| 摘要 |
PURPOSE:To stop a power converter for a fixed period and prevent overvoltage from being generated, by discriminating that a power system is released when DC power is converted to AC power and the output current of the power converter for feeding the power to the power system exceeds a reference value. CONSTITUTION:A DC power source 1 is converted to alternating current by a power converter 2, and is fed to a power system 4 via an interconnection breaker 3. When the breaker 3 is opened due to any cause, then the output current i of the converter 2 is turned into zero and is detected by a CT 6. When reference current i' from a current reference generating circuit 9 and the current i are compared with each other and an error is amplified 10, then it exceeds a control range and a device is saturated with. This saturation output is detected 12, and via a gate amplifying circuit 11, the converter 2 is immediately stopped. This stop signal is retained in a time limiting circuit 13 for a fixed time. The retaining time is set longer than the working time of a system abnormal-state detector 8 without responding excessively to lightning surge, momentary stop, and the like. As a result, excessive response is prevented from being generated, and the terminal voltage of the converter 2 is prevented from being abnormally heightened. |
