Full-control alternating current interconnection device control method and system based on phase-locked loop and feedforward decoupling

Abstract

The invention discloses a full-control alternating current interconnection device control method and system based on a phase-locked loop and feedforward decoupling. The method comprises the following steps: constructing a control model according to a topological structure of a full-control alternating current interconnection device; calculating a synchronous rotation coordinate transformation matrix of the phase-locked loop after the disturbance signal is injected under the condition that the disturbance signal is injected into the grid-connected voltage coupling point of the full-control alternating-current interconnection device; determining a transfer function between the disturbance signal and the phase angle disturbance according to the synchronous rotation coordinate transformation matrix; performing feedforward decoupling on the first output electrical parameter of the grid-connected side of the control model to obtain a modulation signal; according to the control model, the transfer function and the modulation signal, constructing an impedance model of the full-control AC interconnection device; performing impedance adjustment on the full-control alternating current interconnection device according to the impedance model; according to the invention, the stability of accessing the full-control AC interconnection device to the power grid can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of flexible AC power transmission technology, and in particular to a control method and system for a fully controlled AC interconnection device based on phase-locked loop and feedforward decoupling. Background Technology

[0002] To address the long-standing problems in AC power transmission systems, such as slow regulation speed, insufficient power transmission capacity, and low controllability of power flow and voltage, the traditional solution is to use a fully controlled AC interconnection device to control the power and voltage of the transmission lines, thereby achieving comprehensive regulation of the voltage, power, and power flow of the AC power transmission system.

[0003] However, due to the inherent structure and multi-loop control characteristics of the fully controlled AC interconnection device, its complex internal dynamic characteristics are prone to oscillation with the power grid, resulting in poor stability of the fully controlled AC interconnection device when connected to the power grid. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a control method and system for a fully controlled AC interconnection device based on phase-locked loop and feedforward decoupling, which can effectively improve the stability of the fully controlled AC interconnection device connected to the power grid.

[0005] In a first aspect, embodiments of the present invention provide a fully controllable AC interconnection device control method based on phase-locked loop and feedforward decoupling, comprising: Based on the topology of the fully controllable AC interconnection device, a control model is constructed; When a disturbance signal is injected into the voltage coupling point of the fully controlled AC interconnection device connected to the grid, calculate the synchronous rotating coordinate transformation matrix of the phase-locked loop after the disturbance signal is injected; Based on the synchronous rotating coordinate transformation matrix, determine the transfer function between the disturbance signal and the phase angle disturbance; By performing feedforward decoupling on the first output electrical parameters of the grid-connected side of the control model, the modulation signal under the synchronous rotating coordinate transformation matrix is ​​obtained. Based on the control model, the transfer function, and the modulation signal, an impedance model of the fully controllable AC interconnection device is constructed. The impedance of the fully controlled AC interconnect device is adjusted according to the impedance model.

[0006] As an improvement to the above scheme, the step of calculating the synchronous rotating coordinate transformation matrix of the phase-locked loop after the injection of the disturbance signal when the voltage coupling point of the fully controlled AC interconnection device is connected to the grid includes: When a disturbance signal is injected at the voltage coupling point of the fully controlled AC interconnection device connected to the grid, the phase angle disturbance of the phase-locked loop caused by the injection of the disturbance signal is calculated. Calculate the synchronous rotating coordinate transformation matrix based on the phase angle disturbance.

[0007] As an improvement to the above scheme, determining the transfer function between the disturbance signal and the phase angle disturbance based on the synchronous rotating coordinate transformation matrix includes: Without injecting a disturbance signal at the voltage coupling point of the grid-connected control model, calculate the first voltage component of the voltage coupling point in the frequency domain below the dq axis without considering the injected disturbance signal; Based on the transmission relationship between the phase angle disturbance and the frequency domain voltage in the phase-locked loop and the first voltage component, calculate the second voltage component of the voltage coupling point in the lower frequency domain of the dq axis after considering the injected disturbance signal; Based on the synchronous rotating coordinate transformation matrix and the second voltage component, the transfer function between the disturbance signal and the phase angle disturbance is determined.

[0008] As an improvement to the above scheme, the step of feedforward decoupling the first output electrical parameters of the control model on the grid-connected side to obtain the modulation signal under the synchronous rotating coordinate transformation matrix includes: Based on the synchronous rotating coordinate transformation matrix, the multiphase output current in the first output electrical parameters of the grid-connected side of the control model is decoupled by inductor current feedforward, and the first modulation wave signal in the stationary coordinate is calculated. Based on the first modulation wave signal, the output voltage in the first output electrical parameters of the grid-connected side of the control model is decoupled by voltage feedforward to obtain the modulation signal.

[0009] As an improvement to the above scheme, the step of performing inductor current feedforward decoupling on the multiphase output current in the first output electrical parameters of the grid-connected side of the control model according to the synchronous rotating coordinate transformation matrix, and calculating the first modulation wave signal in stationary coordinates, includes: Based on the synchronous rotating coordinate transformation matrix, Park transformation is performed on the multiphase output current in the first output electrical parameters of the grid-connected side of the control model to obtain the first current component in the frequency domain on the dq axis. The multiphase output current is decoupled by inductor current feedforward to obtain a second modulation wave signal in a synchronous rotating coordinate system. Based on the second modulation wave signal, the third modulation wave signal in the frequency domain is obtained; Based on the synchronous rotating coordinate transformation matrix, the third modulation wave signal is subjected to an inverse Parker transformation to obtain the first modulation wave signal of the control model in stationary coordinates.

[0010] As an improvement to the above scheme, the step of constructing the impedance model of the fully controlled AC interconnection device based on the control model, the transfer function, and the modulation signal includes: Using the transfer function and the modulation signal, the positive-sequence impedance characteristics and negative-sequence impedance characteristics of the fully controlled AC interconnect device are calculated through the control model. Based on the positive-sequence impedance characteristics and the negative-sequence impedance characteristics, an impedance model of the fully controlled AC interconnection device is constructed.

[0011] As an improvement to the above solution, the impedance adjustment of the fully controlled AC interconnection device according to the impedance model includes: By using preset stability criteria, the impedance model of the fully controlled AC interconnection device and the impedance characteristics of the power grid to which the fully controlled AC interconnection device is connected are evaluated for stability, and the impedance adjustment parameters that meet the stability criteria are calculated. The impedance of the fully controlled AC interconnection device is adjusted according to the impedance adjustment parameters so that the impedance of the fully controlled AC interconnection device and the power grid to which the fully controlled AC interconnection device is connected meets the stability criterion condition.

[0012] As an improvement to the above scheme, the fully controlled AC interconnection device includes: multiple flexible power flow control modules, multiple reactive power coordination control modules, parallel compensation control modules, and circuit breaker current control modules; wherein, multiple flexible power flow control modules, multiple reactive power coordination control modules, the parallel compensation control modules, and the circuit breaker current control modules are connected in parallel to the power grid bus.

[0013] As an improvement to the above scheme, the step of constructing a control model based on the topology of the fully controllable AC interconnection device includes: Based on the circuit topology of the flexible power flow control module, a first model of the parallel side and the series side of the flexible power flow control module is established; Based on the circuit topology of the reactive power coordination control module, a second model of the reactive power coordination control module is established; Based on the circuit topology of the parallel compensation control module, a third model of the parallel compensation control module is established. Based on the first model, the second model, and the third model, the circuit breaker current control module is regarded as a short-circuit branch under the normal operating conditions of the fully controlled AC interconnection device. The control model is established based on Kirchhoff's current and voltage theory of the topology of the fully controlled AC interconnection device.

[0014] Secondly, embodiments of the present invention provide a fully controllable AC interconnection device control system based on phase-locked loop and feedforward decoupling, comprising: The first model construction module is used to construct a control model based on the topology of the fully controllable AC interconnection device; The phase-locked loop disturbance module is used to calculate the synchronous rotation coordinate transformation matrix of the phase-locked loop after the disturbance signal is injected into the voltage coupling point of the fully controlled AC interconnection device connected to the grid. The transfer function determination module is used to determine the transfer function between the disturbance signal and the phase angle disturbance based on the synchronous rotating coordinate transformation matrix. The feedforward decoupling module is used to perform feedforward decoupling on the first output electrical parameters of the grid-connected side of the control model to obtain the modulation signal under the synchronous rotating coordinate transformation matrix. The second model construction module is used to construct the impedance model of the fully controlled AC interconnection device based on the control model, the transfer function, and the modulation signal. An impedance adjustment module is used to adjust the impedance of the fully controlled AC interconnect device according to the impedance model.

[0015] Compared to existing technologies, this invention provides a control method and system for a fully controlled AC interconnection device based on phase-locked loop (PLL) and feedforward decoupling. First, a control model is constructed based on the topology of the fully controlled AC interconnection device. Then, when a disturbance signal is injected at the voltage coupling point of the fully controlled AC interconnection device connected to the grid, the synchronous rotating coordinate transformation matrix of the PLL after the disturbance signal is injected is calculated. Based on the synchronous rotating coordinate transformation matrix, the transfer function between the disturbance signal and the phase angle disturbance is determined. Next, the first output electrical parameters of the control model on the grid-connected side are decoupled using feedforward to obtain the modulation signal under the synchronous rotating coordinate transformation matrix. Based on the control model, the transfer function, and the modulation signal, an impedance model of the fully controlled AC interconnection device is constructed. Finally, the impedance of the fully controlled AC interconnection device is adjusted according to the impedance model. This invention, by analyzing the impedance characteristics of the fully controlled AC interconnection device connected to the grid, can effectively improve the stability of the fully controlled AC interconnection device when connected to the grid. Attached Figure Description

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

[0017] Figure 1 This is a flowchart of a fully controllable AC interconnection device control method based on phase-locked loop and feedforward decoupling provided in an embodiment of the present invention; Figure 2 This is a circuit diagram of the fully controlled AC interconnection device provided in an embodiment of the present invention; Figure 3This is a circuit diagram of the parallel compensation control module provided in an embodiment of the present invention; Figure 4 This is a circuit diagram of the flexible power flow control module provided in an embodiment of the present invention; Figure 5 This is a circuit diagram of multiple reactive power coordination control modules provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the first impedance characteristic curve of the fully controllable AC interconnection device provided in the embodiment of the present invention; Figure 7 This is a schematic diagram of the second impedance characteristic curve of the fully controllable AC interconnection device provided in the embodiment of the present invention; Figure 8 This is a structural block diagram of a fully controllable AC interconnection device control system based on phase-locked loop and feedforward decoupling, provided by an embodiment of the present invention. Detailed Implementation

[0018] 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.

[0019] It is understood that the various numerical designations used in the embodiments of this invention are merely for descriptive convenience and are not intended to limit the scope of this application. The order of the process numbers does not imply the order of execution; the execution order of each process should be determined by its function and internal logic.

[0020] In embodiments of the invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element. The term "a plurality or several" refers to two or more.

[0021] See Figure 1 , Figure 1This is a flowchart illustrating a fully controllable AC interconnection device control method based on phase-locked loop (PLL) and feedforward decoupling, provided by an embodiment of the present invention. The fully controllable AC interconnection device control method based on PLL and feedforward decoupling specifically includes: S11: Construct a control model based on the topology of the fully controllable AC interconnection device; S12: When a disturbance signal is injected into the voltage coupling point of the fully controlled AC interconnection device connected to the grid, calculate the synchronous rotating coordinate transformation matrix of the phase-locked loop after the disturbance signal is injected; S13: Determine the transfer function between the disturbance signal and the phase angle disturbance based on the synchronous rotating coordinate transformation matrix; S14: Perform feedforward decoupling on the first output electrical parameters of the grid-connected side of the control model to obtain the modulation signal under the synchronous rotating coordinate transformation matrix; S15: Construct the impedance model of the fully controlled AC interconnection device based on the control model, the transfer function, and the modulation signal; S16: Adjust the impedance of the fully controlled AC interconnection device according to the impedance model.

[0022] This invention, based on the topology of a fully controlled AC interconnected device, constructs a corresponding control model. Then, considering the injection of a disturbance signal at the voltage coupling point of the grid-connected control model, it employs symmetrical component analysis and harmonic linearization, taking into account the impact of phase angle disturbances caused by the phase-locked loop (PLL) on the control system, and calculates the synchronous rotating coordinate transformation matrix of the PLL after the disturbance signal is injected. Based on this synchronous rotating coordinate transformation matrix, the transfer function between the disturbance signal and the phase angle disturbance is determined. Subsequently, the first output electrical parameters on the grid-connected side of the control model are decoupled using feedforward decoupling (e.g., inductor current and voltage feedforward decoupling) to obtain the modulation signal under the synchronous rotating coordinate transformation matrix. Then, combining the control model, transfer function, and modulation signal, an impedance model of the fully controlled AC interconnected device is constructed. This invention, based on PLL and feedforward control, performs impedance analysis on the grid-connected fully controlled AC interconnected device. Based on the analyzed impedance model, the impedance of the fully controlled AC interconnected device is adjusted to match the impedance of the device to the grid connection, thus meeting stability requirements and effectively improving the stability of the fully controlled AC interconnected device connected to the grid.

[0023] Furthermore, such as Figure 2 The topology of the fully controlled AC interconnection device shown includes: multiple flexible power flow control modules P, multiple reactive power coordination control modules Q, parallel compensation control modules G, and circuit breaker current control modules D; wherein, the multiple flexible power flow control modules P, the multiple reactive power coordination control modules Q, the parallel compensation control modules G, and the circuit breaker current control modules D are connected in parallel to the power grid bus.

[0024] The parallel compensation control module G includes a voltage source converter VSC and a first capacitor C1 connected in parallel, and a first transformer TR1 and a switch K connected in series, wherein, as Figure 3 As shown, the voltage source converter (VSC) consists of multiple second-type transistors, such as insulated-gate bipolar transistors combined with thyristors.

[0025] The main function of the parallel compensation control module G is to achieve parallel compensation of voltage and reactive power, while also providing power quality management and wideband oscillation suppression. The circuit structure of the parallel compensation control module G is similar to that of a static synchronous compensator, with its main component being a self-commutated voltage-source three-phase full-bridge inverter.

[0026] like Figure 4 As shown, the flexible power flow control module P includes a rectifier full-bridge circuit and an inverter full-bridge circuit connected in parallel on the DC side, and a second capacitor C2. The second capacitor C2 is connected between the inverter full-bridge circuit and the rectifier full-bridge circuit. The AC port of the rectifier full-bridge circuit is connected to a second transformer TR2 (e.g., ...). Figure 2 (As shown). The inverter full-bridge circuit consists of multiple first-type transistors VT1, such as insulated-gate bipolar transistors with capacitors; the rectifier full-bridge circuit consists of multiple second-type transistors VT2, such as insulated-gate bipolar transistors combined with thyristors.

[0027] Among them, the main function of the flexible power flow control module P is to accurately track the voltage difference of the power supply point, and to quickly, flexibly and comprehensively regulate the power flow, thereby achieving flexible regulation of the power flow across the entire range.

[0028] like Figure 5 As shown, the reactive power coordination control module Q includes a reactive power full-bridge circuit and a third capacitor C3 connected in parallel on the DC side. The reactive power full-bridge circuit is composed of multiple first-type transistors, such as insulated-gate bipolar transistors with capacitors.

[0029] Among them, the reactive power coordination control module Q assists in power flow regulation and short-circuit control by adjusting the reactive power component perpendicular to the line current. In addition, during a short-circuit fault, the module can be locked to assist in short-circuit current control.

[0030] like Figure 2 As shown, the circuit breaker current control module D includes a diode rectifier bridge circuit, a fourth capacitor C4 and a fifth capacitor C5 connected to the DC side of the diode rectifier bridge circuit, and a current-carrying branch connected in parallel to the DC or AC side of the diode rectifier bridge circuit; wherein, the diode rectifier bridge circuit is composed of multiple diodes GT; the current-carrying loop is composed of at least two first-type transistors VT1, such as insulated-gate bipolar transistors with capacitors.

[0031] During normal operation, the circuit breaker current control module D bypasses the current-carrying branch. When a short circuit occurs in the system, the DC capacitor (i.e., the fourth capacitor C4 and the fifth capacitor C5 mentioned above) is charged through the diode rectifier bridge circuit to achieve the purpose of quickly blocking the blocking voltage and fault current. Since the embodiment of the present invention is based on impedance modeling analysis under normal operating conditions, the circuit breaker current control module D can be approximated as a short-circuit branch.

[0032] In an optional embodiment, S11: Based on the topology of the fully controllable AC interconnection device, a control model is constructed, including: Based on the circuit topology of the flexible power flow control module, a first model of the parallel side and the series side of the flexible power flow control module is established; For example, the first model of the parallel and series sides of the flexible power flow control module is as follows: (1); (2); Among them, V Pdc Indicates the DC-side voltage of the flexible power flow control module; u Pa u Pb u Pc These represent the phase A, B, and C voltages of the bus at the parallel connection point of the flexible power flow control module; i Pa i Pb i Pc These represent the A, B, and C phase currents on the parallel side of the flexible power flow control module, respectively; u 12a u 12b u 12c These represent the A, B, and C phase voltages of the flexible power flow control module connected in series with the transmission line; i se1a i se1b i se1c L1 and L2 represent the A, B, and C phase currents on the series side of the flexible power flow control module, respectively; L1 and L2 represent the filter inductors on the series and parallel sides of the flexible power flow control module, respectively; m Pa1 m Pb1 m Pc1 These represent the output modulation signals of phases A, B, and C on the parallel side of the flexible power flow control module, respectively; m Pa2 m Pb2 m Pc2 These represent the output modulation signals of phases A, B, and C on the series side of the flexible power flow control module, respectively; s=jω, where j represents the imaginary unit and ω represents the angular frequency.

[0033] Based on the circuit topology of the reactive power coordination control module, a second model of the reactive power coordination control module is established; For example, the second model of the reactive power coordination control module is as follows: (3); (4); Among them, i se2 u represents the output current of the reactive power coordination control module. se2 C3 represents the output modulation voltage of the reactive power coordination control module, and C3 represents the capacitance value of the third capacitor C3 (i.e., the energy storage capacitor) of the reactive power coordination control module. f u represents the output filter capacitor of the reactive power coordination control module. 23 t represents the output voltage of the reactive power coordination control module, and t represents time.

[0034] Based on the circuit topology of the parallel compensation control module, a third model of the parallel compensation control module is established. For example, the third model of the parallel compensation control module is as follows: (5); Among them, V Gdc L3 represents the DC side voltage of the parallel compensation control module; L3 represents the filter inductance of the parallel compensation control module; i Ga i Gb i Gc These represent the output inductor currents of phases A, B, and C of the parallel compensation control module, respectively; u pcca u pccb u pccc These represent the output voltages of phases A, B, and C of the parallel compensation control module, respectively; m Ga m Gb m Gc These represent the output modulation signals of phases A, B, and C of the parallel compensation control module, respectively.

[0035] Based on the first model, the second model, and the third model, the circuit breaker current control module is regarded as a short-circuit branch under the normal operating conditions of the fully controlled AC interconnection device. The control model is established based on Kirchhoff's current and voltage theory of the topology of the fully controlled AC interconnection device.

[0036] For example, by combining the above formulas (1)-(5) and based on Kirchhoff's current and voltage theory of the fully controlled AC interconnection device topology, a complete control model of the fully controlled AC interconnection device based on phase-locked loop and feedforward decoupling is established, as follows: (6); Where L represents the output filter inductance of the fully controlled AC interconnection device, V ga V gb V gcThis represents the A, B, and C phase voltages of the voltage coupling point PCC of a fully controlled AC interconnection device connected to the grid (connected to the power grid), in V. Ra V Rb V Rc I represents the A, B, and C phase voltages at the right-side port of the PCC, the voltage coupling point of the fully controlled AC interconnection device. ga I gb I gc This represents the A, B, and C phase output currents of the fully controlled AC interconnection device, n. Q n represents the number of reactive power coordination control modules. P K represents the number of flexible power flow control modules. mP K mG These represent the modulation coefficients of the flexible power flow control module and the reactive power coordination control module, respectively.

[0037] In an optional embodiment, S12: When a disturbance signal is injected at the voltage coupling point of the fully controlled AC interconnection device connected to the grid, the synchronous rotating coordinate transformation matrix of the phase-locked loop after the disturbance signal is injected is calculated, including: When a disturbance signal is injected at the voltage coupling point of the fully controlled AC interconnection device connected to the grid, the phase angle disturbance of the phase-locked loop caused by the injection of the disturbance signal is calculated. Calculate the synchronous rotating coordinate transformation matrix based on the phase angle disturbance.

[0038] For example, consider injecting a disturbance signal, such as a small disturbance harmonic (which can be a positive or negative sequence disturbance voltage, with a voltage amplitude not exceeding 10% of the power frequency voltage), into the voltage of phase A in the time domain after the disturbance is injected. and current The details are as follows: (7); (8); Among them, V1, V p V n These represent the amplitudes of the fundamental voltage, positive-sequence perturbation voltage, and negative-sequence perturbation voltage, respectively; I1, I p I n Let f1 and f2 represent the amplitudes of the fundamental current, the positive-sequence disturbance current response, and the negative-sequence disturbance current response, respectively; p f n These represent the fundamental frequency, positive-sequence perturbation frequency, and negative-sequence perturbation frequency, respectively. vp , vn These represent the initial phase angles of the positive-sequence and negative-sequence disturbance voltages, respectively. i1 , ip and in denoted by , respectively, the initial phase angles of the fundamental current, the positive-sequence disturbance current response, and the negative-sequence disturbance current response, and t represents time.

[0039] The current of phase A in the time domain after the disturbance will be injected. and voltage By converting to the frequency domain, the positive and negative sequence voltages of phase A in the frequency domain are obtained. and positive sequence and negative sequence current The details are as follows: (9); (10); in, ; ; ; ; ; ; Indicates frequency.

[0040] Considering that injecting a small disturbance causes a phase angle disturbance Δθ in the phase-locked loop, i.e., θ PLL =θ1+Δθ, where θ PLL Let θ1 be the phase angle of the phase-locked loop rotation, and θ2 be the phase angle of the fundamental positive-sequence voltage rotation; then we can obtain... , Therefore, the synchronous rotation coordinate transformation matrix T(θ) PLL ) becomes: (11); In an optional embodiment, S13: Determining the transfer function between the disturbance signal and the phase angle disturbance based on the synchronous rotating coordinate transformation matrix includes: Without injecting a disturbance signal at the voltage coupling point of the grid-connected control model, calculate the first voltage component of the voltage coupling point in the frequency domain below the dq axis without considering the injected disturbance signal; Based on the transmission relationship between the phase angle disturbance and the frequency domain voltage in the phase-locked loop and the first voltage component, calculate the second voltage component of the voltage coupling point in the lower frequency domain of the dq axis after considering the injected disturbance signal; Based on the synchronous rotating coordinate transformation matrix and the second voltage component, the transfer function between the disturbance signal and the phase angle disturbance is determined.

[0041] For example, when the effect of injected perturbations is not considered, θ PLL =θ1, which gives the first voltage component of the voltage at the PCC point in the frequency domain along the dq axis, including the voltage component V along the d axis.d1 and the voltage component V along the q-axis q1 The details are as follows: (12); (13); Where dc represents direct current.

[0042] When considering the phase angle disturbance Δθ corresponding to a small disturbance, the voltage component V of the voltage at the PCC point in the frequency domain along the dq axis is combined with the voltage component V. d1 and voltage component V q1 From formula (11), the second voltage component of the voltage coupling point PCC of the grid-connected inverter in the frequency domain under the dq axis in the synchronous rotating coordinate system can be obtained, including the voltage component V under the d axis. d and the voltage component V along the q-axis q The details are as follows: (14); From Δθ and V in the phase-locked loop q The relationship shows that: H PLL (s) represents the transfer function of the phase-locked loop, H PLL (s)=(k p_PLL +k i_PLL / s) / s;k p_PLL k represents the proportional gain of the phase-locked loop. i_PLL This represents the integral coefficient of the phase-locked loop.

[0043] Assume the propagation relationship between small-signal voltage disturbance and Δθ in the frequency domain (i.e., the propagation relationship between phase angle disturbance and frequency domain voltage) is as follows: (15); Among them, G p (s), G n (s) represent the transfer functions between the positive-sequence small-signal disturbance voltage, the negative-sequence small-signal disturbance voltage, and the small disturbance phase angle (i.e., phase angle disturbance Δθ) of the phase-locked loop, respectively.

[0044] Substituting into the above formula (11), the synchronous rotation coordinate transformation matrix T(θ) is shown. PLL From this, we can obtain V. d and V q The frequency domain representation is as follows: (16); (17); The transfer function between the small-signal voltage disturbance and Δθ is further obtained as follows: (18); make ,because , We can obtain cosθ PLL and sinθ PLL In the frequency domain, it is expressed as: (19); (20).

[0045] In an optional embodiment, S14: feedforward decoupling is performed on the first output electrical parameters of the grid-connected side of the control model to obtain the modulation signal under the synchronous rotating coordinate transformation matrix, including: Based on the synchronous rotating coordinate transformation matrix, the multiphase output current in the first output electrical parameters of the grid-connected side of the control model is decoupled by inductor current feedforward, and the first modulation wave signal in the stationary coordinate is calculated. Based on the first modulation wave signal, the output voltage in the first output electrical parameters of the grid-connected side of the control model is decoupled by voltage feedforward to obtain the modulation signal.

[0046] Specifically, the step of performing inductor current feedforward decoupling on the multiphase output current in the first output electrical parameters of the grid-connected side of the control model based on the synchronous rotating coordinate transformation matrix, and calculating the first modulation wave signal in stationary coordinates, includes: Based on the synchronous rotating coordinate transformation matrix, Park transformation is performed on the multiphase output current in the first output electrical parameters of the grid-connected side of the control model to obtain the first current component in the frequency domain on the dq axis. The multiphase output current is decoupled by inductor current feedforward to obtain a second modulation wave signal in a synchronous rotating coordinate system. Based on the second modulation wave signal, the third modulation wave signal in the frequency domain is obtained; Based on the synchronous rotating coordinate transformation matrix, the third modulation wave signal is subjected to an inverse Parker transformation to obtain the first modulation wave signal of the control model in stationary coordinates.

[0047] For example, the multi-phase output current in the first output electrical parameters of the control model on the grid-connected side of the fully controlled AC interconnection device, such as the A, B, and C phase currents i on the parallel side of the flexible power flow control module. Pa i Pb i P Based on the above synchronous rotation coordinate transformation matrix T(θ) PLL Converted to current component i along the dq axis Pd i Pq The details are as follows: (twenty one).

[0048] Current component i Pd i Pq The frequency domain expression (i.e., the first current component) is: (twenty two); (twenty three).

[0049] Based on the inductor current feedforward decoupling control of the control model corresponding to the fully controlled AC interconnection device, the second modulation wave signal c of the fully controlled AC interconnection device in the synchronous rotating coordinate system can be obtained. d and c q for: (twenty four).

[0050] Among them, I dr I qr K represents the current reference value of the flexible power flow control module along the dq axis. d Hi(s) represents the current decoupling coefficient of the flexible power flow control module, and Hi(s) represents the current PI controller, Hi(s) = k p_I +k i_I / s, where k p_I For the proportional gain of the current PI controller in the flexible power flow control module, k i_I This represents the integral coefficient of the current PI controller in the flexible power flow control module.

[0051] The current component i in the above formulas (22) and (23) Pd i Pq Substituting the frequency domain expression into the above formula (24), we can obtain c. d and c q The frequency domain representation (i.e., the third modulated wave signal) is as follows: (25); (26).

[0052] The first modulated wave signal in the stationary coordinate system can be obtained by inverse dq coordinate transformation (inverse Parker transformation), as follows: (27).

[0053] Among them, T PLL The above synchronous rotation coordinate transformation matrix T(θ) represents... PLL ).

[0054] Considering voltage feedforward control, we can obtain m Pa =c a +K f v a ca To represent the first modulated wave signal of phase A, K f V represents the voltage feedforward coefficient of the flexible power flow control module. a This represents the A-phase output voltage of the flexible power flow control module (i.e., the aforementioned u). Pa ), m Pa This represents the A-phase output modulation voltage (i.e., the modulation signal mentioned above) of the flexible power flow control module after the addition of voltage feedforward control. m can be obtained. Pa The frequency domain expression is: (28).

[0055] In an optional embodiment, S15: Constructing the impedance model of the fully controlled AC interconnect device based on the control model, the transfer function, and the modulation signal, including: Using the transfer function and the modulation signal, the positive-sequence impedance characteristics and negative-sequence impedance characteristics of the fully controlled AC interconnect device are calculated through the control model. Based on the positive-sequence impedance characteristics and the negative-sequence impedance characteristics, an impedance model of the fully controlled AC interconnection device is constructed.

[0056] m Pa Substituting the frequency domain expression into the control model of the fully controlled AC interconnection device based on phase-locked loop and feedforward decoupling, we can obtain the impedance module of the fully controlled AC interconnection device, including the positive impedance model. Negative sequence impedance model The details are as follows: (29); (30); Among them, I drG I qrG HiG(s) represents the current reference value of the parallel compensation control module along the dq axis, and HiG(s) represents the current PI controller of the parallel compensation control module. HiG(s) = k p_GI +k i_GI / s, where k p_GI k is the proportional gain of the current PI controller in the parallel compensation control module. i_GI K represents the integral coefficient of the current PI controller in the parallel compensation control module. dG K represents the voltage feedforward coefficient of the flexible power flow control module. fG This represents the voltage feedforward coefficient of the flexible power flow control module.

[0057] Based on the above positive impedance model Negative sequence impedance model The impedance analysis curve of a fully controlled AC interconnection device can be obtained, such as... Figure 6The positive sequence impedance amplitude-frequency characteristic shown Figure 7 The analytical data of the negative sequence impedance amplitude-frequency characteristics shown are presented, and a model is built on a simulation platform for verification. The verification results are as follows: Figure 6 The positive sequence impedance amplitude-frequency characteristic shown Figure 7 The frequency sweep data of the negative sequence impedance amplitude-frequency characteristic shown is based on Figure 6 , Figure 7 It can be seen that the analytical data and the frequency sweep data basically overlap, and the above positive impedance model Negative sequence impedance model The impedance model conforms to the impedance characteristics of a fully controlled AC interconnection device, verifying the correctness of the impedance model construction.

[0058] In an optional embodiment, S16: According to the impedance model, impedance adjustment is performed on the fully controlled AC interconnect device, including: By using preset stability criteria, the impedance model of the fully controlled AC interconnection device and the impedance characteristics of the power grid to which the fully controlled AC interconnection device is connected are evaluated for stability, and the impedance adjustment parameters that meet the stability criteria are calculated. The impedance of the fully controlled AC interconnection device is adjusted according to the impedance adjustment parameters so that the impedance of the fully controlled AC interconnection device and the power grid to which the fully controlled AC interconnection device is connected meets the stability criterion condition.

[0059] In this embodiment of the invention, the positive impedance model constructed above is used as a basis. Negative sequence impedance model Further analysis is conducted on the impedance characteristics of the grid-connected power grid system. Based on preset stability criteria, such as the Nyquist stability criterion, the oscillation mechanism of the power grid connected to the fully controlled AC interconnection device is analyzed, including the impedance of the fully controlled AC interconnection device (such as the aforementioned positive impedance model). Negative sequence impedance model If the ratio of the impedance of the fully controlled AC interconnection device to the impedance of the power grid is equal to 0, it indicates that the closed-loop system formed by the power grid connected to the fully controlled AC interconnection device is stable; if the ratio of the impedance of the fully controlled AC interconnection device to the impedance of the power grid is not equal to 0, it indicates that the closed-loop system formed by the power grid connected to the fully controlled AC interconnection device is unstable. In this embodiment of the invention, by adjusting the impedance of the fully controlled AC interconnection device, the ratio of the impedance of the fully controlled AC interconnection device to the impedance of the power grid is made equal to 0, so that the impedance of the fully controlled AC interconnection device matches the impedance of the power grid, thereby improving the stability of the power grid connected to the fully controlled AC interconnection device.

[0060] See Figure 8 , Figure 8This invention provides a structural block diagram of a fully controllable AC interconnection device control system based on phase-locked loop and feedforward decoupling. The fully controllable AC interconnection device control system based on phase-locked loop and feedforward decoupling includes: The first model construction module 11 is used to construct a control model based on the topology of the fully controllable AC interconnection device; The phase-locked loop disturbance module 12 is used to calculate the synchronous rotation coordinate transformation matrix of the phase-locked loop after the disturbance signal is injected into the voltage coupling point of the fully controlled AC interconnection device. The transfer function determination module 13 is used to determine the transfer function between the disturbance signal and the phase angle disturbance based on the synchronous rotating coordinate transformation matrix. Feedforward decoupling module 14 is used to perform feedforward decoupling on the first output electrical parameters of the grid-connected side of the control model to obtain the modulation signal under the synchronous rotating coordinate transformation matrix; The second model construction module 15 is used to construct the impedance model of the fully controlled AC interconnection device based on the control model, the transfer function and the modulation signal; Impedance adjustment module 16 is used to adjust the impedance of the fully controlled AC interconnect device according to the impedance model.

[0061] In one optional embodiment, the phase-locked loop disturbance module 12 includes: The phase angle disturbance calculation unit is used to calculate the phase angle disturbance of the phase-locked loop caused by the injection of the disturbance signal when the voltage coupling point of the fully controlled AC interconnection device is connected to the grid. The transformation matrix calculation unit is used to calculate the synchronous rotating coordinate transformation matrix based on the phase angle disturbance.

[0062] In an optional embodiment, the transfer function determination module 13 includes: The first voltage component calculation unit is used to calculate the first voltage component of the voltage coupling point in the dq-axis frequency domain without considering the injected disturbance signal when no disturbance signal is injected at the voltage coupling point of the control model grid connection. The second voltage component calculation unit is used to calculate the second voltage component of the voltage coupling point in the dq-axis frequency domain after considering the injected disturbance signal, based on the transmission relationship between the phase angle disturbance and the frequency domain voltage in the phase-locked loop and the first voltage component. The function determination unit is used to determine the transfer function between the disturbance signal and the phase angle disturbance based on the synchronous rotating coordinate transformation matrix and the second voltage component.

[0063] In an optional embodiment, the feedforward decoupling module 14 includes: The inductor current feedforward decoupling unit is used to perform inductor current feedforward decoupling on the multiphase output current in the first output electrical parameters of the grid-connected side of the control model according to the synchronous rotating coordinate transformation matrix, and to calculate the first modulation wave signal in the stationary coordinate. The voltage feedforward decoupling unit is used to perform voltage feedforward decoupling on the output voltage in the first output electrical parameters of the grid-connected side of the control model according to the first modulation wave signal, so as to obtain the modulation signal.

[0064] In one optional embodiment, the inductor current feedforward decoupling unit includes: The first current component calculation subunit is used to perform Park transformation on the multiphase output current in the first output electrical parameters of the grid-connected side of the control model according to the synchronous rotating coordinate transformation matrix, so as to obtain the first current component in the frequency domain on the dq axis. The first modulation wave signal calculation subunit is used to perform inductor current feedforward decoupling on the multiphase output current to obtain the second modulation wave signal in the synchronous rotating coordinate system. The second modulation wave signal calculation subunit is used to obtain the third modulation wave signal in the frequency domain based on the second modulation wave signal; The third modulation wave signal calculation subunit is used to perform an inverse Park transform on the third modulation wave signal according to the synchronous rotating coordinate transformation matrix to obtain the first modulation wave signal of the control model in stationary coordinates.

[0065] In an optional embodiment, the second model building module 15 includes: The impedance characteristic calculation unit is used to calculate the positive-sequence impedance characteristics and negative-sequence impedance characteristics of the fully controlled AC interconnect device by using the transfer function and the modulation signal through the control model. The impedance model construction unit is used to construct the impedance model of the fully controlled AC interconnection device based on the positive-sequence impedance characteristics and the negative-sequence impedance characteristics.

[0066] In an optional embodiment, the impedance adjustment module 16 includes: The impedance adjustment parameter calculation unit is used to evaluate the stability of the impedance model of the fully controlled AC interconnection device and the impedance characteristics of the power grid to which the fully controlled AC interconnection device is connected, based on preset stability criteria, and to calculate the impedance adjustment parameters that meet the stability criteria. An impedance adjustment unit is used to adjust the impedance of the fully controlled AC interconnection device according to the impedance adjustment parameters, so that the impedance of the fully controlled AC interconnection device and the power grid to which the fully controlled AC interconnection device is connected meets the stability criterion condition.

[0067] In one optional embodiment, the fully controlled AC interconnection device includes: multiple flexible power flow control modules, multiple reactive power coordination control modules, parallel compensation control modules, and circuit breaker current control modules; wherein, the multiple flexible power flow control modules, the multiple reactive power coordination control modules, the parallel compensation control modules, and the circuit breaker current control modules are connected in parallel to the power grid bus.

[0068] In an optional embodiment, the first model building module 11 includes: The first model building unit is used to build a first model of the parallel side and the series side of the flexible power flow control module according to the circuit topology of the flexible power flow control module. The second model building unit is used to build a second model of the reactive power coordination control module based on the circuit topology of the reactive power coordination control module. The third model building unit is used to build a third model of the parallel compensation control module based on the circuit topology of the parallel compensation control module. The control model establishment unit is used to establish the control model based on the first model, the second model, and the third model, treating the circuit breaker current control module as a short-circuit branch under the normal operating conditions of the fully controlled AC interconnection device.

[0069] It should be noted that the working process of each module in the fully controllable AC interconnection device control system based on phase-locked loop and feedforward decoupling described in the embodiments of the present invention can refer to the working process of the fully controllable AC interconnection device control method based on phase-locked loop and feedforward decoupling described in the above embodiments. The technical effect achieved is also the same as that of the fully controllable AC interconnection device control method based on phase-locked loop and feedforward decoupling described in the above embodiments, and will not be repeated here.

[0070] It should be noted that the system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the system embodiments provided by this invention, the connection relationships between modules indicate that they have communication connections, which can be specifically implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.

[0071] The above description represents the preferred embodiments of the present invention. It should be noted that, for those skilled in the art, various improvements and modifications can be made 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 control method for a fully controlled AC interconnected device based on phase-locked loop and feedforward decoupling, characterized in that, include: Based on the topology of the fully controllable AC interconnection device, a control model is constructed; When a disturbance signal is injected into the voltage coupling point of the fully controlled AC interconnection device connected to the grid, calculate the synchronous rotating coordinate transformation matrix of the phase-locked loop after the disturbance signal is injected; Based on the synchronous rotating coordinate transformation matrix, determine the transfer function between the disturbance signal and the phase angle disturbance; By performing feedforward decoupling on the first output electrical parameters of the grid-connected side of the control model, the modulation signal under the synchronous rotating coordinate transformation matrix is ​​obtained. Based on the control model, the transfer function, and the modulation signal, an impedance model of the fully controllable AC interconnection device is constructed. The impedance of the fully controlled AC interconnect device is adjusted according to the impedance model.

2. The control method for a fully controlled AC interconnection device based on phase-locked loop and feedforward decoupling as described in claim 1, characterized in that, When a disturbance signal is injected at the voltage coupling point of the fully controlled AC interconnection device connected to the grid, the synchronous rotating coordinate transformation matrix of the phase-locked loop after the disturbance signal is injected is calculated, including: When a disturbance signal is injected at the voltage coupling point of the fully controlled AC interconnection device connected to the grid, the phase angle disturbance of the phase-locked loop caused by the injection of the disturbance signal is calculated. Calculate the synchronous rotating coordinate transformation matrix based on the phase angle disturbance.

3. The control method for a fully controlled AC interconnected device based on phase-locked loop and feedforward decoupling as described in claim 2, characterized in that, Determining the transfer function between the disturbance signal and the phase angle disturbance based on the synchronous rotating coordinate transformation matrix includes: Without injecting a disturbance signal at the voltage coupling point of the grid-connected control model, calculate the first voltage component of the voltage coupling point in the frequency domain below the dq axis without considering the injected disturbance signal; Based on the transmission relationship between the phase angle disturbance and the frequency domain voltage in the phase-locked loop and the first voltage component, calculate the second voltage component of the voltage coupling point in the lower frequency domain of the dq axis after considering the injected disturbance signal; Based on the synchronous rotating coordinate transformation matrix and the second voltage component, the transfer function between the disturbance signal and the phase angle disturbance is determined.

4. The control method for a fully controlled AC interconnected device based on phase-locked loop and feedforward decoupling as described in claim 1, characterized in that, The step of feedforward decoupling the first output electrical parameters of the grid-connected side of the control model to obtain the modulated signal under the synchronous rotating coordinate transformation matrix includes: Based on the synchronous rotating coordinate transformation matrix, the multiphase output current in the first output electrical parameters of the grid-connected side of the control model is decoupled by inductor current feedforward, and the first modulation wave signal in the stationary coordinate is calculated. Based on the first modulation wave signal, the output voltage in the first output electrical parameters of the grid-connected side of the control model is decoupled by voltage feedforward to obtain the modulation signal.

5. The control method for a fully controlled AC interconnected device based on phase-locked loop and feedforward decoupling as described in claim 4, characterized in that, The step of performing inductor current feedforward decoupling on the multiphase output current in the first output electrical parameters of the grid-connected side of the control model according to the synchronous rotating coordinate transformation matrix, and calculating the first modulation wave signal in stationary coordinates, includes: Based on the synchronous rotating coordinate transformation matrix, Park transformation is performed on the multiphase output current in the first output electrical parameters of the grid-connected side of the control model to obtain the first current component in the frequency domain on the dq axis. The multiphase output current is decoupled by inductor current feedforward to obtain a second modulation wave signal in a synchronous rotating coordinate system. Based on the second modulation wave signal, the third modulation wave signal in the frequency domain is obtained; Based on the synchronous rotating coordinate transformation matrix, the third modulation wave signal is subjected to an inverse Parker transformation to obtain the first modulation wave signal of the control model in stationary coordinates.

6. The control method for a fully controlled AC interconnected device based on phase-locked loop and feedforward decoupling as described in claim 1, characterized in that, The step of constructing the impedance model of the fully controlled AC interconnection device based on the control model, the transfer function, and the modulation signal includes: Using the transfer function and the modulation signal, the positive-sequence impedance characteristics and negative-sequence impedance characteristics of the fully controlled AC interconnect device are calculated through the control model. Based on the positive-sequence impedance characteristics and the negative-sequence impedance characteristics, an impedance model of the fully controlled AC interconnection device is constructed.

7. The control method for a fully controlled AC interconnection device based on phase-locked loop and feedforward decoupling as described in claim 1, characterized in that, The impedance adjustment of the fully controlled AC interconnect device according to the impedance model includes: By using preset stability criteria, the impedance model of the fully controlled AC interconnection device and the impedance characteristics of the power grid to which the fully controlled AC interconnection device is connected are evaluated for stability, and the impedance adjustment parameters that meet the stability criteria are calculated. The impedance of the fully controlled AC interconnection device is adjusted according to the impedance adjustment parameters so that the impedance of the fully controlled AC interconnection device and the power grid to which the fully controlled AC interconnection device is connected meets the stability criterion condition.

8. The control method for a fully controlled AC interconnection device based on phase-locked loop and feedforward decoupling as described in claim 1, characterized in that, The fully controlled AC interconnection device includes: multiple flexible power flow control modules, multiple reactive power coordination control modules, parallel compensation control modules, and circuit breaker current control modules; wherein, multiple flexible power flow control modules, multiple reactive power coordination control modules, the parallel compensation control modules, and the circuit breaker current control modules are connected in parallel to the power grid bus.

9. The control method for a fully controlled AC interconnection device based on phase-locked loop and feedforward decoupling as described in claim 8, characterized in that, The construction of a control model based on the topology of the fully controllable AC interconnection device includes: Based on the circuit topology of the flexible power flow control module, a first model of the parallel side and the series side of the flexible power flow control module is established; Based on the circuit topology of the reactive power coordination control module, a second model of the reactive power coordination control module is established; Based on the circuit topology of the parallel compensation control module, a third model of the parallel compensation control module is established. Based on the first model, the second model, and the third model, the circuit breaker current control module is regarded as a short-circuit branch under the normal operating conditions of the fully controlled AC interconnection device. The control model is established based on Kirchhoff's current and voltage theory of the topology of the fully controlled AC interconnection device.

10. A fully controllable AC interconnection device control system based on phase-locked loop and feedforward decoupling, characterized in that, include: The first model construction module is used to construct a control model based on the topology of the fully controllable AC interconnection device; The phase-locked loop disturbance module is used to calculate the synchronous rotation coordinate transformation matrix of the phase-locked loop after the disturbance signal is injected into the voltage coupling point of the fully controlled AC interconnection device connected to the grid. The transfer function determination module is used to determine the transfer function between the disturbance signal and the phase angle disturbance based on the synchronous rotating coordinate transformation matrix. The feedforward decoupling module is used to perform feedforward decoupling on the first output electrical parameters of the grid-connected side of the control model to obtain the modulation signal under the synchronous rotating coordinate transformation matrix. The second model construction module is used to construct the impedance model of the fully controlled AC interconnection device based on the control model, the transfer function, and the modulation signal. An impedance adjustment module is used to adjust the impedance of the fully controlled AC interconnect device according to the impedance model.

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