JPH048126A - Series compensation type voltage fluctuation compensator - Google Patents

Abstract

PURPOSE:To prevent an overcurrent from being applied to an inverter by a method wherein, when the absolute value of the instantaneous value of the output current of the inverter exceeds a predetermined value, a compensation voltage outputted from the inverter is forcibly turned to zero and then recovered gradually. CONSTITUTION:A pulse width modulation voltage Vp is applied to the driving circuit of an inverter. The instantaneous value of the output current of the inverter is detected by a current transformer 17 and applied to a comparator 19 and compared with a predetermined value. If the instantaneous value of the output current of the inverter is lower than the predetermined value, a non-operation state is selected. If the output current exceeds the predetermined value by load closing, etc., a switch 20 is turned on and a capacitor C is instantaneously discharged and a signal Va inputted to a multiplier 15 is instantaneously turned to zero and the output voltage of the inverter is turned to zero. If the output current becomes lower than the predetermined value, the switch 20 is turned off and the signal Va is gradually elevated from zero with a time constant determined by a resistor R and the capacitor C and the output current is controlled to be within the range of the predetermined value.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a series compensation type voltage fluctuation which is inserted in series in a power supply path from a power supply on the grid side to a load to compensate for voltage fluctuations in the power supply on the grid side in series. This invention relates to a compensation device.

[Prior Art] A conventional series compensation type voltage fluctuation compensator is shown in FIGS. 6 and 7 as a compensator for voltage fluctuations in a power distribution system.

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

As shown in Part 6, this series compensation type voltage fluctuation compensator includes a rectifier circuit 2 that full-wave rectifies the voltage of the power supply 1 on the grid side to obtain DC power, and a DC power supplied from the rectifier circuit 2. A DC capacitor for compensating power storage, for example, a large-capacity electrolytic capacitor 3, which is charged by the electrolytic capacitor 3, and a compensation voltage for compensating for fluctuations in the voltage of the grid-side power supply 1 supplied with power from the electrolytic capacitor 3. ■A combination for series compensation in which an inverter 4 that constantly generates 1 and the output voltage v1 of this inverter 4 is applied to the primary winding and the secondary winding is inserted in the power supply path from the system control power a1 to the load 6. The main component is a transformer 5. In this case, the voltage VH of the secondary winding of the coupling transformer 5 corresponds to the voltage obtained by subtracting the voltage (2) of the power supply 1 on the system side from the target sine wave voltage synchronized with the voltage (2) of the power supply 1 on the system side.

Note that the inverter 4 uses the voltage ■ of the grid side power supply 1.

It is controlled by a control circuit 30 that detects voltage fluctuations. 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 and the compensation voltage ■□ become equal.

Further, the amplitude of the target sine wave voltage is the amplitude of the voltage V of the grid side 'Hdi 1 when it is normal.

With the configuration described above, this series compensation type voltage fluctuation compensator performs full-wave rectification of the voltage 5 of the grid side power supply 1 in the rectifier circuit 2, and uses the output of the rectifier circuit 2 to connect the electrolytic capacitor for compensating power storage. 3 is charged, and the electrolytic capacitor 3 supplies power to the inverter 4, so that the inverter 4 constantly generates a compensation voltage (■) corresponding to the variation in the voltage (■) of the grid side power supply l, and this compensation voltage v1 is applied to the coupling transformer 5. It is added to the voltage (2) of the power supply 1 on the grid side and applied to the load 6 via.

As a result, the load voltage V across the load 6 is always constant regardless of voltage fluctuations in the voltage (2) of the power supply 1 on the grid side.

Here, the specific configuration of the control circuit 30 and its operation will be explained in the seventh section.
This will be explained based on the diagram.

This control circuit 30 controls the voltage V of the system side power supply 1.

is detected by the voltage transformer 11, and the phase synchronization circuit 12 detects the system control voltage a based on the secondary voltage VSI of the voltage transformer 11.
Create a synchronization signal synchronized with the voltage (2) at t. Based on this synchronization signal, the reference sine wave generation circuit 13
A target sine wave voltage Vll with an amplitude corresponding to the normal value of the voltage (2) is generated.

Then, the target sine wave voltage ■ is determined by the subtracter 14.

The difference between and the secondary voltage VSI is calculated, and the obtained differential voltage ■. is applied to the pulse width modulation circuit 16, which compares it with, for example, a triangular wave voltage, and the pulse width modulation circuit 65 outputs a pulse width modulation voltage ■ corresponding to the difference voltage ■o. A width modulation voltage 2 will be applied to the base drive circuit (not shown) of the inverter 4.

As a result, the difference voltage (■) between the target sine wave voltage (■8) from the inverter 4 and the secondary side voltage V31 of the potential transformer 11. A compensation voltage VI corresponding to the variation of the compensation voltage ■1 corresponding to the voltage ■1 of the grid side power supply 1, that is, the voltage ■ of the grid side power supply 1, is output, and this compensation voltage VI corresponds to the voltage ■ of the grid side power supply 1 via the coupling transformer 5.
, and is applied to the load 6, and the load 6
The load voltage {circle around (2)} appearing at both ends of is a value corresponding to the target sine wave voltage {circle around (2)}.

[Problems to be Solved by the Invention] However, in the conventional series compensation type voltage fluctuation compensator, when the load 6 is turned on after startup, a large amount of DC flows from the inverter 4 to the coupling transformer 5.
may be biased.

As a result, when the iron core of the coupling transformer 5 is saturated, the excitation impedance rapidly decreases, and the coupling transformer 5 is transferred from the inverter 4 to the coupling transformer 5.
When a large excitation current flows through the primary winding and exceeds the activation level of the protective relay operation against overcurrent of the inverter 4, the overcurrent relay built in the inverter 4 trips and other protective relay operations are performed. The voltage fluctuation compensation operation will stop.

An object of the present invention is to provide a series compensation type voltage fluctuation compensator that can prevent the voltage fluctuation compensation operation from stopping due to an overcurrent flowing through an inverter during a transient period such as when a load is turned on.

[Means to solve the problem]

The series compensation type voltage fluctuation compensator according to claim (1) connects a primary winding of a coupling transformer to an output terminal of an inverter that generates a compensation voltage corresponding to a variation in voltage of a grid-side power supply, and The secondary winding is inserted in series in the power supply path from the grid power supply to the load.

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 this detected value with a set value.

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

The series compensation type voltage fluctuation compensator according to claim (2) is the series compensation type voltage fluctuation compensator according to claim (1), in which the power supply on the grid side has three phases, and has current detection means for three phases. The comparison means compares the maximum value detected by the current detection means for each phase with a set value.

(Function) According to the configuration described in claim (1), the current detection means always detects the absolute value of the instantaneous value of the output voltage of the inverter, and the comparison means always compares the detected value of the current detection means with a set value. According to the output of the comparison means, when the absolute value of the instantaneous value of the inverter output current is lower than the set value, the compensation voltage temporary suppression means does not operate and the compensation voltage corresponding to the fluctuation in the voltage of the grid side power supply is reduced. is generated from the inverter, combined with the grid-side power supply voltage via a coupling transformer, and applied to the load.

Under the above conditions, if a large amount of DC flows from the inverter to the primary winding of the coupling transformer due to load application, etc., the coupling transformer becomes unbalanced, the iron core of the coupling transformer becomes saturated, and the primary winding of the coupling transformer flows from the inverter to the primary winding of the coupling transformer. A large current will flow through. 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 suppressing means is activated and the compensation voltage output from the inverter is forcibly reduced 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 restored from zero to a voltage corresponding to the fluctuation in the voltage of the grid side power supply.

As a result, although the voltage fluctuation compensation operation becomes temporarily incomplete, it is possible to prevent overcurrent from flowing into the inverter due to saturation of the coupling transformer during a transient period such as when a load is applied.

According to the configuration described in 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 detects the maximum value of the detected value of the current detection means. It is constantly compared with the set value. According to the output of the comparing means, 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, the compensation voltage temporary suppressing means does not operate and the system side T! A compensation voltage corresponding to the variation in the iH voltage is generated from the inverter, combined with the voltage of the grid-side power supply via the coupling transformer, and applied to the load.

Under the above conditions, if a large amount of DC flows from the inverter to the primary winding of the coupling transformer due to load application, etc., the coupling transformer becomes unbalanced, the iron core of the coupling transformer becomes saturated, and the primary winding of the coupling transformer flows from the inverter to the primary winding of the coupling transformer. A large current will flow through. As a result, when the maximum absolute value of the instantaneous value of the inverter's output current exceeds the set value,
The compensation voltage temporary suppression means shared by all phases is activated, and the compensation voltages output from the inverters in all phases are forcibly brought to zero. As a result, when the maximum absolute value of the instantaneous value of the inverter's output current becomes lower than the set value, the compensation voltage of all phases is gradually restored from zero to the voltage corresponding to the voltage fluctuation of the grid side MR. let

As a result, although the voltage fluctuation compensation operation becomes temporarily incomplete, it is possible to prevent 1M1iK from flowing into the inverter due to saturation of the coupling transformer during a transient period such as when a load is applied.

〔Example〕

Embodiment ±1 A first embodiment of the present invention will be described based on FIGS. 1 to 3.

As shown in Figure 1, this series compensation type voltage fluctuation compensator has a current transformer 17 that detects the output current of the inverter 4.
The difference from the conventional example is that a control circuit 7 is provided in place of the control circuit 30, and the other configurations are the same as the conventional example.

Here, the specific configuration and operation of the control circuit 7 will be explained based on the second part and FIG. 3.

This control circuit 7 is the same as that shown in FIG. 7 until the difference voltage V1 is obtained, but the difference voltage V is directly passed to the pulse width modulation circuit 7.
The difference is that the signal is added to the pulse width modulation circuit 16 via the multiplier 15 instead of being added to the pulse width modulation circuit 16.

Hereinafter, the differences from the conventional example shown in FIG. 7 will be explained in detail. That is, in the control circuit 7, a voltage vb with a gain of 1 pu is applied to the terminal 22, and is inputted to the multiplier 15 through the CR circuit 21 as a signal Va. Further, 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 1a which is the absolute value of the instantaneous value of the output current I detected by the current transformer 17. and added to comparator 19. Current transformer 17 and absolute value circuit 18
constitutes a current detection means. The absolute value signal Ia input to the comparator 19, which is a comparison means, is compared with a set value. When the absolute value signal 1a is lower than the set value, the comparator 19 outputs a high level signal to the switch 20, and the switch 20 is turned off. At this time, since the capacitor C of the CR circuit 21 is fully charged, the signal Va input to the multiplier 15 is lpu. Multiplier 15. CR circuit 2
1 and switch 20 constitute compensation voltage temporary suppression means, which is inactive when the absolute value signal 1a is lower than the set value.

However, when the absolute value signal 1a input to the comparator 19 exceeds the set value due to load application, etc., the comparator 19 outputs a low level health signal to the switch 20 and turns on the switch 20.

As a result, the capacitor C of the CR circuit 21 is instantly discharged, and the signal Va input to the multiplier 15 instantly changes from lpu to Opu. 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 1a input to the comparator 19 becomes lower than the set value, the It gradually increases from Qpu with a constant to reach lpu.

Then, the multiplier 15 multiplies the difference voltage ゎ generated from the multiplier 14 and the signal Va to create an inverter reference voltage V7, and applies this inverter reference voltage V to the pulse width modulation circuit 16. . As a result, the inverter reference voltage (2) also gradually increases from O.

Then, with this pulse width modulation circuit 16, the multiplier 1
The inverter reference voltage ■7 outputted from the inverter reference voltage ■7 is compared with the triangular wave voltage as in the conventional example, and a pulse width modulation voltage V corresponding to the inverter reference voltage ■ 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 1ill 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 lpu.
The differential voltage ■ becomes the inverter reference voltage ■7 as it is, and the compensation voltage ■4 corresponding to the differential voltage V between the target sine wave voltage ■9 from the inverter 4 and the voltage VSI on the next side of the instrument transformer 11, i.e. A compensation voltage v1 corresponding to the variation of voltage ~'5 of grid side type #I is output, and this compensation voltage v1 is
', is the voltage of the grid side power supply 1 via the coupling transformer 5,
The load voltage ■, which is added to and applied to the load 6 and appears across the load 6, has a value corresponding to the target sine wave voltage vll.

The operation after the load is applied will be explained with reference to FIG.

When a load is applied at the time, a biased DC load current flows in one direction as shown in FIG. flows. In other words, the output type IR 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 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 shown in Figure 3 (
As shown in C), it instantly becomes Opu. As a result, the inverter reference voltage V becomes 0, and the output voltage v1 of the inverter 4 also becomes 0, as shown in Fig. 2(b).
As shown in , the increase in the output current I of the inverter 4 is suppressed and further decreases. As a result, at time t2, the output type I! When the absolute value of the instantaneous value of Jif becomes lower than the set value, the switch 2o is turned off, charging of the CR circuit 21 starts, and the signal Va applied to the multiplier 15 is connected to the resistor R as shown in FIG. 3(C). With the time constant CR caused by the capacitor C, the voltage gradually increases from Opu to lpu. The inverter reference voltage ■7, which became 0 due to this, is
As shown in 11D(d), the voltage increases with the time constant CR and becomes equal to the differential voltage (2). Furthermore, the output voltage (■) of the inverter 4, which instantaneously became O, also increases with the time constant CR, resulting in a differential voltage (■). Compensation voltage corresponding to the compensation voltage corresponding to the voltage fluctuation of grid side power supply 1■
1 is output. Correspondingly, as shown in FIG. 3(b), the output current of the inverter 4 is suppressed to a low level as soon as it exceeds the set value. By setting the set value lower than the activation level of the protective relay operation against overcurrent of the inverter 4, the overcurrent 'f' of the inverter 4 at the time of applying a load as in the conventional case, ! This can prevent the voltage fluctuation compensation operation from stopping due to this. In addition, if a certain amount of time passes after the load is applied, the coupling transformer 5
Even if the voltage comes out of saturation and the compensation voltage level returns,
This time the inverter current will not exceed the set value.

Disaster Management Team) A second embodiment of the present invention will be described based on the fourth example and FIG.

This series compensation type voltage fluctuation compensator is applied to a three-phase circuit, and as shown in FIG. A compensation circuit 110 that generates a compensation voltage vHA+vNl-vMc is inserted in series with the addition polarity in the power supply path. In addition, 4A4B, 4C are inverters for each phase,
5A, 5B, 5C are coupling transformers for each phase, 17A 1
7B 17C is a current transformer for each phase. The configuration and operation of each phase are the same as in the first embodiment except for the control circuit.

Here, the specific structure of the control circuit and its operation that are different from the first embodiment will be explained based on the fifth section.

Output current T of inverters 4A and 484C for each phase, respectively
A, TI, and IC are detected by current transformers 17A and 17B17c. Absolute value circuits 18A, 18B18C4' detect current transformers 17A, 17B, 17C7 detected output types mlA, I
Absolute value signal r, which is the absolute value of B, Ic, A, I□, 1.
c is created and added to comparator 19. The comparator 19 has absolute value signals 1 mA, l, aB
+ 'The largest one of I aC will be input. And absolute value signal 1 mA□! The largest of II l aC is compared with the set value. The switch 2o operates based on the comparison result, as in the first embodiment. Moreover, the voltage v of the gain Ipu is applied to the terminal 22.
b is added to the multiplier 15 of each phase through the CR circuit 21.
A15B.

15C as a signal Va.

The multipliers 15A, 15B, and 15C each receive a differential voltage V applied from a subtracter (not shown) for each phase.
Multiplying DA, VDI voc and signal Va gives the inverter reference voltage VtaV TB, V
TC and this inverter reference voltage VTA
, Vd1 vtc will be applied to each pulse width modulation circuit (not shown).

By controlling all three phases in this manner, the control circuit can be made simpler than controlling each phase individually.

Then, as in the first embodiment, the set value is transferred to the inverter 4A.
, 4B, 4C protection against overcurrent By setting the level lower than the activation level of the #1 electric operation, it is possible to prevent the voltage fluctuation compensation operation from stopping due to overcurrent of Inharc 4A, 4B, 4C when a load is applied, etc., as in the past. It can be prevented.

〔Effect of the invention〕

In the series compensation type voltage fluctuation compensator according to claim (1), when the absolute value of the instantaneous value of the output of the inverter exceeds a set value, the compensation voltage temporary suppressing means is activated to reduce the compensation voltage output from the inverter. When it is forced to zero and the absolute value of the instantaneous value of the inverter's output current becomes lower than the set value,
By gradually returning the compensation voltage from zero to a voltage corresponding to the fluctuation in the power source voltage on the grid side, the voltage fluctuation compensation operation will be temporarily incomplete, but during transients such as when a load is turned on, In this case, it is possible to prevent overcurrent from flowing to the inverter due to saturation of the coupling transformer.

As a result, a protective relay operation is not performed due to a transient overcurrent of the inverter, and it is possible to prevent the voltage fluctuation compensation operation from stopping due to a transient overcurrent of the inverter.

The series compensation type voltage fluctuation compensator according to claim (2) has the same effect as the series compensation type voltage fluctuation compensator according to claim (1), and furthermore, by controlling the three phases collectively, , the control circuit can be simpler than controlling each phase individually.

[Brief explanation of the drawing]

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 in FIG. 1, and FIG. 3 is a time chart of each part when a load is applied.
FIG. 4 is a block diagram showing the configuration of a second embodiment of the present invention, FIG. 5 is a block diagram showing the configuration of the control circuit in FIG. 4, and FIG. 6 is a block diagram showing the configuration of a conventional example. FIG. 7 is a block diagram showing the configuration of the control circuit shown in FIG. 6. 1.101... Grid side power supply, 4.4A, 4B, 4C.
...Inverter, 5.5A, 5B, 5C...Coupling transformer, 6,106...Load, 15.15A, 1581
5c... Multiplier, 17.17A, 17B, 17C...
・Current transformer, 18.18A, 18B, 18C...absolute (
1st B, 19... Comparator, 20... Switch, 21... CR circuit agent Patent attorney Akio Miyai == F E;i;-
ri; 竺庺'L221 = 1... Grid side power supply 4... Inverter 6... Load l 7... R flow 5

Claims (2)

[Claims] (1) An inverter is provided that generates a compensation voltage corresponding to the variation in voltage of the power supply on the grid side, and the primary winding of the coupling transformer is connected to the output terminal of this inverter, and the secondary winding of the coupling transformer is connected to the grid. In a series compensation type voltage fluctuation compensator inserted in series in a power supply path from a side power supply to a load, current detection means for detecting the absolute value of the instantaneous value of the output current of the inverter is provided, and the detected value by the current detection means is provided. is provided with a comparison means for comparing the voltage with a set value, and based on the output of the comparison means, the compensation voltage is forcibly set to zero during a period in which the absolute value of the instantaneous value of the output current of the inverter exceeds the set value, and the compensation voltage is When the absolute value of the instantaneous value of the output current becomes lower than the set value, the compensation voltage is increased from zero over time to gradually return to a value corresponding to the fluctuation in the voltage of the grid side power supply. A series compensation type voltage fluctuation compensator characterized in that a compensation voltage temporary suppression means is provided. (2) Claim (1) wherein the power supply on the grid side has three phases, has current detection means for three phases, and the comparison means compares the maximum value detected by the current detection means of each phase with a set value. ) The series compensation type voltage fluctuation compensator described in ).