A hybrid voltage regulating transformer and an electrical quantity compensation method

Abstract

This invention discloses a hybrid voltage-regulating transformer and an electrical quantity compensation method, belonging to the field of power quality management technology. The hybrid voltage-regulating transformer includes: an autotransformer, a series transformer, an AC / DC rectifier, and a DC / AC inverter. The main winding of the autotransformer is connected in series with the power supply side input line and the secondary winding of the series transformer via an on-load tap changer, and its auxiliary winding is connected to the AC / DC rectifier. The DC / AC inverter is connected to the primary winding of the series transformer. The autotransformer performs discrete voltage regulation and outputs a reference voltage; the AC / DC rectifier injects compensation current into the auxiliary winding to achieve three-phase unbalanced current compensation; the DC / AC inverter generates a comprehensive compensation voltage based on the differential component and the negative sequence voltage component, which is superimposed on the reference voltage via the series transformer. This invention achieves continuous and smooth regulation and three-phase unbalance management across the entire voltage range, and eliminates the need for a separate power supply transformer, effectively reducing equipment size and cost.

Description

Technical Field

[0001] This invention relates to the field of power quality management technology, and in particular to a hybrid voltage regulating transformer and a method for compensating electrical quantities. Background Technology

[0002] In power system loop operation and daily power supply, on-load tap-changing transformers are typically used to regulate line voltage to avoid large inrush currents caused by voltage differences between the two sides. However, traditional on-load tap-changing transformers, relying on mechanical tap changers, can only perform discrete tap adjustments, failing to meet the grid's requirement for continuous and smooth regulation of the target voltage. Furthermore, traditional transformers can only perform three-phase balance regulation, lacking the ability to provide targeted independent compensation and mitigation when facing three-phase current or voltage imbalances caused by single-phase high-power loads in the grid. To overcome these shortcomings in continuous voltage regulation and three-phase imbalance mitigation, existing conventional solutions typically involve connecting an additional power electronic compensation device in parallel with the grid. However, this external parallel solution requires a separate isolation step-down transformer to provide power, directly leading to a significant increase in the size and cost of the complete equipment. Therefore, this invention aims to solve the technical problems of existing traditional transformers' ability to perform only discrete voltage regulation and their inability to mitigate three-phase imbalances in the grid, as well as the large size and high cost of conventional external compensation solutions due to the need for an additional independent power supply transformer. Summary of the Invention

[0003] This invention provides a hybrid voltage regulating transformer that solves the technical problems of existing traditional transformers that can only perform discrete voltage regulation and cannot manage three-phase imbalance in the power grid, as well as the large size and high cost of conventional external compensation schemes that require additional independent power supply transformers.

[0004] An embodiment of the present invention provides a hybrid voltage regulating transformer, comprising: a transformer body and a power electronic unit; wherein, the transformer body includes an autotransformer and a series transformer; the power electronic unit includes an AC / DC rectifier and a DC / AC inverter; the primary winding of the autotransformer is connected to the power supply input via an on-load tap changer, the secondary winding output of the autotransformer is connected to the first end of the secondary winding of the series transformer, and the second end of the secondary winding of the series transformer is connected to the load output; the auxiliary winding of the autotransformer is connected to the AC input of the AC / DC rectifier; the DC output of the AC / DC rectifier is connected to the DC input of the DC / AC inverter; the AC output of the DC / AC inverter is connected to the primary winding of the series transformer; the autotransformer performs discrete voltage regulation based on the target equal voltage difference adjustment range of the on-load tap changer, and outputs a coarsely adjusted reference voltage from the secondary winding output of the main winding; The AC / DC rectifier is used to acquire the three-phase unbalanced instantaneous current data of the load-side output line to generate a compensation current, and inject the compensation current into the auxiliary winding. The three-phase unbalanced current is compensated through the electromagnetic coupling of the transformer core of the autotransformer. The DC / AC inverter is used to acquire the reference voltage output by the autotransformer, the set adjustment target voltage, and the three-phase unbalanced instantaneous voltage data of the power supply side input line. Based on the difference component between the reference voltage and the adjustment target voltage, and the voltage negative sequence component extracted based on the three-phase unbalanced instantaneous voltage data, a comprehensive compensation voltage is generated. The series transformer then connects the comprehensive compensation voltage in series and superimposes it onto the reference voltage to achieve three-phase unbalanced voltage compensation.

[0005] Furthermore, the autotransformer includes: a main winding connected in a star configuration, an auxiliary winding connected in a star configuration, and an on-load tap changer with multiple equal voltage difference adjustment positions; the three-phase windings of the main winding and the three-phase windings of the auxiliary winding are coupled through the transformer core magnetic circuit of the autotransformer; each phase of the power supply input is connected to the input terminal of the on-load tap changer, and the output terminal of the on-load tap changer is connected to the primary side of the main winding; the secondary output of the main winding is led out from the tap corresponding to the preset intermediate position of the on-load tap changer and connected to the first end of the secondary winding of the series transformer.

[0006] Furthermore, the auxiliary winding leads include: three-phase leads and a neutral point lead; the three-phase leads and the neutral point lead are respectively connected to the AC input terminal of the AC / DC rectifier; the AC / DC rectifier is used to acquire the three-phase unbalanced instantaneous current data of the load-side output line to generate a compensation current, including: acquiring the three-phase unbalanced instantaneous current data of the load-side output line, performing a static coordinate system transformation and a synchronous rotating coordinate system transformation on the acquired three-phase unbalanced instantaneous current data in sequence, and extracting the negative sequence current component reflecting the current imbalance; and inverting the negative sequence current component to generate the corresponding compensation current.

[0007] Furthermore, the AC / DC rectifier is also used to calculate the average value of the three-phase current of the current load-side outgoing line in real time before injecting the compensation current into the auxiliary winding; use the average value as the dynamic compensation target value of the unbalanced current, and compensate the actual current value of each phase of the acquired three-phase unbalanced instantaneous current data to the dynamic compensation target value to obtain the corrected dynamic compensation target value; and correct the compensation current based on the corrected dynamic compensation target value.

[0008] Furthermore, the series transformer includes: a primary winding connected in a delta configuration and a secondary winding connected in a star configuration; the primary winding includes an A-phase primary winding, a B-phase primary winding, and a C-phase primary winding, and each phase of the primary winding has a start end and a finish end; wherein, the start end of the A-phase primary winding is connected to the finish end of the C-phase primary winding to form a first phase-to-phase connection point, the start end of the B-phase primary winding is connected to the finish end of the A-phase primary winding to form a second phase-to-phase connection point, and the start end of the C-phase primary winding is connected to the finish end of the B-phase primary winding to form a third phase-to-phase connection point; the AC output terminal of the DC-AC inverter includes an A-phase inverter output line, a B-phase inverter output line, and a C-phase inverter output line; the A-phase inverter output line is connected to the first phase-to-phase connection point, the B-phase inverter output line is connected to the second phase-to-phase connection point, and the C-phase inverter output line is connected to the third phase-to-phase connection point. The secondary windings include phase A, phase B, and phase C secondary windings, with the first end of each phase secondary winding connected to the secondary output of the corresponding phase of the main winding. The DC-AC inverter generates a comprehensive compensation voltage based on the difference between the reference voltage and the target voltage, as well as the negative sequence voltage component extracted from the three-phase unbalanced instantaneous voltage data. This allows the series transformer to superimpose the comprehensive compensation voltage onto the reference voltage, thereby achieving continuous and smooth adjustment of the target voltage and compensation for three-phase unbalanced voltage.

[0009] Furthermore, the AC / DC rectifier generates the compensation current using the following formula: ; ; ; ; ; ; In the formula, i La , i Lb , i Lc This represents the acquired instantaneous three-phase unbalanced current data of the load-side outgoing lines; These represent the first and second orthogonal components obtained after performing a static coordinate system transformation. Represents the voltage phase angle of the power grid; These represent the direct axis components and quadrature axis components obtained after synchronous rotating coordinate system transformation; , This represents the positive-sequence component obtained after DC extraction of the direct-axis component and the quadrature-axis component; , These represent the direct-axis compensation target value and the quadrature-axis compensation target value of the compensation current generated after the inversion operation is performed.

[0010] Furthermore, the DC-AC inverter generates the comprehensive compensation voltage using the following formula: ; ; ; ; ; ; In the formula, This represents the acquired instantaneous three-phase unbalanced voltage data of the power supply side incoming line; Represents the first and second orthogonal components obtained after the stationary coordinate system transformation; θ represents the voltage phase angle of the power grid. These represent the direct axis components and quadrature axis components obtained after synchronous rotating coordinate system transformation; , The table shows the positive sequence components obtained after DC extraction of the direct-axis and quadrature-axis components. , These represent the direct-axis compensation target value and the quadrature-axis compensation target value of the negative-sequence voltage component generated after the inversion operation.

[0011] Furthermore, the power electronic power unit also includes a filter; the filter is connected in series between the AC input terminal of the AC / DC rectifier and the auxiliary winding.

[0012] Another embodiment of the present invention provides an electrical quantity compensation method based on a hybrid voltage-regulating transformer, applicable to the power electronic power unit of a hybrid voltage-regulating transformer; the hybrid voltage-regulating transformer further includes: a transformer body; wherein, the transformer body includes an autotransformer and a series transformer; the power electronic power unit includes an AC / DC rectifier and a DC / AC inverter; the primary winding of the autotransformer is connected to the power supply input line via an on-load tap changer, the secondary winding output line of the main winding is connected to the first end of the secondary winding of the series transformer, and the second end of the secondary winding of the series transformer is connected to the load side output line; the lead of the auxiliary winding of the autotransformer is connected to the AC input terminal of the AC / DC rectifier; the DC output terminal of the AC / DC rectifier is connected to the DC input terminal of the DC / AC inverter; the AC output terminal of the DC / AC inverter is connected to the primary winding of the series transformer; the electrical quantity compensation method includes: Based on the AC / DC rectifier, the instantaneous three-phase unbalanced current data of the load-side output line is acquired to generate a compensation current, which is then injected into the auxiliary winding. The three-phase unbalanced current is compensated via electromagnetic coupling of the transformer core of the autotransformer. Based on the DC / AC inverter, the reference voltage output from the autotransformer, the set adjustment target voltage, and the instantaneous three-phase unbalanced voltage data of the power supply side input line are acquired. A comprehensive compensation voltage is generated based on the difference between the reference voltage and the adjustment target voltage, and the negative sequence voltage component extracted from the instantaneous three-phase unbalanced voltage data. This comprehensive compensation voltage is then connected in series with the reference voltage via a series transformer to achieve three-phase unbalanced voltage compensation.

[0013] Furthermore, the autotransformer to which the method is applicable includes: a main winding connected in a star configuration, an auxiliary winding connected in a star configuration, and an on-load tap changer with multiple equal voltage difference adjustment positions; the three-phase windings of the main winding and the three-phase windings of the auxiliary winding are coupled through the transformer core magnetic circuit of the autotransformer; each phase of the power supply side input line is connected to the input terminal of the on-load tap changer, and the output terminal of the on-load tap changer is connected to the primary side of the main winding; the secondary side output line of the main winding is led out from the tap corresponding to the preset intermediate position of the on-load tap changer and connected to the first end of the secondary winding of the series transformer.

[0014] The present invention has the following beneficial effects: This invention provides a hybrid voltage-regulating transformer that deeply integrates an autotransformer with a power electronic unit through physical topology. An auxiliary winding is added inside the autotransformer, and the leads of this auxiliary winding are directly connected to the AC input terminal of an AC / DC rectifier. This structural feature utilizes the electromagnetic coupling effect of the same transformer core to directly provide a safe and isolated operating power supply for the power electronic unit, as well as a reverse injection channel for compensation current. This eliminates the need for a separate parallel power supply transformer, which is required in conventional external compensation schemes. It integrates the transformer body and the electronic compensation equipment into one unit, reducing the overall hardware cost of the system and minimizing the size and footprint of the complete equipment.

[0015] Meanwhile, this invention constructs a closed-loop control mechanism that combines mechanical discrete coarse adjustment with electronic continuous fine adjustment. First, it relies on the on-load tap changer to output a reference voltage after discrete voltage regulation. Then, the DC-AC inverter accurately calculates the difference between this reference voltage and the target voltage, and combines this with the extracted negative-sequence voltage component to generate a comprehensive compensation voltage. Finally, a series transformer seamlessly superimposes this compensation voltage into the main circuit. Simultaneously, the AC / DC rectifier extracts current asymmetry characteristics and injects compensation current into the auxiliary winding. This dual active compensation architecture based on difference calculation and electromagnetic superposition not only fills the voltage blind zone between adjacent mechanical taps, achieving continuous and smooth adjustment across the entire voltage range, but also enables the system to have bidirectional management capabilities for asymmetrical loads, solving the technical problem that traditional transformers cannot cope with three-phase imbalance in the power grid. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0017] Figure 1 This is a schematic diagram of the structural topology of a hybrid voltage-regulating transformer provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the three-phase balanced voltage regulation control process provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the three-phase imbalance compensation control process provided in an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached diagram: 10-Autotransformer; 11-On-load tap changer; 12-Main winding; 13-Auxiliary winding; 20-Series transformer; 21-Primary winding; 22-Secondary winding; 30-Power electronic unit; 31-AC / DC rectifier; 32-DC bus capacitor; 33-DC / AC inverter; 40-Bypass circuit breaker; A1, B1, C1-Power supply side incoming lines; A2, B2, C2-Load side outgoing lines; a1, b1, c1-Three-phase outgoing lines; a2, b2, c2-Three-phase inverter outgoing lines. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] like Figure 1 As shown, this embodiment of the invention provides a hybrid voltage regulating transformer, including: a transformer body and a power electronic unit 30; wherein, the transformer body includes an autotransformer 10 and a series transformer 20; the power electronic unit 30 includes an AC / DC rectifier 31 and a DC / AC inverter 33; The primary winding 12 of the autotransformer 10 is connected to the power supply side input lines (A1, B1, C1) via an on-load tap changer 11. The secondary winding output line of the primary winding 12 is connected to the first end of the secondary winding 22 of the series transformer 20. The second end of the secondary winding 22 of the series transformer 20 is connected to the load side output lines (A2, B2, C2). The leads (a1, b1, c1) of the auxiliary winding 13 of the autotransformer 10 are connected to the AC input terminal of the AC / DC rectifier 31; the DC output terminal of the AC / DC rectifier 31 is connected to the DC input terminal of the DC / AC inverter 33; and the AC output terminal (a2, b2, c2) of the DC / AC inverter 33 is connected to the primary winding 21 of the series transformer 20. The autotransformer 10 performs discrete voltage regulation based on the target equal voltage difference adjustment range where the on-load tap changer 11 is located, and outputs the coarsely adjusted reference voltage from the secondary side output of the main winding 12. The AC / DC rectifier 31 is used to acquire the three-phase unbalanced instantaneous current data of the load-side outgoing lines (A2, B2, C2) to generate a compensation current and inject the compensation current into the auxiliary winding 13. The three-phase unbalanced current is compensated through the electromagnetic coupling of the transformer core of the autotransformer 10. It should be noted that the AC / DC rectifier 31 used in this embodiment is not a traditional passive unidirectional rectifier bridge, but a fully controlled four-quadrant active rectifier (PWM rectifier) ​​based on fully controlled power electronic devices (such as IGBTs or SiC MOSFET modules). Simultaneously, the AC / DC rectifier 31 integrates (or is connected via communication) a microcontroller (such as a DSP or FPGA control unit) with high-speed data processing capabilities. Thanks to the combination of the fully controlled active rectifier topology and the microcontroller, the AC / DC rectifier 31 not only possesses bidirectional energy flow capability, enabling it to draw power from the auxiliary winding 13 and rectify it to supply power to the DC bus, but also has comprehensive capabilities for external signal acquisition, execution of complex control algorithms (such as transformation between stationary and rotating coordinate systems), and pulse width modulation (PWM) inverter drive. Therefore, the AC / DC rectifier 31 can calculate the required imbalance compensation amount in real time and actively inject AC compensation current of a specific frequency and phase into the auxiliary winding 13, thereby supporting the complete implementation of the three-phase imbalance current compensation logic at the physical hardware level.

[0021] The DC-AC inverter 33 is used to acquire the reference voltage output by the autotransformer 10, the set adjustment target voltage, and the three-phase unbalanced instantaneous voltage data of the power supply side incoming lines (A1, B1, C1). Based on the difference component between the reference voltage and the adjustment target voltage, and the voltage negative sequence component extracted based on the three-phase unbalanced instantaneous voltage data, a comprehensive compensation voltage is generated. The series transformer 20 then connects the comprehensive compensation voltage in series and superimposes it onto the reference voltage to achieve three-phase unbalanced voltage compensation.

[0022] Furthermore, to facilitate understanding of the actual working principle and advantages of the above topology by those skilled in the art, the following supplementary explanations are provided: Firstly, in practical applications, the aforementioned power electronic power unit 30 is preferably equipped with a DC bus capacitor 32, and the entire system is equipped with a bypass circuit breaker 40. The DC output terminal of the AC / DC rectifier 31 and the DC input terminal of the DC / AC inverter 33 are connected via a common DC bus. The DC bus capacitor 32 is connected in parallel to this DC bus to achieve energy buffering and voltage stabilization on the DC side. The bypass circuit breaker 40 is connected across the power supply side inlet and load side outlet of the voltage regulating transformer, and is connected in parallel with the transformer body. When the voltage regulating transformer body needs maintenance, closing the bypass circuit breaker 40 allows for uninterrupted maintenance; and when the transformer body fails, the bypass circuit breaker 40 can be quickly closed to restore power supply to the main grid line, greatly improving the system reliability.

[0023] Secondly, the series transformer 20 not only serves as a physical channel for the exchange of active and reactive power on the series side, but more importantly, it provides safe electrical isolation between the sensitive power electronic devices (i.e., the DC-AC inverter 33) and the high-voltage main side of the power grid, effectively blocking the DC component and system fault current, thereby ensuring the safety of equipment and personnel.

[0024] Furthermore, regarding the structural design of the autotransformer 10, the on-load tap changer 11 is preferably configured with nine taps in specific implementations, and the voltage difference between each tap is equal. The aforementioned preset intermediate tap is preferably the fifth tap, meaning the secondary winding of the main winding 12 is led out from the main winding corresponding to the fifth tap. This physical design using a center tap provides a bidirectional symmetrical voltage regulation margin for the subsequent fine adjustment of the DC / AC inverter 33.

[0025] In a preferred embodiment, the autotransformer 10 includes: a main winding 12 connected in a star configuration, an auxiliary winding 13 connected in a star configuration, and an on-load tap changer 11 with multiple equal voltage difference adjustment positions. The three-phase winding of the main winding 12 and the three-phase winding of the auxiliary winding 13 are coupled through the transformer core magnetic circuit of the autotransformer 10. Each phase of the power supply side input line (A1, B1, C1) is connected to the input terminal of the on-load tap changer 11, and the output terminal of the on-load tap changer 11 is connected to the primary side of the main winding 12. The secondary winding of the main winding 12 is led out from the tap of the main winding 12 corresponding to the preset intermediate position of the on-load tap changer 11, and connected to the first end of the secondary winding 22 of the series transformer 20.

[0026] In a preferred embodiment, the leads of the auxiliary winding 13 include: three-phase leads (a1, b1, c1) and a neutral point lead; the three-phase leads (a1, b1, c1) and the neutral point lead are respectively connected to the AC input terminal of the AC / DC rectifier 31; the AC / DC rectifier 31 is used to acquire the three-phase unbalanced instantaneous current data of the load-side leads (A2, B2, C2) to generate a compensation current, and its specific execution logic includes: acquiring the three-phase unbalanced instantaneous current data of the load-side leads (A2, B2, C2), performing a static coordinate system transformation and a synchronous rotating coordinate system transformation on the acquired three-phase unbalanced instantaneous current data in sequence, and extracting the negative sequence current component reflecting the current imbalance; and performing an inversion operation on the negative sequence current component to generate the corresponding compensation current.

[0027] In a preferred embodiment, the AC / DC rectifier 31 is further configured to calculate, in real time, the average value of the three-phase currents of the current load-side outgoing lines (A2, B2, C2) before injecting the compensation current into the auxiliary winding 13; use the average value as the dynamic compensation target value of the unbalanced current, and compensate the actual current values ​​of each phase of the acquired three-phase unbalanced instantaneous current data to the dynamic compensation target value to obtain the corrected dynamic compensation target value; and correct the compensation current based on the corrected dynamic compensation target value.

[0028] In a preferred embodiment, the series transformer 20 includes: a primary winding 21 connected in a delta configuration and a secondary winding 22 connected in a star configuration; the primary winding 21 includes an A-phase primary winding, a B-phase primary winding, and a C-phase primary winding, and each phase primary winding has a start end and a finish end; wherein, the start end of the A-phase primary winding is connected to the finish end of the C-phase primary winding to form a first phase-to-phase connection point, the start end of the B-phase primary winding is connected to the finish end of the A-phase primary winding to form a second phase-to-phase connection point, and the start end of the C-phase primary winding is connected to the finish end of the B-phase primary winding to form a third phase-to-phase connection point; The AC output terminals of the DC-AC inverter 33 include phase A inverter line (a2), phase B inverter line (b2), and phase C inverter line (c2); phase A inverter line (a2) is connected to the first phase connection point, phase B inverter line (b2) is connected to the second phase connection point, and phase C inverter line (c2) is connected to the third phase connection point; the secondary winding 22 includes phase A secondary winding, phase B secondary winding, and phase C secondary winding, and the first end of each phase secondary winding is connected to the secondary side output of the corresponding phase of the main winding 12; the DC-AC inverter 33 generates a comprehensive compensation voltage based on the difference component between the reference voltage and the target voltage, and the negative sequence voltage component extracted based on the three-phase unbalanced instantaneous voltage data, so that the series transformer 20 series-superimposes the comprehensive compensation voltage onto the reference voltage, thereby achieving continuous and smooth adjustment of the target voltage and compensation for three-phase unbalanced voltage.

[0029] In a preferred embodiment, the AC / DC rectifier 31 generates the compensation current using the following formula: ; ; ; ; ; ; In the formula, iLa , i Lb , i Lc This represents the acquired three-phase unbalanced instantaneous current data of the load-side outgoing lines (A2, B2, C2); These represent the first and second orthogonal components obtained after performing a static coordinate system transformation. Represents the voltage phase angle of the power grid; These represent the direct axis components and quadrature axis components obtained after synchronous rotating coordinate system transformation; , This represents the positive-sequence component obtained after DC extraction of the direct-axis component and the quadrature-axis component; , These represent the direct-axis compensation target value and the quadrature-axis compensation target value of the compensation current generated after the inversion operation is performed.

[0030] Preferably, the DC-AC inverter 33 generates the comprehensive compensation voltage using the following formula: ; ; ; ; ; ; In the formula, This represents the instantaneous three-phase unbalanced voltage data of the power supply side incoming lines (A1, B1, C1); Represents the first and second orthogonal components obtained after the stationary coordinate system transformation; θ represents the voltage phase angle of the power grid. These represent the direct axis components and quadrature axis components obtained after synchronous rotating coordinate system transformation; , The table shows the positive sequence components obtained after DC extraction of the direct-axis and quadrature-axis components. , These represent the direct-axis compensation target value and the quadrature-axis compensation target value of the negative-sequence voltage component generated after the inversion operation.

[0031] In a preferred embodiment, the power electronic power unit 30 further includes a filter; the filter is connected in series between the AC input terminal of the AC / DC rectifier 31 and the auxiliary winding 13.

[0032] This invention also provides an electrical quantity compensation method based on a hybrid voltage regulating transformer, applicable to the power electronic power unit 30 of the aforementioned hybrid voltage regulating transformer; the hybrid voltage regulating transformer further includes: a transformer body; wherein, the transformer body includes an autotransformer 10 and a series transformer 20; the power electronic power unit 30 includes an AC / DC rectifier 31 and a DC / AC inverter 33; the primary winding 12 of the autotransformer 10 is connected to the power supply side input lines (A1, B1, C1) via an on-load tap changer 11, the secondary winding output line of the primary winding 12 is connected to the first end of the secondary winding 22 of the series transformer 20, and the second end of the secondary winding 22 of the series transformer 20 is connected to the load side output lines (A2, B2, C2). The leads (a1, b1, c1) of the auxiliary winding 13 of the autotransformer 10 are connected to the AC input terminal of the AC / DC rectifier 31; the DC output terminal of the AC / DC rectifier 31 is connected to the DC input terminal of the DC / AC inverter 33; the AC output terminal (a2, b2, c2) of the DC / AC inverter 33 is connected to the primary winding 21 of the series transformer 20; the electrical quantity compensation method includes: Based on the AC / DC rectifier 31, the three-phase unbalanced instantaneous current data of the load-side outgoing lines (A2, B2, C2) are acquired to generate a compensation current, which is then injected into the auxiliary winding 13. The three-phase unbalanced current compensation is achieved through the electromagnetic coupling of the transformer core of the autotransformer 10. Based on the DC / AC inverter 33, the reference voltage output by the autotransformer 10, the set adjustment target voltage, and the three-phase unbalanced instantaneous voltage data of the power supply side incoming lines (A1, B1, C1) are acquired. Based on the difference component between the reference voltage and the adjustment target voltage, and the voltage negative sequence component extracted based on the three-phase unbalanced instantaneous voltage data, a comprehensive compensation voltage is generated. The series transformer 20 then connects the comprehensive compensation voltage in series and superimposes it onto the reference voltage to achieve three-phase unbalanced voltage compensation.

[0033] In a preferred embodiment, the autotransformer 10 to which the method is applied includes: a main winding 12 connected in a star configuration, an auxiliary winding 13 connected in a star configuration, and an on-load tap changer 11 with multiple equal voltage difference adjustment positions; the three-phase windings of the main winding 12 and the three-phase windings of the auxiliary winding 13 are coupled through the transformer core magnetic circuit of the autotransformer 10; each phase of the power supply side input (A1, B1, C1) is connected to the input terminal of the on-load tap changer 11, and the output terminal of the on-load tap changer 11 is connected to the primary side of the main winding 12; the secondary side output of the main winding 12 is led out from the tap of the main winding 12 corresponding to the preset intermediate position of the on-load tap changer 11 and connected to the first end of the secondary winding 22 of the series transformer 20.

[0034] The specific working principle, multi-dimensional control strategy, and energy flow process of the above-mentioned hybrid voltage regulating transformer in a real power grid environment are as follows: Assume the input voltage sampling values ​​of the power supply side incoming lines (A1, B1, C1) are... The system's set target voltage for power grid regulation is The turns ratio parameter of the on-load tap changer 11 of the autotransformer 10 at its current tap position is: The discrete coarse-adjusted reference voltage output from the 12 secondary winding leads of the main winding is: Meanwhile, the actual three-phase load current of the load-side outgoing lines (A2, B2, C2) is During initial system commissioning and power-on, the first step is to initiate the reference voltage establishment and DC bus pre-charging process based on the physical architecture. The autotransformer 10 adjusts the input voltage accordingly. With target voltage The on-load tap changer 11 is quickly switched to the mechanical adjustment position closest to the target voltage. At this time, high-voltage alternating current flows through the primary side of the main winding 12, generating a strong alternating main magnetic flux in the transformer core. Relying on the magnetic circuit coupling effect of the transformer core, the main winding 12 generates a reference voltage at the secondary side output after stepping down or stepping up according to the turns ratio. (Its theoretical value is) / ).

[0035] Meanwhile, the auxiliary winding 13, wound on the same iron core, also cuts the alternating magnetic flux, inducing a safe and isolated low-voltage AC current. This low-voltage AC current is continuously fed into the AC / DC rectifier 31 via the three-phase and neutral point leads (a1, b1, c1, and n1). The AC / DC rectifier 31 performs high-frequency rectification on this AC current and stores the energy in the DC bus capacitor 32, establishing a stable DC bus voltage. Through this process, self-powering and isolation between strong and weak currents are cleverly achieved, providing sufficient operating energy for the entire power electronic power unit 30 and eliminating the space and cost burden of an external independent step-down transformer.

[0036] Since the mechanical tap position step size of the on-load tap changer 11 is a fixed discrete value, under most actual operating conditions, the reference voltage of the coarse adjustment output is... It cannot be directly equal to the target voltage required by the system. There is a certain voltage regulation difference component between the two. Under steady-state operation and continuous smooth voltage regulation with balanced three-phase grid, the underlying logic of the DC / AC inverter 33 accurately captures this minute deviation. The inverter obtains the reference voltage. With adjusting the target voltage The difference component is accurately calculated using logical subtraction. (Right now Subsequently, the DC-AC inverter 33 uses the energy provided by the DC bus capacitor 32 to modulate and generate a precise AC micro-amplitude compensation voltage, and injects it into the primary winding 21 of the series transformer 20 through the AC output terminals (a2, b2, c2).

[0037] Since the secondary winding 22 of the series transformer 20 is directly connected in series in the main power grid circuit, the small voltage injected into the primary winding 21 is seamlessly superimposed onto the secondary winding 22 in a 1:1 ratio or according to a specific turns ratio through electromagnetic coupling. This means that the comprehensive compensation voltage is... This creates a series vector superposition in physical space, ultimately making the voltage of the load-side output line accurately approximate or even completely equal to... For example, if the target voltage of the system is 10000V, and the coarse adjustment reference voltage of the current gear is 9900V, the DC-AC inverter 33 only needs to output a compensation voltage of +100V. After electromagnetic superposition, it can achieve a precise stepless smooth output of 10000V, which greatly reduces the rated power capacity required by the power electronic power unit.

[0038] When the system faces complex operating conditions such as high-power single-phase loads or severely unbalanced loads on the load side, resulting in severe distortion of the three-phase current, simple voltage regulation can no longer maintain the safe operation of the power grid. At this time, the AC / DC rectifier 31 not only serves as a power extraction module, but can also be converted into an active dynamic current compensator. The rectifier collects the instantaneous three-phase unbalanced current data of the load side outgoing line in real time, calculates the mathematical mean of the current three-phase current, and locks the mean as the target value for dynamic compensation of the unbalanced current.

[0039] To accurately isolate imbalances in volatile alternating current (AC), the rectifier's internal control logic sequentially performs a static coordinate transformation (Clark transformation) and a synchronous rotating coordinate transformation (DQ transformation) on the acquired three-phase unbalanced current. Through this mathematical spatial mapping, the three-dimensional abrupt AC signal is reduced in dimension and rotated and projected into direct-axis and quadrature-axis components in a two-dimensional coordinate system. From this specific perspective, the positive-sequence component, representing the fundamental wave of healthy electrical energy, appears as a stable DC straight line, while the negative-sequence component, representing imbalance distortion, appears as AC ripples superimposed on it. The system extracts this positive-sequence DC component through digital low-pass filtering and subtracts it from the total signal to accurately extract the negative-sequence current component. Then, a mathematical inversion operation is performed on this negative-sequence component to obtain the target value of the three-phase compensation current used to fill the imbalance gap. The AC / DC rectifier 31 then injects the reverse compensation current into the auxiliary winding 13 through the input terminal. The anti-bias flux generated by these compensation currents cancels out the unbalanced flux generated by the main winding 12 in the iron core, forcing the main power grid line to output a symmetrical three-phase current waveform.

[0040] Taking a real-world operating condition as an example, if the actual load currents of phases A, B, and C are 150A, 100A, and 50A respectively, the system will use an average value of 100A as the dynamic target and sequentially map and inject equivalent currents of -50A, 0A, and +50A into the auxiliary winding to achieve three-phase current sharing.

[0041] On the other hand, if there is severe distortion in the power supply input line, causing the input three-phase voltage to be severely asymmetrical, the DC-AC inverter 33 will take on the task of actively repairing the voltage imbalance in parallel. While performing the differential component calculation for the continuous voltage regulation mentioned above, the inverter will also collect the instantaneous three-phase asymmetrical voltage data of the power supply side in parallel, and accurately extract the negative sequence voltage component using the same coordinate system space transformation algorithm (i.e., the aforementioned DQ transformation and inversion operation). The inverter's underlying logic performs a complex-domain vector superposition of the differential component required for voltage regulation and the negative-sequence voltage component required for imbalance repair, generating a comprehensive compensation voltage that combines both voltage regulation and imbalance repair functions. This comprehensive compensation voltage is then fully output to the primary winding 21 of the series transformer 20. At this point, the connection topology of the series transformer comes into play: the delta connection of the primary winding 21 physically forms a closed internal circulation channel, confining harmful zero-sequence voltage and zero-sequence current within the loop and preventing them from entering and polluting the external power grid. Meanwhile, the star connection of the secondary winding 22 ensures that the independent compensation voltages of each phase output by the inverter can be accurately and non-interferingly superimposed on the corresponding phases of the main circuit, thereby achieving symmetrical and smooth stability of the three-phase voltage on the load side.

[0042] Furthermore, as a safety net mechanism to ensure the safe operation of the power grid, the hybrid voltage regulating transformer is also equipped with highly reliable bypass cascading protection logic in special operating conditions such as sudden severe short-circuit faults in the transformer body, breakdown of power electronic unit devices, or the need for regular offline maintenance. Once the system detects a serious anomaly or receives a maintenance command, the main control center will immediately control the bypass circuit breaker 40 connected between the power supply side incoming line and the load side outgoing line to close rapidly. The high-voltage power on the power supply side will directly bypass the autotransformer 10 and the series transformer 20, and pass directly to the load side through the bypass channel, thereby physically disconnecting the transformer body with potential faults or under maintenance. The bypass cascading power supply mechanism constructed through this scheme ensures the continuity of power supply to the main lines of the distribution network and gives the entire voltage regulating system a high degree of disaster recovery and risk resistance.

[0043] As can be seen from the above-described deeply integrated working principle, the hybrid voltage regulating transformer and electrical quantity compensation method disclosed in this invention overturns the single-function limitations of traditional distribution network equipment. By utilizing the magnetic circuit coupling effect of the transformer's own iron core, the sensitive power electronic unit 30 is completely electrically isolated from the high-voltage power grid, achieving efficient internal power conversion and compensation injection. This not only eliminates the need for an independent isolation transformer required for external compensation equipment, significantly reducing the system's hardware size and manufacturing cost, but also allows for the concurrent execution of multiple complex algorithms such as continuous smooth voltage regulation, dynamic current sharing compensation, and voltage asymmetry repair on the same hardware platform. Therefore, this invention can not only achieve high-precision continuous voltage regulation across the entire voltage range with minimal equipment rated capacity, but also comprehensively overcome the increasingly prevalent asymmetrical load disturbances in modern power grids, meeting the stringent power quality requirements under complex and harsh operating conditions.

[0044] like Figure 2 The diagram illustrates the three-phase balanced voltage regulation control process provided in this embodiment of the invention. When the three phases of the power grid are balanced and the system only needs to perform continuous and smooth voltage regulation, the control system executes the following sequence of steps: First, the system determines the target voltage based on the actual operating requirements of the power grid; Second, based on the obtained target voltage, the on-load tap changer is selected, i.e., the optimal physical tap position for the autotransformer to be connected is calculated and determined; Next, the on-load tap changer is controlled to switch to the target tap position, and the autotransformer performs coarse voltage regulation, outputting a discretely regulated reference voltage on the secondary side of the main winding; Subsequently, the system enters the electronic fine-tuning stage, performing series compensation voltage calculation, i.e., the DC-AC inverter accurately calculates the difference component between the reference voltage and the target voltage; Finally, the power electronic unit performs voltage compensation, and the DC-AC inverter generates a corresponding AC micro-amplitude comprehensive compensation voltage based on the difference component, which is then superimposed onto the main circuit through a series transformer to complete the stepless continuous and smooth regulation to the target voltage.

[0045] like Figure 3 The diagram shows a schematic of the three-phase imbalance compensation control process provided in an embodiment of the present invention. When a single-phase high-power load or an unbalanced load exists in the power grid, resulting in severe three-phase current or voltage imbalance, the underlying control logic within the power electronic power unit extracts and generates reverse compensation quantities according to the following timing steps: First, the three-phase imbalance quantity is acquired, i.e., the AC / DC rectifier collects the instantaneous three-phase unbalanced current data on the load side in real time, or the DC / AC inverter collects the instantaneous three-phase unbalanced voltage data on the power supply side in real time; Second, the acquired instantaneous three-phase unbalanced data is subjected to Clark transformation and DQ transformation (i.e., stationary coordinate system transformation and synchronous rotating coordinate system transformation) in sequence to reduce the three-dimensional time-domain AC signal and map it to a two-dimensional rotating coordinate system; Next, in this rotating coordinate system, the system calculates the positive-sequence component and the negative-sequence component, i.e., the DC positive-sequence component representing the healthy fundamental wave is extracted by low-pass filtering, and the positive-sequence component is subtracted from the total signal to remove the negative-sequence component representing the asymmetrical disturbance; Subsequently, the system calculates the compensation amount by performing a mathematical inversion operation on the extracted pure negative-sequence components to obtain the reverse compensation target values ​​(direct-axis and quadrature-axis compensation target values) used to fill the imbalance gap. Then, based on these reverse compensation target values, inverse DQ transformation and inverse Clark transformation are sequentially performed to reverse the compensation command in the two-dimensional rotating coordinate system back to the three-phase stationary coordinate system. Finally, the three-phase imbalance compensation amount is obtained. The AC / DC rectifier or DC / AC inverter, based on the restored three-phase imbalance compensation amount, drives the underlying IGBT and other power switching devices to inject reverse compensation current into the auxiliary winding or output a reverse voltage negative-sequence component to the primary winding, thereby neutralizing and eliminating the three-phase imbalance in the main power grid.

[0046] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A hybrid voltage regulating transformer, characterized by include: The transformer body and power electronic unit are included. The transformer body includes an autotransformer and a series transformer. The power electronic unit includes an AC / DC rectifier and a DC / AC inverter. The primary winding of the autotransformer is connected to the power supply input via an on-load tap changer. The secondary winding of the autotransformer is connected to the first end of the secondary winding of the series transformer, and the second end of the secondary winding of the series transformer is connected to the load side output. The auxiliary winding of the autotransformer is connected to the AC input of the AC / DC rectifier. The DC output of the AC / DC rectifier is connected to the DC input of the DC / AC inverter. The AC output of the DC / AC inverter is connected to the primary winding of the series transformer. The autotransformer performs discrete voltage regulation based on the target equal voltage difference adjustment range of the on-load tap changer, and outputs a coarsely adjusted reference voltage from the secondary winding of the primary winding. The AC / DC rectifier is used to acquire the three-phase unbalanced instantaneous current data of the load-side output line to generate a compensation current, and inject the compensation current into the auxiliary winding. The three-phase unbalanced current is compensated through the electromagnetic coupling of the transformer core of the autotransformer. The DC / AC inverter is used to acquire the reference voltage output by the autotransformer, the set adjustment target voltage, and the three-phase unbalanced instantaneous voltage data of the power supply side input line. Based on the difference component between the reference voltage and the adjustment target voltage, and the voltage negative sequence component extracted based on the three-phase unbalanced instantaneous voltage data, a comprehensive compensation voltage is generated. The series transformer then connects the comprehensive compensation voltage in series and superimposes it onto the reference voltage to achieve three-phase unbalanced voltage compensation.

2. The hybrid voltage regulating transformer of claim 1, wherein, The autotransformer includes: a main winding connected in a star configuration, an auxiliary winding connected in a star configuration, and an on-load tap changer with multiple equal voltage difference adjustment positions; the three-phase windings of the main winding and the three-phase windings of the auxiliary winding are coupled through the transformer core magnetic circuit of the autotransformer; each phase of the power supply input is connected to the input terminal of the on-load tap changer, and the output terminal of the on-load tap changer is connected to the primary side of the main winding; the secondary side output of the main winding is led out from the tap corresponding to the preset intermediate position of the on-load tap changer and connected to the first end of the secondary winding of the series transformer.

3. The hybrid voltage regulating transformer of claim 2, wherein, The auxiliary winding leads include: three-phase leads and a neutral point lead; the three-phase leads and the neutral point lead are respectively connected to the AC input terminal of the AC / DC rectifier; the AC / DC rectifier is used to acquire the three-phase unbalanced instantaneous current data of the load-side output line to generate a compensation current, including: acquiring the three-phase unbalanced instantaneous current data of the load-side output line, performing a static coordinate system transformation and a synchronous rotating coordinate system transformation on the acquired three-phase unbalanced instantaneous current data in sequence, and extracting the negative sequence current component reflecting the current imbalance; and inverting the negative sequence current component to generate the corresponding compensation current.

4. The hybrid voltage regulating transformer of claim 3, wherein, The AC / DC rectifier is also used to calculate the average value of the three-phase current of the current load side outgoing line in real time before injecting the compensation current into the auxiliary winding; use the average value as the dynamic compensation target value of the unbalanced current, and compensate the actual current value of each phase of the obtained three-phase unbalanced instantaneous current data to the dynamic compensation target value to obtain the corrected dynamic compensation target value. The compensation current is corrected based on the revised dynamic compensation target.

5. The hybrid voltage regulating transformer of claim 4, wherein, The series transformer includes a primary winding connected in a delta configuration and a secondary winding connected in a star configuration. The primary winding includes an A-phase primary winding, a B-phase primary winding, and a C-phase primary winding, each having a start and a end. The start of the A-phase primary winding is connected to the end of the C-phase primary winding to form a first phase-to-phase connection point; the start of the B-phase primary winding is connected to the end of the A-phase primary winding to form a second phase-to-phase connection point; and the start of the C-phase primary winding is connected to the end of the B-phase primary winding to form a third phase-to-phase connection point. The AC output terminal of the DC-AC inverter includes an A-phase inverter output line, a B-phase inverter output line, and a C-phase inverter output line. The A-phase inverter output line is connected to the first phase-to-phase connection point; the B-phase inverter output line is connected to the second phase-to-phase connection point; and the C-phase inverter output line is connected to the third phase-to-phase connection point. The secondary windings include phase A, phase B, and phase C secondary windings, with the first end of each phase secondary winding connected to the secondary output of the corresponding phase of the main winding. The DC-AC inverter generates a comprehensive compensation voltage based on the difference between the reference voltage and the target voltage, as well as the negative sequence voltage component extracted from the three-phase unbalanced instantaneous voltage data. This allows the series transformer to superimpose the comprehensive compensation voltage onto the reference voltage, thereby achieving continuous and smooth adjustment of the target voltage and compensation for three-phase unbalanced voltage.

6. The hybrid voltage regulating transformer of claim 5, wherein, The AC / DC rectifier generates the compensation current using the following formula: ； ； ； ； ； ； In the formula, i La , i Lb , i Lc This represents the acquired instantaneous three-phase unbalanced current data of the load-side outgoing lines; These represent the first and second orthogonal components obtained after performing a static coordinate system transformation. Represents the voltage phase angle of the power grid; These represent the direct axis components and quadrature axis components obtained after synchronous rotating coordinate system transformation; , represents a positive sequence component obtained after direct current extraction on the direct axis component and the quadrature axis component; , represents the direct axis compensation target value and the quadrature axis compensation target value of the compensation current generated after performing the negation operation.

7. The hybrid voltage regulating transformer of claim 6, wherein, The DC-AC inverter generates the comprehensive compensation voltage using the following formula: ; ; ; ; ； ； In the formula, This represents the acquired instantaneous three-phase unbalanced voltage data of the power supply side incoming line; Represents the first and second orthogonal components obtained after the stationary coordinate system transformation; θ represents the voltage phase angle of the power grid. These represent the direct axis components and quadrature axis components obtained after synchronous rotating coordinate system transformation; , This represents the positive-sequence component obtained after DC extraction of the direct-axis component and the quadrature-axis component; , These represent the direct-axis compensation target value and the quadrature-axis compensation target value of the negative-sequence voltage component generated after the inversion operation.

8. The hybrid voltage regulating transformer of claim 1, wherein, The power electronic power unit further includes a filter; the filter is connected in series between the AC input terminal of the AC / DC rectifier and the auxiliary winding.

9. A method of electrical quantity compensation based on a hybrid voltage regulating transformer, characterized in that, A power electronic power unit applicable to a hybrid voltage-regulating transformer; the hybrid voltage-regulating transformer further includes: a transformer body; wherein the transformer body includes an autotransformer and a series transformer; the power electronic power unit includes an AC / DC rectifier and a DC / AC inverter; the primary winding of the autotransformer is connected to the power supply input via an on-load tap changer, the secondary winding output is connected to the first end of the secondary winding of the series transformer, and the second end of the secondary winding of the series transformer is connected to the load output; the auxiliary winding lead of the autotransformer is connected to the AC input of the AC / DC rectifier; the DC output of the AC / DC rectifier is connected to the DC input of the DC / AC inverter; the AC output of the DC / AC inverter is connected to the primary winding of the series transformer; the electrical quantity compensation method includes: Based on the AC / DC rectifier, the instantaneous three-phase unbalanced current data of the load-side output line is acquired to generate a compensation current, which is then injected into the auxiliary winding. The three-phase unbalanced current is compensated via electromagnetic coupling of the transformer core of the autotransformer. Based on the DC / AC inverter, the reference voltage output from the autotransformer, the set adjustment target voltage, and the instantaneous three-phase unbalanced voltage data of the power supply side input line are acquired. A comprehensive compensation voltage is generated based on the difference between the reference voltage and the adjustment target voltage, and the negative sequence voltage component extracted from the instantaneous three-phase unbalanced voltage data. This comprehensive compensation voltage is then connected in series with the reference voltage via a series transformer to achieve three-phase unbalanced voltage compensation.

10. The electrical quantity compensation method according to claim 9, wherein, The autotransformer to which the method is applicable includes: a main winding connected in a star configuration, an auxiliary winding connected in a star configuration, and an on-load tap changer with multiple equal voltage difference adjustment positions; the three-phase windings of the main winding and the three-phase windings of the auxiliary winding are coupled through the transformer core magnetic circuit of the autotransformer; each phase of the power supply side input line is connected to the input terminal of the on-load tap changer, and the output terminal of the on-load tap changer is connected to the primary side of the main winding; the secondary side output line of the main winding is led out from the tap of the main winding corresponding to the preset intermediate position of the on-load tap changer and connected to the first end of the secondary winding of the series transformer.

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