Power apparatus applied in solid state transformer structure and three-phase power system having the same

1. A power apparatus applied in a solid state transformer structure, the power apparatus comprising:

an AC-to-DC conversion unit having a first side and a second side, wherein the first side of the AC-to-DC conversion unit is coupled to an AC power source,

a first DC bus coupled to the second side of the AC-to-DC conversion unit, and having a bus voltage, and

a plurality of bi-directional DC conversion units, each of the bi-directional DC conversion units having a first side and a second side, and being a single-stage conversion structure or two-stage conversion structure, wherein the first sides of the bi-directional DC conversion units are coupled to the first DC bus, the second side of the bi-directional DC conversion units are configured to form at least one second DC bus, and a number of the at least one second DC bus is a bus number,

wherein the at least one second DC bus is coupled to at least one of a charging station, a photovoltaic array, or an energy storage system,

wherein the charging station is coupled to the at least one second DC bus through a charging station converter, the photovoltaic array is coupled to the at least one second DC bus through a photovoltaic converter, and the energy storage system is coupled to the at least one second DC bus through an energy storage system converter, and the charging station converter, the photovoltaic converter and the energy storage system converter are configured to receive the at least one DC voltage or to provide the at least one external DC voltage,

wherein the bi-directional DC conversion units are configured to receive the bus voltage of the first DC bus and convert the bus voltage into at least one DC voltage whose number is same as the bus number, or the bi-directional DC conversion units are configured to receive at least one external DC voltage whose number is same as the bus number and convert the at least one external DC voltage into the bus voltage of the first DC bus.

2. The power apparatus applied in the solid state transformer structure in claim 1 , wherein each of the bi-directional DC conversion units comprises:

a first stage conversion circuit comprising:

an isolated transformer having a primary side and a secondary side,

a primary side resonant circuit coupled to the primary side, and

a secondary side resonant circuit coupled to the secondary side.

3. The power apparatus applied in the solid state transformer structure in claim 1 , wherein each of the bi-directional DC conversion units comprises:

a first stage conversion circuit comprising:

an isolated transformer having a primary side and a secondary side,

a primary side resonant circuit coupled to the primary side, and

a secondary side resonant circuit coupled to the secondary side, and

a second stage conversion circuit coupled to the secondary side resonant circuit, wherein the second stage conversion circuit is a boost or buck circuit.

4. The power apparatus applied in the solid state transformer structure in claim 1 , wherein if the number of the bi-directional DC conversion units is N, the bus number is from 1 to N.

5. A power system applied in a solid state transformer structure, configured to be coupled to a three-phase AC power source, wherein the power system comprises a plurality of power apparatuses coupled to any one phase of the three-phase AC power source, and each of the power apparatuses comprises:

an AC-to-DC conversion unit having a first side and a second side, wherein the first side of the AC-to-DC conversion unit is coupled to any one phase of the three-phase AC power source,

a first DC bus coupled to the second side of the AC-to-DC conversion unit, and having a bus voltage, and

a plurality of bi-directional DC conversion units, each of the bi-directional DC conversion units having a first side and a second side, and being a single-stage conversion structure or two-stage conversion structure, wherein the first sides of the bi-directional DC conversion units are coupled to the first DC bus, the second side of the bi-directional DC conversion units are configured to form at least one second DC bus, and a number of the at least one second DC bus is a bus number,

wherein the at least one second DC bus is coupled to at least one of a charging station, a photovoltaic array, or an energy storage system,

wherein the charging station is coupled to the at least one second DC bus through a charging station converter, the photovoltaic array is coupled to the at least one second DC bus through a photovoltaic converter, and the energy storage system is coupled to the at least one second DC bus through an energy storage system converter, and the charging station converter, the photovoltaic converter and the energy storage system converter are configured to receive the at least one DC voltage or to provide the at least one external DC voltage,

wherein the AC-to-DC conversion units are coupled in series, and the second sides of the bi-directional DC conversion units are alone configured or at least two of the second sides are coupled in parallel.

6. The power system applied in the solid state transformer structure in claim 5 , wherein the second sides of the corresponding bi-directional DC conversion units of the power apparatuses coupled to different phases of the three-phase AC power source are coupled in parallel.

7. The power system applied in the solid state transformer structure in claim 5 , wherein the AC-to-DC conversion units coupled to one phase of the three-phase AC power source are controlled in an interleaved phase-shift manner.

8. The power system applied in the solid state transformer structure in claim 5 , wherein the number of the power apparatuses coupled to one phase of the three-phase AC power source is determined by a ratio of a system voltage of the three-phase AC power source to a withstand voltage of each power apparatus.