Control system and method for voltage stabilization in electric power system

A power control system for an AC electric arc furnace having an AC power supply line for applying power to an electrode, comprising:

• a variable inductive series reactor connected intermediate the power supply line and the electrode;
• a variable inductive parallel reactor connected in parallel with the power supply line;
• a harmonic capacitive filter bank connected in parallel with the power supply line;
• a control system for mitigating voltage flicker on the power supply line, including:
• (i) current stabilizing means for adjusting the inductive series reactor to stabilize an electrode current to control the voltage flicker;
• (ii) reactive power stabilizing means for adjusting the inductive parallel reactor to stabilize a reactive power draw from the AC power supply line to control the voltage flicker;
• and
• (iii) control means for monitoring voltage flicker on the power supply line and adjusting operating parameters of the current stabilizing means and the reactive power stabilizing means based on the monitored voltage flicker.

A method for controlling voltage flicker in an AC power supply line having a time-varying load connected thereto, comprising:

• (a) providing a variable inductive series reactor intermediate the power supply line and the load;
• (b) providing a variable parallel reactor in parallel with the power supply line;
• (c) varying an inductance of the variable inductive series reactor to reduce voltage flicker;
• and
• (d) varying a reactance of the variable parallel reactor to reduce voltage flicker.

A power control system for an AC power supply line having a time-varying load connected thereto, comprising:

• a variable inductive reactor intermediate the power supply line and the load;
• and
• a control system including:
• a flicker meter for monitoring voltage flicker on the AC power supply line;
• a current stabilizer for varying the variable inductive reactor to stabilize a current draw from the power supply line to reduce voltage flicker on the power supply line when the monitored voltage flicker is above a threshold;
• and
• a real power stabilizer for varying the variable inductive reactor to stabilize a real power draw from the power supply line when the monitored voltage flicker is below the threshold.

A method for controlling voltage flicker in an AC power supply line having a time-varying load connected thereto with a variable inductance series reactor intermediate the power supply line and the load, comprising:

• (a) monitoring voltage flicker on the power supply line;
• (b) monitoring a load current drawn by the load and monitoring a load voltage;
• (c) when the monitored voltage flicker indicates that the voltage flicker exceeds a predetermined threshold, varying the inductance of the series reactor in response to variations in the monitored current to stabilize the load current and thereby reduce the voltage flicker;
• and
• (d) when the monitored voltage flicker indicates that the voltage flicker does not exceed the predetermined threshold, varying the inductance of the series reactor in response to variations in the monitored load current and monitored load voltage to stabilize an impedance of the load and thereby reduce variations in the active power drawn from the power supply line.

A power control system for reducing voltage flicker in an AC power supply line having a time-varying load connected thereto, comprising:

• a variable inductive reactor connected in parallel with the power supply line;
• a harmonic capacitive filter bank connected in parallel with the power supply line;
• a flicker meter for monitoring voltage flicker on the power supply line;
• and
• a controller for monitoring variations in a reactive power draw from the power supply line, selecting only those variations falling within a predetermined frequency range, and adjusting the variable inductive reactor in response to the selected variations to stabilize cumulative reactive power draw of the load, the variable inductive reactor and the capacitive reactor, the controller being responsive to the flicker meter to vary the predetermined frequency range in response to variations in the monitored voltage flicker.

A power control system for reducing voltage flicker in an AC power supply line having a time-varying load connected thereto, comprising:

• a variable inductive reactor connected intermediate the power supply line and the load;
• a flicker meter for monitoring voltage flicker on the power supply line;
• and
• a controller for monitoring variations in the current draw by the load, selecting only those variations falling within a predetermined frequency range, and adjusting the variable inductive reactor in response to the selected variations to stabilize the current draw of the load, the controller being responsive to the flicker meter to vary the predetermined frequency range in response to variations in the monitored voltage flicker.