Multi-port alternating-current and direct-current hybrid topological structure suitable for flexible interconnection of low-voltage transformer area

Abstract

The invention provides a multi-port alternating current and direct current hybrid topological structure suitable for flexible interconnection of a low-voltage transformer area, which comprises an energy storage battery, an AC bus, a DC bus, alternating current and direct current ports and a controller, and is characterized in that the alternating current and direct current ports provide a plurality of ports which are respectively connected with the AC bus, the DC bus, an alternating current load, a direct current load and a power grid, and the alternating current and direct current ports communicate with the controller; the AC / DC port provides a plurality of power conversion modules and comprises a DC / DC module, a DC / AC module I and a DC / AC module II, the AC / DC port provides a port which is connected to an AC micro-grid and a DC micro-grid, supports access to various devices such as an AC / DC source, a load, an energy storage device and a power grid, and adapts to diversified application scenes; a hierarchical control strategy of local control and power supply control is combined, so that system coordination requirements can be balanced, communication links can be reduced, and centralized management of alternating-current and direct-current power supplies is realized; the AC / DC port is provided with a DC / AC module, a DC / DC module and an equalization module, bidirectional conversion of power is realized, and the equalization module can effectively maintain voltage balance between DC buses.

Description

Technical Field

[0001] This invention relates to the field of topology, and in particular to a multi-port AC / DC hybrid topology suitable for flexible interconnection of low-voltage distribution areas. Background Technology

[0002] In recent years, the growth in demand for renewable energy and the emergence of the concept of distributed generation (DG) have spurred the development of distributed power systems and microgrids.

[0003] Among microgrid classifications, hybrid AC / DC microgrids are the most promising structures because they combine the advantages of both AC and DC microgrids. Through multi-port converters that interface AC and DC microgrids, they connect photovoltaic, wind, energy storage, and other distributed power sources to AC / DC loads, enabling power exchange between AC / DC subgrids. This allows them to adapt to a wider variety of distributed power sources and loads, reduces power conversion steps, and improves system rhythm and power reliability. Summary of the Invention

[0004] This invention provides a multi-port AC / DC hybrid topology suitable for flexible interconnection of low-voltage distribution areas, enabling efficient integration and coordinated control of AC / DC sources, AC / DC loads, energy storage batteries, and the power grid. It includes: an energy storage battery, an AC bus, a DC bus, AC / DC ports, and a controller. The AC / DC ports provide multiple ports for connecting to the AC bus, DC bus, AC load, DC load, and the power grid respectively, and communicate with the controller. The AC / DC ports provide multiple power conversion modules, including: a DC / DC module, a DC / AC module I, and a DC / AC module II. One DC end of the DC / DC module is connected to the energy storage battery, and the other DC end is connected to the DC sides of DC / AC module I and DC / AC module II, providing interfaces for connecting DC sources and DC loads. DC / AC module I has its AC side connected to the power grid; DC / AC module II has its AC side connected to AC loads and AC sources.

[0005] Furthermore, the AC / DC ports provide multiple ports for connecting loads and AC / DC sources to form AC links and DC links. The AC / DC ports include: at least one DC source input port P4, at least one DC load port P6, at least one AC source input port P2, at least one AC load port P3, and at least one grid port P1.

[0006] Furthermore, in the AC / DC ports, the grid port P1 is also equipped with a circuit breaker S1 to adapt to islanded mode.

[0007] Furthermore, the controller adopts hierarchical control, including a local controller and a power controller, which communicate with circuit breaker S1, DC / DC module, DC / AC module I, and DC / AC module II to control the operation of the power converter and switch.

[0008] Furthermore, the AC / DC ports adopt a three-wire capacitor-coupled topology, including a four-wire AC port module, an equalization module, and a three-wire DC port. The power grid, AC source, and AC load are connected to the AC side of the four-wire AC port. The four-wire AC port module adopts a three-phase bridge circuit, and the equalization module is connected to the DC side of the four-wire AC port module and the three-wire DC port.

[0009] Furthermore, in DC / AC module I, the AC side is connected to the power grid, and the DC side is connected to the common DC bus via the balancing module; in DC / AC module II, the AC side is connected to the AC load and AC source respectively, and the DC side is connected to the common DC bus via the balancing module; in DC / DC module, one side of the DC side is connected to the DC bus, and the other side of the DC side is connected to the DC source, DC load, and energy storage battery.

[0010] Furthermore, DC / AC module I includes MOSFETs Q1, Q2, Q3, Q5, Q6, and Q7, forming a three-phase bridge circuit. In DC / AC module II, the topology connecting the AC source includes MOSFETs Q17, Q18, Q19, Q20, Q21, and Q22, forming a three-phase bridge circuit with its DC side connected to the DC bus. The topology connecting the AC load includes MOSFETs Q31, Q32, Q33, Q34, Q35, and Q36, forming a three-phase bridge circuit with its DC side connected to the DC bus.

[0011] Furthermore, the equalization module includes: MOSFETs Q4 and Q8, resistor R4, capacitor C4, and capacitor C5 connected to the DC side of DC / AC module I; MOSFETs Q37 and Q38, resistor R12, capacitor C14, and capacitor C15 connected to the DC side of the AC source of DC / AC module II; and MOSFETs Q39 and Q40, resistor R13, capacitor C23, and capacitor C24 connected to the DC side of the AC load of DC / AC module II.

[0012] The beneficial effects of this invention are: This patent application is based on AC / DC ports, providing access to AC and DC microgrids, supporting the connection of various devices such as AC / DC sources, loads, energy storage, and power grids, adapting to diverse application scenarios; and combining hierarchical control strategies of local control and power control, it can simultaneously balance the needs of system coordination and reduce communication links, realizing centralized management of AC and DC power supplies; the AC / DC ports are equipped with DC / AC modules, DC / DC modules, and equalization modules to realize bidirectional power conversion, and the equalization module can effectively maintain voltage balance between DC buses. Attached Figure Description

[0013] Figure 1 This is a diagram of the architecture of a hybrid AC / DC microgrid. Figure 2 This is a circuit configuration diagram for an AC / DC hybrid microgrid. Figure 3 This is a topology diagram of the AC / DC ports. Detailed Implementation

[0014] Figure 1 As shown, it includes: an energy storage battery, an AC bus, a DC bus, AC / DC ports, and a controller. The AC / DC ports provide multiple ports to connect to the AC bus, DC bus, AC load, DC load, and the power grid respectively, and the AC / DC ports communicate with the controller. The AC / DC ports provide multiple power conversion modules, including: a DC / DC module, a DC / AC module I, and a DC / AC module II. The DC / DC module realizes bidirectional energy conversion between the energy storage battery and the DC bus, and supports functions such as constant voltage charging and constant current discharging. One DC end of the DC / DC module is connected to the energy storage battery, and the other DC end is connected to the DC side of DC / AC module I and DC / AC module II, and provides interfaces to connect to DC sources and DC loads. DC / AC module I has its AC side connected to the power grid, and is used to invert DC power on the DC bus into AC power to feed into the power grid. It can also absorb power from the power grid to charge the DC bus, and has the function of bidirectional energy conversion. DC / AC module II is divided into two parts. One part of the AC side is connected to the AC load, and inverts the DC bus power into AC power to supply the load. The other part is connected to the AC source, such as wind power or hydropower.

[0015] Combination Figure 1 , Figure 2 As shown, the AC / DC port provides multiple ports for connecting loads and AC / DC sources to form AC links and DC links. The AC / DC port includes: at least one DC source input port P4, at least one DC load port P6, at least one AC source input port P2, at least one AC load port P3, and at least one grid port P1. The grid port P1 is also equipped with a circuit breaker S1, which enters islanding mode when the circuit breaker S1 is open.

[0016] Furthermore, the controller employs hierarchical control, including a local controller and a power controller, which communicate with circuit breaker S1, the DC / DC module, DC / AC module I, and DC / AC module II to measure relevant signals at each port in real time, thereby achieving optimal system operation. Grid-connected operation: When circuit breaker S1 is closed, the power grid is connected to the AC / DC microgrid system. The AC / DC power supply is used to compensate for each other / switch to supply power to the load, and can charge the energy storage battery and feed the grid. If the grid electricity price is high or the user's electricity consumption is large, and when the energy storage battery SOC is greater than the upper limit threshold (e.g., 90%), the energy storage battery supplies power to the load through the DC bus.

[0017] Islanding Operation: When an abnormal grid voltage or frequency exceeding the limit is detected, the controller issues a command to disconnect the circuit breaker S1, and the system automatically switches to islanding mode. The energy storage battery and DC power source jointly maintain the stability of the DC bus voltage; the DC / AC module II continuously supplies power to the AC load to ensure uninterrupted operation of important loads.

[0018] Combination Figure 2 , Figure 3 As shown, the AC / DC ports adopt a three-wire capacitor-coupled topology, including a four-wire AC port module, an equalization module, and a three-wire DC port. The power grid, AC source, and AC load are respectively connected to the AC side of the four-wire AC port. Figure 2 , Figure 3 Ports P1, P2, and P3 are shown. The four-wire AC port module uses a three-phase bridge circuit. The equalization module is connected to the DC side of the four-wire AC port module and the three-wire DC port to absorb transient voltage spikes and regulate DC voltage balance.

[0019] Furthermore, in DC / AC module I, the AC side is connected to the power grid, and the DC side is connected to the common DC bus via the equalization module. DC / AC module I includes: N-type MOSFETs Q1, Q2, Q3, Q5, Q6, and Q7, forming a three-phase bridge circuit. The DC side of the bridge circuit is connected to the DC bus after passing through the equalization circuit composed of N-type MOSFETs Q4 and Q8, resistor R4, capacitor C4, and capacitor C5.

[0020] Furthermore, the AC side of DC / AC module II is connected to both AC load and AC source. The topology connecting the AC source includes N-type MOSFETs Q17, Q18, Q19, Q20, Q21, and Q22, forming a three-phase bridge circuit. The DC side of this circuit is connected to the common DC bus after passing through an equalization module consisting of N-type MOSFETs Q37 and Q38, resistor R12, capacitor C14, and capacitor C15. The topology connecting the AC load includes N-type MOSFETs Q31, Q32, Q33, Q34, Q35, and Q36. The DC side of the three-phase bridge circuit formed by these components is connected to the DC bus after passing through an equalization module consisting of N-type MOSFETs Q39 and Q40, resistor R13, capacitor C23, and capacitor C24.

[0021] Furthermore, the DC / DC module includes a bridge rectifier circuit consisting of four N-type MOSFETs, a diode connected in parallel at the DC port, and a port capacitor to prevent damage to the capacitors caused by transient voltages.

[0022] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A multi-port AC / DC hybrid topology suitable for flexible interconnection of low-voltage distribution areas, characterized in that, include: The system includes an energy storage battery, an AC bus, a DC bus, AC / DC ports, and a controller. The AC / DC ports provide multiple ports for connecting to the AC bus, DC bus, AC load, DC load, and the power grid, respectively. The AC / DC ports communicate with the controller. The AC / DC port provides multiple power conversion modules, including: a DC / DC module, a DC / AC module I, and a DC / AC module II. One DC terminal of the DC / DC module is connected to the energy storage battery, and the other DC terminal is connected to the DC side of DC / AC module I and DC / AC module II, and provides an interface to connect to a DC source and a DC load. The AC side of DC / AC module I is connected to the power grid. The AC side of DC / AC module II is connected to an AC load and an AC source.

2. The multi-port AC / DC hybrid topology suitable for flexible interconnection of low-voltage distribution areas according to claim 1, characterized in that: The AC / DC port provides multiple ports for connecting loads and AC / DC sources to form AC links and DC links. The AC / DC port includes: at least one DC source input port P4, at least one DC load port P6, at least one AC source input port P2, at least one AC load port P3, and at least one grid port P1.

3. The multi-port AC / DC hybrid topology suitable for flexible interconnection of low-voltage distribution areas according to claim 2, characterized in that: In the AC / DC ports, the grid port P1 is also equipped with a circuit breaker S1, which is adapted to islanded mode.

4. The multi-port AC / DC hybrid topology suitable for flexible interconnection of low-voltage distribution areas according to claim 3, characterized in that: The controller adopts hierarchical control, including a local controller and a power controller, which communicate with circuit breaker S1, DC / DC module, DC / AC module I, and DC / AC module II to control the operation of the power converter and switch.

5. The multi-port AC / DC hybrid topology suitable for flexible interconnection of low-voltage distribution areas according to claim 2, characterized in that: The AC / DC ports adopt a three-wire capacitor-coupled topology, including a four-wire AC port module, an equalization module, and a three-wire DC port. The power grid, AC source, and AC load are connected to the AC side of the four-wire AC port. The four-wire AC port module adopts a three-phase bridge circuit. The equalization module is connected to the DC side of the four-wire AC port module and the three-wire DC port.

6. The multi-port AC / DC hybrid topology suitable for flexible interconnection of low-voltage distribution areas according to claim 5, characterized in that: In DC / AC module I, the AC side is connected to the power grid, and the DC side is connected to the common DC bus via the equalization module; in DC / AC module II, the AC side is connected to the AC load and AC source respectively, and the DC side is connected to the common DC bus via the equalization module; in DC / DC module, one side of the DC side is connected to the DC bus, and the other side of the DC side is connected to the DC source, DC load, and energy storage battery.

7. The multi-port AC / DC hybrid topology suitable for flexible interconnection of low-voltage distribution areas according to claim 6, characterized in that: The DC / AC module I includes MOSFETs Q1, Q2, Q3, Q5, Q6, and Q7, forming a three-phase bridge circuit. The DC / AC module II includes MOSFETs Q17, Q18, Q19, Q20, Q21, and Q22, forming a three-phase bridge circuit with its DC side connected to the DC bus. The topology for connecting the AC load includes MOSFETs Q31, Q32, Q33, Q34, Q35, and Q36, forming a three-phase bridge circuit with its DC side connected to the DC bus.

8. The multi-port AC / DC hybrid topology suitable for flexible interconnection of low-voltage distribution areas according to claim 7, characterized in that: The equalization module includes: MOSFETs Q4 and Q8, resistor R4, capacitor C4, and capacitor C5 connected to the DC side of DC / AC module I; MOSFETs Q37 and Q38, resistor R12, capacitor C14, and capacitor C15 connected to the DC side of the AC source of DC / AC module II; and MOSFETs Q39 and Q40, resistor R13, capacitor C23, and capacitor C24 connected to the DC side of the AC load of DC / AC module II.

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