Negative sequence SAI phase-locked loop for tracking power grid voltage
By employing Clarke transform, SAI negative sequence extraction, Park transform, and PI control, a negative sequence SAI phase-locked loop (PLL) has been developed, which solves the problem that traditional PLLs cannot track synchronization signals when the grid voltage is unbalanced. This enables accurate grid synchronization signal tracking under various conditions and broadens the application range of PLLs.
Patent Information
- Application Number
- CN202423118164.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2025-11-28
- Estimated Expiration
- 2034-12-13
AI Technical Summary
Traditional SRF-PLL phase-locked loops cannot be used when the positive and negative sequence fundamental voltages cannot be directly extracted, resulting in the phase-locked loop being unable to accurately track the grid synchronization signal when the grid voltage is unbalanced.
A negative-sequence SAI phase-locked loop composed of a Clarke transform unit, a SAI negative-sequence extraction unit, a Park transform unit, a PI control unit, and an integrator unit is used to extract the three-phase voltage of the power grid through Clarke transform, separate the negative-sequence fundamental voltage using the SAI negative-sequence extraction unit, transform it to the dq coordinate system using Park transform, adjust the synchronization angular frequency using the PI control unit, and obtain the phase angle using the integrator unit.
It can accurately track the grid synchronization signal under both balanced and unbalanced grid conditions, which improves the application range and accuracy of the phase-locked loop. It has a simple structure, low computational load, and excellent performance.
Smart Images
Figure CN223613052U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to the electric network synchronous tracking technical field especially is involved in a kind of negative sequence SAI phase-locked loop of tracking grid voltage. BACKGROUND
[0002] The main function of phase-locked loop is to track and lock the phase of alternating signal, and also provide the frequency and amplitude information of relevant signal when necessary. In photovoltaic power generation and adaptive compensation control strategy, to realize the grid-side active and reactive power control, the grid voltage phase information needs to be acquired dynamically, so the phase-locked loop is used to phase-lock the grid voltage. In practical application, especially in large-scale photovoltaic grid-connected power generation, it is often required to quickly track the operation of the grid, which puts forward higher technical performance requirements for the corresponding phase-locked loop control. It can be seen that, as one of the core technologies of photovoltaic grid-connected power generation and adaptive compensation control strategy, the performance of phase-locked loop directly affects the performance of compensation control.
[0003] Due to the importance of phase-locked loop, more and more scholars have studied it and proposed many control and design schemes of phase-locked loop, so that the performance of phase-locked loop has been continuously improved and enhanced.
[0004] When the grid voltage is balanced, only positive sequence component exists in the grid voltage, at this time the traditional SRF-PLL can accurately track the synchronization signal of the grid voltage, but the traditional SRF-PLL cannot be applied to the case where the positive sequence fundamental voltage cannot be directly extracted. SUMMARY
[0005] The utility model discloses a kind of negative sequence SAI phase-locked loops of tracking grid voltage, to solve the problems mentioned in the background art.
[0006] To achieve the above object, the utility model provides a kind of negative sequence SAI phase-locked loop of tracking grid voltage, including Clarke transformation unit, SAI negative sequence extraction unit, Park transformation unit, PI control unit and integral unit;
[0007] The Clarke transformation unit is used to extract the grid three-phase voltage, and perform Clarke transformation operation on the grid three-phase voltage to obtain the full voltage.
[0008] The SAI negative sequence extraction unit is connected with the Clarke transformation unit, and is used to separate the extracted negative sequence fundamental voltage, and then subtract the negative sequence fundamental voltage from the full voltage to obtain the positive sequence fundamental voltage.
[0009] The Park transformation unit is connected with the SAI negative sequence extraction unit, and is used for Park transformation operation on the positive sequence fundamental voltage to transform the positive sequence fundamental voltage to the dq coordinate system to obtain the d-axis output voltage and the q-axis output voltage.
[0010] The PI control unit is connected with the Park transformation unit, and is used for adjusting the q-axis output voltage to obtain the synchronous angular frequency of the power grid.
[0011] The integral unit is connected with the PI control unit, and is used for integrating the synchronous angular frequency of the power grid to obtain the phase angle of the power grid.
[0012] Preferably, the SAI negative sequence extraction unit adopts the SAI structure.
[0013] Preferably, the SAI structure adopts a band-pass filter with polarity selection characteristics.
[0014] Preferably, the PI control unit adopts a PI regulator.
[0015] Therefore, the negative sequence SAI phase-locked loop for tracking power grid voltage has the following beneficial effects:
[0016] (1) While accurately tracking the power grid voltage signal, the accuracy of tracking the power grid synchronous signal is improved.
[0017] (2) The structure is relatively simple, the thought is relatively clear, the operation amount is relatively small, and the performance is excellent.
[0018] (3) The scheme can not only accurately track the phase under the balanced state of the power grid, but also accurately obtain the power grid synchronous signal when only the negative sequence harmonic can be extracted under specific conditions, greatly widening the application range of the phase-locked loop and improving the accuracy of tracking the power grid synchronous signal.
[0019] The technical scheme of the present application will be further described in detail below with reference to the drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS
[0020] Figure 1 The structure block diagram of the negative sequence SAI phase-locked loop for tracking power grid voltage of the present application embodiment is shown in the figure.
[0021] Figure 2 The positive sequence fundamental voltage calculation schematic diagram is shown in the figure.
[0022] Figure 3 The negative sequence fundamental extraction schematic diagram is shown in the figure.
[0023] Figure 4 The amplitude-frequency characteristic diagram of the negative sequence fundamental is shown in the figure.
[0024] Figure 5 is a positive and negative sequence separation schematic diagram;
[0025] Figure 6 is a traditional SRF-PLL structure block diagram. DETAILED DESCRIPTION
[0026] The technical scheme of the utility model is further described below through the drawings and embodiments.
[0027] Unless otherwise defined, technical terms or scientific terms used in the utility model should be understood as the usual meaning understood by a person with ordinary skills in the art to which the utility model belongs. The "first", "second" and similar words used in the utility model do not represent any order, quantity or importance, but are only used to distinguish different components. "Include" or "contain" and similar words mean that the elements or objects before the word cover the elements or objects listed after the word and their equivalents, and do not exclude other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connection, but can include electrical connection, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to represent the relative positional relationship, and when the absolute position of the described object changes, the relative positional relationship may also change accordingly.
[0028] EMBODIMENT
[0029] As Figure 1 shown, the utility model provides a kind of negative sequence SAI phase-locked loop of tracking power grid voltage, including Clarke transformation unit, SAI negative sequence extraction unit, Park transformation unit, PI control unit and integral unit.
[0030] Clarke transformation unit is used to extract three-phase voltage of power grid, carries out Clarke transformation operation to three-phase voltage of power grid, obtains voltage under αβ coordinate system (i.e. total voltage).
[0031] SAI negative sequence extraction unit, SAI negative sequence extraction unit is connected with Clarke transformation unit, is used to extract negative sequence fundamental voltage, then total voltage is subtracted from negative sequence fundamental voltage, and positive sequence fundamental voltage is obtained.
[0032] Referring to Figure 2The positive and negative sequence fundamental waves of the grid voltage transformed to the alpha-beta axis are extracted respectively, and the extracted negative sequence fundamental wave voltage is subtracted from the full voltage. Since the positive and negative sequence fundamental wave extraction modules of the SAI are in the form of band-pass filters, other positive and negative sequence harmonic voltages of the positive sequence fundamental wave voltage are filtered out in the extraction process of the positive sequence fundamental wave voltage, so that the positive sequence fundamental wave voltage containing less harmonic can be obtained, and the phase-locked loop is performed to obtain a more accurate grid voltage synchronization signal.
[0033] Referring to Figure 3 The negative sequence SAI extraction method is used to extract the negative sequence fundamental wave component of the voltage, and the positive sequence fundamental wave component is extracted by subtracting the negative sequence component from the full voltage, thereby laying a foundation for tracking the grid voltage synchronization signal.
[0034] Referring to Figure 4 It can be seen that there is a resonance peak at the center angle frequency, and the signals of other frequencies are attenuated. The negative sequence component of -50Hz has a polarity selection effect, and the signals of other frequencies have a filtering effect.
[0035] The SAI negative sequence extraction unit adopts the SAI structure. The SAI structure adopts a band-pass filter with a polarity selection characteristic. Due to the polarity selection effect, it can be used to extract the negative sequence fundamental wave voltage. Referring to Figure 5 The SAI negative sequence extraction unit is composed of a series of SAI structures. The grid voltage is first changed from the abc coordinate system to the alpha-beta coordinate system, and then the SAI structure is used to separate and extract the positive sequence voltage of the required frequency by using the polarity selection effect of different frequencies. The SAI negative sequence extraction unit is used to separate the negative sequence fundamental wave voltage, and then the full voltage is subtracted from the negative sequence fundamental wave voltage to obtain the positive sequence fundamental wave voltage, which can be phase-locked, so that the scheme can be applied to the environment requiring fast tracking of the grid voltage.
[0036] The Park transformation unit is connected with the SAI negative sequence extraction unit and is used for Park transformation operation on the extracted positive sequence fundamental wave voltage to transform the voltage to the dq coordinate system to obtain the output voltage of the d-axis and the output voltage of the q-axis.
[0037] The PI control unit is connected with the Park transformation unit and is used for adjusting the output voltage of the q-axis to obtain the synchronization angle frequency of the grid. The PI control unit adopts a PI regulator.
[0038] The integration unit is connected with the PI control unit and is used for integrating the synchronization angle frequency of the grid to obtain the phase angle of the grid.
[0039] The use method steps of the negative sequence SAI phase-locked loop for tracking the grid voltage of the embodiment are as follows:
[0040] The three-phase voltage of the power grid is extracted, and a voltage in an alpha-beta coordinate system, i.e., a total voltage, is obtained through Clarke transformation operation;
[0041] The negative-sequence fundamental voltage is extracted, and the positive-sequence fundamental voltage is obtained by subtracting the negative-sequence fundamental voltage from the total voltage;
[0042] The extracted positive-sequence fundamental voltage is subjected to Park transformation operation, and is transformed into a d-q coordinate system to obtain a d-axis output voltage and a q-axis output voltage;
[0043] The q-axis output voltage is subjected to a PI regulator to obtain a synchronous angular frequency of the power grid, and is subjected to integration to obtain a phase angle of the power grid.
[0044] Figure 6 The method is as follows: the extracted three-phase power grid voltage is subjected to Clarke and Park transformation, and is transformed into a d-q coordinate system; the q-axis output voltage is subjected to a PI regulator to obtain a synchronous angular frequency of the power grid, and is subjected to integration to obtain a phase angle of the power grid. Figure 2 The SAI negative-sequence extraction unit is added on the basis of the prior art, and the positive-sequence fundamental voltage is obtained by removing the negative-sequence voltage component in the power grid in a case where the positive-sequence fundamental voltage cannot be directly extracted; the new phase-locked method can not only accurately obtain the synchronous signal of the power grid in a three-phase balanced power grid state, but also widens the application range of the phase-locked loop.
[0045] Therefore, the negative-sequence SAI phase-locked loop for tracking the voltage of the power grid can accurately track the voltage signal of the power grid, and improves the accuracy of tracking the synchronous signal of the power grid.
[0046] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application but not to limit it, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.
Claims
1. A negative sequence SAI phase locked loop for tracking grid voltage, characterized by: The Clarke transformation unit, the SAI negative sequence extraction unit, the Park transformation unit, the PI control unit and the integration unit are included. The Clarke transformation unit is configured to extract three-phase grid voltages and perform Clarke transformation on the three-phase grid voltages to obtain total voltages. The SAI negative sequence extraction unit is connected with the Clarke transformation unit and configured to extract a negative sequence fundamental voltage, and subtract the negative sequence fundamental voltage from the total voltages to obtain a positive sequence fundamental voltage. The Park transformation unit is connected with the SAI negative sequence extraction unit and configured to perform Park transformation on the positive sequence fundamental voltage to transform the positive sequence fundamental voltage to a dq coordinate system to obtain a d-axis output voltage and a q-axis output voltage. The PI control unit is connected with the Park transformation unit and configured to adjust the q-axis output voltage to obtain a synchronous angular frequency of the grid. The integration unit is connected with the PI control unit and configured to integrate the synchronous angular frequency of the grid to obtain a phase angle of the grid.
2. A negative sequence SAI phase locked loop for tracking the voltage of an electrical grid according to claim 1, characterized in that: The SAI negative sequence extraction unit adopts an SAI structure.
3. A negative sequence SAI phase locked loop for tracking the voltage of an electrical grid according to claim 2, characterized in that: The SAI structure adopts a band-pass filter with a polarity selection characteristic.
4. A negative sequence SAI phase locked loop for tracking the voltage of an electrical grid according to claim 1, characterized in that: The PI control unit adopts a PI regulator.