Multi-port converter

Abstract

The invention discloses a multi-port converter, and belongs to the technical field of new energy. A non-isolated power conversion module and an isolated power conversion module of the multi-port converter are in circuit connection through a high-frequency transformer, and the non-isolated power conversion module of the multi-port converter comprises a plurality of switch units which are sequentially connected through an inductor. The switch unit comprises input ports and a first switch circuit formed by connecting at least two switch tubes in series, and the input ports are connected to the two sides of the first switch circuit. By adopting the multi-port converter provided by the invention, on the premise that the main circuit structure and the core working principle of the converter are not changed, similar ports are added to realize the access of multiple new energy power generation equipment or multiple energy storage devices, and the expansibility of the converter is improved; and meanwhile, the input ports are not strictly constrained by the voltage magnitude relation, and can stably work under the condition that the input voltage fluctuates greatly, so that effective adaptation to a wide input voltage range is realized.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, and more specifically, to a multi-port converter. Background Technology

[0002] Independent renewable energy power supply systems are an important way to utilize renewable energy. Because the output power of renewable energy power generation equipment such as solar and wind power is unstable, the system must be equipped with energy storage components such as batteries to store and regulate electrical energy to ensure a continuous and stable power supply to the load. Therefore, a typical independent renewable energy power supply system consists of power generation equipment, energy storage devices, and loads.

[0003] With the increasing utilization of new energy sources, the number of new energy power generation devices and energy storage devices connected to independent new energy power supply systems is also increasing. Using a combination of unidirectional and bidirectional converters can effectively achieve system energy management and control, but the large number of converters, their large size and weight, and the presence of multiple power conversion stages in the system lead to low system efficiency. Therefore, without changing the main circuit structure and core working principle, one of the technical problems that needs to be solved is how to increase the number of similar ports to connect multiple new energy power generation devices or multiple energy storage devices.

[0004] In addition, due to the susceptibility of photovoltaic and other new energy power generation equipment to weather conditions and their intermittent nature, their input voltage also varies over a wide range with environmental changes. Therefore, research is essential to implement buck, boost, or buck-boost functions through the topology between converter ports to adapt to changes in photovoltaic cell port voltage and reduce constraints on energy storage port voltage and photovoltaic cell port voltage. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, the present invention aims to provide a multi-port converter that can add similar ports to enable access to multiple new energy power generation devices or multiple energy storage devices without changing the main circuit structure and core working principle of the converter, thereby improving the scalability of the converter. At the same time, the input ports are not strictly constrained by the voltage magnitude relationship, and can operate stably under large fluctuations in input voltage, thereby achieving effective adaptation to a wide input voltage range.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows: This application provides a multi-port converter, characterized in that the non-isolated power conversion module and the isolated power conversion module of the multi-port converter are connected through a high-frequency transformer circuit. The non-isolated power conversion module of the multi-port converter includes multiple switching units, which are connected in sequence through inductors. Each switching unit includes an input port and a first switching circuit composed of at least two switching transistors connected in series. The input port is connected to both sides of the first switching circuit.

[0007] Optionally, the isolated power conversion module of the multi-port converter includes a voltage divider half-bridge circuit.

[0008] Optionally, the voltage divider half-bridge circuit includes at least two voltage divider circuits connected in series and an output port. The voltage divider circuit includes a voltage divider capacitor and a second switching circuit composed of at least two switching transistors connected in series. The voltage divider capacitor is connected to both sides of the second switching circuit. One side of the output port is connected to the input terminal of the first voltage divider circuit, and the other side of the output port is connected to the output terminal of the last voltage divider circuit.

[0009] Optionally, the primary side of the high-frequency transformer circuit includes a primary winding and a primary capacitor connected in series. One end of the primary winding is connected between two switching transistors in the last switching unit, and the other end of the primary capacitor is connected to the negative terminals of multiple input ports and the output terminals of multiple first switching circuits. The secondary side of the high-frequency transformer circuit includes a secondary capacitor, a secondary winding, and a secondary inductor connected in series. One end of the secondary capacitor is connected between two switching transistors in the first voltage divider circuit, and the other end of the secondary inductor is connected between two switching transistors in the last voltage divider circuit.

[0010] Optionally, the input side of the multi-port converter includes two switching units, one of which has an input port for a new energy source and the other has an input port for an energy storage source. The output port of the voltage divider half-bridge circuit is a load port.

[0011] Optionally, the voltage divider half-bridge circuit includes two voltage divider circuits, and the second switching circuit includes two switching transistors. The two switching transistors in the second switching circuit are turned on alternately. When the four switching transistors in the two voltage divider circuits are turned on in sequence, the effective amplitude of the equivalent voltage on the secondary side of the high-frequency transformer circuit is 3 / 4 of the voltage at the load port.

[0012] Optionally, when the voltage of the new energy port is greater than or equal to the voltage of the energy storage port, the duty cycle of the two switching transistors in the first switching circuit corresponding to the energy storage port is 0.5. If the duty cycle of one of the switching transistors in the first switching circuit corresponding to the new energy port is D1, and the duty cycle of the other switching transistor in the first switching circuit corresponding to the new energy port is (1+D1), then the voltage of the new energy port is equal to 1 / 2 of the voltage of the energy storage port divided by D1.

[0013] Optionally, when the external shift ratio of the primary voltage to the secondary voltage of the high-frequency transformer circuit is greater than 0, the primary side of the high-frequency transformer circuit transmits power to the secondary side of the high-frequency transformer circuit; when the external shift ratio of the primary voltage to the secondary voltage of the high-frequency transformer circuit is less than 0, the secondary side of the high-frequency transformer circuit transmits power to the primary side of the high-frequency transformer circuit.

[0014] Optionally, the leakage inductance current of the secondary capacitor at ampere-second balance is: , Among them, I LS_Initial V1 is the leakage inductance current of the secondary capacitor at ampere-second equilibrium, V2 is the battery terminal voltage, V3 is the load terminal voltage, 1:N is the primary to secondary transformation ratio of the high-frequency transformer circuit, φ is the ratio of the primary voltage to the secondary voltage of the high-frequency transformer circuit when shifted outwards, and L is the voltage across the secondary side. s is the secondary inductance, and f is the operating frequency of the two switching transistors in the first switching circuit.

[0015] Optionally, the output power of the multi-port converter is: , Where P0 is the output power, T s For the duty cycle of the multiport converter, V s I is the secondary voltage of the high-frequency transformer circuit. LS This is the leakage inductance current of the secondary capacitor.

[0016] Compared to existing technologies, the advantages of this invention are as follows: The non-isolated power conversion module of the multi-port converter includes multiple switching units, which are connected sequentially via inductors. These multiple switching units can enable the access of multiple new energy power supply devices or energy storage devices, facilitating multi-port expansion. The non-isolated power conversion module and the isolated power conversion module of the multi-port converter are connected via a high-frequency transformer circuit. The high-frequency transformer circuit is used to equivalently realize the function of the inductor in the non-isolated power conversion module, thereby achieving electrical isolation and voltage conversion between ports. The switching unit includes an input port and a first switching circuit composed of at least two switching transistors connected in series. The input port is connected to both sides of the first switching circuit. By adjusting the duty cycle of the switching transistors in different first switching circuits, voltage decoupling between different input ports can be achieved, enabling the non-isolated port to operate stably under any input voltage relationship where the input voltage is higher, lower, or equal to the energy storage device voltage, thus possessing a wide input voltage range adaptability.

[0017] In summary, the multi-port converter provided by this invention can add similar ports to enable access to multiple new energy power generation devices or multiple energy storage devices without changing the main circuit structure and core working principle of the converter, thereby improving the scalability of the converter. At the same time, the input ports are not strictly constrained by the voltage magnitude relationship, and can work stably under large fluctuations in input voltage, thereby achieving effective adaptation to a wide input voltage range. Attached Figure Description

[0018] Figure 1 A schematic diagram of the structure of a multiport converter provided in one embodiment of this application is shown; Figure 2 A schematic diagram of a three-port converter provided in one embodiment of this application is shown; Figure 3 A schematic diagram of the operating mode of a three-port converter provided in one embodiment of this application is shown: Figure 4 The diagram shows a typical operating waveform of a three-port converter provided in one embodiment of this application when the voltage at the new energy port is greater than or equal to the voltage at the energy storage port. Figure 5 The diagram shows a typical operating waveform of a three-port converter provided in one embodiment of this application when the voltage at the new energy port is lower than that at the energy storage port. Figure 6 This paper shows a control system block diagram of a three-port converter according to an embodiment of the present application; Figure 7 The diagram shows the simulation results of mode switching for a three-port converter provided in one embodiment of this application. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] Please refer to Figure 1 This document illustrates a schematic diagram of a multiport converter according to an embodiment of this application. The non-isolated power conversion module and the isolated power conversion module of the multiport converter are connected via a high-frequency transformer circuit. The non-isolated power conversion module of the multiport converter includes multiple switching units, which are sequentially connected via inductors. Each switching unit includes an input port and a first switching circuit composed of at least two switching transistors connected in series. The input port is connected to both sides of the first switching circuit.

[0021] Among them, a non-isolated power conversion module is a power electronic conversion device that has no electrical isolation between its input and output. For example, see [link to example]. Figure 1 The non-isolated power conversion module includes n-1 switching units. Switching unit 1 includes an input port V1 and a junction consisting of at least two switching transistors S. 11 and S 12 The first switching circuit is composed of series connections; the switching unit 2 includes an input port V2 and at least two switching transistors S. 21 and S 22 The first switching circuit is composed of series connections, ..., the switching unit n-1 includes the input port V n-1 and consisting of at least two switching transistors S （n-1）1 and S （n-1）2 The first switching circuit is composed of series connections. Switching unit 1 and switching unit 2 are connected through inductor L1, switching unit 2 and switching unit 3 are connected through inductor L2, ..., switching unit n-2 and switching unit n-1 are connected through inductor L... （n-2） connect.

[0022] Among them, the isolated power conversion module is a power electronic device that achieves energy transfer between input and output through electrical isolation (usually using a high-frequency transformer). Its specific topology is not limited, and full-bridge, half-bridge or other equivalent isolated conversion structures can be selected according to application requirements.

[0023] The non-isolated power conversion module and the isolated power conversion module are connected through a high-frequency transformer circuit. Here, the high-frequency transformer circuit is equivalent to the inductors L1, L2, ... L mentioned earlier. （n-2）High-frequency transformers are core magnetic components in isolated switching power supplies and power conversion systems, used to achieve power transmission, voltage transformation, and electrical isolation at switching frequencies ranging from tens of kHz to several MHz. Compared to traditional power frequency (50 / 60 Hz) transformers, high-frequency transformers have significant advantages such as small size, light weight, and high efficiency, and are widely used in modern power electronic systems. A switching unit refers to the smallest functional circuit module with independent power processing capabilities. Its core consists of power semiconductor switching devices (such as MOSFETs, IGBTs, and SiC / GaN devices), used to realize the switching, regulation, direction control, or voltage transformation of electrical energy.

[0024] The input ports may include ports for new energy power supply equipment or ports for energy storage devices; no limitation is made here. The number of switching units is set according to the number of new energy power supply equipment and energy storage devices, and the number of switching transistors included in each first switching circuit is also not limited.

[0025] The input ports are connected to both sides of the first switching circuit, which consists of at least two switching transistors connected in series, thus forming a half-bridge arm. Multiple such switching units are connected sequentially via inductors to form multi-phase interleaved Buck, Buck-Boost, or cascaded multi-port DC-DC structures. If a multi-phase interleaved Buck array is formed, each phase consists of a half-bridge and an inductor, sharing an output bus, which can be used for high-current voltage reduction. If a cascaded multi-port Buck-Boost is formed, each port can be independently connected to a source or load, exchanging energy through a shared DC-link. If a cascaded multi-port DC-DC structure is formed, multiple inputs are selected by switches using different inductor taps to achieve voltage adaptation.

[0026] As can be seen from the embodiments of this application, the non-isolated power conversion module of the multi-port converter includes multiple switching units, which are connected sequentially through inductors. These multiple switching units can enable the access of multiple new energy power supply devices or energy storage devices, which is beneficial for multi-port expansion. The non-isolated power conversion module and the isolated power conversion module of the multi-port converter are connected through a high-frequency transformer circuit. The high-frequency transformer circuit is used to equivalently realize the function of the inductor in the non-isolated power conversion module, so as to achieve electrical isolation and voltage conversion between ports. The switching unit includes an input port and a first switching circuit composed of at least two switching transistors connected in series. The input port is connected to both sides of the first switching circuit. By adjusting the duty cycle of the switching transistors in different first switching circuits, voltage decoupling between different input ports can be achieved, enabling the non-isolated port to operate stably under any input voltage relationship where the input voltage is higher, lower, or equal to the energy storage device voltage, thereby having a wide input voltage range adaptability.

[0027] In summary, the multi-port converter provided by this invention can add similar ports to enable access to multiple new energy power generation devices or multiple energy storage devices without changing the main circuit structure and core working principle of the converter, thereby improving the scalability of the converter. At the same time, the input ports are not strictly constrained by the voltage magnitude relationship, and can work stably under large fluctuations in input voltage, thereby achieving effective adaptation to a wide input voltage range.

[0028] Please refer to Figure 2 The diagram shows a schematic of the structure of a three-port converter provided in one embodiment of this application.

[0029] In one embodiment provided in this application, the isolated power conversion module of the multi-port converter includes a voltage divider half-bridge circuit.

[0030] The voltage divider half-bridge circuit is a classic and efficient topology in the isolated power conversion module of multi-port converters. It is commonly used in medium-to-high power, wide input voltage range, or isolated DC-DC converters requiring symmetrical drive. Firstly, in the voltage divider half-bridge circuit, each switch only bears a portion of the turn-off voltage. Compared to a single-transistor Buck or Boost converter bearing the full bus voltage, lower voltage-rated and lower on-resistance devices can be selected, thus reducing device cost and conduction losses. Secondly, the output AC voltage of the voltage divider half-bridge circuit oscillates symmetrically around half the input voltage, avoiding DC bias in the transformer and preventing core saturation. This makes it particularly suitable for isolated topologies requiring bidirectional excitation, such as push-pull, full-bridge, and LLC converters.

[0031] In one embodiment provided in this application, the voltage divider half-bridge circuit includes at least two voltage divider circuits connected in series and an output port. The voltage divider circuit includes a voltage divider capacitor and a second switching circuit composed of at least two switching transistors connected in series. The voltage divider capacitor is connected to both sides of the second switching circuit. One side of the output port is connected to the input terminal of the first voltage divider circuit, and the other side of the output port is connected to the output terminal of the last voltage divider circuit.

[0032] like Figure 2 As shown, the voltage divider half-bridge circuit includes voltage divider circuit 1 and voltage divider circuit 2 connected in series, and an output port V3. Voltage divider circuit 1 includes a voltage divider capacitor C. s1 The second switching circuit 1 consists of two switching transistors connected in series, S1 and S2, and the voltage dividing capacitor C. s1 Connected to both sides of the second switching circuit 1; the voltage divider circuit 2 includes a voltage divider capacitor C. s2 The second switching circuit 2 consists of two switching transistors connected in series, S3 and S4, and the voltage dividing capacitor C. s2It is connected to both sides of the second switching circuit 2. One side of the output port V3 is connected to the input terminal of the voltage divider circuit 1, and the other side of the output port V3 is connected to the output terminal of the voltage divider circuit 2. The input terminal of the voltage divider circuit 1 consists of the switching transistor S1 and the voltage divider capacitor C. s1 At one end, the output of voltage divider circuit 2 is the switching transistor S4 and the voltage divider capacitor C. s2 The other end.

[0033] In one embodiment provided in this application, the primary side of the high-frequency transformer circuit includes a primary winding and a primary capacitor connected in series. One end of the primary winding is connected between two switching transistors in the last switching unit, and the other end of the primary capacitor is connected to the negative terminals of multiple input ports and the output terminals of multiple first switching circuits. The secondary side of the high-frequency transformer circuit includes a secondary capacitor, a secondary winding, and a secondary inductor connected in series. One end of the secondary capacitor is connected between two switching transistors in the first voltage divider circuit, and the other end of the secondary inductor is connected between two switching transistors in the last voltage divider circuit.

[0034] like Figure 2 As shown, the primary side of the high-frequency transformer circuit includes a primary winding connected in series and a primary capacitor C. p One end of the primary winding is connected to two switching transistors S in switching unit 2. 21 and S 22 Between, the other end of the primary winding and the primary capacitor C p One end is connected, and the primary capacitor C p The other end is connected to the negative terminals of input ports V1 and V2, as well as the output terminals of the first switching circuits 1 and 2; wherein, the output terminal S of the first switching circuit 1 12 At the other end, the output terminal S of the second switching circuit 2 22 The other end.

[0035] The secondary side of a high-frequency transformer circuit includes a secondary capacitor C connected in series. s Secondary winding and secondary inductor L s One end of the secondary capacitor is connected between the two switching transistors S1 and S2 in the voltage divider circuit 1, and the secondary capacitor C... s The other end is connected to one side of the secondary winding, and the other side of the secondary winding is connected to the secondary inductor L. s One side is connected, and the secondary inductor L s The other side is connected between the two switching transistors S3 and S4 in the voltage divider circuit 2.

[0036] In one embodiment provided in this application, the input side of the multi-port converter includes two switching units, one of which has an input port for a new energy source and the other has an input port for a battery. The output port of the voltage divider half-bridge circuit is a load port.

[0037] like Figure 2 As shown, the input port V1 of switch unit 1 is a new energy port, such as a photovoltaic port, a wind power port, a hydropower port, etc.; the input port V2 of switch unit 2 is an energy storage port, such as a battery port, etc., without specific limitations. At this time, Figure 2 The three-port converter (TPC) shown has three operating modes, enabling bidirectional power flow between the three ports: new energy source, energy storage, and load, to adapt to energy management needs under different operating conditions. Please refer to [the documentation / reference]. Figure 3 For example, in a photovoltaic (PV) power supply mode, where the new energy source is photovoltaic (PV) and the energy storage is a battery, the PV system supplies power to the load via a battery-to-load converter when sunlight intensity is high and PV energy is abundant. The PV system, through a TPC (Transmission Controlled Power Processor), supplies power to both the load and the battery, storing excess PV energy in the battery. In a PV-to-battery-to-load power supply mode, sunlight intensity is lower, and the PV energy is insufficient to independently support AC bus power supply. The PV system and the discharging battery then jointly supply power to the load through a converter. In a battery-to-load power supply mode, the PV output power is zero, and the battery supplies power to the load through the converter.

[0038] In one embodiment provided in this application, the voltage divider half-bridge circuit includes two voltage divider circuits, the second switching circuit includes two switching transistors, the two switching transistors in the second switching circuit are turned on alternately, and when the four switching transistors in the two voltage divider circuits are turned on in sequence, the effective amplitude of the equivalent voltage on the secondary side of the high-frequency transformer circuit is 3 / 4 of the voltage at the load port.

[0039] like Figure 2 As shown, the voltage divider half-bridge circuit includes voltage divider circuit 1 and voltage divider circuit 2. Voltage divider circuit 1 includes a second switching circuit 1, and voltage divider circuit 2 includes a second switching circuit 2. Second switching circuit 1 includes switching transistors S1 and S2, and second switching circuit 2 includes switching transistors S3 and S4. Switches S1 and S2 conduct alternately, and switching transistors S3 and S4 conduct alternately. When the four switching transistors S1, S2, S3, and S4 are conducted sequentially, the equivalent voltage V on the secondary side of the high-frequency transformer circuit... s The effective amplitude is the load port voltage V. s The 3 / 4 of the voltage divider capacitor allows the transformer secondary to operate under relatively low voltage conditions while achieving a higher output voltage, thus realizing high voltage gain. s1 With C s2 By evenly distributing the load voltage V3, the voltage stress on the power devices is effectively reduced.

[0040] In one embodiment provided in this application, when the voltage of the new energy port is greater than or equal to the voltage of the energy storage port, the duty cycle of the two switching transistors in the first switching circuit corresponding to the energy storage port is 0.5. If the duty cycle of one of the switching transistors in the first switching circuit corresponding to the new energy port is D1, and the duty cycle of the other switching transistor in the first switching circuit corresponding to the new energy port is (1+D1), then the voltage of the new energy port is equal to 1 / 2 of the voltage of the battery port divided by D1.

[0041] In one embodiment provided in this application, when the outward shift ratio of the primary voltage and the secondary voltage of the high-frequency transformer circuit is greater than 0, the primary side of the high-frequency transformer circuit transmits power to the secondary side of the high-frequency transformer circuit; when the outward shift ratio of the primary voltage and the secondary voltage of the high-frequency transformer circuit is less than 0, the secondary side of the high-frequency transformer circuit transmits power to the primary side of the high-frequency transformer circuit.

[0042] Please refer to Figure 4 The diagram illustrates a typical operating waveform of a three-port converter according to an embodiment of this application when the voltage at the new energy port is greater than or equal to the voltage at the energy storage port. In the diagram, Ts represents one high-frequency switching cycle, and Ts / 2 represents half a high-frequency switching cycle. Fixed switch S 21 and S 22 The duty cycle is 0.5. The switching transistor S is set... 11 The duty cycle is D1, and the switching transistor S 12 The duty cycle is (1+D1). The primary side voltage V P It is a two-level square wave, i.e., the switching transistor S 21 When the transistor is on, the voltage is 0.5V2, and the switching transistor S... 22 The voltage is -0.5V2 when on. This can be achieved by adjusting the voltage across the primary and secondary sides. P and V S The phase shift ratio φ can adjust the magnitude and direction of power transmission from the primary side to the secondary side. The phase shift ratio is the ratio of the phase shift angle to 180°. When φ > 0, power is transmitted from the primary side to the secondary side; when φ < 0, power is transmitted from the secondary side to the primary side.

[0043] The duty cycle of fixed switching transistors S1 and S4 is 0.5, and there is a fixed shift ratio of 0.5T between switching transistors S1 and S4. S Secondary side voltage V S Similarly, it is a two-level voltage square wave, that is, the voltage is V3 / 4 when the switching transistors S1 and S3 are turned on and the voltage is -V3 / 4 when the switching transistors S2 and S4 are turned on.

[0044] according to Figure 3We can obtain the voltage expression for inductor L1 during each time period of a complete operating cycle of the converter in steady state, and since inductor L1 always satisfies volt-second balance, we can conclude that: .

[0045] Therefore, by adjusting the duty cycle D1, the converter can operate in any situation where V1 and V2 are of arbitrary values, eliminating the voltage constraints of the new energy port and the energy storage port.

[0046] In one embodiment provided in this application, the leakage inductance current of the secondary capacitor at ampere-second balance is: , Among them, I LS_Initial V1 is the leakage inductance current of the secondary capacitor at ampere-second equilibrium, V2 is the energy storage port voltage, V3 is the load port voltage, 1:N is the primary to secondary transformation ratio of the high-frequency transformer circuit, φ is the ratio of the primary voltage to the secondary voltage of the high-frequency transformer circuit when shifted outwards, and L is the voltage across the secondary side. s is the secondary inductance, and f is the operating frequency of the two switching transistors in the first switching circuit.

[0047] according to Figure 3 This allows us to obtain the leakage inductance current i during each time period within a complete operating cycle of the converter in steady state. LS expression:

[0048] From capacitor C S The above I can be obtained from the ampere-second balance. LS_Initial The expression.

[0049] In one embodiment provided in this application, the output power of the multi-port converter is: , Where P0 is the output power, T s For the duty cycle of the multiport converter, V s I is the secondary voltage of the high-frequency transformer circuit. LS This is the leakage inductance current of the secondary capacitor.

[0050] Further analysis of the primary-side switching transistor S 11 -S 22 The soft-switching conditions for secondary-side switches S1-S4 are as follows:

[0051] Switch S 11 With S 12 The soft-switching condition is:

[0052] Switch S 21 With S 22 The soft-switching condition is:

[0053] When the energy storage port voltage V2 and the load port voltage V3 are fixed, the soft-switching range of the secondary-side switching transistors S1-S4 is related to the output power P. O Transformer turns ratio N and leakage inductance L S Related. Primary-side switch S 11 -S 12 The soft-switching range is related to the renewable energy power generation P1, the renewable energy port voltage V1, and the inductance L1. Switch S 21 -S 22 The soft-switching range is quite complex and is affected by both the primary and secondary currents.

[0054] Figure 5 The diagram illustrates a typical operating waveform of a three-port converter according to an embodiment of this application when the voltage at the new energy port is lower than that at the energy storage port. The analysis method under this mode is similar to... Figure 4 The situation where the voltage at the new energy port is greater than or equal to the voltage at the energy storage port is the same, and will not be repeated here.

[0055] Based on the above embodiments, a control system block diagram for the multi-port converter can be designed, such as... Figure 6 As shown. This includes two controllers: an input voltage regulator (IVR) and an output voltage regulator (OVR). When there is no energy output from the renewable energy port, the converter operates in energy storage supply mode to the load. In this case, the IVR does not play a control role; the OVR regulates and stabilizes the load voltage. When there is energy output from the renewable energy port, but it cannot meet the power demand of the load alone, i.e., P... PV <P o_ref The converter operates in a mode where renewable energy and energy storage supply power to the load. In this mode, the IVR adjusts the duty cycle D1 to achieve Maximum Power Point Tracking (MPPT) control for the renewable energy source, and the OVR adjusts the load voltage. When the energy output from the renewable energy source exceeds the power demand of the DC bus, the converter operates in a mode where renewable energy supplies power to both the energy storage and the load. In this mode, the IVR adjusts D1 to achieve MPPT control for the photovoltaic system, and the OVR adjusts φ to control the load voltage.

[0056] To verify the effectiveness of the proposed control strategy, Figure 7Simulation diagrams of the multi-port converter's mode switching are shown, with photovoltaic (PV) as the new energy source and a battery as the energy storage device. Figure (a) shows the switch from PV and battery supplying power to battery supplying power to the load. At 0.4 seconds, the PV power switches from 170W to 0W, and the battery power also switches from discharging 230W to discharging 400W. The load voltage remains stable at 400V, and the power required by the load is always 400W. Figure (b) shows the switch from PV supplying power to both battery and load to PV and battery supplying power to the load together. At 0.5 seconds, the load power switches from 100W to 500W. The waveform shows that the battery power switches from charging 70W to discharging 330W, and the load voltage remains stable at 400V. The PV always operates at MPPT (MPPT), i.e., discharging 170W. Therefore, this control strategy is effective.

Claims

1. A multi-port converter, characterized in that, The non-isolated power conversion module and the isolated power conversion module of the multi-port converter are connected through a high-frequency transformer circuit. The non-isolated power conversion module of the multi-port converter includes multiple switching units, which are connected in sequence through inductors. Each switching unit includes an input port and a first switching circuit composed of at least two switching transistors connected in series. The input port is connected to both sides of the first switching circuit.

2. A multiport converter according to claim 1, characterized in that, The isolated power conversion module of the multi-port converter includes a voltage divider half-bridge circuit.

3. A multiport converter according to claim 2, characterized in that, The voltage divider half-bridge circuit includes at least two voltage divider circuits connected in series and an output port. The voltage divider circuit includes a voltage divider capacitor and a second switching circuit composed of at least two switching transistors connected in series. The voltage divider capacitor is connected to both sides of the second switching circuit. One side of the output port is connected to the input terminal of the first voltage divider circuit, and the other side of the output port is connected to the output terminal of the last voltage divider circuit.

4. A multiport converter according to claim 3, characterized in that, The primary side of the high-frequency transformer circuit includes a primary winding and a primary capacitor connected in series. One end of the primary winding is connected between two switching transistors in the last switching unit, and the other end of the primary capacitor is connected to the negative terminals of multiple input ports and the output terminals of multiple first switching circuits. The secondary side of the high-frequency transformer circuit includes a secondary capacitor, a secondary winding, and a secondary inductor connected in series. One end of the secondary capacitor is connected between two switching transistors in the first voltage divider circuit, and the other end of the secondary inductor is connected between two switching transistors in the last voltage divider circuit.

5. A multiport converter according to claim 4, characterized in that, The input side of the multi-port converter includes two switching units, one of which has an input port for new energy and the other has an input port for energy storage. The output port of the voltage divider half-bridge circuit is the load port.

6. A multiport converter according to claim 5, characterized in that, The voltage divider half-bridge circuit includes two voltage divider circuits, and the second switching circuit includes two switching transistors. The two switching transistors in the second switching circuit are turned on alternately. When the four switching transistors in the two voltage divider circuits are turned on in sequence, the effective amplitude of the equivalent voltage on the secondary side of the high-frequency transformer circuit is 3 / 4 of the voltage at the load port.

7. A multiport converter according to claim 6, characterized in that, When the voltage of the new energy port is greater than or equal to the voltage of the energy storage port, the duty cycle of the two switching transistors in the first switching circuit corresponding to the energy storage port is 0.

5. If the duty cycle of one of the switching transistors in the first switching circuit corresponding to the new energy port is D1, and the duty cycle of the other switching transistor in the first switching circuit corresponding to the new energy port is (1+D1), then the voltage of the new energy port is equal to 1 / 2 of the voltage of the energy storage port divided by D1.

8. A multiport converter according to claim 7, characterized in that, When the ratio of the outward shift of the primary voltage to the secondary voltage of the high-frequency transformer circuit is greater than 0, the primary side of the high-frequency transformer circuit transmits power to the secondary side of the high-frequency transformer circuit; when the ratio of the outward shift of the primary voltage to the secondary voltage of the high-frequency transformer circuit is less than 0, the secondary side of the high-frequency transformer circuit transmits power to the primary side of the high-frequency transformer circuit.

9. A multiport converter according to claim 8, characterized in that, The leakage current of the secondary capacitor at ampere-second equilibrium is: ， Among them, I LS_Initial V1 is the leakage inductance current of the secondary capacitor at ampere-second equilibrium, V2 is the energy storage port voltage, V3 is the load port voltage, 1:N is the primary to secondary transformation ratio of the high-frequency transformer circuit, φ is the ratio of the primary voltage to the secondary voltage of the high-frequency transformer circuit when shifted outwards, and L is the voltage across the secondary side. s is the secondary inductance, and f is the operating frequency of the two switching transistors in the first switching circuit.

10. A multiport converter according to claim 9, characterized in that, The output power of the multi-port converter is: ， Where P0 is the output power, T s For the duty cycle of the multiport converter, V s I is the secondary voltage of the high-frequency transformer circuit. LS This is the leakage inductance current of the secondary capacitor.

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