Power conversion system and control method

Abstract

The embodiment of the present application provides a kind of power conversion system and control method, power conversion system includes multiple power modules, each power module contains first port, second port and third port, wherein, the first port of each power module is connected with external device respectively, the second port of each power module is independent of each other, as independent port output power, the third port of each power module is connected in parallel to form a power bus, and, the power of the third port of each power module flows bidirectionally.Therefore, when the load of output port is unbalanced, the power bus formed by the third port in parallel realizes the power scheduling between multiple power modules, so that the power input by each power module through the first port is as equal as possible, reduce or eliminate the problem of DC link voltage sharing caused by load imbalance.

Description

Technical Field

[0001] The present invention relates to the field of charging technology, and in particular to a power conversion system and control method. Background Technology

[0002] As an application for charging electric vehicles with different input voltages and power levels, charging stations require a power supply architecture with high charging efficiency, multiple charging (isolation) ports, and a wide range of charging voltages.

[0003] Figure 1 This is a schematic diagram of a charging station power supply architecture based on a line frequency transformer (LFT), as shown below. Figure 1 As shown, LFT is used to achieve step-down and medium-voltage isolation. The first-stage AC-DC circuit is a controllable rectifier circuit. The second-stage isolation DC-DC circuit connected to the first-stage AC-DC circuit realizes the charging of the vehicle battery and the electrical isolation between vehicles.

[0004] However, power frequency transformers are not only large and bulky, but also have low charging efficiency due to excitation losses under no-load and light-load conditions. Therefore, power supply architectures based on solid-state transformers (SST) are being used more and more.

[0005] Figure 2 This is a schematic diagram of a charging station power supply architecture based on a solid-state transformer (SST), as shown below. Figure 2 As shown, a common DC bus architecture is adopted. The SST (Self-Propelled Controller Station) is directly connected to the medium-voltage AC power grid and provides a common DC bus. Multiple isolated DC-DC chargers are connected to the common DC bus to charge multiple electric vehicles simultaneously. The first stage of the SST is typically a CHB (Cascade H-Bridge), where each H-bridge is followed by a high-frequency isolated DC-DC circuit for medium-voltage isolation and voltage conversion. The outputs of the second-stage DC-DC circuits of the SST are connected in parallel to form the common DC bus. The multiple DC-DC chargers connected to the common DC bus need to use an isolated conversion topology to achieve vehicle-to-vehicle isolation. While this common DC bus SST power supply architecture uses high-frequency isolation instead of power frequency isolation to reduce size and weight, the repeated isolation from the medium-voltage power grid to the vehicle charging end results in multiple conversion stages. The more conversion stages, the lower the system efficiency and the higher the cost. Summary of the Invention

[0006] This invention provides a power conversion system and control method to achieve high-efficiency charging at multiple independent ports and overcome the DC-link imbalance problem caused by power imbalance at independent ports.

[0007] In a first aspect, embodiments of the present invention provide a power conversion system, comprising:

[0008] A first power module and a second power module, wherein each power module includes a first port, a second port and a third port;

[0009] The second ports of the first power module and the second power module are independent of each other;

[0010] The third ports of the first power module and the second power module are connected in parallel to form a power bus, and the power flows bidirectionally through the third port.

[0011] In some possible embodiments, the first ports of the first power module and the second power module are connected in series with each other and electrically connected to an external device.

[0012] In some possible embodiments, when the power of the second port of the first power module and the power of the second port of the second power module are not equal, the third port of the first power module and the third port of the second power module exchange power through the power bus, so that the power of the first port of the first power module and the power of the first port of the second power module tend to be equal.

[0013] In some possible embodiments, the second port of the first power module and the second port of the second power module respectively output power. When the power output by the second port of the first power module is less than the power output by the second port of the second power module, at least a portion of the input power of the first port of the first power module is transferred to the third port of the first power module, then through the power bus to the third port of the second power module, and finally to the second port of the second power module, so that the input power of the first port of the first power module and the input power of the first port of the second power module tend to be equal.

[0014] In some possible embodiments, the second port of the first power module and the second port of the second power module respectively input power. When the input power of the second port of the first power module is less than the input power of the second port of the second power module, at least a portion of the input power of the second port of the second power module is transferred to the third port of the second power module, then transferred to the third port of the first power module through the power bus, and finally transferred to the first port of the first power module, so that the output power of the first port of the first power module and the output power of the first port of the second power module tend to be equal.

[0015] In some possible embodiments, when the second port of the first power module is used to output power and the second port of the second power module is used to input power, at least a portion of the input power of the second port of the second power module is transmitted to the third port of the second power module, then transmitted to the third port of the first power module through the power bus, and finally transmitted to the second port of the first power module, so that the power of the first port of the first power module and the power of the first port of the second power module tend to be equal.

[0016] In some possible embodiments, both the first power module and the second power module include a first power submodule. The first power submodule includes a first terminal, a second terminal, and a third terminal. The first port is electrically connected to the first terminal of the first power submodule, the second port is electrically connected to the second terminal of the first power submodule, and the third port is electrically connected to the third terminal of the first power submodule. The first and second terminals of the first power submodule are DC terminals.

[0017] In some possible embodiments, the first power submodule includes a first DC-DC converter circuit and a second DC-DC converter circuit. A first terminal of the first power submodule is electrically connected to a first terminal of the first DC-DC converter circuit and a first terminal of the second DC-DC converter circuit. A second terminal of the first DC-DC converter circuit is electrically connected to a second terminal of the first power submodule. A second terminal of the second DC-DC converter circuit is connected to a third terminal of the first power submodule.

[0018] In some possible embodiments, the switching frequencies of the first DC-DC converter circuit and the second DC-DC converter circuit are different.

[0019] In some possible embodiments, the first power module and the second power module further include a third DC-DC conversion circuit and a fourth DC-DC conversion circuit, the second terminal of the first power submodule is electrically connected to the second port through the third DC-DC conversion circuit, and the third terminal of the first power submodule is electrically connected to the third port through the fourth DC-DC conversion circuit.

[0020] In some possible embodiments, the first power submodule includes a multi-winding transformer, which includes a primary winding, a first secondary winding, and a second secondary winding. A first terminal of the first power submodule is electrically connected to the primary winding via an inverter circuit. The first secondary winding is electrically connected to a second terminal of the first power submodule via a first rectifier circuit. The second secondary winding is electrically connected to a third terminal of the first power submodule.

[0021] In some possible embodiments, the second secondary winding is directly electrically connected to the third terminal of the first power submodule and directly electrically connected to the third port.

[0022] In some possible embodiments, the second secondary winding is electrically connected to the third terminal of the first power submodule via a second rectifier circuit.

[0023] In some possible embodiments, both the first power module and the second power module include a fifth DC-DC converter circuit, and the third terminal of the first power submodule is electrically connected to the third port through the fifth DC-DC converter circuit.

[0024] In some possible embodiments, both the first power module and the second power module include a sixth DC-DC converter circuit, and the second terminal of the first power submodule is electrically connected to the second port through the sixth DC-DC converter circuit.

[0025] In some possible embodiments, the first secondary winding is electrically connected to the second terminal of the first power submodule via a first impedance adjustment circuit, the first rectifier circuit; and / or,

[0026] The second secondary winding is electrically connected to the third terminal of the first power submodule through a second impedance adjustment circuit.

[0027] In some possible embodiments, the primary winding is electrically connected to the first terminal of the first power submodule via a third impedance adjustment circuit and the inverter circuit.

[0028] In some possible embodiments, the first impedance adjustment circuit includes a first capacitor; or,

[0029] The first impedance adjustment circuit includes a second capacitor and a first inductor, which are connected in series.

[0030] The second impedance adjustment circuit includes a third capacitor; or,

[0031] The second impedance adjustment circuit includes a fourth capacitor and a second inductor, which are connected in series.

[0032] In some possible embodiments, the third impedance adjustment circuit includes a fifth capacitor; or,

[0033] The third impedance adjustment circuit includes a sixth capacitor and a third inductor, which are connected in series.

[0034] In some possible embodiments, the first power submodule includes an eighth DC-DC converter circuit and a ninth DC-DC converter circuit. A first terminal of the first power submodule is electrically connected to a first terminal of the eighth DC-DC converter circuit, a second terminal of the eighth DC-DC converter circuit is electrically connected to a second terminal of the first power submodule, a first terminal of the ninth DC-DC converter circuit is electrically connected to a second terminal of the eighth DC-DC converter circuit, and a second terminal of the ninth DC-DC converter circuit is electrically connected to a third terminal of the first power submodule.

[0035] In some possible embodiments, the first power submodule includes a tenth DC-DC converter circuit and a first DC-AC converter circuit. A first terminal of the first power submodule is electrically connected to a first terminal of the tenth DC-DC converter circuit, a second terminal of the tenth DC-DC converter circuit is electrically connected to a second terminal of the first power submodule, a first terminal of the first DC-AC converter circuit is electrically connected to a first terminal of the first power submodule, and the first DC-AC converter circuit includes a transformer. The secondary winding of the transformer is electrically connected to a third terminal of the first power submodule.

[0036] In some possible embodiments, the first power submodule includes an eleventh DC-DC converter circuit and a second DC-AC converter circuit. A first terminal of the first power submodule is electrically connected to a first terminal of the eleventh DC-DC converter circuit, and a second terminal of the eleventh DC-DC converter circuit is electrically connected to a second terminal of the first power submodule. A first terminal of the second DC-AC converter circuit is electrically connected to a second terminal of the first power submodule. The second DC-AC converter circuit includes a transformer, and the secondary winding of the transformer is electrically connected to a third terminal of the first power submodule.

[0037] In some possible embodiments, both the first power module and the second power module include a second power submodule, and a first end of the first power submodule is electrically connected to the first port through the second power submodule.

[0038] In some possible embodiments, the second power submodule is an AC-DC converter circuit or a seventh DC-DC converter circuit.

[0039] In a second aspect, embodiments of the present invention provide a three-phase power conversion system, each phase including the power conversion system as described in any of the first aspects; wherein, the first port is an AC port, and the three-phase power conversion system is a delta-connected, star-connected, three-phase three-wire, or three-phase four-wire system.

[0040] In some possible embodiments, the second ports of the first power modules in at least three power conversion systems are connected in parallel, wherein at least one of the at least three power conversion systems belongs to the first phase power conversion system of the three-phase power conversion system, at least one of the at least three power conversion systems belongs to the second phase power conversion system of the three-phase power conversion system, and at least one of the at least three power conversion systems belongs to the third phase power conversion system of the three-phase power conversion system.

[0041] In some possible embodiments, the second ports of the second power modules in the at least three power conversion systems are connected in parallel.

[0042] In some possible embodiments, the power buses of each phase of the three-phase power conversion system are connected in parallel.

[0043] Thirdly, embodiments of the present invention provide a control method for a power conversion system.

[0044] The power conversion system includes a first power module and a second power module, wherein each power module includes a first port, a second port and a third port;

[0045] The second ports of the first power module and the second power module are independent of each other;

[0046] The third ports of the first power module and the second power module are connected in parallel to form a power bus, and the power flows bidirectionally through the third port. The control method includes:

[0047] Calculate the average power of the third port of all power modules and the second port of all power modules;

[0048] The power command for the third port of each power module is calculated based on the average power and the power of the second port of each power module;

[0049] The power of the third port of each power module is controlled according to the power command of the third port of each power module.

[0050] In some possible embodiments, both the first power module and the second power module include a first power submodule and a second power submodule. The first end of the second power submodule is electrically connected to the first port, and the second end of the second power submodule is electrically connected to the first power submodule via a DC link. The second power submodule performs voltage equalization control on the DC link.

[0051] In some possible embodiments, the power command is limited when the power of the third port is greater than the rated power.

[0052] Fourthly, embodiments of the present invention provide a control method for a power conversion system.

[0053] The power conversion system includes a first power module and a second power module, wherein each power module includes a first port, a second port and a third port;

[0054] The second ports of the first power module and the second power module are independent of each other;

[0055] The third ports of the first power module and the second power module are connected in parallel to form a power bus, and the power flows bidirectionally through the third ports. Each power module includes a DC link, and the control method includes:

[0056] Calculate the average DC link voltage of all power modules;

[0057] The output voltage command for each third port is calculated based on the average value of the DC link voltage, the output voltage setpoint of the third port, and the DC link voltage value of each power module.

[0058] The voltage of the third port of each power module is controlled according to the output voltage command of the third port of each power module.

[0059] In some possible embodiments, both the first power module and the second power module include a first power submodule and a second power submodule. A first end of the second power submodule is electrically connected to the first port, and a second end of the second power submodule is electrically connected to the first power submodule through the DC link. The second power submodule performs voltage equalization control on the DC link.

[0060] In some possible embodiments, the power command is limited when the power of the third port is greater than the rated power.

[0061] This invention provides a power conversion system and control method. The power conversion system includes multiple power modules, each power module comprising a first port, a second port, and a third port. The first port of each power module is connected to an external device. The second ports of each power module are independent, serving as independent input or output ports. The third ports of each power module are connected in parallel to form a power bus, and the power flows bidirectionally through the third ports of each power module. Therefore, when the power is unbalanced between the second ports, power scheduling among the multiple power modules is achieved through the power bus formed by the parallel connection of the third ports, so that the power of the first ports of each power module tends to be equal, thereby meeting the different power requirements of the second ports and mitigating or eliminating the DC link voltage equalization problem caused by this imbalance. Attached Figure Description

[0062] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0063] Figure 1 This is a schematic diagram of a power supply architecture for a charging station based on a power frequency transformer.

[0064] Figure 2 A schematic diagram of a charging station power supply architecture based on a solid-state transformer common DC bus;

[0065] Figure 3 This application illustrates a power supply architecture for a charging station based on a multi-port SST.

[0066] Figure 4 A schematic diagram of the structure of a power conversion system provided in an embodiment of this application.

[0067] Figure 5 This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0068] Figure 6 This is a schematic diagram of the structure of a power conversion system provided in an embodiment of this application;

[0069] Figure 7 This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0070] Figure 8This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0071] Figure 9a This is a schematic diagram of the structure of a power module provided in another embodiment of this application;

[0072] Figure 9b This is a schematic diagram of the structure of a power module provided in another embodiment of this application;

[0073] Figure 10a For the reason Figure 9a The diagram shows the structure of a power conversion system composed of power modules.

[0074] Figure 10b For the reason Figure 9b The diagram shows the structure of a power conversion system composed of power modules.

[0075] Figure 11a This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0076] Figure 11b This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0077] Figure 11c This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0078] Figure 12 This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0079] Figure 13 This is a schematic diagram of the structure of a power conversion system according to another embodiment of this application;

[0080] Figure 14 This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0081] Figure 15 This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0082] Figure 16 This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0083] Figure 17 This is a schematic diagram of the structure of a first power submodule provided in an embodiment of this application;

[0084] Figure 18 This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0085] Figure 19A schematic diagram of the structure of a first power submodule provided in another embodiment of this application;

[0086] Figure 20 A schematic diagram of the structure of a first power submodule provided in another embodiment of this application;

[0087] Figure 21 A schematic diagram of the structure of a first power submodule provided in another embodiment of this application;

[0088] Figure 22 This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0089] Figure 23 This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0090] Figure 24 This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0091] Figure 25 This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0092] Figure 26 This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0093] Figure 27 This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application;

[0094] Figure 28 This is a schematic diagram of the structure of a three-phase power conversion system according to an embodiment of this application;

[0095] Figure 29 This is a schematic diagram of the structure of a three-phase power conversion system according to another embodiment of this application;

[0096] Figure 30 A flowchart of a control method for a power conversion system provided in an embodiment of this application;

[0097] Figure 31 A flowchart of a control method for a power conversion system provided in another embodiment of this application;

[0098] Figure 32 A flowchart of a control method for a power conversion system provided in another embodiment of this application. Detailed Implementation

[0099] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0100] As can be seen from the structure of SST, the second-stage DC-DC circuits of SST are isolated from each other, thus forming isolated multi-charging ports to meet the needs of charging different electric vehicles at the same time. Figure 3 This application illustrates a schematic diagram of a charging station power supply architecture based on a multi-port SST. (See attached diagram.) Figure 3 As shown, the power supply from the AC medium-voltage grid to the vehicle only requires one isolation step, which greatly simplifies the entire power supply architecture and can simultaneously improve system efficiency and reduce system costs.

[0101] However, because different electric vehicles have different input voltages and power ratings during charging, when multiple electric vehicles with different input voltages and power ratings are simultaneously charged at different charging ports of the same charging station, the power output from each charging port to each electric vehicle will vary. This results in different input power being obtained from the power supply by each charging port according to its needs, causing DC-link voltage equalization problems. Furthermore, each charging port needs to independently adjust its port voltage to accommodate the different input voltages of the electric vehicles, and this input voltage typically varies over a wide range.

[0102] To address the aforementioned issues, in one embodiment of this application, each Cell in the SST includes a first-stage AC-DC circuit and a second-stage DC-DC circuit. The second-stage DC-DC circuit is a high-frequency isolation circuit, and its output is used for electric vehicle charging. Therefore, the second-stage DC-DC circuit of each Cell can be designed to include at least two multi-output paths. For example, the second-stage circuit of each Cell includes two DC-DC circuits, with one output connected in parallel with one output from another Cell to form a power bus, which can also serve as a parallel port. The other outputs function as independent ports. The power of one output from each Cell used to form the parallel output port can flow bidirectionally. Thus, when power imbalance between multiple independent ports causes DC-link voltage equalization problems, power scheduling between Cells can be performed through the parallel ports, mitigating or eliminating the DC-link voltage equalization problem.

[0103] Figure 4This is a schematic diagram of a power conversion system provided in an embodiment of this application. The power conversion system of this embodiment includes N power modules, where N is a positive integer greater than or equal to 2, and the N power modules are connected in series on the input side.

[0104] In the N power modules, each power module includes a first port, a second port, and a third port.

[0105] Optional, such as Figure 4 As shown, the first ports of the N power modules are independent of each other, and each power module is electrically connected to an external device through its first port. The external device can be, for example, a PV array, energy storage equipment, or a power grid.

[0106] Optional, such as Figure 5 As shown, the first ports of N power modules are connected in series. Optionally, the first ports of the N power modules connected in series can be connected to the same external device. The external device is illustrated using a power supply as an example. The power supply can be an AC power supply; for example, the first ports of the N power modules can be connected in series to any one of phases A, B, and C of a medium-voltage three-phase AC input. Alternatively, it can be a DC power supply.

[0107] The second ports of each of the N power modules output independently. The third ports of each of the N power modules are connected in parallel to form a power bus, and the power in the third port of each power module flows bidirectionally.

[0108] The following explanation uses a power conversion system containing two power modules as an example.

[0109] like Figure 4 As shown, the power conversion system includes a first power module 410 and a second power module 420. Each power module includes a first port 110, a second port 120, and a third port 130. The first power module 410 connects to a first external device (…) through its first port 110. Figure 4 The first external device is a PV array, and the second power module 420 is connected to the second external device through its first port 110. Figure 4 The second external device is a PV array. It should be noted that the first and second external devices can be different devices, for example... Figure 4 The two PV arrays in the diagram have different input powers, or the first ports of N power modules are connected in series to the same external device, for example... Figure 5 The example shown.

[0110] The second port 120 of the first power module 410 and the second port 120 of the second power module 420 are respectively used as independent output ports for separate output.

[0111] The third port 130 of the first power module 410 and the third port 130 of the second power module 420 are connected in parallel to form a power bus. Furthermore, as... Figure 4 As shown, power flows bidirectionally at the third port 130 of each power module; that is, power can flow into and out of the first power module 410 through the third port 130. Similarly, power can flow into and out of the second power module 420 through the third port 130.

[0112] Figure 4 This is an example of a power module with inputs to its first port, applied in a home solar power supply scenario, with the parallel port connected to a storage battery as an example.

[0113] Without loss of generality, when the power of the PV array input to the first port of the first power module is greater than the load power of its second port, the excess power flows into the power bus through its third port.

[0114] When the power of the PV array input at the first port of the second power module is less than the load power at its second port, the insufficient power is obtained from the power bus through its third port. When the total power of the PV array in the power conversion system is greater than the total load power, the energy storage battery will be charged; when the total PV power of the system is less than the total load power, the energy storage battery will be discharged.

[0115] like Figure 5 As shown, the power conversion system includes a first power module 510 and a second power module 520. Each power module includes a first port 110, a second port 120, and a third port 130. Specifically, for each power module, the first port 110 serves as the power input port, and the second port 120 and the third port 130 serve as the power output ports.

[0116] like Figure 5 As shown, the first port 110 of the first power module 510 and the first port 110 of the second power module 520 are connected in series and electrically connected to the power supply.

[0117] The second port 120 of the first power module 510 and the second port 120 of the second power module 520 are respectively used as independent output ports for separate output.

[0118] The third port 130 of the first power module 510 and the third port 130 of the second power module 520 are connected in parallel to form a power bus. Furthermore, as... Figure 5 As shown, power flows bidirectionally at the third port 130 of each power module; that is, power can flow into and out of the first power module 510 through the third port 130. Similarly, power can flow into and out of the second power module 520 through the third port 130.

[0119] exist Figure 4 and Figure 5 In the embodiment shown, when the load on the output port is unbalanced, power scheduling among multiple power modules is achieved through a power bus formed by parallel connection of the third port 130, so that the power input to each power module through the first port 110 is as equal as possible, thereby meeting the power requirements of different loads.

[0120] The following embodiments of this application illustrate the use of an external device as an example, where the first ports of all power modules are connected in series.

[0121] exist Figure 5 Based on the illustrated embodiment, Figure 6 This is a schematic diagram of the structure of a power module provided in one embodiment of this application. Figure 6 As shown, each power module includes a first power submodule 610. In each power module, a first end 611 of the first power submodule 610 is electrically connected to a first port 110, a second end 612 of the first power submodule 610 is electrically connected to a second port 120, and a third end 613 of the first power submodule 610 is electrically connected to a third port 130. Furthermore, power can flow bidirectionally at the third end 613 of the first power submodule 610.

[0122] Figure 7 This is a schematic diagram of the structure of a power module provided in another embodiment of this application. (See attached diagram.) Figure 7 As shown, in Figure 6 Based on the embodiment shown, the first power submodule 610 includes a first DC-DC converter circuit and a second DC-DC converter circuit. The first terminal 611 of the first power submodule 610 is electrically connected to the first terminal of the first DC-DC converter circuit and the first terminal of the second DC-DC converter circuit. The second terminal of the first DC-DC converter circuit is electrically connected to the second terminal 612 of the first power submodule 610. The second terminal of the second DC-DC converter circuit is electrically connected to the third terminal 613 of the first power submodule 610.

[0123] It should be noted that, for Figure 7 The power modules shown can have their first port 110 directly connected to a DC power supply. In this case, the first terminal of the first DC-DC converter circuit and the first terminal of the second DC-DC converter circuit are directly connected to the DC power supply. The input terminals of the first port 110 of each power module form a DC chain.

[0124] Figure 8 This is a schematic diagram of the structure of a power module provided in another embodiment of this application. (See attached diagram.) Figure 8 As shown, in Figure 6 and / or Figure 7 Based on the illustrated embodiment, each power module further includes a second power submodule 620. In each power module, the first end 621 of the second power submodule 620 is connected to the first port 110, and the second end 622 of the second power submodule 620 is connected to the first end 611 of the first power submodule 610, thus forming a DC chain.

[0125] The first and second DC-DC converter circuits are uncoupled and operate independently, for example, at different switching frequencies. Since their first terminals are connected to a DC-link, which typically contains a large energy storage capacitor, a sudden power change at the second terminal of one DC-DC circuit has minimal impact on the other. The output voltages of both circuits are flexibly adjustable, capable of both boosting and bucking, without mutual limitation. Furthermore, the third port, connected in parallel, directly forms a high-power output port, meeting diverse output power requirements. These independent ports are easily expandable; another DC-DC converter circuit can be directly connected to the DC-link.

[0126] Figure 9a This is a schematic diagram of the structure of a power module provided in another embodiment of this application. Figure 9b This is a schematic diagram of the structure of a power module provided in another embodiment of this application. Figure 8 Based on the illustrated embodiments, as Figure 9a As shown, the second power submodule 620 includes an AC-DC conversion circuit.

[0127] for Figure 9a In the embodiment shown, the first terminal of the AC-DC converter circuit is connected to the first terminal 621, and the second terminal of the AC-DC converter circuit is connected to the second terminal 622.

[0128] Or, such as Figure 9b As shown, the second power submodule 620 includes a seventh DC-DC converter circuit.

[0129] for Figure 9bIn the embodiment shown, the first terminal of the seventh DC-DC converter circuit is connected to the first terminal 621, and the second terminal of the seventh DC-DC converter circuit is connected to the second terminal 622.

[0130] When the second power submodule 620 includes an AC-DC conversion circuit, the first port 110 of each power module can be connected to an AC power supply. When the second power submodule 620 includes a seventh DC-DC conversion circuit, the first port 110 of each power module can be directly connected to a DC power supply.

[0131] Figure 10a For the reason Figure 9a The diagram shows the structure of a power conversion system composed of power modules. Figure 10b For the reason Figure 9b The diagram shows the structure of a power conversion system composed of power modules. Figure 10a In the power conversion system shown, the first port can be connected to an AC power source. Figure 10b In the power conversion system shown, the first port is connected to the DC power supply.

[0132] by Figure 10a The power conversion system shown is used as an example for illustration.

[0133] like Figure 10a As shown, both the first power module 510 and the second power module 520 include an AC-DC conversion circuit, a first DC-DC conversion circuit, and a second DC-DC conversion circuit. The AC-DC conversion circuits of the first power module 510 and the second power module 520 are connected in series and then connected to the power supply. The outputs of the first DC-DC conversion circuits of the first power module 510 and the second power module 520 are both independent ports. The outputs of the second DC-DC conversion circuits of the first power module 510 and the second power module 520 are connected in parallel to form a power bus. Wherein, as... Figure 10a As shown, the power bus is used for power dispatch and also has a parallel output port for connection to the load; or the power bus is only used for power dispatch, in which case the power bus does not have a parallel output port.

[0134] Below, with Figures 11a-11c Taking this as an example, we will explain the power scheduling of a power conversion system.

[0135] Example 1: As Figure 11a As shown, the power conversion system includes N power modules. The electric vehicle is charged through the charging port corresponding to the independent output port of the i-th power module. When the independent output ports and parallel output ports of other power modules are not loaded, the load is unbalanced, causing DC link voltage equalization problem.

[0136] In this embodiment of the power conversion system, all N power modules obtain input power from the power supply through the first port. The input power of the i-th power module flows through the first DC-DC converter circuit to the second port 120 to charge the electric vehicle. The input power obtained by the other power modules flows through the second DC-DC converter circuit to the third port 130 and then to the power bus. The power on the power bus flows through the third port 130 of the i-th power module to the second DC-DC converter circuit of the i-th power module, and then through the first DC-DC converter circuit to the second port 120 to charge the electric vehicle. In this way, even if the power conversion system is unbalanced, since the power can flow bidirectionally at the third port 130 of each power module, the power conversion system can perform power scheduling, thereby making the input power obtained by each power module from the power supply tend to be equal.

[0137] Example 2: As Figure 11b As shown, the power conversion system includes N power modules. The charging port corresponding to the independent output port of the j-th power module is for charging electric vehicle 1, and the charging port corresponding to the parallel port is for charging electric vehicle 2. When the independent output ports of other power modules have no load, it leads to load imbalance and causes DC-DC voltage equalization problems. This embodiment is divided into the following cases:

[0138] In the first scenario: the power supplied to electric vehicle 1 through the first port of the j-th power module is insufficient to meet the charging demand. In this case, the input power of the j-th power module is used only to charge electric vehicle 1 through the second port of the first DC-DC converter circuit. The input power obtained by other power modules flows to the power bus through the third port of the second DC-DC converter circuit. At this time, the power on the power bus not only charges electric vehicle 2 through the parallel output port, but also flows through the third port of the j-th power module to the second DC-DC converter circuit of the j-th power module. Then, the input power of this power module is combined and flows through the second port of the first DC-DC converter circuit to charge electric vehicle 1.

[0139] The second scenario: The power supplied to electric vehicle 1 through the first port of the j-th power module just meets the charging requirements. In this case, the input power of the j-th power module is only used to charge electric vehicle 1 through the second port of the first DC-DC converter circuit. The input power obtained by other power modules flows to the power bus through their respective third ports via the second DC-DC converter circuit. In this case, the power on the power bus is only used to charge electric vehicle 2 through the parallel output port.

[0140] The third scenario: The power supplied to electric vehicle 1 through the first port of the j-th power module exceeds the charging demand of electric vehicle 1. In this case, the input power of the j-th power module is used not only to charge electric vehicle 1 through the second port of the first DC-DC converter circuit, but also to flow to the power bus through the third port of the second DC-DC converter circuit. The input power obtained by other power modules flows to the power bus through their respective third ports of the second DC-DC converter circuit. In this case, the power on the power bus is only used to charge electric vehicle 2 through the parallel output port.

[0141] Example 3: As Figure 11c As shown, the power conversion system includes N power modules. The charging port corresponding to the independent output port of the u-th power module is for charging electric vehicle 3, and the charging port corresponding to the independent output port of the v-th power module is for charging electric vehicle 4. When the independent output ports and parallel output ports of other power modules are not loaded, it leads to load imbalance and causes DC-DC voltage equalization problems. This embodiment is divided into the following cases:

[0142] The first scenario is that the power supplied by the first port of one of the two power modules to the electric vehicle is insufficient to meet the charging requirements, while the power supplied by the first port of the other power module to the electric vehicle just meets the charging requirements.

[0143] For example, the power supplied to electric vehicle 3 through the first port of the u-th power module is insufficient to meet the charging demand. In this case, the input power of the u-th power module is used only to charge electric vehicle 3 via the second port of the first DC-DC converter circuit, and the input power of the v-th power module is used only to charge electric vehicle 4 via the second port of the first DC-DC converter circuit. The input power obtained by the other power modules flows to the power bus through their respective third ports via the second DC-DC converter circuit. The power on the power bus then flows through the third port of the u-th power module to the second DC-DC converter circuit of the u-th power module, and after passing through the second DC-DC converter circuit of the u-th power module, it is combined with the input power of that power module and flows through the second port of the first DC-DC converter circuit to charge electric vehicle 3.

[0144] The second scenario is that one of the two power modules cannot provide enough power to the electric vehicle through the first port to meet the charging demand, while the other power module provides more power to the electric vehicle through the first port than the charging demand.

[0145] For example, the power supplied to electric vehicle 3 through the first port of the u-th power module is insufficient to meet the charging demand. In this case, the input power of the u-th power module is used only to charge electric vehicle 3 via the second port of the first DC-DC converter circuit. The input power of the v-th power module is used not only to charge electric vehicle 4 via the second port of the first DC-DC converter circuit, but also to flow to the power bus via the third port of the second DC-DC converter circuit. The input power obtained by other power modules flows to the power bus via their respective third ports through the second DC-DC converter circuit. The power on the power bus then flows to the second DC-DC converter circuit of the u-th power module through its third port, and after passing through the second DC-DC converter circuit, it merges with the input power of that power module and flows to charge electric vehicle 3 via the second port of the first DC-DC converter circuit.

[0146] The third scenario: The power provided by each of the two power modules through the first port to the electric vehicle is insufficient to meet the charging requirements. In this case, the input power of the u-th power module is used only to charge electric vehicle 3 through the second port via the first DC-DC converter circuit, and the input power of the v-th power module is used only to charge electric vehicle 4 through the second port via the first DC-DC converter circuit. The input power obtained by the other power modules flows to the power bus through the third port via the second DC-DC converter circuit.

[0147] At this time, a portion of the power on the power bus flows through the third port of the u-th power module to the second DC-DC converter circuit of the u-th power module. After passing through the second DC-DC converter circuit of the u-th power module, it is combined with the input power of that power module and flows through the second port of the first DC-DC converter circuit to charge electric vehicle 3, thus meeting the charging needs of electric vehicle 3. The remaining power flows through the third port of the v-th power module to the second DC-DC converter circuit of the v-th power module. After passing through the second DC-DC converter circuit of the v-th power module, it is combined with the input power of that power module and flows through the second port of the first DC-DC converter circuit to charge electric vehicle 4, thus meeting the charging needs of electric vehicle 4.

[0148] Although the power conversion system in the above embodiment has a load imbalance problem, the power at the third port 130 in each power module can flow bidirectionally, enabling the power conversion system to perform power scheduling, thereby making the input power obtained by each power module from the power supply as equal as possible.

[0149] Figures 11a-11cThe illustration shows a power conversion system applied in a scenario similar to a charging station. In this case, the power conversion system provides power to the external system, and the load imbalance is caused by the different power outputs of the charging devices connected to the charging ports. Furthermore, based on the inventive concept of this application, the power conversion system can be applied to scenarios combined with energy storage, such as energy storage charging stations, photovoltaic power plants, and also in various other applications requiring energy storage, such as data centers and microgrids. The following explanation uses a photovoltaic power plant as an example.

[0150] The power from the three-phase AC (grid side) flows in through the PV arrays. Each cell is connected to an independent photovoltaic (PV) array. Each PV array group is independently controlled by a distributed maximum power point tracking (MPPT) solar controller based on the amount of sunlight, thereby increasing power generation. When a PV array fails, it can be disconnected without affecting the normal operation of other PV arrays. It is evident that the input power at the ports connected to the PV arrays is affected by the randomness of sunlight and faults, and there is also an imbalance in the input power (the power provided by each PV array to the grid side), leading to DC link voltage equalization problems.

[0151] for Figure 12 In the power conversion system shown, the second port of each power module is connected to the PV array. The second port of each power module is used to input power. However, due to the influence of illumination or the existence of PV array failure, the input power of the two second ports may be different, causing the output power of the first port of the two power modules to be unequal. At this time, power scheduling is performed through the third port.

[0152] For example, the input power at the second port of the first power module is less than the input power at the second port of the second power module, meaning the power provided by the PV array connected to the second port of the first power module is less than the power provided by the PV array connected to the second port of the second power module. In this case, the input power at the second port of the second power module is input to the second power module through the second port of the second power module. A portion of this input power flows to the power bus through the third port of the second power module, and then the power on the power bus flows to the third port of the first power module and enters the first power module. It then merges with the input power flowing in through the second port of the first power module and flows into the grid side through the first port of the first power module. Thus, by utilizing the bidirectional power flow characteristic of the third port of each power module, the third ports are connected in parallel to form a power bus. When the output power of the first ports of the power modules is unequal, the power bus and the third ports of each power module are used for power balancing scheduling among the power modules, ensuring that the output power of the first port of each power module in the power conversion system is equal, thus solving the DC link voltage equalization problem.

[0153] It should be noted that, Figure 12 In the power conversion system shown, when the parallel input port is also connected to the PV array, if the power output of the first port of the two power modules is not equal, the power bus and the third port of each power module can be used to perform power balancing scheduling between the power modules, which will not be elaborated here.

[0154] When some ports in the independent and parallel ports of a power conversion system are connected to an external load and some ports are connected to a power generation device, that is, when the second port of some power modules in the power conversion system is used to input power to the power module and the second port of some power modules is used to output power from the power module, the inventive concept of this application also applies if there is an imbalance in the DC link of the power modules. For example... Figure 13 As shown.

[0155] Figure 13 This is a schematic diagram of the structure of a power conversion system according to another embodiment of this application. Figure 13 As shown, if one of the two independent ports is connected to an external load, that independent port is called an independent output port; if the other is connected to a PV array, that independent port is called an independent input port.

[0156] At least a portion of the power generated by the PV array is transferred to the second port of the first power module 510, then flows into the power bus through the third port of the first power module 510, then flows into the second power module 520 through the third port of the second power module 520, and finally flows to the independent output port through the second port of the second power module 520 to charge the external load.

[0157] In one embodiment, the independent port and parallel port (if ports are provided on the power bus) of each power module in the power conversion system can also be connected to an energy storage device.

[0158] When the energy storage devices connected to the power conversion system are all used for energy storage, that is, when the energy storage devices obtain energy from the power supply, their power scheduling can refer to the description of the power scheduling when the power conversion system is charging the external load, which will not be repeated here.

[0159] When the energy storage devices connected to the power conversion system are all used to release energy, that is, when the energy storage devices provide energy to the outside, such as the grid side, the power dispatch can be referred to the description of the power conversion system connected to the PV array, which will not be repeated here.

[0160] In one embodiment, each power module in the power conversion system has independent ports and parallel ports (if ports are provided on the power bus). Some ports can be connected to energy storage devices, and some ports can be used to charge external loads, such as electric vehicles. Figure 14As shown.

[0161] Figure 14 In this configuration, the parallel port is connected to the energy storage device, and the independent output port of the first power module 510 charges the electric vehicle. If the energy storage device releases energy, the power output from the energy storage device flows through the power bus to the third port of the first power module 510, then through the second DC-DC circuit of the first power module 510 to the first DC-DC circuit of the first power module 510, and finally through the first port of the first DC-DC circuit of the first power module 510 to charge the electric vehicle. Thus, utilizing the bidirectional power flow characteristic at the third port of the power module, the energy released by the energy storage device is provided to the external load to charge it, without requiring a power supply to charge the external load.

[0162] If the energy storage device stores energy, then the power supply provides energy to both the energy storage device and the external load. In this case, since the energy storage device stores energy, it is equivalent to an external load. The power dispatch in this situation can be referenced from the description of power dispatch when a power conversion system charges an external load; it will not be elaborated upon here.

[0163] In one embodiment, each power module in the power conversion system has independent ports and parallel ports (if ports are provided on the power bus), some of which can be connected to energy storage devices and some of which can be connected to PV arrays, such as... Figure 15 As shown.

[0164] Figure 15 In this configuration, the parallel port is connected to the energy storage device, and the independent output port of the first power module 510 is connected to the PV array. At this time, if the energy storage device releases energy, the PV array supplies power to the grid. Because the energy storage device releases energy, its function is the same as the PV array: supplying power to the grid. Power dispatching in this case can be referred to the description of the power conversion system connected to the PV array, which will not be repeated here.

[0165] If the energy storage device stores energy, the power generated by the PV array flows into the first DC-DC circuit through the second port of the first power module 510, then into the second DC-DC circuit of the first power module 510, and finally into the power bus through the third port of the first power module 510, thereby providing energy to the energy storage device. In this way, by utilizing the bidirectional power flow characteristic at the third port of the power module, the energy generated by the PV array is provided to the energy storage device, without the need for a power supply to charge an external load.

[0166] It should be noted that, Figures 11a-15The diagram only shows the case where the power conversion system includes two power modules. When the power conversion system includes multiple power modules, the power bus and the third port of each power module can be used to perform power balancing scheduling between the power modules, which will not be elaborated here.

[0167] Based on the inventive concept of this application, the structure of the power conversion system may further include:

[0168] Figure 16 This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application, as shown below. Figure 16 As shown, each power module includes a third DC-DC converter circuit and / or a fourth DC-DC converter circuit. The second terminal of the first power submodule is electrically connected to the second port via the third DC-DC converter circuit, and the third terminal of the first power submodule is electrically connected to the third port via the fourth DC-DC converter circuit.

[0169] In this embodiment, as Figure 16 As shown, taking the first power submodule including a first DC-DC converter circuit and a second DC-DC converter circuit as an example, the second end of the first DC-DC converter circuit is connected to the second port through the third DC-DC converter circuit, and the second end of the second DC-DC converter circuit is connected to the third port through the fourth DC-DC converter circuit.

[0170] In some embodiments, the first power submodule 610 of each power module includes a multi-winding transformer, wherein the structure of the multi-winding transformer is as follows: Figure 17 As shown, the multi-winding transformer 160 includes a primary winding, a first secondary winding, and a second secondary winding. In each power module, the first end of the first power sub-module is electrically connected to the primary winding, the second end of the first power sub-module is electrically connected to the first secondary winding through a first rectifier circuit, and the third end of the first power sub-module is electrically connected to the second secondary winding.

[0171] like Figure 17 As shown, optionally, the first terminal of the first power submodule is electrically connected to the primary winding via an inverter circuit. Wherein, v i1 to v iN This is the voltage of the DC link.

[0172] The first secondary winding of the multi-winding transformer 160 is connected to the second terminal of the first power submodule via a first rectifier circuit, and the second terminal of the first power submodule is connected to a second port. Wherein, v o1 to v oN This represents the voltage at the second port.

[0173] The second secondary winding of the multi-winding transformer 160 is connected to the third terminal of the first power submodule, and the third terminal of the first power submodule is connected to the third port. Optionally, the second secondary winding can be directly connected to the third terminal of the first power submodule.

[0174] It should be noted that, for Figure 17 The first power submodule shown comprises N power modules. The secondary windings connected to the third port are interconnected in parallel to form a power bus. However, this power bus is not connected to any other devices such as loads or energy storage devices. Therefore, this power bus is used for power dispatching between power modules, solving the DC link voltage equalization problem caused by power imbalance at independent ports. Since the dispatched power only needs to pass through the secondary winding of the transformer, the overall system loss is less affected, resulting in higher efficiency. Furthermore, since power dispatching can be accomplished with only one additional secondary winding, the cost is lower. Additionally, a parallel port can be provided on this power bus for connection to other devices such as loads or energy storage devices.

[0175] Figure 18 This is a schematic diagram of the structure of a power conversion system provided in another embodiment of this application, as shown below. Figure 18 As shown, each power module includes a multi-winding transformer. Among them, in Figure 18 In this multi-winding transformer, the first secondary winding is connected to the second terminal of the first power submodule via a first rectifier circuit, and the second secondary winding is connected to the third terminal of the first power submodule via a second rectifier circuit. The second and third terminals of the first power submodule are directly electrically connected to the second and third ports of the power module, respectively.

[0176] It should be noted that, for Figure 18 The illustrated power conversion system has N power modules whose third ports are connected in parallel to form a power bus. This power bus has parallel ports, allowing it to not only be used for power scheduling between power modules and to solve DC link voltage equalization problems caused by unbalanced loads on independent ports, but also as a power output port to charge external loads (e.g., electric vehicles). In some embodiments, the power bus may be used only for power scheduling between power modules and may not have parallel ports.

[0177] It should be noted that, in Figure 18 The rectifier circuits connected to the two secondary windings are not shown separately.

[0178] Figure 19 This is a schematic diagram of the structure of a first power submodule provided in another embodiment of this application. Figure 19 The first power submodule shown is with Figure 17 The first power submodule shown is similar. Among them, Figure 17 and Figure 19The difference lies in the addition of a parallel port after the power bus. A parallel connection point is formed at the third port of the N power modules. Figure 19 After point A in the circuit, it is connected to the parallel port through the second rectifier circuit.

[0179] To make power dispatching in power-changing systems easier to implement, such as Figure 20 As shown, the third terminal of the first power submodule can be connected to one of the two secondary windings via a first impedance adjustment circuit, and / or the second terminal of the second power submodule can be electrically connected to the other of the two secondary windings via a second impedance adjustment circuit. The first and second impedance adjustment circuits, by adjusting the consistency of the output impedance of the transformers of different power modules, make power dispatching of the power variation system easier to achieve.

[0180] Optionally, the first impedance adjustment circuit includes a first capacitor C1.

[0181] Optionally, the first impedance adjustment circuit includes a second capacitor C2 and a first inductor L1, or the second capacitor C2 and the first inductor L1 are connected in series.

[0182] Optionally, the second impedance adjustment circuit includes a third capacitor C3.

[0183] Optionally, the first impedance adjustment circuit includes a fourth capacitor C4 and a second inductor L2, or the fourth capacitor C4 and the second inductor L2 are connected in series.

[0184] in, Figure 20 The first impedance adjustment circuit shown includes a first capacitor C1, and the second impedance adjustment circuit includes a third capacitor C3. Capacitors C1 and C3 make power dispatching of the power change system easier to achieve by adjusting the consistency of the output impedance of the transformers of different power modules.

[0185] In one embodiment, such as Figure 21 As shown, the primary winding is electrically connected to the first end of the second rate submodule through the third impedance adjustment circuit.

[0186] Optionally, the third impedance adjustment circuit includes a fifth capacitor C5.

[0187] Optionally, the third impedance adjustment circuit includes a sixth capacitor C6 and a third inductor L3, or the sixth capacitor C6 and the third inductor L3 connected in series.

[0188] in, Figure 21 The first impedance adjustment circuit shown includes a second capacitor C2 and a first inductor L1, the second impedance adjustment circuit includes a fourth capacitor C4 and a second inductor L2, and the third impedance adjustment circuit includes a sixth capacitor C6 and a third inductor L3.

[0189] It should be noted that, Figure 20 The first impedance adjustment circuit in the circuit can be replaced with Figure 21 The first impedance adjustment circuit shown in the figure, and / or, Figure 20 The second impedance adjustment circuit in the circuit can be replaced with Figure 21 The second impedance adjustment circuit is shown in the diagram. Similarly, Figure 21 The first impedance adjustment circuit in the circuit can be replaced with Figure 20 The first impedance adjustment circuit shown in the figure, and / or, Figure 21 The second impedance adjustment circuit in the circuit can be replaced with Figure 20 The second impedance adjustment circuit is shown in the figure.

[0190] Figure 22 This is a schematic diagram of a power conversion system provided in another embodiment of this application. Figure 22 As shown, each power module includes Figure 18 Based on the first power submodule shown, each power module further includes a fifth DC-DC converter circuit and a sixth DC-DC converter circuit. The third terminal of the first power submodule is connected to the third port via the fifth DC-DC converter circuit.

[0191] It should be noted that, Figure 22 It can be extended based on the power conversion system shown in any of the above embodiments.

[0192] Optional, such as Figure 22 As shown, each power module may also include: a sixth DC-DC converter circuit, and the second end of the first power submodule is connected to the second port through the sixth DC-DC converter circuit.

[0193] In one embodiment, in Figure 22 In the power conversion system shown, the first power submodule adopts a multi-port DC-DC converter circuit, which is connected to the second and third ports of the power module through a Buck converter. Combined with the AC-DC converter circuit, the power module has a total of three-stage conversion circuits. The multi-port DC-DC converter circuit isolates the output ports, and each output port is connected to a Buck converter circuit, which can realize a wide voltage range output.

[0194] It should be noted that, in Figure 18 Based on the power conversion system shown, a series-parallel switching circuit can also be set in the first power submodule, such as... Figure 23 As shown, this is to achieve a wide range of outputs.

[0195] In some embodiments, the Buck circuit can also be independent of the power module, for example Figure 24 As shown, this facilitates Buck's modularity, allowing users to expand it as needed.

[0196] Figure 25 This is a schematic diagram of a power conversion system provided in another embodiment of this application. Figure 25 As shown, the first power submodule includes an eighth DC-DC converter circuit and a ninth DC-DC converter circuit.

[0197] Specifically, the first terminal of the first power submodule is electrically connected to the first terminal of the eighth DC-DC converter circuit, the second terminal of the eighth DC-DC converter circuit is electrically connected to the second terminal of the first power submodule, the first terminal of the ninth DC-DC converter circuit is electrically connected to the second terminal of the eighth DC-DC converter circuit, and the second terminal of the ninth DC-DC converter circuit is electrically connected to the third terminal of the first power submodule.

[0198] Figure 26 This is a schematic diagram of a power conversion system provided in another embodiment of this application. Figure 26 As shown, the first power submodule includes a tenth DC-DC converter circuit and a first DC-AC converter circuit.

[0199] The first terminal of the first power submodule is electrically connected to the first terminal of the tenth DC-DC converter circuit, the second terminal of the tenth DC-DC converter circuit is electrically connected to the second terminal of the first power submodule, the first terminal of the first DC-AC converter circuit is electrically connected to the first terminal of the first power submodule, the first DC-AC converter circuit includes a transformer, and the secondary winding of the transformer is electrically connected to the third terminal of the first power submodule.

[0200] Figure 27 This is a schematic diagram of a power conversion system provided in another embodiment of this application. Figure 27 As shown, the first power submodule includes an eleventh DC-DC converter circuit and a second DC-AC converter circuit.

[0201] The first terminal of the first power submodule is electrically connected to the first terminal of the eleventh DC-DC converter circuit, the second terminal of the eleventh DC-DC converter circuit is electrically connected to the second terminal of the first power submodule, the first terminal of the second DC-AC converter circuit is electrically connected to the second terminal of the first power submodule, the second DC-AC converter circuit includes a transformer, and the secondary winding of the transformer is electrically connected to the third terminal of the first power submodule.

[0202] This application proposes a three-phase power conversion system, wherein each phase of the three-phase power conversion system includes multiple power conversion systems, and each power conversion system can be the power conversion system shown in any of the above embodiments. The three-phase power conversion system can be a delta-connected, star-connected, three-phase three-wire, or three-phase four-wire system, wherein... Figure 28 This is a schematic diagram of a delta-connected three-phase power change system.

[0203] like Figure 28 As shown, the input is a delta connection, wherein at least one of the three power conversion systems belongs to the first phase power conversion system of the three-phase power conversion system, at least one of the three power conversion systems belongs to the second phase power conversion system of the three-phase power conversion system, and at least one of the three power conversion systems belongs to the third phase power conversion system of the three-phase power conversion system.

[0204] Figure 29 This is a schematic diagram of a three-phase power conversion system according to another embodiment of this application. Figure 29 As shown, in Figure 28 Based on this, the second ports of the second power modules in at least three power conversion systems are connected in parallel to form an output port.

[0205] Optional, in Figure 28 as well as Figure 29 Based on this, the power buses of each phase of the three-phase power conversion system are connected in parallel to form an output port.

[0206] Below, in Figure 8 Based on the power conversion system shown, the power scheduling method of the power conversion system is explained. Figure 8 The power conversion system shown can be replaced by any of the power conversion systems described above.

[0207] exist Figure 8 Based on the power conversion system shown, when the power conversion system includes N power modules, the sum of the power at all third ports is P. s The power at the second port of the i-th power module is P. i The power at the first port is P. Hi The rated power or maximum power of the second and third ports of the power conversion system is P. r The rated power or maximum power of the first port of the power module is 2P. r .

[0208] Figure 30 A flowchart illustrating a control method for a power conversion system provided in an embodiment of this application. Figure 30 As shown, the control method of the power conversion system includes:

[0209] S2701. Calculate the average power of the third port of all power modules and the second port of all power modules.

[0210] In this embodiment, the third ports of all power modules form parallel ports, and the second port of each power module is an independent port. The parallel ports and each independent port serve as charging and discharging ports for charging or discharging external loads. For example, in a charging station, the power of the load connected to each charging and discharging port is different, and not all charging ports are connected to external loads at the same time, which leads to DC-link voltage equalization problems. For the power conversion system shown in this application, the total power of the load connected to the power conversion system is calculated, and then the average power of each power module is calculated based on the total power. The formula for calculating the average power of each power module is, for example, Formula 1:

[0211]

[0212] Among them, P avg This represents the average power of each power module.

[0213] It should be noted that when no external load is connected to the independent port, the power of that independent port is 0.

[0214] S2702. Calculate the power command for the third port of each power module based on the average power and the power of the second port of each power module.

[0215] In this embodiment, the difference between the average power of each power module and the power of its independent port is the power command P of the third port of that power module. si The calculation formula is shown in Formula 2:

[0216] P si =P avg -P i Formula 2

[0217] S2703. Control the power of the third port of each power module according to the power command of the third port of each power module.

[0218] In this embodiment, for the third port of each power module, the power of the third port of the power module is controlled according to the power command of the third port of the power module calculated according to Formula 2.

[0219] It should be noted that the maximum power at the third port of each power module is P. r Therefore, if the power command P of the third port is calculated according to Formula 2... si Greater than P r Then, the power command at the third port of the power module is limited, so that the power command at the third port of the power module is P. r .

[0220] Optionally, if the power module includes a first power submodule and a second power submodule, wherein the second terminal of the second power submodule is electrically connected to the first terminal of the first power submodule via a DC link, when the power command P of the third port of the power module... si Greater than P r In this case, existing methods can be combined (for example, when the second power submodule includes an AC-DC conversion circuit, the reactive current injection method can be used; when the second power submodule includes a DC-DC conversion circuit, the input port voltage adjustment method can be used) to perform DC link voltage equalization control.

[0221] For example, based on the above method, it can also be combined with the reactive current injection method. Specifically, when the required output power at the third port (i.e., the power command P) si ) greater than P r When power balancing of the first port cannot be achieved through the third port, it is necessary to combine existing control methods, such as reactive current injection for the two power submodules. It should be noted that the combination of the above method and reactive current injection is more efficient under heavy load conditions (e.g., when the power of each independent port is greater than its half-load power).

[0222] Figure 31 A flowchart illustrating a control method for a power conversion system provided in another embodiment of this application. (See attached flowchart.) Figure 31 As shown, the control method of the power conversion system includes:

[0223] S2801. Calculate the average value of the DC link voltage of all power modules.

[0224] In this embodiment, each power module in the power conversion system is provided with a DC link. If the power module includes a first power submodule and a second power submodule, the DC link is the circuit connecting the first and second power submodules. If the power module only includes a first power submodule, the DC link is the circuit connecting the first power submodule circuit to the power supply.

[0225] The voltage of the DC link on any power module in the power conversion system is V. dci Calculate the DC link voltage V on all power modules in the power conversion system. dci average value V dcavg The calculation formula is as shown in Formula 3:

[0226]

[0227] Where N represents the total number of power modules.

[0228] S2802. Calculate the output voltage command of each third port based on the average value of the DC link voltage, the output voltage setpoint of the third port, and the DC link voltage value of each power module.

[0229] In this embodiment, the output voltage command for each third port is calculated according to Formula 4:

[0230] V refi =V seti +K d (V dci -V dcavg Formula 4

[0231] Among them, V seti K represents the setpoint output voltage at the third port of the i-th power module. d It is a constant whose value is a given value.

[0232] S2803. Control the voltage of the third port of each power module according to the output voltage command of the third port of each power module.

[0233] In this embodiment, after calculating the output voltage command of the third port of each power module, the voltage of the third port of each power module is controlled in a closed loop according to the output voltage command of the third port, thereby enabling the power of the parallel ports to be automatically distributed.

[0234] It should be noted that the maximum output power of the third port of each power module is P. r Therefore, if the power P at the third port r Then, the power command at the third port of the power module is limited, so that the power at the third port of the power module is P. r .

[0235] Optionally, if the power module includes a first power submodule and a second power submodule, wherein the second terminal of the second power submodule is electrically connected to the first terminal of the first power submodule via a DC link, and without external power supply interference, the power at the first terminal of the first power submodule is the same as the input power of the power module through the first port. When the power command at the third port of the power module is greater than P... r In this case, existing methods can be combined (for example, when the second power submodule includes an AC-DC conversion circuit, the reactive current injection method can be used; when the second power submodule includes a DC-DC conversion circuit, the input port voltage adjustment method can be used) to perform front-end voltage equalization control, that is, to perform voltage equalization control on the DC link.

[0236] It should be noted that in a three-phase power conversion system, when the third ports of the power modules included in each power conversion system are not connected in parallel, it is impossible to achieve the desired result through... Figure 30 and Figure 31 The method shown achieves phase-to-phase power equalization. Therefore, it is necessary to combine existing methods (e.g., the second power submodule includes an AC-DC converter circuit and, when delta-connected, can employ the zero-sequence current injection method) to perform voltage equalization control on the DC link.

[0237] Figure 30 as well as Figure 31 The control principle of the power conversion system control method shown is as follows: when a DC link voltage equalization problem occurs, the first power submodule of the power conversion system is used first for voltage equalization control. Only when the power at the parallel port is limited, or when the downstream stage loses its voltage equalization capability, is the second power submodule used for voltage equalization.

[0238] In one embodiment, the architecture of the power conversion system proposed in this application can also be flexibly configured with a method of voltage equalization using a second power submodule. The first power submodule is used to equalize part of the power, and the second power submodule is used to equalize the remaining unbalanced power. Combining the two can achieve both voltage equalization and goals such as optimal system efficiency. Based on this idea, this application also proposes a control method for the power conversion system, such as... Figure 32 As shown. Among them, Figure 32 The control method of the power conversion system shown is in Figure 8 The explanation is based on the power conversion system shown.

[0239] S2901. Determine the control objectives of the power conversion system.

[0240] In this embodiment, the control objective is to minimize the loss of the power conversion system, and the corresponding objective function is shown in Formula 4:

[0241]

[0242] Where J represents the power conversion system loss; This reflects the losses of the second power submodule. This reflects the losses of the DC-DC circuits corresponding to the parallel ports in the first power submodule. a and b are weighting coefficients, representing the power losses of the second power submodules in each power module, and the impact of the power losses of the DC-DC circuits at the parallel ports in the first power submodules on the total losses of the power conversion system. Note that the weighting coefficients may differ for different systems.

[0243] It should be noted that the DC-DC circuit corresponding to the independent port in the first power submodule also generates losses. However, the losses generated by the DC-DC circuit corresponding to the independent port are constant. Therefore, the losses generated by the DC-DC circuit corresponding to the independent port are not added in Formula 4.

[0244] S2902. Determine the constraints of the power conversion system.

[0245] In this embodiment, the constraints of the power conversion system are shown in Equations 5-7:

[0246]

[0247]

[0248] P Hk =P sk +P k Formula 7

[0249] S2903. Calculate the variables of the power conversion system that satisfy the control objective under the constraints based on the control objective.

[0250] In this embodiment, based on the objective function and constraints, the variable P that satisfies the objective function under the constraints is obtained through optimization algorithms or other calculation methods. Hk and P sk .

[0251] S2904. Control the power of the first port and / or the third port in each power module according to the value of the variable.

[0252] In this embodiment, based on the calculated P Hk and P sk Control the first port in each power module to P Hk And / or, control the power of the third port in each power module to P sk .

[0253] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power conversion system, characterized in that, include: A first power module and a second power module, wherein each power module includes a first port, a second port and a third port; The second ports of the first power module and the second power module are independent of each other; The third ports of the first power module and the second power module are connected in parallel to form a power bus, and the power of the third port flows bidirectionally; when the power of the second port of the first power module and the power of the second port of the second power module are not equal, the third ports of the first power module and the third ports of the second power module exchange power through the power bus, so that the power of the first port of the first power module and the power of the first port of the second power module tend to be equal.

2. The power conversion system according to claim 1, characterized in that, The first ports of the first power module and the second power module are connected in series and then electrically connected to external devices.

3. The power conversion system according to claim 1, characterized in that, The second port of the first power module and the second port of the second power module respectively output power. When the power output by the second port of the first power module is less than the power output by the second port of the second power module, at least a portion of the input power of the first port of the first power module is transferred to the third port of the first power module, then through the power bus to the third port of the second power module, and finally to the second port of the second power module, so that the input power of the first port of the first power module and the input power of the first port of the second power module tend to be equal.

4. The power conversion system according to claim 1, characterized in that, The second port of the first power module and the second port of the second power module respectively input power. When the input power of the second port of the first power module is less than the input power of the second port of the second power module, at least a portion of the input power of the second port of the second power module is transferred to the third port of the second power module, then transferred to the third port of the first power module through the power bus, and finally transferred to the first port of the first power module, so that the output power of the first port of the first power module and the output power of the first port of the second power module tend to be equal.

5. The power conversion system according to claim 1, characterized in that, When the second port of the first power module is used to output power and the second port of the second power module is used to input power, at least a portion of the input power of the second port of the second power module is transmitted to the third port of the second power module, then transmitted to the third port of the first power module through the power bus, and finally transmitted to the second port of the first power module, so that the power of the first port of the first power module and the power of the first port of the second power module tend to be equal.

6. The power conversion system according to claim 1 or 2, characterized in that, Both the first power module and the second power module include a first power submodule. The first power submodule includes a first terminal, a second terminal, and a third terminal. The first port is electrically connected to the first terminal of the first power submodule, the second port is electrically connected to the second terminal of the first power submodule, and the third port is electrically connected to the third terminal of the first power submodule. The first and second terminals of the first power submodule are DC terminals.

7. The power conversion system according to claim 6, characterized in that, The first power submodule includes a first DC-DC converter circuit and a second DC-DC converter circuit. The first terminal of the first power submodule is electrically connected to the first terminal of the first DC-DC converter circuit and the first terminal of the second DC-DC converter circuit. The second terminal of the first DC-DC converter circuit is electrically connected to the second terminal of the first power submodule. The second terminal of the second DC-DC converter circuit is connected to the third terminal of the first power submodule.

8. The power conversion system according to claim 7, characterized in that, The switching frequencies of the first DC-DC converter circuit and the second DC-DC converter circuit are different.

9. The power conversion system according to claim 7, characterized in that, The first power module and the second power module further include a third DC-DC conversion circuit and a fourth DC-DC conversion circuit. The second terminal of the first power submodule is electrically connected to the second port through the third DC-DC conversion circuit, and the third terminal of the first power submodule is electrically connected to the third port through the fourth DC-DC conversion circuit.

10. The power conversion system according to claim 6, characterized in that, The first power submodule includes a multi-winding transformer, which includes a primary winding, a first secondary winding, and a second secondary winding. The first terminal of the first power submodule is electrically connected to the primary winding through an inverter circuit. The first secondary winding is electrically connected to the second terminal of the first power submodule through a first rectifier circuit. The second secondary winding is electrically connected to the third terminal of the first power submodule.

11. The power conversion system according to claim 10, characterized in that, The second secondary winding is directly electrically connected to the third terminal of the first power submodule and directly electrically connected to the third port.

12. The power conversion system according to claim 10, characterized in that, The second secondary winding is electrically connected to the third terminal of the first power submodule through the second rectifier circuit.

13. The power conversion system according to claim 12, characterized in that, Both the first power module and the second power module include a fifth DC-DC converter circuit, and the third terminal of the first power submodule is electrically connected to the third port through the fifth DC-DC converter circuit.

14. The power conversion system according to claim 11 or 13, characterized in that, Both the first power module and the second power module include a sixth DC-DC conversion circuit, and the second terminal of the first power submodule is electrically connected to the second port through the sixth DC-DC conversion circuit.

15. The power conversion system according to any one of claims 10-13, characterized in that, The first secondary winding is electrically connected to the second terminal of the first power submodule through the first impedance adjustment circuit and the first rectifier circuit; and / or, The second secondary winding is electrically connected to the third terminal of the first power submodule through a second impedance adjustment circuit.

16. The power conversion system according to any one of claims 10-13, characterized in that, The primary winding is electrically connected to the first terminal of the first power submodule through the third impedance adjustment circuit and the inverter circuit.

17. The power conversion system according to claim 15, characterized in that, The first impedance adjustment circuit includes a first capacitor; or, The first impedance adjustment circuit includes a second capacitor and a first inductor, which are connected in series. The second impedance adjustment circuit includes a third capacitor; or, The second impedance adjustment circuit includes a fourth capacitor and a second inductor, which are connected in series.

18. The power conversion system according to claim 16, characterized in that, The third impedance adjustment circuit includes a fifth capacitor; or... The third impedance adjustment circuit includes a sixth capacitor and a third inductor, which are connected in series.

19. The power conversion system according to claim 6, characterized in that, The first power submodule includes an eighth DC-DC converter circuit and a ninth DC-DC converter circuit. A first terminal of the first power submodule is electrically connected to a first terminal of the eighth DC-DC converter circuit. A second terminal of the eighth DC-DC converter circuit is electrically connected to a second terminal of the first power submodule. A first terminal of the ninth DC-DC converter circuit is electrically connected to a second terminal of the eighth DC-DC converter circuit. A second terminal of the ninth DC-DC converter circuit is electrically connected to a third terminal of the first power submodule.

20. The power conversion system according to claim 6, characterized in that, The first power submodule includes a tenth DC-DC converter circuit and a first DC-AC converter circuit. The first terminal of the first power submodule is electrically connected to the first terminal of the tenth DC-DC converter circuit. The second terminal of the tenth DC-DC converter circuit is electrically connected to the second terminal of the first power submodule. The first terminal of the first DC-AC converter circuit is electrically connected to the first terminal of the first power submodule. The first DC-AC converter circuit includes a transformer, and the secondary winding of the transformer is electrically connected to the third terminal of the first power submodule.

21. The power conversion system according to claim 6, characterized in that, The first power submodule includes an eleventh DC-DC converter circuit and a second DC-AC converter circuit. The first terminal of the first power submodule is electrically connected to the first terminal of the eleventh DC-DC converter circuit, and the second terminal of the eleventh DC-DC converter circuit is electrically connected to the second terminal of the first power submodule. The first terminal of the second DC-AC converter circuit is electrically connected to the second terminal of the first power submodule. The second DC-AC converter circuit includes a transformer, and the secondary winding of the transformer is electrically connected to the third terminal of the first power submodule.

22. The power conversion system according to claim 6, characterized in that, Both the first power module and the second power module include a second power submodule, and the first end of the first power submodule is electrically connected to the first port through the second power submodule.

23. The power conversion system according to claim 22, characterized in that, The second power submodule includes an AC-DC conversion circuit or a seventh DC-DC conversion circuit.

24. A three-phase power conversion system, characterized in that, Each phase includes a power conversion system as described in any one of claims 1-23; wherein the first port is an AC port, and the three-phase power conversion system is a delta-connected, star-connected, three-phase three-wire, or three-phase four-wire system.

25. The three-phase power conversion system according to claim 24, characterized in that, The second ports of the first power modules in at least three power conversion systems are connected in parallel, wherein at least one of the at least three power conversion systems belongs to the first phase power conversion system of the three-phase power conversion system, at least one of the at least three power conversion systems belongs to the second phase power conversion system of the three-phase power conversion system, and at least one of the at least three power conversion systems belongs to the third phase power conversion system of the three-phase power conversion system.

26. The three-phase power conversion system according to claim 25, characterized in that, The second ports of the second power modules in the at least three power conversion systems are connected in parallel.

27. The three-phase power conversion system according to claim 26, characterized in that, The power buses of each phase power conversion system in the three-phase power conversion system are connected in parallel.

28. A control method for a power conversion system, characterized in that, The power conversion system includes a first power module and a second power module, wherein each power module includes a first port, a second port and a third port; The second ports of the first power module and the second power module are independent of each other; The third ports of the first power module and the second power module are connected in parallel to form a power bus, and the power flows bidirectionally through the third port. The control method includes: Calculate the average power of the third port of all power modules and the second port of all power modules; The power command for the third port of each power module is calculated based on the average power and the power of the second port of each power module; The power of the third port of each power module is controlled according to the power command of the third port of each power module.

29. The control method according to claim 28, characterized in that, Both the first power module and the second power module include a first power submodule and a second power submodule. The first end of the second power submodule is electrically connected to the first port, and the second end of the second power submodule is electrically connected to the first power submodule through a DC link. The second power submodule performs voltage equalization control on the DC link.

30. The control method according to claim 29, characterized in that, When the power of the third port is greater than the rated power, the power command is limited.

31. A control method for a power conversion system, characterized in that, The power conversion system includes a first power module and a second power module, wherein each power module includes a first port, a second port and a third port; The second ports of the first power module and the second power module are independent of each other; The third ports of the first power module and the second power module are connected in parallel to form a power bus, and the power flows bidirectionally through the third ports. Each power module includes a DC link, and the control method includes: Calculate the average DC link voltage of all power modules; The output voltage command for each third port is calculated based on the average value of the DC link voltage, the output voltage setpoint of the third port, and the DC link voltage value of each power module. The voltage of the third port of each power module is controlled according to the output voltage command of the third port of each power module.

32. The control method according to claim 31, characterized in that, Both the first power module and the second power module include a first power submodule and a second power submodule. The first end of the second power submodule is electrically connected to the first port, and the second end of the second power submodule is electrically connected to the first power submodule through the DC link. The second power submodule performs voltage equalization control on the DC link.

33. The control method according to claim 32, characterized in that, When the power of the third port is greater than the rated power, the power command is limited.

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