Method and control system for adaptive adjustment of SOGI damping coefficient based on grid THD

Abstract

The application discloses a method for adaptively adjusting SOGI damping coefficient based on power grid THD, which comprises the following steps: S1: collecting three-phase power grid voltage to obtain two-phase voltage signals and; S2: calculating total harmonic distortion rate of current power grid voltage; S3: based on the value of the total harmonic distortion rate, SOGI damping coefficient k; S4: inputting the dynamically determined SOGI damping coefficient k into two SOGI operation units for processing the two-phase voltage signals and respectively to generate two orthogonal signals and; S5: using the orthogonal signals and output by the SOGI operation unit for subsequent control, and the orthogonal signals and are used for constructing virtual orthogonal signals to realize phase locking or positive and negative sequence separation. The application establishes a closed-loop dynamic mapping relationship between power grid total harmonic distortion rate THD and adaptively adjusted SOGI damping coefficient k.

Description

Technical Field

[0001] This invention relates to the field of adaptive regulation technology for power grids, specifically to a method and control method for adaptively adjusting the SOGI damping coefficient based on the power grid's THD. Background Technology

[0002] With the large-scale grid connection of renewable energy and the widespread application of nonlinear loads in industrial sectors, power quality issues in power grids are becoming increasingly prominent. Among these, the increased Total Harmonic Distortion (THD) caused by voltage waveform distortion has become a key factor affecting the grid-connected performance of power electronic equipment. In high-harmonic-distortion grid environments, the accuracy and speed of grid synchronization are crucial for the stable operation of grid-connected converters, power electronic transformers, active power filters (APFs), and other equipment.

[0003] Currently, phase-locked loops (SOGI-PLLs) or positive-negative sequence separation structures based on second-order generalized integrators (SOGIs) are widely used in power grid synchronization due to their simple structure and ability to extract fundamental components and generate orthogonal signals in a stationary coordinate system. In traditional SOGI structures, the damping coefficient k is usually set to a fixed value to obtain a dynamic response close to critical damping under ideal sinusoidal voltage conditions.

[0004] However, in actual high THD power grid operation, this fixed parameter design has revealed significant limitations: The trade-off between harmonic suppression capability and dynamic response speed: When the grid THD is high, reducing the damping coefficient k can broaden the SOGI bandwidth and accelerate the dynamic response, but it will significantly reduce the suppression capability of harmonic and non-fundamental frequency components, resulting in a large amount of harmonic interference mixed into the output signal, which will seriously degrade the phase and amplitude extraction accuracy. Conversely, increasing the value of k can enhance the harmonic suppression capability, but it will sacrifice the system's response speed. When the grid voltage changes abruptly or there is a fault, it may cause synchronization delay and affect the transient stability of the system.

[0005] Lack of adaptability to the operating environment: Existing technical solutions mostly use offline tuning with a fixed k value, or only adaptively adjust the resonant frequency of SOGI (such as SOGI-FLL), failing to adjust the damping coefficient k—a key parameter determining the SOGI filtering characteristics and dynamic performance—online based on the real-time power quality conditions of the power grid, especially the changing THD level. This makes it impossible for the system to maintain optimal overall performance when harmonic content changes. Therefore, a new method and control system for adaptively adjusting the SOGI damping coefficient based on power grid THD has become a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] This application provides a method for adaptively adjusting the SOGI damping coefficient based on the power grid THD, including the following steps: S1: Acquire the three-phase grid voltage and record it as a three-phase voltage signal. The two-phase voltage signals in the stationary coordinates of phases a and b are obtained by Clarke transform. and ; S2: Based on the two-phase voltage signals and Calculate the total harmonic distortion rate of the current power grid voltage. ; S3: Based on the total harmonic distortion rate The value is then used in conjunction with the preset total harmonic distortion rate. The mapping relationship between the SOGI damping coefficient k and the SOGI damping coefficient k is used to dynamically determine the SOGI damping coefficient k. The mapping relationship is configured such that the value of the SOGI damping coefficient k increases monotonically with the increase of the total harmonic distortion (THD) value. S4: Input the dynamically determined SOGI damping coefficient k into the processing of the two-phase voltage signals respectively. and The two SOGI operation units generate two orthogonal signals. and ; S5: Utilizing the orthogonal signal output by the SOGI processing unit and For subsequent control, the orthogonal signal and Used to construct virtual quadrature signals to achieve phase-locked loop or positive-negative sequence separation.

[0007] Optionally, in step S2, the total harmonic distortion (THD) is calculated using the following method: ; in, This represents the total effective value of the harmonic components. This represents the effective value of the fundamental component. Optionally, in step S3, the preset mapping relationship between the total harmonic distortion (THD) and the SOGI damping coefficient k is a piecewise mapping relationship, which is configured as follows: when At that time, take = , ; when At that time, take = , ; when hour, Value at and Between The minimum value is represented by a monotonically increasing expression. in, , , express The minimum value, express The maximum value that can be obtained.

[0008] Optionally, the The value of is determined by the system's dynamic response requirements. < At that time, the ability of the adaptively adjusted SOGI to suppress power grid harmonics decreases; The value is determined by the stability of the current control loop. > When the bandwidth of the adaptively adjusted SOGI is lower than the required value, the phase-locked loop response delay exceeds the set time t.

[0009] Optionally, in step S4, the operational structure of the SOGI operational unit is set as follows:

[0010] in, and Indicates the input voltage signal. The fundamental angular frequency, and State variables representing orthogonal signals. The damping coefficient is dynamically determined. and This indicates that the SOGI is respectively introduced into the two-phase voltage signals. and The equation of state.

[0011] Optionally, the The The = 3%, the = 8%.

[0012] This application also provides a control system based on adaptive adjustment of SOGI damping coefficient according to power grid THD, including: The coordinate transformation unit is used to acquire three-phase grid voltage and transform it to the αβ stationary coordinate system, outputting voltage signals. and ; The total harmonic distortion (THD) calculation unit, whose input is connected to the coordinate transformation unit, is used to receive the voltage signal. and / or And calculate the total harmonic distortion (THD) of the grid voltage in real time; The damping coefficient mapping unit, whose input is connected to the output of the THD calculation unit, is used to output an adaptive SOGI damping coefficient k based on the THD value and a pre-stored mapping relationship. The second-order generalized integrator processing unit comprises a first SOGI subunit and a second SOGI subunit connected in parallel, which respectively receive... and It receives the k value output by the damping coefficient mapping unit and outputs an orthogonal signal. and It is used for subsequent phase-locked loop or positive-negative sequence separation.

[0013] Optionally, the THD calculation unit uses a sliding window RMS or a sliding window FFT method to calculate the fundamental effective value. Harmonic RMS value Then, THD is calculated.

[0014] Optionally, the structures of the first SOGI subunit and the second SOGI subunit support an external input damping coefficient k.

[0015] The beneficial effects of this application are as follows: 1. This invention establishes a closed-loop dynamic mapping relationship between the total harmonic distortion (THD) of the power grid and the adaptively adjustable SOGI damping coefficient k. By monitoring the THD of the power grid in real time and automatically adjusting the k value accordingly, the SOGI unit can increase damping to enhance filtering robustness and suppress harmonic interference under high harmonic pollution conditions, and decrease damping to accelerate dynamic response speed when power quality is good. This solves the contradiction between the traditional fixed k value scheme and the inability to balance dynamic response speed and harmonic suppression capability, enabling the system to autonomously maintain optimal operating state under all operating conditions. 2. The adaptive logic implementation of this invention is simple and efficient. The THD can be estimated using a simplified RMS algorithm or a sliding window FFT, while the core k-value update can be completed simply through a preset mapping relationship. The entire adjustment process does not require complex optimization algorithms and consumes very little processor computing resources, making it suitable for deployment and application on embedded microcontrollers or DSP platforms with limited computing power. Attached Figure Description

[0016] Figure 1 This is the overall control flowchart of the present invention; Figure 2 The diagram shows the structure of the THD calculation module and the k-adaptive mapping unit. Figure 3 This describes the internal structure of the SOGI module. Figure 4 The simulation comparison chart shows the phase tracking error curves under THD mutations: fixed k vs. adaptive k. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] This application provides a method for adaptively adjusting the SOGI damping coefficient based on the power grid THD, including the following steps: S1: Acquire the three-phase grid voltage and record it as a three-phase voltage signal. The two-phase voltage signals in the stationary coordinates of phases a and b are obtained by Clarke transform. and ; S2: Based on the two-phase voltage signals and Calculate the total harmonic distortion rate of the current power grid voltage. ; In step S2, the total harmonic distortion rate (THD) is calculated as follows: ; in, This represents the total effective value of the harmonic components. This represents the effective value of the fundamental component. S3: Based on the total harmonic distortion rate The value is then used in conjunction with the preset total harmonic distortion rate. The mapping relationship between the SOGI damping coefficient k and the SOGI damping coefficient k is used to dynamically determine the SOGI damping coefficient k. In step S3, the preset mapping relationship between the total harmonic distortion (THD) and the SOGI damping coefficient k is a piecewise mapping relationship, which is configured as follows: when At that time, take = , ; when At that time, take = , ; when hour, Value at and Between The minimum value is represented by a monotonically increasing expression. in, , , express The minimum value, express The maximum value that can be obtained.

[0019] The mapping relationship is configured such that the value of the SOGI damping coefficient k increases monotonically with the increase of the total harmonic distortion (THD) value. S4: Input the dynamically determined SOGI damping coefficient k into the processing of the two-phase voltage signals respectively. and The two SOGI operation units generate two orthogonal signals. and ; In step S4, the operation structure of the SOGI operation unit is set as follows:

[0020] in, and Indicates the input voltage signal. The fundamental angular frequency, and State variables representing orthogonal signals. The damping coefficient is dynamically determined. and Substituting the two-phase voltage signals into the SOGI indicates that... and The equation of state.

[0021] S5: Utilizing the orthogonal signal output by the SOGI processing unit and For subsequent control, the orthogonal signal and Used to construct virtual quadrature signals to achieve phase-locked loop or positive-negative sequence separation.

[0022] The The value of is determined by the system's dynamic response requirements. < At that time, the ability of the adaptively adjusted SOGI to suppress power grid harmonics decreases; The value is determined by the stability of the current control loop. > When the bandwidth of the adaptively adjusted SOGI is lower than the required value, the phase-locked loop response delay exceeds the set time t.

[0023] The The The = 3%, the = 8%.

[0024] This application also provides a control system for adaptively adjusting the SOGI damping coefficient based on the power grid THD, including: The coordinate transformation unit is used to acquire three-phase grid voltage and transform it to the αβ stationary coordinate system, outputting voltage signals. and ; The total harmonic distortion (THD) calculation unit, whose input is connected to the coordinate transformation unit, is used to receive the voltage signal. and / or And calculate the total harmonic distortion (THD) of the grid voltage in real time; The damping coefficient mapping unit, whose input is connected to the output of the THD calculation unit, is used to output an adaptive SOGI damping coefficient k based on the THD value and a pre-stored mapping relationship. The second-order generalized integrator processing unit comprises a first SOGI subunit and a second SOGI subunit connected in parallel, which respectively receive... and It receives the k value output by the damping coefficient mapping unit and outputs an orthogonal signal. and It is used for subsequent phase-locked loop or positive-negative sequence separation.

[0025] The THD calculation unit calculates the fundamental frequency effective value using a sliding window RMS or sliding window FFT method. Harmonic RMS value Then, THD is calculated.

[0026] The structures of the first SOGI subunit and the second SOGI subunit support an external input damping coefficient k.

[0027] It should be noted that the real-time algorithm for the total harmonic distortion (THD) is as follows: In this embodiment, the calculation of THD is implemented using a sliding window discrete Fourier transform, and the specific steps are as follows: 1. To The signal is sampled at a sampling frequency of fs=10kHz, with 200 points per cycle T. 2. Take a data window of 20 ms from the most recent fundamental period, calculate its DFT, and obtain the fundamental amplitude. ; 3. Total effective value of harmonics Estimated by the following formula:

[0028] Where N = 200 is the number of sampling points in one period.

[0029] According to the formula:

[0030] The THD value is updated in real time, and the update period is 10 ms.

[0031] The mapping relationship between THD and the damping coefficient k is determined: The SOGI damping coefficient k is dynamically updated according to the THD value, and the mapping relationship function between the preset THD and k , for example:

[0032] in =1.0， , , ; The specific mapping function of "k increases monotonically with THD" is implemented by piecewise linear interpolation in this embodiment, and its basis comes from a large number of simulations and experimental verifications: When THD ≤ 3%, the harmonic content in the power grid is low, and the system focuses on dynamic response, taking k = 1.0 (lower limit); When THD ≥ 8%, the harmonics in the power grid are serious, and the system focuses on harmonic suppression, taking k = 2.5 (upper limit); When 3% < THD < 8%, k is adjusted by linear interpolation:

[0033] Such as Figure 2 As shown, this mapping reflects the design principle that the more serious the harmonics, the greater the damping, and the attenuation ability of SOGI to harmonics is improved by increasing the k value.

[0034] The state equation of the adaptive regulation SOGI is:

[0035] Where: Among them, and represent the input voltage signal, is the fundamental angular frequency, and represent the state variables of the quadrature signal, The damping coefficient is dynamically determined. and Substituting the two-phase voltage signals into the SOGI indicates that... and The equation of state.

[0036] The adaptive adjustment SOGI state equation is implemented in the DSP using forward Euler discretization:

[0037] in =0.0001 s is the sampling period.

[0038] To verify the effectiveness of this invention, a THD mutation test scenario was built on the PLECS simulation platform: When t < 100 mst < 100 ms, THD = 2%; When t≥100 mst≥100 ms, the THD step jumps to 9%.

[0039] Compared to traditional fixed The scheme with a value of 1.414 and the adaptive scheme of this invention: fixed The proposed solution has a peak phase error of 5.2° and a recovery time > 30 ms. The adaptive scheme has a peak phase error of only 1.3° and a recovery time of < 20 ms.

[0040] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for adaptively adjusting the SOGI damping coefficient based on the power grid THD, characterized in that, Includes the following steps: S1: Acquire the three-phase grid voltage and record it as a three-phase voltage signal. The two-phase voltage signals in the stationary coordinates of phases a and b are obtained by Clarke transform. and ; S2: Based on the two-phase voltage signals and Calculate the total harmonic distortion rate of the current power grid voltage. ; S3: Based on the total harmonic distortion rate The value is then used in conjunction with the preset total harmonic distortion rate. The mapping relationship between the SOGI damping coefficient k and the SOGI damping coefficient k is used to dynamically determine the SOGI damping coefficient k. The mapping relationship is configured such that the value of the SOGI damping coefficient k increases monotonically with the increase of the total harmonic distortion (THD) value. S4: Input the dynamically determined SOGI damping coefficient k into the processing of the two-phase voltage signals respectively. and The two SOGI operation units generate two orthogonal signals. and ; S5: Utilizing the orthogonal signal output by the SOGI processing unit and For subsequent control, the orthogonal signal and Used to construct virtual quadrature signals to achieve phase-locked loop or positive-negative sequence separation.

2. The method for adaptively adjusting the SOGI damping coefficient based on power grid THD according to claim 1, characterized in that, In step S2, the total harmonic distortion rate (THD) is calculated as follows: ； in, This represents the total effective value of the harmonic components. This represents the effective value of the fundamental component.

3. The method for adaptively adjusting the SOGI damping coefficient based on power grid THD according to claim 1, characterized in that, In step S3, the preset mapping relationship between the total harmonic distortion (THD) and the SOGI damping coefficient k is a piecewise mapping relationship, which is configured as follows: when At that time, take = , ; when At that time, take = , ; when hour, Value at and Between The minimum value is represented by a monotonically increasing expression. in, , , express The minimum value, express The maximum value that can be obtained.

4. The method for adaptively adjusting the SOGI damping coefficient based on power grid THD according to claim 3, characterized in that, The The value of is determined by the system's dynamic response requirements. < When the adaptive adjustment of SOGI reduces its ability to suppress grid harmonics, the value of SOGI decreases; the value of SOGI is determined by the stability of the current control loop. > When the bandwidth of the adaptively adjusted SOGI is lower than the required value, the phase-locked loop response delay exceeds the set time t.

5. The method for adaptively adjusting the SOGI damping coefficient based on power grid THD according to claim 1, characterized in that, In step S4, the operation structure of the SOGI operation unit is set as follows: ； in, and Indicates the input voltage signal. The fundamental angular frequency, and State variables representing orthogonal signals. The damping coefficient is dynamically determined. and Substituting the two-phase voltage signals into the SOGI indicates that... and The equation of state.

6. The method for adaptively adjusting the SOGI damping coefficient based on power grid THD according to claim 3, characterized in that, The The The = 3%, the = 8%.

7. A control system for adaptively adjusting the SOGI damping coefficient based on the power grid THD, characterized in that, include: The coordinate transformation unit is used to acquire three-phase grid voltage and transform it to the αβ stationary coordinate system, outputting voltage signals. and ; The total harmonic distortion (THD) calculation unit, whose input is connected to the coordinate transformation unit, is used to receive the voltage signal. and / or And calculate the total harmonic distortion (THD) of the grid voltage in real time; The damping coefficient mapping unit, whose input is connected to the output of the THD calculation unit, is used to output an adaptive SOGI damping coefficient k based on the THD value and a pre-stored mapping relationship. The second-order generalized integrator processing unit comprises a first SOGI subunit and a second SOGI subunit connected in parallel, which respectively receive... and It receives the k value output by the damping coefficient mapping unit and outputs an orthogonal signal. and It is used for subsequent phase-locked loop or positive-negative sequence separation.

8. The control system based on adaptive adjustment of SOGI damping coefficient according to power grid THD as described in claim 8, characterized in that, The THD calculation unit calculates the fundamental frequency effective value using a sliding window RMS or sliding window FFT method. Harmonic RMS value Then, THD is calculated.

9. The control system based on adaptive adjustment of SOGI damping coefficient according to power grid THD as described in claim 8, characterized in that, The structures of the first SOGI subunit and the second SOGI subunit support an external input damping coefficient k.

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