Subsynchronous resonance energy suppression consumption method, system and equipment based on dynamic series compensator and medium

Abstract

The invention provides a subsynchronous resonance energy consumption suppression method, system and device based on a dynamic series compensator and a medium, and the method comprises the steps: obtaining a subsynchronous current through filtering and screening based on a grid-connected point current on a new energy power transmission line; based on the subsynchronous current and the virtual impedance, a suppression modulation wave is obtained through calculation; generating a control modulation wave for controlling the capacitance voltage deviation of the dynamic series compensator based on the fundamental current; and adding the suppression modulation wave and the control modulation wave to obtain a control signal of the dynamic series compensator, and carrying out suppression consumption on the subsynchronous resonance energy. According to the invention, the subsynchronous resonance is suppressed by suppressing the modulated wave, and meanwhile, the subsynchronous energy of the dynamic series compensator is discharged in real time by controlling the modulated wave, so that the condition that protection is triggered to quit operation due to overhigh capacitor voltage is prevented, and the continuity and reliability of the subsynchronous resonance suppression function are fundamentally ensured; therefore, stable transfer and consumption of the subsynchronous resonance energy are realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of power system subsynchronous oscillation, and particularly relates to a subsynchronous resonance energy suppression and consumption method, system, device and medium based on a dynamic series compensator. BACKGROUND

[0002] At present, new energy units, flexible HVDC transmission systems, auxiliary equipment and some power loads all rely on the control and regulation of power electronic devices. However, power electronic devices have control elements with different bandwidths, such as inner and outer loop proportional integral controllers, phase-locked loops, filters and the like. The interactive coupling of these control devices can cause multi-time scale interaction characteristics between power electronic devices, resulting in energy exchange between power electronic devices and power systems in multiple frequency bands, thereby causing oscillation of the interaction system in a wide frequency range, referred to as wide frequency oscillation. The subsynchronous resonance events caused by the connection of double-fed asynchronous wind power plants to the power grid are gradually increasing.

[0003] When the topology structure or control parameters of the power electronic device change, the oscillation frequency of the interaction system will also change, and the frequency will shift within a certain range. Therefore, the subsynchronous resonance caused by the interaction between power electronic devices and the power grid has time-varying characteristics.

[0004] So far, there have been many system subsynchronous resonance accidents involving grid-connected new energy. With the large-scale connection of new energy, the function, structure and form of modern power grids have undergone profound changes, and the characteristics of "double high", i.e. high proportion of renewable energy and high proportion of power electronic devices, are becoming increasingly apparent, which poses new challenges to the safe and stable operation of power grids and reliable power supply. In recent years, series compensation devices have been installed in substations to improve line transmission capacity. The main fixed series compensation devices do not have impedance adjustment capability and may, under certain conditions, induce subsynchronous, supersynchronous and even high-frequency oscillations, thereby affecting the output and consumption of new energy and possibly causing resonance with the shaft torsional vibration of thermal power plants, thereby affecting the safe and stable operation of the entire system. In the future, in the new type of power system dominated by new energy, how to realize the suppression and consumption of subsynchronous resonance energy is one of the important needs of the power grid. SUMMARY

[0005] To overcome the shortcomings of the prior art, the present application provides a subsynchronous resonance energy suppression and consumption method based on a dynamic series compensator, comprising:

[0006] Based on the grid-connected point current on the new energy transmission line, the subsynchronous current in the grid-connected point current at the subsynchronous resonance frequency is obtained through filtering and screening. A series compensation device is provided on the transmission line, and the series compensation device is a dynamic series compensator or a hybrid series compensator based on a dynamic series compensator and a fixed series compensator.

[0007] based on the subsynchronous current and the virtual impedance at the subsynchronous resonance frequency, a subsynchronous resonance suppression voltage and a suppression modulation wave corresponding to the subsynchronous resonance suppression voltage are calculated;

[0008] based on the fundamental current extracted from the grid-connected point current, a control modulation wave for controlling the capacitor voltage deviation of the dynamic series compensator is generated;

[0009] after the suppression modulation wave and the control modulation wave are added, the control signal of the dynamic series compensator is obtained by comparing with the triangular phase-shifted carrier wave of the dynamic series compensator, and based on the control signal, the subsynchronous resonance energy at the subsynchronous resonance frequency is suppressed and consumed.

[0010] Preferably, the calculation of the subsynchronous resonance suppression voltage and the suppression modulation wave corresponding to the subsynchronous resonance suppression voltage based on the subsynchronous current and the virtual impedance at the subsynchronous resonance frequency comprises:

[0011] based on the series compensation device, the system equivalent impedance observed from the new energy to the grid system at the subsynchronous resonance frequency is determined;

[0012] based on the system equivalent impedance, the virtual impedance at the subsynchronous resonance frequency is solved by taking the superposition of the system equivalent impedance and the virtual impedance satisfying the set condition as the target;

[0013] based on the subsynchronous current and the virtual impedance, a subsynchronous resonance suppression voltage and a suppression modulation wave corresponding to the subsynchronous resonance suppression voltage are calculated.

[0014] Preferably, the virtual impedance at the subsynchronous resonance frequency is solved based on the system equivalent impedance by taking the superposition of the system equivalent impedance and the virtual impedance satisfying the set condition as the target, comprising:

[0015] based on the system equivalent impedance and the new energy impedance at the subsynchronous resonance frequency;

[0016] the superposition of the system equivalent impedance and the virtual impedance is taken as a composite impedance, and the parallel equivalent value of the composite impedance and the new energy impedance is taken as the target, which is less than a set multiple of the system equivalent impedance, and through an iterative algorithm, the virtual impedance satisfying the target is output as the virtual impedance at the subsynchronous resonance frequency by cyclic calculation within a preset virtual impedance parameter range.

[0017] Preferably, the calculation of the subsynchronous resonance suppression voltage and the suppression modulation wave corresponding to the subsynchronous resonance suppression voltage based on the subsynchronous current and the virtual impedance comprises:

[0018] based on the subsynchronous current and the virtual impedance, performing coordinate transformation and filtering on the subsynchronous current to obtain a subsynchronous current polar coordinate amplitude;

[0019] multiplying a virtual resistance in the virtual impedance by the subsynchronous current polar coordinate amplitude to obtain a resistive suppression voltage;

[0020] multiplying a virtual reactance in the virtual impedance by the subsynchronous current polar coordinate amplitude while performing polar coordinate angle rotation to obtain an inductive suppression voltage;

[0021] performing coordinate transformation and synthesis on the resistive suppression voltage and the inductive suppression voltage to obtain a subsynchronous resonance suppression voltage;

[0022] calculating a ratio of the subsynchronous resonance suppression voltage to a capacitance DC voltage of the dynamic series compensator to obtain a suppression modulation wave.

[0023] Preferably, the determination of the system equivalent impedance at the subsynchronous resonance frequency from the new energy to the power grid system based on the series compensation device comprises:

[0024] when the series compensation device is the dynamic series compensator, taking the power grid system impedance at the subsynchronous resonance frequency as the system equivalent impedance at the subsynchronous resonance frequency;

[0025] when the series compensation device is the hybrid series compensator, superimposing the power grid system impedance at the subsynchronous resonance frequency with the capacitive reactance of the fixed series compensator to obtain the system equivalent impedance at the subsynchronous resonance frequency.

[0026] Preferably, the generation of the control modulation wave for controlling the capacitance voltage deviation of the dynamic series compensator based on the fundamental wave current extracted from the point of common coupling current comprises:

[0027] based on the point of common coupling current, obtaining a fundamental wave current through phase angle extraction and coordinate transformation;

[0028] based on the fundamental wave current, generating a control modulation wave for controlling the capacitance voltage deviation of the dynamic series compensator.

[0029] Preferably, the generation of the control modulation wave for controlling the capacitance voltage deviation of the dynamic series compensator based on the fundamental wave current comprises:

[0030] based on the capacitance voltage measurement value of the dynamic series compensator, calculating a difference between the capacitance voltage measurement value and a capacitance voltage set value to obtain a capacitance voltage deviation;

[0031] Proportionally and integrally control the capacitor voltage deviation to obtain a fundamental voltage;

[0032] Based on the fundamental current, a product of the fundamental current and the fundamental voltage is calculated to obtain a fundamental voltage instruction, and the fundamental voltage instruction is subjected to amplitude limiting conversion to obtain a control modulation wave.

[0033] Preferably, the grid-connected point current on the new energy power transmission line is filtered to obtain a subsynchronous current in the grid-connected point current at a subsynchronous resonance frequency.

[0034] Based on the grid-connected point current on the new energy power transmission line, current components at different subsynchronous resonance frequencies are extracted through a multi-channel band-pass filter.

[0035] Each of the current components is compared with a preset current threshold, and a current component greater than the current threshold is taken as a subsynchronous current.

[0036] Based on the same inventive concept, the application also provides a subsynchronous resonance energy suppression and consumption system based on a dynamic series compensator, comprising:

[0037] A series compensation device in series with a power transmission line between a new energy and a power grid system, and a subsynchronous suppression control module electrically connected with the series compensation device; the series compensation device is a dynamic series compensator or a hybrid series compensator based on a dynamic series compensator and a fixed series compensator.

[0038] The subsynchronous suppression control module comprises a filtering and screening unit, a suppression modulation wave determination unit, a control modulation wave determination unit, and a modulation wave superposition control unit.

[0039] The filtering and screening unit is configured to filter and screen the grid-connected point current on the power transmission line to obtain a subsynchronous current in the grid-connected point current at a subsynchronous resonance frequency.

[0040] The suppression modulation wave determination unit is configured to calculate a subsynchronous resonance suppression voltage and a suppression modulation wave corresponding to the subsynchronous resonance suppression voltage based on the subsynchronous current and a virtual impedance at the subsynchronous resonance frequency obtained in advance.

[0041] The control modulation wave determination unit is configured to generate a control modulation wave for controlling a capacitor voltage deviation of the dynamic series compensator based on a fundamental current extracted from the grid-connected point current.

[0042] The modulation wave superposition control unit is configured to add the suppression modulation wave and the control modulation wave, compare the result with the dynamic series compensation device's three-phase phase-shifted carrier wave, obtain the control signal of the dynamic series compensation device, and suppress and consume the subsynchronous resonance energy at the subsynchronous resonance frequency based on the control signal.

[0043] Preferably, the suppression modulation wave determination unit comprises:

[0044] An equivalent impedance determination subunit is configured to determine, based on the series compensation device, a system equivalent impedance observed from the new energy to the power grid system at the subsynchronous resonance frequency.

[0045] A virtual impedance solving subunit is configured to solve, based on the system equivalent impedance, a virtual impedance at the subsynchronous resonance frequency, so that the system equivalent impedance and the virtual impedance satisfy a set condition after being superimposed.

[0046] A first modulation wave determination subunit is configured to calculate, based on the subsynchronous current and the virtual impedance, a subsynchronous resonance suppression voltage and a suppression modulation wave corresponding to the subsynchronous resonance suppression voltage.

[0047] Preferably, the virtual impedance solving subunit is specifically configured to:

[0048] based on the system equivalent impedance and a new energy impedance at the subsynchronous resonance frequency;

[0049] superimposition of the system equivalent impedance and the virtual impedance as a composite impedance, so that the parallel equivalent value of the composite impedance and the new energy impedance is less than a set multiple of the system equivalent impedance, and the virtual impedance satisfying the target is output as the virtual impedance at the subsynchronous resonance frequency through iterative algorithm and cyclic calculation within a preset virtual impedance parameter range.

[0050] Preferably, the first modulation wave determination subunit is specifically configured to:

[0051] based on the subsynchronous current and the virtual impedance, performing coordinate transformation and filtering on the subsynchronous current to obtain a subsynchronous current polar coordinate amplitude;

[0052] multiplying a virtual resistance in the virtual impedance and the subsynchronous current polar coordinate amplitude to obtain a resistive suppression voltage;

[0053] multiplying a virtual reactance in the virtual impedance and the subsynchronous current polar coordinate amplitude, and simultaneously performing polar coordinate angle rotation to obtain an inductive suppression voltage;

[0054] performing coordinate transformation and synthesis on the resistive suppression voltage and the inductive suppression voltage to obtain a subsynchronous resonance suppression voltage.

[0055] Calculate the ratio of the subsynchronous resonance suppression voltage and the capacitance DC voltage of the dynamic series compensator to obtain a suppression modulation wave.

[0056] Preferably, the equivalent impedance determination subunit is specifically used for:

[0057] When the series compensation device is the dynamic series compensator, the grid system impedance at the subsynchronous resonance frequency is taken as the system equivalent impedance at the subsynchronous resonance frequency.

[0058] When the series compensation device is the hybrid series compensator, the grid system impedance at the subsynchronous resonance frequency is superimposed with the capacitive reactance of the fixed series compensator to obtain the system equivalent impedance at the subsynchronous resonance frequency.

[0059] Preferably, the control modulation wave determination unit comprises:

[0060] The fundamental current extraction subunit is configured to obtain a fundamental current by phase angle extraction and coordinate transformation based on the grid-connected point current.

[0061] The second modulation wave determination subunit is configured to generate a control modulation wave for controlling the capacitance voltage deviation of the dynamic series compensator based on the fundamental current.

[0062] Preferably, the second modulation wave determination subunit is specifically used for:

[0063] Based on the capacitance voltage measurement value of the dynamic series compensator, the difference between the capacitance voltage measurement value and the capacitance voltage set value is calculated to obtain a capacitance voltage deviation.

[0064] The capacitance voltage deviation is proportionally integrated to obtain a fundamental voltage.

[0065] Based on the fundamental current, the product of the fundamental current and the fundamental voltage is calculated to obtain a fundamental voltage instruction, and the fundamental voltage instruction is subjected to amplitude limiting conversion to obtain a control modulation wave.

[0066] Preferably, the filter screening unit is specifically used for:

[0067] Based on the grid-connected point current on the new energy transmission line, a current component at different subsynchronous resonance frequencies is extracted by a multi-channel band-pass filter.

[0068] Each of the current components is compared with a preset current threshold, and a current component greater than the current threshold is taken as a subsynchronous current.

[0069] Based on the same inventive concept, the present application also provides a computer device comprising: one or more processors;

[0070] a memory for storing one or more programs;

[0071] When the one or more programs are executed by the one or more processors, a sub-synchronous resonance energy suppression and consumption method based on a dynamic series compensator is realized.

[0072] Based on the same inventive concept, the present application also provides a computer readable storage medium having a computer program stored thereon, which, when executed, realizes a sub-synchronous resonance energy suppression and consumption method based on a dynamic series compensator.

[0073] Compared with the closest prior art, the present application has the following beneficial effects:

[0074] The present application provides a sub-synchronous resonance energy suppression and consumption method, system, device and medium based on a dynamic series compensator, which comprises: based on the grid-connected point current on a new energy transmission line, sub-synchronous current in the grid-connected point current at a sub-synchronous resonance frequency is obtained through filtering and screening; a series compensation device is arranged on the transmission line, and the series compensation device is a dynamic series compensator or a hybrid series compensator based on a dynamic series compensator and a fixed series compensator; based on the sub-synchronous current and a virtual impedance at the sub-synchronous resonance frequency obtained in advance, a sub-synchronous resonance suppression voltage and a suppression modulation wave corresponding to the sub-synchronous resonance suppression voltage are calculated; based on the fundamental wave current extracted from the grid-connected point current, a control modulation wave for controlling the capacitance voltage deviation of the dynamic series compensator is generated; after the suppression modulation wave and the control modulation wave are added, they are compared with the triangular phase-shifting carrier wave of the dynamic series compensator to obtain a control signal of the dynamic series compensator, and based on the control signal, sub-synchronous resonance energy at the sub-synchronous resonance frequency is suppressed and consumed. This method suppresses sub-synchronous resonance through a suppression modulation wave, and at the same time, it discharges sub-synchronous energy absorbed by the dynamic series compensator due to the suppression of sub-synchronous resonance oscillation in real time through a control modulation wave, so as to prevent the capacitance voltage of the dynamic series compensator from being too high and triggering protection to exit operation, and fundamentally ensure the persistence and reliability of the sub-synchronous resonance suppression function; thereby realizing stable transfer and consumption of sub-synchronous resonance energy, reducing the risk of sub-synchronous resonance induced by the action of new energy and the power grid system, and enhancing the damping of the power grid system. BRIEF DESCRIPTION OF DRAWINGS

[0075] Figure 1 A sub-synchronous resonance energy suppression and consumption method flowchart based on a dynamic series compensator is provided for the present application.

[0076] Figure 2 A sub-synchronous resonance multi-channel identification and frequency selection process is provided for the present application.

[0077] Figure 3 The equivalent circuit of new energy access power grid provided by the present application;

[0078] Figure 4 The flow chart of the virtual impedance determination method provided by the present application;

[0079] Figure 5 The frequency variable F provided by the present application n1 The process diagram of the corresponding subsynchronous current extraction conversion into d / q axis direct current;

[0080] Figure 6 The acquisition process diagram of the subsynchronous resonance suppression voltage provided by the present application;

[0081] Figure 7 The extraction process diagram of the current synchronous angle provided by the present application;

[0082] Figure 8 The extraction process diagram of the fundamental current provided by the present application;

[0083] Figure 9 The principle diagram of the DSC module direct current voltage control provided by the present application;

[0084] Figure 10 The principle diagram of the modulation wave synthesis and DSC switch signal generation provided by the present application;

[0085] Figure 11 The system architecture diagram of the subsynchronous resonance energy suppression and consumption system based on the dynamic series compensator provided by the present application;

[0086] Figure 12 The structure diagram of the subsynchronous suppression control module provided by the present application;

[0087] Figure 13 The structure diagram of the electronic device provided by the present application. DETAILED DESCRIPTION

[0088] The specific embodiments of the present application will be further described in detail below in combination with the drawings.

[0089] Embodiment 1:

[0090] The subsynchronous resonance energy suppression and consumption method based on the dynamic series compensator provided by the present application, as shown in the figure, comprises: Figure 1

[0091] ​S1, based on the grid-connected point current on the new energy transmission line, the subsynchronous current in the grid-connected point current at the subsynchronous resonance frequency is obtained through filtering and screening; a series compensation device is arranged on the transmission line, and the series compensation device is a dynamic series compensation device or a hybrid series compensation device based on a dynamic series compensation device and a fixed series compensation device;

[0092] S2, based on the subsynchronous current and the virtual impedance at the subsynchronous resonance frequency obtained in advance, a subsynchronous resonance suppression voltage and a suppression modulation wave corresponding to the subsynchronous resonance suppression voltage are calculated;

[0093] S3, based on the fundamental wave current extracted from the grid-connected point current, a control modulation wave for controlling the capacitance voltage deviation of the dynamic series compensation device is generated;

[0094] S4, after adding the suppression modulation wave and the control modulation wave, the dynamic series compensation device is compared with the triangular phase-shifted carrier wave, the control signal of the dynamic series compensation device is obtained, and the subsynchronous resonance energy at the subsynchronous resonance frequency is suppressed and consumed based on the control signal.

[0095] So far, there have been many system subsynchronous resonance accidents caused by new energy grid connection. For example, since 2010, a wind farm in a certain region has experienced multiple system subsynchronous oscillations caused by double-fed wind farms and series compensation equipment. According to the recording wave display, the frequency range of the oscillation current is mostly distributed in 6-9Hz. In July 2015, a wind farm in a certain region experienced subsynchronous oscillation, which caused the torsional vibration protection of a 300km away thermal power unit to act, causing the thermal power unit to shut down. This is the first reported power grid power oscillation event caused by the propagation of subsynchronous oscillation components in multiple power grids. Through analysis of fault recording data, it is found that there are 20Hz / 80Hz, 30Hz / 70Hz harmonic components in the system current, and the amplitude of some harmonics is larger, even higher than the fundamental frequency amplitude, and the harmonic components propagate along the transmission line, and finally reach the downstream power plant unit, causing the torsional vibration protection device of the thermal power unit to act, causing three 660MW thermal power units in the downstream thermal power plant to trip, causing the frequency of the regional power grid to drop by 0.1Hz. In addition, a certain flexible demonstration project has also experienced multiple subsynchronous oscillation accidents caused by wind turbines during commissioning. When the accident occurs, the output of the double-fed wind farm connected increases, exciting the subsynchronous / ultrasub synchronous oscillation with a frequency of about 30Hz / 70Hz. With the large-scale access of new energy, the function, structure and form of modern power grids have undergone profound changes, and the "double high" characteristics are becoming more and more obvious, which brings new challenges to the safe and stable operation of power grids and reliable power supply. In the future, in the new type of power system dominated by new energy, subsynchronous resonance suppression and flexible power flow regulation capability are important requirements of power grids.

[0096] Based on the above problems, this invention suppresses subsynchronous resonance by suppressing the modulation wave, and simultaneously controls the modulation wave to discharge the subsynchronous energy absorbed by the dynamic series compensator due to the suppression of subsynchronous resonance oscillation in real time, preventing the capacitor voltage of the dynamic series compensator from being too high and triggering protection to exit operation, thus fundamentally ensuring the continuity and reliability of the subsynchronous resonance suppression function; thereby achieving stable transfer and consumption of subsynchronous resonance energy, reducing the risk of subsynchronous resonance induced by the interaction between new energy sources and the power grid system, and enhancing the damping of the power grid system.

[0097] This method is based on the Dynamic Series Compensator (DSC) unit. The DSC module is connected in series with the transmission line and consists of a DSC sub-unit and a DSC main controller.

[0098] The Dynamic Series Compensator (DSC) is an active, fast-controllable series compensation device based on IGBTs. It generates an AC voltage with controllable amplitude, phase, and frequency through a power electronic converter and injects it in series into the transmission line.

[0099] A hybrid series compensator (FSC) is a composite compensation device that combines the advantages of a traditional fixed series compensator (FSC) with a direct series compensator (DSC). It achieves an optimal balance between cost and performance. The FSC section, composed of capacitor banks, provides basic, high-capacity capacitive reactive power compensation and undertakes the main series compensation tasks.

[0100] Subsynchronous current refers to the oscillating current with a frequency lower than the system synchronization frequency that occurs when subsynchronous resonance (SSR) occurs in a power system. By monitoring, analyzing, and controlling the subsynchronous current, subsynchronous resonance can be suppressed. In S1 above, a multi-channel bandpass filter is used to filter the subsynchronous current, allowing for accurate determination of the subsynchronous resonance frequency that needs to be suppressed.

[0101] In this embodiment, determining the subsynchronous current in S1 includes:

[0102] Based on the grid connection point current on new energy transmission lines, current components at different subsynchronous resonant frequencies are extracted using a multi-channel bandpass filter.

[0103] Each current component is compared with a preset current threshold, and the current component that is greater than the current threshold is taken as the secondary synchronization current.

[0104] Specifically, such as Figure 2 As shown, subsynchronous resonance multi-channel identification is performed by screening the subsynchronous current, including:

[0105] (1) First, the line current i flowing through the transmission line, i.e. the grid-connected point current, is collected;

[0106] (2) The line current i is transmitted to n channels;

[0107] (3) The number of channels n is determined according to the frequency range in which the subsynchronous resonance current occurs, and each frequency f1, f2, … fn corresponds to a channel; n (An integer number is the main) A band pass filter (Band Pass Butterworth Order) is designed to correspond to a channel;

[0108] (4) After the line current i is screened by the band pass filter, the current signal of the corresponding frequency in the passband range is screened;

[0109] (5) The screened current Issr_f1, Issr_f2, … Issr_fn of each channel is compared with the pre-set current threshold Issr_set through the comparator Comparator, and the channel frequency greater than Issr_set is recorded by the counter Ctr, and Ctr=1 is recorded if the current threshold is exceeded, otherwise Ctr=0, and if there are multiple channel current values exceeding the current threshold, all channels exceeding the current threshold are recorded, and each channel corresponds to a frequency variable F1, F2, … Fn. n , used to store the subsynchronous resonance frequency, and an array variable is used to record the subsynchronous resonance current value;

[0110] (6) The amplitudes of the subsynchronous currents corresponding to the multiple frequency variables obtained by the frequency selection method are compared, and the frequency variable corresponding to the largest amplitude of the subsynchronous harmonic current is selected as the maximum subsynchronous resonance frequency Fmax. n1 The other subsynchronous resonance frequencies F2, F3, … Fn are sequentially sorted from large to small, and the subsynchronous resonance frequencies F2, F3, … Fn are selected. n2 n3 nn

[0111] (7) The frequency variable parameters obtained by screening and the corresponding subsynchronous current array are transmitted to the control program for further processing.

[0112] (8) When the effective value of the subsynchronous resonance modulation wave, i.e. the suppression modulation wave, is less than the set value, the control system determines that the subsynchronous resonance disappears, and the above variables are cleared and re-entered into the initial state.

[0113] ​​​According to the mechanism of the wind farm grid connection subsynchronous resonance, under the condition of the wind farm grid operation, the negative damping (doubly-fed induction generator) is generated at the subsynchronous frequency, which makes the subsynchronous current diverge. At the same time, the new energy impedance is equal to the system impedance, and the phase difference reaches 180°, so that the subsynchronous resonance is further amplified, which endangers the safe and stable operation of the system and the wind farm. To suppress the subsynchronous resonance, the DSC module needs to generate a subsynchronous voltage, which, in the above S2, acts on the subsynchronous current to generate a virtual resistance and a virtual reactance to offset the negative resistance of the doubly-fed induction generator. At the same time, by changing the equivalent impedance of the system through the virtual impedance, the phase angle difference between the wind farm and the system impedance at the subsynchronous resonance frequency is less than 180°, so that the subsynchronous resonance current caused by the new energy access to the system can be suppressed.

[0114] In the embodiment, the above S2 specifically includes:

[0115] S201, determining the system equivalent impedance observed from the new energy to the grid system at the subsynchronous resonance frequency based on the series compensation device;

[0116] S202, based on the system equivalent impedance, the virtual impedance after superposition of the system equivalent impedance and the virtual impedance meets the set condition as the target, and the virtual impedance at the subsynchronous resonance frequency is solved;

[0117] S203, based on the subsynchronous current and the virtual impedance, the subsynchronous resonance suppression voltage and the suppression modulation wave corresponding to the subsynchronous resonance suppression voltage are calculated.

[0118] Since the method can suppress the subsynchronous resonance caused by the new energy grid connection through the DSC alone, it can also be used for the case of suppressing the subsynchronous resonance by the hybrid series compensation device. However, the system equivalent impedances in the two cases are different, so before calculating the virtual impedance in S202, i.e. in the above S201, the type of the series compensation device needs to be determined to determine the system equivalent impedance.

[0119] In the embodiment, the above S201 includes:

[0120] When the series compensation device is the dynamic series compensation device, the grid system impedance at the subsynchronous resonance frequency is taken as the system equivalent impedance at the subsynchronous resonance frequency;

[0121] When the series compensation device is the hybrid series compensation device, the grid system impedance at the subsynchronous resonance frequency and the capacitive reactance of the fixed series compensation device are superimposed to obtain the system equivalent impedance at the subsynchronous resonance frequency.

[0122] According to the mechanism of the new energy access to the system inducing the subsynchronous resonance, as shown in Figure 3As shown, the new energy station access system can be equivalent to a parallel connection of a new energy current source and a new energy impedance and then access the system; wherein, V s is a system voltage; Zs is a system impedance, i.e., a system equivalent impedance; I s is a system current; I x is a new energy current; Zx is a new energy impedance;

[0123] When the new energy is connected to the grid to cause subsynchronous resonance, the system impedance Zs and the new energy impedance Zx are equal in modulus and have a phase angle difference of 180 degrees at the subsynchronous resonance frequency, thereby causing the occurrence of subsynchronous resonance. The present application proposes a method for determining a virtual impedance (virtual resistance and virtual reactance) of subsynchronous resonance in S202 above according to the mechanism of subsynchronous resonance and the equivalent circuit, thereby providing a basis for the selection of subsynchronous suppression parameters.

[0124] In the embodiment, S202 above can include:

[0125] based on the system equivalent impedance and the new energy impedance at the subsynchronous resonance frequency;

[0126] The superposition of the system equivalent impedance and the virtual impedance is taken as a composite impedance, and the parallel connection equivalent value of the composite impedance and the new energy impedance is taken as a target that is less than a set multiple of the system equivalent impedance. Through an iterative algorithm, a loop calculation is performed in a preset virtual impedance parameter range to solve a virtual impedance that meets the target and output the virtual impedance as the virtual impedance at the subsynchronous resonance frequency.

[0127] As shown in the specific process as follows: Figure 4

[0128] (1) Input the system impedance Zs and the new energy impedance Zx at the subsynchronous resonance frequency;

[0129] (2) Assign Zs and Zx to complex variables Rzs+jGzs and Rzx+jGzx; wherein, Rzs and Gzs are the resistance component and the reactance component of the system impedance, respectively, and Rzx and Gzx are the resistance component and the reactance component of the new energy impedance, respectively;

[0130] (3) Select the range of the virtual resistance R (0-Rmax), and the maximum value Rmax of the virtual resistance does not exceed the maximum impedance of the system at the subsynchronous resonance frequency;

[0131] (4) Select the range of the virtual reactance X (0-Xmax), and the maximum value Xmax of the virtual reactance does not exceed the maximum reactance of the system at the subsynchronous frequency;

[0132] Set the step change amount ΔR of the virtual resistance as Rmax / 1000;

[0133] ​Set virtual reactance step change ΔX = Xmax / 1000;

[0134] (5) The main flow of the iterative algorithm program is as follows:

[0135] When the program starts, the initial value of the virtual resistance variable is assigned, i.e. R = 0; the initial value of the virtual reactance variable is assigned, i.e. X = 0; then, the step change of the resistance and reactance is set. The program enters a preset 10000 times of loop calculation process.

[0136] In each loop, first, the values of R and X are updated, i.e. the virtual resistance and virtual reactance are added with the change and then assigned, which is expressed as:

[0137] R = R + ΔR, X = X + ΔX;

[0138] Then, the updated R value is added with the system resistance component Rzs = Rzs + R, and the X value is added with the system reactance component Gzs = Gzs + X, to form the new system impedance superimposed with the virtual impedance, i.e. the composite impedance. Then, the parallel equivalent impedance of the composite impedance and the new energy impedance is calculated, and the modulus thereof, i.e. the parallel equivalent value, is obtained.

[0139] The equivalent resistance Rnew and equivalent reactance Gnew of the parallel equivalent impedance satisfy the following formula:

[0140] Rnew + jGnew = (Rzs + jGzs) / / Rzx + jGzx;

[0141] Wherein, Rzx and Gzx are the resistance component and reactance component of the composite impedance, respectively;

[0142] The key step of the program is to compare the modulus of the parallel equivalent impedance, i.e. the parallel equivalent value, with a set condition. For example, the target is to determine whether the parallel equivalent value is less than the modulus of the original system impedance, i.e. 1.1 times of the modulus of the system equivalent impedance.

[0143] Wherein, the modulus of the parallel equivalent impedance

[0144] The modulus of the system equivalent impedance

[0145] If the condition is met, i.e. Z M <1.1Z s , the loop is immediately terminated, and the current R and X values are output as the result; if the condition is not met, the loop continues, and the new R and X values are used for the next round of calculation. If the loop reaches 10000 times without finding the solution, the loop is exited.

[0146] Ultimately, the virtual resistance variable Sr and virtual reactance variable Sx selected through this procedure constitute the virtual reactance that enables the system to operate stably at a specific subsynchronous frequency.

[0147] By using the above methods and procedures, suitable virtual resistors and reactances can be selected, reducing the impedance magnitude of the new energy source connected in parallel with the system to within 1.1 times the system impedance. This solves the subsynchronous resonance problem caused by the grid connection of new energy sources and provides a basis for the selection of virtual resistors and reactances.

[0148] It should be noted that this invention overcomes the overdamping or underdamping problems that may exist in traditional artificially set virtual impedances by solving the virtual impedance according to the set target. It fully considers the impedance characteristics of the power grid system under different series compensators, so that the suppression effect of the modulation wave calculated based on the virtual impedance is better and more efficient.

[0149] In this embodiment, S203 includes:

[0150] Based on the subsynchronous current and the virtual impedance, the subsynchronous current is subjected to coordinate transformation and filtering to obtain the polar coordinate amplitude of the subsynchronous current;

[0151] Multiplying the virtual resistance in the virtual impedance by the polar coordinate amplitude of the subsynchronous current yields the resistive suppression voltage;

[0152] Multiply the virtual reactance in the virtual impedance by the polar coordinate amplitude of the subsynchronous current, and simultaneously rotate the polar coordinate angle to obtain the inductive suppression voltage.

[0153] The resistive suppression voltage and the inductive suppression voltage are transformed and synthesized to obtain the subsynchronous resonance suppression voltage;

[0154] The ratio of the subsynchronous resonance suppression voltage to the DC voltage of the capacitor of the dynamic series compensator is calculated to obtain the suppressed modulation wave.

[0155] Specifically, when obtaining the polar coordinate amplitude of the subsynchronous current, the following steps are taken:

[0156] The subsynchronous resonance frequency F obtained by screening through the subsynchronous resonance multi-channel identification process n1 F n2 ...F nn Then, generate the corresponding subsynchronous rotation coordinate function, i.e., the cosine function cos;

[0157] like Figure 5 As shown, the subsynchronous resonant frequency F n1 For example, by processing the subsynchronous current using the subsynchronous rotating coordinate function, i.e., the cosine function cos, a three-phase symmetrical subsynchronous current I is generated. xa Ixb I xc Subsequently, the three-phase symmetrical subsynchronous current is input into the phase-locked loop (PLL), and the phase angle An_x of the subsynchronous current is extracted using PLL technology; then, the subsynchronous current I is calculated using the phase angle An_x. a I b I c A transformation from a three-phase stationary coordinate system to a two-phase subsynchronous coordinate system (3To2Transform) is performed to obtain the d / q-axis DC ripple. The AC component in the DC ripple is then removed using a low-pass filter to obtain the d / q-axis DC quantity I. x_d I x_q ;

[0158] Subsequently, as Figure 6 As shown, the DC d / q axis is converted from rectangular coordinates XY to polar coordinates PM to obtain the polar coordinate amplitude I of the subsynchronous current. m3 and phase angle A n3 ;

[0159] It should be noted that, specifically, when acquiring the suppressed modulation wave, the following steps are included:

[0160] The virtual resistance R and virtual reactance ωL are derived from the system study. The virtual reactance ωL can also be represented by X, which is R multiplied by the polar coordinate amplitude I of the subsynchronous current. m3 With the polar coordinate angle unchanged, the resistive subsynchronous suppression voltage amplitude in polar coordinates is obtained, i.e., the resistive suppression voltage amplitude U. sr Multiply ωL by the polar coordinate amplitude of the subsynchronous current, and simultaneously increase the angle by 90 degrees to obtain the amplitude of the inductive subsynchronous suppression voltage, i.e., the amplitude of the inductive suppression voltage U. sL Furthermore, the resistive suppression voltage phase angle U can also be obtained. sr_An Phase angle U of inductive suppression voltage sL_An .

[0161] Will U sr U sL Converting from polar coordinates to rectangular coordinates, corresponding to d / q coordinates, yields the d / q axis quantity U of the resistive suppression voltage. sr_d and U sr_q And the d / q axis quantity U of the inductive suppression voltage. sL_d U sL_q Subsequently, the inverse transformation (2To3 Transform) of the corresponding subsynchronous rotating coordinate function is used to transform the DQ axis quantities and AC quantities, ultimately converting U... sr U sL Converting this to an alternating current, we obtain the three-phase alternating current U of the resistive suppression voltage. sr_a U sr_b U sr_c And the three-phase AC quantity U of the inductive suppression voltagesL_a U sL_b U sL_c .

[0162] If, apart from F, which has the largest suppression amplitude n1 In addition, it is also necessary to suppress the second largest F. n2 If there are , or more subsynchronous resonant frequencies, then the corresponding suppression methods and processes are the same as those for F. n1 Similarly, the modulation waves of different frequencies are added together to obtain the corresponding subsynchronous resonance suppression voltage; the combined voltage is divided by the DC voltage of the module capacitor to obtain the subsynchronous suppression voltage modulation wave, i.e., the suppression modulation wave M. ssr_a .

[0163] The subsynchronous resonant current can be suppressed by suppressing the modulation wave as described above, and the subsynchronous energy will also be suppressed. However, due to the use of a virtual resistor, the resistive component U in the subsynchronous resonant voltage is reduced. sr The interaction between the subsynchronous resonant current and the subsynchronous resonant power is generated. Since the subsynchronous voltage and current are in phase, each DSC module will absorb the subsynchronous resonant power and energy. The absorbed energy will charge the capacitor of the DSC module, which will cause the DC voltage on the capacitor of the DSC module to rise continuously. Eventually, the DSC module will bypass and stop operating due to the excessive DC voltage, thus suppressing the failure of subsynchronous resonance.

[0164] Therefore, in S3 above, the present invention generates a control modulation wave to increase the capacitor voltage generated by the subsynchronous energy, and then discharges it using the fundamental frequency voltage, so that the subsynchronous energy is converted into fundamental wave energy and consumed, thereby stabilizing and controlling the DC voltage of the DSC module capacitor at the target value, and ensuring the suppression effect of subsynchronous resonance.

[0165] In this embodiment, S3 includes:

[0166] S301. Based on the grid connection point current, the fundamental current is obtained through phase angle extraction and coordinate transformation;

[0167] S302. Based on the fundamental current, generate a control modulation wave to control the capacitor voltage deviation of the dynamic series compensator.

[0168] Specifically, S3 extracts the fundamental current signal from the mixed signal of fundamental and subsynchronous current to control the DC voltage of the DSC module capacitor. The process of extracting the fundamental current in S301 is as follows:

[0169] (1) As Figure 7 As shown, the line current is acquired and controlled in phases, with the current of each phase of the line acquired and processed by a delay function e. -sT A three-phase fully symmetrical current is generated, wherein the current in phase A of the line, I... aGenerate a three-phase fully symmetrical current I for phase A as a reference. a I a_b I a_c With the B-phase current I of the line b Generate a three-phase fully symmetrical current I for phase B as a reference. b I b_b I b_c With the C-phase current I of the line c Generate a three-phase fully symmetrical current I for phase C as a reference. c I c_b I c_c ;

[0170] (2) The three-phase fully symmetrical current generated above is passed through a phase-locked loop (PLL) to extract the phase angle as the synchronization angle, which is used for the control of the corresponding phases of the line. A line has three phases A, B, and C, and the three synchronization angles I of phases A, B, and C are obtained respectively. a_Ang I b_Ang I c_Ang ;

[0171] (3) Figure 8 As shown, using three synchronization angles, the coordinate transformation of the three-phase fully symmetrical current generated in each phase of the line is performed, transforming it from a three-phase stationary coordinate system to a two-phase rotating coordinate system (3To2 Transform). Then, it is converted into a d / q-axis DC signal in the two-phase rotating coordinate system through a low-pass filter, yielding the A-phase d / q-axis DC signal I. a_d I a_q B-phase d / q-axis DC signal I b_d I b_q C-phase d / q-axis DC signal I c_d I c_q ;

[0172] (4) Then, through the transformation from a two-phase rotating coordinate system to a three-phase stationary coordinate system (2To3 Transform), the obtained d / q axis DC signal is transformed into an AC quantity. Each line has a total of 3 pairs of d / q axis components. After the transformation, only phase A is retained. The other two phases are processed in the same way to obtain I. ja I jb I jc Three fundamental currents;

[0173] In this embodiment, S302 includes:

[0174] Based on the measured capacitor voltage value of the dynamic series compensator, the difference between the measured capacitor voltage value and the set capacitor voltage value is calculated to obtain the capacitor voltage deviation;

[0175] The fundamental voltage is obtained by performing proportional-integral control on the capacitor voltage deviation;

[0176] Based on the fundamental current, the product of the fundamental current and the fundamental voltage is calculated to obtain the fundamental voltage command, and the fundamental voltage command is subjected to amplitude limiting conversion to obtain the control modulation wave.

[0177] Specifically, such as Figure 9 As shown, the DC voltage of each DSC module capacitor is controlled, and the measured capacitor voltage value V is... dc With capacitor voltage setting value V dc_obj The capacitor voltage deviation is obtained by subtracting the N / D converter, and then sent to the proportional-integral controller to output the fundamental voltage. Figure 9 In the middle, K p T is the proportional gain of the proportional-integral controller. i Let S be the integration time constant and S be the Laplace variable.

[0178] Subsequently, the fundamental current (such as I) ja The fundamental voltage command is introduced and then passed through a limiting circuit to confine it within the safe operating range of the DSC. The limited fundamental voltage command is then multiplied by a proportional coefficient (usually related to the fundamental voltage or modulation coefficient) to ultimately generate the modulation wave used to control the DC voltage of the control module, i.e., the control modulation wave M. a_jb .

[0179] When the suppressed modulation wave M is obtained ssr_a and control modulation wave M a_jb Then, in S4 above, as Figure 10 As shown, M ssr_a The DC voltage-controlled modulation wave M consumes subsynchronous energy a_jb After addition, the values ​​are compared with the triangular phase-shifted carrier to obtain each DSC (DSC1, DSC2...DSC) of phase A. n The PWM on / off signals S of the unit a_DSC1 S a_DSC2 ...S a_DSCn ,correspond Figure 11 The central control system sends corresponding signals PWM1, PWM2...PWM to each DSC module. n The treatment methods for phases B and C are the same as those for phase A.

[0180] Furthermore, this method can also be used to address supersynchronous resonance (50Hz-100Hz) caused by grid connection of wind farms and new energy sources. The implementation principle is similar to that for suppressing subsynchronous resonance; both methods use a DSC to generate a voltage corresponding to the virtual impedance at a specific frequency (50Hz-100Hz) to suppress supersynchronous resonance.

[0181] Example 2:

[0182] Based on the same inventive concept, the application also provides a subsynchronous resonance energy suppression and consumption system based on a dynamic series compensator, as shown in Figure 11 and Figure 12 , comprising:

[0183] a series compensation device in series with a power transmission line between a new energy and a power grid system, and a subsynchronous suppression control module electrically connected with the series compensation device; the series compensation device is a dynamic series compensator or a hybrid series compensator based on a dynamic series compensator and a fixed series compensator;

[0184] The subsynchronous suppression control module comprises a filtering and screening unit, a suppression modulation wave determination unit, a control modulation wave determination unit, and a modulation wave superposition control unit.

[0185] The filtering and screening unit is configured to obtain a subsynchronous current in a grid-connected point current at a subsynchronous resonance frequency through filtering and screening based on the grid-connected point current on the power transmission line.

[0186] The suppression modulation wave determination unit is configured to calculate a subsynchronous resonance suppression voltage and a suppression modulation wave corresponding to the subsynchronous resonance suppression voltage based on the subsynchronous current and a virtual impedance at the subsynchronous resonance frequency obtained in advance.

[0187] The control modulation wave determination unit is configured to generate a control modulation wave for controlling a capacitance voltage deviation of the dynamic series compensator based on a fundamental wave current extracted from the grid-connected point current.

[0188] The modulation wave superposition control unit is configured to add the suppression modulation wave and the control modulation wave, compare the result with a triangular phase-shifted carrier wave of the dynamic series compensator, obtain a control signal of the dynamic series compensator, and suppress and consume subsynchronous resonance energy at the subsynchronous resonance frequency based on the control signal.

[0189] As shown in Figure 11 , taking a dynamic series compensator alone as an example, a plurality of DSC modules (DSC1, DSC2, …, DSC n ) are connected in series on the power transmission line, each DSC module is connected with its own arrester MOV, module bypass switch K, and bypass thyristor valve TBS, and DSC1, DSC2, …, DSC n After the opening-closing signal is triggered by the carrier phase-shift modulation technology, the same modulation wave is used to modulate and integrally combine to form a subsynchronous suppression voltage. PWM1, PWM2, …, PWM nThe corresponding signals of the DSC modules are sent to the control system; the grid-connected point current in the filter selection unit is obtained through a current sampling circuit and a current energy extraction circuit connected to the power transmission line z .

[0190] In this embodiment, the suppression modulation wave determination unit comprises:

[0191] An equivalent impedance determination subunit is configured to determine, based on the series compensation device, a system equivalent impedance observed from the new energy to the power grid system at the subsynchronous resonance frequency;

[0192] A virtual impedance solving subunit is configured to, based on the system equivalent impedance, solve a virtual impedance at the subsynchronous resonance frequency, so that the system equivalent impedance and the virtual impedance satisfy a set condition after being superimposed.

[0193] A first modulation wave determination subunit is configured to, based on the subsynchronous current and the virtual impedance, calculate a subsynchronous resonance suppression voltage and a suppression modulation wave corresponding to the subsynchronous resonance suppression voltage.

[0194] In this embodiment, the virtual impedance solving subunit is specifically configured to:

[0195] based on the system equivalent impedance and the new energy impedance at the subsynchronous resonance frequency;

[0196] The superposition of the system equivalent impedance and the virtual impedance is taken as a composite impedance, and the parallel equivalent value of the composite impedance and the new energy impedance is taken as a target, which is less than a set multiple of the system equivalent impedance. Through an iterative algorithm, a loop calculation is performed within a preset virtual impedance parameter range to output a virtual impedance satisfying the target as the virtual impedance at the subsynchronous resonance frequency.

[0197] In this embodiment, the first modulation wave determination subunit is specifically configured to:

[0198] Based on the subsynchronous current and the virtual impedance, the subsynchronous current is subjected to coordinate transformation and filtering to obtain a subsynchronous current polar coordinate amplitude;

[0199] The virtual resistance in the virtual impedance is multiplied by the subsynchronous current polar coordinate amplitude to obtain a resistive suppression voltage;

[0200] The virtual reactance in the virtual impedance is multiplied by the subsynchronous current polar coordinate amplitude, and at the same time, the polar coordinate angle is rotated to obtain an inductive suppression voltage;

[0201] The resistive suppression voltage and the inductive suppression voltage are subjected to coordinate transformation and synthesis to obtain a subsynchronous resonance suppression voltage;

[0202] The ratio of the subsynchronous resonance suppression voltage and the capacitance DC voltage of the dynamic series compensator is calculated to obtain a suppression modulation wave.

[0203] In this embodiment, the equivalent impedance determination subunit is specifically used for:

[0204] When the series compensation device is the dynamic series compensator, the grid system impedance at the subsynchronous resonance frequency is taken as the system equivalent impedance at the subsynchronous resonance frequency.

[0205] When the series compensation device is the hybrid series compensator, the grid system impedance at the subsynchronous resonance frequency is superimposed with the capacitive reactance of the fixed series compensator to obtain the system equivalent impedance at the subsynchronous resonance frequency.

[0206] In this embodiment, the control modulation wave determination unit includes:

[0207] The fundamental current extraction subunit is configured to obtain a fundamental current by phase angle extraction and coordinate transformation based on the grid-connected point current.

[0208] The second modulation wave determination subunit is configured to generate a control modulation wave for controlling the capacitance voltage deviation of the dynamic series compensator based on the fundamental current.

[0209] In this embodiment, the second modulation wave determination subunit is specifically used for:

[0210] The capacitance voltage deviation is obtained by calculating the difference between the capacitance voltage measurement value and the capacitance voltage set value based on the capacitance voltage measurement value of the dynamic series compensator.

[0211] The fundamental voltage is obtained by performing proportional integral control on the capacitance voltage deviation.

[0212] The product of the fundamental current and the fundamental voltage is calculated based on the fundamental current to obtain a fundamental voltage instruction, and the fundamental voltage instruction is subjected to amplitude limiting conversion to obtain a control modulation wave.

[0213] In this embodiment, the filter screening unit is specifically used for:

[0214] The current components at different subsynchronous resonance frequencies are extracted by a multi-channel band-pass filter based on the grid-connected point current on the new energy transmission line.

[0215] Each current component is compared with a preset current threshold, and the current component greater than the current threshold is taken as a subsynchronous current.

[0216] Embodiment 3

[0217] As Figure 13As shown, the present application also provides an electronic device, which can be a computer device, a single-chip microcomputer device, a smart mobile device, etc. The electronic device in the embodiment can include a processor, a memory, a transceiver component, etc. The memory, the processor and the transceiver component are connected through a bus; the memory can be used to store an execution program, and the exemplary execution program can include instructions; the processor is used to execute the instructions stored in the memory. The memory can also be used to store data, which can be called and / or modified when the instructions are executed.

[0218] The processor can be a central processing unit (CPU), and can also be 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., which are the computing core and control core of the terminal, and are suitable for implementing one or more instructions, and are specifically suitable for loading and executing one or more instructions in the storage medium to implement a corresponding method flow or a corresponding function, so as to implement the steps of the sub-synchronous resonance energy suppression and consumption method based on the dynamic series compensator in the above embodiment.

[0219] Embodiment 4

[0220] Based on the same inventive concept, the present application also provides a readable storage medium, specifically an electronic device readable storage medium (Memory), which is a memory device in the electronic device and is used to store programs and data. It can be understood that the storage medium here can include the built-in storage medium in the electronic device, and of course can also include the expansion storage medium supported by the electronic device. The storage medium provides a storage space, and the storage space stores the operating system of the terminal. Moreover, 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 execution programs (including program codes). It should be noted that the storage medium here can be a high-speed RAM memory, or a non-volatile memory, such as at least one disk memory. The processor loads and executes one or more instructions stored in the storage medium, which can implement the steps of the sub-synchronous resonance energy suppression and consumption method based on the dynamic series compensator in the above embodiment.

[0221] Those skilled in the art will appreciate that embodiments of the application can be devised for a method, a system, or a computer program product. Accordingly, the present application can be embodied in the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code.

[0222] The present application is described in reference to the flowchart and / or block diagrams of the method, apparatus (system) and computer program product according to embodiments of the application. It will be understood that each block of the flowchart and / or block diagrams, and combinations of blocks in the flowchart and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processing system or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 means for carrying out each of the one or more functions specified in the flowchart and / or block diagram block or blocks.

[0223] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 means for carrying out each of the one or more functions specified in the flowchart and / or block diagram block or blocks.

[0224] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 means for carrying out each of the one or more functions specified in the flowchart and / or block diagram block or blocks.

[0225] Finally, it should be noted that the above-mentioned embodiments are merely used to illustrate the technical solutions of the present application, but not to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can make various changes and modifications to the specific embodiments, or equivalent replacements, but these changes, modifications, or equivalent replacements should be within the scope of protection of the present application.

Claims

1. A method for suppressing and consuming subsynchronous resonance energy based on a dynamic series compensator, characterized in that, include: Based on the grid connection point current on the new energy transmission line, the subsynchronous current in the grid connection point current at the subsynchronous resonant frequency is obtained by filtering and screening; the transmission line is equipped with a series compensation device, which is a dynamic series compensator or a hybrid series compensator based on a dynamic series compensator and a fixed series compensator. Based on the subsynchronous current and the virtual impedance at the pre-acquired subsynchronous resonant frequency, the subsynchronous resonant suppression voltage and the suppressed modulation wave corresponding to the subsynchronous resonant suppression voltage are calculated. Based on the fundamental current extracted from the grid connection point current, a control modulation wave is generated to control the capacitor voltage deviation of the dynamic series compensator. After adding the suppressed modulation wave and the control modulation wave, the signal is compared with the triangular phase-shifted carrier of the dynamic series compensator to obtain the control signal of the dynamic series compensator. Based on the control signal, the subsynchronous resonance energy at the subsynchronous resonance frequency is suppressed and consumed.

2. The method as described in claim 1, characterized in that, The calculation of the subsynchronous resonance suppression voltage and the corresponding suppressed modulation wave based on the subsynchronous current and the pre-acquired virtual impedance at the subsynchronous resonant frequency includes: Based on the series compensation device, the system equivalent impedance observed from the new energy source to the power grid system at the subsynchronous resonant frequency is determined; Based on the system's equivalent impedance, and with the goal of satisfying a set condition after the system's equivalent impedance and virtual impedance are superimposed, the virtual impedance at the subsynchronous resonant frequency is obtained by solving. Based on the subsynchronous current and the virtual impedance, the subsynchronous resonance suppression voltage and the corresponding suppressed modulation wave are calculated.

3. The method as described in claim 2, characterized in that, The process of obtaining the virtual impedance at the subsynchronous resonant frequency based on the system's equivalent impedance, with the goal of satisfying a set condition after the system's equivalent impedance and virtual impedance are superimposed, includes: Based on the system equivalent impedance and new energy impedance at the subsynchronous resonant frequency; The sum of the system's equivalent impedance and virtual impedance is taken as the composite impedance. With the goal that the parallel equivalent value of the composite impedance and the new energy impedance is less than a set multiple of the system's equivalent impedance, an iterative algorithm is used to perform iterative calculations within a preset range of virtual impedance parameters, and the output virtual impedance that satisfies the goal is used as the virtual impedance at the subsynchronous resonant frequency.

4. The method as described in claim 2 or 3, characterized in that, The calculation of the subsynchronous resonance suppression voltage and the corresponding suppressed modulation wave based on the subsynchronous current and the virtual impedance includes: Based on the subsynchronous current and the virtual impedance, the subsynchronous current is subjected to coordinate transformation and filtering to obtain the polar coordinate amplitude of the subsynchronous current; Multiplying the virtual resistance in the virtual impedance by the polar coordinate amplitude of the subsynchronous current yields the resistive suppression voltage; Multiply the virtual reactance in the virtual impedance by the polar coordinate amplitude of the subsynchronous current, and simultaneously rotate the polar coordinate angle to obtain the inductive suppression voltage. The resistive suppression voltage and the inductive suppression voltage are transformed and synthesized to obtain the subsynchronous resonance suppression voltage; The ratio of the subsynchronous resonance suppression voltage to the DC voltage of the capacitor of the dynamic series compensator is calculated to obtain the suppressed modulation wave.

5. The method as described in claim 2 or 3, characterized in that, The determination of the system equivalent impedance observed from the new energy source to the power grid system at the subsynchronous resonant frequency based on the series compensation device includes: When the series compensation device is the dynamic series compensator, the power grid system impedance at the subsynchronous resonant frequency is taken as the system equivalent impedance at the subsynchronous resonant frequency. When the series compensation device is the hybrid series compensator, the power grid system impedance at the subsynchronous resonant frequency is superimposed with the capacitive reactance of the fixed series compensator to obtain the system equivalent impedance at the subsynchronous resonant frequency.

6. The method according to any one of claims 1-3, characterized in that, The step of generating a control modulation wave to control the capacitor voltage deviation of the dynamic series compensator based on the fundamental current extracted from the grid connection point current includes: Based on the grid connection point current, the fundamental current is obtained through phase angle extraction and coordinate transformation; Based on the fundamental current, a control modulation wave is generated to control the capacitor voltage deviation of the dynamic series compensator.

7. The method as described in claim 6, characterized in that, The step of generating a control modulation wave based on the fundamental current to control the capacitor voltage deviation of the dynamic series compensator includes: Based on the measured capacitor voltage value of the dynamic series compensator, the difference between the measured capacitor voltage value and the set capacitor voltage value is calculated to obtain the capacitor voltage deviation; The fundamental voltage is obtained by performing proportional-integral control on the capacitor voltage deviation; Based on the fundamental current, the product of the fundamental current and the fundamental voltage is calculated to obtain the fundamental voltage command, and the fundamental voltage command is subjected to amplitude limiting conversion to obtain the control modulation wave.

8. The method according to any one of claims 1-3, characterized in that, The grid connection point current based on the new energy transmission line is filtered to obtain the subsynchronous current in the grid connection point current at the subsynchronous resonant frequency, including: Based on the grid connection point current on new energy transmission lines, current components at different subsynchronous resonant frequencies are extracted using a multi-channel bandpass filter. Each current component is compared with a preset current threshold, and the current component that is greater than the current threshold is taken as the secondary synchronization current.

9. A subsynchronous resonant energy suppression and consumption system, characterized in that, include: A series compensation device connected in series on the transmission line between the new energy source and the power grid system, and a subsynchronous suppression control module electrically connected to the series compensation device; the series compensation device is a dynamic series compensator or a hybrid series compensator based on a dynamic series compensator and a fixed series compensator. The subsynchronous suppression control module includes a filtering and screening unit, a suppression modulation wave determination unit, a control modulation wave determination unit, and a modulation wave superposition control unit; The filtering and screening unit is used to obtain the subsynchronous current in the grid connection point current at the subsynchronous resonant frequency by filtering and screening based on the grid connection point current on the transmission line. The suppression modulation wave determination unit is used to calculate the subsynchronous resonance suppression voltage and the suppression modulation wave corresponding to the subsynchronous resonance suppression voltage based on the subsynchronous current and the virtual impedance obtained in advance at the subsynchronous resonance frequency. The control modulation wave determination unit is used to generate a control modulation wave for controlling the capacitor voltage deviation of the dynamic series compensator based on the fundamental current extracted from the grid connection point current. The modulation wave superposition control unit is used to add the suppressed modulation wave and the control modulation wave, compare them with the triangular phase-shifted carrier of the dynamic series compensator, obtain the control signal of the dynamic series compensator, and suppress and consume the subsynchronous resonance energy at the subsynchronous resonance frequency based on the control signal.

10. The system as described in claim 9, characterized in that, The suppressed modulation wave determination unit includes: An equivalent impedance determination subunit is used to determine the system equivalent impedance observed from the new energy source to the power grid system at the subsynchronous resonant frequency based on the series compensation device. The virtual impedance solving subunit is used to solve for the virtual impedance at the subsynchronous resonant frequency based on the equivalent impedance of the system and with the goal of satisfying a set condition after the superposition of the equivalent impedance and the virtual impedance. The first modulation wave determination subunit is used to calculate the subsynchronous resonance suppression voltage and the suppression modulation wave corresponding to the subsynchronous resonance suppression voltage based on the subsynchronous current and the virtual impedance.

11. The system as claimed in claim 10, characterized in that, The virtual impedance solving subunit is specifically used for: Based on the system equivalent impedance and new energy impedance at the subsynchronous resonant frequency; The sum of the system's equivalent impedance and virtual impedance is taken as the composite impedance. With the goal that the parallel equivalent value of the composite impedance and the new energy impedance is less than a set multiple of the system's equivalent impedance, an iterative algorithm is used to perform iterative calculations within a preset range of virtual impedance parameters, and the output virtual impedance that satisfies the goal is used as the virtual impedance at the subsynchronous resonant frequency.

12. The system as described in claim 10 or 11, characterized in that, The first modulation wave determination subunit is specifically used for: Based on the subsynchronous current and the virtual impedance, the subsynchronous current is subjected to coordinate transformation and filtering to obtain the polar coordinate amplitude of the subsynchronous current; Multiplying the virtual resistance in the virtual impedance by the polar coordinate amplitude of the subsynchronous current yields the resistive suppression voltage; Multiply the virtual reactance in the virtual impedance by the polar coordinate amplitude of the subsynchronous current, and simultaneously rotate the polar coordinate angle to obtain the inductive suppression voltage. The resistive suppression voltage and the inductive suppression voltage are transformed and synthesized to obtain the subsynchronous resonance suppression voltage; The ratio of the subsynchronous resonance suppression voltage to the DC voltage of the capacitor of the dynamic series compensator is calculated to obtain the suppressed modulation wave.

13. The system as described in claim 10 or 11, characterized in that, The equivalent impedance determination subunit is specifically used for: When the series compensation device is the dynamic series compensator, the power grid system impedance at the subsynchronous resonant frequency is taken as the system equivalent impedance at the subsynchronous resonant frequency. When the series compensation device is the hybrid series compensator, the power grid system impedance at the subsynchronous resonant frequency is superimposed with the capacitive reactance of the fixed series compensator to obtain the system equivalent impedance at the subsynchronous resonant frequency.

14. The system according to any one of claims 9-11, characterized in that, The control modulation wave determination unit includes: The fundamental current extraction subunit is used to obtain the fundamental current based on the grid connection point current through phase angle extraction and coordinate transformation; The second modulation wave determination subunit is used to generate a control modulation wave based on the fundamental current to control the capacitor voltage deviation of the dynamic series compensator.

15. The system as described in claim 14, characterized in that, The second modulation wave determination subunit is specifically used for: Based on the measured capacitor voltage value of the dynamic series compensator, the difference between the measured capacitor voltage value and the set capacitor voltage value is calculated to obtain the capacitor voltage deviation; The fundamental voltage is obtained by performing proportional-integral control on the capacitor voltage deviation; Based on the fundamental current, the product of the fundamental current and the fundamental voltage is calculated to obtain the fundamental voltage command, and the fundamental voltage command is subjected to amplitude limiting conversion to obtain the control modulation wave.

16. The method according to any one of claims 9-11, characterized in that, The filtering unit is specifically used for: Based on the grid connection point current on new energy transmission lines, current components at different subsynchronous resonant frequencies are extracted using a multi-channel bandpass filter. Each current component is compared with a preset current threshold, and the current component that is greater than the current threshold is taken as the secondary synchronization current.

17. An electronic device, characterized in that, include: At least one processor and memory; The memory and processor are connected via a bus; The memory is used to store one or more programs; When the one or more programs are executed by the at least one processor, the method for suppressing energy consumption of subsynchronous resonance as described in any one of claims 1 to 8 is implemented.

18. A readable storage medium, characterized in that, It contains an execution program, which, when executed, implements the subsynchronous resonance energy suppression and consumption method as described in any one of claims 1 to 8.

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