A control method and a control system for a three-level converter

Abstract

Embodiments of the present invention provide a control method and a control system for a three-level converter. Among them, the method includes: determining a corresponding voltage-current equation based on the topological structure of the three-level converter; determining a pulse modulation signal by combining dynamic evolution control with the voltage-current equation, and outputting the pulse modulation signal to achieve the control of the three-level converter. The embodiments of the present invention can improve the robustness of the three-level converter during operation.

Description

Technical Field

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

[0002] With the continuous progress 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 strategies of three-level converters usually involve complex algorithms and require precise modulation strategies to ensure the correct execution of switching operations. The performance of these control strategies often depends on the accuracy of system parameters. When the system is subjected to transient or continuous disturbances, changes in parameters may lead to a significant reduction in 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, the embodiments of the present invention provide a control method and a system for a three-level converter, which can improve the robustness of the three-level converter system.

[0006] To achieve the above object, in a first aspect, the embodiments of the present invention provide a control method for a three-level converter, including:

[0007] Based on the topology of the three-level converter, determine the corresponding voltage-current equation;

[0008] Determine a pulse modulation signal by combining dynamic evolution control with the voltage-current equation, and output the pulse modulation signal to control the 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 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.

[0010] Optionally, the determining a pulse modulation signal by combining dynamic evolution control with the voltage-current equation includes:

[0011] Based on the voltage-current equation of the three-level converter, obtain the proportional relationship between the first duty cycle and the second duty cycle corresponding to the modulation pulse signal. 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 a dynamic evolution control strategy;

[0013] Output a first pulse modulation signal and a second pulse modulation signal by using a dynamic evolution control strategy in combination with a proportional relationship.

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

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

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

[0017] Combine the linear function and the initial dynamic evolution strategy to obtain a first constraint relationship of the three-level converter, where the first constraint relationship is the relationship when the voltages across the first capacitor and the second capacitor are in an actual balanced state;

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

[0019] Process the voltage-current equation by using the second constraint relationship to obtain the relationship under the expected balanced state;

[0020] Combine the equations under the first constraint relationship and the second constraint relationship to obtain the dynamic evolution control strategy.

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

[0022] Optionally, in the topological structure of the three-level converter, there are 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 the first pulse modulation signal, and the third switching tube and the fourth switching tube are controlled by the 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, configured to determine a corresponding voltage-current equation based on the topological structure of the three-level converter;

[0025] A dynamic evolution controller, configured to determine a pulse modulation signal by combining dynamic evolution control with the voltage-current equation, and output the pulse modulation signal to implement the control of the 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 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.

[0027] Optionally, determining the pulse modulation signal by combining dynamic evolution control with the voltage-current equation includes:

[0028] Obtaining the proportional relationship between the first duty cycle and the second duty cycle corresponding to the modulation pulse signal based on the voltage-current equation of the three-level converter, where 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] Generating a dynamic evolution control strategy;

[0030] Using the dynamic evolution control strategy in combination with the proportional relationship to output the first pulse modulation signal and the second pulse modulation signal.

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

[0032] Selecting the exponential evolution path corresponding to the dynamic evolution control to generate an initial dynamic evolution strategy;

[0033] Determining the linear function of the voltage error;

[0034] Combining the linear function and the initial dynamic evolution strategy to obtain the first constraint relationship of the three-level converter, where the first constraint relationship is the relationship when the voltages across the first capacitor and the second capacitor are in the actual balanced state;

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

[0036] Processing the voltage-current equation using the second constraint relationship to obtain the relationship under the expected balanced state;

[0037] Combining the equations under the first constraint relationship and the second constraint relationship to obtain the dynamic evolution control strategy.

[0038] The embodiments of the present invention disclose the use of a dynamic evolution control method to achieve the control of a three-level converter. The design is relatively simple. By dynamically controlling the parameter changes of the current and voltage, the precise control of the three-level converter is realized. When the load undergoes a transient change, the dynamic evolution control can timely adjust the output voltage to compensate for the influence brought by the load change and ensure the stability of the output voltage. It can be seen that the control method in the embodiments of the present invention can quickly respond to the load change and the fluctuation of the input voltage, thereby reducing the fluctuation of the system output and improving the robustness and reliability of the system. Description of the Drawings

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only the embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on the provided accompanying drawings.

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

[0041] Figure 2 It is a step schematic diagram of the control method of the three-level converter provided by the embodiment of the present invention.

[0042] Figure 3 It is a schematic diagram of the topological structure of the three-level converter provided by the embodiment of the present invention.

[0043] Figure 4 It is a schematic diagram of the principle for the dynamic evolution controller provided by the embodiment of the present invention to generate the first pulse modulation signal and the second pulse modulation signal.

[0044] Figure 5 It is a process diagram for the dynamic evolution controller provided by the embodiment of the present invention to generate the first pulse modulation signal and the second pulse modulation signal.

[0045] Figure 6 It is a schematic diagram of the simulation verification result provided by the embodiment of the present invention. Detailed implementation manners

[0046] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0047] Figure 1 It is a typical application scenario block diagram 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 redundant power generated by the photovoltaic system can be used to charge and store energy in 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 discharge to supplement the power energy required by the load Rdc through the three-level converter.

[0048] The three-level converter disclosed in this application can be connected to a movable full-scenario photovoltaic energy storage system. The movable full-scenario photovoltaic energy storage system is a new type of photovoltaic energy storage system based on lithium iron phosphate batteries, intelligent battery management systems (BMS), and inverter systems. It is widely used in scenarios such as emergency disaster relief and backup power supplies for important loads. 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, proportional-integral (PI) control is adopted during the operation of the converter. It should be noted that the PI controller usually assumes that the system is fixed and linear when designed. 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 inventor found that (Dynamic Evolution Control, DEC) can force the error function to gradually approach 0 over time, realizing strict error regulation of the parameters in the operating 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, the embodiments of the present invention provide a control method for a three-level converter, refer to Figure 2 As shown, its control process includes:

[0052] S1. Based on the topology of the three-level converter, determine the corresponding voltage-current equation;

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

[0054] The embodiments of the present invention disclose the use of the dynamic evolution control method to achieve the control of the three-level converter. The design is relatively simple. By dynamically controlling the parameter changes of the current and voltage, precise control of the three-level converter is achieved. When the load undergoes a transient change, the dynamic evolution control can timely adjust the output voltage to compensate for the influence brought by the load change and ensure the stability of the output voltage. It can be seen that the control method in the embodiments of the present invention can quickly respond to load changes and fluctuations in the input voltage, thereby reducing the fluctuations in the system output and improving the robustness and reliability of the system.

[0055] Specifically, in the embodiments of the present invention, the pulse width modulation (PWM) signal includes a first pulse width modulation signal (pwm1) and a second pulse width modulation signal (pwm2). The first pulse width modulation signal is used to adjust the voltage across the first capacitor in the three-level converter, and the second pulse width 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 topology of the three-level converter, there are four switching tubes, namely the first switching tube, the second switching tube, the third switching tube, and the fourth switching tube (S1A, S2A, S3A, S4A). The first switching tube and the second switching tube are controlled by the first pulse width modulation signal, and the third switching tube and the fourth switching tube are controlled by the second pulse width modulation signal. The first capacitor C1 is connected across S1A and S2A, and the second capacitor C2 is connected across 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 boost circuit. Among them, 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 (step-up mode). When the three-level converter is in boost mode, the inductor Lpv of the boost circuit and the power switching tube Qpv cooperate to work. 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] In the embodiments of the present invention, the first pulse width modulation signal and the second pulse width modulation signal are generated by using dynamic evolution control (DEC) in combination with voltage-current equations to determine the pulse width modulation signal. Figure 4 This is the schematic diagram for the dynamic evolution controller provided in the embodiments of the present invention to generate the first pulse width modulation signal and the second pulse width modulation signal. Refer to Figure 4As shown in the figure, based on the parameter settings of the voltage-current equation of the three-level converter, the dynamic evolution control method is adopted. According to the voltage-current equation obtained from the main circuit, corresponding pulse width modulation signals (Pulse Width Modulation, pwm), namely pwm1 and pwm2, can be generated. The generated pwm1 and pwm2 can control the opening and closing of the switching tubes (S1A, S2A, S3A, S4A) of the main circuit, and at the same time, the voltage balance across the capacitors C1 and C2 can be maintained. Finally, the normal operation of the three-level converter can be realized.

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

[0060] Step S21: Obtain the proportional relationship between the first duty cycle and the second duty cycle corresponding to the modulation pulse signal based on the voltage-current equation of the three-level converter. 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;

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

[0062]

[0063]

[0064] where d 1 , d 2 are the duty cycles of pwm1 and pwm2 respectively, d 1 is the first duty cycle, and d 2 is the second duty cycle. From Equation 2, the following proportional relationship between d 1 and d 2 can be obtained:

[0065]

[0066] Step S22: Generate a dynamic evolution control strategy;

[0067] The dynamic evolution control strategy (Dynamic Evolution Control, abbreviated as DEC) is an advanced non-linear control method, which is executed 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 through the dynamic adjustment of the control parameters, the system output can quickly and accurately respond to input changes, while improving the stability and robustness of the system.

[0068] In an optional implementation, the steps to generate a dynamic evolution control strategy can be:

[0069] Step S221: Select the exponential evolution path corresponding to the dynamic evolution control to generate an initial dynamic evolution strategy;

[0070] Step S222: Determine the linear function of the voltage error;

[0071] Step S223: Combine the linear function and the initial dynamic evolution strategy to obtain the first constraint relationship of the three-level converter, where the first constraint relationship is the relationship when the voltages across the first capacitor and the second capacitor are in an actual balanced state;

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

[0073] Step S225: Process the voltage-current equation using the second constraint relationship to obtain the relationship under the expected balanced state;

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

[0075] In order to implement the generation of the above steps, in an alternative implementation, it is necessary to first select the exponential evolution path corresponding to the dynamic evolution control. Specifically:

[0076]

[0077] Among them, 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, indicating the rate at which the initial voltage error decreases exponentially to zero. Take the derivative of both sides of Equation 4 to obtain the initial dynamic evolution strategy in the embodiments of the present invention. Specifically:

[0078]

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

[0080]

[0081] Among them, k is the gain coefficient. Substitute Equation 6 into Equation 5 to obtain:

[0082]

[0083] In Equation 7, determine v e (t) = v ref - v dc , v ref is the reference value of v dc of vdc is the high - voltage side voltage of the three - level converter, v e (t) is v dc and the reference value v ref of the voltage error. Therefore, Equation 7 can ultimately be expressed as:

[0084]

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

[0086]

[0087] Combining Equation 8 and Equation 9, we can obtain:

[0088]

[0089] Combining Equation 3 and Equation 10, we can obtain the final control equation regarding d 1 and d 2 :

[0090]

[0091]

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

[0093] Step S23: Use the dynamic evolution control strategy combined with the proportional relationship to output the first pulse modulation signal and the second pulse modulation signal.

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

[0095] Based on the above - mentioned control process, the embodiment of the present invention further conducts simulation verification, and the simulation results are as Figure 6 shown, and the specific parameters are as 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[Converter main circuit parameters (c 1 , c 2 )]]> 440uF 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 content in this application Figure 6As shown, during the time period from t1 to t2, the current of the photovoltaic system set is i pv = 4 A, and the load current i dc1 = 3 A. Therefore, the output power of the photovoltaic system is 1.32 kW, and the load power is 1.8 kW. So the super energy storage system discharges to supplement the power consumed by the load, and i sc is in the discharging state, and at this time, the SOC sc slope drops and the super energy storage system discharges.

[0099] During the time period from t2 to t3, the current of the photovoltaic system set is i pv = 8 A, and the load current i dc1 = 3 A. Therefore, the output power of the photovoltaic system is 2.64 kW, and the load power is 1.8 kW. So the super energy storage system is in the charging state to store the excess power of the photovoltaic system, and i sc is in the charging state, and at this time, the SOC sc slope rises and the super energy storage system charges.

[0100] During the time period greater than t3, the current of the photovoltaic system set is i pv = 8 A, and the load current i dc1 = 6 A. Therefore, the output power of the photovoltaic system is 2.64 kW, and the load power is 3.6 kW. So the super energy storage system discharges to supplement the power consumed by the load, and i sc is in the discharging state, and at this time, the SOC sc slope drops and the super energy storage system discharges.

[0101] On the entire time axis, the voltage v dc remains the same as v ref , and the voltages across the capacitors c 1 and c 2 are maintained at an equilibrium 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 also provide a control system for a three-level converter, and this control system for a three-level converter can execute the control method for a three-level converter provided in any of the above embodiments.

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

[0104] A calculation module, configured to determine the corresponding voltage-current equation based on the topology of the three-level converter;

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

[0106] In an alternative 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 alternative embodiment, a dynamic evolution controller is used to determine a pulse modulation signal by combining a voltage-current equation through dynamic evolution control, and includes:

[0108] Obtain the proportional relationship between the first duty cycle and the second duty cycle corresponding to the modulation pulse signal based on the voltage-current equation of the three-level converter. 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 a dynamic evolution control strategy;

[0110] Use the dynamic evolution control strategy in combination with the proportional relationship to output the first pulse modulation signal and the second pulse modulation signal.

[0111] In an alternative embodiment, a dynamic evolution controller is used to generate a dynamic evolution control strategy, and includes:

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

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

[0114] Combine the linear function and the initial dynamic evolution strategy to obtain a first constraint relationship of the three-level converter. The first constraint relationship is the relationship when the voltages across the first capacitor and the second capacitor are in an actual balanced state;

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

[0116] Use the second constraint relationship to process the voltage-current equation to obtain the relationship under the expected balanced state;

[0117] Combine the equations under the first constraint relationship and the second constraint relationship to obtain a dynamic evolution control strategy.

[0118] In an alternative embodiment, the pulse modulation signal includes proportion and differentiation.

[0119] In an alternative embodiment, in the topology of the three-level converter, there are four switching tubes, namely the first switching tube, the second switching tube, the third switching tube, and the 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 embodiment solutions provided by the embodiments of the present invention. Each alternative described in each embodiment solution can be combined and cross-referenced with each other without conflict, thereby extending multiple possible embodiment solutions, all of which can be considered as the embodiment solutions disclosed and made public by the embodiments of the present invention.

[0121] Although the embodiments of the present invention are disclosed as above, the present application is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, the protection scope of the present application should 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; Determine a pulse modulation signal by combining a voltage-current equation with a dynamic evolution control, output the pulse modulation signal to achieve control of the three-level converter, 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; 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; Using a dynamic evolution control strategy combined with a proportional relationship, outputting a first pulse modulation signal and a second pulse modulation signal; 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.

2. 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.

3. 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.

4. 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, used to determine a pulse modulation signal by combining a voltage-current equation through dynamic evolution control, and output the pulse modulation signal to realize control of the three-level converter, wherein 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 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; 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; Using a dynamic evolution control strategy combined with a proportional relationship, outputting a first pulse modulation signal and a second pulse modulation signal; 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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