Power converter

Abstract

The invention provides a power converter. The power converter is suitable for being connected between an alternating-current power source with a plurality of phases led out of an alternating-current power grid and a load. For each phase of the AC power supply, the power converter includes n power modules, each power module having: an AC input terminal; the m power units are connected to the alternating current input end in parallel and are suitable for converting alternating current into direct current; and m DC output terminals. Wherein the alternating current input ends of the n power modules are sequentially connected in series and are connected between corresponding phases and a common point. And selecting one power unit from each power module, and connecting the direct current output ends of the selected power units in parallel to form a direct current output of the power converter. According to the invention, loads with different requirements can be met at the same time without additionally adding a DC / DC converter, so that the consumption generated in the power conversion process is reduced.

Description

Technical Field

[0001] The invention belongs to the field of electric power supply, and in particular relates to a power converter. Background Art

[0002] In order to meet the power supply needs of high-power DC loads such as data centers and electric vehicle charging, power converters have received extensive attention. Compared with traditional power transformers, power converters are a power electronic solution with high distribution efficiency and small size, which realizes power conversion from high-voltage AC grid to medium- and low-voltage DC. Its front end is connected to the AC grid and the back end is connected to the load, which can achieve higher power density, higher efficiency and lighter weight in ultra-large-scale power supply applications.

[0003] The common power converter topology uses a cascaded H-bridge (CHB) as the rectifier circuit at the front end of the operation, followed by a DC / DC isolation circuit to isolate the low voltage and floating voltage, and then the DC output of the isolation circuit is connected in parallel to a common DC bus. A DC / DC converter is required after the common DC bus to adapt to the voltage range of different loads. It can be seen that this topology requires at least four power electronic stages, which results in higher consumption during the power conversion process and higher costs. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a power converter which can reduce the number of conversion stages from the AC power grid to the load, thereby reducing the consumption generated during the power conversion process.

[0005] The present invention provides a power converter, which is suitable for connecting between an AC power source with multiple phases drawn from an AC power grid and a load. For each phase of the AC power source, the power converter includes n power modules, each of which has: an AC input terminal; m power units, which are connected in parallel to the AC input terminal and are suitable for converting AC into DC; and m DC output terminals. The AC input terminals of the n power modules are sequentially connected in series and connected between the corresponding phases and a common point, and a power unit is selected from each power module, and the DC output terminals of the selected power unit are connected in parallel to form a DC output of the power converter; wherein n and m are both integers greater than 0.

[0006] Optionally, the AC input end includes a first input terminal and a second input terminal; the AC input ends of the n power modules are connected in series in sequence and connected between the corresponding phases and a common point, including: for each phase of the AC power supply: the second input terminal of the i-th power module is connected to the first input terminal of the i+1-th power module, i=1, 2,..., n-1; the first input terminal of the first power module is connected to the output end of the phase; the second input terminal of the n-th power module is connected to the common point.

[0007] Optionally, the input end of the power unit includes a third input terminal and a fourth input terminal; the m power units are connected in parallel to the AC input end, including: for each of the power units: the third input terminal of the power unit is connected to the first input terminal of the power module to which the power unit belongs; the fourth input terminal of the power unit is connected to the second input terminal of the power module to which the power unit belongs.

[0008] Optionally, the DC output end of the power unit includes a first output terminal and a second output terminal; a power unit is selected from each power module, and the DC output ends of the selected power units are connected in parallel to form a DC output of the power converter, including: a power unit is selected from each of the power modules, and the first output terminals of the selected power units are connected together, and the second output terminals of the selected power units are connected together to form a DC output of the power converter.

[0009] Optionally, the power unit is composed of a rectifier circuit and an isolation circuit connected in series.

[0010] Optionally, the rectification circuit includes: an H-bridge as an active front end for AC / DC rectification; and the isolation circuit includes: an isolated DC / DC conversion circuit, and the isolated DC / DC conversion circuit is used for voltage conversion and isolation of floating voltage.

[0011] Optionally, the power unit constituting the kth DC output is connected to a controller, and the controller is used to control the DC output.

[0012] Optionally, the load is a distributed load or a centralized load.

[0013] Optionally, the distributed load includes: a charger for an electric vehicle, or a server in a data center, or a distributed battery for energy storage.

[0014] Optionally, the AC power source with multiple phases drawn from the AC power grid is a three-phase AC power source.

[0015] The power converter of the embodiment of the present invention not only reduces the high voltage electricity of the AC power grid to medium and low voltage to supply power to the load after rectification and isolation, but also can meet the different requirements of loads at the same time without adding an additional DC / DC converter. The number of power electronic stages from the AC power grid to the load is reduced, thereby reducing the consumption generated in the power conversion process, improving conversion efficiency and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a topological schematic diagram of a power converter in the prior art;

[0017] Figure 2 is a topological schematic diagram of a power converter according to an embodiment of the present invention;

[0018] Figure 3 is a schematic diagram of a connection relationship between a power module and a power unit in an R phase according to an embodiment of the present invention;

[0019] Figure 4 Schematic diagram of the topological structure inside a power unit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments herein are only used for illustration and are not intended to limit the present invention. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those of ordinary skill in the art that these specific details are not necessarily used to implement the present invention. In other examples, in order to avoid confusing the present invention, known procedures, materials or methods are not specifically described.

[0021] In the prior art, the power converter needs to realize the conversion from the high voltage of the AC power grid to the medium voltage or low voltage output. Because the input and output powers are the same, the current on the input high voltage side is small and the current on the output medium and low voltage side is large. Therefore, in order to withstand the high voltage from the AC power grid, the medium voltage power converter usually uses p cascaded H bridges per phase as the front-end AC / DC rectifier circuit (where p is an integer greater than 0), and the rectifier circuit is connected to the DC / DA isolation circuit. After the rectifier circuit and the isolation circuit, the voltage drops and the current increases. The DC output of the isolation circuit is connected in parallel to the public DC bus to complete the power conversion. Although the power conversion has been completed, the public DC bus at this time cannot simultaneously connect multiple loads with different requirements to provide services for them. This is because the front-end H bridges are connected in series, so the current values ​​flowing through them are the same. The current obtained by the load from the public DC bus is all flowing through the front-end H bridge. When the load requirements are different, the public DC bus will give priority to the load with large current requirements, which will cause the load with small current requirements to be unable to withstand the excessive current and burn the line and load. For example, in the scenario of a car charging station, there are three electric vehicles with demands of 1A, 5A, and 10A respectively, which need to be connected to the above-mentioned public DC bus for charging. After being connected at the same time, the public DC bus will meet the power supply of the electric vehicle with a demand of 10A. At this time, the current flowing through the line will be greater than the demands of 1A and 5A, which will cause the components and lines in the other two electric vehicles to burn out.

[0022] In order to solve the above problems, the existing power converter will add an additional DC / DC converter at the back end of the common DC bus to adapt to loads with different requirements. Figure 1 , as shown in the topological schematic diagram of the power converter in the prior art, it includes a rectifier circuit (including a p-level CHB), a DC / DC isolation circuit, a common DC bus, and q DC / DC converters connected in sequence, and the output of the DC / DC converter is connected to the load. Where q is an integer greater than 0.

[0023] The inventors have found that this power converter requires at least four power electronic stages from the AC power grid to the load, which results in higher consumption during the power conversion process and higher costs, so there is a need for further improvement.

[0024] In view of the above technical problems, the present invention proposes a new power converter structure, which can remove the additional DC / DC converter, thereby reducing system cost and improving efficiency. Figure 2 The invention is an intention of a power converter according to an embodiment of the present invention. The power converter is suitable for connecting to an AC power source ( Figure 2For each phase of the AC power source, the power converter includes n power modules, each power module having: an AC input terminal, the AC input terminal including a first input terminal and a second input terminal; m power units, the m power units are connected in parallel to the AC input terminal and are suitable for converting AC into DC; and m DC output terminals. The AC input terminals of the n power modules are sequentially connected in series and connected between the corresponding phases and a common point, that is, for the n power modules of each phase, the AC input terminals of the last power module are connected together. Specifically, Figure 3 The figure shows the connection relationship between the power modules and the power units in the R phase. The n power modules from the first power module 110 of the R phase to the nth power module 120 of the R phase are connected in series, that is, the output end of the R phase is connected to the first input terminal of the first power module 110 of the phase, the second input terminal of the i-th power module is connected to the first input terminal of the i+1-th power module (i=1, 2, ..., n-1), and the second input terminal of the n-1-th power module is connected to the first input terminal of the n-th power module 120 in sequence; the second input terminal of the n-th power module 120 is connected to a common point. In some embodiments, the input end of the power unit includes a third input terminal and a fourth input terminal, and the input ends of the m power units in the power module are connected in parallel to the AC input end, including: the third input terminal of each of the power units is connected to the first input terminal of the power module to which the power unit belongs; the fourth input terminal of each of the power units is connected to the second input terminal of the power module to which the power unit belongs. For example, the third input terminal of the power cell 111 in the first power module 110 of the R phase is connected to the first input terminal of the first power module 110, and the fourth input terminal of the power cell 111 is connected to the second input terminal of the first power module 110; the third input terminal of the power cell 121 in the nth power module 120 of the R phase is connected to the first input terminal of the nth power module 120, and the fourth input terminal of the power cell 121 is connected to the second input terminal of the nth power module 120.

[0025] like Figure 2As shown, similarly, for the S phase, the n power modules from the first power module 210 of the S phase to the nth power module 220 of the S phase are connected in series according to the connection mode of the power modules in the R phase, and the second input terminal of the corresponding nth power module 220 is connected to the same common point, and the m power units in each power module of the S phase are connected in parallel at their input ends in the connection mode of the power units in the R phase. For example, the third input terminal of the power unit 211 in the first power module 210 of the S phase is connected to the first input terminal of the first power module 210, and the fourth input terminal of the power unit 211 is connected to the second input terminal of the first power module 210; the third input terminal of the power unit 221 in the nth power module 220 of the S phase is connected to the first input terminal of the nth power module 220, and the fourth input terminal of the power unit 221 is connected to the second input terminal of the nth power module 220.

[0026] For the T phase, the n power modules from the first power module 310 of the T phase to the nth power module 320 of the T phase are connected in series according to the connection mode of the power modules in the R phase, and the second input terminal of the corresponding nth power module 320 is connected to the same common point, and the input terminals of the m power units in each power module of the T phase are connected in parallel in the connection mode of the power units in the R phase. For example, the third input terminal of the power unit 311 in the first power module 310 of the T phase is connected to the first input terminal of the first power module, and the fourth input terminal of the power unit 311 is connected to the second input terminal of the first power module 310; the third input terminal of the power unit 321 in the nth power module 320 of the T phase is connected to the first input terminal of the nth power module 320, and the fourth input terminal of the power unit 321 is connected to the second input terminal of the nth power module 320.

[0027] The DC output end of each power unit includes a first output terminal and a second output terminal; any one power unit is selected from each power module, and the DC output ends of the selected power unit are connected in parallel to form a DC output of the power converter; the selected power unit must not participate in the parallel formation of the DC outputs of other power converters; that is, a DC output of each power converter includes a DC output end of a power unit from each power module, and at the same time, the DC output end of any one power unit in a power module also only participates in the parallel formation of a DC output of the power converter. In some embodiments, the DC output ends of the kth power unit in each power module are connected in parallel to form the kth DC output of the power converter; specifically, the first output terminal of the kth power unit of each power module is connected together, and the second output terminal of the kth power unit of each power module is connected together to form the kth DC output of the power converter. For each phase, the first output terminal of the kth power unit of each power module in the phase is connected, and the second output terminal of the kth power unit is connected to form the DC output of the phase, k = 1, 2...m, n, m, k are all integers greater than 0; then according to the above-mentioned power unit DC output terminal connection method, the DC output terminals of the power units of all phases of the power converter are connected in parallel, and the load can be connected to supply power for it. The power converter of the embodiment of the present invention can have a maximum of m DC output terminals. Figure 2 Taking the power converter shown in the figure as an example, Figure 2If the power converter has three phases, the DC outputs of the three phases can be connected in parallel to directly connect the load and supply power to the load. For example, there are 4 levels of cascaded power modules (i.e., n=4) in the R phase, S phase, and T phase, and each level of power module includes 6 power units with input ends connected in parallel (i.e., m=6). Taking the R phase as an example, the 4 power modules are connected in series; the input ends of the 6 power units in the first power module are connected in parallel, and the internal structure and connection relationship of the 2nd, 3rd, and 4th power modules are the same as those of the 1st power module. Pull out the DC output end of the first power unit in the 1st to 4th power modules respectively, and connect the 4 DC output ends to form the first DC output of the R phase; similarly, connect the output end of the second power unit in the 1st to 4th power modules to form the second DC output of the R phase, connect the output end of the third power unit in the 1st to 4th power modules to form the third DC output of the R phase, connect the output end of the fourth power unit in the 1st to 4th power modules to form the fourth DC output of the R phase, connect the output end of the fifth power unit in the 1st to 4th power modules to form the fifth DC output of the R phase, and connect the output end of the sixth power unit in the 1st to 4th power modules to form the sixth DC output of the R phase. That is, the outputs of the power units with the same sequence in each power module are connected in parallel to form the DC output of the phase. After all are connected in parallel, there can be at most 6 DC outputs in each phase, and the DC output is composed of the outputs of the power units with the same sequence number from the 4 power modules. The component structure and connection method in the S phase and the T phase are the same as those in the R phase. After the 1st DC output of the R phase is connected to the 1st DC output of the S phase and the 1st DC output of the T phase to the 1st DC bus, the load 1 can be directly connected. After the kth DC output of the R phase is connected to the kth DC output of the S phase and the kth DC output of the T phase to the kth DC bus, the load k can be directly connected. The power converter in this example can form 6 DC buses, which can simultaneously meet 6 loads with different requirements. There can also be other parallel connection methods of the DC output terminals of the power units. For example, there are 4 levels of cascaded power modules in the R phase, the S phase, and the T phase respectively (i.e., n=4), and each level of the power module includes 3 power units with input terminals connected in parallel (i.e., m=3). The connection method of the input terminal of the power module and the input terminal of the power unit is the same as above, and will not be repeated here.A power unit is selected from the four power modules, and the DC output ends of the selected power unit are connected in parallel to form a DC output of the power converter. For example, for each phase: the DC output ends of the power unit with a serial number of 1 are selected from the first power module of each phase, the power unit with a serial number of 1 is selected from the second power module, the power unit with a serial number of 2 is selected from the third power module, and the power unit with a serial number of 3 is selected from the fourth power module, and are connected in parallel to form a DC output of the power converter; the DC output ends of the power unit with a serial number of 2 are selected from the first power module of each phase, and the DC output ends of the power unit with a serial number of 3 are selected from the fourth power module, and are connected in parallel to form a DC output of the power converter. The DC output ends of the power unit with sequence number 2 selected from the first power module, the power unit with sequence number 3 selected from the second power module, the power unit with sequence number 3 selected from the third power module, and the power unit with sequence number 1 selected from the fourth power module are connected in parallel to form a DC output of the power converter; the DC output ends of the power unit with sequence number 3 selected from the first power module of each phase, the power unit with sequence number 3 selected from the second power module, the power unit with sequence number 1 selected from the third power module, and the power unit with sequence number 2 selected from the fourth power module are connected in parallel to form a DC output of the power converter. The power converter of the embodiment of the present invention not only reduces the high voltage electricity of the AC power grid to medium and low voltage after rectification and isolation processing to supply power to the load, but also because the load draws power from the corresponding position or sequence of power units in each power module in each phase on average, the process of drawing power does not affect other power units in the same power module, so it can meet the loads with different requirements at the same time. Moreover, the power converter provided by the embodiment of the present invention does not require an additional DC / DC converter, and the number of power electronic stages from the AC power grid to the load is reduced, which can reduce the consumption generated in the power conversion process, improve conversion efficiency, and reduce costs.

[0028] In some embodiments, the third input terminal and the fourth input terminal of the power unit are respectively connected in series with a filter inductor.

[0029] In some embodiments, a filter inductor is connected between the input front end of the power converter and each phase of the AC power grid.

[0030] The power unit is used for rectification and voltage transformation. In some embodiments, the power unit is also used to isolate the floating voltage. The floating voltage can refer to the non-standard voltage generated by the interaction between components, and can also be understood as a disturbance voltage. The isolation of the floating voltage can ensure the normal operation of the circuit. In the same power converter, the internal structure of the power unit is exactly the same, so the structure of the power module is also the same. In some embodiments, each power unit is composed of a rectifier circuit and an isolation circuit connected in series.

[0031] Figure 4The figure is a schematic diagram of the structure of a power unit according to an embodiment of the present invention. In some embodiments, the medium voltage power unit includes an H-bridge as an active front end for AC / DC rectification. In some embodiments, a cascade rectifier circuit of multiple H-bridges can also be considered as an active front end; the rectifier output is connected to an isolated DC / DC conversion circuit, which is used for voltage conversion and isolation of floating voltage.

[0032] In some embodiments, the power units constituting the parallel DC output are connected to a controller, and the controller is used to control the DC output. Preferably, the power units constituting the parallel DC output are connected to share the same controller.

[0033] In some embodiments, the load may be a charger for an electric vehicle or a server in a data center, or a distributed battery for energy storage, or other loads requiring distributed wiring, or a centralized load (when connecting a centralized load, multiple DC output terminals of the power converter need to be connected in parallel).

[0034] The various embodiments of this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments or implementations. The same or similar parts between the various embodiments of the present invention can be referred to each other, and the implementation principles of the inventive concept and the technical effects produced can be referred to each other, which will not be repeated here. In the absence of conflict, the various embodiments or implementations of the present invention can be combined with each other.

[0035] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

[0036] Reference numerals:

[0037] 110-R phase 1st power module;

[0038] 111-R phase power unit in the first power module;

[0039] 120-R phase nth power module;

[0040] 121-R phase power unit in the nth power module;

[0041] 210-S phase 1st power module;

[0042] 211-The power unit in the first power module of S phase;

[0043] 220-S phase nth power module;

[0044] 221-S phase power unit in the nth power module;

[0045] 310-T phase 1st power module;

[0046] 311-T phase power unit in the first power module;

[0047] 320-T phase nth power module;

[0048] 321-T phase power unit in the nth power module.

Claims

1. A power converter, the power converter being suitable for being connected between an AC power source having multiple phases drawn from an AC power grid and a load, characterized in that: For each phase of the AC power supply, the power converter includes n power modules, each power module having: An AC input terminal; m power units, the m power units are connected in parallel to the AC input terminal and are suitable for converting AC into DC; and m DC output terminals, wherein the AC input terminals of the n power modules are sequentially connected in series and connected between the corresponding phases and a common point, and Selecting a power unit from each power module, and connecting the DC output ends of the selected power units in parallel to form a DC output of the power converter; Wherein, n and m are both integers greater than 0.

2. The power converter according to claim 1, characterized in that: The AC input terminal includes a first input terminal and a second input terminal; The AC input terminals of the n power modules are sequentially connected in series and connected between corresponding phases and a common point, including: For each phase of the AC power supply: The second input terminal of the i-th power module is connected to the first input terminal of the i+1-th power module, i=1, 2, ..., n-1; A first input terminal of the first power module is connected to the output of the phase; The second input terminal of the nth power module is connected to the common point.

3. The power converter according to claim 2, characterized in that: The input end of the power unit includes a third input terminal and a fourth input terminal; The m power units are connected in parallel to the AC input end, comprising: For each of the power units: The third input terminal of the power unit is connected to the first input terminal of the power module to which the power unit belongs; The fourth input terminal of the power cell is connected to the second input terminal of the power module to which the power cell belongs.

4. The power converter according to claim 1, characterized in that: The DC output end of the power unit includes a first output terminal and a second output terminal; A power unit is selected from each power module, and the DC output ends of the selected power units are connected in parallel to form a DC output of the power converter, including: A power unit is selected from each of the power modules, the first output terminals of the selected power units are connected together, and the second output terminals of the selected power units are connected together to form a DC output of the power converter.

5. The power converter according to claim 1, characterized in that: The power unit is composed of a rectifier circuit and an isolation circuit connected in series.

6. The power converter according to claim 5, characterized in that: The rectification circuit comprises: an H-bridge as an active front end for AC / DC rectification; and The isolation circuit includes: an isolated DC / DC conversion circuit, and the isolated DC / DC conversion circuit is used for voltage conversion and isolation of floating voltage.

7. The power converter according to claim 1, characterized in that: The power unit constituting the kth DC output is connected to a controller, and the controller is used to control the DC output.

8. The power converter according to claim 1, characterized in that: The load is a distributed load or a centralized load.

9. The power converter according to claim 8, characterized in that: The distributed loads include: chargers for electric vehicles, servers in data centers, or distributed batteries for energy storage.

10. The power converter according to claim 1, characterized in that: The AC power source with multiple phases drawn from the AC power grid is a three-phase AC power source.

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