Multi-mode control method for wide-range input-oriented optical storage direct-flexible universal converter

Abstract

The invention provides a wide-range input-oriented multi-mode control method for an optical storage DC-DC universal converter, and belongs to the field of non-isolated DC-DC converter control methods, and the method comprises the steps: building a unified loss model of an FSBB converter under different inductive current waveforms based on a constraint condition for achieving zero voltage switching of the FSBB converter and the loss distribution of the FSBB converter; determining a load current boundary of the FSBB converter in the QCM method under a fixed frequency condition; according to the current stress of the FSBB converter under the QCM method and the TCM method, expanding the unified loss model into a comprehensive index model for simultaneously optimizing the efficiency and the current stress of the FSBB converter; sampling an input voltage, an output voltage and an output current, optimizing variables based on a load current boundary and a comprehensive index model to obtain an optimal solution, and taking the optimal solution as a control parameter of the FSBB converter; the problems that a multi-mode control strategy of an existing FSBB converter is complex in control and neglects the influence of the current stress of a switching tube on the service life of the 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 universal converter for wide-range input. Background Art

[0002] With the rapid development of energy storage and photovoltaic systems, DC has become a major trend in new power systems. Especially in the field of new energy and DC interconnection, the four-switch Buck-Boost (FSBB) converter can be used as a DC grid interface for photovoltaic, energy storage and other types of power sources because it can flexibly realize the conversion of DC voltage in a wide range and has the characteristics of bidirectional power flow.

[0003] Due to the wide input voltage range of different types of power supplies, the control strategy of the FSBB converter needs to achieve efficiency optimization over the full voltage range and load conditions to ensure efficient energy transmission. However, in traditional control methods, the triangular current control (TCM) method of the FSBB converter performs well under light load, but the efficiency decreases under heavy load, especially under high load demand; while the quadrilateral inductor current control (QCM) method has high efficiency under heavy load conditions, but the current stress is large under light load, which will cause additional losses under low light conditions of the photovoltaic system. Therefore, a multi-mode control strategy is proposed to improve the overall efficiency performance of the FSBB converter by combining the TCM and QCM methods.

[0004] However, the existing multi-mode control strategy only takes efficiency as the optimization target, ignoring the impact of switch tube current stress on converter life. In addition, in the process of efficiency modeling, the traditional multi-mode control strategy needs to establish mathematical models of the two methods separately due to the large difference in inductor current between QCM and TCM methods, which makes the control of the converter complicated. Summary of the invention

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

[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-range input, the method comprising the following steps:

[0007] Step 1: Based on the constraint conditions for realizing zero voltage switching 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;

[0008] Step 2, determine the load current boundary of the FSBB converter under the QCM method under the condition of fixed frequency;

[0009] Step 3: 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 for simultaneously optimizing the efficiency and current stress of the FSBB converter;

[0010] Step 4: Sample the input voltage, output voltage and output current, optimize the variables based on the load current boundary and the comprehensive index model to obtain the optimal solution, 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. An offline model with the best comprehensive index of converter efficiency and current stress is obtained through optimization calculation. 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 switch tube cost of the FSBB converter and extending the overall life of the FSBB converter.

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

[0013] |I 1 |>I zvs ,|I 2 |>I zvs ,|I 3 |>I zvs ,|I 4 |>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 dead It is the dead time of the two power switches in the same bridge arm of the FSBB converter to prevent direct conduction. 1 T for QCM method4 Stage to T 1 The turning current value of the inductor current in the stage, I 2 T for QCM method 1 Stage to T 2 The turning current value of the inductor current in the stage, I 3 T for QCM method 2 Stage to T 3 The turning current value of the inductor current in the stage, I 4 T for QCM method 3 Stage to T 4 The turning current value of the inductor current in the stage, 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 For uniform 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 (d 1 , d 2 ,θ,R g )f s

[0021] P off =E off (d 1 , d 2 ,θ,R g )f s

[0022] Among them, d 1 The main control tube S in the Buck bridge arm 1 The duty cycle, d 2 It is the main control tube S in the Boost bridge arm. 3 The duty cycle of the main control tube S 1 and the main control S 3 The phase shift between s is the switching frequency, R g is the gate resistance, E on 、E off They are respectively 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 the TCM method, R on (T,I ds ) is the drain-source resistance considering 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 the 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-d 2 .

[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 s is the switching period of the FSBB converter.

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

[0036]

[0037] Among them, I peak is the peak value of the inductor current under the QCM method, I zvs To achieve the minimum current for soft switching, L c is the inductance, V in is the input voltage, V o is the output voltage, d 1 The main control tube S in the Buck bridge arm 1 The duty cycle, d 2 It is the main control tube S in the Boost bridge arm. 3 The duty cycle of the main control tube S 1 and the main control S 3 Phase shift between

[0038] The calculation method of the current stress of the FSBB converter under the TCM method is:

[0039]

[0040] Among them, I peak is the peak value of the inductor current under the 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 peakis 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: according to the input voltage V in , output voltage V o The theoretical value of the output current is calculated by comparing the sampled output current I o and the calculated theoretical value to determine the output current I o Is it within the load current boundary? If the output current I o Within the load current boundary, with a duty cycle d 1 , duty cycle d 2 and phase shift angle θ as variables, and different solutions are combined within the reasonable value range of the three variables to calculate the unified loss P under different solutions. loss and 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 d is obtained based on the TCM method. 1 , duty cycle d 2 and phase shift angle θ.

[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 for simultaneously optimizing the efficiency and current stress of the FSBB converter. An offline model with the best comprehensive index of converter efficiency and current stress is obtained through optimization calculation. 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 switch 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 1A circuit topology diagram of the FSBB converter in the multi-mode control method of a photovoltaic-storage-direct-flexible universal converter for wide-range input provided by an embodiment of the present invention;

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

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

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

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

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

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

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

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

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

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

[0061] Figure 14-16 A comparison curve diagram of the changes of the comprehensive index with the output current at different voltages in the multi-mode control method of the photovoltaic-storage-direct-flexible universal converter for wide-range input provided by the embodiment of the present invention;

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

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

[0064] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the technical solution of the present invention is clearly and completely described below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0065] like Figure 1 The circuit topology diagram of the FSBB converter used in the present invention mainly includes a Buck bridge arm and a Boost bridge arm, a power switch tube S 1 , S 2 The Buck bridge arm consists of a midpoint voltage of V A The main control tube of the Buck bridge arm is S 1 , the duty cycle is d 1 , power switch tube S 3 , S 4 The Boost bridge arm consists of two parts, and the main control tube of the Boost bridge arm is S 3 , the duty cycle is d 2 , the midpoint voltage is V B , inductance L cConnected between the midpoints of the two bridge arms, the two power switch tubes on the same bridge arm are complementary turned on, and the diode D 1 -D 4 Respectively connected in anti-parallel to the power switch tube S 1 -S 4 Between the drain and source, the capacitor C oss1 -C oss4 They are respectively power switch tube S 1 -S 4 The parasitic capacitance, capacitance C 0 is the output filter capacitor and resistor R is the load.

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

[0067] Step 1: Based on the constraints of the FSBB converter to achieve zero voltage switching (ZVS) 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: To achieve full power switch tube soft switching (ZVS) mode, the current condition for achieving full power switch tube ZVS is obtained by using formula (1):

[0069]

[0070] In formula (1), C oss is the parasitic capacitance of the power switch tube, t dead The dead time is used to prevent the shoot-through of the two power switch tubes in the same bridge arm of the FSBB converter.

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

[0072] |I 1 |>I zvs ,|I 2 |>I zvs ,|I 3 |>I zvs ,|I 4 |>I zvs ,|I max |>I zvs ,|I min |>I zvs , see Figure 2 and Figure 3 , I 1 T for QCM method 4 Stage to T 1 The turning current value of the inductor current in the stage, I2 T for QCM method 1 Stage to T 2 The turning current value of the inductor current in the stage, I 3 T for QCM method 2 Stage to T 3 The turning current value of the inductor current in the stage, I 4 T for QCM method 3 Stage to T 4 The turning current value of the inductor current in the stage, 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 The unit switching loss expression of the power switch tube under different voltage and current conditions is derived by curve fitting:

[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 obtained as follows:

[0077]

[0078] In formula (3), d 1 The main control tube S in the Buck bridge arm 1 The duty cycle, d 2 It is the main control tube S in the Boost bridge arm. 3 The duty cycle of the main control tube S 1 and the main control S 3 The phase shift between .

[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-d 2 .

[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 turning current I 1 ,I 2 ,I min etc. as variables, or use the switch time T 1 、T on 、T off etc. are used as variables, which results in inconsistent variables in the optimization process and repeated optimization. The present invention shares d 1 ,d 2 , θ represent the effective values ​​of the inductor currents of the two, making the optimization process simple and 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 switch tube. Under the condition of constant frequency, there is a load current boundary. The QCM load current boundary under the condition of constant frequency is obtained by formula (8):

[0097]

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

[0099] Step 3: According to 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 index model for simultaneously optimizing the converter efficiency and current stress.

[0100] The calculation method of the current stress of the FSBB converter under the QCM method is:

[0101]

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

[0103] The calculation method of the current stress of the FSBB converter under the TCM method is:

[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), and determine the functional relationship between the design constraints and the optimization variables. 1 , duty cycle d 2 The optimal solution of the optimization variable corresponding to the best comprehensive index is obtained by optimizing the phase shift angle θ, and the optimal solution is used as the control parameter of the multi-mode control method of the FSBB converter.

[0110] See also Figure 5 and Figure 6 , for variable duty cycle d 1 , duty cycle d 2 The process of optimizing the 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 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 boundary? If the output current I o Within the load current boundary, both the QCM method and the TCM method can achieve the load current requirement at this time. According to the unified loss model, the duty cycle d 1 , duty cycle d 2 and phase shift angle θ as variables, and different solutions are combined within the reasonable value range of the three variables to calculate the unified loss P under different solutions. loss, the minimum value of the unified loss can be obtained. When the unified loss is the minimum, 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 comprehensively considering the two indicators of unified loss and current stress for optimization, 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 two identical minimum values ​​of unified loss are not found, such as the maximum value of the 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 d is solved according to the characteristics of the TCM method itself. 1 , duty cycle d 2 and phase shift angle θ, and the duty cycle d 1 , duty cycle d 2 and phase shift angle θ, as control parameters of the multi-mode control method of the FSBB converter. In Buck mode, the duty cycle d 2 =1, phase shift angle θ = 0, duty cycle d 1 The calculation method is:

[0112]

[0113] In Boost mode, the duty cycle d 1 =1, phase shift angle θ = 1-d 2 , duty cycle d 2 The calculation method is:

[0114]

[0115] Determine the duty cycle d corresponding to the optimal comprehensive index 1 , duty cycle d 2 and phase shift angle θ, according to the duty cycle d 1 , duty cycle d 2The phase shift angle θ generates a PWM wave 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, obtains the best offline model of the comprehensive index of the converter efficiency and current stress through optimization calculation, and uses the variable with the best comprehensive index 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 switch tube cost of the FSBB converter, prolonging the overall life of the FSBB converter, and 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 is carried out based on the MATLAB / SIMULINKL simulation platform and a physical platform of the FSBB converter is built for experimental verification. The specification parameters of the FSBB converter are shown in Table 1.

[0119] Table 1 FSBB converter specifications

[0120] Working conditions & devices Parameters & Models <![CDATA[Input voltage V in > 100～200V <![CDATA[Output voltage V o > 150V <![CDATA[Inductor L c > 21μH <![CDATA[Maximum output current I o_max > 5A <![CDATA[Output capacitor C o > 470μF <![CDATA[Dead time t dead > 200ns <![CDATA[Switching frequency f s > 100kHz DSP TMS320F28035

[0121] The control method and converter parameters of the present invention are simulated and verified by actual experiments. Figure 7 and Figure 8 This is a comparison diagram of FSBB converter losses under the QCM and TCM methods of the present invention; Fig. 9 and Fig.10 This is a comparison diagram 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 is optimized, so the necessity of simultaneous multi-objective optimization is introduced. Fig.11 and Fig.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 there are always areas with poor comprehensive indicators when controlling alone, and the two control methods need to be combined. The comprehensive indicator curve after the combination is the maximum value of the two. Fig.13It is the boundary diagram of the use of QCM and TCM methods in the present invention; Figures 14 to 16 A comparison curve diagram of the comprehensive index in the present invention as the output current changes at different voltages; Fig.17 and Fig.18 They are respectively the waveform diagrams of the steady-state inductor current and ZVS in the Boost mode and Buck mode of the present invention.

[0122] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-mode control method for a photovoltaic storage direct-flexible universal converter with wide input range, characterized in that: The method comprises the following steps: Step 1: Based on the constraint conditions for realizing zero voltage switching 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; Step 2, determine the load current boundary of the FSBB converter under the QCM method under the condition of fixed frequency; Step 3: 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 for simultaneously optimizing the efficiency and current stress of the FSBB converter; Step 4: Sample the input voltage, output voltage and output current, optimize the variables based on the load current boundary and the comprehensive index model to obtain the optimal solution, and use the optimal solution as the control parameter of the FSBB converter.

2. The multi-mode control method of a photovoltaic-storage-direct-flexible universal converter for wide-range input according to claim 1 is characterized in that: The constraint condition for the FSBB converter to achieve zero voltage switching in step 1 is: |I1|>I zvs ,|I2|>I zvs ,|I3|>I zvs ,|I4|>I zvs ,|I max |>I zvs ,|I min |>I zvs , Among them, I zvs To achieve the minimum current for soft switching, C oss is the parasitic capacitance of the power switch tube, t dead is the dead time of the upper and lower power switches in the same bridge arm of the FSBB converter to prevent direct conduction, I1 is the turning current value of the inductor current from stage T4 to stage T1 under the QCM method, I2 is the turning current value of the inductor current from stage T1 to stage T2 under the QCM method, I3 is the turning current value of the inductor current from stage T2 to stage T3 under the QCM method, I4 is the turning current value of the inductor current from stage T3 to stage T4 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.

3. The multi-mode control method of a photovoltaic-storage-direct-flexible universal converter for wide-range input according to claim 1 is characterized in that: The expression of the unified loss model in step 1 is: P loss =P on +P off +P con +P L Among them, P loss For uniform 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.

4. The multi-mode control method of a photovoltaic-storage-direct-flexible universal converter for wide-range input according to claim 3 is characterized in that: The conduction loss P of the power switch tube on and the turn-off loss of the power switch tube P off The calculation method is: P on =E on (d1,d2,θ,R g )f s P off =E off (d1,d2,θ,R g )f s 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 off They are respectively 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 of a photovoltaic-storage-direct-flexible universal converter for wide-range input according to claim 3 is characterized in that: The conduction loss P con The calculation method is: Among them, I rms is the effective value of the inductor current of the FSBB converter under the QCM method and the TCM method, R on (T,I ds ) is the drain-source resistance considering temperature and drain-source current; The inductor loss P L The calculation method is: Among them, I rms is the effective value of the inductor current of the FSBB converter under the QCM method and the 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.

6. The multi-mode control method of a photovoltaic-storage-direct-flexible universal converter for wide-range input according to claim 5 is characterized in that: The inductor current effective value I of the FSBB converter under the QCM method and the TCM method rms The calculation method is: 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.

7. The multi-mode control method of a photovoltaic-storage-direct-flexible universal converter for wide-range input according to claim 1 is characterized in that: The load current boundary of the FSBB converter in the QCM method in step 2 is: 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 s is the switching period of the FSBB converter.

8. The multi-mode control method of a photovoltaic-storage-direct-flexible universal converter for wide-range input 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: Among them, I peak is the peak value of the inductor current under the QCM method, I zvs To achieve the minimum current for soft switching, L c is the inductance, 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 tube S1 and the main control tube S3; The calculation method of the current stress of the FSBB converter under the TCM method is: 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.

9. The multi-mode control method of a photovoltaic-storage-direct-flexible universal converter for wide-range input according to claim 1, characterized in that: The expression of the comprehensive indicator model in step 3 is: 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.

10. The multi-mode control method of a photovoltaic-storage-direct-flexible universal converter for wide-range input according to claim 1, characterized in that: 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 comparing the sampled output current I o and the calculated theoretical value to determine the output current I o Is it within the load current boundary? 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 solutions is calculated. loss and 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, the duty cycle d2 and the phase shift angle θ are obtained based on the TCM method.

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