CN2894027Y - Dynamic capacitance compensation device - Google Patents

Abstract

The utility model discloses a dynamic capacitance compensation device, which includes a compensation circuit composed of a contactor and a power capacitor group, and is characterized in that: the compensation circuit also includes a composite relay circuit, and the compensation circuit is set as a plurality of composite relay compensation branches circuit, and multiple contactor compensation branches, the structure of each compensation branch is: fuse, composite relay or contactor contact, current limiting reactor and delta connection or star connection power capacitor bank are connected in sequence, each The other end of the compensation branch fuse is connected to the busbar in the device. The composite relay is used in the compensation circuit. When the thyristor is turned on, the normally open contact of the relay is also closed. When closed, the contact resistance is very small, and most of the current can pass through the thyristor. The current through the thyristor is almost equal to zero. In this way, during the conduction process, there is no voltage drop and no heat generation on the thyristor, and harmonic waves are eliminated, so that the compensation device can operate reliably.

Description

Dynamic capacitance compensation device

technical field

The utility model relates to a device for compensating reactive power in an AC distribution network, in particular to a capacitance compensation device for a 50HZ, 400V low-voltage distribution network.

Background technique

In order to address the reactive power shortage generated in the process of using electricity, many electrical device manufacturers produce some automatic reactive power compensation devices. These compensation devices are generally composed of three parts: the main circuit, the secondary circuit and the central controller including the single-chip microcomputer system. , and the main circuit is mainly composed of a protection system, a circuit composed of a contactor and a power capacitor. Due to the limitation of the capacitor's ability to withstand inrush current, discharge time and the contactor cannot operate too frequently, this type of product has the following shortcomings:

1. When the compensation capacitor is switched, the current impact is large, and the contactor operates frequently, resulting in a shortened service life.

2. The compensation accuracy is poor, and the compensation follow-up is not strong. When the grid load changes rapidly and fluctuates greatly, it is impossible to perform fast compensation at all.

For this reason, the applicant applied for an invention patent named "Dynamic Capacitance Compensation Device and Its Switching Method" on July 2, 2001, and obtained the patent right on August 18, 2004. The patent number is: 01114333.9 . The compensation problem of the existing low-voltage power distribution network is solved, and the content of the invention is:

"The purpose of this invention is to provide a dynamic capacitance compensation device and its switching method, which should be able to solve the problems of switching device life and switching compensation speed.

The invention includes a main circuit, a secondary circuit and a central controller including a single-chip microcomputer system, wherein the main circuit includes a switch protection system, and a compensation circuit composed of a contactor and a power capacitor, and is characterized in that: the contactor and the power capacitor are composed of A solid-state relay circuit is also added to the compensation circuit, and the compensation circuit is set into several solid-state relay compensation branches and contactor compensation branches. The structure of each compensation branch is: a fuse, a solid-state relay or a contactor normally open contact, limited The flow reactor and the delta capacitor bank are connected in sequence; the other end of each compensation branch fuse is connected to the inner busbar of the device, and the inner busbar is connected to the outer busbar through a switch.

Controlled by the controller and its control system, the measurement feedback system measures the dynamic process of the voltage, current and power factor changes of the distribution network, and reflects the measurement results of reactive power under-compensation or over-compensation to the controller and control system. system, the switching mode of the compensation branch above is:

When the reactive power of the distribution network is under-compensated, the solid-state relay compensation branch is first put into operation, and if the reactive power compensation is still under-compensated, then the contactor compensation branch is put into operation;

When the reactive power of the power distribution network is over-compensated, the solid-state relay compensation branch should be cut first, and if the reactive power compensation is still over-compensated, then the contactor compensation branch should be cut;

The above-mentioned switching compensation is performed until the power factor of the power distribution network enters the range of the set value.

The dynamic capacitance compensation device of this structure combines the advantages of fast action speed of the solid state relay and large contact capacity of the contactor at low cost, and at the same time, it is supplemented by an optimized switching method, so that the compensation process can be completed dynamically, which is comparable to the existing technology. Ratio, high cost performance. Improvements have been made in compensation speed, accuracy and reliability. "

In recent practical applications, the applicant found that, in the above-mentioned dynamic capacitance compensation device, a solid-state relay circuit is used. The solid-state relay is actually composed of bidirectional thyristor or two unidirectional thyristors connected in reverse parallel. It is non-conductive when it is turned off, and it is in a fully conductive state when it is turned on. When a large current passes through the solid-state relay, due to the certain resistance of the multi-layer PN or NP junction of the thyristor, voltage drop, heat generation and bad harmonics will occur, which will seriously burn out components and circuits, and affect the performance of the compensation device. Reliable operation.

Contents of the invention

The purpose of this utility model is to provide a dynamic capacitance compensation device, which should be able to overcome the problems of the above-mentioned solid-state relay, and make the compensation device operate reliably.

The utility model includes a main circuit, a secondary circuit and a central controller, wherein the main circuit includes a switch protection system, and a compensation circuit composed of a contactor and a power capacitor, and is characterized in that: the compensation circuit composed of the contactor and the power capacitor It also includes a composite relay (or composite switch) circuit. The compensation circuit is set into several composite relay compensation branches and contactor compensation branches. The structure of each compensation branch is: fuse, composite relay or contactor normally open Contacts, current-limiting reactors (can be canceled if the contactor has inrush current-limiting function) and delta-connected or star-connected capacitor banks are connected in sequence; the other end of each compensation branch fuse is connected to the power supply of the device.

The compensation circuit of the compensation device with the above structure adopts a composite relay, and the structure of the composite relay is: a normally open contact of a relay is connected to both ends of the bidirectional thyristor or two reversely connected thyristors in parallel; Its working principle is: when it is turned on, the thyristor first crosses zero and conducts, and then the normally open contact of the relay closes. When it is turned off, the normally open contact of the relay opens first, and then the thyristor turns off. The composite relay is used in the compensation circuit. When the thyristor is turned on, the normally open contact of the relay is also closed. When closed, the contact resistance is very small, and most of the current can pass through the thyristor. The current through the thyristor is almost equal to zero. In this way, during the conduction process, there is no voltage drop and no heat generation on the thyristor, and harmonic waves are eliminated, so that the compensation device can operate reliably.

Description of drawings

Fig. 1 is a structural block diagram of the utility model.

As shown in Fig. 2, it is a schematic diagram of the compensation branch circuit of the present invention.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is further described.

As can be seen in Fig. 1, the utility model is composed of a main circuit composed of an overcurrent protector, a composite relay, a contactor and a capacitor bank, a secondary circuit composed of a voltage and current measurement feedback system, and a control circuit composed of a controller. Its working principle is: from the 400V power bus to the overcurrent protector and measurement feedback system of the main circuit, the voltage signal from the power bus and the current signal from the incoming current transformer enter the central control through the measurement feedback system After step-down, filtering, etc., the controller calculates the current power factor value or reactive power shortage based on the feedback voltage and current signals, compares the required power factor value with the reactive power value, and sends out instructions The controller is connected to the main circuit, so that the switching of the capacitor compensation branch is performed according to the preset switching rules of the program, so as to achieve the purpose of ensuring that the power factor or reactive power value is within the set value range.

As shown in Figure 2, it is the schematic diagram of the compensation branch circuit of the utility model. It can be seen in the figure that the composite relay is connected in parallel with a general relay on the structure of the bidirectional thyristor KP or two unidirectional thyristors in reverse parallel. The normally open contact J constitutes. Composite relay is also called composite switch, which can be purchased in the existing market. It is an existing product and technology, such as YBY-30 produced by Shenzhen Youbangyi Electric Technology Co., Ltd.; QFK5F-45 produced by Hangzhou Zhetai Electric Co., Ltd. . The working principle of the composite relay is: when it is turned on, the thyristor KP first crosses zero and turns on, and the normally open contact J of the general relay closes afterward; when it is off, the normally open contact J of the general relay opens first, and then the thyristor KP off. The compensation circuit is composed of multiple composite relay KFJ compensation branches and multiple contactor KM compensation branches. The connection relationship of each compensation branch is: fuse FU, composite relay 1KFJ～MKFJ or contactor normally open contact 1KM～ nKM, delta connection or star connection power capacitor bank C are connected in sequence, where n=1, 2, 3, 4, 5, 6..., M=1, 2, 3, 4, 5, 6 ... is a natural integer, and the other end of each compensation branch fuse FU is connected to the power supply of the device.

In Figure 2, the action sequence of the KFJ compensation branch of the compound relay and the KM compensation branch of the contactor is as follows: when the reactive power of the entire power distribution network is under-compensated, the controller and its system send out a signal of throwing capacitance, and the composite Relay 1KFJ...MKFJ compensation branch, if the amount of reactive power compensation is still insufficient, then input contactor 1KM...nKM compensation branch. When the reactive power of the entire power distribution network is overcompensated, the controller and its system send a signal to cut the capacitance, and first cut off the composite relay 1KFJ...MKFJ compensation branch, if the reactive power compensation is still overcompensated, then cut off the contact Device 1KM...nKM compensation branch. Until the distribution network power factor or reactive value enters the range of the set value.

The device has the advantages of fast compensation speed, high precision, good reliability, easy maintenance, high cost performance, and can completely replace most of the current automatic reactive power compensation devices.

Claims (2)

1, a kind of dynamic capacitance compensation device, it comprises the compensating circuit that contactor (KM) and power capacitor group C constitute, and it is characterized in that:

Described compensating circuit also comprises compound relay (KFJ) circuit, compensating circuit is arranged to several compound relays (KFJ) compensation branch road, form with a plurality of contactors (KM) compensation branch road, structure of each compensation branch road is: ((1KM～nKM), current limiting reactor and corner connection or star connect the power capacitor group and are connected in regular turn for 1KFJ～mKFJ) or contacts of contactor for fuse (FU), compound relay, n=1,2,3,4,5......, the natural integer of m=1,2,3,4,5......; Each other end that compensates branch road fuse (FU) is connected with the device power supply.

2, dynamic capacitance compensation device according to claim 1 is characterized in that:

Described compound relay (compensation branch road of 1KFJ～mKFJ) and contacts of contactor (the controlled device of compensating circuit that the compensation branch road of 1KM～nKM) constitutes and the control of control system thereof, each compensate branch road switching be in proper order:

When the distribution network reactive power is owed the added time, circulation earlier drop into compound relay (1KFJ or～mKFJ) compensation branch road, recirculation drop into contacts of contactor (1KM or～nKM) compensation branch road;

When it's the added time is past the distribution network reactive power, compound relay (the compensation branch road of 1KFJ～mKFJ), recirculation cut-grafting tentaculum contact (the compensation branch road of 1KM～nKM) are cut in circulation earlier.

Above-mentioned switching compensation is till the power factor of distribution network enters in the range of set value.

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