A module level power electronics (MLPE) photovoltaic system and a method for photovoltaic string control are provided. The method is applied to a control unit in the MLPE photovoltaic system. The control unit detects an output current of each photovoltaic string in the MLPE photovoltaic system, and then controls, for photovoltaic strings connected in parallel to a same inverter in the MLPE photovoltaic system, a voltage of a photovoltaic string with larger output current to be reduced, or controls a voltage of a photovoltaic string with smaller output current to be increased, so that backflow current can be reduced to preset range tolerable for MLPE device. The method is from a perspective of the MLPE photovoltaic system, the backflow current is limited by controlling voltage change of associated photovoltaic string without additional hardware cost, effectively protecting MLPE device in the MLPE photovoltaic system.

A module level power electronics (MLPE) photovoltaic system and a method for photovoltaic string control are provided. The method is applied to a control unit in the MLPE photovoltaic system. The control unit detects an output current of each photovoltaic string in the MLPE photovoltaic system, and then controls, for photovoltaic strings connected in parallel to a same inverter in the MLPE photovoltaic system, a voltage of a photovoltaic string with larger output current to be reduced, or controls a voltage of a photovoltaic string with smaller output current to be increased, so that backflow current can be reduced to preset range tolerable for MLPE device. The method is from a perspective of the MLPE photovoltaic system, the backflow current is limited by controlling voltage change of associated photovoltaic string without additional hardware cost, effectively protecting MLPE device in the MLPE photovoltaic system.

An electricity management system for a residential setting includes a controller that is coupled with a plurality of appliances. A plurality of sensors are coupled with the controller and respectively coupled to the plurality of appliances. The controller cooperates with the sensors and the appliances to generate a demand response plan for delivering electrical power to the plurality of appliances. The demand response plan includes a shifting strategy that regulates a delivery of electrical power based upon a regional pattern of electrical consumption, a shedding strategy that maintains a household consumption of electrical power below a household upper consumption limit and a modulating strategy based upon the respective operating cycles of the plurality of appliances that prevents a simultaneous peak electrical event within more than one appliance of the plurality of appliances. The shifting strategy, the shedding strategy and the modulating strategy are implemented contemporaneously.

An electricity management system for a residential setting includes a controller that is coupled with a plurality of appliances. A plurality of sensors are coupled with the controller and respectively coupled to the plurality of appliances. The controller cooperates with the sensors and the appliances to generate a demand response plan for delivering electrical power to the plurality of appliances. The demand response plan includes a shifting strategy that regulates a delivery of electrical power based upon a regional pattern of electrical consumption, a shedding strategy that maintains a household consumption of electrical power below a household upper consumption limit and a modulating strategy based upon the respective operating cycles of the plurality of appliances that prevents a simultaneous peak electrical event within more than one appliance of the plurality of appliances. The shifting strategy, the shedding strategy and the modulating strategy are implemented contemporaneously.

A control device is connected to at least one solar cell module and an inverter, and controls the at least one solar cell module by MPPT control. The control device includes an opening/closing unit and a control unit. The opening/closing unit includes a semiconductor relay and a mechanical relay connected in parallel with the semiconductor relay. The control unit controls opening and closing of the opening/closing unit in response to a control signal from the inverter. In a case of connecting the at least one solar cell module and the inverter, the control unit turns ON the semiconductor relay to turn ON the mechanical relay, and then disconnects the semiconductor relay. In a case of cutting off the connection between the at least one solar cell module and the inverter, the control unit connects the semiconductor relay to disconnect the mechanical relay, and then disconnects the semiconductor relay.

A system and method for synchronizing clocks. The system may include a master device having a reference clock and slave devices whose clocks may be synchronized with the reference clock. The master device may drive a light transmitter (e.g., LED) to produce a light pulse with each clock cycle of the reference clock. The light pluses may be distributed by a transmissive medium, such as a low cost optical fiber.