Reactive power compensation circuit

Abstract

The utility model provides a reactive power compensation circuit, and belongs to the technical field of power compensation. The reactive power compensation circuit comprises a power factor detection module, a central control module, a first switch control module, a second switch control module, a first switch, a first capacitor module, a second capacitor module and a third capacitor module, the first end of the first switch is connected with three-phase power, the second end of the first switch is connected with the first end of the first capacitor module, the second end of the first capacitor module is connected with the third end of the first switch through the first capacitor switch module, and the third end of the first switch is connected with the first end of the second capacitor switch module. The second end of the second capacitor switch module is connected with the first end of the third capacitor module through the second capacitor module, and the second end of the third capacitor module is connected with the first end of the first capacitor module through the third capacitor switch module. The problem that a single compensation mode is difficult to meet actual requirements can be solved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of power compensation, and in particular to a reactive power compensation circuit. Background Art

[0002] With the continuous development of power systems, the power factor of the power grid has become one of the important indicators for measuring power quality. A low power factor means that there is a large amount of reactive power in the power grid, which will not only increase the loss of the power grid, but also reduce the utilization rate of equipment, affecting the stability and economy of the power grid. Therefore, reactive power compensation technology came into being, aiming to improve the power factor and power quality by injecting an appropriate amount of reactive power into the power grid.

[0003] Traditional reactive power compensation systems are often based on a single power factor detection, and reactive power compensation is achieved by controlling the switching of compensation capacitors. However, in actual applications, the load of the power grid is often complex and changeable, and there is a problem of three-phase imbalance, which makes it difficult for a single compensation method to meet actual needs. Utility Model Content

[0004] The disclosed embodiment provides a reactive power compensation circuit to solve the problem that a single compensation method is difficult to meet actual needs.

[0005] The embodiment of the present disclosure provides a reactive power compensation circuit, including:

[0006] Power factor detection module, three-phase unbalance detection module, central control module, first switch control module, second switch control module, first switch SW1, first capacitor switch module SK1, second capacitor switch module SK2, third capacitor switch module SK3, first capacitor module CL1, second capacitor module CL2 and third capacitor module CL3;

[0007] The input end of the three-phase unbalance detection module is connected to the three-phase power, and the output end of the three-phase unbalance detection module is connected to the central control module;

[0008] The first switch control module and the second switch control module are both connected to the central control module;

[0009] The first switch control module is used to control the first switch SW1, and the second switch control module is used to control the first capacitor switch module SK1, the second capacitor switch module SK2 and the third capacitor switch module SK3 respectively;

[0010] The first end of the first switch SW1 is connected to the three-phase electricity, the second end of the first switch SW1 is connected to the first end of the first capacitor module CL1, the second end of the first capacitor module CL1 is connected to the third end of the first switch SW1 through the first capacitor switch module SK1, the third end of the first switch SW1 is connected to the first end of the second capacitor switch module SK2, the second end of the second capacitor switch module SK2 is connected to the first end of the third capacitor module CL3 through the second capacitor module CL2, and the second end of the third capacitor module CL3 is connected to the first end of the first capacitor module CL1 through the third capacitor switch module SK3;

[0011] The first capacitor module CL1, the second capacitor module CL2 and the third capacitor module CL3 are each composed of at least two capacitors connected in parallel.

[0012] In an exemplary embodiment of the present disclosure, the three-phase unbalance detection module comprises three branches with the same circuit structure, and any branch comprises: a resistor R1, a resistor R2, a resistor R3, a capacitor C1 and an operational amplifier U1;

[0013] The first end of the resistor R1 is used to connect to the Au phase power, the second end of the resistor R1 is grounded through the resistor R2, the second end of the resistor R1 is connected to the first end of the resistor R3, the second end of the resistor R3 is grounded through the capacitor C1, the second end of the resistor R3 is connected to the in-phase input end of the operational amplifier U1, the inverting input end of the operational amplifier U1 is grounded, and the output end of the operational amplifier U1 is connected to the central control module.

[0014] In an exemplary embodiment of the present disclosure, any branch further includes: an operational amplifier U2;

[0015] The non-inverting input terminal of the operational amplifier U2 is connected to the second end of the resistor R3 , the output terminal of the operational amplifier U2 is connected to the inverting input terminal of the operational amplifier U2 , and the output terminal of the operational amplifier U2 is connected to the non-inverting input terminal of the operational amplifier U1 .

[0016] In an exemplary embodiment of the present disclosure, any branch further includes: a voltage regulator tube D1 and a variable resistor RP1;

[0017] The cathode of the voltage regulator tube D1 is connected to the VCC power supply, the anode of the voltage regulator tube D1 is grounded, the first end of the variable resistor RP1 is connected to the VCC power supply, the second end of the variable resistor RP1 is grounded, and the sliding end of the variable resistor RP1 is connected to the inverting input end of the operational amplifier U1.

[0018] In an exemplary embodiment of the present disclosure, the first switch control module includes: a switch tube Q1, a resistor R6, a transistor Q2 and a relay SW1;

[0019] The control end of the switch tube Q1 is connected to the central control module, the first end of the switch tube Q1 is connected to the VCC power supply, the second end of the switch tube Q1 is grounded through the resistor R6, the second end of the switch tube Q1 is connected to the base of the transistor Q2, the emitter of the transistor Q2 is connected to the VDD power supply, the collector of the transistor Q2 is connected to the first input end of the relay SW1, and the second input end of the relay SW1 is grounded.

[0020] In an exemplary embodiment of the present disclosure, the first switch control module further includes: an optical coupler U3;

[0021] The first input end of the optocoupler U3 is connected to the second end of the switch tube Q1 , the second input end of the optocoupler U3 is grounded, the first output end of the optocoupler U3 is connected to the VDD power supply, and the second output end of the optocoupler U3 is grounded.

[0022] In an exemplary embodiment of the present disclosure, the first switch control module further includes: a resistor R7, a capacitor C4 and a diode D2;

[0023] The first end of the resistor R7 is connected to the second end of the switch tube Q1, the second end of the resistor R7 is connected to the first input end of the optocoupler U3, the second end of the resistor R7 is grounded through the capacitor C4, the anode of the diode D2 is connected to the second end of the resistor R7, and the cathode of the diode D2 is connected to the first end of the resistor R7.

[0024] In an exemplary embodiment of the present disclosure, it further includes: a communication module;

[0025] The central control module is connected to the remote terminal through the communication module.

[0026] The beneficial effects of a reactive power compensation circuit provided by the embodiment of the present disclosure are:

[0027] The disclosed embodiment realizes real-time monitoring of the power factor of the power grid and effective regulation of the three-phase imbalance by integrating a power factor detection module, a three-phase imbalance detection module and an intelligent central control module. Not only can the reactive power compensation amount be automatically adjusted according to the real-time demand of the power grid, but the access of the capacitor module can be accurately controlled by the first switch control module and the second switch control module to achieve the best compensation effect, significantly improve the power factor of the power grid, reduce reactive power loss, and improve the efficiency of electric energy utilization. At the same time, the introduction of the three-phase imbalance detection module enables the circuit to accurately identify and respond to the imbalance problem between the three phases. By intelligently adjusting the access of the capacitor modules of each phase, the three-phase imbalance phenomenon can be effectively alleviated, and the stability and power quality of the power grid can be further enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 is a structural schematic diagram of a reactive power compensation circuit provided by an embodiment of the present disclosure;

[0030] Figure 2 is a circuit diagram of a three-phase unbalance detection module provided in an embodiment of the present disclosure;

[0031] Figure 3 is a circuit diagram of a first switch control module provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0032] In order to enable people in the technical field to better understand the present solution, the technical solution in the embodiment of the present solution will be clearly described below in conjunction with the drawings in the embodiment of the present solution. Obviously, the described embodiment is an embodiment of a part of the present solution, not all of the embodiments. Based on the embodiments in the present solution, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present solution.

[0033] The term "including" and any other variations in the specification and claims of this solution and the above drawings mean "including but not limited to", and is intended to cover non-exclusive inclusions and is not limited to the examples listed in the text. In addition, the terms "first" and "second" are used to distinguish different objects, not to describe a specific order.

[0034] The following is a detailed description of the implementation of the present disclosure in conjunction with the specific drawings:

[0035] Figure 1 A schematic diagram of a reactive power compensation circuit provided by an embodiment of the present disclosure. Figure 1The reactive power compensation circuit includes: a power factor detection module, a three-phase unbalance detection module, a central control module, a first switch control module, a second switch control module, a first switch SW1, a first capacitor switch module SK1, a second capacitor switch module SK2, a third capacitor switch module SK3, a first capacitor module CL1, a second capacitor module CL2 and a third capacitor module CL3; the input end of the three-phase unbalance detection module is connected to the three-phase power, and the output end of the three-phase unbalance detection module is connected to the central control module; the first switch control module and the second switch control module are both connected to the central control module; the first switch control module is used to control the first switch SW1, and the second switch control module is used to control the first capacitor switch module SK1, the second capacitor switch module SK2, and the third capacitor switch module SK3. 2 and the third capacitor switch module SK3; the first end of the first switch SW1 is connected to the three-phase electricity, the second end of the first switch SW1 is connected to the first end of the first capacitor module CL1, the second end of the first capacitor module CL1 is connected to the third end of the first switch SW1 through the first capacitor switch module SK1, the third end of the first switch SW1 is connected to the first end of the second capacitor switch module SK2, the second end of the second capacitor switch module SK2 is connected to the first end of the third capacitor module CL3 through the second capacitor module CL2, and the second end of the third capacitor module CL3 is connected to the first end of the first capacitor module CL1 through the third capacitor switch module SK3; the first capacitor module CL1, the second capacitor module CL2 and the third capacitor module CL3 are all composed of at least two capacitors connected in parallel.

[0036] In this embodiment, the power factor detection module is used to detect the power factor of the power grid, that is, the ratio of active power to apparent power. The power factor reflects the relative size of active power and reactive power in the power grid, and the size of the power factor is used to determine whether the power grid needs reactive power compensation.

[0037] The central control module controls the working states of the first switch control module and the second switch control module according to the output signal of the power factor detection module.

[0038] The first switch control module is used to control the on / off state of the first switch SW1 according to the instruction of the central control module. The second switch control module is used to control the opening and closing of the first capacitive switch module SK1, the second capacitive switch module SK2 and the third capacitive switch module SK3 according to the instruction of the central control module.

[0039] When the power grid is transmitting electricity, the power factor detection module detects the power factor of the power grid in real time to determine whether reactive power compensation is required. The central control module receives the output signal of the power factor detection module and makes a judgment. Based on the judgment result, the central control module decides whether reactive power compensation needs to be started.

[0040] When the grid needs reactive power compensation, the central control module issues a command to close the first switch SW1, and the capacitor modules (CL1, CL2, CL3) are connected to the circuit through the capacitor switch modules (SK1, SK2, SK3) and start to output reactive power to compensate for the reactive power demand in the grid.

[0041] In this embodiment, the capacitor module is composed of multiple capacitors connected in parallel. The central control module can send different control instructions to the second switch control module according to the detected power factor. The second switch control module controls the capacitor switch modules (SK1, SK2, SK3) according to the instructions. The capacitor switch modules (SK1, SK2, SK3) can adjust the number of connected capacitors according to compensation requirements to achieve the best compensation effect.

[0042] In this embodiment, each capacitor switch module is composed of a plurality of switches, and each switch corresponds to a capacitor connected in series. Figure 1 In the embodiment, the switch S1 is connected in series with the capacitor C5, the switch S7 is connected in series with the capacitor C8, and the switch S4 is connected in series with the capacitor C11. In this embodiment, the corresponding switches can be controlled to be closed according to the requirements, so as to connect capacitors with different capacitance values.

[0043] In practical applications, the load of the power grid may not be completely balanced, and there may be differences in the reactive power requirements between the phases. In order to meet the reactive power requirements of different phases, it is necessary to select compensation capacitors of different capacitances according to the specific conditions of each phase and install them on each phase. This ensures that each phase can obtain appropriate reactive power compensation and improves the power factor and power quality of the power grid. For this reason, a three-phase imbalance detection module is added in this embodiment.

[0044] The three-phase unbalance detection module is used to detect the unbalance of the three-phase electricity and output the detection results to the central control module. The central control module controls the working state of the first switch control module and the second switch control module according to the output signals of the power factor detection module and the three-phase unbalance detection module. The access mode of each capacitor module is adjusted according to the unbalance situation to reduce the three-phase unbalance phenomenon.

[0045] It can be concluded from the above that this embodiment realizes real-time monitoring of the power factor of the power grid and effective regulation of the three-phase imbalance by integrating the power factor detection module, the three-phase imbalance detection module and the intelligent central control module. Not only can the reactive compensation amount be automatically adjusted according to the real-time demand of the power grid, but the access of the capacitor module can be accurately controlled by the first switch control module and the second switch control module to achieve the best compensation effect, significantly improve the power factor of the power grid, reduce reactive loss, and improve the efficiency of electric energy utilization. At the same time, the introduction of the three-phase imbalance detection module enables the circuit to accurately identify and respond to the imbalance problem between the three phases. By intelligently adjusting the access of the capacitor modules of each phase, the three-phase imbalance phenomenon can be effectively reduced, and the stability and power quality of the power grid can be further enhanced.

[0046] like Figure 2 As shown, in one embodiment of the present disclosure, the three-phase unbalance detection module includes three branches with the same circuit structure, and any branch includes: resistor R1, resistor R2, resistor R3, capacitor C1 and operational amplifier U1; the first end of resistor R1 is used to connect to Au phase power, the second end of resistor R1 is grounded through resistor R2, the second end of resistor R1 is connected to the first end of resistor R3, the second end of resistor R3 is grounded through capacitor C1, the second end of resistor R3 is connected to the non-inverting input terminal of operational amplifier U1, the inverting input terminal of operational amplifier U1 is grounded, and the output terminal of operational amplifier U1 is connected to the central control module.

[0047] In this embodiment, the three-phase unbalance detection module detects the three-phase electricity respectively through three branches with the same circuit structure, taking the branch for detecting the Au-phase electricity as an example.

[0048] Resistors R1 and R2 form a voltage divider circuit, which is used to reduce the high voltage Au phase electricity to a voltage range suitable for subsequent circuit processing. A voltage divider point is formed between R1 and R2. The voltage at this voltage divider point is proportional to the voltage of the Au phase electricity, but the amplitude is reduced. Resistor R3 and capacitor C1 form a simple RC low-pass filter, which is used to filter out high-frequency noise in the signal after voltage division, so that the op amp U1 can receive a more stable AC signal. The op amp U1 constitutes a comparator, which generates a pulse signal output value to the central control module after comparison. The Bu phase electricity and the Cu phase electricity are similar, both of which are used to output a pulse signal. The central control module can determine whether there is a three-phase imbalance in the power grid based on the phase and pulse width of the three pulse signals.

[0049] like Figure 2 As shown, in one embodiment of the present disclosure, any branch also includes: an operational amplifier U2; the non-inverting input terminal of the operational amplifier U2 is connected to the second end of the resistor R3, the output terminal of the operational amplifier U2 is connected to the inverting input terminal of the operational amplifier U2, and the output terminal of the operational amplifier U2 is connected to the non-inverting input terminal of the operational amplifier U1.

[0050] In this embodiment, the operational amplifier U2 is configured as a voltage follower, and its non-inverting input terminal is connected to the second end of the resistor R3, that is, receiving the signal filtered by R3 and C1. The output terminal of the operational amplifier U2 is directly connected to its inverting input terminal, forming a negative feedback loop. Since the operational amplifier U2 has the characteristics of high input impedance and low output impedance, this negative feedback loop makes the output voltage of the operational amplifier U2 closely follow its input voltage, that is, keeps the output voltage equal to the input voltage, and reduces the influence of the output resistance on the subsequent circuit.

[0051] In this embodiment, the voltage follower plays a role of signal buffering and isolation. It can isolate the filtered signal from the subsequent input end of the operational amplifier U1, preventing the input impedance of the operational amplifier U1 from affecting the filtering circuit, thereby ensuring the stability and accuracy of the filtering effect.

[0052] like Figure 2 As shown, in one embodiment of the present disclosure, any branch also includes: a voltage regulator tube D1 and a variable resistor RP1; the cathode of the voltage regulator tube D1 is connected to the VCC power supply, the anode of the voltage regulator tube D1 is grounded, the first end of the variable resistor RP1 is connected to the VCC power supply, the second end of the variable resistor RP1 is grounded, and the sliding end of the variable resistor RP1 is connected to the inverting input end of the operational amplifier U1.

[0053] In this embodiment, the variable resistor RP1 provides an adjustable reference level for the operational amplifier U1. This reference level can be compared with the signal at the in-phase input terminal of the operational amplifier U1 to determine whether the Au phase voltage is within the normal range or whether there is an imbalance. By adjusting the position of the sliding terminal of RP1, the voltage at the inverting input terminal of the operational amplifier U1 can be changed, thereby adjusting the reference level of the operational amplifier U1.

[0054] like Figure 3 As shown, in one embodiment of the present disclosure, the first switch control module includes: a switch tube Q1, a resistor R6, a transistor Q2 and a relay SW1; the control end of the switch tube Q1 is connected to the central control module, the first end of the switch tube Q1 is connected to the VCC power supply, the second end of the switch tube Q1 is grounded through the resistor R6, the second end of the switch tube Q1 is connected to the base of the transistor Q2, the emitter of the transistor Q2 is connected to the VDD power supply, the collector of the transistor Q2 is connected to the first input end of the relay SW1, and the second input end of the relay SW1 is grounded.

[0055] In this embodiment, when the central control module needs to control the first switch SW1 to be closed, it sends a low-level control signal to the control end of the switch tube Q1. The switch tube Q1 is cut off, the voltage of its second end is 0, the base voltage of the transistor Q2 is 0, the transistor Q2 is a PNP type, and the transistor Q2 is turned on at this time. The conduction of the transistor Q2 provides sufficient driving current for the relay SW1. In this embodiment, the first switch SW1 can be understood as the action contact of the relay SW1. The first switch SW1 is closed, thereby connecting the power grid with the reactive power compensation capacitor module.

[0056] On the contrary, when the central control module needs to disconnect the first switch SW1, a high-level control signal is sent to the control end of the switch tube Q1. The switch tube Q1 is turned on, and the transistor Q2 is also turned off due to the increase in the base voltage. The relay SW1 loses the driving current, the first switch SW1 is disconnected, and the connection between the grid and the reactive power compensation capacitor module is cut off.

[0057] like Figure 3 As shown, in one embodiment of the present disclosure, the first switch control module also includes: an optocoupler U3; the first input end of the optocoupler U3 is connected to the second end of the switch tube Q1, the second input end of the optocoupler U3 is grounded, the first output end of the optocoupler U3 is connected to the VDD power supply, and the second output end of the optocoupler U3 is grounded.

[0058] In this embodiment, the addition of the optical coupler U3 enables electrical isolation between the control circuit of the switch tube Q1 and the drive circuit of the relay SW1. This means that even if a fault or abnormal conditions such as high voltage or high current occur in the control circuit of the switch tube Q1, the drive circuit of the relay SW1 will not be directly affected, thereby improving the safety and reliability of the entire control module.

[0059] After adding the optocoupler U3, the working principle of the first switch control module is:

[0060] When the central control module needs to control the first switch SW1 to be closed, the central control module sends a high-level control signal to the control end of the switch tube Q1. The switch tube Q1 is turned on, the voltage at its second end is high, the optocoupler U3 is turned on, the base voltage of the transistor Q2 is 0, and the transistor Q2 is turned on. The conduction of the transistor Q2 provides sufficient drive current for the relay SW1, and the first switch SW1 is closed, thereby connecting the power grid to the reactive power compensation capacitor module.

[0061] On the contrary, when the central control module needs to disconnect the first switch SW1, a low-level control signal is sent to the control end of the switch tube Q1. The switch tube Q1 is turned off, the optocoupler U3 is also turned off, and the transistor Q2 is also turned off due to the increase in the base voltage. The relay SW1 loses the driving current, the first switch SW1 is disconnected, and the connection between the grid and the reactive power compensation capacitor module is cut off.

[0062] like Figure 3 As shown, in one embodiment of the present disclosure, the first switch control module also includes: a resistor R7, a capacitor C4 and a diode D2; the first end of the resistor R7 is connected to the second end of the switch tube Q1, the second end of the resistor R7 is connected to the first input end of the optocoupler U3, the second end of the resistor R7 is grounded through the capacitor C4, the anode of the diode D2 is connected to the second end of the resistor R7, and the cathode of the diode D2 is connected to the first end of the resistor R7.

[0063] In this embodiment, the resistor R7 and the capacitor C4 form a buffer circuit. When the switch tube Q1 is turned on, the voltage on the resistor R6 charges the capacitor C4 through the resistor R7. When the switch tube Q1 is turned on, the optocoupler U3 is turned off, and the transistor Q2 is also turned off. Therefore, the relay SW1 is not energized. As the voltage on the capacitor C4 increases, the voltage at the input end of the optocoupler U3 gradually increases, and the current at the first output end of the optocoupler U3 gradually decreases. Then the transistor Q2 will also be slowly turned on to avoid the instantaneous high-voltage pulse generated by the VDD power supply at the moment of power-on from burning the coil inside the relay SW1.

[0064] When the switch tube Q1 is turned off, the voltage on the resistor R6 disappears, and the capacitor C4 is discharged through the diode D2, ensuring that the buffer circuit can operate normally when the switch tube Q1 is turned on next time.

[0065] In this embodiment, the buffer circuit composed of resistor R7, capacitor C4 and diode D2 effectively reduces the impact of the VDD power supply on the internal coil of the relay SW1 at the power-on moment. By gradually increasing the input voltage of the optocoupler U3, the transistor Q2 is slowly turned on, thereby avoiding damage to the relay that may be caused by an instantaneous high-voltage pulse. At the same time, when the switch tube Q1 is turned off, the diode D2 is quickly discharged, which ensures the stability and repeatability of the buffer circuit and improves the safety and reliability of the entire switch control module.

[0066] In this embodiment, the first capacitor switch module SK1, the second capacitor switch module SK2 and the third capacitor switch module SK3 are respectively composed of multiple independent switches, and each independent switch should be provided with a switch control module. The circuit structure of the switch control module is the same as the circuit structure of the first switch control module, which will not be repeated here.

[0067] like Figure 1 As shown, in one embodiment of the present disclosure, it also includes: a communication module; the central control module is communicatively connected with the remote terminal via the communication module.

[0068] In this embodiment, the introduction of the communication module enables the central control module to communicate with the remote terminal. The central control module can send the relevant data obtained by the power factor detection module and the three-phase imbalance detection module, such as the value of the power factor, the balance state of the three-phase electricity, etc., to the remote terminal through the communication module.

[0069] In this embodiment, the existence of the communication module realizes remote monitoring and management of the reactive power compensation circuit, thereby improving the intelligence and convenience of the system.

[0070] The above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A reactive power compensation circuit, characterized in that: include: Power factor detection module, three-phase unbalance detection module, central control module, first switch control module, second switch control module, first switch SW1, first capacitor switch module SK1, second capacitor switch module SK2, third capacitor switch module SK3, first capacitor module CL1, second capacitor module CL2 and third capacitor module CL3; The input end of the three-phase unbalance detection module is connected to the three-phase power, and the output end of the three-phase unbalance detection module is connected to the central control module; The first switch control module and the second switch control module are both connected to the central control module; The first switch control module is used to control the first switch SW1, and the second switch control module is used to control the first capacitor switch module SK1, the second capacitor switch module SK2 and the third capacitor switch module SK3 respectively; The first end of the first switch SW1 is connected to the three-phase electricity, the second end of the first switch SW1 is connected to the first end of the first capacitor module CL1, the second end of the first capacitor module CL1 is connected to the third end of the first switch SW1 through the first capacitor switch module SK1, the third end of the first switch SW1 is connected to the first end of the second capacitor switch module SK2, the second end of the second capacitor switch module SK2 is connected to the first end of the third capacitor module CL3 through the second capacitor module CL2, and the second end of the third capacitor module CL3 is connected to the first end of the first capacitor module CL1 through the third capacitor switch module SK3; The first capacitor module CL1, the second capacitor module CL2 and the third capacitor module CL3 are each composed of at least two capacitors connected in parallel.

2. A reactive power compensation circuit as claimed in claim 1, characterized in that: The three-phase unbalance detection module comprises three branches with the same circuit structure, and any branch comprises: a resistor R1, a resistor R2, a resistor R3, a capacitor C1 and an operational amplifier U1; The first end of the resistor R1 is used to connect to the Au phase power, the second end of the resistor R1 is grounded through the resistor R2, the second end of the resistor R1 is connected to the first end of the resistor R3, the second end of the resistor R3 is grounded through the capacitor C1, the second end of the resistor R3 is connected to the in-phase input end of the operational amplifier U1, the inverting input end of the operational amplifier U1 is grounded, and the output end of the operational amplifier U1 is connected to the central control module.

3. A reactive power compensation circuit as claimed in claim 2, characterized in that: Any branch also includes: op amp U2; The non-inverting input terminal of the operational amplifier U2 is connected to the second end of the resistor R3 , the output terminal of the operational amplifier U2 is connected to the inverting input terminal of the operational amplifier U2 , and the output terminal of the operational amplifier U2 is connected to the non-inverting input terminal of the operational amplifier U1 .

4. A reactive power compensation circuit as claimed in claim 2, characterized in that: Any branch also includes: a voltage regulator tube D1 and a variable resistor RP1; The cathode of the voltage regulator tube D1 is connected to the VCC power supply, the anode of the voltage regulator tube D1 is grounded, the first end of the variable resistor RP1 is connected to the VCC power supply, the second end of the variable resistor RP1 is grounded, and the sliding end of the variable resistor RP1 is connected to the inverting input end of the operational amplifier U1.

5. A reactive power compensation circuit as claimed in claim 1, characterized in that: The first switch control module includes: a switch tube Q1, a resistor R6, a transistor Q2 and a relay SW1; The control end of the switch tube Q1 is connected to the central control module, the first end of the switch tube Q1 is connected to the VCC power supply, the second end of the switch tube Q1 is grounded through the resistor R6, the second end of the switch tube Q1 is connected to the base of the transistor Q2, the emitter of the transistor Q2 is connected to the VDD power supply, the collector of the transistor Q2 is connected to the first input end of the relay SW1, and the second input end of the relay SW1 is grounded.

6. A reactive power compensation circuit as claimed in claim 5, characterized in that: The first switch control module further includes: an optical coupler U3; The first input end of the optocoupler U3 is connected to the second end of the switch tube Q1 , the second input end of the optocoupler U3 is grounded, the first output end of the optocoupler U3 is connected to the VDD power supply, and the second output end of the optocoupler U3 is grounded.

7. A reactive power compensation circuit as claimed in claim 6, characterized in that: The first switch control module further includes: a resistor R7, a capacitor C4 and a diode D2; The first end of the resistor R7 is connected to the second end of the switch tube Q1, the second end of the resistor R7 is connected to the first input end of the optocoupler U3, the second end of the resistor R7 is grounded through the capacitor C4, the anode of the diode D2 is connected to the second end of the resistor R7, and the cathode of the diode D2 is connected to the first end of the resistor R7.

8. A reactive power compensation circuit as claimed in claim 1, characterized in that: Also includes: Communication module; The central control module is connected to the remote terminal through the communication module.

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