Series wave trapper-based power grid system and resonance suppression method thereof

Abstract

The invention discloses a series wave trapper-based power grid system and a resonance suppression method thereof, the system comprises a parallel energy storage module, an AC bus, a load module and a series wave trapper module, and the parallel energy storage module is composed of a plurality of energy storage converter units which are connected in parallel in a multi-stage manner; the series wave trapper module comprises a harmonic suppression circuit and a bypass switch which are connected in parallel, one end of the bypass switch is connected with an alternating current bus, the harmonic suppression circuit comprises a plurality of wave trapper branches which are connected in series, and the resonant frequency of each wave trapper branch is matched with the to-be-suppressed harmonic frequency generated by the parallel energy storage module; the load module comprises a power grid, a third-party load and a grid-connected switch, one end of the grid-connected switch is connected with the power grid and the third-party load, and the other end of the grid-connected switch is connected with the other end of the bypass switch. According to the method, the resonance phenomenon generated under the standby working condition of the parallel energy storage system can be effectively suppressed.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to a power grid system based on a series wave snubber and a resonance suppression method thereof. Background Art

[0002] As an important component of modern power systems, energy storage power stations play an irreplaceable role in improving grid reliability, achieving peak-valley arbitrage, and promoting the consumption of renewable energy. As the core equipment of energy storage power stations, the performance of the power storage converter (PCS) directly affects the efficiency and stability of the entire system. In recent years, the architecture of PCS has gradually evolved from the traditional centralized type to the string type. The string type PCS can effectively improve the capacity and reliability of the system by connecting multiple groups in series and in parallel, while reducing the impact of single-point failures on the overall system.

[0003] However, multiple machines in parallel are prone to resonance problems. In standby mode, the energy storage system is in a non-charging and discharging state, but is still connected to the grid or load. The electrical coupling between the energy storage units and the complexity of the internal impedance characteristics of the system can easily excite resonance at a specific frequency. This resonance can cause abnormal fluctuations in system voltage and current, which not only affects the quality of power, but may also cause serious consequences such as equipment overload and malfunction of protection devices, thereby threatening the stable operation of the system.

[0004] The existing power grid system can only suppress harmonics of specific frequencies. Harmonics that are not effectively filtered out in the system will cause distortion of the voltage and current waveforms, directly affecting the normal operation of various electrical equipment.

[0005] It can be seen that how to design a power grid system based on a series surge arrester to improve the harmonic suppression effect has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0006] The present application provides a resonance suppression method for a power grid system based on a series wave arrester, so as to effectively suppress the resonance phenomenon generated by a parallel energy storage system in a standby condition.

[0007] In order to solve the above technical problems, the embodiment of the present application provides a power grid system based on a series surge arrester, including a parallel energy storage module, an AC bus, a load module and a series surge arrester module, wherein: The parallel energy storage module is composed of a plurality of energy storage converter units connected in parallel at multiple stages, each of which includes a battery pack, a controlled voltage source and a filter branch. The battery pack is connected in parallel with the controlled voltage source, the output end of the controlled voltage source is connected in series with one end of the filter branch, and the other end of the filter branch is connected to the AC bus. The series wave trap module includes a harmonic suppression circuit and a bypass switch connected in parallel, one end of the bypass switch is connected to the AC bus, and the harmonic suppression circuit includes a plurality of wave trap branches connected in series, and the resonant frequency of each wave trap branch is adapted to the harmonic frequency to be suppressed generated by the parallel energy storage module; The load module includes a power grid, a third-party load and a grid-connected switch, one end of the grid-connected switch is connected to the power grid and the third-party load respectively, and the other end of the grid-connected switch is connected to the other end of the bypass switch.

[0008] As one preferred solution, the wave trap branch includes a first resistor, a second resistor, a third resistor, an inductor and a capacitor, wherein: The inductor, the capacitor and the second resistor are connected in series; the first end of the first resistor is connected in series with other wave trap branches, one path of the second end of the first resistor is connected to the series branch of the inductor, the capacitor and the second resistor, and the other path of the second end of the first resistor is connected to the third resistor branch, wherein the series branch of the inductor, the capacitor and the second resistor is connected in parallel with the third resistor branch.

[0009] Another embodiment of the present application provides a resonance suppression method, which is applied to the above-mentioned power grid system based on the series wave trap, and is characterized by comprising: Performing spectrum analysis on the acquired historical voltage harmonic components of each of the energy storage converter units to obtain the frequency and amplitude of each of the historical voltage harmonic components, and determining the harmonic whose amplitude exceeds a preset amplitude threshold as the harmonic frequency to be suppressed; Setting the component parameters of the series wave trap according to the harmonic frequency to be suppressed so that the resonant frequency of the series wave trap corresponds to the harmonic frequency to be suppressed; Acquire real-time operation data of the power grid system, generate a corresponding control signal according to the real-time operation data, send the control signal to the bypass switch, and control the series wave arrester module by turning the bypass switch on and off to achieve harmonic suppression of the power grid system.

[0010] As one preferred solution, before performing spectrum analysis on the acquired historical voltage harmonic components of each of the energy storage converter units, the method further includes: Continuously sampling the output terminal voltage of each energy storage converter unit based on a preset sampling frequency to obtain initial historical voltage harmonic component data of the energy storage converter unit; An outlier removal process is performed on the initial historical voltage harmonic component, and a missing value interpolation process is performed on the historical voltage harmonic component after the outlier removal process to obtain the historical voltage harmonic component.

[0011] As one of the preferred solutions, the spectrum analysis of the acquired historical voltage harmonic components of each of the energy storage converter units includes: Preprocessing the historical voltage harmonic components; Calculating the preprocessed historical voltage harmonic components based on a fast Fourier transform algorithm, and generating a spectrum diagram according to the calculation results; The frequency and amplitude of each of the historical voltage harmonic components are acquired according to the frequency spectrum.

[0012] As one of the preferred solutions, the preprocessing of the historical voltage harmonic components includes: Performing wavelet transform on the historical voltage harmonic components to generate sub-band signals of different frequencies, performing denoising on the sub-band signals by a threshold calculation method, and performing inverse wavelet transform on the denoised sub-band signals to obtain the historical voltage harmonic components after preliminary denoising; Normalizing the historical voltage harmonic component data after preliminary denoising by using a maximum and minimum value method; The data length of the normalized historical voltage harmonic component is compared with the FFT calculation length, and data truncation and zero padding are performed on the normalized historical voltage harmonic component according to the comparison result.

[0013] As one preferred solution, determining the harmonic whose amplitude exceeds a preset amplitude threshold as the harmonic frequency to be suppressed includes: Determining a magnitude threshold value according to power industry standards and characteristics of the power grid system; Comparing the amplitude of each of the historical voltage harmonic components with the amplitude threshold one by one, and screening the harmonics whose amplitude is greater than the amplitude threshold according to the comparison result; The frequency corresponding to the harmonic is determined as the harmonic frequency to be suppressed.

[0014] As one preferred solution, the component parameters include capacitance, resistance and inductance; The step of setting the component parameters of the series wave trap according to the harmonic frequency to be suppressed comprises: Set the initial capacitance value based on historical experience; The initial capacitance value and the harmonic frequency to be suppressed are input into the resonance formula for calculation to obtain the initial inductance value; the resonance formula is expressed as: in, Indicates frequency, represents inductance, Represents capacitance; Inputting the initial capacitance value and the initial inductance value into a quality factor formula for calculation to obtain an initial resistance value; The initial resistance value, the initial capacitance value and the initial inductance value are fine-tuned to match the impedances between the various wave trap branches, thereby obtaining the capacitance value, resistance value and inductance value to be set for the series wave trap.

[0015] As one preferred solution, the acquiring of real-time operation data of the power grid system and generating a corresponding control signal according to the real-time operation data includes: Performing feature extraction on the preprocessed real-time operation data to obtain feature parameters related to the working condition judgment of the power grid system; Matching the characteristic parameters with preset working condition judgment rules, and obtaining the real-time working condition of the power grid system according to the matching results; A control signal corresponding to the real-time operating condition is generated.

[0016] As one preferred solution, the generating of the control signal corresponding to the real-time working condition includes: If the power grid system is in a normal operating condition, generating a control signal to close the bypass switch; If the power grid system is in a standby state, a control signal is generated to control the bypass switch to be disconnected, so as to put the series wave arrester module into operation to achieve harmonic suppression of the power grid system; If the power grid system is in an overvoltage / overcurrent condition, a control signal is generated to control the bypass switch to be disconnected, so as to activate the series surge arrester module to increase the impedance of the power grid.

[0017] Compared with the prior art, the beneficial effects of the embodiments of the present application are: By adding a series surge arrester module to the electric load module, the resonance phenomenon generated under standby conditions can be effectively suppressed, significantly reducing voltage and current fluctuations, and improving system stability and power quality. Multiple series surge arrester branches can also be designed for different resonant frequencies to effectively suppress resonance at specific frequencies. At the same time, the design of the bypass switch allows the system to bypass the surge arrester when filtering operation is not required, thereby improving operating efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of a power grid system based on a series wave trap in one embodiment of the present application; Figure 2 It is a flow chart of a resonance suppression method in one embodiment of the present application. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. The purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] In the description of this application, the terms "first", "second", "third", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of the feature. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0021] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be a connection between the two elements. The terms "vertical", "horizontal", "left", "right", "upper", "lower" and similar expressions used in this article are only for illustrative purposes, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. The term "and / or" used in this article includes any and all combinations of one or more related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0022] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by those skilled in the art. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0023] An embodiment of the present application provides a power grid system based on a series wave trap. For details, see Figure 1 , Figure 1 The structure diagram of the power grid system based on the series surge arrester in one embodiment of the present application is shown, including a parallel energy storage module 11, an AC bus 12, a load module 13 and a series surge arrester module 14, wherein: The parallel energy storage module is composed of a plurality of energy storage converter units connected in parallel at multiple stages, each of which includes a battery pack, a controlled voltage source and a filter branch. The battery pack is connected in parallel with the controlled voltage source, the output end of the controlled voltage source is connected in series with one end of the filter branch, and the other end of the filter branch is connected to the AC bus. The series wave trap module includes a harmonic suppression circuit and a bypass switch connected in parallel, one end of the bypass switch is connected to the AC bus, and the harmonic suppression circuit includes a plurality of wave trap branches connected in series, and the resonant frequency of each wave trap branch is adapted to the harmonic frequency to be suppressed generated by the parallel energy storage module; The load module includes a power grid, a third-party load and a grid-connected switch, one end of the grid-connected switch is connected to the power grid and the third-party load respectively, and the other end of the grid-connected switch is connected to the other end of the bypass switch.

[0024] Specifically, the parallel energy storage module is composed of multiple PCS units. The structure and function of each PCS unit are as follows: First, each PCS unit can be regarded as a system consisting of three parts: a battery pack, a controlled voltage source, and a filter branch. These parts work together to complete the conversion and control of electrical energy. Specifically, Figure 1 As shown in the PCS unit 1, the battery pack B1 is connected in parallel with the controlled voltage source 1, which converts the DC power provided by the battery pack into AC power to meet the needs of the power grid or load; and then connected in series with the filter branch 1. The filter branch effectively filters out the high-frequency harmonics generated during the power conversion process through the designed passive components such as capacitors and inductors to ensure that the output power quality meets the standard requirements. In a multi-unit system, the AC sides of n PCS units are connected in parallel to an AC bus. This parallel configuration not only improves the total power output and redundancy of the system, but also enhances the operational flexibility and reliability of the system.

[0025] The series wave trap module is the key part of the system, which is composed of m wave trap branches connected in series and a bypass branch connected in parallel with all the wave trap branches.

[0026] Preferably, in one embodiment of the present application, the wave trap branch includes a first resistor, a second resistor, a third resistor, an inductor and a capacitor, wherein: The inductor, the capacitor and the second resistor are connected in series; the first end of the first resistor is connected in series with other wave trap branches, one path of the second end of the first resistor is connected to the series branch of the inductor, the capacitor and the second resistor, and the other path of the second end of the first resistor is connected to the third resistor branch, wherein the series branch of the inductor, the capacitor and the second resistor is connected in parallel with the third resistor branch.

[0027] The topology of each wave trap branch is as follows Figure 1 As shown in , the first end of R1 is connected in series with other wave arresters, and the second end is connected to the series branch of L, C, and R2 in one way, and the other way is connected to the R3 branch; wherein, the L, C, and R2 series branch is connected in parallel with the R3 branch. By accurately designing the parameter values ​​of R, L, and C in the branch, the resonant frequency of each branch can correspond to the target suppressed harmonic frequency one by one, so that each branch presents a high impedance characteristic at the target frequency, thereby effectively absorbing the voltage harmonic component of the corresponding frequency, disconnecting the path of the parallel energy storage module and the harmonic voltage in the power grid, and suppressing the occurrence of resonance. At the same time, impedance matching design is used between each branch to avoid the generation of new resonance points and ensure the stable operation of the system. The wave arrester unit is also equipped with a bypass switch. When operating normally, virtual impedance adjustment can be achieved through software control to dynamically suppress the occurrence of resonance. At this time, the bypass switch can be closed to short-circuit the wave arrester branch, thereby improving the operating efficiency of the system.

[0028] The AC bus is the common connection point of n parallel PCS units, which is used for the distribution and transmission of electric energy. The AC power output by the parallel PCS units is collected on the AC bus, connected to the series surge arrester via the AC bus, and then connected to the grid and third-party loads through the grid-connected switch.

[0029] The load module includes the power grid, third-party loads and grid-connected switches. The power grid is an external power supply network, which is equivalent to a series structure of an AC voltage source Ug and an impedance Zg. The output of the power grid is connected to the series wave arrester through the grid-connected switch, and performs bidirectional energy exchange with the energy storage unit through the filter circuit and PCS; the other side is connected to the third-party load, which can be used as one of the energy sources for the third-party load.

[0030] Another embodiment of the present application provides a resonance suppression method for the power grid system based on the series wave trap, for details, see Figure 2 , Figure 2 The figure shows a flow chart of a resonance suppression method in one embodiment of the present application, which includes steps S1-S3: S1: performing spectrum analysis on the acquired historical voltage harmonic components of each of the energy storage converter units to obtain the frequency and amplitude of each historical voltage harmonic component, and determining the harmonic whose amplitude exceeds a preset amplitude threshold as the harmonic frequency to be suppressed; Preferably, in one embodiment of the present application, before performing spectrum analysis on the acquired historical voltage harmonic components of each energy storage converter unit, the method further includes: Continuously sampling the output terminal voltage of each energy storage converter unit based on a preset sampling frequency to obtain initial historical voltage harmonic component data of the energy storage converter unit; The outlier removal processing is performed on the initial historical voltage harmonic components, and the missing value interpolation processing is performed on the historical voltage harmonic components after the outlier removal processing to obtain the historical voltage harmonic components.

[0031] According to the Nyquist sampling theorem, the sampling frequency should be at least twice the highest frequency of the signal. In power grid systems, higher harmonics are usually of concern, so the highest harmonic frequency that may occur should be estimated.

[0032] A high-precision voltage sensor is connected to the output end of the energy storage converter unit. The sensor converts the voltage signal into an electrical signal suitable for processing by the acquisition device. The acquisition device continuously samples the voltage signal at a preset sampling frequency and records the voltage value at each sampling moment, thereby obtaining the initial historical voltage harmonic component data.

[0033] Among them, the common methods for removing outliers from the initial historical voltage harmonic components are statistical methods, such as the 3σ criterion. For a set of voltage data, its mean μ and standard deviation σ are calculated. If the deviation of a data point from the mean exceeds 3σ, the data point is considered to be an outlier. For example, if the deviation of the voltage value collected at a certain moment from the mean voltage in this time period is greater than 3 times the standard deviation, it can be determined as an outlier.

[0034] Some data may be missing due to sampling equipment failure, communication interruption, etc. The commonly used method is linear interpolation.

[0035] Preferably, in one embodiment of the present application, spectrum analysis is performed on the acquired historical voltage harmonic components of each energy storage converter unit, including: Preprocess the historical voltage harmonic components; The pre-processed historical voltage harmonic components are calculated based on the fast Fourier transform algorithm, and a spectrum diagram is generated according to the calculation results; The frequency and amplitude of each historical voltage harmonic component are obtained according to the spectrum diagram.

[0036] The fast Fourier transform algorithm FFT is an efficient discrete Fourier transform algorithm that can convert the voltage signal in the time domain into a frequency domain signal.

[0037] In one embodiment of the present application, by performing FFT calculation on the pre-processed historical voltage harmonic components, a complex number representation of the signal at different frequencies is obtained, the modulus of the complex number represents the amplitude of the frequency component, and the phase represents the phase information of the frequency component. With the frequency as the horizontal axis and the amplitude as the vertical axis, the frequency and amplitude information obtained by the FFT calculation are plotted in the coordinate system to generate a spectrum diagram. The spectrum diagram intuitively shows the amplitude distribution of each frequency component in the historical voltage harmonic components. On the generated spectrum diagram, the frequency corresponding to each peak is determined according to the scale of the horizontal axis, and the amplitude corresponding to the frequency is determined according to the scale of the vertical axis. These frequency and amplitude information are the frequency and amplitude of the historical voltage harmonic components.

[0038] Preferably, in one embodiment of the present application, preprocessing the historical voltage harmonic components includes: Perform wavelet transform on the historical voltage harmonic components to generate sub-band signals of different frequencies, perform denoising on the sub-band signals by threshold calculation method, perform inverse wavelet transform on the denoised sub-band signals to obtain the historical voltage harmonic components after preliminary denoising; The historical voltage harmonic component data after preliminary denoising is normalized by the maximum and minimum value method; The data length of the normalized historical voltage harmonic components is compared with the FFT calculation length, and the data of the normalized historical voltage harmonic components is truncated and zero-filled according to the comparison result.

[0039] Among them, wavelet transform is a time-frequency analysis method that can decompose the signal into different frequency scales. Select a suitable wavelet basis function (such as Daubechies wavelet) to perform wavelet decomposition on the historical voltage harmonic component and decompose the signal into sub-band signals of different frequencies. Use threshold calculation methods (such as soft threshold and hard threshold) to process each sub-band signal. For the wavelet coefficient in the high-frequency sub-band, if its absolute value is less than the set threshold, it is set to zero; for the low-frequency sub-band, a smaller threshold can be selected or no processing can be performed according to the actual situation. Finally, the processed sub-band signal is reconstructed by inverse wavelet transform to obtain the historical voltage harmonic component after preliminary denoising.

[0040] Compare the data length of the normalized historical voltage harmonic components with the FFT calculation length. The FFT algorithm usually requires the input data length to be an integer power of 2, such as 1024, 2048, etc. If the data length is greater than the FFT calculation length, data of appropriate length is intercepted from the beginning of the data sequence; if the data length is less than the FFT calculation length, zeros are added to the end of the data sequence to make it reach the length required for FFT calculation.

[0041] Preferably, in one embodiment of the present application, determining a harmonic whose amplitude exceeds a preset amplitude threshold as a harmonic frequency to be suppressed includes: Determine the amplitude threshold value according to the power industry standards and the characteristics of the power grid system; The amplitude of each historical voltage harmonic component is compared with the amplitude threshold one by one, and the harmonics with amplitudes greater than the amplitude threshold are screened out according to the comparison results; The frequency corresponding to the harmonic is determined as the harmonic frequency to be suppressed.

[0042] The amplitude of each historical voltage harmonic component obtained by spectrum analysis is compared with the determined amplitude threshold. Automatic comparison can be achieved through programming, and each amplitude data can be judged by the threshold. If the amplitude of a harmonic is greater than the amplitude threshold, it is marked as a harmonic to be screened. For the screened harmonics with amplitudes greater than the threshold, their corresponding frequencies are extracted from the spectrum analysis results. These frequencies are the harmonic frequencies that need to be suppressed. Later, the parameters of devices such as series wave arresters can be set according to these frequencies to achieve harmonic suppression.

[0043] S2: setting the component parameters of the series wave snubber according to the harmonic frequency to be suppressed, so that the resonant frequency of the series wave snubber corresponds to the harmonic frequency to be suppressed; Preferably, in one embodiment of the present application, the component parameters include capacitance, resistance and inductance; The component parameters of the series wave trap are set according to the harmonic frequency to be suppressed, including: Set the initial capacitance value based on historical experience; The initial capacitance value and the harmonic frequency to be suppressed are input into the resonance formula for calculation to obtain the initial inductance value; the resonance formula is expressed as: in, Indicates frequency, represents inductance, Represents capacitance; Input the initial capacitance value and the initial inductance value into the quality factor formula for calculation to obtain the initial resistance value; The initial resistance value, the initial capacitance value and the initial inductance value are fine-tuned to match the impedances between the various wave trap branches, and the capacitance value, the resistance value and the inductance value to be set of the series wave trap are obtained.

[0044] Among them, historical experience mainly comes from the application cases of series surge arresters in similar power grid systems in the past. Different types of power grid systems, such as industrial power grids and residential power grids, have different load characteristics and harmonic distributions, and the corresponding series surge arrester capacitance value settings are also different. For example, if there are a large number of nonlinear loads (such as inverters, rectifiers, etc.) in the industrial power grid, the harmonics generated are more complex, and a larger capacitance value may be required to enhance the ability to suppress harmonics; while the load of the residential power grid is relatively stable, and the capacitance value may be set relatively small. At the same time, factors such as the voltage level and capacity of the power grid must also be considered. Generally speaking, high-voltage and large-capacity power grids may require larger capacitance values ​​to meet the requirements of harmonic suppression.

[0045] In the series resonance state, the impedance of the circuit is minimum, and it shows good response characteristics to the signal of a specific frequency. When the resonant frequency of the series wave trap is the same as the frequency of the harmonic to be suppressed, the harmonic can be effectively suppressed.

[0046] Quality Factor It is an important indicator to measure the performance of series resonant circuits, which indicates the selectivity of the circuit to the resonant frequency. A higher quality factor means that the circuit has a stronger response to the signal of the resonant frequency and can more effectively suppress the harmonics near the resonant frequency, but it will also narrow the bandwidth of the circuit; a lower quality factor is the opposite, the bandwidth of the circuit is wider, but the suppression effect of harmonics may be weakened.

[0047] The quality factor formula for a series resonant circuit is , calculate the resistance value according to the quality factor formula.

[0048] In the power grid system, there are usually multiple series surge arrester branches working at the same time. If the impedances between the branches are not matched, the harmonic current will be unevenly distributed among the branches, and some branches may bear excessive current, which will affect the harmonic suppression effect and may even damage the surge arrester components. Therefore, it is necessary to fine-tune the component parameters to match the impedances of each branch.

[0049] Specifically, the power grid system can be modeled using computer simulation software (such as MATLAB, PSCAD, etc.), and the initial resistance, capacitance, and inductance values ​​can be input into the model to simulate the current and voltage distribution of each branch. According to the simulation results, the impedance differences between the branches are analyzed and the component parameters are adjusted appropriately. For example, if it is found that the current in a branch is too large, it may be necessary to increase the resistance value of the branch appropriately to increase its impedance so that the harmonic current is more evenly distributed to each branch.

[0050] At the same time, adjustments can also be made based on actual test data. After the series surge arrester is actually installed, the power quality monitoring equipment is used to monitor the harmonics in the power grid in real time, and the component parameters are further fine-tuned according to the monitoring results until the impedances between the branches are well matched to achieve the ideal harmonic suppression effect.

[0051] S3: Acquire real-time operation data of the power grid system, generate corresponding control signals according to the real-time operation data, send the control signals to the bypass switch, and control the series surge arrester module through the on-off control of the bypass switch to achieve harmonic suppression of the power grid system.

[0052] Preferably, in one embodiment of the present application, acquiring real-time operation data of the power grid system and generating a corresponding control signal according to the real-time operation data include: Extract features from pre-processed real-time operation data to obtain feature parameters related to the working condition judgment of the power grid system; Match the characteristic parameters with the preset working condition judgment rules, and obtain the real-time working condition of the power grid system according to the matching results; Generate control signals corresponding to real-time operating conditions.

[0053] Extract characteristic parameters related to the working condition of the power grid system from the preprocessed data. For example, extract the voltage amplitude change rate, the harmonic content percentage of the current, the power factor, etc. These characteristic parameters can more intuitively reflect the operating status of the power grid.

[0054] According to the power industry standards, equipment manufacturers' recommendations and actual operating experience, formulate judgment rules for different working conditions. For example: Normal operating conditions: The voltage amplitude fluctuates within a certain range of the rated value (such as ±5%), the current is within the rated current range of the equipment, the harmonic content meets the relevant standards, and the power factor is close to 1.

[0055] Standby condition: The energy storage converter unit is in a low-power operating state, and the output power is lower than a certain set threshold.

[0056] Overvoltage / overcurrent condition: The voltage amplitude exceeds a certain percentage (such as 10%) of the rated value or the current exceeds the rated current of the equipment.

[0057] The extracted characteristic parameters are compared with the preset working condition judgment rules one by one. The automatic matching process can be realized through programming, and the current working condition of the power grid system can be judged according to the value range of the characteristic parameters.

[0058] Preferably, in one embodiment of the present application, generating a control signal corresponding to the real-time working condition includes: If the power grid system is in a normal operating condition, a control signal is generated to close the bypass switch; If the power grid system is in standby mode, a control signal is generated to control the bypass switch to be disconnected, so as to put the series wave arrester module into operation to achieve harmonic suppression of the power grid system; If the grid system is in an overvoltage / overcurrent condition, a control signal is generated to control the bypass switch to be disconnected, so as to put the series surge arrester module into operation to increase the impedance of the grid.

[0059] If the grid system is in normal working condition, a control signal is generated to close the bypass switch. Under normal working conditions, the harmonic content in the grid is low, and the series wave arrester module does not need to be involved in the work. Closing the bypass switch can reduce energy loss and improve the operation efficiency of the grid.

[0060] If the power grid system is in standby mode, a control signal is generated to control the bypass switch to be disconnected, so as to put into operation the series surge arrester module to achieve harmonic suppression of the power grid system. In standby mode, although the system power is low, there may still be certain harmonics. Putting into operation the series surge arrester module can effectively suppress these harmonics and ensure the power quality of the power grid.

[0061] If the power grid system is in an overvoltage / overcurrent condition, a control signal is generated to control the bypass switch to be disconnected, so as to put the series wave arrester module into operation to increase the impedance of the power grid. After the series wave arrester module is put into operation, it has a large impedance to the harmonics of a specific frequency, and can also limit overvoltage and overcurrent to a certain extent, protecting the power grid equipment from damage.

[0062] After receiving the control signal, the control module of the bypass switch first decodes and verifies the signal. The verification content includes whether the signal format, check code, amplitude, etc. meet the requirements. If the verification passes, the corresponding action, such as switching on or off, is performed according to the instruction of the control signal; if the verification fails, the signal is rejected and error information is fed back to the control center.

[0063] Compared with the prior art, the beneficial effects of the embodiments of the present application are: By adding a series surge arrester module to the electric load module, the resonance phenomenon generated under standby conditions can be effectively suppressed, significantly reducing voltage and current fluctuations, and improving system stability and power quality. Multiple series surge arrester branches can also be designed for different resonant frequencies to effectively suppress resonance at specific frequencies. At the same time, the design of the bypass switch allows the system to bypass the surge arrester when filtering operation is not required, thereby improving operating efficiency.

[0064] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A power grid system based on a series surge arrester, characterized in that: It includes parallel energy storage module, AC bus, load module and series surge arrester module, among which: The parallel energy storage module is composed of a plurality of energy storage converter units connected in parallel at multiple stages, each of which includes a battery pack, a controlled voltage source and a filter branch. The battery pack is connected in parallel with the controlled voltage source, the output end of the controlled voltage source is connected in series with one end of the filter branch, and the other end of the filter branch is connected to the AC bus. The series wave trap module includes a harmonic suppression circuit and a bypass switch connected in parallel, one end of the bypass switch is connected to the AC bus, and the harmonic suppression circuit includes a plurality of wave trap branches connected in series, and the resonant frequency of each wave trap branch is adapted to the harmonic frequency to be suppressed generated by the parallel energy storage module; The load module includes a power grid, a third-party load and a grid-connected switch, one end of the grid-connected switch is connected to the power grid and the third-party load respectively, and the other end of the grid-connected switch is connected to the other end of the bypass switch.

2. The power grid system based on series wave trap according to claim 1, characterized in that: The wave trap branch includes a first resistor, a second resistor, a third resistor, an inductor and a capacitor, wherein: The inductor, the capacitor and the second resistor are connected in series; the first end of the first resistor is connected in series with other wave trap branches, one path of the second end of the first resistor is connected to the series branch of the inductor, the capacitor and the second resistor, and the other path of the second end of the first resistor is connected to the third resistor branch, wherein the series branch of the inductor, the capacitor and the second resistor is connected in parallel with the third resistor branch.

3. A resonance suppression method, applied to a power grid system based on a series wave trap as claimed in any one of claims 1 to 2, characterized in that: include: Performing spectrum analysis on the acquired historical voltage harmonic components of each of the energy storage converter units to obtain the frequency and amplitude of each of the historical voltage harmonic components, and determining the harmonic whose amplitude exceeds a preset amplitude threshold as the harmonic frequency to be suppressed; Setting the component parameters of the series wave trap according to the harmonic frequency to be suppressed so that the resonant frequency of the series wave trap corresponds to the harmonic frequency to be suppressed; Acquire real-time operation data of the power grid system, generate a corresponding control signal according to the real-time operation data, send the control signal to the bypass switch, and control the series wave arrester module by turning the bypass switch on and off to achieve harmonic suppression of the power grid system.

4. The resonance suppression method according to claim 3, characterized in that: Before performing spectrum analysis on the acquired historical voltage harmonic components of each of the energy storage converter units, the method further includes: Continuously sampling the output terminal voltage of each energy storage converter unit based on a preset sampling frequency to obtain initial historical voltage harmonic component data of the energy storage converter unit; An outlier removal process is performed on the initial historical voltage harmonic component, and a missing value interpolation process is performed on the historical voltage harmonic component after the outlier removal process to obtain the historical voltage harmonic component.

5. The resonance suppression method according to claim 3, characterized in that: The performing spectrum analysis on the acquired historical voltage harmonic components of each of the energy storage converter units includes: Preprocessing the historical voltage harmonic components; Calculating the preprocessed historical voltage harmonic components based on a fast Fourier transform algorithm, and generating a spectrum diagram according to the calculation results; The frequency and amplitude of each of the historical voltage harmonic components are acquired according to the frequency spectrum.

6. The resonance suppression method according to claim 5, characterized in that: The preprocessing of the historical voltage harmonic components includes: Performing wavelet transform on the historical voltage harmonic components to generate sub-band signals of different frequencies, performing denoising on the sub-band signals by a threshold calculation method, and performing inverse wavelet transform on the denoised sub-band signals to obtain the historical voltage harmonic components after preliminary denoising; Normalizing the historical voltage harmonic component data after preliminary denoising by using a maximum and minimum value method; The data length of the normalized historical voltage harmonic component is compared with the FFT calculation length, and data truncation and zero padding are performed on the normalized historical voltage harmonic component according to the comparison result.

7. The resonance suppression method according to claim 3, characterized in that: The step of determining the harmonic whose amplitude exceeds a preset amplitude threshold as the harmonic frequency to be suppressed comprises: Determining a magnitude threshold value according to power industry standards and characteristics of the power grid system; Comparing the amplitude of each of the historical voltage harmonic components with the amplitude threshold one by one, and screening the harmonics whose amplitude is greater than the amplitude threshold according to the comparison result; The frequency corresponding to the harmonic is determined as the harmonic frequency to be suppressed.

8. The resonance suppression method according to claim 3, characterized in that: The component parameters include capacitance value, resistance value and inductance value; The step of setting the component parameters of the series wave trap according to the harmonic frequency to be suppressed comprises: Set the initial capacitance value based on historical experience; The initial capacitance value and the harmonic frequency to be suppressed are input into the resonance formula for calculation to obtain the initial inductance value; the resonance formula is expressed as: in, Indicates frequency, represents inductance, Represents capacitance; Inputting the initial capacitance value and the initial inductance value into a quality factor formula for calculation to obtain an initial resistance value; The initial resistance value, the initial capacitance value and the initial inductance value are fine-tuned to match the impedances between the various wave trap branches, thereby obtaining the capacitance value, resistance value and inductance value to be set for the series wave trap.

9. The resonance suppression method according to claim 3, characterized in that: The acquiring the real-time operation data of the power grid system and generating a corresponding control signal according to the real-time operation data includes: Performing feature extraction on the preprocessed real-time operation data to obtain feature parameters related to the working condition judgment of the power grid system; Matching the characteristic parameters with preset working condition judgment rules, and obtaining the real-time working condition of the power grid system according to the matching results; A control signal corresponding to the real-time operating condition is generated.

10. The resonance suppression method according to claim 9, characterized in that: The generating a control signal corresponding to the real-time working condition comprises: If the power grid system is in a normal operating condition, generating a control signal to close the bypass switch; If the power grid system is in a standby state, a control signal is generated to control the bypass switch to be disconnected, so as to put the series wave arrester module into operation to achieve harmonic suppression of the power grid system; If the power grid system is in an overvoltage / overcurrent condition, a control signal is generated to control the bypass switch to be disconnected, so as to activate the series surge arrester module to increase the impedance of the power grid.

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