The Design Of Power System Stabilizer Based On H_∞Theory And The Coordination Of The Generators

In the modem power system, the interconnection of power grid can provide high power supply reliability and economic efficiency. With the development of the modern electric utilities, heavy load and long-distance transmission increases rapidly, which led to the serious stability problem, the generator synchronous reactance increasing, and the unit inertia time constant decreasing. With the construction of UHV power grid, the power oscillation is likely to emerge. The continuous increase of the power system size and the existing changing operation mode make low-frequency oscillation analysis and control methods more and more difficult.Power system stabilizer (PSS) can prevent low frequency oscillation effectively, so it’s widely used in the modern power grid. It is very effective to improve the dynamic performance of the power system in the inhibition of the low-frequency oscillations due to long-distance transmission and the increasing AVR gain. The principle of the power system stabilizer is to adjust the generator excitation system, make the phase of the PSS is the same as the rotor speed deviation, which can increase the generator rotor oscillation damping. So far, PSS is still the preferred measures to enhance the system damping, and inhibition of low frequency oscillation. When regional oscillation mode between generator groups ocurrs. it’s available to consider the rational allocation of PSS in the whole system and the adjustment the parameters in order to achieve better damping.In contrast to a variety of control methods, robust control theory is choosed to design the required PSS. Combine the robust control model and theories of low frequency oscillation analysis, taking into account the uncertainty and interference, transfer the design aim to the mixed sensitivity problem, and selecte the weighting function by the frequency characteristics of disturbance and uncertainty function, constitute augmented the controlled object with the system nominal model together. The current study is according to a fixed weighting function, however, the issue of coordination between the weight matrix is less involved. Through plenty of simulation, the optimal combination of the weighting matrix is worked out, and therefore the optimization of power system stabilizer is reached. This PSS is tested in the single machine infinite bus system, compared with traditional PSS, H∞PSS presents a good performance. Then, H∞PSS is applied to the multi-machine system.In the multi-machine system, the weak damp poles is detected by PSASP program firstly, and the critical involvement units of various oscillation modes is analysised on the base of these poles. And then,H∞PSS is installed in the key units. Then calculate the weak damp poles again, and compare it with the original poles. Then calculate all kinds of different PSS placement, analysis the best coordination of the PSS. Compare the result with the previous participation factor method. Select the best PSS coordination and draw some theoretical basis.