Control method and control system of F-type three-level inverter for improving grid-connected performance

Abstract

The invention discloses a control method of an F-type three-level inverter for improving grid-connected performance, and the method specifically comprises the steps: 1, obtaining a power grid voltage and a power grid phase, and calculating a current given value # imgabs0 # according to given active power Pref and given reactive power Qref; step 2, inputting a current given value # imgabs 1 # and an actual value # imgabs 2 # of the grid-connected current in a dq coordinate system into an improved linear active disturbance rejection controller to obtain an output voltage reference value uabc; and step 3, using a CBPWM modulation strategy based on modulation wave decomposition to modulate the difference value of the upper capacitor voltage and the lower capacitor voltage of the DC bus, the output current i1abc of the F-type three-level inverter and the output voltage reference value uabc obtained in the step 2 to obtain a driving signal of a switch tube so as to control the F-type three-level grid-connected inverter. The invention further discloses a control system of the F-type three-level inverter for improving the grid-connected performance. According to the invention, the problem of poor anti-interference capability in the prior art is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of inverter control methods, and relates to a control method for an F-type three-level inverter for improving grid connection performance. The present invention also relates to a control system for an F-type three-level inverter for improving grid connection performance. Background Art

[0002] In renewable energy power generation scenarios such as photovoltaic and wind power, inverters are the core equipment in the power conversion process. Compared with traditional two-level inverters, three-level inverters have output current waveforms closer to ideal sine waves, smaller filter volumes, lower equipment costs, and higher practicality.

[0003] Due to its significant economic advantages and low power consumption characteristics, the F-type three-level inverter shows great application potential in the field of new energy power electronics conversion. It has important value in improving the conversion efficiency of new energy and reducing the system deployment cost, and provides key technical support for realizing a sustainable energy system. However, how to improve the power conversion efficiency, enhance the grid connection quality, and better cope with complex working conditions (such as non-ideal grids, system parameter mismatches, etc.) during actual operation is a key problem that needs to be solved by the F-type three-level grid-connected inverter system.

[0004] In summary, the existing F-type three-level grid-connected inverters currently have problems such as poor grid connection quality, weak anti-interference ability, and low operating efficiency. Summary of the Invention

[0005] The purpose of the present invention is to provide a control method for an F-type three-level inverter for improving grid connection performance, which solves the problem of weak anti-interference ability of the F-type three-level grid-connected inverter in the prior art.

[0006] Another purpose of the present invention is to provide a control system for an F-type three-level inverter for improving grid connection performance.

[0007] The technical solution adopted by the present invention is that the control method for an F-type three-level inverter for improving grid connection performance is specifically implemented according to the following steps: Step 1, obtain the grid voltage and grid phase, and then calculate the current reference value according to the given active power P ref and the given reactive power Q ref ; ; Step 2, input the current reference value and the actual value of the grid-connected current in the dq coordinate system into the improved linear auto-disturbance rejection controller to obtain the output voltage reference value u abc ; Step 3: Use the CBPWM modulation strategy based on modulation wave decomposition for the difference between the upper and lower capacitor voltages of the DC bus, the output current of the F-type three-level inverter i 1abc and the output voltage reference value obtained in Step 2 u abc for modulation to obtain the drive signals of the switching tubes, thereby controlling the F-type three-level grid-connected inverter.

[0008] Preferably, Step 1 is specifically as follows: Step 1.1: Use a phase-locked loop (PLL) to obtain the grid voltage in the abc coordinate system E abc and the grid phase θ ; Step 1.2: Transform the grid voltage E abc from the abc coordinate system to the grid voltage E dq in the dq coordinate system; Step 1.3: Then, calculate the current reference value P ref according to the given active power Q ref , the given reactive power E dq , and the grid voltage .

[0009] Preferably, E abc is the grid voltage of the abc three phases, including the grid voltage of phase a E a , the grid voltage of phase b E b , and the grid voltage of phase c E c . In Step 1.2, the grid voltage E abc in the abc coordinate system is transformed to the grid voltage E dq in the dq coordinate system through Clark transformation and Park transformation, E dq is the grid voltage in the dq coordinate system, including the grid voltage of the d axis E d , and the grid voltage of the q axis E q . E abc The transformation to E dq is shown in formula (1) as follows: (1) where, , are the Clark transformation matrix and the Park transformation matrix respectively.

[0010] Preferably, the current reference value in step 1.3 includes the d-axis current reference value and the q-axis current reference value and is specifically calculated according to formula (2):

[0011] Preferably, step 2 is specifically as follows: Step 2.1: Transform the grid-connected current i 2abc in the abc coordinate system to the grid current i 2dq in the dq coordinate system through Clark transformation and Park transformation. The transformation process is as shown in formula (3): (3); Step 2.2: Input the current reference value and the grid current i 2dq into the improved linear active disturbance rejection controller to obtain the reference value u abc of the inverter output voltage in the abc coordinate system. The specific process is as follows: First, calculate the reference value of the inverter output voltage in the dq coordinate system according to the current reference value i 2dq and the grid current u dq , which is specifically as shown in formula (4): (4) In the formula: z 1, z 2, r are intermediate variables in the improved linear active disturbance rejection controller. z 1, z 2 are state variables of the extended state observer in the controller, which respectively track the grid current and the total system disturbance. r is the tracking error of the improved linear active disturbance rejection controller. K p , β 1, β 2 are parameters of the improved linear active disturbance rejection controller. K p is the proportional coefficient of the improved linear active disturbance rejection controller. β 1, β 2 are parameters of the extended state observer in the improved linear active disturbance rejection controller. is the tracking error term; Then, the reference value of the inverter output voltage in the dq coordinate system is u dq transformed to the reference value of the inverter output voltage in the abc coordinate system through the inverse Park transformation and the inverse Clark transformation u abc , specifically: (5) Among them, and are the inverse Clark transformation matrix and the inverse Park transformation matrix respectively.

[0012] Preferably, the modulation process in step 3 is specifically: Step 3.1, the reference value of the inverter output voltage in the abc coordinate system u abc The reference value of the a-phase output voltage of the inverter in u a , the reference value of the b-phase output voltage of the inverter u b , and the reference value of the c-phase output voltage of the inverter u c are allocated according to the numerical magnitude relationship to obtain the maximum-phase voltage reference value u max , the intermediate-phase voltage reference value u mid and the minimum-phase voltage reference value u min ; Step 3.2, the output current of the F-type three-level inverter i 1abc The a-phase output current of the inverter in i 1a , the b-phase output current of the inverter i 1b , and the c-phase output current of the inverter i 1c are allocated according to the numerical magnitude relationship of the inverter output voltage to obtain the maximum-phase current i max , the intermediate-phase current i mid , and the minimum-phase current i min ; Step 3.3, by collecting the voltage difference between the upper and lower capacitors of the DC bus, calculate the average current that needs to be extracted to the midpoint within a carrier period i 0, according to i 0 and the reference values of the inverter output voltage and the inverter output current under the maximum, intermediate, and minimum phases to decompose the modulation wave; Step 3.4: Distribute the decomposed modulation wave to phases a, b, and c to obtain the decomposed dual modulation waves of phases a, b, and c. and ; Step 3.5: Obtain the drive signals of the switching tubes according to the dual modulation wave single-carrier modulation rule. .

[0013] Preferably, in step 3.1 u max , u mid , u min Specifically, calculate according to formula (6): (6); Preferably, in step 3.2 i max , i mid , i min Specifically, calculate according to formula (7): (7).

[0014] Preferably, the modulation wave decomposition in step 3.3 is performed according to formula (8): (8) where , are the dual modulation waves of the maximum phase after decomposition, , are the dual modulation waves of the intermediate phase after decomposition, , are the dual modulation waves of the minimum phase after decomposition, U dc is the DC bus voltage, u z is the zero-sequence voltage value injected into the modulation wave, u c1 , u c2 are the upper and lower capacitor voltages on the DC side respectively, T s is the carrier period, i 0 is the average current that needs to be extracted from the midpoint within one carrier period; Solve formula (8) to obtain , , , , , , specifically: (9); In step 3.4, the decomposed modulation wave is distributed to the abc phases according to formulas (10) and (11): (10) (11) Wherein, and are respectively the double modulation waves after decomposition in the a phase, and are respectively the double modulation waves after decomposition in the a phase, and are respectively the double modulation waves after decomposition in the a phase; Step 3.5 is specifically: (12) Wherein, and are the double modulation waves after decomposition in the abc phases, including the double modulation waves and after decomposition in the a phase, the double modulation waves and after decomposition in the b phase, the double modulation waves and after decomposition in the c phase, and carrer is the carrier wave.

[0015] The second technical solution adopted by the present invention is: a control system for an F-type three-level inverter for improving grid connection performance, which is used for the control method of the above-mentioned F-type three-level inverter for improving grid connection performance, including a data acquisition module, a current reference value output module, an inverter voltage reference value output module, an improved linear active disturbance rejection controller, and a CBPWM modulation module based on modulation wave decomposition.

[0016] The data acquisition module is used to acquire the grid voltage and grid phase, and input them into the current reference value output module; The current reference value output module is used to calculate the current reference value P ref according to the given active power Q ref 、 and the given reactive power based on the grid voltage and grid phase, and input it into the inverter voltage reference value output module; The inverter voltage reference value output module is used to input the current reference value and the actual value of the grid-connected current in the dq coordinate system into the improved linear active disturbance rejection controller; The improved linear active disturbance rejection controller is used to and the actual values of the grid-connected current in the dq coordinate system The reference value of the output voltage is calculated u abc , and input it into the CBPWM modulation module based on modulation wave decomposition; The CBPWM modulation module based on modulation wave decomposition is used to use the CBPWM modulation strategy based on modulation wave decomposition for the difference between the upper and lower capacitor voltages of the DC bus, the output current of the F-type three-level inverter i 1abc and the reference value of the output voltage obtained in step 2 u abc for modulation to obtain the drive signals of the switching tubes.

[0017] The beneficial effects of the present invention are: The present invention improves the traditional linear active disturbance rejection controller. By analyzing the tracking error, it is obtained that the error compensation term compensates the tracking error, improving the anti-disturbance ability and grid connection quality; in addition, the present invention calculates the midpoint current to be injected or extracted to restore the balance state according to the difference between the upper and lower capacitor voltages of the DC bus, and realizes the active balance of the midpoint voltage through modulation, creating stable operating conditions for the system. At the same time, the modulation wave is restricted to reduce the switching loss and improve the efficiency. Therefore, compared with the prior art, the present invention effectively solves the problem of weak anti-interference ability in the prior art. Description of the Drawings

[0018] Figure 1 is the principle block diagram of the control method of the F-type three-level inverter for improving the grid connection performance of the present invention; Figure 2 is the circuit topology diagram of the F-type three-level grid-connected inverter in the control method of the F-type three-level inverter for improving the grid connection performance of the present invention; Figure 3 is the equivalent block diagram of the improved linear active disturbance rejection controller in the control method of the F-type three-level inverter for improving the grid connection performance of the present invention; Figure 4 is the switching sequence diagram of the modulation wave decomposition in CBPWM in the control method of the F-type three-level inverter for improving the grid connection performance of the present invention; Figure 5 is the implementation block diagram of the CBPWM modulation strategy based on modulation wave decomposition in the control method of the F-type three-level inverter for improving the grid connection performance of the present invention; Figure 6 is the grid-connected voltage and current waveforms based on the traditional linear active disturbance rejection control; Figure 7 is the FFT analysis of the grid-connected current based on the traditional linear active disturbance rejection control; Figure 8is the grid-connected voltage and current waveforms adopting the improved linear active disturbance rejection control of the present invention; Figure 9 is the FFT analysis of the grid-connected current adopting the improved linear active disturbance rejection control of the present invention; Figure 10 is the FFT analysis of the grid-connected current based on the traditional linear active disturbance rejection control under the condition of midpoint voltage imbalance; Figure 11 is the FFT analysis of the grid-connected current based on the improved linear active disturbance rejection control of the present invention under the condition of midpoint voltage imbalance; Figure 12 is the grid-connected current waveforms based on the traditional linear active disturbance rejection control under the DC side voltage disturbance; Figure 13 is the grid-connected current waveforms adopting the improved linear active disturbance rejection control of the present invention under the DC side voltage disturbance. Specific embodiments

[0019] The following is a detailed description in combination with specific embodiments.

[0020] The circuit topology of the F-type three-level inverter in the present invention is as Figure 2 shown, including a DC voltage source U dc , DC bus capacitors C 1 and C 2, an F-type inverter (switching tubes S a1 、 switching tubes S a2 、 switching tubes S a3 、 switching tubes S a4 、 switching tubes S b1 、 switching tubes S b2 、 switching tubes S b3 、 switching tubes S b4 、 switching tubes S c1 、 switching tubes S c2 、 switching tubes S c3 and switching tube S c4), LCL filter (high-frequency filtering inductor L 1. Power frequency filtering capacitor C 3 and power frequency filtering inductor L 2) and the power grid ( E a 、 E b and E c ), a total of five parts. Among them, the DC voltage source is connected to the input end of the F-type three-level inverter, the output end of the F-type inverter is connected to the input end of the LCL filter, and the output end of the LCL filter is connected to the power grid. On this basis, the technical solution of the present invention is as follows: Embodiment 1 The control method of the F-type three-level inverter for improving grid connection performance of the present invention has a flow as Figure 1 shown, and is specifically implemented according to the following steps: Step 1: Obtain the grid voltage and grid phase, and then calculate the current reference value according to the given active power P ref and the given reactive power Q ref ; ; Step 2: Input the current reference value and the actual value of the grid-connected current in the dq coordinate system into the improved linear active disturbance rejection controller to obtain the output voltage reference value u abc ; Step 3: Use the CBPWM modulation strategy based on modulation wave decomposition to modulate the difference between the upper and lower capacitor voltages of the DC bus, the output current of the F-type three-level inverter i 1abc and the output voltage reference value obtained in Step 2 u abc to obtain the driving signals of the switching tubes, thereby controlling the F-type three-level grid-connected inverter.

[0021] Embodiment 2 On the basis of Embodiment 1, Step 1 is specifically as follows: Step 1.1: Use the phase-locked loop PLL to obtain the grid voltage E abc in the abc coordinate system θ and the grid phase ; E abc Step 1.2: Transform the grid voltage E dq to the grid voltage E abcis the grid voltage of three phases a, b, and c, including the grid voltage of phase a E a , the grid voltage of phase b E b , and the grid voltage of phase c E c . In step 1.2, the grid voltage in the abc coordinate system is transformed into the grid voltage in the dq coordinate system through Clark transformation and Park transformation E abc . E dq , E dq is the grid voltage in the dq coordinate system, including the grid voltage of the d-axis E d , and the grid voltage of the q-axis E q . E abc The transformation to E dq is shown in formula (10) as follows: (1) where , are the Clark transformation matrix and the Park transformation matrix respectively; In step 1.3, then according to the given active power P ref , the given reactive power Q ref , and the grid voltage E dq calculate the current reference value , which is specifically calculated according to formula (2): (2) Embodiment 3 Based on Embodiment 2, step 2 is specifically as follows: In step 2.1, the grid-connected current in the abc coordinate system is transformed into the grid current in the dq coordinate system through Clark transformation and Park transformation i 2abc . The transformation process is shown in formula (3) as follows: i 2dq (3); (3); In step 2.2, the current reference value and the grid current i 2dq are input into the improved linear active disturbance rejection controller to obtain the reference value of the inverter output voltage in the abc coordinate system u abc, the specific process is as follows: As Figure 3 shown, first, according to the current reference value and the grid current i 2dq calculate the reference value of the inverter output voltage in the dq coordinate system u dq . Specifically, by analyzing the tracking error, the tracking error term can be directly obtained, and then an improved linear active disturbance rejection controller is established according to the tracking error term, as specifically shown in formula (4): (4) In the formula: z 1. z 2. r are intermediate variables in the improved linear active disturbance rejection controller, z 1. z 2 are state variables of the extended state observer in the controller, tracking the grid current and the total system disturbance respectively, r is the tracking error of the improved linear active disturbance rejection controller; K p , β 1. β 2 are parameters of the improved linear active disturbance rejection controller, K p is the proportional coefficient of the improved linear active disturbance rejection controller, β 1. β 2 are parameters of the extended state observer in the improved linear active disturbance rejection controller, is the tracking error term; Then, through the inverse Park transformation and inverse Clark transformation, the reference value of the inverter output voltage u dq in the dq coordinate system is transformed into the reference value of the inverter output voltage u abc in the abc coordinate system, specifically: (5) Among them, , are the inverse Clark transformation matrix and the inverse Park transformation matrix respectively.

[0022] Example 4 On the basis of Example 3, the modulation process in step 3 is as Figure 5 shown, specifically: Step 3.1, the reference value of the inverter a-phase output voltage u abc in the reference value of the inverter output voltage u a, b-phase output voltage reference value u b , c-phase output voltage reference value u c The maximum phase voltage reference value of the inverter output is obtained by distribution according to the numerical magnitude relationship u max , intermediate phase voltage reference value u mid and minimum phase voltage reference value u min ; Step 3.2, the output current of the F-type three-level inverter i 1abc The a-phase output current of the inverter in i 1a , the b-phase output current of the inverter i 1b , the c-phase output current of the inverter i 1c are distributed according to the numerical magnitude relationship of the inverter output voltage to obtain the maximum phase current at the inverter output i max , intermediate phase current i mid , minimum phase current i min ; Step 3.3, by collecting the voltage difference between the upper and lower capacitors of the DC bus, calculate the average current that needs to be extracted from the midpoint within one carrier period i 0, according to i 0 and the inverter output voltage reference values and the inverter output current decomposition modulation waves under the maximum, intermediate, and minimum phases; Step 3.4, distribute the decomposed modulation waves to the a, b, and c phases to obtain the decomposed double modulation waves of the a, b, and c phases , ; Step 3.5, according to the double modulation wave single carrier modulation rule, obtain the drive signals of the switching tubes .

[0023] Example 5 On the basis of Example 4, in Step 3.1 u max , u mid , u min Specifically, calculate according to formula (6): (6); In Step 3.2 i max , i mid ,i min Specifically, it is calculated according to formula (7): (7).

[0024] In step 3.3, the modulation wave decomposition is carried out according to formula (8): (8) Among them, and are the double modulation waves after the maximum phase decomposition, and are the double modulation waves after the intermediate phase decomposition, and are the double modulation waves after the minimum phase decomposition, U dc is the DC bus voltage, u z is the zero-sequence voltage value injected into the modulation wave, u c1 and u c2 are the upper and lower capacitor voltages on the DC side respectively, T s is the carrier period, i 0 is the average current that needs to be extracted from the midpoint within one carrier period; In formula (8), for and constraints are imposed to clamp them to the maximum and minimum values, reducing the number of switching times, thereby reducing switching losses and improving efficiency. For details, see Figure 4 ; By solving formula (8), we get 、 、 、 、 、 , specifically as follows: (9); In step 3.4, the decomposed modulation waves are allocated to the abc phases according to formulas (10) and (11): (10) (11) Among them, 、 are the double modulation waves after the a-phase decomposition respectively, 、 are the double modulation waves after the b-phase decomposition respectively, 、 are the double modulation waves after the c-phase decomposition respectively; Step 3.5 specifically is as follows: (12) Among them, and are the double modulation waves after the abc - phase decomposition, including the double modulation wave and after the a - phase decomposition, the double modulation wave and after the b - phase decomposition, and the double modulation wave and after the c - phase decomposition. carrer is the carrier wave (an isosceles triangular carrier wave with a maximum value of 1 and a minimum value of 0).

[0025] Table 1 shows the relationship between the switch states of each phase of the F - type three - level inverter and the switch states of each switch tube. The logical states 1 and 0 correspond to the on and off states of the switch tube respectively.

[0026] Table 1

[0027] By knowing the switch states of each switch tube, the drive signals of the switch tubes can be obtained, thereby controlling the F - type three - level grid - connected inverter.

[0028] Embodiment 6 Use the Simulink toolbox in Matlab software to build a simulation model of the present invention in a simulation environment, and illustrate the beneficial effects of the present invention through the simulation results. The simulation conditions are shown in Table 2.

[0029] Table 2

[0030] Under the working conditions of Table 2, the traditional linear active disturbance rejection control and the control method of the present invention are respectively simulated and analyzed. The results are as shown in Figure 6 and Figure 7 and Figure 8 and Figure 9 shown. Through the FFT analysis results of the grid - connected current, it can be known that the harmonic distortion rate of the grid - connected current under the traditional linear active disturbance rejection control is 1.38%, and that of the present invention is 1.01%, indicating that the present invention improves the grid - connection quality.

[0031] Under the condition of unbalanced neutral - point potential (the capacitor voltage of the upper DC bus is 350V, and the capacitor of the lower DC bus is 250V), the traditional linear active disturbance rejection control and the control method of the present invention are respectively simulated and analyzed. The results are as shown in Figure 10 and Figure 11As shown in the figure, through the FFT analysis results of the grid-connected current, it can be seen that under the traditional linear active disturbance rejection control, the harmonic distortion rate of the grid-connected current increases from 1.38% to 1.46%, and the harmonic distortion rate increases by 5.8%. In the present invention, it increases from 1.01% to 1.05%, and the harmonic distortion rate increases by 3.9%. This shows that under the interference of the midpoint voltage imbalance, the grid-connected quality of the present invention is less affected and the anti-interference ability is stronger.

[0032] Under the condition of DC-side voltage disturbance (applying an AC disturbance with a peak value of 30V and a frequency of 200Hz on the DC side), the traditional linear active disturbance rejection control and the control method of the present invention are respectively simulated and analyzed. The results are as Figure 12 , Figure 13 shown. Through the FFT analysis results of the grid-connected current, it can be seen that under the traditional linear active disturbance rejection control, the harmonic distortion rate of the grid-connected current increases from 1.38% to 1.8%, and the harmonic distortion rate increases by 30.4%. In the present invention, it increases from 1.01% to 1.03%, and the harmonic distortion rate increases by 2%. This shows that under the interference of the DC-side voltage fluctuation, the grid-connected quality of the present invention is less affected and the anti-interference ability is stronger.

[0033] Embodiment 7 A control system for an F-type three-level inverter for improving grid-connected performance, which is used for the control method of the F-type three-level inverter for improving grid-connected performance in Embodiment 5, includes a data acquisition module, a current reference value output module, an inverter voltage reference value output module, an improved linear active disturbance rejection controller, and a CBPWM modulation module based on modulation wave decomposition.

[0034] The data acquisition module is used to acquire the grid voltage and grid phase and input them into the current reference value output module; The current reference value output module is used to calculate the current reference value P ref according to the given active power Q ref 、 and the given reactive power using the grid voltage and grid phase, and input it into the inverter voltage reference value output module; The inverter voltage reference value output module is used to input the current reference value and the actual value of the grid-connected current in the dq coordinate system into the improved linear active disturbance rejection controller; The improved linear active disturbance rejection controller is used to calculate the output voltage reference value according to the current reference value and the actual value of the grid-connected current in the dq coordinate system u abc , and input it into the CBPWM modulation module based on modulation wave decomposition; The CBPWM modulation module based on modulation wave decomposition is used to modulate the difference between the upper and lower capacitor voltages of the DC bus and the output current of the F-type three-level inverter by using the CBPWM modulation strategy based on modulation wave decomposition i 1abc and the output voltage reference value obtained in step 2 u abc to obtain the driving signals of the switching tubes.

Claims

1. Control method of F-type three-level inverter for improving grid-connected performance, characterized in that, The implementation is specifically carried out according to the following steps: Step 1, obtain the grid voltage and grid phase, and then calculate the current set value according to the given active power P ref and the given reactive power Q ref ; ; Step 2, input the current given value and the actual value of the grid-connected current in the dq coordinate system into the improved linear active disturbance rejection controller to obtain the output voltage reference value u abc ; Step 3, using the CBPWM modulation strategy based on modulation wave decomposition for the difference between the upper and lower capacitor voltages of the DC bus, the output current of the F-type three-level inverter i 1abc and the output voltage reference value obtained in Step 2 u abc are modulated to obtain the driving signals of the switching tubes, thereby controlling the F-type three-level grid-connected inverter.

2. The control method of the F-type three-level inverter for improving grid connection performance according to claim 1, characterized in that, Specifically, step 1 is as follows: Step 1.1, obtaining the grid voltage in the abc coordinate system using a phase-locked loop (PLL) E abc and the grid phase θ ; Step 1.2, transform the grid voltage E abc to the grid voltage in the dq coordinate system E dq , where E abc is the grid voltage of three phases abc, including the grid voltage of phase a E a , the grid voltage of phase b E b , and the grid voltage of phase c E c . In Step 1.2, the grid voltage in the abc coordinate system E abc is transformed to the grid voltage in the dq coordinate system E dq through Clark transformation and Park transformation E dq is the grid voltage in the dq coordinate system, including the grid voltage of the d-axis E d , and the grid voltage of the q-axis E q . E abc is transformed into E dq as shown in formula (10): （1） Among them, and are the Clark transformation matrix and the Park transformation matrix respectively; Step 1.3, and then calculate the current set value according to the given active power P ref , the given reactive power Q ref , and the grid voltage E dq . .

3. The control method of the F-type three-level inverter for improving grid connection performance according to claim 2, wherein, The current set value in Step 1.3 includes the d-axis current set value and the q-axis current set value , and is specifically calculated according to formula (2): （2）。 4. The control method of the F-type three-level inverter for improving grid connection performance according to claim 1, characterized in that, Specifically, step 2 is as follows: Step 2.1, transform the grid-connected current in the abc coordinate system to the grid current in the dq coordinate system through Clark transformation and Park transformation i 2abc The transformation process is as shown in Equation (3): i 2dq , the transformation process is as shown in Equation (3): （3）； Step 2.2, the current reference value and the grid current i 2dq are input into the improved linear active disturbance rejection controller to obtain the reference value of the inverter output voltage in the abc coordinate system u abc . The specific process is as follows: First, according to the current reference value and the grid current i 2dq calculate the reference value of the inverter output voltage in the dq coordinate system u dq , as specifically shown in Equation (4): （4） Wherein: z 1, z 2, r is the intermediate variable in the improved linear active disturbance rejection controller, z 1, z 2 are the state variables of the extended state observer in the controller, tracking the grid current and the total system disturbance respectively, r is the tracking error of the improved linear active disturbance rejection controller; K p , β 1, β 2 are the parameters of the improved linear active disturbance rejection controller, K p is the proportionality coefficient of the improved linear active disturbance rejection controller, β 1, β 2 are the parameters of the extended state observer in the improved linear active disturbance rejection controller, is the tracking error term; Then, through the inverse Park transformation and the inverse Clark transformation, the reference value of the inverter output voltage in the dq coordinate system u dq is transformed into the reference value of the inverter output voltage in the abc coordinate system u abc , specifically: （5） Among them, and are the inverse Clark transformation matrix and the inverse Park transformation matrix, respectively.

5. The control method of the F-type three-level inverter for improving grid connection performance according to claim 4, characterized in that, Specifically, the modulation process in step 3 is as follows: Step 3.1, the reference value of the inverter output voltage in the abc coordinate system u abc The reference value of the a-phase output voltage of the inverter in u a , the reference value of the b-phase output voltage u b , and the reference value of the c-phase output voltage u c are allocated according to the numerical magnitude relationship to obtain the reference value of the maximum phase voltage output by the inverter u max , the reference value of the intermediate phase voltage u mid , and the reference value of the minimum phase voltage u min ; Step 3.2, the output current of the F-type three-level inverter i 1abc the output current of phase a of the inverter in i 1a , the output current of phase b of the inverter i 1b , the output current of phase c of the inverter i 1c are allocated according to the magnitude relationship of the inverter output voltage values to obtain the maximum phase current i max at the inverter output side, the intermediate phase current i mid , and the minimum phase current i min ; Step 3.3: Calculate the average current to be extracted from the midpoint within a carrier period by collecting the voltage difference between the upper and lower capacitors of the DC bus. i 0, according to i 0 and the reference values of the inverter output voltages under the maximum, medium, and minimum phases and the decomposed modulation waves of the inverter output-side currents. Step 3.4, distributing the decomposed modulation wave to the a, b, and c phases to obtain the double modulation waves decomposed in the a, b, and c phases , ; Step 3.5, obtain the driving signal of the switching tube according to the double-modulation-wave single-carrier modulation rule .

6. The control method of the F-type three-level inverter for improving grid connection performance according to claim 5, characterized in that In the said step 3.1 u max , u mid , u min Specifically, it is calculated according to formula (6): （6）； In the said step 3.2 i max , i mid , i min Specifically, it is calculated according to formula (7): （7）。 7. The control method of the F-type three-level inverter for improving grid connection performance according to claim 6, wherein, In step 3.3, the modulation wave decomposition is carried out according to formula (8): （8） Among them, and are the double modulation waves after the maximum phase decomposition, and are the double modulation waves after the intermediate phase decomposition, and are the double modulation waves after the minimum phase decomposition, U dc is the DC bus voltage, u z is the zero-sequence voltage value injected into the modulation wave, u c1 and u c2 are the upper and lower capacitor voltages on the DC side respectively, T s is the carrier period, i 0 is the average current that needs to be extracted from the midpoint within one carrier period; Solve the formula (8) to obtain , , , , , , specifically as follows: （9）。 8. The control method of the F-type three-level inverter for improving grid connection performance according to claim 7, characterized in that In step 3.4, the decomposed modulation wave is allocated to the abc phases according to formulas (10) and (11): （10） （11） Among them, , are respectively the double modulation waves after the decomposition of the a-phase, , are respectively the double modulation waves after the decomposition of the a-phase, , are respectively the double modulation waves after the decomposition of the a-phase; Specifically, step 3.5 is as follows: （12） Among them, and are the double modulation waves after abc phase decomposition, including the double modulation wave and after a-phase decomposition, the double modulation wave and after b-phase decomposition, and the double modulation wave and after c-phase decomposition. carrer is the carrier wave.

9. The control system of an F-type three-level inverter for improving grid connection performance, characterized in that, A control method for an F-type three-level inverter for improving grid connection performance according to claim 8, comprising a data acquisition module, a current reference value output module, an inverter voltage reference value output module, an improved linear active disturbance rejection controller, and a CBPWM modulation module based on modulation wave decomposition.

10. The control system of the F-type three-level inverter for improving grid connection performance according to claim 9, characterized in that, The data acquisition module is used to acquire the grid voltage and grid phase and input them into the current reference value output module; The current set value output module is used to calculate the current set value according to the given active power P ref and the given reactive power Q ref 、 the grid voltage, and the grid phase, and input the calculated current set value into the inverter voltage reference value output module; The inverter voltage reference value output module is used to input the current given value and the actual values of the grid-connected current in the dq coordinate system into the improved linear active disturbance rejection controller; The improved linear active disturbance rejection controller is used to calculate the output voltage reference value according to the given current value and the actual value of the grid-connected current in the dq coordinate system and input it into the CBPWM modulation module based on modulation wave decomposition; u abc ​ The CBPWM modulation module based on modulation wave decomposition is used to modulate the difference between the upper and lower capacitor voltages of the DC bus, the output current of the F-type three-level inverter i 1abc and the output voltage reference value obtained in step 2 u abc to obtain the driving signals of the switching tubes.

Images