Reactive power regulation control method for grid-connected inverter, grid-connected inverter and storage medium

Abstract

The present application relates to the field of microgrid technology, and discloses a reactive power regulation control method for a grid-connected inverter, a grid-connected inverter, and a storage medium, wherein the method includes: obtaining a power factor value, determining a grid-connected reference current, obtaining a grid voltage, and determining the current working area of ​​the grid-connected inverter according to the polarity of the grid voltage and the polarity of the grid-connected reference current; obtaining a DC input voltage, and determining the switching cycle, duty cycle, and high-frequency working sequence of each switch tube in the working area according to the DC input voltage, the grid voltage, and the cycle calculation rule corresponding to the working area; and controlling each switch tube to be turned on at zero voltage in the working area based on its high-frequency working sequence according to the switching cycle, duty cycle, and high-frequency working sequence of each switch tube in the working area. The method of the present application is adopted to realize the zero-voltage turning on of the switch tube when the grid-connected inverter is subjected to reactive power regulation, and effectively reduce the loss caused by the turning on of the switch tube.

Description

Technical Field

[0001] The present application relates to the field of microgrid technology, and in particular to a reactive power regulation control method for a grid-connected inverter, a grid-connected inverter, and a storage medium. Background Art

[0002] Grid-connected inverters are widely used in the field of microgrid technology. Common grid-connected inverters are composed of four switch tubes and a filter circuit. When the grid-connected current phase angle needs to be changed for reactive power regulation, high-frequency current is generated by controlling the high-frequency switching action of the switch tube, and then the industrial frequency AC is fed into the grid after passing through the filter circuit. However, the conventional reactive power regulation hard-on control method will cause large switching losses of the switch tube, which is not conducive to the development of grid-connected inverters towards high frequency and high efficiency. Summary of the invention

[0003] The embodiments of the present application aim to provide a reactive power regulation control method for a grid-connected inverter, a grid-connected inverter and a storage medium, which can achieve zero-voltage conduction of the switch tube during reactive power regulation of the grid-connected inverter and solve the problem of excessive turn-on loss.

[0004] To solve the above technical problems, the present application provides the following technical solutions:

[0005] According to a first aspect of the present application, a reactive power regulation control method for a grid-connected inverter is provided, the method comprising:

[0006] Obtaining a power factor value, and determining a grid-connected reference current according to the power factor value;

[0007] Obtaining a grid voltage, and determining a current working area of ​​the grid-connected inverter according to the polarity of the grid voltage and the polarity of the grid-connected reference current;

[0008] Obtaining a DC input voltage, and determining a switching period, a duty cycle, and a high-frequency working sequence of each switch tube in the working area according to the DC input voltage, the grid voltage, and a period calculation rule corresponding to the working area, wherein the period calculation rule is a calculation rule for a switching period that satisfies a zero voltage switching condition;

[0009] According to the switching period, duty cycle and high-frequency working sequence of each switch tube in the working area, each switch tube is controlled to be turned on with zero voltage in the working area based on its high-frequency working sequence.

[0010] Optionally, before determining the switching period, duty cycle and high-frequency working timing of each switch tube in the working area, the method further includes:

[0011] Determine the start / end time point of the switching cycle that meets the zero voltage switching condition in each of the working regions according to a set of waveform data of the drain-source voltage at both ends of the high-frequency operating switch tube and the corresponding filter inductor current in each of the working regions;

[0012] A calculation rule for the switching period corresponding to each of the working areas is determined based on the start / end time points of the switching period in each of the working areas.

[0013] Optionally, the zero voltage turn-on condition is satisfied when: the start / end time point of the switching cycle is the time point when the filter inductor current and the drain-source voltage in the set of waveform data are both zero.

[0014] Optionally, the grid-connected inverter includes a DC voltage input source, a switch tube , , , And the body diode connected in parallel to the switch tube , , , and output capacitor , , , , connected to the switch tube and Filter inductance of the bridge arm and filter capacitors , connected to the switch tube and Filter inductance of the bridge arm and filter capacitors , the determining of the current working area of ​​the grid-connected inverter according to the polarity of the grid voltage and the polarity of the grid-connected reference current comprises:

[0015] When the polarity of the grid-connected reference current is positive or zero and the polarity of the grid voltage is positive or zero, determining that the current working area of ​​the grid-connected inverter is the first area;

[0016] When the polarity of the grid-connected reference current is negative and the polarity of the grid voltage is positive, determining that the current working area of ​​the grid-connected inverter is the second area;

[0017] When the polarity of the grid-connected reference current is negative or zero and the polarity of the grid voltage is negative or zero, determining that the current working area of ​​the grid-connected inverter is the third area;

[0018] When the polarity of the grid-connected reference current is positive and the polarity of the grid voltage is negative, it is determined that the current working area of ​​the grid-connected inverter is the fourth area.

[0019] Optionally, when the grid-connected inverter operates in the first region or the third region, the first switching cycle that meets the zero voltage switching condition The calculation rules are:

[0020]

[0021] When the grid-connected inverter operates in the second region or the fourth region, the second switching cycle that meets the zero voltage switching condition The calculation rules are:

[0022]

[0023] in,

[0024] ,

[0025] ,

[0026] is the peak value of the filter inductor current in the first region or the third region, is the peak value of the filter inductor current in the second region or the fourth region, is the valley value of the filter inductor current in the second region or the fourth region, is the DC input voltage, is the grid voltage, is the inductance of the filter inductor, is the output capacitor value, is the adjustment value of the first switching period, is the adjustment value of the second switching period, and The value range of is an integer greater than or equal to zero.

[0027] Optionally, determining the high-frequency working timing of each switch tube in the working area includes:

[0028] When the grid-connected inverter operates in the first region, it is determined that the switch tube / In the first switching cycle The first switch conduction stage High frequency action;

[0029] When the grid-connected inverter operates in the second region, it is determined that the switch tube / In the second switching cycle of High frequency action and switch tube / In the second switching cycle of High frequency action;

[0030] When the grid-connected inverter operates in the third region, it is determined that the switch tube / In the first switching cycle The first switch conduction stage High frequency action;

[0031] When the grid-connected inverter operates in the fourth region, it is determined that the switch tube / In the second switching cycle of High frequency action and switch tube / In the second switching cycle of High frequency action.

[0032] Optionally, when the grid-connected inverter operates in the first area and the third area, the first duty cycle that satisfies the zero voltage switching condition for:

[0033]

[0034] When the grid-connected inverter operates in the first area and the third area, the second duty cycle that meets the zero voltage switching condition , the third duty cycle They are:

[0035]

[0036] .

[0037] According to a second aspect of the present application, a grid-connected inverter is provided, the grid-connected inverter comprising an inverter circuit and a controller, the controller being used to execute the method described in the above part.

[0038] According to a third aspect of the present application, a grid-connected inverter is provided, the grid-connected inverter comprising an inverter circuit and a controller, the inverter circuit comprising a DC voltage input source, a switch tube , , , And the body diode connected in parallel to the switch tube , , , and output capacitor , , , , connected to the switch tube and Filter inductance of the bridge arm and filter capacitors , connected to the switch tube and Filter inductance of the bridge arm and filter capacitors , the controller is used to execute the method described above.

[0039] According to a fourth aspect of the present application, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the processor executes the steps of any of the above-mentioned methods for reactive power regulation control of a grid-connected inverter.

[0040] The beneficial effects of the embodiments of the present application are as follows: Different from the prior art, in the embodiments of the present application, a reactive power regulation control method for a grid-connected inverter is provided. First, a power factor value is obtained, a grid-connected reference current is determined, and a grid voltage is obtained. According to the polarity of the grid voltage and the polarity of the grid-connected reference current, the current working area of ​​the grid-connected inverter is determined; then, a DC input voltage is obtained, and the switching cycle, duty cycle and high-frequency working sequence of each switch tube in the working area are determined according to the DC input voltage, the grid voltage and the cycle calculation rule corresponding to the working area; finally, according to the switching cycle, duty cycle and high-frequency working sequence of each switch tube in the working area, each switch tube is controlled to be turned on at zero voltage in the working area based on its high-frequency working sequence. The method of the present application is adopted to realize the zero-voltage turning on of the switch tube when the grid-connected inverter is subjected to reactive power regulation, and effectively reduce the loss caused by the turning on of the switch tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0042] Figure 1 is a schematic structural diagram of a grid-connected inverter provided in an embodiment of the present application;

[0043] Figure 2 is a schematic diagram of the structure of the controller provided in an embodiment of the present application;

[0044] Figure 3 yes Figure 1 Schematic diagram of the PWM drive signal of the switch tube when the grid-connected reference current of the grid-connected inverter leads the grid voltage;

[0045] Figure 4 yes Figure 1 Schematic diagram of the PWM drive signal of the switch tube when the grid-connected reference current of the grid-connected inverter lags behind the grid voltage;

[0046] Figure 5 It is a flow chart of a reactive power regulation control method of a grid-connected inverter provided in an embodiment of the present application;

[0047] Figure 6 yes Figure 3 Middle area A switch tube Drive, drain-source voltage and the first filter inductor current The first set of waveform diagrams;

[0048] Figure 7 yes Figure 3 Middle area A switch tube Drive, drain-source voltage and the first filter inductor current The second set of waveform diagrams;

[0049] Figure 8 yes Figure 3 Middle area B switch tube Drive, drain-source voltage and the second filter inductor current The first set of waveform diagrams;

[0050] Fig. 9 yes Figure 3 Middle area B switch tube Drive, drain-source voltage and the second filter inductor current The second set of waveform diagrams;

[0051] Fig.10 yes Figure 3 Middle area C switch tube Drive, drain-source voltage and the second filter inductor current A set of waveform diagrams;

[0052] Fig.11 yes Figure 3 Middle area D switch tube Drive, drain-source voltage and the first filter inductor current A set of waveform diagrams;

[0053] Fig.12 is Figure 3 Middle area A adopts Figure 1 The simulation control effect diagram of the reactive power regulation control method of the grid-connected inverter;

[0054] Fig.13 is Figure 3 Middle area B adopts Figure 1 The simulation control effect diagram of the reactive power regulation control method of the grid-connected inverter;

[0055] Fig.14 is Figure 3 Middle area D adopts Figure 1 Control effect diagram of the reactive power regulation control method of grid-connected inverter. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0057] In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0058] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0059] See also Figure 1 , Figure 1 Schematic diagram of the structure of the grid-connected inverter provided in the embodiment of the present application. Figure 1 As shown in FIG. 1 , the grid-connected inverter includes an inverter circuit 10, a controller 20, a DC voltage sampling unit 30, and a grid voltage sampling unit 40. The inverter circuit 10 includes a DC voltage input source, a switch tube, and a DC voltage sampling unit. , , , (hereinafter referred to as switch tube ) and connected in parallel to the switch tube The body diode on , , , (Hereinafter referred to as body diode ) and output capacitor , , , (Hereinafter referred to as output capacitor ), connected to the switch tube and Filter inductance of the bridge arm and filter capacitors , connected to the switch tube and Filter inductance of the bridge arm and filter capacitors To maintain topological symmetry, the filter inductor and The selection is consistent, the output capacitor The selection is also the same, that is: and .in, is the inductance of the filter inductor, is the capacitance of the output capacitor.

[0060] The DC voltage sampling unit 30 is arranged at both sides of the DC voltage input source for real-time acquisition of the DC input voltage; the grid voltage sampling unit 40 is arranged at both sides of the grid voltage for real-time acquisition of the grid voltage.

[0061] The controller 20 is connected to the inverter circuit 10, the DC voltage adopting unit 30 and the grid voltage sampling unit 40 respectively. Connection, based on the built-in control program to control the switch In some embodiments, the controller may be a microcontroller unit (MCU) or a digital signal processing (DSP) controller.

[0062] Please refer to Figure 2 , Figure 2 20 is exemplarily shown. Figure 2 As shown, the controller 20 includes at least one processor 21 and a memory 22, wherein the memory 22 may be built in the controller 20 or externally located outside the controller 20, and the memory 22 may also be a remotely located memory connected to the controller 20 via a network.

[0063] The memory 22, as a non-volatile computer-readable storage medium, can be used to store non-volatile software programs, non-volatile computer executable programs and modules. The memory 22 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; the data storage area may store data created according to the use of the terminal, etc. In addition, the memory 22 may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other non-volatile solid-state storage device. In some embodiments, the memory 22 may optionally include a memory remotely arranged relative to the processor 21, and these remote memories may be connected to the terminal 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.

[0064] The processor 21 performs various functions of the terminal and processes data by running or executing software programs and / or modules stored in the memory 22, and calling data stored in the memory 22, thereby monitoring the terminal as a whole, for example, implementing the reactive power regulation control method of the grid-connected inverter described in any embodiment of the present application.

[0065] The processor 21 may be one or more, Figure 2 A processor 21 is taken as an example. The processor 21 and the memory 22 may be connected via a bus or other means. The processor 21 may include a central processing unit (CPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a controller, a field programmable gate array (FPGA) device, etc. The processor 21 may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

[0066] See also Figure 3 and Figure 4 , Figure 3 yes Figure 1 Schematic diagram of the PWM drive signal of the switch tube when the grid-connected reference current of the grid-connected inverter leads the grid voltage; Figure 4 yes Figure 1 Schematic diagram of the PWM drive signal of the switch tube when the grid-connected reference current of the grid-connected inverter lags behind the grid voltage.

[0067] by Figure 3 Taking the grid-connected reference current leading the grid voltage as an example, according to the grid voltage Polarity and grid-connected reference current According to the polarity of the power frequency cycle, the waveform of a power frequency cycle can be divided into four areas: A, B, C, and D. In area A, and , switch tube High frequency action, switch tube Keep off; in area B, and , switch tube All high-frequency actions; in area C, and , switch tube High frequency action, switch tube Keep off; in region D, and , switch tube All high-frequency actions. It should be noted that for and =0, or =0 and 0, or =0 and ,or and = 0 can be divided into any area adjacent to it. For example, =0 and 0 can also be divided into area B.

[0068] When the switch High frequency action, switch tube When the switch is turned off, the current flows from the positive terminal of the DC voltage input source to the positive terminal of the switch. and filter inductor Into the grid The positive electrode, and then the grid The negative pole of the filter inductor And switch tube Return to the negative pole of the DC voltage input source. High frequency action, switch tube When the switch is turned off, the current flows from the positive terminal of the DC voltage input source to the positive terminal of the switch. and filter inductor Into the grid The negative pole of the grid The positive pole, through the filter inductor And switch tube Return to the negative terminal of the DC voltage input source. Figure 3 and Figure 4 It can be seen that the pulse width of the high-frequency PWM (pulse width modulation) drive signal that drives the switch tube changes according to the sinusoidal law.

[0069] See also Figure 5 , Figure 51 is a flowchart of a reactive power regulation control method for a grid-connected inverter provided in an embodiment of the present application. The grid-connected inverter includes an inverter circuit, a controller, a DC voltage sampling unit, and a grid voltage sampling unit. In some embodiments, the grid-connected inverter can be Figure 1 The specific implementation process has been described in detail in the above embodiment and will not be repeated here.

[0070] like Figure 5 As shown, the reactive power regulation control method of the grid-connected inverter includes:

[0071] Step S501, obtaining a power factor value, and determining a grid-connected reference current according to the power factor value.

[0072] In an AC circuit, the phase difference between voltage and current ( ) is called the power factor and is represented by the symbol In numerical terms, power factor is the ratio of active power to apparent power, i.e. In the embodiment of the present application, the power factor value is preset by the user. When the grid-connected inverter performs reactive power regulation, it obtains the power factor value set by the user and calculates the grid-connected reference current based on the following formula:

[0073] (1)

[0074] in, is the amplitude of the grid-connected reference current, is the phase of the grid-connected reference current.

[0075] Step S502, obtaining the grid voltage, and determining the current working area of ​​the grid-connected inverter according to the polarity of the grid voltage and the polarity of the grid-connected reference current.

[0076] In one embodiment, when the polarity of the grid-connected reference current is positive or zero and the polarity of the grid voltage is positive or zero, it is determined that the current working area of ​​the grid-connected inverter is the first area (i.e. Figure 3 When the polarity of the grid-connected reference current is negative and the polarity of the grid voltage is positive, it is determined that the current working area of ​​the grid-connected inverter is the second area (ie Figure 3 When the polarity of the grid-connected reference current is negative or zero and the polarity of the grid voltage is negative or zero, it is determined that the current working area of ​​the grid-connected inverter is the third area (i.e. Figure 3 When the polarity of the grid-connected reference current is positive and the polarity of the grid voltage is negative, it is determined that the current working area of ​​the grid-connected inverter is the fourth area (ie Figure 3 middle area D).

[0077] Step S503, obtaining a DC input voltage, and determining a switching period, a duty cycle, and a high-frequency working sequence of each switch tube in the working area according to the DC input voltage, the grid voltage, and a period calculation rule corresponding to the working area.

[0078] Among them, the cycle calculation rule is the calculation rule of the switching cycle that meets the zero voltage turn-on condition. In different working areas, the high-frequency working timing of each switch tube is different, and the waveform data of the drain-source voltage at both ends of the high-frequency action switch tube and its corresponding filter inductor current are also different, so that the calculation rules of the switching cycle that meets the zero voltage turn-on condition in different working areas are different. The corresponding filter inductor current refers to the current generated on the corresponding filter inductor before the grid-connected current generated by the high-frequency action switch tube flows into the power grid.

[0079] In one embodiment, a method for determining a calculation rule for a switching cycle that satisfies a zero voltage turn-on condition includes: first, based on a set of waveform data of the drain-source voltage at both ends of a high-frequency-operating switch tube in each working area and its corresponding filter inductor current in a switching cycle, determining the start / end time point of the switching cycle that satisfies the zero voltage turn-on condition in each working area; and then, based on the start / end time point of the switching cycle in each working area, using Kirchhoff's voltage-current law, determining the calculation rule for the switching cycle corresponding to each working area. Specifically, first, find the time point when the filter inductor current and the drain-source voltage are both zero in the set of waveform data, then determine the various stages included in the switching cycle and the calculation rule for each stage based on the found time point, and then obtain the switching cycle according to the calculation rule for each stage. The calculation rules of .

[0080] After calculation and analysis, the parameter information involved in the calculation rules of the switching cycle includes the DC input voltage and the grid voltage. Preferably, after determining the calculation rules of the switching cycle corresponding to each working area, they are solidified in the controller of the grid-connected inverter. After the controller determines the current working area of ​​the grid-connected inverter, the switching cycle, duty cycle and high-frequency working timing of each switch tube in the working area can be determined according to the DC input voltage, the grid voltage and the cycle calculation rules corresponding to the current working area. In reactive power regulation, the duty cycle can be obtained according to the calculation rules of the switching cycle. Specifically, duty cycle = switch tube conduction time / switching cycle. When each switch tube corresponds to multiple conduction stages in a switching cycle, the switching cycle may correspond to multiple duty cycles, and each duty cycle is the duration of each conduction stage divided by the switching cycle.

[0081] In one embodiment, the high-frequency operation timing of each switch tube can be determined based on the phases included in the switching cycle and the duration of each phase. It includes five stages: the first switch tube conduction stage , Switch off stage , the first resonance stage , the clamping stage of the body diode and the second resonant stage The second switching cycle corresponding to the second area and the fourth area It includes four stages: the second switch tube conduction stage , the third switch tube conduction stage , the third resonance stage and the fourth resonant stage . The first switching cycle and the second switching cycle The method of dividing the stages and calculating the duration of each stage are described in detail below.

[0082] by Figure 1 Taking the grid-connected inverter as an example, when the grid-connected inverter works in the first area, the high-frequency working sequence of each switch tube is as follows: in the conduction stage of the first switch tube , switch tube / High frequency action, switch tube / Keep off; in other stages, the switch When the grid-connected inverter operates in the second area, the high-frequency operation timing of each switch tube is as follows: in the conduction stage of the second switch tube , switch tube / High frequency action, switch tube / Keep off, in the third switch tube conduction stage , switch tube / High frequency action, switch tube / Keep off, in other stages, the switch When the grid-connected inverter operates in the third area, the high-frequency operation timing of each switch tube is as follows: in the first switch tube conduction stage , switch tube / High frequency action, switch tube / Keep off; in other stages, the switch When the grid-connected inverter operates in the fourth area, the high-frequency operation timing of each switch tube is: in the conduction stage of the second switch tube , switch tube / High frequency action, switch tube / Keep off, in the third switch tube conduction stage , switch tube / High frequency action, switch tube / Keep off, in other stages, the switch Keep off.

[0083] In the prior art, when the grid-connected inverter operates in the second region, only the switch tube / High frequency action; when the grid-connected inverter works in the fourth area, only the switch tube / High-frequency operation. This method makes the high-frequency operation switch tube only open at the valley voltage when the grid-connected inverter works in the second area or the fourth area, and cannot achieve zero voltage opening. In this application, when the grid-connected inverter works in the second area or the fourth area, the switch tube The high-frequency operation can realize zero-voltage switching of the switch tube with high-frequency operation even when the grid-connected inverter works in the area where the grid voltage and the grid-connected reference current have opposite polarities.

[0084] Step S505 , according to the switching period, duty cycle and high-frequency working sequence of each switch tube in the working area, controlling each switch tube to be turned on with zero voltage in the working area based on its high-frequency working sequence.

[0085] by Figure 1 Taking the structure shown in the figure as an example, when the grid-connected inverter works in the first area, the switch tube is controlled / In the first switching cycle The first switch conduction stage Zero voltage turn-on for high frequency operation; when the grid-connected inverter works in the second area, the switch tube is controlled / In the second switching cycle The second switch conduction stage Zero voltage switching for high frequency operation and control of switch tubes / In the second switching cycle The third switch conduction stage Zero voltage turn-on for high frequency operation; when the grid-connected inverter works in the third area, the switch tube is controlled / In the first switching cycle The first switch conduction stage Zero voltage is turned on for high frequency operation; when the grid-connected inverter works in the fourth area, the switch tube is controlled / In the second switching cycle The second switch conduction stage Zero voltage switching for high frequency operation and control of switch tubes / In the second switching cycle The third switch conduction stage Zero voltage turn-on for high frequency operation.

[0086] Below Figure 3 For example, the grid-connected reference current leads the grid voltage. Figure 1 The reactive power regulation control method of the grid-connected inverter is described in detail. Figure 6 , Figure 6 yes Figure 3 Middle area A switch tube Drive, drain-source voltage and the first filter inductor current The first set of waveform diagrams. In area A, and Therefore, the switch High frequency action, switch tube Keep it off, and the grid-connected current will pass through the filter inductor before flowing into the grid. , generating the first filter inductor current .like Figure 6 As shown, a switching cycle in region A can include the following five stages:

[0087] (1) First switch conduction stage

[0088] The first switch conduction stage from Time starts to The moment ends. Specifically, Moment, switch tube / The first filter inductor current is Increases linearly from zero to time, / Shutdown, Increase to the peak current . Because the switch tube / is continuously in the on state, so the drain-source voltage According to Kirchhoff's voltage-current law, The calculation formula is:

[0089] (2)

[0090] In formula (2), , is the first filter inductor current At the peak in region A, is the DC input voltage, is the grid voltage, is the inductance of the filter inductor, is the capacitance of the output capacitor.

[0091] (2) Switching tube off stage

[0092] Switch off stage from Time starts to The moment ends. Specifically, time, Give / Output capacitance Charge, rise from It starts to decrease linearly to time, decreases to zero. Inside, Keep unchanged. According to Kirchhoff's voltage-current law, The calculation formula is:

[0093] (3)

[0094] It should be noted that during the switch off phase The output capacitor can also be included before Charging stage .because The duration of the phase is almost negligible. In order to simplify the calculation when performing reactive power regulation, the calculation of the switching cycle is not included in some embodiments. In other embodiments, in order to obtain a more accurate switching cycle, The duration of the phase is included in the calculation of the switching cycle. Figure 7 As shown, the output capacitor Charging stage from Time starts to The moment is over. time, Give / Output capacitance Charge, Starting from zero, time, During this phase, Approximately maintain unchanged. According to Kirchhoff's voltage-current law, The calculation formula is:

[0095] (4)

[0096] (3) First resonance stage

[0097] First resonance stage from Time starts to The moment ends. Specifically, At this moment, the inverter enters the first resonance stage. , and To form a resonant network, Reverse and give Discharge. time, The voltage at both ends is completely discharged to zero, that is, According to Kirchhoff's voltage-current law, The calculation formula is:

[0098] (5)

[0099] (4) Body diode clamping stage

[0100] Body diode clamping stage from Time starts to The moment ends. Specifically, time, From the body diode Continue current, quilt Clamped to zero, that is ,to time, It rises linearly to zero. According to Kirchhoff's voltage-current law, The calculation formula is:

[0101] (6)

[0102] (5) Second resonance stage

[0103] Second resonance stage from Time starts to The moment ends. Specifically, At this moment, the inverter enters the second resonance stage. and The amplitude changes sinusoidally with the resonance period. time, and All resonate to zero, and can be turned on with zero voltage at this time / According to Kirchhoff's voltage-current law, The calculation formula is:

[0104] (7)

[0105] It is understandable that when the grid-connected inverter works in area A, if there is no external intervention, and It will continue to cycle in the second resonance stage.

[0106] according to Figure 6 Drain-source voltage at each stage of a switching cycle when the grid-connected inverter works in region A and the first filter inductor current The change curve of the drain-source voltage and the first filter inductor current The moment when it is zero is +n The corresponding moment. Among them, n is the adjustment value of the switching cycle, and its value range is an integer greater than or equal to zero. At these moments, zero voltage switching can be achieved. / Therefore, when the grid-connected inverter operates in region A, the first switching cycle that meets the zero voltage turn-on condition Obviously, the switching cycle Minimum If you want to increase the switching cycle, you can set a suitable n value according to actual needs.

[0107] See also Figure 8 , Figure 8 yes Figure 3 Middle area B switch tube Drive, drain-source voltage and the second filter inductor current The first set of waveform diagrams. In area B, and Therefore, the switch Both operate at high frequency, and the grid-connected current passes through the filter inductor before flowing into the grid. , generating the second filter inductor current .like Figure 8 As shown, a switching cycle in region B can include the following four stages:

[0108] (1) The second switch conduction stage

[0109] The second switch conduction stage from Time starts to The moment ends. Specifically, Moment, switch tube / The second filter inductor current is turned on. Increases linearly from zero to time, / Shutdown, Increase to the peak current . Because the switch tube / is continuously in the on state, so the drain-source voltage , According to Kirchhoff's voltage-current law, The calculation formula is:

[0110] (8)

[0111] In formula (8),

[0112] , is the second filter inductor current At the peak in region B, is the DC input voltage, is the grid voltage, is the inductance of the filter inductor, is the output capacitor value.

[0113] (2) The third switch conduction stage

[0114] The third switch conduction stage from Time starts to The moment ends. Specifically, time, Reduced to zero, it can be turned on with zero voltage / , the second filter inductor current from Decreases linearly to time, Reduce to the current valley value , / According to Kirchhoff's voltage-current law, The calculation formula is:

[0115] (9)

[0116] (10)

[0117] in, is the valley value of the second filter inductor current in region B.

[0118] It should be noted that during the conduction phase of the third switch tube Before that, it can also include a dead zone phase .because The duration of the phase is almost negligible. In order to simplify the calculation when performing reactive power regulation, the calculation of the switching cycle is not included in some embodiments. In other embodiments, in order to obtain a more accurate switching cycle, The duration of the phase is included in the calculation of the switching cycle. Fig. 9 As shown, the dead zone stage from Time starts to The moment ends. Specifically, At this moment, all switches are turned off. Give / Output capacitance Charge, give / Output capacitance Discharge to time, Rising from zero from Dropped to zero.

[0119] (3) The third resonance stage

[0120] The third resonance stage from Time starts to The moment ends. Specifically, At this moment, the inverter enters the third resonance stage. and To form a resonant network, Give / Output capacitance Charge, give / Output capacitance Discharge to time, Rising from zero from Down to , from Resonance reaches zero, at which point zero voltage can be turned on / According to Kirchhoff's voltage-current law, The calculation formula is:

[0121] (11)

[0122] (4) Fourth resonance stage

[0123] Fourth resonance stage from Time starts to The moment ends. Specifically, At this moment, the inverter enters the fourth resonance stage. and The amplitude changes sinusoidally with the resonance period. time, and Resonance to zero, Resonance to , at this time, it can also be turned on with zero voltage / According to Kirchhoff's voltage-current law, The calculation formula is:

[0124] (12)

[0125] It is understandable that when the grid-connected inverter works in area B, if there is no external intervention, and It will continue to cycle in the fourth resonance stage.

[0126] according to Figure 8 Drain-source voltage at each stage of a switching cycle when the grid-connected inverter operates in region B and the second filter inductor current The change curve of the drain-source voltage and the second filter inductor current The time when it is zero is +m The corresponding moments, where is the adjustment value of the switching cycle, and its value range is an integer greater than or equal to zero. At these moments, zero voltage switching can be achieved. / Therefore, when the grid-connected inverter operates in region B, the second switching cycle that meets the zero voltage turn-on condition Obviously, the switching cycle Minimum If you want to increase the switching cycle, you can set the appropriate value.

[0127] In the above formula, the inductance of the filter inductor is and the output capacitor value Can be approximated to a fixed value, for example, the inductance value L is equal to the rated inductance value , the output capacitor value C is equal to the rated capacitance In some embodiments, to simplify calculation, a fixed filter inductance value is preset in the controller of the grid-connected inverter. and the output capacitor value .

[0128] In other embodiments, in order to obtain a more accurate output capacitor value C, the output capacitor value C and the DC input voltage may be determined. Grid voltage The mapping relationship of the voltage difference is used to determine the capacitance of the output capacitor according to the real-time voltage difference value. C .Depend on Figure 6 It can be seen that when the grid-connected inverter works in the first area (i.e., area A), during the entire switching cycle Internal switch tube / The drain-source voltage are always equal, that is, the output capacitance / Voltage and Always equal. Since the output capacitance of the switch tube C With the voltage across the capacitor Changes with changes, that is, the capacitance C is the voltage The function of Therefore, the second resonant stage It can be expressed as:

[0129] (13)

[0130] In the second resonance time period Inside, With pressure difference Positive correlation can be expressed as:

[0131] (14)

[0132] therefore, It can also be expressed as:

[0133] (15)

[0134] From the above formula, we can see that when the time period When known, In one embodiment of the present application, the following method is used to determine the capacitance of the output capacitor: With DC input voltage , Grid voltage The mapping relationship between the pressure difference :

[0135] First, based on the multiple sets of waveform data of the drain-source voltage at both ends of the high-frequency switching tube in the first working area and the corresponding filter inductor current at different switching cycles, the DC input voltage at different and different grid voltages Conditional , and based on the measured Use the formula to reversely calculate the corresponding output capacitor value ;

[0136] Secondly, the DC input voltage and different grid voltages The difference ( - ) as input, the different DC input voltage and different grid voltages Calculated output capacitor value As the output, the output capacitor value is obtained by polynomial fitting. With DC input voltage , Grid voltage The mapping relationship between the pressure difference .

[0137] See also Fig.10 and Fig.11 , Fig.10 yes Figure 3 Middle area C switch tube Drive, drain-source voltage and the second filter inductor current A set of waveform diagrams, Fig.11 yes Figure 3 Middle area D switch tube Drive, drain-source voltage and the first filter inductor current A set of waveform diagrams.

[0138] Area C and Therefore, the switch High frequency action, switch tube Keep it off, and the grid-connected current will pass through the filter inductor before flowing into the grid. , generating the second filter inductor current The drain-source voltage in region C and the second filter inductor current The change curves of the drain-source voltage in area A are and the first filter inductor current The change curve is the same, therefore, the calculation rule of the switching period in area C is the same as that in area A.

[0139] Area D and Therefore, the switch Both operate at high frequency, and the grid-connected current passes through the filter inductor before flowing into the grid. , generating the first filter inductor current The drain-source voltage in region D , and the first filter inductor current The change curves of the drain-source voltage in region B are , and the second filter inductor current The change curves of are the same, therefore, the calculation rules of the switching period in area D and the switching period in area B are the same.

[0140] So far, the calculation rules for the switching cycles corresponding to the four regions A, B, C, and D in one power frequency cycle are obtained when the grid-connected reference current leads the grid voltage. Among them, the two regions A and C correspond to the first switching cycle The calculation rules of the two regions B and D correspond to the second switching cycle The calculation rules of the switching period when the grid-connected reference current lags behind the grid voltage are the same as those when the grid-connected reference current leads the grid voltage. The analysis and calculation process is similar and will not be repeated here. Therefore, Figure 1 When the grid-connected inverter works in the first area or the third area, the first switching cycle that meets the zero voltage switching condition The calculation rules are:

[0141]

[0142] in, ,

[0143] is the peak value of the filter inductor current in the first or third region, is the DC input voltage, is the grid voltage, is the inductance of the filter inductor, is the output capacitor value, is the adjustment value of the first switching period, and its value range is an integer greater than or equal to zero.

[0144] According to the first switching cycle The calculation rules of Figure 1 The first duty cycle that satisfies the zero voltage switching condition when the grid-connected inverter operates in the first area or the third area , specifically:

[0145] (15)

[0146] Figure 1 When the grid-connected inverter works in the second area or the fourth area, the second switching cycle that meets the zero-voltage switching condition The calculation rules are:

[0147]

[0148] in,

[0149] ,

[0150] ,

[0151] is the peak value of the filter inductor current when it works in the second or fourth area, is the valley value of the filter inductor current when it operates in the second area or the fourth area, is the adjustment value of the second switching period, and its value range is an integer greater than or equal to zero.

[0152] According to the second switching cycle The calculation rules of Figure 1 The second duty cycle that satisfies the zero voltage switching condition when the grid-connected inverter operates in the second area or the fourth area , the third duty cycle They are:

[0153] (17)

[0154] (18)

[0155] Among them, the second duty cycle The second switching cycle The second switch conduction stage The corresponding duty cycle, the third duty cycle The second switching cycle The third switch is turned on The corresponding duty cycle.

[0156] See also Figure 12-14 , Fig.12 is Figure 3 Middle area A adopts Figure 1 The simulation control effect diagram of the reactive power regulation control method of the grid-connected inverter; Fig.13 is Figure 3 Middle area B adopts Figure 1 The simulation control effect diagram of the reactive power regulation control method of the grid-connected inverter; Fig.14 is Figure 3 Middle area D adopts Figure 1 The simulation control effect diagram of the reactive power regulation control method of the grid-connected inverter. Figure 12-14 It can be seen that the reactive power regulation control method of the grid-connected inverter of the present application can not only realize the zero-voltage turning-on of each switch tube with high frequency action when the grid voltage and the grid-connected reference current have the same polarity, but also realize the zero-voltage turning-on of each switch tube with high frequency action when the grid voltage and the grid-connected reference current have opposite polarities, thereby minimizing the turning-on loss.

[0157] The reactive power regulation control method of the grid-connected inverter provided in the embodiment of the present application first obtains the power factor value, determines the grid-connected reference current, and obtains the grid voltage, and determines the current working area of ​​the grid-connected inverter according to the polarity of the grid voltage and the polarity of the grid-connected reference current; then, obtains the DC input voltage, and determines the switching cycle, duty cycle and high-frequency working sequence of each switch tube in the working area according to the DC input voltage, the grid voltage and the cycle calculation rule corresponding to the working area; finally, according to the switching cycle, duty cycle and high-frequency working sequence of each switch tube in the working area, controls each switch tube to be turned on at zero voltage in the working area based on its high-frequency working sequence. The method of the present application is adopted to realize the zero-voltage turning on of the switch tube when the grid-connected inverter is subjected to reactive power regulation, and effectively reduce the loss caused by the turning on of the switch tube.

[0158] The present application also provides a non-volatile computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are executed by one or more processors, for example, to execute the above-described Figure 5 method steps.

[0159] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Under the concept of the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes in different aspects of the present application as described above, which are not provided in detail for the sake of simplicity. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features can be replaced by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A reactive power regulation control method for a grid-connected inverter, characterized in that: The grid-connected inverter includes a DC voltage input source, a switch tube , , , And the body diode connected in parallel to the switch tube , , , and output capacitor , , , , connected to the switch tube and Filter inductance of the bridge arm and filter capacitors , connected to the switch tube and Filter inductance of the bridge arm and filter capacitors , the method comprising: Obtaining a power factor value, and determining a grid-connected reference current according to the power factor value; Obtaining a grid voltage, and determining a current working area of ​​the grid-connected inverter according to the polarity of the grid voltage and the polarity of the grid-connected reference current; Obtaining a DC input voltage, and determining a switching period, a duty cycle, and a high-frequency working sequence of each switch tube in the working area according to the DC input voltage, the grid voltage, and a period calculation rule corresponding to the working area, wherein the period calculation rule is a calculation rule for a switching period that satisfies a zero voltage switching condition; According to the switching cycle, duty cycle and high-frequency working sequence of each switch tube in the working area, each switch tube is controlled to be turned on at zero voltage based on its high-frequency working sequence in the working area; Determining the current working area of ​​the grid-connected inverter according to the polarity of the grid voltage and the polarity of the grid-connected reference current includes: When the polarity of the grid-connected reference current is negative and the polarity of the grid voltage is positive, determining that the current working area of ​​the grid-connected inverter is the second area; When the polarity of the grid-connected reference current is positive and the polarity of the grid voltage is negative, determining that the current working area of ​​the grid-connected inverter is the fourth area; When the grid-connected inverter operates in the second region or the fourth region, the second switching cycle that meets the zero voltage switching condition The calculation rules are: in, ， ， is the peak value of the filter inductor current in the second region or the fourth region, is the valley value of the filter inductor current in the second region or the fourth region, is the DC input voltage, is the grid voltage, is the inductance of the filter inductor, is the output capacitor value, is the adjustment value of the second switching period, The value range of is an integer greater than or equal to zero; Determining the high-frequency working timing of each switch tube in the working area includes: When the grid-connected inverter operates in the second region, it is determined that the switch tube / In the second switching cycle The second switch conduction stage High frequency action and switch tube / In the second switching cycle The third switch conduction stage High frequency action; When the grid-connected inverter operates in the fourth region, it is determined that the switch tube / In the second switching cycle The second switch conduction stage High frequency action and switch tube / In the second switching cycle The third switch conduction stage High frequency action.

2. The method according to claim 1, characterized in that Before determining the switching period, duty cycle and high-frequency working sequence of each switch tube in the working area, the method further includes: Determine the start / end time point of the switching cycle that meets the zero voltage switching condition in each of the working regions according to a set of waveform data of the drain-source voltage at both ends of the high-frequency operating switch tube and the corresponding filter inductor current in each of the working regions; A calculation rule for the switching period corresponding to each of the working areas is determined based on the start / end time points of the switching period in each of the working areas.

3. The method according to claim 2, characterized in that The zero voltage switching condition is satisfied when the start / end time point of the switching cycle is the time point when the filter inductor current and the drain-source voltage in the set of waveform data are both zero.

4. The method according to any one of claims 1 to 3, characterized in that: The step of determining the current working area of ​​the grid-connected inverter according to the polarity of the grid voltage and the polarity of the grid-connected reference current further comprises: When the polarity of the grid-connected reference current is positive or zero and the polarity of the grid voltage is positive or zero, determining that the current working area of ​​the grid-connected inverter is the first area; When the polarity of the grid-connected reference current is negative or zero and the polarity of the grid voltage is negative or zero, it is determined that the current working area of ​​the grid-connected inverter is the third area.

5. The method according to claim 4, characterized in that When the grid-connected inverter operates in the first region or the third region, the first switching cycle that meets the zero voltage switching condition The calculation rules are: in, is the peak value of the filter inductor current in the first region or the third region, is the adjustment value of the first switching period, The value range of is an integer greater than or equal to zero.

6. The method according to claim 5, characterized in that The step of determining the high-frequency operation timing of each switch tube in the operation area further includes: When the grid-connected inverter operates in the first region, it is determined that the switch tube / In the first switching cycle The first switch conduction stage High frequency action; When the grid-connected inverter operates in the third region, it is determined that the switch tube / In the first switching cycle The first switch conduction stage High frequency action.

7. The method according to claim 5, characterized in that When the grid-connected inverter operates in the first area and the third area, the first duty cycle that meets the zero voltage switching condition for: When the grid-connected inverter operates in the second area and the fourth area, the second duty cycle that meets the zero voltage switching condition , the third duty cycle They are: 。 8. A grid-connected inverter, characterized in that: The grid-connected inverter includes an inverter circuit and a controller. The inverter circuit includes a DC voltage input source, a switch tube, , , , And the body diode connected in parallel to the switch tube , , , and output capacitor , , , , connected to the switch tube and Filter inductance of the bridge arm and filter capacitors , connected to the switch tube and Filter inductance of the bridge arm and filter capacitors , the controller is also used to execute the method described in any one of claims 1-7.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the processor executes the steps of the reactive power regulation control method for a grid-connected inverter according to any one of claims 1 to 7.

Images