Power conversion system and power conversion module

Abstract

The invention provides a power conversion system and a power conversion module, the power conversion system comprises a first module, a second module and a first diode, the first module comprises a first switching circuit, a first auxiliary power supply unit, a first capacitor and a second capacitor, and a first port of the first switching circuit is connected with the second capacitor in parallel; the first module comprises a first switching circuit, a first auxiliary power supply unit, a third capacitor and a fourth capacitor, a first port of the first auxiliary power supply unit is connected with the first capacitor in parallel, and a first terminal of the first capacitor is connected with a first terminal of a second port of the first switching circuit; the second auxiliary power supply unit is connected with a third capacitor in parallel; a first terminal of the third capacitor is connected with a first terminal of a second port of the second switching circuit; a second port of the first switch circuit in the first module is connected in series with a second port of the second switch circuit in the second module, and two ends of the first diode are respectively connected with the first capacitor and the third capacitor.

Description

Technical Field

[0001] The present application relates to the field of electronics and electrical engineering, and in particular to a power conversion system and a power conversion module. Background Art

[0002] With the rapid development of new energy power generation technology, energy storage technology has also developed rapidly. Since medium-voltage direct-mounted energy storage technology does not require transformer access, has fewer conversion links, high operating efficiency, and can quickly respond to dispatching instructions, it has obvious advantages in high-power energy storage. Medium-voltage direct-mounted energy storage systems suitable for medium-voltage DC distribution networks have become a research hotspot. The operation and maintenance of energy storage battery systems require a battery management system (BMS). If the BMS is powered off, it will not be able to monitor the battery and environmental status in time, which may lead to battery inconsistency, resulting in a reduction in the actual charge and discharge depth and cycle life of the battery, causing direct economic losses, or battery overcharge or overtemperature causing failures, and even fire or explosion. Therefore, in any working mode, the auxiliary power supply circuit needs to provide uninterrupted power supply to it, and high reliability of the auxiliary power supply must be required. If the auxiliary power supply of the energy storage system only takes power from the battery side, when the battery is in a state of low power, the undervoltage protection action stops the battery from discharging, which does not meet the requirements of uninterrupted power supply, bringing safety hazards, and the energy cost of the energy storage battery is high. It is easy to cause low power and affect the battery life when working off the grid for a long time, and the economic efficiency is poor.

[0003] At present, medium voltage direct-mounted energy storage mostly adopts a DC chain energy storage structure. Due to the different ground potentials of the cascaded power modules, it is difficult to use a single auxiliary power supply to provide auxiliary power to all power modules. A common auxiliary power supply solution for power conversion systems is as follows: Figure 1 As shown, the auxiliary power supply system includes n power modules, 1≤i≤n, and each power module is provided with an auxiliary power supply 20 and a corresponding isolation transformer 30. The auxiliary power supply 20 draws power from the input port of the power module SMi through the isolation transformer 30. This power-drawing method has a low isolation voltage and is easy to draw power, but because the power module SMi has a redundant working state of exiting operation when it is operating normally, or when the power module SMi fails and is bypassed, the power-drawing method from the input port of the power module fails, and the high reliability of the auxiliary power supply cannot be guaranteed.

[0004] Figure 2This is another common auxiliary power supply system structure, which uses an industrial frequency transformer to draw power from the low-voltage mains. The power conversion system includes n power modules, each of which is provided with an auxiliary power supply 20 and a corresponding isolation transformer 40. The low-voltage mains is connected through the primary side of the i-th industrial frequency transformer, the secondary side of the i-th industrial frequency transformer is connected to the i-th auxiliary power supply, and the i-th auxiliary power supply draws power from the i-th isolation transformer. This auxiliary power supply system draws power from the industrial frequency mains, has high reliability and large output power. However, each isolation transformer needs to be an industrial frequency transformer, and because the industrial frequency transformer needs to be designed according to the system voltage insulation, the module is large in size, low in efficiency, and it is difficult to meet modular requirements.

[0005] Therefore, it is urgent to propose a power conversion system with an efficient and reliable auxiliary power supply system and a power conversion module suitable for modularization. Summary of the invention

[0006] Some embodiments of the present application provide a power conversion system, including: at least two power modules and at least one first diode, the at least two power modules including a first module and a second module;

[0007] The first module includes a first switch circuit, a first auxiliary power supply unit, a first capacitor and a second capacitor, wherein the first port of the first switch circuit is connected in parallel with the second capacitor, the first port of the first auxiliary power supply unit is connected in parallel with the first capacitor, the first capacitor is used to charge the first auxiliary power supply unit, and the first terminal of the first capacitor is connected to the first terminal of the second port of the first switch circuit;

[0008] The second module includes a second switch circuit, a second auxiliary power supply unit, a third capacitor and a fourth capacitor, the first port of the second switch circuit is connected in parallel with the fourth capacitor, the second auxiliary power supply unit is connected in parallel with the third capacitor, the third capacitor is used to charge the second auxiliary power supply unit, and the first terminal of the third capacitor is connected to the first terminal of the second port of the second switch circuit;

[0009] The second port of the first switch circuit in the first module is connected in series with the second port of the second switch circuit in the second module, and both ends of the first diode are connected to the first capacitor and the third capacitor respectively.

[0010] Some embodiments of the present application provide a power conversion module, including: a first module and a first diode connected to the first module;

[0011] The first module includes a first switch circuit, a first auxiliary power supply unit, a first capacitor, a second capacitor and a first diode;

[0012] The first port of the first switching circuit is connected in parallel with the second capacitor, the first port of the first auxiliary power supply unit is connected in parallel with the first capacitor, the first capacitor is used to charge the first auxiliary power supply unit, and the first terminal of the first capacitor is connected to the first terminal of the second port of the first switching circuit.

[0013] Some embodiments of the present application provide a power conversion system and a power conversion module, the power conversion system includes a first module, a second module and a first diode, the first module includes a first switch circuit, a first auxiliary power supply unit, a first capacitor and a second capacitor, the first port of the first switch circuit is connected in parallel with the second capacitor, the first port of the first auxiliary power supply unit is connected in parallel with the first capacitor, and the first capacitor is used to charge the first auxiliary power supply unit. The second module includes a second switch circuit, a second auxiliary power supply unit, a third capacitor and a fourth capacitor, the first port of the second switch circuit is connected in parallel with the fourth capacitor, the second auxiliary power supply unit is connected in parallel with the third capacitor, and the third capacitor is used to charge the second auxiliary power supply unit. The first terminal of the first capacitor is connected to the first terminal of the second port of the first switch circuit, the first terminal of the third capacitor is connected to the first terminal of the second port of the second switch circuit, the second port of the first switch circuit in the first module is connected in series with the second port of the second switch circuit in the second module, and the two ends of the first diode are connected to the first capacitor and the third capacitor respectively. By setting in this way, an electric energy transfer loop of the first capacitor and the third capacitor is formed between the first module and the second module, and after the first capacitor is charged, the first capacitor can charge the third capacitor through the electric energy transfer loop. Since power is not taken from the power unit, when the power unit outputs zero level, it can ensure that the auxiliary power supply unit in each power module is powered, ensuring the reliability of the auxiliary power supply. And there is no need to configure an industrial frequency transformer in each power module, which can reduce the size of the module and facilitate the modularization of the power conversion system. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the present application or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0015] Figure 1 is a circuit schematic diagram of another power conversion system;

[0016] Figure 2 is a circuit schematic diagram of yet another power conversion system;

[0017] Figure 3 A circuit schematic diagram of a power conversion system;

[0018] Figure 4A , Figure 4B as well as Figure 4C All of them are circuit schematics of power units in power conversion systems;

[0019] Figures 5 to 8 A circuit schematic diagram of the power conversion system provided in this application;

[0020] Fig. 9 and Fig.10 All of them are schematic diagrams of energy transfer when a power conversion system fails according to an embodiment of the present application;

[0021] Figures 11 to 14 A circuit diagram of a power conversion system provided in this application;

[0022] FIG. 15A to FIG. 15D A circuit schematic diagram of a power module is provided for an embodiment of the present application;

[0023] Fig.16 A circuit schematic diagram of a power conversion system is provided for another embodiment of the present application;

[0024] FIG. 17A to FIG. 17D A circuit schematic diagram of a power conversion module is provided for another embodiment of the present application;

[0025] 18A to 18H A circuit schematic diagram of a power conversion module is provided for yet another embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the drawings in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0027] The terms "first", "second", "third", "fourth", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances. For example, without departing from the scope of this article, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0028] Figure 3 FIG. 1 is a schematic diagram of the architecture of a power conversion system. Figure 3 As shown, the power conversion system includes a plurality of cascaded power modules 100, each power module 100 includes at least a power unit 10, and each power unit 10 includes a first port. More specifically, the N power modules 100 include power module SM1, power module SM2, power module SM3, ... power module SMn, respectively. The first port of power module SM1 includes a second terminal A1 and a first terminal B1, the first port of power module SM2 includes a second terminal A2 and a first terminal B2, and the first port of power module SM3 includes a second terminal A3 and a first terminal B3. And so on. The first port of power module SMn includes a second terminal An and a first terminal Bn. The first terminal B1 of the first port of power module SM1 serves as the first terminal B of the DC port of the power conversion system. The second terminal A1 of the first port of the power module SM1 is connected to the first terminal B2 of the first port of the power module SM2, the second terminal A2 of the first port of the power module SM2 is connected to the first terminal B3 of the first port of the power module SM3, and so on, the first terminal Bn of the first port of the power module SMn is connected to the second terminal A(n-1) of the first port of the power module SM(n-1), and the second terminal An of the first port of the power module SMn serves as the second terminal A of the DC port of the power conversion system. The DC port of the power conversion system can be connected to the DC bus Ubus through the first circuit breaker K1 and the inductor L1, for example, the first circuit breaker K1 and the inductor L1 are connected between the positive pole of the DC bus Ubus and the first port of the power module 100 at the last stage, and the second circuit breaker K2 is connected between the negative pole of the DC bus Ubus and the first port of the power module 100 at the first stage.

[0029] It should also be noted that different power conversion circuits can be used as modules with different functions in the power units 10 of the multiple power modules 100 in the power conversion system, including but not limited to low-frequency modules using half-bridge conversion circuits or high-frequency modules using full-bridge conversion circuits. Among them, the high-frequency module can be used to control the input current of the power conversion system, and the first port of each power unit 10 used for the low-frequency module is used as a charging and discharging port of the DC voltage, wherein multiple power units 10 participating in the power conversion are cascaded to provide a DC bus voltage Ubus. In order to ensure the reliability of the operation of the power conversion system, multiple redundant power modules 100 can also be set to improve the reliability of the system. The power conversion system can also include multiple bypass switches, and each power module 100 is correspondingly provided with a bypass switch. For example: the power unit in the power module SM1 includes a bypass switch K31, the power unit in the power module SM2 includes a bypass switch K32, the power unit in the power module SM3 includes a bypass switch K33, and so on, the power unit in the power module SMn includes a bypass switch K3n. The bypass switch corresponding to each power conversion module 100 can be used to bypass the power unit 10 in the module when the power unit 10 fails to ensure the reliability of auxiliary power supply; or to shut down the bypass switch to make the corresponding power module 100 exit operation and enter redundancy or start operation from a redundant state.

[0030] Figure 4A , Figure 4B and Figure 4C Each of them is a schematic diagram of the structure of a power unit 10. Figure 4A , Figure 4B and Figure 4C As shown, the power unit 10 includes a switch circuit 110 and a capacitor 140. The switch circuit 110 includes a first port and a second port, wherein the second port of the switch circuit 110 serves as the first port of the power unit 10. The first port of the switch circuit 110 includes a first terminal 111 and a second terminal 112, wherein the first terminal 111 of the first port of the switch circuit 110 is connected to the first terminal 141 of the capacitor 140, and the second terminal 112 of the first port of the switch circuit 110 is connected to the second terminal 142 of the capacitor 140.

[0031] like Figure 4A and Figure 4B As shown, the power unit 10 may further include an energy storage unit 150, the first terminal 111 of the first port of the switch circuit 110 is also connected to the first terminal 151 of the energy storage unit 150, the second terminal 112 of the first port of the switch circuit 110 is also connected to the second terminal 152 of the energy storage unit 150, the energy storage unit 150 is used to store electrical energy or release electrical energy to the outside, and the energy storage unit 150 includes but is not limited to energy storage batteries or super capacitors.

[0032] In some embodiments, the power unit SMi is used as an example. 1≤i≤n, i is a positive integer. Figure 4A and Figure 4B As shown, the switch circuit 110 includes a first switch device Q1i and a second switch device Q2i connected in series, and the second end of the first switch device Q1i serves as the second terminal 112 of the first port of the switch circuit 110. The first end of the second switch device Q2i serves as the first terminal 111 of the first port of the switch circuit 110. Figure 4A In the embodiment, a connection point between a first end of the first switching device Q1i and a second end of the second switching device Q2i serves as a second terminal Ai of a second port of the switching circuit 110, and a first end of the second switching device Q2i serves as a first terminal Bi of the second port of the switching circuit 110. Figure 4B In the embodiment, the first end of the first switch device Q1i serves as the first terminal Ai of the second port of the switch circuit 110, and the connection point between the second end of the first switch device Q1i and the first end of the second switch device Q2i serves as the second terminal Bi of the second port of the switch circuit 110. The control end of the first switch device Q1i receives a first control signal, and the control end of the second switch device Q2i receives a second control signal, and the first control signal controls the first switch device Q1i to be turned on or off. The second control signal controls the second switch device Q2i to be turned on or off. The switch devices include, but are not limited to, power devices such as IGBT or MOSFET.

[0033] In some embodiments, Figure 4C As shown, the switch circuit 110 includes a first switch device Q1i, a second switch device Q2i, a third switch device Q3i, and a fourth switch device Q4i connected in a full bridge. The connection point between the first end of the first switch device Q1i and the second end of the second switch device Q2i serves as the first terminal Ai of the second port. The connection point between the first end of the third switch device Q3i and the second end of the fourth switch device Q4i serves as the second terminal Bi of the second port. The second end of the first switch device Q1i and the second end of the third switch device Q3i are connected as the second terminal 112 of the first port. The first end of the second switch device Q2i and the first end of the fourth switch device Q4i are connected as the first terminal 111 of the first port.

[0034] The control end of the first switching device Q1i receives a first control signal, which controls the on or off state of the first switching device Q1i. The control end of the second switching device Q2i receives a second control signal, which controls the on or off state of the second switching device Q2i. The control end of the third switching device Q3i receives a third control signal, which controls the on or off state of the second switching device Q2i. The control end of the fourth switching device Q4i receives a fourth control signal, which controls the on or off state of the fourth switching device Q4i.

[0035] Some aspects of the embodiments of the present application relate to the above considerations. The following is an example of the solution in combination with some embodiments of the present application. Figures 5 to 14 As shown, the power conversion system provided by some embodiments of the present application includes a plurality of power modules 100, each of which includes a capacitor 130, an auxiliary power supply unit 120 and a power unit 10. The auxiliary power supply unit 120 includes a first port (port 1), and the first port of the auxiliary power supply unit 120 is connected in parallel with the capacitor 130. More specifically, the first terminal of the first port (port 1) of the auxiliary power supply unit 120 is connected to the first terminal 131 of the capacitor 130, and the second terminal of the first port (port 1) of the auxiliary power supply unit 120 is connected to the second terminal 132 of the capacitor 130. The capacitor 130 is used to provide energy to the auxiliary power supply unit 120 so that the output end of the auxiliary power supply unit 120 can supply power to the outside.

[0036] The power unit 10 includes a first port, and the first ports of the power units 10 are connected in cascade in sequence. The cascade connection method of the first ports of the power units 10 has been described in detail. Figure 3 The structure of the power unit 10 can be but is not limited to Figure 4A , Figure 4B or Figure 4C Any one of the structures. That is, the power unit 10 includes a switch circuit 110 and a capacitor 140. The switch circuit 110 includes a first port and a second port, and the second port of the switch circuit 110 serves as the first port of the power unit 10. The first port of the switch circuit 110 is connected in parallel with the capacitor 140. More specifically, the first terminal of the first port of the switch circuit 110 is connected to the first terminal of the capacitor 140. The second terminal of the first port of the switch circuit 110 is connected to the second terminal of the capacitor 140. In some other embodiments, the first port of each power unit 10 may also be connected in parallel with a bypass switch, and more specifically, the first port of the power unit in the power module SMi is connected in parallel with a bypass switch K3i, 1≤i≤n. The bypass switch is used to bypass the power unit in the power module SMi when a power unit fails or exits operation and enters a redundant state.

[0037] The power conversion system also includes a plurality of first diodes 210, each of which is connected to any two power modules 100 connected in series. For ease of description, the power modules where any two power units 10 connected in series are located are referred to as first modules and second modules. For example, the first ports of the power unit in the power module SM1 and the power unit in the power module SM2 are connected in series, the power module SM1 is referred to as the first module, and the power module SM2 is referred to as the second module.

[0038] The capacitor 130 in the first module is called the first capacitor, the auxiliary power supply unit 120 in the first module is called the first auxiliary power supply unit, the switch circuit 110 in the first module is called the first switch circuit, and the capacitor 140 in the first module is called the second capacitor. The capacitor 130 in the second module is called the third capacitor, the auxiliary power supply unit 120 in the second module is called the second auxiliary power supply unit, the switch circuit 110 in the second module is called the second switch circuit, and the capacitor 140 in the second module is called the fourth capacitor.

[0039] The first terminal of the second port of the first switch circuit is also connected to the first terminal of the first capacitor. The first terminal of the second port of the second switch circuit is also connected to the first terminal of the third capacitor. The two ends of the first diode 210 are respectively connected to the first capacitor and the third capacitor. By such an arrangement, electric energy transfer can be achieved between the first capacitor and the third capacitor. That is, energy transfer can be performed unidirectionally between the power modules where the two power units connected in series are located.

[0040] More specifically, for example, the power cell 10 in the power module SM1 is connected in series with the power cell 10 in the power module SM2, the power module SM1 serves as the first module, the power module SM2 serves as the second module, and the capacitor C11 in the power module SM1 charges the capacitor C12 in the power module SM2. The power cell 10 in the power module SM2 is connected in series with the power cell 10 in the power module SM3, the power module SM2 serves as the first module, the power module SM3 serves as the second module, and the capacitor C12 in the power module SM2 charges the capacitor C13 in the power module SM3. And so on, the energy is transmitted step by step until it is transmitted to the capacitor C1n in the power module SMn. In this way, the capacitor 130 in each power module 100 can be charged to supply power to the auxiliary power supply unit 120 in the power module 100.

[0041] In some embodiments, the power conversion system also includes a controller, which is configured to draw power from an auxiliary power supply unit and control the corresponding switch of the first switching circuit in the first module to conduct, so that the first switching circuit outputs a zero level, thereby forming an energy transfer loop so that the electric energy of the first capacitor of the first module is transferred to the third capacitor of the second module.

[0042] Embodiment 1

[0043] The structure of each power unit 10 in the power conversion system is as follows: Figure 4A Taking the structure shown as an example, the following describes the process of the capacitor 130 of the power module SM1 transferring electric energy to the capacitor 130 in the power module SMn step by step.

[0044] like Figure 5As shown, for the series connection between the power unit 10 in the power module SM1 and the power unit 10 in the power module SM2, the second terminal 132 of the capacitor C11 in the power module SM1 is connected to the anode of the first diode D11, and the second terminal 132 of the capacitor C12 in the power module SM2 is connected to the cathode of the first diode D11. The first terminal B1 of the second port of the switch circuit T1 of the power module SM1 is connected to the first terminal 131 of the capacitor C11, and the first terminal B2 of the second port of the switch circuit T2 of the power module SM2 is connected to the first terminal 131 of the capacitor C12. The electric energy transfer circuit between the capacitor C11 in the power module SM1 and the capacitor C12 in the power module SM2 is: from the second terminal 132 of the capacitor C11 in the power module SM1 through the first diode D11, the capacitor C12 in the power module SM2, the first terminal B2 of the second port of the switch circuit T2 in the power module SM2, the second switch device Q21 in the switch circuit T1 in the power module SM1 and the first terminal B1 of the second port of the switch circuit T1 in the power module SM1, back to the first terminal 131 of the capacitor C11 in the power module SM1, by controlling the second switch device Q21 in the switch circuit T1 in the power module SM1 to turn on, the power unit SM1 outputs a zero level, forming an energy transfer circuit, thereby realizing charging of the capacitor C11 in the power module SM1 to the capacitor C12 in the power module SM2.

[0045] like Figure 5As shown, for the series connection between the power unit 10 in the power module SM2 and the power unit 10 in the power module SM3, the second terminal 132 of the capacitor C12 in the power module SM2 is connected to the anode of the first diode D12, and the second terminal 132 of the capacitor C13 in the power module SM3 is connected to the cathode of the first diode D12. The first terminal B2 of the second port of the switch circuit T2 in the power module SM2 is connected to the first terminal 131 of the capacitor C12, and the first terminal B3 of the second port of the switch circuit T3 in the power module SM3 is connected to the first terminal 131 of the capacitor C13. The electric energy transfer circuit (not shown) between the capacitor C12 in the power module SM2 and the capacitor C13 in the power module SM3 is: from the second terminal 132 of the capacitor C12 in the power module SM2 through the first diode D12, the capacitor C13 in the power module SM3, the first terminal B3 of the second port of the switch circuit T3 in the power module SM3, the second switch device Q22 in the switch circuit T2 in the power module SM2 and the first terminal B2 of the second port of the switch circuit T2 in the power module SM2 back to the first terminal 131 of the capacitor C12 in the power module SM2, by controlling the second switch device Q22 in the switch circuit T2 in the power module SM2 to turn on, the power unit SM2 outputs a zero level, forming an energy transfer circuit, thereby realizing the charging of the capacitor C12 in the power module SM2 to the capacitor C13 in the power module SM3.

[0046] By analogy, capacitor C13 in power module SM3 charges capacitor C14 in power module SM4, until capacitor C1(n-1) in power module SM(n-1) charges capacitor C1n in power module SMn, so that capacitor 130 in each power module 100 is fully charged, and each capacitor 130 supplies power to the auxiliary power supply unit 120 in the power module 100, and the auxiliary power supply unit 120 then supplies power to the controller or other circuits.

[0047] In this embodiment, the controller sequentially controls the second switch device Q21 in the power module SM1 to be turned on, the second switch device Q22 in the power module SM2 to be turned on, and the second switch device Q2(n-1) in the power module SM(n-1) to be turned on, so as to ensure that the electric energy is sequentially transferred from the capacitor C11 in the power module SM1 to the capacitor C1n in the power module SMn. By switching the corresponding switch devices in the power module 10 in turn, it is realized that when one power module 10 is put into operation, one power module 10 is bypassed to ensure that the voltage on the DC bus Ubus connected to the power conversion system does not jump, and the stability of the auxiliary power supply system power supply establishment process of the power conversion system is ensured; at the same time, the auxiliary power supply unit 120 is powered by the capacitor 130 instead of the capacitor 140 of the power module itself, so that the power supply path of the auxiliary power supply unit is decoupled from the power module, so as to ensure that when some power modules 100 fail during the auxiliary power supply system power supply establishment process of the power conversion system, the auxiliary power supply unit can still be continuously powered to ensure the reliability of the auxiliary power supply system power supply.

[0048] Embodiment 2

[0049] The structure of each power unit 10 in the power conversion system is as follows: Figure 4B Taking the structure shown as an example, the following describes the process of the capacitor 130 of the power module SMn transferring electric energy to the capacitor 130 in the power module SM1 step by step.

[0050] like Figure 6As shown, the power unit 10 in the power module SMn is connected in series with the power unit 10 in the power module SM(n-1), the second terminal 132 of the capacitor C1n in the power module SMn is connected to the cathode of the first diode D1(n-1), and the second terminal 132 of the capacitor C1(n-1) in the power module SM(n-1) is connected to the anode of the first diode D1(n-1). The first terminal An of the second port of the switch circuit Tn in the power module SMn is connected to the first terminal 131 of the capacitor C1n, and the first terminal A(n-1) of the second port of the switch circuit T(n-1) in the power module SM(n-1) is connected to the first terminal 131 of the capacitor C1(n-1). The electric energy transfer circuit between the capacitor C1n in the power module SMn and the capacitor C1(n-1) in the power module SM(n-1) is: from the first terminal 131 of the capacitor C1n in the power module SMn, through the first terminal An of the second port of the switch circuit Tn in the power module SMn, the first switch device Q1n in the switch circuit Tn in the power module SMn, the first terminal A(n-1) of the second port of the switch circuit T(n-1) in the power module SM(n-1), the capacitor C1(n-1) in the power module SM(n-1) and the first diode D1(n-1), back to the second terminal 132 of the capacitor C1n in the power module SMn, by controlling the first switch device Q1n in the switch circuit Tn in the power module SMn to be turned on, the power module SMn outputs a zero level, forming an energy transfer circuit, thereby realizing the charging of the capacitor C1n in the power module SMn to the capacitor C1(n-1) in the power module SM(n-1).

[0051] like Figure 6As shown, the power unit 10 in the power module SM(n-1) and the power unit 10 in the power module SM(n-2) are connected in series, the second terminal 132 of the capacitor C1(n-1) in the module SM(n-1) is connected to the cathode of the first diode D1(n-2), and the second terminal 132 of the capacitor C1(n-2) in the module SM(n-2) is connected to the anode of the first diode D1(n-2). The first terminal A(n-1) of the second port of the switch circuit T(n-1) in the power module SM(n-1) is connected to the first terminal 131 of the capacitor C1(n-1), and the first terminal A(n-2) of the second port of the switch circuit T(n-2) in the power module SM(n-2) is connected to the first terminal 131 of the capacitor C1(n-2). The power transfer circuit between the capacitor C1(n-1) in the module SM(n-1) and the capacitor C1(n-2) in the module SM(n-2) is (not shown in the figure): from the first terminal 131 of the capacitor C1(n-1) in the module SM(n-1), through the first terminal A(n-1) of the second port in the switch circuit T(n-1) in the module SM(n-1), the first switch device Q1(n-1) in the switch circuit T(n-1) in the module SM(n-1), the first terminal A(n-1) of the second port in the switch circuit T(n-2) in the module SM(n-2), and the first terminal Q2(n-1) of the second port in the switch circuit T(n-2) in the module SM(n-2). A terminal A(n-2), the capacitor C1(n-2) in the module SM(n-2) and the first diode D1(n-2), return to the second terminal 132 of the capacitor C1(n-1) in the module SM(n-1), and through the first switching device Q1(n-1) in the switching circuit T(n-1) in the control module SM(n-1) is turned on, the power module SM(n-1) outputs a zero level, forming an energy transfer loop, thereby realizing the charging of the capacitor C1(n-1) in the module SM(n-1) to the capacitor C1(n-2) in the power module SM(n-2).

[0052] By analogy, the capacitor C1(n-2) in the power module SM(n-2) charges the capacitor C1(n-3) in the power module SM(n-3), until the capacitor C12 in the power module SM2 charges the capacitor C11 in the power module SM1, so that the capacitor 130 in each power module 100 is fully charged, and each capacitor 130 supplies power to the auxiliary power supply unit 120 in the power module 100, and the auxiliary power supply unit 120 then supplies power to the controller or other circuits.

[0053] In this embodiment, the controller sequentially controls the second switching device Q1n in the power unit SMn to turn on, the second switching device Q1(n-1) in the power unit SM2 to turn on, and so on, and the second switching device Q12 in the power unit SM2 to turn on, to ensure that electric energy is sequentially transferred from the capacitor C1n in the power unit SMn to the capacitor C11 in the power unit SM1.

[0054] Embodiment 3

[0055] The power units 10 of the multiple power modules 100 in the power conversion system can use different power conversion circuits. Figure 4A The structure shown in FIG. 1 is that the power unit 10 in the power conversion system has another structure as follows: Figure 4C Taking the structure shown as an example, the following describes the process of the capacitor 130 of the power module SM1 transferring electric energy to the capacitor 130 in the power module SMn step by step.

[0056] like Figure 7 As shown, power modules SM1, SM3 to SMn are Figure 4A The power module SM2 is Figure 4C The structure shown. The power transfer from capacitor C11 in power module SM1 to capacitor C12 in power module SM2, the power transfer from capacitor C13 in power module SM3 to capacitor C1n in power module SMn and Figure 5 The same as in . No further description is given here.

[0057] The power transfer between the capacitor C12 in the power module SM2 and the capacitor C13 in the power module SM3 is specifically as follows: the second terminal 132 of the capacitor C12 in the power module SM2 is connected to the anode of the first diode D12, and the second terminal 132 of the capacitor C13 in the power module SM3 is connected to the cathode of the first diode D12. The first terminal B2 of the second port of the switch circuit T2 in the power module SM2 is connected to the first terminal 131 of the capacitor C12, and the first terminal B3 of the second port of the switch circuit T3 in the power module SM3 is connected to the first terminal 131 of the capacitor C13. The electric energy transfer circuit between the capacitor C12 in the power module SM2 and the capacitor C13 in the power module SM3 is: from the second terminal 132 of the capacitor C12 in the power module SM2, through the first diode D12, the capacitor C13 in the power module SM3, the first terminal B3 of the second port of the switch circuit T3 in the power module SM3, the first switch device Q12 and the third switch device Q32 in the switch circuit T2 in the power module SM2, and the first terminal B2 of the second port of the switch circuit T2 in the power module SM2, back to the first terminal 131 of the capacitor C12 in the power module SM2, by controlling the first switch device Q12 and the third switch device Q32 in the switch circuit T2 in the power module SM2 to be turned on or the second switch device Q22 and the fourth switch device Q42 to be turned on, the power module SM2 outputs a zero level, forming an energy transfer circuit, thereby realizing charging of the capacitor C13 in the power module SM3 from the capacitor C12 in the power module SM2.

[0058] Embodiment 4

[0059] A part of the power module 10 in the power conversion system has the following structure: Figure 4B The structure shown in FIG. 1 is that the power module 10 in the power conversion system has another structure as follows: Figure 4C Taking the structure shown as an example, the following describes the process of the capacitor 130 of the power module SMn transferring electric energy to the capacitor 130 in the power module SM1 step by step.

[0060] like Figure 8 As shown, power module SMn, power module SM(n-2) to power module SM1 are Figure 4B The power module SM(n-1) is Figure 4C The structure shown. The power transfer from capacitor C1n in power module SMn to capacitor C1(n-1) in power module SM(n-1), the power transfer from capacitor C1(n-2) in power module SM(n-2) to capacitor C11 in power module SM1 and Figure 6 The same as in . No further description is given here.

[0061] The power transfer between the capacitor C1(n-1) in the power module SM(n-1) and the capacitor C1(n-2) in the power module SM(n-2) is specifically as follows: the second terminal of the capacitor C1(n-1) in the power module SM(n-1) is connected to the cathode of the first diode D1(n-2), and the second terminal of the capacitor C1(n-2) in the power module SM(n-2) is connected to the anode of the first diode D1(n-2). The second terminal A(n-1) of the second port of the switch circuit T(n-1) in the power module SM(n-1) is connected to the first terminal 131 of the capacitor C1(n-1), and the second terminal A(n-2) of the second port of the switch circuit T(n-2) in the power module SM(n-2) is connected to the first terminal 131 of the capacitor C1(n-2). The power transfer circuit between the capacitor C1(n-1) in the power module SM(n-1) and the capacitor C1(n-2) in the power module SM(n-2) is: from the first terminal 131 of the capacitor C1(n-1) in the power module SM(n-1), through the second terminal A(n-1) of the second port in the switch circuit T(n-1) in the power module SM(n-1), the second switch device Q2(n-1) and the fourth switch device Q4(n-1) in the switch circuit T(n-1) in the power module SM(n-1), the second terminal A(n-2) of the second port of the switch circuit T(n-2) in the power module SM(n-2), the power module S The capacitor C1(n-2) and the first diode D1(n-2) in M(n-2) return to the second terminal 132 of the capacitor C1(n-1) in the power module SM(n-1), and by controlling the first switch device Q1(n-1) and the third switch device Q3(n-1) or the second switch device Q2(n-1) and the fourth switch device Q4(n-1) in the switch circuit T(n-1) in the power module SM(n-1) to be turned on, the power module SM(n-1) outputs a zero level to form a first energy transfer loop, thereby realizing charging of the capacitor C1(n-1) in the power module SM(n-1) to the capacitor C1(n-2) in the power module SM(n-2).

[0062] In the above technical solution, the power conversion system includes a first module, a second module and a first diode. The first module includes a first switch circuit, a first auxiliary power supply unit, a first capacitor and a second capacitor. The first port of the first switch circuit is connected in parallel with the second capacitor, the first port of the first auxiliary power supply unit is connected in parallel with the first capacitor, and the first capacitor is used to charge the auxiliary power supply unit. The second module includes a second switch circuit, a second auxiliary power supply unit, a third capacitor and a fourth capacitor. The first port of the second switch circuit is connected in parallel with the fourth capacitor, the second auxiliary power supply unit is connected in parallel with the third capacitor, and the third capacitor is used to charge the auxiliary power supply unit 120. The first terminal of the first capacitor is connected to the first terminal of the second port of the first switch circuit, the first terminal of the third capacitor is connected to the first terminal of the second port of the second switch circuit, the second port of the first switch circuit in the first module is connected in series with the second port of the second switch circuit in the second module, and the two ends of the first diode 210 are connected to the first capacitor and the third capacitor respectively. By such a setting, an electric energy transfer loop of the first capacitor and the third capacitor is formed between the first module and the second module. After the first capacitor is charged, the first capacitor can charge the third capacitor through the electric energy transfer loop. It should be noted that the path of the energy transfer circuit is not limited to the above-mentioned embodiments. Depending on the different switching circuits used in the power unit 10, an energy circuit between the first capacitor of the first module and the third capacitor of the second module can be formed by opening and closing different switching devices in the switching circuit.

[0063] In addition, it should be noted that even if a power unit 10 fails during the energy transfer process and is bypassed or stops running and enters a redundant state, the electric energy can still be guaranteed to be transferred in the capacitors 130 of each power module 100. Figure 5 Taking the power conversion system shown in as an example, the power unit SM2 fails, for example, any one of the first switch device Q12 and the second switch device Q22 of the power unit SM2 fails, and the power module SM2 is put into the bypass state by closing the bypass switch K32.

[0064] The energy transfer process between capacitor C11 in power module SM1 and capacitor C1n in power module SMn is as follows: Fig. 9 and Fig.10 As shown:

[0065] like Fig. 9As shown, the second switch device Q21 in the power unit SM1 is controlled to be turned on, so that the capacitor C11 in the power unit SM1 transfers electric energy to the capacitor C12 in the power unit SM2 through the first energy transfer loop, and the capacitor C11 in the power unit SM1 transfers electric energy to the capacitor C13 in the power unit SM3 through the second energy transfer loop. At the same time, the capacitor C12 in the power unit SM2 transfers electric energy to the capacitor C13 in the power unit SM3 through the third energy transfer loop.

[0066] The first energy transfer circuit is: the second terminal 132 of the capacitor C11 in the power module SM1 passes through the first diode D11, the capacitor C12, the first terminal B2 of the second port of the switch circuit T2 in the power module SM2, the second switch device Q21 of the switch circuit T1 in the power module SM1, and the first terminal B1 of the second port of the switch circuit T1 in the power module SM1, and returns to the first terminal of the capacitor C11, so that the capacitor C11 in the power module SM1 charges the capacitor C12 in the power module SM2.

[0067] The second energy transfer circuit is: the second end 132 of the capacitor C11 in the power module SM1 passes through the first diode D11, the first diode D12, the capacitor C13 in the power module SM3, the first terminal B3 of the second port of the switch circuit T3 in the power module SM3, the bypass switch K32, and the second switch device Q21 of the switch circuit T1 in the power module SM1, and returns to the first terminal 131 of the capacitor C11, so that the capacitor C11 charges the capacitor C13.

[0068] The third energy transfer circuit (not shown) is: the second terminal 132 of capacitor C12 in power module SM2 also passes through the first diode D13, capacitor C13 in power module SM3, the first terminal B3 of the second port of the switch circuit T3 in power module SM3 and the bypass switch K32, and returns to the first terminal of capacitor C12, so that capacitor C12 charges capacitor C13.

[0069] like Fig.10 As shown, the second switch device Q23 in the power unit SM3 is controlled to be turned on, so that the capacitor C12 in the power unit SM2 transfers electric energy to the capacitor C14 in the power unit SM4 through the fourth energy transfer circuit, and the capacitor C13 in the power unit SM3 transfers electric energy to the capacitor C14 in the power unit SM4 through the fifth transmission path.

[0070] The fourth energy transfer circuit is: the second terminal 132 of the capacitor C12 in the power module SM2 passes through the first diode D12, the first diode D13, the capacitor C14 in the power module SM4, the first terminal B4 of the second port in the switch circuit T4 in the power module SM4, the second switch device Q23 in the switch circuit T3 in the power module SM3, the first terminal B3 of the second port of the switch circuit T3 in the power module SM3, the bypass switch K32, and the second terminal B2 of the second port of the switch circuit T2 in the power module SM2, and returns to the first terminal of the capacitor C12, so that the capacitor C12 in the power module SM2 charges the capacitor C14 in the power module SM4.

[0071] The fifth energy transfer circuit is: the second terminal 132 of the capacitor C13 in the power module SM3 passes through the first diode D13, the capacitor C14 in the power module SM4, the first terminal B4 of the second port in the switch circuit T4 in the power module SM4, the second switch device Q23 in the switch circuit T3 in the power module SM3, the first terminal B3 of the second port of the switch circuit T3 in the power module SM3, and returns to the first terminal 131 of the capacitor C13, so that the capacitor C13 in the power module SM3 charges the capacitor C14 in the power module SM4.

[0072] The energy transfer between capacitor C14 and capacitor C1n is Figure 5 The same as in, no further description is given here.

[0073] Similar to the energy transfer principle of the capacitor 130 in each power module after a module failure occurs during the power establishment process of the auxiliary power supply system in the power conversion system, after the power establishment of the auxiliary power supply system is completed, the power conversion system enters a normal operating state. If SM2 exits operation and enters a redundant state through the bypass switch K32 during normal operation, the power unit in the power module SM1 and the power unit in the power module SM3 are cascaded, and the capacitor C12 in the power module SM2 can still be continuously charged.

[0074] Embodiment 5

[0075] Before the overall power supply of the auxiliary power supply system is established, the capacitor 130 of each power module is not charged. To establish the circuit of the auxiliary power supply system, the power conversion system may further include a power supply unit 200 .

[0076] like Figure 5 and Figure 7As shown, in the first and third embodiments, the power supply unit 200 is connected to the capacitor C11 in the power module SM1, and the power supply unit 200 is used to charge the capacitor C11. The capacitor C11 in the power module SM1 charges the capacitor C12 in the power module SM2, and the capacitor C12 in the power module SM2 charges the capacitor C13 in the power module SM3, and so on, so as to realize the energy transfer from the capacitor C11 in the power module SM1 to the capacitor C12 in the power module SMn.

[0077] like Figure 6 and Figure 8 As shown, in the second embodiment and the fourth embodiment, the power supply unit 200 is connected to the capacitor C1n in the power module SMn, and the power supply unit 200 is used to charge the capacitor C1n. The capacitor C1n in the power module SMn charges the capacitor C1(n-1) in the power module SM(n-1), and the capacitor C1(n-1) in the power module SM(n-1) charges the capacitor C1(n-2) in the power module SM(n-2), and so on, so as to realize the energy transfer from the capacitor C1n in the power module SMn to the capacitor C11 in the power module SM1.

[0078] Embodiment 6

[0079] The power conversion system further includes a plurality of power supply units 200 , each of which is connected to a capacitor 130 in a power module 100 , and each of which corresponds to a different power module 100 .

[0080] like Fig.11 As shown, it is Figure 5 The difference of the power conversion system shown is that the power conversion system includes two power modules 200. The first power module 200 is connected to C11 in the power module SM1, and the first power module 200 charges the capacitor C11 in the power module SM1, and the capacitor C11 in the power module SM1 charges the capacitor C12 in the power module SM2 through the power energy transfer circuit, and the capacitor C12 in the power module SM2 charges the capacitor C13 in the power module SM3 through the power energy transfer circuit, and so on, the capacitor C1(n-1) in the power module SM(n-1) charges the capacitor C1n in the power module SMn through the power energy transfer circuit.

[0081] The second power module 200 charges the capacitor C1m in the power module SMm, and the capacitor C1m in the power module SMm charges the capacitor C1(m+1) in the power module SM(m+1) through the power transfer circuit. And so on, the capacitor C1(n-1) in the power module SM(n-1) charges the capacitor C1n in the power module SMn through the power transfer circuit.

[0082] That is, the electric energy of the first power module 200 is transferred from the capacitor C11 in the power module SM1 to the capacitor C1n in the power module SMn. The electric energy of the first power module 200 is transferred from the capacitor C1m in the power module SMm to the capacitor C1n in the power module SMn. By setting it in this way, the energy transfer in the capacitors 130 in each power module 100 can be accelerated.

[0083] In this embodiment, when the power conversion system has multiple power supply units 200, the switch devices in the power modules 100 connected to the power supply units 200 can be turned on at the same time, so that the switch circuit 110 in the power module 100 outputs a zero level, so that the energy in the multiple power supply units 200 is transmitted simultaneously, and the energy transmission rate is accelerated. More specifically, when the power conversion system includes two power supply units 200, the controller can simultaneously make the two power modules output a zero level, for example: first turn on the second switch device Q21 of the switch circuit T1 in the power module SM1 and the second switch device Q2m of the switch circuit Tm in the power module SMm, then turn on the second switch device Q22 of the switch circuit T2 in the power module SM2 and the second switch device Q2(m+1) of the switch circuit T(m+1) in the power module SM(m+1), and so on.

[0084] Therefore, by setting at least one power supply unit 200 to charge the first capacitor or the third capacitor in the first module or the second module, the initial energy is provided for the establishment of the power supply of the auxiliary power supply system, so as to realize the power supply of a single power supply to loads with different ground potentials. In a power conversion system in which at least two power modules are cascaded, an energy transfer circuit is formed by adding a first diode, a first capacitor and a third capacitor and a switch circuit in the power unit, and the first capacitor and the third capacitor respectively supply power to the auxiliary power supply units of the first module and the second module, without the need to set an industrial frequency transformer in each power module 100 for the auxiliary power supply unit to take power, so that the power module volume is reduced, which is beneficial to the power modularization of the power conversion system, and the charging circuit is constructed by the main power circuit of the power module to simplify the circuit structure and reduce the manufacturing cost of the power module. Since the power supply capacitor of the auxiliary power supply unit is set separately from the capacitor of the power unit 10, when the power unit 10 fails, the auxiliary power supply unit 120 in each power module 100 can still be guaranteed to be continuously powered, thereby ensuring the reliability of the auxiliary power supply.

[0085] Embodiment 7

[0086] The power conversion system may also include a plurality of second diodes 220, each second diode 220 connecting the power modules where any two cascaded power units are located. The power modules where any two power units 10 connected in series are located are referred to as the first module and the second module. The capacitor 130 in the first module is referred to as the first capacitor, the auxiliary power supply unit 120 in the first module is referred to as the first auxiliary power supply unit, the switch circuit 110 in the first module is referred to as the first switch circuit, and the capacitor 140 in the first module is referred to as the second capacitor. The capacitor 130 in the second module is referred to as the third capacitor, the auxiliary power supply unit 120 in the second module is referred to as the second auxiliary power supply unit, the switch circuit 110 in the second module is referred to as the second switch circuit, and the capacitor 140 in the second module is referred to as the fourth capacitor.

[0087] One end of the second diode 220 is connected to the first capacitor, and the other end of the second diode 220 is connected to the third capacitor, so that the first capacitor, the second diode 220 and the third capacitor are connected in series in sequence to form a first branch, and the two ends of the first branch are respectively electrically coupled to the positive and negative poles of the DC bus Ubus, so that the DC bus Ubus charges the first capacitor and the third capacitor through the first branch.

[0088] like Fig.12 The power conversion system shown is Figure 5 The power conversion system shown is different in that Figure 5 In the power conversion system shown, a second diode 220 is added between two power modules 100. To ensure that the first branch is connected to the positive pole of the DC bus Ubus, a second diode 220 is added between the second terminal A of the DC port of the power conversion system and the power module SMn.

[0089] The first terminal 131 of the capacitor C11 in the power module SM1 is connected to the second terminal B of the DC port of the power conversion system, the second terminal 132 of the capacitor C11 in the power module SM1 is connected to the cathode of the second diode D21, and the first terminal 131 of the capacitor C12 in the power module SM2 is connected to the anode of the second diode D21. The second terminal 132 of the capacitor C12 in the power module SM2 is connected to the cathode of the second diode D22, and the first terminal 131 of the capacitor C13 in the power module SM3 is connected to the anode of the second diode D22. By analogy, the second terminal 132 of the capacitor C(n-1) in the power module SM(n-1) is connected to the cathode of the second diode D2(n-1), and the first terminal 131 of the capacitor Cn in the power module SMn is connected to the anode of the second diode D2(n-1). The second terminal 132 of the capacitor C1n in the power module SMn is connected to the cathode of the second diode D2n, and the second terminal A of the DC port of the power conversion system is connected to the anode of the second diode D2n. Through such an arrangement, a first branch is formed by the second diode D2n, capacitor C1n, second diode D2(n-1), capacitor C1(n-1),..., second diode D23, capacitor C13, second diode D22, capacitor C12, second diode D21 and capacitor C11. When the circuit breaker between the DC port of the DC conversion system and the positive and negative poles of the DC bus Ubus is closed, the DC bus Ubus can charge the capacitors 130 in each power module 100 through the first branch.

[0090] Embodiment 8

[0091] like Fig.13 The power conversion system shown is Figure 6 The power conversion system shown is different in that Figure 6 A second diode 220 is added between the two power modules 100 in the power conversion system shown. To ensure that the first branch is coupled to the negative pole of the DC bus Ubus, a second diode 220 is added between the first terminal B of the DC port of the power conversion system and the power module SM1.

[0092] The first terminal 131 of the capacitor C1n in the power module SMn is connected to the second terminal A of the DC port of the power conversion system, the second terminal 132 of the capacitor C1n in the power module SMn is connected to the anode of the second diode D2n, and the first terminal 131 of the capacitor C1(n-1) in the power module SM(n-1) is connected to the cathode of the second diode D2n. The second terminal 132 of the capacitor C1(n-1) in the power module SM(n-1) is connected to the anode of the second diode D2(n-1), and the first terminal 131 of the capacitor C1(n-2) in the power module SM(n-2) is connected to the cathode of the second diode D2(n-1). By analogy, the second terminal 132 of the capacitor C12 in the power module SM2 is connected to the anode of the second diode D22, and the first terminal 131 of the capacitor C11 in the power module SM1 is connected to the cathode of the second diode D22. The second terminal 132 of the capacitor C11 in the power module SM1 is connected to the anode of the second diode D21, and the first terminal B of the DC port of the power conversion system is connected to the cathode of the second diode D21. Through such an arrangement, a first branch is formed by the capacitor C1n, the second diode D2n, the capacitor C1(n-1), the second diode D2(n-1),..., the capacitor C13, the second diode D23, the capacitor C12, the second diode D22, the capacitor C11 and the second diode D21. When the circuit breaker between the DC port of the DC conversion system and the positive and negative poles of the DC bus Ubus is closed, the DC bus Ubus can charge the capacitors 130 in each power module 100 through the first branch.

[0093] In the above technical solution, by adding a second diode, a first branch is formed between the second diode and the capacitor 130. After the power conversion system is connected to the DC bus, the capacitor 130 in the power module put into operation is charged by the DC bus. In the case of a large load on the power conversion system, the charging rate of the capacitor 130 can be increased on the basis of charging the capacitor 130 in the form of an energy transfer loop formed by the first diode, and the voltage balance of each capacitor 130 after being charged by energy transfer through the first diode is ensured.

[0094] Embodiment 9

[0095] like Fig.14 The power conversion system shown is Fig.12The difference of the power conversion system shown is that at least part of the power modules 100 can also include an energy storage unit 150, and the energy storage unit 150 is connected in parallel with the capacitor 140. The second port of the auxiliary power supply unit 120 is connected in parallel with the energy storage unit 150. Through such a configuration, the output end of the auxiliary power supply unit 120 in each power module 100 can draw power from the energy storage unit 150, adding a power supply path, and increasing the reliability of the auxiliary power supply unit 120 in external power supply. The energy storage unit 150 can be but not limited to an energy storage battery, etc. More specifically, before the power supply of the auxiliary power supply system is established and the power supply unit 200 is not connected or is not available, the energy storage unit 150 can charge the capacitor 130 of each power module 100 to establish the power supply of its own auxiliary power supply unit, thereby ensuring reliable startup of the power conversion system.

[0096] Embodiment 10

[0097] like Fig.14 In the power conversion system shown in FIG. 1 , each auxiliary power supply unit 120 includes a third diode 230. FIG. 15A to FIG. 15D As shown, the third diode 230 is connected in series between the second port of the auxiliary power supply unit 120 and the output end of the auxiliary power supply unit 120 .

[0098] like Fig.15A As shown, the anode of the third diode 230 is connected to the positive electrode of the second port of the auxiliary power supply unit 120, the cathode of the third diode 230 is connected to the positive electrode of the output end of the auxiliary power supply unit 120, and the cathode of the third diode 230 is connected to the positive electrode of the first port of the auxiliary power supply unit 120. One terminal of the first port of the auxiliary power supply unit 120 is the positive electrode of the first port of the auxiliary power supply unit 120, one terminal of the second port of the auxiliary power supply unit 120 is the positive electrode of the second port of the auxiliary power supply unit 120, and one end of the output end of the auxiliary power supply unit 120 is the output positive electrode of the auxiliary power supply unit 120. Due to the unidirectional conductivity of the diode, when the voltage of the first port of the auxiliary power supply unit 120 is greater than the voltage of the second port of the auxiliary power supply unit 120, the third diode 230 blocks the energy in the energy storage unit 150 from being transferred to the auxiliary power supply unit 120. When the voltage of the first port of the auxiliary power supply unit 120 is less than the voltage of the second port of the auxiliary power supply unit 120, the third diode 230 enables the energy in the energy storage unit 150 to be transferred to the auxiliary power supply unit 120. By such configuration, the priority of controlling the capacitor 130 to provide electric energy to the auxiliary power supply unit 120 and the energy storage unit 150 to provide electric energy to the auxiliary power supply unit 120 is achieved.

[0099] like FIG. 15B to FIG. 15DAs shown, when the voltage at the first port and / or the voltage at the second port of the auxiliary power supply unit 120 is not equal to the voltage required by the auxiliary power supply, it is necessary to adjust the voltage through the power conversion unit, and then provide power to the controller in the power conversion system or other circuits through the output end of the auxiliary power supply unit. The auxiliary power supply unit 120 of each power module 100 may also include at least one power conversion unit 122.

[0100] like Fig. 15B As shown, the first auxiliary power supply unit 120 includes a power conversion unit 122, a first port of the power conversion unit 122 is connected to the output end of the first auxiliary power supply unit 120, and a second port of the power conversion unit 122 is connected to the second port of the first auxiliary power supply unit 120. The power conversion unit 122 is used to achieve matching between the second port voltage of the auxiliary power supply unit 120 and the output end voltage of the auxiliary power supply unit 120. The third diode 230 is connected in series between the output end of the first auxiliary power supply unit 120 and the first port of the power conversion unit 122.

[0101] More specifically, the anode of the third diode 230 is connected to the positive electrode of the first port of the power conversion unit 122, the cathode of the third diode 230 is connected to the positive electrode of the output terminal of the auxiliary power supply unit 120, and one terminal of the first port of the power conversion unit 122 is the positive electrode of the first port of the power conversion unit 122. When the voltage at the output terminal of the auxiliary power supply unit 120 is greater than the voltage at the second port of the power conversion unit 122, the third diode 230 blocks the energy in the energy storage unit 150 from being transferred to the auxiliary power supply unit 120. When the voltage at the output terminal of the auxiliary power supply unit 120 is less than the voltage of the power conversion unit 122, the third diode 230 enables the energy in the energy storage unit 150 to be transferred to the auxiliary power supply unit 120.

[0102] like Fig. 15C As shown, the first auxiliary power supply unit 120 includes a power conversion unit 122, the first port of the power conversion unit 122 is connected to the first port of the first auxiliary power supply unit 120, the second port of the power conversion unit 122 is connected to the output end of the first auxiliary power supply unit 120, and the power conversion unit 122 is used to achieve matching between the first port voltage of the auxiliary power supply unit 120 and the output end voltage of the auxiliary power supply unit 120. The third diode 230 is connected in series between the output end of the first auxiliary power supply unit 120 and the second port of the first auxiliary power supply unit 120. The conduction principle of the third diode 230 is the same as Fig.15A Similar, no further description is given here.

[0103] like Fig.15DAs shown, the first auxiliary power supply unit 120 includes two power conversion units, namely a first power conversion unit and a second power conversion unit. The first port of the first power conversion unit is connected to the first port of the first auxiliary power supply unit 120, and the second port of the first power conversion unit is connected to the output end of the first auxiliary power supply unit 120. The power conversion unit is used to achieve matching between the first port voltage of the auxiliary power supply unit 120 and the output end voltage of the auxiliary power supply unit 120. The first port of the second power conversion unit is connected to the output end of the first auxiliary power supply unit 120, and the second port of the second power conversion unit is connected to the second port of the first auxiliary power supply unit 120. The power conversion unit is used to achieve matching between the second port voltage of the auxiliary power supply unit 120 and the output end voltage of the auxiliary power supply unit 120. The third diode 230 is connected in series between the output end of the first auxiliary power supply unit 120 and the first port of the second power conversion unit. The conduction principle of the third diode 230 is the same as Fig. 15B Similar, no further description is given here.

[0104] Embodiment 11

[0105] like FIG. 15B to FIG. 15D As shown, each auxiliary power supply unit 150 may further include a capacitor 121, which is connected to the output end of the auxiliary power supply unit 150 and is used to stabilize the voltage at the output end of the auxiliary power supply unit 150. FIG. 15B to FIG. 15D Similarly, capacitor 121 can also be used for Fig.15A The embodiment shown. Fig. 15B For example, the capacitor C3i in the power module SMi is connected in parallel with the capacitor C1i, i is a positive integer, 1≤i≤n, and the capacitor C3i can provide power to the controller in the power conversion system, or provide power to other circuits to form redundancy of the capacitor C1i.

[0106] Embodiment 12

[0107] like FIG. 15A to FIG. 15D As shown, each power module 100 may also be provided with a power sensor 160 for detecting the remaining charge of the energy storage unit 150 in the power module 100. Since the auxiliary power supply unit 120 draws power from the energy storage unit 150, a power sensor 160 is added to each power module 100 to detect the remaining charge of the energy storage unit 150 in real time, so as to prevent the calculation error of the state of charge (SOC) of the energy storage unit 150 caused by the discharge of the battery to the auxiliary power supply unit 120, thereby affecting the battery life and causing economic losses.

[0108] Embodiment 13

[0109] like Fig.16As shown, after the capacitors 130 of each power module 100 in the power conversion system are powered on, each capacitor 130 supplies power to the corresponding auxiliary power supply unit 120, so that the auxiliary power supply unit 120 supplies power to the controller in the power module 100, so that the power unit 10 in each power module 100 is put into power conversion, or exits the working state and enters redundancy. In order to increase the working reliability of each power module 100, the controller in each power module 100 can also draw power from the auxiliary power supply unit 120 in the adjacent power module 100, that is, when an auxiliary power supply unit 120 fails, the controller of the corresponding failed power module 100 can also draw power from the auxiliary power supply unit 120 of the adjacent power module 100.

[0110] During the operation of the cascaded power conversion system, it is very common for the power module 100 to be bypassed. For example, when the power module 100 includes an energy storage unit 150, if the voltage of the energy storage unit 150 after cascading is greater than the DC bus voltage, part of the power module 100 will be bypassed to balance the voltage, or when the charging and discharging speed of the energy storage unit 150 is uneven, the power module 100 with a faster charging and discharging speed of the energy storage unit 150 will be bypassed first. By setting the first diode 210 to form an energy transfer loop of the capacitor 130 in the auxiliary power supply system, the capacitor 130 of the power module 100 in the bypass state can be charged, and when the power module SM1 at the first stage of energy transfer is bypassed, the energy of the capacitor 130 in the power module SM1 can still come from the power supply unit 200 connected thereto, thereby ensuring the reliability of the operation of the auxiliary power supply system of the bypassed power module 100.

[0111] In some cases, such as when the cascade power conversion system is shut down for maintenance, its DC port is disconnected from the DC bus, and the auxiliary power supply system can still obtain power through the power supply unit 200, thereby ensuring that the bypass switch can be operated to ensure the safety of the operator. In the startup phase of the cascade power conversion system, when it has not yet been connected to the DC bus and the auxiliary power supply system does not have the power supply unit 200, the auxiliary power supply unit 120 can be connected to the capacitor 130 or the energy storage unit 150 of the power module 100 to start all power modules 100, so as to achieve a reliable system startup standby. After the auxiliary power supply module of the cascade system obtains electric energy, the bypass switches of all power modules 100 can be controlled to be turned on, so that the power supply unit 200 can charge the capacitors 130 of all power modules 100 at the same time, so as to realize the rapid power-on of the auxiliary power supply system. At the same time, when the second diode 210 is used to connect the capacitors 130 of each power module 100 to the DC bus for charging, it is suitable for scenes with large power requirements of the auxiliary power supply load, and the voltage balancing of each capacitor 130 can be achieved.

[0112] Embodiment 14

[0113] like Figures 17A to 17D As shown, some embodiments of the present application also provide a power conversion module, the power conversion module includes a power module 100 and a first diode 210, and the first diode 210 is connected to the power module. The power module includes a switch circuit 110, an auxiliary power supply unit 120, a capacitor 130 and a capacitor 140, the first port of the switch circuit 110 is connected in parallel with the capacitor 140, the first port of the auxiliary power supply unit 120 is connected in parallel with the capacitor 130, the capacitor 130 is used to charge the auxiliary power supply unit 120, and the first terminal 131 of the capacitor 130 is connected to the first terminal of the second port of the switch circuit 110. Fig.17A and Fig. 17B As shown, the anode of the first diode 120 is connected to the second terminal 132 of the capacitor 130, as shown in FIG. Fig. 17C and Fig.17D As shown, the cathode of the first diode 120 is connected to the second terminal 132 of the capacitor 130 .

[0114] In other embodiments, FIG. 18A to FIG. 8 As shown in FIG. 1 , the power conversion module may further include a second diode 220 connected to the power module 100. Figure 4A The circuit shown in Fig.18A As shown, the anode of the first diode 210 is connected to the second terminal 132 of the capacitor 130, and the anode of the second diode 220 is connected to the first terminal 131 of the capacitor 130. Fig.18B As shown, the anode of the first diode 210 is connected to the second terminal 132 of the capacitor 130, and the cathode of the second diode 220 is connected to the second terminal 132 of the capacitor 130. Fig.18C As shown, the cathode of the first diode 210 is connected to the second terminal 132 of the capacitor 130, the anode of the second diode 220 is connected to the first terminal 131 of the capacitor 130, and the anode of the first diode 210 is connected to the cathode of the second diode 220. Fig.18D As shown, the cathode of the first diode 210 is connected to the second terminal 132 of the capacitor 130 , and the cathode of the second diode 220 is connected to the second terminal 132 of the capacitor 130 .

[0115] The switch circuit 110 is Figure 4B The circuit shown in Fig.18E As shown, the anode of the first diode 210 is connected to the second terminal 132 of the capacitor 130, the cathode of the second diode 220 is connected to the first terminal 131 of the capacitor 130, and the cathode of the first diode 210 is connected to the anode of the second diode 220. Fig.18F As shown, the anode of the first diode 210 is connected to the second terminal 132 of the capacitor 130, and the anode of the second diode 220 is connected to the second terminal 132 of the capacitor 130. Figure 18GAs shown, the cathode of the first diode 210 is connected to the second terminal 132 of the capacitor 130, and the cathode of the second diode 220 is connected to the first terminal 131 of the capacitor 130. Fig.18H As shown, the cathode of the first diode 210 is connected to the second terminal 132 of the capacitor 130 , and the anode of the second diode 220 is connected to the second terminal 132 of the capacitor 130 .

[0116] In some other embodiments, FIG. 17A to FIG. 17D ,as well as 18A to 18H As shown, the power conversion module also includes an energy storage unit 150, the energy storage unit 150 is connected in parallel with the capacitor 140, the second port of the auxiliary power supply unit 120 is connected in parallel with the energy storage unit 150, and the auxiliary power supply unit 12- includes a third diode, and the third diode is connected in series between the second port of the first auxiliary power supply unit and the output end of the first auxiliary power supply unit.

[0117] In some other embodiments, FIG. 17A to FIG. 17D ,as well as 18A to 18H As shown, the power conversion module further includes a power sensor 160 for detecting the remaining charge of the energy storage unit 150 in the power module 100 .

[0118] It should be noted that the structure of the auxiliary power supply unit 120 in the above embodiment is not limited to Figures 17A to 17D ,as well as 18A to 18H In the structure shown, the auxiliary power supply unit 120 can adopt any one of the structures of the above-mentioned embodiment ten, embodiment eleven and embodiment twelve.

[0119] In some embodiments, the first auxiliary power supply unit 120 includes a power conversion unit 122. A first port of the power conversion unit 122 is connected to an output end of the first auxiliary power supply unit 120, a second port of the power conversion unit 122 is connected to a second port of the first auxiliary power supply unit 120, and a third diode 230 is connected in series between the output end of the first auxiliary power supply unit 120 and the first port of the power conversion unit 122.

[0120] In some embodiments, the first port of the power conversion unit 122 is connected to the first port of the first auxiliary power supply unit 120, the second port of the power conversion unit 122 is connected to the output end of the first auxiliary power supply unit 120, and the third diode 230 is connected in series between the output end of the first auxiliary power supply unit 120 and the second port of the first auxiliary power supply unit 120.

[0121] In some embodiments, the first auxiliary power supply unit 120 includes a first power conversion unit 122 and a second power conversion unit 122; the first port of the first power conversion unit 122 is connected to the first port of the first auxiliary power supply unit 120, the second port of the first power conversion unit 122 is connected to the output end of the first auxiliary power supply unit 120, the first port of the second power conversion unit 122 is connected to the output end of the first auxiliary power supply unit 120, the second port of the second power conversion unit 122 is connected to the second port of the first auxiliary power supply unit 120, and the third diode 230 is connected in series between the output end of the first auxiliary power supply unit 120 and the first port of the second power conversion unit 122.

[0122] In some embodiments, each auxiliary power supply unit 150 includes a capacitor 121 , which is connected to an output terminal of the auxiliary power supply unit 150 , and is used to stabilize a voltage at the output terminal of the auxiliary power supply unit 150 .

[0123] The power conversion system described in the above embodiment can be formed by cascading power conversion modules of the same structure. FIG. 17A to FIG. 17D The structure shown is an example. The second port of the switch unit in one power conversion module is connected in series with the second port of the switch unit in the next power conversion module, the anode of the first diode 210 in one power conversion module is connected with the cathode of the first diode in the next power conversion module, and so on, to assemble the power conversion system described in the above embodiment. 18A to 18H The structure shown is FIG. 17A to FIG. 17D The difference between the structures shown is that the anode of the second diode 230 in one power conversion module needs to be connected to the cathode of the second diode in the next power conversion module to assemble the power conversion system described in the above embodiment.

[0124] In the above technical solution, each power unit can be auxiliary powered by only diodes, capacitors and a small amount of insulating components, which has a simple structure, low cost, and can be modularly designed, thereby solving the problems of low power density and high insulation requirements caused by the use of a large number of power frequency transformers or isolation transformers in the existing technical solutions. The power conversion system and power conversion module provided by the present application can be widely used in various modular and multi-level DC topology structures, with a voltage range from low voltage to medium voltage, and a wide range of applications. The structure is simple and the cost is low, which helps to improve the power density of the system. It can effectively combine the three types of power supply, low-voltage mains, energy storage unit and DC bus, has high power supply reliability, and effectively solves the power supply problem during operation and standby.

[0125] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the above embodiments can still be modified, or some or all of the technical features can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A power conversion system, characterized in that: include: At least two power modules and at least one first diode, the at least two power modules comprising a first module and a second module; The first module includes a first switch circuit, a first auxiliary power supply unit, a first capacitor and a second capacitor, wherein a first port of the first switch circuit is connected in parallel with the second capacitor, a first port of the first auxiliary power supply unit is connected in parallel with the first capacitor, the first capacitor is used to charge the first auxiliary power supply unit, and a first terminal of the first capacitor is connected to a first terminal of the second port of the first switch circuit; The second module includes a second switch circuit, a second auxiliary power supply unit, a third capacitor and a fourth capacitor, the first port of the second switch circuit is connected in parallel with the fourth capacitor, the second auxiliary power supply unit is connected in parallel with the third capacitor, the third capacitor is used to charge the second auxiliary power supply unit, and the first terminal of the third capacitor is connected to the first terminal of the second port of the second switch circuit; The second port of the first switch circuit in the first module is connected in series with the second port of the second switch circuit in the second module, and both ends of the first diode are connected to the first capacitor and the third capacitor respectively.

2. The power conversion system according to claim 1, characterized in that: Also includes: A controller is configured to control the corresponding switch of the first switch circuit in the first module to be turned on so that it outputs a zero level, so that the electric energy of the first capacitor of the first module is transferred to the third capacitor of the second module.

3. The power conversion system according to claim 1, characterized in that: The power conversion system further comprises: A power supply unit is connected to the first capacitor in the first module and / or the third capacitor in the second module.

4. The power conversion system according to claim 1, characterized in that: The power conversion system further comprises: The second diode, the first capacitor, the second diode and the third capacitor are sequentially connected in series to form a first branch, and two ends of the first branch are electrically coupled to the positive electrode and the negative electrode of a DC bus respectively.

5. The power conversion system according to claim 1, characterized in that: The second terminal of the first capacitor is connected to the anode of the first diode, and the second terminal of the third capacitor is connected to the cathode of the first diode.

6. The power conversion system according to claim 1, characterized in that: The second terminal of the first capacitor is connected to the cathode of the first diode, and the anode of the first diode is connected to the second terminal of the third capacitor.

7. The power conversion system according to claim 5, characterized in that: The second terminal of the first capacitor is connected to the cathode of the second diode, and the first terminal of the third capacitor is connected to the anode of the second diode.

8. The power conversion system according to claim 6, characterized in that: The second terminal of the first capacitor is connected to the anode of the second diode, and the first terminal of the third capacitor is connected to the cathode of the second diode.

9. The power conversion system according to claim 1, characterized in that: The first module also includes a first energy storage unit, and the first energy storage unit is connected in parallel with the second capacitor.

10. The power conversion system according to claim 9, characterized in that: The second port of the first auxiliary power supply unit is connected in parallel with the first energy storage unit. The first auxiliary power supply unit includes a third diode, which is connected in series between the second port of the first auxiliary power supply unit and the output end of the first auxiliary power supply unit.

11. The power conversion system according to claim 10, characterized in that: The first auxiliary power supply unit includes a power conversion unit, a first port of the power conversion unit is connected to the output end of the first auxiliary power supply unit, a second port of the power conversion unit is connected to the second port of the first auxiliary power supply unit, and the third diode is connected in series between the output end of the first auxiliary power supply unit and the first port of the power conversion unit; or The first auxiliary power supply unit includes a power conversion unit; a first port of the power conversion unit is connected to a first port of the first auxiliary power supply unit, a second port of the power conversion unit is connected to an output end of the first auxiliary power supply unit, and the third diode is connected in series between the output end of the first auxiliary power supply unit and the second port of the first auxiliary power supply unit; or The first auxiliary power supply unit includes a first power conversion unit and a second power conversion unit; the first port of the first power conversion unit is connected to the first port of the first auxiliary power supply unit, the second port of the first power conversion unit is connected to the output end of the first auxiliary power supply unit, the first port of the second power conversion unit is connected to the output end of the first auxiliary power supply unit, the second port of the second power conversion unit is connected to the second port of the first auxiliary power supply unit, and the third diode is connected in series between the output end of the first auxiliary power supply unit and the first port of the second power conversion unit.

12. The power conversion system according to claim 9, characterized in that: A power sensor is also provided in the first module for detecting the remaining charge of the first energy storage unit.

13. The power conversion system according to claim 1, characterized in that: The second ports of the first switch circuit and the second switch circuit further include a bypass switch respectively.

14. The power conversion system according to claim 1, characterized in that: The first switching circuit is a half-bridge circuit.

15. The power conversion system according to claim 1, characterized in that: The second switching circuit is a full-bridge circuit.

16. A power conversion module, characterized in that: include: a first module and a first diode connected to the first module; The first module includes a first switch circuit, a first auxiliary power supply unit, a first capacitor, a second capacitor and a first diode; The first port of the first switching circuit is connected in parallel with the second capacitor, the first port of the first auxiliary power supply unit is connected in parallel with the first capacitor, the first capacitor is used to charge the first auxiliary power supply unit, and the first terminal of the first capacitor is connected to the first terminal of the second port of the first switching circuit.

17. The power conversion module according to claim 16, characterized in that: Include any of the following: An anode of the first diode is connected to a second terminal of the first capacitor; A cathode of the first diode is connected to the second terminal of the first capacitor.

18. The power conversion module according to claim 16, characterized in that: The power conversion module also includes a second diode connected to the first module.

19. The power conversion module according to claim 18, characterized in that: Include any of the following: An anode of the first diode is connected to the second terminal of the first capacitor, and an anode of the second diode is connected to the first terminal of the first capacitor; An anode of the first diode is connected to the second terminal of the first capacitor, and a cathode of the second diode is connected to the second terminal of the first capacitor; The cathode of the first diode is connected to the second terminal of the first capacitor, the anode of the second diode is connected to the first terminal of the first capacitor, and the anode of the first diode is connected to the cathode of the second diode; A cathode of the first diode is connected to the second terminal of the first capacitor, and a cathode of the second diode is connected to the second terminal of the first capacitor.

20. The power conversion module according to claim 18, characterized in that: Include any of the following: An anode of the first diode is connected to the second terminal of the first capacitor, a cathode of the second diode is connected to the first terminal of the first capacitor, and a cathode of the first diode is connected to the anode of the second diode; An anode of the first diode is connected to the second terminal of the first capacitor, and an anode of the second diode is connected to the second terminal of the first capacitor; A cathode of the first diode is connected to the second terminal of the first capacitor, and a cathode of the second diode is connected to the first terminal of the first capacitor; A cathode of the first diode is connected to the second terminal of the first capacitor, and an anode of the second diode is connected to the second terminal of the first capacitor.

21. The power conversion module according to claim 16, characterized in that: The first module further includes a first energy storage unit, and the first energy storage unit is connected in parallel with the second capacitor; The second port of the first auxiliary power supply unit is connected in parallel with the first energy storage unit. The first auxiliary power supply unit includes a third diode, which is connected in series between the second port of the first auxiliary power supply unit and the output end of the first auxiliary power supply unit.

22. The power conversion module according to claim 21, characterized in that: The first auxiliary power supply unit includes a power conversion unit, a first port of the power conversion unit is connected to the output end of the first auxiliary power supply unit, a second port of the power conversion unit is connected to the second port of the first auxiliary power supply unit, and the third diode is connected in series between the output end of the first auxiliary power supply unit and the first port of the power conversion unit; or The first auxiliary power supply unit includes a power conversion unit; a first port of the power conversion unit is connected to a first port of the first auxiliary power supply unit, a second port of the power conversion unit is connected to an output end of the first auxiliary power supply unit, and the third diode is connected in series between the output end of the first auxiliary power supply unit and the second port of the first auxiliary power supply unit; or The first auxiliary power supply unit includes a first power conversion unit and a second power conversion unit; the first port of the first power conversion unit is connected to the first port of the first auxiliary power supply unit, the second port of the first power conversion unit is connected to the output end of the first auxiliary power supply unit, the first port of the second power conversion unit is connected to the output end of the first auxiliary power supply unit, the second port of the second power conversion unit is connected to the second port of the first auxiliary power supply unit, and the third diode is connected in series between the output end of the first auxiliary power supply unit and the first port of the second power conversion unit.

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