JP2009225583A - Device of compensating reactive power and harmonic current - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology that enables a reactive power and a harmonic current to be compensated cost effectively. <P>SOLUTION: An LC circuit 20 has a series resonance circuit, in which capacitors 21u, 21v, 22w (or 22u, 22v, 22w) are connected to reactors 23u, 23v, 23w in series. A series circuit of the series resonance circuit of the LC circuit 20 and secondary windings 31u2, 31v2, 31w2 of a transformer 30 is connected to power lines 3u, 3v, 3w. A control device 50 controls a semiconductor power conversion device 60 to supply primary currents Itu, Itv, Itw for compensation to the primary windings 31u, 31v, 31w of the transformer 30. Thereby, secondary voltages VT (VTu, VTv, VTw) for compensation are outputted from the secondary windings 31u2, 31v2, 31w2 of a transformer 30, and compensation currents IAF (IAFu, IAFv, IAFw), which compensate the reactive currents and harmonic currents, are supplied to the power lines 3u, 3v, 3w. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique capable of preferably compensating reactive power and harmonic current in a power system.

An electric power consumer is provided with an electric power system having an electric power line and a load connected to the electric power line. The power line of the power consumer is connected to the power line of the power system (distribution system) on the distribution side. Generally, the load of a power consumer is a delayed power factor and generates delayed reactive power. The delayed reactive power of the load of the power consumer has various effects on the distribution system. For this reason, it is desirable to provide a reactive power compensator for compensating reactive power of a load on the power demand side. Patent Document 1 discloses a reactive power compensator 110 as shown in FIG. The reactive power compensator 110 illustrated in FIG. 10 is connected to the power lines 3u, 3v, and 3w connected to the load 4 on the power consumer side. The reactive power compensation device 110 includes a transformer 130, capacitors 122u, 122v, 122w, and an inverter 160. The transformer 130 has primary windings 131u1, 131v1, 131w1 and secondary windings 131u2, 131v2, 131w2. The secondary windings 131u2, 131v2, 131w2 of the transformer 130 and the capacitors 122u, 122v, 122w are connected to the power lines 3u, 3v, 3w in a state of being connected in series. Primary windings 131 u 1, 131 v 1, 131 w 1 of the transformer 130 are connected to the inverter 160. The control device (not shown) generates reactive power compensating primary currents Itu, Itv supplied from the inverter 160 to the primary windings 131u1, 131v1, 131w1 of the transformer 110 according to the power factor of the power lines 3u, 3v, 3w. , Itw is controlled and in accordance with the power factor of the power lines 3u, 3v, 3w from the secondary windings 131u2, 131v2, 131w2 of the transformer 130 in phase or in phase with the fundamental voltage of the power lines 3u, 3v, 3w Reactive power compensation secondary voltages VTu, VTv, and VTw having values are output. As a result, the fundamental voltage applied to the capacitors 122u, 122v, 122w, that is, the fundamental currents ICu, ICv, ICw flowing through the capacitors 122u, 122v, 122w change, and the power lines 3u, 3v, Reactive power compensation compensation currents IAFu, IAFv, and 1AFw supplied to 3w change to compensate the power factor (reactive power) of power lines 3u, 3v, and 3w.
JP-A-10-243563

By the way, in recent years, loads using inverters are increasing rapidly for the purpose of energy saving. Such a load generates harmonic current. The harmonic current has various effects on the distribution system. For this reason, it is desired to provide a reactive power and harmonic current compensator capable of compensating not only reactive power but also harmonic current on the consumer side.
Here, in addition to the reactive power compensator disclosed in Patent Document 1, it is conceivable to provide a harmonic current compensator for compensating the harmonic current on the consumer side. However, the reactive power and harmonic current compensator having individual reactive power compensators and harmonic current compensators are large in size and high in cost. Further, it is conceivable to connect a semiconductor power conversion device constituted by an inverter or the like to the power line, and to control the semiconductor power conversion device according to the value of reactive power and the harmonic current of the power line. However, in such a reactive power and harmonic current compensator, [the value of the power line voltage (fundamental wave voltage) × the value of the compensation current (the value of the compensation current for reactive power compensation and the value of the compensation current for harmonic current compensation) Therefore, the cost of the entire device is increased.
The present invention has been made in view of such a point, and an object thereof is to provide a technique capable of compensating reactive power and harmonic current at low cost.

The present invention relates to a reactive power and harmonic current compensation device for compensating reactive power and harmonic current in a power system having a power line and a load connected to the power line. The reactive power and harmonic current compensator of the present invention is preferably provided in the power system on the power consumer side, but can also be provided in the power system on the power provider side.
The present invention includes a series resonant circuit in which a reactor and a capacitor are connected in series, a transformer having a primary winding and a secondary winding, a power conversion device, and a control device. The present invention can be applied to power lines having an appropriate number of phases. The configuration of the series resonant circuit, the transformer, the power conversion device, and the control device is appropriately changed according to the number of phases of the distribution system.
The reactor and the capacitor constituting the series resonance circuit are connected in series as viewed from the power line. The “series resonance circuit” includes a circuit in which a reactor and a capacitor are equivalently connected in series. The frequency characteristics (resonance frequency, etc.) of the series resonance circuit have high impedance for the fundamental frequency of the fundamental current (basic voltage) of the power line and low impedance for the harmonic frequency of the harmonic current flowing into the power line from the load. Is set to be Preferably, it is determined based on a harmonic current component flowing into the power line from a load or the like. For example, when the harmonic current component flowing into the power line from a load or the like contains many components of the fifth harmonic current and the seventh harmonic current (the fifth harmonic current capacity and the In the case where the capacity of the seventh harmonic current is particularly larger than the capacity of other harmonic currents), the impedance of the series resonant circuit is reduced so as to be smaller than the fifth and seventh frequencies. A frequency near the sixth frequency (fundamental wave frequency × 6) between the next frequency and the seventh frequency is set as the resonance frequency.
The series resonant circuit and the secondary winding of the transformer are connected to the power line so as to be in parallel with the load while being connected in series. The primary winding of the transformer is connected to the power converter. As the power converter, for example, a semiconductor power converter having an inverter or the like is used. The control device controls the power conversion device according to the value of the reactive power of the power line and the value of the harmonic current, thereby compensating the reactive power compensation electric quantity for compensating the reactive power of the power line and the harmonic current of the power line. Supply electrical power for harmonic current compensation to the power line. For example, reactive power compensation compensation current (or reactive current compensation compensation current) and harmonic current compensation compensation current are supplied as the reactive power compensation electrical quantity and the harmonic current compensation electrical quantity.
As the “reactive power value of the power line”, the reactive power value (reactive power value after compensation) of the power line on the power source side from the position of the power line to which the reactive power and the harmonic current compensator are connected can be used. The reactive power value of the load side power line (the reactive power value before compensation) can also be used. As the “value of the reactive power of the power line”, “the value of the fundamental reactive power of the power line” is typically used. The mode of “control according to the reactive power value of the power line” includes a mode of controlling according to another detection amount (eg, reactive current value or power factor) corresponding to the reactive power value of the power line. . As an aspect of “controlling the power conversion device according to the reactive power value of the power line”, for example, the power line has a fundamental frequency and a fundamental reactive power value, and the reactive power compensation is in phase opposite to the fundamental reactive power of the power line A mode is used in which the power converter is controlled so that the compensation reactive power for power supply is supplied to the power line. Typically, the secondary voltage for reactive current compensation having a value corresponding to the fundamental frequency of the power line and the fundamental reactive current value of the power line is the same as or opposite to the fundamental voltage of the power line. A mode is used in which the primary current for compensating reactive current is supplied from the power conversion device to the primary winding of the transformer so that it is output from the winding.
The value of the harmonic current of the power line uses the value of the harmonic current of the power line on the power supply side from the location of the power line to which the reactive power and the harmonic current compensator are connected (value of the harmonic current after compensation). It is also possible to use the value of the harmonic current of the power line on the load side (the value of the harmonic current before compensation). As the “value of the harmonic current of the power line”, the value of the h-th harmonic current of the power line is used. In this case, the order h of the harmonic current can be appropriately selected from one or more orders among the orders of the harmonic current flowing into the power line from the load or the like. The mode of “control according to the value of the harmonic current of the power line” includes a mode of control according to another detection amount corresponding to the value of the harmonic current of the power line. As an aspect of “controlling the power converter according to the value of the harmonic current of the power line”, for example, it has the same frequency as the frequency of the harmonic current of the power line and the value of the harmonic current of the power line, A mode is used in which the power conversion device is controlled such that a compensation current for compensating the harmonic current having a phase opposite to that of the current is supplied to the power line. Typically, it has a value corresponding to the frequency of the h-th harmonic current of the power line and the value of the h-th harmonic current of the power line, and the h-th harmonic of the power line is opposite in phase to the h-th harmonic current. A mode in which the primary current for h-th harmonic current compensation is supplied from the power converter to the primary winding of the transformer so that the secondary voltage for wave current compensation is output from the secondary winding of the transformer. Used.
In the present invention, a series circuit of a series resonant circuit in which a reactor and a capacitor are connected in series and a secondary winding of a transformer is connected to a power line so as to be in parallel with a load. Since the impedance of the series resonant circuit is set higher than the fundamental frequency of the power line, the fundamental voltage of the power line is divided by the series resonant circuit and the secondary winding of the transformer in the secondary winding of the transformer. Applied voltage. For this reason, the secondary voltage for reactive power compensation can be output from the secondary winding of the transformer using a small-capacity power converter. Further, the impedance of the series resonance circuit is set to be lower than the frequency of the harmonic current of the power line. Since the value of the harmonic current of the power line is small, a secondary voltage for harmonic current compensation can be generated in the secondary winding of the transformer using a small-capacity power converter. Therefore, reactive power and harmonic current can be compensated using a small-capacity power converter, and a small and inexpensive reactive power and harmonic current compensating apparatus can be provided.

In another aspect of the present invention, the control device includes a reactive power compensation target current value calculated using a reactive power value of the power line and a reactive power compensation control gain, a harmonic current value of the power line, and a harmonic current compensation. The power converter is controlled in accordance with the target current value for harmonic current compensation calculated using the control gain. Further, when the value of the output voltage of the power converter exceeds the first set value, the reactive power compensation control gain according to the value of the power line voltage so that the value of the output voltage of the power converter decreases. Alternatively, at least one of the harmonic current compensation control gains is corrected.
The reactive power compensation target current value is calculated by, for example, multiplying the reactive power compensation control gain by the reactive power value of the power line [reactive power compensating control gain × the reactive power value of the power line]. In this case, the reactive power compensation control gain is supplied to the primary winding of the transformer in order to supply the reactive power compensation value for compensating the reactive power value of the power line and the reactive power compensation electric power to the power line. It is set based on the relationship with the value of the primary current for reactive power compensation. The target current value for harmonic current compensation is calculated by, for example, multiplying the harmonic current compensation control gain by the harmonic current value of the power line [harmonic current compensation control gain × the power line harmonic current value]. The In this case, the control gain for harmonic current compensation is the primary winding of the transformer for supplying the power line with the value of the harmonic current of the power line and the amount of harmonic current compensation for compensating the harmonic current of the power line. It is set based on the relationship with the value of the primary current for harmonic current compensation supplied to the line.
The target current value for harmonic current compensation is calculated for one or more orders h of the harmonic current. Further, the harmonic current compensation control gain may be set in common for each order h of the harmonic current, or may be set corresponding to each order of the harmonic current. Various correction modes can be used as modes for correcting the harmonic current compensation control gain. For example, when a common harmonic current compensation control gain is set for each order h of the harmonic current, a mode of correcting the common harmonic current compensation control gain can be used. When the harmonic current compensation control gain is set corresponding to each order h of the harmonic current, the harmonic current compensation control gain corresponding to each order h is corrected by the same method (for example, the same A mode in which the correction amount is added or subtracted), and the harmonic current compensation control gain corresponding to each order h is corrected by a method corresponding to each order h (for example, a correction amount corresponding to each order h is added or subtracted). ) A mode, or a mode in which only the harmonic current compensation control gain corresponding to the predetermined order h is corrected by a predetermined method (for example, the same correction amount or a correction amount corresponding to the order is added or subtracted) is used. Can do.
As the “first set value”, the rated voltage value of the power converter is preferably used. “When the value of the output voltage of the power converter exceeds the first set value” is, for example, the reactive power compensation 1 having the target current value for reactive power compensation from the power converter to the primary winding of the transformer. Whether the value of the output voltage of the power converter exceeds the first set value when the primary current for h-th harmonic current compensation having the secondary current and the target current value for h-th harmonic current compensation is supplied Is judged by. As the “value of the power line voltage”, the value of the h-th harmonic voltage of the power line, the sum of the values of the h-order harmonic voltage of the power line, the value of the fundamental voltage of the power line, and the like can be used. As an aspect of “correcting at least one of the reactive power compensation control gain and the harmonic current compensation control gain in accordance with the value of the power line voltage so that the value of the output voltage of the power converter is reduced”, power conversion Various correction modes can be used that can reduce the value of the output voltage of the device. For example, when the value of the voltage of the power line (for example, the fundamental voltage or the harmonic voltage) does not exceed the second set value, the value of the output voltage of the power converter is reduced by using one control gain. When the second set value is corrected, the other control gain can be corrected so that the value of the output voltage of the power converter decreases. As the second set value, a management target value for the power line voltage value (for example, a management target value for the fundamental wave voltage value, a management target value for the harmonic voltage value) can be used.
Various modes can be used as modes for controlling the power converter according to the reactive power compensation target current value and the harmonic current compensation target current value. For example, when the value of the output voltage of the power converter does not exceed the first set value when the power converter is controlled according to the calculated target current value for reactive power compensation and the target current value for harmonic current compensation The power converter is controlled according to the calculated reactive power compensation target current value and the harmonic current compensation target current value, and when the first set value is exceeded, the power conversion device is disabled according to the voltage value of the power line. After correcting at least one of the control gain for power compensation or the control gain for harmonic current compensation, recalculate the target current value for reactive power compensation or the target current value for harmonic current compensation, and recalculate the target current for reactive power compensation. A mode in which the power converter is controlled using the value or the target current value for harmonic current compensation can be used. Alternatively, when the first set value is exceeded, at least one of the reactive power compensation control gain and the harmonic current compensation control gain is set according to the voltage value of the power line, and the output voltage value of the power converter is set to the first value. After correcting until the set value of 1 is not exceeded, the reactive power compensation target current value or harmonic current compensation target current value is recalculated, and the recalculated reactive power compensation target current value or harmonic current compensation target current is recalculated. The aspect which controls a power converter device using a value can be used.
In this embodiment, the reactive power and the harmonic current can be compensated while preventing the value of the output voltage of the power converter from exceeding the first set value (preferably the rated voltage value).

In yet another aspect of the present invention, the control device causes the power line harmonics to decrease when the value of the output voltage of the power converter exceeds the first set value. At least one of the reactive power compensation control gain and the harmonic current compensation control gain is corrected according to the value of the wave voltage.
As an aspect of “correcting at least one of the reactive power compensation control gain and the harmonic current compensation control gain according to the value of the harmonic voltage of the power line so that the value of the output voltage of the power conversion device is reduced”, Various correction modes can be used. For example, when the value of the harmonic voltage of the power line (for example, the value of the harmonic voltage of any order h or the value of the harmonic voltage of each order h) does not exceed the second set value Corrects one control gain so that the value of the output voltage of the power converter decreases, and if it exceeds the second set value, the value of the output voltage of the power converter becomes the other control gain. A correction mode for correcting so as to decrease can be used. As the second set value, the management target value for the harmonic voltage value of the power line (for example, the common management target value for the harmonic voltage value of each order h, the management corresponding to each harmonic voltage of each order h) The target value and the management target value for the sum of the harmonic voltage values of each order h) can be used. In addition, as a mode for determining that “the value of the harmonic voltage of the power line exceeds the second set value”, various determination modes can be used. For example, when a common second setting value is set for the harmonic voltage value of each order h, the harmonic voltage value of any order h exceeds the second setting value. It is possible to use a discriminating mode that discriminates whether or not the harmonic voltage values of the plurality of orders h exceed the second set value. Alternatively, when the second set value is set corresponding to each value of the harmonic voltage of each order h, the value of the harmonic voltage of any order h corresponds to the second value corresponding to the order h. It is possible to use a discriminating mode that discriminates when the set value exceeds the second set value corresponding to each order h or when the value of the harmonic voltage of the plurality of orders h exceeds the second set value. Alternatively, when the second set value is set for the sum of the harmonic voltage values of the respective orders, the sum of the harmonic voltage values of the respective orders becomes the second set value. It is possible to use a discrimination mode that discriminates when it exceeds the limit. Various values can be used as the “value obtained by adding the harmonic voltage values of the respective orders”. For example, a value obtained by adding the harmonic voltage values of the respective orders and a square root of the addition value obtained by squaring and adding the harmonic voltage values of the respective orders can be used.
Usually, the value of the harmonic voltage of the power line varies greatly compared to the value of the fundamental voltage of the power line. Therefore, by correcting at least one of the reactive power compensation control gain or the harmonic current compensation control gain according to the value of the harmonic voltage of the power line, the value of the output voltage of the power converter is set to the first set value. The reactive power and the harmonic current can be compensated more appropriately while preventing the above.

In still another embodiment of the present invention, the control device may allow the value of the harmonic voltage of the power line to exceed the second set value when the value of the output voltage of the power conversion device exceeds the first set value. For example, the reactive power compensation control gain is corrected so that the value of the output voltage of the power converter decreases, and if the value of the harmonic voltage of the power line does not exceed the second set value, the harmonic current compensation The control gain is corrected so that the value of the output voltage of the power converter decreases.
In this embodiment, it is possible to easily correct the output voltage value of the power conversion device from exceeding the first set value.

In still another embodiment of the present invention, the control device uses the value of the reactive current of the power line as the value of the reactive power of the power line.
As the “value of the reactive current of the power line”, the value of the fundamental reactive current of the power line is typically used. When the reactive current value of the power line is used as the reactive power value of the power line, appropriate correction is performed. For example, the control device may determine the reactive power compensation target current value calculated according to the reactive power value and the harmonic current value of the power line (or using the reactive power value and reactive power compensation control gain) Instead of a mode of controlling the power converter (according to the harmonic current compensation target gain value calculated using the harmonic current compensation value and the harmonic current compensation control gain), the power line reactive current value and The target current value for reactive current compensation calculated using the value of the harmonic current (or the reactive current compensation value and the control gain for reactive current compensation, and the harmonic current value of the power line and harmonic current compensation) A mode of controlling the power converter is used (in accordance with the target current value for harmonic current compensation calculated using the control gain). In this case, the reactive current compensation control gain is supplied to the primary winding of the transformer to supply the power line with the value of the reactive current of the power line and the amount of reactive current compensation for compensating the reactive current of the power line. It is set based on the relationship with the value of the primary current for reactive current compensation.
In this embodiment, a simple circuit can be used.

  By using the reactive power and harmonic current compensator according to claims 1 to 5, the reactive power and the harmonic current can be compensated at low cost.

Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 and FIG.
The load 4 shown in FIG. 1 is supplied with power from a power source 1 via a power system on the power distribution side (referred to as “power distribution system”) and a power system on the customer side. The power system on the power distribution side has three-phase (U-phase, V-phase, W-phase) power lines 2u, 2v, 2w. Below, the case where the reactive power and harmonic current compensation apparatus 10 of the present embodiment is connected to the power lines 3u, 3v, and 3w of the power system on the consumer side so as to be in parallel with the load 3 will be described. . Note that the reactive power and harmonic compensation apparatus 10 of the present embodiment can be used in various types of power systems to which loads are connected.
Hereinafter, u, v, and w are attached to values corresponding to the U phase, the V phase, and the W phase, and symbols of elements provided in the U phase, the V phase, and the W phase.
In general, most of the reactive power of the power line is the fundamental reactive power. Further, since the fundamental wave voltage of the power line is controlled to be substantially constant, the fundamental wave reactive power of the power line corresponds to the fundamental wave reactive current of the power line. Therefore, in this embodiment, the fundamental reactive current of the power line is detected as the reactive power of the power line.

The reactive power and harmonic current compensator 10 (hereinafter simply referred to as “compensator 10”) of the present embodiment includes an LC circuit 20, a transformer 30, a controller 50, and a semiconductor power converter 60.
The LC circuit 20 includes capacitors 21u, 21v, and 21w connected between the phases U, V, and W, and reactors 23u, 23v, and 23w connected to the U, V, and W phases. . By the capacitors 21u, 21v, 21w and the reactors 23u, 23v, 23w, a series resonance circuit in which the reactor and the capacitor are connected in series is equivalently connected to the U phase, the V phase, and the W phase. As indicated by broken lines in FIG. 1, capacitors 22v, 22v, and 22w connected to the U phase, the V phase, and the W phase can also be used.
The transformer 30 is composed of a three-phase transformer having primary windings 31u1, 31v1, 31w1 and secondary windings 31u2, 31v2, 31w2. The transformer 30 has a turns ratio n [= number of turns of secondary winding / number of turns of primary winding]. The turn ratio n can be set to various values. The series resonance circuit of the secondary windings 31u2, 31v2, 31w2 of the transformer 30 and the LC circuit 20 is connected in series (the series circuit of the series resonance circuit and the secondary winding) is in parallel with the load 3. The power lines 3u, 3v, and 3w are connected to the power lines 3u, 3v, and 3w at connection points xu, xv, and xw. The primary windings 31 u 1, 31 v 1, 31 w 1 of the transformer 30 have terminals on one side connected in common and the terminals on the other side connected to the output terminal of the semiconductor power converter 60. Primary current It (Itu, Itv, Itw) is supplied.

The compensation primary current It (Itu, Itv, Itw) includes a reactive current compensation primary current Itq (Itcu, Itqv, Itqw) having a fundamental wave frequency for compensating the fundamental wave reactive current, and the h th A primary current Ith (Ithu, Ithv, Ithw) for h-th harmonic current compensation having an h-th frequency for compensating the second harmonic current is supplied. The primary current for compensating the h-th harmonic current is supplied corresponding to the order h of the harmonic current to be compensated. The value of the compensation primary voltage (output voltage of the semiconductor power conversion device 60) Vt output from the semiconductor power conversion device 60 is the reactive current compensation primary voltage Vtq (Vtcu, Vtqv, Vtqw) having a fundamental frequency. And the value of the primary voltage Vth (Vthu, Vthv, Vthw) for compensating the h-th harmonic current having the h-th frequency. For example, when compensating the fundamental wave reactive current, the third harmonic current, the fifth harmonic current, and the seventh harmonic current, the primary power of the U phase of the transformer 30 from the semiconductor power conversion device 60 is used. The U-phase compensation primary current Itu supplied to the winding 31u1 includes a U-phase reactive current compensation primary current Itqu having a fundamental frequency and a U-phase third harmonic having a tertiary frequency. Wave current compensation primary current It3u, U-phase fifth harmonic current compensation primary current It5u having the fifth frequency and U-phase seventh harmonic current compensation 1 having the seventh frequency The next current It7u is included. Also, the value of the U-phase compensation primary voltage (the U-phase output voltage of the semiconductor power conversion device 60) Vtu output from the semiconductor power conversion device 60 is the U-phase reactive current compensation primary having the fundamental frequency. The value of the voltage Vtcu, the value of the U-phase third harmonic current compensating primary voltage Vt3u having the third frequency, the U-phase fifth harmonic current compensating primary voltage having the fifth frequency This is the sum of the value of Vt5u and the value of the primary voltage Vt7u for U-phase seventh harmonic current compensation having the seventh frequency.
Further, the secondary windings 31u2, 31v2, and 31w2 of the transformer 30 correspond to the reactive current compensating primary current Itq (Itqu, Itqv, Itqw), and the reactive current compensating secondary voltage VTq ( VTqu, VTqv, VTqw) and hth order harmonic current compensating secondary voltage VTh (hth order harmonic current compensating secondary voltage VTh) corresponding to hth order harmonic current compensating primary current Ith (Ithu, Ithv, Ithw). A compensation secondary voltage VT (VTu, VTv, VTw) including VThu, VThv, VThw is output.

The current detection devices 41u, 41v, and 41w have a power source 1 from connection points xu, xv, and xw where the series resonance circuit of the LC circuit 20 and the series circuit of the secondary windings 31u2, 31v2, and 31w2 of the transformer 30 are connected. The current (compensated current) ILa (ILau, ILav.ILaw) of the power lines 3u, 3v, 3w on the side is detected. The current ILa (ILau, ILav, ILaw) is substantially equal to the current IS (ISu, ISv, ISw) of the power lines 2u, 2v, 2w on the distribution system side.
The current ILa (ILau, ILav, ILaw) includes a fundamental wave reactive current ILaq (ILaq, ILaqv, ILaqw) and an h-th harmonic current ILah (ILahu, ILahv, ILahw) that could not be compensated by the compensation device 10. . The control device 50 is a semiconductor according to the fundamental wave reactive current ILaq (ILaq, ILaqv, ILaqw) and the h-th harmonic current ILah (ILahu, ILahv, ILahw) included in the current ILa (ILau, ILav, ILaw). The compensation primary current It (Itu, Itv, Itw) supplied from the power converter 60 to the primary windings 30u1, 31v1, 31w1 of the transformer 30 is controlled.
The current detection devices 41u, 41v, and 41w are connected from xu, xv, and xw where the series circuit of the LC circuit 20 and the secondary windings 31u2, 31v2, and 31w2 of the transformer 30 are connected. It can also arrange so that current (current before compensation) IL (ILu, ILv, ILw) of power lines 3u, 3v, 3w on the load 4 side may be detected. In this case, the current (current before compensation) IL (ILu, ILv, ILw) flows into the power lines 3u, 3v, 3w from the fundamental wave reactive current ILq (ILqu, ILqv, ILqw) of the load 4, the load 4, etc. The h-th harmonic current ILh (ILhu, ILhv, ILhw) is included. The operation in the case where the current (current before compensation) IL (ILu, ILv, ILw) is detected by the current detection devices 41u, 41v, 41w is the current (current after compensation) ILa (ILau, ILav, ILaw) described below. ), Fundamental wave reactive current ILaq (ILaq, ILaqv, ILaqw), h-order harmonic current ILah (ILahu, ILahv, ILahw), current (current before compensation) IL (ILu, ILv, ILw), fundamental wave invalid The operation is the same as the operation replaced with the current ILq (ILqu, ILqv, ILqw) and the h-th harmonic current ILh (ILhu, ILhv, ILhw).

Based on the current (compensated current) ILa (ILau, ILav, ILaw) of the power lines 3u, 3v, 3w detected by the current detection devices 41u, 41v, 41w, the control device 50 performs a primary current for compensation It ( Compensation target primary current values Itr (Itur, Itvr, Itwr) for Itu, Itv, Itw) are calculated and output to the semiconductor power converter 60.
As described above, as the primary current for compensation It (Itu, Itv, Itw), the reactive current compensation primary current Itq (Itqu, Itqv, Itqw) having a fundamental frequency and the h-th order frequency are expressed as follows. The primary current Ith (Ithu, Ithv, Ithw) for h-th harmonic current compensation is supplied. Therefore, the control device 50 uses the compensation target primary current value Itr (Itur, Itvr, Itwr) as the reactive current compensation target primary current for the reactive current compensation primary current Itq (Itqu, Itqv, Itqw). The target primary current value Ithr (Ithur, Itthvr, Itthwr) for the h-th harmonic current with respect to the value Itqr (Itqur, Itqvr, Itqwr) and the primary current Ith (Ithu, Itth, Ithw) for the h-th harmonic current compensation ) Is calculated. Further, the target primary current value Itqr (Itqur, Itqvr, Itqwr) for reactive current compensation and the target primary current value Ithr (Ithur, Ithvr, Ithwr) for the h-th harmonic current are included (for example, synthesized) for compensation The target primary current value Itr (Itur, Itvr, Itwr) is output.

As shown in FIG. 2, the semiconductor power converter 60 includes a converter (rectifier circuit) 61 composed of diodes D1 to D6, a smoothing capacitor 62, and an inverter (frequency converter) 63. Yes. The inverter 63 includes switching elements Tu1 and Tu2 for U phase, switching elements Tv1 and Tv2 for V phase, and switching elements Tw1 and Tw2 for W phase, and primary windings 31u1, 31v1 of the transformer 30. , 31w1 is supplied with a compensation primary current It (Itu, Itv, Itw). The switching elements Tu1 and Tu2, Tv1 and Tv2, and Tw1 and Tw2 of the inverter 63 are controlled by a U-phase control circuit 65u, a V-phase control circuit 65v, and a W-phase control circuit 65W, respectively.
The U-phase control circuit 65u, the V-phase control circuit 65v, and the W-phase control circuit 65w are the primary currents for compensation It (Itu, It) supplied from the semiconductor power converter 60 to the primary windings 31u1, 31v1, and 31w1 of the transformer 30. The switching elements Tu1 and Tu2, Tv1 and Tv2, and Tw1 and Tw2 are controlled so that the value of Itv, Itw) becomes the compensation target primary current value Itr (Itur, Itvr, Itwr) output from the control device 50.
Since the U-phase control circuit 65u, the V-phase control circuit 65v, and the W-phase control circuit 65w have the same configuration, the U-phase control circuit 65u will be described. The U-phase control circuit 65u includes a comparator 66u, an integrator 67u, and a hysteresis comparator 68u. The comparator 66u outputs the U-phase compensation target primary current value Itur output from the control device 50 (the U-phase reactive current compensation target primary current value Itqur and the U-phase h-th harmonic current compensation target). And a value of the U-phase compensation primary current Itu detected by the current detection device 64u (the U-phase reactive current compensation primary current Itcu and the U-phase first current value). a value obtained by synthesizing the value of the primary current Itu for h-order harmonic current compensation), and a current deviation signal eItu is output. The integrator 67u integrates the current deviation signal eItu and outputs an integration signal eu. The hysteresis comparator 68u outputs an ON signal to the switching element Tu1 and outputs an OFF signal to the switching element Tu2 when the integration signal eu reaches the ON level, and outputs an OFF signal to the switching element Tu1 when the integration signal eu reaches the OFF level. An off signal is output and an on signal is output to the switching element Tu2. In general, in order to prevent a short circuit between the switching elements Tu1 and Tu2, the ON signal is output when a certain period has elapsed since the OFF signal was output.
The semiconductor power conversion device 60 of the present embodiment corresponds to the “power conversion device” of the present invention. In addition, the “power conversion device” of the present invention can be configured only by an inverter.

In FIG. 1, the voltages (compensated voltages) of the power lines 3u, 3v, 3w on the power source 1 side from the connection points xu, xv, xw are represented by VLa (VLau, VLav, VLaw), and the connection points xu , Xv, xw The voltage of the power lines 3u, 3v, 3w on the load 4 side (voltage before compensation) is represented by VL (VLu, VLv, VLw). Moreover, the voltage of the power lines 2u, 2v, 2w on the distribution system side is represented by VS (VSu, VSv, VSw), and the current is represented by IS (ISu, ISv, ISw).
Further, as the compensation current IAF (IAFu, IAFv, IAFw) supplied from the compensation device 10 to the power lines 3u, 3v, 3w on the customer side, the fundamental reactive current ILaq (ILaq, ILaqv, ILaqw) of the power lines 3u, 3v, 3w is used. ) For compensating the reactive current IAFq (IAFqu, IAFqv, IAFqw) having the fundamental frequency and the h-order harmonic current ILah (ILahu, ILahv, ILahw) of the power lines 3u, 3v, 3w. A compensation current IAFh (IAFhu, IAFhv, IAFhw) for compensating the h-th harmonic current having the h-th frequency for compensation is supplied. Reactive current compensation compensation current IAFq (IAFqu, IAFqv, IAFqw) has the value of fundamental wave reactive current ILaq (ILaq, ILaqv, ILaqw) of power lines 3u, 3v, 3w, and the fundamental wave reactive current ILaq (ILaq, ILaqv, ILaqw) and have an opposite phase. Further, the compensation current IAFh (IAFhu, IAFhv, IAFhw) for compensating the h-order harmonic current has the value of the h-order harmonic current ILah (ILahu, ILahv, ILahw) of the power lines 3u, 3v, 3w. It has an opposite phase to the h-th harmonic current ILah (ILahu, ILahv, ILahw). Reactive current compensation compensation current IAFq (IAFau, IAFqv, IAFqw) and h-th harmonic current compensation compensation current IAFh (IAFhu, IAFhv, IAFhw) are fundamental wave reactive currents ILaq of power lines 3u, 3v, 3w. An instantaneous value, an average value, an effective value, and the like of (ILacu, ILaqv, ILaqw) and h-th harmonic current ILah (ILahu, ILahv, ILahw) can be set. The phases of the reactive current compensation compensation current IAFq (IAFqu, IAFqv, IAFqw) and the h-th harmonic current compensation compensation current IAFh (IAFhu, IAFhv, IAFhw) are fundamental wave reactive currents ILaq ( ILaq, ILaqv, ILaqw) and the h-th harmonic current ILah (ILahu, ILahv, ILahw).

  In the present embodiment, the value of the fundamental reactive current corresponds to the “reactive power value” of the present invention, and the value of the h-th harmonic current corresponds to the “harmonic current value” of the present invention. The primary current for compensation corresponds to the “primary current for compensation” of the present invention, the primary current for compensation of the reactive current corresponds to “primary current for compensation of the reactive power” of the present invention, and the h th harmonic. The primary current for wave current compensation corresponds to the “primary current for harmonic current compensation” of the present invention. The compensation target primary current value corresponds to the “compensation target current value” of the present invention, the reactive current compensation target primary current corresponds to the “reactive power compensation target current value” of the present invention, and The primary current for h-order harmonic current compensation corresponds to the “target current value for harmonic current compensation” of the present invention. The primary voltage for compensation corresponds to the “primary voltage for compensation” or “output voltage of the power converter” of the present invention, and the primary voltage for reactive current compensation corresponds to the “primary voltage for reactive power compensation” of the present invention. The primary voltage for h-th harmonic current compensation corresponds to the “primary voltage for harmonic current compensation” of the present invention. The secondary voltage for compensation corresponds to the “secondary voltage for compensation” of the present invention, the secondary voltage for reactive current compensation corresponds to the “secondary voltage for reactive power compensation” of the present invention, and the h-th order harmonic. The secondary voltage for wave current compensation corresponds to the “secondary voltage for harmonic current compensation” of the present invention. Further, the compensation current corresponds to the “compensation current for compensation” of the present invention, the compensation current for reactive current compensation corresponds to the “compensation current for reactive power compensation” of the present invention, and the compensation current for h-th harmonic current compensation. Corresponds to the “compensation current for harmonic current compensation” of the present invention.

First, an outline of the present embodiment will be described.
In the present embodiment, the frequency characteristics of the LC series resonance circuit are such that the impedance of the LC series resonance circuit of the LC circuit 20 is higher than the fundamental frequency of the power lines 3u, 3v, 3w, and the power lines 3u, 3v from the load 4 or the like. 3w is set to be smaller than the frequency of the harmonic current flowing into 3w.
In general, the harmonic current components flowing into the power lines 3u, 3v, and 3w from the load 4 and the like include many components of the fifth harmonic current and the seventh harmonic current (fifth harmonic). The capacity of the current and the capacity of the seventh harmonic current are very large compared to the capacity of the other harmonic components), and the harmonic current components of the thirteenth frequency and higher are extremely small. In such a case, a series resonant circuit having a frequency characteristic with low impedance to the fifth frequency (fundamental frequency × 5) and the seventh frequency (fundamental wave frequency × 7) is used as the series resonant circuit.
Here, the frequency characteristics of a series resonant circuit (hereinafter referred to as “fifth / seventh series resonant circuit”) in which the resonant frequencies are set to the fifth frequency and the seventh frequency, the fifth frequency, FIG. 3 shows frequency characteristics of a series resonance circuit (hereinafter referred to as “sixth series resonance circuit”) in which the resonance frequency is set to a frequency in the vicinity of the sixth order frequency (fundamental frequency × 6) between the seventh order frequencies. Shown in In FIG. 3, the frequency characteristics of the fifth and seventh series resonant circuits are indicated by broken lines, and the frequency characteristics of the sixth series resonant circuit are indicated by solid lines. As shown in FIG. 3, the fifth and seventh series resonant circuits have impedances for the fifth and seventh frequencies that are smaller than the impedance of the sixth series resonant circuit. The impedance for a frequency in the vicinity of is much larger than the impedance of the sixth series resonance circuit. When the harmonic current flowing in from the load 4 or the like in the steady state contains many components of the fifth and seventh frequencies, the harmonic current in the transient state such as when the load fluctuates In addition to the fifth-order frequency component and the seventh-order frequency component, many frequency components near the sixth-order frequency are included. Therefore, when the fifth and seventh series resonant circuits are used, the sixth harmonic current compensation compensation current IAF6 (IAF6u, IAF6v, When outputting the sixth harmonic current compensating secondary voltage VT6 (VT6u, VT6v, VT6w) for supplying the IAF 6w) to the power lines 3u, 3v, 3w, the semiconductor power conversion device 60 uses the sixth voltage of the high voltage. It is necessary to supply the primary voltage Vt6 (Vt6u, Vt6v, Vt6w) for compensating the second harmonic current. On the other hand, in the sixth series resonant circuit, the impedance to the fifth and seventh frequencies is about twice the impedance of the fifth and seventh series resonant circuits. The impedance to the frequency in the frequency range is sufficiently smaller than that of the fifth and seventh series resonance circuits. For this reason, the harmonic current component flowing into the power lines 3u, 3v, and 3w from the load 4 or the like includes many harmonic current components in the frequency range from the fifth frequency to the seventh frequency, and is higher than the thirteenth frequency. When the harmonic current component of is extremely small, it is preferable to use a series resonance circuit in which the resonance frequency is set near the sixth frequency as the series resonance circuit of the LC circuit 20.

The reactive current compensation operation in the case where such a series resonant circuit is used will be described with reference to FIG.
FIG. 4 shows the U-phase portion of the electric circuit diagram in which the series circuit of the series resonant circuit and the secondary windings 31u2, 31v2, 31w2 of the transformer 30 is connected to the power lines 3u, 3v, 3w. . The capacitor 22u and the reactor 23u constitute a U-phase series resonance circuit 20u. In addition, 24u is the resistance of the reactor 23u. A voltage VLu of the power line 3u is applied between the connection point xu of the power line 3u and the ground. Here, when compensating the fundamental wave reactive current, the compensation current IAFqu for reactive current compensation having the fundamental frequency is supplied to the power line 3u. With respect to the fundamental frequency of the power line 3u, a fundamental voltage VLfu of the voltage (load voltage) VLu of the power line 3u is applied between the connection point xu of the power line 3u and the ground.
In this state, when the secondary winding 31u2 of the transformer 30 has the fundamental wave frequency of the power line 3u and the secondary voltage VTqu for reactive current compensation having the same phase as or the opposite phase to the fundamental wave voltage VLfu of the power line 3u is output. The series resonant circuit is applied with a voltage VCqu having a fundamental frequency of the power line 3u and having a sum or difference value between the fundamental wave voltage VLfu and the reactive current compensating secondary voltage VTqu. When the resonance frequency of the series resonance circuit is set to a frequency near the sixth order frequency, the capacity of the reactor 23u is about 3% of the capacity of the capacitor 22u. For this reason, with respect to the fundamental frequency, the voltage VCu applied to the series resonance circuit can be regarded as almost the voltage applied to the capacitor 22c. As a result, the reactive current compensating secondary voltage VTqu having the fundamental frequency of the power line 3u and having the same phase as or the opposite phase to the fundamental wave voltage VLfu of the power line 3u is output from the secondary winding 31u2 of the transformer 30. Thus, the voltage VCqu applied to the capacitor 22u, and hence the reactive current compensation compensation current IAFqu supplied from the compensation circuit 10 to the power line 3u can be controlled, and the fundamental reactive current can be compensated. For example, it is possible to supply the compensation current IAFqu for compensation of the lead reactive current having the value of the delayed fundamental reactive current ILqu of the power line 3u. The value of the reactive current compensation secondary voltage VTqu is set so that the value of the reactive current compensation compensation current IAFqu becomes the value of the fundamental reactive current ILaqu of the power line 3u.
Thus, when compensating the reactive current of the power line 3u, the voltage obtained by dividing the fundamental wave voltage of the power lines 3u, 3v, 3w by the series resonance circuit and the secondary windings 31u2, 31v2, 31w2 of the transformer 30 is transformed. Applied to the secondary windings 31u2, 31v2, 31w2 of the container 30. As a result, the reactive current compensation secondary voltage VTq (VTqu, VTq,) for supplying the reactive current compensation compensation current IAFq (IAFqu, IAFqv, IAFqw) output from the secondary windings 31u2, 31v2, 31w2 of the transformer 30. The value of (VTqv, VTqw) can be reduced. That is, the fundamental reactive current can be compensated by connecting the small-capacity semiconductor power conversion device 60 to the primary windings 31u1, 31v2, and 31w2 of the transformer 30.

Further, the harmonic current compensation operation in the case where such a series resonance circuit is used will be described with reference to FIG.
FIG. 5 shows the U-phase portion of the electric circuit diagram in which the series circuit of the series resonant circuit and the secondary windings 31u2, 31v2, 31w2 of the transformer 30 is connected to the power lines 3u, 3v, 3w. . The capacitor 22u and the reactor 23u constitute a U-phase series resonance circuit 20u. In addition, 24u is the resistance of the reactor 23u. Since the harmonic voltage due to the harmonic current of the power lines 3u, 3v, and 3w is very small, it is not shown in FIG.
In this state, when the secondary voltage 31h2 of the transformer 30 outputs the hth harmonic current compensating secondary voltage VThu having the hth frequency of the power line 3u, the hth order having the hth frequency. A compensation current IAFhu for harmonic current compensation is supplied to the power line 3u via the series resonance circuit and the secondary winding 31u2 of the transformer 30. If the compensation current IAFhu for compensating the h-th harmonic current has the same value as the value of the h-th harmonic current of the power line 3u and has the opposite phase to the h-th harmonic current, The h-order harmonic current of the power line 3u can be compensated (cancelled) by the compensation current IAFhu for h-order harmonic current compensation. Here, the impedance of the series resonant circuit is smaller than the h-th frequency of the power line 3u. Moreover, the value of the h-th harmonic current of the power line 3u is also small. Therefore, the reactive current can be compensated by connecting the small-capacity semiconductor power conversion device 60 to the primary windings 31u1, 31v2, 31w2 of the transformer 30. The value of the h-th harmonic current compensation secondary voltage VThu is set so that the value of the h-th harmonic current compensation compensation current IAFhu becomes the value of the h-order harmonic current ILahu of the power line 3u. , The value of the h-order harmonic current ILahu and the impedance value of the LC series circuit and the secondary winding 31u2 of the transformer 30. The phase of the h-th harmonic current compensation secondary voltage is set so that the phase of the h-th harmonic current compensation current IAFhu is opposite to that of the h-th harmonic current of the power line 3u, that is, in series. It is set by the phase of the impedance of the resonance circuit and the secondary winding 31u2 of the transformer 30.

Next, the process of the control apparatus 50 is demonstrated using the flowchart shown in FIG. The process shown in FIG. 6 is started at an appropriate time.
In step S1, the value of the reactive current ILaq (ILaq, ILaqv, ILaqw) of the power lines 3u, 3v, 3w is detected. In the present embodiment, the value of the fundamental reactive current having the fundamental frequency of the power lines 3u, 3v, and 3w is detected as the reactive current value. The value of the reactive current ILaq (ILaq, ILaqv, ILaqw) of the power lines 3u, 3v, 3w can be calculated from, for example, the current (current after compensation) ILa (ILau, ILav, ILaw) of the power lines 3u, 3v, 3w. it can.
In step S2, the value of the reactive current ILaq (ILaq, ILaqv, ILaqw) of the power lines 3u, 3v, and 3w detected in step S1 and the reactive current compensation control gain Kq are used to change the power of the transformer 30 from the semiconductor power converter 60. Reactive current compensation target primary current value Itqr (Itqur, Itqvr, Itqwr) for reactive current compensation primary current Itq (Itqu, Itqv, Itqw) supplied to the primary windings (31u1, 31v1, 31w1) is calculated. . The target primary current value Itqr (Itqur, Itqvr, Itqwr) for reactive current compensation is, for example, the product of the reactive current ILaq value of the power lines 3u, 3v, 3w and the reactive current compensation control gain Kq [Itqr = Kq × ILaq ]. In this case, the reactive current compensation control gain Kq includes the value of the reactive current ILaq (ILaq, ILaqv, ILaqw) of the power lines 3u, 3v, 3w and the reactive current ILaq (ILaq, ILaqv, ILaqw) of the power lines 3u, 3v, 3w. ) For compensating the reactive current for supplying the primary windings 31u1, 31v1, 31w1 of the transformer 30 to supply the compensation current IAFq (IAFqu, IAFqv, IAFqw) for compensating the reactive current to the power lines 3u, 3v, 3w. It is set based on the relationship with the value of the primary current Itq (Itqu, Itqv, Itqw).

In step S3, the value of the h-th harmonic current ILah (ILahu, ILahv, ILahw) of the power lines 3u, 3v, 3w is detected. As the order h of the harmonic current, one or a plurality of orders are appropriately selected. For example, the order of the harmonic current to be compensated is selected from among the harmonic currents flowing into the power lines 3u, 3v, and 3w from the load 4 or the like. The value of the h-th harmonic current ILah (ILahu, ILahv, ILahw) of the power lines 3u, 3v3w is calculated from, for example, the current of the power lines 3u, 3v, 3w (the load current after compensation) ILa (ILau, ILav, ILaw). can do.
In step S4, using the value of the h-order harmonic current ILah (ILahu, ILahv, ILahw) of the power lines 3u, 3v, 3w detected in step S3 and the harmonic current compensation control gain Kh, the semiconductor power conversion device 60 is used. To the primary windings (31u1, 31v1, 31w1) of the transformer 30 for the primary current Ith (Ithu, Ithv, Ithw) for compensating the hth harmonic current to the target primary for hth harmonic current compensation A current value Ithr (Ithur, Ithvr, Ithwr) is calculated. The target primary current value Ithr (Ithur, Ithvr, Ithwr) for h-th harmonic current compensation is, for example, the value of the h-th harmonic current ILah of the power lines 3u, 3v, 3w and the control gain Kh for harmonic current compensation. Multiply by [Ithr = Kh × ILah]. In this case, the control gain Kh for harmonic current compensation is the value of the h-order harmonic current ILah (ILahu, ILahv, ILahw) of the power lines 3u, 3v, 3w and the compensation line 10 to the power lines 3u, 3v, 3w. Primary current Ith for h-order harmonic current compensation supplied to primary windings 31u1, 31v1, 31w1 of transformer 30 in order to supply compensation current IAFh (IAFhu, IAFhv, IAFhw) for h-order harmonic current compensation It is set based on the relationship with the values of (Ithu, Ithv, Ithw).

In step S5, the semiconductor power conversion device 60 applies the reactive current compensation target primary current value Itqr (Itqur, Itqvr, Itqwr) calculated in step S2 to the primary windings 31u1, 31v1, 31w1 of the transformer 30. H-th harmonic current compensation having the primary current Itq (Itq, Itqv, Itqw) for current compensation and the target primary current value Ithr (Ithur, Ithvr, Ithw) for h-th harmonic current calculation calculated in step S4. Output voltage (compensation primary voltage) Vt (compensation primary voltage) Vt (when the compensation primary current It (Itu, Itv, Itw) including the primary current Ith (Ithu, Itv, Itw)) is supplied. Vtu, Vtv, Vtw) are calculated. The value of the output voltage (compensation primary voltage) Vt (Vtu, Vtv, Vtw) of the semiconductor power conversion device 60 is the reactive current compensation primary voltage by the reactive current compensation primary current Itq (Itqu, Itqv, Itqw). Primary voltage Vth (Vthu, Vthv, Vthw) for h-th harmonic current compensation based on the value of Vtq (Vtcu, Vtqv, Vtqw) and the primary current Ith (Ithu, Ithv, Ithw) for h-th harmonic current compensation This is the sum of the values.
In step S6, it is determined whether or not the value of the output voltage Vt (Vtu, Vtv, Vtw) of the semiconductor power conversion device 60 calculated in step S5 exceeds the first set value Vtr. As the first set value, the rated voltage value of the semiconductor power conversion device 60 is preferably used. If the value of the output voltage Vt of the semiconductor power converter 60 does not exceed the first set value Vtr, the process proceeds to step S13, and if it exceeds, the process proceeds to step S7.

When the value of delayed reactive current ILaq of power lines 3u, 3v, and 3w is large (when [Itqr = Kq · ILaq] is large), control device 50 starts from secondary windings 31u2, 31v2, and 31w2 of transformer 30. The secondary voltage VTq for reactive current compensation having the fundamental frequency to be output is decreased, and the voltage VCq having the fundamental frequency applied to the series resonance circuit is increased. As a result, the value of the reactive current compensation current (advance compensation current) IAFq (IAFqu, IAFqv, IAFqw) supplied to the power lines 3u, 3v, 3w increases. On the other hand, when the value of the h-order harmonic current ILah of the power lines 3u, 3v, and 3w is large (when [Ithr = Kh · ILah] is large), the secondary windings 31u2, 31v2, and 31w2 of the transformer 30 The output secondary voltage VTh for h-th harmonic current compensation having the h-th frequency is increased. This increases the value of the h-th harmonic current compensation compensation current IAFh (IAFhu, IAFhv, IAFhw) supplied to the power lines 3u, 3v, 3w via the series resonance circuit.
Here, when the value of the delay current ILaq of the power lines 3u, 3v, 3w and the value of the h-order harmonic current ILah of the power lines 3u, 3v, 3w are large, the secondary windings 31u2, 31v2, 31w2 of the transformer The secondary voltage VTq for reactive current compensation having the fundamental frequency output from is reduced, and the secondary voltage VTh for compensation of h-th harmonic current having the h-th frequency is increased. For this reason, there is no possibility that the value of the output voltage Vt of the semiconductor power converter 60 exceeds the first set value Vtr (for example, the rated voltage value).
On the other hand, when the value of the delay current ILaq of the power lines 3u, 3v, 3w is small (when [Itqr = Kq · ILaq] is small) and the value of the h-order harmonic current ILah of the power lines 3u, 3v, 3w is large ([ When Ithr = Kh · ILah] is large), the reactive power compensation secondary voltage VTq having the fundamental frequency output from the secondary windings 31u2, 31v2, 31w2 of the transformer and the hth frequency having the hth frequency The secondary voltage VTh for second harmonic current compensation is increased. In this case, the value of the output voltage Vt of the semiconductor power conversion device 60 may exceed a first set value Vtr (for example, a rated voltage value). For this reason, the value of the reactive current of the power lines 3u, 3v, 3w and the value and phase angle of the h-th harmonic current are assumed, and the value of the output voltage Vt of the semiconductor power converter 60 is set to the first set value Vtr (for example, The turn ratio n of the transformer 30 (the number of turns of the secondary winding / the number of turns of the primary winding) is determined so as not to exceed the rated voltage value. However, even when the turns ratio n of the transformer 30 is determined in this way, the value of the reactive current of the load 4 and the value of the h-th harmonic current generated from the load 4 change irregularly, so that the semiconductor power conversion There is a possibility that the value of the output voltage Vt of the device 60 exceeds a first set value (for example, a rated voltage value). When the value of the output voltage Vt of the semiconductor power conversion device 60 exceeds the first set value, it is necessary to perform control to decrease the value of the output voltage Vt of the semiconductor power conversion device 60. In step S6, it is determined whether it is necessary to perform control to decrease the value of the output voltage Vt of the semiconductor power conversion device 60.

In step S7, the value of the h-th harmonic voltage VLah (VLahu, VLahv, VLahw) of the power lines 3u, 3v, 3w is detected. As the order h of the harmonic voltage, of the harmonic currents of the power lines 3u, 3v, and 3w, the order of one or more harmonic currents to be compensated is appropriately selected. The value of the h-th harmonic voltage VLah (VLahu, VLahv, VLahw) of the power lines 3u, 3v, 3w is calculated from the voltage (compensated load voltage) VLa (VLau, VLav, VLaw) of the power lines 3u, 3v, 3w. can do.
In step S8, it is determined whether or not the h-order harmonic voltage VLah (VLahu, VLahv, VLahw) of the power lines 3u, 3v, and 3w detected in step S7 exceeds the second set value VLahr. Various methods can be used as a method of determining whether or not the h-order harmonic voltage VLah (VLahu, VLahv, VLahw) of the power lines 3u, 3v, 3w exceeds the second set value VLahr. For example, the second set value VLahr is set corresponding to each order h, and it is determined whether or not the value of the h-th harmonic current exceeds the second set value VLahr corresponding to the order h. Then, it is determined whether or not the value of the harmonic current of any order h exceeds the second set value corresponding to each order. Alternatively, the second set value VLahr is set in common for each order, and it is determined whether or not the value of the h-order harmonic voltage of any order h exceeds the second set value. Alternatively, whether or not the total value of the plurality of order harmonic voltages is set as the second set value VLahr, and whether or not the total value of the plurality of order harmonic voltages exceeds the second set value VLahr Judging. Various values can be used as the “total value of the harmonic voltages of a plurality of orders”. For example, a value obtained by adding the harmonic voltage values of the respective orders and a square root of the addition value obtained by squaring and adding the harmonic voltage values of the respective orders can be used. As the second set value, a management target value for the harmonic voltage value is preferably set. If the value of the h-th harmonic voltage VLah does not exceed the second set value VLahr, the process proceeds to step S9, and if it exceeds, the process proceeds to step S11.

In step S9, the harmonic current compensation control gain Kh is corrected. For example, the correction value Δa is subtracted from the harmonic current compensation control gain Kh, and the subtraction value is used as the corrected harmonic current compensation control gain Kh. In step S9, since the value of the h-order harmonic voltage of the power lines 3u, 3v, 3w does not exceed the second set value VLahr, the reactive power compensation is prioritized. That is, the control gain Kh for harmonic current compensation is decreased ([Ithr = Kh · ILah] is reduced), and the value of the primary current Ith for h-th harmonic current compensation supplied from the semiconductor power converter 60 is set. Decrease. Thereby, the value of the output voltage Vt of the semiconductor power converter 60 decreases.
In step S10, the value of the h-th harmonic current ILah (ILahu, ILahv, ILahw) of the power lines 3u, 3v, 3w detected in step S3 and the harmonic current compensation control gain Kh corrected in step S9 are used. After recalculating the target primary current value Ithr (Ithur, Ithvr, Ithwr) for h-order harmonic current compensation, the process proceeds to step S13.
In step S11, the reactive current compensation control gain Kq is corrected. For example, the correction value Δb is added to the reactive current compensation control gain Kq, and the added value becomes the corrected reactive current compensation control gain Kq. In step S11, since the value of the h-order harmonic current of the power lines 3u, 3v, and 3w exceeds the second set value VLahr, the harmonic current compensation is prioritized. That is, by increasing the reactive current compensation control gain Kq ([Itqr = Kq · ILaq] is increased), the value of the reactive current compensating primary current Itq output from the semiconductor power converter 60 is decreased. Thereby, the value of the output voltage Vt of the semiconductor power converter 60 decreases.
In step S12, the reactive current compensation target 1 is calculated using the reactive current ILaq (ILaq, ILaqv, ILaqw) values of the power lines 3u, 3v, and 3w detected in step S2 and the reactive current compensation control gain Kq corrected in step S11. After recalculating the next current value Itqr (Itqur, Itqvr, Itqwr), the process proceeds to step S13.

In step S13, the calculated reactive current compensation target primary current value Itqr (Itqur, Itqvr, Itqwr) and the h-th harmonic current compensation target primary current value Ithr (Ithur, Itthvr, Itthwr) are included (for example, The compensated target primary current value Itr (Itur, Itvr, Itwr) is output to the semiconductor power conversion device 60. When the process proceeds from step S6 to step S13, the reactive current compensation target primary current value Itqr (Itqur, Itqvr, Itqwr) calculated in step S2 and the h-th order harmonic current compensation calculated in step S4 are used. Compensation target primary current value Itr (Itur, Itvr, Itwr) including target primary current value Ithr (Ithur, Ithvr, Ithwr) is output to semiconductor power conversion device 60. When the process proceeds from step S10 to step S13, the reactive current compensation target primary current value Itqr (Itqur, Itqvr, Itqwr) calculated in step S2 and the h-th harmonic current compensation recalculated in step S10. The compensation target primary current value Itr (Itur, Itvr, Itwr) including the target primary current value Ithr (Ithur, Ithvr, Ithwr) is output to the semiconductor power converter 60. When the process proceeds from step S12 to step S13, the reactive current compensation target primary current value Itqr (Itqur, Itqvr, Itqwr) recalculated in step S12 and the h-th harmonic current compensation calculated in step S4. The compensation target primary current value Itr (Itur, Itvr, Itwr) including the target primary current value Ithr (Ithur, Ithvr, Ithwr) is output to the semiconductor power converter 60.
In this case, the semiconductor power conversion device 60 has the fundamental frequency in the primary windings 31u1, 31v1, 31w1 of the transformer 30, and the reactive current compensation target primary current value Itqr (Itqur, Itqvr, Itqwr). The reactive power compensating primary current Itq (Itqu, Itqv, Itqw) having a predetermined phase is supplied. As a result, the secondary voltage VTq for compensating the reactive current having the fundamental frequency is output from the secondary windings 31u2, 31v2, and 31w2 of the transformer 30, and the fundamental frequency is applied from the compensator 10 to the power lines 3u, 3v, and 3w. The reactive current compensation compensation current IAFq (IAFqu, IAFqv, IAFqw) is supplied. The phase of the primary current Itq (Itq, Itqv, Itqw) for reactive current compensation supplied to the primary windings 31u1, 31v1, 31w1 of the transformer 30 is for reactive current compensation supplied to the power lines 3u, 3v, 3w. The compensation current IAFq (IAFqu, IAFqv, IAFqw) is set so that the reactive current ILaq (ILaqu, ILaqv, ILaqw) of the power lines 3u, 3v, 3w is compensated (so as to have a phase opposite to that of the reactive current ILaq). Further, the semiconductor power conversion device 60 has the h-th order frequency in the primary windings 31u1, 31v1, 31w1 of the transformer 30, and the target primary current value Ithr (Ithru, Ithrv for h-th harmonic current compensation). , Itrw) for supplying the primary current Ith (Ithu, Ithv, Ithw) for compensating the h-th order harmonic current with a predetermined phase. Thereby, the secondary voltage VTh for h-th harmonic current compensation having the h-th frequency is output from the secondary windings 21u2, 21v2, and 21w2 of the transformer 30, and the compensator 10 supplies the power lines 3u, 3v, and 3w to the power lines 3u, 3v, and 3w. A compensation current IAFh (IAFhu, IAFhv, IAFhw) for h-th harmonic current compensation is supplied. The phase of the primary current Ith for h-th harmonic current compensation supplied to the primary windings 31u1, 31v1, 31w1 of the transformer 30 is output from the secondary windings 31u2, 31v2, 31w2 of the transformer 30. The power line 3u, the h-th harmonic current compensation compensation current IAFh (IAFhu, IAFhv, IAFhw) supplied from the compensation device 1 to the power lines 3u, 3v, 3w by the h-th harmonic current compensation secondary voltage VTh. The third and third w-th harmonic currents ILah (ILahu, ILahv, ILahw) are set so as to be compensated (in phase opposite to the h-th harmonic current ILah). As described above, the primary windings 31u1, 31v1, and 31w1 of the transformer 30 are transferred from the semiconductor power conversion device 60 to the primary current for compensation It (primary current Itq for reactive current compensation and primary for the h-th harmonic current compensation). The total of the current Ith) is supplied, and the compensation secondary including the secondary voltage VTq for reactive current compensation and the secondary voltage VTh for compensating the h-th harmonic current from the secondary windings 31u2, 31v2, 31w2 of the transformer 30 The voltage VT is output.
In step S14, the reactive current compensation control gain Kq and the harmonic current compensation control gain Kh are returned to the initial values, and the process ends.

The waveform of each part of the present embodiment is shown in FIGS. In FIG. 7, the U-phase voltage VSu on the distribution system side is indicated by a broken line, the U-phase current ISu on the distribution system side is indicated by a thin solid line, and the U-phase current (current before compensation) on the consumer side ILu is indicated by a thick solid line. In FIG. 8, the U-phase voltage VSu on the distribution system side is indicated by a broken line, the applied voltage VCu of the U-phase series resonance circuit of the compensation device 10 is indicated by a thin solid line, and the power line from the compensation device 10 to the consumer side The U-phase compensation compensation current IAFu (total of the reactive current compensation compensation current IAFq and the h-th harmonic current compensation compensation current IAFh) supplied to 3u, 3v, and 3w is shown by a thick solid line. As shown in FIGS. 7 and 8, it can be seen that in the present embodiment, the reactive current and the harmonic current of the power lines 3u, 3v, and 3w are compensated.
FIG. 9 also shows the load 4 capacity when the load power factor is 0.9, the fifth harmonic content is 16%, and the seventh harmonic content is 12%. It is the figure which showed the capacity | capacitance of the required semiconductor power converter 60 about this Embodiment and a prior art example. The conventional example is a compensation device in which a semiconductor power conversion device is connected in parallel to power lines 3u, 3v, and 3w. Further, in FIG. 9, the present embodiment is indicated by a black circle, and the conventional example is indicated by a black square. From FIG. 9, it can be seen that this embodiment can significantly reduce the capacity of the semiconductor power conversion device 60 compared to the conventional example.

As described above, in the present embodiment, the series resonant circuit in which the reactor and the capacitor are connected in series and the series circuit of the secondary windings 31u2, 31v2, and 31w2 of the transformer 30 are arranged in parallel with the load 4. The power lines 3u, 3v, 3w are connected to the power lines 3u, 3v, 3w to control the primary currents for compensation It (Itu, Itv, Itw) supplied to the primary windings 31u1, 31v1, 31w1 of the transformer 30. The 3w reactive current Laq (Laq, Laqv, Laqw) and the h-th harmonic current Lah (Lahu, Lahv, Lahw) are compensated. Thereby, reactive power and harmonic current can be compensated for by using an inexpensive semiconductor power conversion device while preventing an increase in size of the device.
When the value of the output voltage Vt of the semiconductor power conversion device 60 exceeds the first set value Vtr (preferably the rated voltage value), the value of the output voltage Vt of the semiconductor power conversion device 60 is the first value. Since control is performed so as not to exceed the set value Vtr, a cheaper semiconductor power conversion device 60 can be used. In particular, in this case, priority is given to compensation of the reactive current ILaq depending on whether or not the value of the h-order harmonic voltage VLah of the power lines 3u, 3v, and 3w exceeds the second set value VLahr. In order to determine whether to give priority to ILah compensation, reactive power and harmonic current compensation can be appropriately performed while reducing the capacity of the semiconductor power conversion device 60.

The present invention is not limited to the configuration described in the embodiment, and various changes, additions, and deletions are possible.
In the embodiment, when the value of the output voltage Vt of the semiconductor power converter 60 exceeds the first set value Vtr, the value of the h-order harmonic voltage of the power lines 3u, 3v, 3w is the second set value. The reactive current compensation gain Kq or the harmonic current compensation control gain Kh is corrected depending on whether or not the current exceeds the threshold current. However, as a correction mode, the reactive current compensation control is performed according to the fundamental voltage of the power lines 3u, 3v, and 3w. A correction mode for correcting the gain Kg or the harmonic current compensation control gain Kh can also be used. In this case, if the fundamental voltage exceeds the second set value, the harmonic current compensation control gain Kh is reduced to reduce the harmonic current compensation primary current (harmonic compensation primary voltage). If the fundamental voltage does not exceed the second setting, the reactive current compensation control gain Kq is increased to reduce the reactive current compensation primary current (reactive current compensation primary voltage). Also, a correction mode for correcting the reactive current compensation gain Kq and the harmonic current compensation control gain Kh can be used. Furthermore, the present invention is not limited to these correction modes, and a correction mode for correcting at least one of the reactive current compensation gain Kq or the harmonic current compensation control gain Kh according to the voltages of the power lines 3u, 3v, and 3w can be used. .
Although the semiconductor frequency converter 60 was controlled according to the reactive current values (values of the reactive current after compensation) ILa of the power lines 3u, 3v, and 3w on the power source 1 side from the connection locations xu, xv, and xw of the compensating device 10, It is also possible to perform control according to the reactive current value IL (value of the reactive current before compensation) IL of the power lines 3u, 3v, and 3w closer to the load 4 than the connection points xu, xv, and xw of the compensation device 10. Further, the semiconductor power conversion device can be controlled according to the value of the reactive power instead of the value of the reactive current. As the reactive power value, the fundamental reactive power value is typically used. The reactive power value is the reactive power value (reactive power value after compensation) of the power lines 3u, 3v, and 3w on the power source 1 side from the connection locations xu, xv, and xw of the compensation device 10 or the connection location xu of the compensation device 10. , Xv, and xw, the reactive power values of the power lines 3u, 3v, and 3w on the load 4 side (reactive power values before compensation) can be used. In the case where the reactive power value is used, a correction is made to make the reactive current value correspond to the reactive power value. Further, the above-described description of “reactive current” is replaced with “reactive power”.
In the power converter, a primary current for reactive power compensation (including a primary current for reactive current compensation) and a primary current for h-th harmonic current compensation are supplied to the primary windings 31u1, 31v1, and 31w1 of the transformer 30. What is necessary is just to be able to supply, and it is not limited to the semiconductor power converter device 60 which has a converter and an inverter.
The present invention is not limited to the processing procedure and processing contents shown in the flowchart of FIG. 6, and reactive power (including reactive current) and harmonic current can be compensated using various processing methods.
The present invention is not limited to the configuration shown in FIG.
The present invention is not limited to a power system in a consumer, but can be used in a power system having various configurations having a load and a power line, for example, a power system on the power provider side.

It is a figure which shows schematic structure of one Embodiment. It is a figure which shows schematic structure of the control apparatus and semiconductor power converter device which are used by one Embodiment. It is a figure which shows one example of the frequency characteristic of the series resonance circuit used by one Embodiment. It is a figure explaining the reactive current compensation operation | movement of one Embodiment. It is a figure explaining the harmonic current compensation operation | movement of one Embodiment. It is a flowchart explaining operation | movement of the control apparatus of one Embodiment. It is a figure which shows the waveform of each part of one Embodiment. It is a figure which shows the waveform of each part of one Embodiment. It is a figure which shows the capacity | capacitance of the semiconductor power converter device in one embodiment and a prior art example. It is a figure which shows schematic structure of the conventional reactive power compensation apparatus.

Explanation of symbols

1 Power supply 2u, 2v, 2w, 3u, 3v, 3w Power line 4 Load 10 Reactive power and harmonic current compensator 20 LC circuit 21u, 21v, 21w, 22u, 22v, 22w, 122u, 122v, 122w Capacitors 23u, 23v, 23w Reactor 30, 130 Transformer 31u1, 31v1, 31w1, 131u1, 131v1, 131w1 Primary winding 31u2, 31v2, 31w2, 131u2, 131v2, 131w2 Secondary winding 41u, 41v, 41w, 64u, 64v, 64w Current detection Device 50 Control device 51u, 51v, 51w Control unit 60, 160 Power conversion device 61 Converter (rectifier circuit)
62 Smoothing capacitor 63 Inverter (frequency conversion circuit)
65u U-phase control circuit 65v V-phase control circuit 65w W-phase control circuits D1 to D6 Diodes Tu1, Tv1, Tw1, Tu2, Tv2, Tw2 Semiconductor elements

Claims (5)

A reactive power and harmonic current compensator in a power system having a power line and a load connected to the power line,
A series resonant circuit in which a reactor and a capacitor are connected in series, a transformer having a primary winding and a secondary winding, a power converter, and a controller;
The series resonant circuit and the secondary winding of the transformer are connected to the power line in parallel with the load in a state of being connected in series,
The primary winding of the transformer is connected to the power converter,
The control device controls the power conversion device according to the reactive power value and the harmonic current value of the power line, thereby compensating the reactive power of the power line and the harmonics of the power line. A reactive power and harmonic current compensator that supplies a harmonic current compensating quantity of electricity for compensating a wave current to the power line.   2. The reactive power and harmonic current compensator according to claim 1, wherein the control device includes a reactive power compensation target current value calculated using a reactive power value of the power line and a reactive power compensation control gain, and The power converter is controlled according to the harmonic current compensation target current value calculated using the harmonic current value of the power line and the harmonic current compensation control gain, and the output voltage of the power converter When the value exceeds the first set value, the reactive power compensation control gain or the harmonic current compensation is performed according to the voltage value of the power line so that the output voltage value of the power converter decreases. A reactive power and harmonic current compensator characterized by correcting at least one of the control gains for use.   3. The reactive power and harmonic current compensator according to claim 2, wherein the control device outputs an output of the power converter when a value of an output voltage of the power converter exceeds a first set value. Reactive power, wherein at least one of the reactive power compensation control gain or the harmonic current compensation control gain is corrected in accordance with the value of the harmonic voltage of the power line so that the value of the voltage decreases. Harmonic current compensator.   4. The reactive power and harmonic current compensator according to claim 3, wherein when the value of the output voltage of the power converter exceeds a first setting value, the control device If the value exceeds the second set value, the reactive power compensation control gain is corrected so that the value of the output voltage of the power converter decreases, and the value of the harmonic voltage of the power line becomes the first value. If the set value of 2 is not exceeded, the reactive power and harmonic current compensator corrects the harmonic current compensation control gain so that the value of the output voltage of the power converter decreases.   5. The reactive power and harmonic current compensator according to claim 1, wherein the control device uses a reactive current value of the power line as a reactive power value of the power line. Reactive power and harmonic current compensator.

Images