High-gain secondary Buck-Boost converter applied to renewable energy sources

Abstract

The invention relates to the field of electrical technology, and discloses a high-gain secondary Buck-Boost converter applied to renewable energy sources, which comprises a first switching tube, a second switching tube, a first diode, a second diode, a third diode, a first inductor, a second inductor, a first capacitor, a second capacitor, a third capacitor, a load resistor and a power supply module, according to the high-gain secondary Buck-Boost converter applied to renewable energy sources, the high-gain secondary Buck-Boost converter has high voltage gain, the voltage stress of a switching device is reduced under the condition of the same output voltage, meanwhile, the converter can work under continuous input end current, the filtering requirement of an input port is greatly reduced, and the conversion efficiency of the converter is improved. Namely, a steady state can be kept in a continuous inductive current mode, so that the device is more suitable for utilization of renewable energy sources.

Description

Technical Field

[0001] The invention relates to the field of electrical technology, and in particular to a high-gain secondary Buck-Boost converter applied to renewable energy. Background Art

[0002] In recent decades, DC-DC converters have been widely used in many fields, such as renewable energy power generation systems, fuel cells, mobile power sources, portable devices, automotive electronic equipment, wind power generation, data transmission interfaces and signal generators. Since the buck-boost converter can easily achieve boost or buck output, the buck-boost converter is more widely used in the above fields. As we all know, Buck-Boost converter and Cuk converter are two of the most typical buck-boost converters. Theoretically, they can both generate extremely high buck or boost output voltage when the duty cycle D is close to 0 or 1. However, in practice, due to the influence of power switches, diodes, and equivalent series resistance (ESR) of inductors and capacitors, the voltage gain is limited. At the same time, increasing the duty cycle to increase the voltage gain will also lead to electromagnetic interference, low efficiency, large volume and other problems. In view of the above problems, a multi-level high-gain topology is studied. This topology increases the output voltage without increasing the duty cycle. Other reasonable solutions include converters based on magnetic coupling. Another option is to use a quadratic gain converter. However, existing research on quadratic converters has problems such as the converter can only work in buck mode, its input and output currents are discontinuous, its application range is limited, and converters with discontinuous input currents may cause increased input and output current ripples, complicating the design of input and output filters, the voltage gain is not high, and the output voltage polarity is negative. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention provides a high-gain secondary Buck-Boost converter for renewable energy, which is used to solve the problems of low voltage gain and discontinuous current in the existing secondary converter.

[0004] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0005] A high-gain secondary Buck-Boost converter for renewable energy comprises: a first switch tube, a second switch tube, a first diode, a second diode, a third diode, a first inductor, a second inductor, a first capacitor, a second capacitor, a third capacitor, a load resistor and a power module; the positive electrode of the power module is connected to one end of the first inductor, the other end of the first inductor is respectively connected to the positive electrode of the first diode, one end of the first switch tube and one end of the second capacitor, the negative electrode of the first diode is respectively connected to one end of the first capacitor and one end of the second switch tube, the other end of the second switch is respectively connected to one end of the second inductor and the negative electrode of the third diode, the other end of the second capacitor is respectively connected to the positive electrode of the second diode and the other end of the second inductor, the positive electrode of the third diode is respectively connected to one end of the third capacitor and one end of the load resistor, and the negative electrode of the power module is respectively connected to the other end of the first capacitor, the other end of the first switch tube, the negative electrode of the second diode, the other end of the third capacitor and the other end of the load resistor.

[0006] The present invention has the following beneficial effects:

[0007] The high-gain secondary Buck-Boost converter for renewable energy proposed in the present invention not only has a higher voltage gain, but also reduces the voltage stress of the switching device under the same output voltage. At the same time, it can operate under continuous input current and greatly reduces the filtering requirements of the input port, that is, it can maintain a steady state under the continuous inductor current mode, making it more suitable for the utilization of renewable energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a schematic diagram of the structure of a high-gain secondary Buck-Boost converter for renewable energy proposed by the present invention;

[0009] Figure 2 Schematic diagram of the equivalent circuit structure of the high-gain secondary Buck-Boost converter when the first switch tube and the second switch tube are synchronously turned on in the embodiment;

[0010] Figure 3 Schematic diagram of the equivalent circuit structure of the high-gain secondary Buck-Boost converter when the first switch tube and the second switch tube are synchronously disconnected in the embodiment;

[0011] Figure 4 Schematic diagram of an equivalent circuit for performing efficiency analysis on a high-gain quadratic Buck-Boost converter in an embodiment. DETAILED DESCRIPTION

[0012] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0013] like Figure 1 As shown, a high-gain secondary Buck-Boost converter applied to renewable energy includes: a first switch tube, a second switch tube, a first diode, a second diode, a third diode, a first inductor, a second inductor, a first capacitor, a second capacitor, a third capacitor, a load resistor and a power module; the positive electrode of the power module is connected to one end of the first inductor, the other end of the first inductor is respectively connected to the positive electrode of the first diode, one end of the first switch tube, and one end of the second capacitor, the negative electrode of the first diode is respectively connected to one end of the first capacitor and one end of the second switch tube, the other end of the second switch is respectively connected to one end of the second inductor and the negative electrode of the third diode, the other end of the second capacitor is respectively connected to the positive electrode of the second diode and the other end of the second inductor, the positive electrode of the third diode is respectively connected to one end of the third capacitor and one end of the load resistor, and the negative electrode of the power module is respectively connected to the other end of the first capacitor, the other end of the first switch tube, the negative electrode of the second diode, the other end of the third capacitor, and the other end of the load resistor.

[0014] In this embodiment, Figure 1 Medium S 1 , S 2 Respectively represent the first switch tube and the second switch tube, C 1 , C 2 , C 3 Respectively represent the first capacitor, the second capacitor, and the third capacitor, L 1 , L 2 Respectively represent the first inductance and the second inductance, D 1 , D 2 , D 3 Respectively represent the first diode, the second diode, and the third diode, R represents the load resistance, V in represents the input voltage of the high-gain secondary Buck-Boost converter, V 0represents the output voltage of the high-gain secondary Buck-Boost converter. In addition, in order to simplify the analysis of the working principle of the high-gain secondary Buck-Boost converter, the following conditions are assumed, specifically: (1) all components in the high-gain secondary Buck-Boost converter are ideal devices; (2) the inductor is large enough to ensure that the high-gain secondary Buck-Boost converter operates in the continuous conduction mode (CCM) of the inductor current.

[0015] like Figure 2 As shown, when the first switch tube and the second switch tube are synchronously turned on, the equivalent circuit of the high-gain secondary Buck-Boost converter includes a power module, a first switch tube, a second opening tube, a first inductor, a second inductor, a first capacitor, a second capacitor, a third capacitor and a load resistor; the positive electrode of the power module is connected to one end of the first inductor, the other end of the first inductor is respectively connected to one end of the first capacitor and one end of the first switch tube, the other end of the second capacitor is connected to one end of the second inductor, the other end of the second inductor is connected to one end of the second switch tube, and the other end of the second switch tube is connected to one end of the first capacitor, the negative electrode of the power module is respectively connected to the other end of the first capacitor, the other end of the first switch tube, one end of the third capacitor, and one end of the load resistor, and the other end of the third capacitor is connected to the other end of the load resistor.

[0016] In this embodiment, Figure 2 The equivalent circuit structure of the high-gain secondary Buck-Boost converter in the synchronous conduction state of the first switch tube and the second switch tube is shown. The principle is: in the conduction state (0~DT s ): During this period, the first switch tube S 1 , the second switch tube S 2 Synchronous conduction, input voltage V in To the first inductor L 1 Provide energy so that the first inductor L 1 The current of the first diode D 1 Connect the first capacitor C 1 At the same time, the reverse bias voltage stored in the first capacitor C 1 The energy and second capacitance C 2 The energy of the second inductor L 2 Provide energy so that the second inductor L 2 The current of the second diode D 2 Withstand the second capacitor C 2 The reverse bias voltage is cut off, and the output energy is provided by the third capacitor C 3 Provided; therefore, according to the working principle of this stage, the relevant differential equation is:

[0017] like Figure 3 As shown, when the first switch tube and the second switch tube are synchronously disconnected, the equivalent circuit of the high-gain secondary Buck-Boost converter includes a power module, a first inductor, a second inductor, a first diode, a second diode, a third diode, a first capacitor, a second capacitor, a third capacitor and a load resistor; the positive electrode of the power module is respectively connected to one end of the first inductor, the other end of the first inductor is respectively connected to the positive electrode of the first diode and one end of the second capacitor, the negative electrode of the first diode is connected to one end of the first capacitor, the other end of the second capacitor is respectively connected to the positive electrode of the second diode and one end of the second inductor, the other end of the second inductor is connected to the negative electrode of the third diode, the positive electrode of the third diode is respectively connected to one end of the third capacitor and one end of the load resistor, and the negative electrode of the power module is respectively connected to the other end of the first capacitor, the negative electrode of the second diode, the other end of the third capacitor and the other end of the load resistor.

[0018] In this embodiment, Figure 3 The equivalent circuit structure of the high-gain secondary Buck-Boost converter in the state where the first switch tube and the second switch tube are synchronously disconnected is shown. The principle is: in the disconnected state (DT s ~T s ): During this period, the first switch tube S 1 , the second switch tube S 2 Synchronous disconnection, the first diode D 1 , the second diode D 2 The positive voltage is turned on and stored in the first inductor L 1 The energy and input voltage V in Through the first diode D 1 , the second diode D 2 Give the first capacitor C 1 , the second capacitor C 2 Charging; at the same time, the third diode D 3 The forward voltage is turned on and stored in the second inductor L 2 The energy passes through the third diode D 3 Output to the third capacitor C 3 and load resistance R; therefore, according to the working principle of this stage, the relevant differential equation is:

[0019] In addition, according to the formula According to the volt-second balance principle, we can get: The voltage gain of the high-gain secondary Buck-Boost converter can be obtained from this formula, that is:

[0020]

[0021] Where M represents the voltage gain of the high-gain secondary Buck-Boost converter, D represents the duty cycle of the first switch tube and the second switch tube being turned on synchronously, V 0 represents the output voltage of the high-gain secondary Buck-Boost converter, V in Represents the input voltage of the high gain quadratic Buck-Boost converter.

[0022] In summary, from the formula It can be seen that the converter can theoretically obtain a higher voltage gain range.

[0023] In addition, the voltage and current stress of the switching device is analyzed to provide theoretical support for the selection of the switching device, that is, to select the appropriate switching device when soldering the circuit board, as shown below:

[0024] Specifically, the voltage stress and current stress of the first switch tube and the second switch tube are:

[0025]

[0026] in, represents the voltage stress of the first switch tube, represents the voltage stress of the first capacitor, represents the voltage stress of the second switch tube, represents the current stress of the first switch tube, represents the current stress of the second switch tube, represents the average current of the first inductor, represents the average current of the second inductor, R represents the load resistance, I 0 Represents the average current at the output of the high gain quadratic Buck-Boost converter.

[0027] Specifically, the voltage stress and current stress of the first diode, the second diode, and the third diode are:

[0028]

[0029] in, represents the voltage stress of the first diode, represents the voltage stress of the second diode, represents the voltage stress of the third diode, represents the voltage stress of the second capacitor, represents the current stress of the first diode, represents the current stress of the second diode, represents the current stress of the third diode.

[0030] In this embodiment, the voltage stress borne by the first switch tube and the second switch tube is the voltage across the two ends of the switch tube when the switch tube is turned off; similarly, the voltage stress borne by the first diode, the second diode, and the third diode is the voltage stress borne by the diode in the cut-off state; in addition, when the proposed converter is in a stable state (steady state means that the inductor and the capacitor are in a stable state of charging and discharging, that is, the energy charged and released by the inductor and the capacitor in one cycle are equal), the first capacitor C 1 , the second capacitor C 2 , the third capacitor C 3 Satisfying the charge balance principle, applying the charge balance principle to the capacitor, the formula and The average current of the first inductor can be obtained The average current of the second inductor and I 0 The relationship is: in At the same time, based on this formula and according to the working principle of the converter when the first switch tube and the second switch tube are synchronously turned on, the current stress flowing through the first switch tube and the second switch tube can be obtained; similarly, according to the working principle of the converter, the current stress of the first diode, the second diode and the third diode can be calculated.

[0031] In addition, the inductor current ripple and critical inductance are analyzed to solve the critical inductance expression. By solving the critical inductance, it is determined whether the inductor works in the continuous conduction mode, as shown below:

[0032] Specifically, the ripple current, minimum current and critical inductance value of the first inductor and the second inductor are:

[0033]

[0034] in, represents the ripple current of the first inductor, represents the ripple current of the second inductor, L 1 , L 2 Respectively represent the first inductance and the second inductance, T s Indicates the switching period of the first switch tube and the second switch tube being turned on or off synchronously, DT s Indicates the conduction time of the first switch tube or the second switch tube, f s Indicates the switching frequency at which the first switch tube and the second switch tube are synchronously turned on or off. represents the minimum current of the first inductor, Indicates the minimum current of the second inductor, L 11 Indicates the critical inductance value of the first inductor, L 2B represents the critical inductance value of the second inductor.

[0035] In this embodiment, based on the working principle of the high-gain secondary Buck-Boost converter and the formula The ripple current of the first inductor and the second inductor can be obtained, namely: And from this formula, it can be seen that when the inductor ripple current and output voltage, duty cycle and switching frequency are known, the appropriate inductance value can be selected according to the actual application. The purpose of selecting the appropriate inductance value is to reduce the current ripple. At the same time, when the converter works in the critical condition mode (BCM), the minimum current flowing through the inductor is zero, so from the formula and The minimum current of the first inductor and the second inductor can be obtained; and based on the minimum current formula of the first inductor and the second inductor, according to the minimum value flowing through the first inductor and the second inductor being equal to zero, it can be concluded that the critical inductance values ​​of the first inductor and the second inductor satisfy the condition: It can be seen from this formula that when L 1 >L 1B , L 2 >L 2B The proposed high gain quadratic Buck-Boost converter operates in the continuous conduction mode (CCM) of the inductor current when the inductor current is constant, otherwise, the converter operates in the discontinuous conduction mode (DCM).

[0036] In addition, the capacitor ripple voltage is analyzed to facilitate the selection of capacitor models. The output voltage ripple can also be determined based on the output ripple voltage of the third capacitor, as shown below:

[0037] Specifically, the ripple voltages of the first capacitor, the second capacitor, and the third capacitor are:

[0038]

[0039] in, represents the ripple voltage of the first capacitor, represents the ripple voltage of the second capacitor, represents the ripple voltage of the third capacitor, C 1 , C 2 , C 3 Represent the first capacitor, the second capacitor, and the third capacitor respectively.

[0040] In this embodiment, according to the high-gain secondary Buck-Boost converter and the formula The ripple voltages of the first capacitor, the second capacitor, and the third capacitor can be obtained, and the ripple voltage formula of the capacitor shows that when the output voltage, the first capacitor, the second capacitor, the third capacitor, the duty cycle, the switching frequency, and the load resistance, the formula The voltage ripples of the first capacitor, the second capacitor, and the third capacitor can be calculated. Similarly, when the output voltage ripples and other conditions (i.e., the output voltage, duty cycle, switching frequency, and resistance value of the load resistor) of the first capacitor, the second capacitor, and the third capacitor are known, the capacitance values ​​of the first capacitor, the second capacitor, and the third capacitor can be calculated.

[0041] In addition, an efficiency loss analysis is performed on the high-gain quadratic Buck-Boost converter to calculate the efficiency of the converter as follows:

[0042] Specifically, the efficiency of the high-gain secondary Buck-Boost converter is:

[0043]

[0044] Where η represents the efficiency of the high-gain secondary Buck-Boost converter, P 0 represents the output power of the high-gain secondary Buck-Boost converter, P S Represents the total power loss of the first switch tube and the second switch tube, P D It represents the total power loss of the first diode, the second diode and the third diode, P L Represents the total power loss of the first inductor and the second inductor, P C Represents the total power loss of the first capacitor, the second capacitor, and the third capacitor.

[0045] In this embodiment, in order to simplify the efficiency analysis, the influence of the ripple current of the inductor and capacitor on the efficiency analysis is ignored; at the same time, taking into account the equivalent resistance of the inductor, capacitor and switch device and the voltage drop of the switch device, the equivalent circuit diagram is as follows: Figure 4 As shown, Figure 4 Medium L1 、r L2 Respectively represent the equivalent resistance of the first inductor and the second inductor, r S1 、r S2 Respectively represent the parasitic resistance of the first switch tube and the second switch tube, r C1 、r C2 、r C3 Respectively represent the parasitic resistance of the first capacitor, the second capacitor, and the third capacitor, V F1 、V F2 、V F3 represents the threshold voltage of the first diode, the second diode, and the third diode, r D1 、r D2、r D3 They represent the parasitic resistance of the first diode, the second diode, and the third diode respectively, and RMS represents the root mean value.

[0046] Among them, the power loss of the switch tube is as follows:

[0047] MOSFET is selected as the power switch tube of the high-gain secondary Buck-Boost converter. The power loss in the power switch includes conduction loss and switching loss. The conduction loss occurs during the conduction state and is specifically calculated as:

[0048] The expressions of conduction loss of the first switch tube and the second switch tube are: The root mean square of the current flowing through the first switch tube and the second switch tube is I S1,rms ,I S2,rms for: Therefore, the root mean square of the current flowing through the first switch tube and the second switch tube is S1,rms ,I S2,rms The expression is introduced The conduction losses of the first switch tube and the second switch tube are obtained, namely:

[0049] The expressions of the switching losses of the first switch tube and the second switch tube are: where t r1 Indicates the rise time of the first switch tube, t f1 Represents the first switch tube, t r2 Indicates the rise time of the second switch tube, t f2 represents the fall time of the second switch tube; therefore, Substituting into the expression of the switching loss of the first switch tube and the second switch tube, the switching loss of the first switch tube and the second switch tube can be obtained as follows:

[0050] In summary, the total power loss of the power switch is the sum of the conduction loss and the switching loss, that is: P S =P sw(1) +P sw(2) .

[0051] Among them, the power loss of the inductor is as follows:

[0052] Inductor loss is divided into two parts: core loss and copper loss. The core loss of the inductor is P fe for: Among them, P fe1 represents the core loss of the first inductor, P fe2represents the core loss of the second inductor, α, b and c are parameter information derived from the data sheet; B is half of the AC magnetic flux; f represents the frequency value; A C1 , A c2 Respectively represent the core area of ​​the first inductor and the second inductor; l m1 , l m2 Both represent the magnetic path length of the iron core of the first inductor and the second inductor; since the inductor copper loss is caused by the winding resistance, and the RMS current passing through the inductor is And suppose the power loss of the first inductor and the second inductor is P cu According to the principle, we can get: The total power loss of the inductor P can be obtained L P L =P fe +P cu .

[0053] Among them, the power loss of the diode is as follows:

[0054] Assume that the root mean square of the current flowing through the first diode, the second diode, and the third diode is I D1,rms ,I D2,rms ,I D3,rms , similarly we can get: Assuming the power loss of the first diode, the second diode, and the third diode is PD, according to the principle, we can get:

[0055] Among them, the power loss of the capacitor is as follows:

[0056] The power loss of the capacitor is caused by the parasitic resistance of the capacitor. According to the instantaneous current flowing through the first capacitor, the second capacitor, and the third capacitor in the on and off states of the switch tube, the RMS current value I of the first capacitor, the second capacitor, and the third capacitor can be obtained. C1,rms ,I C2,rms ,I C3,rms for And suppose the total power loss of the capacitor is P C , the power loss of the first capacitor, the second capacitor, and the third capacitor is calculated from the root mean square of the capacitor current:

[0057] In summary, the total power loss of the high-gain quadratic Buck-Boost converter is the sum of the power losses of the inductor, capacitor, power switch and diode. Obviously, the input power is the sum of the total power loss and the output power, so the efficiency η of the converter can be expressed as

[0058] Specifically, the small signal model of the high-gain secondary Buck-Boost converter is:

[0059]

[0060] Where, d represents the duty cycle of the small AC signal containing DC components. Respectively v 0 ,d,v in The corresponding small AC signal component.

[0061] In this embodiment, in order to analyze the small signal dynamic characteristics of the improved gain quadratic Buck-Boost converter, it is necessary to establish a converter small signal mathematical model, derive the control-output transfer function of small signal modeling, and use the state space averaging method to establish the small signal model equation. Based on the working principle of the proposed converter, the formula We can get: in, express v 0 、v in The corresponding average component.

[0062] When the average variable of each parameter is decomposed, it can be decomposed into the sum of the DC component and the AC small signal component. This breaks down as follows:

[0063] And meet Substituting this formula into the above formula and ignoring the second-order AC term, the small signal model of the high-gain quadratic Buck-Boost converter can be obtained.

[0064] In this embodiment, by comparing the topological structures of the existing converter and the converter proposed in the present invention, the effectiveness of the high-gain secondary Buck-Boost converter applied to renewable energy proposed in the present invention is verified, as shown in Table 1:

[0065] Table 1 Comparison of topological structures of existing converters and the converter proposed by the present invention

[0066]

[0067]

[0068] Table 1 shows a switched capacitor quadratic buck-boost converter, which is a high-gain, low-output ripple voltage quadratic Buck-Boost converter, a single quadratic buck-boost converter, a quadratic buck-boost converter, which is a traditional Boost converter, a traditional Buck-Boost converter and a quadratic buck-boost converter cascaded together with a traditional Buck converter, and uses these three converters to compare with the Buck-Boost converter of the present invention in terms of component quantity, voltage gain, voltage stress, etc., wherein all parameter expressions assume that the components are in an ideal state and the converters operate in the inductor current continuous conduction mode. From the comparison results in Table 1, it can be seen that the voltage gain ratio of the proposed converter is significantly higher than that of the switched capacitor quadratic buck-boost converter, the single quadratic buck-boost converter, and the quadratic buck-boost converter, and is comparable to that of the switched capacitor quadratic buck-boost converter. Compared with the single quadratic buck-boost converter, the Buck-Boost converter proposed in the present invention not only has an increased voltage gain, but also has a significantly reduced number of devices, and the voltage stress of the diode and the switch tube is reduced; compared with the single quadratic buck-boost converter, although the Buck-Boost converter proposed in the present invention has an additional capacitor and a diode, the output voltage gain of the proposed converter is not only greater than the voltage gain of the single quadratic buck-boost converter, but also reduces the voltage stress of the switch tube under the same voltage value, and the input current is continuous; compared with the quadratic buck-boost converter, the number of devices of the quadratic buck-boost converter is significantly increased, and the voltage gain ratio of the Buck-Boost converter proposed in the present invention is higher than that of the quadratic buck-boost converter, so the Buck-Boost converter proposed in the present invention has better performance.

[0069] In summary, the high-gain secondary Buck-Boost converter for renewable energy proposed in the present invention not only has a higher voltage gain, but also reduces the voltage stress of the switching device under the same output voltage, and can operate under continuous input current. In addition, by analyzing the working principle and steady-state performance of the converter under continuous inductor current mode, small signal modeling and power loss analysis are performed, and the proposed converter is compared with the existing secondary Buck-Boost converter, which proves the unique characteristics and effectiveness of the proposed converter.

[0070] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

[0071] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A high-gain secondary Buck-Boost converter for renewable energy, characterized in that: include: a first switch tube, a second switch tube, a first diode, a second diode, a third diode, a first inductor, a second inductor, a first capacitor, a second capacitor, a third capacitor, a load resistor and a power module; the positive electrode of the power module is connected to one end of the first inductor, the other end of the first inductor is respectively connected to the positive electrode of the first diode, one end of the first switch tube and one end of the second capacitor, the negative electrode of the first diode is respectively connected to one end of the first capacitor and one end of the second switch tube, the other end of the second switch is respectively connected to one end of the second inductor and the negative electrode of the third diode, the other end of the second capacitor is respectively connected to the positive electrode of the second diode and the other end of the second inductor, the positive electrode of the third diode is respectively connected to one end of the third capacitor and one end of the load resistor, and the negative electrode of the power module is respectively connected to the other end of the first capacitor, the other end of the first switch tube, the negative electrode of the second diode, the other end of the third capacitor and the other end of the load resistor.

2. The high-gain secondary Buck-Boost converter for renewable energy according to claim 1, characterized in that: When the first switch tube and the second switch tube are synchronously turned on, the equivalent circuit of the high-gain secondary Buck-Boost converter includes a power module, a first switch tube, a second opening tube, a first inductor, a second inductor, a first capacitor, a second capacitor, a third capacitor and a load resistor; the positive electrode of the power module is connected to one end of the first inductor, the other end of the first inductor is respectively connected to one end of the first capacitor and one end of the first switch tube, the other end of the second capacitor is connected to one end of the second inductor, the other end of the second inductor is connected to one end of the second switch tube, and the other end of the second switch tube is connected to one end of the first capacitor, the negative electrode of the power module is respectively connected to the other end of the first capacitor, the other end of the first switch tube, one end of the third capacitor, and one end of the load resistor, and the other end of the third capacitor is connected to the other end of the load resistor.

3. The high-gain secondary Buck-Boost converter for renewable energy according to claim 2, characterized in that: When the first switch tube and the second switch tube are synchronously disconnected, the equivalent circuit of the high-gain secondary Buck-Boost converter includes a power module, a first inductor, a second inductor, a first diode, a second diode, a third diode, a first capacitor, a second capacitor, a third capacitor and a load resistor; the positive electrode of the power module is respectively connected to one end of the first inductor, the other end of the first inductor is respectively connected to the positive electrode of the first diode and one end of the second capacitor, the negative electrode of the first diode is connected to one end of the first capacitor, the other end of the second capacitor is respectively connected to the positive electrode of the second diode and one end of the second inductor, the other end of the second inductor is connected to the negative electrode of the third diode, the positive electrode of the third diode is respectively connected to one end of the third capacitor and one end of the load resistor, and the negative electrode of the power module is respectively connected to the other end of the first capacitor, the negative electrode of the second diode, the other end of the third capacitor and the other end of the load resistor.

4. The high-gain secondary Buck-Boost converter for renewable energy according to claim 3, characterized in that: The voltage gain of the high-gain secondary Buck-Boost converter is: Wherein, M represents the voltage gain of the high-gain secondary Buck-Boost converter, D represents the duty cycle of the first switch tube and the second switch tube being synchronously turned on, V0 represents the output voltage of the high-gain secondary Buck-Boost converter, V in Represents the input voltage of the high gain quadratic Buck-Boost converter.

5. The high-gain secondary Buck-Boost converter for renewable energy according to claim 4, characterized in that: The voltage stress and current stress of the first switch tube and the second switch tube are: in, represents the voltage stress of the first switch tube, represents the voltage stress of the first capacitor, represents the voltage stress of the second switch tube, represents the current stress of the first switch tube, represents the current stress of the second switch tube, represents the average current of the first inductor, represents the average current of the second inductor, R represents the load resistance, and I0 represents the average current at the output of the high gain secondary Buck-Boost converter.

6. The high-gain secondary Buck-Boost converter for renewable energy according to claim 5, characterized in that: The voltage stress and current stress of the first diode, the second diode and the third diode are: in, represents the voltage stress of the first diode, represents the voltage stress of the second diode, represents the voltage stress of the third diode, represents the voltage stress of the second capacitor, represents the current stress of the first diode, represents the current stress of the second diode, represents the current stress of the third diode.

7. The high-gain secondary Buck-Boost converter for renewable energy according to claim 6, characterized in that: The ripple current, minimum current and critical inductance of the first inductor and the second inductor are: in, represents the ripple current of the first inductor, represents the ripple current of the second inductor, L1 and L2 represent the first inductor and the second inductor respectively, T s Indicates the switching period of the first switch tube and the second switch tube being turned on or off synchronously, DT s Indicates the conduction time of the first switch tube or the second switch tube, f s Indicates the switching frequency at which the first switch tube and the second switch tube are synchronously turned on or off. represents the minimum current of the first inductor, Indicates the minimum current of the second inductor, L 1B Indicates the critical inductance value of the first inductor, L 2B represents the critical inductance value of the second inductor.

8. The high-gain secondary Buck-Boost converter for renewable energy according to claim 7, characterized in that: The ripple voltages of the first capacitor, the second capacitor, and the third capacitor are: in, represents the ripple voltage of the first capacitor, represents the ripple voltage of the second capacitor, represents the ripple voltage of the third capacitor, and C1, C2, and C3 represent the first capacitor, the second capacitor, and the third capacitor, respectively.

9. The high-gain secondary Buck-Boost converter for renewable energy according to claim 8, characterized in that: The efficiency of the high-gain secondary Buck-Boost converter is: Where, η represents the efficiency of the high-gain quadratic Buck-Boost converter, P0 represents the output power of the high-gain quadratic Buck-Boost converter, P S Represents the total power loss of the first switch tube and the second switch tube, P D It represents the total power loss of the first diode, the second diode and the third diode, P L Represents the total power loss of the first inductor and the second inductor, P C Represents the total power loss of the first capacitor, the second capacitor, and the third capacitor.

10. The high-gain secondary Buck-Boost converter for renewable energy according to claim 9, characterized in that: The small signal model of the high-gain secondary Buck-Boost converter is: Where, d represents the duty cycle of the small AC signal containing DC components. Respectively v0, d, v in The corresponding small AC signal component.

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