Determining the best sequence of load pickup during power system restoration

Abstract

The first control action in power system restoration concerns the generation restart. In the initial phase of restoration, operators are often concerned with load pickup problems. One of the important problems during load pickup is keeping frequency response in allowable range. The aim of this paper is to determine the best sequence of load pickup by hydro and steam units during power system restoration based on frequency response of prime movers. Hydro power plants and combustion turbine units have the capability of black start operation and can be used for early stages of power system restoration. This paper considers hydro power plants for evaluating the stability and frequency response during load pickup in the early stages of restoration. Load pickup scheme has been developed based on using a pair of interconnected units.

Wide-area frequency control during power system restoration

“…Thus, it is just at the instant of disturbance that the power mismatch is equal to the amount of increased generation or load. Using the estimated power mismatch by (9), the predicted steady-state change can be estimated as:…”

“…Following severe disturbances, such as insertion of a load block or increase of mechanical power of a large generation station, the average frequency will change in the system. Unless the frequency drop is arrested before the frequency reaches 47-48 Hz in a 50 Hz system, thermal units are tripped to avoid damage from prolonged under frequency operation and this worsens the situation [9]. In these situations, it may therefore be necessary to disconnect loads to preserve system integrity.…”

“…Should an attempt be made to pick up a larger load block than can be accommodated by the response capability of generators online, the load block already restored which is subject to under frequency load shedding will be lost. If the frequency swing is severe, one or more generators may trip, precipitating another shutdown [9]. Hence it is desirable to determine the appropriate magnitude of load blocks that can be restored as a guideline for operators.…”

Robustness Area Technique Developing Guidelines for Power System Restoration

“…Planning PSRs requires expertise to deal with limitations and constraints, where poor voltage profile and frequency control problems are recurrent [12][13][14]. Such issues are mainly caused by thermal limitations on GUs and transmission lines stability contrains.…”

Judgment of Temporary over Voltages during Transformer Refurbishment

“…The restoration plan consists of several objectives like total system risk, total served energy in the period of restoration and total restoration time [1]. The simulation work helps in the best way of loading the power plants and is applied for hydro power plant and steam power plant restoration [2]. The power system restoration problem involves so many factors like frequency monitoring, black start unit energization, transmission line energization and transformer energization [3]- [5].…”