Control method and control system of three-level converter

Abstract

The embodiment of the invention provides a control method and system of a three-level converter, and the method comprises the steps: determining a corresponding voltage and current equation based on a topological structure of the three-level converter; and determining a pulse modulation signal through dynamic evolution control in combination with a voltage and current equation, and outputting the pulse modulation signal to realize control of the three-level converter. According to the embodiment of the invention, the robustness of the three-level converter in the operation process can be improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of converter control, and in particular to a control method and a control system for a three-level converter. Background Art

[0002] With the continuous advancement of power electronics technology, three-level converters have been widely used in the field of high voltage and high power conversion due to their advantages such as high efficiency, low loss and high power density.

[0003] In practical applications, the control strategy of three-level converters usually involves complex algorithms and requires precise modulation strategies to ensure the correct execution of switching actions. The performance of these control strategies often depends on the accuracy of system parameters. When the system is subjected to transient or continuous disturbances, parameter changes may lead to significant degradation of control performance.

[0004] Therefore, there is an urgent need to provide a control method for a three-level converter to improve the robustness of the three-level converter system. Summary of the invention

[0005] In view of this, an embodiment of the present invention provides a control method and system for a three-level converter, which can improve the robustness of the three-level converter system.

[0006] To achieve the above objectives, in a first aspect, an embodiment of the present invention provides a control method for a three-level converter, comprising:

[0007] Based on the topological structure of the three-level converter, determine the corresponding voltage and current equations;

[0008] A pulse modulation signal is determined by combining dynamic evolution control with voltage and current equations, and the pulse modulation signal is output to realize control of a three-level converter.

[0009] Optionally, the pulse modulation signal includes a first pulse modulation signal and a second pulse modulation signal, the first pulse modulation signal is used to adjust the voltage across a first capacitor in the three-level converter, and the second pulse modulation signal is used to adjust the voltage across a second capacitor in the three-level converter.

[0010] Optionally, the determining of the pulse modulation signal by combining the voltage and current equations through dynamic evolution control includes:

[0011] Based on the voltage-current equation of the three-level converter, a proportional relationship between a first duty cycle and a second duty cycle corresponding to the modulated pulse signal is obtained, wherein the first duty cycle is the duty cycle corresponding to the first pulse modulation signal, and the second duty cycle is the duty cycle corresponding to the second pulse modulation signal;

[0012] Generate dynamically evolving control strategies;

[0013] A dynamic evolution control strategy is used in combination with a proportional relationship to output a first pulse modulation signal and a second pulse modulation signal.

[0014] Optionally, the generating a dynamic evolution control strategy includes:

[0015] Select the exponential evolution path corresponding to the dynamic evolution control and generate the initial dynamic evolution strategy;

[0016] Determine a linear function of the voltage error;

[0017] Combining the linear function with the initial dynamic evolution strategy to obtain a first constraint relationship of the three-level converter, wherein the first constraint relationship is a relationship in which the voltages across the first capacitor and the second capacitor are in an actual equilibrium state;

[0018] Determine a second constraint relationship, wherein the second constraint relationship is a relationship between a high-voltage side voltage of the three-level converter and a first load voltage and a second load voltage;

[0019] The voltage-current equation is processed by using the second constraint relationship to obtain the relationship under the expected equilibrium state;

[0020] Combining the equations under the first constraint relationship and the second constraint relationship, a dynamic evolution control strategy is obtained.

[0021] Optionally, the pulse modulation signal includes proportion and differentiation.

[0022] Optionally, the topology structure of the three-level converter includes four switching tubes, namely a first switching tube, a second switching tube, a third switching tube and a fourth switching tube. The first switching tube and the second switching tube are controlled by a first pulse modulation signal, and the third switching tube and the fourth switching tube are controlled by a second pulse modulation signal.

[0023] In a second aspect, an embodiment of the present invention provides a control system for a three-level converter, including:

[0024] A calculation module, used for determining a corresponding voltage and current equation based on a topological structure of a three-level converter;

[0025] A dynamic evolution controller is used to determine a pulse modulation signal by combining a voltage and current equation through dynamic evolution control, and output the pulse modulation signal to realize control of a three-level converter.

[0026] Optionally, the pulse modulation signal includes a first pulse modulation signal and a second pulse modulation signal, the first pulse modulation signal is used to adjust the voltage across a first capacitor in the three-level converter, and the second pulse modulation signal is used to adjust the voltage across a second capacitor in the three-level converter.

[0027] Optionally, the determining of the pulse modulation signal by combining the voltage and current equations through dynamic evolution control includes:

[0028] Based on the voltage-current equation of the three-level converter, a proportional relationship between a first duty cycle and a second duty cycle corresponding to the modulated pulse signal is obtained, wherein the first duty cycle is the duty cycle corresponding to the first pulse modulation signal, and the second duty cycle is the duty cycle corresponding to the second pulse modulation signal;

[0029] Generate dynamically evolving control strategies;

[0030] A dynamic evolution control strategy is used in combination with a proportional relationship to output a first pulse modulation signal and a second pulse modulation signal.

[0031] Optionally, the generating a dynamic evolution control strategy includes:

[0032] Select the exponential evolution path corresponding to the dynamic evolution control and generate the initial dynamic evolution strategy;

[0033] Determine a linear function of the voltage error;

[0034] Combining the linear function with the initial dynamic evolution strategy to obtain a first constraint relationship of the three-level converter, wherein the first constraint relationship is a relationship in which the voltages across the first capacitor and the second capacitor are in an actual equilibrium state;

[0035] Determine a second constraint relationship, wherein the second constraint relationship is a relationship between a high-voltage side voltage of the three-level converter and a first load voltage and a second load voltage;

[0036] The voltage-current equation is processed by using the second constraint relationship to obtain the relationship under the expected equilibrium state;

[0037] Combining the equations under the first constraint relationship and the second constraint relationship, a dynamic evolution control strategy is obtained.

[0038] The embodiment of the present invention discloses a method for controlling a three-level converter by using a dynamic evolution control method. The design is relatively simple. By dynamically controlling the parameter changes of current and voltage, the three-level converter is precisely controlled. When the load changes transiently, the dynamic evolution control can adjust the output voltage in time to compensate for the impact of the load change and ensure the stability of the output voltage. It can be seen that the control method in the embodiment of the present invention can quickly respond to load changes and fluctuations in input voltage, thereby reducing fluctuations in system output and improving the robustness and reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0040] Figure 1 This is a block diagram of a typical application scenario of a three-level converter in photovoltaic energy storage.

[0041] Figure 2 A schematic diagram of the steps of a control method for a three-level converter provided by an embodiment of the present invention.

[0042] Figure 3 A schematic diagram of the topological structure of a three-level converter provided in an embodiment of the present invention.

[0043] Figure 4 A schematic diagram of a dynamic evolution controller providing an embodiment of the present invention for generating a first pulse modulation signal and a second pulse modulation signal.

[0044] Figure 5 A process diagram of a dynamic evolution controller providing an embodiment of the present invention generating a first pulse modulation signal and a second pulse modulation signal.

[0045] Figure 6 A schematic diagram of a simulation verification result provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0047] Figure 1 The figure is a block diagram of a typical application scenario of a three-level converter in photovoltaic energy storage. When the power generated by the photovoltaic system (PV System) is greater than the power consumed by the converter load Rdc, the excess power generated by the photovoltaic system can be used to charge and store the supercapacitor energy storage system (SC System) through the three-level converter; when the power generated by the photovoltaic system (PV System) is less than the power consumed by the converter load Rdc, the SC System can also be discharged through the three-level converter to supplement the power energy required by the load Rdc.

[0048] The three-level converter disclosed in the present application can be connected to a mobile full-scenario photovoltaic energy storage system. The mobile full-scenario photovoltaic energy storage system is a new photovoltaic energy storage system based on lithium iron phosphate batteries, intelligent battery management system (BMS) and inverter system. It is widely used in emergency rescue, important load backup power supply and other scenarios. The three-level converter can control the charging and discharging of the battery energy storage system, thereby improving the efficiency and reliability of the system.

[0049] Generally speaking, Proportional Integration (PI) control is used in the working process of the converter. It should be noted that the PI controller is usually designed with the assumption that the system is fixed and linear. If the load or system parameters of the converter change, the PI controller may not be able to adapt to these changes, which may lead to performance degradation.

[0050] Based on this, the inventors found that (Dynamic Evolution Control, DEC) can force the error function to gradually approach 0 over time, achieving strict error adjustment of the parameters under the working state of the three-level converter, thereby effectively improving the stability and robustness of the control system corresponding to the three-level converter.

[0051] Based on the above, an embodiment of the present invention provides a control method for a three-level converter. Figure 2 As shown, the control process includes:

[0052] S1. Determine the corresponding voltage and current equation based on the topological structure of the three-level converter;

[0053] S2. Determine the pulse modulation signal through dynamic evolution control combined with voltage and current equations, and use the pulse modulation signal to control the three-level converter.

[0054] The embodiment of the present invention discloses a method for controlling a three-level converter by using a dynamic evolution control method. The design is relatively simple. By dynamically controlling the parameter changes of current and voltage, the three-level converter is precisely controlled. When the load changes transiently, the dynamic evolution control can adjust the output voltage in time to compensate for the impact of the load change and ensure the stability of the output voltage. It can be seen that the control method in the embodiment of the present invention can quickly respond to load changes and fluctuations in input voltage, thereby reducing fluctuations in system output and improving the robustness and reliability of the system.

[0055] Specifically, in an embodiment of the present invention, the pulse modulation signal (Pulse Width Modulation, pwm) includes a first pulse modulation signal (pwm1) and a second pulse modulation signal (pwm2), the first pulse modulation signal is used to adjust the voltage across the first capacitor in the three-level converter, and the second pulse modulation signal is used to adjust the voltage across the second capacitor in the three-level converter.

[0056] The topology of the three-level converter can be referred to Figure 3 As shown, in the topological structure of the three-level converter, four switch tubes are included, namely the first switch tube, the second switch tube, the third switch tube and the fourth switch tube (S1A, S2A, S3A, S4A), the first switch tube and the second switch tube are controlled by the first pulse modulation signal, the third switch tube and the fourth switch tube are controlled by the second pulse modulation signal, the first capacitor C1 straddles S1A and S2A, and the second capacitor C2 straddles S3A and S4A. The voltages across capacitors C1 and C2 are represented by Vc1 and Vc2, respectively. The DC load Rdc is directly connected to the high-voltage side Vdc of the three-level converter, and its load current is represented by Idcl.

[0057] The photovoltaic system (PV System) is connected to the high voltage side Vdc of the three-level converter through a boost circuit, where the current and voltage of the photovoltaic PV are represented by Ipv and Vpv respectively. The working mode of the three-level converter is divided into buck mode (step-down mode) or boost mode (boost mode). When the three-level converter is in boost mode, the inductor Lpv and the power switch tube Qpv of the boost circuit work together. At the same time, the supercapacitor system (SC System) is directly connected to the low voltage side of the three-level converter. The current and voltage at the supercapacitor system end are represented by Isc and Vsc respectively.

[0058] The first pulse modulation signal and the second pulse modulation signal in the embodiment of the present invention are generated by using Dynamic Evolution Control (DEC) combined with voltage and current equations to determine the pulse modulation signal generation. Figure 4 A schematic diagram of a dynamic evolution controller according to an embodiment of the present invention generating a first pulse modulation signal and a second pulse modulation signal. Figure 4As shown in the figure, based on the parameter setting of the voltage and current equation of the three-level converter, the dynamic evolution control method is adopted, and the corresponding pulse width modulation signal (PulseWidth Modulation, pwm), namely pwm1 and pwm2, can be generated according to the voltage and current equation obtained from the main circuit. The generated pwm1 and pwm2 can control the opening and closing of the switch tube of the main circuit (S1A, S2A, S3A, S4A), and at the same time can maintain the voltage balance across the capacitors C1 and C2, and finally realize the normal operation of the three-level converter.

[0059] In this application, the pulse modulation signal is determined by combining the voltage and current equations through dynamic evolution control. The specific process includes:

[0060] Step S21: obtaining a proportional relationship between a first duty cycle and a second duty cycle corresponding to a modulated pulse signal based on a voltage-current equation of a three-level converter, wherein the first duty cycle is a duty cycle corresponding to a first pulse modulation signal, and the second duty cycle is a duty cycle corresponding to a second pulse modulation signal;

[0061] In an optional implementation, Kirchhoff's voltage and current equation can be listed based on the topology of the three-level converter, as well as the inductor Lsc and the capacitors C1 and C2:

[0062]

[0063]

[0064] Where, d1 and d2 are the duty cycles of pwm1 and pwm2 respectively, d1 is the first duty cycle, and d2 is the second duty cycle. From formula 2, we can get the following proportional relationship between d1 and d2:

[0065]

[0066] Step S22, generating a dynamic evolution control strategy;

[0067] Dynamic Evolution Control (DEC) is an advanced nonlinear control method implemented by a dynamic evolution controller. The core idea of ​​the dynamic evolution control strategy is to use the error function as the evolution path and dynamically adjust the control parameters so that the system output can respond quickly and accurately to input changes, while improving the stability and robustness of the system.

[0068] In an optional implementation, the steps of generating a dynamic evolution control strategy may be:

[0069] Step S221, selecting an exponential evolution path corresponding to the dynamic evolution control, and generating an initial dynamic evolution strategy;

[0070] Step S222, determining a linear function of the voltage error;

[0071] Step S223, combining the linear function and the initial dynamic evolution strategy to obtain a first constraint relationship of the three-level converter, wherein the first constraint relationship is a relationship in which the voltages across the first capacitor and the second capacitor are in an actual equilibrium state;

[0072] Step S224, determining a second constraint relationship, wherein the second constraint relationship is a relationship between the high-side voltage of the three-level converter and the first load voltage and the second load voltage;

[0073] Step S225, using the second constraint relationship to process the voltage-current equation to obtain a relationship under an expected equilibrium state;

[0074] Step S226: Combine the equations under the first constraint relationship and the second constraint relationship to obtain a dynamic evolution control strategy.

[0075] In order to realize the generation of the above steps, in the optional implementation, it is necessary to first select the exponential evolution path corresponding to the dynamic evolution control, specifically:

[0076]

[0077] in, is the dynamic characteristic of the system voltage error, indicating that the voltage error decreases exponentially with time, v eo is the initial voltage error, and m is the exponential coefficient, which indicates the rate at which the initial voltage error decreases to zero exponentially. By taking the derivative of both sides of formula 4, the initial dynamic evolution strategy in the embodiment of the present invention is obtained, specifically:

[0078]

[0079] In practical applications, a linear function of voltage error is generally defined as:

[0080]

[0081] Where k is the gain factor. Substituting Equation 6 into Equation 5 yields:

[0082]

[0083] In formula 7, determine v e (t) = v ref -v dc , v ref v dc The reference value, v dc is the high-side voltage of the three-level converter, v e (t) is v dc With reference value v refTherefore, Equation 7 can be finally expressed as:

[0084]

[0085] From the topology of the three-level converter, we can get v dc =v c1 +v c2 , so Formula 1 can be expressed as:

[0086]

[0087] Combining Formula 8 and Formula 9, we can get:

[0088]

[0089] Combining equation 3 and equation 10, we can get the final control equation for d1 and d2:

[0090]

[0091]

[0092] The coefficients are the voltage and current parameters and controller coefficients of the main circuit, combined with MATLAB / simulink Figure 5 Can represent a specific dynamic evolution controller.

[0093] Step S23: using a dynamic evolution control strategy in combination with a proportional relationship to output a first pulse modulation signal and a second pulse modulation signal.

[0094] The dynamic evolution controller provided by the embodiment of the present invention can dynamically process and output real-time control signals based on the parameters transmitted when the system is subjected to transient or continuous disturbances, quickly respond to load changes and system disturbances, achieve precise control of the three-level converter, reduce fluctuations in the system output, and improve the robustness and reliability of the system.

[0095] Based on the above control process, the embodiment of the present invention further performs simulation verification, and the simulation results are as follows: Figure 6 The specific parameters are shown in Table 1 below:

[0096] Table 1

[0097] parameter value <![CDATA[PV voltage (v pv )]]> 330V <![CDATA[PV current (i pv )]]> 0～15A <![CDATA[SC voltage (v sc )]]> 280V <![CDATA[Converter main circuit parameters (L sc )]]> 5mH <![CDATA[Main circuit parameters of the converter (c1, c2)]]> 440uF The controller parameter k of the converter 2 Converter controller parameter m 1800 <![CDATA[Controller parameters v of the converter ref > 600V

[0098] Combined with the application Figure 6 As shown, during the time period t1-t2, the current of the photovoltaic system is set to i pv =4A, load current i dc1=3A. Therefore, the output power of the photovoltaic system is 1.32kw, and the load power is 1.8kw. Therefore, the super energy storage system discharges to supplement the power consumed by the load, i sc It is in the discharging state, at which SOC sc The slope decreases and the super energy storage system discharges.

[0099] In the time period t2-t3, the current of the photovoltaic system is set to i pv =8A, load current i dc1 =3A. Therefore, the output power of the photovoltaic system is 2.64kw, and the load power is 1.8kw. Therefore, the super energy storage system is used to charge and store the excess power of the photovoltaic system. sc In the charging state, SOC sc The slope rises and the super energy storage system charges.

[0100] In the period greater than t3, the current of the photovoltaic system is set to i pv =8A, load current i dc1 =6A. Therefore, the output power of the photovoltaic system is 2.64kw, and the load power is 3.6kw. Therefore, the super energy storage system discharges to supplement the power consumed by the load, i sc It is in the discharging state, at which SOC sc The slope decreases and the super energy storage system discharges.

[0101] Over the entire time axis, the voltage v dc Keep with v ref Similarly, the voltage across capacitors c1 and c2 is maintained at a balanced state of 300 V. The simulation results verify the effectiveness.

[0102] As another optional implementation of the disclosed content of the embodiments of the present invention, the embodiments of the present invention further provide a control system for a three-level converter, which can execute the control method for the three-level converter provided in any of the above embodiments.

[0103] Specifically, the control system of the three-level converter may specifically include:

[0104] A calculation module, used for determining a corresponding voltage and current equation based on a topological structure of a three-level converter;

[0105] A dynamic evolution controller is used to determine a pulse modulation signal by combining a voltage and current equation through dynamic evolution control, and output the pulse modulation signal to realize control of a three-level converter.

[0106] In an optional embodiment, the pulse modulation signal includes a first pulse modulation signal and a second pulse modulation signal, the first pulse modulation signal is used to adjust the voltage across the first capacitor in the three-level converter, and the second pulse modulation signal is used to adjust the voltage across the second capacitor in the three-level converter.

[0107] In an optional embodiment, a dynamic evolution controller is used to determine a pulse modulation signal by combining a voltage and current equation through dynamic evolution control, including:

[0108] Based on the voltage-current equation of the three-level converter, a proportional relationship between a first duty cycle and a second duty cycle corresponding to the modulated pulse signal is obtained, wherein the first duty cycle is the duty cycle corresponding to the first pulse modulation signal, and the second duty cycle is the duty cycle corresponding to the second pulse modulation signal;

[0109] Generate dynamically evolving control strategies;

[0110] A dynamic evolution control strategy is used in combination with a proportional relationship to output a first pulse modulation signal and a second pulse modulation signal.

[0111] In an optional embodiment, the dynamic evolution controller is used to generate a dynamic evolution control strategy, including:

[0112] Select the exponential evolution path corresponding to the dynamic evolution control and generate the initial dynamic evolution strategy;

[0113] Determine a linear function of the voltage error;

[0114] Combining the linear function with the initial dynamic evolution strategy to obtain a first constraint relationship of the three-level converter, wherein the first constraint relationship is a relationship in which the voltages across the first capacitor and the second capacitor are in an actual equilibrium state;

[0115] Determine a second constraint relationship, wherein the second constraint relationship is a relationship between a high-voltage side voltage of the three-level converter and a first load voltage and a second load voltage;

[0116] The voltage-current equation is processed by using the second constraint relationship to obtain the relationship under the expected equilibrium state;

[0117] Combining the equations under the first constraint relationship and the second constraint relationship, a dynamic evolution control strategy is obtained.

[0118] In an optional embodiment, the pulse modulation signal includes a proportion and a differential.

[0119] In an optional embodiment, the topology structure of the three-level converter includes four switching tubes, namely a first switching tube, a second switching tube, a third switching tube and a fourth switching tube. The first switching tube and the second switching tube are controlled by a first pulse modulation signal, and the third switching tube and the fourth switching tube are controlled by a second pulse modulation signal.

[0120] The above describes multiple implementation schemes provided by the embodiments of the present invention. The various optional methods introduced in the implementation schemes can be combined and cross-referenced with each other without conflict, thereby extending a variety of possible implementation schemes, which can all be considered as implementation schemes disclosed and open in the embodiments of the present invention.

[0121] Although the embodiments of the present invention are disclosed above, the present application is not limited thereto. Any person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present application. Therefore, the protection scope of the present application shall be subject to the scope defined by the claims.

Claims

1. A control method for a three-level converter, characterized in that: include: Based on the topological structure of the three-level converter, determine the corresponding voltage and current equations; A pulse modulation signal is determined by combining dynamic evolution control with voltage and current equations, and the pulse modulation signal is output to realize control of the three-level converter.

2. The control method of the three-level converter according to claim 1, characterized in that: The pulse modulation signal includes a first pulse modulation signal and a second pulse modulation signal, wherein the first pulse modulation signal is used to adjust the voltage across a first capacitor in a three-level converter, and the second pulse modulation signal is used to adjust the voltage across a second capacitor in the three-level converter.

3. The control method of the three-level converter according to claim 2, characterized in that: The method of determining the pulse modulation signal by combining the voltage and current equations with the dynamic evolution control includes: Based on the voltage-current equation of the three-level converter, a proportional relationship between a first duty cycle and a second duty cycle corresponding to the modulated pulse signal is obtained, wherein the first duty cycle is the duty cycle corresponding to the first pulse modulation signal, and the second duty cycle is the duty cycle corresponding to the second pulse modulation signal; Generate dynamically evolving control strategies; A dynamic evolution control strategy is used in combination with a proportional relationship to output a first pulse modulation signal and a second pulse modulation signal.

4. The control method of the three-level converter according to claim 3, characterized in that: The generating of the dynamic evolution control strategy comprises: Select the exponential evolution path corresponding to the dynamic evolution control and generate the initial dynamic evolution strategy; Determine a linear function of the voltage error; Combining the linear function with the initial dynamic evolution strategy to obtain a first constraint relationship of the three-level converter, wherein the first constraint relationship is a relationship in which the voltages across the first capacitor and the second capacitor are in an actual equilibrium state; Determine a second constraint relationship, wherein the second constraint relationship is a relationship between a high-voltage side voltage of the three-level converter and a first load voltage and a second load voltage; The voltage-current equation is processed using the second constraint relationship to obtain the relationship under the expected equilibrium state; Combining the equations under the first constraint relationship and the second constraint relationship, a dynamic evolution control strategy is obtained.

5. The control method of the three-level converter according to claim 1, characterized in that: The pulse modulation signal includes a proportional and a differential.

6. The control method of the three-level converter according to claim 1, characterized in that: The topological structure of the three-level converter includes four switching tubes, namely a first switching tube, a second switching tube, a third switching tube and a fourth switching tube. The first switching tube and the second switching tube are controlled by a first pulse modulation signal, and the third switching tube and the fourth switching tube are controlled by a second pulse modulation signal.

7. A control system for a three-level converter, characterized in that: include: A calculation module, used for determining a corresponding voltage and current equation based on a topological structure of a three-level converter; A dynamic evolution controller is used to determine a pulse modulation signal by combining a voltage and current equation through dynamic evolution control, and output the pulse modulation signal to realize control of a three-level converter.

8. The control system of the three-level converter according to claim 7, characterized in that: The pulse modulation signal includes a first pulse modulation signal and a second pulse modulation signal, wherein the first pulse modulation signal is used to adjust the voltage across a first capacitor in a three-level converter, and the second pulse modulation signal is used to adjust the voltage across a second capacitor in the three-level converter.

9. The control system of the three-level converter according to claim 8, characterized in that: The method of determining the pulse modulation signal by combining the voltage and current equations with the dynamic evolution control includes: Based on the voltage-current equation of the three-level converter, a proportional relationship between a first duty cycle and a second duty cycle corresponding to the modulated pulse signal is obtained, wherein the first duty cycle is the duty cycle corresponding to the first pulse modulation signal, and the second duty cycle is the duty cycle corresponding to the second pulse modulation signal; Generate dynamically evolving control strategies; A dynamic evolution control strategy is used in combination with a proportional relationship to output a first pulse modulation signal and a second pulse modulation signal.

10. The control system of the three-level converter according to claim 9, characterized in that: The generating of the dynamic evolution control strategy comprises: Select the exponential evolution path corresponding to the dynamic evolution control and generate the initial dynamic evolution strategy; Determine a linear function of the voltage error; Combining the linear function with the initial dynamic evolution strategy to obtain a first constraint relationship of the three-level converter, wherein the first constraint relationship is a relationship in which the voltages across the first capacitor and the second capacitor are in an actual equilibrium state; Determine a second constraint relationship, wherein the second constraint relationship is a relationship between a high-voltage side voltage of the three-level converter and a first load voltage and a second load voltage; The voltage-current equation is processed using the second constraint relationship to obtain the relationship under the expected equilibrium state; Combining the equations under the first constraint relationship and the second constraint relationship, a dynamic evolution control strategy is obtained.

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