Lightweight flexible phase shifter topology and control method thereof

Abstract

This invention relates to the field of flexible power transmission and transformation equipment technology, and particularly to a lightweight flexible phase shifter topology and its control method. The flexible phase shifter is a three-phase independent structure, and each phase circuit includes: a parallel-side transformer T1 with a single-winding input and a dual-winding output, a flexible power conversion unit P, and a series-coupled transformer T2; the input winding of transformer T1 is connected in parallel to the main circuit of the power system, and the two output windings of T1 are respectively connected to the non-common terminals of the upper and lower bridge arms of unit P; the common terminal of the upper and lower bridge arms of unit P is connected to the primary winding of transformer T2, and a filter capacitor C is connected in parallel to the common terminal. o The secondary winding of transformer T2 is connected in series to the main circuit of the power system to inject series compensation voltage into the main circuit. This invention significantly reduces the number of power devices used, simplifies the system structure, and provides a fundamental guarantee for achieving lightweight, compact, and cost-optimized equipment.

Description

Technical Field

[0001] This invention relates to the field of flexible power transmission and transformation equipment technology, and in particular to a lightweight flexible phase shifter topology and its control method. Background Technology

[0002] With the continuous growth of renewable energy installed capacity and the increasing complexity of power load characteristics, modern power systems are facing unprecedented challenges in power flow control. The randomness and volatility of distributed energy sources such as wind and solar power, as well as the increasing power exchange between regional grids, have led to uneven power flow distribution and a significant increase in the risk of transmission section overruns. Against this backdrop, traditional mechanical phase shifters, due to their slow adjustment speed (response time on the order of seconds or even minutes), ability to achieve only stepped regulation, and frequent operation and maintenance, are no longer sufficient to meet the urgent needs of the power grid for precise dynamic power flow control. Flexible phase shifting technology using power electronics, with its ability to achieve millisecond-level rapid response and continuous smooth regulation, is becoming a key technological direction for solving the power flow control problems of modern power grids.

[0003] Flexibility is one of the core requirements of modern power grids for power flow control equipment. It demands that phase shifters not only be able to quickly and accurately adjust voltage phase and amplitude to achieve flexible allocation of active power flow across lines, but also possess intelligent adjustment capabilities to adapt to changes in system operating conditions. This flexibility is reflected in the following aspects: First, the equipment should be able to achieve bidirectional and continuous power regulation, eliminating the impact of traditional mechanical switching operations; second, it needs to have a rapid response capability to cope with system transient processes and effectively suppress power oscillations; third, it should support more complex control strategies, such as adaptive regulation and damped control, to adapt to the development needs of smart grids. Currently, flexible phase shifters based on fully controllable power devices offer a possibility for achieving the above goals, but their practical application still faces significant constraints.

[0004] While pursuing flexible performance, power systems also have an equally urgent need for lightweight equipment. Existing mainstream flexible phase-shifting solutions, such as... Figure 1 (a) The back-to-back modular multilevel converter (MMC) topology, while achieving excellent control performance, requires six bridge arms and hundreds of sub-modules, resulting in a complex system structure, large size, and considerable weight. The more complex modular multilevel matrix converter (M3C) topology, while improving upon this by reducing the number of components, still has a large number of power modules and high control complexity, such as... Figure 1As shown in (b). These factors directly lead to high equipment costs, large footprint, and difficulties in installation and transportation, severely restricting its application in space-constrained scenarios such as urban power grid transformation and offshore wind power platforms. Therefore, how to significantly reduce the number of power devices through topology innovation while maintaining or even improving flexible control performance, and achieve lightweight and compact equipment, has become a technical bottleneck that the industry urgently needs to overcome.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] This invention provides a lightweight flexible phase shifter topology and its control method, thereby effectively solving the problems in the background art.

[0007] To achieve the above objectives, the technical solution adopted by this invention is: a lightweight flexible phase shifter topology, wherein the flexible phase shifter is a three-phase independent structure, and each phase circuit includes: The parallel-side transformer T1 with single-winding input and double-winding output, the flexible power conversion unit P, and the series coupling transformer T2; The input winding of the transformer T1 is connected in parallel to the main circuit of the power system, and the two output windings of T1 are respectively connected to the non-common terminals of the upper and lower bridge arms of unit P. The common terminal of the upper and lower bridge arms of unit P is connected to the primary winding of transformer T2, and a filter capacitor C is connected in parallel to the common terminal. o ; The secondary winding of the transformer T2 is connected in series to the main circuit of the power system to inject series compensation voltage into the main circuit.

[0008] Furthermore, the common point of the two output windings of the transformer T1 is grounded, and the output terminal voltages generated by the two output windings under rated operating conditions have equal amplitudes and a phase difference of π.

[0009] Furthermore, the upper and lower arms of the flexible power conversion unit P are each composed of N full-bridge submodules cascaded together and connected to a filter inductor L. f The full-bridge submodules are connected in series; each submodule includes four power devices and a DC bus capacitor C. dc Furthermore, the AC output terminals of each full-bridge submodule are cascaded sequentially and connected to inductor L. f connect.

[0010] This invention also includes a lightweight flexible phase shifter topology control method, which controls the topology as described above, comprising the following steps: The main parameters for detecting the voltage and current of the main circuit of the power system and calculating the reference value of the series compensation voltage based on the detected values ​​are: Closed-loop control is implemented for the main circuit power to generate a correction amount for the series compensation voltage reference value; Based on the obtained series compensation voltage reference value, the output voltage reference signal of the flexible power conversion unit P is calculated, and closed-loop control is implemented on the output voltage and output current of P to generate differential mode voltage reference signals for the upper and lower bridge arms of each phase. Closed-loop control is implemented on the bridge arm capacitor voltage and input current of P to generate common-mode voltage reference signals for the upper and lower bridge arms of each phase. Based on the differential-mode and common-mode voltage reference signals, the final voltage reference signals of the upper and lower bridge arms are generated, and combined with the capacitor voltage equalization control strategy within the bridge arms, the drive signals of each full-bridge submodule are generated.

[0011] Furthermore, the reference value for detecting the voltage and current of the main circuit of the power system and calculating the series compensation voltage based on the detected values ​​includes: S11: Detect the three-phase voltage u of the main circuit pA u pB and u pC and line current i LA i LB and i LC Calculate the corresponding voltage vector u respectively p and current vector i L : ; Where j is the imaginary number sign, u pα and u pβ u p The real and imaginary components, i Lα and i Lβ i L The real and imaginary parts are calculated as follows: ; and: ; S12: Calculate the voltage vector u of the equivalent voltage source of the power grid. g : ; Where u gα and u gβ u g The real and imaginary parts of X; L The equivalent impedance of the line; S13: Calculate the desired line voltage power angle: ; Where arcsin is the arcsine function; U g RMS value of rated line voltage of main circuit; P p * To transmit active power to the desired line; S14: Calculate the dominant term u of the series compensation voltage reference value. sp1 * : ; in, and They are vectors u sp1 * The real and imaginary parts; For vector u g The phase angle satisfies: ; The atan2 function represents the phase angle acquisition function, which generates a phase angle in the range of [-π, π].

[0012] Furthermore, the closed-loop control of the main circuit power to generate a correction amount for the series compensation voltage reference value includes: S21: Based on the expected line transmission active power P of the main circuit p * and reactive power Q p * Calculate the reference current i of the line. * Lα and i * Lβ : ; in, This is the real part of the main circuit voltage vector. It is the imaginary part of the main circuit voltage vector; S22: Perform closed-loop control on the line current to generate a correction vector u for the series compensation voltage reference value. sp2 * , that is u sp2 * real part and the virtual part satisfy: ; In the formula G cL (s) represents the line current closed-loop controller, where s stands for the Laplace operator. The actual current vector of the line The real part, The actual current vector of the line The imaginary part.

[0013] Further, the step of calculating the output voltage reference signal of the flexible power conversion unit P based on the obtained series compensation voltage reference value, and implementing closed-loop control on the output voltage and output current of P to generate differential mode voltage reference signals for each phase upper and lower bridge arm, includes: S31: Considering the turns ratio of the primary and secondary sides of the series transformer, calculate the output voltage reference signal u of the flexible power conversion unit based on the dominant term of the series compensation voltage reference value and the correction vector of the series compensation voltage reference value. o * : ; In the formula, k st This represents the turns ratio of the primary and secondary sides of transformer T2. and They are vectors u o The real and imaginary parts; S32: Calculate the reference value u of the output voltage of each phase of the flexible power conversion unit. oA * u oB * u oC * : ; S33: The following control methods are adopted for phases A, B, and C of the flexible power conversion unit: S331: Collect the upper arm current i of phase x. ux and lower bridge arm current i lx Where x represents A, B, or C, the differential-mode component of the bridge arm current is calculated as the output current i of that phase. ox : ; S332: Acquire the x-phase output voltage u ox The reference value i for generating the output current is obtained by using voltage closed-loop control. ox * : ; In the formula G uo (s) is the closed-loop controller for the output voltage of the flexible power converter; S333: For output current i ox The differential mode component u of the bridge arm voltage of the flexible power conversion unit is generated by closed-loop control. rdx * : ; In the formula G io (s) is the closed-loop controller for the output current of the flexible power converter.

[0014] Furthermore, the closed-loop control of the bridge arm capacitor voltage and input current of P to generate common-mode voltage reference signals for the upper and lower bridge arms of each phase includes: S41: Collect the capacitor voltage u of all full-bridge submodules in the upper arm. dcuxi and the capacitor voltage u of all full-bridge submodules in the lower arm dclxi Where x represents the phase and i represents the sequence number of the submodule in the corresponding bridge arm, i=1,2,......,N. Calculate the average capacitor voltage u of all submodules. dcx_ave : ; S42: For the average capacitor voltage u dcx_ave The reference value i for generating the x-phase input current is obtained by performing notch filtering and closed-loop control. ix * Where x represents phase, i.e., i ix * satisfy: ; In the formula G udc (s) is the closed-loop controller for the average capacitor voltage of the flexible power exchanger, H nf (s) is the average capacitor voltage notch filter for the flexible power switch. The phase of the x-phase voltage in the main circuit. This is the average capacitor voltage reference value for all submodules; S43: Based on the upper arm current i of phase x ux and lower bridge arm current i lx The common-mode component of the bridge arm current is calculated as the input current i of that phase. ix : ; S44: For input current i ix Closed-loop control is used to generate the common-mode component u of the bridge arm voltage of the flexible power conversion unit. rcx * : ; In the formula G ii (s) is the input current closed-loop controller for the flexible power converter. This is the input voltage of the x-phase flexible power conversion unit.

[0015] Furthermore, based on the differential-mode and common-mode voltage reference signals, the final voltage reference signals for the upper and lower bridge arms are generated, and combined with the capacitor voltage equalization control strategy within the bridge arms, drive signals for each full-bridge submodule are generated, including: S51: Calculate the reference voltage signals for the upper and lower bridge arms: ; S52: Calculate the number N of sub-modules required for the upper and lower bridge arms respectively. rux and N rlx : ; In the formula, U dc The rated voltage of each submodule capacitor is represented by [ ], where [ ] indicates the floor function; u rux * The reference voltage signal for the upper arm of phase x; u rlx * The reference voltage signal for the lower arm of phase x; u rcx * The common-mode component reference signal for the x-phase bridge arm voltage; u rdx * This is the reference signal for the differential mode component of the bridge arm voltage; S53: The set of capacitor voltages of all full-bridge submodules in the upper arm {u dcuxi Sort the submodules from largest to smallest, and allocate the number of submodules according to the following rules: S531: If u rux * i ux If ≥0, then take the last N after sorting. rux One submodule is put into operation, while the remaining submodules are in a zero-output state. Among them, i ux Let x be the upper bridge arm current; S532: If u rux * i ux If < 0, then take the first N sorted values. rux One submodule is put into operation, while the remaining submodules are in a zero-output state. Among them, i ux Let x be the upper bridge arm current; S54: The set of capacitor voltages of all full-bridge submodules in the lower arm {u dclxi Sort the data from largest to smallest and add it to the submodule according to the following rules: S531: If u rlx * i lx If ≥0, then take the last N after sorting. rlx One submodule is put into operation, while the remaining submodules are in a zero-output state. Among them, i lx Let x be the lower bridge arm current; S532: If u rlx * i lx If < 0, then take the first N sorted values. rlx One submodule is put into operation, while the remaining submodules are in a zero-output state. Among them, ilx Let x be the lower bridge arm current; S55: Determine the switching state of each submodule. For the i-th submodule, determine the state of each power device according to the following rules: S551: If this submodule is to be put into operation, then when u ryx * When u ≥ 0, power devices T1 and T4 are turned on, and T2 and T3 are turned off; if u ryx * <0, power devices T1 and T4 are off, T2 and T3 are on; where the subscript y is u or l, representing the reference voltage of the upper or lower bridge arm respectively, where u ryx * The reference voltage signal for the x-phase y-arm bridge is given by the subscript r, which indicates the reference quantity. S552: If this submodule is to operate in a zero-output state, then determine the switch state according to any of the following methods: S5521: T1 and T3 are on, T2 and T4 are off; S5522: T1 and T3 are off, T2 and T4 are on.

[0016] Furthermore, the phase angle It is obtained by phase-locking the three-phase voltage of the main circuit.

[0017] The beneficial effects of this invention are as follows: Compared to back-to-back MMC topologies, this design reduces sub-modules by 50%, and compared to matrix converter topologies, it reduces sub-modules by one-third. This significantly reduces the number of power devices used, simplifies the system structure, and provides a fundamental guarantee for achieving lightweight, compact, and cost-optimized equipment. While simplifying the hardware, this invention achieves rapid and precise control of the series voltage through a hierarchical control strategy, possessing fully flexible adjustment performance comparable to complex topologies. It can achieve wide-range continuous adjustment of amplitude and phase while maintaining stable system operation, perfectly balancing the dual goals of hardware simplification and performance optimization. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 For existing flexible phase shifter topologies: (a) a scheme based on back-to-back modular multilevel converters; (b) a scheme based on modular multilevel matrix converters; Figure 2This invention presents the topology of a lightweight flexible phase shifter. Figure 3 This invention provides a control method for a lightweight flexible phase shifter. Figure 4 The simulation results are for the lightweight flexible phase shifter in the embodiments of the present invention; Figure 5 This is a schematic diagram of the structure of the computer device of the present invention. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] In this embodiment, a lightweight flexible phase shifter topology and its control method are proposed to address the flexible power flow regulation requirements of power systems. The topology is as follows: Figure 2 As shown, this topology is a three-phase independent structure. Each phase circuit includes a transformer T1 with a single-winding input and a dual-winding output, a flexible power conversion unit P, and a series transformer T2. The input winding of transformer T1 is connected in parallel to the main circuit of the power system, and the two output windings are connected to the non-common terminals of the upper and lower arms of unit P, respectively. The common terminal of the upper and lower arms of unit P is connected to the primary winding of transformer T2. A filter capacitor C is also connected in parallel to the common terminal. o The secondary winding of transformer T2 is connected in series to the main circuit of the power system.

[0022] In practical implementation, the input winding of the parallel-side transformer T1 is directly connected in parallel to the main circuit of the power system, such as to a 35kV or 220kV medium-high voltage power grid line. The two output windings of T1 are designed with equal voltage amplitudes and a phase difference of π to provide symmetrical AC power. The common point of the transformer's output windings is grounded to ensure normal system parameter operation. Typical parameter example: The input winding voltage is the effective value U of the grid phase voltage. p (e.g., U) p = The effective value of the output winding phase voltage can be set to 12kV, and the primary-to-secondary transformer ratio of T1 is approximately 10.59:1. The capacity of T1 is comparable to that of transformer T2, determined by the phase difference that the power grid needs to regulate. For example, within a ±20° regulation range, the combined capacity of the two transformers is approximately [amount missing] of the line's rated capacity. The phase difference between the two output windings is achieved through a special arrangement of the transformer windings, such as using a Z-connection or a dedicated magnetic core design, to minimize flux leakage and improve efficiency.

[0023] The flexible power conversion unit P is the core power conversion component of this topology, consisting of an upper arm and a lower arm. The non-common terminals of the upper and lower arms are connected to the two output windings of T1, respectively, while the common terminal is connected to a 10-50μF transformer T2. The withstand voltage rating is designed based on the rated output voltage of P, for example, considering a 12kV effective value. Each arm consists of N full-bridge submodules and one filter inductor L. f The sub-modules are cascaded together. The choice of N depends on the input voltage level and the DC bus voltage withstand capability of each sub-module. For example, in applications with an effective input phase voltage of 12kV and a sub-module withstand voltage of 1200V, the minimum value of N is 29. More sub-modules are needed to consider module redundancy. A cascaded structure of N full-bridge sub-modules can achieve multi-level output and significantly reduce harmonics. The full-bridge sub-module adopts a standard H-bridge structure, including four power devices T1-T4 (e.g., IGBTs, rated voltage 1200V, current 500A) and a DC bus capacitor C. dc (Capacity 5-20mF, withstand voltage 13500V). All full-bridge submodules are cascaded sequentially on their AC output sides to form a multi-level voltage waveform, which is then connected to L... f (Inductance value 1-5mH, rated current determined by the rated output current of P) are connected in series to filter out switching ripple and limit short-circuit current.

[0024] The secondary winding of series-coupled transformer T2 is directly connected in series into the main circuit of the power system for injecting compensation voltage. The primary winding of T2 is connected to the common terminal of P, with a turns ratio k. st Typically 1:1, to match the injection voltage amplitude (e.g., secondary-side injection voltage is 5-20% of the grid voltage). The capacity of T2 is similar to that of T1.

[0025] The lightweight advantage of the entire topology is reflected in the following: compared to the traditional back-to-back MMC (which requires a total of 12 bridge arms), this structure only requires 2 bridge arms per phase (requiring a total of 6 bridge arms), reducing the number of submodules by approximately 50%; compared to the M3C topology (which requires a total of 9 bridge arms), it reduces the number of bridge arms by 6. The overall volume is expected to be controlled within 5m². 3 Within a certain range, weighing no more than 2 tons, it is suitable for space-constrained substation scenarios.

[0026] The control block diagram of the control method in this embodiment is as follows: Figure 3 As shown, the method is implemented using a digital signal processor (DSP) with a sampling frequency of 10kHz and a control period of 100μs. The method consists of five main steps: calculating the dominant compensation voltage term, power closed-loop correction, differential-mode voltage control, common-mode voltage control, and drive signal generation. Each step is described in detail below.

[0027] Step S1: Calculate the dominant term of the series compensation voltage reference value; First, detect the three-phase voltage u of the main circuit. pA upB and u pC and line current i LA i LB and i LC Calculate the corresponding voltage vector u respectively p and current vector i L : (1) Where j is the imaginary number sign, u pα and u pβ u p The real and imaginary components, i Lα and i Lβ i L The real and imaginary parts are calculated as follows: (2) and: (3) Next, the voltage vector u of the equivalent voltage source of the remote power grid is calculated. g : (4) Where u gα and u gβ u g The real and imaginary parts of X; L The equivalent impedance of the line can be calculated in advance based on the grid planning or estimated online using the harmonic injection method.

[0028] Then, the desired line voltage power angle is calculated: (5) Where arcsin is the arcsine function; U g RMS value of rated line voltage of main circuit; P p * The desired active power to be transmitted through the line is determined by the upper-level dispatch setting, such as 20MW.

[0029] Finally, the dominant term u of the series compensation voltage reference value is calculated. sp1 * : (6) in, and They are vectors u sp1 * The real and imaginary parts; For vector u g The phase angle satisfies: (7) The atan2 function represents the phase angle acquisition function, which generates a phase angle in the range of [-π, π].

[0030] Step S2: Power closed-loop correction; First, based on the expected line transmission active power P of the main circuit. p * and reactive power Q p * Calculate the reference current i of the line. * Lα and i * Lβ : (8) in, This is the real part of the main circuit voltage vector. It is the imaginary part of the main circuit voltage vector; Secondly, closed-loop control is performed on the line current to generate a correction vector u for the series compensation voltage reference value. sp2 * , that is u sp2 * real part and the virtual part satisfy: (9) In the formula G cL (s) represents the line current closed-loop controller, where s stands for the Laplace operator. The actual current vector of the line The real part, The actual current vector of the line The imaginary part. In this invention, a preferred G cL (s) is a proportional-resonant controller, and its expression is: (10) Where, k p1 For G cL The proportionality coefficient of (s), k r1 For G cL The resonant control parameters of (s), such as k p1 =20、k r1 =400; For example, the angular frequency of the power grid. .

[0031] Step S3: Differential mode voltage control; First, considering the turns ratio of the primary and secondary sides of the series transformer, the output voltage reference signal u of the flexible power conversion unit is calculated based on the dominant term of the series compensation voltage reference value and the correction vector of the series compensation voltage reference value. o* : (11) In the formula, k st This represents the turns ratio of the primary and secondary sides of transformer T2. and They are vectors u o The real and imaginary parts.

[0032] Secondly, calculate the reference value u of the output voltage of each phase of the flexible power conversion unit. oA * u oB * u oC * : (12) Collect the upper arm current i of phase x ux and lower bridge arm current i lx Where x represents A, B, or C, the differential-mode component of the bridge arm current is calculated as the output current i of that phase. ox : (13) Collect the output voltage u of phase x ox The reference value i for generating the output current is obtained by using voltage closed-loop control. ox * : (14) In the formula G uo (s) is a closed-loop controller for the output voltage of a flexible power converter. In this invention, a preferred G... uo (s) is a proportional-resonant controller, and its expression is: (15) Where, k p2 For G uo The proportionality coefficient of (s), k r2 For G uo The resonant control parameters of (s), such as k p2 =0.1、k r2 =20. Simultaneously, for the output current i ox The differential mode component u of the bridge arm voltage of the flexible power conversion unit is generated by closed-loop control. rdx * : (16) In the formula G io (s) is a closed-loop controller for the output current of a flexible power converter. In this invention, a preferred G... io(s) is a proportional-resonant controller, and its expression is: (17) Where, k p3 For G io The proportionality coefficient of (s), k r3 For G io The resonant control parameters of (s), such as k p3 =50、k r3 =600.

[0033] Step S4: Common-mode voltage control; First, collect the capacitor voltage u of all full-bridge submodules in the upper arm. dcuxi (i=1,2,......,N) and the capacitor voltage u of all full-bridge submodules in the lower arm. dclxi (x=1,2,......,N), calculate the average capacitor voltage u of all submodules. dcx_ave : (18) Secondly, regarding the average capacitor voltage u dcx_ave The reference value i for generating the input current is used for notch filtering and closed-loop control. ix * , i.e. i ix * satisfy: (19) In the formula G udc (s) is the closed-loop controller for the average capacitor voltage of the flexible power exchanger; H nf (s) represents the average capacitor voltage notch filter for the flexible power switch; j upx The phase of the x-phase voltage in the main circuit can be obtained from the main circuit voltage using a phase-locked loop algorithm. In this invention, a preferred G... udc (s) is a proportional-integral controller, and its expression is: (20) Where, k p4 For G udc The proportionality coefficient of (s), k i4 For G udc The integral control parameters of (s), such as k p4 =1, k i4 =100. A preferred notch filter H nf The expression for (s) is: (twenty one) Notch filter H nf (s) is used to filter out the double power frequency component in the full-bridge submodule.

[0034] Then, based on the upper bridge arm current i of phase x ux and lower bridge arm current i lx The common-mode component of the bridge arm current is calculated as the input current i of that phase. ix : (twenty two) For input current i ix Closed-loop control is used to generate the common-mode component u of the bridge arm voltage of the flexible power conversion unit. rcx * : (twenty three) In the formula G ii (s) is the input current closed-loop controller for the flexible power converter. This refers to the input voltage of the x-phase flexible power conversion unit. In this invention, a preferred G... io (s) is a proportional-resonant controller, and its expression is: (twenty four) Where, k p5 For G ii The proportionality coefficient of (s), k r5 For G io The resonant control parameters of (s), such as k p5 =50、k r5 =600.

[0035] Step S5: Drive signal generation; First, calculate the reference voltage signals for the upper and lower bridge arms: (25) Calculate the number N of submodules required for the upper and lower bridge arms respectively. rux and N rlx : (26) In the formula, U dc The rated voltage of each submodule capacitor is represented by [ ], where [ ] indicates the floor function; u rux * The reference voltage signal for the upper arm of phase x; u rlx * The reference voltage signal for the lower arm of phase x; u rcx * The common-mode component reference signal for the x-phase bridge arm voltage; u rdx * This is the reference signal for the differential mode component of the bridge arm voltage; Secondly, the set {u} of capacitor voltages of all full-bridge submodules in the upper arm. dcuxiSort the submodules from largest to smallest, and add them according to the following rules: If u rux * i ux If ≥0, then take the last N after sorting. rux One submodule is operational, while the remaining submodules are in a zero-output state; if u rux * i ux If < 0, then take the first N sorted values. rux One submodule is in operation, while the remaining submodules are in a zero-output state, where i ux Let x be the current in the upper arm of phase x.

[0036] At the same time, the set {u} of capacitor voltages of all full-bridge submodules in the lower bridge arm dclxi Sort u in descending order and add it to the submodule according to the following rules: If u rlx * i lx If ≥0, then take the last N after sorting. rlx One submodule is operational, while the remaining submodules are in a zero-output state; if u rlx * i lx If < 0, then take the first N sorted values. rlx One submodule is in operation, while the remaining submodules are in a zero-output state, where i lx Let x be the current in the lower arm of phase x.

[0037] Finally, the switching state of each submodule is determined. For the i-th submodule, the state of each power device is determined according to the following rules: ① If this submodule is to be put into operation, then when u ryx * When u ≥ 0, power devices T1 and T4 are turned on, and T2 and T3 are turned off; if u ryx * <0, power devices T1 and T4 are off, T2 and T3 are on; where the subscript y is u or l, representing the reference voltage of the upper or lower bridge arm respectively, where u ryx * The reference voltage signal for the x-phase y-arm bridge is given by the subscript r, which indicates the reference quantity.

[0038] ② If the submodule should operate in a zero-output state, the switch state shall be determined according to any of the following methods: T1 and T3 are on, T2 and T4 are off; T1 and T3 are off, T2 and T4 are on.

[0039] In this embodiment, the control parameters of each closed-loop controller are designed in the frequency domain according to the desired dynamic and steady-state response performance.

[0040] Table 1 shows the key system parameters applicable to the lightweight phase shifter.

[0041] Table 1 In this embodiment, the simulation results of the lightweight flexible phase shifter BMAC under stable power transmission conditions are as follows: Figure 4 As shown. By Figure 4 As shown in (a), both the active and reactive power transmitted from the input-side grid to the BMAC can quickly reach a steady state. Figure 4 Figure (b) shows the BMAC bridge arm voltage waveform. It can be seen that after a brief start-up process, the bridge arm voltage is quickly controlled and stabilized near the reference value with small voltage ripple. This verifies the effectiveness of the BMAC submodule capacitor voltage equalization control strategy and provides stable voltage support for reliable power conversion. Figure 4 (c) shows the current waveforms on the input and output sides of the BMAC. It can be seen that the three-phase currents have high symmetry and exhibit standard sinusoidal waveforms with low total harmonic distortion (THD). This indicates that the BMAC controller has excellent dynamic and steady-state performance, achieving high-quality control of the grid-side current. The above demonstrates that the BMAC and its control strategy proposed in this embodiment can achieve rapid and stable power transmission while ensuring power quality on both sides of the line.

[0042] In summary, this invention proposes a lightweight phase shifter topology and its control method. The topology requires only six bridge arms to achieve three-phase flexible phase shifting, significantly reducing the number of modules, floor space, and device weight required for the flexible phase shifter. Furthermore, the control method proposed for the invented topology exhibits high dynamic and steady-state performance, meeting the flexible power flow regulation requirements of power systems.

[0043] Please see Figure 5 The diagram shows a structural schematic of a computer device provided in an embodiment of this application. An embodiment of this application provides a computer device 400, including a processor 410 and a memory 420. The memory 420 stores a computer program executable by the processor 410. When the computer program is executed by the processor 410, it performs the method described above.

[0044] This application embodiment also provides a storage medium 430, on which a computer program is stored, and the computer program is executed by a processor 410 to perform the above method.

[0045] The storage medium 430 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0046] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. "A plurality of" means two or more, unless otherwise explicitly specified.

[0047] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0048] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0049] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0050] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0051] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0052] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0053] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A lightweight flexible phase shifter topology, characterized in that, The flexible phase shifter has a three-phase independent structure, and each phase circuit includes: The parallel-side transformer T1 with single-winding input and double-winding output, the flexible power conversion unit P, and the series coupling transformer T2; The input winding of the transformer T1 is connected in parallel to the main circuit of the power system, and the two output windings of T1 are respectively connected to the non-common terminals of the upper and lower bridge arms of unit P. The common end of the upper and lower bridge arms of the unit P is connected to the primary winding of the transformer T2, and the common end is connected in parallel with a filter capacitor C o ; The secondary winding of the transformer T2 is connected in series to the main circuit of the power system to inject series compensation voltage into the main circuit.

2. The lightweight flexible phase shifter topology according to claim 1, characterized in that, The common point of the two output windings of the transformer T1 is grounded, and the output terminal voltages generated by the two output windings under rated operating conditions have equal amplitudes and a phase difference of π.

3. The lightweight flexible phase shifter topology according to claim 1, characterized in that, The upper bridge arm and the lower bridge arm of the flexible power conversion unit P are connected in series by cascading N full-bridge sub-modules and a filter inductor L f ; each full-bridge sub-module comprises four power devices and a DC bus capacitor C dc , and the AC output ends of the full-bridge sub-modules are connected in series by cascading. f ​ 4. A lightweight flexible phase shifter topology control method, characterized in that, Controlling the topology as described in any one of claims 1 to 3 includes the following steps: The main parameters for detecting the voltage and current of the main circuit of the power system and calculating the reference value of the series compensation voltage based on the detected values ​​are: Closed-loop control is implemented for the main circuit power to generate a correction amount for the series compensation voltage reference value; Based on the obtained series compensation voltage reference value, the output voltage reference signal of the flexible power conversion unit P is calculated, and closed-loop control is implemented on the output voltage and output current of P to generate differential mode voltage reference signals for the upper and lower bridge arms of each phase. Closed-loop control is implemented on the bridge arm capacitor voltage and input current of P to generate common-mode voltage reference signals for the upper and lower bridge arms of each phase. Based on the differential-mode and common-mode voltage reference signals, the final voltage reference signals of the upper and lower bridge arms are generated, and combined with the capacitor voltage equalization control strategy within the bridge arms, the drive signals of each full-bridge submodule are generated.

5. The lightweight flexible phase shifter topology control method according to claim 4, characterized in that, The reference value for detecting the voltage and current of the main circuit of the power system and calculating the series compensation voltage based on the detected values ​​includes: S11: Detect the three-phase voltage u of the main circuit pA u pB and u pC and line current i LA i LB and i LC Calculate the corresponding voltage vector u respectively p and current vector i L : ； Where j is the imaginary number sign, u pα and u pβ u p The real and imaginary components, i Lα and i Lβ i L The real and imaginary parts are calculated as follows: ； and: ； S12: Calculate the voltage vector u of the equivalent voltage source of the power grid. g : ； Where u gα and u gβ u g The real and imaginary parts of X; L The equivalent impedance of the line; S13: Calculate the desired line voltage power angle: ； Where arcsin is the arcsine function; U g RMS value of rated line voltage of main circuit; P p * To transmit active power to the desired line; S14: Calculate the dominant term u of the series compensation voltage reference value. sp1 * : ； in, and They are vectors u sp1 * The real and imaginary parts; For vector u g The phase angle satisfies: ； The atan2 function represents the phase angle acquisition function, which generates a phase angle in the range of [-π, π].

6. The lightweight flexible phase shifter topology control method according to claim 4, characterized in that, The closed-loop control of the main circuit power, generating a correction amount for the series compensation voltage reference value, includes: S21: Based on the expected line transmission active power P of the main circuit p * and reactive power Q p * Calculate the reference current i of the line. * Lα and i * Lβ : ； in, It is the real part of the main circuit voltage vector. It is the imaginary part of the main circuit voltage vector; S22: Perform closed-loop control on the line current to generate a correction vector u for the series compensation voltage reference value. sp2 * , that is u sp2 * real part and the virtual part satisfy: ； In the formula G cL (s) represents the line current closed-loop controller, where s stands for the Laplace operator. The actual current vector of the line The real part, The actual current vector of the line The imaginary part.

7. The lightweight flexible phase shifter topology control method according to claim 4, characterized in that, The step of calculating the output voltage reference signal of the flexible power conversion unit P based on the obtained series compensation voltage reference value, and implementing closed-loop control of the output voltage and output current of P to generate differential mode voltage reference signals for each phase upper and lower bridge arm, includes: S31: Considering the turns ratio of the primary and secondary sides of the series transformer, calculate the output voltage reference signal u of the flexible power conversion unit based on the dominant term of the series compensation voltage reference value and the correction vector of the series compensation voltage reference value. o * : ； In the formula, k st This represents the turns ratio of the primary and secondary sides of transformer T2. and They are vectors u o The real and imaginary parts; S32: Calculate the reference value u of the output voltage of each phase of the flexible power conversion unit. oA * u oB * u oC * : ； S33: The following control methods are adopted for phases A, B, and C of the flexible power conversion unit: S331: Collect the upper arm current i of phase x. ux and lower bridge arm current i lx Where x represents A, B, or C, the differential-mode component of the bridge arm current is calculated as the output current i of that phase. ox : ； S332: Acquire the x-phase output voltage u ox The reference value i for generating the output current is obtained by using voltage closed-loop control. ox * : ； In the formula G uo (s) is the closed-loop controller for the output voltage of the flexible power converter; S333: For output current i ox The differential mode component u of the bridge arm voltage of the flexible power conversion unit is generated by closed-loop control. rdx * : ； In the formula G io (s) is the closed-loop controller for the output current of the flexible power converter.

8. The lightweight flexible phase shifter topology control method according to claim 4, characterized in that, The closed-loop control of the bridge arm capacitor voltage and input current of P to generate common-mode voltage reference signals for the upper and lower bridge arms of each phase includes: S41: Collect the capacitor voltage u of all full-bridge submodules in the upper arm. dcuxi and the capacitor voltage u of all full-bridge submodules in the lower arm dclxi Where x represents the phase and i represents the sequence number of the submodule in the corresponding bridge arm, i=1,2,......,N. Calculate the average capacitor voltage u of all submodules. dcx_ave : ； S42: For the average capacitor voltage u dcx_ave The reference value i for generating the x-phase input current is obtained by performing notch filtering and closed-loop control. ix * Where x represents phase, i.e., i ix * satisfy: ； In the formula G udc (s) is the closed-loop controller for the average capacitor voltage of the flexible power exchanger, H nf (s) is the average capacitor voltage notch filter for the flexible power switch. The phase of the x-phase voltage in the main circuit. This is the average capacitor voltage reference value for all submodules; S43: Based on the upper arm current i of phase x ux and lower bridge arm current i lx The common-mode component of the bridge arm current is calculated as the input current i of that phase. ix : ； S44: For input current i ix Closed-loop control is used to generate the common-mode component u of the bridge arm voltage of the flexible power conversion unit. rcx * : ； In the formula G ii (s) is the input current closed-loop controller for the flexible power converter. This is the input voltage of the x-phase flexible power conversion unit.

9. The lightweight flexible phase shifter topology control method according to claim 4, characterized in that, The method generates final voltage reference signals for the upper and lower bridge arms based on differential and common-mode voltage reference signals, and, combined with the capacitor voltage equalization control strategy within the bridge arms, generates drive signals for each full-bridge submodule, including: S51: Calculate the reference voltage signals for the upper and lower bridge arms: ； S52: Calculate the number N of sub-modules required for the upper and lower bridge arms respectively. rux and N rlx : ； In the formula, U dc The rated voltage of each submodule capacitor is represented by [ ], where [ ] indicates the floor function; u rux * The reference voltage signal for the upper arm of phase x; u rlx * The reference voltage signal for the lower arm of phase x; u rcx * The common-mode component reference signal for the x-phase bridge arm voltage; u rdx * This is the reference signal for the differential mode component of the bridge arm voltage; S53: The set of capacitor voltages of all full-bridge submodules in the upper arm {u dcuxi Sort the submodules from largest to smallest, and allocate the number of submodules according to the following rules: S531: If u rux * i ux If ≥0, then take the last N after sorting. rux One submodule is put into operation, while the remaining submodules are in a zero-output state. Among them, i ux Let x be the upper arm current of phase x; S532: If u rux * i ux If < 0, then take the first N sorted values. rux One submodule is put into operation, while the remaining submodules are in a zero-output state. Among them, i ux Let x be the upper arm current of phase x; S54: The set of capacitor voltages of all full-bridge submodules in the lower arm {u dclxi Sort the data from largest to smallest and add it to the submodule according to the following rules: S541: If u rlx * i lx If ≥0, then take the last N after sorting. rlx One submodule is put into operation, while the remaining submodules are in a zero-output state. Among them, i lx Let x be the lower bridge arm current; S542: If u rlx * i lx If < 0, then take the first N sorted values. rlx One submodule is put into operation, while the remaining submodules are in a zero-output state. Among them, i lx Let x be the lower bridge arm current; S55: Determine the switching state of each submodule. For the i-th submodule, determine the state of each power device according to the following rules: S551: If this submodule is to be put into operation, then when u ryx * When u ≥ 0, power devices T1 and T4 are turned on, and T2 and T3 are turned off; if u ryx * <0, power devices T1 and T4 are off, T2 and T3 are on; where the subscript y is u or l, representing the reference voltage of the upper or lower bridge arm respectively, where u ryx * The reference voltage signal for the x-phase y-arm bridge is given by the subscript r, which indicates the reference quantity. S552: If this submodule is to operate in a zero-output state, then determine the switch state according to any of the following methods: S5521: T1 and T3 are on, T2 and T4 are off; S5522: T1 and T3 are off, T2 and T4 are on.

10. The lightweight flexible phase shifter topology control method according to claim 8, characterized in that, The phase angle It is obtained by phase-locking the three-phase voltage of the main circuit.

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