Synchronous phase angle synthesis method, synchronous compensator control method, synchronous phase angle synthesis system, synchronous compensator control equipment and medium

Abstract

The invention relates to a synchronous phase angle synthesis method, a synchronous compensator control method, a synchronous phase angle synthesis system, synchronous compensator control equipment and a medium. According to the synchronous phase angle synthesis method, the synchronous phase angle can be rapidly synthesized through the electrical parameters of the converter, the control transfer function and the controlled oscillator, and amplitude networking control can be achieved. According to the synchronous compensator control method, the synchronous phase angle can be rapidly synthesized through the synchronous phase angle synthesis method, so that the virtual potential control algorithm accurately outputs the reference current according to the amplitude of the virtual potential, the synchronous phase angle and the power grid alternating current voltage, the response speed of a current converter in the synchronous compensator can be improved, and the service life of the current converter is prolonged. And the active power of the current converter in the synchronous compensator can be quickly controlled through the reference current, so that the stability of the synchronous compensator can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of parallel power electronic converters, and in particular to a synchronous phase angle synthesis and synchronous compensator control method, system, equipment and medium. Background Art

[0002] Accurately and quickly obtaining information such as the amplitude, frequency, and phase angle of the grid AC voltage is a prerequisite for the normal operation of the grid-connected parallel power electronic converter. The widely used synchronization method based on the grid AC voltage is the phase-locked loop (PLL). In addition to the phase-locked loop based on the grid AC voltage, there are also Figure 1 The active power based synchronization and Figure 2 Synchronization based on DC voltage is shown.

[0003] like Figure 1 As shown, P ref is the reference value of active power, and P is the active power at the access point of the power electronic converter. ref The difference is ΔP, and the transfer function G P There are many options, three of which are typical: Figure 3 Proportional k in active power droop control d , Figure 4 Proportional k in active power synchronous control psc ( Figure 4 where t represents time) and Figure 5 1 / (Js+D) in virtual synchronous machine control, where J represents the moment of inertia and D represents the damping coefficient. The active power difference ΔP is calculated by the transfer function G P Then the corresponding angular velocity deviation Δω is obtained. The angular velocity deviation Δω and the reference angular velocity ω of the grid AC voltage 0 The sum is the estimated angular velocity ω. The angular velocity ω is passed through a controlled oscillator (the transfer function of the controlled oscillator is 1 / s) to obtain the phase angle θ.

[0004] like Figure 2 As shown, U DCref is the reference value of DC voltage, U DC is the measured value of the DC voltage of the power electronic converter. The measured value of the DC voltage U DC and reference value U DCref The difference is ΔU DC . After the transfer function G DC Then the corresponding angular velocity deviation Δω is obtained. The angular velocity deviation Δω and the reference angular velocity ω of the grid AC voltage 0 The sum is the estimated angular velocity ω. The angular velocity ω is passed through the controlled oscillator to obtain the phase angle θ.

[0005] Existing research conclusions show that when the AC grid is strong, the phase-locked loop based on the AC voltage of the grid makes the power electronic converter have higher stability; but when the AC grid is weak, both the synchronization based on active power and the synchronization based on DC voltage can make the power electronic converter have higher stability. At present, there is no synchronization method that combines the advantages of both.

[0006] Figure 6 A typical control block diagram of a static synchronous compensator (STATCOM) is given. The device-level control of STATCOM consists of five parts, namely synchronous control, DC voltage control, AC voltage control, current control, and modulation control. Synchronous control usually uses a phase-locked loop (PLL) based on the AC voltage of the power grid. The input quantity is usually the three-phase voltage v at the common connection point in the main circuit for simulation analysis. The corresponding angular velocity ω and phase angle θ are found through a typical three-phase phase-locked loop as the control reference for current control and voltage control. DC voltage control adjusts the size of the active power exchanged between STATCOM and the power grid by controlling the size of the active component of the output current, thereby stabilizing the DC voltage of STATCOM. The input quantity of DC voltage control is the DC voltage deviation Δv of the power electronic converter. dc , the output is the d-axis reference current i dref AC voltage control adjusts the amplitude of the AC voltage at the STATCOM access point or the common connection point by controlling the reactive power of the input grid. The input of AC voltage control is usually the deviation ΔV of the AC voltage at the STATCOM access point or the common connection point, and the output is the reference current i of the q axis. qref dq axis cross decoupling current control is a popular current control, the output is the three-phase voltage reference value v ref The current control goal is to ensure that the STATCOM output current can accurately and quickly track the corresponding reference current. The modulation control goal is to convert the voltage command into a pulse trigger signal received by power electronic switching devices such as the Insulate-Gate Bipolar Transistor (IGBT) in the power electronic converter. There are usually two types of modulation: Pulse Width Modulation (PWM) and Nearest Level Modulation (NLM).

[0007] The existing STATCOM device-level control agreement assumes that the AC grid is strong, so that the STATCOM follows the grid AC voltage and operates as a controlled current source. It cannot output current quickly within the device overload capacity when the grid AC voltage suddenly changes, like a synchronous condenser. Therefore, it is necessary to transform the STATCOM device-level control strategy so that the STATCOM can quickly output current within the device overload capacity when the grid AC voltage suddenly changes, like a synchronous condenser, and also enable the STATCOM to quickly respond to reactive power commands in reactive power control mode.

[0008] The grid-forming converter can be equivalent to the series connection of an ideal voltage source and an equivalent impedance. When the AC voltage of the power grid is disturbed, the amplitude and phase angle of the ideal voltage source remain unchanged. Within the overload capacity of the power electronic converter, it can output reactive / active power autonomously, which can be called amplitude and phase angle grid-forming control. For STATCOM, since there is no supercapacitor group, lithium battery or other energy storage device on the DC side of the power electronic converter, the energy stored in the DC capacitor is small. When grid-forming control is adopted, it is only hoped that the amplitude of the ideal voltage source remains unchanged, and the phase angle of the ideal voltage source can quickly track the phase angle of the AC voltage of the power grid, so that reactive power can be provided autonomously while facilitating the stability of the DC voltage of the power electronic converter. The corresponding grid-forming control can be called amplitude grid-forming control. At present, there is no corresponding amplitude grid-forming control strategy for STATCOM. Summary of the invention

[0009] In order to solve the technical problems existing in the prior art, the first aspect of the present invention provides a synchronous phase angle synthesis method, the method comprising:

[0010] Based on the electrical parameters of the converter, outputting the angular velocity deviation of the converter using a control transfer function;

[0011] Based on the angular velocity deviation of the converter, outputting the phase angle deviation of the converter using a controlled oscillator;

[0012] A synchronization phase angle is synthesized based on the phase angle deviation of the converter and the estimated phase angle of the grid AC voltage.

[0013] Optionally, the electrical parameters include DC voltage and active power;

[0014] The method of outputting the angular velocity deviation of the converter by using a control transfer function based on the electrical parameters of the converter comprises:

[0015] Based on the DC voltage and the active power, an angular velocity deviation of the converter is outputted using a control transfer function of DC voltage feedback and a control transfer function of active power feedback.

[0016] Optionally, the outputting the angular velocity deviation of the converter based on the DC voltage and the active power by using a control transfer function of DC voltage feedback and a control transfer function of active power feedback comprises:

[0017] Calculating a voltage deviation between a measured value of the DC voltage and a reference value of the DC voltage;

[0018] Based on the voltage deviation, outputting a reference value of the active power using a control transfer function of the DC voltage feedback;

[0019] Calculating an active power deviation between the measured value of the active power and the reference value of the active power;

[0020] Based on the active power deviation, an angular velocity deviation of the converter is outputted using a control transfer function of active power feedback.

[0021] Optionally, the outputting the angular velocity deviation of the converter based on the DC voltage and the active power by using a control transfer function of DC voltage feedback and a control transfer function of active power feedback comprises:

[0022] Calculating a voltage deviation between a measured value of the DC voltage and a reference value of the DC voltage;

[0023] Based on the voltage deviation, outputting a first standby angular velocity deviation using a control transfer function of the DC voltage feedback;

[0024] Calculating an active power deviation between the measured value of the active power and the reference value of the active power;

[0025] Based on the active power deviation, outputting a second standby angular velocity deviation using a control transfer function of the active power feedback;

[0026] The sum of the first standby angular velocity deviation and the second standby angular velocity deviation is used as the angular velocity deviation of the inverter.

[0027] Optionally, the electrical parameter includes active power;

[0028] The method of outputting the angular velocity deviation of the converter by using a control transfer function based on the electrical parameters of the converter comprises:

[0029] Calculating an active power deviation between the measured value of the active power and the reference value of the active power;

[0030] Based on the active power deviation, an angular velocity deviation of the converter is outputted using a control transfer function of active power feedback.

[0031] Optionally, the electrical parameter includes a DC voltage;

[0032] The method of outputting the angular velocity deviation of the converter by using a control transfer function based on the electrical parameters of the converter comprises:

[0033] Calculating a voltage deviation between a measured value of the DC voltage and a reference value of the DC voltage;

[0034] Based on the voltage deviation, the angular velocity deviation of the converter is outputted using a control transfer function of DC voltage feedback.

[0035] Optionally, the method for determining the estimated phase angle of the grid AC voltage includes:

[0036] Based on the AC voltage of the power grid, using a phase-locked loop to output an estimated phase angle of the AC voltage of the power grid; or,

[0037] Based on the grid AC voltage, an estimated phase angle of the grid AC voltage is outputted using a frequency locked loop.

[0038] Optionally, the outputting an estimated phase angle of the grid AC voltage by using a phase-locked loop based on the grid AC voltage includes:

[0039] When the converter adopts split-phase control, the grid AC voltage is a single-phase AC voltage, and the phase-locked loop is a voltage phase-locked loop, based on the single-phase AC voltage and the feedback phase angle output by the voltage phase-locked loop, the estimated phase angle of the grid AC voltage is output by using a phase detector, a loop filter and a controlled oscillator in the voltage phase-locked loop;

[0040] When the converter adopts non-phase control, the grid AC voltage is the positive sequence component of the three-phase AC voltage, and the phase-locked loop is a typical three-phase phase-locked loop, based on the positive sequence component of the three-phase AC voltage and the feedback phase angle output by the typical three-phase phase-locked loop, the estimated phase angle of the grid AC voltage is output by using the phase detector, loop filter and controlled oscillator in the typical three-phase phase-locked loop, wherein the phase detector of the typical three-phase phase-locked loop is a Park transform of equal amplitude, and the loop filter of the typical three-phase phase-locked loop is a proportional integral.

[0041] Optionally, the outputting an estimated phase angle of the grid AC voltage by using a frequency locked loop based on the grid AC voltage includes:

[0042] When the converter adopts split-phase control and the grid AC voltage is a single-phase AC voltage, based on the single-phase AC voltage, a frequency-locked loop without gain normalization is used to output an estimated phase angle of the grid AC voltage; or,

[0043] When the converter adopts phase-splitting control and the grid AC voltage is a single-phase AC voltage, based on the single-phase AC voltage, a frequency-locked loop with a gain normalized to one is used to output an estimated phase angle of the grid AC voltage; or,

[0044] When the converter adopts non-phase control, the grid AC voltage is the positive sequence component of the three-phase AC voltage, and the frequency locked loop is a three-phase frequency locked loop, based on the positive sequence component of the three-phase AC voltage, a three-phase frequency locked loop with normalized gain is used to output the estimated phase angle of the grid AC voltage.

[0045] Optionally, the outputting the estimated phase angle of the grid AC voltage based on the single-phase AC voltage using a frequency locked loop without gain normalization includes:

[0046] Based on the reference angular velocity, the quadrature-axis feedback voltage fed back by the second-order generalized integrator in the frequency-locked loop without gain normalization, the deviation of the direct-axis feedback voltage and the single-phase AC voltage, the angular velocity is estimated by using the output of the frequency locker in the frequency-locked loop;

[0047] Based on the estimated angular velocity, the deviation between the direct-axis feedback voltage and the single-phase AC voltage, outputting the direct-axis voltage and the quadrature-axis voltage using the second-order generalized integrator;

[0048] When the DC component of the single-phase AC voltage is less than a preset voltage threshold, based on the direct-axis voltage and the quadrature-axis voltage, a four-quadrant inverse tangent function is used to output an estimated phase angle of the AC voltage of the power grid;

[0049] When the DC component of the single-phase AC voltage is greater than or equal to a preset voltage threshold, based on the DC feedback voltage output by the controlled oscillator and the deviation between the direct-axis feedback voltage and the single-phase AC voltage, using the controlled oscillator to output an estimated DC voltage of the converter;

[0050] Based on the difference between the direct-axis voltage, the quadrature-axis voltage and the estimated direct-current voltage, an estimated phase angle of the alternating-current voltage of the power grid is output using a four-quadrant inverse tangent function.

[0051] Optionally, the outputting the estimated phase angle of the grid AC voltage by using a gain-normalized frequency-locked loop based on the single-phase AC voltage comprises:

[0052] Based on the gain normalization coefficient, the reference angular velocity, the quadrature-axis feedback voltage fed back by the second-order generalized integrator in the frequency-locked loop with gain normalization, the deviation of the direct-axis feedback voltage and the single-phase AC voltage, the angular velocity is estimated using the output of the frequency locker in the frequency-locked loop;

[0053] Based on the estimated angular velocity, the deviation between the direct-axis feedback voltage and the single-phase AC voltage, outputting the direct-axis voltage and the quadrature-axis voltage using the second-order generalized integrator;

[0054] When the DC component of the single-phase AC voltage is less than a preset voltage threshold, based on the direct-axis voltage and the quadrature-axis voltage, a four-quadrant inverse tangent function is used to output an estimated phase angle of the AC voltage of the power grid;

[0055] Wherein, the gain normalization coefficient is a coefficient output by a gain normalization function in the frequency locked loop based on the direct axis voltage, the quadrature axis voltage, and the estimated angular velocity;

[0056] When the DC component of the single-phase AC voltage is greater than or equal to a preset voltage threshold, based on the DC feedback voltage output by the controlled oscillator and the deviation between the direct-axis feedback voltage and the single-phase AC voltage, using the controlled oscillator to output an estimated DC voltage of the converter;

[0057] Based on the difference between the direct-axis voltage, the quadrature-axis voltage and the estimated direct-current voltage, outputting an estimated phase angle of the alternating-current voltage of the power grid using a four-quadrant inverse tangent function;

[0058] The gain normalization coefficient is a coefficient output by a gain normalization function in the frequency locked loop based on the direct-axis voltage, the difference between the quadrature-axis voltage and the estimated direct-current voltage, and the estimated angular velocity.

[0059] Based on the same inventive concept, the second aspect of the present invention provides a synchronous phase angle synthesis system, the system comprising:

[0060] an angular velocity deviation determining unit, configured to output an angular velocity deviation of the inverter using a control transfer function based on electrical parameters of the inverter;

[0061] a phase angle deviation determining unit, configured to output the phase angle deviation of the converter using a controlled oscillator based on the angular velocity deviation of the converter;

[0062] The synchronous phase angle synthesis unit is used to synthesize the synchronous phase angle based on the phase angle deviation of the converter and the estimated phase angle of the AC voltage of the power grid.

[0063] Based on the same inventive concept, the third aspect of the present invention provides a synchronous compensator control method, the method comprising:

[0064] Based on the electrical quantity of the synchronous compensator, the amplitude of the virtual potential is outputted by utilizing the control algorithm in the synchronous compensator;

[0065] Based on the electrical parameters of the converter, the synchronization phase angle is determined by using the synchronization phase angle synthesis method described in any one of the first aspects above;

[0066] Based on the amplitude of the virtual potential, the synchronous phase angle and the AC voltage of the power grid, a reference current is outputted using a virtual potential control algorithm in the synchronous compensator;

[0067] Based on the reference current, a converter in the synchronous compensator is controlled.

[0068] The control algorithm is a reactive power control algorithm, and the electrical quantity includes a virtual current value and an effective value of the AC voltage of the power grid;

[0069] The method of outputting the amplitude of the virtual potential based on the electrical quantity of the synchronous compensator and utilizing the control algorithm in the synchronous compensator includes:

[0070] Based on the virtual current value and the effective value of the AC voltage of the power grid, a reactive power control algorithm in the synchronous compensator is used to output a feedback voltage amplitude, or a feedforward voltage amplitude and a feedback voltage amplitude;

[0071] The amplitude of the virtual potential is obtained based on the feedback voltage amplitude, or the feedforward voltage amplitude and the feedback voltage amplitude.

[0072] Optionally, the control algorithm is an AC voltage control algorithm, and the electrical quantity includes an AC voltage deviation, a virtual current value, and a current extreme value;

[0073] The method of outputting the amplitude of the virtual potential based on the electrical quantity of the synchronous compensator and utilizing the control algorithm in the synchronous compensator includes:

[0074] Based on the AC voltage deviation, an AC voltage control algorithm in a synchronous compensator is used to output the amplitude of a virtual potential; or,

[0075] Based on the virtual current value and the current extreme value, an AC voltage control algorithm in a synchronous compensator is used to output the amplitude of the virtual potential.

[0076] Optionally, controlling the converter in the synchronous compensator based on the reference current includes:

[0077] Calculating a current difference between a current at an access side of the synchronous compensator and the reference current;

[0078] Based on the current difference and the voltage at the access side of the synchronous compensator, a reference value of the three-phase voltage is determined by using a current tracking algorithm;

[0079] Based on the reference value of the three-phase voltage, the capacitor voltage balance correction value, and the triangular carrier, a modulation wave control algorithm is used to determine the modulation wave of the switch tube in the synchronous compensator;

[0080] Based on the modulation wave of the switch tube in the synchronous compensator, the converter in the synchronous compensator is controlled.

[0081] Based on the same inventive concept, a fourth aspect of the present invention provides a synchronous compensator control system, the system comprising:

[0082] A virtual potential amplitude determination unit, configured to output the amplitude of the virtual potential based on the electrical quantity of the synchronous compensator and using a control algorithm in the synchronous compensator;

[0083] A synchronization phase angle determination unit, configured to determine the synchronization phase angle based on electrical parameters of the converter and using the synchronization phase angle synthesis method described in any one of the first aspects above;

[0084] a reference current determination unit, configured to output a reference current using a virtual potential control algorithm in the synchronous compensator based on the amplitude of the virtual potential, the synchronous phase angle and the grid AC voltage;

[0085] A synchronous compensator control unit is used to control the converter in the synchronous compensator based on the reference current.

[0086] Based on the same inventive concept, a fifth aspect of the present invention provides a computer device, including: one or more processors;

[0087] The processor is used to store one or more programs;

[0088] When the one or more programs are executed by the one or more processors, the synchronous phase angle synthesis method as described in any one of the first aspects, or the synchronous compensator control method as described in any one of the second aspects is implemented.

[0089] Based on the same inventive concept, the sixth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed, it implements the synchronous phase angle synthesis method as described in any one of the first aspects, or the synchronous compensator control method as described in any one of the second aspects.

[0090] Compared with the prior art, the present invention has the following beneficial effects:

[0091] The present invention provides a synchronous phase angle synthesis method, which can quickly synthesize the synchronous phase angle through the electrical parameters of the converter, the control transfer function and the controlled oscillator, and is conducive to realizing amplitude network control.

[0092] The present invention provides a synchronous compensator control method, which can quickly synthesize a synchronous phase angle through a synchronous phase angle synthesis method, so that a virtual potential control algorithm can accurately output a reference current according to the amplitude of the virtual potential, the synchronous phase angle and the AC voltage of the power grid, thereby facilitating the improvement of the response speed of the converter in the synchronous compensator, and the active power of the converter in the synchronous compensator can be quickly controlled through the reference current, thereby facilitating the improvement of the stability of the synchronous compensator. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Figure 1 A basic block diagram based on active power synchronization provided by the present invention;

[0094] Figure 2 A basic block diagram based on DC voltage synchronization provided by the present invention;

[0095] Figure 3 A basic block diagram of active power droop control provided by the present invention;

[0096] Figure 4 A basic block diagram of active power synchronous control provided by the present invention;

[0097] Figure 5 A basic block diagram of a virtual synchronous machine control provided by the present invention;

[0098] Figure 6 A control block diagram of a STATCOM provided by the present invention;

[0099] Figure 7 A schematic diagram of a main circuit for simulation analysis provided by the present invention;

[0100] Figure 8 A flow chart of a synchronous phase angle synthesis method provided by the present invention;

[0101] Fig. 9 A basic block diagram of a hybrid synchronization of DC voltage feedback and active power feedback in series provided by the present invention;

[0102] Fig.10 A basic block diagram of a hybrid synchronization of DC voltage feedback and active power feedback in parallel provided by the present invention;

[0103] Fig.11 A basic block diagram of hybrid synchronization based on active power feedback provided by the present invention;

[0104] Fig.12 A basic block diagram of hybrid synchronization based on DC voltage feedback provided by the present invention;

[0105] Fig.13 A basic block diagram based on a voltage phase-locked loop provided by the present invention;

[0106] Fig.14 Another basic block diagram based on a voltage phase-locked loop provided by the present invention;

[0107] Fig.15 A flow chart of determining the estimated phase angle of the AC voltage of a power grid using a frequency locked loop without gain normalization provided by the present invention;

[0108] Fig.16A basic block diagram of a frequency-locked loop gain not being normalized provided by the present invention;

[0109] Fig.17 A flow chart of determining the estimated phase angle of the AC voltage of a power grid by using a gain-normalized frequency-locked loop provided by the present invention;

[0110] Fig.18 A basic block diagram of a gain-normalized frequency-locked loop provided by the present invention;

[0111] Fig.19 A basic block diagram of a three-phase frequency-locked loop with gain normalization provided by the present invention;

[0112] Fig. 20 A block diagram of a synchronous phase angle synthesis system provided by the present invention;

[0113] Fig.21 A flow chart of a synchronous compensator control method provided by the present invention;

[0114] Fig. 22 A basic block diagram of STATCOM control using hybrid synchronization provided by the present invention;

[0115] Fig.23 A reactive power closed-loop control block diagram provided by the present invention;

[0116] Fig.24 A reactive power open-loop control block diagram provided by the present invention;

[0117] Fig.25 A schematic diagram of a rapid estimation of amplitude based on SOGI provided by the present invention;

[0118] Fig.26 A schematic diagram of a rapid amplitude estimation method based on αβ transformation provided by the present invention;

[0119] Fig. 27 A control strategy block diagram of a static synchronous compensator provided by the present invention;

[0120] Fig.28 A waveform curve diagram of voltage phase angle step during amplitude network control provided by the present invention;

[0121] Fig.29 A block diagram of a synchronous compensator control system provided by the present invention;

[0122] Fig.30 A block diagram of a computer device provided by the present invention. DETAILED DESCRIPTION

[0123] Before describing the specific implementation of the present invention in detail, the main circuit used in the embodiment of the present invention is described. Figure 7 As shown, Figure 7 The schematic diagram of the main circuit for simulation analysis provided by the present invention is shown in FIG. The structure and parameters of the main circuit are set according to the actual project and simplified appropriately. The corresponding supplementary explanations are as follows: 1) For AC signals, the per-unit value is calculated according to the peak value of the reference value, that is, under rated conditions, the peak value of the AC signal after per-unit is 1.0; 2) The voltage level of the high-voltage side of the step-up transformer is 500kV, and the reference value is 500kV, where v s Indicates the voltage on the high voltage side of the step-up transformer; 3) The voltage level on the low voltage side of the step-up transformer is 35kV, and the reference value is 35kV; 4) The transformation ratio of the transformer is set to 500kV / 35kV; 5) If there is no special explanation, only the waveform of phase a is given; 6) v dcMax v dc1 to v dc12 The maximum value in v dc1 is the DC voltage output by H-bridge 1 in the H-bridge cascade STATCOM, v dc12 is the DC voltage output by H bridge 12 in the H bridge cascade STATCOM; 7)v dcMin v dc1 to v dc12 The minimum value among 8)u dcAve v dc1 to v dc12 DC component u dc The average value of; 9)v rms is the effective value of voltage v (i.e. three-phase voltage v at the common connection point); 10)i rms is the effective value of current i; 11)P 1 and Q 1 is the corresponding fundamental active power and fundamental reactive power; θ 0 for Figure 7 Medium power supply V g The initial phase angle is in degrees. The H-bridge cascade STATCOM includes a converter.

[0124] The technical solution of the present invention is described in detail through the following examples.

[0125] Embodiment 1:

[0126] Figure 8 A flow chart of a synchronous phase angle synthesis method provided by the present invention is as follows: Figure 8 As shown, the method may include the following steps:

[0127] In step 801, based on the electrical parameters of the inverter, the angular velocity deviation of the inverter is output using a control transfer function.

[0128] The converter may be a power electronic converter, and the electrical parameters may include DC voltage and / or active power. The calculation of active power needs to take into account the influence of waveform distortion and DC component of voltage and current. The control transfer function may include a control transfer function of DC voltage feedback (i.e., control transfer function G DC ) or the control transfer function of active power feedback (i.e., the control transfer function G P ), control transfer function G DC It can be a combination of proportional (P), proportional integral (PI), proportional differential (PD), proportional integral differential (PID), first-order inertia, proportional resonance (PR), proportional differential (PD) and first-order inertia. The control transfer function G P is the second control transfer function, which may be proportional (P), first-order inertia, the product of proportional integral and first-order inertia, or a second-order low-pass filter.

[0129] In this step, the deviation value corresponding to the DC voltage and / or active power can be used to output the angular velocity deviation of the converter using a control transfer function.

[0130] It should be noted that the DC voltage and active power of the converter can be input into the control transfer function so that the control transfer function outputs the angular velocity deviation of the converter.

[0131] In step 802, based on the angular velocity deviation of the inverter, a phase angle deviation of the inverter is outputted using a controlled oscillator.

[0132] The transfer function of the controlled oscillator may be 1 / s, where s is a complex variable representing a frequency in a Laplace Transform domain.

[0133] It should be noted that the angular velocity deviation of the inverter can be input into the controlled oscillator, and the controlled oscillator outputs the phase angle deviation of the inverter.

[0134] In step 803, a synchronization phase angle is synthesized based on the phase angle deviation of the converter and the estimated phase angle of the grid AC voltage.

[0135] The AC voltage of the power grid can be Figure 7 The three-phase voltage v at the common connection point is shown in .

[0136] The estimated phase angle of the AC voltage of the power grid (which can be calculated using θ Uac(represented by) is the estimated phase angle of the AC voltage; the estimated phase angle of the grid AC voltage may be the phase angle of the AC voltage power frequency component or the phase angle of the three-phase AC voltage power frequency positive sequence component. In some embodiments, the power electronic converter adopts different control methods, and the estimated phase angle of the grid AC voltage may be different. For example, when the power electronic converter adopts phase-splitting control, the estimated phase angle of the grid AC voltage is the phase angle of the AC voltage power frequency component; when the phase-splitting control is not adopted, the estimated phase angle of the grid AC voltage is the phase angle of the three-phase AC voltage power frequency positive sequence component. The method for determining the estimated phase angle of the grid AC voltage includes: based on the grid AC voltage, using a phase-locked loop to output the estimated phase angle of the grid AC voltage; or, based on the grid AC voltage, using a frequency-locked loop to output the estimated phase angle of the grid AC voltage.

[0137] The above technical solution can quickly synthesize the synchronous phase angle through the electrical parameters of the converter, the control transfer function and the controlled oscillator, which is conducive to realizing amplitude network control.

[0138] above Figure 8 A possible implementation of step 801 shown may be: when the electrical parameters include active power, calculating the active power deviation between the measured value of the active power and the reference value of the active power; based on the active power deviation, using the control transfer function of active power feedback to output the angular velocity deviation of the converter.

[0139] above Figure 8 Another possible implementation of the step 801 shown may be: when the electrical parameters include DC voltage, calculating the voltage deviation between the measured value of the DC voltage and the reference value of the DC voltage; based on the voltage deviation, using the control transfer function of the DC voltage feedback to output the angular velocity deviation of the converter.

[0140] above Figure 8 Another possible implementation of step 801 may include the following steps:

[0141] In step 801, when the electrical parameters include DC voltage and active power, based on the DC voltage and active power, the angular velocity deviation of the converter is output using a control transfer function of DC voltage feedback and a control transfer function of active power feedback.

[0142] A specific implementation method of step 801 is to calculate the voltage deviation between the measured value of the DC voltage and the reference value of the DC voltage; based on the voltage deviation, use the control transfer function of the DC voltage feedback to output the reference value of the active power; calculate the active power deviation between the measured value of the active power and the reference value of the active power; based on the active power deviation, use the control transfer function of the active power feedback to output the angular velocity deviation of the converter.

[0143] Another specific implementation of step 801 may be to calculate a voltage deviation between a measured value of a DC voltage and a reference value of the DC voltage; based on the voltage deviation, output a first standby angular velocity deviation using a control transfer function of DC voltage feedback; calculate an active power deviation between a measured value of active power and a reference value of active power; based on the active power deviation, output a second standby angular velocity deviation using a control transfer function of active power feedback; and use the sum of the first standby angular velocity deviation and the second standby angular velocity deviation as the angular velocity deviation of the converter.

[0144] For example, the above Figure 8 A specific implementation of a synchronous phase angle synthesis method is shown as follows:

[0145] Fig. 9 The basic block diagram of a hybrid synchronization of DC voltage feedback and active power feedback in series provided by the present invention is as follows: Fig. 9 As shown in FIG. 1 , the hybrid synchronization method of DC voltage feedback and active power feedback in series is specifically composed of four links, which are connected in series in sequence according to the DC voltage feedback link, the active power feedback link, the controlled oscillation link and the phase angle synthesis link:

[0146] DC voltage feedback link, the input is the measured value of DC voltage U DC and reference value U DCref , the output is the reference value of active power P ref , the converter DC voltage deviation ΔU DC (i.e., the voltage deviation between the measured value of the DC voltage and the reference value of the DC voltage) is controlled by the transfer function G DC (i.e., the control transfer function of DC voltage feedback) to obtain the reference value of active power P ref Active power feedback link, the input is the measured value P and reference value P of active power ref The output is the estimated angular velocity deviation Δω (i.e., the angular velocity deviation of the converter), and the active power deviation ΔP (i.e., the active power deviation between the measured active power and the reference active power) is calculated by the control transfer function G P (i.e., the control transfer function of active power feedback) to obtain the angular velocity deviation Δω. In the controlled oscillation link, the input is the angular velocity deviation Δω, and the output is the estimated phase angle deviation Δθ (i.e., the phase angle deviation of the converter). The angular velocity deviation Δω is used to obtain the phase angle deviation Δθ through the controlled oscillator. In the phase angle synthesis link, the input is the phase angle deviation Δθ and the estimated phase angle θ of the grid AC voltage. Uac (i.e. the estimated phase angle of the grid AC voltage), the output is the estimated phase angle θ (i.e. the synchronous phase angle). For modular series three-phase converters, if phase-splitting control is adopted, the deviation of the converter DC voltage ΔU DC is the sum of the DC voltages of the power modules in the phase (i.e. the measured value of the DC voltage UDC ) and the reference value. If non-phase control is used, the converter DC voltage deviation ΔU DC is the sum of the DC voltages of the three-phase converter modules (i.e. the measured value of the DC voltage U DC ) deviation from the reference value.

[0147] Fig.10 The basic block diagram of a hybrid synchronization of DC voltage feedback and active power feedback in parallel provided by the present invention is as follows: Fig.10 As shown in FIG. 1 , the hybrid synchronization method of DC voltage feedback and active power feedback in parallel is specifically composed of four links. The DC voltage feedback link and the active power feedback link are connected in parallel, and then connected in series with the controlled oscillation link and the phase angle synthesis link in sequence:

[0148] DC voltage feedback link, the input is the measured value of DC voltage U DC and reference value U DCref , the output is the estimated angular velocity deviation Δω U , the converter DC voltage deviation ΔU DC Through the control block diagram G DC (i.e., the control transfer function of DC voltage feedback) to obtain the angular velocity deviation Δω U (i.e. the first standby angular velocity deviation). Active power feedback link, the input is the measured value P and the reference value P of active power ref , the output is the estimated angular velocity deviation Δω P (i.e., the second standby angular velocity deviation), the active power deviation ΔP is controlled by the transfer function G P Get the angular velocity deviation Δω P . Controlled oscillation link, the input is the angular velocity deviation Δω P With Δω U The sum of Δω, the output is the estimated phase angle deviation Δθ (i.e. the phase angle deviation of the converter), and the angular velocity deviation Δω is used to obtain the phase angle deviation Δθ through the controlled oscillator. In the phase angle synthesis link, the input is the phase angle deviation Δθ and the estimated phase angle θ of the grid AC voltage. Uac , the output is the estimated phase angle θ.

[0149] Fig.11 A basic block diagram of a hybrid synchronization based on active power feedback provided by the present invention, such as Fig.11 As shown in the figure, the hybrid synchronization method based on active power feedback is composed of three links, which are connected in series in the active power feedback link, the controlled oscillation link and the phase angle synthesis link: the active power feedback link, the input of which is the measured value P and the reference value P of the active power ref The output is the estimated angular velocity deviation Δω, and the active power deviation ΔP is controlled by the transfer function G PThe angular velocity deviation Δω is obtained. In the controlled oscillation link, the input is the angular velocity deviation Δω, and the output is the estimated phase angle deviation Δθ. The angular velocity deviation Δω is used to obtain the phase angle deviation Δθ through the controlled oscillator. In the phase angle synthesis link, the input is the phase angle deviation Δθ and the estimated phase angle θ of the grid AC voltage. Uac , the output is the estimated phase angle θ.

[0150] Fig.12 A basic block diagram of a hybrid synchronization based on DC voltage feedback provided by the present invention is as follows: Fig.12 As shown in FIG. 1 , the hybrid synchronization method based on DC voltage feedback is specifically composed of three links, which are connected in series in the DC voltage feedback link, the controlled oscillation link and the phase angle synthesis link: the DC voltage feedback link, the input quantity is the measured value of the DC voltage U DC and reference value U DCref The output is the estimated angular velocity deviation Δω and the converter DC voltage deviation ΔU DC Through the control block diagram G DC The angular velocity deviation Δω is obtained. In the controlled oscillation link, the input is the angular velocity deviation Δω, and the output is the estimated phase angle deviation Δθ. The angular velocity deviation Δω is used to obtain the phase angle deviation Δθ through the controlled oscillator. In the phase angle synthesis link, the input is the phase angle deviation Δθ and the estimated phase angle θ of the grid AC voltage. Uac The output is the estimated phase angle θ.

[0151] above Figure 8 The specific implementation of estimating the phase angle of the AC voltage of the power grid in step 803 may include the following steps:

[0152] Based on the grid AC voltage, a phase-locked loop is used to output an estimated phase angle of the grid AC voltage; or based on the grid AC voltage, a frequency-locked loop is used to output an estimated phase angle of the grid AC voltage.

[0153] Optionally, the specific implementation of estimating the phase angle in the above-mentioned embodiment of outputting the estimated phase angle of the grid AC voltage based on the grid AC voltage by using a phase-locked loop may include the following steps:

[0154] In step 1, when the converter adopts phase-splitting control, the grid AC voltage is a single-phase AC voltage, and the phase-locked loop is a voltage phase-locked loop, based on the single-phase AC voltage and the feedback phase angle output by the voltage phase-locked loop, the phase detector, loop filter and controlled oscillator in the voltage phase-locked loop are used to output the estimated phase angle of the grid AC voltage.

[0155] For example, Fig.13 A basic block diagram based on a voltage phase-locked loop provided by the present invention, such as Fig.13As shown in FIG. 1 , a phase-locked loop based on the AC voltage of the power grid (i.e., a voltage phase-locked loop) is usually composed of a phase detector (PD), a loop filter (G F ) and a controlled oscillator (1 / s). The input of the phase detector is the AC voltage of the power grid (i.e. the AC voltage signal of the power grid U ac ) and the feedback phase angle of the voltage phase-locked loop output (i.e., the signal θ output by the controlled oscillator), where when the power electronic converter adopts phase-splitting control, the grid AC voltage U ac is a single-phase AC voltage signal, and the output of the phase detector is the phase angle deviation Δθ of the two input signals. The loop filter can be expressed as F To express, its output is the corresponding angular velocity deviation Δω, the angular velocity deviation Δω and the reference angular velocity ω of the grid AC voltage 0 The sum is the angular velocity ω estimated by the phase-locked loop. For a grid with a nominal frequency of 50 Hz, the reference angular velocity ω 0 The value is 100π; for a grid with a nominal frequency of 60Hz, the reference angular velocity ω 0 The value is 120π; for low-frequency AC power grid, such as the rated frequency is 20Hz, the reference angular velocity ω 0 The value is 40π. The controlled oscillator can be expressed by the integral transfer function 1 / s. The phase angle θ of the output signal of the controlled oscillator (i.e., the estimated phase angle of the AC voltage of the power grid) is based on the angular velocity ω of the input signal (i.e., the angular velocity estimated by the phase-locked loop). The phase angle deviation Δθ is reduced by changing the output phase angle of the controlled oscillator, and finally the synchronization of the output signal of the controlled oscillator and the AC voltage signal of the power grid is achieved.

[0156] In step 2, when the converter adopts non-phase control, the grid AC voltage is the positive sequence component of the three-phase AC voltage, and the phase-locked loop is a typical three-phase phase-locked loop, based on the positive sequence component of the three-phase AC voltage and the feedback phase angle output by the typical three-phase phase-locked loop, the estimated phase angle of the grid AC voltage is output by using the phase detector, loop filter and controlled oscillator in the typical three-phase phase-locked loop.

[0157] Among them, the phase detector of a typical three-phase phase-locked loop is a Park transform of equal amplitude, and the loop filter of a typical three-phase phase-locked loop is a proportional integral. The Park transform formula of equal amplitude can be the following formula (1), (2) or (3):

[0158]

[0159] In the above formula (1), (2) or (3), d is the direct-axis voltage, q is the quadrature-axis voltage, a is the positive-sequence component of the a-phase AC voltage, b is the positive-sequence component of the b-phase AC voltage, and c is the positive-sequence component of the c-phase AC voltage. It is agreed that the sum of the 0-axis is 0, and there may be no 0-axis.

[0160] For example, Fig.14 Another basic block diagram based on a voltage phase-locked loop provided by the present invention is as follows: Fig.14 As shown, when the power electronic converter does not adopt phase control (that is, the converter adopts non-phase control), the grid AC voltage U abc It should be the positive sequence component of the three-phase AC voltage. The phase detector adopts Park coordinate transformation to transform the AC voltage U abc Converted into direct axis voltage U d and the quadrature axis voltage U q , output U q After normalization After U qn , the normalized quadrature axis voltage U qn Input loop filter (loop filter uses proportional integral (PI) link, the transfer function of proportional integral is K p (1+1 / T i s), K p is the proportional gain, T i is the integration time constant, s is a complex variable, representing the frequency in the Laplace Transform domain), the loop filter outputs the angular velocity deviation Δω, the angular velocity deviation Δω is related to the reference angular velocity ω of the grid AC voltage 0 The sum is the estimated angular velocity ω. The input signal of the controlled oscillator is the estimated angular velocity ω, and the output signal is the phase angle θ (ie, the estimated phase angle of the grid AC voltage).

[0161] Optionally, the specific implementation of estimating the phase angle in the above embodiment of estimating the phase angle based on the grid AC voltage and using a frequency locked loop to output the estimated phase angle of the grid AC voltage may include the following steps:

[0162] When the converter adopts split-phase control and the grid AC voltage is a single-phase AC voltage, an estimated phase angle of the grid AC voltage is output based on the single-phase AC voltage using a frequency-locked loop without gain normalization; or, when the converter adopts split-phase control and the grid AC voltage is a single-phase AC voltage, an estimated phase angle of the grid AC voltage is output based on the single-phase AC voltage using a frequency-locked loop with gain normalization; or, when the converter adopts non-split-phase control and the grid AC voltage is a positive-sequence component of a three-phase AC voltage and the frequency-locked loop is a three-phase frequency-locked loop, an estimated phase angle of the grid AC voltage is output based on the positive-sequence component of the three-phase AC voltage using a three-phase frequency-locked loop with gain normalization.

[0163] Fig.15 The present invention provides a flow chart for determining the estimated phase angle of the AC voltage of the power grid using a frequency locked loop without gain normalization, such as Fig.15As shown, the above implementation method of estimating the phase angle of the AC voltage of the power grid based on the single-phase AC voltage and using a frequency-locked loop without gain normalization may include the following steps:

[0164] In step 1501, the angular velocity is estimated using the output of the frequency locker in the frequency locked loop based on the reference angular velocity, the quadrature-axis feedback voltage fed back by the second-order generalized integrator in the frequency locked loop without gain normalization, and the deviation between the direct-axis feedback voltage and the single-phase AC voltage.

[0165] The direct-axis feedback voltage may be a direct-axis voltage output by a second-order generalized integrator.

[0166] It should be noted that the deviation between the direct-axis feedback voltage fed back by the second-order generalized integrator in the frequency-locked loop without gain normalization and the single-phase AC voltage is calculated to obtain the deviation signal e v , the deviation signal e v , the quadrature axis voltage v fed back by the second-order generalized integrator q and the reference angular velocity ω 0 The frequency-locked loop (FLL) is used to input the error signal e v and the quadrature axis voltage v q The product of f Perform negative gain -γ processing, that is, γ is selected as 46, and the product e after negative gain -γ f Perform controlled oscillation 1 / s processing, and calculate the reference angular velocity ω after the controlled oscillation 1 / s processing 0 The sum of ω and ω is used to obtain the estimated angular velocity ω, which is the estimated angular velocity ω output by the frequency locker.

[0167] In step 1502, based on the estimated angular velocity, the deviation between the direct-axis feedback voltage and the single-phase AC voltage, a second-order generalized integrator is used to output the direct-axis voltage and the quadrature-axis voltage.

[0168] The direct-axis voltage and the quadrature-axis voltage may be a pair of orthogonal signals.

[0169] It should be noted that the deviation signal e v The product of the proportional coefficient and the estimated angular velocity ω is input to the second-order generalized integrator, and the estimated angular velocity ω and the deviation signal e are integrated by the second-order generalized integrator. v The product of the proportional coefficient is processed, the product is multiplied by the angular velocity ω, and then the controlled oscillation 1 / s is processed to obtain the direct axis voltage v d , for the direct axis voltage v d After the controlled oscillation 1 / s processing, multiply it by the angular velocity ω to get the quadrature axis voltage v q , the second-order generalized integrator outputs a pair of orthogonal signals of direct-axis voltage v d With the quadrature axis voltage v q .

[0170] In step 1503, when the DC component of the single-phase AC voltage is less than a preset voltage threshold, the estimated phase angle of the AC voltage of the power grid is output using a four-quadrant inverse tangent function based on the direct-axis voltage and the quadrature-axis voltage.

[0171] It should be noted that the direct-axis voltage and the quadrature-axis voltage are input into the four-quadrant inverse tangent function, and the estimated phase angle of the AC voltage of the power grid is output through the four-quadrant inverse tangent function.

[0172] In step 1504, when the DC component of the single-phase AC voltage is greater than or equal to a preset voltage threshold, the controlled oscillator is used to output an estimated DC voltage of the converter based on the DC feedback voltage output by the controlled oscillator, the deviation of the direct-axis feedback voltage and the single-phase AC voltage.

[0173] The DC feedback voltage may be an estimated DC voltage of the converter.

[0174] It should be noted that for the deviation signal e v The product of the proportional coefficient and the difference between the DC feedback voltage output by the controlled oscillator are processed, multiplied by the angular velocity ω, and then input into the controlled oscillation 1 / s for processing, and the estimated DC voltage v of the converter is output through the controlled oscillator. dc .

[0175] In step 1505, based on the difference between the direct-axis voltage, the quadrature-axis voltage and the estimated DC voltage, a four-quadrant inverse tangent function is used to output an estimated phase angle of the AC voltage of the power grid.

[0176] It should be noted that the difference between the quadrature axis voltage and the estimated DC voltage is calculated to obtain the standby voltage, the direct axis voltage and the standby voltage are input into the four-quadrant inverse tangent function, and the estimated phase angle of the AC voltage of the power grid is output through the four-quadrant inverse tangent function.

[0177] For example, Fig.16 A basic block diagram of a frequency-locked loop gain not normalized provided by the present invention, such as Fig.16 As shown above Fig.15 The specific implementation method of the scheme shown can be that when the power electronic converter adopts phase control, the following can be adopted: Fig.16 The frequency-locked loop with unnormalized gain (i.e., the frequency-locked loop without gain normalization) shown in FIG. 1 is mainly composed of three links. At this time, the frequency response characteristics will change with the input signal U ac The orthogonal signal generation link based on the second-order generalized integrator (SOGI) has the error signal e as the input. v and the angular velocity ω estimated by the frequency-locked loop. The output is a pair of orthogonal signals v d 、vq , k is the proportional coefficient, and the value range of the proportional coefficient k is between 0.5 and 2.0. Frequency Locking Link (FLL), the input is the deviation signal e v and signal v q , the output is the estimated angular velocity ω, ω 0 is the reference angular velocity. In the DC voltage solution phase, the input is the deviation signal e v The product of the proportionality factor and the estimated DC voltage v dc , the output is the estimated DC voltage v dc , calculate the estimated DC voltage v dc and signal v q The deviation of the signal v qm (i.e. standby voltage). Phase angle solution link, the input is signal v d and signal v qm , the output is the estimated grid AC voltage phase angle θ Uac (i.e., the estimated phase angle of the grid AC voltage), atan2 (i.e., the four-quadrant inverse tangent function) is the four-quadrant inverse tangent of y / x expressed in radians, and the signs of y and x determine the corresponding quadrant.

[0178] Fig.17 The present invention provides a flow chart for determining the estimated phase angle of the AC voltage of the power grid using a gain-normalized frequency-locked loop, such as Fig.17 As shown, the above implementation method of outputting the estimated phase angle of the grid AC voltage based on the single-phase AC voltage using a gain-normalized frequency-locked loop may include the following steps:

[0179] In step 1701, the angular velocity is estimated using the output of the frequency locker in the frequency locked loop based on the gain normalization coefficient, the reference angular velocity, the quadrature-axis feedback voltage fed back by the second-order generalized integrator in the gain-normalized frequency locked loop, and the deviation between the direct-axis feedback voltage and the single-phase AC voltage.

[0180] It should be noted that the gain normalization coefficient k ef , deviation signal e v , the quadrature axis voltage v fed back by the second-order generalized integrator q and the reference angular velocity ω 0 The frequency locker in the frequency locked loop is used to lock the deviation signal e v , quadrature axis voltage v q and gain normalization coefficient k ef Multiply them together to get the product e f , for the product e f Perform negative gain-γ processing, that is, γ is selected as 46, and the product e after negative gain-γ processing f Perform controlled oscillation 1 / s Processing, and after the controlled oscillation 1 / s processing, calculate the reference angular velocity ω0 The sum of ω and ω is used to obtain the estimated angular velocity ω. The frequency locker in the gain-normalized frequency-locked loop outputs the estimated angular velocity ω.

[0181] In step 1702, based on the estimated angular velocity, the deviation between the direct-axis feedback voltage and the single-phase AC voltage, a second-order generalized integrator is used to output the direct-axis voltage and the quadrature-axis voltage.

[0182] It should be noted that the deviation signal e v The product of the proportional coefficient and the estimated angular velocity ω is input to the second-order generalized integrator, and the estimated angular velocity and the deviation signal e are integrated by the second-order generalized integrator. v The product of the proportional coefficient is processed to output a pair of orthogonal signal direct axis voltage v d With the quadrature axis voltage v q .

[0183] In step 1703, when the DC component of the single-phase AC voltage is less than a preset voltage threshold, an estimated phase angle of the grid AC voltage is output using a four-quadrant inverse tangent function based on the direct-axis voltage and the quadrature-axis voltage.

[0184] The gain normalization coefficient is a coefficient output by a gain normalization function in the frequency locked loop based on the direct-axis voltage, the quadrature-axis voltage, and the estimated angular velocity.

[0185] It should be noted that the first square value of the direct-axis voltage and the second square value of the quadrature-axis voltage are calculated, and the ratio of the first square value and the second square value to the estimated angular velocity is calculated after summing the first square value and the second square value. The ratio is multiplied by the proportional coefficient k to obtain the gain normalization coefficient k. ef .

[0186] In step 1704, when the DC component of the single-phase AC voltage is greater than or equal to a preset voltage threshold, the controlled oscillator is used to output an estimated DC voltage of the converter based on the DC feedback voltage output by the controlled oscillator, the deviation of the direct-axis feedback voltage and the single-phase AC voltage.

[0187] It should be noted that for the deviation signal e v The product of the proportional coefficient and the difference between the DC feedback voltage output by the controlled oscillator are processed, multiplied by the angular velocity ω, and then input into the controlled oscillator to output the estimated DC voltage v of the converter. dc .

[0188] In step 1705, based on the difference between the direct-axis voltage, the quadrature-axis voltage and the estimated DC voltage, a four-quadrant inverse tangent function is used to output an estimated phase angle of the AC voltage of the power grid.

[0189] The gain normalization coefficient is a coefficient output by a gain normalization function in a frequency locked loop based on the difference between the direct-axis voltage, the quadrature-axis voltage and the estimated direct-current voltage and the estimated angular velocity.

[0190] It should be noted that the difference between the quadrature axis voltage and the estimated DC voltage is calculated to obtain the standby voltage, the direct axis voltage and the standby voltage are input into the four-quadrant inverse tangent function, and the estimated phase angle of the AC voltage of the power grid is output through the four-quadrant inverse tangent function. The first square value of the direct axis voltage and the second square value of the standby voltage are calculated, and the ratio of the first square value and the second square value to the estimated angular velocity is calculated after summing the first square value and the second square value, and the ratio is multiplied by the proportional coefficient k to obtain the gain normalization coefficient k ef .

[0191] For example, Fig.18 A basic block diagram of a gain-normalized frequency-locked loop provided by the present invention is as follows: Fig.18 As shown above Fig.17 The specific implementation method of the scheme shown can be that when the power electronic converter adopts phase control, the following can be adopted: Fig.18 The gain-normalized frequency-locked loop shown in the figure is mainly composed of four links. At this time, the frequency response characteristics will not change with the input signal U ac The orthogonal signal generation link based on the second-order generalized integrator (SOGI) has an input quantity of the AC voltage signal U ac and the angular velocity ω estimated by the frequency-locked loop, the output is a pair of orthogonal signals v d 、v q and deviation signal e v k is the proportional coefficient, and the value range of the proportional coefficient k is between 0.5 and 2.0. In the frequency locking link, the input is the deviation signal e v 、Signal v q and gain normalization coefficient k ef , the output is the estimated angular velocity ω, ω 0 is the reference angular velocity. In the gain normalization link, the input is the signal v d 、Signal v qm and the estimated angular velocity ω, the output is the gain normalization coefficient k ef In the DC voltage solution phase, the input is the deviation signal e v and estimate the DC voltage v dc , the output is the estimated DC voltage v dc , calculate the estimated DC voltage v dc and signal v q The deviation of the signal v qm Phase angle solution link, the input is signal v d and signal v qm , the output is the estimated grid AC voltage phase angle θ Uac, atan2 is the four-quadrant inverse tangent of y / x expressed in radians. The signs of y and x determine the corresponding quadrant.

[0192] For example, Fig.19 A basic block diagram of a three-phase frequency-locked loop with gain normalization provided by the present invention is as follows: Fig.19 As shown, based on the positive sequence component of the three-phase AC voltage, a specific implementation method of estimating the phase angle of the AC voltage of the power grid using a three-phase frequency-locked loop with gain normalization can be, when the power electronic converter does not adopt phase control, the following can be adopted: Fig.19 The gain-normalized three-phase frequency-locked loop shown in the figure is mainly composed of five links. In the coordinate transformation link, the equal-amplitude Clarke transformation (abc\αβ) is adopted, and the input quantity is the three-phase voltage (i.e., the positive sequence component u of the a-phase AC voltage). a , the positive sequence component u of phase b AC voltage b , the positive sequence component u of phase c AC voltage c ), the output is orthogonal to u α and u β Based on the orthogonal signal generation link of second-order generalized integrator (SOGI), the inputs are respectively orthogonal u α 、u β and the angular velocity ω estimated by the frequency-locked loop, the outputs are orthogonal signals v αd 、v αq , deviation signal e vα and the orthogonal signal v βd 、v βq , deviation signal e vβ , k is the proportional coefficient, and the value range of the proportional coefficient k is between 0.5 and 2.0. Positive sequence calculation link (PSC), the input quantity is the orthogonal signal v αd 、v αq and the orthogonal signal v βd 、v βq , the output is α β Positive sequence component v in the coordinate system αp and v βp Frequency Locking Link (FLL), the input is the deviation signal e vα and e vβ , q-axis signal v αq and v βq , positive sequence component v αp and v βp , the output is the estimated angular velocity ω, ω 0 is the reference angular velocity. In the phase angle solution phase, the input is the orthogonal signal v αp and v βp , the output is the estimated AC voltage phase angle θ Uac, atan2 is the four-quadrant inverse tangent of y / x expressed in radians, and the signs of y and x determine the corresponding quadrant. The frequency locking process includes FLL gain normalization

[0193] Embodiment 2:

[0194] Based on the same inventive concept, Fig. 20 A block diagram of a synchronous phase angle synthesis system provided by the present invention, such as Fig. 20 As shown, the system may include: an angular velocity deviation determination unit, used to output the angular velocity deviation of the converter using a control transfer function based on the electrical parameters of the converter; a phase angle deviation determination unit, used to output the phase angle deviation of the converter using a controlled oscillator based on the angular velocity deviation of the converter; and a synchronous phase angle synthesis unit, used to synthesize the synchronous phase angle based on the phase angle deviation of the converter and the estimated phase angle of the AC voltage of the power grid.

[0195] Optionally, the electrical parameters include DC voltage and active power; the angular velocity deviation determination unit includes: an angular velocity deviation determination module, which is used to output the angular velocity deviation of the converter based on the DC voltage and the active power, using the control transfer function of DC voltage feedback and the control transfer function of active power feedback. Optionally, the angular velocity deviation determination module is specifically used to: calculate the voltage deviation between the measured value of the DC voltage and the reference value of the DC voltage; based on the voltage deviation, output the reference value of the active power using the control transfer function of DC voltage feedback; calculate the active power deviation between the measured value of the active power and the reference value of the active power; based on the active power deviation, output the angular velocity deviation of the converter using the control transfer function of active power feedback.

[0196] Optionally, the angular velocity deviation determination module is specifically used to: calculate the voltage deviation between the measured value of the DC voltage and the reference value of the DC voltage; based on the voltage deviation, output a first standby angular velocity deviation using a control transfer function of DC voltage feedback; calculate the active power deviation between the measured value of the active power and the reference value of the active power; based on the active power deviation, output a second standby angular velocity deviation using a control transfer function of active power feedback; and use the sum of the first standby angular velocity deviation and the second standby angular velocity deviation as the angular velocity deviation of the converter.

[0197] Optionally, the electrical parameters include active power; an angular velocity deviation determination unit, specifically used to: calculate the active power deviation between the measured value of the active power and the reference value of the active power; based on the active power deviation, use the control transfer function of the active power feedback to output the angular velocity deviation of the converter.

[0198] Optionally, the electrical parameters include DC voltage; an angular velocity deviation determination unit, specifically used to: calculate a voltage deviation between a measured value of the DC voltage and a reference value of the DC voltage; based on the voltage deviation, output an angular velocity deviation of the converter using a control transfer function fed back by the DC voltage.

[0199] Optionally, the system also includes: an estimated phase angle determination unit; the estimated phase angle determination unit includes: an estimated phase angle determination module, which is used to output the estimated phase angle of the grid AC voltage based on the grid AC voltage using a phase-locked loop; or, based on the grid AC voltage, using a frequency-locked loop to output the estimated phase angle of the grid AC voltage.

[0200] Optionally, the estimated phase angle determination module is specifically used for: when the converter adopts phase-split control, the grid AC voltage is a single-phase AC voltage, and the phase-locked loop is a voltage phase-locked loop, based on the single-phase AC voltage and the feedback phase angle output by the voltage phase-locked loop, the estimated phase angle of the grid AC voltage is output by the phase detector, loop filter and controlled oscillator in the voltage phase-locked loop; when the converter adopts non-phase-split control, the grid AC voltage is the positive sequence component of the three-phase AC voltage, and the phase-locked loop is a typical three-phase phase-locked loop, based on the positive sequence component of the three-phase AC voltage and the feedback phase angle output by the typical three-phase phase-locked loop, the estimated phase angle of the grid AC voltage is output by the phase detector, loop filter and controlled oscillator in the typical three-phase phase-locked loop, wherein the phase detector of the typical three-phase phase-locked loop is an equal-amplitude Park transform, and the loop filter of the typical three-phase phase-locked loop is a proportional integral.

[0201] Optionally, the estimated phase angle determination module includes: an estimated phase angle determination submodule, which is used to output the estimated phase angle of the grid AC voltage based on the single-phase AC voltage and using a non-gain-normalized frequency-locked loop when the converter adopts phase-splitting control and the grid AC voltage is a single-phase AC voltage; or, when the converter adopts phase-splitting control and the grid AC voltage is a single-phase AC voltage, output the estimated phase angle of the grid AC voltage based on the single-phase AC voltage and using a gain-normalized frequency-locked loop; or, when the converter adopts non-phase-splitting control and the grid AC voltage is a positive-sequence component of a three-phase AC voltage and the frequency-locked loop is a three-phase frequency-locked loop, output the estimated phase angle of the grid AC voltage based on the positive-sequence component of the three-phase AC voltage and using a gain-normalized three-phase frequency-locked loop.

[0202] Optionally, the estimated phase angle determination submodule is specifically used to: estimate the angular velocity based on the reference angular velocity and the deviation between the direct-axis feedback voltage fed back by the second-order generalized integrator in the frequency-locked loop without gain normalization and the AC voltage of the power grid, and use the frequency locker in the frequency-locked loop to output the estimated angular velocity; use the second-order generalized integrator to output the direct-axis voltage and the quadrature-axis voltage based on the estimated angular velocity and the deviation between the direct-axis feedback voltage and the AC voltage of the power grid; use the controlled oscillator to output the estimated DC voltage of the converter based on the DC voltage output by the controlled oscillator, the deviation between the direct-axis feedback voltage and the AC voltage of the power grid; and use the four-quadrant inverse tangent function to output the estimated phase angle of the AC voltage of the power grid based on the difference between the direct-axis voltage, the quadrature-axis voltage and the estimated DC voltage.

[0203] Optionally, the estimated phase angle determination submodule is specifically used to: estimate the angular velocity based on the gain normalization coefficient, the reference angular velocity, the quadrature-axis feedback voltage fed back by the second-order generalized integrator in the gain-normalized frequency-locked loop, the deviation of the direct-axis feedback voltage and the AC voltage of the power grid, and use the frequency locker output in the frequency-locked loop to estimate the angular velocity; based on the estimated angular velocity and the deviation of the direct-axis feedback voltage and the AC voltage of the power grid, use the second-order generalized integrator to output the direct-axis voltage and the quadrature-axis voltage; based on the DC feedback voltage output by the controlled oscillator, the deviation of the direct-axis feedback voltage and the AC voltage of the power grid, use the controlled oscillator to output the estimated DC voltage of the converter; based on the difference between the direct-axis voltage, the quadrature-axis voltage and the estimated DC voltage, use the four-quadrant inverse tangent function to output the estimated phase angle of the AC voltage of the power grid; wherein the gain normalization coefficient is a coefficient output by the gain normalization function in the frequency-locked loop based on the difference between the direct-axis voltage, the quadrature-axis voltage and the estimated DC voltage and the estimated angular velocity.

[0204] Embodiment 3:

[0205] Based on the same inventive concept, Fig.21 A flowchart of a synchronous compensator control method provided by the present invention, the method may include the following steps:

[0206] In step 2101, based on the electrical quantity of the synchronous compensator, the amplitude of the virtual potential is outputted using a control algorithm in the synchronous compensator.

[0207] The control algorithm includes a reactive power control algorithm and / or an AC voltage control algorithm, and the electrical quantity includes a virtual current value and an effective value of the AC voltage of the power grid, and may also include an AC voltage deviation, a virtual current value and a current extreme value.

[0208] In this step, a possible implementation method is: when the electrical quantity includes a virtual current value and an effective value of the grid AC voltage, based on the virtual current value and the effective value of the grid AC voltage, a reactive power control algorithm in the synchronous compensator is used to output a feedback voltage amplitude, or a feedforward voltage amplitude and a feedback voltage amplitude; based on the feedback voltage amplitude, or the feedforward voltage amplitude and the feedback voltage amplitude, the amplitude of the virtual potential is obtained.

[0209] It should be noted that the reactive power control can output the feedback voltage amplitude through the input virtual current value and the effective value of the grid AC voltage, and use the feedback voltage amplitude as the amplitude of the virtual potential, or can output the feedforward voltage amplitude and the feedback voltage amplitude through the input virtual current value and the effective value of the grid AC voltage, perform signal processing on the feedback voltage amplitude (for example: integration processing, filtering processing or proportional resonance processing, etc.), sum the feedback voltage amplitude and the feedforward voltage amplitude to obtain the amplitude of the virtual potential.

[0210] In this step, another possible implementation method is: when the electrical quantity includes AC voltage deviation, virtual current value and current extreme value, based on the AC voltage deviation, the AC voltage control algorithm in the synchronous compensator is used to output the amplitude of the virtual potential; or, the virtual current value and the current extreme value, the AC voltage control algorithm in the synchronous compensator is used to output the amplitude of the virtual potential.

[0211] It should be noted that the implementation method of the AC voltage control algorithm is to perform sign processing on the virtual current value, and to obtain the standby current by taking the difference between the virtual current value after sign processing and the current extreme value allowed by the static synchronous compensator, and to perform signal processing (for example: filtering processing, proportional processing or inertia processing, etc.) on the standby current to obtain the amplitude of the virtual potential.

[0212] Optionally, based on the AC voltage deviation, an AC voltage control algorithm in a synchronous compensator is used to output the amplitude of the virtual potential.

[0213] In step 2102, based on the electrical parameters of the converter, the synchronization phase angle is determined using the synchronization phase angle synthesis method described above.

[0214] In step 2103, based on the amplitude of the virtual potential, the synchronous phase angle and the AC voltage of the power grid, a reference current is output using a virtual potential control algorithm in the synchronous compensator.

[0215] It should be noted that the virtual potential is obtained by oscillating the amplitude and synchronous phase angle of the virtual potential through the virtual potential control algorithm, and the difference between the virtual potential and the AC voltage of the power grid is calculated to obtain the standby voltage difference, which is converted into the standby current. The RMS (Root Mean Square) processing is performed on the standby current to obtain the virtual current value, and the reference current is obtained by limiting the current.

[0216] In step 2104, the converter in the synchronous compensator is controlled based on the reference current.

[0217] In this step, possible implementation methods may be: calculating the current difference between the current at the access side of the synchronous compensator and the reference current; determining the reference value of the three-phase voltage using a current tracking algorithm based on the current difference and the voltage at the access side of the synchronous compensator; determining the modulation wave of the switch tube in the synchronous compensator using a modulation wave control algorithm based on the reference value of the three-phase voltage, the capacitor voltage balance correction value, and the triangular carrier; and controlling the converter in the synchronous compensator based on the modulation wave of the switch tube in the synchronous compensator.

[0218] The above technical scheme can quickly synthesize the synchronous phase angle through the synchronous phase angle synthesis method, so that the virtual potential control algorithm can accurately output the reference current according to the amplitude of the virtual potential, the synchronous phase angle and the AC voltage of the power grid, which is beneficial to improving the response speed of the converter in the synchronous compensator. The active power of the converter in the synchronous compensator can be quickly controlled through the reference current, which is beneficial to improving the stability of the synchronous compensator.

[0219] For example, Fig. 22 A basic block diagram of STATCOM control using hybrid synchronization provided by the present invention is as follows: Fig. 22 As shown, it consists of four parts:

[0220] The reactive power control part (i.e., reactive power control algorithm), referred to as Q control, is the control with reactive power Q as the control target. The AC voltage control part (i.e., AC voltage control algorithm), referred to as V control, is the control with AC voltage V as the control target. The virtual potential phase angle control part (i.e., synchronous phase angle synthesis method), referred to as θ control, is the control with the phase angle of virtual potential as the output. The virtual potential control part (i.e., virtual potential control algorithm) obtains the corresponding current reference value through virtual potential control technology.

[0221] STATCOM can operate in Q control mode, that is, Fig. 22 The Q control part in the control mode works; it can also run in the V control mode, that is, Fig. 22The V control part in it works; it can also run neither in Q control mode nor in V control mode; but it cannot run in Q control mode and V control mode at the same time. Q control and V control can be switched online as required, that is, switch from Q control to V control online, or switch from V control to Q control online. The final output of both Q control and V control is the amplitude E of the virtual potential control part, that is, the amplitude of the virtual potential e. Among them, when the reactive power provided by the agreed STATCOM is capacitive, the corresponding reactive power Q value in Q control and V control is greater than 0; when the reactive power provided by the agreed STATCOM is inductive, the corresponding Q value of Q control and V control is less than 0. It is also possible that when the reactive power provided by the agreed STATCOM is capacitive, the corresponding reactive power Q value of Q control and V control is less than 0; when the reactive power provided by the agreed STATCOM is inductive, the corresponding Q value of Q control and V control is greater than 0. At this time, Fig. 22 The positive and negative signs in the control block diagram need to be changed accordingly. Fig. 22 ΔQ, Q set and ΔV, which can be the quantity on the low voltage side of the STATCOM access point or the quantity on the high voltage side after passing through the step-up transformer. QV It is shared by V control and Q control, G QV It can be an integral, or the product of an integral and first-order inertia, a low-pass filter, or a proportional resonance.

[0222] for Fig. 22 G with mid-Q control QI , you can use Fig.23 The closed-loop control can also be achieved by Fig.24 This is achieved by open-loop control. Fig.23 The closed loop control and Fig.24 The open-loop control shown can be switched online as required, that is, from open-loop control to closed-loop control online, and from closed-loop control to open-loop control online. When closed-loop control is used, Fig.23 The calculation of reactive power deviation ΔQ shown here only considers the reactive power of the power frequency component, where Fig.23 G in Q It can be an integral (I) link, a proportional integral (PI) link, or a proportional integral differential (PID) link. Fig.24 In the open-loop control shown in the figure, the input quantity of Q control is the set value of reactive power Q set , voltage value V rms and the virtual current value I v_rms Among them, the virtual current value I v_rms for Fig. 22 The output of the virtual potential control part. Among them, the voltage value V rms and the virtual current value I v_rmsIt can be an effective value (root mean square value), fundamental wave amplitude, fundamental wave positive sequence amplitude, fast estimated amplitude based on SOGI, or fast estimated amplitude based on αβ transformation.

[0223] The above quick estimates based on SOGI, such as Fig.25 As shown, the input quantity is the voltage value V rms Or virtual current value I v_rms The corresponding three-phase instantaneous value of phase a, phase b or phase c (i.e. v x ), the obtained values ​​are the rapid estimated amplitudes of phase a, phase b or phase c. The input ω is Fig. 22 Angular velocity in theta control. Fig.25 Taking voltage as an example, current is similar. The above-mentioned rapid estimation of amplitude based on αβ transformation is as follows: Fig.26 As shown, the input quantity is the voltage value V rms Or virtual current value I v_rms The corresponding three-phase instantaneous values ​​of phase a, phase b and phase c (i.e. v a 、v b 、v c ), the obtained three-phase rapid estimated amplitudes are phase a, phase b and phase c.

[0224] Q control can have two control branches: feedforward and feedback. V_ref The obtained E fw The feedforward control branch of the value and according to I V_ref and I V_rms The obtained E Q There can also be only one control branch, that is, only one control branch according to I V_ref and I V_rms The obtained E Q The feedback control branch of the value. Q Value input to G QV , get E fb Value, virtual current reference value I V_ref Available Fig.23 The transfer function G Q Output reactive power reference value Q ref (ie N) or Fig.24 Medium reactive power setting value Q set (i.e. N) divided by the voltage value V rms (ie D) to obtain (ie N / D). According to the reactive power setting value Q set Or reactive power reference value Q ref Is it a three-phase value, voltage value V rms Is it the line voltage or the phase voltage value? The coefficient difference.

[0225] In Q control, the box represents the input quantity IV_rms and Sign(I V_ref ), where Sign(I V_ref ) is a sign function, when I V_ref When it is positive, it is 1.0; when I V_ref When it is negative, it is -1.0; when I V_ref When it is 0, it is 0.0. In Q control, G Qfw It can be a linear proportional link, or a combination of a linear proportional link and first-order inertia and low-pass filtering, where the first-order inertia and low-pass filtering are mainly used to filter out high-frequency signals. Qfb It can be a linear proportional link or a combination of a linear proportional link and a first-order inertia and low-pass filter. The first-order inertia and low-pass filter are used to filter out high-frequency signals.

[0226] like Fig. 22 The V control shown in the figure has the AC voltage deviation ΔV and the maximum allowable current value I V and the virtual current value I v_rms Among them, the current extreme value I V Refers to the maximum current amplitude allowed by STATCOM. Different values ​​should be selected according to the duration of the current to maximize the use of STATCOM overload capacity. Specifically, it can be a steady-state value, usually 1.1pu; it can be a transient value of 1.2pu with a duration of no more than 2s; or it can be a transient value of 1.3pu with a duration of only a few power frequency cycles. If the capacitive reactive power is agreed to be a positive value, the maximum allowable current value I V When it corresponds to capacitive reactive power, its value is also positive; when it corresponds to inductive reactive power, its value is negative. If the permissible capacitive reactive power is agreed to be a negative value, the permissible current extreme value I V When it corresponds to capacitive reactive power, its value is also negative; when it corresponds to inductive reactive power, its value is positive.

[0227] In V control, G Vac It can be a linear proportional link or a combination of a linear proportional link and a first-order inertia and a low-pass filter, wherein the first-order inertia and the low-pass filter are used to filter out high-frequency signals. Iv It can be a linear proportional link or a combination of a linear proportional link and a first-order inertia and low-pass filter. The first-order inertia and low-pass filter are used to filter out high-frequency signals. V ) is a sign function, when I V When it is positive, its value is 1.0; when I V When it is negative, its value is -1.0; when I V When it is 0, its value is 0.0.

[0228] In V control, when the output current is not limited or does not reach the extreme value, the value of V control state is 1.0, indicating that the AC voltage deviation ΔV branch is put into operation; when the output current is limited or reaches the extreme value, the value of V control state is 0.0, indicating that the AC voltage deviation ΔV branch is out of operation; when the output current is not limited or does not reach the extreme value, the value of I control state is 0.0, indicating that the current extreme value I V The branch is out of operation; when the output current is limited or reaches the extreme value, the value of I control state is 1.0, indicating that the current extreme value I V The branch line was put into operation.

[0229] For the θ control part, there are four options according to the different combinations of DC voltage feedback and active power feedback: DC voltage feedback and active power feedback in series, such as Fig. 9 As shown; the scheme of DC voltage feedback and active power feedback in parallel, such as Fig.10 As shown; the scheme based on active power feedback, such as Fig.11 As shown; DC voltage-based solutions, such as Fig.12 shown.

[0230] The input of the θ control part is the AC voltage v of the power grid, the measured value of active power P and the measured value of DC voltage U. DC , the output is the synchronous phase angle θ (i.e. the phase angle θ of the command voltage e).

[0231] The input of the virtual potential control part is the amplitude E of the command voltage e, the phase angle θ of the command voltage e, the instantaneous value v of the AC voltage (i.e. the AC voltage of the power grid), and the output is the virtual current value I v_rms and the reference value of the output current i ref , where the instantaneous value of the AC voltage v can be the low-voltage side value of the STATCOM access point, such as Figure 7 The low voltage side voltage v (i.e. the three-phase voltage v at the common connection point) shown can also be the high voltage side value after passing through the step-up transformer. The instantaneous value v of the AC voltage can be conditioned by a first-order inertia link or a low-pass filter.

[0232] In the virtual potential control part, the amplitude E and the synchronous phase angle θ of the virtual potential e are oscillated to obtain the virtual potential e (that is, the input of CO is the amplitude E and the synchronous phase angle θ of the virtual potential e, and the output is the virtual potential e), and the difference between the virtual potential e and the AC voltage v of the power grid is calculated to obtain the standby voltage difference, which is then used by G VZ The voltage difference to current conversion link in the circuit converts the standby voltage difference into the standby current i v , perform RMS (Root-Mean–Square) processing on the current to be used to obtain the virtual current value I v_rms , the current to be used is limited to obtain the reference current iref .

[0233] In the virtual potential control part, CO is a controlled oscillator, and the instantaneous value e generation part in the virtual potential control can be generated by cosine, that is, e = E*cos(θ), and sine, that is, e = E*sin(θ); G VZ It includes two links, which are connected in series in the following order: a voltage difference to current link and a current conditioning link. Among them, the voltage difference to current link can adopt a first-order inertia link, and the corresponding transfer function of the first-order inertia is 1 / (R+Ls). L can be a preset fixed value or be adjusted in real time according to the operating conditions of STATCOM. The value range of L is 0.05 pu to 2.0 pu, and the per-unit reference value adopts the rated capacity and rated AC voltage value of STATCOM; R can be a preset fixed value or be adjusted in real time according to the operating conditions of STATCOM. The value range of R is between 0.1 and 2.0 times the power frequency value corresponding to L.

[0234] The current conditioning link is not necessary. When there is no current conditioning link, the corresponding transfer function is 1.0. If it is introduced, the corresponding filtering link is added, and the following options are available: only suppress the gain of the high-frequency band (higher than the reference frequency) to make the converter present a larger high-frequency impedance; only suppress the gain of the low-frequency band (lower than the reference frequency) to make the converter present a larger low-frequency impedance; suppress the gain of both the high-frequency band and the low-frequency band at the same time to make the converter present a larger high-frequency impedance and low-frequency impedance.

[0235] If a three-phase circuit is introduced, the power frequency positive-sequence, negative-sequence and zero-sequence components can be obtained, among which the power frequency positive-sequence, negative-sequence and zero-sequence components are multiplied by their respective coefficients and then added to obtain the conditioned quantity, so that the system obtains the corresponding characteristics. The negative-sequence component is multiplied by a positive value of 0.5 or less, or even 0, so that the converter presents a larger negative-sequence impedance, or even nearly infinite power frequency negative-sequence impedance; the zero-sequence component is multiplied by a positive value of 0.5 or less, or even 0, so that the converter presents a larger zero-sequence impedance, or even nearly infinite power frequency zero-sequence impedance; the negative-sequence component is multiplied by a positive value of 2.0 to 20.0, so that the converter presents a smaller power frequency negative-sequence impedance; the zero-sequence component is multiplied by a positive value of 2.0 to 20.0, so that the converter presents a smaller power frequency zero-sequence impedance.

[0236] The virtual potential control part can be limited according to the allowable peak value. Different values ​​should be selected according to the different current duration to make the best use of the STATCOM overload capacity: it can be the allowable peak value corresponding to 1.1 pu for long-term operation, the allowable peak value corresponding to 1.2 pu with a duration of no more than 2 s, or the allowable peak value corresponding to 1.3 pu with a duration of only a few power frequency cycles.

[0237] Optionally, the above Fig.21 The specific implementation of the scheme shown can be as follows Fig. 27 As shown, Fig. 27 A control strategy block diagram of a static synchronous compensator provided by the present invention, wherein Q control, V control, θ control, and virtual potential control correspond to Fig. 22 Q control, V control, θ control, and virtual potential control. Fig. 22 G in QI use Fig.24 Open loop control in. Fig. 22 The θ control in Fig. 9 The hybrid synchronization method of DC voltage feedback and active power feedback in series, where the transfer function G DC Using PID control, the transfer function G P Proportional control is adopted, phase angle θ Uac use Fig.18 The gain-normalized frequency-locked loop based on a second-order generalized integrator is shown in FIG. γ is selected as 46, the reference angular velocity ω 0 The value is 100π.

[0238] like Fig. 27 As shown, in Fig. 22 Based on this, a current tracking link G is added i , using proportional resonance (PR) control. The phase capacitor voltage balance control adopts the classic method of adjusting the output voltage along the output current direction. The PWM adopts unipolar PWM with carrier phase shift, the triangular carrier frequency is 370Hz, and the industrial frequency active power P 1 and power frequency reactive power Q 1 The data is obtained by fast Fourier transform (FFT) calculation based on 128 sampling points in one power frequency cycle and is updated point by point. It is agreed that when the reactive power provided by STATCOM is capacitive, the corresponding reactive power Q value is greater than 0; when the reactive power provided is inductive, the corresponding reactive power Q value is less than 0. Fig.24 Q set The quantity on the low voltage side of the step-up transformer, V rms Using effective value (root mean square value), I v_rms Use effective value (root mean square value), G Qfw Using the proportional link, G Qfb Use proportional links.

[0239] ΔV is the value on the high voltage side, I v The value is 1.2pu, G Vac Using the proportional link, G IvA proportional link is used. When the voltage value on the high-voltage side is between 0.9pu and 1.1pu, the value of the V control state is 1.0, and the value of the I control state is 0.0; when the voltage value on the high-voltage side is outside 0.9pu and 1.1pu, the value of the V control state is 0.0, the value of the I control state is 1.0, and the G control state is 0.0. QV Adopting the integral link, CO link adopts e=E*cos(θ), G VZ It is a first-order inertia link, without signal conditioning link, and the standby current i v The amplitude is limited according to the corresponding value of 1.2pu. Due to the use of phase-splitting control, the phases are no longer distinguished.

[0240] Fig.28 When STATCOM is in V control mode, Figure 7 The ideal voltage source v g Initial phase angle θ 0 The waveform curve of a 90° jump occurs at 1.0s. From the voltage source v g The initial phase angle changes from 1.0s to the fundamental reactive power Q 1 It takes about 161.135ms to enter the area between 90% and 110% of the quasi-steady-state value, that is, the recovery time t is about 8.06 power frequency cycles, and the fundamental reactive power Q 1 The fluctuation range is not small, 1.435pu, the fundamental active power P 1 The fluctuation range is relatively large, about 1.941pu. The fluctuation range of the converter DC voltage is not large, about 0.281pu, among which the minimum DC voltage is about 1.106pu and the maximum is about 0.825pu. The key to maintaining the STATCOM DC voltage within the normal range is that, Fig. 22 The central θ control link can quickly estimate the phase angle θ of the AC voltage of the power grid Uac , which significantly reduces the difference in STATCOM active power during transients and shortens their duration, while relatively small DC voltage fluctuations are caused by Fig. 9 The DC voltage feedback and active power feedback links with slightly slower response speed are used to deal with the challenges brought by phase angle jumps, thereby better handling them.

[0241] Embodiment 4:

[0242] Based on the same inventive concept, Fig.29 A block diagram of a synchronous compensator control system provided by the present invention, such as Fig.29As shown, the system may include: a virtual potential amplitude determination unit, which is used to determine the electrical quantity of the synchronous compensator and output the amplitude of the virtual potential using the control algorithm in the synchronous compensator; a synchronous phase angle determination unit, which is used to determine the synchronous phase angle based on the electrical parameters of the converter and using the synchronous phase angle synthesis method of any one of the first aspects mentioned above; a reference current determination unit, which is used to output the reference current based on the amplitude of the virtual potential, the synchronous phase angle and the AC voltage of the power grid and using the virtual potential control algorithm in the synchronous compensator; and a synchronous compensator control unit, which is used to control the converter in the synchronous compensator based on the reference current.

[0243] Optionally, the control algorithm is a reactive power control algorithm; the virtual potential amplitude determination unit is specifically used to: based on the virtual current value and the effective value of the grid AC voltage, utilize the reactive power control algorithm in the synchronous compensator to output the feedback voltage amplitude, or the feedforward voltage amplitude and the feedback voltage amplitude; based on the feedback voltage amplitude, or the feedforward voltage amplitude and the feedback voltage amplitude, obtain the amplitude of the virtual potential.

[0244] Optionally, the control algorithm is an AC voltage control algorithm; the virtual potential amplitude determination unit is specifically used to: based on the virtual current value, use the AC voltage control algorithm in the synchronous compensator to output the amplitude of the virtual potential.

[0245] Optionally, the synchronous compensator control unit includes: a current difference determination module, which is used to calculate the current difference between the current on the access side of the synchronous compensator and the reference current; a reference value determination module, which is used to determine the reference value of the three-phase voltage based on the current difference and the voltage on the access side of the synchronous compensator using a current tracking algorithm; a modulation wave determination module, which is used to determine the modulation wave of the switch tube in the synchronous compensator based on the reference value of the three-phase voltage, the capacitor voltage balance correction value, and the triangular carrier using a modulation wave control algorithm; and a converter control module, which is used to control the converter in the synchronous compensator based on the modulation wave of the switch tube in the synchronous compensator.

[0246] Embodiment 5:

[0247] Based on the same inventive concept, the present invention also provides a computer device, such as Fig.30As shown, the computer device includes a processor and a memory, the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in the computer storage medium, so as to realize the corresponding method flow or corresponding function, so as to realize a synchronous phase angle synthesis method or a step of a synchronous compensator control method in the above embodiment.

[0248] Embodiment 6:

[0249] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It can be understood that the computer-readable storage medium here can include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement a synchronous phase angle synthesis method or a step of a synchronous compensator control method in the above-mentioned embodiment.

[0250] It will be appreciated by those skilled in the art that the embodiments provided by the present invention may be methods, systems or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0251] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0252] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0253] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0254] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A synchronous phase angle synthesis method, characterized in that: The method comprises: Based on the electrical parameters of the converter, outputting the angular velocity deviation of the converter using a control transfer function; Based on the angular velocity deviation of the converter, outputting the phase angle deviation of the converter using a controlled oscillator; A synchronization phase angle is synthesized based on the phase angle deviation of the converter and the estimated phase angle of the grid AC voltage.

2. The method according to claim 1, characterized in that The electrical parameters include DC voltage and active power; The method of outputting the angular velocity deviation of the converter by using a control transfer function based on the electrical parameters of the converter comprises: Based on the DC voltage and the active power, an angular velocity deviation of the converter is outputted using a control transfer function of DC voltage feedback and a control transfer function of active power feedback.

3. The method according to claim 2, characterized in that The outputting of the angular velocity deviation of the converter based on the DC voltage and the active power by using a control transfer function of DC voltage feedback and a control transfer function of active power feedback comprises: Calculating a voltage deviation between a measured value of the DC voltage and a reference value of the DC voltage; Based on the voltage deviation, outputting a reference value of the active power using a control transfer function of the DC voltage feedback; Calculating an active power deviation between the measured value of the active power and the reference value of the active power; Based on the active power deviation, an angular velocity deviation of the converter is outputted using a control transfer function of active power feedback.

4. The method according to claim 2, characterized in that: The outputting of the angular velocity deviation of the converter based on the DC voltage and the active power by using a control transfer function of DC voltage feedback and a control transfer function of active power feedback comprises: Calculating a voltage deviation between a measured value of the DC voltage and a reference value of the DC voltage; Based on the voltage deviation, outputting a first standby angular velocity deviation using a control transfer function of the DC voltage feedback; Calculating an active power deviation between the measured value of the active power and the reference value of the active power; Based on the active power deviation, outputting a second standby angular velocity deviation using a control transfer function of the active power feedback; The sum of the first standby angular velocity deviation and the second standby angular velocity deviation is used as the angular velocity deviation of the inverter.

5. The method according to claim 1, characterized in that The electrical parameters include active power; The method of outputting the angular velocity deviation of the converter by using a control transfer function based on the electrical parameters of the converter comprises: Calculating an active power deviation between the measured value of the active power and the reference value of the active power; Based on the active power deviation, an angular velocity deviation of the converter is outputted using a control transfer function of active power feedback.

6. The method according to claim 1, characterized in that The electrical parameters include DC voltage; The method of outputting the angular velocity deviation of the converter by using a control transfer function based on the electrical parameters of the converter comprises: Calculating a voltage deviation between a measured value of the DC voltage and a reference value of the DC voltage; Based on the voltage deviation, the angular velocity deviation of the converter is outputted using a control transfer function of DC voltage feedback.

7. The method according to any one of claims 1 to 6, characterized in that: The method for determining the estimated phase angle of the grid AC voltage includes: Based on the AC voltage of the power grid, using a phase-locked loop to output an estimated phase angle of the AC voltage of the power grid; or, Based on the grid AC voltage, an estimated phase angle of the grid AC voltage is outputted using a frequency locked loop.

8. The method according to claim 7, characterized in that The method of outputting an estimated phase angle of the grid AC voltage by using a phase-locked loop based on the grid AC voltage comprises: When the converter adopts split-phase control, the grid AC voltage is a single-phase AC voltage, and the phase-locked loop is a voltage phase-locked loop, based on the single-phase AC voltage and the feedback phase angle output by the voltage phase-locked loop, the estimated phase angle of the grid AC voltage is output by using a phase detector, a loop filter and a controlled oscillator in the voltage phase-locked loop; When the converter adopts non-phase control, the grid AC voltage is the positive sequence component of the three-phase AC voltage, and the phase-locked loop is a typical three-phase phase-locked loop, based on the positive sequence component of the three-phase AC voltage and the feedback phase angle output by the typical three-phase phase-locked loop, the estimated phase angle of the grid AC voltage is output by using the phase detector, loop filter and controlled oscillator in the typical three-phase phase-locked loop, wherein the phase detector of the typical three-phase phase-locked loop is a Park transform of equal amplitude, and the loop filter of the typical three-phase phase-locked loop is a proportional integral.

9. The method according to claim 7, characterized in that: The method of outputting an estimated phase angle of the AC voltage of the power grid by using a frequency locked loop based on the AC voltage of the power grid comprises: When the converter adopts split-phase control and the grid AC voltage is a single-phase AC voltage, based on the single-phase AC voltage, a frequency-locked loop without gain normalization is used to output an estimated phase angle of the grid AC voltage; or, When the converter adopts phase-splitting control and the grid AC voltage is a single-phase AC voltage, based on the single-phase AC voltage, a frequency-locked loop with a gain normalized to one is used to output an estimated phase angle of the grid AC voltage; or, When the converter adopts non-phase control, the grid AC voltage is the positive sequence component of the three-phase AC voltage, and the frequency locked loop is a three-phase frequency locked loop, based on the positive sequence component of the three-phase AC voltage, a three-phase frequency locked loop with normalized gain is used to output the estimated phase angle of the grid AC voltage.

10. The method according to claim 9, characterized in that The method of outputting the estimated phase angle of the grid AC voltage based on the single-phase AC voltage using a frequency locked loop without gain normalization comprises: Based on the reference angular velocity, the quadrature-axis feedback voltage fed back by the second-order generalized integrator in the frequency-locked loop without gain normalization, the deviation of the direct-axis feedback voltage and the single-phase AC voltage, the angular velocity is estimated by using the output of the frequency locker in the frequency-locked loop; Based on the estimated angular velocity, the deviation between the direct-axis feedback voltage and the single-phase AC voltage, outputting the direct-axis voltage and the quadrature-axis voltage using the second-order generalized integrator; When the DC component of the single-phase AC voltage is less than a preset voltage threshold, based on the direct-axis voltage and the quadrature-axis voltage, a four-quadrant inverse tangent function is used to output an estimated phase angle of the AC voltage of the power grid; When the DC component of the single-phase AC voltage is greater than or equal to a preset voltage threshold, based on the DC feedback voltage output by the controlled oscillator and the deviation between the direct-axis feedback voltage and the single-phase AC voltage, using the controlled oscillator to output an estimated DC voltage of the converter; Based on the difference between the direct-axis voltage, the quadrature-axis voltage and the estimated direct-current voltage, an estimated phase angle of the alternating-current voltage of the power grid is output using a four-quadrant inverse tangent function.

11. The method according to claim 9, characterized in that The method of outputting the estimated phase angle of the grid AC voltage based on the single-phase AC voltage by using a frequency locked loop with a gain normalized to one includes: Based on the gain normalization coefficient, the reference angular velocity, the quadrature-axis feedback voltage fed back by the second-order generalized integrator in the frequency-locked loop with gain normalization, the deviation of the direct-axis feedback voltage and the single-phase AC voltage, the angular velocity is estimated using the output of the frequency locker in the frequency-locked loop; Based on the estimated angular velocity, the deviation between the direct-axis feedback voltage and the single-phase AC voltage, outputting the direct-axis voltage and the quadrature-axis voltage using the second-order generalized integrator; When the DC component of the single-phase AC voltage is less than a preset voltage threshold, based on the direct-axis voltage and the quadrature-axis voltage, a four-quadrant inverse tangent function is used to output an estimated phase angle of the AC voltage of the power grid; Wherein, the gain normalization coefficient is a coefficient output by a gain normalization function in the frequency locked loop based on the direct axis voltage, the quadrature axis voltage, and the estimated angular velocity; When the DC component of the single-phase AC voltage is greater than or equal to a preset voltage threshold, based on the DC feedback voltage output by the controlled oscillator and the deviation between the direct-axis feedback voltage and the single-phase AC voltage, using the controlled oscillator to output an estimated DC voltage of the converter; Based on the difference between the direct-axis voltage, the quadrature-axis voltage and the estimated direct-current voltage, outputting an estimated phase angle of the alternating-current voltage of the power grid using a four-quadrant inverse tangent function; The gain normalization coefficient is a coefficient output by a gain normalization function in the frequency locked loop based on the direct-axis voltage, the difference between the quadrature-axis voltage and the estimated direct-current voltage, and the estimated angular velocity.

12. A synchronous phase angle synthesis system, characterized in that: The system comprises: an angular velocity deviation determining unit, configured to output an angular velocity deviation of the inverter using a control transfer function based on electrical parameters of the inverter; a phase angle deviation determining unit, configured to output the phase angle deviation of the converter using a controlled oscillator based on the angular velocity deviation of the converter; The synchronous phase angle synthesis unit is used to synthesize the synchronous phase angle based on the phase angle deviation of the converter and the estimated phase angle of the AC voltage of the power grid.

13. A synchronous compensator control method, characterized in that: The method comprises: Based on the electrical quantity of the synchronous compensator, the amplitude of the virtual potential is outputted by utilizing the control algorithm in the synchronous compensator; Based on the electrical parameters of the converter, the synchronization phase angle is determined by using the synchronization phase angle synthesis method described in any one of claims 1 to 11 above; Based on the amplitude of the virtual potential, the synchronous phase angle and the AC voltage of the power grid, a reference current is outputted using a virtual potential control algorithm in the synchronous compensator; Based on the reference current, a converter in the synchronous compensator is controlled.

14. The method according to claim 13, characterized in that The control algorithm is a reactive power control algorithm, and the electrical quantity includes a virtual current value and an effective value of the AC voltage of the power grid; The method of outputting the amplitude of the virtual potential based on the electrical quantity of the synchronous compensator and utilizing the control algorithm in the synchronous compensator includes: Based on the virtual current value and the effective value of the AC voltage of the power grid, a reactive power control algorithm in the synchronous compensator is used to output a feedback voltage amplitude, or a feedforward voltage amplitude and a feedback voltage amplitude; The amplitude of the virtual potential is obtained based on the feedback voltage amplitude, or the feedforward voltage amplitude and the feedback voltage amplitude.

15. The method according to claim 13, characterized in that The control algorithm is an AC voltage control algorithm, and the electrical quantities include AC voltage deviation, virtual current value and current extreme value; The method of outputting the amplitude of the virtual potential based on the electrical quantity of the synchronous compensator and utilizing the control algorithm in the synchronous compensator includes: Based on the AC voltage deviation, an AC voltage control algorithm in a synchronous compensator is used to output the amplitude of a virtual potential; or, Based on the virtual current value and the current extreme value, an AC voltage control algorithm in a synchronous compensator is used to output the amplitude of the virtual potential.

16. The method according to claim 13, characterized in that The controlling the converter in the synchronous compensator based on the reference current includes: Calculating a current difference between a current at an access side of the synchronous compensator and the reference current; Based on the current difference and the voltage at the access side of the synchronous compensator, a reference value of the three-phase voltage is determined by using a current tracking algorithm; Based on the reference value of the three-phase voltage, the capacitor voltage balance correction value, and the triangular carrier, a modulation wave control algorithm is used to determine the modulation wave of the switch tube in the synchronous compensator; Based on the modulation wave of the switch tube in the synchronous compensator, the converter in the synchronous compensator is controlled.

17. A synchronous compensator control system, characterized in that: The system comprises: A virtual potential amplitude determination unit, configured to output the amplitude of the virtual potential based on the electrical quantity of the synchronous compensator and using a control algorithm in the synchronous compensator; A synchronization phase angle determination unit, configured to determine the synchronization phase angle based on electrical parameters of the converter and using the synchronization phase angle synthesis method according to any one of claims 1 to 11; a reference current determination unit, configured to output a reference current using a virtual potential control algorithm in the synchronous compensator based on the amplitude of the virtual potential, the synchronous phase angle and the grid AC voltage; A synchronous compensator control unit is used to control the converter in the synchronous compensator based on the reference current.

18. A computer device, characterized in that: include: one or more processors; The processor is used to store one or more programs; When the one or more programs are executed by the one or more processors, the synchronous phase angle synthesis method as described in any one of claims 1 to 11, or the synchronous compensator control method as described in any one of claims 13 to 16 is implemented.

19. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed, the synchronous phase angle synthesis method as described in any one of claims 1 to 11, or the synchronous compensator control method as described in any one of claims 13 to 16 is implemented.

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