JP3980515B2 - Voltage fluctuation compensation device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a voltage fluctuation compensator that detects and compensates for voltage fluctuation when the voltage of a power system supplied to a load fluctuates instantaneously.
[0002]
[Prior art]
The voltage of the electric power system is instantaneously reduced by lightning, etc., and precision equipment such as factories malfunctions or is temporarily stopped, which can cause great damage on the production line. In order to prevent such damage, a voltage fluctuation compensator that monitors voltage fluctuation such as instantaneous voltage drop of the power system and compensates for the voltage drop is used.
A conventional voltage fluctuation compensator is configured by a plurality of voltage compensation circuits that are connected in series to a power system and output a compensation voltage with either positive or negative polarity. Each voltage compensation circuit is provided with a full bridge inverter composed of four semiconductor switching elements with diodes connected in antiparallel, and a charging capacitor, which converts the DC voltage of the charging capacitor into AC and outputs it. In addition, a high-speed mechanical steady short-circuit switch is provided in parallel at the output terminal of each voltage compensation circuit. The charging capacitors in each voltage compensation circuit are charged with different voltages by the charging diode and the charging transformer, and the voltage ratio is set to a power ratio of about 2.
Constantly, current flows through a steady short circuit switch. When the voltage of the power system is lowered, a desired combination is selected from a plurality of voltage compensation circuits according to the error voltage, and the voltage drop of the power system is compensated by the sum of the output voltages (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP 2002-359929 A (page 1, page 6, page 8, FIG. 1, FIG. 6)
[0004]
[Problems to be solved by the invention]
The conventional voltage fluctuation compensator is configured as described above, and compensates for an instantaneous voltage drop in the power system with high accuracy in order to output the compensation voltage by gradation control. When the maximum voltage specification to be output cannot be satisfied, the compensation limit is reached, thereby determining the time during which voltage fluctuation compensation can be continued. In order to ensure the compensation time, it is necessary to proportionally increase the capacity of the charging capacitor in each voltage compensation circuit, that is, to provide a large capacity capacitor at a plurality of locations. In general, in the voltage fluctuation compensating device, the size of the capacitor for storing energy largely determines the size of the device, and thus there is a problem that the device becomes large.
Further, since the energy of the capacitor is proportional to the square of the voltage, the higher the voltage stored in the initial stage, the more energy can be stored. Therefore, in order to reduce the size of the device, the charging voltage to the charging capacitor in each voltage compensation circuit is set high in advance, so that the compensation time can be extended without increasing the capacity of each charging capacitor. However, there is a problem that the gradation width of the compensation voltage increases as the voltage is increased, so that fine gradation control cannot be performed and the compensation accuracy is lowered.
[0005]
The present invention has been made to solve the above-described problems, and a plurality of voltage compensation circuits are connected in series to an electric power system and stored in energy storage means in each voltage compensation circuit. An object of the present invention is to enable voltage compensation for a long period of time with high accuracy without increasing the size of the voltage fluctuation compensator that outputs the converted DC voltage to AC.
[0006]
[Means for Solving the Problems]
The voltage fluctuation compensator according to the present invention includes a control unit that monitors voltage drop in a power system and performs power feeding control based on the voltage drop, and is connected in series to the power system, and stores in different energy storage means that store different voltages. A plurality of (N) voltage compensation circuits that convert the converted DC voltage into AC and output the output voltage, and when the voltage of the power system drops, the output voltage can include those of opposite polarity. A predetermined combination is selected from the voltage compensation circuit, and the voltage drop of the power system is compensated for by the sum of each output voltage by the combination including the output voltage polarity (hereinafter referred to as an output pattern) and generated in the load. Reduce voltage fluctuations. A second energy storage means and a chopper circuit having a capacity larger than that of the energy storage means are arranged in front of the energy storage means in K voltage compensation circuits (K <N) among the plurality of voltage compensation circuits. And supplying energy from the second energy storage means to the energy storage means via the chopper circuit.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below. 1 is a block diagram of a voltage fluctuation compensating apparatus according to Embodiment 1 of the present invention.
As shown in FIG. 1, a first to third voltage compensation units 1 to 3 as a plurality of voltage compensation circuits are connected in series to the power system 4, and their output terminals are connected in parallel to a high-speed mechanical type. A steady short-circuit switch 5 is connected. The first to third voltage compensation units 1 to 3 are connected in series to each phase power line from the power system 4, but in FIG. 1, what is connected to the U-phase power line 7u is shown. Show. 7v is a V-phase power line. In addition, a control circuit 6 that performs voltage drop monitoring and power supply control based on the voltage drop in the power system is provided, and the output voltages of the first to third voltage compensation units 1 to 3 are serially connected to the system according to a command from the control circuit 6 To compensate for the system voltage drop.
[0008]
The first to third voltage compensation units 1 to 3 include first to third single-phase inverters 10, 20, and 30 and charging capacitors (first capacitor C 1, second capacitor as first energy storage means). And the AC side of the single-phase inverters 10, 20, and 30 are connected in series to the power system, and the single-phase inverters 10, 20, and 30 are DC voltages of the charging capacitors C1 to C3. Is converted into alternating current and output. Further, the ratio of the voltages (V1, V2, V3) charged in the first to third capacitors C1 to C3 in each voltage compensation unit 1 to 3 is set to a power ratio of about 2: 4: 2: 1
A first capacitor C1 in the first voltage compensation unit 1 is preceded by a large-capacitance capacitor C0 (hereinafter referred to as a capacitance capacitor C0) as a second energy storage unit, and a first capacitor C1. And a DC / DC converter 11 as a chopper circuit that connects the capacitor C0.
Further, the first to third capacitors C1 to C3 and the capacitive capacitor C0 are connected to the other phase via the first to third single-phase inverters 10, 20, and 30 from the phase (U-phase) power line 7u. In this case, charging is performed using the line voltage of the power system by the charging circuit connected to the V-phase power line 7v. The charging circuit in each voltage compensation unit 1 to 3 includes charging resistors R11 to R13, R21, R22, R31, R32, diodes D1, D2, D3, and Zener diodes D11, D12, D13. The Zener diodes D11, D12, and D13 can be charged efficiently, but can be charged without them.
[0009]
The configuration of the first to third single-phase inverters 10, 20, and 30 is shown in FIG. As shown in the figure, it is composed of a full-bridge inverter composed of four IGBTs 8 with diodes connected in antiparallel. The full bridge inverter may be composed of a self-extinguishing semiconductor switching element other than the IGBT. Further, the configuration is not limited to a full bridge, and may be a configuration of an inverter that generates a voltage, such as a half bridge.
[0010]
Next, the operation will be described.
Normally, the steady short-circuit switch 5 is in an ON state, and the current bypasses the voltage fluctuation compensation device and flows through the steady short-circuit switch 5, so that the device loss is reduced. Further, when the voltage of the power system is instantaneously decreased (at the time of a sag), the steady short-circuit switch 5 is turned off and a sag compensation operation is started. That is, the compensation voltage is output in each of the voltage compensation units 1 to 3 selected according to the error voltage. These outputs are combined in the system to generate a voltage output of 8 gradations from “000” to “111”, and the maximum compensation voltage is 7 × V3.
The ratio of the voltages (V1, V2, V3) charged in the first to third capacitors C1 to C3 in each voltage compensation unit 1 to 3 is approximately a power of 2, but is not limited to this. Absent. Further, the compensation voltage output from each voltage compensation unit 1 to 3 may include one having a polarity opposite to that of the system voltage. A pattern as shown in FIG. 3 can be considered as the relationship between the voltages V1, V2, and V3 and the gradation level of the output voltage. For example, the pattern G has the largest number of gradations, and the three voltage compensation units 1 to 3 can obtain 13 gradations. Therefore, it is possible to finely control the gradation of the output voltage, and to eliminate the output filter. Can do.
[0011]
Further, the voltage V0 of the capacitor C0 is charged sufficiently high in the initial stage, and the voltage V1 of the first capacitor C1 becomes a predetermined value by the DC / DC converter 11 having the voltage V0 of the capacitor C0 as an input. Control as follows. Note that the same effect can be obtained even if the capacitor C0 and the first to third capacitors C1 to C3 are not capacitors but energy storage means such as a battery.
As described above, the first to third capacitors C1 to C3 and the capacitive capacitor C0 are connected to the phase (U-phase) power line 7u through the first to third single-phase inverters 10, 20, and 30, respectively. Charging is performed using the line voltage of the power system by the charging circuit connected to the power line 7v of the other phase, in this case V-phase. This charging operation is performed at the time of starting up the apparatus and at a steady time when the power system does not cause an instantaneous drop.
[0012]
The first capacitor C1 in the first voltage compensation unit 1 is supplied with energy from the large-capacity capacitor C0 via the DC / DC converter 11, but the second and third voltage compensation units 2, The energy of the second and third capacitors C2 and C3 in FIG.
FIG. 4 shows another example of the relationship between the gradation level of the output voltage when the relationship between the voltages V1, V2, and V3 is 4: 2: 1, 5: 2: 1, and 6: 2: 1. . For example, as shown in FIG. 4A, when the same 1 is output as the output gradation level, there are three patterns. In the first case, only V3 is output from the third voltage compensation unit 3 with the minimum output, and in this case, energy is only released from the third capacitor C3. However, in the second case, V2 is output from the second voltage compensation unit 2 as positive and V3 is output as negative from the third voltage compensation unit 3, so that energy is released from the second capacitor C2, and the third Energy is supplied to the capacitor C3. In the third case, energy is released from the first capacitor C1, and energy is supplied to the second and third capacitors C2, C3.
In this way, energy can be transferred from the first capacitor C1 to the second and third capacitors C2 and C3 by using a plurality of patterns even if the output gradation level is the same. Such a selection pattern exists even in the case of other gradation output levels as shown in FIG.
[0013]
In this embodiment, when the power system is instantaneously reduced, the output voltage can include those of reverse polarity, and a predetermined combination is selected from the voltage compensation units 1 to 3, and each voltage according to the output pattern is selected. The sum of the output voltages of the compensation units 1 to 3 compensates for the voltage drop of the power system. At the time of compensation, the DC / DC converter 11 controls the voltage V1 of the first capacitor C1 that stores the maximum voltage to be a predetermined value with the voltage V0 of the capacitor C0 as an input. The second and third capacitors C2 and C3 perform output control so that the energy transfer by the energy release and the energy supply from the first capacitor C1 is balanced as much as possible. That is, the output pattern determined by the combination of the voltage compensation units 1 to 3 selected including the output voltage polarity is determined so that the energy transfer in the second and third capacitors C2 and C3 is balanced as much as possible. Output compensation voltage.
[0014]
For this reason, not only the first capacitor C1 but also the second and third capacitors C2 and C3 can be suppressed in voltage drop, and the continuous compensation time for voltage fluctuation can be lengthened. Also, when the maximum voltage specification that should be output cannot be satisfied because the energy of the capacity capacitor C0 is almost exhausted, the compensation limit is reached and the compensation ends, so the energy held by the first to third capacitors C1 to C3 at that time is As a result, it remains unused. Therefore, it is important for the effective use of energy to keep the capacities of the first to third capacitors C1 to C3 as small as possible. Thus, it is sufficient to provide one capacitance capacitor C0, which is a large-capacity capacitor, and it is possible to secure compensation time without increasing the size of the device. Further, as long as the voltage V1 of the first capacitor C1 is maintained at a predetermined value or more, it is possible to continuously compensate for voltage fluctuations. Therefore, the charging voltage of the capacitors C1 to C3 is increased more than necessary to widen the gradation width. Therefore, the gradation control of the output voltage can be performed finely and with high accuracy.
[0015]
Embodiment 2. FIG.
Next, in the voltage fluctuation compensator shown in the first embodiment, the operation for determining the output pattern and outputting the compensation voltage so as to balance the energy exchange between the second and third capacitors C2 and C3 as much as possible is described in detail. To do.
Here, for the sake of simplification, the second and third voltage compensation units 2 and 3 will be referred to as “filter units”. First, the case where the relationship between the voltages V1, V2, and V3 is 4: 2: 1 will be described. FIG. 5A shows output patterns of the filter units 2 and 3 and the maximum output unit (first voltage compensation unit 1) when each output gradation level is obtained. Here, Va is a voltage having a gradation width, and in this case, is equal to V3. FIG. 5B shows the energy amounts of the filter units 2 and 3 and the maximum output unit 1 when a sine wave is output by gradation control with a maximum of five levels.
First, considering only the filter units 2 and 3, the gradation levels that can be output only by the filter units 2 and 3 are 1 to 3, and the minimum output unit (the third voltage compensation unit 3) is responsible for 1 level. And 3 levels. At the first level and the third level, there is a pattern in which the minimum output unit 3 outputs voltage with both positive and negative polarities. That is, in the 1st level and 3rd level output conditions that the minimum output unit 3 takes in among the voltages generated by the filter units 2 and 3, there are a case where energy is supplied to the third capacitor C3 and a case where energy is released. Both exist. Therefore, if the energy of the second capacitor C2 does not increase or decrease under the conditions of gradation levels 1 to 3 generated by the filter units 2 and 3, the energy of the third capacitor C3 can be adjusted freely. Become.
[0016]
Next, in order not to increase or decrease the energy of the second capacitor C2, the amount of energy released from the entire filter units 2 and 3 may be supplied from the first capacitor C1.
As shown in FIG. 5B, when a sine wave is output by gradation control up to a maximum level of 5, it can be seen that the energy transfer between the filter units 2 and 3 is almost balanced. In this state, the energy transfer of the filter units 2 and 3 can be made substantially zero and balanced by selecting the output pattern. However, as can be seen from FIG. 5 (a), at the gradation levels of 6 and 7, the filter units 2 and 3 have outputs of 2Va and 3Va, that is, only patterns that emit energy. With the voltage output at the gradation level, the energy of the filter units 2 and 3 decreases.
[0017]
Next, when the relationship between the voltages V1, V2, and V3 is 5: 2: 1, FIG. 6A shows the filter units 2 and 3 and the maximum output unit (when the output gradation levels are obtained). The output pattern of the first voltage compensation unit 1) is shown. FIG. 6B shows the energy amounts of the filter units 2 and 3 and the maximum output unit 1 when a sine wave is output by gradation control with a maximum of 6 levels.
As shown in FIG. 6 (b), when a sine wave is output by gradation control up to a maximum level of 6, it is understood that the energy transfer between the filter units 2 and 3 is almost balanced. In this state, the energy transfer of the filter units 2 and 3 can be made substantially zero and balanced by selecting the output pattern. However, as can be seen from FIG. 6A, at the gradation level of 7, since the filter units 2 and 3 have only 2Va output, that is, a pattern that emits energy, the energy of the filter units 2 and 3 decreases. Will do.
Next, when the relationship between the voltages V1, V2, and V3 is 6: 2: 1, FIG. 7A shows the filter units 2 and 3 and the maximum output unit ( The output pattern of the first voltage compensation unit 1) is shown. FIG. 7B shows the energy amounts of the filter units 2 and 3 and the maximum output unit 1 when a sine wave is output by gradation control with a maximum of 7 levels.
As shown in FIG. 7B, when the sine wave is output by gradation control up to a maximum level of 7, it can be seen that the energy transfer between the filter units 2 and 3 is almost balanced. In this state, the energy transfer of the filter units 2 and 3 can be made substantially zero and balanced by selecting the output pattern.
[0018]
The energy of the filter units 2 and 3 changes as described above when the relationship among the voltages V1, V2 and V3 is 4: 2: 1, 5: 2: 1 and 6: 2: 1. When a sine wave is output by gradation control up to a maximum level of 5, 4: 2: 1 is used, and when gradation control is required up to a maximum level of 6, it is switched to 5: 2: 1. When gradation control is required up to 7, switching to 6: 2: 1 makes it possible to balance the energy transfer of the filter units 2 and 3 to almost zero. As described above, the energy of the third capacitor C3 can be adjusted in the entire filter units 2 and 3, so that the voltage V3 of the third capacitor C3 is constant.
As described above, in order to switch the relationship between the voltages V1, V2, and V3, the voltage V1 of the first capacitor C1 may be increased from a value of 4 determined by 1: 2: 4 to a value of 5 or 6. I understand that.
As a result, the capacitance values of the second and third capacitors C2 and C3 can be made as small as possible, and the remaining energy can be reduced when the maximum voltage specification to be output cannot be satisfied. This can increase the energy utilization rate of the apparatus and lead to a reduction in the size of the apparatus.
[0019]
Note that the relationship among the voltages V1, V2, and V3 is not fixed at 5: 2: 1 or 6: 2: 1. For example, when 1 level is output as the output gradation level, when 5: 2: 1 or 6: 2: 1, energy cannot be supplied to the filter units 2 and 3 as shown in FIGS. Therefore, in such a case, the energy in the filter units 2 and 3 is immediately lost. On the other hand, when 4: 2: 1 is used, energy can be supplied to the filter units 2 and 3 even when the output gradation level is 1 or 2 as shown in FIG.
Therefore, according to the situation of each capacitor C0 to C3, according to the occurrence situation of the instantaneous drop, or according to the situation of energy transfer to the filter units 2 and 3 or the voltage situation of the capacitors C2 and C3, By changing the voltage V1 of the first capacitor C1 by the DC / DC converter 11, more effective use of energy becomes possible.
[0020]
Further, there is a limit to reducing the capacitance values of the capacitors C2 and C3 of the filter units 2 and 3. For example, as can be seen from FIGS. 5 to 7, the increase or decrease of the energy of the filter units 2 and 3 is, of course, the result of the integration of the half cycle of the sine wave, so that the voltage is kept stable during the half cycle. Only a capacitance value is required.
Further, when the instantaneous drop situation suddenly changes, the voltage of the first capacitor C1 needs to be suddenly changed and set to a predetermined voltage. Therefore, the capacitance value of the first capacitor C1 also in this respect Should be smaller. For example, once the voltage V1 of the first capacitor C1 is set to the 6th level, a situation where the instantaneous drop becomes lighter and it must be reduced to the 4th level is conceivable.
That is, it is desirable that (capacitance value of capacitor C1) <(capacitance value of capacitors C2 and C3).
[0021]
Embodiment 3 FIG.
Next, in the voltage fluctuation compensating apparatus shown in the first embodiment, an operation for compensating voltage fluctuation by changing the voltage V1 of the first capacitor C1 by the DC / DC converter 11 will be described.
FIG. 8 is a flowchart showing an output voltage setting and voltage fluctuation compensation operation of the DC / DC converter 11 which is a chopper circuit.
It is assumed that the relationship among the voltages V1, V2, and V3 is set to 4: 2: 1 at the initial time point. First, when an instantaneous drop in the power system is detected (S1), the output voltage of the DC / DC converter 11 is A target value level of a certain chopper voltage V1 is set to 4 (S2). Subsequently, it is determined whether the maximum magnitude of the compensation voltage to be output is 7 gradations (S3), and if it is not necessary, it is determined whether the maximum 6 gradations are necessary (S4). 4 is a maximum of 5 gradations or less, the gradation generation pattern of the logic table shown in FIG. 4A is V3: V2: V1 = 1: 2: 4 (S5), and V3 is the minimum output voltage. If V3 is lower than the specified value, the mode (output pattern) in which V3 is charged is selected. If V3 is higher than the specified value, the mode in which V3 is discharged is selected (S6). The power supply voltage drop is compensated for by the sum of the output voltages from (S7). Thereafter, the process returns to S3.
[0022]
In S3, if the maximum magnitude of the compensation voltage to be output is 7 gradations, the target value level of the chopper voltage V1 is set to 6 (S12), and V3: V2: V1 shown in FIG. = 1: 2: 6 The gradation generation pattern in the logic table is determined (S15). If V3 which is the minimum output voltage is lower than the specified value, the mode in which V3 is charged is selected, and V3 is the specified value. If it is higher, the mode in which V3 is discharged is selected (S16), and the instantaneous drop of the power system is compensated by the sum of the output voltages from the voltage compensation units 1 to 3 (S17). Thereafter, the process returns to S15.
In S4, if the maximum value of the compensation voltage to be output is 6 gradations, the target value level of the chopper voltage V1 is set to 5 (S22), and V3: V2: V1 shown in FIG. = 1: 2: 5 The gradation generation pattern in the logic table is determined (S25), and if the minimum output voltage V3 is lower than the specified value, the mode in which V3 is charged is selected, and V3 is the specified value. If it is higher, the mode in which V3 is discharged is selected (S26), and the instantaneous drop of the power system is compensated by the sum of the output voltages from the voltage compensation units 1 to 3 (S27). Subsequently, it is determined whether the magnitude of the compensation voltage to be output requires a maximum of 7 gradations (S28). If unnecessary, the process proceeds to S22, and if necessary, the process proceeds to S12.
[0023]
Next, FIG. 9 is a flowchart showing a second example of the setting of the output voltage of the DC / DC converter 11 which is a chopper circuit and the compensation operation for voltage fluctuation.
In this case, after steps S7, S17, and S27 of the voltage fluctuation compensation operation in the case shown in FIG. 8, it always returns to S3 to determine whether the magnitude of the compensation voltage to be output requires a maximum of 7 gradations. If unnecessary, it is determined in S4 whether a maximum of 6 gradations is necessary.
In this case, it is effective when the instantaneous drop situation changes greatly, and the necessary output pattern can be set appropriately even if the output voltage changes for the instantaneous drop level that changes from moment to moment. The chopper voltage V1 is set repeatedly. Thus, for example, when 7 level output is required and 2 level output is required thereafter, V3: V2: V1 is once changed to 1: 2: 6 and then returned to 1: 2: 4. Operate. In this way, it is possible to deal with various instantaneous drop situations.
In the examples shown in FIGS. 8 and 9, the relationship of V3: V2: V1 is set according to the required compensation voltage gradation, and the voltage V3 of the third capacitor C3 is monitored. Although used for control, it is not necessary to monitor the voltage V2 of the second capacitor C2, so that the circuit is simplified.
[0024]
Next, FIG. 10 is a flowchart showing a third example of the setting of the output voltage of the DC / DC converter 11 which is a chopper circuit and the compensation operation for voltage fluctuation.
It is assumed that the relationship among the voltages V1, V2, and V3 is set to 4: 2: 1 at the initial time point. First, when an instantaneous drop in the power system is detected (T1), the output voltage of the DC / DC converter 11 is A target value level of a certain chopper voltage V1 is set to 4 (T2). Subsequently, it is determined whether or not the difference between the voltage V2 of the second capacitor C2 and the specified value is within a certain range (T3). When the difference is outside the certain range, it is determined whether or not the voltage V2 is higher than the specified value (T4). ). When V2 is higher than the specified value, switching is performed to increase the target value level of the chopper voltage V1 (T5a), and when V2 is equal to or lower than the specified value, switching is performed to decrease the target value level of the chopper voltage V1 (T5b). ) Control the chopper. Thereafter, the tone generation pattern (V3: V2: V1) is switched to one of 1: 2: 4, 1: 2: 5, or 1: 2: 6 according to the target value level of the chopper voltage V1 (T6). ) If the voltage V2 of the second capacitor C2 is lower than the specified value, the mode (output pattern) in which V2 is charged is selected. If V2 is higher than the specified value, the mode in which V2 is discharged is selected (T7). ). If the minimum output voltage V3 is lower than the specified value, the mode in which V3 is charged is selected. If V3 is higher than the specified value, the mode in which V3 is discharged is selected (T8). The instantaneous drop of the power system is compensated by the sum of the output voltages from the units 1 to 3 (T9). Thereafter, the process returns to T3.
When the difference between the voltage V2 and the specified value is within a certain range at T3, the gradation generation pattern (V3: V2: V1) is set at T6 without changing the target value level of the chopper voltage.
[0025]
In the example shown in FIG. 10, the voltages V2 and V3 of the second and third capacitors C2 and C3 are monitored and the voltage V1 is controlled by the DC / DC converter 11 which is a chopper circuit. Each can be kept constant, and compensation with high accuracy is possible for a long time.
Note that the gradation generation pattern switching timing may be immediately after the target value of the chopper voltage V1 is changed, or may be when the actual voltage of V1 reaches the target value.
[0026]
In addition, regarding the setting of the target value of the chopper voltage V1, in all of the above explanations, the gradation level is changed one by one between 4 and 6, but by increasing or decreasing the voltage value below one gradation. Even if there is, there is no problem as long as the logical table for determining the output pattern is rewritten. Of course, the gradation width is not always constant, but voltage compensation by highly accurate gradation control as a whole can be performed.
Furthermore, in the example shown in FIG. 10, the voltages V2 and V3 of the second and third capacitors C2 and C3 are monitored. These voltage values can also be obtained by calculation, for example, the system current and the output mode. Thus, the changes in the voltages V2 and V3 can be calculated, and thereby the setting of the chopper voltage can be determined.
[0027]
Embodiment 4 FIG.
As described above, the chopper voltage V1 is controlled so that the energy transfer between the second and third capacitors C2 and C3 is balanced as much as possible, the output pattern is determined, and the compensation voltage is output. (Pulse width) can be adjusted to correct energy transfer and to approach zero.
For example, if the voltage V2 is lower than a specified value, the pulse width of the voltage generation compensation time is slightly changed so that the charging is increased and the discharging is reduced in the time for generating the voltage V2. At this time, since the effective value of the output voltage is lowered, the time for generating the voltage V1 may be slightly extended.
FIG. 11 shows adjustment of compensation time (pulse width) by each output pattern when a sine wave is output by gradation control with a maximum level of 7 levels. It can be seen that, with the generated voltage in which the pulse width is corrected with respect to the normal generated voltage, the pulse width at the gradation level of 3 to 5 is widened, and the pulse width at the 7th level is narrowed. If the tone generation pattern (V3: V2: V1) is 1: 2: 6, the generated voltage with the corrected pulse width increases the amount of charge with respect to the normal generated voltage and decreases the amount of discharge. Become. Therefore, the energy transfer of the filter units 2 and 3 can be changed by correcting the pulse width. That is, when the energy amount of the filter units 2 and 3 is small, the energy amount is recovered by widening the pulse width of the output pattern for charging and narrowing the pulse width of the output pattern for discharging. The energy exchange between the units 2 and 3 can be made almost zero.
[0028]
Embodiment 5 FIG.
Next, a fifth embodiment of the present invention will be described. In the first embodiment shown in FIG. 1, the capacitor C0 and the DC / DC converter 11 as a chopper circuit are provided in the first stage of the first capacitor C1 in the first voltage compensation unit 1. In the embodiment, as shown in FIG. 12, a step-down chopper 12, a step-up chopper 13 or a step-up / step-down chopper 14 is provided between a capacitance capacitor C0 having a voltage V0 and a first capacitor C1 having a voltage V1. Other configurations are the same as those in the first embodiment.
First, the case where the step-down chopper 12 shown to 12 (a) is used is demonstrated using FIG. FIG. 13A is a diagram showing the configuration of the voltage fluctuation compensation device. For convenience, the third voltage compensation unit 3, the steady short circuit switch 5, and the control circuit 6 are not shown. As shown in the figure, a step-down chopper 12 including a chopper switch 12a, a diode 12b, and a reactor 12c is provided between a capacitive capacitor C0 and a first capacitor C1. R0x and R0y are charging resistors for charging the capacitor C0, R1x and R1y are charging resistors for charging the first capacitor C1, and R2x and R2y are charging resistors for charging the second capacitor C2. It is.
[0029]
Next, the operation will be described.
When the U-phase potential is higher than the V-phase potential, the U-phase captured from the U-phase power line 7u via the output terminal of the first single-phase inverter 10 in the first voltage compensation unit 1 which is the maximum output unit. The voltage passes through the diode of the upper arm (right side in the figure) of the first single-phase inverter 10 and passes through the C1 + terminal, charges the first capacitor C1, passes through the charging resistor R1y, passes through the diode D1, and passes through the V phase. Return to power line. Further, the capacitor C0 is charged from the C1 + terminal to the C0 + terminal, further passes through the charging resistor R0y, passes through the diode D1, and returns to the V-phase power line. When the U-phase potential is lower than the V-phase potential, D1 is turned off, so that the charges charged in the capacitor C0 and the first capacitor C1 are maintained as they are. The magnitude of the voltage V0 of the capacitor C0 and the voltage V1 of the first capacitor C1 is finally determined by the respective voltage divisions by the charging resistors R0x, R0y, R1x, R1y, and by selecting these values It can be set to a predetermined value.
[0030]
As an operation of the voltage sag compensation, the steady short-circuit switch 5 is turned on in a steady state, and at that time, the outputs of the single-phase inverters 10 and 20 are zero, that is, the upper arm side can be turned on. At this time, the lower arm side may be turned on. In this case, the same operation can be obtained by inverting the polarities of the diodes D1 to D3). Therefore, in the steady state, the point where the inverter output potentials of the first single-phase inverter 10 and the second single-phase inverter 20 are connected is the same as the U potential. Therefore, also in the second voltage compensation unit 2, the second capacitor C2 is charged by the charging resistors R2x and R2y and the diode D2, and the voltage V2 can be set to a predetermined value by selecting the resistance value. It is. Note that the third capacitor C3 can be charged similarly for the third voltage compensation unit 3 (not shown).
For example, consider a case in which V1, V2, and V3 are first charged in a 4: 2: 1 relationship and charged under the condition of V0> V1. In the state where the initial charging is completed, V0 is set higher than V1. R0x, R0y, R1x, R1y represent the respective resistance values, and when (Vrms * 1.141) is the effective value of the line voltage, when the initial charge is completed,
V0 = R0x / (R0x + R0y) * (Vrms * 1.141)
V1 = R1x / (R1x + R1y) * (Vrms * 1.141)
FIG. 13B shows the relationship between the time T and the voltages V1 and V0. At T = 0, an instantaneous drop occurs in the power system, and compensation is started. At this time, for the sake of simplification, it is assumed that the voltage drop condition does not require changing the target value of the voltage V1. The voltage of the capacitor C0 is transferred to the first capacitor C1 using the step-down chopper 12 so that the voltage V1 of the first capacitor C1 does not decrease while compensating for the voltage sag from T = 0. As a result, the voltage V0 of the capacitive capacitor C0 gradually decreases, eventually V0 = V1, and almost reaches the limit of compensation.
[0031]
Next, the case of using the boost chopper 13 shown in 12 (b) will be described with reference to FIG. FIG. 14A is a diagram showing the configuration of the voltage fluctuation compensating apparatus. For convenience, only the first voltage compensation unit 1 is shown here.
As shown in the figure, a step-up chopper 13 including a chopper switch 13a, a diode 13b, and a reactor 13c is provided between a capacitive capacitor C0 and a first capacitor C1. R0x and R0y are charging resistors, and R1x and R1y do not exist.
Next, the operation will be described.
When the U-phase potential is higher than the V-phase potential, in the first voltage compensation unit 1, the U-phase voltage captured from the U-phase power line 7 u via the output terminal of the first single-phase inverter 10 is the first voltage compensation unit 1. The first capacitor C1 and the capacitor C0 are charged through the diode of the upper arm (right side in the figure) of the single-phase inverter 10 and then returned to the V-phase power line through the diode D0 and the charging resistor R0y. At this time, the voltage V0 of the capacitor C0 and the voltage V1 of the first capacitor C1 are set to be equal. When initial charging is complete,
V0 = R0x / (R0x + R0y) * (Vrms * 1.141) = V1.
FIG. 14B shows the relationship between the time T and the voltages V1 and V0. At T = 0, an instantaneous drop in the power system occurs and the voltage V0 decreases as the instantaneous drop compensation proceeds. However, the energy of the capacitive capacitor C0 is transferred to the first capacitor C1 using the boost chopper 13. Therefore, even if the voltage V0 decreases, the first capacitor C1 can always be set to the constant voltage V1. In this case, compensation can be continued until the voltage V0 of the capacitor C0 becomes zero.
[0032]
Next, a case where the step-up / step-down chopper 14 shown in FIG. 12C is used will be described with reference to FIG. FIG. 15A is a diagram showing a configuration of the voltage fluctuation compensating device. For convenience, only the first voltage compensation unit 1 is shown here.
As shown in the figure, a step-up / step-down chopper 14 including a chopper switch 14a, a diode 14b, and a reactor 14c is provided between a capacitive capacitor C0 and a first capacitor C1. R0x and R0y are charging resistors, and R1x and R1y do not exist.
Next, the operation will be described.
In the steady state, all the arms of the first single-phase inverter 10 are turned on. As a result, the first capacitor C1 is not charged, and the voltage V0 determined by the divided voltage of the Rox and Roy resistors is charged only to the capacitor C0.
V0 = R0x / (R0x + R0y) * (Vrms * 1.141)
FIG. 15B shows the relationship between the time T and the voltages V1 and V0.
At T = 0, an instantaneous power supply voltage drop occurs, and at that time, the voltage V1 is zero. Therefore, each arm of the first single-phase inverter 10 is fully turned off, and the voltage V1 of the first capacitor C1 is immediately The step-up / step-down chopper 14 is controlled so as to obtain a predetermined value. Then, instantaneous drop compensation is started. As the compensation proceeds, the voltage V0 decreases. However, since the energy of the capacitive capacitor C0 is transferred to the first capacitor C1 using the step-up / step-down chopper 14, even if the voltage V0 decreases, the first capacitor C1. Can always be a constant voltage V1. In this case, since the configuration of the chopper 14 is a step-up / step-down type, the voltage V1 can be kept constant even when V0 <V1, and compensation is continued until the voltage V0 of the capacitor C0 finally becomes zero. Is possible.
[0033]
Next, another example in which the step-up / step-down chopper shown in 12 (c) is used will be described with reference to FIG. FIG. 16A is a diagram showing the configuration of the voltage fluctuation compensation device. For convenience, only the first voltage compensation unit 1 is shown here.
As shown in the figure, a step-up / step-down chopper 15 including a chopper switch 15a, a diode 15b, and a reactor 15c is provided between a capacitive capacitor C0 and a first capacitor C1. R0x and R0y are charging resistors for charging the capacitor C0, and R1x and R1y are charging resistors for charging the first capacitor C1. The diode D1 has a positive electrode connected to the charging resistor R1y and a negative electrode connected to the first capacitor C1.
Next, the operation will be described.
In the steady state, the upper arm of the first single-phase inverter 10 is turned on. Thereby, when the potential of the U phase is higher than the potential of the V phase, the capacitor C0 can be charged, and when the potential of the U phase is lower than the potential of the V phase, the first capacitor C1 can be charged. In this case, when charging is performed under the condition of V0> V1 and initial charging is completed, V0 is set higher than V1. When initial charging is complete,
V0 = R0x / (R0x + R0y) * (Vrms * 1.141)
V1 = R1x / (R1x + R1y) * (Vrms * 1.141)
FIG. 15B shows the relationship between the time T and the voltages V1 and V0.
At T = 0, an instantaneous drop in the power system occurs and compensation is started. As the compensation proceeds, the voltage V0 decreases, but the energy of the capacitive capacitor C0 is transferred to the first capacitor C1 using the step-up / step-down chopper 15, so even if the voltage V0 decreases, the first voltage V0 decreases. The capacitor C1 can always be a constant voltage V1. In this case, since the configuration of the chopper 15 is a step-up / step-down type, even if V0 <V1, the voltage V1 can be kept constant, and compensation is continued until the voltage V0 of the capacitive capacitor C0 finally becomes zero. Is possible.
[0034]
In each of the above embodiments, the capacitors C0 to C3 are charged using the line voltage of the power system, but may be charged with a charging transformer.
Further, when the number of voltage compensation units increases, the capacitor and the chopper circuit may be provided not only in the maximum output unit but also in two or more voltage compensation units.
[0035]
【The invention's effect】
As described above, the voltage fluctuation compensator according to the present invention includes a control unit that performs voltage drop monitoring and power feeding control based on the voltage drop in the power system, and energy that is connected in series to the power system and stores different voltages. A plurality of (N) voltage compensation circuits that convert the DC voltage stored in the storage means into AC and output it, and when the voltage of the power system drops, the output voltage can include those of opposite polarity A predetermined combination is selected from the plurality of voltage compensation circuits, and the voltage drop of the power system is compensated by the sum of the output voltages by the combination including the output voltage polarity (hereinafter referred to as an output pattern). Suppresses voltage fluctuations that occur in the load. A second energy storage means and a chopper circuit having a capacity larger than that of the energy storage means are arranged in front of the energy storage means in K voltage compensation circuits (K <N) among the plurality of voltage compensation circuits. Since the energy is supplied from the second energy storage means to the energy storage means via the chopper circuit, voltage compensation with high accuracy and a long continuous compensation time can be achieved without increasing the size of the apparatus. Can be done.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a voltage fluctuation compensating apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a configuration diagram of a single-phase inverter according to Embodiment 1 of the present invention.
FIG. 3 is a voltage generation pattern of the single-phase inverter according to the first embodiment of the present invention.
FIG. 4 is another example of the voltage generation pattern of the single-phase inverter according to the first embodiment of the present invention.
FIG. 5 is a diagram showing an output pattern and an energy amount of each voltage compensation unit according to Embodiment 2 of the present invention.
FIG. 6 is a diagram showing an output pattern and an energy amount of each voltage compensation unit according to another example of the second embodiment of the present invention.
FIG. 7 is a diagram showing another example of the output pattern and energy amount of each voltage compensation unit according to another example of the second embodiment of the present invention.
FIG. 8 is a flowchart showing an output voltage setting and voltage fluctuation compensation operation of a chopper circuit according to a third embodiment of the present invention.
FIG. 9 is a flowchart showing an output voltage setting and voltage fluctuation compensating operation of a chopper circuit according to another example of the third embodiment of the present invention.
FIG. 10 is a flowchart showing an output voltage setting and voltage fluctuation compensating operation of a chopper circuit according to another example of the third embodiment of the present invention.
FIG. 11 is a diagram showing adjustment of compensation time of each output pattern according to Embodiment 4 of the present invention.
FIG. 12 is a configuration diagram of a voltage fluctuation compensating apparatus according to Embodiment 5 of the present invention.
FIG. 13 is a detailed configuration diagram and an operation explanatory diagram of a voltage fluctuation compensator according to Embodiment 5 of the present invention;
FIG. 14 is a detailed configuration diagram and an operation explanatory diagram of a voltage fluctuation compensator according to another example of the fifth embodiment of the present invention;
FIG. 15 is a detailed configuration diagram and an operation explanatory diagram of a voltage fluctuation compensator according to another example of the fifth embodiment of the present invention;
FIG. 16 is a detailed configuration diagram and an operation explanatory diagram of a voltage fluctuation compensator according to another example of the fifth embodiment of the present invention;
[Explanation of symbols]
1-3 First to third voltage compensation units as voltage compensation circuits,
4 power system, 6 control circuit, 10 first single-phase inverter,
11 DC / DC converter as chopper circuit, 12 step-down chopper,
13 Boost chopper, 14, 15 Buck-boost chopper,
20 second single-phase inverter, 30 third single-phase inverter,
C0 capacitive capacitor as second energy storage means,
C1 to C3 First to third capacitors as energy storage means.

Claims (5)

A controller that performs voltage drop monitoring and power supply control based on the voltage drop in the power system, and a DC voltage stored in the energy storage means connected in series to the power system and storing different voltages is converted into an AC. A plurality of (N) voltage compensation circuits for outputting, and when the voltage of the power system drops, it is possible to include output voltages having a reverse polarity, so that a predetermined combination of the plurality of voltage compensation circuits is provided. In the voltage fluctuation compensation device that suppresses the voltage fluctuation generated in the load by compensating for the voltage drop of the power system with the sum of each output voltage by the combination including the output voltage polarity (hereinafter referred to as an output pattern), Among the plurality of voltage compensation circuits, K energy (K <N) in the voltage compensation circuit, the second energy having a capacity larger than that of the energy storage means is provided in the preceding stage. It provided a product means the chopper circuit, the energy storage means of the second through the chopper circuit voltage fluctuation compensating apparatus characterized by supplying energy to said energy storage means. The second energy storage means and the chopper circuit are provided only before the energy storage means for storing the maximum voltage (hereinafter referred to as the maximum energy storage means) among the plurality of energy storage means in which different voltages are stored. The voltage fluctuation compensation apparatus according to claim 1, wherein the voltage fluctuation compensation apparatus is provided. The output pattern is determined so that energy transfer in the voltage compensation circuit other than the voltage compensation circuit having the maximum energy storage means (hereinafter referred to as the maximum output compensation circuit) is balanced when the voltage drop of the power system is compensated. The voltage fluctuation compensating apparatus according to claim 2, wherein: By controlling the chopper circuit, the voltage of the maximum energy storage means that becomes the output voltage of the maximum output compensation circuit can be controlled, and when the voltage of the power system drops, the maximum energy storage means 4. The voltage fluctuation compensator according to claim 3, wherein the voltage is controlled. When compensating the voltage drop of the power system by the determined output pattern, adjusting the compensation time by the output pattern so as to balance the transfer of energy in the voltage compensation circuit other than the maximum output compensation circuit. The voltage fluctuation compensating apparatus according to claim 3 or 4, characterized in that:

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