Grid forming over distribution grid with renewable sources and loads

A method for operation of a system that is coupled to a distribution grid and a power transmission grid, the method comprising:

• controlling, through a control module, a connect-disconnect switch to connect or disconnect a first segment of the distribution grid to or from a second segment of the distribution grid having a plurality of loads, each load coupled to the second segment of the distribution grid via a demand-response controller, the second segment of the distribution grid further having a plurality of energy generators, each energy generator coupled to the second segment of the distribution grid via a flexible alternating current (AC) transmission system (FACTS) based controller, wherein the second segment of the distribution grid is coupled to a shunt inverter system comprising a 4-quadrant DC-to-AC inverter and a battery, wherein the first segment of the distribution grid is transformer coupled to the power transmission grid through a step-down transformer operable to convert a high voltage of the power transmission grid to a medium or low voltage of the distribution grid;
• providing, through the control module, switching instructions to the 4-quadrant DC-to-AC inverter to provide a power factor correction to the plurality of loads when the connect-disconnect switch connects the first segment of the distribution grid to the second segment of the distribution grid, thereby connecting the power transmission grid to the second segment of the distribution grid with the plurality of loads and the plurality of energy generators;
• operating, through the control module, the shunt inverter system to provide switching and current control instructions to sustain continued operation of the distribution grid in an event the connect-disconnect switch has disconnected the first segment of the distribution grid from the second segment of the distribution grid;
• performing, through the control module operating the connect-disconnect switch and the 4-quadrant DC-to-AC inverter, a restart and grid formation of the distribution grid after recovery operation from a grid failure of the second segment of the distribution grid coupled to the plurality of loads;
• and
• operating, through the control module, the system in the following modes:
• when the connect-disconnect switch is closed, power to charge the battery of the shunt inverter system and power to the plurality of loads, through the demand-response controller, is supplied by the power transmission grid through the closed connect-disconnect switch;
• and
• when the connect-disconnect switch is open, (i) the battery is charged and power to the plurality of loads is supplied by the plurality of energy generators, (ii) the power to the plurality of loads is supplied by the energy generators in conjunction with power from the shunt inverter system, or (iii) the power to the plurality of loads is supplied by the shunt inverter system acting in a grid formation mode.

A tangible, non-transitory, computer-readable media having instructions thereupon which, when executed by a processor, cause the processor to perform operations comprising:

• controlling, through a control module, a connect-disconnect switch to connect or disconnect a first segment of a distribution grid to or from a second segment of the distribution grid, the first segment of the distribution grid being transformer coupled to a power transmission grid through a step-down transformer operable to convert a high voltage of the power transmission grid to a medium or low voltage of the distribution grid, the second segment having energy generators coupled to the second segment via flexible alternating current (AC) transmission system (FACTS) based controllers, the second segment further having a plurality of loads coupled to the second segment via a demand-response controller, the second segment having a battery coupled to the second segment via a 4-quadrant DC-to-AC inverter as a shunt inverter system, wherein when the connect-disconnect switch connects the first segment of the distribution grid to the second segment of the distribution grid, the second segment of the distribution grid is connected to the power transmission grid, wherein when the connect-disconnect switch disconnects the first segment of the distribution grid from the second segment of the distribution grid, the second segment of the distribution grid is disconnected from the power transmission grid;
• operating, through the control module, the connect-disconnect switch to connect the first segment of the distribution grid to the second segment of the distribution grid thereby connecting the distribution grid to the power transmission grid wherein power to the plurality of loads is supplied by power from the energy generators and power from the power transmission grid;
• operating, through the control module, the connect-disconnect switch to disconnect the second segment of the distribution grid from the first segment of the distribution grid;
• providing, through the control module, switching instructions to the 4-quadrant DC-to-AC inverter to provide a power factor correction to the plurality of loads coupled to the second segment of the distribution grid when the second segment of the distribution grid is connected to the power transmission grid;
• operating, through the control module, the shunt inverter system to provide switching and current control instructions to sustain continued operation of the plurality of loads when the second segment of the distribution grid is disconnected from the transmission grid;
• operating, through the control module, the connect-disconnect switch and the shunt inverter system, to perform a restart and grid formation of the second segment of the distribution grid after recovery operation from grid failure;
• and
• operating, through the control module, in the following modes:
• when the connect-disconnect switch is closed, power to charge the battery of the shunt inverter system and power to the plurality of loads, through the demand-response controller, is supplied by the power transmission grid through the closed connect-disconnect switch;
• and
• when the connect-disconnect switch is open, (i) the battery is charged and power to the plurality of loads is supplied by the energy generators, (ii) the power to the plurality of loads is supplied by the energy generators in conjunction with power from the shunt inverter system, or (iii) the power to the plurality of loads is supplied by the shunt inverter system acting in a grid formation mode.