Thyristor starter

A thyristor starter configured to start a synchronous machine, comprising:

• a converter that converts AC power into DC power;
• a DC reactor that smoothes the DC power;
• an inverter that converts the DC power applied from the converter through the DC reactor into AC power with a variable frequency and supplies the AC power to the synchronous machine;
• a position detector that detects a rotor position of the synchronous machine;
• a voltage detector that detects DC voltage input to the inverter;
• a first controller that controls a firing phase of a thyristor in the inverter, based on a detection signal of the position detector;
• and
• a second controller that controls a firing phase of a thyristor in the converter such that DC current flowing through the DC reactor matches a current command value, based on a detection signal of the position detector, wherein
• the thyristor starter accelerates the synchronous machine from a stop state to a predetermined rotation speed by successively performing a first mode of performing commutation of the inverter by intermittently setting the DC current to zero and a second mode of performing commutation of the inverter by induced voltage of the synchronous machine,
• the second controller includes
• a current controller at least including an integral element integrating a deviation of the DC current from the current command value, the current controller generates a voltage command value of output voltage of the converter by performing control calculation of the deviation, and
• a control angle calculator that calculates a phase control angle of a thyristor in the converter, based on the voltage command value,
• in the first mode, the control angle calculator sets the DC current to zero for a predetermined pause time by narrowing the phase control angle simultaneously with a commutation command for the inverter, and
• in the first mode, when the control calculation is resumed immediately after the pause time, the current controller uses DC voltage detected by the voltage detector immediately before the pause time as a preset value of the integral element immediately after the pause time.

A thyristor starter configured to start a synchronous machine, comprising:

• a converter that converts AC power into DC power;
• a DC reactor that smoothes the DC power;
• an inverter that converts the DC power applied from the converter through the DC reactor into AC power with a variable frequency and supplies the AC power to the synchronous machine;
• a voltage detector that detects AC voltage supplied from the inverter to the synchronous machine;
• a first controller that generates a firing command to be applied to a thyristor in the inverter, based on a detection signal of the voltage detector;
• and
• a second controller that controls a firing phase of a thyristor in the converter such that DC current flowing through the DC reactor matches a current command value, wherein
• the thyristor starter accelerates the synchronous machine from a stop state to a predetermined rotation speed by successively performing a first mode of performing commutation of the inverter by intermittently setting the DC current to zero and a second mode of performing commutation of the inverter by induced voltage of the synchronous machine,
• the second controller includes
• a current controller at least including an integral element integrating a deviation of the DC current from the current command value, the current controller generates a voltage command value of output voltage of the converter by performing control calculation of the deviation, and
• a control angle calculator that calculates a phase control angle of a thyristor in the converter, based on the voltage command value,
• in the first mode, the control angle calculator sets the DC current to zero for a predetermined pause time by narrowing the phase control angle simultaneously with a commutation command for the inverter, and
• in the first mode, the current controller
• calculates DC voltage appearing between input terminals of the inverter, based on a detection signal of the voltage detector and the firing command, and
• when the control calculation is resumed immediately after the pause time, uses the calculated DC voltage as a preset value of the integral element immediately after the pause time.

A thyristor starter configured to start a synchronous machine, comprising:

• a converter that converts AC power supplied from an AC power supply into DC power;
• a DC reactor that smoothes the DC power;
• an inverter that converts the DC power applied from the converter through the DC reactor into AC power with a variable frequency and supplies the AC power to the synchronous machine;
• a first controller that controls a firing phase of a thyristor in the inverter;
• and
• a second controller that controls a firing phase of a thyristor in the converter such that DC current flowing through the DC reactor matches a current command value, wherein
• the thyristor starter accelerates the synchronous machine from a stop state to a predetermined rotation speed by successively performing a first mode of performing commutation of the inverter by intermittently setting the DC current to zero and a second mode of performing commutation of the inverter by induced voltage of the synchronous machine,
• the second controller includes
• a current controller at least including an integral element integrating a deviation of the DC current from the current command value, the current controller generates a voltage command value of output voltage of the converter by performing control calculation of the deviation, and
• a control angle calculator that calculates a phase control angle of a thyristor in the converter, based on the voltage command value,
• in the first mode, the control angle calculator sets the DC current to zero for a predetermined pause time by narrowing the phase control angle simultaneously with a commutation command for the inverter, and
• in the first mode, when the control calculation is resumed immediately after the pause time, the current controller uses a value obtained by adding an amount of voltage drop by commutation inductance on an input side of the converter to an estimate value of DC voltage input to the inverter, as a preset value of the integral element immediately after the pause time.