TWI719533B - Power apparatus applied in sst structure and three-phase power source system having the same - Google Patents

Abstract

A power apparatus applied in SST structure includes a first AC-to-DC conversion unit, a first DC bus, an isolated transformer, a DC-to-AC conversion unit, a second AC-to-DC conversion unit, and a second DC bus. The first AC-to-DC conversion unit has a first three-level bridge arm and a second three-level bridge arm. A first DC voltage is across on the first DC bus. The isolated transformer has a primary side and a secondary side. The DC-to-AC conversion unit has a third three-level bridge arm and a fourth three-level bridge arm. The second AC-to-DC conversion unit has a fifth three-level bridge arm and a sixth three-level bridge arm. A second DC voltage is across on the second DC bus.

Description

Power supply device and three-phase power system applied to solid-state transformer architecture

The present invention relates to a power supply device and a three-phase power supply system, in particular to a power supply device and a three-phase power supply system applied to a solid-state transformer architecture.

With the development of power electronic components and the vigorous development of distributed power supplies and smart power grids, solid state transformers (SST) have become more and more popular research topics. Solid-state transformers have multi-functional and high-performance characteristics, including integration of microgrids, power factor correction, reactive power compensation, fault current isolation, and output voltage adjustment.

However, the power supply devices applied to the solid-state transformer architecture still face problems that need to be overcome, such as the problem of DC side voltage balance, wiring design difficulties, high man-hours and high costs, complex control circuits, and the size cannot be reduced... etc. For this reason, how to design a power supply device and a three-phase power system applied to a solid-state transformer architecture to solve the aforementioned technical problems is an important subject studied by the inventors of this case.

The purpose of the present invention is to provide a power supply device applied to a solid-state transformer structure to solve the problems of the prior art.

In order to achieve the purpose of the foregoing disclosure, the power supply device applied to the solid-state transformer architecture proposed by the present invention includes a first AC-DC conversion unit, a first DC bus, an isolation transformer, a DC-AC conversion unit, and a second AC-DC conversion unit And the second DC bus. The first AC-DC conversion unit has a first three-level bridge arm and a second three-level bridge arm coupled to the first three-level bridge arm. The first side of the first AC-DC conversion unit is coupled to an AC power supply. The first DC bus bar is coupled to the second side of the first AC-DC conversion unit and has a first DC voltage. The isolation transformer has a primary side and a secondary side. The DC-AC conversion unit has a third three-level bridge arm and a fourth three-level bridge arm coupled to the third three-level bridge arm. The first side of the DC-AC conversion unit is coupled to the first DC bus bar, and the DC The second side of the AC conversion unit is coupled to the primary side. The second AC-DC conversion unit has a fifth three-level bridge arm and a sixth three-level bridge arm coupled to the fifth three-level bridge arm. The first side of the second AC-DC conversion unit is coupled to the secondary side. The second DC bus bar is coupled to the second side of the second AC-DC conversion unit and has a second DC voltage.

With the proposed power supply device applied to the solid-state transformer architecture, wiring can be simplified, the design of the control circuit can be simplified, and the circuit volume can be reduced.

The purpose of the present invention is to provide a three-phase power system applied to a solid-state transformer architecture to solve the problems of the prior art.

In order to achieve the aforementioned purpose, the present invention proposes a three-phase power system applied to a solid-state transformer architecture, in which any phase AC power source is coupled to a plurality of power supply devices. The first AC-DC conversion unit of the power supply device is coupled in series, and the second DC bus bar of the power supply device is coupled in parallel.

The proposed three-phase power supply system applied to the solid-state transformer architecture can make wiring easy, simplify the design of the control circuit, reduce the circuit volume, and achieve voltage equalization and power supply balance.

In order to further understand the technology, means and effects of the present invention to achieve the intended purpose, please refer to the following detailed description of the present invention and the accompanying drawings. I believe the purpose and features of the present invention And the characteristics, when you can get an in-depth and specific understanding, however, the accompanying drawings are only for reference and description, and are not used to limit the present invention.

11: The first AC-DC conversion unit

12: The first DC bus

13: Isolation transformer

14: DC/AC conversion unit

15: The second AC-DC conversion unit

16: The second DC bus

17: Switch unit

111: The first three-level bridge arm

112: second three-level bridge arm

131: Primary side

132: secondary side

141: The third three-level bridge arm

142: The fourth three-level bridge arm

151: Fifth three-level bridge arm

152: Sixth three-level bridge arm

S11~S18: Power switch

S21~S28: Power switch

S31~S38: Power switch

D1~D12: Diode

P10: midpoint of potential

P20: midpoint of potential

P11: The first contact

P12: second contact

P13: third contact

P14: Fourth contact

P21: Fifth contact

P22: The sixth contact

Vac: AC power

Vdc: DC power supply

Vdc1: the first DC voltage

Vdc2: second DC voltage

Cr: Resonant capacitor

Llk1: Leakage inductance

V1: first voltage

V2: second voltage

V3: third voltage

V _AN : Phase voltage

Fig. 1A~ Fig. 1B are circuit diagrams of a power supply device applied to a solid-state transformer structure according to the present invention.

Figure 2: is a block diagram of a three-phase power system applied to a solid-state transformer architecture according to the present invention.

Fig. 3 is a schematic diagram of the interleaving phase shift mode control of the first AC-DC conversion unit of the present invention.

The technical content and detailed description of the present invention are described below in conjunction with the drawings.

Please refer to FIG. 1 (consisting of FIG. 1A and FIG. 1B), which is a circuit diagram of a power supply device with a solid-state transformer architecture according to the present invention. The power supply device applied to the solid-state transformer architecture includes a first AC-DC conversion unit 11, a first DC bus 12, an isolation transformer 13, a DC-AC conversion unit 14, a second AC-DC conversion unit 15, and a second DC bus 16.

The first AC-DC conversion unit 11 has a first three-level bridge arm 111 and a second three-level bridge arm 112 coupled to the first three-level bridge arm 111, and the first side of the first AC-DC conversion unit 11 is coupled AC power supply Vac. The first DC bus bar 12 is coupled to the second side of the first AC-DC conversion unit 11 and has a first DC voltage Vdc1. The isolation transformer 13 has a primary side 131 and a secondary side 132.

The first AC-DC conversion unit 11 is coupled to an AC power source Vac through an EMI transformer and a boost inductor, or can be called a power grid.

The DC-AC conversion unit 14 has a third three-level bridge arm 141 and a fourth three-level bridge arm 142 coupled to the third three-level bridge arm 141. The first side of the DC-AC conversion unit 14 is coupled to the first DC The second side of the DC-AC conversion unit 14 is coupled to the primary side 131 of the isolation transformer 13. The DC-AC conversion unit 14 switches the voltage of the first DC bus 12 into a high-frequency AC signal, and isolates it The transformer 13 transmits. The second AC-DC conversion unit 15 has a fifth three-level bridge arm 151 and a sixth three-level bridge arm 152 coupled to the fifth three-level bridge arm 151, and the first side of the second AC-DC conversion unit 15 is coupled Isolate the secondary side 132 of the transformer 13. The second DC bus 16 is coupled to the second side of the second AC-DC conversion unit and has a second DC voltage Vdc2. The second AC-DC conversion unit 15 receives the high-frequency AC signal from the secondary side 132 of the isolation transformer 13, and Converted into a second direct current voltage Vdc2.

The first three-level bridge arm 111 includes two series-connected power switches S11, S12 and a diode D1 coupled to the common contact point of the two power switches S11, S12, and two series-connected power switches S13, S14 and The power switch S13, S14 have a common contact diode D2. In addition, the power switch S12 is coupled to the power switch S13, and is commonly connected to the first contact P11, and the diode D1 is coupled to the diode D2, and is commonly connected to the potential midpoint P10, thus forming a three-level bridge Arm, by controlling this bridge arm, three voltage levels can be output (see Figure 3 for cooperation). Among them, the power switches S11 to S14 can be composed of MOSFET power transistors, or IGBT insulated gate bipolar transistors and anti-parallel diodes. In addition, the power switches S11 to S14 and the diodes D1, D2 can be integrated into a modular structure, which can reduce the number of pins, facilitate the layout, and reduce the difference between components.

The second three-level bridge arm 112 includes two series-connected power switches S15, S16 and a diode D3 coupled to the common contact point of the two power switches S15, S16, and two series-connected power switches S17, S18 and The power switch S17 and S18 have a common contact diode D4. In addition, the power switch S16 is coupled to the power switch S17 and is commonly connected to the second contact P12, and the diode D3 is coupled to the diode D4 and is commonly connected to the potential midpoint P10. its Among them, the power switches S15~S18 can be composed of MOSFET power transistors, or IGBT insulated gate bipolar transistors and anti-parallel diodes. Moreover, the power switches S15~S18 and the diodes D3 and D4 can also be integrated into a modular structure. Furthermore, the first contact P11 and the second contact P12 of the first AC-DC conversion unit 11 are coupled to the AC power source Vac, since the first three-level bridge arm 111 and the second three-level bridge arm 112 can output three There are two voltage levels, so it can be controlled to have multiple different voltage levels between the first contact P11 and the second contact P12 (Vdc1,1/2*Vdc1,0,-1/2*Vdc1,-Vdc1) In this way, the switching stress can be reduced and the harmonics can be reduced. The control method can use methods such as space vector pulse width modulation (SVPWM) to generate the control signal, but it is not limited to this, as long as it can be used in the first It is sufficient that a plurality of different voltage levels are generated between the contact point P11 and the second contact point P12.

Similarly, the third three-level bridge arm 141 includes two series-connected power switches S21, S22 and a diode D5 coupled to the common contact point of the two power switches S21, S22, and two series-connected power switches S23, S24 and a coupling Connect to the diode D6 at the common contact point of the two power switches S23 and S24. Moreover, the power switch S22 is coupled to the power switch S23 and is commonly connected to the third contact P13, and the diode D5 is coupled to the diode D6 and is commonly connected to the potential midpoint P10. Among them, the power switches S21~S24 can be composed of MOSFET power transistors, or IGBT insulated gate bipolar transistors and anti-parallel diodes. Moreover, the power switches S21 to S14 and the diodes D5 and D6 can also be integrated into a modular structure.

The fourth three-level bridge arm 142 includes two series-connected power switches S25, S26 and a diode D7 coupled to the common contact point of the two power switches S25, S26, and two series-connected power switches S27, S28 and The power switch S27, S28 have a common contact diode D8. Moreover, the power switch S26 is coupled to the power switch S27 and is commonly connected to the fourth contact P14, and the diode D7 is coupled to the diode D8 and is commonly connected to the potential midpoint P10. Among them, the power switches S25~S28 can be composed of MOSFET power transistors, or IGBT insulated gate bipolar transistors and anti-parallel diodes. Similarly, the power switches S25~S28 and diodes D7 and D8 can also be integrated into a modular structure. Furthermore, the third three-level bridge arm 141 and the fourth three-level bridge arm 142 of the DC/AC conversion unit 14 are three-level bridge arms, which can reduce the switching stress.

Similarly, the fifth three-level bridge arm 151 includes two series-connected power switches S31, S32 and a diode D9 coupled to the common contact point of the two power switches S31, S32, and two series-connected power switches S33, S34 and Connect to the diode D10 at the common contact point of the two power switches S33 and S34. Moreover, the power switch S32 is coupled to the power switch S33 and is commonly connected to the fifth contact point P21, and the diode D9 is coupled to the diode D10 and is commonly connected to the potential midpoint P20. Among them, the power switches S31 to S34 can be composed of MOSFET power transistors, or IGBT insulated gate bipolar transistors and anti-parallel diodes. In addition, the power switches S31 to S34 and the diodes D9 and D10 can be integrated into a modular structure, which can reduce the number of pins, make wiring easy, and reduce the difference between components.

The sixth three-level bridge arm 152 includes two series-connected power switches S35, S36 and a diode D11 coupled to the common contact point of the two power switches S35, S36, and two series-connected power switches S37, S38 and The power switch S37 and S38 have a common contact diode D12. In addition, the power switch S36 is coupled to the power switch S37 and is commonly connected to the sixth contact point P22, and the diode D11 is coupled to the diode D12 and is commonly connected to the potential midpoint P20. Among them, the power switches S35~S38 can be composed of MOSFET power transistors or IGBT insulated gate bipolar transistors and anti-parallel diodes. In addition, the power switches S35 to S38 and the diodes D11 and D12 can be integrated into a modular structure, which can reduce the number of pins, make wiring easy, and reduce the difference between components. Furthermore, the fifth contact point P21 and the sixth contact point P22 of the fifth three-level bridge arm 151 and the sixth three-level bridge arm 152 of the second AC-DC conversion unit 15 are coupled to the secondary side of the isolation transformer 13 132. The principle of receiving the AC signal from the secondary side is similar to that of the aforementioned first AC-DC conversion unit 11, which will not be repeated here.

In one embodiment, the above-mentioned modularized first three-level bridge arm 111 to sixth three-level bridge arm 152 can have the same modular structure, so they can be substituted for each other in the use of the system. It saves installation man-hours and avoids assembly errors, and can simplify the design and control strategy of the control circuit.

The primary side 131 of the isolation transformer 13 has an LLC resonant tank. The LLC resonant tank shown in FIG. 1 is presented in a parametrically symmetrical manner, that is, each branch has 2Cr (resonant capacitor) and 1/2Llk1 (leakage inductance), can also be represented by Cr and Llk1 in a branch. Among them, the isolation transformer 13 is used to electrically isolate the circuit on the primary side 131 and the circuit on the secondary side 132.

The power supply device applied to the solid-state transformer architecture disclosed in the present invention is mainly applied to the first DC voltage Vdc1 on the first DC bus 12 that is substantially equal to or substantially similar to the second DC voltage Vdc2 on the second DC bus. For example, but not limited to, the first DC voltage Vdc1 is 1580 volts, and the second DC voltage Vdc2 is 1500 volts. Such a voltage is close to the power generation system of a photovoltaic power station, and is suitable for connecting to the DC voltage bus of a photovoltaic power station for conversion and regulation of electrical energy. . In this way, the first three-level bridge arm 111 to the sixth three-level bridge arm 152 of the same modular structure have the same specifications, so they can be substituted for each other in the use of the system, which can save installation man-hours. , And can simplify the design and control strategy of the control circuit.

The power supply device of the present invention has a bidirectional power flow operation mode, and the bidirectional mode can be an energy-storing mode, or forward operation and energy-releasing mode, or Called reverse operation (reverse operation). The so-called forward operation means that the power supply device receives AC power Vac (or electric energy provided by the grid) and converts it into DC power Vdc through the first AC-DC conversion unit 11, the DC-AC conversion unit 14, and the second AC-DC conversion unit 15. For DC loads, such as charging stations or energy storage systems. Specific applications can be, for example, but not limited to, the power provided by the power grid is used to supply the power required by the charging station to power the electric vehicle for charging, or the off-peak operation of the power grid or the excess power of the distributed power generation device can be stored in the energy storage system .

On the contrary, the so-called reverse operation means that the DC power supply Vdc is converted into the AC power supply Vac via the second AC-DC conversion unit 15, the DC-AC conversion unit 14 and the first AC-DC conversion unit 11. Specific applications can be, for example, but not limited to, photovoltaic cells (photovoltaic cells), or solar cells output its DC power source, as compensation for peak power demand in the region, adjustment of power supply quality, and even power supply. Sold to the grid (power company). In addition, the circuit of the power supply device presents a symmetrical configuration, which can simplify the design and control strategy of the control circuit during forward operation and reverse operation.

In the embodiment of the present invention, the switching frequency of the power switches S11~S18 of the first three-level bridge arm 111 and the second three-level bridge arm 112 is the first switching frequency, and the third three-level bridge arm 141, the fourth The switching frequency of the power switches of the three-level bridge arm 142, the fifth three-level bridge arm 151, and the sixth three-level bridge arm 152 is the second switching frequency, where the first switching frequency is smaller than the second switching frequency, for example , The first switching frequency can be between 7kHz~12kHz, and the second switching frequency can be between 200kHz~400kHz. Specifically, since the DC-AC conversion unit 14, the second AC-DC conversion unit 15 and the LLC resonant tank form a resonant conversion circuit, the power switches of the third three-level bridge arm 141 and the fourth three-level bridge arm 142 and the fifth The power switches of the three-level bridge arm 151 and the sixth three-level bridge arm 152 operate in soft switching. Therefore, the second switching frequency of its switching can reach 200kHz~400kHz, which can reduce the size of the transformer. Compared with the power frequency transformer of the traditional power system, the isolation transformer 13 achieves the purpose of electrical isolation and is greatly reduced in size. In addition, since the power switches of the first three-level bridge arm 111 and the second three-level bridge arm 112 of the first AC-DC conversion unit 11 are operated in hard switching, the first switching frequency for controlling the switching is relatively low. The second switching frequency is small, for example, 7 kHz to 12 kHz, so that the switching loss of the first AC-DC conversion unit 11 can be reduced and the efficiency can be improved.

The power supply device of the present invention further includes a switch unit 17 which is coupled in series to a branch on the second side of the second AC-DC conversion unit 15. The switch unit 17 is mainly used when multiple power supply devices are used in parallel, so that the output of the power supply device does not affect the system voltage of the parallel architecture by turning off the switch unit 17.

Please refer to FIG. 2, which is a block diagram of a three-phase power system applied to a solid-state transformer architecture according to the present invention. FIG. 2 shows a schematic diagram of the connection of multiple power supply devices included in the three-phase power supply system, wherein the AC power supply Vac side is coupled in series, and each second DC bus 16 is coupled in parallel. Specifically, taking the A phase of the three-phase power supply as an example, it has multiple sets of power supply devices with isolated DC power supplies. The number of settings is determined by the ratio of the system voltage to the withstand voltage of each power supply device. For example, when the line-to-line voltage of the system voltage is 13.2kV (the phase-to-phase voltage is 7.62kV), if the withstand voltage of each power supply device When it is 0.847kV, the number of power supply devices for each phase can be designed as nine groups. Therefore, the first AC-DC conversion units 11 of the nine groups of power supply devices are coupled in series, and the second DC bus bars 16 of each group of power supply devices are coupled in parallel with each other to provide a DC power supply Vdc (in forward operation) ) Supply power to charging stations or energy storage systems, or receive DC power Vdc from photovoltaic cells (under reverse operation). Furthermore, each phase structure shown in FIG. 2 can be combined into a three-phase multi-group structure. Specifically, the AC power supply Vac side is connected in a Y connection and neutral point N is grounded, and each group of the three-phase power supply devices can be coupled in parallel with each other. Taking the number of power supply devices in each phase of the aforementioned nine groups as an example, by combining the three phases, the 27 groups of second DC bus bars 16 are connected in parallel with each other. In this way, the effects of voltage equalization and power supply balance can be achieved. Taking the charging station as an example, the electric energy required by the charging station can be supplied through the DC power supply Vdc provided by 27 sets of power supply devices. Among them, 27 groups of power supply devices can provide the power required by the charging station equally or proportionally, but the present invention is not limited by the power supply mode described.

Please refer to FIG. 3, which is a schematic diagram of the interleaved phase shift mode control of the first AC-DC conversion unit of the present invention. The first AC-DC conversion units 11 coupled to each phase in the three-phase power system are controlled in an interleaved phase-shift manner. For example, taking three power supply devices per phase as an example, and the first contact P11 and the second contact P12 of the first first AC-DC conversion unit 11 are controlled to the first voltage V1, and the second The first AC-DC conversion unit 11 is controlled to a second voltage V2 and the third first AC-DC conversion unit 11 is controlled to a third voltage V3. Among them, each voltage V1~V3 has multiple voltage levels (Vdc1,1/2*Vdc1,0,-1/2*Vdc1,-Vdc1) as mentioned above, and each voltage V1~V3 corresponds to The first AC-DC conversion unit 11 performs switching control at 10kHz, and the phase angle is 120 degrees apart. Then _{the frequency (system frequency) of the phase voltage V AN} of each phase can be doubled to 30kHz, thereby making each group The first AC-DC conversion unit 11 has a lower switching frequency to improve efficiency, and enables the system to have better total harmonic distortion (THD) and can use smaller filter elements.

In summary, the present invention has the following features and advantages:

1. Replacing traditional transformers with solid-state transformers can increase the efficiency and reduce the occupied volume.

2. The modularization of the first three-level bridge arm to the sixth three-level bridge arm can reduce the number of pins, make the layout easier, and reduce the difference between components.

3. Since the first three-level bridge arm to the sixth three-level bridge arm of the same modular structure have the same specifications, they can be substituted for each other in the use of the system, which can save installation man-hours, and can simplify control Circuit design and control strategy.

4. For the first three-level bridge arm and the second three-level bridge arm (and the third three-level bridge arm, the fourth three-level bridge arm and the fifth three-level bridge arm, and the sixth three-level bridge arm) Arm) uses a three-level bridge arm to reduce switching stress and reduce harmonics.

5. The DC-AC conversion unit, the second AC-DC conversion unit and the LLC resonant tank form a resonant conversion circuit, so the power switches of the third three-level bridge arm and the fourth three-level bridge arm and the fifth three-level bridge arm are connected with each other. The power switch of the sixth and third-level bridge arm operates in soft switching. Therefore, the second switching frequency of its switching can reach 200kHz~400kHz, which can greatly reduce the size of the transformer.

6. By combining the three phases, all the second DC busbars are connected in parallel, so that the effect of voltage equalization and power supply balance can be achieved

7. The first AC-DC conversion unit of each phase is controlled through the interlaced phase shift method, so that each group of the first AC-DC conversion unit can have a lower switching frequency, which can improve efficiency and make the system have a better overall resonance. Wave distortion and smaller filter elements can be used.

The above are only detailed descriptions and drawings of the preferred embodiments of the present invention. However, the features of the present invention are not limited to these, and are not intended to limit the present invention. The full scope of the present invention should be as follows The scope of patent application shall prevail. All embodiments that conform to the spirit of the patent application scope of the present invention and similar changes should be included in the scope of the present invention. Anyone familiar with the art in the field of the present invention can easily think about it. And the changes or modifications can be covered in the following patent scope of this case.

11: The first AC-DC conversion unit

12: The first DC bus

14: DC/AC conversion unit

111: The first three-level bridge arm

112: second three-level bridge arm

141: The third three-level bridge arm

142: The fourth three-level bridge arm

S11~S18: Power switch

S21~S28: Power switch

P10: midpoint of potential

P11: The first contact

P12: second contact

P13: third contact

P14: Fourth contact

Vac: AC power

Vdc1: the first DC voltage

Claims (13)

A complex power supply device applied to a solid-state transformer architecture, each of the power supply devices includes: a first AC-DC conversion unit having a first three-level bridge arm and a second, third-level bridge arm coupled to the first three-level bridge arm Level bridge arm, a first side of the first AC-DC conversion unit is coupled to an AC power source; a first DC bus bar is coupled to a second side of the first AC-DC conversion unit, and has a first side A DC voltage; an isolation transformer with a primary side and a secondary side; a DC AC conversion unit with a third three-level bridge arm and a fourth three-level bridge arm coupled to the third three-level bridge arm Bridge arm, a first side of the DC/AC conversion unit is coupled to the first DC bus, and a second side of the DC/AC conversion unit is coupled to the primary side; a second AC/DC conversion unit has a A fifth three-level bridge arm and a sixth three-level bridge arm coupled in parallel to the fifth three-level bridge arm, a first side of the second AC-DC conversion unit is coupled to the secondary side; and The second DC bus bar is coupled to a second side of the second AC-DC conversion unit and has a second DC voltage; wherein the inputs of the first AC-DC conversion units of the power supply devices are coupled in series, And the outputs of the second DC bus bars are coupled in parallel; wherein, the first three-level bridge arm to the sixth three-level bridge arm have the same modular structure. As described in the first item of the scope of patent application, the plurality of power supply devices applied to the solid-state transformer architecture, wherein the first three-level bridge arm has a first contact coupled to the AC power supply, and the second three-level The bridge arm has a second contact coupled to the AC power source, and there are a plurality of different voltage levels between the first contact and the second contact. As described in the first item of the scope of patent application, the plurality of power supply devices applied to the solid-state transformer architecture, wherein the primary side of the isolation transformer has an LLC resonance tank. As described in the first item of the scope of patent application, the plurality of power supply devices applied to the solid-state transformer architecture, wherein the first direct current voltage and the second direct current voltage are substantially equal or substantially similar. As described in the first item of the scope of patent application, a plurality of power supply devices applied to a solid-state transformer architecture, wherein the power supply device has a bidirectional power flow operation mode. As described in the first item of the scope of patent application, the multiple power supply device applied to the solid-state transformer architecture, wherein the switching frequency of the power switches of the first three-level bridge arm and the second three-level bridge arm is a first switching frequency, The switching frequency of the power switches of the third three-level bridge arm, the fourth three-level bridge arm, the fifth three-level bridge arm, and the sixth three-level bridge arm is a second switching frequency, wherein the The first switching frequency is less than the second switching frequency. As described in item 6 of the scope of patent application, the multiple power supply device applied to the solid-state transformer architecture, wherein the first switching frequency is between 7k Hz and 12k Hz. As described in item 6 of the scope of patent application, the plurality of power supply devices applied to the solid-state transformer architecture, wherein the second switching frequency is between 200k Hz and 400k Hz. As described in the first item of the scope of patent application, the plurality of power supply devices applied to the solid-state transformer architecture, wherein the second side of the second AC-DC conversion unit has a switch unit coupled in series. A three-phase power system applied to a solid-state transformer architecture, wherein the three-phase power system has a three-phase AC power source, and each phase of the AC power source is coupled to a plurality of units such as any one of items 1 to 9 in the scope of the patent application The power supply devices, the first AC and DC of the power supply devices of each phase The inputs of the conversion unit are coupled in series, and the outputs of the second DC bus bars of the power supply devices are coupled in parallel. As described in item 10 of the scope of patent application, the three-phase power system applied to the solid-state transformer architecture, wherein the first AC-DC conversion units coupled to each phase are controlled in a staggered phase shift manner. As described in item 10 of the scope of patent application, the three-phase power system applied to the solid-state transformer architecture, wherein the number of multiple power devices coupled to each phase is determined by the ratio of the system voltage to the withstand voltage of each power device. As described in item 10 of the scope of patent application, the three-phase power system applied to the solid-state transformer architecture, wherein the second DC bus of each phase is connected to any one of a charging station, a photovoltaic cell, and an energy storage system.

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