A method for detecting sudden change of angle between three-phase power grid and restoring power

Abstract

The invention discloses a method for detecting angle mutation of a three-phase power grid and restoring power. The method comprises the following steps: firstly configuring a digital signal processor and a clock timer, wherein the clock timer changes its count according to a preset clock frequency and a preset clock variable; configuring a voltage zero-crossing interrupt and a counter for each phase, wherein the counter obtains the clock timer count when the voltage of the phase is interrupted by zero-crossing; obtaining and storing the angle offset between the phases, and configuring an angle mutation label; setting an angle offset reference value, and determining an angle mutation if the difference between the angle offset between any two phases and the angle offset reference value is greater than a first preset comparison value in M ​​consecutive cycles; and saving the on-site state of the system until the on-site state is restored after the angle mutation ends, thereby realizing a response to power grid fluctuations and zero current angle crossing, avoiding damage to inverter equipment or a machine off-grid state caused by the angle mutation, and improving the adaptive capability of the inverter equipment to power grid fluctuations.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic grid-connected power generation and inverters, and in particular to a method for detecting sudden changes in the grid angle of a three-phase power grid and recovering power for adaptively controlling the grid angle of a photovoltaic product. Background Art

[0002] Due to the influence of environmental and weather factors, the working process of the photovoltaic power generation system grid side often has unavoidable fluctuations. The specific manifestation of the impact of this fluctuation is that during the operation of the grid side, its working voltage, phase angles, etc. will have sudden changes.

[0003] Taking the grid angle as an example, the grid angle mutation is also called angle crossing. In a conventional three-phase grid, each phase of electricity may experience the aforementioned mutation separately or simultaneously. Depending on the size of the mutation angle in the mutation situation and the length of the angle mutation (angle crossing) time, the impact on the system and inverter will also be different.

[0004] Under the existing technology, the photovoltaic power generation inverter system design does not consider special response to angle mutation, and only relies on the inverter equipment's own hard resistance adjustment. The requirement for the inverter's own hard resistance adjustment is only that the angle mutation or the through device equipment does not enter protection and the system does not go off the grid. System entry protection refers to the shutdown and off-grid action caused by triggering overcurrent and overvoltage, and the relay will be in the disconnected state in the off-grid state.

[0005] The response method that relies on the inverter's own hard resistance adjustment can be applied in most scenarios where the sudden change angle is small or the sudden change ride-through time is short. However, when the sudden change angle is large and / or the sudden change ride-through time is long, it is very easy to fail to restore the power after the machine protection is disconnected from the grid if the inverter is relied on to adjust the hard resistance. This is because the phase-locked loop obtains the wrong angle value when the angle sudden change rides through the device, especially the unbalanced angle sudden change, which will lead to a large output current during the ride-through period and damage the inverter.

[0006] In view of the fact that in actual applications, the time when on-site photovoltaic conditions and power grid systems produce sudden abnormalities is uncertain, and considering that the angle mutation projects in some countries' certification also require that the photovoltaic inverter does not go off the grid, and that the equipment can quickly restore the power before the mutation after the angle mutation, a new three-phase power grid angle mutation detection method and a corresponding power grid power recovery method should be proposed. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides a three-phase power grid phase angle mutation detection and power recovery method capable of identifying and responding to a three-phase power grid phase angle mutation.

[0008] In order to solve the above technical problems, the present invention adopts a method for detecting sudden angle changes and restoring power of a three-phase power grid, wherein the method comprises the following steps: step S1 of configuring a digital signal processor and a corresponding clock timer, wherein the clock timer changes its count according to a preset clock frequency and a preset clock variable until its value reaches an extreme value and then resets; step S2 of configuring a voltage zero-crossing interrupt and a counter for each phase, wherein the counter obtains the clock timer count when the voltage of the phase crosses zero; step S3 of obtaining and storing the angle offset between each phase according to the value of each phase counter; step S4 of configuring an angle mutation label. 4. The angle mutation tag has at least two identification states, one of which is a normal state and the other is a mutation state; the angle offset reference value is set according to the clock frequency of the clock timer and the power grid cycle, and after repeating the steps S2 to S3 to obtain N groups of the angle offsets, if there are any two phases, the difference between the angle offset of the two phases and the angle offset reference value is greater than the first preset comparison value in M ​​consecutive cycles, then it is determined that an angle mutation occurs, and the angle mutation identifier is configured as a mutation state in step S5; the system site state is saved until the angle mutation ends, and the system site is restored in step S6.

[0009] As a preferred embodiment of the present solution, in step S2, a counter is configured for each phase, and the counter obtains the clock timer count when the phase voltage is interrupted by zero crossing. Specifically, the phases of the three-phase power grid are set to be R phase, S phase and T phase, respectively, and a counter is configured at the zero-crossing interruption of the line voltage or phase voltage of each phase, and the counters of each phase are defined as GridRCounter, GridSCounter, and GridTCounter respectively; then in step S3, according to the values ​​of the counters of each phase, the step of obtaining and storing the angle offsets between the phases is specifically as follows: three groups of angle offsets are defined, namely, a first angle offset PhaseDiffRS, a second angle offset PhaseDiffST and a third angle offset PhaseDiffTR, which satisfies:

[0010] PhaseDiffRS=GridRCounter-GridSCounter;

[0011] PhaseDiffST=GridSCounter-GridTCounter;

[0012] PhaseDiffTR=GridTCounter-GridRCounter.

[0013] As a further preferred embodiment of the present invention, in step S5, the step of setting the angle offset reference value according to the clock frequency of the clock timer and the grid cycle is specifically as follows: the angle offset reference value PhaseBase satisfies:

[0014]

[0015] Wherein, T is the mains cycle, and h is the frequency of the clock timer.

[0016] As a further preferred embodiment of the present invention, in the step S5, a step of determining the first preset comparison value according to the angle offset reference value is also included.

[0017] As a further preferred embodiment of the present invention, in step S6, the step of saving the system field status is specifically: obtaining and saving the current voltage of Mppt, and exiting the Mppt control loop, and exiting the Boost drive loop and the voltage and current loop on the inverter side.

[0018] As a further preferred embodiment of the present invention, in step S6, the step of judging the end of the angle mutation is specifically as follows: repeating steps S2 to S3 to obtain group I of the angle offsets; if for any two phases, the difference between the angle offsets of the two phases and the angle offset reference value is less than a second preset comparison value for J consecutive cycles, then it is judged that the angle mutation is ended, and step S5 in which the angle mutation flag is restored to a normal state is further preferred in the present invention, wherein the second preset comparison value is less than the first preset comparison value.

[0019] As a further preferred embodiment of the present scheme, in step S6, the step of restoring the system on site is specifically as follows: using the Mppt current voltage value saved during the mutation as the target voltage, soft-starting the PV voltage by the current sampled voltage, and restoring the Mppt loop control step, as well as restoring the Boost drive loop and the voltage and current loop on the inverter side.

[0020] Due to the adoption of the above technical solution, the present invention has the following beneficial technical effects compared with the prior art:

[0021] 1. Configure a clock timer, and configure a counter for each phase of the three-phase power grid to obtain the clock timer count at the zero-crossing interruption, and obtain the difference between the counts of any two counters as the angle offset value, so that the sudden change of the phase angle of the three-phase power grid can be characterized by the change of the difference between the count values ​​of the counters;

[0022] 2. After realizing the recognition of sudden angle changes, it can ensure that the equipment will not be disconnected from the grid without protection, realize zero current angle crossing, avoid damage to the inverter equipment or machine disconnection caused by sudden angle changes, and improve the inverter equipment's ability to adapt to grid fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram showing an output waveform of a three-phase power grid in a preferred embodiment of the present invention;

[0024] Figure 2 is a flow chart showing the process of the grid angle mutation detection part in the three-phase grid grid angle mutation detection and power recovery method in the preferred embodiment of the present invention;

[0025] Figure 3 is a flow chart showing the control process after the angle changes suddenly in the preferred embodiment;

[0026] Figure 4 is an equivalent circuit diagram, which shows an equivalent circuit structure of configuring zero-crossing interruption in the R phase in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0027] An embodiment of a method for detecting sudden changes in angle of a three-phase power grid and restoring power according to the present invention will be described below with reference to the accompanying drawings. It will be appreciated by those skilled in the art that the described embodiments may be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the drawings and descriptions are illustrative in nature and are not intended to limit the scope of protection of the claims. In addition, in this specification, the drawings are not drawn to scale and the same reference numerals represent the same parts.

[0028] It should be noted that the expressions “first” and “second” used in the embodiments of the present invention are intended to distinguish two non-identical entities with the same name or non-identical parameters. It can be seen that “first” and “second” are only for the convenience of expression and should not be understood as limitations on the embodiments of the invention. The subsequent embodiments will not explain this one by one.

[0029] The preferred embodiment of the present invention is proposed to solve the technical problem that the existing photovoltaic power generation inverter system design lacks a mechanism to deal with sudden changes in grid angles. When the system equipment lacks a strategy to deal with sudden changes in angles, and operates in a scenario where the sudden changes in grid angles are large and / or the angle sudden changes take a long time to cross, the inverter is used to resist the serious consequence that the power cannot be restored after the machine protection is disconnected from the grid.

[0030] The response to angle mutations is roughly divided into three steps: mutation detection, on-site preservation, and on-site recovery. Among them, as mentioned above, due to the uncertainty of the on-site photovoltaic conditions and the time when the grid system produces abnormal mutations, the detection or response to the system's angle mutations becomes the primary problem that needs to be solved, and it is also a difficult problem.

[0031] In combination with the above aspects, the following aspects should be considered for the response of the system to sudden changes in angle:

[0032] 1) Seek appropriate parameters and methods to characterize the electrical angles of each phase, and at the same time, determine the offset between the angles of each phase through the set parameters;

[0033] 2) Setting appropriate reference values ​​to define the occurrence of angle mutation state and the recovery of angle normal state;

[0034] 3) Configure an angle mutation tag for the system. Once the system is able to judge and respond to angle mutations, the state of the angle mutation tag is configured to identify whether the current network angle has changed suddenly, and then take corresponding response strategies.

[0035] On the basis of the above-mentioned improvement ideas, the first aspect of the preferred embodiment of the present invention is to seek to represent the grid angle and the offset between each phase, so as to reflect the current angle mutation status of the system through the angle offset.

[0036] Look first Figure 1 , Figure 1 The schematic diagram shows the output waveform of the three-phase power grid in a preferred embodiment of the present invention. The phase voltage or line voltage waveform of any phase in the three-phase power grid is as follows: Figure 1 In the preferred embodiment of the present invention, for the convenience of explanation, the three phases in the three-phase power grid are defined as R phase, S phase and T phase respectively. Figure 1 , Figure 1 The waveforms of the phase voltage outputs of the three phases are schematically shown in FIG. The angle between each phase of the three-phase power grid should be maintained at 120°, that is, the S phase lags 120° behind the R phase, the T phase lags 120° behind the S phase, and the R phase lags 120° behind the T phase. It can be seen that under ideal conditions, when the system is in steady-state operation without sudden angle changes, the voltages of each phase are output with a difference of 120°.

[0037] At another angle, if the system does not have a sudden change in angle, and the zero crossing point of the rising edge of each phase is used as the reference point, it can be concluded that the angle of the first rising edge zero crossing of the R phase is 120° ahead of the first rising edge zero crossing of the S phase, and the same can be said for other phases. It is thus conceivable that when a sudden change in angle occurs, that is, the angle between the voltages of each phase is no longer maintained at 120°. In other words, when a sudden change occurs in any phase, the angle of the zero crossing of its rising edge is no longer 120° ahead of and / or behind the zero crossing of the rising edge of the adjacent phase.

[0038] Under actual working conditions, it is difficult for the existing three-phase power grid to characterize the real-time angle of each phase of the power grid during its operation, which makes it difficult for the existing equipment to respond to the sudden change of each phase angle. Based on the above content, the preferred embodiment of the present invention does not seek to characterize the real-time value of each phase power grid angle, but converts the method of identifying the grid angle by parameters into representing the offset of the grid angle by parameters.

[0039] Specifically, in a preferred embodiment of the present invention, a digital signal processor (DSP) is first configured, and a clock with a frequency of 10000 Hz is obtained through pre-scaling according to the signal of the digital signal processor, that is, CPUtimer. The configuration of CPUtimer can be the following two ways:

[0040] 1) The clock is configured to start from a preset value, and decrease according to a preset clock frequency / period, according to a preset clock variable, until it decreases to zero and then resets to an accumulator of a preset value;

[0041] 2) The clock is configured to start from zero, accumulate according to a preset clock frequency / period, and accumulate according to a preset clock variable until the accumulator reaches an extreme value and then resets to zero.

[0042] In a preferred embodiment of the present invention, the clock timer is set in the first manner. For example, for a 10000 Hz clock, it is decremented from 0xFFFFFFFF in a period of 10 μs.

[0043] Then configure the corresponding counter at the zero-crossing interruption of the phase voltage of each phase, and the counter will obtain the count of the clock timer during the zero-crossing interruption. Set the zero-crossing interruption counters of the corresponding three phases to GridRCounter, GridSCounter, and GridTCounter, and obtain the angle offset between each phase. That is, define three groups of angle offsets, namely the first angle offset PhaseDiffRS, the second angle offset PhaseDiffST, and the third angle offset PhaseDiffTR, and satisfy:

[0044] PhaseDiffRS=GridRCounter-GridSCounter;

[0045] PhaseDiffST=GridSCounter-GridTCounter;

[0046] PhaseDiffTR=GridTCounter-GridRCounter.

[0047] Using three sets of parameters, the offset between each phase at each rising edge interruption is obtained and recorded, so that the sudden change of each relative network angle can be converted into the angle offset, or in other words, the change of the angle offset is used to characterize whether the relative network angle has a sudden change.

[0048] Furthermore, when the corresponding phase voltage is interrupted by zero crossing, the counter obtains the value of the clock timer. According to the characteristics of the three-phase power grid, when there is no sudden change in angle, that is, each phase leads or lags according to the preset interval, the difference between the three counters should be a fixed value. Here, the fixed value is defined as the angle offset reference value. Figure 1 In a three-phase power grid, since the phases are 120° apart from each other, the value corresponding to the angle offset reference value should be one-third of a complete sinusoidal waveform cycle of any phase. Therefore, the angle offset reference value PhaseBase satisfies the following relationship:

[0049]

[0050] Wherein, T is the mains cycle, and h is the frequency of the clock timer. Taking the above example as an example, if the mains cycle is set to 20ms, then according to the previous Captimer, in the R phase zero-crossing interruption, the total value of its counter should be 20ms / 10μs=2000. Then the angle offset reference value is one third of the total value. In the absence of a sudden change in angle, the first to third angle offsets corresponding to each should be equal to the angle offset reference value, and when the first to third angle offsets change, it is deduced that the relative grid angles of the system have suddenly changed.

[0051] The following is a detailed description of the determination process when a sudden angle change occurs. The system continuously assigns the value of the clock timer to each corresponding counter (GridRCounter, GridSCounter, GridTCounter) according to the preset cycle. At the same time, it will also obtain and store the values ​​of the first to third angle offsets at the current moment, and repeat the above process until N groups of angle offset data are obtained, and then determine the relationship between the angle offset and the angle offset reference value.

[0052] It should be noted here that the standards for identifying angle mutations may be different for different systems and field environments. For example, it may be desired to identify an angle mutation state when the angle mutation is greater than 2°, or it may be desired to identify an angle mutation state when the angle mutation is greater than 3°. The above adjustment is achieved by setting a first preset comparison value (trip value) when the angle offset is not equal to the angle offset reference value, and judging the relationship between the difference between the angle offset and the angle offset reference value and the first preset comparison value. If the difference between the angle offset and the angle offset reference value is greater than the first preset comparison value for M consecutive cycles, it can be determined that the system has experienced an angle mutation.

[0053] For example, obtain two sets of angle offsets for two consecutive periods: wPhaseDiffR1 and wPhaseDiffR2.

[0054] |(wPhaseDiffR1–uwPhaseBase)|>TripValue,

[0055] and,

[0056] |(wPhaseDiffR2–uwPhaseBase)|>TripValue,

[0057] Of course, in actual design, the number of angle offset collections can be adjusted as needed, as well as the number of consecutive period judgments when the difference between the angle offset and the angle offset reference value is greater than the first preset comparison value. The preferred embodiment of the present invention should not be limited by the above two numbers.

[0058] It is worth mentioning that in judging the sudden change of angle, as long as there are any two phases, and the difference between the angle offset between the two phases and the angle offset reference value satisfies the above comparison formula, it is determined that the system has a sudden change of angle. That is, within two consecutive cycles, as long as any one of the following three comparison formulas is satisfied, it is determined that the angle has a sudden change:

[0059] |(wPhaseDiffR–uwPhaseBase)|>TripValue;

[0060] |(wPhaseDiffS–uwPhaseBase)|>TripValue;

[0061] |(wPhaseDiffT–uwPhaseBase)|>TripValue.

[0062] As for the selection of the first preset comparison value, referring to the above description, in the preferred embodiment, when the set angle changes by more than 2°, it is determined that the angle has changed suddenly, and the first preset comparison value TripValue satisfies the following relationship:

[0063]

[0064] In this embodiment, the value of TripValue is set to 12 according to the aforementioned angle offset reference value (666).

[0065] When it is determined that an angle mutation occurs, the system will configure the state of the angle mutation flag. In a preferred embodiment of the present invention, the angle mutation flag is a parameter with two states, including at least a normal state indicating that no mutation has occurred, and a mutation state indicating that a mutation has occurred. For example, an angle mutation flag (AnglTrigFlag) may include two states, 0 and 1. When AnglTrigFlag is set to 0, it indicates that the current system is in a normal state and no angle mutation has occurred. When AnglTrigFlag is set to 1, it indicates that an angle mutation has occurred in the current system.

[0066] So far, the complete process of detecting a sudden change in the angle of the three-phase power grid and power recovery method described in the preferred embodiment of the present invention has been described. The judgment flow chart can be found in Figure 2 .

[0067] Next, it is the control step after determining whether there is a sudden change in angle. Figure 3 , Figure 3 It is a flow chart showing the control process after the angle mutation in this preferred embodiment of the present invention.

[0068] Specifically, the control after the angle mutation mainly includes three steps: on-site saving, judging the end of the angle mutation, and on-site recovery. During the on-site saving process, the Mppt voltage is assigned to a temporary variable, the Mppt voltage value at the moment of the angle mutation is saved, and the Mppt control loop is exited. Then the voltage loop and current loop integrals on the boost side are cleared to 0, the boost drive loop is exited, and the voltage loop and current loop integrals on the inverter side are cleared to 0, and the voltage and current loops on the inverter side are exited. This is until the system determines that the angle mutation has ended.

[0069] The determination process of the end of the angle mutation is similar to the determination process of the angle mutation sound. In a preferred embodiment of the present invention, when the angle mutation occurs, I groups of angle offsets are repeatedly obtained. If for any two phases, the difference between the angle offset between the two phases and the angle offset reference value is less than the second preset comparison value for J consecutive cycles, the angle mutation is determined to be over, and the angle mutation flag is restored to a normal state.

[0070] Still based on the above example, in the process of determining the end of the angle mutation, a second preset comparison value (RebackValue) is set. The setting principle of the second preset comparison value is similar to that of the first preset comparison value. The value of the second preset comparison value is determined according to the angle offset reference value and the angle mutation end determination criteria under different standards, but the size of the second preset comparison value is smaller than the size of the first preset comparison value. For example, in this preferred embodiment, when the first preset comparison value is 12, the second preset comparison value is 6.

[0071] Therefore, the comparison formula for determining the end of the angle mutation can be written as:

[0072] |(wPhaseDiffR–uwPhaseBase)|<RebackValue;

[0073] |(wPhaseDiffS–uwPhaseBase)|<RebackValue;

[0074] |(wPhaseDiffT–uwPhaseBase)|<RebackValue.

[0075] The judgment of the end of angle mutation is different from the judgment of angle mutation. Only when any two phases satisfy the above comparison formula can the system be considered to have angle mutation. That is, in two consecutive cycles, the above three comparison formulas must be satisfied at the same time to determine the end of angle mutation.

[0076] When the angle mutation ends, the angle mutation flag is set to 0, which is the normal state. At the same time, the on-site recovery steps are performed. Specifically, the Mppt voltage saved by the aforementioned temporary variable is used as the target value, the system PV voltage is soft-started from the current sampled voltage to the Mppt voltage point saved when the angle mutation occurs, and the Mppt loop control is restored. At the same time, the boost drive loop and the voltage and current loop control on the inverter side are restored.

[0077] The following is an example to illustrate the above process. Figure 4 As shown, Figure 4It is an equivalent circuit diagram, which shows the equivalent circuit structure of configuring a zero-crossing interrupt in the R phase in a preferred embodiment of the present invention. Taking the R phase as an example, a zero-crossing circuit is configured, and the zero-crossing circuits of the S phase and the T phase can be set with reference to the zero-crossing circuits of the S phase and the T phase. Under simulation conditions, taking a 50hz three-phase power grid as an example, the mains cycle is 20ms. According to the configuration of CpuTimer as above, in the zero-crossing interrupt of the R phase, the total value GridRSCounter should be 20ms / 10us=2000; the angle offset reference value is designed to be PhaseBase=1 / 3*2000=666. If there is no sudden angle change in the three-phase power grid, the three angle offsets PhaseDiffTR, PhaseDiffRS, and PhaseDiffST are equal to the default value PhaseBase, and the simulation results are shown in Table 1:

[0078]

[0079] 1) Test scenario 1: When no angle mutation occurs, the angles of each phase of the three-phase power grid are staggered by 120°. At this time, the angle offsets PhaseDiffTR=666, PhaseDiffRS=667, and PhaseDiffST=667. The photovoltaic inverter operates normally, no angle mutation is detected, and the angle mutation flag is set to 0.

[0080] 2) Test scenario 2: The R phase angle changes suddenly by 60°, at which time the angle offsets PhaseDiffTR=682, PhaseDiffRS=487, and PhaseDiffST=831. The photovoltaic inverter detects the sudden change in the grid angle and immediately performs the corresponding blocking operation. The angle crossing time is 0.4s. During the crossing period, the machine has no power output, but the machine is not disconnected from the grid;

[0081] 3) Test scenario 3: The R phase angle is restored, and the three-phase grid returns to normal potential. At this time, PhaseDiffTR = 666, PhaseDiffRS = 667, and PhaseDiffST = 667. The photovoltaic inverter detects that the grid angle mutation ends and immediately performs the corresponding recovery operation. The inverter can reach the power before the angle mutation within 400ms;

[0082] 4) Test scenario 4: The S phase angle suddenly changes by 60°. The logic is the same as when the R phase suddenly changes (as in test scenario 2). Differences: When the S phase suddenly changes by 60°, PhaseDiffTR=487, PhaseDiffRS=833, PhaseDiffST=682;

[0083] 5) Test scenario 5: S phase angle mutation recovery. Looking back at test scenario 3, in test scenario 5, the recovery logic of the S phase angle mutation is the same as the recovery logic of the R phase angle mutation in test scenario 3;

[0084] 6) Test case 6: The T phase angle suddenly changes by 60°, which is the same as the R phase (as in test case 2). Differences: When the S phase suddenly changes by 60°, PhaseDiffTR=831, PhaseDiffRS=683, PhaseDiffST=487;

[0085] 7) Test scenario 7: T phase angle sudden recovery, logically the same as R phase angle sudden recovery (as in test scenario 3)

[0086] 8) Test scenario 8: The R phase, S phase and T phase simultaneously experience a 20° lagging angle mutation. At this time, the steady-state angle offset is PhaseDiffTR=666, PhaseDiffRS=667, PhaseDiffST=667, but the angle offset at the moment of mutation can reach PhaseDiffTR=657, PhaseDiffRS=566, PhaseDiffST=777. The photovoltaic inverter detects the grid angle mutation and immediately performs the corresponding wave blocking operation. The angle crossing time is 60s. During the crossing period, the machine has no power output, but the machine is not disconnected from the grid;

[0087] 9) Test situation 9: The three-phase angles of R phase, S phase and T phase are restored, and the three-phase grid returns to normal potential. At this time, PhaseDiffTR=666, PhaseDiffRS=667, and PhaseDiffST=667. The photovoltaic inverter detects that the grid angle mutation ends and immediately performs the corresponding recovery operation. The inverter can reach the power before the angle mutation within 400ms; for machines that do not add angle mutation detection, after the 20° angle mutation ends;

[0088] 10) Test scenario 10: The R phase, S phase and T phase simultaneously experience a 20° leading angle mutation, and the logic is the same as test scenario 8. The difference is that the angle offset at the moment of mutation can reach PhaseDiffTR=569, PhaseDiffRS=775, PhaseDiffST=656. The angle mutation recovery logic is the same as test scenario 9.

[0089] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the attached claims.

Claims

1. A method for detecting sudden changes in the angle between a three-phase power grid and restoring power, wherein: The method comprises the following steps: Step S1 of configuring a digital signal processor and a corresponding clock timer, wherein the clock timer changes its count according to a preset clock frequency and a preset clock variable until its value reaches an extreme value and then resets; Step S2 of configuring a voltage zero-crossing interrupt and a counter for each phase, wherein the counter obtains the clock timer count when the voltage of the phase crosses zero; Step S3 of acquiring and storing the angle offset between each phase according to the value of each phase counter; Step S4 of configuring an angle mutation tag, wherein the angle mutation tag has at least two identification states, one of which is a normal state and the other is a mutation state; An angle offset reference value is set according to the clock frequency of the clock timer and the grid cycle, and after repeating steps S2 to S3 to obtain N groups of the angle offsets, if there are any two phases, the difference between the angle offset of the two phases and the angle offset reference value is greater than the first preset comparison value in M ​​consecutive cycles, then it is determined that an angle mutation occurs, and the angle mutation flag is configured as a mutation state in step S5; The system site status is saved until the angle mutation ends and the system site is restored in step S6.

2. The method for detecting sudden change of angle between the three-phase power grid and restoring power according to claim 1, characterized in that: In step S2, a counter is configured for each phase, and the steps of obtaining the clock timer count when the phase voltage is interrupted by zero crossing are specifically as follows: The phases of the three-phase power grid are set to be R phase, S phase and T phase respectively. A counter is configured at the zero-crossing interruption of the line voltage or phase voltage of each phase. The counters of each phase are defined as GridRCounter, GridSCounter and GridTCounter respectively. Then in step S3, according to the value of each phase counter, the steps of obtaining and storing the angle offset between each phase are specifically as follows: Define three groups of angle offsets, namely the first angle offset PhaseDiffRS, the second angle offset PhaseDiffST and the third angle offset PhaseDiffTR, then: PhaseDiffRS=GridRCounter-GridSCounter; PhaseDiffST=GridSCounter-GridTCounter; PhaseDiffTR=GridTCounter-GridRCounter.

3. The method for detecting sudden angle change of a three-phase power grid and restoring power according to claim 2, characterized in that: In step S5, the step of setting the angle offset reference value according to the clock frequency of the clock timer and the grid cycle is specifically as follows: The angle offset reference value PhaseBase satisfies: Wherein, T is the mains cycle, and h is the frequency of the clock timer.

4. The method for detecting sudden angle change of a three-phase power grid and restoring power according to claim 3 is characterized in that: In the step S5, a step of determining the first preset comparison value according to the angle offset reference value is also included.

5. The method for detecting sudden angle change of a three-phase power grid and restoring power according to claim 4, characterized in that: In step S6, the step of saving the system on-site status is specifically as follows: Get and save the current voltage of Mppt, exit the Mppt control loop, and, Exit the Boost drive loop and the voltage and current loop on the inverter side.

6. The method for detecting sudden angle change of a three-phase power grid and restoring power according to claim 5, characterized in that: In step S6, the step of determining the end of the angle mutation is specifically as follows: Repeat steps S2 to S3 to obtain group I of the angle offsets. If, for any two phases, the difference between the angle offset between the two phases and the angle offset reference value is less than a second preset comparison value for J consecutive cycles, it is determined that the angle mutation is over, and the angle mutation flag is restored to a normal state in step S5.

7. The method for detecting sudden angle change of a three-phase power grid and restoring power according to claim 6, characterized in that: The second preset comparison value is smaller than the first preset comparison value.

8. The method for detecting sudden change of angle between three-phase power grid and restoring power according to claim 7, characterized in that: In step S6, the steps of restoring the system on site are specifically as follows: The current voltage value of Mppt saved during the mutation is used as the target voltage, the PV voltage is soft-started by the current sampled voltage, and the steps of restoring the Mppt loop control, and, Restore the Boost drive loop and the voltage and current loop on the inverter side.

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