JP2006014445A - Distribution line voltage fluctuation compensator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a distribution line voltage fluctuation compensator in which a power quality compensator for compensating effective power and reactive power can perform voltage fluctuation compensation stably regardless of fluctuation state of a load being connected with a distribution line. <P>SOLUTION: A transformer 4 with taps is disposed closer to the AC system 2 side than the connecting position of a power quality compensating means 9 of a distribution line 1 and arranged such that the effective power and reactive power of a load 3 are detected by a load power detector 7. A tap position adjuster 8 determines the voltage drop up to the load end from the effective power and reactive power of the load 3 and then adjusts the tap position of the transformer 4 with taps to compensate for that voltage drop. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a distribution line voltage fluctuation compensation device that compensates for voltage fluctuations in a distribution line that supplies power of an AC system to a load.

  With the progress of electric power liberalization, it is considered that power is often supplied to the load of distribution lines by distributed power sources such as wind power generation and solar power generation. When power is supplied from a distributed power source, fluctuations in the distribution line voltage due to instantaneous power outages and load fluctuations tend to increase.

  Conventionally, it is known to compensate for voltage fluctuations in a distribution line by combining a reactive power compensator and a tapped transformer. This is described, for example, in Patent Document 1 below. However, in order to supply power to the load in the event of a large voltage drop such as an instantaneous power failure, it is necessary to perform active power compensation in addition to reactive power compensation.

  In order to solve this problem, a power quality compensation device that performs active power compensation and reactive power compensation has been proposed. The power quality compensator is an energy storage device that connects a smoothing capacitor and a large-capacity power storage capacitor in parallel to the DC side of a self-excited converter that converts alternating current to direct current. In order to suppress voltage fluctuation and increase the operating efficiency of the self-excited converter, control is performed to keep the DC voltage of the smoothing capacitor constant by a chopper connected between the smoothing capacitor and the power storage capacitor. The power storage capacitor is charged during normal operation of the AC system in preparation for an instantaneous power failure. Such a power quality compensation device is described in Non-Patent Document 1 below, for example.

JP 2002-281669 A 2003 IEEJ Industrial Electric Power Application Study Material IEA-03-28, June 2003

  A power quality compensator that performs active power compensation and reactive power compensation may cause a situation in which voltage fluctuation compensation cannot be performed by deviating from the voltage fluctuation compensation range if a large voltage fluctuation occurs during voltage fluctuation compensation due to load fluctuation. There is.

  An object of the present invention is to provide a distribution line voltage fluctuation compensation device that can stably perform voltage fluctuation compensation by a power quality compensation device that compensates active power and reactive power regardless of the load fluctuation state of a load connected to the distribution line. It is in.

  A feature of the present invention is that a transformer with a tap is provided on the AC system side from the connection position of the power quality compensation means of the distribution line, and the load power supplied to the load is detected to reduce the voltage drop to the load end. In other words, the tap position of the tapped transformer is adjusted to compensate for this voltage drop.

  The present invention instantaneously compensates for voltage fluctuations in the distribution line by the power quality compensator, and then compensates for voltage fluctuations compensated by the power quality compensator by the transformer with a tap that operates stepwise in units of minutes. Therefore, the chance of deviating from the voltage fluctuation compensation range of the power quality compensation device due to load fluctuation can be significantly reduced, and voltage fluctuation compensation by the power quality compensation device can be performed stably.

  The distribution line supplies the AC system power to the load. The distribution line is provided with a tapped transformer for controlling the distribution line voltage. The load power supplied to the load is detected by the load power detection means. The tap position adjustment means inputs the load power, calculates the active power and reactive power based on the set power factor of the load, and tap position of the transformer with tap so as to compensate for the voltage drop to the load end due to this active power and reactive power. Adjust. The power quality compensation means is connected to the distribution line on the load side of the transformer with tap, and supplies active power and reactive power to the distribution line so that the distribution line voltage becomes a set voltage.

  The power quality compensation means includes a self-excited converter that converts alternating current into direct current, a smoothing capacitor that smoothes the direct current output of the self-excited converter, a power storage capacitor that is connected in parallel with the smoothing capacitor, a smoothing capacitor, and a power storage capacitor. And a chopper for charging and discharging the power storage capacitor.

  FIG. 1 shows an embodiment of the present invention.

  In FIG. 1, a load 3 connected to the distribution line 1 is supplied with power from an AC system (substation) 2. The distribution line 1 is provided with a tapped transformer (SVR) 4 for controlling the distribution line voltage. A transformer 5 and a current transformer 6 are provided on the primary side (AC system side) of the transformer 4 with taps. The distribution line voltage (load voltage) detected by the transformer 5 and the load current detected by the current transformer 6 are input to the load power detector 7.

  The load power detector 7 detects the active power and reactive power of the load fed to the load 3 based on the load voltage and load current, and applies them to the tap position adjuster 8. The tap position adjuster 8 inputs active power and reactive power, and adjusts the tap position of the tapped transformer 4 so as to compensate the voltage drop to the load (load end) 3.

  The power quality compensator (PQC) 9 is connected to the distribution line 1 on the load side of the transformer 4 with a tap, and supplies active power and reactive power to the distribution line 1 so that the distribution line voltage becomes the set voltage Vs. In FIG. 1, the resistance of the distribution line 1 is shown as R and the reactance as X.

  FIG. 2 shows an example configuration of the power quality compensator 9. The AC side of the self-excited converter 10 that converts AC to DC is connected to the distribution line 1 via a conversion transformer 11. A smoothing capacitor 12 for smoothing the DC output and a power storage capacitor 13 are connected in parallel to the DC side of the self-excited converter 10. A chopper 14 that charges and discharges the power storage capacitor 13 is connected between the smoothing capacitor 12 and the power storage capacitor 13.

  The self-excited converter 10 is subjected to pulse width modulation control (PWM control) by the converter controller 15. The converter control device 15 is supplied with the voltage setting value Vs of the distribution line voltage and the reference phase signal θo of the distribution line 1, performs non-interference vector calculation for the effective part and the invalid part, and performs PWM control of the self-excited converter 10. As the self-excited converter 10, a voltage-type self-excited converter is used, and as the power storage capacitor 13, an electric double layer capacitor capable of performing charge and discharge at high speed and high efficiency is used.

  In FIG. 2, the control device for the chopper 14 is not shown.

  Next, the operation will be described.

  The power quality compensator 9 compensates for voltage fluctuations in the distribution line 1 as follows.

The voltage drop ΔVa accompanying the load change of the transmission line and the distribution line is approximately expressed by Expression 1.
ΔVa≈X · ΔQ + R · ΔP (Formula 1)
ΔP, ΔQ: Changes in active power and reactive power of the load 3 Generally, since X >> R in the transmission line, it can be approximated as ΔVa≈X · ΔQ. However, the distribution line 1 is X≈R, and a voltage drop due to the resistance R of the distribution line 1 cannot be ignored.

  The reactive power compensator compensates for the voltage drop by compensating the reactive power change ΔQ. However, the distribution line 3 has substantially the same resistance R and reactance X, and compensation for only the reactive power change ΔQ cannot compensate for the voltage drop due to the active power change ΔP. This is similar to the fact that even if the reactive power compensator tries to compensate for a voltage drop due to an AC system 2 accident or the like instead of a load change, it cannot be compensated if the voltage drop becomes large. This is because the reactive power compensator compensates only for a voltage drop due to reactive power, and voltage cannot be established without supplying active power to the load 3 for voltage compensation at the time of a system fault or the like.

  Since the power quality compensator 9 performs active power compensation in addition to reactive power compensation, it is possible to compensate for a voltage drop of the distribution line 1 due to a change in active power in addition to a voltage change due to a change in reactive power. In addition, since both the active power and the reactive power can be compensated for the load 3 even in the event of a momentary power failure or a power failure due to an accident in the AC system 2, voltage fluctuation compensation can be performed to supply power to the load 3.

  In this way, when the power quality compensator 9 is performing voltage fluctuation compensation of the distribution line 1, the tapped transformer 4 compensates for voltage fluctuation as follows.

The load power detector 7 is based on the instantaneous AC voltages Eu, Ev, Ew of the distribution line 1 detected by the transformer 5 and the instantaneous AC currents Iu, Iv, Iw detected by the current transformer 6. Q is calculated. The effective power P is obtained by Equation 2.
P = Eu · Iu + Ev · Iv + Ew · Iw (Formula 2)

  The reactive power Q is obtained in the same manner as the active power P by the AC voltage and the AC current delayed by 90 ° in the electrical angles of the AC voltages Eu, Ev, Ew and the AC currents Iu, Iv, Iw of Equation 2.

The active power P and the reactive power Q detected by the load power detector 7 are added to the tap position adjuster 8. The tap position adjuster 8 obtains the voltage drop ΔVb of the distribution line 1 to the terminal of the load 3 using Equation 3 using the input active power P and reactive power Q.
ΔVb = R · P + X · Q (Formula 3)

The tap position adjuster 8 adjusts the tap position of the tapped transformer 4 so as to compensate for the voltage drop ΔVb to the load (load end) 3 due to the active power P and the reactive power Q. The tap position adjustment of the transformer with tap 4 is performed in steps of about 1 to 2 minutes. In this way, the voltage drop ΔVb at the load end 3 is adjusted by adjusting the tap position of the transformer 4 with tap. To compensate. That is, the voltage drop ΔVb obtained by detecting the load power PL flowing through the distribution line 1 is compensated by adjusting the tap position of the transformer 4 with a tap.

  The power quality compensator 9 compensates for the voltage drop that cannot be compensated for by the tapped transformer 4. Therefore, the power quality compensation device 9 can keep the voltage fluctuation compensation output small by compensating for the voltage fluctuation in cooperation with the tapped transformer 4, and can fully compensate even if a large voltage fluctuation occurs. it can. The tap switching operation of the transformer 4 with taps is in units of minutes, and voltage fluctuations with a shorter period are compensated by the power quality compensator 9.

  In addition, the active power of the power quality compensator 9 performs charge / discharge operation on the DC power storage capacitor 13 so as to suppress the active power fluctuation of the load 3, for example, to keep the power flow of the distribution line 1 constant regardless of the load fluctuation. Let it be done.

  In this way, voltage fluctuation compensation of the distribution line is performed, but the voltage variation of the distribution line is instantaneously compensated by the power quality compensator, and then a transformer with a tap that operates stepwise in units of minutes is compensated for the power quality compensation. Since the voltage fluctuation that has been compensated by the device is compensated, the chance of deviating from the voltage fluctuation compensation range of the power quality compensator due to the load fluctuation can be significantly reduced, and voltage fluctuation compensation by the power quality compensator can be performed stably. it can.

  This will be described with reference to FIG. The power quality compensator (PQC) 9 compensates for voltage fluctuation and voltage drop by compensating for changes in the active power and reactive power of the distribution line 1. On the other hand, the transformer with tap (SVR) 4 adjusts the tap position by detecting voltage fluctuation or voltage drop of the distribution line 1. Both operate so as to keep the voltage at the load end 3 at the set voltage.

  The response time of the PQC 9 is in ms units, and the SVR 4 is accompanied by switching operation of the circuit breaker, and therefore is in units of minutes. Therefore, when controlling the voltage at the load end 3, if the slow voltage fluctuation of the minute unit or more is compensated by the SVR 4 and the relatively fast fluctuation of the ms unit is compensated by the PQC 9, the gentle fluctuation and the high speed fluctuation only by the PQC 9, Larger variations can be compensated than both.

  FIG. 3A shows voltage fluctuation due to load fluctuation, and after time t2 when the voltage fluctuation is large, the voltage fluctuation compensation range of the PQC 9 cannot be compensated. FIG. 3B detects a gradual voltage fluctuation in the load fluctuation of FIG. 3A, and adjusts the tap position of the SVR 4 at time t1. FIG. 3C shows a case where the tap position control of the SVR 4 is performed, and the fast fluctuation of the response that cannot be compensated is compensated by the PQC 9. As is apparent from FIG. 3C, voltage compensation can be performed without exceeding the voltage fluctuation compensation range of the PQC 9 by performing control in cooperation with the SVR 4.

It is a block diagram which shows one Example of this invention. It is a block diagram which shows an example of an electric power quality compensation apparatus. It is a wave form diagram for demonstrating this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Distribution line, 2 ... AC system, 3 ... Load, 4 ... Transformer with tap, 5 ... Transformer, 6 ... Current transformer, 7 ... Load power detector, 8 ... Tap position adjuster, 9 ... Power quality Compensator, 10 ... Self-excited converter, 11 ... Transformer for conversion, 12 ... Smoothing capacitor, 13 ... Power storage capacitor, 14 ... Chopper, 15 ... Converter control device.

Claims (3)

  A distribution line that feeds power of an AC system to a load, a transformer with a tap provided in the distribution line, load power detection means that detects load power fed to the load, and the load power is input and the A tap position adjusting means for obtaining a voltage drop to the load end and adjusting the tap position of the tap transformer so as to compensate for the voltage drop, and connected to the distribution line on the load side of the transformer with the tap. A distribution line voltage fluctuation compensation device comprising: power quality compensation means for supplying active power and reactive power to the distribution line so that the distribution line voltage becomes a set voltage.   A distribution line that feeds power of an AC system to a load; a transformer with a tap that is provided in the distribution line and controls a distribution line voltage; a load power detection unit that detects active power and reactive power of the load; and the load Tap position for inputting the active power and reactive power of the load detected by the power detection means and adjusting the tap position of the tap transformer so as to compensate for the voltage drop to the load end due to the active power and reactive power Adjustment means, and power quality compensation means connected to the distribution line on the load side from the transformer with tap and supplying active power and reactive power to the distribution line so that the distribution line voltage becomes a set voltage. A distribution line voltage fluctuation compensation device comprising: The power quality compensation means according to any one of claims 1 and 2, wherein the power quality compensating means includes a self-excited converter that converts alternating current into direct current, a smoothing capacitor that smoothes a direct current output of the self-excited converter, and the smoothing capacitor. A distribution line voltage fluctuation compensating apparatus comprising: a power storage capacitor connected in parallel; and a chopper connected between the smoothing capacitor and the power storage capacitor to charge and discharge the power storage capacitor.

Images