Grid-connected control method, grid-connected control circuit and electronic device

Abstract

The application discloses a grid-connected control method, a grid-connected control circuit and electronic equipment. The grid-connected control method comprises the following steps: acquiring a grid voltage, an inverter current and an inverter voltage in an inverter grid-connected circuit; triggering the inverter grid-connected circuit to be connected to the grid when a voltage difference between the inverter voltage and the grid voltage is less than a first threshold range and a phase difference between the inverter voltage and the grid voltage is less than a second threshold range; obtaining a grid-connected current by using the inverter current and the inverter voltage; obtaining a grid-connected compensation voltage by multiplying the grid-connected current by a virtual impedance; obtaining an inverter modulation voltage by subtracting the grid-connected compensation voltage from the grid voltage; generating a first control signal by using the inverter modulation voltage; and sending the first control signal to the inverter grid-connected circuit and continuously setting a time length, so as to adjust the grid-connected current. In the above manner, the grid-connected control method adopts the virtual impedance for grid-connected compensation, does not increase the hardware cost, and effectively suppresses the grid-connected impact current by using the software algorithm.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of grid-connected power generation technology, in particular to a grid-connected control method, a grid-connected control circuit and an electronic device. BACKGROUND

[0002] Nowadays, with the rapid development of photovoltaic power generation, wind power generation, super capacitor energy storage and other power generation and energy storage technologies, how to reasonably control the grid-connected inverter to reliably connect to the power grid is becoming a hot research topic in the field of power generation.

[0003] However, before cutting into the grid, the output voltage of the inverter and the grid voltage cannot be completely the same in the mathematical sense, and at the same time, the grid switch is usually a mechanical switch including a relay and a contactor, and there is an unavoidable error in the action time of the grid switch. The grid algorithm cutting into work and the actual grid switch closing also have a time difference, so there is an impact current between the grid-connected inverter and the grid at the moment of grid connection. This impact current will affect the reliability of the grid switch and the inverter power semiconductor circuit, and also cause grid voltage distortion. SUMMARY

[0004] The technical problem solved by the present application is to provide a grid-connected control method, a grid-connected control circuit and an electronic device, which can solve the problem of unavoidable impact current in related art grid-connected control, thereby affecting the reliability of the hardware circuit and also causing grid voltage distortion.

[0005] To solve the above technical problem, one technical solution adopted by the present application is to provide a grid-connected control method applied to grid-connected control of an inverter grid-connected circuit, wherein the grid-connected control method comprises: obtaining a grid voltage, an inverter current and an inverter voltage in the inverter grid-connected circuit; detecting whether a voltage difference between the inverter voltage and the grid voltage is less than a first threshold range; if the voltage difference is less than the first threshold range, detecting whether a phase difference between the inverter voltage and the grid voltage is less than a second threshold range; if the phase difference is less than the second threshold range, sending a switch closing instruction to the inverter grid-connected circuit to trigger the inverter grid-connected circuit to be connected to the grid; obtaining a grid-connected current by using the inverter current and the inverter voltage; obtaining a grid-connected compensation voltage by multiplying the grid-connected current by a virtual impedance; obtaining an inverter modulation voltage by subtracting the grid-connected compensation voltage from the grid voltage; generating a first control signal by using the inverter modulation voltage; sending the first control signal to the inverter grid-connected circuit and continuously setting a time length to trigger the inverter grid-connected circuit to change a switching state, thereby adjusting the grid-connected current.

[0006] The step of obtaining the grid-connected compensation voltage by multiplying the grid-connected current by the virtual impedance comprises: performing a Park transformation on the grid-connected current to obtain a rotating transformed current; and obtaining the grid-connected compensation voltage by multiplying the rotating transformed current by the virtual impedance.

[0007] The step of subtracting the grid compensation voltage from the grid voltage to obtain the inverter modulation voltage comprises: performing a Park transformation on the grid voltage to obtain a rotating transformation voltage; and subtracting the grid compensation voltage from the rotating transformation voltage to obtain the inverter modulation voltage.

[0008] The step of generating the first control signal by using the inverter modulation voltage comprises: performing a Park inverse transformation on the inverter modulation voltage to obtain a transformed inverter voltage; and performing a space vector pulse width modulation on the transformed inverter voltage to obtain the first control signal.

[0009] The step of multiplying the grid current by the virtual impedance to obtain the grid compensation voltage comprises: multiplying the grid current by the virtual impedance to obtain an initial compensation voltage; and performing a filtering adjustment on the initial compensation voltage to obtain the grid compensation voltage.

[0010] The step of multiplying the grid current by the virtual impedance to obtain the grid compensation voltage is performed after the steps of obtaining the grid voltage, the inverter current and the inverter voltage in the inverter grid-connected circuit, and before the step of detecting whether the voltage difference between the inverter voltage and the grid voltage is less than the first threshold range, the method further comprising: performing an operation processing on the grid current by using a preset adjustment function to obtain the virtual impedance; wherein the virtual impedance is positively correlated with the grid current.

[0011] The step of detecting whether the voltage difference between the inverter voltage and the grid voltage is less than the first threshold range is performed after the steps of obtaining the grid voltage, the inverter current and the inverter voltage in the inverter grid-connected circuit, and before the step of multiplying the grid current by the virtual impedance to obtain the grid compensation voltage, the method further comprising: performing a proportional integral adjustment on an error value between the grid voltage and the inverter voltage to obtain an adjustment output value; generating a second control signal by using the adjustment output value; and sending the second control signal or the first control signal to the inverter grid-connected circuit to trigger the inverter grid-connected circuit to change a switching state, so as to adjust the inverter voltage.

[0012] The step of sending the first control signal to the inverter grid-connected circuit and maintaining for a set time length to trigger the inverter grid-connected circuit to change the switching state, so as to adjust the grid current is performed after the steps of obtaining the grid voltage, the inverter current and the inverter voltage in the inverter grid-connected circuit, and before the step of detecting whether the voltage difference between the inverter voltage and the grid voltage is less than the first threshold range, the method further comprising: performing an operation processing on the grid current and the grid voltage by using a grid adjustment algorithm to obtain a third control signal; and sending the third control signal to the inverter grid-connected circuit to trigger the inverter grid-connected circuit to change the switching state, so as to adjust the grid current.

[0013] To solve the above technical problems, another technical solution adopted by the present application is to provide a grid-connected control circuit, wherein the grid-connected control circuit is coupled with an inverter grid-connected circuit; and the grid-connected control circuit implements grid-connected control on the inverter grid-connected circuit by using the grid-connected control method as described in any one of the above.

[0014] To solve the above technical problems, still another technical solution adopted by the present application is to provide an electronic device, wherein the electronic device comprises a shell and a grid-connected control circuit connected to the shell; and the grid-connected control circuit is the grid-connected control circuit as described above.

[0015] The beneficial effects of the present application are: different from the prior art, the grid-connected control method provided by the present application obtains the grid voltage, the inverter current and the inverter voltage in the inverter grid-connected circuit, and when the voltage difference between the inverter voltage and the grid voltage is less than a first threshold range and the phase difference between the inverter voltage and the grid voltage is less than a second threshold range, the inverter grid-connected circuit is triggered to be connected to the grid, the inverter current and the inverter voltage are used to obtain the grid-connected current, the grid-connected current is multiplied by the virtual impedance to obtain the grid-connected compensation voltage, the grid-connected compensation voltage is subtracted from the grid voltage to obtain the inverter modulation voltage, the inverter modulation voltage is used to generate the first control signal, the first control signal is sent to the inverter grid-connected circuit, and the grid-connected current is continuously adjusted for a set time period, so that the grid-connected current can be negatively superimposed on the grid-connected current by multiplying the grid-connected current by the virtual impedance to form a negative feedback with the grid-connected current before the inverter grid-connected state, i.e., before the inverter grid-connected circuit is connected to the grid, so as to reduce the impact current existing when the inverter grid-connected circuit is connected to the grid; and the inverter voltage does not affect the tracking of the grid voltage before grid connection, and the grid-connected impact current is negatively fed back to inhibit the grid-connected impact current during grid connection, so as to effectively inhibit the grid-connected impact current by software algorithm without increasing the hardware cost. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0017] Figure 1 is a flowchart of the first embodiment of the grid-connected control method of the present application;

[0018] Figure 2 is a structural schematic diagram of the first embodiment of the grid-connected control circuit of the present application;

[0019] Figure 3 is Figure 1 a flowchart of an embodiment of S16 in the method;

[0020] Figure 4 is Figure 1 a logic framework diagram of an embodiment of the signal processing process in the grid-connected control method;

[0021] Figure 5 is Figure 1 a flowchart of another embodiment of S16 in the method;

[0022] Figure 6 is Figure 1 a logic framework diagram of another embodiment of the signal processing process in the grid-connected control method;

[0023] Figure 7 is Figure 1 a flowchart of an embodiment of the grid-connected control method in S17;

[0024] Figure 8 is Figure 1 a flowchart of an embodiment of the grid-connected control method in S18;

[0025] Figure 9 is a flowchart of a second embodiment of the grid-connected control method of the present application;

[0026] Figure 10 is a structural diagram of a second embodiment of the grid-connected control circuit of the present application;

[0027] Figure 11 is Figure 9 a waveform diagram of an embodiment of the signal related to the timing control strategy of the grid-connected control method;

[0028] Figure 12 is a flowchart of a third embodiment of the grid-connected control method of the present application;

[0029] Figure 13 is a structural diagram of an embodiment of the electronic device of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] The terms "first", "second", "third", "etc." are used only for descriptive purposes and do not connote or imply a relative importance or a specific order of importance. Thus, features defined with "first", "second" or "third" can include at least one of the features. In the description of the present application, the meaning of "a plurality" is at least two, for example, two, three, etc., unless otherwise specifically defined. All directional references, such as, for example, upper, lower, left, right, front, back, rear, etc., are in relation to the particular orientation of the figure in which the component is shown. Directional references are made only for the purpose of illustrating and describing the preferred embodiments and are in no way a limitation of the scope of the application. In addition, the terms "comprise", "comprising", "have", "having", "include", "including", "contain", "containing", etc. are used in the description of the application and are intended to be construed as "including", but not "consisting of". For example, a process, method, system, product, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements but can include additional steps or elements not expressly listed or inherent to such process, method, system, product, or apparatus.

[0032] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive or alternative embodiments. It is expressly understood that the embodiments described herein are merely examples from a whole class of comparable embodiments which those skilled in the art will readily appreciate. The term "comprises the use of" does not exclude additional steps or additional, unrecited materials used in the process, method, system, product or apparatus.

[0033] The application will be described in detail below with reference to the attached drawings and embodiments.

[0034] Reference is made to Figure 1 and Figure 2 wherein, Figure 1 is a flowchart of a first embodiment of the grid-connected control method of the present application, Figure 2 is a structural schematic diagram of a first embodiment of the grid-connected control circuit of the present application. Specifically, it can include the following steps:

[0035] S11: Obtain the grid voltage, the inverter current and the inverter voltage in the inverter grid-connected circuit.

[0036] It can be understood that the grid-connected control method in the present embodiment is specifically applied to the grid-connected control of the first inverter grid-connected circuit 30 as shown in Figure 2 The first grid-connected control circuit 20 is coupled to the first inverter grid-connected circuit 30 to implement grid-connected control on the first inverter grid-connected circuit 30 by using any one of the grid-connected control methods described herein.

[0037] It is worth mentioning that the grid-connected control is a key technology system to ensure the safe and stable access of distributed power sources (such as photovoltaic, wind power, energy storage, etc.) or power generation equipment to the power grid, and the core is to realize the coordinated management of power quality, power balance and system protection.

[0038] The power grid is a comprehensive power network system connecting power generation, power transmission, power distribution and power consumption links, and its core function is to realize safe and efficient transmission and dynamic balance regulation of electric energy.

[0039] In addition, "coupling" in this paper refers to any direct and indirect connection means. Therefore, if the first circuit is coupled to the second circuit in the text, it means that the first circuit can be directly connected to the second circuit through electrical connection or wireless transmission, optical transmission, etc. Signal connection method, or indirectly electrically connected or signal connected to the second circuit through other circuits or connection means.

[0040] In some embodiments, the first inverter grid-connected circuit 30 can be a three-phase full-bridge inverter circuit, a three-phase half-bridge inverter circuit, a single-phase bridge inverter circuit, or any other reasonable form of circuit topology, and the present embodiment does not limit this.

[0041] In some embodiments, the first grid-connected control circuit 20 can specifically include one of any reasonable circuit unit with signal processing function, such as control chip, DSP (Digital Signal Processing) chip, MCU (Micro Controller Unit) circuit, CPU (Central Processing Unit), single-chip microcomputer, field programmable gate array, programmable logic device, discrete gate or transistor logic device, discrete hardware, etc. The present application does not limit this.

[0042] Specifically, the first grid-connected control circuit 20 samples the inverter current and inverter voltage from the first inverter grid-connected circuit 30 in real time, and synchronously acquires the grid voltage for subsequent grid-connected condition judgment and feedback control.

[0043] The grid voltage refers to the alternating voltage signal from the grid side; the inverter voltage is the output voltage of the first inverter grid-connected circuit 30; and the inverter current is the output current of the first inverter grid-connected circuit 30, i.e. the current before grid connection.

[0044] In some embodiments, the grid voltage, inverter current and inverter voltage can be obtained by one or more of any reasonable sampling methods such as current sensor, voltage sensor, sampling resistor, Hall sensor or circuit model estimation, and the present application does not limit this.

[0045] S12: detecting whether the voltage difference between the inverter voltage and the grid voltage is less than a first threshold range.

[0046] It can be understood that, in order to ensure that no impact current or damage to equipment caused by too large voltage difference when grid-connected, it is necessary to ensure that the voltage and phase of the inverter voltage and the grid voltage are close enough before grid-connected.

[0047] Specifically, a first threshold range is set according to actual grid-connected requirements, such as ± 5% to ± 10% of the rated voltage, and whether the voltage difference between the inverter voltage and the grid voltage is less than the first threshold range is detected, so as to determine whether the inverter voltage and the grid voltage are close to synchronization.

[0048] It is worth noting that the first threshold range is specifically a change range of the voltage difference that is allowed to exist to ensure that no impact current or damage to equipment caused by too large voltage difference when grid-connected; and since the inverter voltage and the grid voltage are alternating voltages, the voltage difference actually corresponds to the difference between the effective value of the inverter voltage and the effective value of the grid voltage.

[0049] Wherein, if the voltage difference is less than the first threshold range, S13 is performed, and if the voltage difference is not less than the first threshold range, S15 is performed.

[0050] S13: detecting whether the phase difference between the inverter voltage and the grid voltage is less than a second threshold range.

[0051] Further, a second threshold range is set according to actual grid-connected requirements, and the phase information of the inverter voltage and the grid voltage is extracted, such as using phase-locked loop or FFT (fast Fourier transform) to respectively obtain and calculate the phase difference between the inverter voltage and the grid voltage, so as to determine whether the current obtained phase difference is less than the second threshold range, so as to further determine whether the inverter voltage and the grid voltage are close to phase synchronization.

[0052] It is worth noting that the second threshold range is specifically a change range of the phase difference that is allowed to exist to prevent power impact and grid disturbance caused by different phase.

[0053] Wherein, if the phase difference is less than the second threshold range, S14 is performed, and if the phase difference is not less than the second threshold range, S15 is performed.

[0054] S14: sending a switch-on instruction to the inverter grid-connected circuit to trigger the inverter grid-connected circuit to be connected to the grid.

[0055] It can be understood that when it is determined that the voltage difference between the current obtained inverter voltage and the grid voltage is less than the first threshold range, and the phase difference is also less than the second threshold range, it is determined that the current grid connection condition has been met, and the grid connection operation between the first inverter grid connection circuit 30 and the grid can be performed.

[0056] Specifically, the switch closing instruction is sent to any reasonable switching element such as a relay, a grid connection switch or a contactor in the first inverter grid connection circuit 30 for realizing grid connection, so that the first inverter grid connection circuit 30 is connected to the grid.

[0057] S15: Obtain the grid connection current by using the inverter current and the inverter voltage.

[0058] It is worth noting that in the actual grid connection scenario, the process of triggering the reliable closing of the grid connection switch to connect the first inverter grid connection circuit 30 to the grid will last for a certain time, that is, the closing duration of the grid connection switch cannot be ignored. Therefore, during the grid connection duration after the grid connection switch is closed until the grid connection output is stable, an impulse current will inevitably occur, and in order to avoid a sudden increase in current, a soft start strategy needs to be combined to gradually increase the output power of the first inverter grid connection circuit 30 during the grid connection duration; and before the grid connection switch is closed, the voltage and phase of the inverter voltage in the first inverter grid connection circuit 30 also need to be adjusted in real time to approach the voltage and phase of the grid in order to meet the grid connection condition.

[0059] Specifically, before the first inverter grid connection circuit 30 does not satisfy the grid connection condition, that is, before the grid connection switch is closed and / or after the first inverter grid connection circuit 30 is connected to the grid, the grid connection current is obtained by performing a corresponding function operation on the inverter current and the inverter voltage according to Kirchhoff's current law or by estimating the grid connection current through a corresponding mathematical model.

[0060] S16: Multiply the grid connection current by the virtual impedance to obtain the grid connection compensation voltage.

[0061] It can be understood that in order to suppress the grid connection impulse current during the grid connection duration, improve the grid connection current waveform quality, suppress resonance, enhance system stability, simulate line impedance characteristics, a virtual impedance is set, that is, an analog equivalent impedance existing in the algorithm, which is usually any two or three of a virtual resistor, a virtual inductor and a virtual capacitor in series or parallel combination network, or a pure virtual resistor, to simplify the algorithm, so that the grid connection current can be compensated by using the virtual impedance.

[0062] Specifically, the current obtained grid connection current is multiplied by the pre-set virtual impedance to obtain the grid connection compensation voltage.

[0063] S17: subtract the grid voltage from the grid compensation voltage to obtain an inverter modulation voltage.

[0064] It is worth noting that the grid voltage can be understood as the target reference voltage of the first inverter grid connection circuit 30, that is, the target voltage to which the inverter voltage is adjusted, which is also used as the target waveform basis for driving control. However, due to the impact current during grid connection, the grid voltage cannot be directly used as the target reference voltage of the first inverter grid connection circuit 30 to effectively suppress the grid connection impact current. Therefore, the grid voltage needs to be compensated and adjusted to reduce or increase the target reference voltage, so as to reduce or increase the output power of the first inverter grid connection circuit 30 by adjusting the on and off time, thereby suppressing the grid connection impact current.

[0065] Specifically, the grid voltage is subtracted from the currently obtained grid compensation voltage to obtain an inverter modulation voltage, which is used as the target waveform basis for driving control of the first inverter grid connection circuit 30.

[0066] It can be understood that before the grid connection switch of the first inverter grid connection circuit 30 is closed, that is, before the grid connection, the first inverter grid connection circuit 30 has not formed an electrical circuit with the grid, and the grid connection current is zero (in actual grid connection scenarios, due to sampling errors and calculation errors, the grid connection current is a small value, but it does not affect the adjustment of the inverter voltage). The control amount of the grid connection current through the virtual impedance, that is, the inverter modulation voltage, is zero (approximately zero), that is, the virtual impedance link does not affect the inverter voltage following the grid voltage.

[0067] After the grid connection switch is closed, before entering the grid connection state, that is, during the grid connection duration, the first inverter grid connection circuit 30 will form an electrical circuit with the grid, and the grid connection current will not be zero. The grid compensation voltage obtained through the virtual impedance link is negatively superimposed on the grid voltage to obtain an inverter modulation voltage, which is used to suppress the grid connection impact current.

[0068] When the grid connection current is positive, the inverter modulation voltage is reduced by negatively superimposing the grid voltage through the virtual impedance link, and the output voltage of the first inverter grid connection circuit 30 driven and adjusted, that is, the inverter voltage, is reduced, thereby forming a negative feedback to reduce the positive grid connection impact current. Conversely, when the grid connection current is negative, the inverter modulation voltage is increased by negatively superimposing the grid voltage through the virtual impedance link, and the output voltage of the first inverter grid connection circuit 30 driven and adjusted, that is, the inverter voltage, is increased, thereby forming a negative feedback to reduce the absolute value of the negative grid connection impact current.

[0069] S18: generate a first control signal using the inverter modulation voltage.

[0070] When the inverter modulation voltage is acquired, the current acquired inverter modulation voltage can be processed by using a voltage loop and / or a current loop to obtain a first control signal by using a PI (Proportional Integral) adjustment algorithm, a PID (Proportional Integral Derivative) adjustment algorithm, or any other reasonable feedback adjustment algorithm, and the duty cycle of the first control signal is dynamically adjusted.

[0071] In some embodiments, the first control signal can be one or more of a PWM (Pulse Width Modulation) signal, a PFM (Pulse Frequency Modulation) signal, or any other reasonable control signal, and the present application does not limit the same.

[0072] S19: The first control signal is sent to the inverter grid-connected circuit, and a set duration is continued to trigger the inverter grid-connected circuit to change the switching state, so as to adjust the grid-connected current.

[0073] The first control signal in dynamic adjustment is sent to the first inverter grid-connected circuit 30, and a set duration is continued to trigger the first inverter grid-connected circuit 30 to change the switching state in real time, so as to dynamically adjust the power supply output and the grid-connected current of the first inverter grid-connected circuit 30, and to suppress the impact current that may occur to the grid-connected current within the grid-connected duration.

[0074] It is worth noting that the set duration is the grid-connected duration with the switching-on instruction sent to the grid-connected switch in the first inverter grid-connected circuit 30 as the starting time, and is greater than the time required for reliable closure of the grid-connected switch, and can be set according to the maximum value of the time required for reliable closure of different grid-connected switches in any grid-connected scenario.

[0075] The above scheme reduces the inrush current existing when the first inverter grid-connected circuit 30 is connected with the power grid by multiplying the grid-connected current by a virtual impedance to negatively superimpose the grid-connected current to form a negative feedback with the grid-connected current before the first inverter grid-connected circuit 30 is connected with the power grid; and does not affect the inverter voltage tracking the grid voltage before grid connection, and forms a negative feedback inhibition effect on the grid inrush current during grid connection, so as to effectively suppress the grid inrush current by a software algorithm without increasing hardware cost. The method combines voltage synchronous detection, phase matching judgment, virtual impedance compensation and closed-loop current regulation mechanism, and aims to realize safe, stable and efficient connection of the inverter output to the power grid. The virtual impedance control can effectively enhance the system robustness, improve the grid current quality and suppress the resonance, and can be widely applied to photovoltaic grid-connected systems, energy storage inverter systems, microgrid grid-connected controllers and other new energy power electronic applications.

[0076] Further, in some embodiments, S16 can specifically include, after S11 and before S16: performing operation processing on the grid-connected current by using a preset adjustment function to obtain the virtual impedance.

[0077] It can be understood that, in order to suppress the grid inrush current during the grid connection duration, the virtual impedance can be a constant value, so that the grid compensation voltage is linearly and positively related to the grid-connected current, thereby forming a negative feedback on the grid-connected current; and in order to suppress the possible large grid inrush current, the virtual impedance can be further dynamically adjusted, and the virtual impedance is positively related to the grid-connected current, that is, when the grid-connected current is large, the virtual impedance is large, the negative feedback compensation amplitude on the grid-connected current is large, so as to more greatly suppress the grid inrush current; and when the grid-connected current is small, the virtual impedance is small, the negative feedback compensation amplitude on the grid-connected current is small, so as to more greatly suppress the grid inrush current.

[0078] In some embodiments, the preset adjustment function can be a linear function or a nonlinear monotonic function, or any reasonable monotonic function, which is not limited in the present application.

[0079] Please continue to refer to Figure 3 , Figure 3 is Figure 1 a flowchart of an embodiment of S16. In an embodiment, the grid connection control method of the present application further includes some more specific steps in addition to S11-S19. Specifically, S16 can further include the following steps:

[0080] S1611: performing Park transformation on the grid-connected current to obtain a rotating transformed current.

[0081] Please continue to refer to Figure 4 , Figure 4 is Figure 1The logic framework diagram of an embodiment of the signal processing flow in the grid-connected control method.

[0082] It can be understood that, in order to simplify the control algorithm and reduce the calculation dimension, the Park transformation can also be performed on the grid-connected current.

[0083] It is worth noting that the αβ→dq (Clarke-Park transformation) is used to convert the electrical quantities in the stationary two-phase coordinate system (αβ) to the synchronous rotating coordinate system (dq), which converts the alternating quantities to direct quantities, simplifying the control system design.

[0084] In which, the stationary coordinate system (αβ) is converted to the rotating coordinate system (dq), and the formula is:

[0085] ;

[0086] In which, θ is the rotation angle (usually the rotor electrical angle), the d-axis is aligned with the rotor magnetic field, and the q-axis leads the d-axis by 90°.

[0087] In addition, the αβ (Clarke) Clarke transformation is a mathematical tool used to simplify the analysis and control of three-phase systems. When applied to three-phase voltage, the transformation is represented as:

[0088] ;

[0089] The inverse transformation of mapping the αβ components back to the original three-phase voltage is:

[0090] ;

[0091] These transformations can also be similarly applied to three-phase currents, achieving a consistent representation of voltage and current in the αβ reference coordinate system. This method simplifies the control and analysis of three-phase systems by reducing a three-dimensional problem to two dimensions, improving computational efficiency and system performance.

[0092] Specifically, the grid-connected current is subjected to Park transformation by the above transformation formula to obtain the rotating transformed current, i.e. the first rotating component current i q and the second rotating component current i d .

[0093] Of course, in other embodiments, the grid-connected current can also not be subjected to Park transformation, but calculated in the form of three-phase current; and when the power grid is actually a single-phase power supply system, the grid-connected current is a single-phase current, and therefore does not need to be subjected to Park transformation.

[0094] S1612: Multiply the rotating transformed current by the virtual impedance to obtain the grid-connected compensation voltage.

[0095] Further, the rotating transformed current, i.e. the first rotating component current i q and the second rotating component current i d are multiplied by the preset virtual impedance Z respectively to obtain the grid-connected compensation voltage, and the grid-connected compensation voltage also corresponds to the first component compensation voltage and the second component compensation voltage.

[0096] Please continue to refer to Figure 5 , Figure 3 is Figure 1 the flowchart of another embodiment of S16 in FIG. 6. In an embodiment, the grid-connected control method of the present application further includes some more specific steps in addition to the above-mentioned S11-S19. Specifically, the above-mentioned S16 can further include the following steps:

[0097] S1621: multiplying the grid-connected current by the virtual impedance to obtain the initial compensation voltage.

[0098] Please continue to refer to Figure 6 , Figure 6 is Figure 1 the logic framework diagram of another embodiment of the signal processing flow in the grid-connected control method in FIG. 7.

[0099] It can be understood that, in order to ensure high-frequency stability, a filter link can be further connected in series after the virtual impedance Z link to improve the stability of the grid-connected compensation voltage.

[0100] Specifically, the grid-connected current currently obtained is multiplied by the preset virtual impedance Z to obtain the initial compensation voltage.

[0101] S1622: filtering and adjusting the initial compensation voltage to obtain the grid-connected compensation voltage.

[0102] The grid-connected compensation voltage, including the first component compensation voltage and the second component compensation voltage, is obtained by filtering and adjusting the initial compensation voltage by using the virtual filter component F.

[0103] Please continue to refer to Figure 7 , Figure 7 is Figure 1 the flowchart of an embodiment of S17 in FIG. 8. In an embodiment, the grid-connected control method of the present application further includes some more specific steps in addition to the above-mentioned S11-S19. Specifically, the above-mentioned S17 can further include the following steps:

[0104] S171: performing park transformation on the grid voltage to obtain the rotating transformed voltage.

[0105] Similarly, in order to simplify the control algorithm and reduce the calculation dimension, the park transformation is performed on the grid voltage to obtain the rotating transformed voltage, i.e. the first rotating component voltage e q and the second rotating component voltage ed .

[0106] Of course, in other embodiments, the grid voltage can also not be Park-transformed, but calculated in three-phase voltage form; and when the grid is actually a single-phase power supply system, the grid voltage is a single-phase voltage, and no Park transformation is needed.

[0107] S172: subtract the grid compensation voltage from the rotation-transformed voltage to obtain the inverter modulation voltage.

[0108] Further, the rotation-transformed voltage, i.e., the first rotation component voltage e q and the second rotation component voltage e d are respectively subtracted by the first component compensation voltage and the second component compensation voltage to obtain the first component inverter modulation voltage v q and the second component inverter modulation voltage v d .

[0109] Please continue to refer to Figure 8 , Figure 8 is Figure 1 the flowchart of an embodiment of S18. In an embodiment, the grid-connected control method of the present application further includes some more specific steps in addition to the above-mentioned S11-S19. Specifically, the above-mentioned S18 can further include the following steps:

[0110] S181: perform Park inverse transformation on the inverter modulation voltage to obtain the transformed inverter voltage.

[0111] Specifically, after obtaining the inverter modulation voltage, i.e., the first component inverter modulation voltage and the second component inverter modulation voltage, Park inverse transformation can be performed to convert it again into the stationary two-phase coordinate system to obtain the transformed inverter voltage, including the first transformed component voltage v α and the second transformed component voltage v β .

[0112] S182: perform space vector pulse width modulation on the transformed inverter voltage to obtain the first control signal.

[0113] It is worth mentioning that the main idea of SVPWM (Space Vector Pulse Width Modulation) is to take the ideal stator flux circle of three-phase symmetrical motor as the reference standard when three-phase symmetrical sine wave voltage is supplied, to make appropriate switching of different switching modes of three-phase inverter, so as to form PWM wave, and to track the accurate flux circle with the actual flux vector formed. The traditional SPWM method generates a sine wave power supply with adjustable frequency and voltage from the perspective of power supply, while the SVPWM method considers the inverter system and asynchronous motor as a whole, the model is relatively simple, and it is also convenient for real-time control of microprocessor.

[0114] Specifically, the first transformed component voltage v α and the second transformed component voltage v β are subjected to space vector pulse width modulation to obtain a first control signal PWM1.

[0115] Please refer to Figure 9 and Figure 10 , wherein, Figure 9 is a flowchart of the grid-connected control method of the second embodiment of the application, Figure 10 is a structural schematic diagram of the grid-connected control circuit of the second embodiment of the application. The grid-connected control method of the embodiment is a detailed embodiment of the grid-connected control method in Figure 1 , and specifically includes the following steps:

[0116] S41: obtaining the grid voltage, the inverter current and the inverter voltage in the inverter grid-connected circuit.

[0117] It can be understood that the grid-connected control method in the embodiment can be specifically the second grid-connected control circuit 50 to the grid voltage, the inverter current and the inverter voltage in the inverter grid-connected circuit as Figure 10The second inverter grid-connected circuit 60 shown realizes grid-connected control to connect to the power grid 102 after grid-connected regulation by the second inverter grid-connected circuit 60 using the independent power supply 101. The second inverter grid-connected circuit 60 includes an input voltage stabilizing circuit 61, a first power switch circuit 62, a second power switch circuit 63, a first filter inductor circuit 64, a second filter inductor circuit 65, a filter capacitor circuit 66, and a grid-connected switch 67. The input voltage stabilizing circuit 61 includes a first input capacitor Cr1 and a second input capacitor Cr2. The first power switch circuit 62 includes a first power switch tube Qg1, a second power switch tube Qg2, a third power switch tube Qg3, a fourth power switch tube Qg4, a fifth power switch tube Qg5, and a sixth power switch tube Qg6. The second power switch circuit 63 includes a first switch tube Q1, a second switch tube Q2, a third switch tube Q3, a fourth switch tube Q4, a fifth switch tube Q5, and a sixth switch tube Q6. The first filter inductor circuit 64 includes a first pre-inductor L11, a second pre-inductor L12, and a third pre-inductor L13. The second filter inductor circuit 65 includes a first post-inductor L21, a second post-inductor L22, and a third post-inductor L23. The filter capacitor circuit 66 includes a first capacitor C1, a second capacitor C2, and a third capacitor C3.

[0118] The first end of the first input capacitor Cr1 is coupled to the second end of the first switch tube Q1, the second end of the second switch tube Q2, the second end of the third switch tube Q3, and is used for being coupled to the first end of the independent power supply 101. The second end of the first input capacitor Cr1 is coupled to the first end of the second input capacitor Cr2, the third end of the first power switch tube Qg1, the third end of the second power switch tube Qg2, the third end of the third power switch tube Qg3, to form an o node. The second end of the second input capacitor Cr2 is coupled to the third end of the fourth switch tube Q4, the third end of the fifth switch tube Q5, the third end of the sixth switch tube Q6, and is used for being coupled to the second end of the independent power supply 101. The second end of the first power switch tube Qg1 is coupled to the second end of the second power switch tube Qg2. The second end of the third power switch tube Qg3 is coupled to the second end of the fourth power switch tube Qg4. The second end of the fifth power switch tube Qg5 is coupled to the second end of the sixth power switch tube Qg6. The third end of the second power switch tube Qg2 is coupled to the third end of the first switch tube Q1, the second end of the fourth switch tube Q4, and the first end of the first pre-inductor L11, to form an a node. The third end of the fourth power switch tube Qg4 is coupled to the third end of the second switch tube Q2, the second end of the fifth switch tube Q5, and the first end of the second pre-inductor L12, to form a b node. The third end of the sixth power switch tube Qg6 is coupled to the third end of the third switch tube Q3, the second end of the sixth switch tube Q6, and the first end of the third pre-inductor L13, to form a c node. The second end of the first pre-inductor L11 is coupled to the first end of the first post-inductor L21 and the first end of the first capacitor C1. The second end of the second pre-inductor L12 is coupled to the first end of the second post-inductor L22 and the first end of the second capacitor C2. The second end of the third pre-inductor L13 is coupled to the first end of the third post-inductor L23 and the first end of the third capacitor C3. The second end of the first capacitor C1 is coupled to the second end of the second capacitor C2 and the second end of the third capacitor C3. The second end of the first post-inductor L21 is coupled to the first end of the grid-connected switch 67. The second end of the second post-inductor L22 is coupled to the second end of the grid-connected switch 67. The second end of the third post-inductor L23 is coupled to the third end of the grid-connected switch 67. The fourth end, the fifth end, and the sixth end of the grid-connected switch 67 are used for being coupled to the A-phase access end, the B-phase access end, and the C-phase access end of the power grid 102, respectively.The second grid-connected control circuit 50 is coupled to the second end of the first pre-inductor L11, the second end of the second pre-inductor L12, the second end of the third pre-inductor L13, the first end of the first post-inductor L21, the first end of the second post-inductor L22, the first end of the third post-inductor L23, and the grid-connected switch 67, and is coupled to the first end of each of the first power switch Qg1, the second power switch Qg2, the third power switch Qg3, the fourth power switch Qg4, the fifth power switch Qg5, the sixth power switch Qg6, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, the fifth switch Q5, and the sixth switch Q6.

[0119] In some embodiments, the first power switch Qg1, the second power switch Qg2, the third power switch Qg3, the fourth power switch Qg4, the fifth power switch Qg5, the sixth power switch Qg6, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, the fifth switch Q5, and the sixth switch Q6 can specifically be one of a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a transistor, a thin film transistor, or a field effect transistor, or any other reasonable switch, to trigger the conduction or turn-off of the second end and the third end thereof when the first end thereof receives the driving control signal PWM sent by the second grid-connected control circuit 50, and the present application does not limit this.

[0120] In other embodiments, the second inverter grid-connected circuit 60 can specifically be a three-phase full-bridge inverter circuit, a three-phase half-bridge inverter circuit, a single-phase bridge inverter circuit, a single-phase inverter, a double-fire inverter, or any other reasonable circuit topology, and the present embodiment does not limit this.

[0121] Specifically, the second grid-connected control circuit 50 samples the inverter current Iinv and the inverter voltage Uinv in real time from the first filter inductor circuit 64 and the second filter inductor circuit 65, respectively, and synchronously samples the grid voltage Ugrid in real time from the input side of the grid 102, for subsequent grid-connected condition judgment and feedback control. inv-abc and the inverter voltage Uinv inv-abc , and the grid voltage Ugrid input from the grid 102. g-abc for subsequent grid-connected condition judgment and feedback control.

[0122] S42: proportionally and integrally adjusting the error value between the grid voltage and the inverter voltage to obtain an adjusted output value.

[0123] Please continue to refer to Figure 11 , Figure 11 is Figure 9 a waveform diagram of an embodiment of the grid-connected control method timing control strategy related signals in

[0124] It can be understood that, in the process of inverter grid connection, since the amplitude of the inverter voltage U inv-abc is from zero to the grid voltage U g-abc , and the inverter voltage U inv-abc needs to follow the phase of the grid voltage U g-abc , until the difference between the effective value of the inverter voltage U inv-abc and the effective value of the grid voltage U g-abc is less than a first threshold range, and the phase difference between the inverter voltage U inv-abc and the grid voltage U g-abc is less than a second threshold range, the grid connection switch 67 is triggered to be closed, and after a first time T1 from the grid connection switch 67 closing signal being sent out, the grid connection switch 67 can be reliably closed, and three different control stages can be divided therefrom, and different control algorithms can be used for the actual control requirements of different control stages.

[0125] Among them, the second grid connection control circuit 50 sends a closing instruction to the grid connection switch 67 at t0 moment, and after a first time T1, the grid connection switch 67 is reliably closed at t1 moment. The grid connection control of the second inverter grid connection circuit 60 can be specifically divided into a first control stage before t0 moment, a second control stage between t0 moment and t2 moment, and a third control stage after t2 moment.

[0126] It is worth noting that the t2 moment specifically refers to the corresponding moment after a second time T2 from the t0 moment as the starting moment. And the second time T2 is greater than the first time T1, so as to correspond to ensure that in different grid connection scenarios, each grid connection switch 67 can be reliably closed, and a safety margin time is left.

[0127] Specifically, in the first control stage, that is, before t0 moment, the second grid connection control circuit 50 can specifically set the grid voltage U g-abc as a target reference voltage, subtract the inverter voltage U g-abc from the grid voltage U inv-abc to obtain an error value, and perform proportional integral adjustment on the error value of U g-abc to obtain an adjustment output value.

[0128] S43: generating a second control signal by using the adjustment output value.

[0129] The preset control algorithm or the preset adjustment function is used to operate and process the adjustment output value to obtain the second control signal.

[0130] S44: sending the second control signal to the inverter grid connection circuit to trigger the inverter grid connection circuit to change the switch state, so as to adjust the inverter voltage.

[0131] The second control signal is sent to the first power switch Qg1, the second power switch Qg2, the third power switch Qg3, the fourth power switch Qg4, the fifth power switch Qg5, the sixth power switch Qg6, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, the fifth switch Q5, and the sixth switch Q6, respectively, to trigger the conduction or turn-off of each switch, so as to control the inverter voltage U inv-abc to gradually approach the target reference voltage, i.e., the grid voltage U g-abc , so as to approach the grid-connected condition.

[0132] S45: detecting whether the voltage difference between the inverter voltage and the grid voltage is less than a first threshold range.

[0133] It can be understood that, in the embodiment, when the voltage difference and the phase difference between the inverter voltage U inv-abc and the grid voltage U g-abc do not satisfy the grid-connected condition, i.e., the switch closing instruction is not sent to the grid-connected switch 67, the inverter voltage U inv-abc is still adjusted at the time t0, and thus the feedback control algorithm of the first control stage needs to be used, i.e., the method steps corresponding to S42-S44 are used.

[0134] Specifically, whether the voltage difference between the inverter voltage U inv-abc and the grid voltage U g-abc is less than the first threshold range is detected, so as to determine whether the inverter voltage U inv-abc and the grid voltage U g-abc are close to synchronization.

[0135] If the voltage difference is less than the first threshold range, S46 is executed, and if the voltage difference is not less than the first threshold range, S42 is executed.

[0136] S46: detecting whether the phase difference between the inverter voltage and the grid voltage is less than a second threshold range.

[0137] Specifically, whether the phase difference between the inverter voltage U inv-abc and the grid voltage U g-abc is less than the second threshold range is detected, so as to further determine whether the inverter voltage U inv-abc and the grid voltage U g-abc are close to phase synchronization.

[0138] If the phase difference is less than the second threshold range, S47 is executed, and if the phase difference is not less than the second threshold range, S42 is executed.

[0139] S47: send a switch-on instruction to the inverter grid-connected circuit to trigger the inverter grid-connected circuit to be connected to the power grid.

[0140] S48: obtain a grid-connected current by using the inverter current and the inverter voltage.

[0141] S49: multiply the grid-connected current by a virtual impedance to obtain a grid-connected compensation voltage.

[0142] S410: subtract the grid-connected compensation voltage from the grid voltage to obtain an inverter modulation voltage.

[0143] S411: generate a first control signal by using the inverter modulation voltage.

[0144] wherein S47, S48, S49, S410 and S411 are the same as S14, S15, S16, S17 and S18 in Figure 1 , and details are described in S14, S15, S16, S17 and S18 and related text description, which will not be repeated here.

[0145] S412: send the first control signal to the inverter grid-connected circuit and maintain for a certain time length to trigger the inverter grid-connected circuit to change the switch state, so as to adjust the grid-connected current.

[0146] It can be understood that after the grid-connected switch 67 is triggered to be closed, that is, between t0 and t2, the second control stage will be entered, and in order to effectively suppress the grid-connected inrush current, the feedback control algorithm needs to be switched to the virtual impedance algorithm, that is, the method steps corresponding to S47-S411 are used to perform real-time adjustment control on the inverter voltage U inv-abc .

[0147] Therefore, it can be known that before t0, the driving control signal PWM sent by the second grid-connected control circuit 50 to the second inverter grid-connected circuit 60 is actually the second control signal, and between t0 and t2, the driving control signal PWM is switched to the first control signal.

[0148] In other embodiments, in the first control stage before t0, the second grid-connected control circuit 50 can also specifically use the virtual impedance algorithm, that is, S47-S411 is used to perform real-time adjustment control on the inverter voltage U inv-abc , that is, the first control signal is used to realize driving control on the second inverter grid-connected circuit 60, which is not limited in the present application.

[0149] Specifically, the first control signal is sent to the first power switch tube Qg1, the second power switch tube Qg2, the third power switch tube Qg3, the fourth power switch tube Qg4, the fifth power switch tube Qg5, the sixth power switch tube Qg6, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, the fourth switch tube Q4, the fifth switch tube Q5, and the sixth switch tube Q6, and the first duration T1 is continuously operated, so as to trigger the conduction or turn-off of each switch tube, thereby dynamically adjusting the grid-connected current I g-abc in the grid-connected duration, i.e. between t0 and t2, to form an effective inhibition of the impact current that may occur. g-abc

[0150] Further, in some embodiments, the above S48 can specifically include: calculating the capacitor current I inv-abc using the inverter voltage U C-abc and the capacitance values of the first capacitor C1, the second capacitor C2, and the third capacitor C3; subtracting the capacitor current I inv-abc from the inverter current I C-abc to obtain the grid-connected current I g-abc .

[0151] It can be understood that the second inverter grid-connected circuit 60 specifically outputs power supply through the filter capacitor circuit 66, since the capacity of the filter capacitor circuit 66 is known, the capacitor current I inv-abc can be calculated according to the inverter voltage U C-abc and the capacitance values of the capacitors, and then the grid-connected current I inv-abc is calculated according to the Kirchhoff's current law by subtracting the capacitor current from the inverter current I g-abc , i.e. I g-abc = I inv-abc -I C-abc .

[0152] Please refer to Figure 12 , Figure 12 is a flowchart of the third embodiment of the grid-connected control method of the present application. The grid-connected control method of the present embodiment is a detailed embodiment of the grid-connected control method in the first embodiment of the grid-connected control method of the present application, and specifically includes the following steps: Figure 1

[0153] S71: obtaining the grid voltage, the inverter current in the inverter grid-connected circuit, and the inverter voltage.

[0154] S72: detecting whether the voltage difference between the inverter voltage and the grid voltage is less than a first threshold range.

[0155] S73: detecting whether the phase difference between the inverter voltage and the grid voltage is less than a second threshold range.

[0156] ​​S74: send a switch-on instruction to the inverter grid-connected circuit to trigger the inverter grid-connected circuit to connect to the power grid.

[0157] S75: obtain the grid-connected current by using the inverter current and the inverter voltage.

[0158] S76: multiply the grid-connected current by the virtual impedance to obtain the grid-connected compensation voltage.

[0159] S77: subtract the grid-connected compensation voltage from the grid voltage to obtain the inverter modulation voltage.

[0160] S78: generate the first control signal by using the inverter modulation voltage.

[0161] S79: send the first control signal to the inverter grid-connected circuit and keep for a set time period to trigger the inverter grid-connected circuit to change the switch state, thereby adjusting the grid-connected current.

[0162] Wherein, S71, S72, S73, S74, S75, S76, S77, S78 and S79 are the same as S11, S12, S13, S14, S15, S16, S17, S18 and S19 in Figure 1 , please refer to S11, S12, S13, S14, S15, S16, S17, S18 and S19 and their related text description, which will not be repeated here.

[0163] S710: obtain the third control signal by using the grid-connected regulation algorithm to perform operation processing on the grid-connected current and the grid voltage.

[0164] It can be understood that, as shown in Figure 11 , in the third control phase after t2, the grid-connected switch in the first inverter grid-connected circuit 30 has been reliably closed, at this time the first inverter grid-connected circuit 30 has also been reliably connected to the power grid, therefore the grid-connected regulation algorithm needs to be used to realize driving control of the first inverter grid-connected circuit 30.

[0165] Specifically, the grid-connected regulation algorithm is used to obtain the third control signal by performing real-time operation processing on the grid-connected current and the grid voltage.

[0166] It is worth mentioning that after the first inverter grid-connected circuit 30 is reliably connected to the power grid, the grid-connected regulation algorithm realized for the first inverter grid-connected circuit 30 is a relatively mature technical means in the art, which will not be repeated here.

[0167] S711: send the third control signal to the inverter grid-connected circuit to trigger the inverter grid-connected circuit to change the switch state, thereby adjusting the grid-connected current.

[0168] After the time t2, the first grid-connected control circuit 20 sends a driving control signal to the first inverter grid-connected circuit 30, and the driving control signal is switched to a third control signal. The third control signal is used to trigger the switching elements inside the first inverter grid-connected circuit 30 to change the switching state in real time, so as to dynamically adjust the power supply output and the grid-connected current of the first inverter grid-connected circuit 30.

[0169] The application also provides an electronic device, please refer to Figure 13 , Figure 13 is a structural schematic diagram of an embodiment of the electronic device of the application. In the embodiment, the electronic device 80 comprises a shell 81 and a third grid-connected control circuit 82 connected to the shell 81.

[0170] It should be noted that the third grid-connected control circuit 82 described in the embodiment is the first grid-connected control circuit 20 or the second grid-connected control circuit 50 described in any of the above embodiments. For details, please refer to Figures 1-12 and related text content, which will not be repeated here.

[0171] The application has the following advantages: Unlike the prior art, the grid-connected control method provided by the application obtains the grid voltage, the inverter current and the inverter voltage in the inverter grid-connected circuit, and when the voltage difference between the inverter voltage and the grid voltage is less than a first threshold range and the phase difference between the inverter voltage and the grid voltage is less than a second threshold range, the inverter grid-connected circuit is triggered to be connected to the grid. The inverter current and the inverter voltage are used to obtain the grid-connected current, the grid-connected current is multiplied by the virtual impedance to obtain the grid-connected compensation voltage, the grid voltage is subtracted by the grid-connected compensation voltage to obtain the inverter modulation voltage, the first control signal is generated by using the inverter modulation voltage, the first control signal is sent to the inverter grid-connected circuit, and the grid-connected current is continuously adjusted for a certain period of time. Therefore, before the inverter grid-connected circuit is connected to the grid, the grid-connected current is negatively superimposed on the grid-connected current by multiplying the grid-connected current by the virtual impedance, which forms a negative feedback with the grid-connected current, so as to reduce the impact current when the inverter grid-connected circuit is connected to the grid. Before the grid connection, the inverter voltage does not affect the tracking of the grid voltage, and the grid-connected impact current is negatively fed back during the grid connection process, so as to effectively suppress the grid-connected impact current by software algorithm without increasing the hardware cost.

[0172] The above is only an embodiment of the application, and does not limit the patent scope of the application. Any equivalent structure or equivalent flow transformation obtained by using the content of the specification and the drawings, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the application.

Claims

1. A grid-connected control method applied to grid-connected control of an inverter grid-connected circuit, characterized by, The grid-connected control method comprises: obtaining grid voltage, inverter current and inverter voltage in the inverter grid-connected circuit; detecting whether a voltage difference between the inverter voltage and the grid voltage is less than a first threshold range; if the voltage difference is less than the first threshold range, detecting whether a phase difference between the inverter voltage and the grid voltage is less than a second threshold range; if the phase difference is less than the second threshold range, sending a switch closing instruction to the inverter grid-connected circuit to trigger the inverter grid-connected circuit to be connected to the grid; obtaining a grid-connected current by using the inverter current and the inverter voltage; multiplying the grid-connected current by a virtual impedance to obtain a grid-connected compensation voltage; subtracting the grid-connected compensation voltage from the grid voltage to obtain an inverter modulation voltage; wherein, when the grid-connected current is positive, the inverter modulation voltage is correspondingly reduced; when the grid-connected current is negative, the inverter modulation voltage is correspondingly increased; generating a first control signal by using the inverter modulation voltage; sending the first control signal to the inverter grid-connected circuit for a set time period to trigger the inverter grid-connected circuit to change a switch state, so as to adjust the grid-connected current.

2. The grid-connected control method according to claim 1, characterized in that, The step of multiplying the grid-connected current by a virtual impedance to obtain a grid-connected compensation voltage comprises: performing a Park transformation on the grid-connected current to obtain a rotationally transformed current; multiplying the rotationally transformed current by the virtual impedance to obtain the grid-connected compensation voltage.

3. The grid-connected control method according to claim 2, characterized in that, The step of subtracting the grid-connected compensation voltage from the grid voltage to obtain an inverter modulation voltage comprises: performing a Park transformation on the grid voltage to obtain a rotationally transformed voltage; subtracting the grid-connected compensation voltage from the rotationally transformed voltage to obtain the inverter modulation voltage.

4. The grid-connected control method according to claim 3, characterized in that, The step of generating a first control signal by using the inverter modulation voltage comprises: performing a Park inverse transformation on the inverter modulation voltage to obtain a transformed inverter voltage; performing a space vector pulse width modulation on the transformed inverter voltage to obtain the first control signal.

5. The grid-connected control method according to claim 1, characterized in that, The step of multiplying the grid-connected current by a virtual impedance to obtain a grid-connected compensation voltage comprises: multiplying the grid-connected current by a virtual impedance to obtain an initial compensation voltage; performing a filtering adjustment on the initial compensation voltage to obtain the grid-connected compensation voltage.

6. The grid-connected control method of any one of claims 1-5, wherein, Before the step of multiplying the grid-connected current by a virtual impedance to obtain a grid-connected compensation voltage, the method further comprises: performing an operation processing on the grid-connected current by using a preset adjustment function to obtain the virtual impedance; wherein, the virtual impedance is positively correlated with the grid-connected current.

7. The grid-connected control method of any one of claims 1-5, wherein, After the step of obtaining grid voltage, inverter current and inverter voltage in the inverter grid-connected circuit, and before the step of detecting whether a voltage difference between the inverter voltage and the grid voltage is less than a first threshold range, the method further comprises: performing a proportional integral adjustment on an error value between the grid voltage and the inverter voltage to obtain an adjustment output value; generating a second control signal by using the adjustment output value; sending the second control signal or the first control signal to the inverter grid-connected circuit to trigger the inverter grid-connected circuit to change a switch state, so as to adjust the inverter voltage.

8. The grid-connected control method of any one of claims 1-5, wherein, The step of sending the first control signal to the inverter grid-connected circuit and maintaining for a time duration to trigger the inverter grid-connected circuit to change the switching state so as to adjust the grid-connected current further comprises: adopting a grid-connected regulation algorithm to perform operation processing on the grid-connected current and the grid voltage to obtain a third control signal; sending the third control signal to the inverter grid-connected circuit to trigger the inverter grid-connected circuit to change the switching state so as to adjust the grid-connected current.

9. A grid-tie control circuit, characterized by The grid-connected control circuit is coupled with the inverter grid-connected circuit. The grid-connected control circuit adopts the grid-connected control method according to any one of claims 1-8 to implement grid-connected control on the inverter grid-connected circuit.

10. An electronic device, comprising: The electronic device comprises a shell and a grid-connected control circuit connected to the shell. The grid-connected control circuit is the grid-connected control circuit according to claim 9.

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