CN112019077A - A novel single-phase inverter based on buck circuit and its control method - Google Patents

Abstract

The invention discloses a novel single-phase inverter based on a buck circuit and a control method thereof; a main circuit unit includes a DC power supply, a main circuit and an AC load, and the main circuit is respectively connected with the DC power supply and the AC load for realizing single-phase DC/AC inverter function; the main control unit includes: an output detection unit, a given signal, a feedback signal, a controller and a PWM generator, the main circuit unit is controlled and connected by the PWM generator, and the output detection unit receives the main circuit The output signal is sent to the controller as a feedback signal to form a closed-loop control, so that the output signal is equal to the given signal; the invention can automatically adjust the size and frequency of the output AC voltage through the controller, and has the advantages of small switching loss and harmonic current. It has the advantages of small size, small filter inductance and capacitance, simple structure and working principle.

Description

A novel single-phase inverter based on buck circuit and its control method

technical field

The invention relates to the technical field of inverters, in particular to a novel single-phase inverter based on a buck circuit and a control method thereof.

Background technique

With the increasingly tight global energy supply, people pay more attention to the use of new energy distributed power generation technology. Although the use of distributed power generation technology can effectively utilize the abundant clean and renewable energy in various places, with the penetration rate of distributed power generation grid-connected power generation The increasing of power supply also brings new problems to the power supply stability and power quality of the traditional power system. The inverter is used as the energy conversion interface between the renewable energy generation unit and the power grid. In order to reduce the adverse impact on the large power grid after the distributed power source is connected to the power grid, it is necessary to ensure the safety and Stable and high quality. However, the existing typical single-phase inverters cannot work in the soft switching state, and the switching loss is large; the filter inductor and capacitance values are relatively large; and the grid-connected current contains rich switching harmonics during grid-connected operation.

At present, in order to reduce the switching loss to realize the soft switching function, the main method is to use the resonance principle. For example, the publication number CN206517306U discloses a soft-switching inverter with a resonant DC link on September 22, 2017, which uses the inductor and the capacitor to resonate to achieve the The voltage or current of the power electronic device is zero at the switching time, and the switch when the voltage is zero at the turn-on and turn-off time is called zero-voltage switching (ZVS); the switch when the current is zero at the turn-on and turn-off time is called zero current. switch (ZCS). However, using this method needs to add additional inductance or capacitor devices, which increases the weight, volume and cost of the inverter, and at the same time increases the difficulty of control and reduces the reliability of the inverter.

In order to reduce the inductance and capacitance values of the LC filter, thereby reducing the volume of the filter, such as publication number CN105450021A on March 20, 2016, an aviation-specific low-voltage DC constant power load stabilization method is designed, in which a filter based on the inductor current is designed. The high-frequency components of the LC filter are directly injected into the duty cycle method, which significantly reduces the inductance and capacitance of the LC filter under the same power load. However, this method is to reduce the inductance and capacitance of the LC filter through a control method under alternating current. This method can only reduce the inductance and capacitance of the filter to a limited extent. However, the voltage and current passed by the LC filter in the present invention are DC amount, so the volume of the filter can be reduced to a greater extent.

It can be seen from the above description that the current improved new single-phase inverters or control methods are all improved or optimized for the deficiencies of a certain aspect of the existing classic full-bridge single-phase inverters. A new type of single-phase inverter based on buck circuit and its control method have outstanding advantages such as small switching loss, small harmonic current, small filter inductance and capacitance, simple structure and working principle, and reliability.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art, such as being unable to work in a soft switching state, large switching loss, large filter inductance and capacitance, and grid-connected current containing rich switching harmonics during grid-connected operation, and provides a A novel single-phase inverter based on buck circuit and its control method.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

A new type of single-phase inverter based on buck circuit, comprising: a main circuit unit, including a DC power supply, a main circuit and an AC load, the main circuit is respectively connected with the DC power supply and the AC load for realizing single-phase DC/AC inverter function; the main control unit includes: an output detection unit, a given signal, a feedback signal, a controller and a PWM generator; the main circuit unit is controlled and connected through the PWM generator, and the output detection unit receives the output signal of the main circuit, And it is sent to the controller as a feedback signal to form a closed-loop control, so that the output signal is equal to the given signal.

Preferably, the main circuit unit includes: a DC power supply, a main circuit and an AC load; the main circuit includes: a buck circuit, which is composed of a fifth power switch tube, a power diode, a filter capacitor and a filter inductor, the filter capacitor and the filter inductor The LC filter is formed, the DC power supply is connected to the fifth power switch tube, the fifth power switch tube is connected to the power diode and the LC filter circuit, and the duty cycle of the fifth power switch tube in the buck circuit varies with the sine half-wave variation law. change (ie α=|sin(ωt)|, α is the duty cycle of the fifth power switch tube), the output is a pulse square wave equivalent to a sine half wave, and the LC filter circuit turns the pulse square wave into a smooth one Half-sine wave; H bridge, composed of four power switch tubes from the first to the fourth, the LC filter is connected to the H bridge, the output of the H bridge is connected to the AC load, and the output of the buck circuit is continuously changed at a frequency of 50Hz. Signal polarity so that the voltage waveform across the AC load is sinusoidal.

Preferably, the given signal of the main control unit is different from the feedback signal, and then the error signal is sent to the controller, the controller tracks the error in real time, the controller is connected to the PWM generator, and the PWM signal and the control signal are generated by the PWM generator , which controls five power switching devices in the main circuit.

Preferably, the given signal is a sinusoidal signal.

Preferably, the controller includes a first adder, a PR controller, a second adder and a proportional controller K; the given signal and the feedback signal are transmitted to the first adder, and the output of the first adder and its The output of the PR controller is sent to the second adder, and the second adder is connected to the proportional controller K.

Preferably, the PWM generator includes an absolute value operation unit |U _k | and a comparator; the output signal U _k of the proportional controller K is passed into the absolute value operation unit |U _k |, and the output sine half-wave signal is the same as the The required reference signal is compared in the comparator, and the PWM signal is output (for the control of the fifth power switch), or the output signal U _k of the proportional controller K is directly compared with the required reference signal in the comparator (for H The control of the bridge power switch tube), and output the control signal.

Preferably, the control method of the novel single-phase inverter based on the buck circuit is divided into: the control of the fifth power switch tube, the duty cycle of which is controlled by the PWM signal to change with the sine half-wave (ie α=|sin( ωt)|, α is the duty cycle of the fifth power switch tube), and generates a voltage square wave equivalent to a sine half-wave; the control of the first and third power switch tubes, when the main control unit detects that the voltage first crosses At zero point, the first and third power switch tubes are controlled to be in an on state, and the second and fourth power switch tubes are in an off state; the control of the second and fourth power switch tubes, when the main control unit detects that the voltage second exceeds At zero point, the second and fourth power switch tubes are controlled to be in an on state, and the first and third power switch tubes are in an off state.

(其中 K_p为比例项系数，K_R为谐振系数，ω₀为谐振频率)，所述ΔU与G(s)输入第二加法器后接着传入比例控制器K，再传入绝对值运算单元|U_k|，将控制信号求绝对值后，得到正弦半波控制信号，最后再与三角波参照信号在比较器进行比较输出第五功率开关管的PWM信号。Preferably, the control method of the fifth power switch tube is as follows: set U _ref as a given signal, U ₀ as a feedback signal, U _ref and U ₀ form a negative feedback voltage closed-loop control through a first adder, and the first adder The output error signal ΔU is directly sent to the second adder, and the control signal output by the first adder is the AC quantity, so the PR controller is selected for control, and the transfer function of the PR controller is:

(where K _p is the proportional term coefficient, K _R is the resonance coefficient, and ω ₀ is the resonance frequency), the ΔU and G(s) are input to the second adder, and then passed to the proportional controller K, and then passed to the absolute value operation The unit |U _k | obtains the sine half-wave control signal after obtaining the absolute value of the control signal, and finally compares it with the triangular wave reference signal in the comparator to output the PWM signal of the fifth power switch tube.

Preferably, the control methods of the first and third power switch tubes and the control methods of the second and fourth power switch tubes are: the output signal U _k of the proportional controller K is compared with 0 to obtain the first The control signals of the first and third power switches, that is, when the voltage is a positive half cycle, the first and third power switches are in the on state, and the second and fourth power switches are in the off state; The control signal of the second and fourth power switch tubes can be obtained by comparing the value of 0 less than 0, that is, when the voltage is in the negative half cycle, the second and fourth power switch tubes are in the on state, and the first and third power switch tubes are in the off state. off state.

Preferably, the new inverter based on buck circuit can be controlled to generate 4 switching modes, which are:

Mode _{1 :} S5 is turned _on , S1 and S3 are turned _on , and S2 and S4 are turned off _; at this time, the current forms a loop through Vs, S5, L, Z, S1 and S3, and the DC power supply Vs charges the capacitor C to AC load Z power supply;

Mode 2: S ₅ is turned off, S ₁ and S ₃ are turned on, and S ₂ and S ₄ are turned off; at this time, the current forms a loop through VD, L, Z, S1 and S3, and the capacitor C discharges, and VD plays a freewheeling role ;

Mode ₃ : S5 is turned _on , S1 and S3 are turned off, S2 and _S4 are turned _{on ;} the current forms a loop through Vs, S5, Z, S4 and S2, at this time, the DC power supply Vs charges the capacitor L, which is the AC load Z powered by;

Mode 4: S ₅ is turned off, S ₁ and S ₃ are turned off, and S ₂ and S ₄ are turned on; at this time, the current forms a loop through VD, L, S4, Z and S2, the capacitor C discharges, and VD freewheels;

Mode 1 and Mode 2 correspond to the positive half cycle of the AC output, Mode 3 and Mode 4 correspond to the negative half cycle of the AC output, Mode 2 and Mode 4 are when the switch S5 is turned off, the current flows through the diode VD freewheeling to form a loop, so that the final output standard is sinusoidal voltage waveform.

Compared with the prior art, the present invention has the advantages that the switching loss is small, and the four open tubes of the H-bridge of the traditional inverter work in a hard-switching state, while the H-bridge of the present invention works in a soft-switching state, that is, zero-voltage conduction. On (ZVS) state, and the switching frequency is 50Hz, so the switching frequency is low and the loss is small; the harmonics of the grid-connected current are small during grid-connected operation, and the operating frequency of the four switching tubes of the traditional inverter H-bridge is the carrier frequency, resulting in The output current is rich in high-order switching harmonics, while the H-bridge switch of this inverter works at the AC frequency of 50Hz, and the output harmonics are small; the LC filter is small, and the filter of the traditional inverter is designed according to the AC current, while the The invented LC filter passes direct current, so the filter can be designed according to the direct current. Compared with the traditional filter, the inductance and capacitance here are smaller under the same filtering effect; the structure and working principle are simple and reliable, through the buck circuit and H bridge The simple combination, the working principle is simple and reliable, but it can overcome many shortcomings of the existing single-phase inverter.

Description of drawings

Fig. 1 is the main circuit topology diagram of the main circuit unit of the present invention;

Fig. 2 is the principle structure block diagram of the main control unit of the present invention;

FIG. 3 is a schematic diagram of the control method of the fifth power switch tube in the present invention;

FIG. 4 is a schematic diagram of the control method of the first and third power switch tubes in the present invention;

5 is a schematic diagram of the control method of the second and fourth power switch tubes in the present invention;

6 is a schematic diagram of the current loop of the main circuit switching mode 1 of the present invention;

FIG. 7 is a schematic diagram of the current loop in the main circuit switching mode 2 of the present invention;

FIG. 8 is a schematic diagram of the current loop of the main circuit switching mode 3 of the present invention;

FIG. 9 is a schematic diagram of the current loop of the main circuit switching mode 4 of the present invention;

10 is a waveform diagram of the voltage and current output on the AC load when the simulation example of the present invention is V _ref =200V;

FIG. 11 is a waveform diagram of the voltage and current output on the AC load when the simulation example of the present invention is V _ref =150V.

1. DC power supply; 2. Fifth power switch tube; 3. Power diode; 4. Filter inductor; 5, Filter capacitor; 6, First power switch tube; 7, Second power switch tube; 8, Third power switch tube; 9. the fourth power switch tube; 10, AC load; 11, given signal; 12, feedback signal; 13, controller; 14, PWM generator; 15, output detection unit.

Detailed ways

The present invention is further described below in conjunction with specific embodiments.

Embodiment 1: As shown in Figures 1 and 2, a new type of single-phase inverter based on a buck circuit includes: a main circuit unit, including a DC power supply (1), a main circuit and an AC load (10), the main circuits are respectively is connected with the DC power supply (1) and the AC load (10), and is used to realize the single-phase DC/AC inverter function; the main control unit includes: an output detection unit (15), a given signal (11), and a feedback signal (12) ), a controller (13) and a PWM generator (14); the main circuit unit is controlled and connected by the PWM generator (14), and the output detection unit (15) receives the output signal of the main circuit and uses it as a feedback signal ( 12) Send it to the controller (13) to form a closed-loop control, so that the output signal is equal to the given signal (11).

As shown in FIG. 1 , the main circuit unit includes: a DC power supply (1), a main circuit and an AC load (10); the main circuit includes: a buck circuit, which is composed of a fifth power switch tube (2), a power diode ( 3), a filter capacitor (4) and a filter inductor (5) are composed, the filter capacitor (4) and the filter inductor (5) constitute an LC filter, the DC power supply (1) is connected to the fifth power switch tube (2), the first The five power switch tubes (2) are connected to the power diode (3) and the LC filter circuit, and the duty cycle of the fifth power switch tube (2) in the buck circuit changes with the change law of the half-sine wave (ie α=|sin( ωt)|, α is the duty cycle of the fifth power switch tube), the output is a pulsed square wave equivalent to a half-sine wave (that is, a pulsed square wave at V ₀₁ ), and the LC filter circuit changes the pulsed square wave into Smooth half sine wave (that is, half sine wave at V ₀₂ ); H bridge, consisting of the first to fourth power switch tubes (6-9) in total, the LC filter is connected to the H bridge, the H bridge The output of 10 is connected to the AC load (10), and the output signal of the buck circuit is continuously changed at a frequency of 50Hz to change its polarity, so that the voltage waveform through the AC load (10) is a sine curve (that is, a sine curve at V ₀₃ ). The H bridge in this embodiment works in a soft switching state, that is, a zero voltage conduction (ZVS) state, and the switching frequency is 50 Hz, so the switching frequency is low and the loss is small.

As shown in FIG. 2 , the given signal (11) of the main control unit is different from the feedback signal (12), and then the error signal is sent to the controller (13), and the controller (13) tracks the error in real time, and the controller (13) Connect the PWM generator (14), generate the PWM signal and the control signal through the PWM generator (14), control the 5 power switching devices in the main circuit, and finally make the feedback signal (12) and the given signal (11) The error is zero, that is, the absolute value of the output signal of the inverter is equal to the given signal (11).

As shown in Figure 2, the given signal (11) is a sinusoidal signal.

As shown in Figure 3, the controller (13) includes a first adder, a PR controller, a second adder and a proportional controller K; the given signal and the feedback signal are sent to the first adder, the first The output of the adder and its output after being sent to the PR controller are both sent to the second adder, which is then connected to the proportional controller K.

As shown in FIG. 3 to FIG. 5 , the PWM generator (14) includes an absolute value operation unit |U _k | and a comparator; the output signal U _k of the proportional controller K is passed into the absolute value operation unit |U _k |, the output sine half-wave signal is compared with the required reference signal in the comparator (for the control of the fifth power switch), and the PWM signal is output, or the output signal U _k of the proportional controller K is directly and the required reference signal The comparator is compared (for the control of the H-bridge power switch tube), and the control signal is output.

As shown in Fig. 2 to Fig. 9, the control method of the novel single-phase inverter based on the buck circuit is divided into: the control of the fifth power switch tube (2), the duty cycle of which is controlled by the PWM signal with the sinusoidal half wave changes (ie α=|sin(ωt)|, α is the duty cycle of the fifth power switch), and generates a voltage square wave equivalent to a half-sine wave; the first and third power switches (6) , (8), when the main control unit detects the first zero-crossing point of the voltage, it controls the first and third power switch tubes (6), (8) to be in a conducting state, and the second and fourth power switch tubes (7). ) and (9) are in the off state; the control of the second and fourth power switch tubes (7) and (9), when the main control unit detects the second zero-crossing point of the voltage, controls the second and fourth power switch tubes ( 7), (9) are in a conducting state, and the first and third power switch tubes (6), (8) are in an off state.

(其中K_p为比例项系数，K_R为谐振系数，ω₀为谐振频率)，所述ΔU与G(s)输入第二加法器后接着传入比例控制器K，再传入绝对值运算单元|U_k|，将控制信号求绝对值后，得到正弦半波控制信号，最后再与三角波参照信号在比较器进行比较输出第五功率开关管(2)的PWM信号。As shown in FIG. 3, the control method of the fifth power switch tube (2) is as follows: set U _ref as a given signal (11), U ₀ as a feedback signal (12), and U _ref and U ₀ through the first addition The first adder forms a negative feedback voltage closed-loop control, the error signal ΔU output by the first adder is directly sent to the second adder, and the control signal output by the first adder is the AC quantity, so the PR controller is selected for control, and the transmission of the PR controller The function is:

(where K _p is the proportional term coefficient, K _R is the resonance coefficient, and ω ₀ is the resonance frequency), the ΔU and G(s) are input to the second adder, and then passed to the proportional controller K, and then passed to the absolute value operation The unit |U _k | obtains the sine half-wave control signal after obtaining the absolute value of the control signal, and finally compares it with the triangular wave reference signal in the comparator to output the PWM signal of the fifth power switch tube (2).

As shown in FIG. 4 and FIG. 5 , the control methods of the first and third power switch tubes (6), (8) and the control methods of the second and fourth power switch tubes (7), (9) are: proportional The output signal U _k of the controller K can be compared with 0 to obtain the control signals of the first and third power switch tubes (6), (8), that is, when the voltage is a positive half cycle, the first and third power switch tubes (6), (8). The third power switch tubes (6), (8) are in the on state, and the second and fourth power switch tubes (7), (9) are in the off state; and the control signals of the fourth power switch tubes (7), (9), that is, when the voltage is in the negative half cycle, the second and fourth power switch tubes (7), (9) are in the conducting state, the first and third The power switch tubes (6) and (8) are turned off. In this way, the alternating conduction of the four power switch tubes of the H-bridge is realized, so that the output of the inverter is a standard sine wave.

As shown in Figure 6 to Figure 9, the new inverter based on buck circuit can be controlled to generate 4 switching modes, which are:

Mode ₁ (shown in Figure ₆ ): S5 is turned _on , S1 and S3 are turned _on , and S2 and S4 are turned off _; at this time, the current forms a loop through Vs, S5, L, Z, S1 and S3, while the DC power supply Vs Charge the capacitor C and supply power to the AC load Z;

Mode 2 (shown in Figure 7): S ₅ is turned off, S ₁ and S ₃ are turned on, and S ₂ and S ₄ are turned off; at this time, the current forms a loop through VD, L, Z, S1 and S3, and the capacitor C discharges at the same time. VD plays the role of freewheeling;

Mode ₃ (shown in Figure ₈ ): S5 is turned _on , S1 and S3 are turned off, S2 and S4 are turned _{on ;} the current forms a loop through VS, S5, Z, S4 and S2, and the DC power supply Vs is the capacitor L at this time Charge, supply power to AC load Z;

Mode 4 (shown in Figure 9): S ₅ is turned off, S ₁ and S ₃ are turned off, and S ₂ and S ₄ are turned on; at this time, the current forms a loop through VD, L, S4, Z and S2, the capacitor C discharges, and VD continuous flow;

Mode 1 and Mode 2 correspond to the positive half cycle of the AC output, Mode 3 and Mode 4 correspond to the negative half cycle of the AC output, Mode 2 and Mode 4 are when the switch S5 is turned off, the current flows through the diode VD freewheeling to form a loop, so that the final output standard is sinusoidal voltage waveform.

The present invention further provides a specific simulation example: setting relevant parameters: a. DC power supply voltage: Vs=200V; b. filter inductance: L=6e ^- 4H; c. filter capacitor: C=2e- ^5F ; d . Load resistance: R=5Ω; e. Resonance frequency: ω ₀ =100π; f. Proportional term coefficient: K _R =1.

(1) When setting the command voltage V _ref = 200V, the voltage and current output waveforms on the AC load are shown in Figure 10: ① The voltage and current waveforms are very smooth, and the distortion rate is small; ② The voltage and current dynamic response is fast, 0.07s has been Basically stable; ③The output voltage does not reach 200V, this is because the DC power supply is set to 200V, and the output voltage is slightly less than 200V due to the voltage loss of the output impedance.

(2) When the command voltage V _ref = 150V is set, the voltage and current output waveforms on the AC load are shown in Figure 11. At this time, the command voltage setting value is less than the DC power supply voltage setting value, and the command voltage output voltage reaches 150V, which realizes the No static control.

To sum up, the present invention also has outstanding advantages such as small switching loss, small harmonic current, small filter inductance and capacitance, simple structure and working principle, and reliability.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims (10)

1. The utility model provides a novel single-phase inverter based on buck circuit which characterized in that includes:

the main circuit unit comprises a direct current power supply, a main circuit and an alternating current load, wherein the main circuit is respectively connected with the direct current power supply and the alternating current load and is used for realizing a single-phase DC/AC inversion function;

a main control unit comprising: the device comprises an output detection unit, a given signal, a feedback signal, a controller and a PWM generator; the PWM generator is connected with the main circuit unit in a control mode, the output detection unit receives an output signal of the main circuit and transmits the output signal to the controller as a feedback signal to form closed-loop control, and the output signal is equal to a given signal.

2. The novel buck circuit-based single-phase inverter as claimed in claim 1, wherein the main circuit comprises:

the Buck circuit consists of a fifth power switching tube, a power diode, a filter capacitor and a filter inductor, the filter capacitor and the filter inductor form an LC filter, the direct-current power supply is connected with the fifth power switching tube, the fifth power switching tube is connected with the power diode and the LC filter circuit, the duty ratio of the fifth power switching tube in the Buck circuit changes along with the change rule of a sine half-wave, a pulse square wave equivalent to the sine half-wave is output, and the LC filter circuit changes the pulse square wave into a smooth sine half-wave;

and the H bridge consists of 4 power switching tubes from the first to the fourth, the LC filter is connected with the H bridge, the output end of the H bridge is connected with an alternating current load, the polarity of an output signal of the buck circuit is continuously changed at the frequency of 50Hz, and the voltage waveform passing through the alternating current load is a sine curve.

3. The method for controlling a novel single-phase inverter based on a buck circuit as claimed in any one of claims 1 to 3, wherein the given signal of the main control unit is subtracted from the feedback signal, and then the error signal is sent to the controller, the controller tracks the error in real time, the controller is connected to the PWM generator, and the PWM generator generates the PWM signal and the control signal to control 5 power switching devices in the main circuit.

4. A control method according to claim 3, characterized in that the given signal is a sinusoidal signal.

5. The control method according to claim 3, wherein the controller includes a first adder, a PR controller, a second adder, and a proportional controller K; the given signal and the feedback signal are transmitted into a first adder, the output of the first adder and the output of the first adder after the given signal and the feedback signal are transmitted into a second adder, and the second adder is connected with a proportional controller K.

6. Control method according to claim 3, characterized in thatThe PWM generator includes an absolute value operation unit | U_kAnd a comparator; output signal U of the proportional controller K_kThe absolute value arithmetic unit | U is transmitted_kComparing the output sine half-wave signal with the required reference signal in a comparator to output PWM signal or output signal U of the proportional controller K_kThe control signal is directly compared with the required reference signal in a comparator to output the control signal.

7. A control method according to claim 3, characterized by the following steps:

the control of a fifth power switch tube, the duty ratio of which is controlled by the PWM signal to change along with the sine half-wave, and a voltage square wave equivalent to the sine half-wave is generated;

when the main control unit detects a first zero crossing point of the voltage, the first power switching tube and the third power switching tube are controlled to be in a conducting state, and the second power switching tube and the fourth power switching tube are controlled to be in a turn-off state;

and the second power switch tube and the fourth power switch tube are controlled to be in a conducting state, and the first power switch tube and the third power switch tube are controlled to be in a turn-off state when the main control unit detects a second zero crossing point of the voltage.

8. The control method of claim 7, wherein the control method of the fifth power switch tube is as follows: is provided with a U_refFor a given signal, U₀For feedback signals, U_refAnd U₀The negative feedback voltage closed-loop control is formed through a first adder, an error signal delta U output by the first adder is directly sent to a second adder, and a control signal output by the first adder is an alternating current quantity, so that a PR controller is selected for control, and the transfer function of the PR controller is as follows:

(wherein K is_pIs the coefficient of the proportional term, K_RIs the resonance coefficient, omega₀At resonant frequency), the Δ U and G(s) are input to a second adder and then input to a ratioThe controller K then transmits the absolute value unit | U_kAnd finally comparing the control signal with a triangular wave reference signal in a comparator to output a PWM signal of a fifth power switch tube.

9. The control method of claim 7, wherein the control method of the first and third power switching tubes and the control method of the second and fourth power switching tubes comprises: output signal U of proportional controller K_kComparing the voltage with 0 to obtain control signals of the first power switch tube and the third power switch tube, namely when the voltage is positive half cycle, the first power switch tube and the third power switch tube are in a conducting state, and the second power switch tube and the fourth power switch tube are in a turn-off state; if the voltage is less than 0, the control signals of the second and fourth power switch tubes can be obtained, namely, when the voltage is negative for a half cycle, the second and fourth power switch tubes are in a conducting state, and the first and third power switch tubes are in a turn-off state.

10. The control method according to claim 7, 8 or 9, characterized in that: steerable novel inverter based on buck circuit produces 4 kinds of switching mode, is respectively:

mode 1: s₅Opening, S₁And S₃Opening, S₂And S₄Turning off; at the moment, current forms a loop through Vs, S5, L, Z, S1 and S3, and meanwhile, a direct current power supply Vs charges a capacitor C to supply power to an alternating current load Z;

mode 2: s₅Off, S₁And S₃Opening, S₂And S₄Turning off; at the moment, the current forms a loop through VD, L, Z, S1 and S3, and meanwhile, the capacitor C discharges, and VD plays a role of follow current;

mode 3: s₅Opening, S₁And S₃Off, S₂And S₄Opening; the current forms a loop through VS, S5, Z, S4 and S2, and the direct current power supply Vs charges the capacitor L and supplies power to the alternating current load Z;

mode 4: s₅Off, S₁And S₃Off, S₂And S₄Opening; at the moment, the current forms a loop through VD, L, S4, Z and S2, the capacitor C discharges, and VD continues current;

mode 1 and mode 2 correspond to the positive half cycle of the alternating current output, mode 3 and mode 4 correspond to the negative half cycle of the alternating current output, and mode 2 and mode 4 are that when the switch S5 is turned off, current freewheels through the diode VD, a loop is formed, and a standard sinusoidal voltage waveform is finally output.

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