A non-isolated three-port dc converter and variation control method

Abstract

The present application relates to the technical field of inverter control architecture, and especially to a non-isolated three-port DC converter and a variable control method. An input port, a battery port, an output port, a switch tube group, a standard inductor, a coupling inductor, a first intermediate energy storage capacitor, a second intermediate energy storage capacitor, an output capacitor and a diode group are provided. The input port is connected to the No. 2 switch tube through the No. 1 diode and the standard inductor in sequence. The battery port is connected to the common connection point of the No. 1 switch tube and the No. 4 switch tube. The output port is connected to the common connection point of the No. 5 switch tube and the output capacitor. The present application replaces the traditional multiple independent converter discrete combination scheme with a single integrated converter, effectively improves the device multiplexing rate, greatly reduces the system volume and manufacturing cost, and eliminates the complex communication and coordination links between converters with centralized control, so that the control logic is more simple and reliable.

Description

Technical Field

[0001] This invention relates to the field of DC-DC converter technology, and in particular to a non-isolated three-port DC-DC converter and a variation control method. Background Technology

[0002] With the rapid development of new energy power generation technologies and distributed energy storage systems, DC microgrids and DC power distribution technologies have received widespread attention. In these application scenarios, because the output voltage of photovoltaic panels is low and fluctuates greatly, while DC buses or loads often require higher voltage levels, DC-DC converters that can convert low-voltage DC to high-voltage DC have become key core equipment.

[0003] However, in current applications, multiple independent converters are often used in discrete combinations, resulting in non-reusable components, large system size, and high cost. Energy transfer between ports requires multiple stages of conversion, which can easily generate circulating current and redundant switching, severely shortening the lifespan of energy storage components. Discrete structures require additional communication and centralized control links, increasing system complexity. Traditional topologies are limited by the switching duty cycle, and the voltage gain is usually only between 1 and 10 times, which cannot meet the high gain requirements of low-voltage input and high-voltage output of new energy sources.

[0004] Therefore, a non-isolated three-port DC-DC converter and its control method are needed to meet the current environmental requirements. Summary of the Invention

[0005] In view of the aforementioned existing problems, the present invention is proposed.

[0006] Therefore, this invention provides a non-isolated three-port DC-DC converter and a variable control method to solve the problems in the prior art where multiple independent converters are combined separately, resulting in non-reusable components, large system size, and high cost; energy transfer between ports requires multiple stages of transformation, which easily generates circulating current and redundant switching, severely shortening the lifespan of energy storage components; the discrete structure increases system complexity; and the voltage gain of traditional topologies is usually only between 1 and 10 times, which cannot meet the high gain requirements of low-voltage input and high-voltage output of new energy sources.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a non-isolated three-port DC-DC converter, comprising: Input port, battery port, output port, as well as switching transistor group, standard inductor, coupling inductor, first intermediate energy storage capacitor, second intermediate energy storage capacitor, output capacitor and diode group; The input port is connected to the switching transistor No. 2 via diode No. 1 and a standard inductor in sequence; The battery terminal is connected to the common connection point of switch transistors 1 and 4; The output port is connected to the common connection point of the No. 5 switching transistor and the output capacitor; The coupling inductor is connected to switch 3 through the first intermediate energy storage capacitor and to diode 4 through the second intermediate energy storage capacitor.

[0008] As a preferred embodiment of the non-isolated three-port DC-DC converter described in this invention, wherein: The anode of diode 1 is connected to the positive terminal of the input port, and the cathode of diode 1 is connected to switch 1 and the standard inductor. The drain of switch 2 is connected to the standard inductor, the coupling inductor, and the anode of diode 3. The source of switch 2 is connected to the anode of diode 2 and the negative terminal of the first intermediate energy storage capacitor. The positive terminal of the first intermediate energy storage capacitor is connected to the same-name terminal of the primary side of the coupling inductor and the drain of the No. 3 switch. The positive terminal of the second intermediate energy storage capacitor is connected to the cathode of the No. 3 diode and the anode of the No. 4 diode. The negative terminal of the second intermediate energy storage capacitor is connected to the non-same-name terminal of the secondary side of the coupled inductor; The anode of diode 5 is connected to the drain of switch 4 and the cathode of diode 4, and the cathode of diode 5 is connected to the drain of switch 5. The source of switch transistor #4 is connected to the drain of switch transistor #1 and the positive terminal of the battery port. The source of switch 5 is connected to the positive terminal of the output capacitor and the positive terminal of the output port.

[0009] Secondly, the present invention provides a change control method, comprising:

[0010] The converter can be configured to operate in single-input single-output mode, dual-input single-output mode, or single-input dual-output mode. In single-input single-output mode, the converter selectively executes any of the following power supply states: State 1: The input port supplies power to the output port; State 2: The input port supplies power to the battery port; State 3: The battery port supplies power to the output port; In dual-input single-output mode, the control input port and the battery port supply power to the output port together; In single-input dual-output mode, the control input port supplies power to both the battery port and the output port simultaneously.

[0011] As a preferred embodiment of the change control method described in this invention, wherein: In single-input single-output mode, when in state one, the input port supplies power to the output port, and one switching cycle includes: In the first mode, switch transistors 2 and 3 are turned on while the rest of the switches are turned off. The input port and the first intermediate energy storage capacitor charge the standard inductor and the coupled inductor through switch transistors 2 and 3. The coupled inductor transfers energy from the primary side to the secondary side to charge the second intermediate energy storage capacitor. In the second mode, switch 5 is turned on while the other switches are turned off. The input port, standard inductor, and coupling inductor charge the first intermediate energy storage capacitor through diode 2, and charge the output capacitor and output port through the second intermediate energy storage capacitor, diode 4, and diode 5.

[0012] As a preferred embodiment of the change control method described in this invention, wherein: In single-input single-output mode, when in state two, the input port supplies power to the battery port. One switching cycle includes: In the first mode, switch transistors 2 and 3 are turned on while the rest of the switches are turned off. The input port and the first intermediate energy storage capacitor charge the standard inductor and the coupled inductor through switch transistors 2 and 3. The coupled inductor transfers energy from the primary side to the secondary side to charge the second intermediate energy storage capacitor. In the second mode, switch #4 is turned on while the other switches are turned off. The input port, standard inductor, and coupling inductor charge the first intermediate energy storage capacitor through diode #2, and charge the battery port through the second intermediate energy storage capacitor and diode #4. As a preferred embodiment of the change control method described in this invention, wherein: In single-input single-output mode, when in state three, when the battery port supplies power to the output port, one switching cycle includes: In the first mode, switch transistors 1, 2, and 3 are turned on while the remaining switches are turned off. The battery port and the first intermediate energy storage capacitor charge the standard inductor and the coupled inductor through switch transistors 1, 2, and 3. The coupled inductor transfers energy from the primary side to the secondary side to charge the second intermediate energy storage capacitor. In the second mode, switch transistors 1 and 5 are turned on while the rest are turned off. The battery port, standard inductor, and coupling inductor charge the first intermediate energy storage capacitor through diode 2, and charge the output capacitor and output port through the second intermediate energy storage capacitor, diode 4, and diode 5.

[0013] As a preferred embodiment of the change control method described in this invention, wherein: In dual-input single-output mode, the converter executes state one and state three of single-input single-output mode in a time-sharing manner within one control cycle; During state one operation, power is supplied from the input port to the output port; During state three operation, power is supplied from the battery port to the output port; By coordinating the timing of states one and three, the input port and the battery port can alternately supply power to the output port in a time-sharing manner, so that both can jointly supply power to the output port.

[0014] As a preferred embodiment of the change control method described in this invention, wherein: In single-input dual-output mode, the input port supplies power to both the battery port and the output port simultaneously. One switching cycle includes: In the first mode, switch transistors 2 and 3 are turned on while the rest of the switches are turned off. The input port and the first intermediate energy storage capacitor charge the standard inductor and the coupled inductor through switch transistors 2 and 3. The coupled inductor transfers energy from the primary side to the secondary side to charge the second intermediate energy storage capacitor. In the second mode, switch 4 is turned on and the other switches are turned off. The input port, standard inductor and coupling inductor charge the first intermediate energy storage capacitor through diode 2, and charge the battery port through the second intermediate energy storage capacitor and diode 4. In the third mode, switch 5 is turned on while the other switches are turned off. The input port, standard inductor, and coupling inductor charge the first intermediate energy storage capacitor through diode 2, and charge the output port through the second intermediate energy storage capacitor, diode 4, and diode 5.

[0015] As a preferred embodiment of the change control method described in this invention, wherein: The voltage gain of the converter is positively correlated with the turns ratio of the coupled inductor and also with the duty cycles of switches 2 and 3.

[0016] As a preferred embodiment of the change control method described in this invention, wherein: In single-input single-output mode, the voltage gain between the output port and the input port is changed by adjusting the turn-on duration of switch 2 and switch 3 within one switching cycle. By controlling the turn-on duration, the output voltage of the output port can be adjusted between 1 and 200 times the input voltage of the input port.

[0017] Compared with existing technologies, the beneficial effects of this invention are as follows: Compared with existing technologies, this invention replaces the traditional scheme of multiple independent converters in discrete combination with a single integrated converter. While effectively improving the device reuse rate, significantly reducing the system size and manufacturing cost, it eliminates the complex communication and coordination links between converters through centralized control, making the control logic simpler and more reliable. At the same time, the topology can eliminate the circulating current and redundant charging and discharging losses caused by multi-stage energy conversion, thereby effectively protecting the energy storage components and extending their service life. Most importantly, the voltage gain of this invention can reach 1 to 200 times in the duty cycle range of 0 to 0.9, completely breaking the bottleneck that the gain of traditional converters is limited to only 1 to 10 times, and can fully meet the actual application requirements of low-voltage input and high-voltage output in new energy power generation systems. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a topological structure overall framework diagram of an embodiment of the present invention.

[0020] Figure 2 This is a flowchart of mode 1, which shows the input port V1 supplying power to the output port V3 in a single-input single-output mode according to an embodiment of the present invention.

[0021] Figure 3 This is a flowchart illustrating the mode 2 process of powering the input port V1 to the output port V3 in a single-input single-output mode according to an embodiment of the present invention.

[0022] Figure 4 This is a flowchart illustrating mode 1 of the single-input single-output mode of the present invention, in which the input port V1 supplies power to the battery port V2.

[0023] Figure 5 This is a flowchart illustrating the mode 2 process of powering the input port V1 to the battery port V2 in a single-input single-output mode according to an embodiment of the present invention.

[0024] Figure 6 This is a flowchart of mode 1, in which the battery port V2 supplies power to the output port V3 in a single-input single-output mode according to an embodiment of the present invention.

[0025] Figure 7 This is a flowchart illustrating the mode 2 process of powering the battery port V2 to the output port V3 in a single-input single-output mode according to an embodiment of the present invention.

[0026] Figure 8 This is a flowchart of mode 1, which shows that in a dual-input single-output mode according to an embodiment of the present invention, the battery port V2 and the input port V1 jointly supply power to the output port V3.

[0027] Figure 9 This is a flowchart of mode 2, which shows that in a dual-input single-output mode according to an embodiment of the present invention, the battery port V2 and the input port V1 jointly supply power to the output port V3.

[0028] Figure 10 This is a flowchart of mode 3, which shows that in a dual-input single-output mode according to an embodiment of the present invention, the battery port V2 and the input port V1 jointly supply power to the output port V3.

[0029] Figure 11 This is a flowchart of mode 4, which shows the battery port V2 and input port V1 jointly supplying power to output port V3 in a dual-input single-output mode according to an embodiment of the present invention.

[0030] Figure 12 This is a flowchart of mode 5, which shows the battery port V2 and input port V1 jointly supplying power to output port V3 in a dual-input single-output mode according to an embodiment of the present invention.

[0031] Figure 13 This is a flowchart of mode 6, which shows the battery port V2 and input port V1 jointly supplying power to output port V3 in a dual-input single-output mode according to an embodiment of the present invention.

[0032] Figure 14 This is a flowchart of mode 7, which shows the battery port V2 and input port V1 jointly supplying power to output port V3 in a dual-input single-output mode according to an embodiment of the present invention.

[0033] Figure 15 This is a flowchart of mode 8, which shows the battery port V2 and input port V1 jointly supplying power to output port V3 in a dual-input single-output mode according to an embodiment of the present invention.

[0034] Figure 16 This is a flowchart of mode 9, which shows the battery port V2 and input port V1 jointly supplying power to output port V3 in a dual-input single-output mode according to an embodiment of the present invention.

[0035] Figure 17 This is a flowchart of mode 10, which shows that in a dual-input single-output mode according to an embodiment of the present invention, the battery port V2 and the input port V1 jointly supply power to the output port V3.

[0036] Figure 18 This is a flowchart of mode 1, which shows the input port V1 supplying power to the battery port V2 and the output port V3 in a single-input dual-output mode according to an embodiment of the present invention.

[0037] Figure 19 This is a flowchart illustrating mode 2 of a single-input dual-output mode according to an embodiment of the present invention, showing how the input port V1 supplies power to the battery port V2 and the output port V3. Figure 20 This is a flowchart illustrating mode 3 of a single-input dual-output mode according to an embodiment of the present invention, showing how input port V1 supplies power to battery port V2 and output port V3. Detailed Implementation

[0038] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0039] Reference Figure 1 As one embodiment of the present invention, a non-isolated three-port DC-DC converter is provided, comprising: This embodiment provides a specific hardware architecture for a non-isolated three-port DC-DC converter, used to achieve energy integration and flexible scheduling between the input port, battery port, and output port. The converter mainly includes an input port V1, a battery port V2, an output port V3, and a core power circuit consisting of switching transistors S1 to S5 (1 to 5), a standard inductor L1, a coupling inductor L2, a first intermediate energy storage capacitor C1, a second intermediate energy storage capacitor C2, an output capacitor Co, and diodes D1 to D5 (1 to 5).

[0040] In the specific circuit connection, the positive terminal of input port V1 is connected in series with diode D1 (number 1) and then connected to the first end of standard inductor L1. The other end of standard inductor L1 is connected to the drain of switch S2 (number 2). The positive terminal of battery port V2 is connected to the common connection point of switch S1 (number 1) and switch S4 (number 4), enabling the battery port to function as both a power supply for discharging and an energy storage load for receiving electrical energy, depending on control requirements.

[0041] The positive terminal of output port V3 is connected to the common point between the source of switch S5 (No. 5) and the positive terminal of output capacitor Co. Output capacitor Co smooths and filters the output voltage, ensuring the stability of the load power supply. This specific device layout allows the standard inductor L1 and the coupled inductor L2 to form a compact, stepped energy transfer path in the circuit. Compared to the traditional multi-inductor parallel structure, this embodiment utilizes a single coupled inductor that acts as both an energy storage element and a voltage multiplier, eliminating the need for additional discrete energy storage inductors and significantly saving circuit board space.

[0042] In this embodiment, the coupling inductor L2 serves as a crucial energy transfer and boosting element, positioned at the center of the circuit. Specifically, the primary side of the coupling inductor L2 is connected to the positive terminal of the first intermediate energy storage capacitor C1, while the negative terminal of C1 is connected to the source of switch S2 (number 2), and the positive terminal of C1 is also connected to the drain of switch S3 (number 3). The non-primary side of the coupling inductor L2 and its secondary side are both connected to the drain of switch S2, while the non-secondary side of the coupling inductor L2 is connected to the negative terminal of the second intermediate energy storage capacitor C2. The positive terminal of the second intermediate energy storage capacitor C2 is connected to the cathode of diode D3 (number 3) and the anode of diode D4 (number 4).

[0043] The anode of diode D5 (No. 5) is connected to the common node of the drain and cathode of switch S4 (No. 4), while the cathode of diode D5 is connected to the drain of switch S5 (No. 5). The drain of switch S1 (No. 1) is connected to the cathode of diode D1 (No. 1) on one hand, and also to the positive terminal of battery port V2 on the other hand. The source of switch S1 (No. 1) serves as an internal common reference node.

[0044] This embodiment seamlessly integrates three independent ports into a single power conversion network using the aforementioned composite topology of standard inductor L1 and coupled inductor L2. The arrangement of the switches, diodes, and energy storage capacitors ensures that when energy flows between any two ports, the alternating storage and release of energy by standard inductor L1 and coupled inductor L2 enables voltage boosting from low to high voltage and effectively reduces redundant energy exchange between energy storage components.

[0045] Compared to the traditional approach of using three independent DC-DC converters in a discrete combination, the hardware architecture of this embodiment achieves a high degree of reuse of power devices, significantly reduces the number of magnetic components and switching devices, makes the overall converter more compact, significantly reduces manufacturing costs, and is also easier to integrate on the power board.

[0046] By eliminating the bulky and expensive high-frequency isolation transformer, this implementation effectively reduces the overall weight during assembly and avoids voltage spike interference caused by transformer excitation losses and leakage inductance. This non-isolated design allows for shared connection of the output and input grounds in suitable applications, further simplifying system grounding design, reducing the complexity of grounding protection, and lowering the overall system cost in multiple ways. Furthermore, the non-isolated topology effectively avoids high-frequency electromagnetic radiation and core eddy current losses associated with transformers, exhibiting superior power density advantages in small-to-medium power distributed power supply systems for new energy sources.

[0047] In some embodiments, refer to Figures 1-17This embodiment is mainly based on the hardware architecture of a non-isolated three-port DC-DC converter, and describes in detail the specific control execution process in single-input single-output mode and dual-input single-output mode, so as to realize the directional transmission of energy between different ports.

[0048] In single-input single-output mode, the converter selectively executes any one of the following three power supply states according to the actual power generation and energy storage requirements.

[0049] State 1: Input port V1 supplies power to output port V3. A complete switching control cycle includes two operating modes.

[0050] In the first mode, control switches S2 and S3 are turned on, while all other switches are turned off. Input port V1 and the first intermediate energy storage capacitor C1 charge the magnetizing inductance of energy storage inductor L1 and coupling inductor L2 through the turned-on switches S2 and S3. Due to the electromagnetic coupling between the primary and secondary windings of coupling inductor L2, the energy stored on the primary side is transferred to the secondary side and charges the second intermediate energy storage capacitor C2, establishing a positive voltage across C2.

[0051] The first mode, serving as the energy storage phase of the entire control cycle, utilizes the simultaneous conduction of switches S2 (No. 2) and S3 (No. 3) to store input energy simultaneously in both the standard inductor L1 and the coupled inductor L2. Compared to a single inductor energy storage scheme, the dual energy storage and isolated transfer properties of the coupled inductor allow for higher energy storage requirements to be met with a shorter turn-on time. This characteristic not only shortens the inductor magnetization time but also reduces the conduction losses of the switching transistors at high switching frequencies, thereby improving energy conversion efficiency.

[0052] In the second mode, switch S5 (controller 5) is turned on, while all other switches are turned off. At this time, input port V1, standard inductor L1, and coupling inductor L2 together charge the first intermediate energy storage capacitor C1 through diode D2 (controller 2), replenishing the charge released by C1 in mode one.

[0053] Meanwhile, the second intermediate energy storage capacitor C2 serves as an auxiliary voltage source, releasing energy to the output capacitor Co and the output port V3 through diodes D4 and D5 in sequence, thereby achieving input-to-output boost power supply.

[0054] In the second mode, the output capacitor Co and the second intermediate energy storage capacitor C2 work together to maintain the stability of the output port voltage. During the conduction of switch S5 (No. 5), energy transfer is not limited by the charging circuit current, allowing for a smooth transfer of energy from the energy storage element to the load, minimizing voltage drops at the load. Simultaneously, as a separate switch for the main output channel, switch S5's on-state achieves complete physical isolation between the input and output terminals, preventing direct impact of input voltage fluctuations on the load voltage and enhancing the stability of the load power supply.

[0055] State 2: Input port V1 supplies power to battery port V2. When the power generation capacity of new energy sources such as photovoltaics is sufficient and the battery charge is low, the converter switches to State 2.

[0056] The first mode of state two is exactly the same as state one, that is, controlling switch S2 and switch S3 to conduct, using standard inductor L1 and coupling inductor L2 to store energy, and coupling the energy to the secondary side to charge C2.

[0057] In the subsequent second mode, the difference from state one is that this mode controls switch S4 (number 4) to be turned on, while the other switches are turned off. The energy stored in input port V1, standard inductor L1, and coupling inductor L2 charges the first intermediate energy storage capacitor C1 through diode D2 (number 2); simultaneously, the energy stored in the second intermediate energy storage capacitor C2 flows through diode D4 (number 4) and the drain of switch S4 (number 4) to the positive terminal of battery port V2, achieving safe and controllable charging of the battery.

[0058] During the process of powering the battery from input port V1 to battery port V2, the second mode of state two effectively constructs an independent energy receiving circuit for the battery by controlling the on / off state of switch S4 (number 4). When S4 is on, battery port V2 passively receives the electrical energy transferred from the second intermediate energy storage capacitor C2. This process is entirely controlled by the charge of the second intermediate energy storage capacitor C2, avoiding the impact of sudden charging current changes on the battery plates in traditional charging methods, and helping to extend the cycle life of the energy storage battery.

[0059] State 3: Battery port V2 supplies power to output port V3. State 3 is activated at night or when photovoltaic energy is insufficient and the battery needs to independently support the load.

[0060] In the first mode, switch transistors S1, S2, and S3 are simultaneously turned on. Battery port V2 is introduced into the main circuit through switch transistor S1, and together with the first intermediate energy storage capacitor C1, it charges the standard inductor L1 and the coupling inductor L2. The coupling inductor L2 transfers energy to the second intermediate energy storage capacitor C2.

[0061] In the second mode, control switches S1 and S5 are turned on, while the others are turned off. The remaining energy at battery port V2, the energy released from standard inductor L1 and coupling inductor L2, charges the first intermediate energy storage capacitor C1 through diode D2. Simultaneously, the second intermediate energy storage capacitor C2 discharges through diodes D4 and D5 to output capacitor Co and output port V3, completing the entire control cycle of the battery supplying power to the load.

[0062] In battery-powered mode, the continuous conduction of switch S1 (No. 1) is crucial for ensuring reliable energy access to the circuit from the battery. The coordinated operation of S1 and S5 allows the battery to receive dual voltage boost support from the standard inductor L1 and the coupled inductor L2 during discharge, preventing power interruption at the load when the battery voltage drops. This robust discharge support mechanism ensures that the battery maintains a basic output voltage level even at low charge levels, enhancing the system's redundancy under harsh operating conditions.

[0063] Furthermore, this embodiment also includes a dual-input single-output mode. In dual-input single-output mode, the converter executes the control processes of state one and state three in a time-sharing manner within a relatively long control cycle. When executing state three mode, the battery port V2 is mainly responsible for providing power to the output port V3; when executing state one mode, the input port V1 is mainly responsible for providing power to the output port V3. Through the timing coordination of state one and state three, the input port V1 and the battery port V2 alternately supply power to the output terminal in a time-sharing manner, ultimately enabling these two energy sources to jointly deliver electrical energy to the load.

[0064] To more clearly demonstrate the alternating power supply feature of the dual-input ports in this embodiment, the following ten operating modes under the dual-input single-output mode are executed sequentially throughout the entire control cycle: First mode reference Figure 8 The system controls the conduction of switches S1, S2, and S3, while turning off the remaining switches. Battery port V2 and the first intermediate energy storage capacitor C1 charge the standard inductor L1 through switches S1, S2, and S3. Simultaneously, the first intermediate energy storage capacitor C1 transfers energy from the primary to the secondary side of the coupling inductor L2 to charge the second intermediate energy storage capacitor C2. The output capacitor Co supplies power to output port V3. In the first mode, energy from battery port V2 is introduced into the boost network, and through the cross-energy storage of the coupling inductor L2, the voltage across the second intermediate energy storage capacitor C2 is initially established.

[0065] Second mode reference Figure 9The system controls the conduction of switches S1, S2, and S3, while turning off the remaining switches. Battery port V2 and the first intermediate energy storage capacitor C1 charge the standard inductor L1 and the coupled inductor L2 through switches S1, S2, and S3. Simultaneously, battery port V2 transfers energy from the primary side of the coupled inductor L2 to the secondary side, charging the second intermediate energy storage capacitor C2. The output capacitor Co continues to supply power to output port V3. Compared to the first mode, the second mode widens the excitation path of the coupled inductor L2, allowing battery port V2 to transfer energy to the secondary side through more loops, further increasing the charge on the second intermediate energy storage capacitor C2.

[0066] Third mode reference Figure 10 The system controls the conduction of switches S1, S2, and S3, while turning off the remaining switches. At this time, the current in the coupled inductor L2 flows in the reverse direction. The battery port V2 and the first intermediate energy storage capacitor C1 charge the standard inductor L1 through switches S1, S2, and S3. The output capacitor Co continues to supply power to the output port V3. In this mode, the direction of the magnetic field energy inside the coupled inductor L2 reverses. This reverse current effectively balances the magnetic flux on the primary and secondary sides of the coupled inductor L2, preventing it from entering magnetic saturation and ensuring safe operation of the circuit under high duty cycle conditions.

[0067] Fourth Modal Reference Figure 11 The system controls the conduction of switches S1 (1) and S5 (5), while turning off the remaining switches. Battery port V2 and standard inductor L1 charge the first intermediate energy storage capacitor C1 through coupling inductor L2 and diode D2 (2). Simultaneously, the second intermediate energy storage capacitor C2 charges the output capacitor Co and output port V3 through diodes D4 (4) and D5 (5). At this time, the current inside coupling inductor L2 flows in reverse and gradually decreases. In this mode, standard inductor L1 and coupling inductor L2 begin to release energy, directing the current through the diode branches to the first intermediate energy storage capacitor C1 and output port V3 respectively, achieving a smooth switching between energy storage and discharge.

[0068] Fifth Modal Reference Figure 12The system controls the conduction of switches S1 (number 1) and S5 (number 5), while turning off the remaining switches. Battery port V2 and standard inductor L1 charge the first intermediate energy storage capacitor C1 through coupling inductor L2 and diode D2 (number 2). Simultaneously, battery port V2 and the second intermediate energy storage capacitor C2 supply power to output capacitor Co and output port V3 through diodes D4 (number 4) and D5 (number 5). The fifth mode is the final step in the power supply process from battery port V2 to output port V3. Through a dual-diode channel, the energy from the battery port V2 branch and the second intermediate energy storage capacitor C2 branch is simultaneously channeled to output port V3, significantly improving the peak current capability of battery port V2.

[0069] Sixth Modal Reference Figure 13 The system controls switches S2 and S3 to be turned on, while the remaining switches are turned off. Input port V1 and the first intermediate energy storage capacitor C1 charge the standard inductor L1 through switches S2 and S3. Simultaneously, the first intermediate energy storage capacitor C1 transfers energy from the primary side to the secondary side of the coupling inductor L2 to charge the second intermediate energy storage capacitor C2. Output capacitor Co charges output port V3. In the sixth mode, the system switches from battery power to power from the new energy input port. By controlling the conduction of switches S2 and S3, input port V1 is successfully connected to the main circuit and a new round of energy storage begins.

[0070] Seventh Modal Reference Figure 14 The system controls the conduction of switches S2 and S3, while turning off the remaining switches. Input port V1 and the first intermediate energy storage capacitor C1 charge the standard inductor L1 through switches S2 and S3. Simultaneously, input port V1 directly transfers energy to the secondary side of the coupling inductor L2 to charge the second intermediate energy storage capacitor C2. Output capacitor Co continues to supply power to output port V3. In the seventh mode, by directly introducing input port V1 into the excitation circuit of coupling inductor L2, the charging effect of input port V1 on the second intermediate energy storage capacitor C2 is significantly enhanced, thereby improving the energy utilization rate of input port V1.

[0071] Eighth Modal Reference Figure 15 The system controls switches S2 and S3 to turn on, while the remaining switches are turned off. At this time, the current in the coupling inductor L2 flows in the reverse direction. The input port V1 and the first intermediate energy storage capacitor C1 charge the standard inductor L1 through switches S1, S2, and S3. The output capacitor Co supplies power to the output port V3. Similar to the third mode, the eighth mode also utilizes the reverse current inside the coupling inductor L2 to balance the magnetic circuit, preventing core bias caused by continuous high-current charging on the input side, thus providing good protection for the coupling inductor L2 and the switches.

[0072] Ninth Modal Reference Figure 16The system controls switch S5 (number 5) to turn on, while the other switches are turned off. Input port V1 and standard inductor L1 charge the first intermediate energy storage capacitor C1 through coupling inductor L2 and diode D2 (number 2). Simultaneously, the second intermediate energy storage capacitor C2 charges the output capacitor Co and output port V3 through diodes D4 (number 4) and D5 (number 5). The current inside coupling inductor L2 flows in reverse and gradually decreases. The ninth mode successfully connects the energy storage release on the input side, sending the energy stored in input port V1, standard inductor L1, and coupling inductor L2 to the first intermediate energy storage capacitor C1, ensuring the continuity of power supply.

[0073] Tenth Modal Reference Figure 17 The system controls switch S5 (number 5) to turn on, while the other switches are turned off. Input port V1 and standard inductor L1 charge the first intermediate energy storage capacitor C1 through coupling inductor L2 and diode D2 (number 2). Simultaneously, input port V1 and the second intermediate energy storage capacitor C2 supply power to output capacitor Co and output port V3 through diodes D4 (number 4) and D5 (number 5). In the tenth mode, the final operation, input port V1 is directly connected in parallel with output port V3 and the second intermediate energy storage capacitor C2 to release energy, maximizing the transfer of power from input port V1 to output port V3, achieving seamless connection with the power supply from the front-end battery port V2.

[0074] Through precise switching of the aforementioned 10 operating modes, this embodiment fully reveals the energy flow mechanism under the dual-input single-output mode. The first five modes utilize the battery port V2 as the main power supply unit for energy storage and release, while the latter five modes switch to the input port V1 as the main power supply unit. This mode decomposition method allows the control command to precisely trigger the corresponding mode branch when the converter faces drastic changes in the power of the input port V1, ensuring a uniform distribution of current stress on each switching device and effectively avoiding the energy backflow problem caused by the direct parallel connection of the input port V1 and the battery port V2.

[0075] Meanwhile, since the coupling inductor L2 plays a role in magnetic coupling and reverse demagnetization at each stage, the operation of each switch is well buffered during the alternating operation of the system, which greatly reduces the hard turn-off loss of switch 1 to switch 5 S1~S5, and improves the power conversion efficiency and long-term operational reliability of the entire three-port converter.

[0076] The dual-input single-output mode in this embodiment utilizes a time-division scheduling method to simultaneously achieve power aggregation from two input sources using a single physical topology. This time-division power supply strategy ensures that input port V1 and battery port V2 always maintain an energy complementary state, avoiding the backflow current problem that may occur when directly connected in parallel, and ensuring that the internal components of each port are always within a safe voltage stress range.

[0077] In some embodiments, refer to Figures 1-20 This embodiment focuses on describing how the converter can simultaneously power the battery and the load port in single-input dual-output mode, and how to achieve high-gain boost voltage by adjusting the switching transistor drive signal.

[0078] This embodiment focuses on describing how the converter can simultaneously power the battery port V2 and the output port V3 in single-input dual-output mode, and how to achieve high-gain boost voltage by adjusting the switching transistor drive signal.

[0079] In single-input dual-output mode, the converter sequentially switches between three operating modes within one switching control cycle, so that the input port V1 can simultaneously supply energy to both the battery port V2 and the output port V3.

[0080] The first mode is the energy storage stage, as referenced. Figure 18 The system controls the conduction of switches S2 and S3, while turning off the remaining switches. The energy from input port V1 and the first intermediate energy storage capacitor C1 flows through switches S2 and S3, passing through the primary side of standard inductor L1 and coupling inductor L2 for electromagnetic energy storage. Simultaneously, coupling inductor L2 transfers the energy induced on the primary side to the secondary side, where it is stored by the second intermediate energy storage capacitor C2.

[0081] The energy storage stage of the first mode is equally crucial in the single-input dual-output mode. Its magnetization circuit is identical to that of the single-input single-output mode, ensuring a high degree of consistency in the control strategy. This reused design significantly reduces the complexity of switching between different operating modes during controller development. It eliminates the need to recalibrate the initial state parameters of the standard inductor L1 or the first intermediate energy storage capacitor C1 and the second intermediate energy storage capacitor C2 during mode switching, simplifying the control program execution process.

[0082] The second mode is the battery charging stage, see reference. Figure 19The first mode controls the conduction of switch S4 (number 4) while turning off the other switches. The energy stored in input port V1, standard inductor L1, and coupling inductor L2 replenishes the first intermediate energy storage capacitor C1 through diode D2 (number 2). Simultaneously, the second intermediate energy storage capacitor C2, having completed its energy storage in the first mode, charges battery port V2 through diode D4 (number 4). In this mode, output port V3 is temporarily powered by output capacitor Co. The second mode is specifically designed for the charging needs of battery port V2. At the instant switch S4 is turned on, energy is injected unidirectionally into battery port V2 through a restrictive channel. This isolated charging path runs parallel to the power supply branch of output port V3, ensuring that the charging process of battery port V2 is completely independent of the power supply process of output port V3. Even if sudden current fluctuations occur in output port V3, the stability of the charging circuit will not be affected, achieving true multi-port uninterrupted collaborative operation.

[0083] The third mode is the load power supply stage, refer to Figure 20 The system controls switch S5 (number 5) to turn on, while the other switches are turned off. At this time, the energy at input port V1 continues to replenish the first intermediate energy storage capacitor C1 through diode D2 (number 2). Simultaneously, the second intermediate energy storage capacitor C2, after completing its energy storage, releases energy to output capacitor Co and output port V3 sequentially through diode D4 (number 4), diode D5 (number 5), and switch S5 (number 5), ensuring that voltage fluctuations at output port V3 are controlled within acceptable limits. Through the cyclical alternation of the first, second, and third modes, energy distribution from input port V1 to both battery port V2 and output port V3 is completed.

[0084] In the third mode, the path for supplying energy to the output port V3 is completely consistent with the single-input single-output path in state one, further ensuring the power supply consistency of the output port V3 in different overall modes. Under the cyclical drive of the three modes, the input port V1 not only achieves energy bootstrapping through the coupling inductor L2, but also allocates energy to the battery port V2 and the output port V3 according to a predetermined ratio, making energy management very clear and very suitable for the complex power supply management architecture of multi-load or backup batteries in photovoltaic energy storage systems.

[0085] This embodiment also includes a specific control method for the high-gain voltage characteristics of the converter. The magnitude of the voltage gain mainly depends on the turns ratio n of the coupling inductor L2 and the duty cycle D of switches S2 and S3. In actual control, simply adjusting the on-time of switches S2 and S3 within one switching cycle, i.e., adjusting the duty cycle D, can effectively change the voltage gain relationship between the output port V3 and the input port V1.

[0086] Thanks to the cascading boost effect of the standard inductor L1 and the coupled inductor L2 in the topology, as well as the voltage multiplication effect brought about by the primary-secondary turns ratio n, the three-port converter can achieve a wide range of voltage adjustment between 1 and 200 times the voltage of the input port V1 by changing the duty cycle D of the switching transistor.

[0087] In this embodiment of the gain adjustment method, the duty cycle D is no longer limited to the narrow effective range of the traditional topology. Thanks to the special turns ratio n design of the coupled inductor L2, even if the duty cycle D fluctuates within a wide range of 0 to 0.9, the output port V3 can still maintain a voltage boost of 1 to 200 times. In practical applications, this wide gain adjustment method allows the converter to adapt to the wide fluctuations in output characteristics of the input port V1 under different solar irradiance levels, without the need for additional adjustable tap inductors or external mechanical switches. This greatly improves the engineering practicality of distributed new energy power supply systems and achieves a wider range of voltage adaptability.

[0088] In single-input dual-output mode, energy distribution between two switching channels is involved. In this mode, in addition to the duty cycles D1 of switches S2 (2) and S3 (3), the duty cycle D2 of switch S4 (4) is also required to jointly control the voltage distribution and energy flow between output port V3 and battery port V2. By adjusting the ratio of D1 to D2, the system can simultaneously meet the differentiated voltage requirements of output port V3 and battery port V2, achieving independent and flexible control of the voltages at multiple output ports.

[0089] Compared to traditional DC-DC converters, the control method in this embodiment overcomes the gain limitations of traditional switching power devices without requiring an additional front-end boost unit, enabling the converter to be compatible with both low-voltage output at input port V1 and high-voltage output at output port V3. This wide-range adjustable gain characteristic, combined with the single-input dual-output operating mode, allows the converter of this invention to function as an independent energy dispatch node in a photovoltaic energy storage system. It can flexibly boost the low-voltage DC power from input port V1 to the DC microgrid bus to supply output port V3, and automatically shunt excess power from output port V3 or the input port V1 bus to charge battery port V2. The overall system adaptability is greatly enhanced, effectively alleviating the voltage compatibility problem faced when distributed new energy sources are connected to the distribution network.

[0090] In single-input single-output operating mode, the voltage relationship between the converter ports can be derived by performing volt-second balance analysis on the standard inductor L1. Specifically: Under the two energy flow states of power supply from input port V1 to output port V3 in state one and power supply from input port V1 to battery port V2 in state two, the output voltage and input voltage satisfy the following gain relationship, where V1, V2, and V3 represent the voltage levels of input port V1, battery port V2, and output port V3, respectively, and n represents the turns ratio of the coupling inductor L2, i.e., the ratio of the number of turns in the secondary winding to the number of turns in the primary winding, which is a fixed physical parameter. ; ; When in state three, i.e., when battery port V2 supplies power to output port V3, the output voltage and the battery input voltage satisfy the same gain expression: .

[0091] In single-input dual-output mode, where input port V1 simultaneously supplies power to both battery port V2 and output port V3, the voltage relationship becomes more complex and exhibits multi-degree-of-freedom modulation characteristics due to the independent control of switch S4 in the system's switching timing. A volt-second balance analysis of the power circuit in single-input dual-output mode yields the following voltage expression for output port V3: ; Parameter D1 specifically refers to the percentage of turn-on time for switches S2 and S3 in a single switching cycle; parameter D2 specifically refers to the percentage of turn-on time for switch S4 in the same switching cycle; parameter n still represents the turns ratio of the coupling inductor L2.

[0092] The formula clearly reveals from a mathematical perspective that in the single-input dual-output mode of this invention, the output voltage is not only affected by the voltages of the input port V1 and the battery port V2, but also closely coupled with two independent duty cycle parameters D1 and D2. In actual control, by reasonably adjusting the on-time of switch S2 (2), switch S3 (3), and switch S4 (4), it is possible to ensure stable power supply to output port V3 while accurately allocating excess energy to battery port V2 for charging, thus avoiding the defects of mutual restraint and voltage runaway in traditional dual-output topologies.

[0093] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A non-isolated three-port DC-DC converter, characterized in that: include, Input port (V1), battery port (V2), output port (V3), as well as switching transistor group (S1~S5), standard inductor (L1), coupling inductor (L2), first intermediate energy storage capacitor (C1), second intermediate energy storage capacitor (C2), output capacitor (Co) and diode group (D1~D5); The input port (V1) is connected to the switch transistor (S2) via diode (D1) and standard inductor (L1) in sequence. The battery terminal (V2) is connected to the common connection point of switch transistor 1 (S1) and switch transistor 4 (S4); The output port (V3) is connected to the common connection point of the No. 5 switching transistor (S5) and the output capacitor (Co); The primary side of the coupling inductor (L2) is connected to the No. 3 switch (S3) through the first intermediate energy storage capacitor (C1), and the secondary side of the coupling inductor (L2) is connected to the No. 4 diode (D4) through the second intermediate energy storage capacitor (C2).

2. The non-isolated three-port DC-DC converter according to claim 1, characterized in that: The anode of diode 1 (D1) is connected to the positive terminal of the input port (V1), and the cathode of diode 1 (D1) is connected to the source of switch 1 (S1) and one end of the standard inductor (L1). The drain of switch 2 (S2) is connected to the other end of standard inductor (L1), the non-same-name terminal of the primary side of coupling inductor (L2), the same-name terminal of the secondary side of coupling inductor (L2), and the anode of diode 3 (D3). The source of switch 2 (S2) is connected to the anode of diode 2 (D2) and the negative terminal of the first intermediate energy storage capacitor (C1). The cathode of diode 2 (D2), the source of switch 3 (S3), the negative terminal of input port (V1), the negative terminal of battery port (V2), the negative terminal of output port (V3), the negative terminal of output capacitor (Co), the negative terminal of first intermediate energy storage capacitor (C1), and the negative terminal of second intermediate energy storage capacitor (C2) are all connected to the same common reference terminal. The positive terminal of the first intermediate energy storage capacitor (C1) is connected to the same-name terminal of the primary side of the coupling inductor (L2) and the drain of the No. 3 switch (S3). The positive terminal of the second intermediate energy storage capacitor (C2) is connected to the cathode of the No. 3 diode (D3) and the anode of the No. 4 diode (D4). The negative terminal of the second intermediate energy storage capacitor (C2) is connected to the non-same terminal of the secondary side of the coupled inductor (L2); The anode of diode 5 (D5) is connected to the drain of switch 4 (S4) and the cathode of diode 4 (D4), and the cathode of diode 5 (D5) is connected to the drain of switch 5 (S5). The source of switch 4 (S4) is connected to the drain of switch 1 (S1) and the positive terminal of the battery terminal (V2); The source of switch S5 is connected to the positive terminal of the output capacitor Co and the positive terminal of the output port V3.

3. A variable control method, applied to the non-isolated three-port DC-DC converter of claim 2, and, The converter can be configured to operate in single-input single-output mode, dual-input single-output mode, or single-input dual-output mode. In single-input single-output mode, the converter selectively executes any of the following power supply states: State 1: Input port (V1) supplies power to output port (V3); State 2: Input port (V1) supplies power to battery port (V2); State 3: The battery terminal (V2) supplies power to the output terminal (V3); In dual-input single-output mode, the control input port (V1) and the battery port (V2) jointly supply power to the output port (V3); In single-input dual-output mode, the control input port (V1) supplies power to both the battery port (V2) and the output port (V3) simultaneously.

4. The change control method according to claim 3, characterized in that: In single-input single-output mode, when in state one, the input port (V1) supplies power to the output port (V3), and one switching cycle includes: In the first mode, switch 2 (S2) and switch 3 (S3) are turned on, while the other switches are turned off. The input port (V1) and the first intermediate energy storage capacitor (C1) charge the standard inductor (L1) and the coupling inductor (L2) through switch 2 (S2) and switch 3 (S3). The coupling inductor (L2) transfers energy from the primary side to the secondary side to charge the second intermediate energy storage capacitor (C2). In the second mode, switch 5 (S5) is turned on while the other switches are turned off. The input port (V1), standard inductor (L1), and coupling inductor (L2) charge the first intermediate energy storage capacitor (C1) through diode 2 (D2), and charge the output capacitor (Co) and output port (V3) through the second intermediate energy storage capacitor (C2), diode 4 (D4), and diode 5 (D5).

5. The change control method according to claim 4, characterized in that: In single-input single-output mode, when in state two, the input port (V1) supplies power to the battery port (V2). One switching cycle includes: In the first mode, switch 2 (S2) and switch 3 (S3) are turned on, while the other switches are turned off. The input port (V1) and the first intermediate energy storage capacitor (C1) charge the standard inductor (L1) and the coupling inductor (L2) through switch 2 (S2) and switch 3 (S3). The coupling inductor (L2) transfers energy from the primary side to the secondary side to charge the second intermediate energy storage capacitor (C2). In the second mode, switch 4 (S4) is turned on while the other switches are turned off. The input port (V1), standard inductor (L1), and coupling inductor (L2) charge the first intermediate energy storage capacitor (C1) through diode 2 (D2), and charge the battery port (V2) through the second intermediate energy storage capacitor (C2) and diode 4 (D4).

6. The change control method according to claim 5, characterized in that: In single-input single-output mode, when in state three, when the battery port (V2) supplies power to the output port (V3), one switching cycle includes: In the first mode, switch transistors 1 (S1), 2 (S2), and 3 (S3) are turned on, while the remaining switches are turned off. The battery terminal (V2) and the first intermediate energy storage capacitor (C1) are charged through switch transistors 1 (S1), 2 (S2), and 3 (S3) to the standard inductor (L1) and the coupling inductor (L2). The coupling inductor (L2) transfers energy from the primary side to the secondary side to charge the second intermediate energy storage capacitor (C2). In the second mode, switch 1 (S1) and switch 5 (S5) are turned on, while the remaining switches are turned off. The battery port (V2), standard inductor (L1), and coupling inductor (L2) charge the first intermediate energy storage capacitor (C1) through diode 2 (D2), and charge the output capacitor (Co) and output port (V3) through the second intermediate energy storage capacitor (C2), diode 4 (D4), and diode 5 (D5).

7. The change control method according to claim 6, characterized in that: In dual-input single-output mode, the converter executes state one and state three of single-input single-output mode in a time-sharing manner within one control cycle; During operation in state one, power is supplied from the input port (V1) to the output port (V3); During operation in state three, power is supplied from the battery port (V2) to the output port (V3); By coordinating the timing of states one and three, the input port (V1) and the battery port (V2) alternately supply power to the output port (V3) in a time-sharing manner, so that both can jointly supply power to the output port (V3).

8. The change control method according to claim 7, characterized in that: In single-input dual-output mode, the input port (V1) supplies power to both the battery port (V2) and the output port (V3) simultaneously. One switching cycle includes: In the first mode, switch 2 (S2) and switch 3 (S3) are turned on, while the other switches are turned off. The input port (V1) and the first intermediate energy storage capacitor (C1) charge the standard inductor (L1) and the coupling inductor (L2) through switch 2 (S2) and switch 3 (S3). The coupling inductor (L2) transfers energy from the primary side to the secondary side to charge the second intermediate energy storage capacitor (C2). In the second mode, switch 4 (S4) is turned on while the other switches are turned off. The input port (V1), standard inductor (L1), and coupling inductor (L2) charge the first intermediate energy storage capacitor (C1) through diode 2 (D2), and charge the battery port (V2) through the second intermediate energy storage capacitor (C2) and diode 4 (D4).

9. The change control method according to claim 8, characterized in that: In single-input dual-output mode, the input port (V1) supplies power to both the battery port (V2) and the output port (V3) simultaneously. A switching cycle also includes a third mode: In the third mode, switch 5 (S5) is turned on and the other switches are turned off. The input port (V1), standard inductor (L1) and coupling inductor (L2) charge the first intermediate energy storage capacitor (C1) through diode 2 (D2), and charge the output port (V3) through the second intermediate energy storage capacitor (C2), diode 4 (D4) and diode 5 (D5).

10. The change control method according to claim 9, characterized in that: The voltage gain of the converter is positively correlated with the turns ratio of the coupling inductor (L2); In state one of the single-input single-output modes, the on-time of switch 2 (S2) and switch 3 (S3) within one switching cycle is adjusted to change the voltage gain between the output port (V3) and the input port (V1).

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