The ac/dc conversion system necessary to supply the superconducting coils of the magnet system and the auxiliary heating systems of ITER experiment can absorb a total active and reactive power up to 500 MW and 950 Mvar, respectively. The allowable limit value of reactive power absorbed from the grid is 200 Mvar; therefore a Reactive Power Compensation system (RPC) rated for a nominal power of 750 Mvar will be provided. The current reference design of the) is based on Static Var Compensation technology with Thyristor Controlled Reactor (TCR) and Tuned Filter. The RPC has to minimize the demand of reactive power from the grid; its control is based on a feed-forward method, where the corrective input is the measurement of the reactive power consumption of the ac/dc converters. This is derived from the Fast Fourier Transform (FFT) at 50 Hz of the measurements of the three-phase voltages and currents, then this signal is converted in a firing angle of the TCR thyristors by a lookup table. The delay introduced by the FFT calculation and the slow response of the TCR could make the response speed of the RPC not sufficient to face the fast variations of the reactive power demand, causing the fast voltage variation of the 66 kV busbar, and this can occur as a consequence of the Plasma Control System (PCS) operation, for example vertical displacement control, or intervention of the fast discharge units. In this paper a new controller of the RPC able to overcome this shortcoming is proposed. It is based on the calculation of the predicted consumption of the reactive power by using the voltage reference signals coming from the PCS and the dc current measurements of the ac/dc converters, and on the speed up of the RPC control by introducing a lead-lag transfer function. Its effectiveness is verified in different operating conditions of the ac/dc conversion system.
Improvement of the dynamic response of the ITER Reactive Power Compensation system
Gaio E;
2014
Abstract
The ac/dc conversion system necessary to supply the superconducting coils of the magnet system and the auxiliary heating systems of ITER experiment can absorb a total active and reactive power up to 500 MW and 950 Mvar, respectively. The allowable limit value of reactive power absorbed from the grid is 200 Mvar; therefore a Reactive Power Compensation system (RPC) rated for a nominal power of 750 Mvar will be provided. The current reference design of the) is based on Static Var Compensation technology with Thyristor Controlled Reactor (TCR) and Tuned Filter. The RPC has to minimize the demand of reactive power from the grid; its control is based on a feed-forward method, where the corrective input is the measurement of the reactive power consumption of the ac/dc converters. This is derived from the Fast Fourier Transform (FFT) at 50 Hz of the measurements of the three-phase voltages and currents, then this signal is converted in a firing angle of the TCR thyristors by a lookup table. The delay introduced by the FFT calculation and the slow response of the TCR could make the response speed of the RPC not sufficient to face the fast variations of the reactive power demand, causing the fast voltage variation of the 66 kV busbar, and this can occur as a consequence of the Plasma Control System (PCS) operation, for example vertical displacement control, or intervention of the fast discharge units. In this paper a new controller of the RPC able to overcome this shortcoming is proposed. It is based on the calculation of the predicted consumption of the reactive power by using the voltage reference signals coming from the PCS and the dc current measurements of the ac/dc converters, and on the speed up of the RPC control by introducing a lead-lag transfer function. Its effectiveness is verified in different operating conditions of the ac/dc conversion system.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
