Dual phase-locked grid-connected inverter wireless carrier synchronization method, device and medium

Abstract

The present invention proposes a wireless carrier synchronization method, device and medium for a grid-connected inverter with dual phase locking. Compared with wired carrier synchronization, it does not require a synchronization signal line, realizes power frequency phase synchronization under wireless connection conditions, and realizes wireless carrier synchronization on this basis. For the first phase locking, multiple zero crossings are easily caused under the condition of power grid fluctuations, and zero crossing anti-shake measures are proposed to effectively deal with multiple zero crossings. Carrier synchronization does not require the addition of a hardware synchronization signal circuit, and carrier synchronization of two or more grid-connected inverters can be achieved. The present invention can take into account the advantages of fast speed and high precision of software phase locking, and realizes carrier level synchronization by introducing the dual effects of zero-crossing capture phase locking and software phase locking.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic inverters and photovoltaic inverters, and in particular to a wireless carrier synchronization method, device and medium for a dual phase-locked grid-connected inverter. Background Art

[0002] The disadvantage of the traditional capture zero-crossing phase lock is that it is easy to fail in phase lock in a harsh power grid environment. The reason is that the harsh power grid has defects in zero-crossing detection, which easily produces multiple zero-crossing points and causes phase lock failure. In addition, the traditional capture zero-crossing phase lock angle output is not accurate enough.

[0003] When multiple inverters are connected in parallel, carrier synchronization is required to suppress zero-sequence circulating current. Traditional carrier synchronization technology performs carrier synchronization based on the output results of traditional capture of zero-crossing phase lock. Since the output results of traditional capture of zero-crossing phase lock are not accurate enough, carrier synchronization is not timely, and additional hardware connections are required, which increases system complexity and reduces reliability. Summary of the invention

[0004] The technical problem to be solved by the present invention is that a bad power grid has defects in zero-crossing detection, and it is easy to generate multiple zero-crossing points, which leads to phase-lock failure, and then leads to untimely carrier synchronization, and requires additional hardware connections, which increases system complexity and reduces reliability.

[0005] The technical solution of the present invention is to provide a wireless carrier synchronization method for a grid-connected inverter based on double phase locking, comprising the following steps: Step 1: when K jitters occur, record ecap1, ecap2, ..., ecap k , ecap1+ecap2+…+ecap k+1 As the detection value of the zero-crossing period; where ecap k It represents the time difference between two interruptions generated by the ECAP peripheral of the DSP in the grid-connected inverter between two adjacent zero-crossing flip signals; Step 2: According to the detection value of the zero-crossing period, the PWM carrier is adjusted by the first method based on capturing the zero-crossing phase-locked loop; Step 3: The PWM carrier adjusted in step 2 is adjusted by the second software phase-locked loop, and the PWM carrier after the first carrier synchronization is synchronized according to the PWM carrier angle output of the second software phase-locked loop.

[0006] Preferably, the step 1 comprises the following steps: Step 101: when K jitters occur, determine whether it is a K jitter signal, if so, proceed to the next step; Step 102: if no jitter occurs subsequently, ecap1+ecap2+…+ecap k+1 As the detection value of the zero-crossing period.

[0007] Preferably, in the step 101: when K jitters occur, record ecap1, ecap2, …, ecap k , if ecap1 < conrolthreshold, ecap1 + ecap2 < conrolthreshold, ecap1 + ecap2 + … + ecap k < conrolthreshold, it is determined as a jitter signal.

[0008] Preferably, in the step 2, change the PWM carrier period count value by the first - stage capture - zero phase - locked loop method, but the angle output does not work.

[0009] Preferably, in the step 2, use the grid zero - crossing as the common synchronization signal for multiple inverters. By the first - stage capture - zero phase - locked loop method, make the target zero - crossing moments align with the synchronization signal. Under the condition that the number of PWM period interruptions N in a single power - frequency cycle is the same, achieve the carrier synchronization of grid - connected inverters.

[0010] Preferably, in the step 2, configure the grid zero - crossing capture interrupt, record the time difference between the grid zero - crossing moment and the target zero - crossing moment obtained through step 1, and perform the first - stage capture - zero phase - locked loop method.

[0011] Preferably, in the step 3, when the second - stage software phase - locked loop adjustment is executed, it is adjusted by the capture - zero phase - locked loop method, so that it has the dual functions of power - frequency synchronization and carrier synchronization.

[0012] Preferably, the method adopts a single - phase system phase - locked loop or a three - phase system phase - locked loop.

[0013] The present invention also proposes a wireless carrier synchronization device for grid - connected inverters based on dual phase - locked loops, including a processor and a memory. The memory is used to store instructions, and the processor is used to execute the instructions. After the processor executes the instructions, the control device executes a wireless carrier synchronization method for grid - connected inverters based on dual phase - locked loops as described in any one of the above.

[0014] The present invention also proposes a computer - readable storage medium. The computer - readable storage medium stores instructions. When it runs on a computer, it enables the computer to execute a wireless carrier synchronization method for grid - connected inverters based on dual phase - locked loops as described in any one of the above.

[0015] The present invention proposes a dual phase-locked wireless carrier synchronization method, device and medium for grid-connected inverters. Compared with wired carrier synchronization, no synchronization signal line is required. For the first phase lock, multiple zero crossings are easily caused under the condition of power grid fluctuations, and zero crossing anti-jitter measures are proposed to effectively deal with multiple zero crossings. The present invention can achieve industrial frequency phase synchronization under wireless connection conditions, and achieve wireless carrier synchronization on this basis. The present invention does not need to add a hardware synchronization signal circuit to achieve carrier synchronization. The advantage of the present invention is that the carrier synchronization of two or more grid-connected inverters can be achieved without a hardware synchronization circuit. The dual carrier synchronization scheme based on this method can fully take into account the advantages of fast speed and high precision of software phase locking. The zero-crossing capture phase locking method introduced to achieve carrier-level synchronization realizes dual phase locking without affecting software phase locking. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of power grid zero-crossing cycle detection;

[0017] Figure 2 Schematic diagram of the anti-shake algorithm for zero-crossing period detection of the power grid during a shake;

[0018] Figure 3 Schematic diagram of the anti-shake algorithm for zero-crossing period detection of the power grid when there are three shakes;

[0019] Figure 4 It is a schematic diagram of the first phase lock, the second phase lock and the synchronization signal;

[0020] Figure 5 Schematic diagram of the first phase locking and traditional phase locking;

[0021] Figure 6 It is a schematic diagram of the second phase locking and the traditional phase locking;

[0022] Figure 7 Schematic diagram of grid-connected inverter synchronization. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0024] Implement zero-crossing anti-shake processing. The disadvantage of traditional capture zero-crossing phase locking is that it is easy to fail to lock in a harsh power grid environment. The reason is that the harsh power grid has defects in zero-crossing detection, which easily generates multiple zero-crossing points and causes phase locking failure. The wireless carrier synchronization solution based on dual phase locking must introduce zero-crossing anti-shake function.

[0025] Step 1: When K jitters occur, record ecap1, ecap2, …, ecap k , and use ecap1 + ecap2 + … + ecap k+1 as the detection value of the zero-crossing period. Here, ecap k represents the time difference between two interrupts generated by the ECAP peripheral of the DSP in the grid-connected inverter between two adjacent zero-crossing flip signals, and its physical meaning can be expressed as the grid cycle count value; among them, the zero-crossing flip signal is generated by the grid voltage sampling and conditioning circuit; the DSP needs to configure the ECAP interrupt enable function.

[0026] Step 101: When K jitters occur, determine whether it is a K - time jitter signal. If so, enter the next step. Specifically, record ecap1, ecap2, …, ecap k . If ecap1 < conrolthreshold, ecap1 + ecap2 < conrolthreshold, ecap1 + ecap2 + … + ecap k < conrolthreshold, it is determined as a jitter signal.

[0027] Step 102: If no more jitters occur subsequently, use ecap1 + ecap2 + … + ecap k+1 as the detection value of the zero-crossing period.

[0028] When one jitter occurs, record ecap1. When ecap1 < conrolthreshold, it is determined as a jitter signal. When three jitters occur, record ecap1, ecap2, ecap3. When ecap1 < conrolthreshold, ecap1 + ecap2 < conrolthreshold, ecap1 + ecap2 + ecap3 < conrolthreshold, it is determined as a three - time jitter signal, as Figure 1 shown.

[0029] Regarding the situation when one jitter occurs, as Figure 2 shown, if no more jitters occur subsequently, that is, ecap2 > conrolthreshold, then use ecap1 + ecap2 as the detection value of the complete grid zero-crossing period this time.

[0030] Regarding the situation when three jitters occur, as Figure 3 shown, if no more jitters occur subsequently, that is, ecap4 > conrolthreshold, then use ecap1 + ecap2 + ecap3 + ecap4 as the detection value of the complete grid zero-crossing period this time.

[0031] Step 2: Implement the first level of PLL regulation based on capturing zero crossings.

[0032] like Figure 4 and Figure 5 As shown, configure the grid zero-crossing capture interrupt, record the time difference between the grid zero-crossing moment and the target zero-crossing moment in step 1, this time difference is the phase difference between the target zero-crossing point and the grid zero-crossing point, and perform capture zero-crossing phase-locked loop adjustment. The method used here is a phase-locked loop method based on zero-crossing capture, and the specific phase-locked adjustment principle is not repeated. It should be emphasized that the result of zero-crossing capture phase-locked loop adjustment is to change the PWM carrier cycle count value, and at the same time output the PWM angle for the inverter control loop.

[0033] In the embodiment of the present invention, the zero-crossing capture phase-locked loop is used as the first phase-locked loop, and its functions are: first, the zero-crossing of the power grid is used as the common synchronization signal of multiple inverters to achieve the alignment of the target zero-crossing moment with the synchronization signal, and to achieve carrier synchronization under the condition that the number of PWM cycle interruptions N is consistent within a single power frequency cycle; second, in the application of grid-connected inverters, the performance of the zero-crossing capture phase-locked loop is not as good as that of the software phase-locked loop, so the angle output of the zero-crossing capture phase-locked loop does not work, and the software phase-locked loop is mainly used. The periodic zero-crossing point of the PWM angle output of the software phase-locked loop is used as the target zero-crossing moment point of the capture zero-crossing phase-locked loop.

[0034] Step 3: Implement the second level of software phase-locked loop based regulation.

[0035] like Figure 6 and Figure 7 As shown, the software phase-locked loop is adjusted in each PWM interrupt cycle. The method used here is the software phase-locked loop method, and its specific phase-locked adjustment principle is not repeated. It should be emphasized that in the traditional method, the execution cycle of the software phase-locked loop, that is, the PWM interrupt cycle Tpwm remains unchanged. In the embodiment of the present invention, the core point is that the software phase-locked loop is used as the second phase lock, and its execution time base will be adjusted by the first phase-locked loop, so that it has the dual functions of power frequency synchronization and carrier synchronization. For grid-connected inverter applications, it can be a single-phase system phase-locked loop or a three-phase system phase-locked loop.

[0036] The present invention provides an embodiment of a wireless carrier synchronization method, device and medium for a double phase-locked grid-connected inverter. Compared with wired carrier synchronization, no synchronization signal line is required, and power frequency phase synchronization is achieved under wireless connection conditions, and wireless carrier synchronization is achieved on this basis. For the first phase lock, multiple zero crossings are easily caused under the condition of power grid fluctuations, and zero crossing anti-jitter measures are proposed to effectively deal with multiple zero crossings. Carrier synchronization does not require the addition of a hardware synchronization signal circuit, and carrier synchronization of two or more grid-connected inverters can be achieved. The present invention can take into account the advantages of fast speed and high precision of software phase locking, and realize carrier level synchronization by introducing the dual effects of zero-crossing capture phase locking and software phase locking.

[0037] Another aspect of the present embodiment is a wireless carrier synchronization device for a grid-connected inverter based on dual phase locking, comprising a processor and a memory, wherein the memory is used to store instructions, and the processor is used to execute the instructions. After the processor executes the instructions, the wireless carrier synchronization device for a grid-connected inverter based on dual phase locking executes the above-mentioned wireless carrier synchronization method for a grid-connected inverter based on dual phase locking.

[0038] Another aspect of the present embodiment is to provide a computer-readable storage medium storing instructions, which, when executed on a computer, enables the computer to execute the above-mentioned wireless carrier synchronization method for a grid-connected inverter based on double phase locking.

Claims

1. A wireless carrier synchronization method for grid-connected inverters based on double phase locking, characterized in that: The following steps are involved: Step 1: When K jitters occur, record ecap1, ecap2, …, ecap k , ecap1+ecap2+…+ecap k+1 As the detection value of the zero-crossing period; Among them, ecap k It indicates the time difference between two interruptions generated by the ECAP peripheral of the DSP in the grid-connected inverter between two adjacent zero-crossing flip signals; Step 2: Configure the grid zero-crossing capture interruption according to the detection value of the zero-crossing cycle, record the time difference between the grid zero-crossing moment and the target zero-crossing moment obtained by step 1, use the first capture zero-crossing phase-locked loop method to change the PWM carrier cycle count value, and adjust the PWM carrier on the premise that the angle output does not work; The grid zero crossing is used as the common synchronization signal for multiple inverters. The target zero crossing moment is aligned with the synchronization signal through the first-level capture zero crossing phase-locked loop method. Under the condition that the number of PWM cycle interruptions N is consistent within a single power frequency cycle, the grid-connected inverter carrier synchronization is achieved. Step 3: Under the condition of power grid fluctuation after adjustment in step 2, the PWM carrier undergoes a second software phase-locked loop adjustment. In step 3, the second software phase-locked loop adjustment is adjusted by the method based on capturing zero-crossing phase-locked loop, so that it has the dual functions of power frequency synchronization and carrier synchronization. The PWM carrier after the first carrier synchronization is synchronized according to the PWM carrier angle output of the second software phase-locked loop.

2. A wireless carrier synchronization method for a grid-connected inverter based on double phase locking as claimed in claim 1, characterized in that: The step 1 comprises the following steps: Step 101: When K jitters occur, determine whether it is a K jitter signal, if so, proceed to the next step; Step 102: If jitter does not occur later, ecap1+ecap2+…+ecap k+1 As the detection value of the zero-crossing period.

3. A wireless carrier synchronization method for a grid-connected inverter based on double phase locking as claimed in claim 1, characterized in that: In step 101: When K jitters occur, record ecap1, ecap2, …, ecap k , if ecap1 < conrolthreshold, ecap1 + ecap2 < conrolthreshold, ecap1 + ecap2 + … + ecap k < conrolthreshold, it is determined as a jitter signal.

4. A wireless carrier synchronization method for a grid-connected inverter based on double phase locking as claimed in claim 1, characterized in that: The method adopts a single-phase system phase-locked loop or a three-phase system phase-locked loop.

5. A wireless carrier synchronization device for grid-connected inverter based on double phase locking, characterized in that: It includes a processor and a memory, the memory is used to store instructions, the processor is used to execute the instructions, and after the processor executes the instructions, the wireless carrier synchronization device for a grid-connected inverter based on double phase locking executes a wireless carrier synchronization method for a grid-connected inverter based on double phase locking as described in any one of claims 1-4.

6. A computer-readable storage medium, characterized in that The computer-readable storage medium stores instructions, which, when executed on a computer, enable the computer to execute a wireless carrier synchronization method for a grid-connected inverter based on double phase locking according to any one of claims 1 to 4.

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