3. 2 is an inverter consisting of a thyristor, the input side is connected to the overhead line T via the circulating current suppressing reactor 3, and the output side is connected to the regenerative transformer (
It is connected to an alternating current power supply via a circuit (see 25 in FIG. 3), and its internal configuration consists of, for example, a circuit shown at 24 in FIG.

4 is a current control means for controlling the load current or (and) the circulating current between the converter 1 and the inverter 2 (hereinafter, in the description of the embodiment, these currents may be collectively referred to as converter current); The amplifier 25 is a voltage control amplifier serving as a voltage control means for controlling the voltage of the input and output terminals 2.

The input signal of the current control amplifier 4 is obtained by detecting the converter current or the setting value IC5c (plus input for setting the above-mentioned circulating current) and the converter current Ic via the current transformer 6a, and converting it into an AC/
It was converted to direct current by a DC converter 7a. It consists of a signal (minus input) proportional to the converter current. The output of the current control amplifier 4 is such that the converter current Ic is the set value Ics.
The setting is such that when the value exceeds this value, the upper limit becomes a positive value.

The input signals of the voltage control amplifier 5 include an inverter voltage set value Vs (plus input), a signal proportional to the overhead line voltage detected via the DC/DC converter 8 (minus input), and an output signal of the current control amplifier 4 (plus input). Here, the voltage setting value vs is set somewhat higher than the no-load voltage (Edo in FIG. 2) of the converter at the rated power supply. The output signal of the voltage control amplifier 5 is supplied to the control electrode of the thyristor constituting the inverter 2 via a phase shifter 9 and a gate circuit 10, as is well known, to control its phase.

Among the input signals of the current control amplifier 4, the set value Ics
is changed to a specific reference value when the regenerative current increases and becomes It>Ir5 (Ir is the inverter current, Is is a predetermined value related to the inverter radio wave). That is, the input terminal of the set value Ics is an electronic switch (normally open contact) SW.
It is connected to a reference potential, for example O■, via the terminal. The electronic switch SW is configured to be turned on when the output of the comparator (-CP) 11 is at a low level. The comparator 11 is
It has a hysteresis characteristic and is configured so that when the input is negative, the output is high and when the input is positive, the output is low, and the input signal is the set value I of the inverter radio wave.
zs (negative input) and inverter current II to current transformer 6
b, and is proportional to the inverter current that is converted to DC by the AC/DC converter 7b (positive input).
It becomes more.

Further, the hysteresis width is set such that hysteresis width>llll5I-lIC3+.

In the control system shown in FIG. 1, a loop passing through a current control amplifier 4, a voltage control amplifier 5, a phase shifter 9, a gate circuit 10, an inverter 2, a converter 1, a current transformer 6a, and an A C/DC converter 7a. constitutes a control loop (main loop) for the load current or (and) circulating current between the converter 1 and the inverter 2, and includes a voltage control amplifier 5, a phase shifter 9, a gate circuit 10, an inverter 2 and a DC/DC converter. The loop passing through the DC converter 8 constitutes an inverter voltage control loop (subloop).

(Operation of the embodiment of the control device for a DC substation of the present invention) (
(FIGS. 1 and 2) Next, the operation of the embodiment shown in FIG. 1 will be explained with reference to FIG. 2 as well.

(+) When the converter current IC is set during power running (+
When it is larger than ti I cs (region (1) in FIG. 2), the output of the current control amplifier 4 is plus j+'t(A)
The setting value of the voltage control amplifier 5 is [V S+(A)
]. Therefore, the voltage at In/ζ-2 increases corresponding to this [Vs+(A)], and the voltage at
Circulating currents from 1 are substantially blocked. During actual power driving, since IQ>>Ics, the current control amplifier 4
The output becomes a positive upper limit value, and the inverter 2 operates at this upper limit value. Note that this upper limit value does not change even if there is a fluctuation in the AC power supply. Then, the output is supplied from the converter 1 to the load according to the voltage fluctuation rate of the converter 1.

(2) Humpertough 1i flow Ic decreases and Ics≧Ic
(region (2) in Fig. 2), the current control amplifier 4
operates so that IC=IC3, and the voltage control amplifier 5 also receives the output of the current control amplifier 4 and controls the inverter 2 so as to satisfy the relationship of Ic=Ics. As a result, in region (1), all of the output current of converter l flows to the load, but in region (2), inverter current II begins to flow, and the partners and relationships of these lit currents are shown in Figure 1. IC=II-IL. Then, when the load −[flow IL becomes zero (second
Point c) in the figure, flows from converter 1 to in-2'
The current is only a circulating current. That is, in the area shown in Figure 2 (2), ab represents the converter current (=load current) at the time when the inverter current starts flowing, and cd represents the time when the load current becomes zero and the overhead line voltage reaches the no-load voltage Edo. Represents inverter current (=circulating current). During the transition from AB to CD, the converter current, that is, the sum of the load current and circulating current, remains constant. In the region (2) of FIG. 2, on the left side of I cs' (= I , cs), the inverter current II increases due to the regenerative voltage.

In the state shown in (-), since II<IIS still holds, the output of the comparator 11 in FIG. 1 remains at a high level.

(3) When the regenerative current increases and becomes r>rrs (second
(Area (3) in the figure) The output of the comparator 11 becomes low level, the electronic switch SW is turned on, and the current control amplifier 4
The potential at the converter current set value (ICs) input terminal of the converter changes to a specific reference value, for example, about Ovt. This results in
The input to the current control amplifier 4 is only the feedback signal of the converter current, but since the converter current is zero, the control system shown in FIG. 1 essentially shifts to constant voltage control by the voltage control amplifier 5. And the same amplifier 5 is DC/D
The phase of the thyristor constituting the inverter 2 is controlled according to the deviation between the signal proportional to the overhead line voltage detected by the C converter 8 and the inverter voltage set value Vs (controlled by a gun), and the overhead line voltage is maintained at a predetermined value. do.

Accordingly, circulating current between converter 1 and inverter 2 is substantially blocked, and inverter current If is substantially formed only by regenerated radio waves. The comparator 11 has a hysteresis characteristic, and its hysteresis width is set to hysteresis width > 1IXsl - 1Icsl, so hunting of the comparator output is prevented.
The above state is maintained as long as the inverter current does not become smaller than Ics.

” in the control device of FIG.

In the region of FIG. 2(1) where IC>IC5, converter 1 is operated according to its voltage fluctuation rate and circulating current between converter 1 and inverter 2 is substantially blocked. Further, in the region of FIG. 2 (2) where Ic≦Ics, the sum of the load current and the circulating radio waves is controlled to be substantially constant. Therefore, the above-mentioned circulating current flows only when switching from power operation to regenerative operation, which reduces power loss caused by excessive circulating current during power operation, and also when switching from power operation to regenerative operation. Switching is performed quickly, and an abnormal increase in overhead wire voltage at the start of regeneration can be avoided.

In the region of FIG. 2 (3) where Il>Ics, the control system is essentially switched to constant voltage control using only the voltage control amplifier 5, and since the comparator 11 has hysteresis characteristics, the inverter current line The voltage can be maintained substantially constant.

In the above description, the converter 1 is made of a diode, but the present invention can be similarly applied to a case where the converter is made of a silice.

(Effects of the Invention) As described above, according to the present invention, the circulating current is stopped flowing between the converter and the inlet-outlet only when switching from the power operation to the regenerative operation, and this circulating current is stopped. It is especially useful to limit power loss due to excessive circulating current, and to quickly switch from power operation to regeneration operation to avoid an abnormal rise in overhead line voltage at the start of the first regeneration. When the inverter current exceeds a predetermined value, the control is switched to constant voltage control using substantially only the voltage control amplification means, and this state can be maintained regardless of fluctuations in the inverter current within a predetermined range.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main parts of an embodiment of the control device for a DC substation according to the present invention, FIG. 2 is a voltage-current characteristic curve diagram explaining the operation of the device in FIG. 1, and FIG. A circuit diagram showing the schematic configuration of a conventional DC substation control device, Fig. 3
FIG. 3 is a voltage-current characteristic curve diagram illustrating the operation of the circuit shown in the figure. Description of symbols 1: Converter, 2: Inverter, 3: Reactor for suppressing circulating current, 4: Current control amplifier, 5: Voltage control amplifier, 6a, 6b: Current transformer, 7a. 7b2 AC/DC converter, 8: DC/DC converter,
11: Comparator with hysteresis characteristics, SW: 1rf
, child switch. Figure 1 Figure 2 Figure 4

Claims (3)

[Claims] (1) A converter that rectifies the AC output of the power source and supplies DC power to the load, an inverter that converts the regenerative DC power generated by the load into AC and returns it to the power source, and a signal proportional to the current of the converter and the converter. current control means that receives as input the amount of deviation from the current setting value; voltage control means that receives as input the amount of deviation between a signal proportional to the voltage of the inverter and the inverter voltage setting value and the output signal of the current control means; A control device for a DC substation, comprising: switch means having hysteresis characteristics for switching the control device to constant voltage control by the voltage control means when the current of the inverter is larger than a predetermined value. (2) The DC substation according to claim (1), wherein the switch means is means for changing the converter current setting value for the current control means to a specific reference value when the inverter current is larger than a predetermined value. Control device. (3) The switch means receives as input a signal proportional to the inverter current and a signal representing a predetermined value of the inverter current, and is controlled by a comparator having hysteresis characteristics. DC substation control equipment.