System and method for regulating unbalanced current of distribution transformer capacity expansion and split-phase output

Abstract

The embodiment of the application discloses a power distribution transformer capacity increasing and unbalanced current adjusting system and method for split-phase output, wherein the power distribution transformer capacity increasing and unbalanced current adjusting system for split-phase output is provided with a single-phase transformer, a single-phase bridge rectifier and a three-phase full-bridge inverter, the high-voltage side of the single-phase transformer is connected to the high-voltage side of the power distribution transformer, the single-phase bridge rectifier connected to the low-voltage side of the single-phase transformer converts alternating current from the single-phase transformer into direct current to supply the three-phase full-bridge inverter, the three-phase full-bridge inverter is connected to three-phase lines through a three-phase reactor, three-phase negative sequence currents and three-phase zero sequence currents are obtained by sequentially decomposing and processing three-phase load currents, three-phase reference currents are calculated by combining capacitor voltage control components, hysteresis loop control is performed on the three-phase reference currents, corresponding three-phase compensation currents are output to each phase of the three-phase lines through the three-phase full-bridge inverter, and thus three-phase unbalanced current adjustment is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to an unbalanced current regulation system and method for capacity increase and phase-split output of a distribution transformer. Background Art

[0002] With the advancement of new power system construction, single-phase distributed power sources are being connected to a large number of substations. Due to the random and intermittent nature of distributed power sources and household single-phase loads, as well as different electricity usage habits of users, the irregular switching on and off of distributed power sources and single-phase loads makes it difficult to achieve balanced load current distribution among the three phases A, B, and C of the distribution transformer. This can cause severe overload on one phase, seriously shortening the service life of the distribution transformer and even causing it to burn out.

[0003] In the prior art, a master controller controls phase-changing switches to adjust the load-side current to achieve optimal three-phase distribution of the user's load. However, this approach lacks stepless regulation and cannot fully achieve three-phase current balance. Therefore, achieving full three-phase current balance in distribution transformers has become a pressing technical challenge for those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides a system and method for regulating unbalanced current for capacity expansion and phase-splitting output of distribution transformers, which are used to solve the problems of insufficient capacity of distribution transformers and unbalanced three-phase current in the prior art. In addition, the connection of single-phase transformers can also achieve capacity expansion of distribution transformers.

[0005] To achieve one, part, or all of the above objectives or other objectives, in a first aspect, the present invention is applied to a power distribution system, the power distribution system comprising a distribution transformer and a phase a line, a phase b line, a phase c line, and a neutral line n connected to a low-voltage side of the distribution transformer;

[0006] The embodiment of the present invention provides a system and method for regulating unbalanced current for increasing the capacity of a distribution transformer and outputting split-phase output, including:

[0007] A single-phase transformer, the input end of which is connected to any two phases of the three-phase line on the high-voltage side of the distribution transformer. The single-phase transformer is used to convert the high voltage of the distribution transformer into a low voltage. The single-phase transformer is also used to increase the capacity of the substation. The increased capacity of the substation is the capacity of the single-phase transformer. The capacity of the single-phase transformer is determined by the load size of the distribution transformer.

[0008] A single-phase bridge rectifier, comprising a rectifier input, a DC positive output, and a DC negative output. The rectifier input is connected to the output of the single-phase transformer. The single-phase bridge rectifier is used to convert the AC power on the low-voltage side of the single-phase transformer into DC power, and can also invert DC power into AC power for transmission to the power grid.

[0009] A three-phase full-bridge inverter, comprising a positive inverter input terminal, a negative inverter input terminal, and an inverter output terminal, wherein the positive inverter input terminal is connected to the DC positive output terminal, the negative inverter input terminal is connected to the DC negative output terminal, and the inverter output terminal is connected to the a-phase line, the b-phase line, and the c-phase line respectively through a three-phase reactor; the three-phase full-bridge inverter is configured to output corresponding compensation currents to the a-phase line, the b-phase line, and the c-phase line respectively through the three-phase reactor to perform three-phase unbalanced current regulation;

[0010] A first filter capacitor is connected to the positive inverter input terminal and the DC positive output terminal;

[0011] A second filter capacitor is connected in series with the first filter capacitor, and the second filter capacitor is connected to the negative inverter input terminal and the DC negative output terminal, and the neutral line n is connected between the first filter capacitor and the second filter capacitor.

[0012] In a second aspect, an embodiment of the present invention further provides a method for regulating unbalanced current for capacity expansion and phase-splitting output of a distribution transformer, which is applied to the unbalanced current regulation system for capacity expansion and phase-splitting output of a distribution transformer as described in the embodiment of the first aspect above. The method for regulating unbalanced current for capacity expansion and phase-splitting output of a distribution transformer includes:

[0013] Obtaining an initial unbalance degree according to the a-phase load current of the a-phase line, the b-phase load current of the b-phase line, and the c-phase load current of the c-phase line;

[0014] When the initial unbalance degree is greater than a preset starting value, performing sequence component decomposition processing on the a-phase load current, the b-phase load current, and the c-phase load current to obtain corresponding a-phase negative-sequence current, b-phase negative-sequence current, and c-phase negative-sequence current, as well as a-phase zero-sequence current, b-phase zero-sequence current, and c-phase zero-sequence current;

[0015] The a-phase capacitor voltage control component, the b-phase capacitor voltage control component, and the c-phase capacitor voltage control component are calculated based on the voltage between the positive and negative ends of the first filter capacitor and the second filter capacitor after being connected in series and a preset reference voltage;

[0016] obtain a phase a compensation current reference value according to the phase a negative-sequence current, the phase a zero-sequence current, and the phase a capacitor voltage control component; obtain a phase b compensation current reference value according to the phase b negative-sequence current, the phase b zero-sequence current, and the phase b capacitor voltage control component; and obtain a phase c compensation current reference value according to the phase c negative-sequence current, the phase c zero-sequence current, and the phase c capacitor voltage control component;

[0017] The corresponding a-phase compensation current, b-phase compensation current and c-phase compensation current are output to the a-phase line, the b-phase line and the c-phase line respectively, and the output a-phase compensation current, the b-phase compensation current and the c-phase compensation current are made to track the a-phase compensation current reference value, the b-phase compensation current reference value and the c-phase compensation current reference value respectively through hysteresis control, so as to adjust the unbalanced current in phases.

[0018] Preferably, the method for regulating unbalanced current of distribution transformer capacity increase and phase-splitting output in the embodiment of the present invention further includes: obtaining a current unbalance degree, wherein the current unbalance degree is obtained by the current a-phase load current, the b-phase load current, and the c-phase load current;

[0019] Obtaining an imbalance change amplitude according to the initial imbalance and the current imbalance;

[0020] When the imbalance degree change amplitude reaches a preset offset value, three-phase unbalanced current adjustment is performed according to the current a-phase load current, the b-phase load current, the c-phase load current, the a-phase capacitor voltage control component, the b-phase capacitor voltage control component and the c-phase capacitor voltage control component.

[0021] Preferably, the calculation of the a-phase capacitor voltage control component, the b-phase capacitor voltage control component, and the c-phase capacitor voltage control component based on the voltage between the positive and negative ends of the first filter capacitor and the second filter capacitor connected in series and a preset reference voltage includes:

[0022] Acquire a filter voltage, where the filter voltage is used to represent a voltage between a positive terminal and a negative terminal of the first filter capacitor and the second filter capacitor connected in series;

[0023] Calculating the difference between the filtered voltage and a preset voltage reference value to obtain a capacitor voltage difference;

[0024] Obtaining a D-axis active component required for phase coordinate transformation processing according to the capacitor voltage difference;

[0025] Phase coordinate transformation processing is performed according to the D-axis active component and the preset Q-axis reactive component to obtain the a-phase capacitor voltage control component, the b-phase capacitor voltage control component and the c-phase capacitor voltage control component, wherein the Q-axis reactive component is preset to zero.

[0026] Preferably, the unbalanced current regulation system for capacity expansion and phase-splitting output of the distribution transformer further includes a PI controller, and the D-axis active component required for phase coordinate transformation processing is obtained according to the capacitor voltage difference, including:

[0027] The capacitor voltage difference is input into the PI controller to obtain the D-axis active component required for phase coordinate transformation processing.

[0028] Preferably, the a-phase compensation current reference value is obtained according to the a-phase negative-sequence current, the a-phase zero-sequence current and the a-phase capacitor voltage control component, the b-phase compensation current reference value is obtained according to the b-phase negative-sequence current, the b-phase zero-sequence current and the b-phase capacitor voltage control component, and the c-phase compensation current reference value is obtained according to the c-phase negative-sequence current, the c-phase zero-sequence current and the c-phase capacitor voltage control component, in accordance with the following formula:

[0029]

[0030]

[0031]

[0032] Among them, I a_ref Indicates the a-phase compensation current reference value, I b_ref Indicates the b-phase compensation current reference value, I c_ref Indicates the reference value of the phase C compensation current; represents the negative sequence current of phase a, represents the negative sequence current of phase b, Represents the negative sequence current of phase c; I a * represents the a-phase capacitor voltage control component, I b * represents the b-phase capacitor voltage control component, I c * represents the c-phase capacitor voltage control component.

[0033] Preferably, the unbalanced current regulation system for capacity increase and phase-split output of the distribution transformer further includes a hysteresis controller, and the inverter output end includes an inverter a-phase output end, an inverter b-phase output end, and an inverter c-phase output end;

[0034] The method further comprises:

[0035] Calculating the difference between the a-phase compensation current reference value and the a-phase compensation current to obtain an a-phase compensation current difference value, calculating the difference between the b-phase compensation current reference value and the b-phase compensation current to obtain a b-phase compensation current difference value, and calculating the difference between the c-phase compensation current reference value and the c-phase compensation current to obtain a c-phase compensation current difference value;

[0036] Inputting the a-phase compensation current difference, the b-phase compensation current difference, and the c-phase compensation current difference into the hysteresis controller to obtain a switching signal of the three-phase full-bridge inverter;

[0037] Controlling the three-phase full-bridge inverter to output a-phase output current, b-phase output current, and c-phase output current to the three-phase reactor through the inverter a-phase output terminal, the inverter b-phase output terminal, and the inverter c-phase output terminal according to the switching signal;

[0038] The three-phase reactor outputs the corresponding a-phase compensation current, b-phase compensation current and c-phase compensation current to the a-phase line, the b-phase line and the c-phase line respectively according to the a-phase output current, the b-phase output current and the c-phase output current to perform three-phase imbalance control.

[0039] Preferably, a method for regulating unbalanced current of a distribution transformer with capacity increase and phase-splitting output according to an embodiment of the present invention further includes:

[0040] When the three-phase load of the distribution transformer is balanced, the three-phase full-bridge inverter is controlled to output the same current to the a-phase line, the b-phase line and the c-phase line respectively, so as to provide electric energy for the load on the low-voltage side of the distribution transformer.

[0041] In a third aspect, an embodiment of the present invention further provides a computer device, including:

[0042] at least one memory;

[0043] at least one processor;

[0044] at least one computer program;

[0045] The computer program is stored in the memory, and the processor executes at least one computer program to implement:

[0046] As described in the above-mentioned method of the second aspect embodiment.

[0047] In a fourth aspect, an embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, wherein the computer-executable instructions are used to cause a computer to execute:

[0048] As described in the above-mentioned second aspect embodiment.

[0049] The implementation of the present invention will have the following beneficial effects:

[0050] The unbalanced current regulation system for capacity expansion and phase-split output of a distribution transformer in an embodiment of the present invention is provided with a single-phase transformer, a single-phase bridge rectifier and a three-phase full-bridge inverter. The high-voltage side of the single-phase transformer is connected to the high-voltage side of the distribution transformer. The single-phase bridge rectifier connected to the low-voltage side of the single-phase transformer converts the alternating current from the single-phase transformer into direct current to supply the three-phase full-bridge inverter. The three-phase full-bridge inverter is connected to the three-phase line through a three-phase reactor. The three-phase load current is decomposed by sequence components to obtain three-phase negative-sequence current and three-phase zero-sequence current. Then, combined with the capacitor voltage control component, a three-phase reference current is calculated. The three-phase reference current is then hysteresis controlled to output a corresponding three-phase compensation current to each phase of the three-phase line through the three-phase full-bridge inverter to achieve three-phase current imbalance regulation, thereby accurately suppressing the negative-sequence current generated by the system and the zero-sequence current on the neutral line, effectively solving the three-phase imbalance problem, greatly reducing the loss of the transmission line, and improving the power quality of the system. And because the single-phase bridge rectifier obtains power from the high-voltage side of the distribution transformer through a single-phase transformer alone, when the three-phase load of the distribution transformer is balanced, the three-phase full-bridge inverter can also be used as a power supply to supply power to the load on the low-voltage side of the distribution transformer, thereby maximizing the utilization of equipment capacity and improving the economy of the system.

[0051] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained through the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] 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.

[0053] in:

[0054] Figure 1 A schematic diagram of the circuit structure of an unbalanced current regulation system for increasing the capacity of a distribution transformer and outputting split-phase power in one embodiment;

[0055] Figure 2 A flow chart of a method for regulating unbalanced current of a distribution transformer with increased capacity and split-phase output in one embodiment;

[0056] Figure 3 A flow chart of a method for regulating unbalanced current in a distribution transformer with increased capacity and split-phase output in another embodiment;

[0057] Figure 4 A flow chart of a method for regulating unbalanced current in a distribution transformer with increased capacity and split-phase output in another embodiment;

[0058] Figure 5 A flow chart of a method for regulating unbalanced current in a distribution transformer with increased capacity and split-phase output in another embodiment;

[0059] Figure 6 1 is a waveform diagram of three-phase unbalanced current on the load side in one embodiment;

[0060] Figure 7 is a current waveform diagram output by a three-phase full-bridge inverter in one embodiment;

[0061] Figure 8 This is a current waveform diagram of a target current after adjustment using the unbalanced current adjustment method for capacity increase and phase-splitting output of a distribution transformer provided by the present invention in one embodiment;

[0062] Figure 9 FIG. 1 is a structural diagram of a computer device in one embodiment. DETAILED DESCRIPTION

[0063] 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. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0064] An embodiment of the present invention provides an unbalanced current regulation system for capacity expansion and phase-split output of a distribution transformer, which is provided with a single-phase transformer, a single-phase bridge rectifier and a three-phase full-bridge inverter. The high-voltage side of the single-phase transformer is connected to the high-voltage side of the distribution transformer. The single-phase bridge rectifier connected to the low-voltage side of the single-phase transformer converts the alternating current from the single-phase transformer into direct current to supply the three-phase full-bridge inverter. The three-phase full-bridge inverter is connected to the three-phase line through a three-phase reactor. By performing sequence component decomposition processing on the three-phase load current, a three-phase negative-sequence current and a three-phase zero-sequence current are obtained. Then, combined with the capacitor voltage control component, a three-phase reference current is calculated. The three-phase reference current is then hysteresis controlled to output a corresponding three-phase compensation current to each phase of the three-phase line through the three-phase full-bridge inverter to achieve three-phase current imbalance regulation, thereby accurately suppressing the negative-sequence current generated by the system and the zero-sequence current on the neutral line, effectively solving the three-phase imbalance problem, greatly reducing the loss of the transmission line, and improving the power quality of the system. And because the single-phase bridge rectifier obtains power from the high-voltage side of the distribution transformer through a single-phase transformer alone, when the three-phase load of the distribution transformer is balanced, the three-phase full-bridge inverter can also be used as a power supply to supply power to the load on the low-voltage side of the distribution transformer, thereby maximizing the utilization of equipment capacity and improving the economy of the system.

[0065] To facilitate understanding, embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0066] Please refer to Figure 1 , Figure 1 The figure is a schematic diagram of the circuit structure of an unbalanced current regulation system for increasing the capacity of a distribution transformer and providing split-phase output, provided in an embodiment of the present invention. Specifically, the unbalanced current regulation system for increasing the capacity of a distribution transformer and providing split-phase output is applied to a power distribution system, which includes a distribution transformer and phase lines a, b, and c, as well as a neutral line n, connected to the low-voltage side of the distribution transformer, i.e., the load side of the distribution system.

[0067] Specifically, the unbalanced current regulation system for capacity increase and phase-splitting output of the distribution transformer includes a single-phase transformer 1, a single-phase bridge rectifier 2, a three-phase full-bridge inverter 5, a three-phase reactor 6, a first filter capacitor 3 and a second filter capacitor 4;

[0068] Specifically, the input end of the single-phase transformer 1 is connected to any two phases of the three-phase line on the high-voltage side of the distribution transformer. The single-phase transformer 1 is used to convert the high voltage of the distribution transformer into a low voltage. The single-phase transformer 1 is also used to increase the capacity of the substation corresponding to the distribution transformer. The capacity of the substation increased is the capacity of the single-phase transformer 1. The capacity of the single-phase transformer 1 is determined by the load size of the distribution transformer.

[0069] Specifically, the single-phase bridge rectifier 2 includes a rectifier input terminal, a DC positive output terminal, and a DC negative output terminal. The rectifier input terminal is connected to the output terminal of the single-phase transformer 1. The single-phase bridge rectifier 2 is used to convert the AC power from the single-phase transformer 1 into DC power for output, and can also invert DC power into AC power and transmit it to the power grid, that is, to the high-voltage side of the distribution transformer.

[0070] Specifically, the three-phase full-bridge inverter 5 is provided with a positive inverter input terminal, a negative inverter input terminal, and an inverter output terminal. The positive inverter input terminal is connected to the DC positive output terminal, the negative inverter input terminal is connected to the DC negative output terminal, and the inverter output terminal is connected to the a-phase line, the b-phase line, and the c-phase line respectively through the three-phase reactor 6. The three-phase full-bridge inverter 5 is used to output corresponding compensation currents to the a-phase line, the b-phase line, and the c-phase line respectively through the three-phase reactor 6 to perform three-phase unbalanced current regulation.

[0071] A first filter capacitor 3 is connected to the positive inverter input terminal and the DC positive output terminal;

[0072] The second filter capacitor 4 is connected in series with the first filter capacitor 3 , and the second filter capacitor 4 is connected to the negative inverter input terminal and the DC negative output terminal, and the neutral line n is connected between the first filter capacitor 3 and the second filter capacitor 4 .

[0073] The single-phase transformer 1 can draw power from the high-voltage side of the distribution transformer, so that the single-phase bridge uncontrolled rectifier connected to the single-phase transformer 1 can convert the AC power from the single-phase transformer 1 into DC power to supply the three-phase full-bridge inverter 5. The three-phase full-bridge inverter 5 is connected to the three-phase line through the three-phase reactor 6. When the imbalance corresponding to the three-phase line is greater than the preset starting value, the three-phase load current is decomposed into sequence components to obtain a three-phase negative-sequence current and a three-phase zero-sequence current; based on the three-phase negative-sequence current, the three-phase zero-sequence current and the capacitor voltage control component, the three-phase reference current is calculated, and then the three-phase reference current is hysteresis controlled to output the corresponding three-phase compensation current to each phase of the three-phase line through the three-phase full-bridge inverter 5 to achieve three-phase current imbalance regulation, thereby accurately suppressing the negative-sequence current generated by the system and the zero-sequence current on the neutral line, effectively solving the three-phase imbalance problem, greatly reducing the loss of the transmission line, and improving the system power quality. And because the single-phase bridge rectifier 2 obtains power from the high-voltage side of the distribution transformer alone through the single-phase transformer 1, when the three-phase load of the distribution transformer is balanced, the three-phase full-bridge inverter 5 can also be used as a power source to supply power to the load on the low-voltage side of the distribution transformer, thereby maximizing the utilization of the equipment capacity and improving the economy of the system.

[0074] In one embodiment, when the load currents of the three-phase lines are balanced, the three-phase full-bridge inverter 5 outputs equal power to the three-phase lines.

[0075] It should be noted that in the embodiment of the present invention, the capacitance values ​​of the first filter capacitor 3 and the second filter capacitor 4 are selected according to actual conditions, and the inductance value of the three-phase reactor 6 is selected according to actual conditions. This application does not impose any specific restrictions on this.

[0076] The unbalanced current regulation system for capacity increase and phase-splitting output of distribution transformers and the application scenarios described in the embodiments of the present invention are intended to more clearly illustrate the technical solutions of the embodiments of the present invention, and do not constitute a limitation on the technical solutions provided by the embodiments of the present invention. Those skilled in the art will appreciate that with the evolution of the distribution system and the emergence of new application scenarios, the technical solutions provided by the embodiments of the present invention are equally applicable to similar technical problems.

[0077] It will be understood by those skilled in the art that Figure 1 The unbalanced current regulation system for increasing the capacity of the distribution transformer and outputting split-phase output shown in the figure does not constitute a limitation on the embodiments of the present invention, and may include more or fewer components than shown in the figure, or combine certain components, or arrange the components differently.

[0078] Reference Figure 2 The embodiment of the present invention proposes a method for regulating unbalanced current of distribution transformer capacity increase and phase output, the method for regulating unbalanced current of distribution transformer capacity increase and phase output includes but is not limited to steps S100 to S600. Figure 1 The unbalanced current regulation method for distribution transformer capacity increase and phase-splitting output is described in detail.

[0079] Step S100, obtaining an initial unbalance degree according to the a-phase load current of the a-phase line, the b-phase load current of the b-phase line, and the c-phase load current of the c-phase line;

[0080] Step S200, when the initial unbalance is greater than a preset starting value, performing sequence component decomposition processing on the load current of phase a, the load current of phase b, and the load current of phase c to obtain the corresponding negative-sequence current of phase a, the negative-sequence current of phase b, and the negative-sequence current of phase c, as well as the zero-sequence current of phase a, the zero-sequence current of phase b, and the zero-sequence current of phase c;

[0081] Step S300, calculating the a-phase capacitor voltage control component, the b-phase capacitor voltage control component, and the c-phase capacitor voltage control component based on the voltage between the positive and negative ends of the first filter capacitor and the second filter capacitor connected in series and a preset reference voltage;

[0082] Step S400, obtaining a phase a compensation current reference value based on the phase a negative-sequence current, the phase a zero-sequence current, and the phase a capacitor voltage control component, obtaining a phase b compensation current reference value based on the phase b negative-sequence current, the phase b zero-sequence current, and the phase b capacitor voltage control component, and obtaining a phase c compensation current reference value based on the phase c negative-sequence current, the phase c zero-sequence current, and the phase c capacitor voltage control component;

[0083] Step S500, obtaining a phase a modulation voltage according to a phase a compensation current reference value and a currently output phase a compensation current, obtaining a phase b modulation voltage according to a phase b compensation current reference value and a currently output phase b compensation current, and obtaining a phase c modulation voltage according to a phase c compensation current reference value and a currently output phase c compensation current;

[0084] In step S600, the corresponding a-phase compensation current, b-phase compensation current and c-phase compensation current are output to the a-phase line, b-phase line and c-phase line respectively, and the output a-phase compensation current, b-phase compensation current and c-phase compensation current are made to track the a-phase compensation current reference value, b-phase compensation current reference value and c-phase compensation current reference value respectively through hysteresis control to adjust the unbalanced current in phases.

[0085] Specifically, in this embodiment, when the initial imbalance is greater than the preset starting value, it indicates that the three-phase load of the distribution transformer is unbalanced. In this case, the three-phase load current is decomposed into current sequence components, and the three-phase negative-sequence current and three-phase zero-sequence current on the low-voltage side of the distribution transformer, that is, the load side, are calculated to determine the three-phase negative-sequence current component and three-phase zero-sequence current component that require imbalance compensation. Then, based on the three-phase negative-sequence current, three-phase zero-sequence current and capacitor voltage control component, the three-phase compensation current reference value is calculated. By making the three-phase current output by the three-phase full-bridge inverter to the three-phase line on the low-voltage side of the distribution transformer track the three-phase compensation current reference value, three-phase balance of the current is achieved.

[0086] Reference Figure 3 The method for regulating unbalanced current of distribution transformer capacity increase and phase-splitting output in the embodiment of the present invention further includes steps S700 to S900:

[0087] Step S700, obtaining a current imbalance, where the current imbalance is obtained from the current a-phase load current, b-phase load current, and c-phase load current;

[0088] Step S800, obtaining the imbalance change range according to the initial imbalance and the current imbalance;

[0089] Step S900: When the imbalance degree variation reaches a preset offset value, the three-phase unbalanced current is adjusted according to the current a-phase load current, b-phase load current, c-phase load current, a-phase capacitor voltage control component, b-phase capacitor voltage control component and c-phase capacitor voltage control component.

[0090] By detecting the current imbalance multiple times during the adjustment process, the compensation current reference value can be iterated to adapt to the imbalance situation in the current situation, thereby making the adjustment process more accurate.

[0091] Reference Figure 4 Step S300 also includes but is not limited to steps S310 to S340:

[0092] Step S310: obtaining a filter voltage, where the filter voltage is used to represent the voltage between the positive terminal and the negative terminal of the first filter capacitor and the second filter capacitor connected in series;

[0093] Step S320, calculating the difference between the filtered voltage and a preset voltage reference value to obtain a capacitor voltage difference;

[0094] Step S330, obtaining the D-axis active component required for phase coordinate transformation processing according to the capacitor voltage difference;

[0095] Step S340 , performing phase coordinate transformation processing according to the D-axis active component and the preset Q-axis reactive component to obtain the a-phase capacitor voltage control component, the b-phase capacitor voltage control component and the c-phase capacitor voltage control component, wherein the Q-axis reactive component is preset to zero.

[0096] Specifically, the filter voltage is the voltage difference between the positive and negative terminals of the first filter capacitor and the second filter capacitor connected in series, and is expressed as U dc The preset voltage reference value is the voltage reference value of the positive and negative terminals of the first filter capacitor and the second filter capacitor connected in series, and is represented by U dc_ref Representation. Calculate the difference between the filtered voltage and the preset voltage reference value to obtain a reference voltage difference, and input the obtained reference voltage difference into the PI controller to obtain the active component parameter. The active component parameter is used to characterize the d-axis active component required for the phase coordinate transformation process; then perform dq / abc coordinate transformation based on the active component parameter and the preset reactive component parameter to obtain the capacitor voltage control component, wherein the reactive component parameter is used to characterize the q-axis reactive component required for the phase coordinate transformation process, and the reactive component parameter is set to 0. After dq / abc transformation, the capacitor voltage control component is obtained.

[0097] Specifically, Park's Transformation is used to perform dq / abc conversion processing.

[0098] In one embodiment, a system for phase-splitting control of unbalanced current of a distribution transformer according to an embodiment of the present invention is further provided with a hysteresis controller for sending a switching signal to a three-phase full-bridge inverter, and the three-phase full-bridge inverter tracks a compensation current reference value according to the switching signal.

[0099] In one embodiment, a system for phase-by-phase regulation of unbalanced current in a distribution transformer according to an embodiment of the present invention is further provided with a linear controller.

[0100] Specifically, the linear controller adopts a proportional integral (PI) controller to adjust the capacitor voltage difference through the PI controller to obtain the D-axis active component required for the phase coordinate transformation process.

[0101] Specifically, the unbalanced current regulation system for capacity expansion and phase-splitting output of the distribution transformer also includes a PI controller, which obtains the D-axis active component required for phase coordinate transformation processing based on the capacitor voltage difference, including inputting the capacitor voltage difference into the PI controller to obtain the D-axis active component required for phase coordinate transformation processing.

[0102] In one embodiment, the negative-sequence and zero-sequence currents are superimposed on the capacitor voltage control components Ia*, Ib*, and Ic* to obtain compensation current reference values ​​Ia_ref, Ib_ref, and Ic_ref; and the actual output compensation currents Ioa, Iob, and Ioc are obtained by making the actual compensation current output by the three-phase full-bridge inverter track the compensation current reference values ​​Ia_ref, Ib_ref, and Ic_ref.

[0103] Specifically, the a-phase compensation current reference value is obtained according to the a-phase negative-sequence current, the a-phase zero-sequence current, and the a-phase capacitor voltage control component; the b-phase compensation current reference value is obtained according to the b-phase negative-sequence current, the b-phase zero-sequence current, and the b-phase capacitor voltage control component; and the c-phase compensation current reference value is obtained according to the c-phase negative-sequence current, the c-phase zero-sequence current, and the c-phase capacitor voltage control component, in accordance with the following formula:

[0104]

[0105]

[0106]

[0107] Among them, I a_ref Indicates the reference value of phase a compensation current, I b_ref Indicates the reference value of phase b compensation current, I c_ref Indicates the reference value of phase C compensation current; Indicates the negative sequence current of phase a, Indicates the negative sequence current of phase b, Indicates the negative sequence current of phase c; I a * represents the a-phase capacitor voltage control component, I b * represents the b-phase capacitor voltage control component, I c* Represents the c-phase capacitor voltage control component.

[0108] In one embodiment, the unbalanced current regulation system for distribution transformer capacity expansion and phase-splitting output further includes a hysteresis controller.

[0109] Reference Figure 5 A method for controlling unbalanced current of a distribution transformer by phase separation according to an embodiment of the present invention further includes steps S1000 to S1300:

[0110] Step S1000, calculating the difference between the a-phase compensation current reference value and the a-phase compensation current to obtain the a-phase compensation current difference, calculating the difference between the b-phase compensation current reference value and the b-phase compensation current to obtain the b-phase compensation current difference, calculating the difference between the c-phase compensation current reference value and the c-phase compensation current to obtain the c-phase compensation current difference;

[0111] Step S1100, inputting the a-phase compensation current difference, the b-phase compensation current difference, and the c-phase compensation current difference into a hysteresis controller to obtain a switching signal of a three-phase full-bridge inverter;

[0112] Step S1200, controlling the three-phase full-bridge inverter to output phase a output current, phase b output current, and phase c output current to the three-phase reactor through the inverter phase a output terminal, the inverter phase b output terminal, and the inverter phase c output terminal according to the switching signal;

[0113] In step S1300, the three-phase reactor outputs corresponding a-phase compensation current, b-phase compensation current and c-phase compensation current to the a-phase line, b-phase line and c-phase line respectively according to the a-phase output current, b-phase output current and c-phase output current to perform three-phase imbalance control.

[0114] Specifically, the switching signal of the three-phase full-bridge inverter is obtained by subtracting Ia_ref from Ioa, Ib_ref ​​from Iob, and Ic_ref from Ioc, and the differences are respectively sent to the hysteresis controller. The hysteresis controller outputs the switching signal of the three-phase full-bridge inverter, thereby being able to track the current reference values ​​Ia_ref, Ib_ref, and Ic_ref through hysteresis control to output the actual compensation currents Ioa, Iob, and Ioc.

[0115] In some embodiments, when the three-phase load of the distribution transformer is balanced, the three-phase full-bridge inverter is controlled to output the same current to the a-phase line, the b-phase line and the c-phase line respectively to provide electrical energy to the load on the low-voltage side of the distribution transformer. Since the single-phase bridge rectifier obtains power from the high-voltage side of the distribution transformer through the single-phase transformer alone, when the three-phase load of the distribution transformer is balanced, the three-phase full-bridge inverter can also be used as a power source to supply power to the load on the low-voltage side of the distribution transformer, thereby maximizing the utilization of equipment capacity and improving the economy of the system.

[0116] Please refer to Figure 6 to Figure 8 ,in, Figure 6 is a waveform diagram of the three-phase unbalanced current on the load side in one embodiment, Figure 7 is a current waveform diagram output by a three-phase full-bridge inverter in one embodiment, Figure 8 The figure is a current waveform diagram of the target current after being adjusted using the unbalanced current adjustment method for increasing the capacity of the distribution transformer and outputting split-phase in one embodiment of the present invention.

[0117] Depend on Figure 6 It can be calculated that the current imbalance of the three-phase initial current is 66.6%. Figure 8 The current imbalance of the target current can be calculated to be 1.2%. Therefore, the unbalanced current regulation method for distribution transformer capacity increase and phase-splitting output proposed in the embodiment of the present invention can fully achieve three-phase current balance, solving the problem of three-phase current imbalance in the prior art.

[0118] Based on Figure 1 The unbalanced current regulation system for increasing the capacity of the distribution transformer and outputting split-phase output is shown. The embodiment of the present invention also provides a computer device, including:

[0119] at least one memory;

[0120] at least one processor;

[0121] at least one program;

[0122] Programs are stored in a memory, and a processor executes at least one program to implement the above-mentioned method for increasing the capacity of a distribution transformer and regulating unbalanced current for split-phase output. The computer device can be any intelligent terminal, including a mobile phone, a tablet computer, a personal digital assistant (PDA), an in-vehicle computer, and the like.

[0123] The following combination Figure 9 The computer device according to the embodiment of the present invention is introduced in detail.

[0124] like Figure 9 , Figure 9 The hardware structure of a computer device according to another embodiment is shown. The computer device includes:

[0125] The processor 1210 may be implemented as a general-purpose central processing unit (CPU), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits, and is configured to execute relevant programs to implement the technical solutions provided in the embodiments of the present disclosure.

[0126] The memory 1220 can be implemented in the form of a read-only memory (ROM), a static storage device, a dynamic storage device, or a random access memory (RAM). The memory 1220 can store an operating system and other application programs. When the technical solutions provided in the embodiments of this specification are implemented through software or firmware, the relevant program code is stored in the memory 1220 and is called by the processor 1210 to execute the unbalanced current regulation method for increasing the capacity of the distribution transformer and split-phase output according to the embodiment of the present disclosure.

[0127] Input / output interface 1230, used for information input and output;

[0128] Communication interface 1240, used to implement communication interaction between this device and other devices, which can be achieved through wired means (such as USB, network cable, etc.) or wireless means (such as mobile network, WiFi, Bluetooth, etc.);

[0129] bus 1250 , which transmits information between various components of the device (e.g., processor 1210 , memory 1220 , input / output interface 1230 , and communication interface 1240 );

[0130] The processor 1210 , the memory 1220 , the input / output interface 1230 , and the communication interface 1240 are communicatively connected to each other within the device via a bus 1250 .

[0131] The embodiment of the present disclosure also provides a computer-readable storage medium storing computer-executable instructions for causing a computer to execute the above-mentioned method for regulating unbalanced current for capacity increase and phase-split output of a distribution transformer.

[0132] The memory, as a non-transient computer-readable storage medium, can be used to store non-transient software programs and non-transient computer executable programs. In addition, the memory may include a high-speed random access memory and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some embodiments, the memory may optionally include a memory remotely arranged relative to the processor, and these remote memories may be connected to the processor via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0133] The embodiments described in the embodiments of the present disclosure are intended to more clearly illustrate the technical solutions of the embodiments of the present disclosure and do not constitute a limitation on the technical solutions provided by the embodiments of the present disclosure. Those skilled in the art will appreciate that with the evolution of technology and the emergence of new application scenarios, the technical solutions provided by the embodiments of the present disclosure are also applicable to similar technical problems.

[0134] Those skilled in the art will understand that the technical solutions shown in the drawings do not constitute a limitation on the embodiments of the present disclosure, and may include more or fewer steps than shown in the drawings, or a combination of certain steps, or different steps.

[0135] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, i.e., they may be located in one place or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of this embodiment.

[0136] Those skilled in the art will appreciate that all or some of the steps in the methods, systems, and functional modules / units in the devices disclosed above may be implemented as software, firmware, hardware, or appropriate combinations thereof.

[0137] The terms "first", "second", "third", "fourth", etc. (if any) in the specification of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0138] It should be understood that in this application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0139] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0140] Units described as separate components may or may not be physically separate, and components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0141] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0142] The integrated unit, if implemented in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application essentially or say the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes multiple instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the embodiments of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (Read-Only Memory, ROM), a random access memory (Random Access Memory, RAM), a magnetic disk or an optical disk, and various program storage media.

[0143] The above only discloses the preferred embodiments of the present application, and of course cannot limit the scope of the rights of the present application, so the equivalent changes made according to the claims of the present application still fall within the scope of the present application.

Claims

1. An unbalanced current regulation system for increasing the capacity of a distribution transformer and performing phase-splitting output, applied to a power distribution system comprising a distribution transformer and phase lines a, b, c, and a neutral line n connected to the low-voltage side of the distribution transformer; It is characterized in that include: A single-phase transformer, the input end of which is connected to any two phases of the three-phase line on the high-voltage side of the distribution transformer. The single-phase transformer is used to convert the high voltage of the distribution transformer into a low voltage. The single-phase transformer is also used to increase the capacity of the substation. The increased capacity of the substation is the capacity of the single-phase transformer. The capacity of the single-phase transformer is determined by the load size of the distribution transformer. A single-phase bridge rectifier, comprising a rectifier input, a DC positive output, and a DC negative output. The rectifier input is connected to the output of the single-phase transformer. The single-phase bridge rectifier is used to convert the AC power on the low-voltage side of the single-phase transformer into DC power for transmission to the power grid. A three-phase full-bridge inverter, comprising a positive inverter input terminal, a negative inverter input terminal, and an inverter output terminal, wherein the positive inverter input terminal is connected to the DC positive output terminal, the negative inverter input terminal is connected to the DC negative output terminal, and the inverter output terminal is connected to the a-phase line, the b-phase line, and the c-phase line respectively through a three-phase reactor; the three-phase full-bridge inverter is configured to output corresponding compensation currents to the a-phase line, the b-phase line, and the c-phase line respectively through the three-phase reactor to perform three-phase unbalanced current regulation; A first filter capacitor is connected to the positive inverter input terminal and the DC positive output terminal; A second filter capacitor is connected in series with the first filter capacitor, and the second filter capacitor is connected to the negative inverter input terminal and the DC negative output terminal, and the neutral line n is connected between the first filter capacitor and the second filter capacitor.

2. A method for regulating unbalanced current of distribution transformer capacity increase and phase split output, characterized in that: An unbalanced current regulation system for increasing the capacity and splitting the phase output of a distribution transformer as claimed in claim 1; The method comprises: Obtaining an initial unbalance degree according to the a-phase load current of the a-phase line, the b-phase load current of the b-phase line, and the c-phase load current of the c-phase line; When the initial unbalance degree is greater than a preset starting value, performing sequence component decomposition processing on the a-phase load current, the b-phase load current, and the c-phase load current to obtain corresponding a-phase negative-sequence current, b-phase negative-sequence current, and c-phase negative-sequence current, as well as a-phase zero-sequence current, b-phase zero-sequence current, and c-phase zero-sequence current; The a-phase capacitor voltage control component, the b-phase capacitor voltage control component, and the c-phase capacitor voltage control component are calculated based on the voltage between the positive and negative ends of the first filter capacitor and the second filter capacitor after being connected in series and a preset reference voltage; obtain a phase a compensation current reference value according to the phase a negative-sequence current, the phase a zero-sequence current, and the phase a capacitor voltage control component; obtain a phase b compensation current reference value according to the phase b negative-sequence current, the phase b zero-sequence current, and the phase b capacitor voltage control component; and obtain a phase c compensation current reference value according to the phase c negative-sequence current, the phase c zero-sequence current, and the phase c capacitor voltage control component; The corresponding a-phase compensation current, b-phase compensation current and c-phase compensation current are output to the a-phase line, the b-phase line and the c-phase line respectively, and the output a-phase compensation current, the b-phase compensation current and the c-phase compensation current are made to track the a-phase compensation current reference value, the b-phase compensation current reference value and the c-phase compensation current reference value respectively through hysteresis control, so as to adjust the unbalanced current in phases.

3. The method for regulating unbalanced current of distribution transformer capacity increase and phase-splitting output according to claim 2, characterized in that: Also includes: Obtaining a current imbalance, where the current imbalance is obtained from the current a-phase load current, the b-phase load current, and the c-phase load current; Obtaining an imbalance change amplitude according to the initial imbalance and the current imbalance; When the imbalance degree change amplitude reaches a preset offset value, three-phase unbalanced current adjustment is performed according to the current a-phase load current, the b-phase load current, the c-phase load current, the a-phase capacitor voltage control component, the b-phase capacitor voltage control component and the c-phase capacitor voltage control component.

4. The method for regulating unbalanced current of distribution transformer capacity increase and phase-splitting output according to claim 2, characterized in that: The step of calculating the a-phase capacitor voltage control component, the b-phase capacitor voltage control component, and the c-phase capacitor voltage control component based on the voltage between the positive and negative ends of the first filter capacitor and the second filter capacitor connected in series and a preset reference voltage includes: Acquire a filter voltage, where the filter voltage is used to represent a voltage between a positive terminal and a negative terminal of the first filter capacitor and the second filter capacitor connected in series; Calculating the difference between the filtered voltage and a preset voltage reference value to obtain a capacitor voltage difference; Obtaining a D-axis active component required for phase coordinate transformation processing according to the capacitor voltage difference; Phase coordinate transformation processing is performed according to the D-axis active component and the preset Q-axis reactive component to obtain the a-phase capacitor voltage control component, the b-phase capacitor voltage control component and the c-phase capacitor voltage control component, wherein the Q-axis reactive component is preset to zero.

5. The method for regulating unbalanced current of distribution transformer capacity increase and phase-splitting output according to claim 4, characterized in that: The unbalanced current regulation system for capacity increase and phase-splitting output of the distribution transformer further includes a PI controller, and the D-axis active component required for phase coordinate transformation processing is obtained according to the capacitor voltage difference, including: The capacitor voltage difference is input into the PI controller to obtain the D-axis active component required for phase coordinate transformation processing.

6. The method for regulating unbalanced current of distribution transformer capacity increase and phase-splitting output according to claim 2, characterized in that: The a-phase compensation current reference value is obtained according to the a-phase negative-sequence current, the a-phase zero-sequence current, and the a-phase capacitor voltage control component; the b-phase compensation current reference value is obtained according to the b-phase negative-sequence current, the b-phase zero-sequence current, and the b-phase capacitor voltage control component; and the c-phase compensation current reference value is obtained according to the c-phase negative-sequence current, the c-phase zero-sequence current, and the c-phase capacitor voltage control component, in accordance with the following formula: Among them, I a_ref Indicates the a-phase compensation current reference value, I b_ref Indicates the b-phase compensation current reference value, I c_ref Indicates the reference value of the phase C compensation current; represents the negative sequence current of phase a, represents the negative sequence current of phase b, Represents the negative sequence current of phase c; I a * represents the a-phase capacitor voltage control component, I b * represents the b-phase capacitor voltage control component, I c * represents the c-phase capacitor voltage control component, represents the zero-sequence current of phase a, represents the zero-sequence current of the b-phase, Represents the zero-sequence current of the c phase.

7. The method for regulating unbalanced current of distribution transformer capacity increase and phase-splitting output according to claim 2, characterized in that: The unbalanced current regulation system for capacity increase and phase-split output of the distribution transformer further includes a hysteresis controller, and the inverter output end includes an inverter a-phase output end, an inverter b-phase output end, and an inverter c-phase output end; The method further comprises: Calculating the difference between the a-phase compensation current reference value and the a-phase compensation current to obtain an a-phase compensation current difference value, calculating the difference between the b-phase compensation current reference value and the b-phase compensation current to obtain a b-phase compensation current difference value, and calculating the difference between the c-phase compensation current reference value and the c-phase compensation current to obtain a c-phase compensation current difference value; Inputting the a-phase compensation current difference, the b-phase compensation current difference, and the c-phase compensation current difference into the hysteresis controller to obtain a switching signal of the three-phase full-bridge inverter; Controlling the three-phase full-bridge inverter to output a-phase output current, b-phase output current, and c-phase output current to the three-phase reactor through the inverter a-phase output terminal, the inverter b-phase output terminal, and the inverter c-phase output terminal according to the switching signal; The three-phase reactor outputs the corresponding a-phase compensation current, b-phase compensation current and c-phase compensation current to the a-phase line, the b-phase line and the c-phase line respectively according to the a-phase output current, the b-phase output current and the c-phase output current to perform three-phase imbalance control.

8. The method for regulating unbalanced current of distribution transformer capacity increase and phase-splitting output according to claim 2, characterized in that: Also includes: When the three-phase load of the distribution transformer is balanced, the three-phase full-bridge inverter is controlled to output the same current to the a-phase line, the b-phase line and the c-phase line respectively, so as to provide electric energy for the load on the low-voltage side of the distribution transformer.

9. A computer device, characterized in that: include: at least one memory; at least one processor; at least one computer program; The computer program is stored in the memory, and the processor executes at least one computer program to implement: The method according to any one of claims 2 to 8.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are used to cause a computer to execute: The method according to any one of claims 2 to 8.

Images