Power system stability analysis with a high penetration of distributed generation

The operation and structure of distribution system is changing with the integration of distributed generation, based on alternative energy sources, including renewable energy sources (wind, solar). Among the new issues, there is the question of stability of distribution systems in the presence of a large penetration of distributed generation (DG).;For long-term voltage stability analysis, bus-based voltage indices are implemented using Power-Voltage curves (PV curves) to analyze the contribution of DG. Large-penetration of DG also has an impact on the short-term stability (voltage stability and transient stability) of the system. Indices are developed to rank contingencies and show how different DG interconnections affect the system during faults. Time-domain simulations are used to perform those studies. For short-term voltage stability, voltage dips at load buses are monitored following a large disturbance. The maximum rotor speed deviations of centralized synchronous generators are used to study the transient stability of the overall system.;All of the indices defined above are tested on three commonly used test systems: the IEEE RTS-96 24-bus system, the IEEE 39-bus New England system and the IEEE 118 bus system. The studies conclude that, regardless of its technology, DG mostly improves the long-term voltage stability particularly when located in areas near large loads. With DG injecting reactive power, the voltage security margin is increased. Synchronous machine based DG has the greatest impact on the short-term stability when located near large centralized generators. For short-term voltage stability, the contribution of DG is most noticeable when it absorbs reactive power, thus lowering the voltage dips.;With power systems operating near their loadability limits, voltage stability becomes an important issue. Many utilities have implemented long-term solutions to counter this problem, such as adding transmission lines and new power plants in order to improve the reliability of the power system. An alternative solution consists in increase of generation at the distribution level. This is also a way of meeting growing economical, technical and environmental constraints. The size, the technology and the placement of DG play an important role in the operation of distribution systems.