A single-phase transformer isolated series dynamic voltage regulation device

Abstract

The present invention discloses a single-phase transformer-isolated series-connected dynamic voltage regulation device, belonging to the field of dynamic voltage regulation technology. The present invention comprises a control unit, a rectifier unit, an energy storage unit, a power inverter unit, a transformer isolation unit, and a bypass unit; the input end of the rectifier unit is electrically connected to the output end of a three-phase AC power supply; the output end of the rectifier unit is electrically connected to the energy storage unit; the output end of the energy storage unit is electrically connected to the input end of the power inverter unit; the output end of the power inverter unit is electrically connected to the input end of the transformer isolation unit; and the output end of the transformer isolation unit is electrically connected to the bypass unit. When voltage instability occurs on the load side, the present invention can achieve dynamic compensation for voltage instability by disconnecting the circuit breaker QF3 and compensating for voltage drop through a single-phase isolation transformer. At the same time, the three single-phase isolation transformers are independently arranged to prevent mutual interference between different single-phase isolation transformers.

Description

Technical Field

[0001] The present invention relates to the technical field of dynamic voltage regulation, and in particular to a single-phase transformer isolated series dynamic voltage regulation device. Background Art

[0002] The growth of nonlinear and impact loads has led to many power quality issues, such as voltage sag, flicker, current harmonics, and imbalance, which have seriously affected the stability of the power system and the safety of sensitive users.

[0003] In addition, when a transformer transforms three-phase alternating current, mutual interference is easily generated due to electromagnetic changes. In order to solve the above problem, the present invention provides a single-phase transformer isolated series type dynamic voltage regulation device. Summary of the Invention

[0004] In response to the above-mentioned technical deficiencies, the purpose of the present invention is to provide a single-phase transformer isolated series dynamic voltage regulation device. When voltage instability occurs on the load side, the circuit breaker QF3 can be disconnected and the voltage drop can be compensated by the single-phase isolation transformer; dynamic compensation for voltage instability can be achieved; at the same time, the three single-phase isolation transformers are set independently of each other to ensure that there is no mutual interference between different single-phase isolation transformers.

[0005] To solve the above technical problems, the present invention adopts the following technical solution: The present invention provides a single-phase transformer isolated series dynamic voltage regulation device, comprising: a control unit, a rectifier unit, an energy storage unit, a power inverter unit, a voltage transformation isolation unit, and a bypass unit; the control unit is electrically connected to the rectifier unit, the energy storage unit, the power inverter unit, the voltage transformation isolation unit, and the bypass unit respectively;

[0006] The input end of the rectifier unit is electrically connected to the output end of the three-phase AC power supply, and is used to rectify the three-phase AC power into DC power; the output end of the rectifier unit is electrically connected to the energy storage unit, and is used to store DC power in the energy storage unit; the output end of the energy storage unit is electrically connected to the input end of the power inverter unit, and is used to invert the DC power output by the energy storage unit into three-phase AC power; the output end of the power inverter unit is electrically connected to the input end of the transformer isolation unit, and is used to transform the three-phase AC power; the output end of the transformer isolation unit is electrically connected to the bypass unit, and is used to directly output the three-phase AC power of the three-phase AC power supply or output the three-phase AC power compensated by the energy storage unit.

[0007] As a preferred technical solution, the rectifier unit includes a rectifier bridge, an IGBT and an inductor; the three-phase AC power output end is electrically connected to the rectifier bridge input end for rectifying the three-phase AC power; the rectifier bridge is electrically connected to the IGBT and the inductor in turn.

[0008] As a preferred technical solution, the energy storage unit includes a supercapacitor unit and a discharge resistor circuit; the supercapacitor unit is connected in parallel with the discharge resistor circuit; the supercapacitor unit includes several 3V / 600F power supercapacitors, 48 ​​in series and 2 in parallel to form a 144V / 25F supercapacitor module group, and 4 supercapacitor modules are connected in series to form a 576V / 6.25F supercapacitor unit; the discharge resistor circuit includes a discharge resistor and a contactor connected in series.

[0009] As a preferred technical solution, the power inverter unit includes an A-phase inverter circuit, a B-phase inverter circuit and a C-phase inverter circuit; the A-phase inverter circuit includes an A-phase inverter module and a thyristor switch SRC_A connected in series; the B-phase inverter circuit includes a B-phase inverter module and a thyristor switch SRC_B connected in series; the C-phase inverter circuit includes a C-phase inverter module and a thyristor switch SRC_C connected in series.

[0010] As a preferred technical solution, each of the A-phase inverter module, the B-phase inverter module, and the C-phase inverter module includes four IGBTs connected in parallel for inverting direct current into alternating current.

[0011] As a preferred technical solution, the transformer isolation unit includes three single-phase isolation transformers; the three single-phase isolation transformers are respectively connected in series with the A-phase inverter circuit, the B-phase inverter circuit and the C-phase inverter circuit.

[0012] As a preferred technical solution, the bypass unit includes a circuit breaker QF1, a circuit breaker QF2 and a circuit breaker QF3; the circuit breaker QF1 is connected in series between the three-phase AC power supply output end and the rectifier unit; the circuit breaker QF2 is connected in series between the output end and the single-phase isolation transformer; and the circuit breaker QF3 is connected in series on the direct connection line between the three-phase AC power supply output end and the output end.

[0013] The beneficial effects of the present invention are:

[0014] 1. When voltage instability occurs on the load side, the present invention can disconnect the circuit breaker QF3 to supply power to the energy storage unit, and compensate for the voltage drop through the single-phase isolation transformer, thereby achieving dynamic compensation for voltage instability.

[0015] 2. The three single-phase isolation transformers of the present invention are respectively connected in series with the A-phase inverter circuit, the B-phase inverter circuit and the C-phase inverter circuit. The three single-phase isolation transformers are independently arranged. The three single-phase isolation transformers can be covered with anti-electromagnetic interference covers respectively, and the spacing distance can be adjusted to prevent mutual interference between different single-phase isolation transformers.

[0016] 3. In the present invention, when in hot standby mode, a fault occurs, or maintenance is being performed, the thyristor switch SRC_A, the thyristor switch SRC_B, and the thyristor switch SRC_C are closed and turned on, and the secondary winding of the single-phase isolation transformer is short-circuited to ensure the magnetic balance of the single-phase isolation transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 A circuit diagram of a single-phase transformer isolated series dynamic voltage regulation device provided by an embodiment of the present invention.

[0019] Figure 2 for Figure 1 Enlarged view of the rectifier unit.

[0020] Figure 3 for Figure 1 Enlarged view of the energy storage unit.

[0021] Figure 4 for Figure 1 An enlarged view of the power inverter unit in FIG.

[0022] Figure 5 for Figure 1 An enlarged view of the transformer isolation unit in Figure 2.

[0023] Figure 6 for Figure 1 Magnified view of the bypass unit in .

[0024] Figure 7 This is a circuit diagram of the A-phase inverter module, the B-phase inverter module, and the C-phase inverter module in the present invention, each of which includes four IGBTs connected in parallel. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] Example: Figures 1 to 7As shown, the present invention provides a single-phase transformer-isolated series dynamic voltage regulation device, including: a control unit, a rectifier unit, an energy storage unit, a power inverter unit, a transformer isolation unit and a bypass unit; the control unit is electrically connected to the rectifier unit, the energy storage unit, the power inverter unit, the transformer isolation unit and the bypass unit respectively; in fact, the control unit is used to control the switches of the circuits in the rectifier unit, the power inverter unit, the transformer isolation unit and the bypass unit, and is also used to control the charging and discharging of the energy storage unit and to control the voltage compensation range by controlling the power inverter unit; at the same time, the transformer isolation unit is connected to the power supply side incoming line and the load, and is responsible for providing load voltage and power supply isolation; in addition, the control unit is also connected to the human-machine interface to realize centralized control and display.

[0027] The input end of the rectifier unit is electrically connected to the output end of the three-phase AC power supply, and is used to rectify the three-phase AC power into DC power. Specifically, the rectifier unit includes a rectifier bridge, an IGBT, and a reactor. The output end of the three-phase AC power supply is electrically connected to the input end of the rectifier bridge, and is used to rectify the three-phase AC power. The rectifier bridge is electrically connected to the IGBT and the reactor in turn.

[0028] The output end of the rectifier unit is electrically connected to the energy storage unit to store direct current in the energy storage unit. Specifically, the energy storage unit includes a supercapacitor unit and a discharge resistor circuit. The supercapacitor unit and the discharge resistor circuit are connected in parallel. The supercapacitor unit includes a number of 3V / 600F power supercapacitors, 48 ​​in series and 2 in parallel to form a 144V / 25F supercapacitor module, and 4 supercapacitor modules are connected in series to form a 576V / 6.25F supercapacitor unit. The discharge resistor circuit includes a discharge resistor and a contactor connected in series. When maintenance is performed, the contactor can be closed to discharge the supercapacitor module through the discharge resistor. At the same time, each supercapacitor module is equipped with a temperature sensor and a patrol meter to monitor the status of the supermodule in real time.

[0029] The output end of the energy storage unit is electrically connected to the input end of the power inverter unit, and is used to invert the DC power output by the energy storage unit into three-phase AC power. The power inverter unit includes an A-phase inverter circuit, a B-phase inverter circuit, and a C-phase inverter circuit. The A-phase inverter circuit includes an A-phase inverter module and a thyristor switch SRC_A connected in series. The B-phase inverter circuit includes a B-phase inverter module and a thyristor switch SRC_B connected in series. The C-phase inverter circuit includes a C-phase inverter module and a thyristor switch SRC_C connected in series. Figure 7 As shown, the A-phase inverter module, the B-phase inverter module, and the C-phase inverter module each include four parallel-connected IGBTs for inverting DC power into AC power. Specifically, the DC power is inverted into AC power by controlling the on / off switching of the four parallel-connected IGBTs. Alternatively, the DC power can be inverted into AC power of different voltages by controlling the on / off switching of the four parallel-connected IGBTs.

[0030] The output end of the power inverter unit is electrically connected to the input end of the transformer isolation unit for transforming three-phase AC power. Specifically, the transformer isolation unit includes three single-phase isolation transformers. The three single-phase isolation transformers are respectively connected in series with the A-phase inverter circuit, the B-phase inverter circuit, and the C-phase inverter circuit. The three single-phase isolation transformers are independently arranged. The three single-phase isolation transformers can be covered with an anti-electromagnetic interference cover, and the spacing distance can be adjusted to prevent mutual interference between different single-phase isolation transformers.

[0031] The output end of the transformer isolation unit is electrically connected to the bypass unit, and is used to directly output the three-phase AC power of the three-phase AC power supply or output the three-phase AC power compensated by the energy storage unit; specifically, the bypass unit includes a circuit breaker QF1, a circuit breaker QF2 and a circuit breaker QF3; the circuit breaker QF1 is connected in series between the output end of the three-phase AC power supply and the rectifier unit; the circuit breaker QF2 is connected in series between the output end and the single-phase isolation transformer; the circuit breaker QF3 is connected in series on the direct connection line between the output end and the output end of the three-phase AC power supply.

[0032] A specific parameter scheme of the present invention:

[0033] Transformer capacity: compensation power is 300kW, voltage compensation range is 0.6~0.9Un, grid-connected system capacity is 1000kVA, and the capacity of three single-phase isolation transformers is 3*100kW;

[0034] Primary side rating: The rated voltage of the primary side (grid side) of the single-phase isolation transformer is 220V*0.3=66V, and the rated current is 1520A;

[0035] Secondary side rating: The rated voltage of the secondary side (load side) of the single-phase isolation transformer is 220V and the rated current is 455A;

[0036] Insertion voltage drop: The primary side of the single-phase isolation transformer is connected in series in the power circuit. When the load current passes through, a certain voltage drop will be generated. Based on the rated load of 1000kVA, the voltage drop amplitude of each transformer is 66*4%=2.64V, and the impact on the load can be ignored.

[0037] Insulation: The primary and secondary sides of the single-phase isolation transformer, as well as the primary and secondary sides to the ground, shall all be in accordance with the power frequency withstand voltage of AC3000V1min.

[0038] When the present invention is actually used:

[0039] (1) In hot standby mode: the thyristor switch SRC_A, the thyristor switch SRC_B and the thyristor switch SRC_C are closed and turned on, and the secondary winding of the single-phase isolation transformer is short-circuited to ensure the magnetic balance of the single-phase isolation transformer. The primary phase voltage insertion drop changes linearly with the load current. The voltage drop amplitude is 2.64V under the rated load current, and the phase is related to the load current phase. Since the primary side insertion voltage drop of the single-phase isolation transformer is very small in this state, the impact on the load voltage level can be ignored.

[0040] (2) In voltage compensation mode: the control unit detects the three-phase voltage at the output end, i.e., the load end, in real time; if it detects that the voltage amplitude of any phase or the three phases is lower than 0.9, the circuit breaker QF3 is immediately disconnected, and the voltage drop is compensated by the single-phase isolation transformer, and the phase voltage at the load end is compensated to 100% Un (which can be set by parameters); thus, dynamic compensation is achieved when the voltage is unstable.

[0041] (3) Charging mode: After the voltage compensation is completed, charging is carried out through the charging circuit. At this time, the thyristor switch SRC_A, the thyristor switch SRC_B and the thyristor switch SRC_C are closed and turned on, the output pulse of the single-phase isolation transformer is locked, and the chopper switch in the charging circuit starts to work. The energy storage element is quickly charged to the rated high voltage in the constant current source mode (the default is 30A, which can be adjusted by parameters); the rated power of the inverter charging circuit is 15kW, and the temporary sag interval allowed by the system is 10s.

[0042] (4) In bypass mode: When a fault occurs or maintenance is performed, the thyristor switch SRC_A, the thyristor switch SRC_B and the thyristor switch SRC_C are closed and turned on, short-circuiting the secondary winding of the single-phase isolation transformer to ensure the magnetic balance of the single-phase isolation transformer.

[0043] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A single-phase transformer isolated series type dynamic voltage regulator, characterized in that: include: A control unit, a rectifier unit, an energy storage unit, a power inverter unit, a voltage transformation and isolation unit, and a bypass unit; the control unit is electrically connected to the rectifier unit, the energy storage unit, the power inverter unit, the voltage transformation and isolation unit, and the bypass unit respectively; The input end of the rectifier unit is electrically connected to the output end of the three-phase AC power supply, and is used to rectify the three-phase AC power into DC power; The output end of the rectifier unit is electrically connected to the energy storage unit for storing direct current in the energy storage unit; The output end of the energy storage unit is electrically connected to the input end of the power inverter unit, and is used to invert the direct current output by the energy storage unit into three-phase alternating current; The output end of the power inverter unit is electrically connected to the input end of the voltage transformation isolation unit, and is used for transforming the three-phase alternating current; The output end of the transformer isolation unit is electrically connected to the bypass unit, and is used to directly output the three-phase AC power of the three-phase AC power supply or output the three-phase AC power compensated by the energy storage unit; The rectifier unit includes a rectifier bridge, an IGBT and a reactor; the output end of the three-phase AC power supply is electrically connected to the input end of the rectifier bridge for rectifying the three-phase AC power; the rectifier bridge is electrically connected to the IGBT and the reactor in turn; The energy storage unit includes a supercapacitor unit and a discharge resistor circuit; the supercapacitor unit and the discharge resistor circuit are connected in parallel; the supercapacitor unit includes a number of 3V / 600F power supercapacitors, 48 ​​of which are connected in series and 2 in parallel to form a 144V / 25F supercapacitor module, and four supercapacitor modules are connected in series to form a 576V / 6.25F supercapacitor unit; the discharge resistor circuit includes a discharge resistor and a contactor connected in series; each supercapacitor module is equipped with a temperature sensor and a patrol meter to monitor the status of the supermodule in real time; The power inverter unit includes an A-phase inverter circuit, a B-phase inverter circuit, and a C-phase inverter circuit; the A-phase inverter circuit includes an A-phase inverter module and a thyristor switch SRC_A connected in series; the B-phase inverter circuit includes a B-phase inverter module and a thyristor switch SRC_B connected in series; the C-phase inverter circuit includes a C-phase inverter module and a thyristor switch SRC_C connected in series; The bypass unit includes a circuit breaker QF1, a circuit breaker QF2 and a circuit breaker QF3; the circuit breaker QF1 is connected in series between the three-phase AC power output end and the rectifier unit; the circuit breaker QF2 is connected in series between the output end and the single-phase isolation transformer; the circuit breaker QF3 is connected in series on the direct connection line between the three-phase AC power output end and the output end.

2. The single-phase transformer isolated series dynamic voltage regulator according to claim 1, characterized in that: The A-phase inverter module, the B-phase inverter module, and the C-phase inverter module each include four IGBTs connected in parallel, which are used to invert direct current into alternating current.

3. The single-phase transformer isolated series dynamic voltage regulator according to claim 2, characterized in that: The transformer isolation unit includes three single-phase isolation transformers; the three single-phase isolation transformers are respectively connected in series with the A-phase inverter circuit, the B-phase inverter circuit and the C-phase inverter circuit.

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