Grid forming vector current control
The present disclosure provides a grid forming vector current control system configured to emulate a virtual synchronous machine (VSM). The disclosed system comprises a droop control unit, a current control unit, a virtual admittance unit and a phase locked loop (PLL) unit. The virtual admittance unit and the PLL unit are configured to emulate an inertia of the VSM. A virtual current source is connected in parallel to the VSM.
1. A grid forming vector current control system configured to emulate a virtual synchronous machine (VSM), the system comprising:
a droop control unit;
a current control unit;
a virtual admittance unit; and
a phase locked loop (PLL) unit,
wherein the virtual admittance unit and the PLL unit are configured to emulate an inertia of the VSM,
wherein a virtual current source is connected in parallel to the VSM, and
wherein a factor k VSM is configured to change one or more characteristics of the system continuously from voltage source to current source by proportionally scaling output signals of the virtual admittance unit with the factor k VSM .
2. The system according to claim 1 , wherein an output signal of the droop control unit is connected to the virtual current source.
3. The system according to claim 1 , wherein an output signal of the droop control unit is connected to the PLL unit.
4. The system according to claim 1 , further comprising an active voltage regulator (AVR) unit.
5. The system according to claim 1 , wherein the system is deployed in at least one of a micro grid converter, a photovoltaic (PV) inverter, an uninterruptable power supply (UPS), a grid intertie converter, a railway grid intertie converter, a high voltage direct current (HVDC) converter, or a battery energy storage system (BESS).
6. The system according to claim 1 , wherein the factor k VSM is fed into at least one of the droop control unit, the virtual admittance unit, or the PLL unit in order to increase or decrease an inertial response of the system to disturbances in a main grid.
7. The system according to claim 6 , wherein the system is deployed in at least one of a micro grid converter, a photovoltaic (PV) inverter, an uninterruptable power supply (UPS), a grid intertie converter, a railway grid intertie converter, a high voltage direct current (HVDC) converter, or a battery energy storage system (BESS), and wherein the at least one of the micro grid converter, the PV inverter, the UPS, the grid intertie converter, the railway grid intertie converter, the HVDC converter, or the BESS is connected to the main grid.
8. The system according to claim 6 , wherein the system is deployed in at least one of a micro grid converter, a photovoltaic (PV) inverter, or an uninterruptable power supply (UPS), and wherein the at least one of the micro grid converter, the PV inverter, or the UPS is connected to the main grid.
9. The system according to claim 1 , wherein the factor k VSM scales a nominal power of the VSM by proportionally scaling the output signals of the virtual admittance unit with the factor k VSM , inversely proportionally scaling a proportional gain of the PLL unit with the factor k VSM , and/or proportionally scaling a droop constant with the factor k VSM .
10. The system according to claim 1 , wherein the factor k VSM scales at least one of a spinning wheel factor or a transient power or the inertia.
11. The system according to claim 1 , wherein the droop control unit comprises a fast current source.
12. The system according to claim 4 , wherein the AVR unit is configured to keep a magnitude of a voltage, at a Point of Common Coupling (PCC), constant.
13. The system according to claim 1 , wherein the PLL unit is configured to measure a voltage at a Point of Common Coupling (PCC).
14. A method for controlling a grid forming vector current control emulating a Virtual Synchronous Machine (VSM), the method comprising:
providing a droop control unit,
providing a current control unit,
providing a virtual admittance unit, and
providing a phase locked loop (PLL) unit,
emulating an inertia of the VSM, and
controlling a virtual current source connected in parallel to the VSM,
wherein a factor k VSM changes one or more characteristics of a system, comprising the droop control unit, current control unit, virtual admittance unit, and PLL unit, continuously from voltage source to current source by proportionally scaling output signals of the virtual admittance unit with the factor k VSM .
15. The method according to claim 14 , wherein an output signal of the droop control unit is connected to the virtual current source.
16. The method according to claim 14 , wherein an output signal of the droop control unit is connected to the PLL unit.
17. The method according to claim 14 , further comprising feeding the factor k VSM into at least one of the droop control unit, the virtual admittance unit, or the PLL unit in order to increase or decrease an inertial response of the system to disturbances in a main grid.
18. A method for controlling a grid forming vector current control emulating a Virtual Synchronous Machine (VSM), the method comprising:
providing a droop control unit,
providing a current control unit,
providing a virtual admittance unit, and
providing a phase locked loop (PLL) unit,
emulating an inertia of the VSM,
controlling a virtual current source connected in parallel to the VSM, and
scaling a nominal power of the VSM by one or more of:
proportionally scaling output signals of the virtual admittance unit with a factor kVSM;
inversely proportionally scaling a proportional gain of the PLL unit with the factor kVSM; or
proportionally scaling a droop constant with the factor kVSM.