JPS5899225A - Reactive power detecting circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a circuit for detecting reactive power of a load using a W source separated by a distance.

TECHNICAL BACKGROUND OF THE INVENTION The present invention provides a circuit that uses a static reactive power compensation system to control self-defense in arc furnaces, etc., where reactive power is irregularly and rapidly reduced. Static reactive power compensation equipment crotch! If the location is far away] and a power factor improvement capacitor is installed on the arc furnace side, the direct current from the capacitor or The purpose of this invention is to obtain a circuit that detects delayed reactive power only in a load without using a voltage input.

When improving the power factor of a load circuit, the most effective method is to install a capacitor near the load. Therefore, for loads with large reactive power such as arc furnaces, the voltage of the distribution line from the power source to the load is In order to compensate for the descent,
It is often installed close to arc furnace equipment.

On the other hand, the static passive power compensator has a power supply amount I! It is generally installed in This is due to the fact that when multiple arc furnaces are connected to the same power supply bus, utilization improves. Fig. 1 shows this, where 10 is a power supply, l is a power supply side power supply bus, C is a fixed type reactive power compensator,
J is power factor improvement capacitor equipment, dream is load arc furnace equipment,! is a distribution line for arc furnace equipment.

In this way, in a system in which the power factor improvement capacitor equipment 3 is installed near the furnace and the static static power compensator 1 is installed on the power supply bus 1llI, the distance between these two equipments is Electrical wire! If a current transformer for the output line of the arc furnace equipment is used in the control input circuit of the static passive power compensator, it will be possible to improve the delayed reactive power and power factor of the arc furnace equipment. The combined value of the forward reactive power of the capacitor equipment J is input.

By the way, the object to be controlled by the static passive power compensator λ is only the delayed reactive power from the arc furnace equipment≠, and the actual control input is the value obtained by subtracting the amount for the capacitor equipment J from the vector-combined input. There is a need.

Conventionally, as a countermeasure against this problem, as shown in Fig. 1, the electric current 11F of the arc furnace equipment is derived through a current transformer n, and the electric current N
There is a method of supplying the power supply bus voltage detected from the ll1 power supply bus 1 via the voltage transformer V to the static non-active power detection control circuit.

Alternatively, by subtracting the current 1° of only the capacitor equipment J as shown in No. JWJ and the combined current 1 to the arc furnace equipment @ reference and the capacitor equipment J, by subtracting the secondary current of the auxiliary flow device J. , a method has been adopted in which the current is replaced only by the Ata reactor.

Problems with the Background Art When these conventional measures are adopted, if the distance from the power source IO to the arc furnace equipment becomes long, three current transformers or J/ secondary circuit wiring will be required in between, and this wiring will also be required. However, there was a drawback that the problem of corrosion resistance had to be considered as a problem.

Purpose of the Invention The present invention has been made to overcome the difficulties of the conventional device.
) is constant and the current flowing through the capacitor is proportional to the applied voltage. It is an object of the present invention to provide a reactive power detection circuit that derives a capacitor current and can calculate the arc furnace current in a cost-effective manner.

Summary of the Invention The present invention provides an instrument transformer for detecting the amount of power supply bus voltage of the power supply in a power supply @ that supplies power to a circuit including a load/arc furnace equipment and a capacitor equipment connected in parallel thereto; This reactive power detection circuit is equipped with a current transformer that derives the current flowing through the circuit, a subtraction mechanism that produces the current iF that flows only through the load, and multipliers 1 and 1g.

however, The monk is the angular frequency of the power source, 00 is the capacitance of the capacitor.

ljx is the distribution WaS impedance from the power source to the load, r is the resistance, and X is the reactance.

Embodiment of the Invention Figure 1 is a block diagram showing the configuration of an embodiment of the present invention.

The impedance r + jX of the distribution line j from electric f110 to the arc equipment reference, the power supply bus voltage V of the power supply 10,
Arc furnace equipment aM and capacitor equipment JK from power supply IC
From the flowing composite electric current fIIE, the terminal voltage v0 of the power factor conditioner J is VO=V″″zx(r+jz)...
・・・・・・・・・・・・(/1 Also, the current i flowing through the capacitor equipment 3 is 1×0oxv0001.0.
．． ．． 9101.1. (Formula) The current i flowing through the arc furnace equipment and the capacitor current = 11+.

;Work IF" .

Each of these variables is the feed bus voltage 1 composite current, and all of them are values that can be easily obtained in the one-member side feed circuit.

Therefore, a static reactive power compensator! In the case of a small power supply/('l), it is possible to calculate and derive the arc furnace current r without using the arc furnace current transformer n.

Since (Equation 3) is the value in the main circuit, it is converted to the current transformer J3 secondary circuit and the potential transformer l secondary circuit Oo,
By using constant values Oo', r', and jx' of r and jx, it is possible to perform analog addition and subtraction within the control circuit.

1, -1-(ωXOO'X(delirium-1x(r"+jx)
))...In the song (French style) Part 3-, a composite current i is obtained by the current transformer 33, and this composite current Z is led to the impedance setter≠/ to obtain 1x(r'+jx'), which is This is the first multiplier. By subtracting this value from the voltage obtained by the voltage transformer IK, the capacitor terminal voltage is determined. Obtain the voltage v-1 (r'+jx'). The capacitor current iF can be obtained by calculating the indensine speed of the third multiplier for this voltage and subtracting this value from the composite current i.

By using the present invention, it is no longer necessary to run one control cable from the arc furnace equipment to the snow installation site. If it is possible to reduce erroneous signals in the input circuit to the equipment, and if the distance between the arc furnace equipment and the static static power compensator is considerable, the problem of induction along the way will be solved, and the current It is expected that the burden on the current transformer will be reduced and the control performance of static non-active power control devices will be improved.

In addition, certain harmonics generated by the arc equipment flow into the power factor improvement conditioner equipment, but since no current transformer is installed near the arc furnace equipment, the current waveform to be detected is Improved Favorable for control.

[Brief explanation of the drawing]

Fig. 1 is a route diagram of a general arc furnace equipment having a static passive power compensator; Fig. 1 is a block diagram for detecting the input to the conventional static passive power compensator from the arc furnace equipment;
Figure 3 is a block diagram for detecting the input to the conventional static reactive power compensation snow system from the distribution line from the power supply to the arc furnace equipment and the capacitor equipment, and Figure 3 is a block diagram showing the configuration of one embodiment of the present invention. It is a diagram. 10...Power source, C...Power supply side power supply bus, C...Static passive power compensator, J...Capacitor equipment for power factor improvement, Reference...Arc furnace equipment! ... Distribution line for arc furnace equipment, 1 ... Instrument transformer, u, J/, jj
...Current transformer, Co...Reactive power detection/control circuit of static type passive power compensator, J Co...Auxiliary current transformer for subtraction,
ai... A first multiplier for the distribution line impedance and current that has set the distribution line impedance, phrase... A first multiplier for co/density/pedance and voltage. Applicant's agent Kiyoshi Inomata 1 M V-1zl Figure 3 and J Fusuma 4

Claims (1)

[Claims] 1. In power measurement for supplying power to a circuit that includes a load and a capacitor connected in parallel to the load, an instrument transformer that detects the power supply bus voltage amount of the power supply and a power supply that connects the circuit to the circuit. A current transformer is installed to derive the flowing current, and the current flowing only through the load is 1, the angular frequency of the power source is ω, the capacitance of the capacitor is 00, and the impedance of the wire from the power source to the load is resistance. r and reactance XK, 6r+, 1x. Iy=I((klXOOX(V-1x(!"+j3C
)))) A reactive power detection circuit characterized in that the circuit is configured to perform the following calculations. The current derived from the electrician is the distribution line impedance r + 3
given to the first multiplier to be multiplied by x. The voltage obtained by subtracting the output of the seventh multiplier from the detected voltage of the voltage quantity is input to the first multiplier where it is multiplied by the impedance/beadance of the capacitor -0ot-, and the voltage obtained by subtracting the output of the seventh multiplier from the detected voltage of the voltage quantity is inputted to the first multiplier, which is multiplied by the i/beadance of the capacitor. 2. The reactive power detection circuit according to claim 1, which is obtained by subtracting the output of the multiplier No. 2.