Composite control method and system for optimizing dynamic performance of resonant converter

Abstract

The invention provides a composite control method and system for optimizing the dynamic performance of a resonant converter, and belongs to the technical field of power electronics, and the method comprises the steps: employing open-loop control when a load suddenly changes, matching a corresponding steady-state working point according to the input voltage and output current of a current resonant converter, and obtaining the output frequency of the open-loop control; receiving the output voltage of the resonant converter in real time, and obtaining the output frequency of closed-loop control based on the reference voltage of the resonant converter; and adding the output frequency of the open-loop control and the output frequency of the closed-loop control to obtain the switching frequency of the resonant converter. According to the invention, the dynamic response of the resonant converter under the working condition of large-range load abrupt change is optimized.

Description

Technical Field

[0001] The present application belongs to the field of power electronics technology, and more specifically, to a composite control method and system for optimizing the dynamic performance of a resonant converter. Background Art

[0002] With the rapid development of technologies such as cloud computing, big data, and artificial intelligence, the scale of data centers continues to expand, and the number of servers has increased dramatically, resulting in an increasing market demand for efficient and reliable server power supplies. At the same time, companies' demand for data processing capabilities is also increasing, which has put forward higher requirements for the power density and stability of power supplies. Server power supplies are particularly important in the wave of digital transformation.

[0003] In the field of server power supply, resonant converters have many advantages, such as: maintaining high efficiency over a wide load range; being able to work stably over a wide input voltage range, adapting to power supply in different regions and conditions; generating low electromagnetic interference (EMI) and having good electromagnetic compatibility, etc. At the same time, there are also many problems that need to be solved. One of the most significant problems is that the dynamic response of the resonant converter is poor under the condition of large-scale load mutation, which cannot meet the requirements of the server power supply for power quality stability. Summary of the invention

[0004] In view of the defects of the prior art, the purpose of the present application is to provide a composite control method and system for optimizing the dynamic performance of a resonant converter, aiming to solve the problem that the dynamic response of the resonant converter under a wide range of load mutation conditions is poor and cannot meet the power quality stability requirements of the server power supply.

[0005] To achieve the above objectives, on the one hand, the present application provides a composite control method for optimizing the dynamic performance of a resonant converter, comprising the following steps:

[0006] When a sudden load change occurs, open-loop control is used to match the corresponding steady-state operating point according to the current input voltage and output current of the resonant converter to obtain the output frequency of the open-loop control;

[0007] receiving the output voltage of the resonant converter in real time, and obtaining the output frequency of the closed-loop control based on the reference voltage of the resonant converter;

[0008] The output frequency of the open-loop control is added to the output frequency of the closed-loop control to obtain the switching frequency of the resonant converter.

[0009] Further preferably, the open-loop control specifically comprises the following steps:

[0010] The gain of the resonant cavity is obtained by dividing the rated input voltage of the resonant converter by the input voltage of the resonant converter; the output current of the resonant converter is multiplied by the proportional coefficient to convert into the corresponding quality factor;

[0011] When the gain and quality factor of the resonant cavity exceed a preset range, the corresponding frequency is looked up in the steady-state operating point table to obtain the output frequency of the open-loop control.

[0012] Further preferably, the method for obtaining the steady-state operating point table comprises the following steps:

[0013] According to the rated power of the resonant converter, the capacitance value of the resonant capacitor, the inductance value of the resonant inductor, the inductance value of the excitation inductor and the resonant frequency, a curve diagram of the gain of the resonant cavity versus the quality factor and the switching frequency of the resonant converter is obtained; wherein the X-axis represents the ratio between the switching frequency and the resonant frequency; and the Y-axis represents the gain of the resonant cavity;

[0014] A straight line parallel to the X-axis is drawn with the preset gain interval of the resonant cavity, and the intersection with the curve is the steady-state operating point at different loads under the input voltage represented by the current straight line; wherein different loads are characterized by the output current of the resonant converter;

[0015] The gains of different resonant cavities, different quality factors, and the ratio between the switching frequency and the resonant frequency are recorded in a table to obtain a steady-state operating point table.

[0016] Further preferably, the method for obtaining the proportionality coefficient is:

[0017] Calculate the load resistance of the resonant converter according to the output voltage and output current of the resonant converter;

[0018] Obtaining a primary side fundamental wave equivalent resistance based on a load resistance of the resonant converter and a turns ratio between a primary side and a secondary side of the resonant converter;

[0019] According to the type of resonant converter, combined with the primary side fundamental wave equivalent resistance, the relationship between the quality factor and the output current of the resonant converter is calculated to obtain the proportionality coefficient.

[0020] Further preferably, when the resonant converter is an LLC resonant converter, the proportionality coefficient is:

[0021]

[0022] Where k is the proportionality coefficient; C r is the capacitance value of the resonant capacitor; L r is the inductance of the resonant inductor; N is the turns ratio between the primary and secondary sides of the resonant transformer; V o is the output voltage of the resonant converter.

[0023] Further preferably, the closed-loop control specifically includes the following steps:

[0024] Subtract the output voltage of the resonant converter from the reference voltage of the resonant converter to obtain a voltage error signal;

[0025] The voltage error signal is proportionally integrated to obtain the output frequency of the closed-loop control.

[0026] On the other hand, the present application provides a composite control system for optimizing the dynamic performance of a resonant converter, comprising: an open-loop control module, a closed-loop control module, and an addition module;

[0027] The open-loop control module is used to adopt open-loop control when a sudden load change occurs. According to the input voltage and output current of the current resonant converter, the corresponding steady-state operating point is matched to obtain the output frequency of the open-loop control.

[0028] The closed-loop control module is used to receive the output voltage of the resonant converter in real time, and obtain the output frequency of the closed-loop control based on the reference voltage of the resonant converter;

[0029] The adding module is used to add the output frequency of the open-loop control and the output frequency of the closed-loop control to obtain the switching frequency of the resonant converter.

[0030] Further preferably, the open-loop control module comprises: a first multiplication unit, a second multiplication unit, and a steady-state operating point search unit; the output ends of the first multiplication unit and the second multiplication unit are connected to the search unit;

[0031] The first multiplication unit is used to obtain the gain of the resonant cavity by dividing the rated input voltage of the resonant converter by the input voltage of the resonant converter;

[0032] The second multiplication unit is used to convert the output current of the resonant converter into a corresponding quality factor by multiplying the proportional coefficient;

[0033] The steady-state operating point search unit is used to search for the corresponding frequency in the steady-state operating point table when the gain and quality factor of the resonant cavity exceed a preset range, and obtain the output frequency of the open-loop control.

[0034] Further preferably, the steady-state operating point search unit comprises: a curve plotter, a steady-state operating point acquirer and a table generator;

[0035] The curve plotter is used to obtain a curve graph of the gain of the resonant cavity versus the quality factor and the switching frequency of the resonant converter according to the rated power of the resonant converter, the capacitance value of the resonant capacitor, the inductance value of the resonant inductor, the inductance value of the excitation inductor and the resonant frequency; wherein the X-axis represents the ratio between the switching frequency and the resonant frequency; and the Y-axis represents the gain of the resonant cavity;

[0036] The steady-state operating point acquirer is used to draw a straight line parallel to the X-axis at a preset gain interval of the resonant cavity, and the intersection with the curve is the steady-state operating point at different loads under the input voltage represented by the current straight line; wherein the different loads are characterized by the output current of the resonant converter;

[0037] The table generator is used to record the gains of different resonant cavities, different quality factors and the ratio between the switching frequency and the resonant frequency through a table to obtain a steady-state operating point table.

[0038] Further preferably, the open-loop control module also includes: a proportional coefficient acquisition unit, which is used to calculate the load resistance of the resonant converter based on the output voltage and output current of the resonant converter; based on the load resistance of the resonant converter and the turns ratio between the primary and secondary sides of the resonant converter, obtain the primary fundamental wave equivalent resistance; according to the type of the resonant converter, combined with the primary fundamental wave equivalent resistance, calculate the relationship between the quality factor and the output current of the resonant converter to obtain the proportional coefficient.

[0039] Further preferably, when the resonant converter is an LLC resonant converter, the proportional coefficient in the proportional coefficient acquisition unit is:

[0040]

[0041] Where k is the proportionality coefficient; C r is the capacitance value of the resonant capacitor; L r is the inductance of the resonant inductor; N is the turns ratio between the primary and secondary sides of the resonant transformer; V o is the output voltage of the resonant converter.

[0042] Further preferably, the closed-loop control module includes an adder and a voltage controller;

[0043] The adder is used to obtain a voltage error signal by subtracting the output voltage of the resonant converter from the reference voltage of the resonant converter;

[0044] The voltage controller is used to perform proportional-integral operation on the voltage error signal to obtain the output frequency of the closed-loop control.

[0045] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art:

[0046] The present application provides a composite control method for optimizing the dynamic performance of a resonant converter. On the basis of the traditional control method, only an open-loop control part is added. When a sudden load change occurs, open-loop control is adopted to match the corresponding steady-state operating point according to the input voltage and output current of the current resonant converter to obtain the output frequency of the open-loop control. There is no complex calculation and no additional computing pressure is brought to the MCU (microcontroller).

[0047] The present application provides a composite control method for optimizing the dynamic performance of a resonant converter. The two sampled input voltages V in And the output current I o It is usually required for control and protection of the original circuit. It is easy to implement and deploy without adding any additional circuits or sampling circuits.

[0048] The present application provides a composite control method for optimizing the dynamic performance of a resonant converter, and the dynamic performance optimization effect is obvious. Since the open-loop control part can make the frequency jump over a large range within a control cycle during the dynamic process, compared with the traditional control method that relies on the continuous and slow adjustment of the PI controller, its dynamic performance is significantly optimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is a control block diagram of a composite control method for optimizing the dynamic performance of a resonant converter provided in an embodiment of the present application;

[0050] Figure 2 is a topological diagram of a resonant converter provided in an embodiment of the present application;

[0051] Figure 3 The resonant cavity gain G provided in the embodiment of the present application varies with and the cluster of curves of Q variation;

[0052] FIG. 4( a ) is a diagram of an embodiment of the present application. Figure 3 The first area in the figure is enlarged, showing the diagram of the steady-state operating point selection under some input voltages;

[0053] FIG. 4( b ) is a diagram of an embodiment of the present application. Figure 3 The second area in the figure is enlarged to show the diagram of the steady-state operating point selection under some input voltages;

[0054] Figure 5 is a steady-state operating point table provided in an embodiment of the present application;

[0055] Figure 6 It is the no-load to full-load dynamic response provided by the embodiment of the present application without using compound control;

[0056] Figure 7 This is the no-load to full-load dynamic response using compound control provided in an embodiment of the present application. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0058] The term "and / or" in this article is a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The symbol " / " in this article indicates that the associated objects are in an or relationship, for example, A / B means A or B.

[0059] The terms “first”, “second” and the like in the specification and claims herein are used to distinguish different objects rather than to describe a specific order of the objects.

[0060] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0061] In the description of the embodiments of the present application, unless otherwise specified, “plurality” means two or more than two.

[0062] The technical solutions provided in the embodiments of the present application are introduced.

[0063] The present application provides a composite control method for optimizing the dynamic performance of a resonant converter. The composite control method includes an open-loop control part and a closed-loop control part. Whether it is the composite control method or the open-loop control part and the closed-loop control part contained therein, the control quantity is the switching frequency f s The output of the compound controller is the sum of the output of the open-loop control part and the output of the closed-loop control part.

[0064] Example 1

[0065] like Figure 1 As shown, the embodiment of the present application provides a composite control method for optimizing the dynamic performance of a resonant converter. The circuit state parameter required to be sampled by the composite control method is the input voltage V in , output voltage V o And the output current I o , the output is the switching frequency f of the resonant converter s , the specific resonant converter topology is as follows Figure 2 As shown;

[0066] The output frequency f of the open loop control so When there is no large-scale load mutation, it is a constant value; when a large-scale load mutation occurs, its output frequency changes according to the current circuit state (input voltage V in And the output current Io ), matching the corresponding steady-state operating point, so that the output frequency jumps to the corresponding output frequency f of the next state so ;

[0067] The feedback quantity of the closed-loop control is the output voltage V of the resonant converter. o , its output frequency f sc It changes slightly in each control cycle to stabilize the output voltage in steady state;

[0068] The output of the composite control method is the switching frequency f of the resonant converter. s , whose value is the output frequency f of the open-loop control so The output frequency f of the closed-loop control sc Addition;

[0069] A composite control method for optimizing the dynamic performance of a resonant converter, wherein a method for selecting a steady-state operating point comprises the following steps:

[0070] (1) Setting the circuit parameters of the resonant converter;

[0071] (2) Using the obtained circuit parameters to calculate, simulate or test the actual machine, the gain G of the resonant cavity is obtained along with the quality factor Q and the switching frequency f s The X-axis represents the switching frequency f s With the resonant frequency f n The Y axis represents the gain G of the resonant cavity; the resonant converter includes a resonant cavity;

[0072] (3) A straight line is drawn parallel to the X-axis (representing the same input voltage) with an appropriate gain interval of the resonant cavity. The intersection of the straight line and the curve is the steady-state operating point at different loads under the input voltage represented by the current straight line; where the output current I o Characterization;

[0073] In order to more clearly illustrate the process of selecting the steady-state operating point, the following will be supplemented with design examples and diagrams to demonstrate the process; this example is a 3200W 12V LLC resonant converter design, and the specific design parameters are as follows;

[0074]

[0075] Where P is the rated output power of the resonant converter; C r is the capacitance value of the resonant capacitor; L r is the inductance value of the resonant inductor; L m is the inductance of the excitation inductor; N is the turns ratio of the primary and secondary sides of the transformer; f n C r and L rThe series resonant frequency of

[0076] The LLC circuit parameters are used to obtain the LLC resonant converter (LLC resonant converter, LLC refers to a resonant cavity composed of two inductors (L) and a capacitor (C) by using the simulation method. The gain G of the resonant cavity varies with the quality factor Q and the switching frequency f s The changing curve, such as Figure 3 As shown, due to the relationship between Q and I o is proportional, so in Figure 3 Directly convert Q to I o Instead, it is more intuitive to convert the load size into output current I o size.

[0077] Draw straight lines parallel to the X-axis (representing the same input voltage) at appropriate intervals. The intersection of the straight line and the curve is the steady-state operating point at different loads under the input voltage represented by the current straight line. The corresponding horizontal axis is the normalized switching frequency at the current steady-state operating point. Further multiply by the resonant frequency f n The switching frequency at the current steady-state operating point can be obtained. The selection of the steady-state operating point is specifically shown in Figures 4(a) and 4(b). It should be noted that Figures 4(a) and 4(b) only show the straight lines represented by part of the input voltage to illustrate the method of selecting the steady-state operating point.

[0078] (4) Finally, the obtained data is organized into a table, and the table is looked up in each control cycle to determine the output frequency of the open-loop controller. The steady-state operating point table obtained according to the above embodiment is as follows: Figure 5 As shown; the table records the gain of different resonant cavities, different quality factors (characterizing the load) and the switching frequency f s With the resonant frequency f n The ratio between .

[0079] Further preferably, after determining the appropriate steady-state operating point, the open-loop control specifically comprises the following steps:

[0080] (1) Collecting the input voltage V of the resonant converter in and the output current I of the resonant converter o ;

[0081] (2) Using the rated input voltage V of the resonant converter N Divide by the collected current input voltage V in , get the gain G of the current resonant cavity;

[0082] (3) Using output current I o Multiply by the proportional coefficient to convert to the corresponding quality factor Q. The conversion method is given in formulas (5) and (6). In this example, k = 0.00138 can be calculated;

[0083] More specifically, I o The conversion between I and Q is a simple proportional relationship. Taking LLC resonant converter as an example, o The relationship between Q is deduced as follows:

[0084] According to the definition of quality factor Q:

[0085]

[0086] Among them, R ac is the primary side fundamental wave equivalent resistance;

[0087] The primary side fundamental wave equivalent resistance R ac With load resistance R L There are the following relations:

[0088]

[0089] Where N is the ratio of the primary to secondary turns of the transformer;

[0090] Because the load resistance R L With the output voltage V o and output current I o There are the following relations:

[0091]

[0092] Combining formulas (1) to (3), we can obtain:

[0093]

[0094] Output voltage V o In this control mode, it can be regarded as a fixed value, and the other parameters are constants that have been determined in the parameter design stage. Therefore, taking the LLC resonant converter as an example, the output current I o The relationship with the quality factor Q can be expressed as:

[0095] Q=k·I o (5)

[0096] The expression of constant k is:

[0097]

[0098] It should be understood that some of the above formulas for calculating the k value are slightly different in different resonant converters, but the calculation ideas and the rule that k is a constant are applicable to resonant converters controlled by any frequency;

[0099] (4) If the change of G and Q does not exceed the specified range, the output of the open-loop controller remains unchanged; if the value change of G and Q exceeds the specified range, the values ​​of G and Q are approximated, and the corresponding frequency in the steady-state operating point table is found using the corresponding G and Q, which is the output frequency f of the open-loop controller. so .

[0100] It is worth noting that since G and Q in the steady-state operating point table are limited to a few discrete values, not all calculated G and Q can find the corresponding operating point in the table, so it is necessary to approximate the calculated G and Q to correspond to the points in the table. There are many methods to choose from for data approximation. It should be noted that the purpose of data approximation is to find the corresponding values ​​of all calculated G and Q in the table, and then determine the output frequency. Therefore, the method and logic of data approximation are not elaborated in detail here. It should be pointed out here that the number of steady-state operating points selected, that is, the number of elements in the steady-state operating point table, is related to the number of different quality factors Q selected and the number of different input voltages V in If m steady-state operating points with different quality factors under n different input voltages are selected, the number of elements in the steady-state operating point table is m*n.

[0101] The closed loop control is as follows Figure 1 The closed-loop controller part shown in the figure specifically includes the following steps:

[0102] S1: Collect output voltage V o ;

[0103] S2: Output voltage V o With reference voltage V ref The voltage error signal V e ;

[0104] S3: Perform proportional integral (PI) operation on the error signal to obtain the closed-loop controller output frequency f sc Finally, the output frequency of the open-loop controller is added to the output frequency of the closed-loop controller to obtain the output frequency of the composite controller, that is, the switching frequency f of the resonant converter. s .

[0105] In summary, taking a 3200W 12V LLC resonant converter as an example, the composite control method for optimizing the dynamic performance of the LLC resonant converter is explained in detail, and the implementation steps of the control method proposed in this application are explained. The composite control provided in this application has an optimization effect on the dynamic performance of the LLC resonant converter. Figure 6 and Figure 7 , the composite control method converts the input voltage V in =450V, the voltage drop when switching from no-load to full-load is reduced from 3.9V to 0.5V, which effectively optimizes the dynamic performance of the LLC resonant converter.

[0106] Example 2

[0107] The present application provides a composite control system for optimizing the dynamic performance of a resonant converter, comprising: an open-loop control module, a closed-loop control module and an addition module;

[0108] The open-loop control module is used to adopt open-loop control when a sudden load change occurs. According to the input voltage and output current of the current resonant converter, the corresponding steady-state operating point is matched to obtain the output frequency of the open-loop control.

[0109] The closed-loop control module is used to receive the output voltage of the resonant converter in real time, and obtain the output frequency of the closed-loop control based on the reference voltage of the resonant converter;

[0110] The adding module is used to add the output frequency of the open-loop control and the output frequency of the closed-loop control to obtain the switching frequency of the resonant converter.

[0111] Further preferably, the open-loop control module comprises: a first multiplication unit, a second multiplication unit, and a steady-state operating point search unit; the output ends of the first multiplication unit and the second multiplication unit are connected to the search unit;

[0112] The first multiplication unit is used to obtain the gain of the resonant cavity by dividing the rated input voltage of the resonant converter by the input voltage of the resonant converter;

[0113] The second multiplication unit is used to convert the output current of the resonant converter into a corresponding quality factor by multiplying the proportional coefficient;

[0114] The steady-state operating point search unit is used to search for the corresponding frequency in the steady-state operating point table when the gain and quality factor of the resonant cavity exceed a preset range, and obtain the output frequency of the open-loop control.

[0115] Further preferably, the steady-state operating point search unit comprises: a curve plotter, a steady-state operating point acquirer and a table generator;

[0116] The curve plotter is used to obtain a curve graph of the gain of the resonant cavity versus the quality factor and the switching frequency of the resonant converter according to the rated power of the resonant converter, the capacitance value of the resonant capacitor, the inductance value of the resonant inductor, the inductance value of the excitation inductor and the resonant frequency; wherein the X-axis represents the ratio between the switching frequency and the resonant frequency; and the Y-axis represents the gain of the resonant cavity;

[0117] The steady-state operating point acquirer is used to draw a straight line parallel to the X-axis at a preset gain interval of the resonant cavity, and the intersection with the curve is the steady-state operating point at different loads under the input voltage represented by the current straight line; wherein the different loads are characterized by the output current of the resonant converter;

[0118] The table generator is used to record the gains of different resonant cavities, different quality factors and the ratio between the switching frequency and the resonant frequency through a table to obtain a steady-state operating point table.

[0119] Further preferably, the open-loop control module also includes: a proportional coefficient acquisition unit, which is used to calculate the load resistance of the resonant converter based on the output voltage and output current of the resonant converter; based on the load resistance of the resonant converter and the turns ratio between the primary and secondary sides of the resonant converter, obtain the primary fundamental wave equivalent resistance; according to the type of the resonant converter, combined with the primary fundamental wave equivalent resistance, calculate the relationship between the quality factor and the output current of the resonant converter to obtain the proportional coefficient.

[0120] Further preferably, when the resonant converter is an LLC resonant converter, the proportional coefficient in the proportional coefficient acquisition unit is:

[0121]

[0122] Where k is the proportionality coefficient; C r is the capacitance value of the resonant capacitor; L r is the inductance of the resonant inductor; N is the turns ratio between the primary and secondary sides of the resonant transformer; V o is the output voltage of the resonant converter.

[0123] Further preferably, the closed-loop control module includes an adder and a voltage controller;

[0124] The adder is used to obtain a voltage error signal by subtracting the output voltage of the resonant converter from the reference voltage of the resonant converter;

[0125] The voltage controller is used to perform proportional-integral operation on the voltage error signal to obtain the output frequency of the closed-loop control.

[0126] In summary, this application has the following advantages:

[0127] The present application provides a composite control method for optimizing the dynamic performance of a resonant converter. On the basis of the traditional control method, only an open-loop control part is added. When a sudden load change occurs, open-loop control is adopted to match the corresponding steady-state operating point according to the input voltage and output current of the current resonant converter to obtain the output frequency of the open-loop control. There is no complex calculation and no additional computing pressure is brought to the MCU.

[0128] The present application provides a composite control method for optimizing the dynamic performance of a resonant converter. The two sampled input voltages V in And the output current I o It is usually required for control and protection of the original circuit. It is easy to implement and deploy without adding any additional circuits or sampling circuits.

[0129] The present application provides a composite control method for optimizing the dynamic performance of a resonant converter, and the dynamic performance optimization effect is obvious. Since the open-loop control part can make the frequency jump over a large range within a control cycle during the dynamic process, compared with the traditional control method that relies on the continuous and slow adjustment of the PI controller, its dynamic performance is significantly optimized.

[0130] It should be understood that the above-mentioned system is used to execute the methods in the above-mentioned embodiments. The implementation principles and technical effects of the corresponding program modules in the system are similar to those described in the above-mentioned methods. The working process of the system can refer to the corresponding process in the above-mentioned method and will not be repeated here.

[0131] It should be understood that the various numerical numbers involved in the embodiments of the present application are only used for the convenience of description and are not used to limit the scope of the embodiments of the present application.

[0132] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A composite control method for optimizing the dynamic performance of a resonant converter, characterized in that: The following steps are involved: When a sudden load change occurs, open-loop control is used to match the corresponding steady-state operating point according to the current input voltage and output current of the resonant converter to obtain the output frequency of the open-loop control; receiving the output voltage of the resonant converter in real time, and obtaining the output frequency of the closed-loop control based on the reference voltage of the resonant converter; The output frequency of the open-loop control is added to the output frequency of the closed-loop control to obtain the switching frequency of the resonant converter.

2. The composite control method according to claim 1, characterized in that: The open-loop control specifically includes the following steps: The gain of the resonant cavity is obtained by dividing the rated input voltage of the resonant converter by the input voltage of the resonant converter; The output current of the resonant converter is multiplied by the proportional coefficient to convert it into the corresponding quality factor; When the gain and quality factor of the resonant cavity exceed a preset range, the corresponding frequency is looked up in the steady-state operating point table to obtain the output frequency of the open-loop control.

3. The composite control method according to claim 2, characterized in that: The method for obtaining the steady-state operating point table includes the following steps: According to the rated power of the resonant converter, the capacitance value of the resonant capacitor, the inductance value of the resonant inductor, the inductance value of the excitation inductor and the resonant frequency, a curve diagram of the gain of the resonant cavity versus the quality factor and the switching frequency of the resonant converter is obtained; wherein the X-axis represents the ratio between the switching frequency and the resonant frequency; and the Y-axis represents the gain of the resonant cavity; A straight line parallel to the X-axis is drawn with the gain interval of the preset resonant cavity, and the intersection with the curve is the steady-state operating point at different loads under the input voltage represented by the current straight line; wherein different loads are characterized by the output current of the resonant converter; The gains of different resonant cavities, different quality factors, and the ratio between the switching frequency and the resonant frequency are recorded in a table to obtain a steady-state operating point table.

4. The composite control method according to any one of claims 1 to 3, characterized in that: The method to obtain the proportional coefficient is: Calculate the load resistance of the resonant converter according to the output voltage and output current of the resonant converter; Obtaining a primary side fundamental wave equivalent resistance based on a load resistance of the resonant converter and a turns ratio between a primary side and a secondary side of the resonant converter; According to the type of resonant converter, combined with the primary side fundamental wave equivalent resistance, the relationship between the quality factor and the output current of the resonant converter is calculated to obtain the proportionality coefficient.

5. The composite control method according to claim 4, characterized in that: When the resonant converter is an LLC resonant converter, the proportionality factor is: Where k is the proportionality coefficient; C r is the capacitance value of the resonant capacitor; L r is the inductance of the resonant inductor; N is the turns ratio between the primary and secondary sides of the resonant transformer; V o is the output voltage of the resonant converter.

6. The composite control method according to claim 1, characterized in that: The closed-loop control specifically includes the following steps: Subtract the output voltage of the resonant converter from the reference voltage of the resonant converter to obtain a voltage error signal; The voltage error signal is proportionally integrated to obtain the output frequency of the closed-loop control.

7. A composite control system for optimizing the dynamic performance of a resonant converter, characterized in that: include: Open-loop control module, closed-loop control module and addition module; The open-loop control module is used to adopt open-loop control when a sudden load change occurs. According to the input voltage and output current of the current resonant converter, the corresponding steady-state operating point is matched to obtain the output frequency of the open-loop control. The closed-loop control module is used to receive the output voltage of the resonant converter in real time, and obtain the output frequency of the closed-loop control based on the reference voltage of the resonant converter; The adding module is used to add the output frequency of the open-loop control and the output frequency of the closed-loop control to obtain the switching frequency of the resonant converter.

8. The composite control system according to claim 7, characterized in that: The open-loop control module includes: a first multiplication unit, a second multiplication unit, and a steady-state operating point search unit; the output ends of the first multiplication unit and the second multiplication unit are connected to the search unit; The first multiplication unit is used to obtain the gain of the resonant cavity by dividing the rated input voltage of the resonant converter by the input voltage of the resonant converter; The second multiplication unit is used to convert the output current of the resonant converter into a corresponding quality factor by multiplying the proportional coefficient; The steady-state operating point search unit is used to search for the corresponding frequency in the steady-state operating point table when the gain and quality factor of the resonant cavity exceed a preset range, and obtain the output frequency of the open-loop control.

9. The composite control system according to claim 8, characterized in that: The steady-state operating point search unit includes: a curve plotter, a steady-state operating point acquirer and a table generator; The curve plotter is used to obtain a curve graph of the gain of the resonant cavity versus the quality factor and the switching frequency of the resonant converter according to the rated power of the resonant converter, the capacitance value of the resonant capacitor, the inductance value of the resonant inductor, the inductance value of the excitation inductor and the resonant frequency; wherein the X-axis represents the ratio between the switching frequency and the resonant frequency; and the Y-axis represents the gain of the resonant cavity; The steady-state operating point acquirer is used to draw a straight line parallel to the X-axis at a preset gain interval of the resonant cavity, and the intersection with the curve is the steady-state operating point at different loads under the input voltage represented by the current straight line; wherein the different loads are characterized by the output current of the resonant converter; The table generator is used to record the gains of different resonant cavities, different quality factors and the ratio between the switching frequency and the resonant frequency through a table to obtain a steady-state operating point table.

10. The composite control system according to claim 7, characterized in that: The closed-loop control module includes an adder and a voltage controller; The adder is used to obtain a voltage error signal by subtracting the output voltage of the resonant converter from the reference voltage of the resonant converter; The voltage controller is used to perform proportional-integral operation on the voltage error signal to obtain the output frequency of the closed-loop control.

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