Abstract: A ground-fault detecting device includes: a first detecting module, having a first input terminal, a second input terminal, and a third input terminal coupled to a first-phase electric power, a second-phase electric power, and a third-phase electric power on an AC side of a photovoltaic power generating system respectively, for sampling voltages of the first-phase electric power, the second-phase electric power, and the third-phase electric power to generate a first sampled voltage, a second sampled voltage, and a third sampled voltage respectively; and a controller, coupled to the first detecting module, for determining if a ground-fault occurs in the AC side before the photovoltaic power generating system is connected to a grid according to the first sampled voltage, the second sampled voltage, and the third sampled voltage; wherein the controller generates an alarm signal when the ground-fault occurs in the AC side.

Abstract: A method and a system for switching from grid-connected to grid-disconnected, and a power conversion system are provided. The method includes determining whether a power grid is abnormal based on a power grid parameter obtained when a PCS is grid-connected and operates in a current source mode, turning off a switching cabinet if the power grid is abnormal, switching from a current source mode to a voltage source mode, sending a command to instruct a grid-connected/grid-disconnected switch to switch from a grid-connected loop to a grid-disconnected loop, controlling an output parameter to smoothly transit from an abnormal parameter value recorded when the power grid is abnormal to a rated parameter value, and supplying power to a load according to the rated parameter value. In this way, seamless switching from grid-connected to grid-disconnected can be achieved, thereby ensuring stability of power supply.

Abstract: A method and a system for switching from grid-connected to grid-disconnected, and a power conversion system are provided. The method includes determining whether a power grid is abnormal based on a power grid parameter obtained when a PCS is grid-connected and operates in a current source mode, turning off a switching cabinet if the power grid is abnormal, switching from a current source mode to a voltage source mode, sending a command to instruct a grid-connected/grid-disconnected switch to switch from a grid-connected loop to a grid-disconnected loop, controlling an output parameter to smoothly transit from an abnormal parameter value recorded when the power grid is abnormal to a rated parameter value, and supplying power to a load according to the rated parameter value. In this way, seamless switching from grid-connected to grid-disconnected can be achieved, thereby ensuring stability of power supply.

Abstract: A ground-fault detecting device includes: a first detecting module, having a first input terminal, a second input terminal, and a third input terminal coupled to a first-phase electric power, a second-phase electric power, and a third-phase electric power on an AC side of a photovoltaic power generating system respectively, for sampling voltages of the first-phase electric power, the second-phase electric power, and the third-phase electric power to generate a first sampled voltage, a second sampled voltage, and a third sampled voltage respectively; and a controller, coupled to the first detecting module, for determining if a ground-fault occurs in the AC side before the photovoltaic power generating system is connected to a grid according to the first sampled voltage, the second sampled voltage, and the third sampled voltage; wherein the controller generates an alarm signal when the ground-fault occurs in the AC side.

Abstract: A communication method and a communication device based on a parallel system, a terminal and a computer readable storage medium are provided. The parallel system includes a fieldbus and two or more communication nodes connected to the fieldbus in parallel. The communication method includes: acquiring a status parameter of a target communication node; converting the status parameter into a logic level signal; generating an input differential signal based on the logic level signal; sending the input differential signal to the fieldbus and synchronously receiving an output differential signal from the fieldbus, where the output differential signal is generated by the fieldbus by performing a wired-AND operation on input differential signals received from the two or more communication nodes; and acquiring information of the communication nodes connected to the fieldbus based on the output differential signal.

Abstract: A communication method and a communication device based on a parallel system, a terminal and a computer readable storage medium are provided. The parallel system includes a fieldbus and two or more communication nodes connected to the fieldbus in parallel. The communication method includes: acquiring a status parameter of a target communication node; converting the status parameter into a logic level signal; generating an input differential signal based on the logic level signal; sending the input differential signal to the fieldbus and synchronously receiving an output differential signal from the fieldbus, where the output differential signal is generated by the fieldbus by performing a wired-AND operation on input differential signals received from the two or more communication nodes; and acquiring information of the communication nodes connected to the fieldbus based on the output differential signal.

Abstract: The invention relates to a three-phase boost rectifier circuit and a control, method thereof, and an uninterrupted power supply which contains at least first battery packs BAT+, second battery packs BAT?, and a boost rectifier module; the boost rectifier module comprises a first bidirectional thyristor SCR1, a second bidirectional thyristor SCR2, a third bidirectional thyristor SCR3, a fourth bidirectional thyristor SCR6, a first unidirectional thyristor SCR4, a second unidirectional thyristor SCR5, a first inductor L1, a second inductor L2, a third inductor L3, a three-phase fully controlled rectifier bridge, a first capacitor C1 and a second capacitor C2. The invention can ensure the balance of positive and negative bus's voltage without the balancing device under battery operated boost mode, while improving the efficiency and reliability of the battery operated boost mode.

Abstract: The invention relates to a three-phase boost rectifier circuit and a control method thereof, and an uninterrupted power supply, which contains at least first battery packs BAT+, second battery packs BAT?, and a boost rectifier module; the boost rectifier module comprises a first bidirectional thyristor SCR1, a second bidirectional thyristor SCR2, a third bidirectional thyristor SCR3, a fourth bidirectional thyristor SCR6, a first unidirectional thyristor SCR4, a second unidirectional thyristor SCR5, a first inductor L1, a second inductor L2, a third inductor L3, a three-phase fully controlled rectifier bridge, a first capacitor C1 and a second capacitor C2. The invention can ensure the balance of positive and negative bus's voltage without the balancing device under battery operated boost mode, while improving the efficiency and reliability of the battery operated boost mode.