JP2016067124A - Power compensator and power compensation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that when connecting an unbalance compensator using STATCOM with a three-phase AC system, a reactor is required in each phase in addition to a voltage type inverter constituting the STATCOM, when connecting the unbalance compensator with a three-phase AC system, and its installation area is large.SOLUTION: In an unbalance compensator including two series circuits of a reactor and an arm constituted of one unit converter, including a switching element and an energy storage element, or a series connection of a plurality of unit converters, the two reactors included in two series circuits are magnetically coupled.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power compensation device and a power compensation method, and more particularly, to a power compensation device and a power compensation method suitable for compensating unbalance in a three-phase system caused by a single-phase load.

For example, in a multi-phase power system formed of three phases, the voltages and phases of the plurality of phases are supplied in an aligned manner. For example, when a load with large power consumption or a special load is connected to this power system, an unbalance may occur between the plurality of phases.

This phenomenon will be described by taking an AC powered electric railway as an example. In the case of an AC-powered electric railway, power is received from one line voltage of the three-phase AC system, that is, the electric railway may be connected as a single-phase load in the three-phase AC system ( A single-phase load may be connected to a three-phase AC system as well as an electric railway). When a single-phase load is connected to the three-phase AC system, current flows only in two phases to which the single-phase load is connected, and no current flows in the remaining one phase. In other words, when a single-phase load is connected, an unbalanced current flows through the three-phase AC system.

Thus, when an unbalanced current flows, the voltage drop in the transmission system impedance (referred to as system impedance) to the load receiving point becomes unbalanced, and the voltage near the load receiving point also becomes unbalanced. . Since voltage imbalance can adversely affect other three-phase loads connected in parallel, it must be controlled within a certain tolerance.

Therefore, for the purpose of suppressing the voltage imbalance within an allowable range, a device for supplying a current that cancels the negative phase component (possibly the positive phase component) included in the unbalanced current may be connected. By balancing the current, the voltage drop of the system impedance is also balanced, and as a result, the voltage near the power receiving point of the single-phase load and the unbalance compensator can be balanced.

For example, [Non-Patent Document 1] discloses a configuration of an unbalance compensator using a separately-excited static var compensator (SVC) using a thyristor-controlled reactor (TCR). Yes. In Non-Patent Document 1, the unbalance compensation device is referred to as “load balancer”.
On the other hand, [Patent Document 1] discloses a technique for unbalance compensation by using a plurality of reactive power compensators (SVC) and connecting the reactive power compensators (SVC) through a reactor. .

Japanese Patent Laid-Open No. 7-257238

R. Gr? Nbaum, “FACTS for power quality improvement in grids feeding high speed rail traction,” in Proc. IEEE International Electric Machines & Drives Conference 2007.

By providing multiple power converters via each reactor, power compensation is possible. However, however, the same number of reactors as the power converters are required, and the installation area of the reactors must be increased. In other words, it cannot withstand the recent demands for small size and low cost. In other words, when connecting to an AC system, a reactor corresponding to each phase is required in addition to the power converter to be configured, resulting in a problem that the installation area is large.
An object of the present invention is to provide a power compensation device and a power compensation method capable of downsizing a reactor and reducing the installation area of the entire device.

In order to achieve the above object, according to the present invention, in the power compensator that compensates the power of the power path by converting the supplied power to the power path formed of a plurality of phases by power conversion, A first series circuit in which the first power conversion unit and the first reactor are connected in series to the power path, and a second series in which the second power conversion unit and the second reactor are connected in series. A circuit was connected so that the first reactor and the second reactor were magnetically coupled.
In addition, a first series circuit in which the first reactor and the first power converter are connected in series is connected to the power path, and the second reactor and the second magnetically coupled to the first reactor A power converter is connected to the power path, and the supplied power is converted by the first power converter and the second power converter to convert the power path to the power path. To compensate for the power of the power path.

According to the present invention, it is possible to reduce the size of the reactor, so that it is possible to reduce the installation area of the entire apparatus.

1st form by this invention Full-bridge type unit converter Half-bridge type unit converter Double half bridge type unit converter Schematic waveform when unbalance compensator is stopped Schematic waveform when the unbalance compensator is operating Reactor with iron core Sorashin reactor 2nd form by this invention When a single-phase STATCOM is installed in parallel with the AC feeder railway system Example of phasor diagram when reactor is not magnetically coupled Example of phasor diagram when the reactor is magnetically coupled 1 Example 2 of phasor diagram when reactor is magnetically coupled

A first embodiment of the present invention will be described.

The first embodiment is an unbalance compensator configured by connecting two series circuits of an arm and a reactor configured by connecting one or a plurality of unit converters in series to a three-phase AC system.

This embodiment is characterized in that the reactors included in the two series circuits are magnetically coupled via a magnetic material such as an iron core or a non-magnetic material such as air. More specifically, it is characterized in that it is magnetically coupled so that magnetomotive forces due to positive currents flowing through the two reactors are intensified.

According to the present embodiment, the effect that the number of turns of the reactor for obtaining a certain inductance can be reduced, that is, the reactor can be reduced in size.

The overall configuration of the first embodiment will be described below with reference to FIG.

FIG. 1 shows a configuration in which an AC feeding railway system 104 and an unbalance compensator 105 according to the present invention are connected to a power receiving point 103 via a system impedance 102 of a three-phase AC system 101.

The AC feeding railway system 104 receives single-phase power from two phases of the c-phase and a-phase of the power receiving point 103, and is a single-phase load. Therefore, when viewed from the three-phase AC system 101, it is an unbalanced load.

The unbalance compensation device 105 is connected to the power receiving point 103 in parallel with the AC feeder railway system 104.

The AC feeder railway system 104 is an example of a single-phase load connected to the power receiving point 103, and the effects of the present embodiment can be obtained even with other types of loads as long as it is a single-phase load. Can do.

In the present specification, the line voltage of the three-phase AC system 101 is expressed as VSab, VSbc, and VSca, respectively, and it is assumed that the voltage source is approximately balanced.

The line voltage at the power receiving point 103 is expressed as VRab, VRbc, VRca, respectively.

Further, currents flowing through the three-phase AC system 101 are denoted as ISa, ISb, and ISc, respectively, and currents flowing through the AC feeder railway system 104 are denoted as ILca.

Further, currents flowing from the power receiving point to the unbalance compensation device 105 are denoted as ICa, ICb, and ICc, respectively.

Hereinafter, the internal configuration of the AC feeder railway system 104 will be described. In addition, the AC feeder railway system 104 in FIG. 1 is a diagram schematically illustrating an AT (auto-transformer) feeder AC railway.

The AC feeder railway system 104 includes, for example, a transformer 106, a train 107, and a single-turn transformer 108.

The primary winding of the transformer 106 is connected between the c-a phases of the power receiving point 103. As shown in FIG. 1, the secondary winding of the transformer 106 has a configuration in which a middle point r is drawn out. The three terminals of the secondary winding are referred to as t point, r point, and f point, respectively.

The train 107 is connected between the t point and the r point. Moreover, the autotransformer 108 is connected to the t point, the r point, and the f point.

Current accompanying powering or regeneration of the train 107 flows only in the c-phase and a-phase of the power receiving point 103 and does not flow in the b-phase.

Therefore, when the unbalance compensator 105 is stopped, that is, when ICa, ICb, and ICc are all zero, the currents ISa, ISb, and ISc that flow through the three-phase AC system 101 are expressed by equations (1) to ( It can be written as 3).
[Equation 1]
ISa = -ILca (1)
[Equation 2]
ISb = 0 (2)
[Equation 3]
ISc = ILca (3)

Since the current ISb flowing in the b phase is zero, the currents shown in the equations (1) to (3) are unbalanced.

Hereinafter, the internal configuration of the unbalance compensator 105 according to the present invention will be described.

The unbalance compensator 105 includes an ab phase arm 109ab, a bc phase arm 109bc, and a coupling reactor 110.

Each of the ab phase arm 109ab and the bc phase arm 109bc is a circuit in which one or a plurality of unit converters 111 are connected in series. The internal configuration of the unit converter 111 will be described later.

The coupling reactor 110 includes an ab phase winding 112ab and a bc phase winding 112bc.

A series circuit of an ab phase arm 109ab and an ab phase winding 112ab is connected to the ab phase of the power receiving point 103.

In addition, a series circuit of a bc phase arm 109bc and a bc phase winding 112bc is connected to the bc phase of the power receiving point 103.

In FIG. 1, the ab phase arm 109ab is connected to the power receiving point 103 closer to the a phase, and the ab phase winding 112ab is connected to the closer to the c phase, but the ab phase arm 109ab and the ab phase winding are connected. The connection position of the line 112ab may be reversed.

Similarly, in FIG. 1, the bc phase winding 112ab is connected to the side closer to the b phase of the power receiving point 103 and the bc phase arm 109bc is connected to the side closer to the c phase, but the bc phase windings 112ab and bc The connection position of the phase arm 109bc may be reversed.

In the following description, the ab-phase arm 109ab and the bc-phase arm 109bc are collectively referred to simply as “arm 109” unless it is necessary to distinguish between them.

In this specification, the voltage between both ends of the ab-phase arm 109ab is denoted as VCab, and the voltage between both ends of the bc-phase arm 109bc is denoted as VCbc. Further, the current flowing through the ab phase arm 109ab is denoted as ICab, and the current flowing through the bc phase arm 109bc is denoted as ICbc.

Further, as shown in FIG. 1, the voltage across the ab phase winding 112ab is denoted as VLab, and the voltage across the bc phase winding 112bc is denoted as VLbc.

In the coupled reactor 110, the self-inductance of the ab phase winding 112ab and the bc phase winding 112bc is expressed as L, and the mutual inductance is expressed as M.

The relationship between the currents ICab and ICbc flowing through the arms 109 of the unbalance compensator 105 and the currents ICa, ICb and ICc flowing from the power receiving point to the unbalance compensator 105 should be written as in equations (4) to (6). Can do.
[Equation 4]
ICa = ICab (4)
[Equation 5]
ICb = −ICab + ICbc (5)
[Equation 6]
ICc = −ICbc (6)

The principle of unbalance compensation by the unbalance current compensator 105 will be described later with reference to FIGS. 5 and 6, but before that, the internal configuration of the unit converter 111 will be described with reference to FIGS. . Further, the principle that the unbalance compensator controls the currents ICab and ICbc will be described.

Hereinafter, an internal configuration of the unit converter 111 and an output voltage control method will be described.

Three examples of the internal configuration of the unit converter 111 will be described with reference to FIGS.

Hereinafter, the internal configuration of the full-bridge unit converter 111a and the method for controlling the output voltage will be described with reference to FIG.

An anti-parallel circuit of x-phase upper switching element 201xp and x-phase upper free-wheeling diode 202xp and an anti-parallel circuit of x-phase lower switching element 201xn and x-phase lower free-wheeling diode 202xn are connected in series at point x. This is referred to as a first series circuit.

The anti-parallel circuit of the y-phase upper switching element 201yp and the y-phase upper circulating diode 202yp and the anti-parallel circuit of the y-phase lower switching element 201yn and the y-phase lower circulating diode 202yn are connected in series at the point y. This is referred to as a second series circuit. The full bridge unit converter 111a includes a capacitor 203 as an energy storage element.

The full bridge type unit converter 111a has a configuration in which the first and second series circuits and the capacitor 203 are connected in parallel at the p point and the n point.

In the following, unless it is particularly necessary to distinguish, the x-phase upper switching element 201xp, the x-phase lower switching element 201xn, the y-phase upper switching element 201yp, the y-phase lower switching element 201yn, and each of FIGS. Switching elements are collectively referred to simply as “switching element 201”.

Similarly, when it is not necessary to distinguish between them, the x-phase upper freewheeling diode 202xp, the x-phase lower freewheeling diode 202xn, the y-phase upper freewheeling diode 202yp, the y-phase lower freewheeling diode 202yn, and each of FIGS. The freewheeling diodes are collectively referred to simply as “freewheeling diodes 202”.

Hereinafter, the voltage / current in the full-bridge unit converter 111a is defined.

The voltage at the point x with respect to the point y is referred to as the output voltage of the full-bridge unit converter 111a and is expressed as VCjk.

Further, the voltage of the capacitor 203 is expressed as VDjk.

Here, j = ab, bc, which means the arm 109 to which the full bridge unit converter 111a belongs. k = 1, 2,..., N, which means the number of the full bridge unit converter 111 a in the arm 109. N is the number of unit converters 111 in the arm 109.

Hereinafter, a method for controlling the output voltage VCjk by controlling the on / off state of the switching element 201 will be described.

When the x-phase upper switching element 201xp is on, the x-phase lower switching element 201xn is off, the y-phase upper switching element 201yp is on, and the y-phase lower switching element 201yn is off, The voltage is almost zero. That is, VCjk = 0.

When the x-phase upper switching element 201xp is on, the x-phase lower switching element 201xn is off, the y-phase upper switching element 201yp is off, and the y-phase lower switching element 201yn is on, The voltage is approximately equal to the voltage VDjk of the capacitor 203. That is, VCjk = VDjk.

When the x-phase upper switching element 201xp is off, the x-phase lower switching element 201xn is on, the y-phase upper switching element 201yp is on, and the y-phase lower switching element 201yn is off, The voltage is approximately equal in magnitude to the voltage VDjk of the capacitor 203 and has a reverse polarity. That is, VCjk = −VDjk.

When the x-phase upper switching element 201xp is off, the x-phase lower switching element 201xn is on, the y-phase upper switching element 201yp is off, and the y-phase lower switching element 201yn is on, The voltage is almost zero. That is, VCjk = 0.

From the above, it can be seen that the output voltage VCjk of the full-bridge unit converter 111a can be controlled by controlling on / off of the switching element.

  Here, in FIGS. 2 and 3 and 4 to be described later, an IGBT (insulated-gate bipolar transistor) symbol is drawn as a switching element. However, the present invention is not limited to this, and an on / off control type is shown. For switching devices, other types of switching such as BJT (bipolar junction transistor), MOSFET (metal-oxide-semiconductor field-effect transistor), GTO (gate turn-off) thyristor, IGCT (integrated gate-commutated thyristor), etc. Even when an element is used, the effects of the present invention can be obtained.

Hereinafter, an internal configuration of the half-bridge type unit converter 111b and a method for controlling the output voltage will be described with reference to FIG.

The antiparallel circuit of the x-phase upper switching element 201xp and the x-phase upper freewheeling diode 202xp and the antiparallel circuit of the x-phase lower switching element 201xn and the x-phase lower freewheeling diode 202xn are connected in series at the point x. This is referred to as a first series circuit.

The half-bridge unit converter 111b includes two capacitors, an upper capacitor 203p and a lower capacitor 203n, as energy storage elements.

The upper capacitor 203p and the lower capacitor 203n are connected in series at m points. This is referred to as a second series circuit.

The half-bridge type unit converter 111b has a configuration in which the first and second series circuits are connected in parallel at the p point and the n point.

Hereinafter, the voltage / current in the half-bridge type unit converter 111b is defined.

The voltage at the point x with respect to the point m is referred to as the output voltage of the half-bridge unit converter 111b and is denoted as VCjk.

The voltage of the upper capacitor 203p is expressed as VDPjk, and the voltage of the lower capacitor 203n is expressed as VDNjk.

Hereinafter, a method for controlling the output voltage VCjk by controlling the on / off state of the switching element 201 will be described.

When the x-phase upper switching element 201xp is on and the x-phase lower switching element 201xn is off, the voltage at the x point with respect to the m point is substantially equal to the voltage VDPjk of the upper capacitor 203p. That is, VCjk = VDPjk. In this case, the current Ij flowing through the unit converter 111b flows through the upper capacitor 203p.

When the x-phase upper switching element 201xp is off and the x-phase lower switching element 201xn is on, the voltage at the x point with respect to the m point is approximately equal to the voltage VDNjk of the lower capacitor 203n, and The voltage has a reverse polarity. That is, VCjk = −VDNjk. In this case, the current Ij flowing through the unit converter flows through the lower capacitor 203n.

From the above, it can be seen that the output voltage VCjk of the half-bridge unit converter 111b can be controlled by controlling on / off of the switching element.

Hereinafter, the internal configuration of the double half bridge type unit converter 111c will be described with reference to FIG.

The double half-bridge type unit converter 111c has a configuration in which an x-phase half bridge 401x and a y-phase half bridge 401y are connected in reverse series at m points.

In the following description, the x-phase half bridge 401x and the y-phase half bridge 401y are collectively referred to simply as “half bridge 401” unless it is necessary to distinguish between them.

Hereinafter, the internal configuration of the half bridge 401x will be described.

The antiparallel circuit of the x-phase upper switching element 201xp and the x-phase upper freewheeling diode 202xp and the antiparallel circuit of the x-phase lower switching element 201xn and the x-phase lower freewheeling diode 202xn are connected in series at the point x. This is referred to as a first series circuit.

Further, the half bridge 401x includes two capacitors, an x-phase upper capacitor 203xp and an x-phase lower capacitor 203xn, as energy storage elements.

The x-phase upper capacitor 203xp and the x-phase lower capacitor 203xn are connected in series at m points. This is referred to as a second series circuit.

The half bridge 401x has a configuration in which the first and second series circuits are connected in parallel at the px point and the nx point.

Next, the internal configuration of the half bridge 401y will be described.

The anti-parallel circuit of the y-phase upper switching element 201yp and the y-phase upper circulating diode 202yp and the anti-parallel circuit of the y-phase lower switching element 201yn and the y-phase lower circulating diode 202yn are connected in series at the point y. This is referred to as a first series circuit.

The half bridge 401y includes two capacitors, a y-phase upper capacitor 203yp and a Y-phase lower capacitor 203yn, as energy storage elements.

The y-phase upper capacitor 203yp and the X-phase lower capacitor 203yn are connected in series at m points. This is referred to as a second series circuit. This m point is common with the m point of the x-phase half bridge 401.

The half bridge 401y has a configuration in which the first and second series circuits are connected in parallel at the py point and the ny point.

As described above, the m points of the x-phase half bridge 401x and the Y-phase half bridge 401y are connected.

Hereinafter, the voltage / current in the double half bridge type unit converter 111c is defined.

The voltage at the point x with respect to the point y is referred to as the output voltage of the double half bridge unit converter 111c and is expressed as VCjk.

The voltage of the x-phase upper capacitor 203xp is expressed as VDxpjk, and the voltage of the x-phase lower capacitor 203xn is expressed as VDxnjk.

Similarly, the voltage of the y-phase upper capacitor 203yp is expressed as VDypjk, and the voltage of the y-phase lower capacitor 203YN is expressed as VDynjk.

Hereinafter, a method for controlling the output voltage VCjk by controlling the on / off state of the switching element 201 will be described.

However, in the following description, it is assumed that the voltages of the four capacitors 203 are substantially equal, and the description will be made by approximating VDxpjk = VDxnjk = VDypjk = VDynjk = VDjk.

When the x-phase upper switching element 201xp is on, the x-phase lower switching element 201xn is off, the y-phase upper switching element 201yp is on, and the y-phase lower switching element 201yn is off, The voltage is the difference between the voltage of the x-phase upper capacitor 203xp and the voltage of the y-phase upper capacitor 203yp, that is, approximately VCjk = 0. In this case, the current Ij flowing through the unit converter 111c passes through the x-phase upper capacitor 203xp and the y-phase upper capacitor 203yp.

When the x-phase upper switching element 201xp is on, the X-phase lower switching element 201xn is off, the Y-phase upper switching element 201yp is off, and the Y-phase lower switching element 201yn is on, The voltage is the sum of the voltage of the x-phase upper capacitor 203xp and the voltage of the Y-phase lower capacitor 203yn, that is, approximately VCjk = 2VDjk. In this case, the current Ij flowing through the unit converter 111c passes through the x-phase upper capacitor 203xp and the Y-phase lower capacitor 203yn.

When the x-phase upper switching element 201xp is off, the x-phase lower switching element 201xn is on, the y-phase upper switching element 201yp is on, and the y-phase lower switching element 201yn is off, The voltage is a voltage having a polarity opposite to the sum of the voltage of the x-phase lower capacitor 203xn and the voltage of the y-phase upper capacitor 203yp, that is, approximately VCjk = -2VDjk. In this case, the current Ij flowing through the unit converter passes through the x-phase lower capacitor 203xn and the Y-phase upper capacitor 203yp.

When the x-phase upper switching element 201xp is off, the X-phase lower switching element 201xn is on, the y-phase upper switching element 201yp is off, and the y-phase lower switching element 201yn is on, The voltage is the difference between the voltage of the x-phase lower capacitor 203xp and the voltage of the y-phase lower capacitor 203yn, that is, approximately VCjk = 0. In this case, the current Ij flowing through the unit converter passes through the x-phase lower capacitor 203xn and the y-phase lower capacitor 203yn.

From the above, it can be seen that the output voltage VCjk of the double half bridge type unit converter 111c can be controlled by controlling on / off of the switching element.

The three examples of the internal configuration of the unit converter 111 have been described above.

Even if any of the unit converters 111a, 111b, 111c shown in FIGS. 2 to 4 is used as the unit converter 111 included in the arm 109, the effect of the present invention can be obtained.

Even if the unit converters 111a, b, and c shown in FIGS. 2 to 4 are mixed in one arm 109, the effect of the present invention can be obtained.

Further, in the half-bridge type unit converter 111b of FIG. 3 and the double half-bridge type unit converter 111c of FIG. 4, the current Ij always supplies any capacitor regardless of the on / off state of the switching element 201. Pass through.

Since the capacitor theoretically has an infinite impedance to direct current, either the half-bridge type unit converter 111b of FIG. 3 or the double half-bridge type unit converter 111c of FIG. The current Ij flowing through the arm 109 does not include a DC component, but includes only an AC component.

In other words, when either the half-bridge type unit converter 111b of FIG. 3 or the double half-bridge type unit converter 111c of FIG. 4 is included in the arm 109, a direct current is supplied from the arm to the three-phase AC system 101. Can be prevented from flowing out.

Hereinafter, a method for controlling the current ICab flowing through the ab phase arm 109ab and the current ICbc flowing through the bc phase arm 109bc will be described.

Since details will be described later with reference to FIGS. 11 to 13, only the outline will be described below.

First, a method for controlling the current ICab of the ab phase arm 109ab will be described. Further, it will be described that the ab phase arm 109ab and the winding 112ab can supply reactive power to the power receiving point 103 through the control of ICab.

However, in order to simplify the explanation, the following description will be made assuming that the mutual inductance M of the ab phase winding 112ab and the bc phase winding 112bc is zero, and later, referring to FIGS. Next, the principle by which the coupling reactor 110 can be miniaturized will be described.

In FIG. 1, the voltage VCab across the ab phase arm 109ab is the sum of the output voltages of one or the unit converter 111 included in the ab phase arm 109ab. Therefore, the voltage VCab across the ab phase arm 109ab can be controlled by controlling the output voltage of the unit converter 111.

The frequency and phase of the both-end voltage VCab of the ab-phase arm 109ab are controlled so as to match the frequency and phase of the ab phase line voltage VRab of the power receiving point 103, and the VCab amplitude matches the VRab amplitude. When the control is performed, the voltage VLab across the winding 112ab is substantially zero.

The current ICab flowing through the winding 112ab is proportional to the time integration of the voltage VLab. As described above, when VLab is zero, the current ICab is substantially zero.

In this case, the power that the ab phase arm 109ab and the ab phase winding 112ab exchange with the power receiving point 103 is zero.

The frequency and phase of the both-end voltage VCab of the ab-phase arm 109ab are controlled so as to coincide with the frequency and phase of the ab phase line voltage VRab of the power receiving point 103, and the amplitude of VCab is larger than the amplitude of VRab. When the voltage is controlled to be high, the voltage VLab across the winding 112ab has a phase opposite to that of VRab.

The current ICab flowing through the winding 112ab is a current whose phase is delayed by 90 ° with respect to VLab in a steady sine wave state. As described above, when VLab is a voltage having a phase opposite to that of VRab, the current ICab is a current whose phase is advanced by 90 ° with respect to VRab.

That is, the ab phase arm 109ab supplies capacitive reactive power to the power receiving point 103.

The frequency and phase of the both-end voltage VCab of the ab-phase arm 109ab are controlled so as to coincide with the frequency and phase of the ab phase line voltage VRab of the power receiving point 103, and the amplitude of VCab is larger than the amplitude of VRab. When controlled to be low, the voltage VLab across the winding 112ab has the same phase as VRab.

The current ICab flowing through the winding 112ab is a current whose phase is delayed by 90 ° with respect to VLab in a steady sine wave state. As described above, when VLab is a voltage having the same phase as VRab, the current ICab is a current whose phase is delayed by 90 ° with respect to VRab.

That is, the ab phase arm 109ab supplies inductive reactive power to the power receiving point 103.

The method for controlling the current ICab flowing through the ab phase arm 109ab has been described above.

The method of controlling the current ICbc flowing through the bc phase arm 109bc may be read by replacing “ab” in the above description with “bc”, and thus the description is omitted.

Hereinafter, the unbalance compensation principle by the unbalance compensation device 105 will be described with reference to FIGS.

In this embodiment, it is assumed that the power factor of the AC feeding railway system 104 viewed from the power receiving point 103 is approximately 1 because the train 107 includes a PWM (pulse-width modulation) rectifier. Yes.

FIG. 5 is a schematic waveform when the unbalance compensator 105 is stopped, that is, when ICab and ICbc are zero.

5 shows, from above, the line voltages VSab, VSbc, VSca of the three-phase AC system 101, the current ILca of the AC feeding railway system, the currents ICab, ICbc flowing through the arms 109 of the unbalance compensator 105, and the three-phase AC system. 101 is a schematic waveform of the phase voltages VSa, VSb, VSc of 101, currents ICa, ICb, ICc flowing from the power receiving point 103 to the unbalance compensator 105, and currents ISa, ISb, ISc flowing in the three-phase AC system.

The AC powered railway system 104 is connected as a load having a power factor of 1 between the c-a phases of the power receiving point 103. Therefore, the phases of VSca and ILca are almost the same.

As described using the equations (1) to (3), when the unbalance compensator 105 is stopped, ILca does not flow in the b phase, and therefore, ISb becomes zero. The flowing currents ISa, ISb, ISc are unbalanced.

When ISa, ISb, ISc are unbalanced, the voltage drop of the system impedance 102 is unbalanced, and the line voltages VRab, VRbc, VRca at the power receiving point 103 are unbalanced. Since an unbalanced voltage may adversely affect other loads (not shown) connected to the power receiving point 103, it must be suppressed within an allowable range.

FIG. 6 is a schematic waveform when the unbalance compensator 105 is operating.

In order to compensate for the unbalanced current caused by the AC feeding railway system 104, the ab phase arm 109ab generates capacitive reactive power, and the bc phase arm 109bc generates inductive reactive power.

That is, as can be seen by comparing the points B and D in FIG. 6, ICab is advanced by approximately 90 ° with respect to VSab.

Further, as can be seen by comparing the points A and C in FIG. 6, the ICbc is approximately 90 ° behind the VSbc.

As a result, the phase difference between ICab and ICbc is approximately 60 ° as can be seen by comparing point E and point F.

Note that the amplitudes of ICab and ICbc are approximately 1 / √3 times the amplitude of ILca.

As will be described later, the present invention is characterized in that the reactor is miniaturized by utilizing the fact that the phase difference between ICab and ICbc is approximately 60 °, as can be seen by comparing the E point and the F point.

Currents ICa, ICb, and ICc flowing from the power receiving point 103 to the unbalance compensator 105 can be drawn according to equations (4) to (6).

When the unbalance compensator 105 is operating, the currents ISa, ISb, ISc flowing through the three-phase AC system 101 are the sum of ISa, ISb, ISc in FIG. 5 and ICa, ICb, ICc in FIG.

As shown in FIG. 6, ISa, ISb, and ISc are approximately balanced, and the power factor is approximately 1 as can be seen by comparing the G point and the H point.

The principle of unbalance compensation by the unbalance compensation device 105 has been described above.

Hereinafter, with reference to FIGS. 11 to 13, the principle that can reduce the size of the reactor by magnetically coupling the ab phase winding 112ab and the bc phase winding 112bc, which is a feature of the present invention, will be described.

11 to 13 are phasor diagrams.

First, with reference to FIG. 11, a description will be given of the relationship between the voltage and current of each part when the ab phase winding 112ab and the bc phase winding 112bc are not magnetically coupled.

In the following, an example will be described in which the ab phase arm 109ab supplies capacitive reactive power and the bc phase arm 109bc supplies inductive reactive power.

The voltage Vab across the ab-phase arm 109ab has a phase equal to the phase of the line voltage VRab at the power receiving point 103, and an amplitude greater than that of VRab.

In this case, as shown in FIG. 11, the both-ends voltage VLab of the ab phase winding 112ab has a voltage opposite in phase to VRab.

Therefore, the current ICab flowing in the ab phase winding 112ab is a current delayed by 90 ° from VLab.

From the above, ICab becomes a current advanced by 90 ° from VRab. Therefore, as described above, the ab phase arm 109ab supplies the reactive power having capacity to the power receiving point 103.

On the other hand, the voltage Vbc across the bc-phase arm 109bc has the same phase as the phase of the line voltage VRbc at the power receiving point 103, and the amplitude is smaller than the amplitude of VRbc.

In this case, as shown in FIG. 11, the voltage VLbc across the bc phase winding 112bc has the same phase as that of VRbc.

Therefore, the current ICab flowing in the ab phase winding 112ab is a current delayed by 90 ° from VLab.

From the above, ICab becomes a current advanced by 90 ° from VRab. Therefore, as described above, the ab phase arm 109ab supplies inductive reactive power to the power receiving point 103.

Now, when the ab phase winding 112ab and the bc phase winding 112bc are magnetically coupled, FIG. 11 changes as shown in FIG.

Note that k in FIGS. 12 and 13 is a coupling rate.

The voltage across the ab phase winding 112ab is the vector sum of VLab and k × VLbc, that is, VLabtotal.

Similarly, the voltage across the bc phase winding 112bc is the vector sum of VLbc and k × VLab, that is, VLbctotal.

Here, the amplitude of VLabtotal in FIG. 12 is larger than the amplitude of VLab in FIG.

Similarly, the amplitude of VLbctotal in FIG. 12 is larger than the amplitude of VLbc in FIG.

In other words, an equivalently large inductance can be obtained by magnetically coupling the ab phase winding 112ab and the bc phase winding 112bc.

Further, when inductances of the same magnitude are required, the number of turns can be reduced by magnetically coupling the ab phase winding 112ab and the bc phase winding 112bc, so that an effect that the reactor can be reduced in size can be obtained.

However, in FIG. 12, the voltage VCab across the ab phase arm 109ab and the current ICab flowing through the arm are not orthogonal.

Similarly, the both-ends voltage VCbc of the bc phase arm 109bc and the current ICbc flowing through the arm are not orthogonal.

In this case, since the effective power flowing into and out of each arm 109 is not zero, the capacitor voltage VDjk of the unit converter 111 included in each arm 109 continuously increases or decreases, and the unbalance compensation device 105 is operating normally. There is a risk of disturbing proper driving.

Therefore, as shown in FIG. 13, by changing the phases of the currents ICab and ICbc from FIGS. 11 and 12, VCab and ICab and VCbc and ICbc can be made orthogonal to each other.

As a result, the unbalance compensator 105 can be continuously operated.

Also in FIG. 13, the amplitude of VLabtotal is larger than the amplitude of VLab in FIG.

Similarly, the amplitude of VLbctotal in FIG. 13 is larger than the amplitude of VLbc in FIG.

In other words, an equivalently large inductance can be obtained by magnetically coupling the ab phase winding 112ab and the bc phase winding 112bc.

Further, when inductances of the same magnitude are required, the number of turns can be reduced by magnetically coupling the ab phase winding 112ab and the bc phase winding 112bc, so that an effect that the reactor can be reduced in size can be obtained.

Hereinafter, the internal configuration of the magnetic coupling reactor 110 will be described with reference to FIGS.

FIG. 7 shows a configuration in which an ab phase winding 112ab and a bc phase winding 112bc are wound around an iron core 701.

That is, the ab phase winding 112ab and the bc phase winding 112bc are magnetically coupled via the iron core 701.

The polarity of the magnetic coupling is such that the magnetomotive force due to the current ICab and the magnetomotive force due to the current ICbc reinforce each other.

FIG. 8 shows a configuration in which the ab phase winding 112ab and the bc phase winding 112bc are magnetically coupled via air.

Similarly to FIG. 7, in FIG. 8, the polarity of the magnetic coupling is in the direction in which the magnetomotive force due to the current ICab and the magnetomotive force due to the current ICbc are intensified.

Even when an iron core is used as shown in FIG. 7 or when magnetic coupling is performed via air without using an iron core as shown in FIG. 8, the effect of this embodiment can be obtained.

In the above description, the case where the electric power is consumed such as when the train 107 is powered is described as an example.

On the other hand, when the electric power is generated such as when the train 107 is regenerating, unlike the above description, the ab phase arm 109ab generates inductive power and the bc phase arm 109bc generates capacity reactive power. Equilibrium can be compensated.

Even in such a case, it is possible to obtain the effect of the present invention that the reactor is downsized.

Moreover, in the above description, the case where the AC feeding railway system 104 is connected between the c-a phases of the power receiving point 103 has been described as an example.

When the AC feeder railway system 104 is connected between the a and b phases of the power receiving point 103, by replacing “ab” with “bc” and “bc” with “ca” in the description of this embodiment, Similar effects can be obtained.

Further, when the AC feeder railway system 104 is connected between the bc phases of the power receiving point 103, “ab” in the description of this embodiment is replaced with “ca” and “bc” is replaced with “ab”. The same effect can be obtained.
Although the present embodiment has been described by taking an AC powered electric railway as an example, it can be applied to other technologies, and can be applied to, for example, a so-called STATCOM or a self-excited SVC. .

A second embodiment of the present invention will be described.

The present embodiment has a configuration in which another arm and a reactor are added to the unbalance compensator described in the first embodiment. The parts different from the first embodiment will be described, and the other parts are the same as those of the first embodiment, and the description thereof will be omitted.

In the first embodiment, it is assumed that the power factor of the AC feeder railway system 104 viewed from the power receiving point 103 is approximately 1 because the train 107 includes a PWM rectifier.

When the power factor of the AC feeder railway system 104 viewed from the power receiving point 103 is not approximately 1, the power factor cannot be improved only by the unbalance compensator 105 of the first embodiment.

Therefore, in this embodiment, another set of arm and reactor was added to enable power factor improvement.

The overall configuration of the second embodiment will be described below with reference to FIG.

However, only the difference from the first embodiment will be described.

The unbalance compensator 105 of the first embodiment (FIG. 1) was provided with two arms, that is, an ab phase arm 109ab, a bc phase arm 109ab, and a coupling reactor 110.

In addition to this, the unbalance compensator 901 of this embodiment (FIG. 9) has a configuration in which a series circuit of a reactor 903 and a ca-phase arm 902 is connected between the c-a phases of the power receiving point 103.

When the AC feeding railway system 104 has a delay power factor, the power factor of the AC feeding railway system 104 can be improved by supplying reactive power that is capacitive from the ca-phase arm 902.

Similarly, when the AC feeding railway system 104 has a leading power factor, the power factor of the AC feeding railway system 104 can be improved by supplying inductive reactive power from the ca-phase arm 902.

The operations of the ab phase arm 109ab and the bc phase arm 109ab are substantially the same as those in the first embodiment.

As a result, even when the power factor cannot be controlled because the train 107 uses a diode rectifier, for example, the current ISa, ISb, ISc flowing through the AC system 101 can be balanced.

The circuit configuration of unit converter 904 included in ca phase arm 902 is the same as the circuit configuration of unit converter 111, that is, FIGS.

Note that the same effect can be obtained when a series circuit of an arm 1002 and a reactor 1003 is provided in parallel with the train 107 as shown in FIG.

The circuit configuration of the unit converter 1004 included in the arm 1102 is the same as the circuit configuration of the unit converter 111, that is, FIGS.

101 ... Three-phase AC system 102 ... System impedance 103 ... Power receiving point 104 ... AC feeding railway system 105, 901, 1001 ... Unbalance compensator 106 ... Transformer 107 ... · Train 108 ··· Single-turn transformer 109, 902, 1002 ··· Arm 110 ··· Reactor 111, 904, 1004 ··· Unit converter 112 · · · Winding 201 · · · Switching element 202 · ..Flux diode 203 ... Capacitor 401 ... Half bridge 701 ... Core

Claims (10)

In a power compensator that compensates the power of the power path by converting the supplied power to a power path formed of a plurality of phases by power conversion, the power path includes a first power conversion unit and a first power converter. And a second series circuit in which a second power converter and a second reactor are connected in series, and the first reactor and the first reactor are connected in series. A power compensator characterized by magnetically coupling two reactors. The first power conversion unit or the second power conversion unit according to claim 1, wherein the first power conversion unit or the second power conversion unit includes an arm configured by connecting one or more unit converters each including a switching element and an energy storage element in series. A power compensator characterized by comprising. The first series circuit and the second series circuit according to claim 1, wherein one of the first series circuit and the second series circuit is connected between certain phases of the three-phase AC system, and the other is connected between other phases of the three-phase AC system. A power compensator characterized by the above. 3. The power compensator according to claim 2, wherein a part or all of the unit converter is a full bridge circuit, a half bridge circuit, or a double half bridge circuit. 3. The power compensation apparatus according to claim 2, wherein unit converters configured by a full bridge circuit, a half bridge circuit, or a double half bridge circuit are mixed in the arm. 3. The power compensation device according to claim 2, wherein one of the arms has a function of supplying capacitive reactive power and the other supplying inductive reactive power. In Claim 1, the 3rd series circuit which connected the 3rd power converter and the 3rd reactor in series is connected to the power path, The 1st reactor, the 2nd reactor, and the 3rd reactor Any one of the two reactors is magnetically coupled to each other. In Claim 7, one of the three series circuits is connected between certain phases of the three-phase AC system, the other is between the other phases of the three-phase AC system, and the other is between the remaining phases of the three-phase AC system. A power compensation device connected to the power supply. 8. The system according to claim 7, wherein one of the three series circuits is connected between certain phases of the three-phase AC system, the other is connected between other phases of the three-phase AC system, and the other is connected to the three-phase AC system. A power compensator connected to the system via a transformer between the remaining phases. A first series circuit in which a first reactor and a first power conversion unit are connected in series is connected to a power path, and a second reactor and a second power are magnetically coupled to the first reactor. A second series circuit in which converters are connected in series is connected to the power path, and the supplied power is converted into power by the first power converter and the second power converter and supplied to the power path. A power compensation method for compensating power in the power path.