CN102157945B - Individual compensation type low-voltage intelligent combined reactive power compensator - Google Patents

Abstract

The utility model is a sub-complementary low-voltage intelligent combined reactive power compensator. The CPU unit is connected with a control panel unit; the CPU unit is connected with an external RS485 communication unit; the CPU unit is connected with a temperature sensor unit; the CPU unit is connected with an output Control the connection of the power switch switching unit; the CPU unit is connected with the signal amplification and rectification circuit and collects the grid voltage and current data; the output control power switch switching unit is connected with the power switching module through the terminal, and the power switching module is equipped with a Zero switching IC. The sub-compensation low-voltage intelligent combined reactive power compensator described in the utility model has the advantages of safe switching, small impact current on the power grid, long life, low cost, overvoltage, overcurrent, and overtemperature protection, and is easy to install and operate. Intuitive, the operator only requires ordinary electricians to ensure reliable operation of the equipment.

Description

A split-compensation low-voltage intelligent combined reactive power compensator

technical field

The utility model relates to an intelligent combined power capacitor for low-voltage 0.4KV reactive power compensation, in particular to a sub-compensation low-voltage intelligent combined reactive power compensator.

Background technique

At present, the electricity used by the grid is mainly used for industrial electricity, accounting for about 70%, and most of the industrial electricity is used for inductive loads, such as motors, and some are used for resistive loads, such as electric heating, etc. . The electricity consumption environment is complicated, such as: frequent start and stop of the motor, electric heating adjusts the power according to the required temperature, and many electric heating only use single-phase, that is, AC220V power supply. In this regard, capacitors are usually connected in parallel on the line to supplement the reactive power loss of the line. In the past, capacitors were pre-added in advance, and it was easy to overcompensate during the low power consumption stage, but now they are basically eliminated and not used. At present, the reactive power compensation measures for users are usually to control the switching of multiple groups of power capacitors through the power factor controller at the 0.4KV power distribution panel, so that the power factor can reach about 0.95.

The existing reactive power compensation mechanism of the power distribution panel includes: electric knife switch, fuse, reactive power compensation detection device, capacitor switching relay, power capacitor, etc. If the harmonic elimination function is required, additional harmonic Eliminate the reactance coil. It has the following disadvantages: large switching current, surge current to the line, short service life of the contacts of the capacitor switching relay, complicated wiring, large space occupation, inconvenient maintenance and repair, high cost, many mechanical connection parts, and easy equipment invalidated. However, the existing smart or quasi-smart products on the market have a cumbersome control interface and require high technical requirements for the control personnel. Special personnel are required to track technical guidance, which cannot be popularized in a large area, which greatly limits the promotion of reactive power compensators. use, resulting in energy waste.

Utility model content

Aiming at the defects existing in the prior art, the purpose of this utility model is to provide a sub-complementary low-voltage intelligent combined reactive power compensator, which is safe in switching, has small impact current on the power grid, long life, low cost, and has overvoltage , Over-current, over-temperature protection, easy and intuitive installation and operation, and only ordinary electricians are required for operators to ensure reliable operation of the equipment.

For achieving above object, the technical scheme that the utility model takes is:

A sub-compensation low-voltage intelligent combined reactive power compensator, characterized in that it includes:

A power converter 1 receives AC380v power input, and provides one VCC-5v, one VDD+12v, and two VDD+5v power supplies for CPU unit 5 and the following units and circuits; among them, the main power supply VDD1+5v is supplied to CPU unit 5 In use, VDD1+5V and VCC-5V are provided to the signal amplification and rectification circuit 3 at the same time, and VDD2+12V is supplied to the first, second and third power switching modules 7A, 7B, 7C and each zero-crossing throw in the power switching modules Cut IC10, VDD3+5V is provided to RS485 communication unit 8;

The CPU unit 5 is connected to a control panel unit 4 through a cable, and the control panel unit 4 is used for man-machine dialogue and displays relevant information;

The CPU unit 5 is connected with an RS485 communication unit 8 through a cable;

The CPU unit 5 is connected to the temperature sensing amplifier unit 9 through a cable; the temperature sensing amplifier unit 9 is used to collect the temperature of the capacitor to realize over-temperature protection for the capacitor;

The CPU unit 5 is connected to the signal amplification and rectification circuit 3 through a cable;

The signal amplification and rectification circuit 3 receives the data of the signal acquisition unit 2;

The signal acquisition unit 2 includes three voltage transformers 21 and three current transformers 22; the current transformers 22 detect the currents of the three phases, and the voltage transformers 21 detect the voltages of the three phases;

The CPU unit 5 is connected to the output control power switch switching unit 6 through a cable;

The output control power switch switching unit 6 is connected to the first, second, and third power switching modules 7A, 7B, and 7C through connection terminals, and each power switching module is equipped with a zero-crossing switching IC10;

The first, second, and third power switching modules 7A, 7B, and 7C are connected to three power capacitors CAP1, CAP2, and CAP3 connected in "star shape". The three power capacitors CAP1, CAP2 and CAP3 are low-voltage 0.4KV power capacitors for compensation.

On the basis of the above technical solution, the K1 pin of the first power switching module 7A is connected to the A phase of the three-phase phase line,

The K1 pin of the second power switching module 7B is connected to the B phase of the three-phase phase line,

The K1 pin of the third power switching module 7C is connected to the C phase of the three-phase phase line,

The K2 pin of the first power switching module 7A is connected to the A1 terminal of the three power capacitors connected in "star shape",

The K2 pin of the second power switching module 7B is connected to the B1 terminal of the three power capacitors connected in "star shape",

The K2 pin of the third power switching module 7C is connected to the C1 terminal of the three power capacitors connected in "star shape",

The neutral line N connects the neutral points of the three power capacitors.

On the basis of the above technical solution, the model of the CPU unit 5 is STC12C5620AD.

On the basis of the above-mentioned technical scheme, the lower part of the control panel unit 4 is provided with a setting key, an up key, and a down key, and a main LED display frame is provided in the middle, and several LED indications for displaying the current working state are provided around the main LED display frame. lamp.

On the basis of the above-mentioned technical scheme, the temperature sensing amplifier unit 9 includes a thermistor RT, the thermistor RT is an NTC device, subject to temperature changes, its own resistance value will also decrease, the thermistor RT and the voltage dividing resistor The voltage is divided in series and input to the CPU unit 5. After the internal analog/digital conversion of the CPU unit 5, it is compared with the set value of the control panel unit 4 to determine whether it is overheated and whether to cut off the power capacitor.

On the basis of the above technical scheme, the model of the current transformer 22 is CT05-1, and the current transformer 22 converts the signal current of 0-5A generated by the power distribution three-phase input current of the primary current transformer into the signal current of the CPU unit 5. The current signal that can be accepted is measured by the internal analog/digital conversion of the CPU unit 5 to measure the grid current signal; and the CPU unit 5 is electrically isolated from the external power system;

The model of the voltage transformer 21 is PT01-4. The voltage transformer 21 converts the distribution voltage 220V into a voltage signal acceptable to the CPU unit 5, and electrically isolates the CPU unit 5 from the external power system. After the analog/digital conversion, compare it with the set value of the control panel unit 4 to detect whether it is overvoltage or undervoltage, and cut off the power capacitor when it is overvoltage. Reliable operation of power capacitors will not be damaged;

At the same time, the three-phase voltage signal is compared with the three-phase current signal, and the reactive power is calculated according to the difference in phase angle. When the reactive power exceeds the set value of the control panel unit 4, a power capacitor is used for reactive power compensation. Improve the power supply efficiency of power lines.

On the basis of the above-mentioned technical scheme, the output control power switch switching unit 6 is controlled by the CPU unit 5, by controlling the S2 and S4 pins of the first, second, and third power switching modules 7A, 7B, and 7C. Level, close or disconnect each power switching module;

The S1 and S3 pins of the power switching module are connected to the power supply VDD2+12V,

The S1 and S2 pins are connected to both ends of the coil of the magnetic latching relay J1 located in the power switching module.

The S3 and S4 pins are connected to the zero-crossing switching IC10 set in the power switching module,

The power switching module is also equipped with anti-parallel thyristors SCR1 and SCR2,

One of the pair of normally open contacts of the magnetic latching relay J1 is connected to the anode A pole of the thyristor SCR1 and the cathode K pole of SCR2, and the other contact is connected to the cathode K pole of the thyristor SCR1 and the anode A pole of SCR2.

The anode A pole of the thyristor SCR1 and the cathode K pole of the SCR2 are connected to the K1 terminal,

The cathode K pole of the thyristor SCR1 and the anode A pole of the SCR2 are connected to the K2 terminal,

One output control terminal of the zero-crossing switching IC is connected to the gate G of the thyristor SCR1, and the other output control terminal of the zero-crossing switching IC is connected to the gate G of the thyristor SCR2.

On the basis of the above technical solutions, the model of zero-crossing switching IC10 is MOC3083.

The sub-compensation low-voltage intelligent combined reactive power compensator described in the utility model has the advantages of safe switching, small impact current on the power grid, long life, low cost, overvoltage, overcurrent, and overtemperature protection, and is easy to install and operate. Intuitive, the operator only requires ordinary electricians to ensure reliable operation of the equipment.

Description of drawings

The utility model has following drawings:

Fig. 1 Structural block diagram of sub-compensation low-voltage intelligent combined reactive power compensator,

Figure 2 Schematic diagram of the control panel unit,

Figure 3 Schematic diagram of zero-crossing switching IC structure.

Detailed ways

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

The sub-complementary low-voltage intelligent combined reactive power compensator described in the utility model takes the CPU unit 5 as the core, and samples the external voltage signal and current signal through three voltage transformers and three current transformers. Its specific structure is shown in Figure 1, including:

A power converter 1 receives AC380v power input, and provides one VCC-5v, one VDD+12v, and two VDD+5v power supplies for CPU unit 5 and the following units and circuits; among them, the main power supply VDD1+5v is supplied to CPU unit 5 In use, VDD1+5V and VCC-5V are provided to the signal amplification and rectification circuit 3 at the same time, and VDD2+12V is supplied to the first, second and third power switching modules 7A, 7B, 7C and each zero-crossing throw in the power switching modules Cut IC10, VDD3+5V is provided to RS485 communication unit 8;

The CPU unit 5 is connected to a control panel unit 4 through a cable, and the control panel unit 4 is used for man-machine dialogue and displays related information; , one can be set as the master (communication address is set to zero address) through the control panel unit 4, and the others are slaves (communication address is set to non-zero and non-repeated serial numbers); the host is used as the master control device to collect and calculate power distribution information And according to the calculation result compared with the control target, the capacitor switching command is issued to the slave machine, and the capacitor switching of the slave machine is controlled in a cyclic switching mode to realize small-scale connection and avoid individual work of each unit. Cut off together to make the power factor low;

The CPU unit 5 is connected to a RS485 communication unit 8 through a cable; the sub-compensation type low-voltage intelligent combined reactive power compensator described in the utility model can perform 485 communication through the RS485 communication unit 8 to realize the networking control function; RS485 communication Unit 8 can be implemented using prior art;

The CPU unit 5 is connected to the temperature sensing amplifier unit 9 through a cable; the temperature sensing amplifier unit 9 is used to collect the temperature of the capacitor to realize over-temperature protection for the capacitor; the temperature sensing amplifier unit 9 can be realized by using existing technologies;

The CPU unit 5 is connected to the signal amplification and rectification circuit 3 through a cable;

The signal amplification and rectification circuit 3 receives the data of the signal acquisition unit 2;

The signal acquisition unit 2 includes three voltage transformers 21 and three current transformers 22; the current transformers 22 detect the currents of the three phases, and the voltage transformers 21 detect the voltages of the three phases;

The CPU unit 5 is connected to the output control power switch switching unit 6 through a cable;

The output control power switch switching unit 6 is connected to the first, second, and third power switching modules 7A, 7B, and 7C through connection terminals, and each power switching module is equipped with a zero-crossing switching IC10;

The first, second, and third power switching modules 7A, 7B, and 7C are connected to three power capacitors CAP1, CAP2, and CAP3 connected in "star shape". The three power capacitors CAP1, CAP2 and CAP3 are low-voltage 0.4KV power capacitors for compensation.

On the basis of the above technical solution, the model of the CPU unit 5 is STC12C5620AD. The CPU unit 5 is the control core, and the CPU unit 5 adopts the STC12C5620AD single-chip microcomputer of Hongjing Technology. This single-chip microcomputer can work in 1T mode, which is 8 to 12 times faster than the ordinary 51 series single-chip microcomputer. It integrates 8 channels of 10-bit ADC and other peripheral devices. , to meet the product measurement control requirements.

On the basis of the above technical solution, the K1 pin of the first power switching module 7A is connected to the A phase of the three-phase phase line,

The K1 pin of the second power switching module 7B is connected to the B phase of the three-phase phase line,

The K1 pin of the third power switching module 7C is connected to the C phase of the three-phase phase line,

The K2 pin of the first power switching module 7A is connected to the A1 terminal of the three power capacitors connected in "star shape",

The K2 pin of the second power switching module 7B is connected to the B1 terminal of the three power capacitors connected in "star shape",

The K2 pin of the third power switching module 7C is connected to the C1 terminal of the three power capacitors connected in "star shape",

The neutral line N connects the neutral points of the three power capacitors. The "star" connection of the three power capacitors is a known technology and can be realized with existing technology.

On the basis of the above-mentioned technical scheme, as shown in Figure 2, the lower part of the control panel unit 4 is provided with a setting key, an up key, and a down key; LED indicator for current working status.

The operating process of the control panel unit 4 is as follows:

After power-on and reset, the main LED display box displays the company's pinyin abbreviation, which is on for 1 second, and then the sub-compensation low-voltage intelligent combined reactive power compensator enters the automatic operation state, and the automatic LED indicator light is on.

After entering the automatic operation state, the main LED display box will display the values of the following parameters in sequence and the corresponding LED indicators will be on: capacitor compensation reactive capacity (capacity LED indicator is on), power factor lower limit (lower limit LED indicator is on), switching capacitor delay time (delay LED indicator is on), current transformer ratio (transformation ratio LED indicator is on), capacitor overvoltage protection value (overvoltage LED indicator is on), capacitor overtemperature protection temperature value (over-temperature LED indicator is on), this The communication address of the machine (the address LED indicator light is on), each parameter display stays for 1 second, and the LED indicator light goes out after the parameter display is completed. After the above parameters are displayed, the frequency LED indicator light is on, and the main LED display box displays the grid frequency. Then the sub-compensation low-voltage intelligent combined reactive power compensator enters the automatic control state.

After entering the automatic control state, when an overvoltage occurs, the main LED display box will display the overvoltage voltage value, and the overvoltage LED indicator light will be on at the same time. It is forbidden to re-input the capacitor before the value is below 10VAC; when over-temperature occurs, the main LED display box will display the over-temperature temperature value, and the over-temperature LED indicator will light up at the same time, cut off the capacitor that has been put in, and when the temperature of the capacitor drops below the over-temperature protection value It is forbidden to reconnect the capacitor before 5°C.

When the sub-complementary low-voltage intelligent combined reactive power compensator is in the automatic operation state (the automatic LED indicator light is on), press the set button, and the main LED display box will display the frequency, three-phase voltage, three-phase current, and power factor in sequence. The corresponding frequency indicator, voltage indicator and corresponding three-phase (A phase, B phase, C phase LED indicator), current indicator and corresponding three-phase (A phase, B phase, C phase LED indicator indicator light), power factor indicator light and corresponding three phases (phase A, phase B, phase C LED indicators) are on.

When the sub-compensation type low-voltage intelligent combined reactive power compensator is in the automatic operation state (the automatic LED indicator light is on), press the SET key and the UP key at the same time, or press the UP key and hold it and then press the SET key, the sub-compensation Type low-voltage intelligent combined reactive power compensator enters the setting state, and then press the setting button to set the capacitor compensation reactive capacity, power factor lower limit, capacitor switching delay, current transformer ratio, capacitor overvoltage protection value, capacitor overvoltage Switch between the temperature protection temperature value and the communication address of the machine, and the corresponding LED indicator lights up at the same time. Press the up key to increase the parameter value of the current setting parameter, and press the down key to decrease the parameter value of the current setting parameter. Parameter values are saved automatically. Among them, after setting the communication address of the machine, it is necessary to press the setting key again to return to the automatic operation state.

When the sub-compensation low-voltage intelligent combined reactive power compensator is in the automatic operation state (the automatic LED indicator light is on), press the SET button and the down button at the same time, or press the down button first and hold it, and then press the SET button, The sub-compensation low-voltage intelligent combined reactive power compensator enters the manual state (manual LED indicator is on), press the up key to put in the capacitor, the LED indicators Ca, Cb, and Cc are on, press the down key to cut off the capacitor, and the capacitor LED indicator Ca , Cb, Cc are off, press the set key to return to the automatic operation state.

When the sub-compensation low-voltage intelligent combined reactive power compensator is in the automatic operation state (the automatic LED indicator light is on), press the up key and the down key at the same time, or press the down key first and then press the up key, the sub-complement The type low-voltage intelligent combined reactive power compensator enters the debugging state (the debugging LED indicator is on), press the up key and the capacitor LED indicators Ca, Cb, and Cc are on, but the capacitor does not work; press the down key for the capacitor LED indicators Ca, Cb , Cc off, but the capacitor does not act, press the set button to return to the automatic operation state. The debugging state is mainly used to test whether the buttons and display components of the display circuit board are normal.

The intuitive and humanized control panel adopted by the above-mentioned control panel unit 4 has the following advantages: the display content is intuitive, the display content of the main LED display frame and the status indicator LED etc. However, it misleads the operator and causes wrong operation. For example, the LED screen cannot distinguish between "T" and "J". The requirements for the operator are very low, as long as ordinary electricians can operate, and the corresponding detailed instructions are not necessarily required.

On the basis of the above-mentioned technical solution, the temperature sensing amplifier unit 9 includes a thermistor RT, which is an NTC (negative temperature coefficient) device, and its own resistance value will also decrease when the temperature changes. RT is connected in series with the voltage divider resistor to divide the voltage and then input to CPU unit 5. After the internal analog/digital conversion of CPU unit 5, it is compared with the set value of control panel unit 4 to judge whether it is overheated, whether to cut off the power capacitor, and at the same time, it can be controlled Query the current temperature value on the panel unit 4.

On the basis of the above technical scheme, the model of the current transformer 22 is CT05-1, and the current transformer 22 converts the signal current of 0-5A generated by the power distribution three-phase input current of the primary current transformer into the signal current of the CPU unit 5. The current signal that can be accepted is measured by the internal analog/digital conversion of the CPU unit 5 to measure the grid current signal; and the CPU unit 5 is electrically isolated from the external power system;

The model of the voltage transformer 21 is PT01-4. The voltage transformer 21 converts the distribution voltage 220V into a voltage signal acceptable to the CPU unit 5, and electrically isolates the CPU unit 5 from the external power system. After the analog/digital conversion, compare it with the set value of the control panel unit 4 to detect whether it is overvoltage or undervoltage, and cut off the power capacitor when it is overvoltage. Reliable operation of power capacitors will not be damaged;

At the same time, the three-phase voltage signal is compared with the three-phase current signal, and the reactive power is calculated according to the difference in phase angle. When the reactive power exceeds the set value of the control panel unit 4, a power capacitor is used for reactive power compensation. Improve the power supply efficiency of power lines;

The sub-complementary low-voltage intelligent combined reactive power compensator described in the utility model needs three current transformers and three voltage transformers, the current transformer 22 is used to detect the current of the three-phase phase line, and the voltage transformer 21 It is used to detect the voltage of the three phases, and the current power factor and reactive power can be obtained after CPU operation. If the current power factor is lower than the set value, it is inductive, and the lagging LED indicator is on and the reactive power of this phase is greater than the reactive power of the capacitor. When the set value is compensated, the phase is connected to the corresponding phase power capacitor to compensate and improve the power factor. By measuring the phase angle difference, when the grid is capacitive, the leading LED indicator light is on and the phase compensation power capacitor is cut off. In the utility model, the three-phase power capacitors are connected in a "star shape" to compensate each phase respectively, three current transformers 22 and three voltage transformers 21, after the signal is sampled, it is calculated by the CPU unit 5, and then with the control panel Comparing the set value of unit 4, it is decided to switch on or off. For the inductive load and resistive load on the same line, more fine compensation can be realized.

For example, the current of low voltage A is 100A, the voltage is 0.4kV, the active power is 8KW, and the power factor is increased to above 0.96, then the apparent power is:

S=UaIa=220×50=11kVA (1)

Reactive power:

$\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; S</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; 11</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; 8</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 7.55</span>}\mathrm{<span\; class="notranslate">\; kVAR</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Original power factor:

cosΦ=P/S=0.72 (3)

Compensation capacitance:

$\begin{array}{c}{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; [</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ]</span>\\ <span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 5.377</span>}\mathrm{<span\; class="notranslate">\; kVAR</span>}\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

According to the calculation, it is more appropriate to compensate the sub-compensation capacitance of 5.377KVar accordingly. The intelligent sub-compensation capacitor selects 5KVar phase-splitting compensation capacitor, and puts A-phase 5KVar phase-splitting compensation capacitor according to the calculation result (at this time, the capacitance LED indicator Ca lights up), which can achieve better reactive power compensation.

On the basis of the above-mentioned technical scheme, the output control power switch switching unit 6 is controlled by the CPU unit 5, by controlling the S2 and S4 pins of the first, second, and third power switching modules 7A, 7B, and 7C. Level, close or disconnect each power switching module;

The S1 and S3 pins of the power switching module are connected to the power supply VDD2+12V,

The S1 and S2 pins are connected to both ends of the coil of the magnetic latching relay J1 located in the power switching module.

The S3 and S4 pins are connected to the zero-crossing switching IC10 set in the power switching module,

The power switching module is also equipped with anti-parallel thyristors SCR1 and SCR2,

One of the pair of normally open contacts of the magnetic latching relay J1 is connected to the anode A pole of the thyristor SCR1 and the cathode K pole of SCR2, and the other contact is connected to the cathode K pole of the thyristor SCR1 and the anode A pole of SCR2.

The anode A pole of the thyristor SCR1 and the cathode K pole of the SCR2 are connected to the K1 terminal,

The cathode K pole of the thyristor SCR1 and the anode A pole of the SCR2 are connected to the K2 terminal,

One output control terminal of the zero-crossing switching IC is connected to the gate G of the thyristor SCR1, and the other output control terminal of the zero-crossing switching IC is connected to the gate G of the thyristor SCR2.

The S1, S2, S3, and S4 pins are all controlled by the CPU unit 5 through the output control power switch switching unit 6 . When the CPU detects that the power factor drops below the setting requirement, the power capacitor is switched on, and when the power factor reaches the setting requirement or is overcompensated, the power capacitor is cut off under the control of the CPU.

The working process of the output control power switch switching unit 6 and the power switching module is as follows taking A-phase compensation as an example:

1. When the CPU unit 5 is internally calculated and compared with the set value of the control panel unit 4, when it is necessary to put in a phase A power capacitor:

A. There are three power switching modules 7A, 7B and 7C in the specific embodiment shown in FIG. 1 ;

B. The S3 pin of the power switching module is connected to the power supply VDD2+12V, and the S3 and S4 pins of the power switching module are connected to the internal zero-crossing switching IC10. When the AC voltage crosses zero, the zero-crossing switching IC conduction,

C. The S1 pin of the power switching module is connected to VDD2+12V, the S1 and S2 pins of the power switching module are connected to both ends of the internal magnetic latching relay coil, and when the positive voltage is obtained, the magnetic latching relay is closed;

D. When the phase A compensation capacitor is input, the CPU unit 5 outputs the control signal through the output control power switch switching unit 6 to drive the S2 of the power switching module 7A to low level, and after 20mS, the CPU unit 5 outputs the control signal Through the output control power switch switching unit 6, the S4 of the power switching module 7A is driven to a low level, and after 50 ms, the S2 of the power switching module 7A is driven to a high level, so that when the power capacitor is input, the reduction Minimize or prevent the impact current on the grid.

The cut-off process is opposite to the above input process. The CPU unit 5 outputs a control signal to control the power switch switching unit 6 to drive S2 of the power switching module 7A to a low level, and the CPU unit 5 outputs a control signal to control the power through the output. The switching unit 6 drives S4 of the power switching module 7A to a high level, and after 50 ms, drives S2 of the power switching module 7A to a high level. The zero-crossing switching IC model is MOC3083. Considering the reliability, two MOC3083 can be used in series as shown in Figure 3. The magnetic latching relay J1 can be realized by using the existing technology.

The thyristors SCR1 and SCR2 are connected in reverse parallel, and then connected in parallel with the normally open contact of the relay J1. The thyristors SCR1 and SCR2 are controlled by the zero-crossing switching IC. When the CPU unit drives the zero-crossing switching IC through the terminals S3 and S4, the thyristor When the power supply voltage crosses zero, it is turned on to minimize the surge current to the power grid. The magnetic latching relay J1 is turned on for a certain period of time later than the zero-crossing switching IC, such as 20mS, which can protect the relay contacts from high current impact and prolong The service life of the relay. After the magnetic latching relay J1 is turned on, the anode and cathode voltages of the thyristors SCR1 and SCR2 are zero. According to the working principle of the thyristors: when the anode and cathode voltages of the thyristors are not enough to maintain conduction, the thyristors are cut off and quit working. At this time, regardless of whether the zero-crossing switching IC is turned on or not, the thyristors are all cut off, so that the thyristors will not heat up and burn out.

The working principle of the utility model is as follows:

Through the current transformer, the strong current is converted into a weak voltage signal proportional to the current, and through the voltage transformer, the high voltage is converted into a weak voltage signal; the converted current signal and voltage signal are sent to the signal amplification and rectification circuit 3, and the The analog signal is converted into a digital signal through the ADC function of the CPU unit 5. The CPU unit 5 calculates the phase difference between the two signals, and then calculates the power factor and reactive power to determine whether to input the compensation capacitor or cut off the power capacitor. The driving circuit drives the thyristor on the power module and the magnetic latching relay composite switching circuit to realize zero-crossing switching, avoid large current impact on the power grid, and prolong the contact life of the magnetic latching relay.

The specific implementation principle is: when the CPU unit 5 detects that the reactive power exceeds the set value, after a delay, the thyristor is first driven, so that the thyristor is turned on when the voltage crosses zero, and the power capacitor is connected to the grid without impact current. After 1-2 waveform cycles, that is, after 10-20ms, the magnetic latching relay is turned on, and the two ends of the thyristor are short-circuited to achieve a smooth transition. It can be known from the working characteristics of the thyristor that when the voltage drop across the thyristor is zero, the thyristor is turned off. The process of cutting off the power module is opposite to the process of switching on. First cut off the magnetic latching relay, and after 1-2 cycles, that is, 10-20ms, then cut off the thyristor when the current crosses zero, which also ensures the life of the magnetic latching contact and eliminates the impact on the grid surge current. Influence.

Claims (8)

1. a minute compensation type low-voltage intelligent combined reactive power compensator, is characterized in that, comprising:

A supply convertor (1), receives the input of AC380v power supply, and a road VCC-5v, a road VDD+12v, two-way VDD+5v power supply are provided; Wherein, main power source VDD1+5v is for CPU element (5), VDD1+5V and VCC-5V offer signal amplification rectification circuit (3) simultaneously, VDD2+12V supplies with each operating passing zero IC(10 in first, second, third power switching module (7A, 7B, 7C) and first, second, third power switching module), VDD3+5V offers RS485 communication unit (8);

CPU element (5) is connected with a control panel unit (4) by cable, and control panel unit (4) are for human-computer dialogue and show relevant information;

CPU element (5) is connected with a RS485 communication unit (8) by cable;

CPU element (5) is connected with temperature sensing amplifier unit (9) by cable; Temperature sensing amplifier unit (9), for gathering capacitor temperature, is realized overheat protector to capacitor;

CPU element (5) is amplified rectification circuit (3) by cable and signal and is connected;

Signal amplifies the data that rectification circuit (3) receives signal gathering unit (2);

Described signal gathering unit (2) comprises three voltage transformers (21) and three current transformers (22); Current transformer (22) detects the electric current of three-phase, and voltage transformer (21) detects the voltage of three-phase;

CPU element (5) is connected with output power ratio control switch on-off unit (6) by cable;

Output power ratio control switch on-off unit (6) is connected with first, second, third power switching module (7A, 7B, 7C) by splicing ear, in described first, second, third power switching module, is equipped with an operating passing zero IC(10);

Three power capacitor CAP1, the CAP2 that first, second, third power switching module (7A, 7B, 7C) is connected with " star-like ", CAP3 connect, three power capacitors that power capacitor CAP1, CAP2, CAP3 are the low pressure 0.4KV for compensating.

2. as claimed in claim 1 minute compensation type low-voltage intelligent combined reactive power compensator, is characterized in that: the K1 pin of the first power switching module (7A) is connected with the A of three-phase phase line,

The K1 pin of the second power switching module (7B) is connected with the B of three-phase phase line,

The K1 pin of the 3rd power switching module (7C) is connected with the C of three-phase phase line,

The A1 terminal of three power capacitors that the K2 pin of the first power switching module (7A) is connected with " star " connects,

The B1 terminal of three power capacitors that the K2 pin of the second power switching module (7B) is connected with " star " connects,

The C1 terminal of three power capacitors that the K2 pin of the 3rd power switching module (7C) is connected with " star " connects,

Neutral line N connects the neutral point of three power capacitors.

3. as claimed in claim 1 minute compensation type low-voltage intelligent combined reactive power compensator, is characterized in that: the model of CPU element (5) is STC12C5620AD.

4. as claimed in claim 1 minute compensation type low-voltage intelligent combined reactive power compensator, it is characterized in that: bottom, control panel unit (4) is provided with setting key, upwarding key, down Arrow, middle part is provided with a main LED display box, is provided with the LED light of some demonstration work at present states around main LED display box.

5. as claimed in claim 1 minute compensation type low-voltage intelligent combined reactive power compensator, it is characterized in that: temperature sensing amplifier unit (9) comprises a thermistor RT, thermistor RT is a NTC device, with temperature, raise, itself resistance also can reduce, thermistor RT connects with divider resistance after dividing potential drop and is input to CPU element (5), after CPU element (5) internal simulation/digital conversion, contrast with control panel unit (4) set point, judge whether excess temperature, whether cut off power capacitor.

6. as claimed in claim 1 minute compensation type low-voltage intelligent combined reactive power compensator, it is characterized in that: the model of current transformer (22) is CT05-1, the signal code of the 0-5A that current transformer (22) produces the distribution three-phase input current by current transformer is transformed into the receptible current signal of CPU element (5), after CPU element (5) internal simulation/digital conversion, measure power network current signal; And CPU element (5) and external power system are carried out to electrical isolation;

The model of voltage transformer (21) is PT01-4, voltage transformer (21) is transformed into the receptible voltage signal of CPU element (5) by distribution voltage 220V, and CPU element (5) and external power system are carried out to electrical isolation, after CPU element (5) internal simulation/digital conversion, contrast with control panel unit (4) set point, detect whether overvoltage, under-voltage, when overvoltage, cut off power capacitor, when under-voltage, forbid dropping into power capacitor, but allow excision power capacitor, thereby guarantee that power capacitor reliability service can not damage;

Meanwhile, three-phase voltage signal and three-phase current signal contrast, according to the gap at phase angle, calculating reactive power size, when this reactive power surpasses control panel unit (4) set point, drops into power capacitor, carry out reactive power compensation, promote power circuit power supplying efficiency.

7. as claimed in claim 1 minute compensation type low-voltage intelligent combined reactive power compensator, it is characterized in that: output power ratio control switch on-off unit (6) is controlled by CPU element (5), by controlling the S2 of first, second, third power switching module (7A, 7B, 7C) and the level of S4 pin, closed or disconnect each power switching module;

The S1 pin of first, second, third power switching module is connected with power vd D2+12V with S3 pin,

S1, S2 pin are connected to the coil two ends of being located at the magnetic latching relay J1 in first, second, third power switching module,

S3, S4 pin are connected to the operating passing zero IC(10 being located in first, second, third power switching module),

In first, second, third power switching module, be also provided with thyristor SCR1 and the SCR2 of reverse parallel connection,

A contact in a pair of normally opened contact of magnetic latching relay J1 connects the anode A utmost point of thyristor SCR1, the negative electrode K utmost point of SCR2, and another contact connects the negative electrode K utmost point of thyristor SCR1, the anode A utmost point of SCR2,

The negative electrode K utmost point of the anode A utmost point of thyristor SCR1, SCR2 is connected to K1 terminal,

The negative electrode K utmost point of thyristor SCR1, the anode A utmost point of SCR2 are connected to K2 terminal,

An output control terminal of operating passing zero IC is connected to the gate pole G utmost point of thyristor SCR1, and another output control terminal of operating passing zero IC is connected to the gate pole G utmost point of thyristor SCR2.

8. as claimed in claim 1 minute compensation type low-voltage intelligent combined reactive power compensator, is characterized in that: operating passing zero IC(10) model is MOC3083.