JP2002247760A - Starting method of serial compensator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a starting method of a serial compensator using a method for charging a DC voltage without the use of an initial charging circuit. SOLUTION: When the compensator is started, a bypass switch 14 is turned off, to input a serial capacitor 5 into a system. In this case, a voltage generated at the serial capacitor 5 is applied to a serial capacitor 11 via a diode 9. Thereafter, a voltage-type converter 10 is started via a zero-current control to set to zero the output current of the voltage-type converter 10. When a current command is given under this condition to a current control circuit 21 from a serial voltage control circuit 22 to allow an effective current to the serial capacitor 11 from a serial transformer 6, power is supplied to the serial capacitor 11 via the voltage-type converter 10 from an AC system, to perform initial charge of the serial capacitor 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for starting a series compensator connected in series to an AC system via a transformer.

[0002]

2. Description of the Related Art FIG. 9 shows a basic circuit configuration of a conventional series compensator. In FIG. 9, reference numeral 1 denotes a power transmission side AC voltage Vs,
2 is a receiving side AC voltage Vo, 3 is a transmission line, 4 is a line reactance X of the transmission line, 5 is a series capacitor C, 6 is a series transformer Tr, 7 is a reactor L, 8 is a self-extinguishing element, 9
Is a diode, 10 is a self-extinguishing element 8 and a diode 9
11, a DC capacitor; 12, an initial charging circuit; 13, a reverse current blocking diode for preventing current from flowing from the DC capacitor 11 to the initial charging circuit 12; 14, a bypass switch; Is a system current detector, 16 is a phase detector, 17 is an output current detector for detecting the output current of the voltage source converter 10, 18 is an output voltage detector for detecting the voltage of the series capacitor 5, and 19 is a DC capacitor 11 DC voltage detector 20 for detecting the output voltage of the voltage source converter 10, 21 a current control circuit for controlling the output current, 21
Reference numeral 2 denotes a DC voltage control circuit for controlling a DC voltage.

FIG. 10 is a block diagram showing a more detailed configuration example of the current control circuit 21. As shown in FIG. In FIG.
Is a line / phase conversion circuit for converting the detection signal of the output voltage detection circuit 18 from a line voltage signal to a phase voltage signal, and 24 is a three-phase / 2 for converting a three-phase voltage signal into a two-phase voltage signal.
A phase conversion circuit, 25 is a rotation conversion circuit for converting a two-phase signal to a dq signal, and 26 is a three-phase / 2 for converting a detection signal of the output current detector 17 from a three-phase voltage signal to a two-phase voltage signal. A phase conversion circuit, 27 is a rotation conversion circuit for converting a two-phase signal into a dq signal, and 28 is a current control command value Icmpd.
*, Icmpq * and an adder circuit for obtaining a deviation between the output signal of the rotation conversion circuit 27, 29 is an amplification circuit for performing output control based on the deviation, and 30 is a rotation conversion circuit 25 for outputting the output of the amplification circuit 29. Is a rotation conversion circuit for converting the dq signal into a two-phase signal, and 32 is a rotation conversion circuit for converting the two-phase signal into a three-phase signal.
This is a phase / 3-phase conversion circuit. Note that, of the current control command values Icmpd * and Icmpq * input to the addition circuit 28, Icmpq * is supplied from the DC voltage control circuit 22 and Icmpd * is given inside the addition circuit 28 or an external higher-level control. Provided by the system (not shown).

FIG. 11 is a block diagram showing a more detailed configuration example of the DC voltage control circuit 22. As shown in FIG. In FIG. 11, reference numeral 33 denotes an addition circuit for obtaining a deviation between the DC voltage command value Vdc * and the output signal Vdc of the DC voltage detector 19, and reference numeral 34 denotes an amplification circuit for performing output control based on the deviation of the addition circuit 33. , 35 are multipliers for inverting the output signal of the amplifier circuit 34 in positive and negative directions. The output signal Icmpq * of the multiplier 35 is supplied to the adding circuit 28 of the current control circuit 21.

The circuit operation will be described with reference to the voltage-current vector diagrams of FIGS. 9 to 11 and FIG. A d-axis current is taken in the same phase as the system current and a q-axis is taken in the direction leading 90 degrees in phase. The series capacitor 5 has the system current Is and the output current I
cmp flows, and the two currents have the same phase relationship. Therefore, only the magnitude of the output voltage Vo is variable without changing the phase, and the same effect as when the capacitance of the series capacitor 5 changes apparently can be obtained. . When the q-axis current of the output current flowing from the series transformer 6 to the series capacitor 5 is controlled using the current control circuit 21, the phase of the output voltage Vo changes.

Thus, a voltage of any magnitude and phase can be output in series with the AC system, and an impedance compensation operation of the AC system becomes possible.

In the control of the q-axis component of the output current, the active power flows into and out of the voltage source converter 10 from the AC system.
When a current in the negative direction of the q-axis is output, the voltage type converter 10 absorbs power from the AC system, so that the voltage of the DC capacitor 11 can be charged. DC voltage control is performed by controlling the q-axis current.

FIG. 13 shows a starting procedure of the conventional series compensator. It is assumed that the system current Is flows through the bypass switch 14 with the voltage source converter 10 stopped and the bypass switch 14 turned on (turned on) as an initial state before the series compensator is started.

At the start of operation, the bypass switch 14 is turned off and the series capacitor 5 is turned on to the AC system (step S131). At this time, the voltage source converter 10 is stopped, but the output voltage generated in the series capacitor 5 is connected to the DC capacitor 11 through the diode 9 of the voltage source converter 10.
Therefore, a DC voltage is generated in the DC capacitor 11 in consideration of the turns ratio of the series transformer 6. Thereafter, the initial charging circuit 12 is started, and the voltage of the DC capacitor 11 is charged to the rated voltage (Step S132). When the DC capacitor voltage reaches the rated voltage, the initial charging circuit 12 is stopped, and the current control of the voltage source converter 10 is started (step S133).

Thus, the series compensator can be started to perform the impedance compensation operation of the AC system.

[0011]

As described above, in this conventional device, the initial charging circuit 12 is used, and the DC voltage is reduced to the rated voltage by the initial charging circuit 12 before the voltage source converter 10 is operated. The series compensator was operated by charging and then starting current control.

However, when the voltage type converter 10 is operated with the DC voltage command of the DC voltage control circuit 22 as the rated voltage while the DC voltage is low, the active power is supplied from the system and the DC voltage is charged to the rated voltage. be able to.

Accordingly, an object of the present invention is to provide a method of starting a series compensator using a method of charging a DC voltage without using an initial charging circuit.

[0014]

According to a first aspect of the present invention, there is provided a method for starting a series compensator, comprising: a series capacitor connected in series to an AC system; Voltage-type converter using a DC-type element, a DC capacitor connected to the DC part of the voltage-type converter, a series transformer and a reactor for connecting the voltage-type converter and a series capacitor, and a series capacitor. In a series compensator including a bypass switch, a current control circuit for controlling an output current of the voltage source converter, and a DC voltage control circuit for controlling a DC voltage, after opening the bypass switch, the current control circuit and the DC voltage The control circuit receives active power from an AC system and performs initial charging of DC voltage and output current control.

According to the method of activating the series compensator according to the first aspect of the present invention, the DC voltage is charged by receiving the power from the AC system without using the initial charging circuit, and the series compensator is operated. Can be activated.

According to a second aspect of the present invention, there is provided a method for starting a series compensator, comprising: a series capacitor connected in series to an AC system; a voltage source converter using a self-extinguishing element; DC capacitor connected to the DC section of the series converter, a series transformer and reactor for connecting the voltage type converter and the series capacitor, a bypass switch for the series capacitor, and between the series transformer and the series capacitor. In a series compensator provided with an interconnection switch to be installed, a current control circuit for controlling the output current of the voltage source converter, and a DC voltage control circuit for controlling the DC voltage, a predetermined time has elapsed since the bypass switch was opened. Turn on the rear connection switch, and the current control circuit and DC voltage control circuit
It is characterized by receiving active power supply from an AC system and performing initial charging of DC voltage and output current control.

According to the method for starting the series compensator according to the present invention, the DC voltage is charged by receiving power from the AC system without using the initial charging circuit, and the series compensator is started. Can be activated. Also, when the interconnection switch is turned on, the voltage of the series capacitor applied to the series transformer is a voltage in which no DC component is superimposed, so that the inrush current to the voltage type converter can be suppressed,
The rating of the voltage source converter can be reduced.

According to a third aspect of the present invention, there is provided a method for starting a series compensator, comprising: a series capacitor connected in series to an AC system; a voltage source converter using a self-extinguishing element; Controls the DC capacitor connected to the DC section of the series converter, the series transformer and reactor for connecting the series converter with the series converter, the bypass switch of the series capacitor, and the output current of the series converter A current compensating circuit, and a DC compensating device comprising a DC voltage controlling circuit for controlling a DC voltage, wherein all self-extinguishing elements of the voltage source converter are turned on, a bypass switch is opened, and then the current controlling circuit and The DC voltage control circuit receives an active power supply from an AC system and performs initial charging of DC voltage and output current control.

According to the third aspect of the present invention, the series compensating device is started up by receiving power from an AC system and charging a DC voltage without using an initial charging circuit. Can be activated. Also, when the bypass switch is opened and the series capacitor is put into the system, the reactor is connected and the voltage generated in the series capacitor can be reduced, so that the rating of the series capacitor can be lowered, The rating of the voltage source converter can be reduced.

According to a fourth aspect of the present invention, there is provided a method for starting a series compensator, comprising: a series capacitor connected in series to an AC system; a voltage source converter using a self-extinguishing element; Controls the DC capacitor connected to the DC section of the series converter, the series transformer and reactor for connecting the series converter with the series converter, the bypass switch of the series capacitor, and the output current of the series converter A current control circuit, an output voltage control circuit for controlling the output voltage of the series capacitor, and a DC voltage control circuit for controlling the DC voltage, the output voltage control circuit reduces the voltage of the series capacitor to zero. After controlling and opening the bypass switch, the current control circuit and the DC voltage control circuit receive the supply of active power from the AC system,
It is characterized in that initial charging of DC voltage and output current control are performed.

According to the method of activating the series compensator according to the present invention, the DC voltage is charged by receiving the power from the AC system without using the initial charging circuit, and the series compensator is operated. Can be activated. In addition, when the bypass switch is opened and the series capacitor is turned on, the voltage of the series capacitor is controlled to zero, so all system current flows through the voltage-source converter. Can be reduced.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that, in the following drawings, the same reference numerals indicate the same or corresponding portions, including those showing the conventional example.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a circuit configuration diagram illustrating a series compensator according to the embodiment. FIG. 1 is different from FIG. 9 showing a conventional circuit configuration diagram.
The circuit configuration is such that the initial charging circuit 12 and the reverse current blocking diode 13 are omitted.

FIG. 2 shows a starting procedure according to the first embodiment. Assume that the state before the series compensator is started is an initial state, the voltage-source converter 10 is stopped, the bypass switch 14 is on (turned on), and the system current Is is flowing through the bypass switch 14.

At the start of activation, the bypass switch 14 is turned off and a series capacitor is supplied to the system (step S).
21). At this time, since the system current Is flows through the series capacitor 5, a voltage corresponding to the system current Is is generated in the series capacitor 5. Since this voltage is applied to the DC capacitor 11 via the diode 9 of the voltage source converter 10, the voltage source converter 10 is stopped, but a DC voltage corresponding to the number of turns of the series transformer 6 is generated in the DC capacitor 11. I do.

Thereafter, the voltage source converter 10 is started under zero current control, and the output current Icmp of the voltage source converter 10 is controlled.
u, Icmpv, and Icmpw are set to zero (step S
22). From this state, current command Icmpq * is sent from DC voltage control circuit 22 to current control circuit 21 such that a negative current in the q-axis direction flows from series transformer 6 to series capacitor 11.
, Power is supplied from the AC system to the DC capacitor 11 via the voltage source converter 10, and the DC capacitor 11 can be initially charged (step S2).
3).

As a result, the DC capacitor 11 can be initially charged by using the current control circuit 21 and the DC voltage control circuit 22, and the series compensator can be started without using the initial charging circuit.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
FIG. 3 is a circuit configuration diagram illustrating a series compensator according to the embodiment. In FIG. 3, reference numeral 36 denotes an interconnection switch for connecting the series capacitor 5 and the series transformer 6.

FIG. 4 shows a starting procedure according to the second embodiment. The state before the start of the series compensator is set as an initial state, the voltage source converter 10 is stopped, the bypass switch 14 is turned on (turned on), the interconnection switch 36 is turned off, and the system current Is flows through the bypass switch 14. It is assumed that

At the start of the startup, the bypass switch 14 is turned off to put the series capacitor 5 into the system (step S41). At this time, since the interconnection switch 36 is off, the voltage source converter 10 is disconnected from the system, and no current flows from the system to the voltage source converter 10 or the DC capacitor 11.

The off operation of the bypass switch 14 is normally performed when the system current flowing through the bypass switch 14 passes through a zero point.
Immediately after turning off, the voltage of the series capacitor 5 has a voltage waveform in which a DC component is superimposed.

However, this DC component is
And the resistance component of the transmission line attenuates over time, eventually resulting in a symmetrical AC waveform with no DC component. For example, after a lapse of several seconds, when the interconnection switch 36 is turned on in a state where the DC component has disappeared, the voltage of the series capacitor 5 applied to the series transformer 6 becomes a voltage where no DC component is superimposed. And the charging voltage of the DC capacitor 11 can be suppressed (Step S42).

Thereafter, the voltage source converter 10 is started under zero current control, and the output current Icmp of the voltage source converter 10 is controlled.
u, Icmpv, and Icmpw are set to zero (step S
43). From this state, current command Icmpq * is sent from DC voltage control circuit 22 to current control circuit 21 such that a negative current in the q-axis direction flows from series transformer 6 to series capacitor 11.
, Power is supplied from the AC system to the DC capacitor 11 via the voltage source converter 10, and the DC capacitor 11 can be initially charged (step S4).
4).

As a result, the DC capacitor 11 can be initially charged by using the current control circuit 21 and the DC voltage control circuit 22, and the series compensator can be started without using the initial charging circuit. . Further, when the interconnection switch 36 is turned on, the voltage of the series capacitor 5 applied to the series transformer 6 is a voltage in which no DC component is superimposed. Thus, the rating of the voltage source converter 10 can be reduced.

(Third Embodiment) FIG. 5 shows a startup procedure in the third embodiment. The circuit configuration of the series compensator in the second embodiment is the same as the circuit configuration of the series compensator in the first embodiment shown in FIG.

Assume that the state before the series compensator is started is an initial state, the voltage source converter 10 is stopped, the bypass switch 14 is on (turned on), and the system current Is flows through the bypass switch 14. I do.

At the start of activation, all the self-extinguishing elements 8 of the voltage source converter 10 are turned on (step S51). As a result, the state is the same as that in which the reactor 7 is connected in parallel with the series capacitor 5 via the series transformer 6. Next, the bypass switch 14 is turned off to put the series capacitor 5 into the system (step S52). At this time, since the reactors 7 are connected in parallel, the system current I
s is shunted to the series capacitor 5 and the reactor 7, and the voltage generated in the series capacitor 5 decreases.

Thereafter, the voltage source converter 10 is started under zero current control, and the output current Icmp of the voltage source converter 10 is controlled.
u, Icmpv, and Icmpw are set to zero (step S
53). From this state, a current command Icmpq * is sent from the DC voltage control circuit 22 to the current control circuit 21 so that a negative current in the q-axis direction flows from the series transformer 10 to the series capacitor 5.
, Power is supplied from the AC system to the DC capacitor 11 via the voltage source converter 10, and the DC capacitor 11 can be initially charged (step S5).
4).

Thus, the DC capacitor 11 can be initially charged using the current control circuit 21 and the DC voltage control circuit 22, and the series compensator can be started without using the initial charging circuit. Further, when the bypass switch 14 is turned off and the series capacitor 5 is turned on, the reactor 7 is connected in parallel,
Since the voltage generated in the series capacitor 5 can be reduced, the rating of the series capacitor 5 can be reduced, and the rating of the voltage source converter 10 can be reduced.

(Fourth Embodiment) FIG. 6 shows a fourth embodiment of the present invention.
FIG. 3 is a circuit configuration diagram illustrating a series compensator according to the embodiment. 6, reference numeral 37 denotes an output voltage control circuit, and FIG. 7 is a block diagram showing a detailed configuration example of the output voltage control circuit 37.

In FIG. 7, reference numeral 38 denotes a system current detector 15.
Is a three-phase / two-phase conversion circuit for converting the three-phase voltage signal into a two-phase voltage signal, 39 is a rotation conversion circuit for converting a two-phase signal to a dq signal, and 40 is an output voltage detector 18. Is a three-phase / two-phase conversion circuit for converting the three-phase voltage signal from the three-phase voltage signal to the two-phase voltage signal.
A rotation conversion circuit for converting the signal into a signal; 42, an addition circuit for obtaining a deviation between the output voltage control command value Vcd * and the output signal of the rotation conversion circuit 41; 43, an amplification circuit for performing output control based on the deviation , 44 are addition circuits for adding the output of the rotation conversion circuit 39 to the output of the amplification circuit 43, and output a current control command Icmpd *.

FIG. 8 shows a starting procedure according to the fourth embodiment. It is assumed that the state before the series compensator is started is an initial state, the voltage source converter 10 is stopped, the bypass switch 14 is on (turned on), and the system current Is is flowing through the bypass switch 14.

Upon start-up, the output voltage control circuit 37 and the current control circuit 38 as its lower control circuit are started so that the output voltage Vc becomes zero (step S).
81). Thereafter, the bypass switch 14 is turned off and the series capacitor 5 is turned on (step S82).
At this time, since the voltage source converter 10 operates so that the output voltage Vc becomes zero, the system current I
An operation is performed such that all s flows through the voltage source converter 10.

Next, when a current command Icmpq * is applied from the DC voltage control circuit 22 to the current control circuit 21 so that a negative current in the q-axis direction flows from the series transformer 10 to the series capacitor 5, a voltage-type conversion is performed from the AC system. Power is supplied to the DC capacitor 11 through the
Can be initially charged (step S83).

As a result, the DC capacitor can be initially charged using the current control circuit 21 and the DC voltage control circuit 22, and the series compensator can be started without using the initial charging circuit. Also, since the voltage-source converter 10 operates so that the output voltage Vc becomes zero when the series capacitor 5 is supplied to the system,
As a result, all the system current Is flows through the voltage-source converter 10, and the oscillation of the voltage with respect to the system when the series capacitor 5 is turned on can be reduced.

[0046]

As described above, according to the present invention,
In a series compensator in which a voltage source converter is connected via a series capacitor and a series transformer, power is supplied from an AC system to charge a DC voltage without using an initial charging circuit, and the series compensator is started. be able to.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a series compensator according to a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating a startup procedure according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a series compensator according to a second embodiment of the present invention.

FIG. 4 is a flowchart illustrating a startup procedure according to the second embodiment of the present invention.

FIG. 5 is a flowchart illustrating a startup procedure according to a third embodiment of the present invention.

FIG. 6 is a circuit diagram showing a series compensator according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram showing a detailed configuration example of an output voltage control circuit of the series compensator shown in FIG. 6;

FIG. 8 is a flowchart illustrating a startup procedure according to the fourth embodiment of the present invention.

FIG. 9 is a circuit diagram showing a conventional series compensator.

FIG. 10 is a block diagram showing a detailed configuration example of a current control circuit of the series compensator shown in FIG. 9;

FIG. 11 is a block diagram showing a detailed configuration example of a DC voltage control circuit of the series compensator shown in FIG. 9;

FIG. 12 is a voltage-current vector diagram of the series compensator.

FIG. 13 is a flowchart showing a startup procedure of a conventional series compensation device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transmission side AC voltage Vs 2 ... Receiving side AC voltage Vo 3 ... Transmission line 4 ... Line reactance X of transmission line 5 ... Series capacitor C 6 ... Series transformer Tr 7 ... Reactor L 8 ... Self-extinguishing element 9 ... Diode 10 ... Voltage source converter 11 ... DC capacitor 12 ... Initial charging circuit 13 ... Reverse current blocking diode 14 ... Bypass switch 15 ... System current detector 16 ... Phase detector 17 ... Output current detector 18 ... Output voltage detector 19 ... DC voltage detector 20 ... PWM control circuit 21 ... Current control circuit 22 ... DC voltage control circuit 23 ... Line-to-phase conversion circuit 24 ... 3-phase / 2-phase conversion circuit 25 ... Rotation conversion circuit 26 ... 3-phase / 2-phase Conversion circuit 27 ... Rotation conversion circuit 28 ... Addition circuit 29 ... Amplification circuit 30 ... Addition circuit 31 ... Rotation conversion circuit 32 ... 2-phase / 3-phase conversion circuit 33 ... Addition circuit 34 ... Amplification Path 35 Multiplication circuit 36 Interconnection switch 37 Output voltage control circuit 38 Three-phase / two-phase conversion circuit 39 Rotation conversion circuit 40 Three-phase / two-phase conversion circuit 41 Rotation conversion circuit 42 Addition circuit 43 Amplifier circuit 44 ... Addition circuit

Continued on front page F term (reference) 5G066 DA04 DA07 FA01 FB01 FB13 FC11 5H007 AA07 CA05 CB02 CB05 CC32 DA05 DA06 DB01 DC02 DC05 GA01 5H740 AA00 AA01 BA02 BB05 BB07 BB08 BC06 NN17 NN18

Claims (4)

[Claims] 1. A series capacitor connected in series to an AC system, a voltage source converter using a self-extinguishing element, a DC capacitor connected to a DC part of the voltage source converter, and the voltage source converter A series transformer and a reactor for connecting a transformer and the series capacitor, a bypass switch of the series capacitor, a current control circuit for controlling an output current of the voltage source converter, and a DC voltage control for controlling a DC voltage. And a series compensator comprising: a circuit, after opening the bypass switch, receiving active power from the AC system by the current control circuit and the DC voltage control circuit, initial charging of DC voltage and output current control. And starting the series compensator. 2. A series capacitor connected in series to an AC system, a voltage source converter using a self-extinguishing element, a DC capacitor connected to a DC part of the voltage source converter, and the voltage source converter. A series transformer and a reactor for connecting a transformer and the series capacitor, a bypass switch of the series capacitor, an interconnection switch installed between the series transformer and the series capacitor, In a series compensator including a current control circuit that controls an output current and a DC voltage control circuit that controls a DC voltage, after opening the bypass switch, turning on the interconnection switch after a predetermined time has passed, The current control circuit and the DC voltage control circuit receive active power from the AC system and perform initial charging of DC voltage and output current control. The starting method of the series compensating device. 3. A series capacitor connected in series to an AC system, a voltage source converter using a self-extinguishing element, a DC capacitor connected to a DC part of the voltage source converter, and the voltage source converter. A series transformer and a reactor for connecting a transformer and the series capacitor, a bypass switch of the series capacitor, a current control circuit for controlling an output current of the voltage source converter, and a DC voltage control for controlling a DC voltage. A series compensator comprising a circuit, wherein all the self-extinguishing elements of the voltage-source converter are turned on;
After opening the bypass switch, the current control circuit and the DC voltage control circuit receive a supply of active power from the AC system to perform initial charging of DC voltage and output current control. How to start. 4. A series-connected capacitor connected in series to an AC system, a voltage source converter using a self-extinguishing element, a DC capacitor connected to a DC part of the voltage source converter, and the voltage source converter. A series transformer and a reactor for connecting a transformer and the series capacitor, a bypass switch of the series capacitor, a current control circuit for controlling an output current of the voltage source converter, and controlling an output voltage of the series capacitor. An output voltage control circuit for controlling the DC voltage, and a DC voltage control circuit for controlling the DC voltage, wherein the output voltage control circuit controls the voltage of the series capacitor to zero, and after opening the bypass switch, The current control circuit and the DC voltage control circuit receive an active power supply from the AC system, and perform initial charging of DC voltage and output current control. Controlling the series compensator.