Turboexpander islanding operation

A method for providing power to an electrical load with a turboexpander generator, the method comprising:

• supplying power from a power grid to the electrical load through an active grid inverter, the active grid inverter configured to provide power for the electrical load and/or for the turboexpander generator, the active grid inverter circuit being further configured to provide power to the power grid from the turboexpander generator;
• determining that the power grid is no longer supplying power to the electrical load;
• generating an alternating current using the turboexpander generator;
• directing the alternating current generated by the turboexpander generator through a bidirectional power converter circuit to convert the alternating current into a direct current, the bidirectional power converter circuit coupled to the active grid rectifier by a direct current (DC) bus;
• directing the direct current to an islanding mode inverter circuit on the DC bus to convert the direct current from the bidirectional power converter circuit into an alternating current that comprises a frequency and an amplitude suitable for delivery to the electrical load, the islanding mode inverter circuit coupled to the active grid rectifier by the DC bus;
• and
• directing the alternating current from the islanding mode inverter circuit to the electrical load.

A system comprising:

• a process gas pipeline configured to transport a process gas, the process gas pipeline comprising a pressure control valve configured to control pressure of the process gas that flows through the process gas pipeline;
• an electric generator in parallel to the pressure control valve, the electric generator comprising:
• a process gas inlet configured to receive process gas from the process gas pipeline through a flow control valve;
• a turbine wheel configured to receive the process gas from the process gas inlet and rotate in response to an expansion of the process gas flowing into an inlet of the turbine wheel and out of an outlet of the turbine wheel, the outlet of the turbine wheel to couple to a process gas outlet, wherein the process gas outlet couples to the process gas pipeline downstream of the pressure control valve, the process gas having a first pressure at the process gas inlet and a second pressure at the process gas outlet, wherein the first pressure is greater than the second pressure;
• a rotor coupled to the turbine wheel and configured to rotate with the turbine wheel, and
• a stator, the electric generator to generate an alternating current upon rotation of the rotor within the stator;
• and
• a power electronics system comprising:
• a bidirectional power converter circuit coupled to an electrical output of the electric generator, the bidirectional power converter circuit to convert alternating current from the electric generator into direct current, and
• an islanding mode inverter circuit coupled to an electrical output of the bidirectional power converter circuit by a direct current (DC) bus, the islanding mode inverter circuit to convert direct current from the bidirectional power converter circuit into an alternating current that comprises a frequency and an amplitude to provide power to an electrical load, and
• an active grid inverter circuit coupled to the islanding mode inverter circuit and the bidirectional power converter circuit by the DC bus, the active grid inverter circuit configured to provide power for the electrical load and/or for the electric generator and is configured to provide power to a power grid from the electric generator;
• wherein the power electronics system is coupled in parallel to the electrical load and the power grid that supplies power to the electrical load, the power electronics system further comprising:
• a master controller circuit to:
• determine that the power grid is no longer supplying power to the electrical load, and
• cause the islanding mode inverter circuit to direct power, generated by the electric generator from the expansion of the process gas received by the process gas inlet, to the electrical load based on the determination that the power grid is no longer supplying power to the electrical load.