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 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 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 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.