Step-up / step-down inverter and control method thereof

Abstract

This application discloses a buck-boost inverter and a control method thereof. The buck-boost inverter includes components such as an input power supply, a coupled inductor, a filter unit, a first switch, a second switch, a third switch, and a fourth switch, where the filter unit comprises a filter inductor, a damping resistor, and a filter capacitor. The first and second switches are complementary switches. When the input voltage is greater than the grid voltage and the grid voltage is in a positive half-cycle, the third switch is always on and the fourth switch is always off. The grid current is controlled to track a first reference current by adjusting the duty ratio of the first switch. At other times, the first and third switches switch simultaneously at high frequency, and the second and fourth switches switch simultaneously at high frequency. The grid current is controlled to track a second reference current by adjusting the duty ratio of the first switch. This invention achieves buck-boost conversion, eliminates common-mode leakage current in non-isolated photovoltaic inverters, and employs single-stage conversion to improve system conversion efficiency.

Description

[Technical field]

[0001] The present application relates to the field of inverters, and in particular to a buck-boost inverter and a method for controlling the same. [Background technology]

[0002] In the non-isolated inverter, because there is no isolation between the photovoltaic assembly and the grid, the common-mode leakage current may flow through the photovoltaic assembly due to the parasitic capacitance to ground. This common-mode leakage current may cause electromagnetic interference, increase system losses, and even pose a threat to human safety. Experts and scholars at home and abroad have carried out a series of effective research on how to suppress the common-mode leakage current of the non-isolated inverter. Common methods include improving modulation technology, adding switch devices, adding filters, and improving control methods. However, the effect of suppressing the common-mode leakage current by the above methods is easily affected by the parasitic capacitance to ground of the photovoltaic assembly and the changes in circuit parameters.

[0003] In addition, the output voltage of the photovoltaic assembly is usually low, which requires a non-separate inverter to realize the function of step-up and step-down conversion. The conventional method adopts a two-stage conversion, i.e., a step-up converter and an inverter are cascaded to realize step-up and step-down conversion, which reduces the system efficiency.

[0004] Therefore, it is necessary to research an inverter topology and a control method thereof that can fundamentally eliminate common-mode leakage current and realize highly efficient step-up / step-down conversion. Summary of the Invention

[0005] The objective of the present application is to provide a buck-boost inverter and a control method thereof for solving the problem that conventional inverters cannot realize buck-boost conversion, eliminating the common mode leakage current phenomenon, and improving the conversion efficiency of a photovoltaic inverter system.

[0006] In order to achieve the above object, the present application is realized by the following technical solutions.

[0007] A step-up / step-down inverter, an input power source having a negative pole connected to a negative pole of a grid and having a negative pole and a negative pole of the grid commonly grounded; a filter unit including a filter inductor, a damping resistor, and a filter capacitor, a first end of the filter inductor being connected to a positive electrode of the grid, a first end of the damping resistor being connected to a second end of the second switch and a negative electrode of the grid respectively, and a second end of the damping resistor being connected to a first end of the filter capacitor; a coupled inductor including a primary winding and a secondary winding, a first end of the primary winding is connected to a second end of a filter inductor, a second end of a filter capacitor, and a fourth end of the secondary winding of the coupled inductor, and a second end is connected to a positive electrode of the input power source via a third switch and a first switch, respectively; a first closed circuit is formed by the primary winding of the coupled inductor, a grid, a filter unit, the input power source, the third switch, and the first switch; and a first freewheeling circuit is formed by the primary winding of the coupled inductor, the grid, the filter unit, the third switch, and the second switch; a coupled inductor having a third end of a secondary winding of the coupled inductor connected to a negative electrode of a grid via a fourth switch and the second switch, the coupled inductor including a secondary winding of the coupled inductor, a grid, the filter unit, the fourth switch, the second switch, and a second freewheeling circuit; a control driving unit, whose input ends are respectively connected to a grid, an input power source, the primary winding of the coupled inductor and the secondary winding of the coupled inductor, and whose output ends are respectively connected to the first switch, the second switch, the third switch and the fourth switch, and which is respectively used to drive and control the switching of each switch, communicate each closed circuit, and further complete the adjustment of the grid current.

[0008] Most preferably, the control and drive unit comprises: a sensor system whose input terminals are respectively connected to a grid, an input power source, a primary winding of the coupled inductor, and a secondary winding of the coupled inductor, and which respectively collects a grid voltage feedback signal of the grid, a voltage feedback signal of the input power source, a first current feedback signal of the primary winding of the coupled inductor, and a second current feedback signal of the secondary winding of the coupled inductor; a DSP whose input is connected to the first output of the sensor system, for performing voltage signal processing on the grid voltage feedback signal and generating the first current reference signal and the second current reference signal respectively; a control circuit having a first input terminal connected to an output terminal of the DSP and a second input terminal connected to an output terminal of the sensor system, performing current comparison control based on the first current reference signal, the second current reference signal, and a signal obtained by subtracting the first current feedback signal and the second current feedback signal, and generating a first switch logic signal, a second switch logic signal, a third switch logic signal, and a fourth switch logic signal, respectively; a drive circuit having an input terminal connected to an output terminal of the control circuit and an output terminal connected to the first switch, the second switch, the third switch and the fourth switch, respectively, and generating a first drive signal, a second drive signal, a third drive signal and a fourth drive signal according to the first switch logic signal, the second switch logic signal, the third switch logic signal and the fourth switch logic signal, respectively, to drive switching of each switch.

[0009] Most preferably, the sensor system comprises: A grid voltage sensor, the input of which is connected to a grid and the first output of which is connected to the input of the DSP, is used for collecting and transmitting the grid voltage feedback signal to the DSP; an input voltage sensor, an input end of which is connected to the input power source and a first output end of which is connected to the input end of the DSP, for collecting and transmitting a voltage feedback signal of the input power source to the DSP; A first current sensor, whose input end is connected to the primary winding of the transformer and whose output end is connected to the second input end of the control circuit, is used for collecting the first current feedback signal and transmitting it to the control circuit; a second current sensor, the input terminal of which is connected to the secondary winding of the transformer and the output terminal of which is connected to a second input terminal of the control circuit, used for collecting and transmitting the second current feedback signal to the control circuit.

[0010] Most preferably, the digital signal processor (DSP) comprises: a first analog-to-digital conversion module, the input terminal of which is connected to the first output terminal of the grid voltage sensor, for performing a first analog-to-digital conversion on the grid voltage feedback signal to obtain a first digital signal; a phase-locked loop whose input is connected to the first output terminal of the first analog-to-digital conversion module, and which performs digital processing on the first digital signal to obtain a voltage phase of a grid; a second analog-to-digital conversion module, the input terminal of which is connected to the output terminal of the input voltage sensor, for performing a second analog-to-digital conversion on the input voltage feedback signal to obtain a second digital signal; a first current reference calculation module, the first input terminal of which is connected to the first output terminal of the phase locked loop and the second input terminal of which is connected to the second output terminal of the first analog-to-digital conversion module, for calculating a first current reference signal according to the first digital signal and the voltage phase to obtain a first current reference digital signal; a first digital-to-analog conversion module, whose input terminal is connected to the output terminal of the first current reference calculation module, for performing a first digital-to-analog conversion on the first current reference digital signal to obtain a first current reference signal; a second current reference calculation module, the first input terminal of which is connected to the second output terminal of the phase locked loop, the second input terminal of which is connected to the third output terminal of the first analog-to-digital conversion module, and the third input terminal of which is connected to the output terminal of the second analog-to-digital conversion module, and the second current reference calculation module calculates a second current reference signal according to the voltage phase, the first digital signal, and the second digital signal to obtain a second reference digital signal; a second digital-to-analog conversion module, the input terminal of which is connected to the output terminal of the second current reference calculation module, for performing a second digital-to-analog conversion on the second reference digital signal to obtain a second current reference signal.

[0011] Most preferably, the driving circuit further includes a first driving circuit, a second driving circuit, a third driving circuit and a fourth driving circuit, the output terminals of which are connected to the first switch, the second switch, the third switch and the fourth switch, respectively.

[0012] Most preferably, the control circuit comprises: a first comparator, the first input terminal of which is connected to the second output terminal of the grid voltage sensor and the second input terminal of which is connected to the second output terminal of the input voltage sensor, for comparing the input voltage feedback signal with the grid voltage feedback signal to obtain a first mode selection signal; a second comparator, the input terminal of which is connected to the third output terminal of the grid voltage sensor, for comparing the grid voltage feedback signal with ground to obtain a second mode selection signal; a first phase inverter, the input terminal of which is connected to the first output terminal of the first comparator and which receives a third mode selection signal; a second phase inverter, the input terminal of which is connected to the first output terminal of the second comparator to obtain a fourth mode selection signal; a first current regulator, the first input terminal of which is connected to the output terminal of the first digital-to-analog conversion module and the second input terminal of which is connected to an output terminal of a signal obtained by subtracting the first current feedback signal from the second current feedback signal, and the first current reference signal is subjected to a first current adjustment to obtain a first high frequency switching signal; a second current regulator, the first input terminal of which is connected to the output terminal of the second digital-to-analog conversion module and the second input terminal of which is connected to an output terminal of a signal obtained by subtracting the first current feedback signal from the second current feedback signal, and the second current reference signal is subjected to a second current adjustment to obtain a second high frequency switching signal; a third phase inverter, the input terminal of which is connected to the first output terminal of the second current regulator and which receives a third high frequency switching signal; a first AND gate, the first input terminal of which is connected to the second output terminal of the first comparator and the second input terminal of which is connected to the second output terminal of the second comparator, and the first AND gate is configured to obtain a fifth mode selection signal according to the first mode selection signal and the second mode selection signal; a second AND gate, the first input terminal of which is connected to the output terminal of the first phase inverter and the second input terminal of which is connected to the third output terminal of the second comparator, and the second AND gate is configured to derive a sixth mode selection signal according to the second mode selection signal and the third mode selection signal; a third AND gate, the first input terminal of which is connected to the second output terminal of the second current regulator and the second input terminal of which is connected to the output terminal of the second phase inverter, and the third AND gate is configured to obtain a fourth high frequency switching signal according to the second high frequency switching signal and the second mode selection signal; a fourth AND gate, a first input terminal of which is connected to the output terminal of the third phase inverter and a second input terminal of which is connected to the output terminal of the second AND gate, and which obtains a fifth high frequency switching signal according to the sixth mode selection signal and the third high frequency switching signal; a first OR gate, the first input terminal of which is connected to the output terminal of the fourth AND gate and the second input terminal of which is connected to the output terminal of the third AND gate, and the first OR gate is configured to obtain a sixth high frequency switching signal according to the fourth high frequency switching signal and the fifth high frequency switching signal; a second OR gate, the first input terminal of which is connected to the first output terminal of the first OR gate and the second input terminal of which is connected to the first output terminal of the first AND gate, for obtaining a third switch logic signal according to the fifth mode selection signal and the sixth high frequency switching signal, and transmitting the third switch logic signal to the third driving circuit; a fifth AND gate, the first input terminal of which is connected to the second output terminal of the first AND gate and the second input terminal of which is connected to the output terminal of the first current regulator, and the fifth AND gate is configured to obtain a seventh high frequency switching signal according to the fifth mode selection signal and the first high frequency switching signal; a third OR gate, the first input terminal of which is connected to the output terminal of the fifth AND gate and the second input terminal of which is connected to the second output terminal of the second OR gate, for obtaining a first switch logic signal according to the seventh high frequency switching signal and the third switch logic signal, and transmitting the first switch logic signal to the first driving circuit; a fourth phase inverter, the input terminal of which is connected to the second output terminal of the third OR gate, for obtaining a second switch logic signal according to the first switch logic signal and transmitting the second switch logic signal to the second driving circuit; a fifth phase inverter, the input terminal of which is connected to the third output terminal of the first AND gate to obtain a seventh mode selection signal; a sixth phase inverter, the input terminal of which is connected to the second output terminal of the first OR gate to obtain an eighth high frequency switching signal; a sixth AND gate having a first input terminal connected to the output terminal of the fifth phase inverter, a second input terminal connected to the output terminal of the sixth phase inverter, and an output terminal connected to the input terminal of the fourth driving circuit, for obtaining a fourth switch logic signal according to the seventh mode selection signal and the eighth high frequency switching signal, and transmitting the fourth switch logic signal to the fourth driving circuit.

[0013] The present invention provides a step-up / step-down inverter control method realized based on a step-up / step-down inverter, the step-up / step-down inverter control method comprising: Step 1, a sensor system monitors an input voltage and a grid voltage in real time, and performs a first determination on the magnitude of the input voltage and the grid voltage to determine whether the input voltage is greater than or less than the grid voltage; Step 2: a sensor system monitors the grid voltage in real time, and performs a second determination on the power frequency period of the grid voltage to determine whether the power frequency period of the grid voltage is a positive half period or a negative half period; Step 3: when the utility frequency period of the grid voltage is a positive half period and the input voltage is greater than the grid voltage, the control and driving unit adjusts the first switch and / or the second switch to turn on the first closed circuit and / or the first return circuit, so that the signal obtained by subtracting the first current feedback signal and the second current feedback signal tracks the first reference current, thereby completing the grid current regulation; and step 4, when the power frequency period of the grid voltage is a negative half period or the power frequency period of the grid voltage is a positive half period and the input voltage is smaller than the grid voltage, the control and drive unit adjusts the first switch, the second switch, the third switch and / or the fourth switch to make the first closed circuit and / or the second freewheeling circuit conductive, so as to make the signal obtained by subtracting the first current feedback signal and the second current feedback signal track the second reference current, thereby completing the grid current regulation.

[0014] Most preferably, the driving unit adjusts the first switch and / or the second switch of the inverter by: Step 3.1, the control and driving unit adjusts the fourth switch to be turned off and the third switch to be turned on, and turns off the second freewheel circuit; Step 3.2: subtracting the first current feedback signal and the second current feedback signal collected in real time by the first current sensor and the second current sensor, respectively, and then comparing the subtracted first current feedback signal and the second current feedback signal with a first current reference signal generated by the DSP; Step 3.3: when the signal obtained by subtracting the first current feedback signal and the second current feedback signal is smaller than the first current reference signal, the control and drive unit adjusts the first switch transistor to be conductive, so as to make the first closed circuit conductive, and adjusts the input power source to increase the current of the filter inductor through the first closed circuit, thereby completing the grid current adjustment; and step 3.4, when the signal obtained by subtracting the first current feedback signal and the second current feedback signal is greater than the first current reference signal, the control and drive unit adjusts the first switch transistor to be off, so that the first freewheeling circuit is conductive, the current of the filter inductor is reduced, and the grid current regulation is completed.

[0015] Most preferably, the control and drive unit adjusts the first switch, the second switch, the third switch and / or the fourth switch of the inverter. Step 4.1 performing a second determination of the operating mode of the inverter to determine whether the operating mode of the inverter is a boost mode or a buck-boost mode; Step 4.2: comparing a signal obtained by subtracting the first current feedback signal and the second current feedback signal collected in real time by the first current sensor and the second current sensor, respectively, with a second current reference signal generated by the DSP; Step 4.3: when the utility frequency period of the grid voltage is a positive half period and the input voltage is less than the grid voltage, the working mode of the inverter is a boost mode, and the control and drive unit adjusts all switches to high frequency switching; Step 4.4: if the signal obtained by subtracting the first current feedback signal and the second current feedback signal is greater than the second current reference signal, the control and drive unit adjusts the first switch transistor and the third switch transistor to be conductive, so as to make the first closed circuit conductive, and adjusts the input power source to reduce the current of the filter inductor through the first closed circuit, thereby completing the grid current adjustment; Step 4.5: if the signal obtained by subtracting the first current feedback signal and the second current feedback signal is smaller than the second current reference signal, the control and drive unit adjusts the first switch transistor and the third switch transistor to be turned off, so that the second freewheel circuit is conductive, and the current of the filter inductor increases, completing the grid current regulation; Step 4.6, when the utility frequency period of the grid voltage is a negative half period, the working mode of the inverter is a buck-boost mode, and the control and drive unit adjusts all the switches to high frequency switching; Step 4.7: when the signal obtained by subtracting the first current feedback signal and the second current feedback signal is smaller than the second current reference signal, the control and drive unit adjusts the first switch transistor and the third switch transistor to be conductive, so as to make the first closed circuit conductive, and adjusts the input power source to make the current of the filter inductor decrease in a negative direction through the first closed circuit, thereby completing the grid current adjustment; Step 4.8 includes: when the signal obtained by subtracting the first current feedback signal and the second current feedback signal is greater than the second current reference signal, the control and drive unit adjusts the first switch transistor and the third switch transistor to be off, so that the second freewheeling circuit is conductive, and the current of the filter inductor increases in the negative direction, completing the grid current regulation.

[0016] Most preferably, the third switch and the fourth switch are devices capable of withstanding forward and reverse voltages, such as two MOSFETs or IGBTs connected in reverse series.

[0017] By using this invention, the problem of low step-up and step-down conversion efficiency of the conventional photovoltaic inverter is solved, the common mode leakage current phenomenon is eliminated, step-up and step-down conversion is realized, and the conversion efficiency of the photovoltaic inverter system is improved. Effect of the Invention

[0018] The present application has the following advantages over the prior art:

[0019] 1. The inverter of the present invention is a single-stage conversion, which improves the conversion efficiency of the inverter system.

[0020] 2. The inverter of the present invention can realize step-up and step-down conversion.

[0021] 3. In the inverter according to the present invention, the input power supply and the grid are commonly grounded, which can effectively eliminate the common-mode leakage current of the photovoltaic inverter. [Brief description of the drawings]

[0022] In order to more clearly describe the technical solutions of the embodiments of the present patent, the following briefly introduces the drawings that need to be used in the description of the embodiments. It is obvious that the drawings attached in the following description are only some embodiments of the present patent, and those skilled in the art can obtain other drawings based on these drawings without paying creative labor. [Figure 1] FIG. 2 is a circuit schematic of this inverter according to an embodiment of the present application. [Diagram 2] FIG. 2 is a circuit schematic diagram of a control and drive unit according to an embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described below in conjunction with the accompanying drawings. The described embodiments should not be regarded as limitations on the present application, and all other embodiments obtained by those skilled in the art without any creative effort belong to the scope of protection of the present application.

[0024] Although the following description refers to "some embodiments," "one or more embodiments," a subset of all possible embodiments is described, it should be understood that "some embodiments," "one or more embodiments" may be the same or different subsets of all possible embodiments and may be combined with each other without conflict.

[0025] It is to be understood that the terms "first / second / third" in the following description are merely references to similar objects and do not represent a particular order of the objects, and that "first / second / third" may be interchanged with the particular order or order when permitted such that the embodiments of the present application described herein may be practiced in orders other than those illustrated or described.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms used herein are for the purpose of describing the embodiments of this application only and are not intended to be limiting of this application.

[0027] The present invention provides a buck-boost inverter, as shown in FIG. in , a coupled inductor L, a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a filter capacitor C1, and a filter inductor L g , damping resistor R d and a control drive unit (not shown).

[0028] Input power supply U in The negative pole of is connected to the negative pole of the grid U, and the input power supply U in The negative pole of the input power supply U and the negative pole of the grid U are commonly grounded. in is used to supply electrical energy to the inverter, and the input power supply U in and grid U are commonly grounded, which can effectively eliminate the common mode leakage current of this inverter. inmay be a photovoltaic cell, a car battery, a fuel cell, or the like.

[0029] The filter unit consists of a filter inductor L g and the damping resistor R d and a filter capacitor C1, and a filter inductor L g The first end of is connected to the positive pole of grid U, and the damping resistor R d The first terminal of the second switch S2 is connected to the second terminal of the second switch S3 and the negative electrode of the grid U, respectively, and the damping resistor R d a second end of the filter capacitor C1 connected to a first end of the filter capacitor C2; The coupled inductor L is connected to the primary winding N P and the secondary winding N S and a primary winding N of a coupled inductor L. P The first end of each filter inductor L g the second end of the filter capacitor C1 and the secondary winding N of the coupled inductor S The fourth end of the coupled inductor L is connected to the primary winding N P The second terminal of each of the input power supply U in is connected to the positive pole of The input power supply U in are the first switch S1, the third switch S3, and the primary winding N of the coupled inductor. P , connected in series with the filter unit and grid U, The primary winding N of the coupled inductor is connected to form a first return circuit. P are connected in series to the third switch S3, the second switch S2, the grid U and the filter unit, Secondary winding N of coupled inductor S The third terminal of each of the first and second switches S1 and S2 is connected to the negative electrode of the grid U via the fourth switch S4 and the second switch S2, respectively. The secondary winding N of the coupled inductor is connected to form a second freewheeling circuit. S are connected in series to the fourth switch S4, the second switch S2, the grid U and the filter unit, The input terminals of the control drive unit are the grid U and the input power supply Uin , the primary winding of the coupled inductor N P and the secondary winding of the coupled inductor N S The output terminal is connected to a first switch S1, a second switch S2, a third switch S3 and a fourth switch S4, respectively, for driving and controlling the switching of each switch, connecting each closed circuit, and further completing the adjustment of the grid current.

[0030] In this embodiment, the filter capacitor C1 is a non-polarized capacitor.

[0031] Among them, the first switch S1 and the second switch S2 are both metal oxide semiconductor field effect (MOS) transistors and / or insulated gate bipolar transistors (IGBTs), and the third switch S3 and the fourth switch S4 are both two metal oxide semiconductor field effect (MOS) transistors and / or insulated gate bipolar transistors (IGBTs) connected in reverse series.

[0032] As shown in FIG. 2, the control and driving unit further includes a sensor system 1, a digital signal processor (DSP) 2, a control circuit 3, and a driving circuit 4.

[0033] The input terminals of the sensor system 1 are the grid U and the input power supply U. in , the primary winding of the coupled inductor N P and the secondary winding N of the coupled inductor S and the grid voltage feedback signal u gf , input power U in Voltage feedback signal U inf , the primary winding of the coupled inductor N P The first current feedback signal i L1f and the secondary winding N of the coupled inductor S The second current feedback signal i L2f Collect and The input terminal of the DSP 2 is connected to the first output terminal of the sensor system 1, and receives the grid voltage feedback signal u of the grid U. gf and respectively process the voltage signal for the first current reference signal i ref1 and the second current reference signal i ref2 Generate A first input terminal of the control circuit 3 is connected to the output terminal of the DSP 2, a second input terminal is connected to the output terminal of the sensor system 1, and a first current reference signal i ref1 , the second current reference signal i ref2 , and the first current feedback signal i L1f and the second current feedback signal i L2f and performing a comparison control of the current based on the signal obtained by subtracting The input terminal of the drive circuit 4 is connected to the output terminal of the control circuit 3, and the output terminal is connected to the first switch S1, the second switch S2, the third switch S3 and the fourth switch S4, respectively, and drives the switching of the switches S1-S4 by generating a first drive signal, a second drive signal, a third drive signal and a fourth drive signal according to the first switch logic signal O1, the second switch logic signal O2, the third switch logic signal O3 and the fourth switch logic signal O4, respectively.

[0034] Among them, sensor system 1 is: The input terminal is connected to the grid U, the first output terminal is connected to the input terminal of the DSP 2, and the grid voltage feedback signal u of the grid U is gf A grid voltage sensor 101 used to collect and transmit to the DSP 2; Input terminal is input power supply U in , the first output terminal is connected to the input terminal of DSP 2, and the input power supply U in Input voltage feedback signal U inf and an input voltage sensor 102 used to collect and transmit to the DSP 2; The input terminal is the primary winding N of the transformer P, and the output terminal is connected to the second input terminal of the control circuit 3, and the first current feedback signal i L1f and a first current sensor 103 used to collect and transmit to the control circuit 3; The input terminal is the secondary winding N of the transformer S , and the output terminal is connected to the second input terminal of the control circuit 3, and the second current feedback signal i L2f and a second current sensor 104 used to collect and transmit to the control circuit 3.

[0035] Digital Signal Processor (DSP) 2 is The input terminal is connected to a first output terminal of the grid voltage sensor 101 in the sensor system 1, and a grid voltage feedback signal u of the grid U is gf a first analog-to-digital conversion module AD1 for performing a first analog-to-digital conversion on the input signal to obtain a first digital signal; a phase-locked loop 201, whose input end is connected to the first output end of the first analog-to-digital conversion module AD1, for performing digital processing on the first digital signal to obtain a voltage phase φ of the grid U; The input terminal is connected to the output terminal of the input voltage sensor 102 in the sensor system 1, and the input power supply U in Input voltage feedback signal U inf a second analog-to-digital conversion module AD2 for performing a second analog-to-digital conversion on the input signal to obtain a second digital signal; a first current reference calculation module 202, the first input terminal of which is connected to the first output terminal of the phase locked loop 201 and the second input terminal of which is connected to the first output terminal of the first analog-to-digital conversion module AD1, for calculating a first current reference signal according to the first digital signal and the voltage phase φ of the grid U to obtain a first current reference digital signal; a first digital-to-analog conversion module, whose input terminal is connected to the output terminal of the first current reference calculation module, for performing a first digital-to-analog conversion on the first current reference digital signal to obtain a first current reference signal; The input terminal is connected to the output terminal of the first current reference calculation module 202, and the first current reference digital signal is subjected to a first digital-to-analog conversion to obtain a first current reference signal i ref1 a first digital-to-analog conversion module DA1 for acquiring a first current reference signal i ref1 teeth,

[0036]

number

[0037] Fulfill a first digital-to-analog conversion module DA1; a second current reference calculation module 203, whose first input terminal is connected to the second output terminal of the phase locked loop 201, whose second input terminal is connected to the third output terminal of the first analog-to-digital conversion module AD1, and whose third input terminal is connected to the output terminal of the second analog-to-digital conversion module AD2, for calculating a second current reference signal according to the voltage phase φ of the grid U, the first digital signal, and the second digital signal to obtain a second reference digital signal; The input terminal is connected to the output terminal of the second current reference calculation module 203, and the second reference digital signal is subjected to a second digital-to-analog conversion to obtain a second current reference signal i ref2 a second digital-to-analog conversion module DA2 for acquiring a second current reference signal i ref2 teeth,

[0038]

number

[0039] Fulfill a second digital-to-analog conversion module DA2; The driving circuit 4 further includes a first driving circuit 401, a second driving circuit 402, a third driving circuit 403, and a fourth driving circuit 404, the output terminals of which are respectively connected to a first switch S1, a second switch S2, a third switch S3, and a fourth switch S4.

[0040] Among them, the control circuit 3 includes: The first input terminal is connected to the second output terminal of the grid voltage sensor 101 in the sensor system 1, the second input terminal is connected to the second output terminal of the input voltage sensor 102 in the sensor system 1, and the input power supply U in The input voltage feedback signal U inf and the grid voltage feedback signal u of grid U gf and a first comparator 301 for obtaining a first mode selection signal; The input terminal is connected to the third output terminal of the grid voltage sensor 101 in the sensor system 1, and the grid voltage feedback signal u of the grid U is gf and a second comparator 302 for comparing the first input with ground to obtain a second mode selection signal; a first phase inverter 303 whose input terminal is connected to the first output terminal of the first comparator 301 and which receives a third mode selection signal; a second phase inverter 304, the input of which is connected to the first output of the second comparator 302 to obtain a fourth mode selection signal; The first input terminal is connected to the output terminal of the first digital-to-analog conversion module DA1, and the second input terminal is connected to the first current feedback signal i L1f and the second current feedback signal i L2f and a first current feedback signal i L1f and the second current feedback signal i L2f The signal i obtained by subtracting Lf and the first current reference signal i ref1 a first current regulator 305 for performing a first current regulation on the first high frequency switching signal; The first input terminal is connected to the output terminal of the second digital-to-analog conversion module DA2, and the second input terminal is connected to the first current feedback signal i L1f and the second current feedback signal i L2f and a first current feedback signal i L1f and the second current feedback signal i L2f The signal i obtained by subtracting Lf and the second current reference signal i ref2a second current regulator 306 for adjusting the current for a second time to obtain a second high frequency switching signal; a third phase inverter 307, whose input end is connected to the first output end of the second current regulator 306 and which obtains a third high frequency switching signal; a first AND gate 308, the first input terminal of which is connected to the second output terminal of the first comparator 301 and the second input terminal of which is connected to the second output terminal of the second comparator 302, and which obtains a fifth mode selection signal according to the first mode selection signal and the second mode selection signal; a second AND gate 309, the first input terminal of which is connected to the output terminal of the first phase inverter 303 and the second input terminal of which is connected to the third output terminal of the second comparator 302, and the second AND gate 309 is configured to obtain a sixth mode selection signal based on the second mode selection signal and the third mode selection signal; a third AND gate 310, a first input terminal of which is connected to the second output terminal of the second current regulator 306 and a second input terminal of which is connected to the output terminal of the second phase inverter 304, and which derives a fourth high frequency switching signal according to the second high frequency switching signal and the second mode selection signal; a fourth AND gate 311, the first input terminal of which is connected to the output terminal of the third phase inverter 307 and the second input terminal of which is connected to the output terminal of the second AND gate 309, and the fourth AND gate 311 is configured to obtain a fifth high frequency switching signal according to the sixth mode selection signal and the third high frequency switching signal; a first OR gate 312, the first input terminal of which is connected to the output terminal of the fourth AND gate 311 and the second input terminal of which is connected to the output terminal of the third AND gate 310, for obtaining a sixth high frequency switching signal according to the fourth high frequency switching signal and the fifth high frequency switching signal; a second OR gate 313, the first input terminal of which is connected to the first output terminal of the first OR gate 312 and the second input terminal of which is connected to the first output terminal of the first AND gate 308, for obtaining a third switch logic signal O3 for controlling the third switch S3 according to the fifth mode selection signal and the sixth high frequency switching signal, and transmitting the third switch logic signal O3 to the third driving circuit 40 in the driving circuit 4; a fifth AND gate 314, the first input terminal of which is connected to the second output terminal of the first AND gate 308 and the second input terminal of which is connected to the output terminal of the first current regulator 305, and the fifth AND gate 314 is configured to obtain a seventh high frequency switching signal according to the fifth mode selection signal and the first high frequency switching signal; a third OR gate 315, the first input terminal of which is connected to the output terminal of the fifth AND gate 314 and the second input terminal of which is connected to the second output terminal of the second OR gate 313, for obtaining a first switch logic signal O1 for controlling the first switch S1 according to the seventh high frequency switching signal and the third switch logic signal O3 of the third switch S3, and transmitting the first switch logic signal O1 to the first driving circuit 401 in the driving circuit 4; a fourth phase inverter 316, whose input terminal is connected to the second output terminal of the third OR gate 315, for obtaining a second switch logic signal O2 for controlling the second switch S2 according to the first switch logic signal O1 of the first switch S1, and transmitting the second switch logic signal O2 to the second driving circuit 402 in the driving circuit 4; a fifth phase inverter 317, the input terminal of which is connected to the third output terminal of the first AND gate 308 to obtain a seventh mode selection signal; a sixth phase inverter 318, the input terminal of which is connected to the second output terminal of the first OR gate 312 to obtain an eighth high frequency switching signal; a sixth AND gate 319, the first input terminal of which is connected to the output terminal of the fifth phase inverter 317, the second input terminal of which is connected to the output terminal of the sixth phase inverter 318, and the output terminal of which is connected to the input terminal of the fourth driving circuit 404 in the driving circuit 4, for obtaining a fourth switch logic signal O4 for controlling the fourth switch S4 according to the seventh mode selection signal and the eighth high frequency switching signal, and transmitting the fourth switch logic signal O4 to the fourth driving circuit 404 in the driving circuit 4.

[0041] In this embodiment, the first current regulator 305 and the second current regulator 306 adopt either PI control, hysteresis control or proportional resonance control.

[0042] The present invention further provides a buck inverter control method realized based on a buck-boost inverter, the buck inverter control method including the following steps:

[0043] Step 1: The sensor system 1 receives the input voltage U in and the grid voltage u g In real time, the input voltage U in and the grid voltage u g The first judgment is made on the magnitude of the input power U in Determine whether the voltage of is greater than or less than the voltage of grid U, Of which, the input voltage U in and the grid voltage u g The first check against the size of Input power supply U in Input voltage feedback signal U inf and the grid voltage feedback signal u of grid U gf Step 1.1, determining the size of Input power supply U in Input voltage feedback signal U inf and the grid voltage feedback signal u of grid U gf Based on the size of the input power U in and step 1.2 determining whether the voltage is greater or less than the voltage of grid U.

[0044] Step 2: The sensor system detects the grid voltage u g Real-time monitoring of grid voltage u g A second judgment is made for the utility frequency period of the grid voltage u g Determine whether the power frequency period of is a positive half period or a negative half period; Of these, the grid voltage u g The second judgment is made for the power frequency period of Grid voltage feedback signal u for grid U gf Step 2.1 to determine the positive or negative value of Grid voltage feedback signal u for grid U gf and step 2.2 determining whether the utility frequency period of the voltage of grid U is a positive half period or a negative half period based on the positive or negative value of

[0045] Step 3: The utility frequency cycle of the voltage of grid U is a positive half cycle and the input power supply U in When the voltage of the grid U is greater than the voltage of the grid U, the control and drive unit adjusts the first switch S1 and / or the second switch S2 to turn on the first closed circuit and / or the first return circuit, thereby obtaining the first current feedback signal i L1f and the second current feedback signal i L2f The signal i obtained by subtracting Lf The first reference current i ref1 to track and complete grid current regulation; Wherein, the driving unit adjusts the first switch S1 and / or the second switch S2 of the inverter; Step 3.1: the control and driving unit adjusts the fourth switch S4 to be disconnected and the third switch S3 to be connected, and turns off the second freewheel circuit; A first current feedback signal i collected in real time by the first current sensor 103 and the second current sensor 104 in the sensor system 1 is L1f and the second current feedback signal i L2f The signal i obtained by subtracting Lf The first current reference signal i generated by DSP 2 ref1 Compare with step 3.2, First current feedback signal i L1f and the second current feedback signal i L2f The signal i obtained by subtracting Lf is the first current reference signal i ref1 If the input power supply is smaller than the filter inductor L, the control and driving unit adjusts the first switch transistor S1 to be conductive, so that the first closed circuit is conductive, and the input power supply is connected to the filter inductor L through the first closed circuit. g Adjust the current of the grid to increase, and complete step 3.3 to adjust the current of the grid. First current feedback signal i L1f and the second current feedback signal i L2f The signal i obtained by subtracting Lf is the first current reference signal i ref1If it is greater than 1, the control and driving unit adjusts the first switch transistor S1 to be turned off, making the first freewheeling circuit conductive, and the filter inductor L g and step 3.4, where the current in the grid is decreased to complete the current regulation of the grid.

[0046] Step 4: When the power frequency period of the voltage of the grid U is a negative half period or the power frequency period of the voltage of the grid U is a positive half period and the input power source U in When the voltage is smaller than the voltage of the grid U, the control and drive unit adjusts the first switch S1, the second switch S2, the third switch S3 and / or the fourth switch S4 to make the first closed circuit and / or the second freewheeling circuit conductive, thereby obtaining the first current feedback signal i L1f and the second current feedback signal i L2f The signal i obtained by subtracting Lf The second reference current i ref2 , and completes the grid current regulation.

[0047] Wherein, the control driving unit adjusts the first switch S1, the second switch S2, the third switch S3 and / or the fourth switch S4 of the inverter; Step 4.1 performing a second determination of the operating mode of the inverter to determine whether the operating mode of the inverter is a boost mode or a buck-boost mode; A first current feedback signal i collected in real time by the first current sensor 103 and the second current sensor 104 in the sensor system 1 is L1f and the second current feedback signal i L2f The signal i obtained by subtracting Lf The second current reference signal i generated by DSP 2 ref2 Compare with step 4.2, When the utility frequency period of the voltage of grid U is a positive half period and the input power supply U in Step 4.3, when the voltage of grid U is smaller than the voltage of grid U, the working mode of the inverter is a boost mode, and the control and drive unit adjusts all switches to high frequency switching; First current feedback signal i L1f and the second current feedback signal i L2f The signal i obtained by subtracting Lf is the second current reference signal i ref2 If the input power supply is greater than 1 V, the control and driving unit adjusts the first switch transistor S1 and the third switch transistor S3 to be conductive, so as to make the first closed circuit conductive, and the input power supply is connected to the filter inductor L g Step 4.4 to adjust the current of the grid to decrease the current of the grid; First current feedback signal i L1f and the second current feedback signal i L2f The signal i obtained by subtracting Lf is the second current reference signal i ref2 If the filter inductor L g The current of the grid is increased and step 4.5 is completed to regulate the current of the grid. Step 4.6, when the utility frequency period of the voltage of grid U is a negative half period, the working mode of this inverter is a buck-boost mode, and the control drive unit adjusts all the switches to be high frequency switching; First current feedback signal i L1f and the second current feedback signal i L2f The signal i obtained by subtracting Lf is the second current reference signal i ref2 If the input voltage Vcc is smaller than 1 V, the control and driving unit adjusts the first switch transistor S1 and the third switch transistor S3 to be conductive, so that the first closed circuit is conductive, and the input power supply U in However, the first closed circuit causes the filter inductor L g Step 4.7: adjust the current of the grid to decrease in the negative direction to complete the grid current adjustment; First current feedback signal i L1f and the second current feedback signal i L2f The signal i obtained by subtracting Lf is the second current reference signal iref2 If it is greater than , the control drive unit adjusts the first switch transistor S1 and the third switch transistor S3 to be turned off, so that the second freewheeling circuit is conductive, and the filter inductor L g The current increases in the negative direction, completing step 4.8 of the grid current regulation.

[0048] The working principle of the present invention is as follows.

[0049] The sensor system monitors the input voltage and the grid voltage in real time, and performs a first judgment on the magnitude of the input voltage and the grid voltage to judge whether the input voltage is greater than or less than the grid voltage. The sensor system monitors the grid voltage in real time, and performs a second judgment on the power frequency period of the grid voltage to judge whether the power frequency period of the grid voltage is a positive half period or a negative half period. When the power frequency period of the grid voltage is a positive half period and the input voltage is greater than the grid voltage, the control and driving unit adjusts the first switch and / or the second switch of the inverter to make the first closed circuit and / or the first return circuit conductive, so as to make the first current reference signal track the signal obtained by subtracting the first current feedback signal and the second current feedback signal, thereby completing the grid current regulation. When the power frequency period of the grid voltage is in a negative half period or the power frequency period of the grid voltage is in a positive half period and the input voltage is smaller than the grid voltage, the control and drive unit adjusts the first switch, the second switch, the third switch and / or the fourth switch of the inverter to make the first closed circuit and / or the second freewheeling circuit conductive, so as to make the signal obtained by subtracting the first current feedback signal and the second current feedback signal track the second current reference signal, and completes the grid current regulation.

[0050] As described above, the buck-boost inverter and its control method of the present invention solve the problem of low buck-boost conversion efficiency of conventional photovoltaic inverters, eliminate the common mode leakage current phenomenon, realize buck-boost conversion, and improve the conversion efficiency of the photovoltaic inverter system.

[0051] The above is merely an embodiment of the present application, and is not intended to limit the scope of protection of the present application. All modifications, equivalent replacements, improvements, etc. made within the spirit and scope of the present application are included in the scope of protection of the present application.

Claims

1. A step-up / step-down inverter, an input power source having a negative pole connected to a negative pole of a grid and having a negative pole and a negative pole of the grid commonly grounded; a filter unit including a filter inductor, a damping resistor, and a filter capacitor, a first end of the filter inductor being connected to a positive electrode of the grid, a first end of the damping resistor being connected to a second end of the second switch and a negative electrode of the grid respectively, and a second end of the damping resistor being connected to a first end of the filter capacitor; a coupled inductor including a primary winding and a secondary winding, a first end of the primary winding being connected to a second end of a filter inductor, a second end of a filter capacitor, and a fourth end of the secondary winding of the coupled inductor, and a second end being connected to a positive electrode of the input power source via a third switch and a first switch, respectively; a first closed circuit is formed by the primary winding of the coupled inductor, a grid, a filter unit, the input power source, the third switch, and the first switch; and a first freewheeling circuit is formed by the primary winding of the coupled inductor, the grid, the filter unit, the third switch, and the second switch; a coupled inductor having a third end of a secondary winding of the coupled inductor connected to a negative electrode of a grid via a fourth switch and the second switch, respectively, and a second freewheeling circuit being formed by the secondary winding of the coupled inductor, the grid, the filter unit, the fourth switch, and the second switch; a control and driving unit, whose input terminals are respectively connected to a grid, an input power source, the primary winding of the coupled inductor and the secondary winding of the coupled inductor, and whose output terminals are respectively connected to the first switch, the second switch, the third switch and the fourth switch, and which is used to drive and control the switching of each switch, to communicate each closed circuit, and to complete the adjustment of the current of the grid; the first closed circuit and the second return circuit constitute a charge / discharge circuit, When a commercial frequency cycle of the grid voltage is a positive half cycle and an input voltage of the input power source is lower than a voltage of the grid, an operation mode of the buck-boost inverter is a boost mode; In charging the coupled inductor in the boost mode, the first switch and the third switch are turned off and the second switch and the fourth switch are turned on, so that in the second freewheel circuit of the charge / discharge circuit, the grid charges the secondary winding; In discharging the coupled inductor in the boost mode, the first switch and the third switch are turned on and the second switch and the fourth switch are turned off, so that the primary winding discharges to the input power supply and the grid in the first closed circuit of the charge / discharge circuit. A step-up / step-down inverter.

2. The control drive unit includes: a sensor system whose input terminals are respectively connected to a grid, an input power source, a primary winding of the coupled inductor, and a secondary winding of the coupled inductor, and which respectively collects a grid voltage feedback signal of the grid, a voltage feedback signal of the input power source, a first current feedback signal of the primary winding of the coupled inductor, and a second current feedback signal of the secondary winding of the coupled inductor; a DSP whose input is connected to the first output of the sensor system, for performing voltage signal processing on the grid voltage feedback signal and generating a first current reference signal and a second current reference signal respectively; a control circuit having a first input terminal connected to an output terminal of the DSP and a second input terminal connected to an output terminal of the sensor system, performing current comparison control based on the first current reference signal, the second current reference signal, and a signal obtained by subtracting the first current feedback signal and the second current feedback signal, and generating a first switch logic signal, a second switch logic signal, a third switch logic signal, and a fourth switch logic signal, respectively; 2. The buck-boost inverter according to claim 1 , further comprising: a drive circuit having an input terminal connected to an output terminal of the control circuit and an output terminal connected to the first switch, the second switch, the third switch and the fourth switch, respectively, and generating a first drive signal, a second drive signal, a third drive signal and a fourth drive signal according to the first switch logic signal, the second switch logic signal, the third switch logic signal and the fourth switch logic signal, respectively, to drive switching of each switch.

3. The sensor system includes: a grid voltage sensor, the input of which is connected to a grid and the first output of which is connected to the input of the DSP, for collecting and transmitting the grid voltage feedback signal to the DSP; an input voltage sensor, whose input end is connected to the input power source and whose first output end is connected to the input end of the DSP, is used for collecting and transmitting a voltage feedback signal of the input power source to the DSP; a first current sensor, an input terminal of which is connected to the primary winding and an output terminal of which is connected to a second input terminal of the control circuit, being used for collecting the first current feedback signal and transmitting it to the control circuit; 3. The buck-boost inverter as claimed in claim 2, further comprising: a second current sensor, the input terminal of which is connected to the secondary winding and the output terminal of which is connected to a second input terminal of the control circuit, for collecting and transmitting the second current feedback signal to the control circuit.

4. The DSP includes: a first analog-to-digital conversion module, the input terminal of which is connected to the first output terminal of the grid voltage sensor, for performing a first analog-to-digital conversion on the grid voltage feedback signal to obtain a first digital signal; a phase-locked loop having an input connected to the first output of the first analog-to-digital conversion module, for performing digital processing on the first digital signal to obtain a voltage phase of a grid; a second analog-to-digital conversion module, the input terminal of which is connected to the output terminal of the input voltage sensor, for performing a second analog-to-digital conversion on the voltage feedback signal of the input power source to obtain a second digital signal; a first current reference calculation module, the first input terminal of which is connected to the first output terminal of the phase locked loop and the second input terminal of which is connected to the second output terminal of the first analog-to-digital conversion module, for calculating a first current reference signal according to the first digital signal and the voltage phase to obtain a first current reference digital signal; a first digital-to-analog conversion module, the input terminal of which is connected to the output terminal of the first current reference calculation module, for performing a first digital-to-analog conversion on the first current reference digital signal to obtain a first current reference signal; a second current reference calculation module, the first input terminal of which is connected to the second output terminal of the phase locked loop, the second input terminal of which is connected to the third output terminal of the first analog-to-digital conversion module, and the third input terminal of which is connected to the output terminal of the second analog-to-digital conversion module, and the second current reference calculation module calculates a second current reference signal according to the voltage phase, the first digital signal, and the second digital signal to obtain a second reference digital signal; 4. The buck-boost inverter according to claim 3 , further comprising: a second digital-to-analog conversion module, the input terminal of which is connected to the output terminal of the second current reference calculation module, the second digital-to-analog conversion module being configured to perform a second digital-to-analog conversion on the second reference digital signal to obtain a second current reference signal.

5. 2. The buck-boost inverter according to claim 1, wherein the drive circuit further includes a first drive circuit, a second drive circuit, a third drive circuit, and a fourth drive circuit, the output terminals of which are connected to the first switch, the second switch, the third switch, and the fourth switch, respectively.

6. The control circuit includes: a first comparator, the first input terminal of which is connected to the second output terminal of the grid voltage sensor and the second input terminal of which is connected to the second output terminal of the input voltage sensor, for comparing the voltage feedback signal of the input power source with the grid voltage feedback signal to obtain a first mode selection signal; a second comparator, the input terminal of which is connected to the third output terminal of the grid voltage sensor, for comparing the grid voltage feedback signal with ground to obtain a second mode selection signal; a first phase inverter having an input connected to the first output of the first comparator to receive a third mode selection signal; a second phase inverter, the input terminal of which is connected to the first output terminal of the second comparator to obtain a fourth mode selection signal; a first current regulator, the first input terminal of which is connected to the output terminal of the first digital-to-analog conversion module and the second input terminal of which is connected to an output terminal of a signal obtained by subtracting the first current feedback signal from the second current feedback signal, for performing a first current adjustment on the signal obtained by subtracting the first current feedback signal from the second current feedback signal and the first current reference signal to obtain a first high frequency switching signal; a second current regulator, the first input terminal of which is connected to the output terminal of the second digital-to-analog conversion module and the second input terminal of which is connected to an output terminal of a signal obtained by subtracting the first current feedback signal from the second current feedback signal, the second current regulator performing a second current adjustment on the signal obtained by subtracting the first current feedback signal from the second current feedback signal and the second current reference signal to obtain a second high frequency switching signal; a third phase inverter, the input terminal of which is connected to the first output terminal of the second current regulator and which receives a third high frequency switching signal; a first AND gate having a first input terminal connected to the second output terminal of the first comparator and a second input terminal connected to the second output terminal of the second comparator, the first AND gate being configured to obtain a fifth mode selection signal according to the first mode selection signal and the second mode selection signal; a second AND gate, the first input terminal of which is connected to the output terminal of the first phase inverter and the second input terminal of which is connected to the third output terminal of the second comparator, for deriving a sixth mode selection signal according to the second mode selection signal and the third mode selection signal; a third AND gate, the first input terminal of which is connected to the second output terminal of the second current regulator and the second input terminal of which is connected to the output terminal of the second phase inverter, and the third AND gate is configured to derive a fourth high frequency switching signal according to the second high frequency switching signal and the second mode selection signal; a fourth AND gate, the first input terminal of which is connected to the output terminal of the third phase inverter and the second input terminal of which is connected to the output terminal of the second AND gate, and the fourth AND gate is configured to obtain a fifth high frequency switching signal according to the sixth mode selection signal and the third high frequency switching signal; a first OR gate, the first input terminal of which is connected to the output terminal of the fourth AND gate and the second input terminal of which is connected to the output terminal of the third AND gate, for obtaining a sixth high frequency switching signal according to the fourth high frequency switching signal and the fifth high frequency switching signal; a second OR gate, the first input terminal of which is connected to the first output terminal of the first OR gate and the second input terminal of which is connected to the first output terminal of the first AND gate, for obtaining a third switch logic signal according to the fifth mode selection signal and the sixth high frequency switching signal, and transmitting the third switch logic signal to a third driving circuit; a fifth AND gate, the first input terminal of which is connected to the second output terminal of the first AND gate and the second input terminal of which is connected to the output terminal of the first current regulator, and the fifth AND gate is configured to obtain a seventh high frequency switching signal according to the fifth mode selection signal and the first high frequency switching signal; a third OR gate, the first input terminal of which is connected to the output terminal of the fifth AND gate and the second input terminal of which is connected to the second output terminal of the second OR gate, for obtaining a first switch logic signal according to the seventh high frequency switching signal and the third switch logic signal, and transmitting the first switch logic signal to a first driving circuit; a fourth phase inverter, the input terminal of which is connected to the second output terminal of the third OR gate, for obtaining a second switch logic signal according to the first switch logic signal and transmitting the second switch logic signal to a second driving circuit; a fifth phase inverter, the input terminal of which is connected to the third output terminal of the first AND gate to obtain a seventh mode selection signal; a sixth phase inverter, the input terminal of which is connected to the second output terminal of the first OR gate to obtain an eighth high frequency switching signal; 4. The buck-boost inverter as claimed in claim 3, further comprising: a sixth AND gate, the first input terminal of which is connected to the output terminal of the fifth phase inverter, the second input terminal of which is connected to the output terminal of the sixth phase inverter, and the output terminal of which is connected to the input terminal of a fourth driving circuit, the sixth AND gate being adapted to obtain a fourth switch logic signal according to the seventh mode selection signal and the eighth high frequency switching signal, and transmit the fourth switch logic signal to the fourth driving circuit.

7. A step-up / step-down inverter control method realized based on the step-up / step-down inverter according to any one of claims 1 to 6, Step 1, a sensor system monitors an input voltage and a grid voltage in real time, and performs a first determination on the magnitude of the input voltage and the grid voltage to determine whether the input voltage is greater than or less than the grid voltage; Step 2, in which a sensor system monitors a grid voltage in real time and performs a second determination on the power frequency period of the grid voltage to determine whether the power frequency period of the grid voltage is a positive half period or a negative half period; Step 3: when the utility frequency period of the grid voltage is a positive half period and the input voltage is greater than the grid voltage, the control and driving unit adjusts the first switch and / or the second switch to turn on the first closed circuit and / or the first return circuit, so that the signal obtained by subtracting the first current feedback signal and the second current feedback signal tracks the first reference current, thereby completing the grid current regulation; and when the power frequency period of the grid voltage is a negative half period or the power frequency period of the grid voltage is a positive half period and the input voltage is smaller than the grid voltage, the control and drive unit adjusts the first switch, the second switch, the third switch and / or the fourth switch to turn on a first closed circuit and / or a second freewheeling circuit, so as to make a signal obtained by subtracting the first current feedback signal and the second current feedback signal track a second reference current, thereby completing grid current regulation.

8. The control drive unit adjusts the first switch and / or the second switch, Step 3.1: the control and driving unit adjusts the fourth switch to be turned off and the third switch to be turned on, and turns off the second freewheel circuit; Step 3.2: subtracting the first current feedback signal and the second current feedback signal collected in real time by the first current sensor and the second current sensor, respectively, and comparing the subtracted signal with a first current reference signal generated by the DSP; Step 3.3: when the signal obtained by subtracting the first current feedback signal and the second current feedback signal is smaller than the first current reference signal, the control and drive unit adjusts the first switch to be conductive, makes the first closed circuit conductive, and adjusts the input power source to increase the current of the filter inductor through the first closed circuit, thereby completing the grid current adjustment; 8. The buck-boost inverter control method of claim 7, further comprising: step 3.4, when the signal obtained by subtracting the first current feedback signal and the second current feedback signal is greater than the first current reference signal, the control and driving unit adjusts the first switch to be off, so that the first freewheeling circuit is conductive, so that the current of the filter inductor decreases, and grid current regulation is completed.

9. The control and driving unit adjusts the first switch, the second switch, the third switch, and / or the fourth switch. Step 4.1: performing a second determination of the operation mode of the inverter to determine whether the operation mode of the buck-boost inverter is a boost mode or a buck-boost mode; Step 4.2: comparing a signal obtained by subtracting the first current feedback signal and the second current feedback signal collected in real time by the first current sensor and the second current sensor, respectively, with a second current reference signal generated by the DSP; Step 4.3: when the utility frequency period of the grid voltage is a positive half period and the input voltage is less than the grid voltage, the working mode of the inverter is a boost mode, and the control and drive unit adjusts all the switches to high frequency switching; Step 4.4: if the signal obtained by subtracting the first current feedback signal and the second current feedback signal is greater than the second current reference signal, the control and drive unit adjusts the first switch and the third switch to be conductive, so as to make the first closed circuit conductive, and adjusts the input power source to reduce the current of the filter inductor through the first closed circuit, thereby completing the grid current adjustment; Step 4.5: if the signal obtained by subtracting the first current feedback signal and the second current feedback signal is smaller than the second current reference signal, the control and driving unit adjusts the first switch and the third switch to be off, so that the second freewheel circuit is conductive, and the current of the filter inductor increases, completing the grid current regulation; Step 4.6: when the utility frequency period of the grid voltage is a negative half period, the working mode of the inverter is a buck-boost mode, and the control and drive unit adjusts all the switches to high frequency switching; Step 4.7: if the signal obtained by subtracting the first current feedback signal and the second current feedback signal is smaller than the second current reference signal, the control and drive unit adjusts the first switch and the third switch to be conductive, so as to make the first closed circuit conductive, and adjusts the input power source to make the current of the filter inductor decrease in a negative direction through the first closed circuit, thereby completing the grid current adjustment; 8. The method for controlling a buck-boost inverter according to claim 7, further comprising: when the signal obtained by subtracting the first current feedback signal and the second current feedback signal is greater than the second current reference signal, the control and driving unit adjusts the first switch and the third switch to be off, so that the second freewheeling circuit is conductive, so that the current of the filter inductor increases in a negative direction, and grid current regulation is completed.

10. 8. The method for controlling a step-up / step-down inverter according to claim 7, wherein the third switch and the fourth switch are devices that can withstand forward and reverse voltages.

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