Multi-mode control method for optical storage and direct-drive universal converter facing wide range input

Abstract

The application provides a wide-range input-oriented optical storage direct-flexible general converter multi-mode control method, and belongs to the field of non-isolated DC-DC converter control methods. The method comprises the following steps: based on the constraint condition of zero-voltage turn-on of an FSBB converter and the loss distribution of the FSBB converter, a unified loss model of the FSBB converter under different inductance current waveforms is established; the load current boundary of the FSBB converter under the QCM method is determined under the condition of fixed frequency; according to the current stress of the FSBB converter under the QCM method and the TCM method, the unified loss model is extended to a comprehensive index model for simultaneously optimizing the efficiency and current stress of the FSBB converter; the input voltage, the output voltage and the output current are sampled, and based on the load current boundary and the comprehensive index model, the optimal solution is obtained by optimizing the variables, and the optimal solution is used as the control parameter of the FSBB converter; the problems of complex control and ignoring the influence of the current stress of the switching tube on the service life of the converter existing in the current multi-mode control strategy of the FSBB converter are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of non-isolated DC-DC converter control methods, and in particular to a multi-mode control method for a photovoltaic, storage, direct-flexible, and universal converter for wide-range input. Background Art

[0002] With the rapid development of energy storage and photovoltaic systems, DC conversion has become a major trend in new power systems. In particular, in the fields of renewable energy and DC interconnection, the four-switch Buck-Boost (FSBB) converter, with its flexible ability to convert DC voltages across a wide range and its bidirectional power flow, is a suitable DC grid interface for various power sources, including photovoltaic and energy storage.

[0003] Due to the wide range of input voltages for different types of power sources, the control strategy for FSBB converters needs to optimize efficiency across the entire voltage range and load conditions to ensure efficient energy transmission. However, among traditional control methods, the triangular current control (TCM) method of the FSBB converter performs well under light loads, but its efficiency decreases under heavy loads, especially under high load demands. The quadrilateral inductor current control (QCM) method, on the other hand, is more efficient under heavy loads but suffers from high current stress under light loads, which can lead to additional losses under low-light conditions in photovoltaic systems. Therefore, a multi-mode control strategy has been proposed that combines the TCM and QCM methods to improve the overall efficiency performance of the FSBB converter.

[0004] However, existing multi-mode control strategies focus solely on efficiency optimization, ignoring the impact of switch current stress on converter life. Furthermore, efficiency modeling in traditional multi-mode control strategies requires separate mathematical models for the QCM and TCM methods, due to significant differences in inductor currents. This complicates converter control. Summary of the Invention

[0005] The technical problem to be solved by the present invention is how to solve the problems of complex control in the current multi-mode control strategy of the FSBB converter and neglect of the influence of the switch tube current stress on the converter life.

[0006] The present invention solves the above technical problems through the following technical solutions: a multi-mode control method for a photovoltaic storage direct-flexible universal converter for wide input range, the method comprising the following steps:

[0007] Step 1: Based on the constraints of the FSBB converter to achieve zero voltage turn-on and the loss distribution of the FSBB converter, a unified loss model of the FSBB converter under different inductor current waveforms is established;

[0008] Step 2: Determine the load current boundary of the FSBB converter in the QCM method under constant frequency conditions;

[0009] Step 3: Based on the current stress of the FSBB converter under the QCM method and the TCM method, the unified loss model is expanded into a comprehensive indicator model for simultaneously optimizing the efficiency and current stress of the FSBB converter;

[0010] Step 4: Sample the input voltage, output voltage, and output current, and optimize the variables to obtain the optimal solution based on the load current boundary and the comprehensive indicator model, and use the optimal solution as the control parameter of the FSBB converter.

[0011] The present invention unifies the loss models under the traditional QCM method and the TCM method, establishes a unified loss model suitable for the FSBB converter, solves the problem that the traditional FSBB converter loss model has different expressions under different control methods, can simplify the control of the FSBB converter, and according to the current stress of the FSBB converter under the QCM method and the TCM method, expands the unified loss model into a comprehensive index model for simultaneously optimizing the efficiency and current stress of the FSBB converter. Through optimization calculation, an offline model with the best comprehensive index of converter efficiency and current stress is obtained. The variable with the best comprehensive index is used as the control parameter of the FSBB converter, which can significantly improve the theoretical maximum efficiency of the FSBB converter and reduce the current stress of the FSBB converter, thereby reducing the switching tube cost of the FSBB converter and extending the overall life of the FSBB converter.

[0012] Preferably, the constraint conditions for the FSBB converter to achieve zero voltage switching in step 1 are:

[0013] |I1|>I zvs ,|I2|>I zvs ,|I3|>I zvs ,|I4|>I zvs ,|I max |>I zvs ,|I min |>I zvs ,

[0014]

[0015] Among them, I zvs To achieve the minimum current for soft switching, C oss is the parasitic capacitance of the power switch tube, t deadis the dead time of the two power switches in the same bridge arm of the FSBB converter to prevent shoot-through, I1 is the turning current value of the inductor current from the T4 stage to the T1 stage under the QCM method, I2 is the turning current value of the inductor current from the T1 stage to the T2 stage under the QCM method, I3 is the turning current value of the inductor current from the T2 stage to the T3 stage under the QCM method, I4 is the turning current value of the inductor current from the T3 stage to the T4 stage under the QCM method, I max TCM method on Stage to T off The turning current value of the inductor current in the stage, I min TCM method off Stage to T on The turning current value of the inductor current in this stage.

[0016] Preferably, the expression of the unified loss model in step 1 is:

[0017] P loss =P on +P off +P con +P L

[0018] Among them, P loss To unify the loss, P on is the conduction loss of the power switch tube, P off is the turn-off loss of the power switch tube, P con is the conduction loss, P L is the inductor loss.

[0019] Preferably, the conduction loss P of the power switch tube is on And the turn-off loss of the power switch tube P off The calculation method is:

[0020] P on =E on (d1, d2, θ, R g )f s

[0021] P off =E off (d1, d2, θ, R g )f s

[0022] Where d1 is the duty cycle of the main control tube S1 in the Buck bridge arm, d2 is the duty cycle of the main control tube S3 in the Boost bridge arm, θ is the phase shift between the main control tube S1 and the main control tube S3, and f s is the switching frequency, R g is the gate resistance, E on 、E offThey are the turn-on energy loss and turn-off energy loss of the power switch tube at the provided drain-source voltage and drain-source current levels in the data sheet.

[0023] Preferably, the conduction loss P con The calculation method is:

[0024]

[0025] Among them, I rms is the effective value of the inductor current of the FSBB converter under the QCM method and TCM method, R on (T, I ds ) is the drain-source resistance taking into account temperature and drain-source current;

[0026] The inductor loss P L The calculation method is:

[0027]

[0028] Among them, I rms is the effective value of the inductor current of the FSBB converter under the QCM method and TCM method, R L is the inductor winding resistance, V core is the core volume, k, α and β are the core material parameters, and ΔB is the amplitude of the magnetic flux density change.

[0029] Preferably, the effective value of the inductor current I of the FSBB converter under the QCM method and the TCM method is rms The calculation method is:

[0030]

[0031] Among them, V in is the input voltage, V o is the output voltage, T s is the switching period of the FSBB converter. In the Buck mode of the TCM method, θ is zero, and in the Boost mode, θ is 1-d2.

[0032] Preferably, in step 2, the load current boundary of the FSBB converter in the QCM method is:

[0033]

[0034] Among them, I o is the output current, V in is the input voltage, V o is the output voltage, I zvs To achieve the minimum current for soft switching, L c is the inductance, T sis the switching period of the FSBB converter.

[0035] Preferably, the current stress of the FSBB converter in step 3 is calculated using the QCM method as follows:

[0036]

[0037] Among them, I peak is the peak inductor current under the QCM method, I zvs To achieve the minimum current for soft switching, L c is the inductor, V in is the input voltage, V o is the output voltage, d1 is the duty cycle of the main control tube S1 in the Buck bridge arm, d2 is the duty cycle of the main control tube S3 in the Boost bridge arm, and θ is the phase shift between the main control tubes S1 and S3;

[0038] The current stress of the FSBB converter under the TCM method is calculated as follows:

[0039]

[0040] Among them, I peak is the inductor current peak value under TCM method, T s is the switching period of the FSBB converter, I o is the output current.

[0041] Preferably, the expression of the comprehensive indicator model in step 3 is:

[0042]

[0043] Among them, I o is the output current, V o is the output voltage, P loss For uniform loss, I peak is the peak value of the inductor current under the QCM method or TCM method.

[0044] Preferably, the process of optimizing the variables to obtain the optimal solution in step 4 includes: in , output voltage V o The theoretical value of the output current is calculated by the load current boundary and compared with the sampled output current I o And the calculated theoretical value, determine the output current I o Is it within the load current limit? If the output current I o Within the load current boundary, with duty cycle d1, duty cycle d2 and phase shift angle θ as variables, different solutions are combined within the reasonable value range of the three variables, and the unified loss P under different solution combinations is calculated. lossand current stress I peak , comprehensively considering the unified loss P loss and current stress I peak The two indicators are optimized to obtain the optimal solution; if the output current I o Outside the load current boundary, the duty cycle d1, duty cycle d2 and phase shift angle θ are obtained based on the TCM method.

[0045] The advantages provided by the present invention are:

[0046] (1) The present invention unifies the loss models under the traditional QCM method and the TCM method, establishes a unified loss model suitable for the FSBB converter, solves the problem that the traditional FSBB converter loss model has different expressions under different control methods, and can simplify the control of the FSBB converter. According to the current stress of the FSBB converter under the QCM method and the TCM method, the unified loss model is expanded into a comprehensive index model that simultaneously optimizes the efficiency and current stress of the FSBB converter. Through optimization calculation, an offline model with the best comprehensive index of converter efficiency and current stress is obtained. The variable with the best comprehensive index is used as the control parameter of the FSBB converter, which can significantly improve the theoretical maximum efficiency of the FSBB converter and reduce the current stress of the FSBB converter, thereby reducing the switching tube cost of the FSBB converter and extending the overall life of the FSBB converter.

[0047] (2) The present invention combines the advantages of the TCM method and the QCM method, and realizes efficient and stable energy transmission of the FSBB converter under different working conditions by dynamically adjusting the control mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A circuit topology diagram of the FSBB converter in the multi-mode control method for a wide-range input PV-storage-direct-flexible universal converter provided by an embodiment of the present invention;

[0049] Figure 2 A schematic diagram of the switch drive waveform and inductor current waveform under the QCM method in the multi-mode control method of a photovoltaic-storage-direct-flexible universal converter for wide input range provided by an embodiment of the present invention;

[0050] Figure 3 A schematic diagram of the switch tube drive waveform and inductor current waveform under the TCM method in the multi-mode control method of the photovoltaic storage direct-flexible universal converter for wide input range provided by an embodiment of the present invention;

[0051] Figure 4 A load current boundary diagram for a multi-mode control method of a photovoltaic-storage-direct-flexible universal converter with wide input range provided by an embodiment of the present invention;

[0052] Figure 5Schematic diagram of a multi-mode control method for a wide-range input photovoltaic-storage-direct-flexible universal converter provided by an embodiment of the present invention;

[0053] Figure 6 A sub-flowchart of a multi-mode control method for a wide-range input PV-storage-direct-flexible universal converter provided by an embodiment of the present invention;

[0054] Figure 7 A simulation diagram of the FSBB converter loss under the QCM method for the multi-mode control method of the PV-storage-direct-flexible universal converter for wide input range provided by an embodiment of the present invention;

[0055] Figure 8 A simulation diagram of the FSBB converter loss under the TCM method for the multi-mode control method of the photovoltaic storage direct-flexible universal converter for wide input range provided by an embodiment of the present invention;

[0056] Figure 9 A simulation diagram of the current stress of the FSBB converter using the QCM method for the multi-mode control method of the photovoltaic-storage-direct-flexible universal converter for wide input range provided by an embodiment of the present invention;

[0057] Figure 10 A simulation diagram of the current stress of the FSBB converter under the TCM method for the multi-mode control method of the photovoltaic-storage-direct-flexible universal converter for wide input range provided by an embodiment of the present invention;

[0058] Figure 11 A simulation diagram of the comprehensive indicators of the FSBB converter under the QCM method for the multi-mode control method of the photovoltaic-storage-direct-flexible universal converter for wide input range provided by an embodiment of the present invention;

[0059] Figure 12 A simulation diagram of the comprehensive indicators of the FSBB converter under the TCM method for the multi-mode control method of the photovoltaic-storage-direct-flexible universal converter for wide input range provided by an embodiment of the present invention;

[0060] Figure 13 Boundary diagrams of the use of QCM and TCM methods in Boost mode and Buck mode respectively for the multi-mode control method of the photovoltaic storage direct-flexible universal converter for wide input range provided by the embodiment of the present invention;

[0061] Figures 14-16 A comparison graph showing how comprehensive indicators change with output current at different voltages in a multi-mode control method for a wide-range input photovoltaic-storage-direct-flexible universal converter provided by an embodiment of the present invention;

[0062] Figure 17 Waveforms of steady-state inductor current and ZVS in Boost mode for a multi-mode control method of a photovoltaic-storage-direct-flexible universal converter with wide input range provided by an embodiment of the present invention;

[0063] Figure 18 The waveform diagram of the steady-state inductor current and ZVS in Buck mode of the multi-mode control method of the photovoltaic-storage-direct-flexible universal converter with wide input range provided by the embodiment of the present invention. DETAILED DESCRIPTION

[0064] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the following describes the technical solutions of the present invention in a clear and complete manner with reference to specific embodiments and the accompanying drawings. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0065] like Figure 1 The circuit topology of the FSBB converter used in the present invention mainly includes the Buck bridge arm and the Boost bridge arm. The Buck bridge arm consists of power switches S1 and S2, and the midpoint voltage is V A The main control tube of the Buck bridge arm is S1, and the duty cycle is d1. The Boost bridge arm consists of power switch tubes S3 and S4. The main control tube of the Boost bridge arm is S3, and the duty cycle is d2. The midpoint voltage is V B , inductance L c Connected between the midpoints of the two bridge arms, the two power switches on the same bridge arm are complementary turned on, diodes D1-D4 are anti-parallel connected between the drain and source of the power switches S1-S4, and capacitor C oss1 -C oss4 They are the parasitic capacitances of the power switch tubes S1-S4, capacitor C0 is the output filter capacitor, and resistor R is the load.

[0066] This embodiment provides a multi-mode control method for a wide-range input PV-storage DC-flexible universal converter, including the following steps:

[0067] Step 1: Based on the constraints of achieving zero voltage switching (ZVS) of the FSBB converter and the loss distribution of the FSBB converter, a unified loss model of the FSBB converter under different inductor current waveforms is established. Specifically, the following steps are included:

[0068] Step 1.1: Under the full-power switch tube soft switching (ZVS) mode, the current condition for achieving full-power switch tube ZVS is obtained using formula (1):

[0069]

[0070] In formula (1), C ossis the parasitic capacitance of the power switch tube, t dead The dead time for preventing shoot-through of the upper and lower power switches in the same bridge arm of the FSBB converter.

[0071] The constraints for the FSBB converter to achieve ZVS are:

[0072] |I1|>I zvs ,|I2|>I zvs ,|I3|>I zvs ,|I4|>I zvs ,|I max |>I zvs ,|I min |>I zvs , see Figure 2 and Figure 3 , I1 is the inductor current breakover value from T4 stage to T1 stage under the QCM method, I2 is the inductor current breakover value from T1 stage to T2 stage under the QCM method, I3 is the inductor current breakover value from T2 stage to T3 stage under the QCM method, I4 is the inductor current breakover value from T3 stage to T4 stage under the QCM method, I max TCM method on Stage to T off The turning current value of the inductor current in the stage, I min TCM method off Stage to T on The turning current value of the inductor current in this stage.

[0073] Step 1.2: According to the data sheet, the power switch tube has a specific drain-source voltage and a specific drain-source current level. on and turn-off energy loss E off Curve fitting derives the unit switching loss expression of the power switch tube under different voltage and current conditions as follows:

[0074]

[0075] In formula (2), P on is the conduction loss of the power switch tube, P off is the turn-off loss of the power switch tube, V ds is the instantaneous voltage when the power switch is switched on and off, I ds is the instantaneous current when the power switch is switched on and off, f s is the switching frequency of the FSBB converter, R g is the gate resistance.

[0076] After transforming formula (2), the general expression of the switching loss of the FSBB converter is:

[0077]

[0078] In formula (3), d1 is the duty cycle of the main control transistor S1 in the Buck bridge arm, d2 is the duty cycle of the main control transistor S3 in the Boost bridge arm, and θ is the phase shift between the main control transistors S1 and S3.

[0079] Step 1.3: Integrate the inductor current expression under the QCM method to obtain the effective value of the inductor current of the FSBB converter under the QCM method and the TCM method.

[0080] The inductor current expression under the QCM method is:

[0081]

[0082] The effective value of the inductor current of the FSBB converter under the QCM method and TCM method is:

[0083]

[0084] In formula (4), V in is the input voltage, V o is the output voltage, T s is the switching period of the FSBB converter. In the Buck mode of the TCM method, θ is zero, and in the Boost mode, θ is 1-d2.

[0085] At present, the formulas for the effective value of the inductor current in the QCM method and the TCM method are calculated separately, or the inductor currents I1, I2, and I min etc. as variables, or use the switch time T1, T on 、T off etc. are represented as variables, which leads to inconsistent variables in the optimization process and repeated optimization. The present invention uses d1, d2, and θ to represent the effective values ​​of the inductor currents of the two, making the optimization process simpler and more accurate.

[0086] According to formula (4), the conduction loss of the FSBB converter is calculated as:

[0087]

[0088] In formula (5), R on (T, I ds ) is the drain-source resistance taking temperature and drain-source current into account.

[0089] Step 1.4: Calculate the inductance loss of the FSBB converter using formula (6):

[0090]

[0091] In formula (6), R L is the inductor winding resistance, V core is the core volume, k, α and β are the core material parameters, and ΔB is the amplitude of the magnetic flux density change.

[0092] According to the FSBB converter switching loss P on 、P off , conduction loss P con and inductor loss P L , the expression of the unified loss model of FSBB converter under different control methods is calculated by formula (7):

[0093] P loss =P on +P off +P con +P L (7)

[0094] In formula (7), P loss represents uniform loss.

[0095] Step 2: Determine the load current boundary of the QCM method under constant frequency conditions.

[0096] The QCM method realizes ZVS of full-power switching tubes. Under constant frequency conditions, there is a load current boundary. The QCM load current boundary under constant frequency conditions is obtained using formula (8):

[0097]

[0098] The QCM load current boundary obtained under the working conditions of the present invention is as follows Figure 4 As shown, the TCM method has no load current boundary.

[0099] Step 3: Based on the current stress of the FSBB converter under the QCM method and the TCM method, the unified loss model of the FSBB converter established in step 1 is expanded into a comprehensive indicator model that simultaneously optimizes the converter efficiency and current stress.

[0100] The current stress of the FSBB converter under the QCM method is calculated as follows:

[0101]

[0102] In formula (9), I peak is the peak value of the inductor current under the QCM method.

[0103] The current stress of the FSBB converter under the TCM method is calculated as follows:

[0104]

[0105] In formula (10), I peak is the peak value of the inductor current under the TCM method.

[0106] The unified loss model of the FSBB converter established in step 1 is expanded to the converter efficiency η and current stress I peak The comprehensive indicator model optimized at the same time, the expression of the comprehensive indicator model is:

[0107]

[0108] Among them, the converter efficiency

[0109] Step 4. Based on the load current boundary and the comprehensive index model, establish the optimization goal (high efficiency and low current stress), determine the functional relationship between the design constraints and the optimization variables, optimize the variables duty cycle d1, duty cycle d2 and phase shift angle θ, and obtain the optimal solution of the optimization variables corresponding to the best comprehensive index. The optimal solution is used as the control parameter of the FSBB converter multi-mode control method.

[0110] See Figure 5 and Figure 6 The process of optimizing the variable duty cycle d1, duty cycle d2 and phase shift angle θ includes: in , output voltage V o and output current I o Sampling the input voltage V in , output voltage V o Substitute the load current boundary into the calculation formula (8) to calculate the theoretical value of the output current under this working condition. Compare the sampled value of the output current with the theoretical value to determine the output current I o Is it within the load current limit? If the output current I o Within the load current boundary, both the QCM method and the TCM method can achieve the load current requirements at this time. According to the unified loss model, with duty cycle d1, duty cycle d2 and phase shift angle θ as variables, different solutions are combined within the reasonable value range of the three variables to calculate the unified loss P under different solution combinations. loss, the minimum value of the unified loss can be obtained. When the unified loss is minimized, the converter efficiency is the highest, but the current stress at this time is not necessarily optimal. It is also necessary to substitute the three parameters corresponding to the minimum value of the unified loss under the QCM method into the current stress calculation formula (9) under the QCM method to calculate the current stress value under the QCM method, and substitute the three parameters corresponding to the minimum value of the unified loss under the TCM method into the current stress calculation formula (10) under the TCM method to calculate the current stress value under the TCM method. Considering the unified loss and current stress comprehensively, the three parameters corresponding to the small unified loss and the small current stress value are selected as the control parameters of the FSBB converter multi-mode control method. For example, in the process of optimizing by comprehensively considering the two indicators of unified loss and current stress, if the minimum value of the unified loss under the QCM method and the TCM method are the same, the parameter value corresponding to the smaller current stress under the two methods will be selected as the optimal solution. If no two identical minimum values ​​of unified loss are found, such as the maximum converter efficiency of the QCM method (converter efficiency According to P loss The calculated maximum efficiency is only 0.1% higher than the maximum converter efficiency of the TCM method, but the current stress of the TCM method accounts for 90% of the current stress of the QCM method. In this case, the TCM method will be selected.

[0111] If the output current I o Outside the load current boundary, only the TCM method can be used. At this time, the duty cycle d1, duty cycle d2, and phase shift angle θ are solved according to the characteristics of the TCM method itself. The duty cycle d1, duty cycle d2, and phase shift angle θ obtained are used as the control parameters of the FSBB converter multi-mode control method. In Buck mode, duty cycle d2 = 1, phase shift angle θ = 0, and duty cycle d1 is calculated as:

[0112]

[0113] In Boost mode, duty cycle d1 = 1, phase shift angle θ = 1-d2, and duty cycle d2 is calculated as:

[0114]

[0115] The duty cycle d1, duty cycle d2 and phase shift angle θ corresponding to the optimal comprehensive index are determined, and a PWM wave is generated according to the duty cycle d1, duty cycle d2 and phase shift angle θ to drive the switch tube in the FSBB converter.

[0116] The present invention unifies the loss models under the traditional QCM method and the TCM method, establishes a unified loss model suitable for the FSBB converter, solves the problem that the traditional FSBB converter loss model has different expressions under different control methods, can simplify the control of the FSBB converter, and according to the current stress of the FSBB converter under the QCM method and the TCM method, expands the unified loss model into a comprehensive index model for simultaneously optimizing the efficiency and current stress of the FSBB converter. Through optimization calculation, an offline model with the best comprehensive index of converter efficiency and current stress is obtained. The variable with the best comprehensive index is used as the control parameter of the FSBB converter, which can significantly improve the theoretical maximum efficiency of the FSBB converter and reduce the current stress of the FSBB converter, thereby reducing the switching tube cost of the FSBB converter and extending the overall life of the FSBB converter, which is conducive to further optimization of the efficiency and current stress of the FSBB converter.

[0117] The method of the present invention combines the advantages of the TCM method and the QCM method, and realizes efficient and stable energy transmission of the FSBB converter under different working conditions by dynamically adjusting the control mode.

[0118] In order to further verify the effectiveness of the present invention, simulation verification was carried out based on the MATLAB / SIMULINKL simulation platform and a physical platform of the FSBB converter was built for experimental verification. The specifications of the FSBB converter are shown in Table 1.

[0119] Table 1 FSBB converter specifications

[0120] Operating conditions & components Parameters & models <![CDATA[输入电压V in ]]> 100～200V Output voltage V o ]]> 150V Inductance L c ]]> 21 μΗ <![CDATA[最大输出电流I o_max ]]> 5A <![CDATA[输出电容C o ]]> 470 μΡ <![CDATA[死区时间t dead ]]> 200 ns <![CDATA[开关频率f s ]]> 100 kHz DSP TMS320F28035

[0121] Simulation and physical experiment verification are carried out according to the control method and converter parameters of the present invention. Figure 7 and Figure 8 This is a comparison diagram of FSBB converter losses under the QCM and TCM methods of the present invention; Figure 9 and Figure 10 The figure shows a comparison of the current stress of the FSBB converter under the QCM and TCM methods in the present invention. It shows that the changing trends of efficiency and current stress are quite different, and it is impossible to ensure that the current stress is optimized at the same time as the efficiency optimization, which leads to the necessity of simultaneous multi-objective optimization. Figure 11 and Figure 12 This is a comparison chart of the comprehensive indicators of the FSBB converter under the QCM and TCM methods in the present invention; it can be seen that when controlling alone, there are always areas with poor comprehensive indicators, and the two control methods need to be combined. The comprehensive indicator curve after combination is the maximum value of the two. Figure 13 It is the boundary diagram of the use of QCM and TCM methods in the present invention; Figures 14 to 16 This is a comparison curve diagram of the comprehensive indicators of the present invention as the output current changes at different voltages;Figure 17 and Figure 18 Figures 8 and 9 are waveform diagrams of the steady-state inductor current and ZVS in the Boost mode and Buck mode, respectively, of the application.

[0122] The above examples are only used to illustrate the technical solutions of the present application, and not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A multi-mode control method for a photovoltaic-storage-direct-flexible universal converter with wide input range, characterized by: The method comprises the following steps: Step 1: Based on the constraints for achieving zero voltage turn-on of the FSBB converter and the loss distribution of the FSBB converter, a unified loss model of the FSBB converter under different inductor current waveforms is established; the FSBB converter is a four-switch Buck-Boost converter; Step 2: Determine the load current boundary of the FSBB converter under the QCM method under constant frequency conditions; the QCM method is a quadrilateral inductor current control method; Step 3: Based on the current stress of the FSBB converter under the QCM method and the TCM method, the unified loss model is expanded into a comprehensive indicator model for simultaneously optimizing the efficiency and current stress of the FSBB converter; the TCM method is a triangle current control method; Step 4: Sample the input voltage, output voltage, and output current, and optimize the variables to obtain the optimal solution based on the load current boundary and the comprehensive indicator model, and use the optimal solution as the control parameter of the FSBB converter.

2. The multi-mode control method for a wide-range input PV-storage DC-flexible universal converter according to claim 1 is characterized in that: The constraints for the FSBB converter to achieve zero voltage switching in step 1 are: ， ， ， ， ， ， in, To achieve the minimum current for soft switching, is the parasitic capacitance of the power switch tube, The dead time for the two power switches in the same bridge arm of the FSBB converter to prevent shoot-through. is the turning current value of the inductor current from the T4 stage to the T1 stage under the QCM method, is the turning current value of the inductor current from stage T1 to stage T2 under the QCM method, is the turning current value of the inductor current from stage T2 to stage T3 under the QCM method, is the turning current value of the inductor current from stage T3 to stage T4 under the QCM method, TCM method on Stage to T off The turning current value of the inductor current in the stage, TCM method off Stage to T on The turning current value of the inductor current in this stage.

3. The multi-mode control method for a wide-range input PV-storage DC-flexible universal converter according to claim 1, characterized in that: The expression of the unified loss model in step 1 is: in, To unify the loss, is the conduction loss of the power switch tube, is the turn-off loss of the power switch tube, is the conduction loss, is the inductor loss.

4. The multi-mode control method for a wide-range input PV-storage-direct-flexible universal converter according to claim 3 is characterized in that: The conduction loss of the power switch tube and the turn-off loss of the power switch tube The calculation method is: in, The main control tube in the Buck bridge arm S A duty cycle of 1, It is the main control tube in the Boost bridge arm S A duty cycle of 3, θ Main controller S 1 and main control tube S Phase shift between 3, is the switching frequency, is the gate resistance, 、 They are the turn-on energy loss and turn-off energy loss of the power switch tube at the provided drain-source voltage and drain-source current levels in the data sheet.

5. The multi-mode control method for a wide-range input PV-storage-direct-flexible universal converter according to claim 3 is characterized in that: The conduction loss The calculation method is: in, is the effective value of the inductor current of the FSBB converter under the QCM method and TCM method, is the drain-source resistance considering temperature and drain-source current; The inductor loss The calculation method is: in, is the effective value of the inductor current of the FSBB converter under the QCM method and TCM method, is the inductor winding resistance, is the core volume, k 、 and are the core material parameters, is the amplitude of the magnetic flux density change.

6. The multi-mode control method for a wide-range input PV-storage-direct-flexible universal converter according to claim 5, characterized in that: The inductor current effective value of the FSBB converter under the QCM method and TCM method The calculation method is: in, is the input voltage, is the output voltage, is the switching cycle of the FSBB converter, in the Buck mode of the TCM method, θ Zero, in Boost mode θ for .

7. The multi-mode control method for a wide-range input PV-storage DC-flexible universal converter according to claim 1, characterized in that: The load current boundary of the FSBB converter in the QCM method in step 2 is: in, is the output current, is the input voltage, is the output voltage, To achieve the minimum current for soft switching, is the inductor, is the switching period of the FSBB converter.

8. The multi-mode control method for a wide-range input PV-storage DC-flexible universal converter according to claim 1, characterized in that: The calculation method of the current stress of the FSBB converter under the QCM method in step 3 is: in, is the peak value of the inductor current under the QCM method, To achieve the minimum current for soft switching, is the inductor, is the input voltage, is the output voltage, The main control tube in the Buck bridge arm S A duty cycle of 1, It is the main control tube in the Boost bridge arm S A duty cycle of 3, θ Main controller S 1 and main control tube S Phase shift between 3; The current stress of the FSBB converter under the TCM method is calculated as follows: in, is the inductor current peak value under the TCM method, is the switching period of the FSBB converter, is the output current.

9. The multi-mode control method for a wide-range input PV-storage DC-flexible universal converter according to claim 1, characterized in that: The expression of the comprehensive indicator model in step 3 is: in, is the output current, is the output voltage, To unify the loss, is the peak value of the inductor current under the QCM method or TCM method.

10. The multi-mode control method for a wide-range input PV-storage DC-flexible universal converter according to claim 1, characterized in that: The process of optimizing the variables to obtain the optimal solution in step 4 includes: , output voltage The theoretical value of the output current is calculated based on the load current boundary and compared with the sampled output current. and the calculated theoretical value to determine the output current Is it within the load current limit? If the output current Within the load current boundary, the duty cycle , duty cycle and phase shift angle As variables, different solutions are combined within the reasonable value range of the three variables, and the unified loss under different solution combinations is calculated. and current stress , comprehensively considering the unified loss and current stress The two indicators are optimized to obtain the optimal solution; if the output current Outside the load current boundary, the duty cycle is obtained based on the TCM method , duty cycle and phase shift angle .

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