Single-phase phase-locked loop system with intelligent parameter adjustment

Abstract

This invention discloses a single-phase phase-locked loop system with intelligent parameter adjustment, comprising: a spectrum analysis unit that outputs a fundamental frequency f. c ω c and cascaded delay signal cancellation parameter n i The adaptive single-phase lock-in unit includes a third-order generalized integrator, a dq converter, a cascaded delay signal canceller (CDSC), a PI controller, an integrator, and a modulus extractor. The cascaded delay signal canceller (CDSC) operates at the fundamental frequency f. c Using the reference frequency and the fundamental angular velocity ω c As the reference angular velocity at the integrator input, the angular velocity increment Δω output by the PI controller is related to the fundamental angular velocity ω. c The summation determines the phase-locked angle θ, and the proportional coefficient k of the PI controller... p Integral coefficient k i External online refresh and immediate effect; intelligent optimization unit for control parameters, based on the Mirage Search Optimization Algorithm (MSO) iteratively obtains the optimal [k] p ,k i The data is then written to a non-volatile memory. The single-phase phase-locked loop system with intelligent parameter adjustment provided by this invention eliminates the need for manual parameter adjustment, and provides fast, accurate, and long-term stable phase locking.

Description

Technical Field

[0001] This invention specifically relates to a single-phase phase-locked loop system with intelligent parameter adjustment. Background Technology

[0002] With the widespread integration of distributed photovoltaic, energy storage, and electric vehicle charging facilities, the power quality of low-voltage distribution networks is deteriorating. Traditional single-phase phase-locked loops (PLLs) typically employ fixed-parameter PI controllers and fixed-delay filters, which struggle to simultaneously achieve fast locking, low steady-state error, and high disturbance rejection performance under these conditions. Some literature proposes adaptive PI controllers or variable-delay filters, but their parameter update rules rely on expert experience, lacking systematic and intelligent online tuning methods, resulting in a massive workload for on-site commissioning. Therefore, there is an urgent need for a PLL system capable of identifying grid characteristics in real time and autonomously optimizing parameters. Summary of the Invention

[0003] This invention provides a single-phase phase-locked loop system with intelligent parameter adjustment to solve the technical problem of inaccurate traditional early warning methods mentioned above. The specific technical solution is as follows:

[0004] A single-phase phase-locked loop system with intelligent parameter adjustment, comprising:

[0005] The spectrum analysis unit is used to perform real-time frequency domain transformation on single-phase grid voltage and output the fundamental frequency f in real time. c ω c and cascaded delay signal cancellation parameter n i ;

[0006] An adaptive single-phase lock-in loop unit, arranged sequentially along the signal path, comprises an improved third-order generalized integrator, a dq converter, a cascaded delay signal canceller (CDSC), a PI controller, an integrator, and a modulus extractor. The cascaded delay signal canceller (CDSC) operates at the fundamental frequency f. c Using the reference frequency and the fundamental angular velocity ω c As the reference angular velocity at the integrator input, the angular velocity increment Δω output by the PI controller is related to the fundamental angular velocity ω. c The summation determines the phase-locked angle θ, and the proportional coefficient k of the PI controller... p Integral coefficient k i Refreshed online from outside and takes effect immediately;

[0007] The intelligent optimization unit for control parameters uses the Mirage Search Optimization (MSO) algorithm to iteratively find the optimal [k] parameter. p ,k i And pass it to the adaptive single-phase phase-locked loop unit.

[0008] Furthermore, the spectrum analysis unit processes the sliding circular queue using an FFT at a resolution of 5 Hz, and extracts the five spectral lines with the largest amplitudes using a five-element min-heap, thereby calculating the fundamental frequency f. c ω c and cascaded delay signal cancellation parameter n i .

[0009] Furthermore, the spectrum analysis unit updates the current fundamental frequency f every 10 minutes. c ω c and cascaded delay signal cancellation parameter n i Write to Flash to restore historical parameters after a power outage and restart.

[0010] Furthermore, the improved third-order generalized integrator sets a stopped pole at zero frequency and generates a pair of orthogonal signals at the output for use by the dq converter to eliminate DC offset and higher-order harmonics.

[0011] Furthermore, the cascaded delay signal canceller (CDSC) consists of four stages of series delay signal cancellation units, with each stage having a delay amount Δt. i =1 / (n i ·f c ), where n1 to n4 correspond to the 2nd to 5th major harmonics, respectively, to achieve successive filtering.

[0012] Furthermore, the PI controller receives a new [k] p ,k i After that, the coefficients are updated through a non-disruptive switching method to ensure continuous operation of the phase-locked loop and stepless output.

[0013] Furthermore, the objective function of the intelligent optimization unit for control parameters is:

[0014]

[0015] Where Δω(t) is the value of the error Δω output by the single-phase phase-locked loop PI controller at time t, and T is the time required for the phase-locked loop to successfully lock the phase.

[0016] Furthermore, the MSO initializes 20 observation positions, and in the total iteration round T... o Alternately perform global search in the upper mirage and local search in the lower mirage, and take the position with the minimum output fitness as the optimal [k]. p ,k i ].

[0017] Furthermore, in the upper mirage stage, the left or right correction direction of the observation position is determined by the random direction flag dir∈{1,2}, and the correction amount decreases linearly with iteration.

[0018] Furthermore, the intelligent optimization unit for control parameters will obtain the optimal [k] p ,k i Write to non-volatile memory, which is Flash, and simultaneously store the optimization enable flag, optimization completion flag, and history [k]. p ,k i This is used by the system state machine to achieve one-click self-tuning.

[0019] The single-phase phase-locked loop system with intelligent parameter adjustment provided by this invention eliminates the need for manual parameter adjustment, and provides fast, accurate, and long-term stable phase locking. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of a single-phase phase-locked loop system with intelligent parameter adjustment according to the present invention. Detailed Implementation

[0022] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0023] like Figure 1 As shown, this application discloses a single-phase phase-locked loop system with intelligent parameter adjustment, comprising: a spectrum analysis unit, an adaptive single-phase phase-locked loop unit, and a control parameter intelligent optimization unit.

[0024] The spectrum analysis unit analyzes the fundamental and harmonic signals of the single-phase grid voltage signal in real time. Specifically, the spectrum analysis unit performs frequency domain transformation on the single-phase grid voltage in real time and outputs the fundamental frequency f in real time. c ω c and cascaded delay signal cancellation parameter n i .

[0025] The adaptive single-phase phase-locked loop unit sequentially includes an improved third-order generalized integrator, a dq converter, a cascaded delay signal canceller (CDSC), a PI controller, an integrator, and a modulus extractor along the signal path. The cascaded delay signal canceller (CDSC) operates at the fundamental frequency f. c Using the reference frequency and the fundamental angular velocity ωc As the reference angular velocity at the integrator input, the angular velocity increment Δω output by the PI controller is related to the fundamental angular velocity ω. c The summation determines the phase-locked angle θ, and the proportional coefficient k of the PI controller... p Integral coefficient k i It is refreshed externally online and takes effect immediately. The PI controller's internal double-buffering mechanism enables k... p k i Updates can be completed within a single interruption cycle without disrupting the continuous operation of the phase-locked loop.

[0026] The intelligent optimization unit for control parameters uses the Mirage Search Optimization Algorithm (MSO) to iteratively find the optimal [k] parameter. p ,k i The optimal control parameters are then passed to the adaptive single-phase phase-locked loop unit. The intelligent optimization unit will also optimize [k]... p ,k i The parameters are written to non-volatile memory to complete parameter self-tuning in a closed-loop manner. The intelligent optimization unit for control parameters completes parameter self-tuning in a closed-loop manner, which means that it not only provides the optimal parameters once, but can also re-trigger the MSO when the power grid conditions change again, achieving true lifetime commission-free operation.

[0027] In the embodiments of this application, the spectrum analysis unit processes the sliding circular queue using an FFT at a resolution of 5 Hz, and extracts the five spectral lines with the largest amplitudes using a five-element min-heap, thereby calculating the fundamental frequency f. c ω c and cascaded delay signal cancellation parameter n i .

[0028] Specifically, the spectrum analysis unit continuously receives the instantaneous voltage value u measured by the grid voltage divider check circuit of the inverter, puts the voltage value u into the signal loop queue, and when the data storage of the signal loop queue overflows, it overwrites the historical signal data in a first-in-first-out manner, and starts the fast Fourier transform to calculate the data of the signal loop queue, and outputs a frequency domain complex array with a resolution of 5Hz.

[0029] Calculate the modulus of each element of the complex array in the frequency domain to obtain the amplitude array for each frequency component. Remove the amplitude of the 0Hz component, i.e., set the first element of the array to 0. Construct a min-heap with 5 elements to search the amplitude array, find the 5 elements with the largest amplitudes, and store their amplitudes and array indices. The search result of the min-heap is {(Idx i, Amp i ),1≤i≤5},Idx i The index value of the original array, Amp i This represents the amplitude of the frequency component.

[0030] Sort the elements in the min-heap from largest to smallest according to their amplitude Ampi, and convert the results into the frequency and amplitude of the components {(f i Amp i ),1≤i≤5}. Where, f i =5×(Idx) i- 1) is the frequency.

[0031] The fundamental frequency of the signal is f c =f1, the four main harmonic frequencies are (f2, f3, f 4, f5). Calculate the fundamental angular velocity ω. c =2πf c Cascaded delay signal cancellation parameter n i =2·(f i+1 / f1-1), 1≤i≤4,n i Round to the nearest integer.

[0032] Fundamental frequency f c ω c The cascaded delay signal cancellation parameters n1, n2, n3, and n4 are transmitted in real time to the single-phase phase-locked loop unit. The fundamental frequency f... c The reference frequency for the cascaded delay signal canceller. Fundamental angular velocity ω c The reference angular velocity, used as the input of the integrator, is added to the control quantity Δω at the output of the PI controller.

[0033] In the embodiments of this application, the spectrum analysis unit updates the current fundamental frequency f every 10 minutes. c ω c and cascaded delay signal cancellation parameter n i Write to Flash to restore historical parameters after a power outage and restart.

[0034] The adaptive single-phase phase-locked loop unit queries whether the fundamental frequency f is stored in the Flash memory. c ω c Cascaded delay signal cancellation parameter n i PI controller parameters [k p ,k i If a value exists, it is read and assigned to the corresponding adaptive parameter of the phase-locked loop; otherwise, a default parameter value is assigned. The default values ​​of the adaptive parameters are shown in Table 1.

[0035] Table 1: Default values ​​of adaptive parameters for phase-locked loop

[0036] 50 (Hz) 4 8 16 32 0.5 0.1

[0037] In the embodiments of this application, the cascaded delay signal canceller (CDSC) is composed of four stages of series delay signal cancellation units, with each stage having a delay amount Δt. i =1 / (n i ·f c ), where n1 to n4 correspond to the 2nd to 5th major harmonics, respectively, achieving successive filtering. Specifically, the cascaded delay signal cancellation parameters n1, n2, n3, and n4 are assigned to the first, second, third, and fourth delay signal cancellers of the cascaded delay signal canceller, respectively, with the delay amount of the corresponding delay signal canceller being 1 / (n i ·f c ).

[0038] In the embodiments of this application, the improved third-order generalized integrator sets a band-stop pole at zero frequency and generates a pair of quadrature signals at the output for use by the dq converter to eliminate DC offset and higher-order harmonics.

[0039] In embodiments of this application, the PI controller receives a new [k] p ,k i After that, the coefficients are updated through a non-disruptive switching method to ensure continuous operation of the phase-locked loop and stepless output.

[0040] The system queries the intelligent optimization flag for control parameters. If the flag is not enabled, the intelligent optimization unit is not started. If the flag is enabled, the optimization completion flag is set to invalid, a PI control parameter optimization model is constructed, and the Mirage Search Optimization (MSO) algorithm is started to solve for the optimal PI controller parameters. The optimal PI controller parameter results are saved to Flash storage, and the PI parameters are simultaneously transmitted to the PI controller of the single-phase lock-in loop, ensuring that the PI parameters are updated and effective in real time.

[0041] In the embodiments of this application, MSO initializes 20 observation positions, and in the total iteration round T o Alternately perform global search in the upper mirage and local search in the lower mirage, and take the position with the minimum output fitness as the optimal [k]. p ,k i ].

[0042] In the embodiments of this application, the left or right correction direction of the observation position is determined by the random direction flag dir∈{1,2} during the upper mirage stage, and the correction amount decreases linearly with iteration.

[0043] In the embodiments of this application, the objective function of the intelligent optimization unit for control parameters is:

[0044]

[0045] Where Δω(t) is the value of the error Δω output by the single-phase phase-locked loop PI controller at time t, and T is the time required for the phase-locked loop to successfully lock the phase.

[0046] Specifically, the observation positions of the MSO algorithm are initialized. The PI controller parameters are an observation position x = [k p ,k i Initialize 20 observation positions x i 0 =[p i 0 i i 0 ], i∈[1,20], where the subscript i represents the observation position number, and the superscript 0 indicates that the algorithm iteration count is 0, i.e., the initial value. The initialization method is as follows, where rand is a random number between 0 and 1.

[0047]

[0048] The objective function of the mirage search algorithm is set as follows:

[0049]

[0050] Where Δω(t) is the value of the error Δω output by the PI controller of the adaptive single-phase phase-locked loop unit at time t, T is the time required for the phase-locked loop to successfully lock the phase, and the objective function value is the adaptive value. For each initial position x i 0. Calculate the fitness value f(x) based on the objective function. i 0 For each observation with fitness value i∈[1,20], sort the fitness values ​​and assign the observation position with the smallest fitness value to x. best Its fitness value is stored as f best .

[0051] Simulate the formation principle of the upper mirage and globally search for the optimal observation position. Randomly select n observation positions and update the observation positions based on the upper mirage position exploration method.

[0052]

[0053] Where t o Let T be the current iteration of the MSO algorithm. o Let x be the total number of iterations allowed by the MSO algorithm. Update the selected n observation positions x according to the following formula: i observation height h i .

[0054]

[0055] Update the α and β coefficients at the observation position according to the following formula.

[0056]

[0057] The location of the upper mirage is explored and updated, generating a random integer dir = randi(2) of 1 or 2.

[0058] If dir=1, it indicates a left-side update. Observe the position correction amount, as shown in the following formula.

[0059]

[0060] If dir = 2 and α < β < 0.5π, it indicates a right-side update. Observe the position correction amount, as shown in the following formula.

[0061]

[0062] If dir = 2 and β < α < 0.5π, it indicates a right-side update. Observe the position correction amount, as shown in the following formula.

[0063]

[0064] The positions are corrected for the n randomly selected observation positions as follows:

[0065]

[0066] Corrected observation position Find its fitness value based on the objective function. Sort the fitness values ​​and assign the observation position with the smallest fitness value to x. best Its fitness value is stored as f best .

[0067] The optimal observation position is explored locally based on the principle of mirage formation. The observation height h at each observation position is updated as follows:

[0068]

[0069] Update γ The coefficient ω is given by the following formula:

[0070]

[0071] The positional correction for all observation locations based on the mirage layout is as follows:

[0072]

[0073] The position of all observation locations is corrected as follows:

[0074]

[0075] Corrected observation position Find its fitness value based on the objective function. Sort the fitness values ​​and assign the observation position with the smallest fitness value to x. best Its fitness value is stored as f best .

[0076] Reaching the maximum number of iterations T in the MSO algorithm o Then, save x best =[k pbest ,k ibest The parameters are stored in the Flash storage medium, where k pbest k ibest These are the PI controller parameter values ​​intelligently optimized using the MSO algorithm. The optimized PI controller parameter values ​​are then passed to the adaptive single-phase phase-locked loop unit, with the optimization enable flag set to disabled and the optimization complete flag set to enabled.

[0077] In the embodiments of this application, the non-volatile memory is Flash, which simultaneously stores the optimization enable flag, the optimization completion flag, and the history [k]. p ,k i This is used by the system state machine to achieve one-click self-tuning.

[0078] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A single-phase phase-locked loop system with intelligent parameter adjustment, characterized in that, include: The spectrum analysis unit is used to perform real-time frequency domain transformation on single-phase grid voltage and output the fundamental frequency f in real time. c ω c and cascaded delay signal cancellation parameter n i ; The adaptive single-phase phase-locked loop unit, for the single-phase grid voltage signal received by the spectrum analysis unit, sequentially sets up a third-order generalized integrator, a dq converter, a cascaded delay signal canceller (CDSC), a PI controller, a second integrator, and a modulus extractor along the signal path. The cascaded delay signal canceller (CDSC) receives the cascaded delay signal cancellation parameter n. i and at the fundamental frequency f c The angular velocity increment output by the PI controller is used as a reference frequency. ω and fundamental angular velocity ω c The summed values ​​serve as the reference angular velocity at the input of the second integrator. After passing through the second integrator and the modulus extractor, the phase-locked angle θ is determined, and the proportional coefficient k of the PI controller is also considered. p Integral coefficient k i Refreshed online from outside and takes effect immediately; The intelligent optimization unit for control parameters uses the Mirage Search Optimization (MSO) algorithm to iteratively find the optimal [k] parameter. p ,k i And transmit it to the PI controller; The angular velocity increment Δω output by the PI controller is related to the fundamental angular velocity ω. c After addition, the values ​​are input into the third-order generalized integrator as the internal angular velocity parameters of the third-order generalized integrator. The phase-locked angle θ is fed back to the dq converter as the rotation angle calculated internally by the dq converter; The angular velocity increment Δω output by the PI controller is input to the intelligent optimization unit of control parameters as a calculation parameter of the objective function of the intelligent optimization unit of control parameters.

2. The single-phase phase-locked loop system with intelligent parameter adjustment according to claim 1, characterized in that, The spectrum analysis unit processes the sliding circular queue using a 5Hz resolution FFT and extracts the five spectral lines with the largest amplitudes using a five-element min-heap, thereby calculating the fundamental frequency f. c ω c and cascaded delay signal cancellation parameter n i .

3. The single-phase phase-locked loop system with intelligent parameter adjustment according to claim 2, characterized in that, The spectrum analysis unit updates the current fundamental frequency f every 10 minutes. c ω c and cascaded delay signal cancellation parameter n i Write to Flash to restore historical parameters after a power outage and restart.

4. The single-phase phase-locked loop system with intelligent parameter adjustment according to claim 1, characterized in that, The third-order generalized integrator has a stopped pole at zero frequency and generates a pair of quadrature signals at the output for use by the dq converter to eliminate DC offset and higher-order harmonics.

5. The single-phase phase-locked loop system with intelligent parameter adjustment according to claim 1, characterized in that, The cascaded delay signal canceller CDSC consists of four stages of series delay signal cancelling units, with a delay amount Δt in each stage. i =1 / (n i ·f c ), where n1~n4 correspond to the 2nd~5th major harmonics respectively, to achieve successive filtering.

6. The single-phase phase-locked loop system with intelligent parameter adjustment according to claim 1, characterized in that, The PI controller receives a new [k] p ,k i After that, the coefficients are updated through a non-disruptive switching method to ensure continuous operation of the phase-locked loop and stepless output.

7. The single-phase phase-locked loop system with intelligent parameter adjustment according to claim 1, characterized in that, The objective function of the intelligent optimization unit for control parameters is: in ω Error of the single-phase phase-locked loop PI controller output ω is the value at time t, where T is the time required for the phase-locked loop to successfully lock onto a phase.

8. The single-phase phase-locked loop system with intelligent parameter adjustment according to claim 7, characterized in that, The Mirage Search Optimization (MSO) algorithm initializes 20 observation positions and performs iterations in total round T. o Alternately perform global search in the upper mirage and local search in the lower mirage, and take the position with the minimum output fitness as the optimal [k]. p ,k i ].

9. The single-phase phase-locked loop system with intelligent parameter adjustment according to claim 8, characterized in that, In the upper mirage stage, the left or right correction direction of the observation position is determined by the random direction flag dir∈{1,2}, and the correction amount decreases linearly with iteration.

10. The single-phase phase-locked loop system with intelligent parameter adjustment according to claim 1, characterized in that, The intelligent optimization unit for the control parameters will obtain the optimal [k] p ,k i Write to non-volatile memory, which is Flash, and simultaneously store the optimization enable flag, optimization completion flag, and history [k]. p ,k i ].

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