Control circuit, method and system of unified power quality conditioner

Abstract

The present invention provides a control circuit, method and system of a unified power quality conditioner, wherein the control circuit includes a thyristor module, a conversion module and a control module, wherein the control module is used to stop providing a trigger pulse to the thyristor module through a first control terminal when a system power supply abnormality is detected, stop the conversion module from operating in a current source mode, send a first drive signal to the conversion module through a second control terminal, and output a first conversion voltage through three output terminals of the conversion module to turn off the thyristor module; wherein the first conversion voltage is associated with the current switching cycle number of the power tube under the first drive signal, the preset voltage amplitude change, the current absolute value difference, and the grid voltage on the input side of the load in the current switching cycle. The circuit can gradually turn off the thyristor module in steps, thereby avoiding the problem of too fast current change of the thyristor module and reducing the impact on the grid.

Description

Technical Field

[0001] The present invention relates to the field of circuit technology, and in particular to a control circuit, method and system of a unified power quality conditioner. Background Art

[0002] In the related art, a parallel UPQC usually includes a voltage source converter and a fast switching switch composed of thyristors. The input end of the fast switching switch is connected to the system power supply, and the output end of the fast switching switch is connected to the load. In the grid-connected state, the thyristor continuously receives trigger pulses. When a temporary drop in the system voltage is detected, the trigger pulse of the thyristor is extinguished. Since the thyristor cannot be turned off immediately, it can only be turned off naturally when the current passes through zero. Therefore, it is usually necessary to control the output voltage of the bridge arm port of the voltage source converter to force the thyristor to turn off. However, when the related art forces the thyristor to turn off, the current of the thyristor changes too fast, causing a large impact on the power grid. Summary of the invention

[0003] The object of the present invention is to provide a control circuit, method and system for a unified power quality conditioner to avoid the problem of too fast current change of thyristor modules and reduce the impact on the power grid.

[0004] The present invention provides a control circuit of a unified power quality conditioner, the circuit comprising: a thyristor module, having a first control end, a first input end, a second input end, a third input end, a first output end, a second output end, and a third output end; the first input end of the thyristor module is connected to the A phase of the system power supply, the second input end of the thyristor module is connected to the B phase of the system power supply, the third input end of the thyristor module is connected to the C phase of the system power supply, and the first output end, the second output end, and the third output end of the thyristor module are connected to the load; a conversion module, having a second control end, a first output end, a second output end, and a third output end; the first output end of the conversion module is connected to the first output end of the thyristor module, the second output end of the conversion module is connected to the second output end of the thyristor module, and the third output end of the conversion module is connected to the third output end of the thyristor module; a control module, used to detect the working state of the system power supply, and when the working state indicates that the system power supply is normal, the first control module is used to detect the working state of the system power supply, and ... The control terminal provides a trigger pulse to the thyristor module to supply power to the load through the thyristor module, and controls the conversion module to work in the current source mode; when the working state indicates that the system power supply is abnormal, the trigger pulse is stopped from being provided to the thyristor module through the first control terminal, the conversion module is stopped from working in the current source mode, and a first drive signal is sent to the conversion module through the second control terminal to control the on and off of the power tube in the conversion module, and a first conversion voltage is output through the first output terminal, the second output terminal and the third output terminal of the conversion module to turn off the thyristor module; wherein the first conversion voltage is associated with the current switching cycle number of the power tube under the first drive signal, the preset voltage amplitude change, the current absolute value difference, and the grid voltage on the input side of the load in the current switching cycle; the current absolute value difference is: the difference between the absolute value of the current flowing through the thyristor module sampled in the current switching cycle and the absolute value of the current flowing through the thyristor module sampled in the previous switching cycle.

[0005] Furthermore, the first conversion voltage is calculated by the following formula:

[0006]

[0007] in, represents the first conversion voltage; Indicates the grid voltage on the input side of the load in the current switching cycle; Indicates the change in the preset voltage amplitude; Indicates the current switching cycle number of the power tube under the first driving signal; Indicates the current flowing through the thyristor module; Indicates the absolute value difference of current; is a symbolic function.

[0008] Furthermore, when When ≤0, =1; when >0 o'clock, =-1.

[0009] Further, with The larger it is, the faster the thyristor module turns off.

[0010] Further, the conversion module includes: an energy storage module having a first end and a second end;

[0011] The converter module has a first input end, a second input end, a control end, a first output end, a second output end and a third output end; the first input end of the converter module is connected to the first end of the energy storage module; the second input end of the converter is connected to the second end of the energy storage module;

[0012] The filter module comprises a first input end, a second input end, a third input end, a first output end, a second output end and a third output end; the first input end of the filter module is connected to the first output end of the converter module, the second input end of the filter module is connected to the second output end of the converter module, the third input end of the filter module is connected to the third output end of the converter module, the first output end of the filter module is connected to the first output end of the thyristor module, the second output end of the filter module is connected to the second output end of the thyristor module, and the third output end of the filter module is connected to the third output end of the thyristor module.

[0013] Further, the converter module includes: a first inductor having a first end and a second end, the first end of the first inductor being connected to the first end of the energy storage module; a first power tube having a first end, a second end and a control end, the first end of the first power tube being connected to the second end of the first inductor; the second end of the first power tube being connected to the second end of the energy storage module; the control end of the first power tube being used to receive a first drive signal or a second drive signal output by the control module; wherein the second drive signal is a drive signal sent by the control module to the conversion module when the system power supply is normal;

[0014] A second power tube has a first end, a second end and a control end, the second end of the second power tube is connected to the second end of the first inductor, and the control end of the second power tube is used to receive the first drive signal or the second drive signal output by the control module; a first capacitor has a first end and a second end, the first end of the first capacitor is connected to the first end of the second power tube; the second end of the first capacitor is connected to the second end of the first power tube; a three-phase full-bridge inverter circuit has a first input end, a second input end, a control end, a first output end, a second output end and a third output end, the first input end of the three-phase full-bridge inverter circuit is connected to the first end of the first capacitor; the second input end of the three-phase full-bridge inverter circuit is connected to the second end of the first capacitor; the first output end, the second output end and the third output end of the three-phase full-bridge inverter circuit are respectively used as the first output end, the second output end and the third output end of the converter module.

[0015] Furthermore, the filtering module is an LC filtering circuit.

[0016] Furthermore, the thyristor module includes three thyristors.

[0017] The present invention provides a control method for a unified power quality conditioner, the method comprising: detecting the working state of a system power supply; when the working state indicates that the system power supply is normal, providing a trigger pulse to a thyristor module through a first control terminal, so as to supply power to a load through the thyristor module, and controlling a conversion module to work in a current source mode; when the working state indicates that the system power supply is abnormal, stopping providing a trigger pulse to the thyristor module through the first control terminal, stopping the conversion module from working in a current source mode, sending a first drive signal to the conversion module through a second control terminal, so as to control the on and off of a power tube in the conversion module, and outputting a first conversion voltage through a first output terminal, a second output terminal, and a third output terminal of the conversion module, so as to turn off the thyristor module; wherein the first conversion voltage is associated with the current switching cycle number of the power tube under the first drive signal, a preset voltage amplitude change, a current absolute value difference, and a grid voltage on the input side of the load in the current switching cycle; and the current absolute value difference is: the difference between the absolute value of the current flowing through the thyristor module sampled in the current switching cycle and the absolute value of the current flowing through the thyristor module sampled in the previous switching cycle.

[0018] The present invention provides a control system for a unified power quality conditioner, comprising a system power supply, a load, and a control circuit of any one of the above unified power quality conditioners.

[0019] The present invention provides a control circuit, method and system of a unified power quality conditioner, wherein the control circuit includes a thyristor module, a conversion module and a control module, wherein the control module is used to stop providing a trigger pulse to the thyristor module through a first control terminal, stop the conversion module from operating in a current source mode, send a first drive signal to the conversion module through a second control terminal, and output a first conversion voltage through three output terminals of the conversion module to turn off the thyristor module; wherein the first conversion voltage is associated with the current switching cycle number of the power tube under the first drive signal, the preset voltage amplitude change, the current absolute value difference, and the grid voltage on the input side of the load in the current switching cycle. The circuit can gradually turn off the thyristor module in steps, thereby avoiding the problem of too fast current change of the thyristor module and reducing the impact on the grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic diagram of a control circuit of a unified power quality conditioner provided by an embodiment of the present invention;

[0022] Figure 2 A schematic diagram of another unified power quality conditioner control circuit provided by an embodiment of the present invention;

[0023] Figure 3 A flow chart of a control method for a unified power quality conditioner provided by an embodiment of the present invention;

[0024] Figure 4 A schematic diagram of a control system of a unified power quality conditioner provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the related art, when a temporary drop in system voltage is detected, the trigger pulse of the thyristor is extinguished. Since the thyristor cannot be turned off immediately, it can only be turned off naturally when the current passes through zero. Therefore, it is usually necessary to control the output voltage of the bridge arm port of the voltage source converter. When the thyristor current is detected to drop to 0, the thyristor can be forced to turn off. However, when the thyristor is forced to turn off, the current of the thyristor changes too quickly, causing a greater impact on the power grid. In addition, when the thyristor is forced to turn off, it is very important to detect whether the current direction is correct. If the current flowing through the thyristor When the current direction is small, it is easy to make mistakes in current direction detection. Once an error occurs, there will be a switching cycle current amplification, which will cause an impact on the power grid; for example, when the current When the measurement is relatively small, the measurement error will lead to inaccurate measurement, which will The direction of change is judged incorrectly, resulting in the output of -Udc when it should output Udc. If Udc is output, it will cause becomes smaller, the output -Udc will make The current will increase, which will cause an impact on the power grid; secondly, this solution has high requirements on the wiring direction of the CT (Current Transformer). If the wiring is wrong, the direction of the current will be wrong, which may cause device protection. Based on this, the embodiment of the present invention provides a control circuit, method and system for a unified power quality conditioner, which can be applied to applications that require control of a unified power quality conditioner.

[0027] To facilitate understanding of this embodiment, firstly, a control circuit of a unified power quality conditioner disclosed in an embodiment of the present invention is introduced. Figure 1 As shown, the control circuit includes: a thyristor module 10, a conversion module 11 and a control module 12; the thyristor module 10 has a first control end, a first input end, a second input end, a third input end, a first output end, a second output end and a third output end; the first input end of the thyristor module 10 is connected to the A phase of the system power supply, the second input end of the thyristor module 10 is connected to the B phase of the system power supply, the third input end of the thyristor module 10 is connected to the C phase of the system power supply, and the first output end, the second output end and the third output end of the thyristor module 10 are connected to the load;

[0028] The above-mentioned thyristor module 10 usually includes a plurality of thyristors, for example, one thyristor corresponds to each phase, that is, one thyristor corresponds to each phase A, B and C of the system power supply, then the thyristor module 10 includes three thyristors; the thyristor module 10 has three input terminals, which are respectively connected to the three phases of the system power supply; the above-mentioned load can be a nonlinear load, a sensitive load, etc., wherein the nonlinear load refers to the power drawn from the power system by an electrical device with nonlinear impedance characteristics. The electrical device with nonlinear impedance characteristics has an impedance that changes with the change of the external voltage or current, or its impedance is a function of the voltage or current; the sensitive load refers to a load that will not work normally or its function will decrease if the voltage changes or changes suddenly. The three output terminals of the above-mentioned thyristor module 10 are respectively connected to the load; the first control terminal of the thyristor module 10 can receive a trigger pulse to control each thyristor in the thyristor module 10 to conduct.

[0029] The conversion module 11 has a second control terminal, a first output terminal, a second output terminal and a third output terminal; the first output terminal of the conversion module 11 is connected to the first output terminal of the thyristor module 10, the second output terminal of the conversion module 11 is connected to the second output terminal of the thyristor module 10, and the third output terminal of the conversion module 11 is connected to the third output terminal of the thyristor module 10; the conversion module 11 generally includes a three-phase full-bridge inverter circuit, and the working mode can be changed according to whether the system power supply is normal. For example, when the system power supply is normal, the conversion module 11 can work in the current source mode, and when the system power supply is abnormal, the conversion module 11 can work in the voltage source mode. The second control terminal of the conversion module 11 can receive a corresponding drive signal to control the conduction and shutdown of each power tube in the conversion module 11. The three output terminals of the conversion module 11 are respectively connected to the three output terminals of the thyristor module 10.

[0030] The control module 12 is used to detect the working state of the system power supply. When the working state indicates that the system power supply is normal, a trigger pulse is provided to the thyristor module 10 through the first control terminal to supply power to the load through the thyristor module 10, and the conversion module 11 is controlled to work in the current source mode. In the grid-connected state, when the system power supply is normal, the control module 12 usually provides a trigger pulse to the thyristor module 10 all the time, so that each thyristor in the thyristor module 10 is in the on state. When each thyristor in the thyristor module 10 is in the on state, the conversion module 11 works in the current source mode. It cannot work in the voltage source mode, because the system power supply is usually a voltage source. If the conversion module 11 works in the voltage source mode, the parallel connection between the two will form a large circulating current, thereby causing damage to the conversion module 11. Therefore, the conversion module 11 can only work in the voltage source mode after waiting for each thyristor in the thyristor module 10 to be completely turned off.

[0031] When the working state indicates that the system power supply is abnormal, the trigger pulse is stopped from being provided to the thyristor module 10 through the first control terminal, the conversion module 11 is stopped from working in the current source mode, the first drive signal is sent to the conversion module 11 through the second control terminal to control the on and off of the power tube in the conversion module 11, and the first conversion voltage is output through the first output terminal, the second output terminal and the third output terminal of the conversion module 11 to turn off the thyristor module 10; when the system power supply is abnormal, such as when the system voltage drops temporarily, the control module 12 stops supplying the trigger pulse to each thyristor module 10. The thyristor provides a trigger pulse, and the trigger signal can only trigger its conduction, but cannot control the cutoff of the controller, so that the thyristor will naturally cut off when the next current passes through zero. At the same time, the working mode of the conversion module 11 can be controlled to switch from the current source mode to the voltage source mode. In this voltage source mode, the control module 12 can send a first drive signal to the conversion module 11 through the second control terminal, and output a first conversion voltage by controlling the conduction and cutoff of the power tube in the conversion module 11, so that the current flowing through each thyristor in the thyristor module 10 passes through zero as soon as possible, thereby causing each thyristor to be quickly turned off.

[0032] Among them, the first conversion voltage is associated with the current switching cycle number of the power tube under the first driving signal, the preset voltage amplitude change, the current absolute value difference, and the grid voltage on the input side of the load in the current switching cycle; the current absolute value difference is: the difference between the absolute value of the current flowing through the thyristor module 10 sampled in the current switching cycle and the absolute value of the current flowing through the thyristor module 10 sampled in the previous switching cycle. The above-mentioned current switching cycle number can be understood as the switching cycle of the power tube under the first driving signal. For example, taking the power tube as IGBT as an example, the switching cycle refers to the switching cycle of the IGBT. The operating frequency of the IGBT is usually controlled at 10kHz~20kHz, and the switching cycle can be determined according to the operating frequency; the above-mentioned preset voltage amplitude change can be understood as the amplitude of the voltage change in each switching cycle, and the voltage amplitude change can be set according to actual needs; the above-mentioned current absolute value difference can be used to indicate whether the change direction of the current flowing through the thyristor module 10 is larger or smaller compared with the previous switching cycle in the current switching cycle.

[0033] The control circuit of the unified power quality conditioner includes a thyristor module 10, a conversion module 11 and a control module 12. The control module 12 is used to stop providing a trigger pulse to the thyristor module 10 through the first control terminal when a system power supply abnormality is detected, stop the conversion module 11 from working in the current source mode, send a first drive signal to the conversion module 11 through the second control terminal, and output a first conversion voltage through the three output terminals of the conversion module 11 to turn off the thyristor module 10; wherein the first conversion voltage is associated with the current switching cycle number of the power tube under the first drive signal, the preset voltage amplitude change, the current absolute value difference, and the grid voltage on the input side of the load in the current switching cycle. The circuit can gradually turn off the thyristor module 10 in steps, thereby avoiding the problem of too fast current change of the thyristor module 10 and reducing the impact on the grid.

[0034] Furthermore, in the process of forcing the thyristors in the thyristor module 10 to turn off, the first conversion voltage is calculated by the following formula:

[0035]

[0036] in, represents the first conversion voltage; Indicates the grid voltage on the input side of the load in the current switching cycle; Indicates the change in the preset voltage amplitude, for example, it can be the incremental value, that is, the amplitude of the voltage increase in each switching cycle; Indicates the current switching cycle number of the power tube under the first driving signal; Indicates the current flowing through the thyristor module; Indicates the absolute value difference of current; is a symbolic function.

[0037] Furthermore, when When ≤0, =1; when >0 o'clock, =-1.

[0038] Can be used to represent each switching cycle The direction of change, when When it becomes smaller, it can be considered that the direction of current change is correct, and the direction of output voltage change can be kept in an arithmetic progression, that is, the voltage difference of the output voltage is kept unchanged.

[0039] Further, with The larger M is, the faster the turn-off speed of the thyristor module 10 is. When M is larger, the amplitude of the voltage increase in each switching cycle is larger, and the speed of forcing each thyristor in the thyristor module 10 to turn off is faster.

[0040] Further, such as Figure 2 A schematic diagram of a control circuit of a unified power quality conditioner is shown, wherein the conversion module 11 includes: an energy storage module, a converter module and a filter module;

[0041] The energy storage module has a first end and a second end; in one embodiment, the energy storage module can be a capacitor Csc accomplish;

[0042] The converter module has a first input end, a second input end, a control end, a first output end, a second output end and a third output end; the first input end of the converter module is connected to the first end of the energy storage module; the second input end of the converter is connected to the second end of the energy storage module;

[0043] The filter module has a first input end, a second input end, a third input end, a first output end, a second output end and a third output end; the first input end of the filter module is connected to the first output end of the converter module, the second input end of the filter module is connected to the second output end of the converter module, the third input end of the filter module is connected to the third output end of the converter module, the first output end of the filter module is connected to the first output end of the thyristor module 10, the second output end of the filter module is connected to the second output end of the thyristor module 10, and the third output end of the filter module is connected to the third output end of the thyristor module 10.

[0044] In actual implementation, the two input terminals of the converter module are connected to the energy storage module Csc The three output ends of the converter module are connected to the three input ends of the filter module respectively. The control end of the converter module corresponds to the second control end of the above-mentioned conversion module 11, that is, it can receive the corresponding drive signal to control the conduction and shutdown of each power tube in the conversion module 11. The three output ends of the filter module are respectively connected to the three output ends of the thyristor module 10. The filter module can filter out useless frequency signals and reduce ripple. In the grid-connected mode, the energy storage module can be charged through the filter module and the converter module. While charging, if there is still residual capacity, the residual capacity can also be used to compensate for the reactive power and harmonics of the system.

[0045] Furthermore, the converter module includes: a first inductor L d , the first power tube S 1. Second power tube S 2. The first capacitor C dc and three-phase full-bridge inverter circuit;

[0046] First Inductor L d Having a first end and a second end, a first inductorL d The first end of the first inductor is connected to the first end of the energy storage module; L d The sense value can be set according to actual needs.

[0047] The first power tube S 1 has a first end, a second end and a control end, the first power tube S 1 is connected to the first inductor L d The second end of the first power tube S The second end of 1 is connected to the energy storage module Csc The second end of the first power tube S The control end of 1 is used to receive the first drive signal or the second drive signal output by the control module 12; wherein the second drive signal is the drive signal sent by the control module 12 to the conversion module 11 when the system power supply is normal; the first power tube S 1 can be realized by IGBT, etc.; when the system power supply is normal, the converter module works in the current source mode, and the first power tube S The control end of 1 can receive the second driving signal sent by the control module 12 to turn on or off according to the second driving signal; when the system power supply is abnormal, the converter module works in the voltage source mode, and the first power tube S The control end of 1 can receive the first driving signal sent by the control module 12 to turn on or off according to the first driving signal; the first driving signal and the second driving signal can be the same or different, and a suitable driving signal can be selected according to actual needs.

[0048] The second power tube S 2 has a first end, a second end and a control end, and the second power tube S The second end of 2 is connected to the first inductor L d The second end of the second power tube S The control end of 2 is used to receive the first drive signal or the second drive signal output by the control module 12; the second power tube S 2 can be realized by IGBT, etc. When the system power supply is normal, the converter module works in the current source mode, and the second power tube S The control end of the control module 2 can receive the second driving signal sent by the control module 12 to turn on or off according to the second driving signal; when the system power supply is abnormal, the converter module works in the voltage source mode, and the second power tube S The control end of 2 can receive the first driving signal sent by the control module 12 to be turned on or off according to the first driving signal.

[0049] First capacitor Cdc Having a first terminal and a second terminal, a first capacitor C dc The first end is connected to the second power tube S The first end of 2; the first capacitor C dc The second end is connected to the first power tube S 1; the second end of the first capacitor C dc The capacitance value can be set according to actual needs.

[0050] The three-phase full-bridge inverter circuit has a first input terminal, a second input terminal, a control terminal, a first output terminal, a second output terminal and a third output terminal. The first input terminal of the three-phase full-bridge inverter circuit is connected to the first end of the first capacitor; the second input terminal of the three-phase full-bridge inverter circuit is connected to the second end of the first capacitor; the first output terminal, the second output terminal and the third output terminal of the three-phase full-bridge inverter circuit are respectively used as the first output terminal, the second output terminal and the third output terminal of the converter module. The two input terminals of the three-phase full-bridge inverter circuit are respectively connected to the first capacitor. C dc The three output ends of the three-phase full-bridge inverter circuit are respectively used as the three output ends of the converter module, and are respectively connected to the three input ends of the filter module; each power tube in the three-phase full-bridge inverter circuit can be implemented by IGBT, etc., and the control end of the three-phase full-bridge inverter circuit can receive the first drive signal or the second drive signal output by the control module 12 to control the conduction or shutdown of each power tube.

[0051] Furthermore, the filter module is an LC filter circuit. In actual implementation, the filter module may include three filter inductors: L f 1. L f 2 and L f 3, and three filter capacitors C f 1. C f 2 and C f 3. Filter inductor L f The first end of 1 is connected to the first output end of the three-phase full-bridge inverter circuit, and the filter inductor L f The second end of 1 is connected to the filter capacitor C f 1 and the first output end of the thyristor module 10, the current filtering inductor L f The current of 1 is i fa ; Filter inductorL f The first end of 2 is connected to the second output end of the three-phase full-bridge inverter circuit, and the filter inductor L f The second end of 2 is connected to the filter capacitor C f 2 and the second output end of the thyristor module 10, the current filtering inductor L f The current of 2 is i fb ; Filter inductor L f The first end of 3 is connected to the third output end of the three-phase full-bridge inverter circuit, and the filter inductor L f The second end of 3 is connected to the filter capacitor C f 3 and the third output terminal of the thyristor module 10, the current filtering inductor L f The current of 3 is i fc ; Filter capacitor C f The second end of 1, filter capacitor C f The second end of 2 and the filter capacitor C f The second ends of 3 are connected to each other.

[0052] Further, such as Figure 2 As shown, the thyristor module 10 includes three thyristors. In actual implementation, the A phase, the B phase and the C phase of the system power supply may correspond to a thyristor respectively, and the thyristor module 10 includes three thyristors T1, T2 and T3.

[0053] In the initial few switching cycles of the control circuit, the output voltage of the converter module is not much different from the grid voltage, and should not cause impact to the grid. The number of initial switching cycles mentioned here is usually the same as the preset voltage amplitude change. For example, if the preset voltage amplitude change is If it is set to 2V, the voltage difference with the grid voltage is only about 8V in the first 4 cycles, which has little impact on the grid. After these 4 switching cycles, the direction of voltage change has been confirmed, and then the amplitude of the voltage difference increases in one direction, which can accelerate the current change and make the current flowing through the thyristor pass through zero as soon as possible, so that the thyristor is turned off as soon as possible. This method uses the change of current amplitude as feedback to determine the direction of voltage change, thus reducing the requirements for the wiring direction of the CT and having better robustness.

[0054] In this system, if the forced commutation speed of the thyristor is slow, the preset voltage amplitude change M value can be adjusted appropriately to speed up the thyristor shutdown speed. Since the effective direction of the output voltage difference can be detected by using the initial few switching cycles, whether the current direction is correct has no effect on the shutdown result. The system gradually realizes the current zero crossing in steps, with a slow speed and less impact on the power grid.

[0055] The present invention provides a unified power quality conditioner control method, such as Figure 3 As shown, the method comprises the following steps:

[0056] Step S302, detecting the working status of the system power supply;

[0057] Step S304, when the working state indicates that the system power supply is normal, providing a trigger pulse to the thyristor module through the first control terminal, so as to supply power to the load through the thyristor module, and controlling the conversion module to operate in a current source mode;

[0058] Step S306, when the working status indicates that the system power supply is abnormal, stop providing the trigger pulse to the thyristor module through the first control terminal, stop the conversion module from working in the current source mode, send the first drive signal to the conversion module through the second control terminal to control the on and off of the power tube in the conversion module, and output the first conversion voltage through the first output terminal, the second output terminal and the third output terminal of the conversion module to turn off the thyristor module; wherein the first conversion voltage is associated with the current switching cycle number of the power tube under the first drive signal, the preset voltage amplitude change, the current absolute value difference, and the grid voltage on the input side of the load in the current switching cycle; the current absolute value difference is: the difference between the absolute value of the current flowing through the thyristor module sampled in the current switching cycle and the absolute value of the current flowing through the thyristor module sampled in the previous switching cycle.

[0059] The present invention provides a unified power quality conditioner control system, such as Figure 4 As shown, it includes a system power supply, a load, and a control circuit of a unified power quality conditioner of any of the above items.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention 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 replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A control circuit of a unified power quality conditioner, characterized in that: The circuit comprises: A thyristor module, comprising a first control end, a first input end, a second input end, a third input end, a first output end, a second output end, and a third output end; the first input end of the thyristor module is connected to phase A of a system power supply, the second input end of the thyristor module is connected to phase B of the system power supply, the third input end of the thyristor module is connected to phase C of the system power supply, and the first output end, the second output end, and the third output end of the thyristor module are connected to a load; A conversion module, having a second control end, a first output end, a second output end and a third output end; the first output end of the conversion module is connected to the first output end of the thyristor module, the second output end of the conversion module is connected to the second output end of the thyristor module, and the third output end of the conversion module is connected to the third output end of the thyristor module; A control module, used for detecting the working state of the system power supply, and when the working state indicates that the system power supply is normal, providing a trigger pulse to the thyristor module through the first control end, so as to supply power to the load through the thyristor module, and controlling the conversion module to operate in a current source mode; when the working state indicates that the system power supply is abnormal, stopping providing a trigger pulse to the thyristor module through the first control end, stopping the conversion module from operating in the current source mode, sending a first drive signal to the conversion module through the second control end, so as to control the on and off of the power tube in the conversion module, and outputting a first conversion voltage through the first output end, the second output end, and the third output end of the conversion module, so as to turn off the thyristor module; The first conversion voltage is associated with the current switching cycle number of the power tube under the first driving signal, the preset voltage amplitude change, the current absolute value difference, and the grid voltage on the input side of the load in the current switching cycle; the current absolute value difference is: the difference between the absolute value of the current flowing through the thyristor module sampled in the current switching cycle and the absolute value of the current flowing through the thyristor module sampled in the previous switching cycle; The first conversion voltage is calculated by the following formula: in, represents the first conversion voltage; Indicates the grid voltage at the input side of the load in the current switching cycle; Indicates the change in the preset voltage amplitude; Indicates the current number of switching cycles of the power tube under the first driving signal; represents the current flowing through the thyristor module; Indicates the absolute value difference of current; is a symbolic function; when When ≤0, =1; when >0 o'clock, =-1.

2. The circuit according to claim 1, characterized in that along with The larger the value, the faster the thyristor module turns off.

3. The circuit according to claim 1, characterized in that The transformation module comprises: An energy storage module having a first end and a second end; A converter module, having a first input end, a second input end, a control end, a first output end, a second output end and a third output end; the first input end of the converter module is connected to the first end of the energy storage module; the second input end of the converter is connected to the second end of the energy storage module; A filter module comprises a first input end, a second input end, a third input end, a first output end, a second output end and a third output end; the first input end of the filter module is connected to the first output end of the converter module, the second input end of the filter module is connected to the second output end of the converter module, the third input end of the filter module is connected to the third output end of the converter module, the first output end of the filter module is connected to the first output end of the thyristor module, the second output end of the filter module is connected to the second output end of the thyristor module, and the third output end of the filter module is connected to the third output end of the thyristor module.

4. The circuit according to claim 3, characterized in that The converter module comprises: A first inductor having a first end and a second end, wherein the first end of the first inductor is connected to the first end of the energy storage module; A first power tube, having a first end, a second end and a control end, wherein the first end of the first power tube is connected to the second end of the first inductor; the second end of the first power tube is connected to the second end of the energy storage module; the control end of the first power tube is used to receive the first drive signal or the second drive signal output by the control module; wherein the second drive signal is a drive signal sent by the control module to the conversion module when the system power supply is normal; A second power tube having a first end, a second end and a control end, the second end of the second power tube being connected to the second end of the first inductor, and the control end of the second power tube being used to receive the first drive signal or the second drive signal output by the control module; A first capacitor has a first end and a second end, wherein the first end of the first capacitor is connected to the first end of the second power tube; and the second end of the first capacitor is connected to the second end of the first power tube; A three-phase full-bridge inverter circuit comprises a first input terminal, a second input terminal, a control terminal, a first output terminal, a second output terminal and a third output terminal, wherein the first input terminal of the three-phase full-bridge inverter circuit is connected to the first end of the first capacitor; the second input terminal of the three-phase full-bridge inverter circuit is connected to the second end of the first capacitor; the first output terminal, the second output terminal and the third output terminal of the three-phase full-bridge inverter circuit respectively serve as the first output terminal, the second output terminal and the third output terminal of the converter module.

5. The circuit according to claim 3, characterized in that The filtering module is an LC filtering circuit.

6. The circuit according to claim 1, characterized in that The thyristor module includes three thyristors.

7. A control method for a unified power quality conditioner, characterized in that: The method comprises: Detect the working status of the system power supply; When the working state indicates that the system power supply is normal, a trigger pulse is provided to the thyristor module through the first control terminal, so as to supply power to the load through the thyristor module, and control the conversion module to operate in a current source mode; When the working state indicates that the system power supply is abnormal, stop providing the trigger pulse to the thyristor module through the first control end, stop the conversion module from operating in the current source mode, send a first drive signal to the conversion module through the second control end to control the on and off of the power tube in the conversion module, and output a first conversion voltage through the first output end, the second output end, and the third output end of the conversion module to turn off the thyristor module; The first conversion voltage is associated with the current switching cycle number of the power tube under the first driving signal, the preset voltage amplitude change, the current absolute value difference, and the grid voltage on the input side of the load in the current switching cycle; the current absolute value difference is: the difference between the absolute value of the current flowing through the thyristor module sampled in the current switching cycle and the absolute value of the current flowing through the thyristor module sampled in the previous switching cycle; The first conversion voltage is calculated by the following formula: in, represents the first conversion voltage; Indicates the grid voltage at the input side of the load in the current switching cycle; Indicates the change in the preset voltage amplitude; Indicates the current number of switching cycles of the power tube under the first driving signal; represents the current flowing through the thyristor module; Indicates the absolute value difference of current; is a symbolic function; when When ≤0, =1; when >0 o'clock, =-1.

8. A control system for a unified power quality conditioner, characterized in that: It comprises a system power supply, a load, and a control circuit of the unified power quality conditioner as described in any one of claims 1-6.

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