JPS6263322A - Reactive power compensator - Google Patents

Abstract

PURPOSE:To make the impedance of parallel circuits sufficiently large and to reduce the power loss of a load which produces phase-lagged power at the time of idling, by causing a reactor capable of saturation at an unsaturated state to make parallel resonance together with a phase-advancing capacitor which is connected in parallel with the reactor. CONSTITUTION:A capacity-fixed phase advancing capacitor 11 is connected in parallel with the reactor 9 capable of saturation. The capacity of the capacitor 11 is fixed to such a value that the capacitor 11 can have the same size of reactance as the reactance of the reactor 9 when it is unsaturated, namely, the reactor 9 capable for saturation at the unsaturated state and capacitor 11 can make parallel resonance. Since the DC excitation of the reactor 9 is controlled to a weaker level and the absolute value of the impedance of the reactor 9 is selected in such a way that the absolute value can become equal to that of the capacitor 11 which is connected in parallel with the reactor 9 when the impedance of the reactor 9 becomes higher, a parallel resonating condition is obtained. In other words, the composite impedance of the reactor 9 and phase-advancing capacitor 11 at this time can infinitely be made higher when the pure resistance quantities of both the apparatuses are ignored.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a reactive power compensator installed in an AC power distribution system, and more particularly to a reactive power compensator for reducing power loss that occurs during operation.

[Technical background of the invention and its problems]

One of the problems related to the quality of AC power distribution systems is the problem of voltage fluctuations. Generally, in an AC power distribution system, the impedance on the power supply side is reactive, and most of the loads generate lagging reactive power, so voltage fluctuations in the form of voltage drops usually occur. One measure to be taken when this voltage fluctuation value exceeds a permissible value is to perform reactive power compensation, and various compensation methods are used depending on the target equipment. Among these conventional systems, there is a reactive power compensator of a system that combines a phase leading reactive power generator and a variable capacity lagging reactive power generator connected in parallel thereto. FIG. 4 shows a typical example of a system including the above-described conventional reactive power compensator and a load that generates delayed phase reactive power. In the figure, a phase advance capacitor 1 (which may also serve as a harmonic filter) is a phase advance reactive power generator, and flows a constant phase advance current. Furthermore, by controlling the AC reactor 2 connected in parallel with the AC reactor 2 by a sirisk switch 4 connected thereto, the slow phase current flowing through the AC reactor 2 can be continuously changed. In other words, a variable capacitance R slow phase reactive power generation device is formed. Here, by controlling the thyristor switch 4 by the control device 6, the slow phase current flowing through the AC reactor 2 is adjusted to be equal to the phase leading current flowing through the phase advancing capacitor +J1, so that the current phases of both are mutually equal to each other. Since they differ by 180 degrees, the combined current will be zero. That is, the amount of reactive power compensation for the power source is zero.

Further, the cyrisk switch 4 is controlled by the control device @6,
If the current flowing through the AC reactor 2 is completely reduced to zero, only a phase advance current corresponding to the capacity of the phase advance capacitor 1 will flow through the power supply.

That is, for the power supply, the amount of phase-advanced reactive power compensation becomes maximum. Furthermore, if the thyrisk switch 4 is controlled at any point between the two control points mentioned above, the phase-advanced reactive power compensation a for the power supply can also be arbitrarily selected. That is, the phase-advanced reactive power compensation group can perform arbitrary phase-advanced reactive power compensation from zero to the capacity of the phase-advanced capacitor 1, which is the maximum phase-advanced power compensation a. In Figure 4, if there is no reactive power compensator, if phase reactive power lags the load 7, the source impedance will be 8.
A voltage drop proportional to the product of the delayed phase reactive power generated by the load 7 and the delayed phase reactive power generated by the load 7 occurs.

The reactive power compensator is intended to prevent the above-mentioned voltage drop, and is designed to cause the sum of reactive power flowing to the power supply to become zero by flowing leading-phase reactive power commensurate with the lagging-phase reactive power generated from the load 7. to prevent voltage drop.

In this way, since the reactive power compensator compensates for reactive power by flowing leading phase reactive power commensurate with the delayed phase reactive power generated by the load 7, when there is no delayed phase reactive power generated by the load 7, ( (When the load is at rest) Naturally, it is desirable that the phase-advanced reactive power generated by the reactive power compensator is also zero.

Let's consider the operation at this time. Phase-progressing condenser I)
Since a constant phase-advanced reactive current commensurate with its capacity flows through the AC reactor 2, the thyristor switch 4 is controlled by the control device 6 so that the slow-phase reactive current flowing through the AC reactor 2 is equal to the current of the phase-advanced capacitor 1. However, the vector-composed current is zero.

In this way, in the case of the reactive power compensator shown in FIG. 4, when the load 7 that generates the lagging phase power is at rest, the lagging phase current commensurate with the phase advancing capacitor 1 and the capacitor capacity is This means that a current must always flow through each of the reactors 2.

On the other hand, if we consider the power loss due to the operation of these reactive power compensators, as long as the power supply voltage is constant, the power loss due to the operation of the phase advance capacitor 1 is constant; The smaller the load 7 that is the target of reactive power compensation, the larger the current needs to be, so the smaller the load 7, the greater the power loss generated by the reactive power compensator. Therefore, load 7
The reactive power compensator has the unreasonable problem of generating the most power loss when the system is at rest, and at the same time,
This goes against the way we think about energy conservation in recent years.

In order to reduce the power loss generated by the reactive power compensator to zero when the load is stopped, the only way to do so is to disconnect the main equipment that makes up the reactive power compensator using a circuit breaker, which cannot be applied due to its switching frequency and safety restrictions. It was difficult. One solution to this problem was proposed in Patent Application No. 115524 of 1982. As shown in FIG. 5, this reactive power compensator has a saturable reactor 9 connected in series to a leading reactive power generator 2 and a lagging reactive power generator 1 which are connected in parallel to each other. , which aims to reduce power loss that occurs during operation. When lagging reactive power is generated from the load 7, the reactive power compensator generates leading reactive power.
The control device 6 controls the si-risk switch 4 to throttle the current flowing through the AC reactor 2 to a target value so that the leading phase reactive power generated by the reactive power compensator and the lagging phase reactive power generated by the load 7 become equal. Make it. In this way, the total sum of reactive power flowing through the power supply is brought to zero, thereby preventing a voltage drop due to the power supply impedance 8. In this respect, the operation is the same as that of the non-voltage compensator shown in FIG. At this time, let us consider the operation of the saturable reactor 9 that constitutes a part of the reactive power compensator. That is, the saturable reactor 9 is brought into a completely saturated state by increasing the DC excitation by the control device 10 thereof. In other words, when the reactive power compensator performs phase advance compensation, the saturable reactor 9 becomes saturated (because it is saturated, the impedance is very small) and does not interfere with phase advance compensation. It is controlled as follows.

On the other hand, when the load 7 is stopped and the delayed reactive power generated thereby becomes zero, the advanced reactive power generated by the reactive power compensator must also be reduced to zero, so the IT/J control device 6 controls the thyristor switch. 4 can be controlled to increase the current flowing through the AC reactor 2, thereby reducing the phase-advanced reactive power generated by the reactive power compensator to zero. However, the maximum operating power loss occurs from each component, and an effective current corresponding to the total power loss of all components flows through the saturable reactor 9. Therefore, when such a state occurs, the DC excitation of the saturable reactor 9 is immediately weakened by its control device 10 to significantly increase the impedance of the saturable reactor 9 in order to significantly reduce this power loss. It is. By doing this, most of the power supply voltage applied to the reactive power compensator is shared by the saturable reactor 9, and at the same time, the above-mentioned active current (corresponding to power loss) hardly flows through the reactive power compensator. .

That is, the power loss from the reactive power compensator during load suspension can be reduced to almost zero.

The current capacity of the AC winding of the saturable reactor 9 must be commensurate with the maximum compensation capacity of the reactive power compensator, but the self-capacity as a saturable reactor must be the capacity commensurate with the power loss of the reactive power compensator. That's a good thing,
For this reason, the normal power loss of the saturable reactor itself can be reduced. This is because the saturable reactor 9 is used in a non-saturated region when the phase advance power compensation amount of the reactive power compensator becomes zero and only the active current corresponding to the power loss is allowed to flow. This is because all that is required is the ability to move from a completely saturated state to an unsaturated state.

However, the above device had the following drawbacks.

That is, as a characteristic necessary for the saturable reactor 9, the ratio of the impedance value when saturated to the impedance value when unsaturated (the impedance value when DC excitation is zero) must be very large. This is because when the reactive power compensator is not compensated, that is, when the load 7 is at rest, the current values flowing through the phase advance condenser 1 and the AC reactor 2 are the same, but the currents have a phase difference of 180' or a value close to this. The current generated is very small.

In other words, when the phase advance capacitor 1 and AC reactor 2 in this state are collectively viewed, they are in parallel resonance or a state close to parallel resonance, and have high impedance. In this state, the saturable reactor 9 has to have a higher impedance than the impedance described above so that most of the voltage is applied to both ends of the saturable reactor. On the other hand, when the reactive power compensator is not compensated, as mentioned earlier, the saturable reactor 9 must be completely saturated and its impedance must be small enough not to interfere with reactive power compensation. . However, in view of the manufacturing technology of the saturable reactor 9, there is a limit to how high the impedance ratio can be at saturation, and the above-mentioned effect aimed at saving energy could not be fully exhibited.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and it is possible to generate electric power from a reactive power compensator at the same time as the load 7 that generates delayed phase power is stopped, without being affected by the characteristics of the saturable reactor 9. It is an object of the present invention to provide a reactive power compensator that can immediately reduce loss.

[Summary of the invention]

The present invention is achieved by additionally connecting a phase advancing capacitor in parallel to the saturable reactor 9 of the device shown in FIG. The saturable reactor and the additional phase advance capacitor when not saturated resonate in parallel.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention. The same reference numerals as in FIG. 5 do not indicate similar members. 11 is a phase advance capacitor. Here, the portion RP surrounded by the dashed-dotted line in FIG. 1 is the equipment configuration of the reactive power compensator of the present invention.

Now, the reactive power compensator of the present invention having the above-mentioned equipment configuration is almost the same as that explained in FIG. It's different.

The capacitance of the phase advancing capacitor 11 is set to a value such that it has the same reactance as the reactance of the saturable reactor 9 when it is not saturated, that is, the saturable reactor 9 and the capacitor 11 when they are not saturated resonate in parallel. It is a rule.

As mentioned above, in the apparatus of FIG.
Because it is difficult to set the impedance ratio between saturated and unsaturated values to a necessary and sufficient value, it has been difficult to obtain a sufficient energy saving effect.

-6 In the case of FIG. 1 of the present invention, the DC excitation of the saturable reactor 9 is weakened, and at the same time the impedance of the saturable reactor 9 becomes high, the absolute value of the impedance at this time is Since it is selected to be equal to the absolute value of the impedance of the phase capacitor 11, a parallel resonance state occurs. That is, the combined impedance of the saturable reactor 9 and the phase advance capacitor 11 at this time can be increased to infinity if the pure resistance valves of both devices are ignored. By taking advantage of this remarkable feature, even if it is difficult to obtain a sufficiently high impedance ratio of the saturable reactor in the case of FIG. It can be raised sufficiently. That is, when the load 7 is at rest, when the impedance of the saturable reactor 9 of the present invention is increased, the impedance becomes even higher due to parallel resonance with the phase advance capacitor 11, and most of the power supply voltage is transferred to the saturable reactor 9 and the phase advance capacitor 11. It can be concentrated on both ends of 11, that is,
Almost no voltage is applied across the phase advancing capacitor 1 and the AC reactor 2, and the power loss generated from both can be extremely reduced.

Note that the AC reactor 2 in FIG. 1 can be replaced with the high impedance transformer 3 shown in FIG. 2, and the combination of the AC reactor 2 in FIG. It is possible to replace each with a saturation reactor 5.

〔Effect of the invention〕

As described above, according to the present invention, since the saturable reactor 9 in the unsaturated state resonates in parallel with the phase advance capacitor connected in parallel to it, the impedance of the parallel circuit can be made sufficiently large, and R It is possible to reduce power loss when a load that generates phase power is at rest.

[Brief explanation of the drawing]

1 to 3 are block diagrams showing embodiments of the present invention, and FIGS. 4 and 56 are block diagrams of conventional reactive power compensators. 1... Phase advance capacitor, 2... AC reactor, 3
...High impedance transformer, 4...Zyristor switch, 5...Saturable reactor, 6...Control device, 7...Load, 8...Power source impedance, 9...
...Saturable reactor, 10...Control device, 11...
- Phase advance capacitor. Applicant's agent Mr. Sato Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] a phase-leading reactive power generator; a variable capacity type lagging reactive power generator connected in parallel to the phase-leading reactive power generator;
A saturable reactor is connected in series to these leading-phase reactive power generators and lagging-phase reactive power generators, and is connected in parallel to this saturable reactor and has a reactance of the same magnitude as the unsaturated reactance of the saturable reactor. A reactive power compensator having a capacitor.