Integrated three-port converter topology circuit suitable for space environment

Abstract

The integrated three-port converter topology circuit suitable for the space environment has the advantages of being low in device cost, high in conversion efficiency, high in topology integration level, good in space environment adaptability and the like. Wherein the cost of the device is low due to the fact that only three MOS tubes, two diodes and one inductor are needed; the conversion efficiency is high due to the fact that power transmission between any two ports is single-stage conversion; the topology integration level is high because the multiplexing degree of devices and branches is high; the space environment is well adapted due to the fact that forward Buck-Boost conversion is carried out between a photovoltaic cell port and a storage battery port and between the photovoltaic cell port and a load port, and the problem that the voltage of the photovoltaic cell port changes in a large range due to great changes of illumination intensity and environment temperature in the space environment can be solved.

Description

Technical Field

[0001] The invention belongs to the technical field of switching power supplies, and in particular relates to an integrated three-port converter topology circuit suitable for a space environment. Background Art

[0002] The three-port converter is one of the core components of the distributed photovoltaic power generation system and is crucial for power transmission and voltage conversion.

[0003] At present, three-port converters are mostly distributed structures, that is, they are composed of three independent two-port converters, and any two ports are two-stage conversions, with low conversion efficiency, low topological integration, and high device cost. Some researchers have proposed the concept of integrated three-port converters and given specific implementation plans, which have improved topological integration and power conversion efficiency and reduced device costs. However, in the space environment, where the light intensity and ambient temperature vary widely, the voltage at the photovoltaic cell port varies widely, and the existing integrated three-port converter topology cannot cope with it well. For example, it usually cannot take into account the requirements of low device cost and wide voltage regulation range.

[0004] Therefore, it is necessary to propose a three-port converter topology that has the advantages of low device cost, high conversion efficiency, high topological integration and good adaptability to the space environment. Summary of the invention

[0005] To this end, the present invention proposes an integrated three-port converter topology circuit suitable for the space environment, which takes into account the advantages of low device cost, high conversion efficiency, high topological integration and good adaptability to the space environment. Among them, the device cost is low because only 3 MOS tubes, 2 diodes and 1 inductor are needed; the conversion efficiency is high because the power transmission between any two ports is a single-stage conversion; the topological integration is high because the device and branch reuse degree is high; the space environment adaptability is good because the photovoltaic cell port and the battery port, and the photovoltaic cell port and the load port are all forward Buck-Boost conversion, which can solve the problem of large-scale changes in the photovoltaic cell port voltage caused by large changes in light intensity and ambient temperature in the space environment.

[0006] The present invention specifically includes the following contents: basic circuit design; modal division and modal circuit design; working mode division and combined circuit design; output voltage calculation method.

[0007] In the basic circuit design described above, the devices used are MOS tubes S1-S3, diodes D1-D2, filter inductor L, filter capacitors C1-C3, and the circuit diagram is shown in FIG. Figure 1As shown. The circuit contains three ports, namely the photovoltaic cell access port, the battery access port and the power load access port, and any two ports are single-stage conversion, so that the conversion efficiency is effectively guaranteed. MOS tubes S1~S3 and diodes D1~D2 are not always in working state. The specific working conditions are determined by the system working mode affected by light intensity, ambient temperature, battery charge state, and load power. Different working modes are participated by different MOS tubes and diodes.

[0008] In the above-mentioned modal division and modal circuit design, it is necessary to Figure 1 Based on the above, the modal circuit is divided into four modes: (1) Mode 1: The photovoltaic cell charges the inductor L. At this time, the MOS tube S1 is in the on state. Figure 2 (a) is the circuit corresponding to mode 1; (2) Mode 2: the inductor L discharges the load, and the MOS tube S2 and the diode D2 are in the on state. Figure 2 (b) is the circuit corresponding to mode 2; (3) Mode 3: the inductor L charges the battery, and the diodes D1~D2 are in the on state. Figure 2 (c) is the circuit corresponding to mode 3; (4) Mode 4: the battery charges the inductor L and supplies power to the load. At this time, MOS tubes S2~S3 are in the on state. Figure 2 (d) is the circuit corresponding to mode 4.

[0009] In the above-mentioned division of working modes and design of combination circuits, the working modes are mainly divided according to the power balance relationship between the three ports, and then different combination circuits are designed according to different working modes. The working modes are specifically divided into: (1) Dual-input mode (DI mode): The maximum output power of the photovoltaic cell is greater than the power required by the load, and the battery state of charge (SOC) is less than 100%. At this time, the photovoltaic cell supplies power to the load and also charges the battery. In the same switching cycle, it sequentially experiences mode 1, mode 3 and mode 2, and the combination circuit in this sequence is the working circuit of the DI mode. (2) Dual-output mode (DO mode): The maximum output power of the photovoltaic cell is less than the power required by the load. At this time, the photovoltaic cell and the battery jointly supply power to the load. In the same switching cycle, it sequentially experiences mode 1, mode 4 and mode 2, and the combination circuit in this sequence is the working circuit of the DO mode. (3) PV-Only mode: The maximum output power of the photovoltaic cell is greater than or equal to the power required by the load, and the battery SOC is equal to 100%. At this time, only the photovoltaic cell supplies power to the load. In the same switching cycle, mode 1 and mode 2 are experienced in sequence, and the combination circuit in this sequence is the working circuit of the PV-Only mode. (4) Single-input single-output mode (SISO mode): The photovoltaic cell cannot output power, but the load demand power is not zero. At this time, the load is only powered by the battery. In the same switching cycle, mode 4 and mode 2 are experienced in sequence, and the combination circuit in this sequence is the working circuit of the SISO mode. (5) PV-Battery mode: The load demand power is zero, and the battery SOC is less than 100%. At this time, the photovoltaic cell only charges the battery. In a switching cycle, mode 1 and mode 3 are experienced in sequence, and the combination circuit in this sequence is the working circuit of the PV-Battery mode.

[0010] In the output voltage calculation method described above, the volt-second balance principle needs to be applied, that is, in the same switching cycle, the charging energy and the discharging energy on the inductor L are equal. The calculation formula for the output voltage is determined according to different working modes. The calculation method diagram is shown in the figure below: Figure 3 As shown in the figure, u pv 、u b 、u o They are the photovoltaic cell port voltage, battery port voltage and load port voltage respectively; d1, d2, d3 are the duty cycles of MOS tubes S1, S2, S3 respectively.

[0011] The innovation of the present invention is:

[0012] The energy transmission process inside the three-port converter is divided into four modes according to the energy flow mode of each port. Modal circuits are designed for different modes, the working state of the semiconductor tube and the charging and discharging state of the inductor are determined, and the disassembly of the basic circuit is realized.

[0013] According to the power balance relationship among the photovoltaic cell port, the battery port and the load port, the three-port converter is divided into five working modes, and the mode types, quantities and sequences under different working modes are determined. According to the principle of the same switching cycle, the modal circuits are combined, and the working circuits under different working modes are designed to ensure that single-stage conversion is achieved between any two ports among the photovoltaic cell port, the battery port and the load port, thus achieving the high conversion efficiency of the proposed three-port converter.

[0014] The volt-second balance principle was applied, and the energy balance equation on the inductor L in the same switching cycle under five working modes was listed. The expression of the output voltage under different working modes was calculated, indicating that both the photovoltaic cell port and the battery port, and the photovoltaic cell port and the load port are forward Buck-Boost conversions, ensuring the adaptability to the space environment with a large range of light intensity and ambient temperature changes.

[0015] The beneficial effects of the present invention are

[0016] The present invention only needs 3 MOS tubes and 2 diodes. The power conversion between any two ports of the photovoltaic cell port, the battery port and the load port is single-stage conversion. Moreover, the power conversion between the photovoltaic cell port and the battery port, and between the photovoltaic cell port and the load port are all forward Buck-Boost conversions. The present invention has good adaptability to a wide range of photovoltaic cell port voltage changes, and well takes into account the advantages of low device cost, high topological integration, high conversion efficiency, and good adaptability to the space environment. It can meet the use requirements of photovoltaic power generation systems of aerospace equipment such as satellites. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the basic circuit diagram of a three-port converter.

[0018] Figure 2 The circuit diagrams corresponding to different modes.

[0019] Figure 3 Schematic diagram of the output voltage calculation method under different working modes. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The present invention is an integrated three-port converter topology circuit suitable for a space environment, and the specific implementation method includes:

[0022] according to Figure 1 Based on the basic circuit shown, design the schematic diagram of the proposed three-port converter and determine the types and quantities of components.

[0023] according to Figure 2 The modal circuit shown is Figure 1 The basic circuit in the circuit is divided into modes to confirm the direction of energy flow, the working status of MOS tubes S1~S3 and diodes D1~D2 in each mode, and the charging and discharging status of inductor L.

[0024] Taking into account the changes in light intensity, ambient temperature, battery charge state and load power, the actual working state of the proposed three-port converter is divided into five modes according to the power balance relationship between the photovoltaic cell port, the battery port and the load port:

[0025] (1) When the maximum output power of the photovoltaic cell is greater than the load demand power and the battery state of charge (SOC) is less than 100%, it is defined as dual input mode (DI mode).

[0026] (2) When the maximum output power of the photovoltaic cell is less than the load demand power, it is defined as dual input and output mode (DO mode).

[0027] (3) When the maximum output power of the photovoltaic cell is greater than or equal to the load demand power and the battery SOC is equal to 100%, it is defined as PV-Only mode.

[0028] (4) When the photovoltaic cell cannot output power, but the load demand power is not zero, it is defined as single-input single-output mode (SISO mode).

[0029] (5) When the load demand power is zero and the battery SOC is less than 100%, it is defined as PV-Battery mode.

[0030] According to the defined working mode, Figure 2 Based on this, the types, quantities and sequences of modes under different working modes are determined, and the working circuits under different working modes are obtained by combination. The specific operations are as follows:

[0031] (1) The same switching cycle goes through mode 1, mode 3 and mode 2 in sequence. The combination circuit in this order is the working circuit in DI mode.

[0032] (2) The same switching cycle goes through mode 1, mode 4 and mode 2 in sequence. The combination circuit in this order is the working circuit of DO mode.

[0033] (3) The same switching cycle goes through mode 1 and mode 2 in sequence. The combined circuit in this order is the working circuit of the PV-Only mode.

[0034] (4) The same switching cycle goes through mode 4 and mode 2 in sequence. The combination circuit in this order is the working circuit of the SISO mode.

[0035] (5) The same switching cycle goes through mode 1 and mode 3 in sequence. The combined circuit in this order is the working circuit of the PV-Battery mode.

[0036] Using the principle that the charging energy and discharging energy on the inductor L are equal in the same switching cycle, according to Figure 3 Write the volt-second balance equation under different working modes, and calculate the output voltage calculation formula under different working modes. pv 、u b 、u o They are the photovoltaic cell port voltage, battery port voltage and load port voltage respectively; d1, d2, d3 are the duty cycles of MOS tubes S1, S2, S3 respectively.

[0037] The present invention is not limited to the above specific implementations, and the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made to the above implementations based on the technical essence of the present invention shall be included in the protection scope of the present invention.

Claims

1. An integrated three-port converter topology circuit suitable for space environment, characterized in that: It includes MOS tubes S1-S3, diodes D1-D2, filter inductors L, and filter capacitors C1-C3; the circuit includes three ports, namely, a photovoltaic cell access port, a battery access port, and an electrical load access port, and any two ports are single-stage conversions; The circuit is specifically divided into 4 modes: Mode 1: The photovoltaic cell charges the inductor L, and the MOS tube S1 is in the on state; Mode 2: The inductor L discharges the load, and the MOS tube S2 and the diode D2 are in the on state; Mode 3: Inductor L charges the battery, and diodes D1-D2 are in the on state. Mode 4: The battery charges the inductor L and supplies power to the load. At this time, MOS tubes S2-S3 are in the on state.

2. The integrated three-port converter topology circuit suitable for space environment according to claim 1, characterized in that: The working modes are specifically divided into: (1) Dual-input mode: The maximum output power of the photovoltaic cell is greater than the power required by the load, and the battery state of charge is less than 100%. At this time, the photovoltaic cell supplies power to the load and charges the battery at the same time. In the same switching cycle, it experiences mode 1, mode 3 and mode 2 in sequence; (2) Dual output mode: The maximum output power of the photovoltaic cell is less than the power required by the load. At this time, the photovoltaic cell and the battery jointly supply power to the load. In the same switching cycle, they experience mode 1, mode 4 and mode 2 in sequence. (3) PV-Only mode: The maximum output power of the photovoltaic cell is greater than or equal to the load demand power, and the battery SOC is equal to 100%. At this time, the photovoltaic cell alone supplies power to the load. In the same switching cycle, it goes through mode 1 and mode 2 in turn; (4) Single-input single-output mode: The photovoltaic cell cannot output power, but the load power demand is not zero. At this time, the load is powered only by the battery. In the same switching cycle, it experiences mode 4 and mode 2 in sequence. (5) PV-Battery mode: The load demand power is zero and the battery SOC is less than 100%. At this time, the photovoltaic cell only charges the battery. In one switching cycle, it goes through mode 1 and mode 3 in sequence.

3. The integrated three-port converter topology circuit suitable for space environment according to claim 2, characterized in that: In the output voltage calculation, it is necessary to apply the volt-second balance principle, that is, in the same switching cycle, the charging energy and the discharging energy on the inductor L are equal.

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