Three-phase asymmetric hybrid cascaded inverter prediction control method and inverter system

Abstract

The application discloses a three-phase asymmetric hybrid cascaded inverter prediction control method and an inverter system. The prediction control method comprises the following steps: establishing a continuous time domain state space equation of the system in an alpha-beta coordinate system; discretizing the continuous time domain state space equation to obtain a discrete state equation according to a trapezoidal numerical integration principle, and obtaining three-phase sampling currents through sampling and substituting the three-phase sampling currents into the discrete state equation; designing an evaluation function of a prediction algorithm of alternating current side output currents; solving the discrete state equation of the system to obtain an optimal output voltage vector of the system by taking the minimum value of the evaluation function as a constraint condition; constructing a Diophantine equation according to the optimal output voltage vector and the discrete state space equation of the inverter system; and obtaining the output switching state of the three-phase asymmetric hybrid cascaded inverter system and outputting the same according to the Diophantine equation. The application removes the rolling optimization process of the prediction control, can quickly and efficiently predict control the system, and enables the system to realize higher switching frequency application.

Description

Technical Field

[0001] This invention relates to the field of electrical engineering, and in particular to a predictive control method and inverter system for a three-phase asymmetric hybrid cascaded inverter. Background Technology

[0002] Multilevel inverters are widely used in new energy power transmission, medium-voltage motor speed regulation, and static reactive power compensators. Compared to traditional symmetrical cascaded multilevel inverters, asymmetric hybrid cascaded inverters can generate more voltage levels with the same number of semiconductor switches, saving material costs and improving output current quality. However, due to its asymmetric characteristics, the modulation strategy design for this topology is relatively complex; model predictive control can effectively simplify its control costs.

[0003] Traditional model predictive controllers (MMDCs) used in three-phase inverter systems include three-phase independent MDCs and three-phase MDCs. Three-phase independent MDCs utilize output levels for rolling optimization, which has a short execution time but results in overly lengthy code. Three-phase MDCs utilize three-phase voltage vectors for rolling optimization, offering clear logic and shorter control code, but are time-consuming. Furthermore, both traditional MDC methods suffer from the problem of increased processor computation due to the rolling optimization process, making it difficult to increase the switching frequency of the inverter system. Summary of the Invention

[0004] The purpose of this invention is to provide a predictive control method and inverter system for a three-phase asymmetric hybrid cascade inverter, which eliminates the rolling optimization process of predictive control, enables rapid and efficient predictive control of the system, and allows the system to achieve applications with higher switching frequencies.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A predictive control method for a three-phase asymmetric hybrid cascaded inverter includes the following steps: Based on the topology of the three-phase asymmetric hybrid cascaded inverter system, its continuous time domain state-space equation in the αβ coordinate system is established. Based on the principle of trapezoidal numerical integration, the continuous time domain state space equation in the αβ coordinate system is discretized to obtain the discrete state equation of the three-phase asymmetric hybrid cascade inverter system. The AC side output current of the system is sampled to obtain the three-phase sampled current, and the three-phase sampled current is substituted into the discrete state equation of the inverter system. For the AC side output current of a three-phase asymmetric hybrid cascaded inverter system, an evaluation function for the prediction algorithm of AC side output current is designed to calculate the three-phase predicted current. The minimum value of the evaluation function is used as a constraint to determine the three-phase predicted current, and the discrete state equation of the inverter system is solved to obtain the optimal output voltage vector of the inverter system. Diophantine equations are constructed based on the optimal output voltage vector and the discrete state-space equations of the inverter system. The output switching state of the three-phase asymmetric hybrid cascaded inverter system is obtained and output by solving the Diophantine equation.

[0006] Furthermore, based on any one or a combination of the aforementioned technical solutions, the evaluation function expression for the AC output side current of the inverter system is as follows: in, , , i α (k+1) and i β (k+1) is αβ The predicted three-phase current at time k+1 in the coordinate system. i αref (k+1) and i βref (k+1) is αβ The three-phase reference current at time k+1 in the coordinate system.

[0007] Furthermore, following any one or a combination of the aforementioned technical solutions, using the minimum value of the evaluation function as a constraint, the discrete state equations of the inverter system are solved to obtain the optimal output voltage vector of the inverter system. The expression for the optimal output voltage vector is: in, and This represents the optimal output voltage vector of the inverter system. i α (k) and i β (k) represents the inverter system in αβ The three-phase sampled current at time k in the coordinate system. i αref (k+1) and i βref (k+1) is αβ The three-phase reference current at time k+1 in the coordinate system. L For load inductance, R For load resistance, T s The sampling period is V dc，eqThe equivalent bus voltage of a three-phase asymmetrical hybrid cascaded inverter is given by the following definition: V dc，eq The calculation formula is: in, V dc1 and V dc2 These are the voltage values ​​of the two independent DC voltage sources in a three-phase asymmetrical hybrid cascaded inverter. D for V dc1 and V dc2 The ratio of .

[0008] Furthermore, following any one or a combination of the aforementioned technical solutions, the method is characterized in that a Diophantine equation is constructed based on the optimal output voltage vector and the discrete state-space equation of the inverter system, wherein the Diophantine equation is: in, and The optimal output voltage vector of the inverter system, and the output level matrix of the inverter system. The values ​​of each element are in the range of [-N, N], where N is the level number. When D=1, N=3; when D=2, N=4.

[0009] Furthermore, following any one or a combination of the aforementioned technical solutions, the characteristic is that the output switching state of the three-phase asymmetric hybrid cascaded inverter system is obtained and output based on the Diophantine equation, the general solution of the Diophantine equation is the switching state of the system, and the expression for the general solution of the Diophantine equation is: in, It is the output level matrix of the inverter system. , , N represents the level number.

[0010] Furthermore, following any one or a combination of the foregoing technical solutions, the following is characterized in that: Pick and of the median.

[0011] Furthermore, based on any one or a combination of the aforementioned technical solutions, the continuous-time domain state-space equations of the three-phase asymmetric hybrid cascade inverter system in the αβ coordinate system are established in the following manner: Based on the inverter system topology, the relationship between the output state variables and the output voltage of the inverter system in the three-phase abc coordinate system is obtained. Based on the Clark transformation matrix, the state-space equations of the inverter system in the αβ coordinate system are obtained; According to Kirchhoff's laws, the state-space equations of the inverter system on the AC output side in the αβ coordinate system are obtained as follows: in, i α and i β The AC output current is in the αβ coordinate system. S a , S b , S c This refers to the inverter voltage level state. L For load inductance, R For load resistance, V dc，eq The equivalent bus voltage of a three-phase asymmetrical hybrid cascaded inverter is given by the following definition: V dc，eq The calculation formula is: in, V dc1 and V dc2 These are the voltage values ​​of the two independent DC voltage sources in a three-phase asymmetrical hybrid cascaded inverter. D for V dc1 and V dc2 The ratio of .

[0012] Furthermore, following any one or a combination of the aforementioned technical solutions, the three-phase asymmetric hybrid cascaded inverter system is discretized using the trapezoidal integral formula to obtain the discrete state equation of the inverter system. The discrete state equation is as follows: in, i α (k+1) and i β (k+1) is αβ The predicted three-phase current at time k+1 in the coordinate system. i α (k) and i β (k) is α β The three-phase sampled current at time k in the coordinate system.L For load inductance, R For load resistance, T s The sampling period is S a , S b , S c This refers to the inverter voltage level state. V dc，eq The equivalent bus voltage of a three-phase asymmetrical hybrid cascaded inverter is given by the following definition: V dc，eq The calculation formula is: in, V dc1 and V dc2 These are the voltage values ​​of the two independent DC voltage sources in a three-phase asymmetrical hybrid cascaded inverter. D for V dc1 and V dc2 The ratio of .

[0013] Furthermore, following any one or a combination of the aforementioned technical solutions, when the evaluation function is 0, the voltage vector of the inverter system is the optimal output voltage vector. Substituting the optimal output voltage vector into the Diophantine equation and solving the Diophantine equation yields the optimal output switching state of the three-phase asymmetrical hybrid cascaded inverter system; and / or, The number of output levels of an inverter system varies depending on the voltage ratio of its independent DC sources.

[0014] According to another aspect of the present invention, a three-phase asymmetric hybrid cascaded inverter system is provided, including a three-phase asymmetric hybrid cascaded inverter and a processor, wherein the processor uses the method described herein to perform predictive control on the three-phase asymmetric hybrid cascaded inverter system.

[0015] The beneficial effects of the technical solution provided in this disclosure are as follows: a. The prediction method provided by this invention constructs the optimal output voltage vector expression and Diophantine equation, uses the minimum value of the evaluation function as a constraint, and combines it with the discrete state equation to obtain the optimal output voltage vector of the system. The optimal output switching state of the system is obtained by solving the Diophantine equation using the optimal output voltage vector. Compared with the traditional predictive control method, it removes the rolling optimization process and can perform predictive control of the inverter system more quickly. b. The predictive control method provided by this invention does not require a rolling optimization process, which can reduce the burden on the system processor. It can meet the usage requirements by using a lower-cost processor, improve the system's operating frequency, obtain a better quality AC output current waveform, and enable the system to achieve higher switching frequencies. c. The predictive control method provided by this invention is applicable to three-phase asymmetrical cascaded hybrid inverter systems with different DC voltage ratios. The number of output levels of the inverter system changes according to the voltage ratio of its independent DC sources. When the DC voltage ratio changes, there is no need to remodel or adjust the input parameters, which enables more efficient predictive control of the inverter system. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of a three-phase asymmetric hybrid cascade inverter predictive control method provided by an exemplary embodiment of the present invention; Figure 2 This is a schematic diagram of the control structure of a three-phase asymmetric hybrid cascaded inverter system provided in an exemplary embodiment of the present invention; Figure 3 This is a schematic diagram of the circuit topology of a three-phase asymmetric hybrid cascaded inverter system provided in an exemplary embodiment of the present invention; Figure 4 This is a simulation waveform diagram of the steady-state three-phase current and line voltage of a three-phase asymmetric hybrid cascaded inverter system provided by an exemplary embodiment of the present invention when the DC voltage ratio D is 1. Figure 5 This is a simulation waveform diagram of the three-phase current and line voltage of a three-phase asymmetric hybrid cascaded inverter system under dynamic conditions when the DC voltage ratio D is 1, provided by an exemplary embodiment of the present invention. Figure 6 This is a simulation waveform diagram of the steady-state three-phase current and line voltage of a three-phase asymmetric hybrid cascaded inverter system provided by an exemplary embodiment of the present invention when the DC voltage ratio D is 2. Figure 7 This is a simulation waveform diagram of the three-phase current and line voltage of a three-phase asymmetric hybrid cascaded inverter system under dynamic conditions when the DC voltage ratio D is 2, provided by an exemplary embodiment of the present invention. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, apparatus, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0020] In one embodiment of the present invention, a predictive control method for a three-phase asymmetric hybrid cascaded inverter is provided, see [link to relevant documentation]. Figure 1 and Figure 2 The predictive control method includes: Based on the topology of the three-phase asymmetric hybrid cascaded inverter system, its continuous time domain state-space equation in the αβ coordinate system is established. Based on the principle of trapezoidal numerical integration, the continuous time domain state space equation in the αβ coordinate system is discretized to obtain the discrete state equation of the three-phase asymmetric hybrid cascade inverter system. The AC side output current of the system is sampled to obtain the three-phase sampled current, and the three-phase sampled current is substituted into the discrete state equation of the inverter system. For the AC side output current of a three-phase asymmetric hybrid cascaded inverter system, an evaluation function for the prediction algorithm of AC side output current is designed to calculate the three-phase predicted current. The minimum value of the evaluation function is used as a constraint to determine the three-phase predicted current, and the discrete state equation of the inverter system is solved to obtain the optimal output voltage vector of the inverter system. Diophantine equations are constructed based on the optimal output voltage vector and the discrete state-space equations of the inverter system. The output switching state of the three-phase asymmetric hybrid cascaded inverter system is obtained and output by solving the Diophantine equation.

[0021] This invention proposes a predictive control method for a three-phase asymmetric hybrid cascaded inverter. By constructing the optimal output voltage vector expression and Diophantine equation, and using the minimum value of the evaluation function as a constraint, the optimal output voltage vector of the system is obtained by combining it with the discrete state equation. The optimal output switching state of the system is obtained by solving the Diophantine equation using the optimal output voltage vector. Compared with traditional predictive control methods, this method eliminates the rolling optimization process, enables rapid current change tracking, has good dynamic performance, reduces the burden on the system processor, saves controller costs, or increases the system's operating frequency, enabling the system to achieve higher frequency applications.

[0022] An embodiment of the present invention also provides a three-phase asymmetric hybrid cascaded inverter system, including a three-phase asymmetric hybrid cascaded inverter and a processor, wherein the processor uses the method described above to perform predictive control on the three-phase asymmetric hybrid cascaded inverter system.

[0023] The following preferred embodiment further illustrates the method for predictive control of a three-phase asymmetric hybrid cascade inverter system using the present invention.

[0024] See Figure 3 This invention provides a main circuit topology for a three-phase asymmetric hybrid cascaded inverter system, wherein each subunit of the system has two independent DC voltage sources V. dc1 and V dc2 Its independent DC source voltage ratio is D, and four fully controlled semiconductor devices (S 11 ,S 12 ,S 21 ,S 22 The inverter system consists of two cascaded sub-units per phase. The number of output voltage levels varies depending on the DC voltage ratio D. When D=1, the phase voltage is 7 levels and the line voltage is 11 levels; when D=2, the phase voltage is 9 levels and the line voltage is 13 levels.

[0025] The continuous-time-domain state-space equations of the three-phase asymmetric hybrid cascaded inverter system in the αβ coordinate system are established as follows: Based on the inverter system topology, the relationship between the output state variables and the output voltage of the inverter system in the three-phase abc coordinate system is obtained. Based on the Clark transformation matrix, the state-space equations of the inverter system in the αβ coordinate system are obtained; According to Kirchhoff's laws, the state-space equations of the inverter system on the AC output side in the αβ coordinate system are obtained as follows: in, i α and iβ The AC output current is in the αβ coordinate system. S a , S b , S c This refers to the inverter voltage level state. L For load inductance, R For load resistance, V dc，eq The equivalent bus voltage of a three-phase asymmetrical hybrid cascaded inverter is given by the following definition: V dc，eq The calculation formula is: in, V dc1 and V dc2 These are the voltage values ​​of the two independent DC voltage sources in a three-phase asymmetrical hybrid cascaded inverter. D for V dc1 and V dc2 The ratio of .

[0026] Furthermore, the three-phase asymmetric hybrid cascaded inverter system is discretized using the trapezoidal integral formula to obtain the discrete state equations of the inverter system, which are as follows: in, i α (k+1) and i β (k+1) is αβ The predicted three-phase current at time k+1 in the coordinate system. i α (k) and i β (k) is α β The three-phase sampled current at time k in the coordinate system. L For load inductance, R For load resistance, T s The sampling period is S a , S b , S c This refers to the inverter voltage level state. V dc，eq This is the equivalent bus voltage of a three-phase asymmetric hybrid cascaded inverter.

[0027] The evaluation function expression for the AC output current of the inverter system is as follows: in, , , i α (k+1) and i β (k+1) is αβ The predicted three-phase current at time k+1 in the coordinate system. i αref (k+1) and i βref (k+1) is αβ The three-phase reference current at time k+1 in the coordinate system.

[0028] Using the minimum value of the evaluation function as a constraint, the discrete state equations of the inverter system are solved to obtain the optimal output voltage vector of the inverter system. Preferably, when the evaluation function is 0, the obtained voltage vector of the inverter system is the optimal output voltage vector, and the expression for the optimal output voltage vector is: in, and This represents the optimal output voltage vector of the inverter system. i α (k) and i β (k) represents the inverter system in αβ The three-phase sampled current at time k in the coordinate system. i αref (k+1) and i βref (k+1) is αβ The three-phase reference current at time k+1 in the coordinate system. L For load inductance, R For load resistance, T s The sampling period is V dc，eq This is the equivalent bus voltage of a three-phase asymmetric hybrid cascaded inverter.

[0029] Based on the optimal output voltage vector and the discrete state-space equations of the inverter system, a Diophantine equation is constructed, which is: in, and The optimal output voltage vector of the inverter system, and the output level matrix of the inverter system. The values ​​of each element are in the range of [-N, N], where N is the level number. When D=1, N=3; when D=2, N=4.

[0030] Substituting the optimal output voltage vector into the Diophantine equation and solving it yields the optimal output switching state of the three-phase asymmetrical hybrid cascaded inverter system, which is then output. The general solution of the Diophantine equation represents the system's switching state, and its expression is as follows: in, It is the output level matrix of the inverter system. , , N represents the level number.

[0031] Preferably, Pick and The median value is used to obtain the optimal output switching state of the three-phase asymmetric hybrid cascaded inverter system.

[0032] To verify the feasibility of this invention, this embodiment focuses on a three-phase asymmetric hybrid cascaded inverter system using predictive control based on this invention. Simulations were built using Matlab / Simulink under different DC voltage ratios. Specific simulation parameters are shown in Table 1, where D represents the DC voltage ratio.

[0033] Table 1 Specific parameters for simulation verification The first objective of this simulation verification is to verify the steady-state current tracking performance of the inverter system under DC voltage ratios D=1 and 2. The second objective is to verify the dynamic current tracking performance of the inverter system under DC voltage ratios D=1 and 2.

[0034] The specific simulation results are as follows: Figure 4 The simulation waveforms of steady-state three-phase current and line voltage of the three-phase asymmetric hybrid cascaded inverter system obtained for target 1 when the DC voltage ratio D is 1 are shown. When the reference current is 5A, the three-phase current waveforms are good, and the phase voltage is at level 7 and the line voltage is at level 11.

[0035] Figure 5This is a simulation waveform of the three-phase current and line voltage of the three-phase asymmetrical hybrid cascaded inverter system obtained for objective 2 under dynamic conditions when the DC voltage ratio D is 1. At t=0.3, the reference current jumps from 2A to 5A, and the line voltage changes from level 5 to level 11. At t=0.65, the reference current jumps from 5A to 2A, and the line voltage changes from level 11 to level 9. The current waveform has a good shape and a fast dynamic response.

[0036] Figure 6 The simulation waveforms of steady-state three-phase current and line voltage of the three-phase asymmetric hybrid cascaded inverter system obtained for target 1 when the DC voltage ratio D is 2 are shown. When the reference current is 6.5A, the three-phase current waveforms are good, and the phase voltage is at level 9 and the line voltage is at level 13.

[0037] Figure 7 This is a simulation waveform diagram of the three-phase current and line voltage of the three-phase asymmetrical hybrid cascaded inverter system obtained for objective 2 under dynamic conditions when the DC voltage ratio D is 2. At t=0.3, the reference current jumps from 3A to 6.5A, and the line voltage changes from level 7 to level 13. At t=0.65, the reference current jumps from 6.5A to 5A, and the line voltage changes from level 13 to level 11.

[0038] This invention proposes a predictive control method for a three-phase asymmetric hybrid cascaded inverter. It constructs the optimal output voltage vector expression and Diophantine equation. Compared to traditional predictive control methods, it eliminates the rolling optimization process, enabling rapid current change tracking and better dynamic performance. It also reduces the burden on the system processor, saving controller costs or increasing the system's operating frequency. Through a universal modeling of the three-phase asymmetric hybrid cascaded inverter system, this invention eliminates the need for remodeling or adjusting input parameters when the system's DC voltage ratio changes, enabling more efficient predictive control of the system.

[0039] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0040] The above description is only a specific embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A predictive control method for a three-phase asymmetric hybrid cascaded inverter, characterized in that, Includes the following steps: Based on the topology of the three-phase asymmetric hybrid cascaded inverter system, its continuous time domain state-space equation in the αβ coordinate system is established. Based on the principle of trapezoidal numerical integration, the continuous time domain state space equation in the αβ coordinate system is discretized to obtain the discrete state equation of the three-phase asymmetric hybrid cascade inverter system. The AC side output current of the system is sampled to obtain the three-phase sampled current, and the three-phase sampled current is substituted into the discrete state equation of the inverter system. For the AC side output current of a three-phase asymmetric hybrid cascaded inverter system, an evaluation function for the prediction algorithm of AC side output current is designed to calculate the three-phase predicted current. The minimum value of the evaluation function is used as a constraint to determine the three-phase predicted current, and the discrete state equation of the inverter system is solved to obtain the optimal output voltage vector of the inverter system. Diophantine equations are constructed based on the optimal output voltage vector and the discrete state-space equations of the inverter system. The output switching state of the three-phase asymmetric hybrid cascaded inverter system is obtained and output by solving the Diophantine equation; Using the minimum value of the evaluation function as a constraint, the discrete state equations of the inverter system are solved to obtain the optimal output voltage vector of the inverter system. The expression for the optimal output voltage vector is as follows: ； in, and This represents the optimal output voltage vector of the inverter system. i α (k) and i β (k) represents the inverter system in αβ The three-phase sampled current at time k in the coordinate system. i αref (k+1) and i βref (k+1) is αβ The three-phase reference current at time k+1 in the coordinate system. L For load inductance, R For load resistance, T s The sampling period is V dc，eq The equivalent bus voltage of a three-phase asymmetrical hybrid cascaded inverter is given by the following definition: V dc，eq The calculation formula is: ； in, V dc1 and V dc2 These are the voltage values ​​of the two independent DC voltage sources in a three-phase asymmetrical hybrid cascaded inverter. D for V dc1 and V dc2 The ratio; Based on the optimal output voltage vector and the discrete state-space equations of the inverter system, a Diophantine equation is constructed, which is: ； in, and The optimal output voltage vector of the inverter system, and the output level matrix of the inverter system. The values ​​of each element are in the range of [-N, N], where N is the level number. When D=1, N=3; when D=2, N=4.

2. The three-phase asymmetric hybrid cascade inverter predictive control method according to claim 1, characterized in that, The evaluation function expression for the AC output current of the inverter system is as follows: ； in, , , i α (k+1) and i β (k+1) is αβ The predicted three-phase current at time k+1 in the coordinate system. i αref (k+1) and i βref (k+1) is αβ The three-phase reference current at time k+1 in the coordinate system.

3. The three-phase asymmetric hybrid cascade inverter predictive control method according to claim 1, characterized in that, The output switching states of the three-phase asymmetric hybrid cascaded inverter system are obtained and output by solving the Diophantine equation. The general solution of the Diophantine equation represents the switching states of the system, and its expression is as follows: ； in, It is the output level matrix of the inverter system. ， ， N represents the level number.

4. The three-phase asymmetric hybrid cascade inverter predictive control method according to claim 3, characterized in that, Pick and of the median.

5. The predictive control method for a three-phase asymmetric hybrid cascaded inverter according to claim 1, characterized in that, The continuous-time-domain state-space equations of the three-phase asymmetric hybrid cascaded inverter system in the αβ coordinate system are established as follows: Based on the inverter system topology, the relationship between the output state variables and the output voltage of the inverter system in the three-phase abc coordinate system is obtained. Based on the Clark transformation matrix, the state-space equations of the inverter system in the αβ coordinate system are obtained; According to Kirchhoff's laws, the state-space equations of the inverter system on the AC output side in the αβ coordinate system are obtained as follows: ； in, i α and i β The AC output current is in the αβ coordinate system. S a , S b , S c This refers to the inverter voltage level state. L For load inductance, R For load resistance, V dc，eq The equivalent bus voltage of a three-phase asymmetrical hybrid cascaded inverter is given by the following definition: V dc，eq The calculation formula is: ； in, V dc1 and V dc2 These are the voltage values ​​of the two independent DC voltage sources in a three-phase asymmetrical hybrid cascaded inverter. D for V dc1 and V dc2 The ratio of .

6. The predictive control method for a three-phase asymmetric hybrid cascaded inverter according to claim 1, characterized in that, The three-phase asymmetric hybrid cascaded inverter system is discretized using the trapezoidal integral formula, yielding the discrete state equations of the inverter system. These discrete state equations are: ； in, i α (k+1) and i β (k+1) is αβ The predicted three-phase current at time k+1 in the coordinate system. i α (k) and i β (k) is αβ The three-phase sampled current at time k in the coordinate system. L For load inductance, R For load resistance, T s The sampling period is S a , S b , S c This refers to the inverter voltage level state. V dc，eq The equivalent bus voltage of a three-phase asymmetrical hybrid cascaded inverter is given by the following definition: V dc，eq The calculation formula is: ； in, V dc1 and V dc2 These are the voltage values ​​of the two independent DC voltage sources in a three-phase asymmetrical hybrid cascaded inverter. D for V dc1 and V dc2 The ratio of .

7. The predictive control method for a three-phase asymmetric hybrid cascaded inverter according to claim 3, characterized in that, When the evaluation function is 0, the voltage vector of the inverter system is the optimal output voltage vector. Substituting the optimal output voltage vector into the Diophantine equation and solving the Diophantine equation yields the optimal output switching state of the three-phase asymmetrical hybrid cascaded inverter system; and / or, The number of output levels of an inverter system varies depending on the voltage ratio of its independent DC sources.

8. A three-phase asymmetric hybrid cascaded inverter system, characterized in that, The system includes a three-phase asymmetric hybrid cascaded inverter and a processor, wherein the processor performs predictive control of the three-phase asymmetric hybrid cascaded inverter system using the method described in any one of claims 1 to 7.

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