Research On Auxiliary Primary Frequency Regulation By HVDC Links And Its Dynamic Characteristics

Primary frequency regulation is the important means to maintain the frequency stability of power systems. In a heavy load center supplied by fuel generators, such as Shanghai power system, steady value of frequency deviation goes beyond the frequency standard in case of insufficient reserve capacity of frequency regulation. Moreover, primary frequency regulation may not provide satisfied response for the sudden load disturbance for the slightly large delay of turbo-generators.In this case a little large frequency deviation may be produced. There are several HVDC links in Shanghai power system. It will have a good advantage if HVDC links can take part in primary frequency regulation, since HVDC are controllable and fast response.Based on two areas system with the parallel AC-DC links, the feasibility of auxiliary primary frequency regulation (APFR) of HVDC links is analyzed in this thesis. Dynamic characteristics of APFR of HVDC links are studied. The main work is as following.(1) A system of primary frequency regulation is modeled and simulated. It shows that frequency deviation may go beyond the standard in transient procedure while sudden load disturbance is happened in the system.(2) The conception of auxiliary primary frequency regulation (APFR) of HVDC links is developed. Overlapping decompositions and pole configuration method are used to design APFR controller. Simulation results show APFR of HVDC links is effective and feasible. The power of HVDC links would be under the limit of overload, so that HVDC links can operate over a long period of time.(3) Dynamic characteristics of APFR are studied. Results show that bandwidth of primary frequency regulation is promoted and speed of primary frequency regulation is impoved. In higer frequencies, bigger gain of system benefits primary frequency regulation. Different frequency components are responded by the governor and APFR, and their advantages can be cooperated to regulate primary frequency better. (4) Proportion coefficient of APFR controller is discussed. Dynamic characteristics and time domain simulation are analyzed with diffient coefficient. The results show that rather bigger or smaller proportion coefficients of APFR controller are unsuitable and it had better be in appropriate range. And coefficient from equal regulation coefficient method is just within the range.It can be seen that APFR of HVDC is feasible and the dynamic characteristic of frequency can be improved effectively. A new means is provided to settle the problem of insufficient reserve capacity of frequency regulation and improve dynamic characteristics of primary frequency regulation.