The invention concerns a district energy system comprising: - at least one cogeneration or heat pump unit, - a first pipe system for district heating and/or cooling consisting of at least one liquid or vapor CO.sub.2 pipe; characterized by the fact that is also comprises a second pipe system consisting of at least one fluid line for the transport of CO.sub.2 or O.sub.2. The invention also relates to the use of a district energy system comprising: - at least one cogeneration or heat pump unit, - a first pipe system, - a second pipe system; characterized by the fact that that liquid or vapor CO.sub.2 is used in the first pipe system for district heating and/or cooling and that a fluid of CO.sub.2 or O.sub.2 is used in the second pipe system.

A system architecture and method for enabling hierarchical intelligent control with appropriate-speed communication and coordination of control using intelligent distributed impedance/voltage injection modules, local intelligence centers, other actuator devices and miscellaneous FACTS coupled actuator devices is disclosed. Information transfer to a supervisory utility control is enabled for responding to integral power system disturbances, system modelling and optimization. By extending the control and communication capability to the edge of the HV power grid, control of the distribution network through FACTS based Demand response units is also enabled. Hence an integrated and hierarchical total power system control is established with distributed impedance/voltage injection modules, local intelligence centers, connected other actuator devices, miscellaneous FACTS coupled devices and utility supervisory all networked at appropriate speeds allowing optimization of the total power system from generation to distribution.

An integrated load management controller for directing electrical current generated by a plurality of solar photovoltaic modules exposed to ambient light selectively through a diverter to a battery bank for storage and to a current conditioner for supply of electrical current into an electrical grid, based on a supply demand communicated by an electrical grid demand controller, for managing the generation, storage, and supply of electrical current from the solar photovoltaic modules. A method of supplying supplemental electrical current to an electrical grid servicing load center using a solar-energy electricity generation system is disclosed.

The invention discloses an islanding detection method in DC microgrids based on MPPT trapezoidal voltage disturbance. The steps are as follows: start the MPPT strategy; set the starting signal threshold of disturbance; measure the output current of PVA at the maximum power; calculate the same environmental factor of PVA with different capacities under the same light intensity and temperature in real time; when the environmental factor is greater than the starting signal threshold of the disturbance, periodic trapezoidal disturbance is carried out to the PVA port voltage reference; if the PCC voltage Upcc exceeds the threshold set by the passive method, it is judged as islanding; otherwise, it is judged whether the change rule of Upcc is consistent with the change rule of the calculated PCC voltage Upccp under the trapezoidal disturbance; If it is consistent, it is judged as islanding; otherwise, it is pseudo islanding.

A method of controlling a microgrid comprises receiving, by a power management system, PMS, of the microgrid, operating point values for a plurality of controllable assets. The method comprises determining, by the PMS, an asset headroom. The method comprises determining, by the PMS, a modified operating point value that is dependent on the received operating point value of the controllable asset, the determined asset headroom of the controllable asset, and a total power offset of the microgrid. The method comprises controlling, by the PMS, the controllable assets for which the modified operating point values have been determined in accordance with the modified operating point values.

Provided in the present invention are a microgrid control system and a microgrid, the microgrid control system comprising: a grid-connected switch, an energy router, a first controller and a second controller; the first controller controls the grid-connected switch and sends a first control instruction; the second controller receives the first control instruction and responds to the first control instruction for controlling the energy router.

The present innovations control and improve operation of one or more microgrids optionally and/or intermittently coupled to an Electric Power System(s).

A method for designing a distributed communication topology of a micro-grid based on network mirroring and global propagation rates includes the following steps: first, determining the communication connectivity of distributed directed networks in the micro-grid; next, obtaining, for connected directed communication networks, mirror networks thereof based on a mirroring operation, and selecting an optimal distributed directed communication topology corresponding to a maximum performance indicator based on algebraic connectivity and communication costs; solving, for the optimized distributed communication topology, pinned distributed generation sets corresponding to different pinning numbers based on global propagation rates and out-degrees; and finally, establishing a distributed secondary voltage control of the micro-grid based on the optimal distributed communication network and pinned nodes of the micro-grid, to achieve accurate reactive power sharing and average voltage restoration.

A fault isolating device for use in a microgrid disconnected from a main power grid includes a voltage meter for detecting a voltage anomaly indicative of an electrical fault, a timer for establishing a time window that begins and ends a predetermined time after a voltage anomaly is detected, a switch that is opened at the start of the time window, and a microcontroller that determines whether to leave the switch open to isolate a faulted portion of the microgrid or to close the switch. A plurality of fault isolating devices can be distributed throughout a microgrid to isolate a faulted branch or faulted branches of an islanded microgrid without interfering with normal fuse operation when the microgrid is connected to the main power grid.

A method of controlling a microgrid includes receiving, by a power management system, PMS, of the microgrid, operating point values for a plurality of controllable assets. The method includes determining, by the PMS, an asset headroom. The method includes determining, by the PMS, a modified operating point value that is dependent on the received operating point value of the controllable asset, the determined asset headroom of the controllable asset, and a total power offset of the microgrid. The method includes controlling, by the PMS, the controllable assets for which the modified operating point values have been determined in accordance with the modified operating point values.