Abstract: An apparatus is provided for controlling uninterruptible power supply (UPS) for grid. It comprises a power bus; an energy storage system connected to the power bus; a load connected to the power bus; a renewable energy connected to the power bus; an extra generator connected to the power bus; a static switch connected to mains and the energy storage system; and a synchronizing switch connected to the extra generator. When the grid is turned from mains-connected to islanding or is already operated in an islanding mode owing to the failure of the energy storage system, the extra generator can be used as a voltage source. The stability and safety of the grid is enhanced. Furthermore, the voltage source can be put under the control of either the energy storage system or the extra generator according to requirements. Thus, stability and reliability of power supply for the grid are increased.

Abstract: A smart grid monitoring device with multi-agent function is provided, which may include a measurement module, a communication module and a control module. The measurement module may measure at least one real-time electric signal of a power transaction system or an electric unit. The control module may execute a self-developed program to provide at least one agent functionality and then control the electric unit according to the at least one real-time electric signals measured; the communication module can transmit the at least one real-time electric signal to other monitoring devices or the main computer of the power dispatch transaction system, and can control the electric unit according to the at least one electric signal. The communication module can receive electric demand signals from the power company or other monitoring devices of the power dispatch transaction system via the main computer to execute the electricity transaction with the bidding mechanism.

Abstract: A smart grid monitoring device with multi-agent function is provided, which may include a measurement module, a communication module and a control module. The measurement module may measure at least one real-time electric signal of a power transaction system or an electric unit. The control module may execute a self-developed program to provide at least one agent functionality and then control the electric unit according to the at least one real-time electric signals measured; the communication module can transmit the at least one real-time electric signal to other monitoring devices or the main computer of the power dispatch transaction system, and can control the electric unit according to the at least one electric signal. The communication module can receive electric demand signals from the power company or other monitoring devices of the power dispatch transaction system via the main computer to execute the electricity transaction with the bidding mechanism.

Abstract: A three-phase current converter and a three-phase D-? control method with varied inductances are provided. In this method, two current variations of a first phase current, a second phase current and a third phase current flowing through a first inductor, a second inductor and a third inductor of the three-phase current converter respectively and two phase voltages of a first phase voltage, a second phase voltage and a third phase voltage are obtained. A first calculation is executed according to inductances of the inductors, the current variations and a switching period of a vector space modulation to obtain a calculation result. A second calculation is executed according to the phase voltages and the calculation result to obtain a duty ratio of the switching period of switch sets of the three-phase current converter. The inductances vary with the phase currents respectively.

Abstract: A household Grid-Connected inverter applied to a solar power generation system with maximum power tracking function includes a solar power module; a MPPT power converter connected to the solar power module; and a DC/AC filter connected to the MPPT power converter. The DC/AC filter can be connected to the household grid in parallel. The solar power module is used to convert and output the solar energy in form of DC voltage. The MPPT power converter converts the DC into a high-frequency current with envelope of the same phase as the household grid, and also maximizes the output power. The DC/AC filter is used to output to the current which has the same phase as the household power and of the wave current form. Thereby, a simplified structure which can increase the device expanding flexibility and provide maximum output performance for solar power generation is achieved with lower cost.

Abstract: A circuit is provided to reduce power loss on switching. A pair of auxiliary switching devices is switched on before a pair of switching devices. The switching devices are switched on after a corresponding capacitor to the auxiliary switching devices is discharged to zero. Thus, the power loss of the switching devices is reduced.

Abstract: A circuit is provided to reduce power loss on switching. A pair of auxiliary switching devices is switched on before a pair of switching devices. The switching devices are switched on after a corresponding capacitor to the auxiliary switching devices is discharged to zero. Thus, the power loss of the switching devices is reduced.

Abstract: A fault-tolerant device is kept functioning in an alternating-current inverter for fuel cell even if an inverter unit in the device is malfunctioned. The malfunctioned inverter unit is rep laced with a backup inverter unit to keep the device functioning.

Abstract: A fault-tolerant device is kept functioning in an alternating-current inverter for fuel cell even if an inverter unit in the device is malfunctioned. The malfunctioned inverter unit is rep laced with a backup inverter unit to keep the device functioning.