阅读说明：本技术 一种基于z源逆变器的直流链电压控制系统及其方法 (Direct-current link voltage control system and method based on Z-source inverter ) 是由 徐书豪 李琳 刘海龙 于 2019-12-23 设计创作，主要内容包括：一种基于Z源逆变器的直流链电压控制系统及其方法,系统包括阻抗网络,所述阻抗网络的信号输出端与电容电压采集电路的信号输入端相连,所述电容电压采集电路的信号输出端与线性自抗扰控制模块的信号输入端相连,线性自抗扰控制模块的信号输出端与SPWM控制模块的信号输入端相连接,SPWM控制模块的信号输出端与逆变桥中开关管的信号输入端相连；通过采集电容电压,再将其转化为直流链电压,再将直流链电压与直流链电压参考峰值进行运算得到直通占空比偏差值Δd,再给Δd加上上一时刻直通占空比得到当前时刻直通占空比D<Sub>0</Sub>,将占空比D<Sub>0</Sub>输入至SPWM控制模块中,调节SPWM控制模块中的直通零矢量的导通时间,进而控制逆变桥,实现直流链电压U<Sub>dc</Sub>的稳定；本发明具有稳定可靠的优点。(A direct current link voltage control system based on a Z-source inverter and a method thereof are disclosed, the system comprises an impedance network, the signal output end of the impedance network is connected with the signal input end of a capacitance voltage acquisition circuit, the signal output end of the capacitance voltage acquisition circuit is connected with the signal input end of a linear active disturbance rejection control module, the signal output end of the linear active disturbance rejection control module is connected with the signal input end of an SPWM control module, and the signal output end of the SPWM control module is connected with the signal input end of a switching tube in an inverter bridge; the method comprises the steps of collecting capacitor voltage, converting the capacitor voltage into direct-current link voltage, calculating the direct-current link voltage and a direct-current link voltage reference peak value to obtain a direct-through duty ratio deviation value delta D, and adding the direct-current duty ratio delta D at the previous moment to obtain a direct-through duty ratio D at the current moment 0 Will duty ratio D 0 Inputting the voltage into the SPWM control module, adjusting the conduction time of a through zero vector in the SPWM control module, further controlling an inverter bridge, and realizing the DC link voltage U dc The stability of (2); the invention has the advantages of stability and reliability。)

1. The direct-current link voltage control system based on the Z-source inverter is characterized by comprising a power supply module (1), wherein the power supply module (1) is in electric connection with an impedance network (2), the impedance network (2) is in electric connection with an inverter bridge (3), two ends of a capacitor in the impedance network (2) are in signal connection with a capacitance voltage acquisition circuit (4), the capacitance voltage acquisition circuit (4) is in signal connection with a master controller (5), and the master controller (5) is in signal connection with a switching tube in the inverter bridge (3).

2. The direct current link voltage control system based on the Z-source inverter is characterized in that the power module (1) comprises a direct current power DC, one end of the direct current power DC is connected with one end of a diode D1, and the other end of the diode D1 is connected with one end of a first inductance coil L1; the other end of the direct current power supply DC is connected to the other end of the second inductor L2.

3. The Z-source inverter-based direct-current link voltage control system according to claim 1, wherein the impedance network (2) comprises a first inductance coil L1 and a second inductance coil L2, one end of the first inductance coil L1 is connected with one end of a first capacitor C1, and the other end of the first inductance coil L1 is connected with one end of a first capacitor C2; one end of the second inductor L2 is connected to the other end of the first capacitor C1, and the other end of the second inductor L2 is connected to the other end of the second capacitor C2.

4. The direct current link voltage control system based on the Z source inverter is characterized in that the inverter bridge (3) comprises a first branch, a second branch and a third branch; the first branch, the second branch and the third branch are in parallel connection;

the first branch circuit comprises a first switch tube K1 and a second switch tube K2 which are connected in series;

the second branch comprises a third switching tube K3 and a fourth switching tube K4 which are connected in series;

the third branch circuit comprises a fifth switch tube K5 and a sixth switch tube K6 which are connected in series.

5. The Z-source inverter-based direct-current link voltage control system is characterized in that the overall controller (5) internally comprises a first operation module (10), a linear active disturbance rejection control module (6), a third operation module (12) and an SPWM control module (7);

the first operation module (10) processes the capacitor voltage U received by the master controller (5) from the capacitor voltage acquisition circuit (4)_c(ii) a The first operation module (10) processes the signal to obtain a direct current chain voltage U_dcAnd applying a DC link voltage U_dcSending the signal to a linear active disturbance rejection control module (6);

the first calculation module (10) obeys the formula 1-1:

the U is_cIs a capacitor voltage, U_dcIs a direct-current link voltage, and is,

the linear active disturbance rejection control module (6) converts the direct current link voltage U_dcCombined with DC link voltage reference peak value U_dc，refThe operation processing is carried out to obtain a direct-through duty ratio deviation value delta d, and then the direct-through duty ratio deviation value delta d is output to a third operation module (12);

the linear active disturbance rejection control module (6) obeys the formulas 1-2, 1-3 and 1-4

u₀＝k_p(r-z₁) (1-3)

R represents a DC link voltage reference peak value U_dc，refU represents the through duty deviation Δ d, k_pTo control the ratio, u₀To operate on intermediate quantities, z₁As a function of the first output signal, z₂As a function of the second output signal,as a function of the first output signal z₁The derivative function of (a) is,

the third operation module (12) combines the direct duty ratio deviation value delta D with the direct duty ratio D at the previous moment₀ ^*Obtaining the direct duty ratio D of the current moment₀(ii) a The third operation module (12) obeys the following equations 1 to 5:

D₀＝D₀ ^*+Δd (1-5)

said D₀For the present moment through duty cycle, D₀ ^*The direct duty ratio at the last moment is delta d, and the direct duty ratio deviation value is delta d;

the third operation module (12) leads the current time to be directly connected with the duty ratio D through the signal output end of the master controller (5)₀Output to the SPWM control module (7);

the SPWM control module (7) receives the current-time direct duty ratio D sent by the third operation module (12)₀Then the SPWM control module (7) generates a control signal, and the control signal is sent to the inverter bridge (3) through the signal output end of the master controller (5)And a control end of each switching tube.

6. The Z-source inverter-based direct-current link voltage control system according to claim 5, wherein the linear active disturbance rejection control module (6) comprises a linear state feedback law operation module (9), a second operation module (11) and a linear state expansion observer (8);

the linear state feedback law operation module (9) receives a first output signal z sent from a linear state extended observer (8)₁A linear state feedback law operation module (9) outputs a first output signal z₁And the DC link voltage reference peak value U_dc，rafPerforming operation to obtain an intermediate value u₀(ii) a The linear state feedback law operation module (9) obeys the following formula 1-3:

u₀＝k_p(r-z₁) (1-3)

the linear state feedback law operation module (9) then calculates the intermediate value u₀Sending the data to a second operation module (11);

the second calculation module (11) also receives a second output signal z sent from the linear state extended observer (8)₂The second operation module (11) is used for calculating the intermediate value u₀And a second output signal z₂Performing operation to obtain an output u of a second operation module (11); the second operation module (11) sends the output u to the linear state extended observer (8) and the third operation module (12);

the second operation module (11) obeys the following formula 1-4:

u＝Δd＝(-z₂+u₀)/b (1-4)

the value range of b is 10-80;

the linear expansion state observation module 8 obeys a mathematical model having the form of equations 1-2:

7. the Z-source inverter based DC link voltage control system according to claim 5 or 6, wherein the prototype of the formula 1-2 is formula 1-6:

wherein U represents a through duty deviation value delta d, and y represents a capacitor voltage U_cU and y are both inputs to equations 1-4;

c is [ 10 ], and C is an output matrix of the linear extended observer;

based on the input and output of the linear expansion state observation module 8, equations 1 to 6 are rewritten into equations 1 to 7:

further modifications to formulae 1-7Trade, order

8. the control method based on the dc link voltage control system according to any one of claims 1 to 7, comprising the steps of:

step one, recording the instantaneous value of the through duty ratio at the last moment as D₀ ^*Acquiring capacitance voltage information U through a capacitance voltage acquisition circuit (4)_cFurther, according to the formula 1-1

Calculating out DC link voltage U_dc；

The U is_cIs a capacitor voltage, U_dcIs a direct-current link voltage, and is,

step two, converting the DC link voltage U_dcAnd the DC link voltage reference peak value U_dc，refInputting the linear active disturbance rejection control module (6) and then according to the formulas 1-2, 1-3 and 1-4;

u₀＝k_p(r-z₁) (1-3)

obtaining u representing the direct duty ratio deviation value delta d after operation;

r represents a DC link voltage reference peak value U_dc，refU represents the through duty deviation Δ d, k_pTo control the ratio, u₀To operate on intermediate quantities, z₁As a function of the first output signal, z₂As a function of the second output signal,

step three, directly connecting the duty ratio instantaneous value D at the last moment₀ ^*Adding the direct duty ratio deviation value delta D to obtain the direct duty ratio D at the current moment₀；

Step four, the through duty ratio D₀The direct current link voltage is input into an SPWM control module (7), the SPWM control module (7) controls the conduction time of a direct-connection zero vector to further control a switching tube in an inverter bridge (3), and finally, the direct current link voltage U is realized_dcThe stability of (2).

Technical Field

The invention relates to the technical field of voltage control, in particular to a direct-current link voltage control system and a direct-current link voltage control method based on a Z-source inverter.

Background

As people pay more and more attention to the environment, clean energy such as fuel cells, photovoltaic power generation, wind power generation and the like are widely paid attention to and applied. However, the power generation output direct current voltage of the fuel cell and the photovoltaic cell has a large fluctuation range, when the fuel cell and the photovoltaic cell are used as the input of the inverter, the direct current link voltage of the inverter is influenced and fluctuates, and the inverter can cause error accumulation under the condition of lacking closed-loop control, so that the output of the inverter is greatly influenced; in order to stabilize the dc link voltage of the inverter, a closed loop control system needs to be added to the dc link voltage of the inverter.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a direct current link voltage control system based on a Z-source inverter and a method thereof, which can stabilize the output range of direct current voltage and have the characteristics of safety and reliability.

In order to achieve the purpose, the invention adopts the following technical scheme:

a direct current link voltage control system based on a Z-source inverter comprises a power supply module 1, wherein the power supply module 1 is in electric connection with an impedance network 2, the impedance network 2 is in electric connection with an inverter bridge 3, two ends of a capacitor in the impedance network 2 are in signal connection with a capacitance voltage acquisition circuit 4, the capacitance voltage acquisition circuit 4 is in signal connection with a master controller 5, and the master controller 5 is in signal connection with a switching tube in the inverter bridge 3.

The impedance network 2 comprises a first inductance coil L1 and a second inductance coil L2, one end of the first inductance coil L1 is connected with one end of a first capacitor C1, and the other end of the first inductance coil L1 is connected with one end of a first capacitor C2; one end of the second inductor L2 is connected to the other end of the first capacitor C1, and the other end of the second inductor L2 is connected to the other end of the second capacitor C2.

The power supply module 1 comprises a direct current power supply DC, one end of the direct current power supply DC is connected with one end of a diode D1, and the other end of the diode D1 is connected with one end of a first inductance coil L1; the other end of the direct current power supply DC is connected to the other end of the second inductor L2.

The inverter bridge 3 comprises a first branch, a second branch and a third branch; the first branch, the second branch and the third branch are in parallel connection;

the first branch circuit comprises a first switch tube K1 and a second switch tube K2 which are connected in series;

the second branch comprises a third switching tube K3 and a fourth switching tube K4 which are connected in series;

the third branch comprises a fifth switching tube K5 and a sixth switching tube K6 which are connected in series;

the master controller 5 comprises a first operation module 10, a linear active disturbance rejection control module 6, a third operation module 12 and an SPWM control module 7;

the first operation module 10 processes the capacitor voltage U received by the master controller 5 from the capacitor voltage acquisition circuit 4_c(ii) a The first operation module 10 processes the signal to obtain the dc link voltage U_dcAnd applying a DC link voltage U_dcSending the signal to a linear active disturbance rejection control module 6;

the first operation module 10 obeys the formula 1-1:

the U is_cIs a capacitor voltage, U_dcIs a direct-current link voltage, and is,

a last-time through duty cycle;

the linear active disturbance rejection control module 6 converts the DC link voltage U_dcCombined with DC link voltage reference peak value U_dc，refPerforming operation processing to obtain a direct-through duty ratio deviation value Δ d, and outputting the direct-through duty ratio deviation value Δ d to the third operation module 12;

the linear active disturbance rejection control module 6 obeys the expressions 1-2, 1-3 and 1-4

u₀＝k_p(r-z₁) (1-3)

R represents a DC link voltage reference peak value U_dc，refU represents the through duty deviation Δ d, k_pTo control the ratio, u₀To operate on intermediate quantities, z₁As a function of the first output signal, z₂As a function of the second output signal,

as a function of the first output signal z₁The derivative function of (a) is,function z of the second output signal₂Derivative function of, said₁＝2ω₀,l₂＝ω₀ ²ω is said₀The bandwidth of the observation module is linearly expanded, and the value range of b is 10-80;

the third operation module 12 combines the direct duty deviation value Δ D with the direct duty D at the previous moment₀ ^*Obtaining the direct duty ratio D of the current moment₀(ii) a The third operation module 12 obeys the expressions 1 to 5:

D₀＝D₀ ^*+Δd (1-5)

said D₀For the present moment through duty cycle, D₀ ^*And d is the direct duty ratio deviation value at the last moment.

The third operation module 12 passes through the current time through duty ratio D through the signal output end of the master controller 5₀Output to the SPWM control module 7;

the SPWM control module 7 receives the current-time direct-connection duty ratio D sent by the third operation module 12₀Then the SPWM control module 7 generates a control signal, and sends the control signal to the control end of each switching tube in the inverter bridge 3 through the signal output end of the master controller 5.

The linear active disturbance rejection control module 6 comprises a linear state feedback law operation module 9, a second operation module 11 and a linear state extended observer 8;

the linear state feedback law operating module 9 receives the first output signal z sent from the linear state extended observer 8₁The linear state feedback law operation module 9 outputs the first output signal z₁And the DC link voltage reference peak value U_dc，refPerforming operation to obtain an intermediate value u₀(ii) a The linear state feedback law operation module 9 obeys the following expression 1-3:

u₀＝k_p(r-z₁) (1-3)

the linear state feedback law operation module 9 then calculates the intermediate value u₀Sending to the second operation module 11;

the second calculation module 11 also receives a second output signal z sent from the linear state extended observer 8₂The second operation module 11 pairs the intermediate value u₀And a second output signal z₂Performing operation to obtain an output u of the second operation module 11; the second operation module 11 sends the output u to the linear state extended observer 8 and the third operation module 12;

the second operation module 11 obeys the following equations 1 to 4:

u＝Δd＝(-z₂+u₀)/b (1-4)

the value range of b is 10-80;

the linear expansion state observation module 8 obeys a mathematical model having the form of equations 1-2:

the prototype of formula 1-2 is of formula 1-6:

wherein U represents a through duty deviation value delta d, and y represents a capacitor voltage U_cU and y are both inputs to equations 1-6;

knock-on to linear expansionOpening a state matrix of an observer;

is the state vector of the linear extended observer;

b is an input matrix, and the value of B ranges from 10 to 80;

l is an observer gain matrix of the linear extended observer;

c is [ 10 ], and C is an output matrix of the linear extended observer;

based on the input and output of the linear expansion state observation module 8, equations 1 to 6 are rewritten into equations 1 to 7:

further transform equations 1-7 into

l₁＝2ω₀,l₂＝ω₀ ²To obtain the formula 1-2:

a direct current link voltage control method based on a Z-source inverter comprises the following steps:

step one, recording the instantaneous value of the through duty ratio at the last moment as D₀ ^*Acquiring capacitance voltage information U through the capacitance voltage acquisition circuit 4_cFurther, according to formula 1-1:

calculating out DC link voltage U_dc；

The U is_cIs a capacitor voltage, U_dcIs a direct-current link voltage, and is,

a last-time through duty cycle;

step two, converting the DC link voltage U_dcAnd the DC link voltage reference peak value U_dc，refInputting the linear active disturbance rejection control module 6, and then according to the formulas 1-2, 1-3 and 1-4;

u₀＝k_p(r-z₁) (1-3)

obtaining u representing the direct duty ratio deviation value delta d after operation;

r represents a DC link voltage reference peak value U_dc，refU represents the through duty deviation Δ d, k_pTo control the ratio, u₀To operate on intermediate quantities, z₁As a function of the first output signal, z₂As a function of the second output signal,

as a function of the first output signal z_fThe derivative function of (a) is,

function z of the second output signal₂Derivative function of, said₁＝2ω₀,l₂＝ω₀ ²ω is said₀Linearly expanding the bandwidth of the observation module;

step three, directly connecting the duty ratio instantaneous value D at the last moment₀ ^*Adding the direct duty ratio deviation value delta D to obtain the direct duty ratio D at the current moment₀；

Step four, the through duty ratio D₀The direct current link voltage U is input into an SPWM control module 7, the SPWM control module 7 controls the on-time of a direct-connection zero vector to further control a switching tube in the inverter bridge 3, and finally the direct current link voltage U is realized_dcThe stability of (2).

The invention has the beneficial effects that: the invention establishes a closed-loop control system from the impedance network 1 to the SPWM control module 7 and then to the impedance network 1, can gradually reduce the error range under the condition of no external disturbance, and can gradually recover to a balanced state even if the external disturbance is received.

Drawings

Fig. 1 is a circuit schematic of the present invention.

Fig. 2 is a control flow diagram of the present invention.

Fig. 3 is the internal working logic of the linear active disturbance rejection control module 6 of the present invention.

1. A power supply module; 2. an impedance network; 3. an inverter bridge; 4. a voltage capacitance acquisition circuit; 5. a master controller; 6. a linear active disturbance rejection control module; 7. an SPWM control module; 8. a linear expansion state observation module; 9. a linear state feedback law operation module; 10. a first operation module; 11. a second operation module; 12. and a third operation module.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

A direct current link voltage control system based on a Z-source inverter comprises a power supply module 1, wherein the power supply module 1 is in electric connection with an impedance network 2, the impedance network 2 is in electric connection with an inverter bridge 3, two ends of a capacitor in the impedance network 2 are in signal connection with a capacitance voltage acquisition circuit 4, the capacitance voltage acquisition circuit 4 is in signal connection with a master controller 5, and the master controller 5 is in signal connection with a switching tube in the inverter bridge 3.

The impedance network 2 comprises a first inductance coil L1 and a second inductance coil L2, one end of the first inductance coil L1 is connected with one end of a first capacitor C1, and the other end of the first inductance coil L1 is connected with one end of a first capacitor C2; one end of the second inductor L2 is connected to the other end of the first capacitor C1, and the other end of the second inductor L2 is connected to the other end of the second capacitor C2.

The power supply module 1 comprises a direct current power supply DC, one end of the direct current power supply DC is connected with one end of a diode D1, and the other end of the diode D1 is connected with one end of a first inductance coil L1; the other end of the direct current power supply DC is connected to the other end of the second inductor L2.

The inverter bridge 3 comprises a first branch, a second branch and a third branch; the first branch, the second branch and the third branch are in parallel connection;

the first branch circuit comprises a first switch tube K1 and a second switch tube K2 which are connected in series;

the second branch comprises a third switching tube K3 and a fourth switching tube K4 which are connected in series;

the third branch comprises a fifth switching tube K5 and a sixth switching tube K6 which are connected in series;

the master controller 5 comprises a first operation module 10, a linear active disturbance rejection control module 6, a third operation module 12 and an SPWM control module 7;

the first operation module 10 processes the capacitor voltage U received by the master controller 5 from the capacitor voltage acquisition circuit 4_c(ii) a The first operation module 10 processes the signal to obtain the dc link voltage U_dcAnd applying a DC link voltage U_dcSending the signal to a linear active disturbance rejection control module 6;

the first operation module 10 obeys the formula 1-1:

the U is_cIs a capacitor voltage, U_dcIs a direct-current link voltage, and is,

a last-time through duty cycle;

the linear active disturbance rejection control module 6 converts the DC link voltage U_dcCombined with DC link voltage reference peak value U_dc，refPerforming operation processing to obtain a direct-through duty ratio deviation value Δ d, and outputting the direct-through duty ratio deviation value Δ d to the third operation module 12;

the linear active disturbance rejection control module 6 obeys the expressions 1-2, 1-3 and 1-4

u₀＝k_p(r-z₁) (1-3)

R represents a DC link voltage reference peak value U_dc，refU represents the through duty deviation Δ d, k_pTo control the ratio, u₀To operate on intermediate quantities, z₁As a function of the first output signal, z₂As a function of the second output signal,

as a function of the first output signal z₁The derivative function of (a) is,

function z of the second output signal₂Derivative function of, said₁＝2ω₀,l₂＝ω₀ ²ω is said₀The bandwidth of the observation module is linearly expanded, and the value of b is 45;

the third operation module 12 combines the direct duty deviation value Δ D with the direct duty D at the previous moment₀ ^*Obtaining the direct duty ratio D of the current moment₀(ii) a The third operation module 12 obeys the expressions 1 to 5:

D₀＝D₀ ^*+Δd (1-5)

said D₀For the present moment through duty cycle, D₀ ^*And d is the direct duty ratio deviation value at the last moment.

The third operation module 12 passes through the current time through duty ratio D through the signal output end of the master controller 5₀Output to the SPWM control module 7;

the SPWM control module 7 receives the current-time direct-connection duty ratio D sent by the third operation module 12₀Then the SPWM control module 7 generates a control signal, and sends the control signal to the control end of each switching tube in the inverter bridge 3 through the signal output end of the master controller 5.

The linear active disturbance rejection control module 6 comprises a linear state feedback law operation module 9, a second operation module 11 and a linear state extended observer 8;

the linear state feedback law operating module 9 receives the first output signal z sent from the linear state extended observer 8₁The linear state feedback law operation module 9 outputs the first output signal z₁And the DC link voltage reference peak value U_dc，refPerforming operation to obtain an intermediate value u₀(ii) a The linear state feedback law operation module 9 obeys the following expression 1-3:

u₀＝k_p(r-z₁) (1-3)

the linear state feedback law operation module 9 then calculates the intermediate value u₀Sending to the second operation module 11;

the second calculation module 11 also receives a second output signal z sent from the linear state extended observer 8₂The second operation module 11 pairs the intermediate value u₀And a second output signal z₂Performing operation to obtain an output u of the second operation module 11; the second operation module 11 sends the output u to the linear state extended observer 8 and the third operation module 12;

the second operation module 11 obeys the following equations 1 to 4:

u＝Δd＝(-z₂+u₀)/b (1-4)

the value range of b is 45;

the linear expansion state observation module 8 obeys a mathematical model having the form of equations 1-2:

the prototype of formula 1-2 is of formula 1-6:

wherein U represents a through duty deviation value delta d, and y represents a capacitor voltage U_cU and y are both inputs to equations 1-6;

knocking into a state matrix of the linear extended observer;

is the state vector of the linear extended observer;

b is an input matrix, and the value of B is in the range of 45;

l is an observer gain matrix of the linear extended observer;

c is [ 10 ], and C is an output matrix of the linear extended observer;

based on the input and output of the linear expansion state observation module 8, equations 1 to 6 are rewritten into equations 1 to 7:

further transform equations 1-7 into

l₁＝2ω₀,l₂＝ω₀ ²To obtain the formula 1-2:

a direct current link voltage control method based on a Z-source inverter comprises the following steps:

step one, recording the instantaneous value of the through duty ratio at the last moment as D₀ ^*Acquiring capacitance voltage information U through the capacitance voltage acquisition circuit 4_cFurther, according to formula 1-1:

calculating out DC link voltage U_dc；

The U is_cIs a capacitor voltage, U_dcIs a direct-current link voltage, and is,

a last-time through duty cycle;

step two, converting the DC link voltage U_dcAnd the DC link voltage reference peak value U_dc，refInputting the linear active disturbance rejection control module 6, and then according to the formulas 1-2, 1-3 and 1-4;

u₀＝k_p(r-z₁) (1-3)

obtaining u representing the direct duty ratio deviation value delta d after operation;

r represents a DC link voltage reference peak value U_dc，refU represents the through duty deviation Δ d, k_pTo control the ratio, u₀To operate on intermediate quantities, z₁As a function of the first output signal, z₂As a function of the second output signal,

as a function of the first output signal z₁The derivative function of (a) is,

function z of the second output signal₂Derivative function of, said₁＝2ω₀,l₂＝ω₀ ²ω is said₀Linearly expanding the bandwidth of the observation module;

step three, directly connecting the duty ratio instantaneous value D at the last moment₀ ^*Adding the direct duty ratio deviation value delta D to obtain the direct duty ratio D at the current moment₀；

Step four, the through duty ratio D₀The direct current link voltage U is input into an SPWM control module 7, the SPWM control module 7 controls the on-time of a direct-connection zero vector to further control a switching tube in the inverter bridge 3, and finally the direct current link voltage U is realized_dcThe stability of (2).

The working principle of the invention is as follows: by collecting the capacitor voltage U_cThen converting it into DC link voltage U_dcThen applying the DC link voltage U_dcAnd the DC link voltage reference peak value U_dc，_refCalculating to obtain a direct-through duty ratio deviation value delta D, and adding the direct-through duty ratio D at the previous moment to the delta D₀ ^*Obtaining the direct duty ratio D of the current time₀D is₀Inputting the voltage into the SPWM control module 7, adjusting the conduction time of a through zero vector in the SPWM control module 7, and further controlling the inverter bridge 3 to realize the DC link voltage U_dcThe stability of (2).