Control method, device and equipment for inverter power grid voltage ride through

Abstract

The invention provides an inverter power grid voltage ride-through control method, device and equipment, and relates to the technical field of power electronics. According to the method, when the power grid voltage is abnormal and meets the voltage ride-through condition, the duty ratio of the inverter before voltage ride-through is stored, and smooth transition of the inverter after the power grid voltage is recovered is ensured. According to the method, the preset slope coefficient is introduced to calculate and recover the duty ratio, so that smooth adjustment of the duty ratio is realized, and unstable output of the inverter possibly caused by sudden change of the duty ratio is avoided.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and more particularly to a control method, device and apparatus for inverter grid voltage ride-through. Background Art

[0002] Due to the influence of various external factors and internal load changes, the power grid will have a large range of voltage fluctuations. When the fluctuation of the power grid exceeds a certain threshold, the grid-connected standard requires that the inverter that is currently connected to the grid output needs to quickly identify the fluctuation and respond within the specified time, that is, no power is output to the grid to complete high voltage ride-through or low voltage ride-through.

[0003] Generally speaking, the high and low voltage ride-through of the power grid mainly involves the grid voltage sampling and DSP control of the inverter, and its core is the control program and algorithm of the DSP. The response and ride-through time of the ride-through voltage are completed based on the logical judgment after the basic grid voltage sampling. The main difficulty lies in the recovery of the inverter power after the grid voltage is restored. Since the grid connection standard requires the inverter to recover to the power before the grid fluctuation within the specified time, this requires the inverter to quickly start the corresponding switch tube after the grid voltage is restored and adjust the output power to the power before the ride-through. If the power is adjusted too quickly, the power semiconductor of the inverter may be damaged due to the excessive energy processing. If the power is adjusted too slowly, the recovery time may not meet the standard requirements. For photovoltaic panels, if the inverter is improperly adjusted, it may not provide enough energy to the inverter to support grid connection.

[0004] Therefore, for the recovery of the grid voltage after crossing, it is necessary to ensure that the inverter can quickly obtain sufficient energy from the photovoltaic panels and quickly find the power point before crossing, while also taking into account the working status of the internal components of the inverter to prevent damage. Summary of the invention

[0005] In view of the above problems, the present application provides a control method, device and equipment for inverter grid voltage ride-through, including the following contents:

[0006] In a first aspect, the present application provides a method for controlling inverter grid voltage ride-through, the method comprising:

[0007] When the grid voltage meets the voltage ride-through condition, the duty cycle before the voltage ride-through is obtained as the first duty cycle and saved;

[0008] After completing the voltage ride-through, calculating the recovery duty cycle by using a preset slope coefficient, the first duty cycle and the current duty cycle;

[0009] When the recovery duty cycle is greater than the first duty cycle, the first duty cycle is used as the final recovery duty cycle, and the inverter is controlled to output power at the final recovery duty cycle.

[0010] Optionally, the method further includes:

[0011] During the loop calculation process, continuously monitoring the absolute value of the difference between the duty cycle calculated by the loop and the first duty cycle;

[0012] When the absolute value is smaller than the preset switching threshold, the current actual output duty cycle is switched to the duty cycle calculated by the loop, and the loop performs subsequent closed-loop regulation.

[0013] Optionally, calculating the restored duty cycle by using a preset slope coefficient, the first duty cycle and the current duty cycle includes:

[0014] The product of the preset slope coefficient and the first duty cycle is summed with the current duty cycle as the calculated recovery duty cycle.

[0015] Optionally, the method is applicable to a two-stage inverter topology and a one-stage inverter topology;

[0016] For the two-stage inverter topology, the first duty cycle is applied to control the DC / DC converter and the DC / AC inverter respectively;

[0017] For the one-stage inverter topology, the first duty cycle is applied to control a DC / DC converter that simultaneously implements maximum power point tracking MPPT and pseudo bus sinusoidal modulation.

[0018] Optionally, for the DC / AC conversion process in the two-stage inverter topology and the one-stage inverter topology, the first duty cycle is the maximum duty cycle in a half-wave period of the power frequency before the voltage crosses;

[0019] For the DC / DC conversion process in the two-stage inverter topology, the first duty cycle is directly taken as the current duty cycle before the transition.

[0020] In a second aspect, the present application provides a control device for inverter grid voltage ride-through, the device comprising:

[0021] An acquisition unit, used for acquiring a duty cycle before voltage ride-through as a first duty cycle and saving the duty cycle when the grid voltage meets a voltage ride-through condition;

[0022] a calculation unit, configured to calculate a restored duty cycle by using a preset slope coefficient, the first duty cycle and a current duty cycle after completing voltage ride-through;

[0023] An output unit is used to use the first duty cycle as the final recovery duty cycle when the recovery duty cycle is greater than the first duty cycle, and control the inverter to output power with the final recovery duty cycle.

[0024] Optionally, the device further comprises:

[0025] A detection unit, used for continuously monitoring the absolute value of the difference between the duty cycle calculated by the loop and the first duty cycle during the loop calculation process;

[0026] The switching unit is used to switch the current actual output duty cycle to the duty cycle calculated by the loop when the absolute value is less than a preset switching threshold, and the loop performs subsequent closed-loop regulation.

[0027] Optionally, the calculation unit calculates the restored duty cycle by using a preset slope coefficient, the first duty cycle and the current duty cycle, including:

[0028] The product of the preset slope coefficient and the first duty cycle is summed with the current duty cycle as the calculated recovery duty cycle.

[0029] Optionally, for the two-stage inverter topology, the first duty cycle is applied to control of a DC / DC converter and a DC / AC inverter respectively;

[0030] For the one-stage inverter topology, the first duty cycle is applied to control a DC / DC converter that simultaneously implements maximum power point tracking MPPT and pseudo bus sinusoidal modulation.

[0031] Optionally, for the DC / AC conversion process in the two-stage inverter topology and the one-stage inverter topology, the first duty cycle is the maximum duty cycle in a half-wave period of the power frequency before the voltage crosses;

[0032] For the DC / DC conversion process in the two-stage inverter topology, the first duty cycle is directly taken as the current duty cycle before the transition.

[0033] In a third aspect, the present application provides a device comprising a memory and a processor, wherein the memory is used to store instructions or codes, and the processor is used to execute the instructions or codes so that the device executes the control method for inverter grid voltage crossing introduced in any implementation of the first aspect.

[0034] In a fourth aspect, the present application provides a computer-readable storage medium, in which a code is stored. When the code is executed, the device executing the code implements the control method of the inverter grid voltage crossing introduced in any implementation method of the first aspect.

[0035] The present application provides a control method for inverter grid voltage ride-through. The method includes, when the grid voltage meets the voltage ride-through condition, obtaining the duty cycle before the voltage ride-through as the first duty cycle and saving it, after completing the voltage ride-through, calculating the recovery duty cycle by using the preset slope coefficient, the first duty cycle and the current duty cycle, when the recovery duty cycle is greater than the first duty cycle, taking the first duty cycle as the final recovery duty cycle, and controlling the inverter to output power with the final recovery duty cycle. The method can quickly and effectively save the key parameter of the inverter operation, i.e., the duty cycle before the voltage ride-through, when the grid voltage is abnormal and meets the voltage ride-through condition, thereby ensuring the smooth transition of the inverter after the grid voltage is restored. In addition, by introducing a preset slope coefficient to calculate the recovery duty cycle, not only can the rapid rise of power after the ride-through recovery be guaranteed without damaging the device, but also the adjustable recovery time after the ride-through can be realized, and the inverter output instability or system shock caused by the sudden change of the duty cycle can be avoided while achieving the smooth adjustment of the duty cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in this embodiment or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 A flow chart of a method for controlling voltage ride-through of an inverter grid provided in an embodiment of the present application;

[0038] Figure 2 A schematic diagram of a two-stage inverter topology structure provided in an embodiment of the present application;

[0039] Figure 3 A schematic diagram of a one-stage inverter topology structure provided in an embodiment of the present application;

[0040] Figure 4 A graph showing a change trend of a duty cycle during a voltage ride-through process provided in an embodiment of the present application;

[0041] Figure 5 A schematic diagram of the structure of a control device for inverter grid voltage ride-through provided in an embodiment of the present application. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0043] Figure 1 A flowchart of a method for controlling voltage ride-through of an inverter grid provided in an embodiment of the present application. Figure 1 As shown, the control method of the inverter grid voltage ride-through provided in the embodiment of the present application may include:

[0044] S101. When the grid voltage meets a voltage ride-through condition, obtain a duty cycle before the voltage ride-through as a first duty cycle and save the first duty cycle.

[0045] Grid voltage ride-through means that when a power system fault or disturbance causes abnormal grid voltage (such as voltage drop or surge), the power generation equipment or power electronic equipment can maintain grid-connected operation within a certain range and time interval to avoid the expansion of the grid fault and support the grid to return to normal.

[0046] The grid voltage satisfies the voltage ride-through judgment condition when the grid voltage drops below a preset safety threshold. At this time, it is considered that the control system needs to respond quickly and adopt corresponding control strategies to maintain the stable operation of the equipment. At this time, the duty cycle before the voltage ride-through is obtained as the first duty cycle and saved in order to have a benchmark value or reference value in the subsequent control process.

[0047] After the grid meets the conditions for voltage ride-through, the duty cycle Dref before the ride-through is copied through the register in the digital signal processor (DSP), and then the integral in the control loop is cleared. The control loop is an important part of the power electronic control system for regulating and stabilizing the output voltage or current. The control loop is usually composed of sensors, controllers and actuators, which can monitor the state of the system in real time and adjust the system according to a preset algorithm. In the scenario of grid voltage ride-through, the control loop needs to ensure that the inverter can maintain stable output when the grid voltage is abnormal, and quickly restore power output after the grid returns to normal. In the control loop, the integrator is usually used to eliminate static errors and improve the stability and accuracy of the system. However, in some cases, the integrator may accumulate too much error, resulting in a slow system response or instability. In particular, in abnormal situations such as grid voltage ride-through, the integrator may accumulate a large amount of error due to sudden changes in the grid voltage. By clearing the integrator, the error accumulated during the grid voltage ride-through process can be eliminated to avoid the negative impact of the error on the stability and accuracy of the system.

[0048] After completing the integral clearing operation of the control loop, in order to ensure a complete reset of the system state, the DSP duty cycle is cleared immediately to allow the inverter to enter the zero power ride-through state, that is, to ensure a smooth transition without power flow, thereby meeting the requirements of relevant grid-connected standards.

[0049] S102: After completing the voltage ride-through, calculating the recovery duty cycle by using a preset slope coefficient, the first duty cycle and the current duty cycle.

[0050] After completing the voltage crossing, the inverter needs to calculate the recovery duty cycle in order to smoothly restore to normal power output. It is understandable that for the recovery after the grid voltage crossing, it is necessary to ensure that the inverter can quickly find the power point before the crossing, and at the same time it cannot be recovered too quickly, that is, the working state of the internal components of the inverter must be taken into account without damage. In this regard, a slope coefficient is set in the present application, which can ensure that the power rises quickly after the crossing recovery without damaging the components, and at the same time, the recovery time after the crossing can be adjusted. In an embodiment of the present application, the recovery duty cycle is calculated by multiplying a preset slope coefficient with a first duty cycle (i.e., the duty cycle before the voltage crossing or a known initial duty cycle), and then adding the result to the current duty cycle.

[0051] The formula can be expressed as: Recovery duty cycle = (slope coefficient k × first duty cycle) + current duty cycle. The slope coefficient is an adjustable parameter, which is used to control the speed at which the duty cycle recovers from the current value to the target value. By adjusting the slope coefficient, the duty cycle recovery process can be optimized according to the degree of grid voltage fluctuation and the hardware characteristics of the inverter. If the grid voltage fluctuates greatly or the inverter hardware is not very tolerant to rapid changes, a smaller slope coefficient can be selected to slow down the recovery process, thereby protecting the inverter from damage. On the contrary, if the grid voltage fluctuates less and the inverter hardware can withstand rapid changes, a larger slope coefficient can be selected to speed up the recovery process, thereby achieving faster power recovery.

[0052] After calculating the recovery duty cycle, it is still necessary to compare it with the first duty cycle. The current duty cycle when calculating the recovery duty cycle for the first time is the duty cycle when the voltage crosses, that is, 0. When the calculated recovery duty cycle is less than the first duty cycle, the currently calculated recovery duty cycle is used as the new current duty cycle, and the recovery duty cycle is recalculated using the above formula, that is, the above process of calculating the recovery duty cycle and comparing it with the first duty cycle is repeated until the calculated recovery duty cycle is greater than the first duty cycle, then the calculation is stopped.

[0053] S103: When the restored duty cycle is greater than the first duty cycle, use the first duty cycle as the final restored duty cycle, and control the inverter to output power at the final restored duty cycle.

[0054] After calculating the recovery duty cycle, the DSP control program will perform a judgment operation. Specifically, if the recovery duty cycle is greater than the first duty cycle, the initial duty cycle is directly set as the final recovery duty cycle, and the working state of the inverter is controlled accordingly.

[0055] In this step, the inverter will output power according to the final recovery duty cycle. It is understandable that when the calculated value of the recovery duty cycle exceeds the range of the initial duty cycle, it may mean that the system attempts to recover at an excessively high power level, which may cause unnecessary stress or damage to the inverter and the grid it is connected to. Therefore, in order to avoid this situation, it is chosen to limit the recovery duty cycle to the level of the initial duty cycle to ensure that the inverter can safely and stably return to normal working conditions.

[0056] The above introduces the process of calculating the recovery duty cycle. In addition, in the recovery of the inverter power after the grid voltage is restored, loop calculation needs to be performed synchronously. During the loop calculation process, the absolute value of the difference between the duty cycle calculated by the loop and the first duty cycle is continuously monitored. When the absolute value is less than the preset switching threshold, the current actual output duty cycle is switched to the duty cycle calculated by the loop, and the loop performs subsequent closed-loop adjustment.

[0057] After the grid voltage is restored, the inverter enters the power recovery phase. In this phase, the DSP control program first calculates the recovery duty cycle based on the preset slope coefficient, the first duty cycle, and the current duty cycle. Subsequently, the DSP control program starts synchronous loop calculation to achieve precise control of the inverter output power.

[0058] During the loop calculation process, the DSP control program will continuously monitor the absolute value of the difference between the duty cycle calculated by the loop and the first duty cycle. This monitoring process is to determine whether the result of the loop calculation is close enough to the initial duty cycle, so that it can be safely switched to the duty cycle calculated by the loop for subsequent closed-loop adjustment.

[0059] When the absolute value detected is less than the preset switching threshold, the DSP control program believes that the result of the loop calculation is close enough to the initial duty cycle, and will switch the current actual output duty cycle to the duty cycle calculated by the loop. After the switch is completed, the DSP control program will continue to perform subsequent closed-loop adjustments by the loop to ensure that the inverter can smoothly and accurately restore to normal power output.

[0060] Among them, loop calculation is used to achieve precise control of the inverter output power. After the grid voltage is restored, the inverter needs to gradually adjust its output power through loop calculation to achieve smooth access to the grid and power recovery. In addition, during the loop calculation process, the DSP control program needs to continuously monitor the difference between the duty cycle obtained by the loop calculation and the initial duty cycle. This monitoring process is to ensure that the result of the loop calculation does not differ too much from the initial duty cycle, thereby avoiding unnecessary impact or damage to the inverter or the grid.

[0061] The switching threshold is a preset parameter used to determine whether the result of the loop calculation is close enough to the initial duty cycle. When the absolute value of the difference between the monitored duty cycle and the initial duty cycle is less than the switching threshold, the DSP control program believes that the result of the loop calculation is accurate enough and can be safely switched to the duty cycle calculated by the loop for subsequent closed-loop regulation. After the switch is completed, the DSP control program will continue the subsequent closed-loop regulation by the loop. Closed-loop regulation is a feedback control method that continuously compares the difference between the actual output and the expected output and adjusts the control parameters accordingly to achieve precise control of the inverter output power.

[0062] In summary, the inverter power recovery process after grid voltage recovery requires synchronous loop calculation and duty cycle monitoring. By accurately controlling the timing of loop calculation and duty cycle switching, the DSP control program can ensure that the inverter can smoothly and accurately recover to normal power output.

[0063] The above embodiment introduces the control method of the inverter grid voltage ride-through. It should be noted that the above method is not only applicable to the two-stage inverter topology structure, but also to the one-stage inverter topology structure. Figure 2 A schematic diagram of a two-stage inverter topology structure provided in an embodiment of the present application is shown in FIG. Figure 3 A schematic diagram of a one-stage inverter topology structure provided for an embodiment of the present application, which includes ① photovoltaic components; ② power grid; ③ DC / DC MPPT topology; ④ high-voltage bus capacitors; ⑤ DC / AC inverter topology; ⑥ DC / DC MPPT+sinusoidal modulation topology; ⑦ Unfolding industrial frequency commutation topology; ⑧ relay.

[0064] like Figure 2 As shown in the figure, in a two-stage inverter topology, it is usually composed of two main parts: DC / DC converter and DC / AC inverter. The characteristic of this topology is that the direct energy of its inverter comes from the high-voltage bus capacitor, which requires the DC / AC inverter topology to quickly open the duty cycle to output energy after the voltage ride-through is restored. At the same time, the DC / DC MPPT topology also needs to find the power point before the ride-through as soon as possible to maintain energy for the bus capacitor. If the MPPT changes too slowly, the bus capacitor will be short of energy and cause the output power to drop.

[0065] In the two-stage inverter topology, the first duty cycle is applied to the control of the DC / DC converter and the DC / AC inverter. For the DC / DC converter, the first duty cycle is used to adjust its output voltage or current to ensure that the subsequent DC / AC inverter can obtain a stable DC input. For the DC / AC inverter, the first duty cycle is used to control the waveform and power of its output AC power.

[0066] In the DC / AC conversion process of the two-stage inverter topology, the first duty cycle is set to the maximum duty cycle in the power frequency half-wave cycle before the voltage crosses. The purpose of this value method is to ensure that the inverter can quickly and smoothly recover to the power output level before the crossover after the voltage crosses. By using the maximum duty cycle in the power frequency half-wave cycle before the crossover as the recovery starting point, the fluctuation of power recovery can be minimized, thereby improving the stability and reliability of the system. When the output is restored after the crossover, the restored duty cycle Drt is also the maximum duty cycle in each sinusoidal half-wave. Each duty cycle of the actual output is executed according to |Drt*sin|, thereby ensuring that the output current is sinusoidal.

[0067] In the DC / DC conversion process of the two-stage inverter topology, the first duty cycle directly takes the current duty cycle before the voltage ride-through. This is because the main function of the DC / DC converter is to adjust the voltage level, and during the voltage ride-through, the rapid change of the voltage level may require the DC / DC converter to respond quickly to maintain the stability of the output voltage. Therefore, using the current duty cycle before the ride-through as the recovery starting point can ensure that the DC / DC converter can immediately operate at an appropriate duty cycle after the voltage ride-through, thereby maintaining the stability of the output voltage.

[0068] Different from the two-stage inverter topology, the one-stage inverter topology is more compact. Figure 3 As shown in the figure, it usually only contains a DC / DC converter that can realize multiple functions at the same time. This converter is not only responsible for the voltage level conversion, but also needs to modulate the sine waveform to realize the direct conversion of direct current into alternating current that meets the requirements of the power grid.

[0069] In the one-stage inverter topology, the first duty cycle is applied to the control of this multifunctional DC / DC converter. At this time, the first duty cycle is not only used to adjust the voltage level, but also needs to be combined with the maximum power point tracking (MPPT) algorithm to ensure that the inverter can always capture the maximum power from renewable energy sources such as solar panels or wind turbines under different light or wind speed conditions. At the same time, the first duty cycle is also used to control the modulation process of the sinusoidal waveform to ensure that the waveform quality and power factor of the output AC meet the requirements of the power grid.

[0070] In the one-stage inverter topology, since the inverter realizes the functions of maximum power point tracking (MPPT) and sinusoidal waveform modulation at the same time, the method of selecting the first duty cycle is similar to the DC / AC conversion process in the two-stage inverter topology. That is, the first duty cycle is set to the maximum duty cycle in the power frequency half-wave cycle before the voltage crosses. This method of selecting values ​​is also intended to ensure that the inverter can quickly and smoothly restore to the power output level before the cross-over after the voltage cross-over. Like the DC / AC in the two-stage inverter topology, when the output is restored after the cross-over, Drt is also the maximum duty cycle in each sinusoidal half-wave. Each duty cycle of the actual output is executed according to |Drt*sin|, thereby ensuring that the output current is sinusoidal.

[0071] In summary, the method is widely used in both two-stage inverter topology and one-stage inverter topology. By accurately controlling the first duty cycle, the system can achieve precise regulation of the inverter output power, thereby ensuring the stable operation of the power grid and the efficient use of renewable energy. In addition, the method for taking the first duty cycle is different in the two-stage inverter topology and the one-stage inverter topology, which mainly depends on the specific links in the inverter process and the characteristics of the topological structure. By reasonably selecting the method for taking the first duty cycle, it can be ensured that the inverter can quickly and smoothly return to the normal power output level after voltage crossing, thereby improving the stability and reliability of the system.

[0072] The above embodiment introduces the applicable scenarios of the control method for voltage ride through of an inverter grid provided by the present application. Figure 4 The change process of duty cycle in each stage of grid voltage ride-through and the corresponding control method are introduced. Figure 4 A diagram showing a change trend of a duty cycle during a voltage ride-through process provided in an embodiment of the present application. Figure 4 In the curve shown, t0~t1 represents the duty cycle before crossing, which is controlled by the loop output. Its Dref is stable, indicating that the inverter is running stably. At t1, the grid fluctuates. The DSP saves Dref and adjusts the duty cycle to 0, that is, zero power output. The inverter maintains zero power crossing from t1 to t2. At t2, the grid is restored, and the DSP begins to adjust the inverter duty cycle to output power. The dotted line represents that the duty cycle is quickly adjusted to Dref through Drt, while the solid line represents that the DSP adjusts the duty cycle output of the loop to Dref through loop calculation Dloop. The time from t2 to t3 is the recovery time required by the standard. The power recovery slope can be adjusted by adjusting the coefficient k, thereby ensuring that the recovery time and device stress tolerance are balanced. The solid line from t2 to t4 indicates that the speed of loop adjustment can be relatively slow. At t4, the output of the loop is close to Dref before the duty cycle is taken over, ensuring that the loop output after t4 will not experience large fluctuations and oscillations.

[0073] The above are some specific implementations of a control method for inverter grid voltage ride-through provided in the embodiment of the present application. Based on this, the present application also provides a corresponding device. The device provided in the embodiment of the present application will be introduced from the perspective of functional modularization.

[0074] Figure 5 A schematic diagram of the structure of a control device for inverter grid voltage ride-through provided in an embodiment of the present application. Figure 5 As shown, the control device 500 for inverter grid voltage ride-through provided in the embodiment of the present application includes:

[0075] An acquisition unit 510, configured to acquire a duty cycle before voltage ride-through as a first duty cycle and save the duty cycle when the grid voltage meets a voltage ride-through condition;

[0076] A calculation unit 520, configured to calculate a restored duty cycle by using a preset slope coefficient, the first duty cycle and a current duty cycle after completing voltage ride-through;

[0077] The output unit 530 is used to use the first duty cycle as the final recovery duty cycle when the recovery duty cycle is greater than the first duty cycle, and control the inverter to output power with the final recovery duty cycle.

[0078] In one implementation of the embodiment of the present application, the device further includes:

[0079] A detection unit, used for continuously monitoring the absolute value of the difference between the duty cycle calculated by the loop and the first duty cycle during the loop calculation process;

[0080] The switching unit is used to switch the current actual output duty cycle to the duty cycle calculated by the loop when the absolute value is less than a preset switching threshold, and the loop performs subsequent closed-loop regulation.

[0081] In an implementation of the embodiment of the present application, the calculation unit calculates the recovery duty cycle by using a preset slope coefficient, the first duty cycle and the current duty cycle, including:

[0082] The product of the preset slope coefficient and the first duty cycle is summed with the current duty cycle as the calculated recovery duty cycle.

[0083] In an implementation of the embodiment of the present application, for the two-stage inverter topology, the first duty cycle is applied to control of the DC / DC converter and the DC / AC inverter respectively;

[0084] For the one-stage inverter topology, the first duty cycle is applied to control a DC / DC converter that simultaneously implements maximum power point tracking MPPT and pseudo bus sinusoidal modulation.

[0085] In one implementation of the embodiment of the present application, for the DC / AC conversion process in the two-stage inverter topology and the one-stage inverter topology, the first duty cycle takes the maximum duty cycle in the previous power frequency half-wave cycle before the voltage crosses;

[0086] For the DC / DC conversion process in the two-stage inverter topology, the first duty cycle is directly taken as the current duty cycle before the transition.

[0087] The embodiments of the present application also provide corresponding devices and computer storage media for implementing the solutions provided by the embodiments of the present application.

[0088] The device includes a memory and a processor, the memory is used to store instructions or codes, and the processor is used to execute the instructions or codes so that the device executes the method described in any embodiment of the present application.

[0089] The computer storage medium stores codes, and when the codes are executed, a device executing the codes implements the method described in any embodiment of the present application.

[0090] Through the description of the above implementation methods, it can be known that those skilled in the art can clearly understand that all or part of the steps in the above-mentioned embodiment method can be implemented by means of software plus a general hardware platform. Based on such an understanding, the technical solution of the present application can be embodied in the form of a software product, which can be stored in a storage medium, such as a read-only memory (ROM) / RAM, a magnetic disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network communication device such as a router) to execute the methods described in each embodiment of the present application or some parts of the embodiments.

[0091] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0092] It should also be noted that the various embodiments in this specification are described in a progressive manner, and the same and similar parts between the various embodiments can refer to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device and apparatus embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiments. The device and apparatus embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components indicated as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0093] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A control method for inverter grid voltage ride-through, characterized in that: The method comprises: When the grid voltage meets the voltage ride-through condition, the duty cycle before the voltage ride-through is obtained as the first duty cycle and saved; After completing the voltage ride-through, calculating the recovery duty cycle by using a preset slope coefficient, the first duty cycle and the current duty cycle; When the recovery duty cycle is greater than the first duty cycle, the first duty cycle is used as the final recovery duty cycle, and the inverter is controlled to output power at the final recovery duty cycle.

2. The method according to claim 1, characterized in that The method further comprises: During the loop calculation process, continuously monitoring the absolute value of the difference between the duty cycle calculated by the loop and the first duty cycle; When the absolute value is smaller than the preset switching threshold, the current actual output duty cycle is switched to the duty cycle calculated by the loop, and the loop performs subsequent closed-loop regulation.

3. The method according to claim 1, characterized in that The step of calculating the restored duty cycle by using the preset slope coefficient, the first duty cycle and the current duty cycle includes: The product of the preset slope coefficient and the first duty cycle is summed with the current duty cycle as the calculated recovery duty cycle.

4. The method according to any one of claims 1 to 3, characterized in that: The method is applicable to two-stage inverter topology and one-stage inverter topology; For the two-stage inverter topology, the first duty cycle is applied to control the DC / DC converter and the DC / AC inverter respectively; For the one-stage inverter topology, the first duty cycle is applied to control a DC / DC converter that simultaneously implements maximum power point tracking MPPT and pseudo bus sinusoidal modulation.

5. The method according to claim 4, characterized in that For the DC / AC conversion process in the two-stage inverter topology and the one-stage inverter topology, the first duty cycle is the maximum duty cycle in the previous power frequency half-wave cycle before the voltage crosses; For the DC / DC conversion process in the two-stage inverter topology, the first duty cycle is directly taken as the current duty cycle before the transition.

6. A control device for inverter grid voltage ride-through, characterized in that: The device comprises: An acquisition unit, used for acquiring a duty cycle before voltage ride-through as a first duty cycle and saving the duty cycle when the grid voltage meets a voltage ride-through condition; a calculation unit, configured to calculate a restored duty cycle by using a preset slope coefficient, the first duty cycle and a current duty cycle after completing voltage ride-through; An output unit is used to use the first duty cycle as the final recovery duty cycle when the recovery duty cycle is greater than the first duty cycle, and control the inverter to output power with the final recovery duty cycle.

7. The device according to claim 6, characterized in that The device also includes: A detection unit, used for continuously monitoring the absolute value of the difference between the duty cycle calculated by the loop and the first duty cycle during the loop calculation process; The switching unit is used to switch the current actual output duty cycle to the duty cycle calculated by the loop when the absolute value is less than a preset switching threshold, and the loop performs subsequent closed-loop regulation.

8. The device according to claim 7, characterized in that The calculation unit calculates the recovery duty cycle by using a preset slope coefficient, the first duty cycle and the current duty cycle, including: The product of the preset slope coefficient and the first duty cycle is summed with the current duty cycle as the calculated recovery duty cycle.

9. A control device for inverter grid voltage ride-through, characterized in that: The device comprises: a memory and a processor; The memory is used to store computer programs; The processor is configured to implement the method according to any one of claims 1 to 5 when executing the computer program.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.

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