Power conversion device with multiple working modes

Abstract

The utility model discloses a power supply conversion device with multiple working modes. The power supply conversion device comprises a control unit, and an input filtering unit, an AC / DC conversion unit, a Buck / Boost conversion unit and an LLC isolation conversion unit which are connected in sequence. The input filtering unit is connected with an AC source or an equivalent load. The LLC isolation conversion unit is connected with a DC source or an equivalent load. The input filtering unit, the AC / DC conversion unit, the Buck / Boost conversion unit and the LLC isolation conversion unit are all circuits with a bidirectional conversion function; and the control unit judges a working mode according to the voltage and current signals of each unit acquired by the signal sampling circuit, or a command input by the keyboard unit, or a command obtained by external communication, and switches the power conversion device into a corresponding working mode. The utility model has the advantages of high integration level, small occupied space, high cost performance and the like.

Description

Technical Field

[0001] The utility model relates to a switching power supply, and particularly to a power conversion device with multiple working modes. Background Art

[0002] In the field of microgrids, such as in local areas of small power grids (such as islands), mobile means of transportation (such as ships, cars, airplanes), etc., because complex equipment or control systems need to be powered, it is usually necessary to be equipped with a battery backup power supply system or an energy storage system to ensure that when there is no power grid or the generator cannot generate power by itself, the battery system can still provide uninterrupted power supply. Therefore, it is usually necessary to configure a charger (or rectifier), a grid-connected inverter (grid-connected mode), and an off-grid inverter (off-grid mode). At the same time, for safety and reliability, the system also needs to be equipped with a battery detector to regularly detect and maintain the battery system, or quickly repair and troubleshoot problems when problems occur in the battery system. The system composed of multiple independent devices that meet the above requirements occupies a large space, is relatively complex to operate, and has poor economic practicality. Summary of the Utility Model

[0003] Purpose of the Utility Model: The purpose of the utility model is to provide a power conversion device with multiple working modes for the problems of complex system, large volume, and low cost performance existing in the existing bidirectional AC-DC conversion device.

[0004] Technical Solution: The power conversion device with multiple working modes described in the utility model includes a control unit, and an input filter unit, an AC / DC conversion unit, a Buck / Boost conversion unit, and an LLC isolation conversion unit connected in sequence; the input filter unit is connected to an AC source or an equivalent load, and the LLC isolation conversion unit is connected to a DC source or an equivalent load; the input filter unit, the AC / DC conversion unit, the Buck / Boost conversion unit, and the LLC isolation conversion unit are all circuits with bidirectional conversion functions.

[0005] The control unit includes an arithmetic processing unit, a signal sampling circuit, a communication unit, an auxiliary power supply, a keyboard unit, and a driving unit. The arithmetic processing unit is respectively connected to the signal sampling circuit, the communication unit, the keyboard unit, and the driving unit. The auxiliary power supply is respectively connected to the arithmetic processing unit, the signal sampling circuit, the communication unit, the keyboard unit, and the driving unit; the driving unit is respectively connected to the input filter unit, the AC / DC conversion unit, the Buck / Boost conversion unit, and the LLC isolation conversion unit; the signal sampling circuit is used to collect the voltage and current signals of each unit, and the communication unit is used to receive external communication commands.

[0006] Further, a non-polar capacitor is adopted at the connection point between the Buck / Boost conversion unit and the LLC isolation conversion unit, and there is no large-capacity electrolytic capacitor.

[0007] Further, the Buck / Boost conversion unit has a two-level or three-level structure; the Buck / Boost conversion unit can be connected as a buck-boost function conversion or a boost-buck function conversion according to needs in the forward and reverse paths.

[0008] Further, the two-level structure has terminals A, B, C, D, switching tubes K1 and K2, capacitors C1 and inductors L1, where terminal A, switching tube K1, inductor L1, and terminal C are connected in sequence, terminal B and terminal D are connected, one end of switching tube K2 is connected to terminal B or terminal D, and the other end is connected between switching tube K1 and inductor L1; one end of capacitor C1 is connected to terminal B or terminal D, and the other end is connected between inductor L1 and terminal C; the three-level structure is symmetrically connected with the negative bus as the central bus, and switching tubes and inductors are provided on both the positive and negative buses.

[0009] Further, the LLC isolation conversion unit can adjust the DC terminal voltage outside the device, and the bus voltage at the connection point of the Buck / Boost conversion unit and the LLC isolation conversion unit is an open-loop uncontrolled object.

[0010] Further, N such power conversion devices are used in parallel, the AC terminals are connected in parallel, the DC terminals are connected in parallel, and at the same time, the control units of each power conversion device are connected through an AC phase synchronization signal.

[0011] Beneficial effects: Compared with the prior art, the present utility model has the following advantages:

[0012] (1) The structure is normalized and integrated. The rectification, grid-connected inversion, off-grid inversion, and maintainability are realized from the hardware by using the AC / DC conversion unit, the Buck / Boost conversion unit, and the LLC isolation conversion unit, reducing the redundant functional units of multiple devices and the space occupation.

[0013] (2) The operation is simplified. The multi-working mode control is carried out through the control unit to meet the switching of five working modes: charging mode, grid-connected inversion mode, off-grid inversion mode, detection mode, and standby mode, enabling the power conversion device to adaptively adjust according to the mode requirements.

[0014] (3) Due to the reduction of devices, the functional compounding, the operation simplification, and the reduction of space occupation, a higher cost performance is achieved. Description of the Drawings

[0015] Figure 1 is a schematic structural diagram of the power conversion device provided by the embodiment of the present utility model;

[0016] Figure 2 is a schematic structural diagram of the control unit in the embodiment of the present utility model;

[0017] Figure 3 It is a schematic structural diagram of a Buck / Boost conversion unit in an embodiment of the present utility model;

[0018] Figure 4 It is a schematic structural diagram of another Buck / Boost conversion unit in an embodiment of the present utility model;

[0019] Figure 5 It is a schematic diagram of the charging (rectifying) mode of a power conversion device in an embodiment of the present utility model;

[0020] Figure 6 It is a schematic diagram of the inversion mode of a power conversion device in an embodiment of the present utility model;

[0021] Figure 7 It is a schematic diagram of the detection mode of multiple parallel power conversion devices in an embodiment of the present utility model. Specific embodiments

[0022] The present utility model will be further described below with reference to the accompanying drawings.

[0023] As Figure 1 shown, an embodiment of the present utility model provides a power conversion device with multiple working modes, including a control unit, and an input filter unit, an AC / DC conversion unit, a Buck / Boost conversion unit, and an LLC isolation conversion unit connected in sequence. The input filter unit is connected to an AC source or an equivalent load, and the LLC isolation conversion unit is connected to a DC source or an equivalent load. The input filter unit, the AC / DC conversion unit, the Buck / Boost conversion unit, and the LLC isolation conversion unit are all circuits with bidirectional conversion functions. Moreover, a non-polar capacitor is used at the connection point between the Buck / Boost conversion unit and the LLC isolation conversion unit, and there is no large-capacity electrolytic capacitor.

[0024] Combined with Figure 2 , the control unit includes an arithmetic processing unit, a signal sampling circuit, a communication unit, an auxiliary power supply, a keyboard unit, and a driving unit. The arithmetic processing unit is respectively connected to the signal sampling circuit, the communication unit, the keyboard unit, and the driving unit. The auxiliary power supply is respectively connected to the arithmetic processing unit, the signal sampling circuit, the communication unit, the keyboard unit, and the driving unit. The driving unit is respectively connected to the input filter unit, the AC / DC conversion unit, the Buck / Boost conversion unit, and the LLC isolation conversion unit. The signal sampling circuit is used to collect voltage and current signals of each unit, and the communication unit is used to receive external communication commands.

[0025] As Figure 3As shown, the Buck / Boost conversion unit has a two-level structure, with terminals A, B, C, D, switching transistors K1 and K2, capacitor C1, and inductor L1. Among them, terminal A, switching transistor K1, inductor L1, and terminal C are connected in sequence. Terminal B and terminal D are connected. One end of switching transistor K2 is connected to terminal B or terminal D, and the other end is connected between switching transistor K1 and inductor L1. One end of capacitor C1 is connected to terminal B or terminal D, and the other end is connected between inductor L1 and terminal C. The AB terminal is connected to the AC / DC conversion unit, and the CD terminal is connected to the LLC isolation conversion unit. Figure 3 The Buck / Boost conversion unit with bidirectional conversion function shown can meet the requirements of two-level conversion.

[0026] For high-voltage conversion, such as Figure 4 As shown, the Buck / Boost conversion unit can also be a three-level structure, that is, with the negative bus in the figure as the central bus, symmetrically connected, and there are switching transistors and inductors on both the positive and negative buses. Figure 4 In it, the ABA' terminal is connected to the AC / DC conversion unit, and the CDC' terminal is connected to the LLC isolation conversion unit.

[0027] In addition to Figure 3 and Figure 4 the connection methods shown, the Buck / Boost conversion unit can also be such that the AB terminal or the ABA' terminal is connected to the LLC isolation conversion unit, and the CD terminal or the CDC' terminal is connected to the AC / DC conversion unit. At this time, it can also be called a Boost / Buck conversion unit, that is, changing the step-down-boost function of the original positive and negative paths of the Buck / Boost conversion unit to a boost-step-down function.

[0028] Such as Figure 7 As shown, in order to expand the power, N (N≥2) power conversion devices can be used in parallel. The AC terminals are connected in parallel, and the DC terminals are connected in parallel. At the same time, the control units of each power conversion device are connected through AC phase synchronization signals.

[0029] In this embodiment, the input filter unit, the AC / DC conversion unit, and the LLC isolation conversion unit are all implemented based on existing general circuit structures.

[0030] This embodiment of the utility model also provides a control method for the power conversion device described in the embodiment of the utility model, including:

[0031] (1) The control unit makes a working mode determination according to the voltage and current signals of each unit collected by the signal sampling circuit, or the commands input by the keyboard unit, or the commands obtained through external communication. The determination method is a prior art; the working modes include a charging mode, a grid-connected inverter mode, an off-grid inverter mode, a detection mode, and a standby mode;

[0032] (2) The control unit switches the power conversion device to the corresponding operating mode, that is, controls the power conversion device to operate in the charging mode, grid-connected inverter mode, off-grid inverter mode, detection mode or standby mode.

[0033] It is assumed that the Buck / Boost conversion unit connects the AB terminal or the ABA' terminal to the AC / DC conversion unit and connects the CD terminal or the CDC' terminal to the LLC isolation conversion unit.

[0034] When the control unit determines it is the charging mode, as Figure 5 shown, the AC source or the equivalent load serves as the input source, supplies power to the AC / DC conversion unit through the input filter unit, controls the AC / DC conversion unit to operate in the forward rectification state, and the connection port with the Buck / Boost conversion unit outputs high-voltage DC; the Buck / Boost conversion unit operates in the Buck (step-down) state, and at the same time the control unit controls the LLC isolation conversion unit to operate in the fixed-frequency open-loop mode. The optimal value of the fixed frequency in this mode is the resonant frequency of the LLC isolation conversion unit, so that soft-switching conversion can be obtained to the greatest extent and ultimately high-efficiency conversion can be achieved. Since the operating frequency of the LLC isolation conversion unit is fixed, the control unit directly adjusts the duty cycle of the corresponding switching tube inside the Buck / Boost conversion unit according to the feedback of the output voltage and current of the terminal, so as to achieve the required output voltage and current of the device. In addition, for a wider range of output voltage or current control, the LLC isolation conversion unit can also operate in the frequency closed-loop regulation mode to participate in the control, further increasing the regulation of the output voltage and current by the Buck / Boost conversion unit.

[0035] As Figure 6As shown, when the control unit determines that it is in the inverter mode, the DC source (battery terminal) or equivalent load externally connected to the LLC isolation conversion unit serves as the DC input source to supply power to the LLC isolation conversion unit. The control unit controls the LLC isolation conversion unit to operate in a fixed-frequency open-loop mode. The optimal value of the fixed frequency in this mode is the resonant frequency of the LLC isolation conversion unit, so that soft-switching conversion can be obtained to the greatest extent and high-efficiency conversion can be finally achieved. At the same time, the Buck / Boost conversion unit operates in the Boost (step-up) state, outputs high-voltage DC to supply power to the AC / DC conversion unit. The AC / DC conversion unit operates in the inverter state to output AC and supplies power to the AC source or equivalent load through the input filter unit. At this time, if the control unit determines that it is in the grid-connected inverter mode, the AC / DC conversion unit operates in the current control mode, outputs AC in the reverse grid-connected current source inverter state, and supplies power to the grid-connected AC source or equivalent load through the input filter unit. If the control unit determines that it is in the off-grid inverter mode, the AC / DC conversion unit operates in the voltage control mode, outputs AC in the reverse off-grid voltage source inverter state, and supplies power to the equivalent load through the input filter unit.

[0036] When the control unit determines that it is in the detection mode, the power conversion device operates in the off-grid or grid-connected inverter mode and adjusts the Buck / Boost conversion unit according to the control requirements, so that the Buck / Boost conversion unit operates under the detection mode control, thereby adjusting the voltage or current of the DC input port, recording relevant parameters, and making a judgment based on the detection data (the judgment method is the prior art), to achieve the detection of the DC (battery) terminal device.

[0037] In addition, for a wider range of output voltage or current control, in the inverter mode or maintenance mode, the LLC isolation conversion unit can also operate in the frequency closed-loop regulation mode to participate in the control, further increasing the adjustment of the output voltage and current by the Buck / Boost conversion unit.

[0038] When the power conversion device operates in the detection mode, the output voltage of the Buck / Boost conversion unit is adjusted according to the input voltage of the DC (battery) terminal, and it can be inconsistent with the voltage when operating in the inverter mode or charging (rectification) mode.

[0039] From the above working principle, it can be seen that the LLC isolation conversion unit can adjust the DC terminal voltage outside the device in a wide range, and the bus voltage at the connection point of the Buck / Boost conversion unit and the LLC isolation conversion unit can be an open-loop uncontrolled object.

[0040] When multiple parallel power conversion devices operate in the off-grid inverter mode, the control units of each power conversion device automatically set one of them as the host and the others as slaves by detection. The host sends out an AC phase synchronization signal, and the slaves perform phase-locking work on the synchronization signal. The AC / DC conversion units of each power conversion device use an open-loop load duty ratio dot-point table query or droop control method to perform inverter parallel operation, and at the same time, the DC input current sharing of each LLC isolation conversion unit is achieved by controlling the Buck / Boost conversion unit. And it cooperates with the AC / DC conversion units of each power conversion device to achieve better automatic current sharing.

[0041] When multiple parallel power conversion devices operate in the charging mode, the droop current sharing method is adopted to achieve automatic current sharing among the power conversion devices by detecting the current at the DC output end, or a total current detection device is added outside each power conversion device, and the signal is transmitted to the control unit of each power conversion device for current sharing control, or the current values of each power conversion device are interacted in real time through the external communication of each power conversion device to perform current sharing control.

[0042] It should be noted that in some cases, if the EMC performance of the system is good, the power conversion device with multiple working modes may also not have an input filter unit, that is, the AC source or equivalent load is directly connected to the AC / DC conversion unit, and the function of the power conversion device will not change.

[0043] In summary, the power conversion device with multiple working modes provided by the embodiments of the present invention realizes the integration of the rectification and inversion functions in terms of the hardware system principle, and at the same time uses the combined control of the inverter mode control and the LLC isolation conversion unit to realize the detection and maintenance functions, thereby realizing that one device replaces traditional multiple devices (charger, grid-connected inverter, off-grid inverter, detection equipment), achieving the simplification of the structure and the compounding of functions, effectively improving the space utilization, and using multi-mode control to simplify the operation, saving a large amount of space and improving the cost performance for some specific occasions such as islands, ships, automobiles, etc.

Claims

1. A power conversion device with multiple working modes, characterized in that: It includes a control unit, and an input filter unit, an AC / DC conversion unit, a Buck / Boost conversion unit and an LLC isolation conversion unit connected in sequence; the input filter unit is connected to an AC source or an equivalent load, and the LLC isolation conversion unit is connected to a DC source or an equivalent load; the input filter unit, the AC / DC conversion unit, the Buck / Boost conversion unit and the LLC isolation conversion unit are all circuits with a bidirectional conversion function; The control unit includes an operation processing unit, a signal sampling circuit, a communication unit, an auxiliary power supply, a keyboard unit and a driving unit. The operation processing unit is respectively connected to the signal sampling circuit, the communication unit, the keyboard unit and the driving unit. The auxiliary power supply is respectively connected to the operation processing unit, the signal sampling circuit, the communication unit, the keyboard unit and the driving unit; the driving unit is respectively connected to the input filtering unit, the AC / DC conversion unit, the Buck / Boost conversion unit and the LLC isolation conversion unit; the signal sampling circuit is used to collect voltage and current signals of each unit, and the communication unit is used to receive external communication commands.

2. The power conversion device according to claim 1, characterized in that: The connection point between the Buck / Boost conversion unit and the LLC isolation conversion unit adopts a non-polar capacitor without a large-capacity electrolytic capacitor.

3. The power conversion device according to claim 1, characterized in that: The Buck / Boost conversion unit is a two-level or three-level structure; the Buck / Boost conversion unit can be connected as a buck-boost function conversion or a boost-buck function conversion in the forward and reverse paths as required.

4. The power conversion device according to claim 3, characterized in that: The two-level structure has A, B, C, D terminals, switches K1 and K2, capacitor C1 and inductor L1, wherein the A terminal, switch K1, inductor L1 and C terminal are connected in sequence, the B terminal and the D terminal are connected, one end of the switch K2 is connected to the B terminal or the D terminal, and the other end is connected between the switch K1 and the inductor L1; One end of capacitor C1 is connected to terminal B or terminal D, and the other end is connected between terminal L1 and terminal C; the three-level structure takes the negative bus as the central bus, is symmetrically connected, and switches and inductors are provided on both the positive and negative buses.

5. The power conversion device according to claim 1, characterized in that: The LLC isolation conversion unit can adjust the DC terminal voltage outside the device, and the bus voltage at the connection point between the Buck / Boost conversion unit and the LLC isolation conversion unit is an open-loop uncontrolled object.

6. The power conversion device according to claim 1, characterized in that: N of the power conversion devices are used in parallel, the AC ends are connected in parallel, the DC ends are connected in parallel, and the control units of the power conversion devices are connected via an AC phase synchronization signal.

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