Study Of Power System Voltage Stability And Its Control

The main aspect of voltage losing stability is voltage collapse. It is an urgent problem that needs to be solved because of the wide area affect and huge economic losses.In the steady state voltage stability, domestic and foreign experts had put forward many voltage stability indexes and judgment method. With the development of the grid and the improvement of the real time requirements, steady state Voltage stability exposed a lot of defeats. Phase measurement unit (PMU) was developed successfully which provided dynamic data for real time voltage stability analysis and realized voltage stability on line monitoring and analyzing.Regarding regional power network as target and according to practical situation combining the function of power system analysis software BPA, a model which can accurately simulate the operation of regional power network was constructed. Steady state voltage stability was simulated by sensitivity analysis and maximum-power methods. The voltage stability weak nodes and key lines were found out and an optimal configuration scheme of phase measurements units in this regional power network was proposed. On the base of PMU real–time data, through the analysis of power flow calculation, the Jacobian matrix can be solved directly, the minimum singular value of the Jacobian matrix was put forward as an index of voltage stability, the regulation of generator output and load shedding procedure under critical state were verified. The online steady state voltage stability monitoring and control measures based on the phase measurement unit (PMU) were realized.In the aspect of dynamic voltage stability, based on the time domain simulation and transient stability model in PSASP, multi-machine system was simulated under large disturbance. In this paper, the influence of different cases on dynamic voltage stability under large disturbance was analyzed. The different cases were load models, different induction motor load proportion, fault clearing time and short-circuit location. The influence of wind power on dynamic voltage stability was analyzed. Based on the small disturbance voltage stability model in PSASP, the low frequency oscillation was analyzed under small disturbance. The power system stabilizer (PSS) was installed to stabilize the generator voltage phase angel according to the eigenvalues, damping ratio, frequency and electrical circuit ratio of the oscillation mode, and the configuration strategy of PSS was researched by the simulation.