Partial power converter and control method thereof

Abstract

This invention discloses a partial power converter and its control method, relating to the field of power electronics technology. Based on a three-port isolated converter, the first port is connected to DC power as the input port, the second port is connected in forward series with the first port, and the third port is connected in reverse series with the first port, forming the entire output port. Based on this connection method, the total output voltage of the output port is the difference between the sum of the first and second port voltages and the third port voltage. Therefore, in buck mode, the voltage at the second port can be controlled to equal a preset reference voltage, and the voltage at the third port can vary according to the output voltage of the output port. In boost mode, the voltage at the third port can be controlled to equal a preset reference voltage, and the voltage at the second port can vary according to the output voltage of the output port. This invention achieves dual-mode operation (boost and buck) by changing the connection method of the output ports, improving the converter's operating conditions when the input and output voltages are close.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a partial power converter and its control method. Background Technology

[0002] In recent years, the rapid development of DC distribution networks, photovoltaics, energy storage, and new energy vehicles has driven an urgent demand for high-efficiency, high-power DC-DC converters. To address this, Partial Power Processing (PPP) technology has emerged. By allowing most of the power to be transferred directly from the source to the load, the converter only processes the remaining small portion of the power, thereby improving efficiency and power density while reducing losses and costs.

[0003] In existing technologies, series-type partial power converters such as phase-shifted full-bridge and MAB (Multi-Active Bridge) partial power converters improve efficiency by adding additional power flow paths through changes in connection methods. Typically, one port of a two-port DC-DC converter is connected to a DC source as the input port, and the other port is connected in forward series with the input port to form the overall output port. However, achieving boost / buck conversion requires the use of bipolar switches. Some literature also suggests adding an H-bridge after the output port of a MAB-type partial power converter to form a two-stage partial power converter to achieve boost / buck conversion, thereby expanding the overall voltage regulation range.

[0004] In existing partial power conversion schemes, the output voltage of the internal converter approaches zero as the input and output voltages become increasingly similar. This often necessitates the partial power converter to operate at extremely low duty cycles or very small phase shift angles. This not only leads to extremely high control precision requirements and makes the switching devices susceptible to parasitic parameters, but also limits power transfer capability and degrades dynamic response. Furthermore, with the existing connection methods for partial power converters, using unipolar switches and without an H-bridge, the partial power converter can only achieve either boost or buck voltage, significantly narrowing its voltage regulation range. Summary of the Invention

[0005] Therefore, it is necessary to provide a partial power converter and its control method to address the aforementioned technical problems.

[0006] The present invention adopts the following technical solution: This invention provides a partial power converter, comprising: a three-port isolated DC-DC converter; the three-port isolated DC-DC converter includes: a first port, a second port, and a third port; wherein, the first port is connected to DC power as an input port; the second port is connected in forward series with the first port, and the third port is connected in reverse series with the first port; the first port, the second port, and the third port together serve as an output port; when operating in buck mode, the port voltage of the second port is controlled to be equal to a preset reference voltage, and the port voltage of the third port changes according to the output voltage of the output port; when operating in boost mode, the port voltage of the third port is controlled to be equal to the preset reference voltage, and the port voltage of the second port changes according to the output voltage of the output port.

[0007] This invention provides a control method for a partial power converter. First, the output voltage reference value of the output port of the partial power converter is obtained. Then, the operating mode of the partial power converter is determined based on the output voltage reference value and the port voltage of the first port in the partial power converter. Then, if the partial power converter is in buck mode, the port voltage reference value of the second port in the partial power converter is set to the preset reference voltage; the port voltage sample value of the second port in the partial power converter and the output voltage sample value of the output port are obtained at the current moment; based on the error between the output voltage reference value and the output voltage sample value, the error between the preset reference voltage and the port voltage sample value of the second port, a shift ratio is obtained after PI regulation to control the partial power converter; If the partial power converter is in boost mode, the port voltage reference value of the third port in the partial power converter is set to the preset reference voltage; the port voltage sample value of the third port in the partial power converter and the output voltage sample value of the output port are obtained at the current moment; based on the error between the output voltage reference value and the output voltage sample value, and the error between the preset reference voltage and the port voltage sample value of the third port, a shift ratio is obtained after PI regulation to control the partial power converter. Finally, phase-shift modulation is performed based on the phase shift ratio to obtain the control signals for each switch in the partial power converter, so as to control the partial power converter to perform power conversion.

[0008] The above-mentioned at least one technical solution adopted in this invention can achieve the following beneficial effects: This invention is based on a three-port isolated converter. The first port is connected to DC power as the input port, the second port is connected in series with the first port in the forward direction, and the third port is connected in series with the first port in the reverse direction. All three ports together form the output port. Based on this connection method, the total output voltage is the difference between the sum of the first and second port voltages and the third port voltage. Therefore, in buck mode, the voltage at the second port can be controlled to equal a preset reference voltage, and the voltage at the third port can vary according to the output voltage of the output port. In boost mode, the voltage at the third port can be controlled to equal a preset reference voltage, and the voltage at the second port can vary according to the output voltage of the output port. This invention achieves dual-mode operation (boost and buck) by changing the connection method of the output ports, effectively expanding the voltage regulation range of some power converters. When the input and output voltages are close, this invention can control the voltages at the second and third ports to be close, avoiding operation in extremely low duty cycles or extremely small phase shift regions. Attached Figure Description

[0009] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0010] Figure 1 A schematic diagram of a partial power converter circuit topology and connection method provided by the present invention; Figure 2 This invention provides a schematic diagram of the operating waveform of a partial power converter. Figure 3 An equivalent circuit diagram provided by the present invention; Figure 4 A schematic diagram illustrating the relationship between port voltage and input / output voltage provided by the present invention; Figure 5 A simplified schematic diagram of a partial power converter connection method provided by the present invention. Figure 1 ; Figure 6 A simplified schematic diagram of a partial power converter connection method provided by the present invention. Figure 2 ; Figure 7 A simplified schematic diagram of a partial power converter connection method provided by the present invention. Figure 3 ; Figure 8 This is a schematic flowchart of a control method for a partial power converter provided by the present invention; Figure 9 This is a schematic control block diagram of a partial power converter provided by the present invention. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0012] Currently, existing partial power conversion schemes transfer more energy and achieve higher efficiency when the input and output voltages are closer together. However, due to the inherent characteristics of these partial power converters, they often need to operate at extremely low duty cycles or very small phase shift angles. This not only leads to extremely high control precision requirements and makes the switching devices susceptible to parasitic parameters, but also limits power transfer capability and degrades dynamic response. Furthermore, it is impossible for practical switching devices to operate at extremely low duty cycles or very small phase shift angles continuously. This creates a small transition region when the input and output voltages are close, within which the partial power converter cannot be precisely controlled.

[0013] Meanwhile, transformers designed for minute voltage regulation must balance high frequency, large winding turns ratio, and high coupling accuracy, posing significant challenges to the design and manufacturing processes of magnetic component parameters and winding turns. Furthermore, with the existing connection methods of some power converters, using unipolar switches and without an H-bridge, the converter can only achieve either step-up or step-down, greatly reducing the voltage regulation range of some power converters.

[0014] This invention proposes a partial power converter and its control strategy. By changing the connection method of the output port, it achieves dual-mode operation of boost and buck converters, effectively expanding the voltage regulation range of the partial power converter. Simultaneously, an optimized control strategy is proposed to improve the converter's operating conditions when the input and output voltages are close, avoiding its operation in extremely low duty cycles or extremely small phase shift angle regions. This significantly alleviates the design pressure on the transformer and improves the stability and reliability of the system operation.

[0015] The technical solutions provided by the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0016] Figure 1 This is a schematic diagram of a partial power converter circuit topology and connection method according to the present invention. Figure 1 As can be seen, this power converter includes a three-port isolated DC-DC converter; the three-port isolated DC-DC converter includes: a first port, a second port, and a third port. Figure 1 The left port is designated as the first port, and the right ports, from top to bottom, are designated as the second and third ports.

[0017] The first port is connected to DC power as an input port; the second port is connected in series with the first port in the forward direction; the third port is connected in series with the first port in the reverse direction; and the first port, the second port, and the third port together serve as an output port.

[0018] When operating in buck mode, the voltage at the second port is equal to the preset reference voltage, and the voltage at the third port changes according to the output voltage at the output port. When operating in boost mode, the voltage at the third port is equal to the preset reference voltage, and the voltage at the second port changes according to the output voltage at the output port.

[0019] for Figure 1 In the topology shown, the main circuit includes a supporting capacitor at port 1. C 1. Port 2 supporting capacitor C 2. Port 3 supports capacitor C 3 (Each supporting capacitor is connected in parallel on the corresponding port to stabilize the port voltage), power transfer inductor L 1. L 2. L 3. High-frequency transformer T (The ratio is 1:) n 2: n 3) Switching transistors S1~S 12 And its anti-parallel diode. Among them, port 1 is the input port, port 2 is connected in series with port 1 in the forward direction, port 3 is connected in series with port 1 in the reverse direction, and the three ports together serve as the output port. Load Indicates load, V out Indicates the output voltage. I out Indicates the output current. V 1. V 2. V 3 represents the port voltages of ports 1, 2, and 3, respectively. V H1 , V H2 , V H3 These represent the bridge port voltages at ports 1, 2, and 3, respectively. High-frequency transformer. T Multiple power transfer inductors are used for power transfer, and the output voltage of the output port is obtained by adjusting the shift ratio based on the output voltage of the input port.

[0020] Some power converters use a single-phase-shift control method. Figure 2 This is a schematic diagram of the operating waveforms of a partial power converter according to the present invention. φ 12 , φ 13 , φ 23 These represent the phase shift angles of ports 1 and 2, ports 1 and 3, and ports 2 and 3, respectively. To simplify calculations, all parameters are referred to the primary side, and the corresponding partial power converter Y-Δ equivalent circuit is shown below. Figure 3 As shown, Figure 3 This is a schematic diagram of an equivalent circuit in this invention. Figure 3 The diagram on the left shows the equivalent Y-type circuit. Figure 3 The diagram on the right side shows the Δ-type equivalent circuit. Figure 3 middle for L The value is calculated to the primary side after 2-fold conversion. for L The value calculated from the first side is 3 times. For the current flowing through the inductor L The current value of 2 converted to the primary side, For the current flowing through the inductor L The current of 3 is converted to the value on the primary side. For inductance L The voltage on 2 is referred to the primary side. For inductance L The voltage on point 3 is referred to the primary side. The equivalent inductance is... L 12 , L 13 , L 23 It can be represented as:

[0021] .

[0022] Depend on Figure 3 As shown in the diagram on the right, there is only one equivalent inductance between any two square wave voltage sources. Therefore, the transmission power is calculated in the same way as that of the DAB converter, and thus the transmission power can be expressed as: .

[0023] in, Compared to the shift between port 1 and port 2, Compared to the shift between port 1 and port 3, Compared to the shift between port 2 and port 3, The transmission power between port 1 and port 2, The transmission power between port 1 and port 3, For the transmission power between port 2 and port 3, D xy = φ xy / π , ( x =1,2,3y =1,2,3), D 23 = D 13 - D 12 , f s This represents the switching frequency.

[0024] The transmission power of each port can be obtained by adding or subtracting the transmission power between the ports. Based on the series structure of the circuit, the power flowing through part of the power converter P F With system output power P out The ratio is ( V 2+ V 3) and V out The ratio, specifically expressed as: .

[0025] Assuming the efficiency of the partial power converter is η Overall system efficiency η sys It can be approximated as follows: .in, P in This refers to the input power.

[0026] To improve the operation of some power converters when the input and output voltages are close, avoid their operation in the region of minimum phase shift angle, and alleviate the design pressure on the transformer, the following measures are proposed: Figure 4 The port voltage control method shown is as follows: Figure 4 This is a schematic diagram illustrating the relationship between port voltage and input / output voltage in this invention. Partial power transformer turns ratio 1: n 2: n 3 designed as 1: V base / V 1: V base / V 1, V base This indicates the reference voltage, and its design should be determined based on the rated voltage level.

[0027] when V out < V 1. That is, when part of the power converter operates in buck mode, the control... V 2= V base , V 3 According toV out It changes with the change, and its value should satisfy the following: V out = V 1+ V 2- V 3, that is V 3= V 1+ V base - V out .

[0028] when V out ≥ V 1. That is, when part of the power converter operates in boost mode, the control... V 3= V base , V 2 According to V out It changes with the change, and its value should satisfy the following: V out = V 1+ V 2- V 3, that is V 2= V base + V out - V 1.

[0029] This port voltage control strategy can meet the partial power output conditions while avoiding an excessively large input-output voltage ratio of the partial power converter. Furthermore, regardless of the operating mode, it ensures that one of the output ports (port 2 or port 3) of the partial power converter operates in DCX mode, thereby improving the efficiency of the partial power converter itself and thus improving the overall system efficiency.

[0030] Furthermore, in one or more embodiments of the present invention, the three-port isolated DC / DC converter includes not only the original three-port isolated DC / DC converter, but also any isolated DC / DC converter that can be configured into three ports, such as a three-port isolated converter formed by series / parallel connection of two-port isolated converters, such as... Figure 5 , Figure 6 , Figure 7 As shown. Figure 5 This is a simplified illustration of a partial power converter connection method in this invention. Figure 1 (Three-port isolated converter) Figure 6 This is a simplified illustration of a partial power converter connection method in this invention. Figure 2 (Two-port isolated converters in parallel) Figure 7This is a simplified illustration of a partial power converter connection method in this invention. Figure 3 (Two-port isolated converter in series).

[0031] This invention is based on a three-port isolated converter. The first port is connected to DC power as the input port, the second port is connected in forward series with the first port, and the third port is connected in reverse series with the first port. All three ports together form the output port. Based on this connection method, the total output voltage is the difference between the sum of the first and second port voltages and the third port voltage. Therefore, in buck mode, the voltage at the second port can be controlled to equal a preset reference voltage, and the voltage at the third port can vary according to the output voltage of the output port. In boost mode, the voltage at the third port can be controlled to equal a preset reference voltage, and the voltage at the second port can vary according to the output voltage of the output port. This invention achieves dual-mode operation (boost and buck) by changing the connection method of the output ports, effectively expanding the voltage regulation range of some power converters, improving the operating conditions of the converter when the input and output voltages are close, and avoiding operation in extremely low duty cycles or extremely small phase shift regions.

[0032] This invention employs a three-port isolated converter, connecting the second port in forward series with the first port (which serves as the input port), and the third port in reverse series with the first port. It proposes a unique converter port voltage control strategy, effectively solving the challenges of transformer design difficulties and high control precision requirements caused by the converter operating at extremely small duty cycles or phase-shifted duty cycles when the input and output voltages of partial power converters are close. Furthermore, the proposed converter also boasts advantages such as a wide voltage regulation range, high efficiency, and high power density. In summary, this invention provides a more practical partial power conversion scheme, successfully overcoming the limitations of existing technologies.

[0033] Figure 8 This is a schematic flowchart of a control method for a partial power converter according to the present invention, which specifically includes the following steps: S101: Obtain the reference value of the output voltage at the output port of the partial power converter. V out_ref The operating mode of the partial power converter is determined based on the output voltage reference value and the port voltage of the first port in the partial power converter.

[0034] S102: If the partial power converter is in buck mode, then the port voltage reference value of the second port in the partial power converter is set to the preset reference voltage. V base Obtain the current port voltage sample value of the second port in the partial power converter. V 2. and the output voltage sampling value of the output port V out According to the output voltage reference valueV out_ref and output voltage sampling value V out Error between, preset reference voltage V base Port voltage sample value of the second port V The error between 2 is adjusted by PI to obtain the shift ratio used to control part of the power converter.

[0035] S103: If the partial power converter is in boost mode, then set the port voltage reference value of the third port in the partial power converter to the preset reference voltage. V base Obtain the current port voltage sample value of the third port in the partial power converter. V 3. and the output voltage sampling value of the output port V out According to the output voltage reference value V out_ref and output voltage sampling value V out Error between, preset reference voltage V base and the port voltage sample value of the third port V The error between 3 and 4 is adjusted by PI to obtain the shift ratio used to control part of the power converter.

[0036] S104: Perform phase-shift modulation based on the phase shift ratio to obtain the control signals of each switch in the partial power converter, so as to control the partial power converter to perform power conversion.

[0037] When applying the control method for a partial power converter provided by this invention, it is not necessary to... Figure 8 The steps shown are executed in sequence. The specific execution order of each step can be determined as needed, and this invention does not impose any restrictions on it.

[0038] Figure 9 For the present invention corresponding to Figure 8 A schematic diagram of the control block of a partial power converter. Figure 9 In boost mode, the left-side modules input the value corresponding to port "1". In buck mode, the left-side modules input the value corresponding to port "2". The difference between each pair is then adjusted via a PI controller to obtain the shift ratio between port 1 and port 2. D 12 And the shift ratio between port 1 and port 3 D 13 Finally, after phase-shift modulation, the control signals S1~S2 of each switch in the partial power converter are obtained. 12 .

[0039] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the methods described above. Any references to memory, storage, databases, or other media used in the embodiments provided by this invention can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, or optical storage, etc. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0040] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this invention.

Claims

1. A partial power converter, characterized in that, include: Three-port isolated DC-DC converter; The three-port isolated DC-DC converter includes: a first port, a second port, and a third port; The first port is connected to DC power as an input port; The second port is connected in forward series with the first port, and the third port is connected in reverse series with the first port. The first port, the second port, and the third port together serve as an output port. When operating in buck mode, the port voltage of the second port is controlled to be equal to the preset reference voltage, and the port voltage of the third port is made to change according to the output voltage of the output port. When operating in boost mode, the port voltage of the third port is controlled to be equal to the preset reference voltage, and the port voltage of the second port is made to change according to the output voltage of the output port.

2. The partial power converter as described in claim 1, characterized in that, The winding ratio of the first port, the second port, and the third port is 1: V base / V 1: V base / V 1; in, V base For the preset reference voltage, V 1 represents the port voltage of the first port.

3. The partial power converter as described in claim 1, characterized in that, The three-port isolated DC-DC converter includes any one of the following: a three-port isolated DC-DC converter, or a three-port isolated DC-DC converter obtained by connecting two-port isolated converters in series or in parallel.

4. The partial power converter as described in claim 1, characterized in that, The first port, the second port, and the third port are all connected in parallel with supporting capacitors; Each of the aforementioned supporting capacitors is used to stabilize the port voltage of the corresponding port.

5. The partial power converter as described in claim 1, characterized in that, The three-port isolated DC-DC converter also includes: a high-frequency transformer and multiple power transfer inductors; The high-frequency transformer and the plurality of power transmission inductors are used for power transmission, and the output voltage of the output port is obtained by adjusting the input voltage of the input port based on the shift ratio.

6. A control method for a partial power converter as described in any one of claims 1 to 5, characterized in that, include: Obtain the output voltage reference value of the output port of the partial power converter, and determine the operating mode of the partial power converter based on the output voltage reference value and the input voltage of the partial power converter; If a portion of the power converter is in buck mode, the port voltage reference value of the second port in the portion of the power converter is set to a preset reference voltage; the current port voltage sample value of the second port in the portion of the power converter and the output voltage sample value of the output port are obtained. Based on the error between the output voltage reference value and the output voltage sample value, the error between the preset reference voltage and the port voltage sample value of the second port, a shift ratio is obtained after PI regulation to control part of the power converter. If a portion of the power converter is in boost mode, the port voltage reference value of the third port in the portion of the power converter is set to the preset reference voltage. Obtain the current port voltage sample value of the third port and the output voltage sample value of the output port in the partial power converter; Based on the error between the output voltage reference value and the output voltage sample value, and the error between the preset reference voltage and the port voltage sample value of the third port, a shift ratio is obtained after PI regulation to control part of the power converter. Phase-shift modulation is performed based on the phase shift ratio to obtain the control signals for each switch in the partial power converter, so as to control the partial power converter to perform power conversion.

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