JP2518441B2 - Series compensation type voltage fluctuation compensator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a series-compensation type voltage fluctuation which is inserted in series in a power feeding path from a grid-side power supply to a load and series-compensates for a voltage fluctuation of the grid-side power supply. It relates to a compensator.

[Conventional technology]

A conventional series compensation type voltage fluctuation compensating apparatus is shown in FIGS. 6 and 7 as a compensating apparatus for voltage fluctuations in a distribution system.

A conventional series compensation type voltage fluctuation compensator will be described in detail with reference to FIG.

As shown in FIG. 6, this series compensation type voltage fluctuation compensator includes a rectifier circuit 2 that obtains DC power by full-wave rectifying the voltage V _S of the system-side power supply 1, and a DC power supplied from the rectifier circuit 2. A DC capacitor for compensating electric power storage, which is charged with, for example, a large-capacity electrolytic capacitor 3 and a compensating voltage for compensating for a variation of the voltage V _S of the system side power supply 1 supplied from the electrolytic capacitor 3. An inverter 4 that constantly generates V _I, and an output voltage V _I of this inverter 4 are applied to the primary winding, and a secondary winding is inserted in the power supply path from the system side power source 1 to the load 6 for series compensation. The coupling transformer 5 is the main constituent element. In this case, the voltage V _H of the secondary winding of the coupling transformer 5 corresponds to the voltage obtained by subtracting the voltage V _S of the system side power supply 1 from the target sine wave voltage synchronized with the voltage V _S of the system side power supply 1.

The inverter 4 is controlled by the control circuit 30 which detects a voltage variation of the voltage V _S of the system side power supply 1. Further, the turns ratio of the coupling transformer 5 is set to 1: 1 or another value, and in the case of 1: 1, the compensation voltage V _I and the compensation voltage V _H become equal.

Also, the amplitude of the target sine wave voltage is the voltage of the system side power supply 1.
The amplitude of V _S is normal.

With the configuration described above, this series compensation type voltage fluctuation compensating device performs full-wave rectification on the voltage V _S of the system side power supply 1 by the rectification circuit 2, and the output of this rectification circuit 2 provides an electrolytic capacitor for power storage for compensation. 3 is charged, power is supplied to the inverter 4 from this electrolytic capacitor 3, and a compensation voltage V _I corresponding to the fluctuation of the voltage V _S of the system side power supply 1 is constantly generated from the inverter 4 and this compensation voltage V _I is connected to the coupling transformer. The voltage is added to the voltage V _{S of the} power supply 1 on the system side via 5 and applied to the load 6.

As a result, the load voltage V _L across the load 6 is always constant regardless of the voltage fluctuation of the voltage V _S of the system side power supply 1.

Here, the concrete configuration of the control circuit 30 and its operation will be described in a seventh section.
It will be described with reference to the drawings.

This control circuit 30 detects the voltage V _S of the system side power source 1 by the instrument transformer 11, and the phase synchronization circuit 12 detects the voltage of the system side power source 1 based on the secondary side voltage V _S1 of the instrument transformer 11. Create a sync signal synchronized to V _S. Based on this synchronizing signal, the reference sine wave generating circuit 13 generates a target sine wave voltage V _R having an amplitude corresponding to the normal value of the voltage V _S of the system side power supply 1.

Then, the difference between the target sine wave voltage V _R and the secondary side voltage V _S1 is calculated by the subtractor 14, and the obtained difference voltage V _D is added to the pulse width modulation circuit 16, and this pulse width modulation circuit 16 Therefore, for example, compared with the triangular wave voltage, the pulse width modulation circuit 65 outputs a pulse width modulation voltage V _P corresponding to the difference voltage V _D ,
This pulse width modulation voltage V _P is applied to the base drive circuit (not shown) of the inverter 4.

As a result, the compensation voltage V _I corresponding to the difference voltage V _D between the target sine wave voltage V _R and the secondary side voltage V _S1 of the instrument transformer 11 from the inverter 4, that is, the fluctuation of the voltage V _S of the system side power supply 1 The compensating voltage V _I corresponding to that amount is output, and this compensating voltage V _I is added to the voltage V _S of the system side power supply 1 via the coupling transformer 5 and applied to the load 6, and both ends of the load 6 are connected. The load voltage V _L appearing at is a value corresponding to the target sine wave voltage V _R.

[Problems to be Solved by the Invention]

However, the conventional series compensation type voltage fluctuation compensator is
When the load 6 is turned on after the start-up, a large DC component may flow from the inverter 4 to the coupling transformer 5 to demagnetize the coupling transformer 5. As a result, the coupling transformer 5
When the iron core becomes saturated, the exciting impedance decreases sharply, and a large exciting current flows from the inverter 4 to the temporary winding of the coupling transformer 5. When this exceeds the operation level of the protective relay operation against the overcurrent of the inverter 4, the built-in inverter 4 The protective relay operation is performed, such as the tripped overcurrent relay, and the voltage fluctuation compensation operation is stopped.

An object of the present invention is to provide a series-compensation type voltage fluctuation compensating device capable of preventing the voltage fluctuation compensating operation from being stopped due to an overcurrent of an inverter flowing during a transition such as load application.

[Means for solving the problem]

The series compensation type voltage fluctuation compensator according to claim (1),
The primary winding of the coupling transformer is connected to the output terminal of the inverter that generates a compensation voltage corresponding to the fluctuation of the voltage of the system side power supply, and the secondary winding of the coupling transformer is connected to the load from the system side power supply to the load. In series.

Further, a current detection means is provided to detect the absolute value of the instantaneous value of the output current of the inverter, and a comparison means is further provided to compare the detected value with the set value.

Further, provided with a compensation voltage temporary suppression means, based on the output of the comparison means, the compensation voltage is forcibly set to zero during the period when the absolute value of the instantaneous value of the output current of the inverter exceeds the set value,
When the absolute value of the instantaneous value of the inverter output current becomes lower than the set value, the compensation voltage is increased from zero over time and gradually returned to a value corresponding to the fluctuation of the voltage of the grid side power supply. ing.

The series compensation type voltage fluctuation compensator according to claim (2) is
In the serial compensation type voltage fluctuation compensating apparatus according to claim 1, the system side power supply has three phases, the current detecting means has three phases, and the maximum value of the detection values of the current detecting means of each phase in the comparing means. Is compared with the set value.

[Action]

According to the configuration of claim (1), the current detecting means always detects the absolute value of the instantaneous value of the output voltage of the inverter, and the comparing means constantly compares the detected value of the current detecting means with the set value. When the absolute value of the instantaneous value of the output current of the inverter is lower than the set value due to the output of the comparison means, the compensation voltage temporary suppression means does not operate, and the compensation voltage corresponding to the fluctuation of the voltage of the system side power supply is output from the inverter. It is generated, combined with the voltage of the power supply on the system side via the coupling transformer, and added to the load.

In the above condition, when a large DC component flows from the inverter to the temporary winding of the coupling transformer due to load application, the coupling transformer is demagnetized, the iron core of the coupling transformer is saturated, and the primary winding of the coupling transformer from the inverter. A large current will flow into. As a result, when the absolute value of the instantaneous value of the output current of the inverter exceeds the set value, the compensation voltage temporary suppression means operates to forcibly set the compensation voltage output from the inverter to zero. As a result, when the absolute value of the instantaneous value of the output current of the inverter becomes lower than the set value, the compensation voltage is gradually returned from zero to a voltage corresponding to the fluctuation of the voltage of the system side power supply. As a result, although the voltage fluctuation compensating operation becomes temporarily incomplete, it is possible to prevent an overcurrent from flowing to the inverter due to saturation of the coupling transformer during a transition such as when a load is applied.

According to the configuration of claim (2), the current detection means in each phase always detects the absolute value of the instantaneous value of the output voltage of the inverter in each phase, and the comparison means determines the maximum value of the detection values of the current detection means. The set value is constantly compared. When the maximum absolute value of the instantaneous value of the output current of the inverter of each phase is lower than the set value due to the output of the comparison means, the compensation voltage temporary suppression means does not operate and the fluctuation of the voltage of the system side power supply in each phase. The compensating voltage corresponding to the amount is generated from the inverter, is combined with the voltage of the system side power supply via the coupling transformer, and is applied to the load.

In the above condition, when a large amount of direct current flows from the inverter to the primary winding of the coupling transformer due to load application, the coupling transformer is demagnetized and the iron core of the coupling transformer is saturated. A large current will flow into. As a result, when the maximum absolute value of the instantaneous value of the output current of the inverter exceeds the set value, the compensation voltage temporary suppression means for all phases operates and the compensation voltage output from the inverter is forced to zero in all phases. To With this, when the maximum absolute value of the instantaneous value of the output current of the inverter becomes lower than the set value, the compensation voltage of all phases gradually returns from zero to the voltage corresponding to the fluctuation of the voltage of the system side power supply. Let As a result, although the voltage fluctuation compensating operation becomes temporarily incomplete, it is possible to prevent an overcurrent from flowing to the inverter due to saturation of the coupling transformer during a transition such as when a load is applied.

〔Example〕

Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS. 1 to 3.

As shown in FIG. 1, this series compensation type voltage fluctuation compensating device is provided with a current transformer 17 for detecting the output current I of the inverter 4 and uses a control circuit 7 instead of the control circuit 30 in the conventional example. Unlike the above, other configurations are the same as those of the conventional example.

Here, the specific configuration and operation of the control circuit 7 will be described in the second section.
It will be described with reference to FIGS.

This control circuit 7 is the same as that shown in FIG. 7 until the difference voltage V _D is obtained, but the difference voltage V _D is not added to the pulse width modulation circuit 16 as it is, but the pulse width modulation circuit is supplied via the multiplier 15.
It is different in that it is added to 16.

Hereinafter, differences from the conventional example shown in FIG. 7 will be described in detail. That is, in the control circuit 7, the voltage Vb having a gain of 1 pu is applied to the terminal 22, and the multiplier 15 is supplied through the CR circuit 21.
Is input as a signal Va. In addition, the instantaneous value of the output current I of the inverter 4 is detected by the current transformer 17, and the absolute value circuit 18
Creates an absolute value signal Ia which is the absolute value of the instantaneous value of the output current I detected by the current transformer 17 and adds it to the comparator 19. The current transformer 17 and the absolute value circuit 18 form a current detecting means. The absolute value signal Ia input to the comparator 19 as a comparison means is compared with the set value, and when the absolute value signal Ia is lower than the set value, the comparator 19 outputs a high level signal to the switch 20 and the switch 20 is off. is there. CR circuit at this time
Since the capacitor C of 21 is fully charged, the signal Va input to the multiplier 15 is 1pu. The multiplier 15, the CR circuit 21, and the switch 20 constitute a compensation voltage temporary suppression means, and are in a non-operation state when the absolute value signal Ia is lower than the set value.

However, when the absolute value signal Ia input to the comparator 19 exceeds the set value due to load application, etc., the comparator 19 outputs a low level signal to the switch 20,
Turn on 20. As a result, the capacitor C of the CR circuit 21
Is instantaneously discharged, and the signal Va input to the multiplier 15 instantly changes from 1 pu to 0 pu. As a result, the output voltage of the inverter 4 is suppressed, and therefore the output current of the inverter 4 is also reduced, and when the absolute value signal Ia input to the comparator 19 becomes lower than the set value, the time due to the resistance R and the capacitor C of the CR circuit 21 increases. With a constant, it gradually increases from 0pu to 1pu.

Then, the multiplier 15 calculates the difference voltage generated by the subtractor 14.
The inverter reference voltage V _T is created by multiplying V _D and the signal Va, and this inverter reference voltage V _T is applied to the pulse width modulation circuit 16. As a result, the inverter reference voltage V _T also gradually rises from zero.

Then, with this pulse width modulation circuit 16, the multiplier 15
The inverter reference voltage V _T output from the inverter is compared with the triangular wave voltage as in the conventional example, and the pulse width modulation voltage V _P corresponding to the inverter reference voltage V _T is applied to the base drive circuit (not shown) of the inverter 4.

As a result, when the absolute value of the instantaneous value of the output current I of the inverter 4 is lower than the set value, the switch 20 is off and the signal Va input to the multiplier 15 is 1 pu, so the difference voltage V _D
Becomes the inverter reference voltage V _{T as} it is, and the compensation voltage V _I corresponding to the difference voltage V _D between the target sine wave voltage V _R and the secondary side voltage V _S1 of the instrument transformer 11 from the inverter 4, that is, the system side power source 1 Compensation voltage V _I corresponding to the fluctuation of voltage V _S
Is output, and this compensation voltage V _I is added to the voltage V _S of the system side power supply 1 via the coupling transformer 5 and applied to the load 6, and the load voltage V _L appearing across the load 6 is The value corresponds to the target sine wave voltage V _R.

The operation after load application will be described with reference to FIG. Times of Day
When the load is turned on at t ₀ , a DC-like load current that is biased in one direction as shown in FIG. 3 (a) flows, which saturates the coupling transformer 5, lowers its exciting impedance, and causes a large exciting current. Flowing. That is, the output current I of the inverter 4 increases as shown in FIG. 3 (b). In such a case, when the absolute value of the instantaneous value of the output current I of the inverter 4 exceeds the set value at time t ₁ , the switch 20 is turned on, the capacitor C of the CR circuit 21 is instantly discharged, and the multiplier 15 The signal Va input to is instantly 0 pu as shown in FIG. 3 (c). As a result, the inverter reference voltage V _T becomes 0, and further, the output voltage of the inverter 4
V _I also becomes 0, and as shown in FIG.
Output current I is suppressed from increasing and further decreases. Thus, the absolute value of the instantaneous value of the output current I at time t ₂ becomes lower than the set value switch 20 is turned off, the charging starts the CR circuit 21, the signal Va applied to the multipliers 15 Figure 3 (c ), The time constant CR of the resistor R and the capacitor C gradually increases from 0 pu to 1 pu. As a result, the inverter reference voltage V _{T, which} has become 0, is
As shown in FIG. 7D, after the time t ₂ , it increases with the time constant CR and becomes equal to the difference voltage V _D. Furthermore, the output voltage V _I of the inverter 4 which becomes 0 instantaneously also increases with the time constant CR after that, and the compensation voltage corresponding to the difference voltage V _D , that is, the system side power source 1
The compensation voltage V _I corresponding to the fluctuation of the voltage of is output. Correspondingly, the output current I of the inverter 4 is suppressed to a low level as soon as it exceeds the set value, as shown in FIG. 3 (b). Then, by setting the set value lower than the operation level of the protective relay operation against the overcurrent of the inverter 4, it is possible to prevent the stop of the voltage fluctuation compensating operation due to the overcurrent of the inverter 4 when a load is applied as in the conventional case. You can Note that the coupling transformer 5 will also come out of saturation after a certain amount of time has passed after the load is applied,
Even if the level of the compensation voltage is restored, the inverter current does not exceed the set value this time.

Second Embodiment A second embodiment of the present invention will be described with reference to FIGS. 4 and 5.

This series compensation type voltage fluctuation compensator is applied to a three-phase circuit, and as shown in FIG. 4, the system side power supply 101 consisting of three phases of A phase, B phase and C phase, and a load 106 of three phases. The compensation circuit 110 for generating the compensation voltages V _HA , V _HB , and V _HC is inserted in series in the addition polarity in the feeding path to. In addition, 4A,
4B and 4C are inverters of each phase, 5A, 5B and 5C are coupling transformers of each phase, and 17A, 17B and 17C are current transformers of each phase. The configuration and operation in each phase are the same as those in the first embodiment except the control circuit.

Here, the specific structure of the control circuit and its operation will be described with reference to FIG. 5 for the parts different from those of the first embodiment.

Output current I _{A of} each phase inverter 4A, 4B, 4C,
I _B and I _C are detected by current transformers 17A, 17B and 17C. Absolute value circuit 1
In 8A, 18B and 18C, absolute value signals I _aA , I _aB and I which are absolute values of the output currents I _A , I _B and I _C detected by the current transformers 17A, 17B and 17C.
_aC is created and added to comparator 19. The maximum value of the absolute value signals I _aA , I _aB , and I _aC is input to the comparator 19. And the absolute value signal I _aA ,
The largest of I _aB and I _aC is compared with the set value. The switch 20 operates according to the comparison result in the first embodiment.
Is the same as Further, a voltage Vb with a gain of 1 pu is applied to the terminal 22, and the multipliers 15A, 15
The signal Va is input to B and 15C.

The multipliers 15A, 15B, and 15C are provided with difference voltages V _DA , V _DB , and V _DB , which are applied from a subtracter (not shown) for each phase.
Inverter reference voltages V _TA , V _TB , and V _TC are created by multiplying V _DC and signal Va, and these inverter reference voltages V _TA , V _TB , and V _TC are applied to respective pulse width modulation circuits (not shown). Will be added.

By collectively controlling the three phases in this way, the control circuit can be simplified as compared with the control for each phase.

Then, as in the first embodiment, the set value is set to the inverter 4
By setting it lower than the operation level of protection relay operation for A, 4B, 4C overcurrent, it is possible to stop the voltage fluctuation compensation operation due to the overcurrent of inverters 4A, 4B, 4C when a load is applied as in the past. Can be prevented.

〔The invention's effect〕

The series compensation type voltage fluctuation compensator according to claim (1),
When the absolute value of the instantaneous value of the inverter output current exceeds the set value, the compensation voltage temporary suppression means operates and the compensation voltage output from the inverter is forced to zero, and the absolute value of the instantaneous value of the inverter output current becomes When the voltage becomes lower than the set value, the compensation voltage is gradually returned from zero to the voltage corresponding to the fluctuation of the voltage of the power supply on the system side. It is possible to prevent an overcurrent from flowing through the inverter due to saturation of the coupling transformer during a transition such as when a load is applied. As a result, the protective relay operation due to the overcurrent of the inverter at the time of transition is not performed, and the stop of the voltage fluctuation compensation operation due to the transient overcurrent of the inverter can be prevented.

The series compensation type voltage fluctuation compensator according to claim (2) is
The series compensation type voltage fluctuation compensating device according to claim (1) has the same effect, and further, by collectively controlling the three phases, the control circuit can be made simpler than the control for each phase. You can

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the configuration of a first embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of the control circuit of FIG. 1, and FIG. FIG. 4 is a block diagram showing the configuration of the second embodiment of the present invention, FIG. 5 is a block diagram showing the configuration of the control circuit of FIG. 4, and FIG. 6 is the configuration of the conventional example. FIG. 7 is a block diagram showing the configuration of the control circuit of FIG. 1,101 ... Power supply on the system side, 4,4A, 4B, 4C ... Inverter, 5,5A, 5
B, 5C… Coupling transformer, 6,106… Load, 15,15A, 15B, 15C…
Multiplier, 17,17A, 17B, 17C ... Current transformer, 18,18A, 18B, 18C ... Absolute value circuit, 19 ... Comparator, 20 ... Switch, 21 ... CR circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A 61-116934 (JP, A) JP-A 1-170328 (JP, A) JP-A 2-30246 (JP, A)

Claims (2)

(57) [Claims] 1. An inverter is provided which generates a compensation voltage corresponding to the fluctuation of the voltage of the power supply on the system side, and the primary winding of a coupling transformer is connected to the output terminal of this inverter.
In a series compensation type voltage fluctuation compensating device in which a secondary winding of the coupling transformer is inserted in series in a power feeding path from a system side power source to a load, current detecting means for detecting an absolute value of an instantaneous value of an output current of the inverter. And comparing means for comparing the detected value by the current detecting means with a set value, and based on the output of the comparing means, the compensation is performed during the period when the absolute value of the instantaneous value of the output current of the inverter exceeds the set value. When the absolute value of the instantaneous value of the output current of the inverter becomes lower than the set value by forcibly setting the voltage to zero, the compensation voltage is increased from zero with the lapse of time to change the voltage of the system side power supply. A series compensation type voltage fluctuation compensating device comprising a compensation voltage temporary suppressing means for gradually returning to a value corresponding to a minute. 2. The power supply on the system side has three phases, the current detection means has three phases, and the maximum value of the detection values of the current detection means of each phase is compared with the set value by the comparison means. (1) The serial compensation type voltage fluctuation compensating device described in (1).