Three-port DC-to-DC converter, power supply system and energy conversion method

Abstract

The embodiment of the invention provides a three-port DC-to-DC converter, a power supply system and an energy conversion method. The converter comprises an energy storage inductor, a first diode, an energy storage control branch, a control element and a booster circuit, the positive electrode of the photovoltaic power supply is sequentially connected in series with a first diode and an energy storage inductor and then connected to a first circuit node; the anode of the energy storage power supply is connected in parallel with the energy storage inductor through an energy storage control branch; the cathode of the energy storage power supply is connected to the first circuit node through the first end of the control element; the first end of the booster circuit is connected to the first circuit node, the second end of the booster circuit, the cathode of the photovoltaic power supply, the cathode of the energy storage power supply and the second end of the control element are connected to the cathode output end, and the third end of the booster circuit is connected to the anode output end; the anode output end is connected with the anode of the load, and the cathode output end is connected with the cathode of the load. Therefore, high voltage gain and switching of different working modes are realized.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a three-port DC-DC converter, a power supply system, and an energy conversion method. Background Technology

[0002] As the global energy structure transitions towards cleaner and lower-carbon energy, new energy sources such as photovoltaic (PV) and wind power are widely used in distributed energy systems, smart grids, microgrids, and industrial energy management scenarios. However, the output of new energy sources is inherently random and intermittent, requiring energy storage systems to achieve smooth energy regulation and stable output. Virtual energy storage technology, leveraging the regulation capabilities of existing load infrastructure, effectively avoids the high cost of traditional physical energy storage, becoming a key support for the efficient absorption of new energy sources. In the three-port energy interaction scenario of PV energy storage loads, the three-port DC-DC converter (TPC), as the core energy conversion unit, directly determines the efficiency and reliability of the system, making it a key focus of current technological research and development.

[0003] Existing three-port DC-DC converters typically employ variable architectures integrating basic converters such as Buck and Boost converters, offering a wide input range and compact structure. Alternatively, they may utilize coupled inductors and soft-switching technology to achieve high voltage gain and low switching losses. While these solutions have achieved energy conversion in some scenarios, they are all designed for adaptation to traditional energy storage and new energy sources.

[0004] However, the above solutions still have significant limitations: some solutions have fixed port voltage constraints, making them unsuitable for the wide voltage output characteristics of new energy sources; some solutions have unreasonable energy transfer paths, requiring intermediate ports for transfer, leading to efficiency reduction and posing safety hazards due to non-common grounding of ports; the converter mode switching flexibility is insufficient, making it difficult to adapt to the energy distribution requirements of complex operating conditions; the voltage stress of switching devices is high, resulting in increased hardware costs and losses, making it difficult to balance high power density and low cost; at the same time, there is a lack of refined control design for virtual energy storage and new energy synergy scenarios, limiting the deep integration and application of the two. Summary of the Invention

[0005] This application provides a three-port DC-DC converter, a power supply system, and an energy conversion method to achieve high voltage gain and switching between different operating modes.

[0006] In a first aspect, embodiments of this application provide a three-port DC-DC converter connected between a photovoltaic power source, an energy storage power source, and a load, comprising: an energy storage inductor, a first diode, an energy storage control branch, a control element, and a boost circuit;

[0007] The positive terminal of the photovoltaic power source is connected to the first circuit node after being connected in series with the first diode and the energy storage inductor.

[0008] The positive terminal of the energy storage power supply is connected to the energy storage inductor through the energy storage control branch; the negative terminal of the energy storage power supply is connected to the first circuit node through the first terminal of the control element.

[0009] The first terminal of the boost circuit is connected to the first circuit node. The second terminal of the boost circuit, the negative terminal of the photovoltaic power supply, the negative terminal of the energy storage power supply, and the second terminal of the control element are connected to the negative output terminal. The third terminal of the boost circuit is connected to the positive output terminal.

[0010] The positive output terminal is connected to the positive terminal of the load, and the negative output terminal is connected to the negative terminal of the load.

[0011] In one feasible implementation, in conjunction with the first aspect, the energy storage control branch includes a discharge control branch and a charging control branch;

[0012] The positive terminal of the energy storage power supply is connected to the second circuit node between the first diode and the energy storage inductor through a discharge control branch;

[0013] The positive terminal of the energy storage power supply is connected to the first circuit node through the charging control branch.

[0014] In one feasible implementation, in conjunction with the first aspect, the discharge control branch is the first switching transistor.

[0015] In one feasible implementation, in conjunction with the first aspect, the charging control branch includes a second switching transistor and a second diode;

[0016] The positive terminal of the energy storage power supply is connected to the negative terminal of the second diode through the second switching transistor, and the positive terminal of the second diode is connected to the first circuit node.

[0017] In one feasible implementation, in conjunction with the first aspect, the boost circuit includes: a third diode, a fourth diode, a fifth diode, a first energy storage capacitor, a second energy storage capacitor, a third energy storage capacitor, a fourth energy storage capacitor, and a coupling inductor.

[0018] The coupled inductor includes a first winding and a second winding that are coupled to each other; the opposite end of the first winding and the same end of the second winding are connected to the positive terminal of the first energy storage capacitor; the same end of the first winding is connected to the negative terminal of the third diode, the positive terminal of the fourth diode, and the positive terminal of the second energy storage capacitor; the opposite end of the second winding is connected to the negative terminal of the third energy storage capacitor.

[0019] The negative terminal of the first energy storage capacitor and the positive terminal of the third diode are the first terminals of the boost circuit; the negative terminal of the fourth diode and the positive terminal of the third energy storage capacitor are connected to the positive terminal of the fifth diode; the negative terminal of the fifth diode and the positive terminal of the fourth energy storage capacitor are the third terminals of the boost circuit; the negative terminal of the fourth energy storage capacitor is the second terminal of the boost circuit.

[0020] In one feasible implementation, in conjunction with the first aspect, the turns ratio of the first winding and the second winding is 1:n, where n is a positive real number.

[0021] In one feasible implementation, in conjunction with the first aspect, the three-port DC-DC converter is configured to switch between multiple operating modes by controlling the conduction states of the first, second, and third switches. These multiple operating modes include photovoltaic standalone power supply mode, energy storage standalone power supply mode, photovoltaic-energy storage combined power supply mode, and photovoltaic power supply and energy storage charging mode.

[0022] In one feasible implementation, in conjunction with the first aspect, the first, second, and third switching transistors all employ a unipolar PWM control strategy to achieve switching between multiple operating modes.

[0023] Secondly, embodiments of this application provide a power supply system, including: a three-port DC-DC converter as described in any of the first aspects;

[0024] A photovoltaic power generation unit connected to the photovoltaic input terminal of the converter; and a load connected to the output terminal of the converter.

[0025] Thirdly, embodiments of this application provide an energy conversion method for controlling a three-port DC-DC converter as described in any of the first aspects, the method comprising:

[0026] Obtain the photovoltaic input power and the total load power demand;

[0027] By comparing the magnitude of photovoltaic input power and total load demand power, the comparison results are obtained.

[0028] Based on the comparison results, control signals are generated and output to the first, second, and third switches of the converter to switch the converter to the corresponding operating mode.

[0029] This application provides a three-port DC-DC converter, a power supply system, and an energy conversion method. The converter includes: an energy storage inductor, a first diode, an energy storage control branch, a control element, and a boost circuit. The positive terminal of the photovoltaic power supply is connected to a first circuit node via a series connection of the first diode and the energy storage inductor. The positive terminal of the energy storage power supply is connected in parallel with the energy storage inductor through the energy storage control branch. The negative terminal of the energy storage power supply is connected to the first circuit node through a first terminal of the control element. The first terminal of the boost circuit is connected to the first circuit node, and the second terminal of the boost circuit, the negative terminal of the photovoltaic power supply, the negative terminal of the energy storage power supply, and the second terminal of the control element are connected to the negative output terminal. The third terminal of the boost circuit is connected to the positive output terminal. The positive output terminal is connected to the positive terminal of the load, and the negative output terminal is connected to the negative terminal of the load. By integrating the photovoltaic power supply, the energy storage power supply, and the load through a single converter, the system size is reduced. Furthermore, by flexibly adjusting the output voltage and power flow direction through the duty cycle and the turns ratio of the coupling inductor, high voltage gain and switching between different operating modes are achieved. Attached Figure Description

[0030] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0031] Figure 1 This is a schematic diagram of an integration scheme between traditional new energy sources and virtual energy storage devices;

[0032] Figure 2 This is a schematic diagram of the TPC structure in related technologies;

[0033] Figure 3 This is a circuit diagram of a non-isolated, wide-operating-range three-port DC-DC converter in related technologies;

[0034] Figure 4 This is a circuit diagram of a high-gain soft-switching three-port DC-DC converter in related technologies;

[0035] Figure 5 This is a schematic diagram of the topology of a three-port DC-DC converter provided in an embodiment of this application;

[0036] Figure 6 Schematic diagrams of different operating modes of the three-port DC-DC converter provided in the embodiments of this application;

[0037] Figure 7 Key waveform diagrams of the main components of the three-port DC-DC converter provided in this application embodiment under different operating modes;

[0038] Figure 8 A schematic diagram of the equivalent circuit of a three-port DC-DC converter in SISO1 mode for different switching modes provided in the embodiments of this application;

[0039] Figure 9 A schematic diagram of the equivalent circuit of a three-port DC-DC converter in SISO2 mode for different switching modes provided in the embodiments of this application;

[0040] Figure 10 A schematic diagram of the equivalent circuit of a three-port DC-DC converter in DISO mode for different switching modes provided in the embodiments of this application;

[0041] Figure 11 A schematic diagram of the equivalent circuit of a three-port DC-DC converter in SIDO mode for different switching modes provided in the embodiments of this application;

[0042] Figure 12 This is a schematic flowchart of the energy conversion method provided in an embodiment of this application.

[0043] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0044] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0045] First, the application background of the embodiments of this application will be explained:

[0046] As the global energy structure transitions towards cleaner and lower-carbon energy, new energy sources such as photovoltaic and wind power are widely used in distributed energy systems, smart grids, microgrids, and industrial energy management scenarios. However, the output of new energy sources is inherently random and intermittent, requiring energy storage systems to achieve smooth energy regulation and stable output. Virtual energy storage technology, leveraging the regulation capabilities of existing load infrastructure, effectively avoids the high cost of traditional physical energy storage, becoming a key support for the efficient consumption of new energy sources.

[0047] like Figure 1 As shown, in traditional integration schemes, the integration methods of new energy and virtual energy storage devices can include three types: front-end parallel connection, back-end parallel connection, and series connection. Among them, P Pv For photovoltaic power, P VES For virtual energy storage power, P oThis represents the load power. It can be seen that this method requires a large number of converters and incurs high costs. Furthermore, the system involves multiple energy conversion stages, resulting in relatively low system efficiency.

[0048] To improve system power density, reduce system size, and lower design costs, the three-port DC-DC converter (TPC) is the core energy conversion unit in three-port energy interaction scenarios for photovoltaic energy storage loads. Its performance directly determines the system's efficiency and reliability, making it a key focus of current technology research and development. For example... Figure 2 As shown, this is the general structure of a TPC, which only requires one converter to complete power management and energy control between photovoltaic power sources, virtual energy storage devices, and loads.

[0049] In some existing three-port DC-DC converter schemes, the three-port DC-DC converter can be a variable structure scheme integrating Buck, Boost, and Buck-Boost converters, such as... Figure 3 As shown, this converter features a wide input range and a compact structure. Alternatively, a three-port DC-DC converter can employ a solution using coupled inductors and soft-switching technology, such as... Figure 4 As shown, this converter can achieve zero-voltage turn-on of the switching transistor and zero-current turn-off of the diode in various operating modes, thus achieving high voltage gain and low switching losses.

[0050] However, the above solutions still have significant limitations: for example, the scheme using coupled inductors and soft-switching technology suffers from fixed port voltage constraints, making it unsuitable for the wide voltage output characteristics of new energy sources. In schemes integrating Buck, Boost, and Buck-Boost converters, the energy transfer path is unreasonable, requiring intermediate ports for transfer, leading to efficiency degradation and posing a safety hazard due to non-common grounding of ports. Furthermore, these schemes suffer from insufficient flexibility in converter mode switching, making it difficult to adapt to the energy distribution requirements of complex operating conditions; high voltage stress on switching devices increases hardware costs and losses, making it difficult to balance high power density and low cost; and a lack of refined control design for virtual energy storage and new energy synergy scenarios limits their deep integration and application.

[0051] To overcome the constraint of energy storage port voltage on photovoltaic cell port voltage and meet the application requirements of wide input voltage range variations in photovoltaic ports, this application proposes a multi-condition high-gain three-port DC-DC converter (HGTPC) integrating new energy and virtual energy storage for connecting to a photovoltaic energy storage system. This converter features low voltage stress on switching devices and high voltage gain, and can flexibly adjust the output voltage and power flow direction by adjusting the duty cycle and coupling inductor turns ratio to switch between different operating modes.

[0052] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0053] Figure 5 This is a schematic diagram of the topology of a three-port DC-DC converter provided in an embodiment of this application. Figure 5 As shown, the three-port DC-DC converter provided in this embodiment includes: an energy storage inductor L1, a first diode D a Energy storage control branch, control components, and boost circuit.

[0054] Photovoltaic power supply U Pv The positive terminal is connected in series with the first diode D. a After connecting to the energy storage inductor L1, it is connected to the first circuit node. Energy storage power supply U ves The positive terminal is connected in parallel with the energy storage inductor L1 through the energy storage control branch; the energy storage power supply U ves The negative terminal is connected to the first circuit node through the first terminal of the control element. The photovoltaic power source U... Pv voltage U Pv Smaller than energy storage power source U ves voltage U VES .

[0055] Specifically, the energy storage control branch includes a discharge control branch and a charging control branch. Energy storage power supply U ves The positive terminal is connected to the first diode D through the discharge control branch. a The second circuit node between the energy storage inductor L1 and the energy storage power supply U; ves The positive terminal is connected to the first circuit node through the charging control branch.

[0056] The discharge control branch is the first switching transistor S. a The charging control branch includes the second switching transistor S. b Second diode D b Energy storage power supply U ves The positive terminal is connected to the second switch S. b Connected to the second diode D b The negative terminal, the second diode D b The positive terminal is connected to the first circuit node.

[0057] In this embodiment, a coupled inductor-switched capacitor boost unit and a bidirectional power flow energy storage port are introduced into the Boost converter, namely, by the first switching transistor S... a Second switch S bSecond diode D b The energy storage control branch can flexibly adjust the output voltage and power flow direction by adjusting the duty cycle and the turns ratio of the coupling inductor. The first switching transistor S... a This forms a discharge branch for energy storage. This is achieved by controlling the first switching transistor S. a The duty cycle can control the discharge power of the stored energy. The second switch S... b Second diode D b This constitutes the charging branch for energy storage. This is achieved by controlling the second switch S. b The duty cycle can control the energy storage power supply U. ves The charging power. Second diode D a Connect it in series with the photovoltaic power source UPV in the positive direction to prevent current from flowing back to the photovoltaic power source U. Pv .

[0058] In this converter, the first terminal of the boost circuit is connected to the first circuit node, and the second terminal of the boost circuit is connected to the photovoltaic power source U. Pv The negative terminal, energy storage power supply U ves The negative terminal and the second terminal of the control element are connected to the negative output terminal, and the third terminal of the boost circuit is connected to the positive output terminal; the positive output terminal is connected to the positive terminal of the load, and the negative output terminal is connected to the negative terminal of the load.

[0059] Specifically, the boost circuit includes three diodes, four energy storage capacitors, and a coupling inductor, namely, the third diode D1, the fourth diode D2, and the fifth diode D... o First energy storage capacitor C1, second energy storage capacitor C2, third energy storage capacitor C3, fourth energy storage capacitor C o .

[0060] The coupled inductor includes a first winding N1 and a second winding N2 that are coupled to each other. The turns ratio of the first winding N1 and the second winding N2 is 1:n, where n is a positive real number. For example, the value of n can be 1, 2, or 3, or it can be 1.5 or 2.5, etc. This embodiment does not limit the specific value of the turns ratio of the first winding N1 and the second winding N2.

[0061] The opposite-named terminal of the first winding N1 and the same-named terminal of the second winding N2 are connected to the positive terminal of the first energy storage capacitor C1; the same-named terminal of the first winding N1 is connected to the negative terminal of the third diode D1, the positive terminal of the fourth diode D2, and the positive terminal of the second energy storage capacitor C2; the opposite-named terminal of the second winding N2 is connected to the negative terminal of the third energy storage capacitor C3. The negative terminal of the first energy storage capacitor C1 and the positive terminal of the third diode D1 form the first terminal of the boost circuit; the negative terminal of the fourth diode D2 and the positive terminal of the third energy storage capacitor C3 are connected to the fifth diode D1. o The positive terminal; the fifth diode D o The negative electrode and the fourth energy storage capacitor Co The positive terminal is the third terminal of the boost circuit; the fourth energy storage capacitor C o The negative terminal is the second terminal of the boost circuit.

[0062] In this embodiment, the three-port DC-DC converter is configured to control the first switching transistor S by employing a unipolar PWM control strategy. a Second switch S b The conduction state of the third switch S1 switches between multiple operating modes.

[0063] Specifically, according to photovoltaic power source U Pv The relationship between input power and load power requirements; various operating modes of the converter, including single input single output 1 (SISO1), single input single output 2 (SISO2), dual input single output (DISO), and single input dual output (SIDO). Figure 6 As shown.

[0064] In SISO1 mode: Photovoltaic power supply U Pv Power is supplied to the load independently, and the virtual energy storage device does not participate in operation. In this operating mode, the first switching transistor S... a Second switch S b Always in the off state, and photovoltaic power supply U Pv Power P Pv With load power P o Equal. SISO2 mode: Photovoltaic power supply U Pv The input power is zero, and only the energy storage power supply supplies power to the load. In this operating mode, the first switching transistor S... a Keep it normally open, second switch S b Keep it normally closed, and the power P of the energy storage power source VES Equal to load power P o DISO mode: The photovoltaic power generation is less than the total power required by the load. Photovoltaic power supply U Pv Together with the energy storage power source, it provides energy to the load. In this operating mode, the second switching transistor S... b Keep it normally closed, and the power P of the photovoltaic power source Pv With the power P of the energy storage power source VES The sum equals the load power P o SIDO mode: The photovoltaic power generation capacity exceeds the total power required by the load. Photovoltaic power supply U PvIt provides energy to the energy storage power source and the load. In this operating mode, the first switching transistor S... a Keep it normally closed, and the power P of the photovoltaic power source Pv Equal to the power P of the energy storage power source VES Total power P required by the load o sum.

[0065] For the sake of circuit simplicity, all components of the hypothetical converter are assumed to operate under ideal conditions. The leakage inductance on the coupled inductor is ignored in the steady-state analysis. The coupled inductor is an ideal transformer with a turns ratio of n = N2: N1 between the windings. Figure 7 The key waveforms for four operating modes are shown. The switching period is T, the duty cycle of the third switch S1 is D, and the first switch S... a Second switch S b The duty cycles of the conduction are respectively D a and D b .

[0066] Specifically, in combination Figure 8 In SISO1 mode, the first switching transistor S a Second switch S b When the circuit is not conducting, the third switch S1 is conducting within DT, allowing current to flow. The current in the energy storage inductor L1 increases linearly after the third switch S1 is turned on and decreases after the third switch S1 is turned off, controlled by the photovoltaic power source U. Pv Power supply, energy storage inductor L1 is inside DT (U pv ) energy storage, the rest of the time (U pv -U c2 Release energy.

[0067] Mode 1 (e.g.) Figure 8 (a) shows that the third switch S1 is turned on, and the third diode D1 and the fifth diode D1 are also turned on. o Reverse cutoff. Photovoltaic power supply U Pv Energy is transferred to the energy storage inductor L1. At this time, the energy storage inductor current i L1 As the capacitance increases linearly, the first energy storage capacitor C1 transfers energy to the first winding N1. The fourth energy storage capacitor C... o Energy is released to the load R. The voltage relationship is as follows:

[0068] (1)

[0069] Mode 2 (e.g.) Figure 8 (b) shows: The third switch S1 is turned off, and the third diode D1 and the fifth diode D1 are... o Forward conduction. The energy storage inductor L1 transfers energy to the second energy storage capacitor C2 through the third diode D1. At this time, the energy storage inductor current i L1It will decrease linearly. The first winding N1 and the second winding N2 supply energy to the fourth energy storage capacitor C. o Energy is transferred. The voltage relationship is as follows:

[0070] (2)

[0071] Among them, U L1 For inductor voltage, U NX and U CX For winding N X and capacitor C X The voltage on it.

[0072] According to the inductor volt-second balance principle (the average voltage applied to the inductor over one cycle is zero), we know that:

[0073] (3)

[0074] Combining the above formulas (1) and (3), we can obtain:

[0075] (4)

[0076] In SISIO2 mode, combined with Figure 9 First switching transistor S a The second switch S is turned on. b When the circuit is not conducting, the third switch S1 is conducting within DT, allowing current to flow. The current in the energy storage inductor L1 increases linearly after the third switch S1 is turned on and decreases after the third switch S1 is turned off, controlled by the energy storage power supply U. ves Power supply, energy storage inductor L1 is inside DT (U VES ) energy storage, the rest of the time (U VES -U c2 Release energy.

[0077] The only difference between SISO2 and SISO1 operating modes is that the input source is a photovoltaic power source U. Pv Instead, it can be changed to energy storage. Similarly, we can obtain:

[0078] (5)

[0079] In DISO mode, combined Figure 10 First switching transistor S a In D a The second switch S is turned on within time T. b The third switch S1 is not conducting during the DT time period, and the photovoltaic power supply U... Pv and energy storage power U vesSimultaneously, power is supplied to the energy storage inductor L1, and the current in the energy storage inductor L1 rises rapidly. It can be seen that compared to the SISO1 operating mode, the DISO operating mode only has one additional operating state (energy storage power supply U). ves (Discharge process). The following is a simplified analysis of the DISO operating mode.

[0080] Mode 1 (e.g.) Figure 10 (a) shows the voltage relationship:

[0081] (6)

[0082] Mode 2 (e.g.) Figure 10 (b) shows the voltage relationship:

[0083] (7)

[0084] Mode 3 (e.g.) Figure 10 (c) shows the voltage relationship:

[0085] (8)

[0086] According to the inductor volt-second balance principle (the average voltage applied to the inductor over one cycle is zero), we know that:

[0087] (9)

[0088] Combining the above formulas (6) and (9), we can obtain:

[0089] (10)

[0090] In SIDO mode, combined Figure 11 The second switch S b In D b The first switching transistor S is turned on within time T. a The third switch S1 is not conducting during the DT time period, and the voltage of the energy storage inductor L1 is U during the DT time period. pv In D b U within time T pv -U c2 The third switch S1 is in D b The presence of current within time T indicates that the photovoltaic power source U Pv Simultaneously serving as an energy storage power source U ves And load power supply. It can be seen that, compared to the SISO1 operating mode, the SIDO operating mode only has one additional operating state (energy storage power supply U). ves (Charging process). The following is a simplified analysis of the SIDO operating modes.

[0091] Mode 1 (e.g.) Figure 11 (a) shows the voltage relationship:

[0092] (11)

[0093] Mode 2 (e.g.) Figure 11 (b) shows the voltage relationship:

[0094] (12)

[0095] Mode 3 (e.g.) Figure 11 (c) shows the voltage relationship:

[0096] (13)

[0097] According to the inductor volt-second balance principle (the average voltage applied to the inductor over one cycle is zero), we know that:

[0098] (14)

[0099] Combining the above formulas (11) and (14), we can obtain:

[0100] (15)

[0101] The converter in this embodiment of the application uses an energy storage inductor L1 and a first diode D. a Coupled inductors, energy storage control branches, control components, and boost circuits; photovoltaic power supply U Pv The positive terminal is connected in series with the first diode D. a After connecting to the energy storage inductor L1, it is connected to the first circuit node; energy storage power supply U ves The positive terminal is connected in parallel with the energy storage inductor L1 through the energy storage control branch; the energy storage power supply U ves The negative terminal is connected to the first circuit node through the first terminal of the control element; the first terminal of the boost circuit is connected to the first circuit node, and the second terminal of the boost circuit and the photovoltaic power supply U Pv The negative terminal, energy storage power supply U ves The negative terminal and the second terminal of the control element are connected to the negative output terminal, and the third terminal of the boost circuit is connected to the positive output terminal; the positive output terminal is connected to the positive terminal of the load, and the negative output terminal is connected to the negative terminal of the load. A photovoltaic power supply U is completed through a converter. Pv Energy storage power supply U ves The integration with the load reduces the system size, and the output voltage and power flow direction can be flexibly adjusted by the duty cycle and the turns ratio of the coupling inductor, enabling high voltage gain and switching between different operating modes.

[0102] This application also provides a power supply system, including: a three-port DC-DC converter as described in the above embodiments, a photovoltaic power generation unit connected to the photovoltaic input terminal of the converter, and a load connected to the output terminal of the converter.

[0103] The power supply system provided in this application embodiment can flexibly adjust the output voltage and power flow direction by adjusting the duty cycle and the turns ratio of the coupling inductor, thereby achieving high voltage gain and switching between different operating modes.

[0104] Figure 12 This is a schematic flowchart illustrating the energy conversion method provided in an embodiment of this application. Figure 12 As shown, this method is used to control the three-port DC-DC converter as described in the above embodiment. Specifically, the method may include the following steps: 110 and 130.

[0105] Step 110: Obtain the photovoltaic input power and the total load power demand.

[0106] Step 120: Compare the relationship between the photovoltaic input power and the total load demand power to obtain the comparison results.

[0107] Step 130: Based on the comparison results, generate and output control signals to the first switch, second switch and third switch of the converter to switch the converter to the corresponding operating mode.

[0108] The converter has multiple operating modes, including photovoltaic single-output mode (SISO1), energy storage single-output mode (SISO2), photovoltaic-energy storage combined power supply mode (Dual-input single-output, DISO), and photovoltaic power supply and energy storage charging mode (Single-input dual-output, SIDO). For details, please refer to the relevant descriptions of the multiple operating modes of the converter in the above embodiments, which will not be repeated here.

[0109] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0110] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0111] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0112] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0113] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0114] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A three-port DC-DC converter, connected between a photovoltaic power source, an energy storage power source, and a load, characterized in that, include: Energy storage inductor, first diode, energy storage control branch, control components, and boost circuit; The positive terminal of the photovoltaic power source is connected to the first circuit node after being connected in series with the first diode and the energy storage inductor. The positive terminal of the energy storage power supply is connected to the energy storage inductor through the energy storage control branch; the negative terminal of the energy storage power supply is connected to the first circuit node through the first end of the control element. The first terminal of the boost circuit is connected to the first circuit node, the second terminal of the boost circuit, the negative terminal of the photovoltaic power supply, the negative terminal of the energy storage power supply, and the second terminal of the control element are connected to the negative output terminal, and the third terminal of the boost circuit is connected to the positive output terminal. The positive output terminal is connected to the positive terminal of the load, and the negative output terminal is connected to the negative terminal of the load.

2. The three-port DC-DC converter according to claim 1, characterized in that, The energy storage control branch includes a discharge control branch and a charging control branch; The positive terminal of the energy storage power supply is connected to the second circuit node between the first diode and the energy storage inductor through the discharge control branch; The positive terminal of the energy storage power source is connected to the first circuit node through the charging control branch.

3. The three-port DC-DC converter according to claim 2, characterized in that, The discharge control branch is the first switching transistor.

4. The three-port DC-DC converter according to claim 2, characterized in that, The charging control branch includes a second switching transistor and a second diode; The positive terminal of the energy storage power supply is connected to the negative terminal of the second diode through the second switching transistor, and the positive terminal of the second diode is connected to the first circuit node.

5. The three-port DC-DC converter according to any one of claims 1-4, characterized in that, The boost circuit includes: a third diode, a fourth diode, a fifth diode, a first energy storage capacitor, a second energy storage capacitor, a third energy storage capacitor, a fourth energy storage capacitor, and a coupling inductor; The coupled inductor includes a first winding and a second winding that are coupled to each other; the opposite end of the first winding and the same end of the second winding are connected to the positive terminal of the first energy storage capacitor; the same end of the first winding is connected to the negative terminal of the third diode, the positive terminal of the fourth diode, and the positive terminal of the second energy storage capacitor; the opposite end of the second winding is connected to the negative terminal of the third energy storage capacitor. The negative terminal of the first energy storage capacitor and the positive terminal of the third diode are the first terminals of the boost circuit; the negative terminal of the fourth diode and the positive terminal of the third energy storage capacitor are connected to the positive terminal of the fifth diode; the negative terminal of the fifth diode and the positive terminal of the fourth energy storage capacitor are the third terminals of the boost circuit; and the negative terminal of the fourth energy storage capacitor is the second terminal of the boost circuit.

6. The three-port DC-DC converter according to claim 5, characterized in that, The turns ratio of the first winding to the second winding is n, where n is a positive real number.

7. The three-port DC-DC converter according to claim 5, characterized in that, The three-port DC-DC converter is configured to switch between multiple operating modes by controlling the conduction states of the first, second, and third switching transistors. The multiple operating modes include photovoltaic stand-alone power supply mode, energy storage stand-alone power supply mode, photovoltaic-energy storage combined power supply mode, and photovoltaic power supply and energy storage charging mode.

8. The three-port DC-DC converter according to claim 7, characterized in that, The first switch, the second switch, and the third switch all adopt a unipolar PWM control strategy to achieve the switching of the multiple operating modes.

9. A power supply system, characterized in that, include: The three-port DC-DC converter as described in any one of claims 1 to 8; A photovoltaic power generation unit connected to the photovoltaic input terminal of the converter; And, the load connected to the output of the converter.

10. An energy conversion method, characterized in that, The method for controlling a three-port DC-DC converter as described in any one of claims 1 to 8 includes: Obtain the photovoltaic input power and the total load power demand; By comparing the magnitude of the photovoltaic input power and the total load demand power, a comparison result is obtained; Based on the comparison results, control signals are generated and output to the first switch, second switch, and third switch of the converter to switch the converter to the corresponding operating mode.

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