CN201528205U - Low-voltage intelligent reactive power compensation device - Google Patents

Abstract

The utility model discloses a low-voltage intelligent reactive power compensation device which comprises a singlechip, a current-voltage detection circuit, a current-voltage mutual inductor, a combination switch and a detection driving circuit thereof, and a circuit breaker, wherein the output end of the current-voltage mutual inductor is connected with the current-voltage detection circuit; the output end of the current-voltage detection circuit is connected with the singlechipe, and used for conveying detected current signals and voltage signals of a system triple-phase line to the singlechip; the output end of the circuit breaker is linked to a capacitor bank and a reactor by the combination switch; the detection driving circuit of the combination switch is connected between the combination switch and the singlechip; and the low-voltage intelligent reactive power compensation device is also provided with a man-machine interface and a communication interface, and inputs and sets system parameters by the man-machine interface. The low-voltage intelligent reactive power compensation device can realize the intelligent control of low-voltage reactive compensation, the non-inrush current and non-electrical arc switch of the reactive capacitor bank, and the comprehensive and reasonable optimization of perception power and interoperability power, and has flexible and convenient use and high reactive compensation efficiency.

Description

Low-voltage intelligent reactive power compensation device

technical field

The utility model relates to a low-voltage intelligent reactive power compensation device.

Background technique

In the AC circuit, there are two kinds of electric power supplied by the power supply to the load; one is active power and the other is reactive power. Active power is the electrical power required to maintain the normal operation of electrical equipment, and it is the electrical power that converts electrical energy into other forms of energy (mechanical energy, light energy, thermal energy). Under normal circumstances, electrical equipment not only needs to obtain active power from the power supply, but also needs to obtain reactive power from the power supply. If the reactive power in the power grid is in short supply, the electrical equipment will not have enough reactive power to establish a normal electromagnetic field, and these electrical equipment will not be able to work under rated conditions, and the terminal voltage of the electrical equipment will drop, thereby affecting Normal operation of electrical equipment. Low-voltage distribution network reactive power compensation method The main method to improve power factor is to use low-voltage reactive power compensation technology. There are two main methods we usually use: random compensation and follower compensation. Random compensation is to connect the low-voltage capacitor bank and the motor in parallel, and switch them simultaneously with the motor through the control and protection devices. The random compensation is suitable for compensating the reactive power consumption of the motor, mainly to supplement the excitation reactive power. This method can better limit the reactive power load of the power consumption unit. Follower compensation refers to the compensation method that connects the low-voltage capacitor to the secondary side of the distribution transformer through the low-voltage fuse to compensate the no-load reactive power of the distribution transformer. The reactive load of the distribution transformer at light load or no-load is mainly the no-load excitation reactive power of the transformer, and the no-load reactive power of the distribution transformer is the main part of the reactive load of the power unit. For the distribution transformer with light load, this Partial losses account for a large proportion of power supply, which leads to an increase in the unit price of electricity. Tracking compensation refers to the compensation method that uses reactive power compensation switching devices as control and protection devices, and compensates low-voltage capacitor banks on the 0.4kv busbar of large users. However, the above two compensation methods are not flexible enough to intelligently configure the compensation capacitor bank.

Utility model content

The technical solution to be solved by the utility model is to provide a low-voltage intelligent reactive power compensation device for the above-mentioned deficiencies in the prior art.

In order to solve the above technical problems, the technical solution adopted by the utility model is: a low-voltage intelligent reactive power compensation device, including a single-chip microcomputer, a current and voltage detection circuit, a current and voltage transformer, a composite switch and its detection drive circuit and a circuit breaker; The output end of the transformer is connected to the current and voltage detection circuit, and the output end of the current and voltage detection circuit is connected to the single-chip microcomputer to transmit the detected current signal and voltage signal of the three-phase line of the system to the single-chip microcomputer; the output end of the circuit breaker is connected through a composite switch To the capacitor bank, the detection driving circuit of the composite switch is connected between the composite switch and the single-chip microcomputer.

As a further improved technical solution of the utility model, it also includes a man-machine interface, a memory and a communication interface connected with the single-chip microcomputer respectively; the man-machine interface displays the system parameters output by the single-chip microcomputer and sets the system parameters to the single-chip microcomputer at the same time, and the set system parameters are simultaneously stored in the in memory. The communication interface is used to connect multiple low-voltage intelligent reactive power optimization devices together.

As a further improved technical solution of the utility model, the device is also provided with a temperature sensor, the temperature sensor is placed in the capacitor bank, and the output of the temperature sensor is connected to a single-chip microcomputer.

As a further improved technical solution of the present invention, the current and voltage detection circuit includes an analog switch, an amplifying circuit and a shaping circuit. The analog switch has two outputs, one is connected to the amplifying circuit and then connected to the single-chip microcomputer, and the other is connected to the single-chip microcomputer through the shaping circuit. .

As a further improved technical solution of the utility model, the output end of the circuit breaker is also connected to a reactor.

The utility model adopts a single-chip microcomputer as a controller, detects the current and voltage of the three-phase line of the system through the current-voltage transformer and the current-voltage detection circuit, and accurately calculates the reactive power factor through the single-chip microcomputer, and at the same time, the single-chip microcomputer controls the composite switch to realize zero-crossing switching; in addition, The utility model is also provided with a man-machine interface and a communication interface, through which system parameters can be input and set. The utility model realizes intelligent control of low-voltage reactive power compensation, no inrush current and no arc switching, comprehensive and reasonable optimization of inductive power and capacitive power, flexible and convenient use, and high reactive power compensation efficiency.

Description of drawings

Fig. 1 is a schematic diagram of the system structure of the present utility model.

Fig. 2 is the sine wave-square wave shaping circuit diagram of the utility model.

Fig. 3 is the enlarged circuit diagram of the utility model.

Fig. 4 is a schematic diagram of the connection between the single-chip microcomputer of the present invention, the sine wave-square wave shaping circuit and the amplifier circuit.

Fig. 5 is a schematic diagram of multiple low-voltage intelligent reactive power compensation devices connected through communication interfaces.

Detailed ways

The specific implementation of the utility model will be further described below in conjunction with the accompanying drawings.

Referring to Fig. 1, Fig. 2, Fig. 3 and Fig. 4, a low-voltage intelligent reactive power compensation device includes a single-chip microcomputer, a current and voltage transformer, a current and voltage detection circuit, a composite switch J1, a composite switch J2, a detection drive circuit for the composite switch, Circuit breaker, temperature sensor, human-machine interface, memory and communication interface; when the low-voltage intelligent reactive power compensation device is working, first connect the circuit breaker to the three-phase line of the system, and two of the three output terminals of the circuit breaker are respectively connected to The composite switch is connected to the capacitor bank, and the third circuit is directly connected to the capacitor bank. The two composite switches J1 and J2 are connected to the single-chip microcomputer through the detection drive circuit. The single-chip microcomputer adopts the single-chip microcomputer model NEC1213; On the three-phase line, the output end of the current and voltage transformer is connected to the current and voltage detection circuit, and the output end of the current and voltage detection circuit is connected to the single-chip microcomputer to transmit the detected current signal and voltage signal of the three-phase line of the system to the controller; The machine interface, memory and communication interface are respectively connected with the single chip microcomputer.

Among them, the current and voltage transformer and the current and voltage detection circuit are existing technologies. The current and voltage detection circuit includes an analog switch, an absolute value amplification circuit and a shaping circuit. The current and voltage transformer is installed on the three-phase line of the system. The current and voltage of the three-phase line are converted into a sine wave signal of the same proportion. The sine wave signal is divided into two channels after passing through the analog switch, and one is connected to the absolute value amplifier circuit. The absolute value amplifier circuit amplifies the signal and sends it to A The /D terminal is used to calculate the magnitude of the current and voltage, and the other one passes through the sine wave-square wave shaping circuit, and is connected to the interrupt and timer port of the microcontroller to calculate the phase difference between the current and voltage, and then calculate the power factor. Man-machine interface, memory and communication interface also all are prior art, present embodiment selects respectively a digital display with keyboard, EEPROM memory and RS485 communication interface from prior art, and digital display is connected with single-chip microcomputer by its driver chip , used to display the system parameters output by the single-chip microcomputer. The keyboard on the digital display can input system parameters to the single-chip microcomputer. The input system parameters are stored in the EEPROM memory at the same time. When the system power is large, a low-voltage intelligent reactive power compensation device cannot reach To achieve the compensation effect, see Figure 5. At this time, multiple low-voltage intelligent reactive power compensation devices can be connected through the RS485 communication interface to realize the joint work of multiple devices. At this time, only one device is required to measure the power factor and send out control signal; placed in the capacitor bank as the temperature sensor of the prior art, the output of the temperature sensor is directly connected to the A/D port of the single-chip microcomputer, when the temperature is too high, directly cut off the capacitor bank, thereby protecting and prolonging the service life of the capacitor bank; two Composite switches J1 and J2 and their drive circuits are also prior art. They are composed of magnetic protection relays with contacts, high-power thyristors and their detection drive circuits. The detection drive circuit of the composite switch detects the difference between the grid voltage and the capacitor bank. When the two voltages are equal, the thyristor is put into the thyristor to reduce the impact of the thyristor. During normal operation, the magnetic latching relay is used to work. Arc switching function.

When the power transmitted on the line is not equal to the natural power, the voltage at each point along the line will deviate from the rated value, sometimes even a large deviation. At this time, a shunt reactor is used to compensate the inductive reactive power, that is, a parallel reactance The reactor is connected in parallel to the three-phase line of the system through a compound switch, and the single-chip microcomputer outputs a control signal to the compound switch to control the switching of the reactor. The above-mentioned reactor can be a magnetically controlled reactor; this can reduce the rise of the line voltage, Make the reactive power in the line balance as much as possible on the spot when the load is light, prevent the unreasonable flow of reactive power and reduce the power loss on the line at the same time.

This embodiment uses the instantaneous reactive power theory and Fourier algorithm to accurately calculate the parameters of the grid system in the case of relatively high harmonics and complete switching of the capacitor bank through the single-chip microcomputer to control the compound switch to realize reactive power compensation. According to the actual load conditions, system parameters such as: CT ratio, switching delay time, voltage upper and lower limits, capacitor protection temperature, and target power factor can be set through the keyboard, and all parameters are stored in the external EEROM, even if the power is off. It will be lost, and it will run automatically when it is powered on. In addition, there is a deviation in the 5V reference voltage of the system, which can be fine-tuned through the keyboard to achieve more accurate measurement.

Claims (5)

1. A low-voltage intelligent reactive power compensation device is characterized in that the affiliated device includes: a single-chip microcomputer, a current and voltage detection circuit, a current and voltage transformer, a composite switch and a detection drive circuit and a circuit breaker; the output terminal of the current and voltage transformer is connected to the current Voltage detection circuit, the output end of the current and voltage detection circuit is connected to the single-chip microcomputer to transmit the detected current signal and voltage signal of the three-phase line of the system to the single-chip microcomputer; the output end of the circuit breaker is connected to the capacitor bank through the composite switch, and the composite switch The detection driving circuit is connected between the composite switch and the single chip microcomputer. 2. The low-voltage intelligent reactive power compensation device according to claim 1, characterized in that: it also includes a man-machine interface, a memory and a communication interface connected with the single-chip microcomputer respectively; the man-machine interface displays the system parameters output by the single-chip microcomputer and sets the system parameters for The single-chip microcomputer, the set system parameters are stored in the memory at the same time; the communication interface connects multiple low-voltage intelligent reactive power optimization devices together. 3. The low-voltage intelligent reactive power compensation device according to claim 1, characterized in that: the device is also provided with a temperature sensor, the temperature sensor is placed in the capacitor bank, and the output of the temperature sensor is connected to a single-chip microcomputer. 4. The low-voltage intelligent reactive power compensation device according to claim 1, 2 or 3, characterized in that: the current and voltage detection circuit includes an analog switch, an amplifying circuit and a shaping circuit, and the analog switch has two outputs, one of which is connected to the amplifying After the circuit is connected with the single-chip microcomputer, the other way is connected with the single-chip microcomputer through the shaping circuit. 5. The low-voltage intelligent reactive power compensation device according to claim 1, 2 or 3, characterized in that: the output end of the circuit breaker is also connected to a reactor.

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