A mode-switching-based transient ride-through phase-locked loop and a working method thereof

Abstract

The application discloses a transient crossing phase-locked loop based on mode switching and a use method thereof, and belongs to the field of phase-locked loop control. The transient crossing phase-locked loop based on mode switching comprises a first sub phase-locked loop, a detection module, a hybrid filter and a state switch. The detection module is arranged to detect transient changes and phase jump angles of a controlled power grid. When transient changes occur in the controlled power grid, the state switch is used for switching, so that the voltage variation of an adder input into the first sub phase-locked loop is 0, the influence of the transient changes of the power grid on the output of the phase-locked angle of the phase-locked loop is avoided, and the phase jump angle is added to the phase-locked angle output by the first sub phase-locked loop to compensate the phase-locked angle, so that the timely tracking of the phase of the power grid is realized. The hybrid filter is further arranged to filter out harmonics.

Description

Technical Field

[0001] This invention relates to the field of phase-locked loop (PLL) control technology, and in particular to a transient traversal PLL based on mode switching and its operating method. Background Technology

[0002] Over the past two decades, the proportion of renewable energy in power systems has continued to increase. These renewable energy sources are typically connected to the power system by grid-connected converters, which use phase-locked loops (PLLs) to synchronize with the power system. The accurate grid phase detected by the PLL plays a crucial role in the normal operation of the grid-connected converters.

[0003] Power quality problems are prevalent in current power systems, such as harmonics, voltage imbalance, and voltage dips. Furthermore, with the integration of a high proportion of renewable energy, power systems are increasingly exhibiting weak grid characteristics, making phase jumps a new power quality issue. These power quality problems pose a challenge to PLLs in detecting power system phases; therefore, many optimizations to PLLs have been proposed in recent years to address different power quality problems in power systems.

[0004] Current research on PLLs mainly focuses on optimizing the transfer function to achieve better transient response. However, the integral term in the transfer function inevitably causes delays in the PLL's transient process. Furthermore, phase jumps, a power quality issue, have received little attention. It's worth noting that phase jumps can cause significant overshoot errors in the frequency and phase of the PLL's output during transients. Therefore, avoiding delays in the transient process and avoiding overshoot errors caused by phase jumps has become a pressing technical problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a transient crossover phase-locked loop based on mode switching and its working mode, so as to avoid the delay of the transient process and track the phase of the power system within one cycle after the phase jump of the power system, thereby avoiding the overshoot error caused by the phase jump.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A transient traversal phase-locked loop based on mode switching includes: a first sub-phase-locked loop, a detection module, a hybrid filter, and a state switch; the first sub-phase-locked loop is a phase-locked loop based on a synchronization reference coordinate system;

[0008] The three first input terminals of the detection module are respectively connected to the three-phase voltage input terminals of the first sub-phase-locked loop; the two second input terminals of the detection module are respectively connected to the d-axis voltage output terminal and the q-axis voltage output terminal of the Park transformation module of the first sub-phase-locked loop.

[0009] The first output terminal of the detection module is connected to the control terminal of the status switch, and the second output terminal of the detection module is connected to the output terminal of the first sub-phase-locked loop through an adder;

[0010] The hybrid filter is positioned between the Clark transform module and the Park transform module of the first sub-phase-locked loop;

[0011] The first input terminal of the state switch is connected to the output terminal of the PI module of the first sub-phase-locked loop, and the second input terminal of the state switch is used to input a zero-value voltage; the output terminal of the state switch is connected to the input terminal of the adder of the first sub-phase-locked loop.

[0012] The detection module is used to detect the voltage transient change rate and phase jump angle of the controlled power grid; the voltage transient change rate is output to the status switch through the first output terminal of the detection module, and the phase jump angle is output to the adder set at the output terminal of the first sub-phase-locked loop through the second output terminal of the detection module.

[0013] The state switch is used to connect the input terminal of the adder of the first sub-phase-locked loop to the second input terminal of the state switch when the voltage transient change rate of the controlled power grid is greater than a preset threshold, so that the adder of the first sub-phase-locked loop inputs a zero voltage value. After one power grid frequency cycle, the phase jump angle of the controlled power grid is added to the phase-locked angle output by the first sub-phase-locked loop, and the input terminal of the adder of the first sub-phase-locked loop is connected to the first input terminal of the state switch.

[0014] The phase jump angle is used to compensate for the phase-locked angle output by the first sub-phase-locked loop;

[0015] The hybrid filter is used to filter the voltage output by the Clark transform module of the first sub-phase-locked loop.

[0016] Optionally, the detection module includes: a second sub-phase-locked loop and a detection unit; the second sub-phase-locked loop is a phase-locked loop based on a synchronization reference coordinate system;

[0017] The three input terminals of the second sub-phase-locked loop are respectively connected to the three-phase voltage input terminals of the first sub-phase-locked loop;

[0018] The first input terminal of the detection unit is connected to the d-axis voltage output terminal or the q-axis voltage output terminal of the abc / dq conversion module of the second sub-phase-locked loop. The two second input terminals of the detection unit are respectively connected to the d-axis voltage output terminal and the q-axis voltage output terminal of the Park conversion module of the first sub-phase-locked loop. The first output terminal of the detection unit is connected to the control terminal of the state switch, and the second output terminal of the detection unit is connected to the output terminal of the first sub-phase-locked loop through an adder.

[0019] Optionally, the voltage transient change rate detected by the detection module is: or

[0020] Among them, S tri Let ΔU be the rate of change of voltage transient. fd The change in the d-axis voltage output by the abc / dq conversion module of the second sub-phase-locked loop is given by Δt, where ΔU is the sampling time interval. fq This refers to the change in the q-axis voltage output by the abc / dq conversion module of the second sub-phase-locked loop.

[0021] Optionally, the phase transition angle detected by the detection module is:

[0022] Where Δθ is the phase jump angle, U sq + and U sd + These are the q-axis and d-axis voltages output by the Park converter module of the first sub-phase-locked loop, respectively.

[0023] Optionally, the hybrid filter includes a cascaded dual generalized second-order integrator and a notch filter.

[0024] Optionally, the causes of transient changes in the controlled grid voltage include: harmonics, voltage imbalance, voltage dips, and phase jumps.

[0025] A method for transient traversal of a phase-locked loop based on mode switching, the method being applied to the aforementioned transient traversal of a phase-locked loop based on mode switching, the method comprising the following steps:

[0026] Acquire the three-phase voltage signals of the controlled power grid;

[0027] The Clark transformation module based on the first sub-phase-locked loop transforms the three-phase voltage signal to obtain the first α-axis voltage and the first β-axis voltage.

[0028] The second α-axis voltage and the second β-axis voltage are obtained by filtering the first α-axis voltage and the first β-axis voltage using a hybrid filter.

[0029] The Park transformation module based on the first phase-locked loop transforms the second α-axis voltage and the second β-axis voltage to obtain the first d-axis voltage and the first q-axis voltage.

[0030] The detection module detects the three-phase voltage signal to obtain the voltage transient change rate and phase jump angle of the controlled power grid.

[0031] When the voltage transient change rate of the controlled power grid exceeds a preset threshold, the input terminal of the adder of the first sub-phase-locked loop is connected to the second input terminal of the state switch, so that the adder of the first sub-phase-locked loop receives a zero voltage. After one power grid frequency cycle, the phase jump angle of the controlled power grid is added to the phase-locked angle output by the first sub-phase-locked loop, and the input terminal of the adder of the first sub-phase-locked loop is connected to the first input terminal of the state switch.

[0032] Optionally, the step of detecting the three-phase voltage signal based on the detection module to obtain the voltage transient change rate and phase jump angle of the controlled power grid specifically includes:

[0033] The abc / dq conversion module based on the second sub-phase-locked loop converts the three-phase voltage signal to obtain the second d-axis voltage and the second q-axis voltage.

[0034] Calculate the voltage transient rate of change of the controlled power grid based on the second d-axis voltage or the second q-axis voltage;

[0035] Calculate the phase transition angle of the controlled power grid based on the first d-axis voltage and the first q-axis voltage.

[0036] Optionally, the step of calculating the voltage transient rate of change of the controlled power grid based on the second d-axis voltage or the second q-axis voltage specifically includes:

[0037] Based on the real-time acquired second d-axis voltage or second q-axis voltage, calculate the change in d-axis voltage or q-axis voltage output by the abc / dq conversion module of the second sub-phase-locked loop;

[0038] Based on the change in d-axis voltage or q-axis voltage output from the abc / dq conversion module of the second sub-phase-locked loop, the voltage transient rate of change is calculated as follows: or

[0039] Among them, S tri Let ΔU be the rate of change of voltage transient. fd The change in the d-axis voltage output by the abc / dq conversion module of the second sub-phase-locked loop is given by Δt, where ΔU is the sampling time interval. fq This refers to the change in the q-axis voltage output by the abc / dq conversion module of the second sub-phase-locked loop.

[0040] Optionally, based on the first d-axis voltage and the first q-axis voltage, the phase transition angle of the controlled power grid is calculated as follows:

[0041] Where Δθ is the phase jump angle, U sq + and U sd + These are the q-axis voltage and d-axis voltage output by the Park converter module of the first sub-phase-locked loop, namely the first q-axis voltage and the first d-axis voltage.

[0042] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0043] This invention discloses a transient-crossing phase-locked loop (PLL) based on mode switching and its usage method, comprising: a first sub-PLL, a detection module, a hybrid filter, and a state switch; the first sub-PLL is a PLL based on a synchronous reference coordinate system. This invention sets up a detection module to detect transient changes and phase jump angles of the controlled power grid. When a transient change occurs in the controlled power grid, a state switch is used to switch the input voltage change of the adder in the first sub-PLL to zero, avoiding the influence of the power grid's transient changes on the PLL's phase-locked loop output angle. Furthermore, this invention adds the phase jump angle to the output phase-locked loop output angle for compensation, achieving timely phase tracking of the power grid. This invention also incorporates a hybrid filter for harmonic filtering. This invention avoids delays in the transient process and tracks the power system phase within one cycle after a phase jump, avoiding overshoot errors caused by phase jumps. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a structural diagram of a transient traversal phase-locked loop based on mode switching provided in an embodiment of the present invention;

[0046] Figure 2 This is a structural diagram of a phase-locked loop based on a synchronous reference coordinate system provided in an embodiment of the present invention;

[0047] Figure 3 A flowchart of the working method of transient traversal phase-locked loop based on mode switching provided in an embodiment of the present invention;

[0048] Figure 4A comparison chart of tracking effects provided in an embodiment of the present invention; Figure 4 (a) in the figure is a comparison of the overshoot error of different phase-locked loops. Figure 4 (b) in the figure shows the voltage phase tracking effect of different phase-locked loops. Detailed Implementation

[0049] 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.

[0050] The purpose of this invention is to provide a transient crossover phase-locked loop based on mode switching and its working mode, so as to avoid the delay of the transient process and track the phase of the power system within one cycle after the phase jump of the power system, thereby avoiding the overshoot error caused by the phase jump.

[0051] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0052] Example 1

[0053] like Figure 1 As shown, Embodiment 1 of the present invention provides a transient crossover phase-locked loop based on mode switching, comprising: a first sub-phase-locked loop, a detection module, a hybrid filter, and a state switch; the first sub-phase-locked loop is a phase-locked loop based on a synchronous reference frame-phase-locked loop (SRF-PLL). Figure 2 As shown, the phase-locked loop based on the synchronous reference coordinate system includes a Clark transform module, a Park transform module, a PI module, an adder, and an integrator connected in sequence.

[0054] like Figure 1As shown, the three first input terminals of the detection module are respectively connected to the three-phase voltage input terminals of the first sub-phase-locked loop; the two second input terminals of the detection module are respectively connected to the d-axis voltage output terminal and the q-axis voltage output terminal of the Park transform module of the first sub-phase-locked loop; the first output terminal of the detection module is connected to the control terminal of the state switch, and the second output terminal of the detection module is connected to the output terminal of the first sub-phase-locked loop through an adder; the hybrid filter is set between the Clark transform module and the Park transform module of the first sub-phase-locked loop; the first input terminal of the state switch is connected to the output terminal of the PI module of the first sub-phase-locked loop, and the second input terminal of the state switch is used to input a zero-value voltage; the output terminal of the state switch is connected to the input terminal of the adder of the first sub-phase-locked loop; the detection module is used to detect the voltage transient change rate and phase of the controlled power grid. The phase transition angle; the voltage transient change rate is output to the state switch through the first output terminal of the detection module, and the phase transition angle is output to the adder set at the output terminal of the first sub-phase-locked loop through the second output terminal of the detection module; the state switch is used to connect the input terminal of the adder of the first sub-phase-locked loop to the second input terminal of the state switch when the voltage transient change rate of the controlled power grid is greater than a preset threshold, so that the adder of the first sub-phase-locked loop inputs a zero voltage value, and after one power grid frequency cycle, the phase transition angle of the controlled power grid is added to the phase-locked angle output by the first sub-phase-locked loop, and the input terminal of the adder of the first sub-phase-locked loop is connected to the first input terminal of the state switch; the phase transition angle is used to compensate the phase-locked angle output by the first sub-phase-locked loop; the hybrid filter is used to filter the voltage output by the Clark transformation module of the first sub-phase-locked loop.

[0055] The detection module includes a second sub-phase-locked loop (PLL) and a detection unit. The second sub-PLL is a PLL based on a synchronous reference coordinate system. The three input terminals of the second sub-PLL are respectively connected to the three-phase voltage input terminals of the first sub-PLL. The first input terminal of the detection unit is connected to the d-axis voltage output terminal or the q-axis voltage output terminal of the abc / dq conversion module of the second sub-PLL. The two second input terminals of the detection unit are respectively connected to the d-axis voltage output terminal and the q-axis voltage output terminal of the Park conversion module of the first sub-PLL. The first output terminal of the detection unit is connected to the control terminal of the state switch, and the second output terminal of the detection unit is connected to the output terminal of the first sub-PLL via an adder. The SRF-PLL (i.e., the second sub-PLL) in the detection module is called a fast PLL, which can respond quickly to changes in the grid voltage. The dq component U output by the fast PLL... fd and U fq It is an important criterion for the detection algorithm.

[0056] The voltage transient change rate detected by the detection module is: or

[0057] Among them, S tri Let ΔU be the rate of change of voltage transient. fd The change in the d-axis voltage output by the abc / dq conversion module of the second sub-phase-locked loop is given by Δt, where ΔU is the sampling time interval. fq This refers to the change in the q-axis voltage output by the abc / dq conversion module of the second sub-phase-locked loop.

[0058] The phase transition angle detected by the detection module is: Where Δθ is the phase jump angle, U sq + and U sd + These are the q-axis and d-axis voltages output by the Park transform module of the first sub-phase-locked loop, respectively. Figure 1 The detection algorithm in the algorithm is an algorithm that completes the voltage transient change rate and phase jump angle.

[0059] After the acquired three-phase voltage signals Ua, Ub, and Uc are input into the TRT-PLL, they first undergo Clark and Park transformations to obtain the α-axis voltage U. α β-axis voltage U β and d-axis voltage U fd q-axis voltage U fq , among which, Figure 1 Middle,U α and U β The α-axis voltage and β-axis voltage output by the Clark converter module of the first sub-phase-locked loop are respectively. fd and U fq For the d-axis and q-axis voltages of the abc / dq conversion module of the second sub-phase-locked loop:

[0060]

[0061]

[0062] In the formula, ω0 is the fundamental angular frequency. and These represent the amplitude and phase angle of the fundamental positive-sequence component, respectively, T. αβ Here is the transformation matrix of the Clark transform. and These represent the amplitude and phase angle of the fundamental negative-sequence component, respectively, where ω0 is the fundamental angular velocity, and U... n and θ n These represent the amplitude and phase angle of the harmonic components, respectively. The angle output by the SRF-PLL (the second sub-phase-locked loop in formula (2)) can be expressed as:

[0063]

[0064] As can be seen from Formula 1, It is the angular frequency output by the second sub-phase-locked loop, which, after Clark transformation, is U. α U β It only includes the fundamental positive-sequence component, the fundamental negative-sequence component, the (6y-1)th negative-sequence harmonic, and the (6y+1)th positive-sequence harmonic, where y takes integer values ​​such as 1, 2, and 3. As can be seen from Formula 2, after the Park transform, U... fd U fq It will include constant components, second negative sequence components, and ±6y harmonic components.

[0065] Among them, U in the first sub-phase-locked loop α + U β + To filter the α-axis and β-axis voltages output by the Clark transform module of the first sub-phase-locked loop, the output α-axis voltage fundamental frequency positive sequence component and β-axis voltage fundamental frequency positive sequence component are obtained. After the Park transform (the transform formula is shown in formula (2)), these components become U. sd + U sq + .

[0066] The abc / dq transformation module in the second sub-phase-locked loop actually includes two processes: Clark transformation (formula (1)) and Park transformation (formula (2)).

[0067] Therefore, this embodiment of the invention sets the hybrid filter to include a cascaded dual second-order generalized integrator (DSOGI) and a notch filter (NF). The purpose is to combine U... α U β The fundamental negative-sequence component, the (6y-1)th negative-sequence harmonic, and the (6y+1)th positive-sequence harmonic are filtered out, with y taking integer values ​​such as 1, 2, and 3. The transfer functions of DSOGI and NF are:

[0068]

[0069]

[0070] In the formula, k is the attenuation coefficient of DSOGI, n is the order of harmonics, ξ is the damping coefficient, s is the state variable, and j is the imaginary unit.

[0071] The causes of transient changes in the voltage of the controlled power grid include: harmonics, voltage imbalance, voltage dips, and phase jumps. The expressions for these four causes are:

[0072]

[0073] Equation (6) indicates that whenever the grid voltage is subjected to the following four conditions: harmonics, voltage imbalance, voltage drop, and phase jump, the dq component output by the fast PLL (the abc / dq conversion module of the second sub-phase-locked loop) will undergo instantaneous changes. Therefore, if ΔU fd / Δt or ΔU fq If / Δt is greater than the set threshold, the grid voltage can be considered abnormal. Specifically, in formula (6), ΔU fdh and ΔU fqh These are the outputs of the abc / dq conversion module of the second sub-phase-locked loop when harmonics suddenly appear in the three-phase voltage. fd and U fq The instantaneous change value, ΔU fdi and ΔU fqi These are the outputs of the abc / dq conversion module of the second sub-phase-locked loop when a sudden unbalanced voltage occurs in the three-phase voltage. fd and U fq The instantaneous change value, ΔU fdvs and ΔU fqvs These represent the outputs of the abc / dq conversion module of the second sub-phase-locked loop when a sudden voltage drop occurs in the three-phase voltage. fd and U fq The instantaneous change value, ΔU fdpj and ΔU fqpj These are the outputs of the abc / dq conversion module of the second sub-phase-locked loop when a sudden phase transition occurs in the three-phase voltage. fd and U fq The instantaneous change value, where ω is the angular frequency of the fundamental frequency.

[0074] Example 2

[0075] Embodiment 2 of the present invention provides a method for transient traversal of a phase-locked loop based on mode switching. This method is applied to the transient traversal of the phase-locked loop based on mode switching described in Embodiment 1, such as... Figure 3 As shown, the method includes the following steps:

[0076] Collect the three-phase voltage signals of the controlled power grid.

[0077] The Clark transformation module based on the first sub-phase-locked loop transforms the three-phase voltage signal to obtain the first α-axis voltage and the first β-axis voltage.

[0078] The second α-axis voltage and the second β-axis voltage are obtained by filtering the first α-axis voltage and the first β-axis voltage using a hybrid filter.

[0079] The Park transformation module based on the first phase-locked loop transforms the second α-axis voltage and the second β-axis voltage to obtain the first d-axis voltage and the first q-axis voltage.

[0080] The detection module detects the three-phase voltage signals to obtain the voltage transient change rate and phase jump angle of the controlled power grid.

[0081] Determine whether the voltage transient change rate of the controlled power grid is greater than a preset threshold, and obtain the determination result.

[0082] If the judgment result indicates yes, then the input terminal of the adder of the first sub-phase-locked loop is connected to the second input terminal of the state switch, so that the adder of the first sub-phase-locked loop receives a zero voltage. After one grid frequency cycle, the phase jump angle of the controlled grid is added to the phase-locked angle output by the first sub-phase-locked loop, and the input terminal of the adder of the first sub-phase-locked loop is connected to the first input terminal of the state switch.

[0083] Specifically, U in the first sub-phase-locked loop α + U β + To filter the α-axis and β-axis voltages output by the Clark transform module of the first sub-phase-locked loop, the resulting fundamental frequency positive-sequence components of the α-axis and β-axis voltages are transformed by the Park transform (see formula 2 for the transformation formula) into U. sd + U sq + Set the input quantity for closed-loop control to U. sq + In the initial state, the state switch is connected to the PI module, Δθ is 0, therefore the input quantity U sq + The feedback quantity is generated after passing through a PI module, a status switch, an adder, and an integrator (1 / s). As a reference value for the Park transform.

[0084] The detection module first differentiates the dq component of the fast PLL and compares the result with a set threshold. Next, once the differentiation result exceeds the threshold, the detection module sends a trigger signal to the state switch. This signal controls the state switch to switch from the PI module to a voltage connected to zero, which remains connected for one grid frequency cycle, i.e., 20ms. During this period, the transient crossover PLL based on mode switching continues to output the correct phase angle obtained from the integral of the angular frequency ω0. Before switching the status switch back to the PI module, it is necessary to determine whether a phase transition has occurred. If so, the phase transition angle needs to be calculated and accumulated. In the middle. Δθ can be calculated in the following way.

[0085]

[0086] The final output of the transient crossover phase-locked loop based on mode switching is the accumulated phase angle.

[0087] Example 3

[0088] To illustrate the effects of the present invention, the following simulation experiment is provided in Embodiment 3 of the present invention:

[0089] When harmonics, voltage imbalance, or voltage dips occur in the power grid (controlled power grid), the transient pass-through phase-locked loop (PLL) based on mode switching provided in this embodiment of the invention (corresponding to...) Figure 4 The TRT-PLL in the system can instantly identify these abnormal situations using the detection module and send a trigger signal to the status switch. The status switch is flipped to 0, and the transient pass-through phase-locked loop based on mode switching changes from closed-loop operation to open-loop operation. In this way, the output phase angle during the transient process of the transient pass-through phase-locked loop based on mode switching continues to be obtained from the integral of the angular frequency ω0. As a result, the output phase angle of the transient pass-through phase-locked loop based on mode switching is accurate without any fluctuation or delay. When the transient process ends, after one power grid cycle, the status switch is flipped back to the PI module, and the transient pass-through phase-locked loop based on mode switching returns to closed-loop operation. When a phase jump occurs in the power grid, the transient pass-through phase-locked loop (PLL) based on mode switching can instantly identify the abnormal situation using the detection module. It sends a trigger signal to the status switch, which is then switched to 0 (i.e., input voltage zero). The PLL based on mode switching switches from closed-loop operation to open-loop operation. At this time, the output phase angle of the PLL based on mode switching continues to be obtained from the integral of the angular frequency ω0. After one power grid cycle, the detection module calculates the angle of the phase jump and adds it to the output phase angle of the PLL based on mode switching. The status switch is then switched back to the PI module, and the PLL based on mode switching switches back to closed-loop operation. This will enable the PLL based on mode switching to accurately track the power grid voltage phase after one power grid cycle.

[0090] Figure 4 It provides the PLL's estimated grid frequency and phase when the grid voltage undergoes a 45° phase transition. From Figure 4(a) It can be seen that the estimated frequency of the mode-switching-based transient crossover phase-locked loop (TRT-PLL) remains at 50 Hz throughout the transient. However, the hybrid filter-based phase-locked loop (HF-PLL) and the quasi-first-order phase-locked loop (QT1-PLL) both exhibit overmodulation of approximately 4 Hz before recovering to 50 Hz after 0.1 s. Figure 4 The results shown in (b) indicate that Figure 4 In (b), θ1, θ2, and θ3 are the phases tracked by QT1-PLL, HF-PLL, and TRT-PLL, respectively. TRT-PLL can track the correct grid phase in just one cycle, while HF-PLL and QT1-PLL require three cycles to achieve grid phase tracking.

[0091] As can be seen from the above embodiments, the present invention avoids the delay of the transient process and tracks the phase of the power system within one cycle after the phase jump of the power system, thus avoiding overshoot error caused by the phase jump.

[0092] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0093] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A transient passthrough phase-locked loop based on mode switching, characterized in that, include: The system comprises a first sub-phase-locked loop, a detection module, a hybrid filter, and a status switch; the first sub-phase-locked loop is a phase-locked loop based on a synchronization reference coordinate system. The three first input terminals of the detection module are respectively connected to the three-phase voltage input terminals of the first sub-phase-locked loop; the two second input terminals of the detection module are respectively connected to the d-axis voltage output terminal and the q-axis voltage output terminal of the Park transformation module of the first sub-phase-locked loop. The first output terminal of the detection module is connected to the control terminal of the status switch, and the second output terminal of the detection module is connected to the output terminal of the first sub-phase-locked loop through an adder; The hybrid filter is positioned between the Clark transform module and the Park transform module of the first sub-phase-locked loop; The first input terminal of the state switch is connected to the output terminal of the PI module of the first sub-phase-locked loop, and the second input terminal of the state switch is used to input a zero-value voltage; the output terminal of the state switch is connected to the input terminal of the adder of the first sub-phase-locked loop. The detection module is used to detect the voltage transient change rate and phase jump angle of the controlled power grid; the voltage transient change rate is output to the status switch through the first output terminal of the detection module, and the phase jump angle is output to the adder set at the output terminal of the first sub-phase-locked loop through the second output terminal of the detection module. The state switch is used to connect the input terminal of the adder of the first sub-phase-locked loop to the second input terminal of the state switch when the voltage transient change rate of the controlled power grid is greater than a preset threshold, so that the adder of the first sub-phase-locked loop inputs a zero voltage value. After one power grid frequency cycle, the phase jump angle of the controlled power grid is added to the phase-locked angle output by the first sub-phase-locked loop, and the input terminal of the adder of the first sub-phase-locked loop is connected to the first input terminal of the state switch. The phase jump angle is used to compensate for the phase-locked angle output by the first sub-phase-locked loop; The hybrid filter is used to filter the voltage output by the Clark transform module of the first sub-phase-locked loop.

2. The transient pass-through phase-locked loop based on mode switching according to claim 1, characterized in that, The detection module includes: a second sub-phase-locked loop and a detection unit; the second sub-phase-locked loop is a phase-locked loop based on a synchronous reference coordinate system; The three input terminals of the second sub-phase-locked loop are respectively connected to the three-phase voltage input terminals of the first sub-phase-locked loop; The first input terminal of the detection unit is connected to the d-axis voltage output terminal or the q-axis voltage output terminal of the abc / dq conversion module of the second sub-phase-locked loop. The two second input terminals of the detection unit are respectively connected to the d-axis voltage output terminal and the q-axis voltage output terminal of the Park conversion module of the first sub-phase-locked loop. The first output terminal of the detection unit is connected to the control terminal of the state switch, and the second output terminal of the detection unit is connected to the output terminal of the first sub-phase-locked loop through an adder.

3. The transient crossover phase-locked loop based on mode switching according to claim 1 or 2, characterized in that, The voltage transient change rate detected by the detection module is: or Among them, S tri Let ΔU be the rate of change of voltage transient. fd The change in the d-axis voltage output by the abc / dq conversion module of the second sub-phase-locked loop is given by Δt, where ΔU is the sampling time interval. fq This refers to the change in the q-axis voltage output by the abc / dq conversion module of the second sub-phase-locked loop.

4. The transient crossover phase-locked loop based on mode switching according to claim 1 or 2, characterized in that, The phase transition angle detected by the detection module is: Where Δθ is the phase jump angle, U sq + and U sd + These are the q-axis and d-axis voltages output by the Park converter module of the first sub-phase-locked loop, respectively.

5. The transient pass-through phase-locked loop based on mode switching according to claim 1, characterized in that, The hybrid filter includes a cascaded dual generalized second-order integrator and a notch filter.

6. The transient pass-through phase-locked loop based on mode switching according to claim 1, characterized in that, The causes of transient changes in the voltage of the controlled power grid include: harmonics, voltage imbalance, voltage dips, and phase jumps.

7. A method for transient traversal of a phase-locked loop based on mode switching, characterized in that, The method is applied to the transient crossover phase-locked loop based on mode switching as described in any one of claims 1-6, and the method includes the following steps: Acquire the three-phase voltage signals of the controlled power grid; The Clark transformation module based on the first sub-phase-locked loop transforms the three-phase voltage signal to obtain the first α-axis voltage and the first β-axis voltage. The second α-axis voltage and the second β-axis voltage are obtained by filtering the first α-axis voltage and the first β-axis voltage using a hybrid filter. The Park transformation module based on the first sub-phase-locked loop transforms the second α-axis voltage and the second β-axis voltage to obtain the first d-axis voltage and the first q-axis voltage. The detection module detects the three-phase voltage signal to obtain the voltage transient change rate and phase jump angle of the controlled power grid. When the voltage transient change rate of the controlled power grid exceeds a preset threshold, the input terminal of the adder of the first sub-phase-locked loop is connected to the second input terminal of the state switch, so that the adder of the first sub-phase-locked loop receives a zero voltage. After one power grid frequency cycle, the phase jump angle of the controlled power grid is added to the phase-locked angle output by the first sub-phase-locked loop, and the input terminal of the adder of the first sub-phase-locked loop is connected to the first input terminal of the state switch.

8. The working method of transient traversal phase-locked loop based on mode switching according to claim 7, characterized in that, The detection module detects the three-phase voltage signal to obtain the voltage transient change rate and phase jump angle of the controlled power grid, specifically including: The abc / dq conversion module based on the second sub-phase-locked loop converts the three-phase voltage signal to obtain the second d-axis voltage and the second q-axis voltage. Calculate the voltage transient rate of change of the controlled power grid based on the second d-axis voltage or the second q-axis voltage; Calculate the phase transition angle of the controlled power grid based on the first d-axis voltage and the first q-axis voltage.

9. The working method of transient traversal phase-locked loop based on mode switching according to claim 8, characterized in that, The calculation of the voltage transient rate of change of the controlled power grid based on the second d-axis voltage or the second q-axis voltage specifically includes: Based on the real-time acquired second d-axis voltage or second q-axis voltage, calculate the change in d-axis voltage or q-axis voltage output by the abc / dq conversion module of the second sub-phase-locked loop; Based on the change in d-axis voltage or q-axis voltage output from the abc / dq conversion module of the second sub-phase-locked loop, the voltage transient rate of change is calculated as follows: or Among them, S tri Let ΔU be the rate of change of voltage transient. fd The change in the d-axis voltage output by the abc / dq conversion module of the second sub-phase-locked loop is given by Δt, where ΔU is the sampling time interval. fq This refers to the change in the q-axis voltage output by the abc / dq conversion module of the second sub-phase-locked loop.

10. The working method of transient traversal phase-locked loop based on mode switching according to claim 8, characterized in that, Based on the first d-axis voltage and the first q-axis voltage, the phase transition angle of the controlled power grid is calculated as follows: Where Δθ is the phase jump angle, U sq + and U sd + These are the q-axis voltage and d-axis voltage output by the Park converter module of the first sub-phase-locked loop, namely the first q-axis voltage and the first d-axis voltage.

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