Three-port direct-current converter with high output voltage gain, power conversion method and system

Abstract

The invention provides a three-port direct-current converter with high output voltage gain and a power conversion method and system, and relates to the field of intelligent power grids, the three-port direct-current converter with high output voltage gain comprises an energy input assembly, an energy conversion assembly, a switch control assembly, a rectification and clamping protection assembly and an output filtering assembly, the energy input assembly is used for being connected with a photovoltaic input source and storing energy, the energy conversion assembly is used for conducting energy conversion and voltage boosting, the switch control assembly is used for changing a circuit topological structure and a working mode, and the rectification and clamping protection assembly is used for converting output of the energy conversion assembly into one-way flowing direct current. And the output filtering assembly is used for filtering the output of the rectification and clamping protection assembly and supplying power to a load, and has the advantage of realizing ultrahigh output voltage gain within a limited duty ratio range.

Description

Technical Field

[0001] This invention relates to the field of smart grids, and in particular to a three-port DC-DC converter with high output voltage gain, a power conversion method, and a system. Background Technology

[0002] With the widespread application of renewable energy sources (such as photovoltaics and fuel cells) and energy storage systems (such as batteries), the demand for efficient, highly integrated, and high-performance power conversion technologies is becoming increasingly urgent. Multi-port converters, due to their ability to integrate multiple energy sources, loads, or energy storage units within a single topology, enabling unified energy management and efficient transmission, have become a research hotspot in modern power electronics systems, particularly in distributed generation, electric vehicles, uninterruptible power supplies (UPS), and microgrids. A core challenge in these applications is that the input voltage of renewable energy sources is generally low (e.g., photovoltaic panels have a wide output voltage range, while fuel cells have low output voltage), while grid connection or driving loads typically requires a higher DC bus voltage (e.g., 400V or higher). This necessitates converters with ultra-high voltage gain capabilities. Traditional boost converters (such as boost converters, cascaded boost converters, or isolated converters) face significant problems such as low efficiency, high cost, and multi-stage power conversion when achieving high gain. Therefore, there is an urgent need to develop novel high-gain, high-efficiency, low-ripple, and easily soft-switching three-port DC-DC converter topologies and their control methods.

[0003] In recent years, researchers have proposed a variety of high-voltage-gain three-port DC-DC converters, which can be divided into coupled inductor type, switched inductor / switched capacitor type, etc. Among them, high-gain DC-DC converters based on switched inductors / switched capacitors have disadvantages such as a large number of components, large size, and high cost. In contrast, high-gain three-port DC-DC converters based on coupled inductors can realize the integration of magnetic components and have advantages such as high power density and low cost, but they also have disadvantages such as large input current ripple and difficulty in achieving soft switching.

[0004] Therefore, there is a need to provide three-port DC-DC converters, power conversion methods, and systems with high output voltage gain to achieve ultra-high output voltage gain within a limited duty cycle range. Summary of the Invention

[0005] This invention provides a three-port DC-DC converter with high output voltage gain, comprising an energy input component, an energy conversion component, a switching control component, a rectification and clamping protection component, and an output filtering component. The energy input component is used to connect to a photovoltaic input source and store energy. The energy conversion component is used for energy conversion and voltage boosting. The switching control component is used to change the circuit topology and operating mode. The rectification and clamping protection component is used to convert the output of the energy conversion component into unidirectional DC current. The output filtering component is used to filter the output of the rectification and clamping protection component to supply power to the load.

[0006] Further, the energy input component includes a photovoltaic input port, an energy storage output terminal, and a photovoltaic series diode connected in series with the photovoltaic input port; the energy conversion component includes an input inductor, a first coupling inductor, and a second coupling inductor, wherein the terminals of the primary winding and the secondary winding of the first coupling inductor are of the same name, and the terminals of the primary winding and the secondary winding of the second coupling inductor are of the same name; the switching control component includes a first switching transistor, a second switching transistor, a third switching transistor, and a fourth switching transistor; the rectification and clamping protection component includes a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a first clamping capacitor, and a third diode. The system includes a second clamping capacitor, a third clamping capacitor, and a fourth clamping capacitor; the output filter component includes an output capacitor; the positive terminal of the photovoltaic input port is connected to the anode of the photovoltaic series diode, the cathode of the photovoltaic input port is connected to the source of the third switching transistor, the drain of the third switching transistor is connected to the positive terminal of the energy storage output terminal, the negative terminal of the energy storage output terminal is connected to the negative terminal of the photovoltaic input port, the positive terminal of the energy storage output terminal is connected to the source of the second switching transistor, the drain of the second switching transistor is connected to the cathode of the first diode, the anode of the first diode is connected to the cathode of the second diode, and the anode of the second diode is connected to the anode of the third diode, one end of the input inductor, and one end of the first clamping capacitor, respectively. The other end of the inductor is connected to the cathode of the photovoltaic input port and the drain of the third switching transistor. The other end of the first clamping capacitor is connected to the terminal of the primary winding of the second coupling inductor. The terminal of the primary winding of the second coupling inductor is connected to the negative terminal of the photovoltaic input port. The cathode of the third diode is connected to the terminal of the primary winding of the first coupling inductor and one end of the second clamping capacitor. The terminal of the primary winding of the first coupling inductor is connected to the anode of the first diode, the cathode of the second diode, the drain of the first switching transistor, and the anode of the fourth diode. The anode of the fourth diode, one end of the third clamping capacitor, and the cathode of the fourth diode are connected to the terminal of the secondary winding of the second coupling inductor. The cathode of the fifth diode is connected to the anode of the first coupling inductor and the anode of the sixth diode. The terminal of the secondary winding of the first coupling inductor is connected to the other end of the third clamping capacitor. The cathode of the sixth diode is connected to one end of the output capacitor and the positive terminal of the load. The other end of the output capacitor and the negative terminal of the load are both connected to one end of the fourth clamping capacitor. The other end of the fourth clamping capacitor is connected to the drain of the fourth switching transistor and the terminal of the secondary winding of the second coupling inductor. The source of the fourth switching transistor is connected to the drain of the first switching transistor. The source of the first switching transistor is connected to the other end of the second clamping capacitor and the negative terminal of the photovoltaic input port.

[0007] This invention provides a power conversion system applied to the aforementioned three-port DC-DC converter with high output voltage gain, comprising: an input power control loop for calculating a first compensation voltage based on the voltage and current of the photovoltaic input port using a maximum power point tracking algorithm; an output voltage control loop for calculating a second compensation voltage based on an output voltage reference value and an output voltage sample value; a mode selection module for generating a first mode selection voltage, a second mode selection voltage, and a third mode selection voltage based on the first and second compensation voltages; and a pulse width modulation module for generating drive signals for a first switch, a second switch, a third switch, and a fourth switch using multiple comparators.

[0008] Furthermore, the input power control loop calculates a first compensation voltage based on the voltage and current of the photovoltaic input port using a maximum power point tracking algorithm, including: calculating a reference voltage for the photovoltaic input port based on the voltage and current of the photovoltaic input port using the maximum power point tracking algorithm; subtracting the reference voltage from the photovoltaic input port voltage to obtain a first voltage difference; and calculating the first compensation voltage based on the first voltage difference using a first compensator. The output voltage control loop calculates a second compensation voltage based on an output voltage reference value and an output voltage sample value, including: subtracting the output voltage reference value from the output voltage sample value to obtain a second voltage difference; and calculating the second compensation voltage based on the second voltage difference using a second compensator.

[0009] Further, the mode selection module generates a first mode selection voltage, a second mode selection voltage, and a third mode selection voltage based on a first compensation voltage and a second compensation voltage, including: subtracting the peak value of the sawtooth wave from the second compensation voltage to obtain a third voltage difference; inputting the second voltage difference to a maximum value selector, with the other input of the maximum value selector being 0; subtracting the output of the maximum value selector from the first compensation voltage to generate the first mode selection voltage; subtracting the second compensation voltage from the first compensation voltage to generate the second mode selection voltage; and using the second compensation voltage as the third mode selection voltage.

[0010] Further, the pulse width modulation module includes a first comparator, a second comparator, a third comparator, an NOT gate, an AND gate, and a NOR gate. A first mode selection voltage is electrically connected to the non-inverting input of the first comparator, a second mode selection voltage is electrically connected to the non-inverting input of the second comparator, and a third mode selection voltage is electrically connected to the non-inverting input of the third comparator. The sawtooth wave is input to the inverting inputs of the first, second, and third comparators. The first comparator outputs the gate drive signal of the first switch. The output of the first comparator is electrically connected to the input of the NOT gate. The output of the NOT gate and the output of the second comparator are electrically connected to the two inputs of the AND gate. The AND gate outputs the gate drive signal of the second switch. The third comparator outputs the gate drive signal of the third switch. The gate drive signals of the first and second switches are respectively electrically connected to the two inputs of the NOR gate. The NOR gate outputs the gate drive signal of the fourth switch.

[0011] Furthermore, when the photovoltaic input power is greater than the power required by the load, the third switch is in the off state.

[0012] Furthermore, when the photovoltaic input power is less than the power required by the load, the second switch is in the off state.

[0013] Furthermore, when the photovoltaic input power is 0, the second switch is in the off state.

[0014] This invention provides a power conversion method applied to the aforementioned power conversion system, comprising: calculating a first compensation voltage based on the voltage and current at the photovoltaic input port using a maximum power point tracking algorithm; calculating a second compensation voltage based on an output voltage reference value and an output voltage sample value; generating a first mode selection voltage, a second mode selection voltage, and a third mode selection voltage based on the first compensation voltage and the second compensation voltage; and generating drive signals for a first switch, a second switch, a third switch, and a fourth switch using multiple comparators.

[0015] Compared with existing technologies, the three-port DC-DC converter, power conversion method, and system with high output voltage gain provided by this invention have at least the following advantages: 1. Achieving ultra-high output voltage gain within a limited duty cycle range breaks through the limitations of traditional converters in voltage boosting, meeting the high-voltage requirements of high-voltage DC buses. Simultaneously, it enables continuous current ripple at the photovoltaic input port. Compared to discontinuous current ripple, continuous current ripple reduces the impact of current surges on photovoltaic modules and circuit components, lowers electromagnetic interference, and improves system stability and reliability. This characteristic allows the converter to more stably convert photovoltaic energy into the required high-voltage DC in renewable energy generation scenarios, reducing losses during energy conversion, improving overall energy conversion efficiency, and providing strong support for efficient connection between renewable energy generation units and high-voltage DC buses.

[0016] 2. Single-stage power conversion achieves integrated and optimized control of photovoltaic (PV), energy storage, and high-voltage DC (HVDC) buses, avoiding the complex structures and increased energy losses associated with multi-stage conversion. Single-stage conversion simplifies the circuit topology, reduces the number of components, and lowers system cost and size. In terms of integrated control, it can intelligently coordinate energy flow among the three components based on PV input power, energy storage status, and load demand, achieving optimal power allocation. For example, when PV power is sufficient, priority is given to powering the load and charging the energy storage device; when PV power is insufficient, the energy storage device replenishes energy promptly, ensuring stable load operation and improving the overall utilization efficiency and flexibility of the new energy power generation system.

[0017] 3. By precisely calculating the compensation voltage and generating the mode selection voltage, and combining this with multiple comparators to generate the switching transistor drive signal, precise control of the switching transistors is achieved. The operating state of the switching transistors is flexibly adjusted according to different photovoltaic input power and load requirements. For example, when the photovoltaic input power exceeds the required load power, the third switching transistor is appropriately shut down; when the photovoltaic input power is zero, the second switching transistor is promptly shut down. This intelligent switching strategy effectively improves the system's energy conversion efficiency, reduces unnecessary energy loss, and enhances the system's adaptability to different operating conditions, ensuring stable and efficient operation in various complex environments. Attached Figure Description

[0018] This specification will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting; in these embodiments, the same reference numerals denote the same structures, wherein: Figure 1 This is a circuit diagram of a three-port DC-DC converter with high output voltage gain, as shown in some embodiments of this specification. Figure 2 This is a block diagram of a power conversion system according to some embodiments of this specification; Figure 3a This is a schematic diagram of the theoretical waveforms of the single-input dual-output mode according to some embodiments of this specification; Figure 3b This is a schematic diagram of the theoretical waveforms of the dual-input single-output mode shown in some embodiments of this specification; Figure 3c This is a schematic diagram of the theoretical waveform of the single-input single-output mode according to some embodiments of this specification; Figure 4 This is a schematic diagram of the equivalent circuit in the dual-input single-output mode shown in some embodiments of this specification; Figure 5 This is a schematic diagram of the equivalent circuit in single-input single-output mode according to some embodiments of this specification; Figure 6a This is a schematic diagram of the steady-state simulation waveform of the single-input dual-output mode according to some embodiments of this specification; Figure 6b This is a schematic diagram of the steady-state simulation waveform of the dual-input single-output mode according to some embodiments of this specification; Figure 6c This is a schematic diagram of the steady-state simulation waveform of the single-input single-output mode according to some embodiments of this specification; Figure 7 This is a schematic diagram of simulation results during load switching according to some embodiments of this specification; Figure 8 This is a schematic diagram of simulation results for photovoltaic input switching according to some embodiments shown in this specification; Figure 9 This is a schematic flowchart illustrating a power conversion method according to some embodiments of this specification. Detailed Implementation

[0019] To more clearly illustrate the technical solutions of the embodiments in this specification, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this specification. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0020] A three-port DC-DC converter with high output voltage gain includes: an energy input component, an energy conversion component, a switching control component, a rectification and clamping protection component, and an output filter component. The energy input component is used to connect to a photovoltaic input source and store energy; the energy conversion component is used to convert energy and boost voltage; the switching control component is used to change the circuit topology and operating mode; the rectification and clamping protection component is used to convert the output of the energy conversion component into unidirectional DC current; and the output filter component is used to filter the output of the rectification and clamping protection component to supply power to the load.

[0021] Figure 1 This is a circuit diagram of a three-port DC-DC converter with high output voltage gain, as shown in some embodiments of this specification, such as... Figure 1 As shown, the energy input component includes a photovoltaic input port. V pv Energy storage output end V bat , and photovoltaic input end V pv Photovoltaic series diode D connected in series pv ; The energy conversion components include an input inductor. L First coupling inductor N 1 (including primary winding) N 1a and secondary winding N 1b ) and second coupled inductor N 2 (including primary winding) N 2a and secondary winding N 2b ), first coupled inductor N In 1, the primary winding N 1a Terminals and secondary winding N 1b The terminals are the same name terminals, the second coupled inductor. N In section 2, the primary winding N 2a Terminals and secondary winding N 2b The terminals are of the same name; The switching control assembly includes a first switching transistor S1, a second switching transistor S2, a third switching transistor S3, and a fourth switching transistor S4. The first switching transistor S1, the second switching transistor S2, the third switching transistor S3, and the fourth switching transistor S4 can be metal-oxide-semiconductor field-effect transistors. For applications with higher power and higher voltage levels, the switching transistors can also be insulated-gate bipolar transistors.

[0022] The rectification and clamping protection assembly includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, and a first clamping capacitor. C 1. Second clamping capacitor C 2. Third clamping capacitor C 3. Fourth clamping capacitor C 4; The output filtering component includes the output capacitor. C o ; Photovoltaic input port V pv The positive electrode of the photovoltaic series diode D pv The anode is connected to the photovoltaic input port. V pv The cathode of the transistor is connected to the source of the third switch S3, and the drain of the third switch S3 is connected to the energy storage output terminal. V bat The positive terminal is connected to the energy storage output terminal. V bat The negative terminal is connected to the photovoltaic input port. V pv The negative terminal, energy storage output terminal V bat The positive terminal of the first diode is connected to the source of the second switch S2, the drain of the second switch S2 is connected to the cathode of the first diode D1, the anode of the first diode D1 is connected to the cathode of the second diode D2, and the anode of the second diode D2 is connected to the anode of the third diode D3 and the input inductor. L One end and the first clamping capacitor C One end of 1 is the input inductor. L The other end is connected to the photovoltaic input port. V pv The cathode and drain of the third diode D3, and the first clamping capacitor. C The other end of 1 is coupled to the second inductor. N 2 primary winding N 2a The terminals are connected, and the second coupled inductor is connected. N 2 primary winding N 2a The terminal is connected to the photovoltaic input port. V pv The negative terminal of the first diode and the cathode of the third diode D3 are respectively connected to the first coupling inductor. N 1 primary winding N 1a Terminals and second clamping capacitors C One end of 2, the first coupled inductor N 1 primary winding N 1aThe terminals are respectively connected to the anode of the first diode D1, the cathode of the second diode D2, the drain of the first switching transistor S1, and the anode of the fourth diode D4, the anode of the fourth diode D4, and the third clamping capacitor. C One end of diode 3 and the cathode of the fourth diode D4 are respectively connected to the second coupling inductor. N 2 secondary winding N 2b The terminal of the first diode is connected to the anode of the fifth diode D5, and the cathode of the fifth diode D5 is connected to the first coupling inductor. N 1 secondary winding N 1b The terminal and the anode of the sixth diode D6, the first coupling inductor N 1 secondary winding N 1b The terminal is connected to the third clamping capacitor. C At the other end of 3, the cathode of the sixth diode D6 is connected to the output capacitor. C o One end of the capacitor is connected to the positive terminal of the load R, and the output capacitor is connected to the positive terminal of the load R. C o The other end and the negative terminal of the load R are both connected to the fourth clamping capacitor. C One end of 4 is connected to the fourth clamping capacitor. C The other end of 4 is connected to the drain of the fourth switching transistor S4 and the second coupling inductor, respectively. N 2 secondary winding N 2b The source of the fourth switching transistor S4 is connected to the drain of the first switching transistor S1, and the source of the first switching transistor S1 is connected to the second clamping capacitor. C The other end of 2 and the photovoltaic input port V pv The negative end.

[0023] A three-port DC-DC converter with high output voltage gain can operate in three modes based on the relationship between the photovoltaic input power and the load power demand: single-input dual-output mode, dual-input single-output mode, and single-input single-output mode. Specifically, when the photovoltaic input power is greater than or equal to the load power demand, the three-port DC-DC converter with high output voltage gain operates in single-input dual-output mode, and the third switch S3 is always off. When the photovoltaic input power is less than the load power demand, the three-port DC-DC converter with high output voltage gain operates in dual-input single-output mode, and the second switch S2 is always off. When the photovoltaic input power is 0, the three-port DC-DC converter with high output voltage gain operates in single-input single-output mode, and the second switch S2 is always off.

[0024] Figure 2These are schematic diagrams of a power conversion system according to some embodiments of this specification, such as... Figure 2 As shown, the power conversion system may include an input power control loop, an output voltage control loop, a mode selection module, and a pulse width modulation module.

[0025] The input power control loop is used to calculate the first compensation voltage based on the voltage and current at the photovoltaic input port using a maximum power point tracking algorithm.

[0026] Specifically, it includes: Maximum power point tracking algorithms (e.g., perturbation-observation algorithm, incremental conductance method, etc.) are used based on the voltage at the photovoltaic input port. V pv and current I pv Calculate the reference voltage at the photovoltaic input port. V pv_ref ; The reference voltage at the photovoltaic input port V pv_ref Voltage at the photovoltaic input port V pv Subtracting them gives the first voltage difference; The first compensation voltage is calculated based on the first voltage difference using the first compensator. v e_IVR The first compensator can be a proportional-integral (PI) compensator, a proportional-integral-derivative (PID) compensator, etc.

[0027] The output voltage control loop is used to calculate the second compensation voltage based on the output voltage reference value and the output voltage sample value.

[0028] Specifically, it includes: Output voltage reference value V o_ref and output voltage sampling value V o Subtracting them gives the second voltage difference; The second compensation voltage is calculated based on the second voltage difference using the second compensator. v e_OVR The second compensator can be a proportional-integral (PI) compensator or a proportional-integral-derivative (PID) compensator.

[0029] The mode selection module is used to select the mode based on the first compensation voltage. v e_IVR Second compensation voltage v e_OVR Generate the first mode selection voltage v c1 Second mode voltage selection vc2 and third mode select voltage v c3 .

[0030] Specifically, it includes: The second compensation voltage v e_OVR With sawtooth waves v saw (The sawtooth wave frequency is the switching frequency of the converter, and the peak value of the sawtooth wave is...) V T peak value V T Subtracting them gives the third voltage difference. The second voltage difference is input to the maximum value selector MAX, and the other input of the maximum value selector MAX is 0. The output of the maximum value selector MAX is compared with the first compensation voltage. v e_IVR Subtraction generates the first mode selection voltage. v c1 ; The second compensation voltage v e_OVR With the first compensation voltage v e_IVR Subtraction generates the second mode selection voltage. v c2 ; The second compensation voltage v e_OVR As a third mode selection voltage v c3 .

[0031] The pulse width modulation module is used to generate drive signals for the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 through multiple comparators.

[0032] Specifically, the pulse width modulation module includes a first comparator CMP1, a second comparator CMP2, a third comparator CMP3, an NOT gate NO1, an AND gate, and a NOR gate, wherein the first mode selection voltage... v c1 The second mode selection voltage is electrically connected to the non-inverting input of the first comparator CMP1. v c2 Electrically connected to the non-inverting input of the second comparator CMP2, the third mode selection voltage. v c3 The non-inverting input of the third comparator CMP3 is electrically connected, and sawtooth waves are input to the inverting inputs of the first comparator CMP1, the second comparator CMP2, and the third comparator CMP3. vsaw ; The first comparator CMP1 outputs the gate drive signal of the first switching transistor S1; The output of the first comparator CMP1 is electrically connected to the input of the NOT gate NO1. The output of the NOT gate NO1 and the output of the second comparator CMP2 are electrically connected to the two inputs of the AND gate. The AND gate outputs the gate drive signal of the second switch S2. The third comparator CMP3 outputs the gate drive signal of the third switch S3; The gate drive signal of the first switch S1 and the gate drive signal of the second switch S2 are electrically connected to the two input terminals of the NOR gate, and the NOR gate outputs the gate drive signal of the fourth switch S4.

[0033] When the photovoltaic input power is greater than the power required by the load, the three-port DC-DC converter with high output voltage gain operates in single-input dual-output mode. The third switch S3 is always off. Maximum power point tracking control of the photovoltaic port and constant voltage control of the load port are achieved by adjusting the duty cycle of the first switch S1 and the second switch S2.

[0034] Specifically, when the photovoltaic input power is greater than or equal to the power required by the load, the first compensation voltage... v e_IVR Satisfy 0 < v e_IVR < V T , V T It is the amplitude of the sawtooth wave, the second compensation voltage. v e_OVR satisfy v e_OVR <0, the output of the maximum value selector MAX is 0, and the first mode selects the voltage. v c1 With the first compensation voltage v e_IVR Equal, first mode selects voltage v c1 Electrically connected to the non-inverting input of the first comparator CMP1, the first comparator CMP1 receives a sawtooth wave input. v saw The duty cycle of the first switch S1 is controlled to achieve maximum power point tracking control of the photovoltaic system. The second mode selects the voltage. v c2 equal v e_IVR and v e_OVR Subtracting them, the result is greater than v e_IVR Second mode selects voltagev c2 Then, a PWM switching signal is generated by combining the signal with a sawtooth carrier wave to control the duty cycle of the switching transistor S2, thereby achieving constant output voltage control. The control signal obtained from the above calculations is then used... v e_OVR A PWM switching signal is generated by combining the sawtooth carrier wave and the transistor S3, controlling the duty cycle of the switch. At this time, the output of the third comparator is 0, and S3 is always off. The drive signals for switches S1 and S2 are passed through a NOR gate to obtain the drive signal for switch S4. The theoretical waveform in this mode is as follows: Figure 3a As shown, where, v gS1 , v gS2 , v gS3 , v gS4 These are the gate drive signals for switching transistors S1 to S4, respectively. i L Input inductance L The inductor current, its direction is... Figure 1 The center is from left to right. i N1 and i N2 These are the first coupled inductor and the primary winding, respectively. N 1a The primary winding of the second coupled inductor N 2b The current, in Figure 1 The middle is positive from top to bottom. i D2 , i D3 , i D4 , i D5 , i D6 These represent the currents in diodes D2, D3, D4, D5, and D6, respectively, with the direction from anode to cathode considered positive. i D2 and i D3 These are the drain-source currents of the first switch S1 and the fourth switch S4, respectively, with the direction from drain to source being positive.

[0035] In this mode, based on the volt-second balance principle of the coupled inductor and the input inductor, it can be known that the output voltage gain of the DC-DC converter under ideal conditions can be expressed as: in, n 1 andn 2 represents the turns ratio of the first coupled inductor and the second coupled inductor, respectively, expressed as... N 1a : N 1b = n 1, N 2a : N 2b = n 2.

[0036] When the photovoltaic input power is less than the power required by the load, the three-port DC-DC converter with high output voltage gain operates in dual-input single-output mode. The second switch S2 is always off. Maximum power point tracking control of the photovoltaic port and constant voltage control of the load port are achieved by adjusting the duty cycle of the first switch S1 and the third switch S3.

[0037] Specifically, when the photovoltaic input power is less than the power required by the load, the first compensation voltage... v e_IVR Satisfy 0 < v e_IVR < V T Second compensation voltage v e_OVR Satisfy 0 < v e_OVR < V T The output of the maximum value selector (MAX) is 0. First mode selects the voltage. v c1 With the first compensation voltage v e_IVR Equal, first compensation voltage v c1 Electrically connected to the non-inverting input of the first comparator CMP1, the first comparator CMP1 receives a sawtooth wave input. v saw The duty cycle of the first switch S1 is controlled to achieve maximum power point tracking control of the photovoltaic system. The second mode selects the voltage. v c2 equal v e_IVR and v e_OVR Subtracting them, the result is less than v e_IVR The result is then combined with a sawtooth carrier wave to generate a PWM switching signal, controlling the duty cycle of switch S2. During this time, the output of the AND gate is always low, and S2 is always off. The control signal obtained from the above calculation... v e_OVRA PWM switching signal is generated by combining the sawtooth carrier wave and the transistor S3, controlling the duty cycle of the switching transistor S3 to achieve constant voltage control of the output voltage. The drive signals of switching transistors S1 and S2 are passed through a NOR gate to obtain the drive signal of switching transistor S4. The theoretical waveform in this mode is as follows: Figure 3b As shown.

[0038] In this mode, based on the volt-second balance principle of the coupled inductor and the input inductor, it can be known that the output voltage gain of the DC-DC converter under ideal conditions can be expressed as: When the photovoltaic input power is 0, the three-port DC-DC converter with high output voltage gain operates in single-input single-output mode, and the second switch S2 is always off. Constant voltage control of the load port is achieved by adjusting the duty cycle of S1.

[0039] Specifically, when the photovoltaic input power is 0, the first compensation voltage v e_IVR Satisfy 0 < v e_IVR < V T Second compensation voltage v e_OVR satisfy v e_OVR > V T The output of the maximum value selector MAX is v e_OVR - V T First mode selects voltage. v c1 equal v e_IVR + v e_OVR - V T The result is greater than 0. v c1 Electrically connected to the non-inverting input of the first comparator CMP1, the first comparator CMP1 receives a sawtooth wave input. v saw The duty cycle of the first switching transistor S1 is controlled to achieve constant voltage control of the output voltage. The second mode selects the voltage. v c2 equal v e_IVR and v e_OVR Subtracting the two, the result is less than 0. This is then combined with the sawtooth carrier wave to generate a PWM switching signal, controlling the duty cycle of switch S2. The output of the second comparator CMP2 is always low, at which point S2 is always off. The control signal obtained from the above calculation is...v e_OVR A PWM switching signal is generated by combining the sawtooth carrier wave and the transistor S3, controlling the duty cycle of the switch S3. The output of the third comparator CMP3 is always high, and S3 is always on. The drive signals of switches S1 and S2 are passed through a NOR gate to obtain the drive signal of switch S4. The theoretical waveform in this mode is as follows: Figure 3c As shown.

[0040] In this mode, based on the volt-second balance principle of the coupled inductor and the input inductor, it can be known that the output voltage gain of the DC-DC converter under ideal conditions can be expressed as: The results above show that the output voltage gain of the converter is related to the turns ratio and duty cycle of the coupling inductor. D 1. Related to duty cycle D The larger the value of 1, the greater the output voltage gain. The larger the turns ratio, the greater the output voltage gain. In single-input single-output mode, the duty cycle is taken as... D 1 = 0.5 n 1= n If 2=2, then the output voltage gain of the converter is 12, which can meet the voltage boosting requirements of renewable energy sources such as photovoltaics to the 400V DC bus.

[0041] The following experiments illustrate the beneficial effects of a three-port DC-DC converter and power conversion system with high output voltage gain.

[0042] A time-domain simulation analysis of a high-output voltage-gain three-port DC-DC converter was performed using PSIM simulation software. The photovoltaic input port was connected to a photovoltaic model with a voltage range of 20V~30V and a current range of 0~20A. The energy storage port was connected to a battery model with a voltage of 36V. The load... R The rated power is 400W, the output voltage is 400V, and the input inductance is... L =100μH, both coupled inductors are equivalent to magnetizing inductors. L m Circuit model with a capacitance of 200μH and a leakage inductance of Lk=5μH, first clamping capacitor. C x1 Second clamping capacitor C x2 Third clamping capacitor C x3 Fourth clamping capacitor C x4 Both are 200μF, and the switching frequency is... f s =100kHz, output filter capacitor C o =1000μF, the turns ratio of the first coupled inductor and the second coupled inductor isn 1= n 2=2. The system simulation results are as follows.

[0043] Figure 6 shows the steady-state simulation results of the high output voltage gain three-port DC-DC converter. Figure 6a This is the steady-state simulation waveform of the converter operating in single-input dual-output mode. Figure 6b This is the steady-state simulation waveform of the converter operating in dual-input single-output mode. Figure 6c This is the steady-state simulation waveform of the converter operating in single-input single-output mode. The simulation results show that the steady-state simulation waveforms in all modes are consistent with the theoretical analysis. In all modes, switches S1 and S4 can achieve zero-voltage turn-on, and diodes D3, D4, D5, and D6 can achieve zero-current turn-off. Therefore, the converter has the advantages of high efficiency and low switching losses.

[0044] Figure 7 The figure shows the load transient simulation results of the high output voltage gain three-port DC-DC converter. At the initial moment, the power at the photovoltaic input port is... P pv With a load power of 300W, a maximum power point voltage (MPPT) of 30V, a MPPT current of 10A, and a load power of 200W, the load power abruptly increases to 400W in 0.65s. The photovoltaic input power remains constant. Simulation results show that the output voltage remains constant at 400V during the load change. The energy storage port switches from the initial charging state to the discharging state, and the photovoltaic port maintains MPPT operation throughout. Simulation results demonstrate that the proposed converter and its control method can achieve single-stage power conversion between photovoltaic, energy storage, and high-voltage loads, and can achieve MPPT control and constant load voltage control at the photovoltaic port.

[0045] Figure 8 The figure shows the input transient simulation results of the high output voltage gain three-port DC-DC converter. At the initial moment, the power at the photovoltaic input port is... P pv =200W, the maximum power point voltage of the photovoltaic port is 30V, the maximum power point current is 6.67A, the load power is 300W, and the power at the photovoltaic input port is... P pvThe power input jumps to 400W, the maximum power point voltage (MPP) at the photovoltaic (PV) port remains at 30V, and the MPP current jumps to 13.3A. The load power remains constant. Simulation results show that when the PV input power changes abruptly, the output voltage remains constant at 400V. The energy storage port switches from the initial discharge state to the charging state, and the PV port maintains MPP tracking operation throughout. Simulation results demonstrate that the proposed converter and its control method can achieve single-stage power conversion between PV, energy storage, and high-voltage loads, and can achieve MPP tracking control and constant load voltage control at the PV port.

[0046] Based on the above theoretical analysis and simulation, it can be seen that the high output voltage gain three-port DC-DC converter has advantages such as simple structure, low cost, high power density, soft switching of semiconductor devices, and three-port single-stage power conversion. It can achieve ultra-high output voltage gain, continuous current ripple at the photovoltaic port, and the control system can achieve maximum power point tracking control and constant load voltage control at the photovoltaic port, and can achieve smooth switching between different modes.

[0047] Figure 9 This is a schematic flowchart of a power conversion method according to some embodiments of this specification, such as... Figure 9 As shown, the power conversion method may include the following steps: The first compensation voltage is calculated based on the voltage and current at the photovoltaic input port using the maximum power point tracking algorithm. The second compensation voltage is calculated based on the output voltage reference value and the output voltage sample value; Based on the first compensation voltage and the second compensation voltage, a first mode selection voltage, a second mode selection voltage and a third mode selection voltage are generated; Multiple comparators are used to generate drive signals for the first, second, third, and fourth switching transistors.

[0048] The power conversion method can be applied to the power conversion system described above, and will not be elaborated further here.

[0049] Finally, it should be understood that the embodiments described in this specification are merely illustrative of the principles of the embodiments described herein. Other variations may also fall within the scope of this specification. Therefore, alternative configurations of the embodiments described herein are intended to be illustrative rather than limiting, and should be considered consistent with the teachings of this specification. Accordingly, the embodiments described herein are not limited to those explicitly introduced and described herein.

Claims

1. A three-port DC-DC converter with high output voltage gain, characterized in that, The device includes an energy input component, an energy conversion component, a switch control component, a rectification and clamping protection component, and an output filter component. The energy input component is used to connect to a photovoltaic input source and store energy. The energy conversion component is used to convert energy and boost voltage. The switch control component is used to change the circuit topology and operating mode. The rectification and clamping protection component is used to convert the output of the energy conversion component into unidirectional direct current. The output filter component is used to filter the output of the rectification and clamping protection component to supply power to the load.

2. The three-port DC-DC converter with high output voltage gain according to claim 1, characterized in that, The energy input component includes a photovoltaic input port, an energy storage output terminal, and a photovoltaic series diode connected in series with the photovoltaic input port; The energy conversion component includes an input inductor, a first coupling inductor, and a second coupling inductor. In the first coupling inductor, the terminals of the primary winding and the secondary winding are of the same name. In the second coupling inductor, the terminals of the primary winding and the secondary winding are of the same name. The switch control assembly includes a first switch transistor, a second switch transistor, a third switch transistor, and a fourth switch transistor; The rectification and clamping protection assembly includes a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a first clamping capacitor, a second clamping capacitor, a third clamping capacitor, and a fourth clamping capacitor; The output filtering component includes an output capacitor; The positive terminal of the photovoltaic input port is connected to the anode of the photovoltaic series diode. The cathode of the photovoltaic input port is connected to the source of the third switching transistor. The drain of the third switching transistor is connected to the positive terminal of the energy storage output terminal. The negative terminal of the energy storage output terminal is connected to the negative terminal of the photovoltaic input port. The positive terminal of the energy storage output terminal is connected to the source of the second switching transistor. The drain of the second switching transistor is connected to the cathode of the first diode. The anode of the first diode is connected to the cathode of the second diode. The anode of the second diode is connected to the anode of the third diode, one end of the input inductor, and one end of the first clamping capacitor. The other end of the input inductor is connected to the cathode of the photovoltaic input port and the drain of the third switching transistor. The other end of the first clamping capacitor is connected to the terminal of the primary winding of the second coupling inductor. The terminal of the primary winding of the second coupling inductor is connected to the negative terminal of the photovoltaic input port. The cathode of the third diode is connected to the terminal of the primary winding of the first coupling inductor and one end of the second clamping capacitor. The first coupling inductor... The terminals of the primary winding are connected to the anode of the first diode, the cathode of the second diode, the drain of the first switching transistor, and the anode of the fourth diode, respectively. The anode of the fourth diode, one end of the third clamping capacitor, and the cathode of the fourth diode are connected to the terminals of the secondary winding of the second coupling inductor and the anode of the fifth diode, respectively. The cathode of the fifth diode is connected to the terminals of the secondary winding of the first coupling inductor and the anode of the sixth diode, respectively. The terminals of the secondary winding of the first coupling inductor are connected to the other end of the third clamping capacitor, respectively. The cathode of the sixth diode is connected to one end of the output capacitor and the positive terminal of the load, respectively. The other end of the output capacitor and the negative terminal of the load are both connected to one end of the fourth clamping capacitor, respectively. The other end of the fourth clamping capacitor is connected to the drain of the fourth switching transistor and the terminals of the secondary winding of the second coupling inductor, respectively. The source of the fourth switching transistor is connected to the drain of the first switching transistor, and the source of the first switching transistor is connected to the other end of the second clamping capacitor and the negative terminal of the photovoltaic input port.

3. A power conversion system, characterized in that, The three-port DC-DC converter with high output voltage gain as described in claim 1 or 2 includes: The input power control loop is used to calculate the first compensation voltage based on the voltage and current at the photovoltaic input port using a maximum power point tracking algorithm. The output voltage control loop is used to calculate the second compensation voltage based on the output voltage reference value and the output voltage sample value; The mode selection module is used to generate a first mode selection voltage, a second mode selection voltage, and a third mode selection voltage based on a first compensation voltage and a second compensation voltage. The pulse width modulation module is used to generate drive signals for the first, second, third, and fourth switching transistors through multiple comparators.

4. The power conversion system according to claim 3, characterized in that, The input power control loop calculates the first compensation voltage based on the voltage and current at the photovoltaic input port using a maximum power point tracking algorithm, including: The reference voltage of the photovoltaic input port is calculated based on the voltage and current of the photovoltaic input port using the maximum power point tracking algorithm. Subtract the reference voltage at the photovoltaic input port from the voltage at the photovoltaic input port to obtain the first voltage difference; The first compensation voltage is calculated based on the first voltage difference using the first compensator; The output voltage control loop calculates the second compensation voltage based on the output voltage reference value and the output voltage sample value, including: Subtract the output voltage reference value from the output voltage sample value to obtain the second voltage difference; The second compensation voltage is calculated based on the second voltage difference using the second compensator.

5. The power conversion system according to claim 3, characterized in that, The mode selection module generates a first mode selection voltage, a second mode selection voltage, and a third mode selection voltage based on a first compensation voltage and a second compensation voltage, including: The third voltage difference is obtained by subtracting the peak value of the sawtooth wave from the second compensation voltage. The second voltage difference is input to the maximum value selector, and the other input of the maximum value selector is 0. The output of the maximum value selector is subtracted from the first compensation voltage to generate the first mode selection voltage; Subtracting the first compensation voltage from the second compensation voltage generates the second mode selection voltage; Use the second compensation voltage as the third mode selection voltage.

6. The power conversion system according to claim 5, characterized in that, The pulse width modulation module includes a first comparator, a second comparator, a third comparator, an NOT gate, an AND gate, and a NOR gate. The first mode selection voltage is electrically connected to the non-inverting input of the first comparator, the second mode selection voltage is electrically connected to the non-inverting input of the second comparator, and the third mode selection voltage is electrically connected to the non-inverting input of the third comparator. The sawtooth wave is input to the inverting inputs of the first, second, and third comparators. The first comparator outputs the gate drive signal of the first switching transistor; The output terminal of the first comparator is electrically connected to the input terminal of the NOT gate, the output terminal of the NOT gate and the output terminal of the second comparator are electrically connected to the two input terminals of the AND gate, and the AND gate outputs the gate drive signal of the second switching transistor; The third comparator outputs the gate drive signal of the third switch. The gate drive signal of the first switch and the gate drive signal of the second switch are electrically connected to the two input terminals of the NOR gate, and the NOR gate outputs the gate drive signal of the fourth switch.

7. The power conversion system according to claim 6, characterized in that, When the photovoltaic input power is greater than the power required by the load, the third switch is in the off state.

8. The power conversion system according to claim 6, characterized in that, When the photovoltaic input power is less than the power required by the load, the second switch is in the off state.

9. The power conversion system according to claim 6, characterized in that, When the photovoltaic input power is 0, the second switch is in the off state.

10. A power conversion method, characterized in that, The power conversion system according to claim 3 includes: The first compensation voltage is calculated based on the voltage and current at the photovoltaic input port using the maximum power point tracking algorithm. The second compensation voltage is calculated based on the output voltage reference value and the output voltage sample value; Based on the first compensation voltage and the second compensation voltage, a first mode selection voltage, a second mode selection voltage and a third mode selection voltage are generated; Multiple comparators are used to generate drive signals for the first, second, third, and fourth switching transistors.

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