Control method and operation control device of grid-connected inverter

Abstract

The invention discloses a grid-connected inverter control method and an operation control device, and relates to the technical field of grid-connected inverters, and the method comprises the steps: obtaining a DC bus voltage signal, carrying out the band elimination filtering of the DC bus voltage signal, and obtaining a DC bus harmonic signal; converting the DC bus harmonic signal into a first control signal, and obtaining a second control signal based on inversion current detection; and generating a feedback control signal for an inverter circuit according to the first control signal and the second control signal. The method has the advantages that suppression of power grid background harmonic waves and harmonic waves of output voltage or grid-connected current under a local nonlinear load can be considered at the same time, and the harmonic suppression effect of the grid-connected inverter is improved.

Description

Technical Field

[0001] The present application relates to the technical field of grid-connected inverters, and in particular to a control method and an operation control device for a grid-connected inverter. Background Art

[0002] Grid-connected inverter control technology has been widely studied by simulating the traditional synchronous machine rotor inertia and damping characteristics and primary voltage and frequency regulation functions, so that the inverter interface renewable energy generation can be connected to the grid in a friendly manner and provide the necessary voltage and frequency support for the system. However, in the actual grid-connected operation of the grid-connected inverter, since the load may contain a large number of nonlinear loads, resulting in harmonic current injection, the harmonic voltage / current in the microgrid deteriorates the power quality of the grid, increases line losses, and causes transformer overheating, which directly affects the safe and stable operation of the distributed power supply and loads in the system.

[0003] In the related art, the grid-connected inverter uses an aforc (amended fractional order repetitive control) algorithm to directly control the grid-connected current, thereby suppressing the harmonic components of the grid-connected current, but does not pay attention to the suppression of the harmonic components of the local voltage; in another technology, a harmonic power droop control method is used to separate the harmonic power through the Fourier decomposition method, and the reference value of each harmonic voltage is obtained through the droop control method, thereby compensating for the harmonic components of the local voltage; therefore, in the related art, most of them are aimed at one of the situations of harmonic suppression of the output voltage or grid-connected current of the grid-connected inverter under the background harmonics of the power grid or the local nonlinear load, and it is difficult to take both into account when the two harmonic sources exist at the same time; In addition, the grid-connected inverter can also detect the harmonic components in the grid-connected current, local voltage or load current based on the instantaneous reactive power theory, and then use the detected grid-connected current harmonic components as the grid-connected inverter output harmonic current reference; or use the detected local voltage distortion components to calculate the harmonic current reference, and then use the detected local nonlinear load harmonic current as the grid-connected inverter output reference current, thereby compensating for the grid current harmonics. However, the harmonic component extraction based on the instantaneous reactive power theory will be limited by the bandwidth of the low-pass filter, and its dynamic response characteristics and insufficient steady-state detection accuracy will affect the compensation effect, resulting in poor harmonic suppression effect of the grid-connected inverter. Summary of the invention

[0004] The purpose of the present application is to solve at least one of the technical problems existing in the prior art, and to provide a control method and an operation control device for a grid-connected inverter, aiming to simultaneously take into account the suppression of background harmonics of the power grid and harmonics of the output voltage or grid-connected current under local nonlinear loads, and to improve the harmonic suppression effect of the grid-connected inverter.

[0005] In a first aspect, an embodiment of the present application provides a control method for a grid-connected inverter, including: Acquire a DC bus voltage signal, perform band-stop filtering on the DC bus voltage signal, and obtain a DC bus harmonic signal; Convert the DC bus harmonic signal into a first control signal, and acquire a second control signal based on inverter current detection; A feedback control signal for an inverter circuit is generated according to the first control signal and the second control signal.

[0006] According to the technical solution of the embodiment of the present application, at least the following beneficial effects are achieved: the harmonic signal in the DC bus voltage signal represents the background harmonics of the power grid. After the DC bus voltage signal is obtained, the harmonic signal in the DC bus voltage signal is extracted. According to the harmonic signal in the DC bus voltage signal, the local nonlinear load harmonic current is compensated for to suppress the grid-connected current harmonics. If a conventional low-pass filtering method is used, when the background harmonic frequency of the power grid is low or high, the filtering effect of the low-frequency harmonics is not ideal, resulting in poor compensation effect. Therefore, after the DC bus voltage signal is obtained, the DC bus voltage signal is subjected to band-stop filtering, which can suppress the background harmonics of the power grid. The wave frequency is specifically designed so that the obtained DC bus harmonic signal is closer to the ideal DC bus harmonic signal, thereby improving the subsequent compensation effect; in addition, a first control signal is obtained according to the DC bus harmonic signal, and a second control signal is obtained based on inverter current detection. The first control signal is a control signal for suppressing background harmonics of the power grid, and the second control signal is a control signal for suppressing harmonics of the grid-connected current of the grid-connected inverter under local nonlinear loads. By combining the first control signal and the second control signal, the suppression of both the background harmonics of the power grid and the harmonics of the output voltage or the grid-connected current under the local nonlinear load is taken into account, thereby further improving the harmonic suppression effect of the grid-connected inverter.

[0007] According to some embodiments of the present application, obtaining a DC bus voltage signal includes: A DC bus voltage analog signal is acquired based on DC bus voltage detection, and the DC bus voltage analog signal is converted into a digital signal to obtain a DC bus voltage signal.

[0008] According to some embodiments of the present application, the step of acquiring a DC bus voltage signal and performing band-stop filtering on the DC bus voltage signal to obtain a DC bus harmonic signal includes: Acquire a DC bus voltage signal, perform a first-order low-pass filter and a second-order band-stop filter on the DC bus voltage signal, and obtain a filtered voltage signal; The filtered voltage signal is subtracted from the DC bus voltage signal to obtain a DC bus harmonic signal.

[0009] According to some embodiments of the present application, the second-order band-stop filtering is performed by a band-stop filter, the center frequency of the band-stop filter is N times the grid frequency, and N is greater than 1.

[0010] According to some embodiments of the present application, the center frequency of the band-stop filter is twice the grid frequency.

[0011] According to some embodiments of the present application, converting the DC bus harmonic signal into a first control signal includes: Proportional gain processing is performed on the DC bus harmonic signal to obtain a first control signal.

[0012] According to some embodiments of the present application, the acquiring the second control signal based on inverter current detection includes: Based on the inverter current detection, an inverter current detection signal is acquired, and a second control signal is obtained according to a preset inverter current reference signal and the inverter current detection signal.

[0013] According to some embodiments of the present application, generating a feedback control signal for an inverter circuit according to the first control signal and the second control signal includes: Adding the first control signal and the second control signal to obtain a PWM reference signal; A PWM feedback signal is acquired based on grid voltage detection, and a feedback control signal for an inverter circuit is generated according to the PWM reference signal and the PWM feedback signal.

[0014] According to some embodiments of the present application, the second control signal is a harmonic suppression main control signal, and the first control signal is used to compensate for the harmonic suppression main control signal.

[0015] According to some embodiments of the present application, the feedback control signal is used to suppress harmonics of the output current of the inverter circuit.

[0016] In a second aspect, an embodiment of the present application provides an operation control device, characterized in that it includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor executes the program to implement the control method described in the first aspect above.

[0017] In a third aspect, an embodiment of the present application provides a grid-connected inverter, comprising the operation control device of the second aspect described above.

[0018] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium storing computer-executable instructions, wherein the computer-executable instructions are used to enable a computer to execute the control method of the first aspect as described above.

[0019] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or understood by practicing the present application. The purpose and other advantages of the present application can be realized and obtained by the structures specifically pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are used to provide further understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0021] The present application is further described below with reference to the accompanying drawings and embodiments; Figure 1 is a flow chart of a control method for a grid-connected inverter provided by an embodiment of the present application; Figure 2 is a schematic diagram of a grid-connected inverter provided by an embodiment of the present application; Figure 3 is a flow chart of a control method for a grid-connected inverter provided by another embodiment of the present application; Figure 4 is a flow chart of a control method for a grid-connected inverter provided by another embodiment of the present application; Figure 5 is a schematic diagram of a grid-connected inverter provided by another embodiment of the present application; Figure 6 is a flow chart of a control method for a grid-connected inverter provided by another embodiment of the present application; Figure 7 is a flow chart of a control method for a grid-connected inverter provided by another embodiment of the present application; Figure 8 is a flow chart of a control method for a grid-connected inverter provided by another embodiment of the present application; Fig. 9 It is a schematic diagram of an operation control device for executing a control method for a grid-connected inverter provided in one embodiment of the present application. DETAILED DESCRIPTION

[0022] This section will describe in detail the specific embodiments of the present application. The preferred embodiments of the present application are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present application, but it cannot be understood as a limitation on the scope of protection of the present application.

[0023] In the description of the present application, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0024] In the description of this application, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used to distinguish the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features. In the description of this application, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in this application based on the specific content of the technical solution.

[0025] The following is combined with Figure 1-8 , various embodiments of the control method of the grid-connected inverter of the present application are further explained.

[0026] like Figure 1 As shown, Figure 1 It is a flow chart of a control method of a grid-connected inverter provided by an embodiment of the present application. The control method of the grid-connected inverter may include but is not limited to step S110, step S120 and step S130.

[0027] Step S110, obtaining a DC bus voltage signal, performing a band-stop filtering process on the DC bus voltage signal, and obtaining a DC bus harmonic signal; Step S120, converting the DC bus harmonic signal into a first control signal, and acquiring a second control signal based on inverter current detection; Step S130: Generate a feedback control signal for the inverter circuit according to the first control signal and the second control signal.

[0028] It is understandable that the grid-connected inverter may include a controller, an analog-to-digital converter, a digital-to-analog converter, a pulse width modulation (PWM) generator, a filter, a detection circuit, an inverter circuit, etc., wherein the controller of the grid-connected inverter is used to accurately adjust the output of the inverter to ensure that it can be connected to the power grid in the best state. The control method of the grid-connected inverter provided in the embodiment of the present application can be applied to grid-connected inverters in different application scenarios, such as photovoltaic power generation systems, wind power generation systems, or energy storage systems. The grid-connected inverter can dynamically adjust the output current to achieve power factor correction by real-time monitoring of parameters such as voltage and current in the power grid and the inverter, while optimizing the power quality and reducing harmonic interference. refer to Figure 2 , Figure 2 is a schematic diagram of a grid-connected inverter provided by an embodiment of the present application. In this embodiment, the filter of the grid-connected inverter includes a band-stop filter. The band-stop filter can suppress specific signals within a specific frequency range and allow signals of other frequencies to pass. If the harmonic frequencies in the signal are known, the use of the band-stop filter can more effectively suppress the harmonics of these specific frequencies; Therefore, a DC bus voltage signal is obtained, and the DC bus voltage signal represents the voltage value of the bus in the grid-connected inverter for receiving the DC power supply. For example, in a photovoltaic power generation system, the DC bus voltage signal represents the voltage value of the bus in the grid-connected inverter for receiving the DC power transmitted by photovoltaics; In this embodiment, the DC bus voltage signal can be detected in a variety of ways, for example, by connecting two resistors in series on the DC bus to form a voltage divider circuit, and measuring the voltage at the voltage divider point to obtain the DC bus voltage; measuring the DC bus voltage by a Hall effect sensor; directly measuring the DC bus voltage by other measurement circuits, etc.; In addition, in order to suppress the background harmonics of the power grid, the detection of the DC bus voltage signal can usually be performed between the DC power supply and the DC input terminal of the inverter; the detection can be performed at both ends of the DC bus capacitor, which is used to smooth the DC input voltage and is located between the DC input terminal and the inverter circuit of the grid-connected inverter; and the detection can also be performed at the DC input terminal of the inverter circuit. It is understandable that the detection of the DC bus voltage signal needs to be performed before the inverter circuit in the grid-connected inverter.

[0029] After obtaining the DC bus voltage signal, the DC bus voltage signal is subjected to band-stop filtering through a band-stop filter. It can be understood that the parameter settings of the band-stop filter include the center frequency, bandwidth, stopband depth and order of the filter, wherein the center frequency is the frequency within the stopband of the band-stop filter, that is, the frequency that is desired to be filtered out; the bandwidth is the frequency range on both sides of the stopband of the band-stop filter, for example, the frequency range from the point at which it drops to -3dB to the point at which it rises to -3dB, and the choice of bandwidth depends on the frequency range that needs to be filtered out; the stopband depth refers to the minimum attenuation that the band-stop filter can provide within the stopband, for example, it can be set to 40dB; the order of the band-stop filter sets the number of filter sections used, and the higher the order, the narrower the transition band and the higher the selectivity of the filter. The better; in this embodiment, in order to suppress harmonics against the background harmonics of the power grid, the parameters of the band-stop filter can be set so that the band-stop filter can filter out other signals except the background harmonics of the power grid. Therefore, the target harmonic frequency can be determined according to the characteristics of the power grid where the grid-connected inverter is located. For example, if the power grid frequency is 50Hz and the background harmonics of the power grid are mainly second harmonics, then the target harmonic frequency can be set to 100Hz; the bandwidth can be defined as the frequency range on both sides of the stop band based on the -3dB point. For example, if the bandwidth is 10Hz, the band-stop filter can provide at least -3dB attenuation between 95Hz and 105Hz; the stop band depth can be set to at least 40dB to ensure that harmonics are effectively suppressed; the order of the band-stop filter can be set to above the second order.

[0030] It can be understood that the parameter setting of the band-stop filter can mainly set the center frequency of the band-stop filter, and other parameters of the band-stop filter and the type of the band-stop filter can be determined according to other factors, for example, the type of the band-stop filter is determined according to the type of the DC bus electrical signal; the bandwidth of the band-stop filter is determined according to the grid stability requirements; the order of the filter and the stopband depth are determined according to the performance indicators of the power grid-connected system; Based on this, the DC bus voltage signal is band-stop filtered to obtain the DC bus harmonic signal, which represents the harmonic amount of the DC bus voltage signal in the grid-connected inverter. Based on the DC bus harmonic signal, a targeted control signal can be generated and fed back to the inverter circuit to suppress the harmonics of the DC bus voltage signal, thereby achieving effective suppression of the background harmonics of the power grid.

[0031] It can be understood that before the DC bus voltage signal is subjected to band-stop filtering, low-frequency interference in the DC bus voltage signal can also be removed, as well as high-frequency noise or unnecessary high-frequency components in the signal; the analog signal can also be converted into a digital signal and preliminarily denoised; in addition, an isolation amplifier or an optical isolator can be used to isolate the signal to prevent noise from propagating through the power line or the ground line.

[0032] Converting the DC bus harmonic signal into a first control signal, the first control signal may be a pulse width modulation (PWM) signal. In one embodiment, the first control signal may also be a phase control signal, which is used for phase control of the inverter circuit, and controls the output of the grid-connected inverter by changing the phase of the trigger pulse. The first control signal may be generated by PI (proportional integral), PID (proportional integral differential) or other control algorithms; The second control signal is obtained based on the inverter current detection, which may be that after detecting the inverter circuit output current signal, the second control signal is generated according to the inverter circuit output current signal and a preset inverter circuit output reference current signal. In this embodiment, the inverter current detection may be performed in a variety of ways, for example, by using a small resistor (shunt) on the DC bus, measuring the voltage drop across the resistor, and obtaining the inverter circuit output current signal according to the voltage drop; measuring the inverter circuit output current signal by a Hall effect sensor; directly measuring the inverter circuit output current signal by other measurement circuits, etc.; the second control signal may be generated by comparing the inverter circuit output current signal with the inverter circuit output reference current signal by a comparator, calculating the error, and inputting the error signal into a PI controller or a PID controller, and the PI controller or the PID controller performs calculations according to predetermined parameters (proportional gain Kp, integral time Ti, differential time Td) to generate the second control signal.

[0033] The first control signal is used to suppress the harmonic amount of the voltage signal of the DC bus in the grid-connected inverter, and the second control signal is used to suppress the harmonic amount of the output current signal of the inverter circuit. Therefore, the first control signal and the second control signal can be combined to generate a feedback control signal for the inverter circuit, for example, the first control signal and the second control signal are added; in addition, it can be understood by those skilled in the art that when generating a feedback control signal for the inverter circuit, in addition to the first control signal and the second control signal, it is also necessary to obtain a voltage detection signal on the grid side, and generate a control signal on the grid side according to a reference signal on the grid side. The control signal on the grid side is used to improve the synchronization between the grid-connected inverter and the grid, and reduce the impact and harmonic interference on the grid. Therefore, when generating the feedback control signal, in addition to combining the first control signal and the second control signal, the voltage detection signal on the grid side is further combined to jointly generate a feedback control signal for feeding back to the inverter circuit, so as to further suppress the output harmonics of the grid-connected inverter.

[0034] like Figure 3 As shown, Figure 3 It is a flow chart of a control method of a grid-connected inverter provided by another embodiment of the present application; regarding the above-mentioned step S110, it may include but is not limited to step S210.

[0035] Step S210: acquiring a DC bus voltage analog signal based on DC bus voltage detection, converting the DC bus voltage analog signal into a digital signal to obtain a DC bus voltage signal.

[0036] In this embodiment, the DC bus voltage analog signal is obtained based on the DC bus voltage detection. The DC bus voltage detection can be performed at both ends of the DC bus capacitor or between the DC input end of the grid-connected inverter and the inverter circuit to obtain the initial DC bus voltage analog signal. The DC bus voltage detection obtains an analog signal. Therefore, the DC bus voltage detection method can be through a resistor voltage divider network, a Hall effect sensor, an operational amplifier circuit, etc. It is understandable that digital signal processing can provide higher resolution and accuracy than analog signals, and digital filters can suppress noise more effectively, especially when processing low-amplitude signals. Digital filters can be designed to have very steep roll-off characteristics to better isolate unwanted frequency components. Therefore, after obtaining the DC bus voltage analog signal, the DC bus voltage analog signal is converted into a digital signal to obtain the DC bus voltage signal, that is, the DC bus voltage signal is a digital signal.

[0037] like Figure 4 As shown, Figure 4 It is a flow chart of a control method of a grid-connected inverter provided by another embodiment of the present application; regarding the above-mentioned step S110, it may include but is not limited to step S310 and step S410.

[0038] Step S310, obtaining a DC bus voltage signal, performing a first-order low-pass filter and a second-order band-stop filter on the DC bus voltage signal, and obtaining a filtered voltage signal; Step S410: subtract the filtered voltage signal from the DC bus voltage signal to obtain a DC bus harmonic signal.

[0039] refer to Figure 5 , Figure 5 is a schematic diagram of a grid-connected inverter provided by another embodiment of the present application. In this embodiment, a DC bus voltage signal is obtained based on DC bus voltage detection, the inverter circuit is a single-phase full-bridge inverter circuit, a second control signal is obtained through a current controller after the inverter current is obtained based on inverter current detection, a grid voltage feedback control signal is obtained through a phase-locked loop after the grid side voltage signal is obtained based on grid voltage detection, the first control signal and the second control signal are added and input into a PWM drive, the grid voltage feedback control signal is also input into the PWM drive, and the PWM input signal is fed back to the single-phase full-bridge inverter circuit; In addition, the filter of the grid-connected inverter includes a band-stop filter and a low-pass filter, and the low-pass filter is a first-order filter, and the band-stop filter is a second-order filter, wherein the band-stop filter can suppress specific signals within a specific frequency range, while allowing signals of other frequencies to pass through. If the harmonic frequency in the signal is known, the use of the band-stop filter can more effectively suppress the harmonics of these specific frequencies; the low-pass filter allows low-frequency signals to pass through, while suppressing high-frequency signals; the DC bus voltage signal is filtered by the band-stop filter and the low-pass filter to obtain the harmonic signal in the DC bus voltage signal; Therefore, a band-stop filter can be set to suppress high-frequency signals in the DC bus voltage signal. In this way, after the DC bus voltage signal passes through the first-order low-pass filter, it is filtered once for the high-frequency signal. However, at this time, due to the insufficient dynamic response characteristics and steady-state detection accuracy of the low-pass filter, some high-frequency signals may still remain in the DC bus voltage signal filtered by the first-order low-pass filter. Therefore, the DC bus voltage signal filtered by the first-order low-pass filter is filtered again by the second-order band-stop filter. Since the second-order band-stop filter is set to suppress high-frequency signals, most of the harmonic signals in the DC bus voltage signal obtained after filtering by the second-order band-stop filter have been filtered out. The filtered voltage signal obtained by the first-order low-pass filter and the second-order band-stop filter can be considered as a fundamental frequency signal without high-frequency harmonics. Based on this, in order to extract the harmonic signal in the DC bus voltage signal, the filtered voltage signal is subtracted from the original DC bus voltage signal, that is, the DC bus voltage signal obtained based on the DC bus voltage detection is subtracted from the filtered voltage signal. In this way, because the original DC bus voltage signal includes high-frequency harmonics and fundamental frequency signals, the filtered voltage signal includes the fundamental frequency signal, and the DC bus harmonic signal finally obtained can be considered as the high-frequency harmonics in the DC bus voltage signal; in this way, compared with the filtered voltage signal obtained only by filtering with a low-pass filter, the high-frequency harmonics in the filtered voltage signal obtained after performing first-order low-pass filtering and second-order band-stop filtering on the DC bus voltage signal are less, and after subtracting the filtered voltage signal from the DC bus voltage signal, a more complete DC bus harmonic signal can be obtained.

[0040] In a control method for a grid-connected inverter provided in another embodiment of the present application, regarding the above step S410, second-order band-stop filtering is performed by a band-stop filter, and the center frequency of the band-stop filter is N times the grid frequency, where N is greater than 1.

[0041] It can be understood that the center frequency of the band-stop filter is the frequency within the stop band of the band-stop filter. When eliminating interference of a specific frequency, the center frequency of the band-stop filter can be set to the specific interference frequency. In the present embodiment, the band-stop filter is used to filter out high-frequency harmonics in the DC bus voltage signal. Therefore, the center frequency of the band-stop filter is N times the grid frequency, and N is greater than 1. For example, the center frequency of the band-stop filter is two, three or four times the grid frequency. The center frequency setting of the band-stop filter can be determined based on the background harmonic frequency of the grid where the grid-connected inverter is located.

[0042] In a control method for a grid-connected inverter provided in another embodiment of the present application, a center frequency of the band-stop filter is twice the grid frequency.

[0043] It is understandable that in the grid-connected inverter, due to the nonlinear characteristics of the switching action and power electronic devices, the second harmonic of the grid frequency is often generated. In addition, when there is a negative-sequence component in the output of the grid-connected inverter, the instantaneous active and reactive power will have a fluctuating component of the second frequency. The center frequency of the band-stop filter is usually set to twice the grid frequency. Therefore, setting the center frequency of the band-stop filter to twice the grid frequency can effectively suppress the influence of the negative-sequence component, that is, effectively suppress the fluctuating component of the second frequency.

[0044] like Figure 6 As shown, Figure 6 It is a flow chart of a control method of a grid-connected inverter provided by another embodiment of the present application; regarding the above-mentioned step S120, it may include but is not limited to step S220.

[0045] Step S220: Perform proportional gain processing on the DC bus harmonic signal to obtain a first control signal.

[0046] It can be understood that proportional gain processing is a signal processing method that maintains a fixed proportional relationship between the output and the input, that is, the output signal is K times the input signal, where K is a proportional coefficient or gain.

[0047] In this embodiment, since the DC bus harmonic signal is a harmonic signal obtained after filtering the DC bus voltage signal, the harmonic signal is superimposed on the fundamental signal, and therefore the amplitude of the harmonic signal is usually smaller than the amplitude of the fundamental signal, the amplitude of the harmonic signal can be amplified by proportional gain processing, so that the control system can more effectively detect and respond to harmonics; in addition, after obtaining the first control signal from the DC bus harmonic signal, it is also necessary to combine the first control signal and the second control signal to obtain a feedback control signal, and the second control signal can be obtained after detecting the output current signal of the inverter circuit, according to the output current signal of the inverter circuit and the preset inverter circuit output The reference current signal is generated by a PI controller or a PID controller. When generating the second control signal, the PI controller or the PID controller will amplify the error signal between the output current signal of the inverter circuit and the preset reference current signal output by the inverter circuit. That is to say, the second control signal may be a control signal that has been processed with a proportional gain. Therefore, in order to match the amplitude of the second control signal, the DC bus harmonic signal is processed with a proportional gain to obtain the first control signal, and the proportional coefficient of the proportional gain of the DC bus harmonic signal may be the same as the proportional coefficient of the PI controller or the PID controller used to generate the second control signal.

[0048] like Figure 7 As shown, Figure 7 It is a flow chart of a control method of a grid-connected inverter provided by another embodiment of the present application; regarding the above-mentioned step S120, it may include but is not limited to step S320.

[0049] Step S320: Based on the inverter current detection, an inverter current detection signal is obtained, and a second control signal is obtained according to a preset inverter current reference signal and the inverter current detection signal.

[0050] In this embodiment, the inverter current detection may refer to detecting the current signal at the output end of the inverter circuit in the grid-connected inverter. The inverter current detection signal obtained based on the inverter current detection is also the current signal at the output end of the inverter circuit in the grid-connected inverter. After obtaining the inverter current detection signal, the error between the preset inverter current reference signal and the inverter current detection signal may be calculated to obtain a current error signal, and then the current error signal may be input into the current controller to generate a second control signal through the current controller.

[0051] It is understandable that the inverter current detection, the preset inverter current reference signal, the current error calculation and the current controller are components of a current feedback loop in the grid-connected inverter, and the current feedback loop in the grid-connected inverter is used to adjust the output current of the inverter.

[0052] like Figure 8 As shown, Figure 8It is a flow chart of a control method of a grid-connected inverter provided by another embodiment of the present application; regarding the above-mentioned step S130, it may include but is not limited to step S230 and step S330.

[0053] Step S230, adding the first control signal and the second control signal to obtain a PWM reference signal; Step S330: acquiring a PWM feedback signal based on grid voltage detection, and generating a feedback control signal for an inverter circuit according to the PWM reference signal and the PWM feedback signal.

[0054] In this embodiment, the first control signal is used to suppress the harmonic amount of the voltage signal of the DC bus in the grid-connected inverter, and the second control signal is used to suppress the harmonic amount of the output current signal of the inverter circuit in the grid-connected inverter, that is, the first control signal and the second control signal are both used for harmonic suppression. Therefore, after the first control signal and the second control signal are generated, the first control signal and the second control signal can be added to obtain a PWM reference signal for inputting a PWM drive, so that the harmonic amount of the voltage signal of the DC bus in the grid-connected inverter and the harmonic amount of the output current signal of the inverter circuit can be suppressed together; In addition, refer to Figure 5 After obtaining the grid-side voltage signal based on grid voltage detection, a grid voltage feedback control signal is obtained through a phase-locked loop, that is, a PWM feedback signal. The PWM feedback signal is used to suppress harmonics in the output signal of the grid-connected inverter. Therefore, it can be considered that the first control signal is a control signal for suppressing grid background harmonics, and the second control signal is a control signal for suppressing the harmonics of the grid-connected current of the grid-connected inverter under local nonlinear loads. The PWM reference signal and the PWM feedback signal are combined to generate a feedback control signal for the inverter circuit. The feedback control signal can take into account the suppression of grid background harmonics and harmonics of the output voltage or grid-connected current under local nonlinear loads.

[0055] In a control method for a grid-connected inverter provided in another embodiment of the present application, the second control signal is a harmonic suppression main control signal, and the first control signal is used to compensate for the harmonic suppression main control signal.

[0056] It can be understood that the main function of the grid-connected inverter is to ensure the quality of the basic output current to meet the power quality requirements of the power grid, and the harmonics caused by the local nonlinear load are generated by the load directly controlled by the grid-connected inverter. Therefore, the inverter can directly control these harmonics and can effectively suppress these harmonics to ensure the quality of the output current. The background harmonics of the power grid are generated by other loads and equipment on the power grid. The grid-connected inverter does not directly control these sources, and the feedback control signal is fed back to the inverter circuit. Therefore, the grid-connected inverter can effectively suppress the harmonics caused by the local nonlinear load; in addition, the impact of the background harmonics of the power grid on the grid current is mainly manifested as a disturbance, and the nonlinear characteristics of the local load may cause the inverter output current to be more volatile and unstable; Based on this, in the feedback control of the grid-connected inverter, the second control signal for suppressing the harmonics of the grid-connected current of the grid-connected inverter under the local nonlinear load can be regarded as the main control signal for harmonic suppression, and the first control signal for suppressing the background harmonics of the power grid can be regarded as the compensation control signal, and the first control signal is used to compensate for the main control signal for harmonic suppression.

[0057] In a control method for a grid-connected inverter provided in another embodiment of the present application, a feedback control signal is used to suppress harmonics of an output current of an inverter circuit.

[0058] It can be understood that the feedback control signal is fed back to the inverter circuit in the grid-connected inverter. Figure 5 The signal output by the PWM drive is fed back to the single-phase full-bridge inverter in the grid-connected inverter. Specifically, the feedback control signal is fed back to the inverter circuit in the grid-connected inverter to control the switch tube in the inverter circuit to be alternately turned on and off according to a predetermined switching mode, thereby adjusting the parameters of the output current signal of the inverter circuit, such as the current amplitude, phase and frequency, etc., so as to suppress the harmonics of the output current of the inverter circuit.

[0059] Based on the control methods of the grid-connected inverters of the above-mentioned various embodiments, various embodiments of the operation control device, the grid-connected inverter and the computer-readable storage medium of the present application are respectively proposed below.

[0060] like Fig. 9 As shown, Fig. 9 Schematic diagram of an operation control device for executing a control method for a grid-connected inverter provided by an embodiment of the present application. The operation control device 900 implemented in the present application includes: a processor 920, a memory 910, and a computer program stored in the memory 910 and executable on the processor 920, wherein: Fig. 9 In the figure, a processor 920 and a memory 910 are taken as an example.

[0061] The processor 920 and the memory 910 may be connected via a bus or other means. Fig. 9 The example of connecting through bus is taken in the following.

[0062] The memory 910, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer executable programs. In addition, the memory 910 may include a high-speed random access memory, and may also include a non-transitory memory, such as at least one disk storage device, a flash memory device, or other non-transitory solid-state storage device. In some embodiments, the memory 910 optionally includes a memory 910 remotely arranged relative to the processor 920, and these remote memories 910 can be connected to the operation control device 900 via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0063] Those skilled in the art will understand that Fig. 9 The device structure shown in the figure does not constitute a limitation on the operation control device 900, and may include more or less components than shown in the figure, or combine certain components, or arrange the components differently.

[0064] exist Fig. 9 In the operation control device 900 shown, the processor 920 can be used to call the control program stored in the memory 910, so as to implement the control method of the grid-connected inverter described above. Specifically, the non-transient software program and instructions required to implement the control method of the grid-connected inverter of the above embodiment are stored in the memory 910, and when executed by the processor 920, the control method of the grid-connected inverter of the above embodiment is executed.

[0065] It is worth noting that since the operation control device 900 of the embodiment of the present application can execute the control method of the grid-connected inverter of any of the above-mentioned embodiments, the specific implementation manner and technical effects of the operation control device 900 of the embodiment of the present application can refer to the specific implementation manner and technical effects of the control method of the grid-connected inverter of any of the above-mentioned embodiments.

[0066] In addition, an embodiment of the present application further provides a grid-connected inverter, which includes the operation control device of the above embodiment.

[0067] It is worth noting that since the grid-connected inverter of the embodiment of the present application includes the operation control device of the above-mentioned embodiment, and the operation control device of the above-mentioned embodiment can execute the control method of the grid-connected inverter of any of the above-mentioned embodiments, the specific implementation methods and technical effects of the grid-connected inverter of the embodiment of the present application can refer to the specific implementation methods and technical effects of the control method of the grid-connected inverter of any of the above-mentioned embodiments.

[0068] In addition, an embodiment of the present application further provides a computer-readable storage medium, which stores computer-executable instructions, and the computer-executable instructions are used to execute the control method of the grid-connected inverter described above. Figure 1 , Figure 3 to Figure 4 , Figures 6 to 8 The method steps in .

[0069] It is worth noting that since the computer-readable storage medium of the embodiment of the present application can execute the control method of the grid-connected inverter of any of the above-mentioned embodiments, the specific implementation methods and technical effects of the computer-readable storage medium of the embodiment of the present application can refer to the specific implementation methods and technical effects of the control method of the grid-connected inverter of any of the above-mentioned embodiments.

[0070] It will be appreciated by those skilled in the art that all or some of the steps and systems in the disclosed methods above may be implemented as software, firmware, hardware and appropriate combinations thereof. Some physical components or all physical components may be implemented as software executed by a processor, such as a central processing unit, a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium or a non-transitory medium and a communication medium or a temporary medium. As known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information such as computer-readable instructions, data structures, program modules or other data. Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disk DVD or other optical disk storage, magnetic cassettes, magnetic tapes, disk storage or other magnetic storage devices, or any other medium that may be used to store desired information and may be accessed by a computer. Furthermore, it is well known to those skilled in the art that communication media typically embodies computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

[0071] In several embodiments provided in the present application, it should be understood that the disclosed systems, apparatuses and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely schematic, for example, the division of units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of apparatuses or units, which can be electrical, mechanical or other forms. The units described as separate components may or may not be physically separated, and the components displayed 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 units may be selected according to actual needs to achieve the purpose of the scheme of this embodiment.

[0072] It should also be understood that the various implementations provided in the embodiments of the present application can be combined arbitrarily to achieve different technical effects.

[0073] The embodiments of the present application are described in detail above in conjunction with the accompanying drawings, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present application.

Claims

1. A control method for a grid-connected inverter, characterized in that: include: Acquire a DC bus voltage signal, perform band-stop filtering on the DC bus voltage signal, and obtain a DC bus harmonic signal; Convert the DC bus harmonic signal into a first control signal, and acquire a second control signal based on inverter current detection; A feedback control signal for an inverter circuit is generated according to the first control signal and the second control signal.

2. The control method according to claim 1, characterized in that: The step of obtaining a DC bus voltage signal comprises: A DC bus voltage analog signal is acquired based on DC bus voltage detection, and the DC bus voltage analog signal is converted into a digital signal to obtain a DC bus voltage signal.

3. The control method according to claim 1, characterized in that: The step of acquiring a DC bus voltage signal and performing band-stop filtering on the DC bus voltage signal to obtain a DC bus harmonic signal includes: Acquire a DC bus voltage signal, perform a first-order low-pass filter and a second-order band-stop filter on the DC bus voltage signal, and obtain a filtered voltage signal; The filtered voltage signal is subtracted from the DC bus voltage signal to obtain a DC bus harmonic signal.

4. The control method according to claim 3, characterized in that: The second-order band-stop filtering is performed by a band-stop filter, the center frequency of the band-stop filter is N times the grid frequency, and N is greater than 1.

5. The control method according to claim 4, characterized in that: The center frequency of the band-stop filter is twice the grid frequency.

6. The control method according to claim 1, characterized in that: The converting the DC bus harmonic signal into a first control signal comprises: Proportional gain processing is performed on the DC bus harmonic signal to obtain a first control signal.

7. The control method according to claim 1, characterized in that: The method of acquiring the second control signal based on inverter current detection includes: Based on the inverter current detection, an inverter current detection signal is acquired, and a second control signal is obtained according to a preset inverter current reference signal and the inverter current detection signal.

8. The control method according to claim 1, characterized in that: The step of generating a feedback control signal for an inverter circuit according to the first control signal and the second control signal comprises: Adding the first control signal and the second control signal to obtain a PWM reference signal; A PWM feedback signal is acquired based on grid voltage detection, and a feedback control signal for an inverter circuit is generated according to the PWM reference signal and the PWM feedback signal.

9. The control method according to claim 1, characterized in that: The second control signal is a harmonic suppression main control signal, and the first control signal is used to compensate for the harmonic suppression main control signal.

10. The control method according to claim 1, characterized in that: The feedback control signal is used to suppress harmonics of the output current of the inverter circuit.

11. An operation control device, characterized in that: The invention comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the control method according to any one of claims 1 to 10.

12. A grid-connected inverter, characterized in that: Includes the operation control device as claimed in claim 11.

13. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are used to enable a computer to execute the control method according to any one of claims 1 to 10.

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