A buck-boost integrated inverter and control method

Abstract

This invention discloses a buck-boost integrated inverter and its control method. The buck-boost integrated inverter includes switching transistors S1, S2, S3, and S4, diodes D1, D2, and D3, and a supporting capacitor C. dc and inductor L in The control method of this invention can suppress the impact of DC input voltage fluctuations on output voltage to a certain extent. It can cope with unstable DC input voltage fluctuations within a certain range. When the DC input voltage is large and the AC output voltage is small, it improves the DC side voltage utilization of the inverter, reduces the withstand voltage requirements of switching transistors S2, S3 and S4, and lowers costs. The buck-boost integrated inverter of this invention can be used as a photovoltaic inverter, realizing the boost inverter function in a single stage. It has high integration and improves efficiency.

Description

Technical Field

[0001] This invention belongs to the field of electronic technology, specifically relating to a buck-boost integrated inverter and its control method. Background Technology

[0002] With the rapid development of DC power sources such as photovoltaics, fuel cells, and batteries, the application of inverters is increasing. In boost inverter applications, to ensure stable AC power output, the inverter needs to have boost capability. Currently, the most common types are traditional two-stage boost inverters and single-stage boost inverters, which are a relatively new research area. In buck inverter applications, since the inverter itself has a buck function, there is less research in this area. However, as the application of inverters increases, the problem of low DC bus voltage utilization in low-gain buck inverters is becoming increasingly prominent. Summary of the Invention

[0003] To address the aforementioned shortcomings in the prior art, this invention provides a buck-boost integrated inverter and control method that solves the limitation problem of existing inverters having either high or low DC gain.

[0004] To achieve the aforementioned objectives, the technical solution adopted by this invention is as follows: a buck-boost integrated inverter, comprising switching transistors S1, S2, S3, and S4, diodes D1, D2, and D3, and a supporting capacitor C. dc and inductor L in ;

[0005] In this configuration, the collector of the switching transistor S1 is connected to the cathode of the diode D2 and is also connected to the positive terminal of the input voltage. The emitter of the switching transistor S1 is connected to the inductor L. in One end, supporting capacitor C dc The negative terminal of the inductor L is connected to the emitter of the switching transistor S3 and the anode of the diode D3. in The other end is connected to the anode of the diode D1 and to the negative terminal of the input voltage. The cathode of the diode D1 is connected to the supporting capacitor C. dc The positive terminal of the diode is connected to the collector of the switching transistor S2 and the collector of the switching transistor S4. The emitter of the switching transistor S4 is connected to the collector of the switching transistor S3 and serves as the second output port. The emitter of the switching transistor S2 is connected to the cathode of the diode D3 and the anode of the diode D2, respectively, and serves as the first output port.

[0006] Furthermore, both the first output port and the second output port are connected to a filter circuit, which is also connected to a load.

[0007] The beneficial effects of the above-mentioned further solutions are as follows: The buck-boost integrated inverter of the present invention has the advantages of realizing a wide range of voltage input, low cost, single-stage boost inverter, improving DC bus voltage utilization during buck inverter, and reducing the withstand voltage requirements of switching transistors S2, S3 and S4.

[0008] A control method for a buck-boost integrated inverter includes the following steps:

[0009] S1. Control the buck-boost integrated inverter to work according to the set working mode combination;

[0010] S2. Control the DC gain of the buck-boost integrated inverter according to the duty cycle of the switching transistor S1 to complete the inverter control.

[0011] Further: S1 specifically refers to:

[0012] The working process of the buck-boost integrated inverter is controlled according to the set working mode combination within each switching cycle, thereby starting the buck-boost integrated inverter to work. The working modes include the first mode to the fourth mode.

[0013] Further: In S1, the method for controlling the buck-boost integrated inverter according to the first mode is specifically as follows:

[0014] Set the start time of the first mode, turn on switch S2 and switch S3 before the start time of the first mode, turn off switch S3 and turn on switch S4 when the first mode is started.

[0015] The specific method for controlling the buck-boost integrated inverter based on the second mode is as follows:

[0016] Set the time to enable the second mode, and turn off switch S4 and turn on switch S3 when the second mode is enabled;

[0017] The specific method for controlling the buck-boost integrated inverter based on the third mode is as follows:

[0018] Set the time when the third mode is activated, and turn off switch S2 and turn on switch S1 when the third mode is activated;

[0019] The specific method for controlling the buck-boost integrated inverter based on the fourth mode is as follows:

[0020] Set the time to activate the fourth mode. At the time of activating the fourth mode, turn off switch S1 and turn on switch S2.

[0021] Furthermore, the specific method for turning on the switching transistor S1 is as follows:

[0022] The first driving signal is obtained by PWM modulation or PFM modulation, and the switching transistor S1 is turned on according to the first driving signal.

[0023] The specific method for turning on the switching transistor S2 is as follows:

[0024] The first driving signal is obtained by PWM modulation or PFM modulation, the first driving signal is inverted to obtain the second driving signal, and the switch S2 is turned on according to the second driving signal.

[0025] The specific method for turning on the switching transistor S3 is as follows:

[0026] The third driving signal is obtained by SPWM modulation, and the switch S3 is turned on according to the third driving signal.

[0027] The specific method for turning on the switching transistor S4 is as follows:

[0028] The third driving signal is obtained by SPWM modulation, and the fourth driving signal is obtained by inverting the third driving signal. Switch S4 is turned on according to the fourth driving signal.

[0029] Furthermore: the PWM modulation method specifically refers to:

[0030] Support capacitor C dc The difference between the preset voltage value and the sampled value is input into the proportional-integral controller PI1 to obtain the modulation signal. This signal, along with the bipolar triangular carrier signal, is input into the non-inverting input and the inverting input of the comparator, respectively. The resulting signal is used as the first driving signal.

[0031] The PFM modulation method is specifically as follows:

[0032] Support capacitor C dc The voltage preset value is subtracted from the sampled value, and the difference is input to the proportional-integral controller PI2 to obtain the frequency signal. The frequency signal is then input to the triangular carrier generator module V. tri A bipolar triangular carrier wave is obtained. 0 and the bipolar triangular carrier wave are input to the non-inverting input and the inverting input of the comparator, respectively. The resulting signal is used as the first driving signal.

[0033] The SPWM modulation method is specifically as follows:

[0034] The difference between the preset effective value of the output voltage of the buck-boost integrated inverter and the sampled effective value is calculated, and the difference is sent to the proportional-integral controller PI3. The signal output by the proportional-integral controller PI3 is used as the amplitude and multiplied with the sinusoidal modulation wave. The generated signal is used as the AC component of the modulation wave.

[0035] The duty cycle of the switch S1 is subtracted from its preset duty cycle value. The difference is input to the proportional-integral controller PI4. The signal output by the proportional-integral controller PI4 is subtracted from the constant 1, and the generated signal is used as the DC component of the modulation wave.

[0036] The DC component and AC component of the modulating wave are added together to obtain the modulating wave. This modulating wave is then input to the non-inverting and inverting inputs of the comparator along with a bipolar triangular carrier wave, respectively. The resulting signal is used as the third driving signal.

[0037] Furthermore: In S2, the DC gain G of the buck-boost integrated inverter in continuous inductor current mode CCM The expression is as follows:

[0038]

[0039] In the formula, d1 is the duty cycle of the switching transistor S1, and M = V o / V c V c To support the capacitor voltage, V o This is the effective value for a buck-boost integrated inverter;

[0040] DC gain G of the buck-boost integrated inverter in discontinuous inductor current mode DCM The expression is as follows:

[0041]

[0042] In the formula, f is the operating frequency of switch S1 or switch S2, and P o This refers to the output power of the buck-boost integrated inverter.

[0043] The beneficial effects of the above-mentioned further solutions are as follows: The buck-boost integrated inverter control method of the present invention can control the DC gain by changing the duty cycle of the switching transistor S1 when the circuit parameters remain unchanged, thereby achieving high-gain inverter output during boost inverter and low-gain inverter output during buck inverter.

[0044] The beneficial effects of this invention are as follows:

[0045] (1) The buck-boost integrated inverter and control method provided by the present invention can suppress the influence of DC input voltage fluctuation on output voltage to a certain extent, and can cope with the working conditions of unstable input DC voltage fluctuating within a certain range.

[0046] (2) The buck-boost integrated inverter of the present invention improves the DC side voltage utilization of the inverter and reduces the withstand voltage requirements of switching transistors S2, S3 and S4 when the DC input voltage is large and the AC output voltage is small, thereby reducing the cost.

[0047] (3) The buck-boost integrated inverter of the present invention can be used as a photovoltaic inverter, and can realize the boost inverter function in a single stage. It has high integration and improves efficiency. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of a buck-boost integrated inverter structure provided by the present invention;

[0049] Figure 2 This is a flowchart of a buck-boost integrated inverter control method provided in an embodiment of the present invention;

[0050] Figure 3 The buck-boost integrated inverter provided in this embodiment of the invention is in u r3 >u r_dc Modal diagrams for each switching cycle;

[0051] Figure 4 The buck-boost integrated inverter provided in this embodiment of the invention operates at u r3 >u r_dc Furthermore, the waveforms of switching transistors S1 and S3, inductor current, and port voltage during one switching cycle are shown in the CCM diagram.

[0052] Figure 5 The buck-boost integrated inverter provided in this embodiment of the invention operates at u r3 >u r_dc Furthermore, the waveforms of switching transistors S1 and S3, inductor current, and port voltage during one switching cycle are shown in the DCM diagram.

[0053] Figure 6 This is a schematic diagram of a buck-boost integrated inverter control method provided in an embodiment of the present invention;

[0054] Figure 7 The diagram shows the input voltage, output voltage, supporting capacitor voltage, port voltage, and waveforms of switching transistors S2 to S4 during buck-boost inverter operation in an embodiment of the present invention.

[0055] Figure 8The waveforms of the input voltage, output voltage, and supporting capacitor voltage of a buck-boost integrated inverter provided in this embodiment of the invention during boost inverter operation are shown.

[0056] Figure 9 This is a transient waveform diagram of a buck-boost integrated inverter provided in an embodiment of the present invention. Detailed Implementation

[0057] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0058] like Figure 1 As shown, in one embodiment of the present invention, a buck-boost integrated inverter is characterized by comprising switching transistors S1, S2, S3, and S4, diodes D1, D2, and D3, and a supporting capacitor C. dc and inductor L in ;

[0059] In this configuration, the collector of the switching transistor S1 is connected to the cathode of the diode D2 and is also connected to the positive terminal of the input voltage. The emitter of the switching transistor S1 is connected to the inductor L. in One end, supporting capacitor C dc The negative terminal of the inductor L is connected to the emitter of the switching transistor S3 and the anode of the diode D3. in The other end is connected to the anode of the diode D1 and to the negative terminal of the input voltage. The cathode of the diode D1 is connected to the supporting capacitor C. dc The positive terminal of the diode is connected to the collector of the switching transistor S2 and the collector of the switching transistor S4. The emitter of the switching transistor S4 is connected to the collector of the switching transistor S3 and serves as the second output port. The emitter of the switching transistor S2 is connected to the cathode of the diode D3 and the anode of the diode D2, respectively, and serves as the first output port.

[0060] In this embodiment, the emitter of switch S1 is connected to terminal n1, the collector of switch S2 is connected to terminal n2, the emitter of switch S2 is connected to output port a, and diodes D2 and D3 are connected to switch S2 through output port a. The anode of diode D2 and the cathode of diode D3 are both connected to output port a, and the anode of diode D3 is connected to terminal n1. Switch S1, switch S2, diode D2, and diode D3 form the first bridge arm.

[0061] The emitter of switch S3 is connected to terminal n1, the collector of switch S4 is connected to terminal n2, and both the collector of switch S3 and the emitter of switch S4 are connected to output port b, forming the second bridge arm.

[0062] Both the first output port and the second output port are connected to the filter circuit, which is also connected to the load.

[0063] like Figure 2 As shown, the control method for the buck-boost integrated inverter includes the following steps:

[0064] S1. Control the buck-boost integrated inverter to work according to the set working mode combination;

[0065] S2. Control the DC gain of the buck-boost integrated inverter according to the duty cycle of the switching transistor S1 to complete the inverter control.

[0066] Specifically, S1 is:

[0067] The working process of the buck-boost integrated inverter is controlled according to the set working mode combination within each switching cycle, thereby starting the buck-boost integrated inverter to work. The working modes include the first mode to the fourth mode.

[0068] In S1, the method for controlling the buck-boost integrated inverter according to the first mode is specifically as follows:

[0069] Set the start time of the first mode, turn on switch S2 and switch S3 before the start time of the first mode, turn off switch S3 and turn on switch S4 when the first mode is started.

[0070] The specific method for controlling the buck-boost integrated inverter based on the second mode is as follows:

[0071] Set the time to enable the second mode, and turn off switch S4 and turn on switch S3 when the second mode is enabled;

[0072] The specific method for controlling the buck-boost integrated inverter based on the third mode is as follows:

[0073] Set the time when the third mode is activated, and turn off switch S2 and turn on switch S1 when the third mode is activated;

[0074] The specific method for controlling the buck-boost integrated inverter based on the fourth mode is as follows:

[0075] Set the time to activate the fourth mode. At the time of activating the fourth mode, turn off switch S1 and turn on switch S2.

[0076] like Figure 3 As shown, in this embodiment, the buck-boost integrated inverter modulates the waveform u. r3 Greater than the DC component of the modulated wave u r_dc The working process within one switching cycle includes the following four modes:

[0077] Mode 1, with a duration of t0-t1:

[0078] Before time t0, switching transistors S2 and S3 are turned on, diode D1 is turned on, and inductor L... in Because it withstands the reverse support capacitor voltage V c In linear discharge, u ab =V c At time t0, switch S3 is turned off and switch S4 is turned on. At this time, u ab =0, inductance L in Because it withstands the reverse support capacitor voltage V c The linear discharge continues until the inductor current is 0 or at time t1. At time t1, mode 1 ends.

[0079] Mode 2, with a duration of t1-t2:

[0080] At time t1, switch S4 is turned off and switch S3 is turned on. At this time, u ab =V c Inductor L in Because it withstands the reverse support capacitor voltage V c The linear discharge continues until the inductor current is 0 or at time t2. At time t2, mode 2 ends.

[0081] Mode 3, with a duration of t2-t3:

[0082] At time t2, switch S2 is off, switch S1 is on, diode D1 is reverse-biased and cut off, and diode D3 is on. At this time, u ab =0, inductance L in Because it is subjected to a positive voltage V i With linear charging, mode 3 ends at time t3;

[0083] Mode 4, with a duration set to t3-t4:

[0084] At time t2, switch S1 is off, switch S2 is on, diode D3 is reverse-biased and cut off, and diode D1 is on. At this time, u ab =V c Inductor L in Because it withstands the reverse support capacitor voltage V cThe linear discharge continues until the inductor current is 0 or at time t4. At time t4, mode 4 ends.

[0085] At the start of the next switching cycle, modes 1-4 above will repeat.

[0086] Buck-boost integrated inverter in modulation wave u r3 Less than the DC component of the modulated wave u rdc The working process and modulation wave u within each switching cycle r3 Greater than the DC component of the modulated wave u rdc The working process within each switching cycle is similar, so it will not be described in detail here.

[0087] like Figure 4 As shown, in this embodiment, the buck-boost integrated inverter operates at a modulation frequency u r3 Greater than the DC component of the modulated wave u r_dc Furthermore, in CCM (Continuous Current Mode), during one switching cycle, switching transistors S1 and S3, and inductor L... in The current and port voltage waveforms conform to the following: Figure 3 Modal analysis is shown.

[0088] like Figure 5 As shown, in this embodiment, the buck-boost integrated inverter operates at a modulation frequency u r3 Greater than the DC component of the modulated wave u r_dc Furthermore, in DCM (Discontinuous Current Mode), during one switching cycle, switching transistors S1 and S3, and inductor L... in The current and port voltage waveforms conform to the following: Figure 3 Modal analysis is shown.

[0089] like Figure 6 As shown, in this embodiment, the method for turning on the switch S1 is specifically as follows:

[0090] The first drive signal is obtained by PWM modulation or PFM modulation, wherein PFM modulation is only applied to the discontinuous inductor current mode. The switch S1 is turned on according to the first drive signal.

[0091] The specific method for turning on the switching transistor S2 is as follows:

[0092] The first driving signal is obtained by PWM modulation or PFM modulation, the first driving signal is inverted to obtain the second driving signal, and the switch S2 is turned on according to the second driving signal.

[0093] The specific method for turning on the switching transistor S3 is as follows:

[0094] The third driving signal is obtained by SPWM modulation, and the switch S3 is turned on according to the third driving signal.

[0095] The specific method for turning on the switching transistor S4 is as follows:

[0096] The third driving signal is obtained by SPWM modulation, and the fourth driving signal is obtained by inverting the third driving signal. Switch S4 is turned on according to the fourth driving signal.

[0097] The PWM modulation method is specifically as follows:

[0098] Support capacitor C dc voltage preset value V dc_ref With V dc The difference between the sampled values ​​is input into the proportional-integral controller PI1 to obtain the modulation signal u. rdc1 Combine it with the bipolar triangular carrier signal u c1 The signals obtained by inputting the non-inverting and inverting inputs of the comparator respectively are used as the first driving signal.

[0099] The PFM modulation method is specifically as follows:

[0100] Support capacitor C dc voltage preset value V dc_ref With sampled value V dc The difference is calculated, and the difference is input into the proportional-integral controller PI2 to obtain the frequency signal f. s , frequency signal f s Input triangular carrier generator module V tri Obtain the bipolar triangular carrier u c2 , with 0 and bipolar triangular carrier u c2 The signals obtained by inputting the non-inverting and inverting inputs of the comparator respectively are used as the first driving signal.

[0101] The SPWM modulation method is specifically as follows:

[0102] The preset value of the effective value of the output voltage of the Buck-Boost integrated inverter is V. o_ref With the effective value V of the sample o The difference is calculated and fed into the proportional-integral controller PI3. The signal output from PI3 is used as the amplitude to modulate the sinusoidal modulation wave u. r_sin Multiply, and use the generated signal as the AC component u of the modulated wave. r3_ac ;

[0103] The duty cycle of the switching transistor S1 is set to its preset duty cycle value d. 1_ref The difference is input into the proportional-integral controller PI4. The constant 1 is subtracted from the signal output by the proportional-integral controller PI4, and the resulting signal is used as the DC component u of the modulated wave. r_dc ;

[0104] The DC component u of the modulated wave r_dc and the AC component u of the modulated wave r3_ac Adding them together yields the modulated wave u r3 Combine it with a bipolar triangular carrier u c3 The signals obtained by inputting the non-inverting and inverting inputs of the comparator respectively are used as the third driving signal.

[0105] In S2, the DC gain G of the buck-boost integrated inverter in continuous inductor current mode CCM The expression is as follows:

[0106]

[0107] In the formula, d1 is the duty cycle of the switching transistor S1, and M = V o / V c V c To support the capacitor voltage, V o This is the effective value for a buck-boost integrated inverter;

[0108] DC gain G of the buck-boost integrated inverter in discontinuous inductor current mode DCM The expression is as follows:

[0109]

[0110] In the formula, f is the operating frequency of switch S1 or switch S2, and P o This refers to the output power of the buck-boost integrated inverter.

[0111] The buck-boost integrated inverter control method of the present invention can control the DC gain by changing the duty cycle of the switching transistor S1 while keeping the circuit parameters unchanged. It can achieve high-gain inverter output during boost inverter and low-gain inverter output during buck inverter. The buck-boost integrated inverter of the present invention has the advantages of achieving a wide range of voltage input, low cost, single-stage boost inverter, improved DC bus voltage utilization during buck inverter, and reduced voltage withstand requirements of switching transistors S2, S3 and S4.

[0112] like Figure 7 As shown in Table 1, in this embodiment, the simulation parameters of a buck-boost integrated inverter for step-down inverter are shown. Based on the step-down inverter, the port voltage is reduced from 1800V to 1300V to improve the DC bus voltage utilization rate. The peak voltages of switching transistors S2, S3 and S4 are reduced from 1800V to 1300V to reduce their withstand voltage requirements.

[0113] Table 1. Simulation parameters of a buck-boost integrated inverter for step-down inverter operation.

[0114]

[0115]

[0116] like Figure 8 As shown in this embodiment, in the boost inverter simulation, a buck-boost integrated inverter has an input voltage of 200V. The supporting capacitor voltage boosts the DC bus voltage to 260V~360V, providing a stable 220V output voltage and realizing boost inverter.

[0117] like Figure 9 As shown in this embodiment, in the transient simulation experiment of the buck-boost integrated inverter provided in this embodiment of the invention, at 2s, 3s, 4s, and 5s, the input voltage changes from 1000V to 1200V, 1400V, 1600V, and 1800V respectively, and the supporting capacitor voltage can be stabilized at 1300V. The output voltage is 220V. The buck-boost integrated inverter provided in this embodiment of the invention has good transient performance.

[0118] The beneficial effects of the present invention are as follows: The buck-boost integrated inverter and control method provided by the present invention can suppress the influence of DC input voltage fluctuation on output voltage to a certain extent, and can cope with the working conditions of unstable input DC voltage fluctuating within a certain range.

[0119] The buck-boost integrated inverter of the present invention improves the DC-side voltage utilization of the inverter and reduces the withstand voltage requirements of switching transistors S2, S3 and S4 when the DC input voltage is large and the AC output voltage is small, thereby reducing costs.

[0120] The buck-boost integrated inverter of the present invention can be used as a photovoltaic inverter, realizing the boost inverter function in a single stage, with high integration and improved efficiency.

[0121] In the description of this invention, it should be understood that the terms "center," "thickness," "upper," "lower," "horizontal," "top," "bottom," "inner," "outer," and "radial," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying the relative importance or the number of technical features implicitly specified. Therefore, a feature defined by "first," "second," and "third" may explicitly or implicitly include one or more of that feature.

Claims

1. A buck-boost integrated inverter, characterized in that, The switching tube S1, the switching tube S2, the switching tube S3, the switching tube S4, the diode D1, the diode D2, the diode D3, the support capacitor C dc and the inductor L in ; In this configuration, the collector of the switching transistor S1 is connected to the cathode of the diode D2 and is also connected to the positive terminal of the input voltage. The emitter of the switching transistor S1 is connected to the inductor L. in One end, supporting capacitor C dc The negative terminal of the inductor L is connected to the emitter of the switching transistor S3 and the anode of the diode D3. in The other end is connected to the anode of the diode D1 and to the negative terminal of the input voltage. The cathode of the diode D1 is connected to the supporting capacitor C. dc The positive terminal of the diode is connected to the collector of the switching transistor S2 and the collector of the switching transistor S4. The emitter of the switching transistor S4 is connected to the collector of the switching transistor S3 and serves as the second output port. The emitter of the switching transistor S2 is connected to the cathode of the diode D3 and the anode of the diode D2, respectively, and serves as the first output port.

2. The buck-boost integrated inverter according to claim 1, characterized in that, Both the first output port and the second output port are connected to the filter circuit, which is also connected to the load.

3. A control method based on the buck-boost integrated inverter according to any one of claims 1 to 2, characterized in that, Includes the following steps: S1. Control the buck-boost integrated inverter to work according to the set working mode combination; S2. Control the DC gain of the buck-boost integrated inverter according to the duty cycle of the switching transistor S1 to complete the inverter control.

4. The control method for the buck-boost integrated inverter according to claim 3, characterized in that, Specifically, S1 is: The working process of the buck-boost integrated inverter is controlled according to the set working mode combination within each switching cycle, thereby starting the buck-boost integrated inverter to work. The working modes include the first mode to the fourth mode.

5. The control method for the buck-boost integrated inverter according to claim 4, characterized in that, In S1, the method for controlling the buck-boost integrated inverter according to the first mode is specifically as follows: Set the start time of the first mode, turn on switch S2 and switch S3 before the start time of the first mode, turn off switch S3 and turn on switch S4 when the first mode is started. The specific method for controlling the buck-boost integrated inverter based on the second mode is as follows: Set the time to enable the second mode, and turn off switch S4 and turn on switch S3 when the second mode is enabled; The specific method for controlling the buck-boost integrated inverter based on the third mode is as follows: Set the time when the third mode is activated, and turn off switch S2 and turn on switch S1 when the third mode is activated; The specific method for controlling the buck-boost integrated inverter based on the fourth mode is as follows: Set the time to activate the fourth mode. At the time of activating the fourth mode, turn off switch S1 and turn on switch S2.

6. The control method for the buck-boost integrated inverter according to claim 5, characterized in that, The specific method for turning on the switching transistor S1 is as follows: The first driving signal is obtained by PWM modulation or PFM modulation, and the switching transistor S1 is turned on according to the first driving signal. The specific method for turning on the switching transistor S2 is as follows: The first driving signal is obtained by PWM modulation or PFM modulation, the first driving signal is inverted to obtain the second driving signal, and the switch S2 is turned on according to the second driving signal. The specific method for turning on the switching transistor S3 is as follows: The third driving signal is obtained by SPWM modulation, and the switch S3 is turned on according to the third driving signal. The specific method for turning on the switching transistor S4 is as follows: The third driving signal is obtained by SPWM modulation, and the fourth driving signal is obtained by inverting the third driving signal. Switch S4 is turned on according to the fourth driving signal.

7. The control method for the buck-boost integrated inverter according to claim 6, characterized in that, The PWM modulation method is specifically as follows: Support capacitor C dc The difference between the preset voltage value and the sampled value is input into the proportional-integral controller PI1 to obtain the modulation signal. This signal, along with the bipolar triangular carrier signal, is input into the non-inverting input and the inverting input of the comparator, respectively. The resulting signal is used as the first driving signal. The PFM modulation method is specifically as follows: Support capacitor C dc The voltage preset value is subtracted from the sampled value, and the difference is input to the proportional-integral controller PI2 to obtain the frequency signal. The frequency signal is then input to the triangular carrier generator module V. tri A bipolar triangular carrier wave is obtained. 0 and the bipolar triangular carrier wave are input to the non-inverting input and the inverting input of the comparator, respectively. The resulting signal is used as the first driving signal. The SPWM modulation method is specifically as follows: The difference between the preset effective value of the output voltage of the buck-boost integrated inverter and the sampled effective value is calculated, and the difference is sent to the proportional-integral controller PI3. The signal output by the proportional-integral controller PI3 is used as the amplitude and multiplied with the sinusoidal modulation wave. The generated signal is used as the AC component of the modulation wave. The duty cycle of the switch S1 is subtracted from its preset duty cycle value. The difference is input to the proportional-integral controller PI4. The signal output by the proportional-integral controller PI4 is subtracted from the constant 1, and the generated signal is used as the DC component of the modulation wave. The DC component and AC component of the modulating wave are added together to obtain the modulating wave. This modulating wave is then input to the non-inverting and inverting inputs of the comparator along with a bipolar triangular carrier wave, respectively. The resulting signal is used as the third driving signal.

8. The control method for the buck-boost integrated inverter according to claim 6, characterized in that, In S2, the DC gain G of the buck-boost integrated inverter in continuous inductor current mode CCM The expression is as follows: In the formula, d1 is the duty cycle of the switching transistor S1, and M = V o / V c V c To support the capacitor voltage, V o This is the effective value for a buck-boost integrated inverter; DC gain G of the buck-boost integrated inverter in discontinuous inductor current mode DCM The expression is as follows: In the formula, f is the operating frequency of switch S1 or switch S2, and P o This refers to the output power of the buck-boost integrated inverter.

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