Thyristor starting device and control method therefor

1. A thyristor starting device, comprising:

a converter which converts AC power supplied from an AC power source into first DC power;

a DC reactor which smooths a first DC current corresponding to the first DC power;

an inverter which converts the first DC power provided from said converter through said DC reactor into AC power, and supplies the AC power to a synchronous machine;

a gate pulse generation circuit which generates a gate pulse to be provided to thyristors of said converter and said inverter;

a control unit which sets a phase control angle of the gate pulse to be provided to the thyristors of said converter, by controlling a current of said converter such that the first DC current flowing into said DC reactor matches a current command value;

an AC current detector which detects an AC current supplied from said AC power source:

a rectification circuit which rectifies an output of said AC current detector to produce second DC current;

and an abnormality detection unit, comprising a first timer and a second timer, which compares a detection value of the second DC current with said current command value, and determines an abnormality in said gate pulse based on a comparison result, wherein said control unit is configured to feedback-control the first DC current based on a deviation between said current command value and the second DC current, said abnormality detection unit compares the second DC current with said current command value, and determines the abnormality in said gate pulse based on a comparison result;

said abnormality detection unit sets an upper limit value and a lower limit value of an acceptable range on a high-current side and a low-current side, respectively, relative to said current command value, compares the detection value of the second DC current with the upper limit value and the lower limit value, and in response to a determination that the first DC current flowing into said DC reactor deviates from said acceptable range, provide a signal to a first timer;

the first timer is configured to measure a first time for which the signal is received and to be reset when the signal stops, the second timer is configured to measure a second time that has elapsed since reception of a start command for the thyristor starting device;

and the abnormality detection circuit is configured to determine that the gate pulse is abnormal when the measured first time reaches a prescribed time and the measured second time exceeds a fixed time.

2. A control method for a thyristor starting device, said thyristor starting device including:

a converter which converts AC power supplied from an AC power source into first DC power,

a DC reactor which smooths a first DC current corresponding to the first DC power,

an inverter which converts the first DC power provided from said converter through said DC reactor into AC power, and supplies the AC power to a synchronous machine,

a gate pulse generation circuit which generates a gate pulse to be provided to thyristors of said converter and said inverter,

an AC current detector which detects an AC current supplied from said AC power source,

and a rectification circuit which rectifies an output of said AC current detector to produce a second DC current, said control method comprising the steps of:

setting a phase control angle of the gate pulse to be provided to the thyristors of said converter, by controlling a current of said converter such that the first DC current flowing into said DC reactor matches a current command value;

setting an upper limit value and a lower limit value of an acceptable range on a high-current side and a low-current side, respectively, relative to said current command value;

comparing a detection value of the second DC current with said upper limit value and said lower limit value, and in response to a determination that the first DC current flowing into the DC reactor deviates from the acceptable range, providing a signal to a first timer:

measuring, using the first timer, a first time for which the signal is received by the first timer and resetting the first timer when the signal stops;

measuring, using a second timer, a second time that has elapsed since reception of a start command for the thyristor starting device;

determining an abnormality in the gate pulse when the measured first time reaches a prescribed time and the measured second time exceeds a fixed time, and feedback-controlling the first DC current based on a deviation between said current command value and the second DC current.