Coordination du réglage de la fréquence entre plusieurs systèmes électriques non-synchrones reliés par un réseau à courant continu haute tension.

摘要

This thesis addresses the problem of frequency control in a power system composed of several non-synchronous AC areas connected by a multi-terminal HVDC grid. For this system, we propose three control schemes, two for primary frequency control and one for secondary frequency control. The rst control scheme, called power-injection-based control scheme, is distributed by nature. Based on remote measurements of the other areas' frequencies, this control scheme modi es the power injections from the di erent AC areas into the DC grid so as to make the system collectively react to load imbalances. This collective reaction allows each individual AC area to downscale its primary reserves. The scheme is inspired by algorithms for the consensus problem extensively studied by the control theory community. As remote measurements are used, the e ects of time-delays on the control scheme's e ectiveness are investigated. A stability analysis of the closed-loop system shows that with some assumptions, as long as the time-delays are within an acceptable limit, the system converges to an equilibrium point at which the AC areas' frequency deviations are equal to each other. Simulation results on a benchmark power system with ve AC areas show the e ectiveness of the control scheme. The second control scheme has the same objective with the rst one, but acts on the DC voltages of the HVDC converters, and thus is called DC-voltage-based control scheme. In particular, it modi es the DC voltage of each converter based on the frequency deviation of the AC area it is connected to. This decentralized nature frees it from the problems related to the dependence on remote information. A theoretical study shows that, by using local information only, the control scheme allows to signi cantly reduce the impact of a power imbalance by distributing the associated frequency deviation over all areas. Simulation results on the same benchmark system illustrate the good performance of the control scheme. The last control scheme aims at restoring the frequencies and the power exchanges to their nominal or scheduled values in the aftermath of a power imbalance. It can be combined with the other two control schemes. To study its stability properties, a timescale decomposition is carried out on the closed-loop system under this control scheme combined with the DC-voltagebased control scheme. The two reduced-order subsystems thus obtained describing the slow and the fast dynamics respectively are both shown to be stable, which implies the stability of the entire system. Simulation results on the benchmark system con rm the good performance of the control scheme.