A three-phase voltage unbalance control device and method based on voltage dynamic compensation

Abstract

The present invention relates to a three-phase voltage imbalance management device and method based on voltage dynamic compensation. By detecting the voltage information of the three phases A, B and C, the processor determines that the three-phase voltage difference exceeds a preset value, and then determines that the three-phase voltage is unbalanced. Then the processor intelligent control device performs inter-phase current transfer according to the voltage imbalance situation to achieve the goal of voltage balance at the terminal installation point. The present invention does not require the additional installation of current transformers, and can solve the problem of dynamic imbalance of three-phase voltage at the terminal installation point of the line in the current distribution network. It can dynamically adjust the three-phase voltage at the device installation point without power outage to ensure reliable operation of the load.

Description

Technical Field

[0001] The invention relates to a three-phase voltage imbalance control device and method based on voltage dynamic compensation. Background Art

[0002] Three-phase power imbalance is a common phenomenon in distribution networks. Since there is a lot of single-phase power consumption in low-voltage power grid systems, and the load current and power consumption time are also different, three-phase imbalance problems are prone to occur in low-voltage areas.

[0003] The three-phase imbalance in the power supply area will lead to increased transformer and line losses, reduced transformer output, and decreased power conversion efficiency; it will also cause a large three-phase voltage deviation at the user end, and the voltage quality cannot be guaranteed; it will also cause the problem of low voltage at the end, and in severe cases it may even damage electrical equipment.

[0004] Therefore, how to solve the problem of three-phase power imbalance in the current distribution network is still an urgent problem to be solved in the industry. Summary of the invention

[0005] The purpose of the present invention is to solve the problem of three-phase voltage imbalance at the end of the current distribution network, improve the voltage qualification rate of the end users of the distribution network, and provide a three-phase voltage imbalance management device and method based on voltage dynamic compensation.

[0006] To achieve the above purpose, the technical solution of the present invention is: a three-phase voltage imbalance control device based on voltage dynamic compensation, which is installed on the three-phase four-wire line of the distribution network, collects the operation information of the distribution network, calculates the three-phase voltage imbalance, and dynamically compensates for the three-phase voltage imbalance at the end of the line caused by the random opening of the single-phase load of the line. The three-phase four-wire line is respectively A phase, B phase, C phase and N line. The device includes:

[0007] A processor, a drive circuit, a PFC inductor, a switching switch, an A-phase AC voltage measurement circuit, a B-phase AC voltage measurement circuit, and a C-phase AC voltage measurement circuit; the switching switch includes an A-phase bridge arm, a B-phase bridge arm, a C-phase bridge arm, and an N-line circuit connected in parallel;

[0008] The A-phase AC voltage measurement circuit, the B-phase AC voltage measurement circuit, and the C-phase AC voltage measurement circuit are connected to the power distribution network and are used to detect voltage information of the A-phase, B-phase, and C-phase;

[0009] The A-phase AC voltage measurement circuit, the B-phase AC voltage measurement circuit, and the C-phase AC voltage measurement circuit are communicatively connected to the processor to transmit voltage information of the A-phase, B-phase, and C-phase to the processor respectively;

[0010] The A phase forms a loop through the A phase AC voltage measurement circuit, the PFC inductor, the C phase bridge arm, the N line circuit, and the N line;

[0011] The B phase forms a loop through the B phase AC voltage measurement circuit, the PFC inductor, the B phase bridge arm, the N line circuit, and the N line;

[0012] The C phase forms a loop through the C phase AC voltage measurement circuit, the PFC inductor, the A phase bridge arm, the N line circuit, and the N line;

[0013] The processor is connected to the switch via a driving circuit.

[0014] In one embodiment of the present invention, the A-phase bridge arm, the B-phase bridge arm, and the C-phase bridge arm are all composed of two IGBT tubes connected in series, and the two IGBT tube connection points are respectively connected to the A-phase AC voltage measurement circuit, the B-phase AC voltage measurement circuit, and the C-phase AC voltage measurement circuit.

[0015] In an embodiment of the present invention, the N-line circuit includes two capacitors connected in series, and a connection point of the two capacitors is connected to the N-line.

[0016] In one embodiment of the present invention, the processor is connected to the A-phase bridge arm, the B-phase bridge arm, and the C-phase bridge arm of the switching switch through the driving circuit to control the opening and closing of the IGBT tube.

[0017] The present invention also provides a three-phase unbalance control method based on voltage dynamic compensation, comprising the following steps:

[0018] S1, detect the voltage information of phase A, phase B and phase C,

[0019] S2. If the processor determines that the three-phase voltage difference exceeds a preset value, it is determined that the three-phase voltage is unbalanced. The processor then performs inter-phase current transfer according to the voltage imbalance to achieve the goal of voltage balance at the terminal installation point.

[0020] In one embodiment of the present invention, the method is based on any of the above-mentioned devices and can effectively perform unbalanced current compensation; there is no need to install additional current transformers to analyze the three-phase current of the load, which greatly reduces the installation workload of the equipment and saves the overall investment cost of the equipment; and the equipment is connected to the grid in parallel, which can achieve installation without power outages and save management costs.

[0021] Compared with the prior art, the present invention has the following beneficial effects: the three-phase voltage imbalance control device based on voltage dynamic compensation can effectively compensate for the unbalanced current and achieve three-phase voltage balance at the device installation point; there is no need to install additional current transformers to analyze the three-phase current of the load, which greatly reduces the installation workload of the equipment and saves the overall investment cost of the equipment. In addition, the equipment is connected to the network in parallel, which can achieve non-stop installation and save management costs. The present invention can solve the problem of three-phase voltage imbalance at the terminal load in the current distribution network, improve the voltage qualification rate of the terminal users of the distribution network, and avoid low voltage for the terminal users. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a schematic diagram of the principle of a three-phase voltage imbalance control device based on voltage dynamic compensation.

[0023] Figure 2 It is a schematic diagram of the principle of an embodiment of the present invention.

[0024] Figure 3 FIG. 4 is a control block diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0026] The present invention discloses a three-phase voltage imbalance control device based on voltage dynamic compensation, which is installed on a three-phase four-wire line of a distribution network, collects distribution network operation information, calculates the three-phase voltage imbalance, and dynamically compensates for the three-phase voltage imbalance at the end of the line caused by the random opening of the single-phase load of the line. The three-phase four-wire line includes A phase, B phase, C phase and N line. The device comprises:

[0027] A processor, a drive circuit, a PFC inductor, a switching switch, an A-phase AC voltage measurement circuit, a B-phase AC voltage measurement circuit, and a C-phase AC voltage measurement circuit; the switching switch includes an A-phase bridge arm, a B-phase bridge arm, a C-phase bridge arm, and an N-line circuit connected in parallel;

[0028] The A-phase AC voltage measurement circuit, the B-phase AC voltage measurement circuit, and the C-phase AC voltage measurement circuit are connected to the power distribution network and are used to detect voltage information of the A-phase, B-phase, and C-phase;

[0029] The A-phase AC voltage measurement circuit, the B-phase AC voltage measurement circuit, and the C-phase AC voltage measurement circuit are communicatively connected to the processor to transmit voltage information of the A-phase, B-phase, and C-phase to the processor respectively;

[0030] The A phase forms a loop through the A phase AC voltage measurement circuit, the PFC inductor, the C phase bridge arm, the N line circuit, and the N line;

[0031] The B phase forms a loop through the B phase AC voltage measurement circuit, the PFC inductor, the B phase bridge arm, the N line circuit, and the N line;

[0032] The C phase forms a loop through the C phase AC voltage measurement circuit, the PFC inductor, the A phase bridge arm, the N line circuit, and the N line;

[0033] The processor is connected to the switch via a driving circuit.

[0034] The present invention also provides a three-phase voltage unbalance control method based on voltage dynamic compensation, comprising the following steps:

[0035] S1, detect the voltage information of phase A, phase B and phase C,

[0036] S2. If the processor determines that the three-phase voltage difference exceeds a preset value, it is determined that the three-phase voltage is unbalanced. The processor then performs inter-phase current transfer according to the voltage imbalance to achieve the goal of voltage balance at the terminal installation point.

[0037] The following is the specific implementation process of the present invention.

[0038] like Figure 1 As shown, the present invention is a three-phase voltage imbalance control device based on voltage dynamic compensation, which is installed on a three-phase four-wire line of a distribution network, collects distribution network operation information, calculates the three-phase voltage imbalance, and dynamically compensates for the three-phase voltage imbalance at the end of the line caused by the random opening of the single-phase load of the line. The three-phase four-wire line is respectively A phase, B phase, C phase and N line, and the device includes:

[0039] A processor, a drive circuit, a PFC inductor, a switching switch, an A-phase AC voltage measurement circuit, a B-phase AC voltage measurement circuit, and a C-phase AC voltage measurement circuit; the switching switch includes an A-phase bridge arm, a B-phase bridge arm, a C-phase bridge arm, and an N-line circuit connected in parallel;

[0040] The A-phase AC voltage measurement circuit, the B-phase AC voltage measurement circuit, and the C-phase AC voltage measurement circuit are connected to the power distribution network and are used to detect voltage information of the A-phase, B-phase, and C-phase;

[0041] The A-phase AC voltage measurement circuit, the B-phase AC voltage measurement circuit, and the C-phase AC voltage measurement circuit are communicatively connected to the processor to transmit voltage information of the A-phase, B-phase, and C-phase to the processor respectively;

[0042] The A phase forms a loop through the A phase AC voltage measurement circuit, the PFC inductor, the C phase bridge arm, the N line circuit, and the N line;

[0043] The B phase forms a loop through the B phase AC voltage measurement circuit, the PFC inductor, the B phase bridge arm, the N line circuit, and the N line;

[0044] The C phase forms a loop through the C phase AC voltage measurement circuit, the PFC inductor, the A phase bridge arm, the N line circuit, and the N line;

[0045] The processor is connected to the switch via a driving circuit.

[0046] The A-phase bridge arm, the B-phase bridge arm, and the C-phase bridge arm are each composed of two IGBT tubes connected in series, and the two IGBT tube connection points are respectively connected to the A-phase AC voltage measurement circuit, the B-phase AC voltage measurement circuit, and the C-phase AC voltage measurement circuit. The N-line circuit includes two capacitors connected in series, and the connection point of the two capacitors is connected to the N line. The processor is respectively connected to the A-phase bridge arm, the B-phase bridge arm, and the C-phase bridge arm of the switching switch through the driving circuit to control the opening and closing of the IGBT tube.

[0047] The working principle of the device of the present invention is described as follows:

[0048] The device of the present invention detects the voltage information of phase A, phase B and phase C (hereinafter referred to as three phases) through voltage sampling. If the processor determines that the voltage difference of the three phases exceeds the preset value, it is determined that the three phase voltage is unbalanced. Then the processor intelligently controls the energy transfer between the A, B, and C three-phase bridge arms connected to the grid to achieve the purpose of regulating the voltage. Figure 2 As shown, the load is considered to be a constant impedance load, and the line impedance is , load impedance For the heavily loaded phase, the voltage change on the line after compensation is , the voltage change on the load after compensation is ,in , the change in device current after compensation is , so we have:

[0049]

[0050] and then, Since the right side of the formula is greater than 0, the change in the overloaded phase voltage after compensation is greater than 0. Therefore, the three-phase unbalanced control equipment has a certain lifting effect on the overloaded phase voltage.

[0051] Control block diagram Figure 3 The detected value of the three-phase voltage of the power grid is compared with the target set value, and the required compensation current value is generated through PI control.

[0052] For example: when the three-phase voltage is unbalanced, and the voltage of phase A is greater than the voltage of phase B and greater than the voltage of phase C, it turns out that the voltage of phase C is low due to excessive load. When the processor determines that the three-phase voltage is unbalanced, the processor will draw current from phase A to phase C for compensation, thereby reducing the current of the phase C line to achieve the goal of raising the voltage of phase C, and ultimately achieve three-phase voltage balance, solving the problem of low voltage in a certain phase caused by unbalanced three-phase load.

[0053] The above are preferred embodiments of the present invention. Any changes made according to the technical solution of the present invention, as long as the resulting functions do not exceed the scope of the technical solution of the present invention, belong to the protection scope of the present invention.

Claims

1. A three-phase voltage unbalance control device based on voltage dynamic compensation, characterized in that: It is installed on the three-phase four-wire line of the distribution network, collects the operation information of the distribution network, calculates the three-phase voltage imbalance, and dynamically compensates for the three-phase voltage imbalance at the end of the line caused by the random opening of the single-phase load of the line. The three-phase four-wire line is composed of phase A, phase B, phase C and line N. The device includes: A processor, a drive circuit, a PFC inductor, a switching switch, an A-phase AC voltage measurement circuit, a B-phase AC voltage measurement circuit, and a C-phase AC voltage measurement circuit; the switching switch includes an A-phase bridge arm, a B-phase bridge arm, a C-phase bridge arm, and an N-line circuit connected in parallel; The A-phase AC voltage measurement circuit, the B-phase AC voltage measurement circuit, and the C-phase AC voltage measurement circuit are connected to the power distribution network and are used to detect voltage information of the A-phase, B-phase, and C-phase; The A-phase AC voltage measurement circuit, the B-phase AC voltage measurement circuit, and the C-phase AC voltage measurement circuit are communicatively connected to the processor to transmit voltage information of the A-phase, B-phase, and C-phase to the processor respectively; The A phase forms a loop through the A phase AC voltage measurement circuit, the PFC inductor, the C phase bridge arm, the N line circuit, and the N line; The B phase forms a loop through the B phase AC voltage measurement circuit, the PFC inductor, the B phase bridge arm, the N line circuit, and the N line; The C phase forms a loop through the C phase AC voltage measurement circuit, the PFC inductor, the A phase bridge arm, the N line circuit, and the N line; The processor is connected to the switch via a driving circuit; The three-phase voltage unbalance control method of the three-phase voltage unbalance control device based on voltage dynamic compensation is: By detecting the voltage information of phase A, phase B and phase C, the processor determines that the three-phase voltage difference exceeds the preset value, and then determines that the three-phase voltage is unbalanced. Then the processor intelligently controls the energy transfer between the A, B, and C three-phase bridge arms connected to the grid to achieve the purpose of regulating the voltage. Specifically: Consider the load as a constant impedance load, the line impedance is Load impedance For the heavily loaded phase, the voltage change on the line after compensation is The voltage change on the load after compensation is in The change in device current after compensation is So we have: and then, Since the right side of the formula is greater than 0, the voltage change of the overloaded phase after compensation is greater than 0, so the three-phase voltage unbalance control device has a lifting effect on the voltage of the overloaded phase; The detected value of the three-phase voltage of the power grid is compared with the target set value, and the required compensation current value is generated through PI control; when the three-phase voltage is unbalanced, and assuming that the voltage of phase A is greater than the voltage of phase B and greater than the voltage of phase C, the voltage of phase C is too low due to excessive load. When the processor determines that the three-phase voltage is unbalanced, the processor will draw current from phase A to phase C for compensation, reducing the current of the phase C line to achieve the goal of raising the voltage of phase C, and finally achieving three-phase voltage balance, solving the problem of low voltage of a phase caused by unbalanced three-phase load, and the same applies to other situations.

2. A three-phase voltage unbalance control device based on voltage dynamic compensation according to claim 1, characterized in that: The A-phase bridge arm, the B-phase bridge arm and the C-phase bridge arm are all composed of two IGBT tubes connected in series, and the two IGBT tube connection points are respectively connected to the A-phase AC voltage measurement circuit, the B-phase AC voltage measurement circuit and the C-phase AC voltage measurement circuit.

3. The three-phase voltage unbalance control device based on voltage dynamic compensation according to claim 1 is characterized in that: The N-line circuit includes two capacitors connected in series, and a connection point of the two capacitors is connected to the N-line.

4. The three-phase voltage unbalance control device based on voltage dynamic compensation according to claim 1 is characterized in that: The processor is respectively connected to the A-phase bridge arm, the B-phase bridge arm and the C-phase bridge arm of the switching switch via the driving circuit to control the opening and closing of the IGBT tube.

5. A three-phase voltage unbalance control method based on voltage dynamic compensation, characterized in that: The steps include: S1, detect the voltage information of phase A, phase B and phase C; S2. If the processor determines that the three-phase voltage difference exceeds a preset value, it is determined that the three-phase voltage is unbalanced. Then the processor performs inter-phase current transfer according to the voltage imbalance to achieve the goal of voltage balance at the terminal installation point; The specific implementation is as follows: Consider the load as a constant impedance load, the line impedance is Load impedance For the heavily loaded phase, the voltage change on the line after compensation is The voltage change on the load after compensation is in The change in device current after compensation is So we have: and then, Since the right side of the formula is greater than 0, the voltage change of the overloaded phase after compensation is greater than 0, so the three-phase voltage unbalance control device has a lifting effect on the voltage of the overloaded phase; The detected value of the three-phase voltage of the power grid is compared with the target set value, and the required compensation current value is generated through PI control; when the three-phase voltage is unbalanced, and assuming that the voltage of phase A is greater than the voltage of phase B and greater than the voltage of phase C, the voltage of phase C is too low due to excessive load. When the processor determines that the three-phase voltage is unbalanced, the processor will draw current from phase A to phase C for compensation, reducing the current of the phase C line to achieve the goal of raising the voltage of phase C, and finally achieving three-phase voltage balance, solving the problem of low voltage of a phase caused by unbalanced three-phase load, and the same applies to other situations.

6. A three-phase voltage unbalance control method based on voltage dynamic compensation according to claim 5, characterized in that: The method is based on the device described in any one of claims 1-4, and can effectively perform unbalanced current compensation; there is no need to install additional current transformers for analyzing the three-phase current of the load, which greatly reduces the installation workload of the equipment and saves the overall investment cost of the equipment; and the equipment is connected to the grid in parallel, which can achieve installation without power outages and save management costs.

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