JPH0667217B2 - DC substation controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a DC substation for electric railways, etc., and particularly to a system for reversely converting regenerative power generated in a load by an inverter and returning it to a power supply. As a control device for a DC substation, it blocks excessive circulating current from the converter to the inverter,
The present invention also relates to a control device capable of avoiding an abnormal voltage rise during regeneration.

(Prior Art) DC substations for electric railways have recently been increasing in type in which regenerative electric power from an electric vehicle is converted back by an inverter to a power source. FIG. 3 shows an example of a conventional return station of this type, in which 21 is a power transformer, 22 is a converter consisting of a diode, 23 is an electric car as a DC load, 24 is an inverter consisting of a thyristor, 25 Is a regenerative transformer, and 26 is a reactor for suppressing circulating current from the converter to the inverter.

In the above configuration, during power running, the AC output of the power source is rectified by the converter 22 via the power transformer 21 and supplied to the electric car 23 via the overhead line T, and at the time of regeneration, the regenerative DC power generated in the electric car 23 is converted into an inverter. It is converted back to alternating current at 24,
It is returned to the power source through the regenerative transformer 25.

In the DC substation configured as described above, at the time of power running, only the converter 22 is in operation and the voltage of the overhead line T
The current characteristics are as shown in the power running region of FIG. Next, the voltage of the overhead wire increases during regeneration, and when it exceeds the regenerative set voltage Vs, a control circuit (not shown) operates and the operation of the inverter 24 is started, and the inverter 24 operates as shown in the regeneration area of FIG. Constant voltage control is performed so that the voltage is maintained at the voltage Vs at the start of regeneration.

(Problems to be Solved by the Invention) In the DC substation configured as described above, when the maximum overhead line voltage (no-load voltage) Edo during power running and the regenerative setting voltage Vs are brought close to each other, the converter 22 and the inverter 24 are connected. Since an excessive circulating current will flow during this period, in order to avoid this, it is necessary to make the regenerative setting voltage Vs considerably higher than the no-load voltage Edo during power running. However, in this way, the inverter 24 remains inoperative until the overhead line voltage reaches the regenerative setting voltage Vs from the no-load voltage Edo during power running, and the regenerative power generated by the electric vehicle 23 is effectively used. In addition, if the start of the operation of the inverter 24 is delayed as described above, the overhead line voltage will rise abnormally, especially when the regenerative current rises quickly, and the electric vehicle 23
Etc. will be adversely affected.

Therefore, the present invention eliminates the above-mentioned drawbacks of the conventional control device of the DC substation in which the regenerative DC power generated in the load is inversely converted by the inverter and returned to the power supply, and the circulating current flows from the converter to the inverter. It is an object of the present invention to provide a control device capable of preventing the generation of an excessive circulating current by stopping the operation only when switching between power running and regeneration.

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

Further, the present invention relates to a DC substation capable of switching the control system to constant voltage control when the inverter current is larger than a predetermined value during regeneration and maintaining this state regardless of fluctuations in the inverter current within a predetermined range. An object is to provide a control device.

(Means for Solving Problems) In order to achieve the above object, a control device for a DC substation according to the present invention includes a converter that rectifies an AC output of a power supply and supplies DC power to the load, and a converter that generates the power. Inverter for converting regenerative DC power into AC and returning it to a power source, current control means for inputting a deviation amount between a signal proportional to the converter current and a converter current setting value, and a signal proportional to the inverter voltage And a voltage control means for inputting the deviation amount between the inverter voltage setting value and the output signal of the current control means, and a switch for switching the present control device to the constant voltage control by the voltage control means when the current of the inverter is larger than a predetermined value. Means having a hysteresis characteristic.

(Operation) Based on the above configuration, the controller of the DC power plant of the present invention substantially blocks the circulating current between the converter and the inverter when the converter current exceeds the set value during the power running operation. If the converter current is about to fall below the set value, it is possible to maintain the sum of the load current and the circulating current substantially constant, especially when the inverter current is at a predetermined value during regenerative operation. When the voltage exceeds the limit, the control system is switched to the constant voltage control by only the voltage control means, and the hunting of the switch means is prevented regardless of the fluctuation of the inverter current within the predetermined range, and the above constant voltage control state is maintained. It

(Embodiment) With reference to FIG. 1 and FIG. 2, a detailed description will be given in the order of the construction and operation of the embodiment of the control device for a DC substation of the present invention.

(Configuration of Embodiment of Control Device of DC Substation of the Present Invention)
(FIG. 1) FIG. 1 shows a main part of an embodiment of a control device for a DC substation according to the present invention. In the figure, 1 is a converter composed of a diode, and an input side is a power source transformer (see FIG. 3). 21)) to the AC power source, and the output side is connected to the overhead line T that feeds the electric vehicle as a load.
It is composed of the circuit indicated by 22 in the figure. Reference numeral 2 is an inverter composed of a thyristor, and the input side is a reactor 3 for suppressing circulating current.
Connected to the overhead line T through the output side of the regenerative transformer (3rd
(See FIG. 25) and is connected to an AC power supply, and its internal configuration is, for example, a circuit shown at 24 in FIG.

4 is load current or / and converter 1 and inverter 2
A current control amplifier as a current control means for controlling a circulating current between (and in the following description of the embodiments, these currents may be collectively referred to as a converter current), and 5 is a voltage control means for controlling the voltage of the inverter 2. Is a voltage controlled amplifier as. The input signal of the current control amplifier 4 detects the set value I _CS (plus input) for setting the converter current or the circulating current and the converter current I _C via the current transformer 6a,
It is composed of a signal (minus input) proportional to the converter current, which is converted into direct current by the AC / DC converter 7a. The output of the current control amplifier 4 is set so as to have a plus upper limit value when the converter current I _C exceeds the set value I _CS .

The input signal of the voltage controlled amplifier 5 is the inverter voltage setting value.
Vs (plus input), a signal proportional to the overhead wire voltage detected via the DC / DC converter 8 (minus input), and an output signal of the current control amplifier 4 (plus or minus input). Here, the voltage setting value Vs is set to be slightly higher than the no-load voltage (Edo in FIG. 2) of the converter 1 when the power supply is rated. The output signal of the voltage controlled amplifier 5 is supplied to the control electrode of the thyristor which constitutes the inverter 2 through the phase shifter 9 and the gate circuit 10 as well known, and controls the phase thereof.

Of the input signals of the current control amplifier 4, the above set value I
_{In CS} , when the regenerative current increases and I _I > I _IS (I _I is the inverter current, I _IS is the predetermined value for the inverter current),
It is changed to a specific reference value. That is, the set value I _CS
The input end of is connected to a reference potential, for example, 0 V, through an electronic switch (normally open contact) SW. The electronic switch SW is configured to turn on when the output of the comparator (-CP) 11 is low level. The comparator 11 has a hysteresis characteristic, and the output when the input is negative is high, the input and the output when the positive is configured to be low, the input signal is the set value I _IS (minus inverter current Input) and the inverter current I _I are detected via the current transformer 6b, and a signal (plus input) proportional to the inverter current converted to direct current by the AC / DC converter 7b. The hysteresis width is set so that the hysteresis width> | I _IS | − | I _CS |.

In the control system shown in FIG. 1, a load current or a load current is looped 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 converter 6a and an AC / DC converter 7a. (And) A loop forming a control loop (main loop) for circulating current between the converter 1 and the inverter 2, and passing through the voltage control amplifier 5, the phase shifter 9, the gate circuit 10, the inverter 2 and the DC / DC converter 8. Constitutes a control loop (sub-loop) for the inverter voltage.

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

(1) During power running, the converter current I _C is the set value I _CS
When it is larger (area (1) in FIG. 2), the output of the current control amplifier 4 becomes a plus amount (A), and the set value of the voltage control amplifier 5 effectively increases to [Vs + (A)]. To do. Therefore, the voltage of the inverter 2 increases corresponding to this [Vs + (A)], and the circulating current from the converter 1 is substantially blocked. During the actual powering operation, since I _C >> I _CS , the output of the current control amplifier 4 has a plus upper limit value, and the inverter 2 operates at this upper limit value. The upper limit value does not change even if the AC power supply fluctuates. And converter 1
The output is supplied from the converter 1 to the load in accordance with the voltage fluctuation rate.

(2) When the converter current I _C decreases and I _CS ≧ I _C (region (2) of FIG. 2), the current control amplifier 4 has I _C = I
_The voltage control amplifier 5 operates so as to become _CS , 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 I _C = I _CS . As a result, in the region (1), all the output current of the converter 1 has flowed to the load, but in the region (2), the inverter current I _I begins to flow, and the mutual relationship of these currents is I the _C = _I I -I _L. When the load current I _L becomes zero (point c in FIG. 2), the circulating current is the only current flowing from the converter 1 to the inverter 2. That is, in the region of FIG. 2 (2), ab represents the converter current (= load current) at the time when the inverter current begins to flow, and cd represents the load current of zero,
Indicates the inverter current (= circulating current) when the overhead line voltage reaches the no-load voltage Edo. And from ab to cd,
The converter current, that is, the sum of the load current and the circulating current becomes constant. I _CS ′ (= I _CS ) in area (2) of FIG.
On the left side of, the regenerative voltage increases the inverter current I _I.

In the above state, the output of the comparator 11 in FIG. 1 remains at high level because I _I <I _IS .

(3) When the regenerative current increases and I _I > I _IS (region (3) in FIG. 2), the output of the comparator 11 becomes low level, the electronic switch SW turns on, and the current control amplifier 4 Converter current setting value (I _CS ) input terminal potential is a specific reference value,
For example, it changes to 0V potential. As a result, the input of the current control amplifier 4 is only the feedback signal of the converter current, but the converter current is zero. Therefore, the control system of FIG. 1 is substantially shifted to the constant voltage control by the voltage control amplifier 5. . Then, the amplifier 5 controls the phase of the thyristor constituting the inverter 2 (gamma control) according to the deviation amount between the signal proportional to the overhead wire voltage detected by the DC / DC converter 8 and the inverter voltage setting value Vs (gamma control), The voltage is maintained at a predetermined value.

Along with this, the circulating current between converter 1 and inverter 2 is substantially blocked, and inverter current I _I is formed substantially only by the regenerative current. Since the comparator 11 has a hysteresis characteristic and its hysteresis width is set to hysteresis width> | I _IS | − | I _CS |, hunting of the comparator output is prevented and the inverter current does not become smaller than I _CS. limit,
The above state is maintained.

As described above, in the control device of FIG. 1, I _C > I _CS
2 (1), the converter 1 is operated according to its voltage fluctuation rate, and the circulating current between the converter 1 and the inverter 2 is substantially blocked. See also I _C
In the region of (2) in FIG. 2 where ≦ I _CS , the sum of the load current and the circulating current is controlled to be substantially constant. Therefore, the circulating current described above flows only when switching from power running to regenerative operation, reducing power loss due to excessive circulating current flowing during power running, and quickly switching from power running to regenerative operation. It is possible to avoid an abnormal rise in the overhead line voltage at the start of regeneration.

Further, in the region of FIG. 2 (3) where I _I > I _CS , the control system is substantially switched to the constant voltage control by only the voltage control amplifier 5, and the comparison switch 11 has a hysteresis characteristic, so that the inverter current Hysteresis width of (> | I _IS | − | I
It is possible to keep the inverter voltage, that is, the overhead line voltage, substantially constant regardless of fluctuations within the range of _CS |).

Although the converter 1 is made of a diode in the above description, the present invention can be similarly applied to the case where the converter 1 is made of a thyristor.

(Effects of the Invention) As described above, according to the present invention, the circulation current is stopped from flowing between the converter and the inverter only when the power running operation is switched to the regenerative operation, and the circulation current is limited. Power loss due to excessive circulating current is reduced, and the switching from power running to regenerative operation is performed quickly, making it possible to avoid an abnormal rise in the overhead line voltage at the start of regenerative operation. When it exceeds, it is switched to the constant voltage control substantially only by the voltage control amplifying means, and this state can be maintained regardless of the fluctuation of the inverter current within the predetermined range.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of an embodiment of a control device for a DC substation of the present invention, FIG. 2 is a voltage-current characteristic curve diagram for explaining the operation of the device of FIG. 1, and FIG. FIG. 4 is a circuit diagram showing a schematic configuration of a conventional DC substation control device.
It is a voltage-current characteristic curve figure explaining operation | movement of the circuit of a 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, 7b: AC / DC converter, 8 : DC / DC converter, 11: Hysteresis comparator, SW: Electronic switch.

Claims (3)

[Claims] 1. A converter for rectifying an AC output of a power supply to supply DC power to a load, an inverter for converting regenerative DC power generated in the load to AC and returning it to a power supply, and a signal proportional to the current of the converter. Input a deviation amount from a predetermined converter current setting value, and output a positive upper limit value when a signal proportional to the converter current is larger than the converter current setting value, and in other cases, to the deviation amount. A current control unit that outputs a proportional value, a signal that is proportional to the DC input voltage of the inverter, and a deviation between the inverter voltage setting value that sets the inverter DC input voltage during regenerative operation and the output signal of the current control unit. Voltage control means for controlling the inverter so that the deviation amount becomes zero, and current control means when the current of the inverter is larger than a predetermined value. A control device for a DC substation, comprising: switch means for stopping the operation of, which has a hysteresis characteristic. 2. The DC transformer according to claim 1, wherein the switch means is means for changing a converter current set 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 according to claim 1, wherein the switch means receives 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 a hysteresis characteristic. Alternatively, the control device for the DC substation according to any one of (2).