JP2686184B2 - Voltage fluctuation compensator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage fluctuation compensating device for a power supply side busbar in a power distribution system for supplying electric power from a power source to a load, and more particularly to reducing the capacity of the reactive power compensating device and reducing fluctuations on the load side. Of course, the present invention relates to a voltage fluctuation compensator capable of coping with load fluctuations on the power supply side.

[0002]

2. Description of the Related Art FIG.
FIG. 16 is a circuit configuration diagram showing a conventional voltage fluctuation compensating device described in the paper “Active Filter and Its Application” on pages 15 to 20 of Vol. 62, No. 6).

In the figure, 1 is an AC power supply (hereinafter, simply referred to as a power supply), 2 and 3 are resistors and reactors inserted in a power supply system, the resistance value of the resistor 2 is R, and the reactance of the reactor 3 is X. Is. Reference numeral 4 denotes a load side busbar connected to the power source 1 via the resistor 2 and the reactor 3, and supplies a load voltage V _A to be compensated. _A variable load 5 is connected to the bus 4 of the power supply system and is supplied with the load voltage V _A.

Reference numeral 6 denotes an active filter, that is, a reactive power compensator, which is connected to the bus 4 in parallel with the load 5.
The output current Ic for compensating the reactive power of the power supply system connected to the bus bar is supplied to the bus bar 4. 7 is the reactive power output from the reactive power compensator 6.
This is a control device for controlling (-jQc), and is a bus current I _A detected by the current transformer 8 and the transformer 9 which are load detecting means.
The inverter in the reactive power compensator 6 is controlled based on the bus voltage V _A and the output current I _F of the inverter in the reactive power compensator 6. Since the absolute value of the reactive power (-jQc) output from the reactive power compensator 6 is Qc, hereinafter, the reactive power for compensation is simply represented by Qc, and the output current corresponding to the reactive power Qc is represented by Ic. Represent.

FIG. 7 is a circuit configuration diagram specifically showing the reactive power compensator 6 and the controller 7 in FIG. As shown in the figure, the reactive power compensator 6 is composed of an active filter using a self-excited inverter composed of transistor switches.

In the figure, 10a to 10c are reactors connected to a bus bar 4 which is a main circuit. Reference numerals 11a to 11f denote transistor switches which are connected to the reactors 10a to 10c and which form an inverter, and each of which is composed of a parallel circuit of a transistor and a diode. Reference numeral 12 is a capacitor of electrostatic capacitance C connected in parallel with the inverter. 13a
And 13b are current transformers provided between the reactors 10a and 10c and the inverter, and detects the output current I _F of the inverter.

Further, in FIG. 7, the control device 7 is as follows.
It is composed of 14 to 16 circuits. Reference numeral 14 is an active power P and a reactive power Q of the load 5 based on the bus current I _A detected by the current transformer 8 and the bus voltage V _A detected by the transformer 9.
Is a detection circuit for detecting. 15 is the output signal of the detection circuit 14
(Active power P and reactive power Q on the load 5 side) and a current control unit to which the output current I _F detected by the current transformers 13a and 13b is input, with the active power P and the reactive power Q as reference values. The output current I _F is feedback controlled. Reference numeral 16 denotes a PWM control unit that modulates the output signal of the current control unit 15. The PWM signal output from the PWM control unit 16 is applied to the reactive power compensator 6 as an on / off signal of the inverter, that is, the transistor switches 11a to 11f. There is.

Next, referring to FIGS. 8 and 9, FIG.
Also, the operation of the conventional voltage fluctuation compensating apparatus shown in FIG. 7 will be described. Normally, the DC voltage Ed charged in the capacitor 12 is PWM-modulated by the transistor switches 11a to 11f which are turned on / off by the PWM signal from the control device 7, and converted into the AC voltage V _I as the inverter output, and then the reactor. Bus 4 on the load 5 side through 10a to 10c
Supplied to

From the above operation of the reactive power compensator 6, the reactive power compensator 6 and the power supply 1 are equivalently represented as shown in FIG. That is, the reactive power compensator 6 acts as an AC power supply of the voltage V _I and is connected to the AC power supply 1 of the voltage V _A via the reactor 3, and the reactor 3 corresponds to the reactive power Qc for compensation. The generated output current Ic flows toward the reactive power compensator 6. Actually, since the sign of the reactive power Qc is negative, a negative output current Ic will flow into the reactive power compensator 6.

FIG. 9 is a waveform diagram showing the output current Ic flowing through the reactive power compensator 6 as an active filter. In FIG. 9, (a) shows the case where the AC voltage V _I is higher than the bus voltage V _A , and the output current Ic becomes a phase advance current. or,
(b) shows the case where the AC voltage V _I is smaller than the bus voltage V _A , and the output current Ic becomes a lag current. As a result, the power supplied from the power source 1 is P + j (Q-, as shown in FIG.
The electric power represented by Qc) and actually supplied to the load 5 becomes P + jQ after removing the reactive power (-jQc).

Next, the voltage fluctuation compensating operation by the reactive power compensator 6 will be described with reference to FIG. FIG.
4 is a timing chart showing changes with time of active power P and reactive power Q on the load 5 side, load voltage, that is, bus voltage _VA , and reactive power Qc output from the reactive power compensator 6.

Now, let the resistance value of the resistor 2 of the power supply system be R
[%] [10MVA (megavolt ampere) base], Reactor 3 reactance X [%] (10MVA base),
It is assumed that there is no load at time T _{0 to} T ₁ and the load 5 is activated at time T ₁ . In this case, increasing the time T ₁ from the active power P [k W] and the reactive power Q [k VAR (kilo bar)] are both reached a constant value at time T _2, and will be reduced from the time T _3.

At this time, the bus voltage V _A drops from the reference voltage (target value) Vr by ΔV _A , and the voltage drop ΔV _A is

[0014]

(Equation 1)

It is represented by

On the other hand, in the control device 7, the detection circuit 14
There detecting the active power P and reactive power Q of the load 5, adjusting the current control unit 15 and the PWM control unit 16 on the basis of the output current I _F of the active power P and reactive power Q and the inverter. That is, after time T ₁ , the voltage drop Δ represented by the formula
In order to make V _A zero, the reactive power Qc in the advanced phase is supplied to the reactive power compensator 6 after the time T ₁ . Leading reactive power Q at this time
c is calculated as follows. That is, from the formula,

[0017]

(Equation 2)

From this,

[0019]

(Equation 3)

Is obtained.

However, the reactive power compensator 6 is
The bus voltage _VA cannot be kept constant unless the reactive power Qc for compensation expressed by the equation is continuously output. Therefore, the capacity and output of the reactive power compensator 6 (reactive power Qc)
Therefore, a large load corresponding to the total change of the load 5 is required. Further, since the reactive power Qc output from the reactive power compensator 6 corresponds only to the voltage fluctuation caused by the fluctuation of the load 5, it is caused by the load fluctuation on the power source 1 side from the reactive power compensator 6. It is not possible to compensate for voltage fluctuations that occur.

[0022]

As described above, the conventional voltage fluctuation compensating device always attempts to prevent the fluctuation of the bus voltage V _A by using only the reactive power compensating device 6 connected to the bus 4. Since the reactive power Qc must be continuously output, the capacity and output of the reactive power compensator 6 are large, which is uneconomical, and cannot cope with load fluctuations on the power source 1 side of the reactive power compensator 6. There was a problem.

The present invention has been made to solve the above problems, and by combining a reactive power compensator comprising a voltage type inverter and a voltage regulator,
The capacitance and output of the reactive power compensator can be reduced without impairing the bus voltage fluctuation compensation function, and the responsiveness can be increased.
In addition, it is an object of the present invention to obtain a voltage fluctuation compensating device capable of dealing with load fluctuations on the power supply side while reducing the generated loss .

[0024]

DISCLOSURE OF THE INVENTION A voltage fluctuation compensating apparatus according to the present invention includes a reactive power compensator connected to a bus and supplying an output current for compensating the reactive power of a system to the bus, the bus and the reactive power. A voltage regulator that is provided on the busbar on the power supply side of the connection point with the compensator to compensate for busbar voltage fluctuations, and disables the busbar voltage fluctuations by detecting busbar voltage fluctuations when the load changes A first control circuit that controls the output current of the power compensator, and a second control circuit that controls the voltage regulator according to the output current to compensate for voltage fluctuations of the busbar, and as a reactive power compensator, Voltage type inverter
Data is used .

[0025]

In the present invention, the responsiveness is fast and the occurrence loss is
Loss compensator composed of voltage type inverter
Using, the control of the reactive power (output current) for compensation by the first control circuit is not performed by the calculation based on the active power and the reactive power of the load, but based on the bus voltage,
The bus voltage is controlled to reach the target value. Further, the second control circuit detects the output current of the reactive power compensator and controls the voltage regulator so that the output current does not become a large output. Thus, in the initial stage of voltage fluctuation, the bus voltage is compensated by the reactive power output from the reactive power compensator, and when the output current of the reactive power compensator is large and continues for a long time (large output), voltage adjustment is performed. The switch is driven to share the bus voltage compensation and reduce the output current of the reactive power compensator.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, and 1 to 6, 15 and 16 are the same as those described above. here
Therefore, the reactive power compensator 6 has a quick response and
A voltage-type inverter with low raw loss is used. 18
Is a voltage regulator that is provided on the bus bar 4 on the power source 1 side of the connection point between the bus bar 4 and the reactive power compensator 6 and that compensates for voltage fluctuations of the bus bar 4. The bus voltage V _A is gradually increased and decreased.

[0027] 19 current transformer for detecting an output current Ic of the reactive power compensator 6, 20 is a voltage detector for detecting a bus voltage V _A, 21 is a deviation [Delta] V _A of the bus voltage V _A and the reference voltage Vr It is a subtractor to be obtained. Reference numeral 22 is a calculation unit that calculates the reactive power compensation capacity based on the voltage deviation ΔV _A , and the calculated reactive power compensation capacity is input to the current control unit 15.

The subtractor 21, the arithmetic unit 22, the current control unit 15, and the PWM control unit 16 detect the voltage fluctuation of the bus bar 4 when the load 5 changes, and disable the bus voltage V _A so that it does not fluctuate. It constitutes a first control circuit for controlling the output current Ic of the power compensator 6.

Reference numeral 23 is a reactive power detector for detecting the reactive power Qc based on the output current Ic and the bus voltage V _A , and 24 is an integrator for integrating the reactive power Qc detected by the reactive power detector 23. Reference numeral 25 denotes a comparator that compares the integrated signal from the integrator 24 with a predetermined positive and negative value, and outputs an ON signal when the integrated signal exceeds the predetermined positive and negative values. Reference numeral 26 is a tap controller that controls the voltage regulator 18 based on each ON signal from the comparator 25, and outputs a tap-up command TU in response to the ON signal when the integrated signal exceeds a positive predetermined value. Then, the tap down command TD is output to the voltage regulator 18 in response to the ON signal when the integrated signal exceeds a predetermined negative value, and the integrator 24 is reset each time the switching commands TU and TD are output. It outputs the signal RS.

Incidentally, the reactive power detector 23, the integrator 24, the comparator
The tap controller 25 and the tap controller 26 constitute a second control circuit that controls the voltage regulator 18 according to the output current Ic to compensate for the voltage fluctuation of the bus bar 4.

Next, the operation of the embodiment of the present invention shown in FIG. 1 will be described with reference to FIG. FIG. 2 shows the reactive power Qc for compensation, the integrated signal, the tap-up command TU,
7 is a timing chart showing changes over time in a tap down command TD and a bus voltage V _A.

As described above, taking as an example the case where the load 5 is turned on from the unloaded state at time T ₁ and the load 5 gradually increases, first, at time T _{1 to} T ₁ ′, the load is invalid. A first control circuit for controlling the power compensator 6 works,
The subtracter 21 belonging to the first control circuit detects the voltage drop ΔV _A due to the increase of the load 5, and the arithmetic unit 22 increases the lead compensation capacity for suppressing the voltage drop ΔV _A. This allows
The reactive power compensator 6 supplies the leading reactive power Qc to the bus bar 4, and the bus line voltage V _A is compensated for the decrease shown by the shaded portion in FIG. 2 and held at the reference voltage Vr.

On the other hand, with the operation of the reactive power compensator 6,
A second control circuit works to control the voltage regulator 18,
The reactive power detector 23 belonging to the second control circuit detects the reactive power Qc for compensation based on the output current Ic and the bus voltage _VA , and the integrator 24 outputs an integrated signal corresponding to the increasing reactive power Qc. Ask. Usually, an instantaneous increase in reactive power is absorbed in the reactive power compensator 6, so the output capacity of the reactive power compensator 6 corresponds to the integral signal. Therefore, in order to suppress the capacity of the reactive power compensator 6, the absolute value of the integrated signal may be suppressed.

In this case, the comparator 25 compares the increasing integral signal with a positive predetermined value + Vup, outputs an ON signal at time T ₁ 'when the predetermined value + Vup is reached, and the tap controller 26 issues a tap-up command. Output TU. At the same time, the reset signal RS is output from the tap controller 26 and the integrator 24 is reset.

In response to this tap-up command TU, the voltage regulator 18 switches the taps in the direction of increasing the bus voltage V _A. As a result, the output of the advanced reactive power Qc is suppressed, and the voltage V _A supplied to the load 5 is held at the reference voltage Vr. In FIG. 2, it can be seen that the portion marked with the bus voltage V _A is compensated by the voltage regulator 18, and the compensation portion by the reactive power compensator 6 in the shaded portion is suppressed. Since the load 5 varies little from time T ₁ ′ to T ₃ ,
The rise of the reactive power Qc is small, and the tap switching operation is unnecessary.

On the other hand, from time T _{3 to} T ₄ , since the load 5 starts to decrease, the reactive power compensator 6 outputs the delayed reactive power Qc and suppresses the bus voltage V _A which tends to rise. And In this case, the integrator 24 increases the negative polarity integration signal, and the comparator 25, when the integration signal reaches the predetermined negative value −Vdn at time T ₄ , instructs the tap controller 26 to perform the tap down command TD. Is output. This allows
The voltage regulator 18 switches the taps in the direction of lowering the bus voltage V _A to reduce the output of the delayed reactive power Qc. Also, the integrator 24 is reset.

As described above, by using the voltage regulator 18 together, the output capacity of the reactive power compensator 6 is reduced,
Further, the bus voltage V _A can be kept constant even if the output capacity of the reactive power compensator 6 is small. If the response of the above control operation is fast, the bus voltage _VA does not change at all.
Also, a voltage type inverter is used as the reactive power compensator 6.
Therefore, the responsiveness is fast and the generated loss is suppressed.

In the above embodiment, the reactive power compensator 6 is used.
As an example, an active filter including an inverter formed of a transistor switch is used, but a reactive power compensation device including an inverter formed of a thyristor switch may be used. Although the tap changer is used as the voltage adjuster 18, a voltage adjuster that changes the secondary side voltage of the transformers connected in series may be used.

Further, in the above embodiment, the detected reactive power Qc is directly input to the integrator 24. However, as shown in FIG. 3, the dead band element 27 is inserted between the reactive power detector 23 and the integrator 24. However, the reactive power Qc below a predetermined value may not be integrated. In this case, if the dead zone is set to a range that does not substantially affect the output capacity of the reactive power compensator 6,
Since the integrator 24 does not operate with respect to the reactive power Qc within the dead zone, the tap switching command is not output and the number of times the voltage regulator 18 operates can be reduced.

Further, in the above embodiment, the integrator 24 is provided in the second control circuit and the integrated signal is used as the signal corresponding to the output capacity of the reactive power Qc. However, as shown in FIG. The reactive power Q is obtained by combining the comparator 25A having a level and the timer 28 which responds to each ON signal of the comparator 25A individually.
A signal corresponding to the output capacity of c may be generated.

In this case, the comparator 25A outputs an ON signal when the reactive power Qc reaches the positive predetermined value + Vup ', and outputs an ON signal when the negative predetermined value -Vdn' is reached. . Further, the timer 28 raises one of the output signals after a lapse of a fixed time T _A from the ON signal in response to the positive predetermined value + Vup ', and at the same time, lapses from the ON signal in response to the negative predetermined value -Vdn' The other output signal rises after T _{B has} elapsed. Therefore, the tap-up command TU and the tap-down command TD from the tap controller 26 are generated at the times T ₁ ′ and T ₄ respectively as shown in FIG. 5, and the voltage regulator 18 operates in the same manner as in the above-described embodiment. The output capacity of the reactive power compensator 6 can be constantly reduced, and the voltage fluctuation in a wide range can be continuously reduced to almost zero.

[0042]

As described above, according to the present invention, the reactive power compensator connected to the bus and supplying the output current for compensating the reactive power of the system to the bus, and the bus and the reactive power compensator are provided. A voltage regulator that is provided on the bus bar closer to the power supply side than the connection point and that compensates for voltage fluctuations on the bus bar, and a var compensator that detects voltage fluctuations on the bus bar when the load changes and does not fluctuate A first control circuit for controlling the output current and a second control circuit for controlling the voltage regulator according to the output current to compensate for the voltage fluctuation of the bus are provided, and reactive power is provided.
Using a voltage-type inverter as a compensator, the reactive power for compensation by the first control circuit is controlled based on the bus voltage, and the bus voltage is controlled to a target value.
Since the second control circuit detects the output current of the reactive power compensator and controls the voltage regulator so that the output current does not become a large output, it is output from the reactive power compensator at the initial stage of voltage fluctuation. When the output current of the reactive power compensator is large and continues for a long time, the bus voltage is compensated by the switching drive of the voltage regulator to reduce the output current of the reactive power compensator by compensating the bus voltage. issued together with is to be able, also, to speed up response
Raw loss can be reduced, and the capacity and output of the reactive power compensator can be reduced without impairing the bus voltage fluctuation compensating function, and a voltage fluctuation compensator that can handle load fluctuations on the power supply side can be obtained. There is.

[Brief description of the drawings]

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

FIG. 2 is a timing chart for explaining the operation of the circuit of FIG. 1;

FIG. 3 is a circuit configuration diagram showing a second embodiment of the present invention.

FIG. 4 is a circuit configuration diagram showing a third embodiment of the present invention.

FIG. 5 is a timing chart for explaining the operation of the circuit in FIG. 4;

FIG. 6 is a circuit configuration diagram showing a conventional voltage fluctuation compensating device.

FIG. 7 is a circuit configuration diagram specifically showing the reactive power compensator and the controller in FIG.

8 is an equalization circuit diagram showing the relationship between the power supply and the reactive power compensator in FIG.

9 is a waveform diagram showing an output current flowing in the reactive power compensator in FIG.

FIG. 10 is a timing chart showing the relationship between reactive power on the load side, bus voltage, and reactive power for compensation.

[Explanation of symbols]

1 Power Supply 4 Bus 5 Load 6 Reactive Power Compensator 15 Current Control Section 16 PWM Control Section 18 Voltage Regulator 21 Subtractor 22 Arithmetic Section 15, 16, 21, 22 First Control Circuit 23 Reactive Power Detector 24 Integrator 25 , 25A Comparator 26 Tap controller 27 Dead band element 28 Timer 23, 24, 25, 25A, 26, 27, 28 Second control circuit _VA Bus voltage Qc Reactive power

Claims (1)

(57) [Claims] 1. A device for compensating for voltage fluctuations in a busbar included in a system for supplying power from a power supply to a load, wherein an output current for compensating for reactive power in the system is connected to the busbar and is supplied to the busbar. A reactive power compensating device, a voltage regulator that is provided on the bus bar on the power source side from the connection point between the bus bar and the reactive power compensating device, and that compensates for voltage fluctuations of the bus bar; and A first control circuit for detecting the voltage fluctuation of the bus bar and controlling the output current of the reactive power compensator so that the voltage of the bus bar does not fluctuate; and controlling the voltage regulator according to the output current. A second control circuit for compensating for voltage fluctuations of the bus bar , wherein a voltage type inverter is used as the reactive power compensator.
A voltage fluctuation compensating device characterized in that