Practical Operation Of Power System Research Articles

Enhanced Flexible Ramping Product Formulation for Alleviating Capacity Shortage in Look-ahead Commitment

The roll-out of a flexible ramping product provides independent system operators (ISOs) with the ability to address the issues of ramping capacity shortage. ISOs procure flexible ramping capability by committing more generating units or reserving a certain amount of headrooms of committed units. In this paper, we raise the concern of the possibility that the procured flexible ramping capability cannot be deployed in real-time operations due to the unit shut-down in a look-ahead commitment (LAC) procedure. As a solution to the issues of ramping capacity shortage, we provide a modified ramping product formulation designed to improve the reliability and reduce the expected operating cost. The trajectories of start-up and shutdown processes are also considered in determining the ramping capability. A new optimization problem is formulated using mixed integer linear programming (MILP) to be readily applied to the practical power system operation. The performance of this proposed method is verified through simulations using a small-scale system and IEEE 118-bus system. The simulation results demonstrate that the proposed method can improve the generation scheduling by alleviating the ramping capacity shortages.

Decision Tree for Online Voltage Stability Margin Assessment Using C4.5 and Relief-F Algorithms

In practical power system operation, knowing the voltage stability limits of the system is important. This paper proposes using a decision tree (DT) to extract guidelines through offline study results for assessing system voltage stability status online. Firstly, a sample set of DTs is determined offline by active power injection and bus voltage magnitude (P-V) curve analysis. Secondly, participation factor (PF) analysis and the Relief-F algorithm are used successively for attribute selection, which takes both the physical significance and the classification capabilities into consideration. Finally, the C4.5 algorithm is used to build the DT because it is more suitable for handling continuous variables. A practical power system is implemented to verify the feasibility of the proposed online voltage stability margin (VSM) assessment framework. Study results indicate that the operating guidelines extracted from the DT can help power system operators assess real time VSM effectively.

Development of a simulation platform for studying on primary frequency regulation characteristics of nuclear units

With the rapid development of nuclear units, the primary frequency regulation (PFR) characteristics of nuclear units have a significant affect on the frequency stability of power system. Power system will suffer great challenge if nuclear units do not participate in PFR, so study on the PFR characteristics of nuclear units has becoming a pressing issue. A detailed, nonlinear, time-varying dynamic mathematical model of a whole pressurized water reactor (PWR) nuclear power plant has been established in the present study. The simulation platform for studying on the PFR characteristics of nuclear units has been developed according to the model established. Using the simulation platform, the operation and control mode of PWR nuclear units participating in PFR of power system is simulated and studied. The simulations results show that PWR nuclear units are feasible in participating in PFR from safety and economy by adopting the operation and control mode presented in the study, which can contribute to the practical operation of power system.

Optimising the balance between security and economy on a probabilistic basis

Decision-making methods based on a deterministic criterion, such as optimal power flow (OPF) and security-constrained optimal power flow (SCOPF), have been widely applied to practical power system operation. With these methods, the operating conditions of the power system are classified as secure or insecure based on predefined deterministic criteria. However, such a binary secure/insecure index based on a deterministic analysis does not take into account the relative risks associated with random outages of generation and transmission facilities. Therefore using deterministic decision-making methods such as OPF and SCOPF to balance the security and economy can be unnecessarily expensive. This study proposes an optimal probabilistic security (OPS) approach, which balances security and economy on a probabilistic basis. The objective of the OPS is to minimise the expected social cost, which is the sum of the expected operating cost and the expected interruption cost. An improved particle swarm optimisation technique is used to solve this probabilistic optimisation problem. Unlike other risk-based decision-making algorithms, the OPS is a self-contained decision-making tool, which does not require the definition of an arbitrary risk threshold. The OPS determines operator actions that optimally balance security and economy for given weather and operating conditions. The OPS is compared with the OPF and SCOPF using a six-bus system and the IEEE-RTS.

The Inclusion of Dynamic Factors in Statistical Power System Cost Models Part II: Part Loading and Reserve Costs

For pt.I see ibid., vol.4, no.2, p.419-25 (1989). Techniques are developed for analyzing the costs of maintaining adequate operating reserver on power systems, within probabilistic production costing models and other based on load distribution functions. The aim is to show that such models can be developed to approximate the full range of dynamic penalties associated with practical power system operation. Algorithms for costing predetermined part loading are presented, taking into account the need for bringing plant online out of strict merit order. The author describes how a prediction error function can be used to estimate the probability that the specified spinning reserve is insufficient and hence approximate for the cost of gas turbine or storage utilization for dynamic control. This allows estimation of optimal reserve levels. The author discusses the analysis of longer term reserve from banked thermal units. Some results of the model are compared to those reported from hourly simulation studies. >

The inclusion of dynamic factors in statistical power system cost models. II. Part loading and reserve costs

This paper develops techniques for analysing the costs of maintaining adequate operating reserve on power systems, within probabilistic production costing models and others based upon load distribution functions. The aim is to show that such models can be developed to approximate the full range of dynamic penalties associated with practical power system operation. Algorithms for costing predetermined part loading are presented, including the need for bringing plant on-line out of strict merit order. The paper then describes how an prediction error function can be used to estimate the probability that the specified spinning reserve is insufficient, and hence approximate the cost of gas turbine or storage utilisation for dynamic control. This allows estimation of optimal reserve levels. The paper also discusses the analysis of longer term reserve from banked thermal units. Finally, some results of the model are compared with those reported from hourly simulation studies.