Typical missions of transmission system operators (TSOs) include the following: reliably operate power transmission, make the electricity market work, be cost effective, implement appropriate transmission tariffs, anticipate future trends and develop transmission assets accordingly. In the wake of deregulation and blackouts, transmission system operators have to revisit procedures. In particular, this is to be seen in the context of the objective to achieve operation that leads to efficient market mechanisms and reduced vulnerability to large-scale outages. This is tightly linked to an appropriate control of active and reactive power.
Last year, we investigated the use series compensation Flexible AC Transmission Systems (FACTS) [1] for active power flow control in electricity markets. We used linear sensitivity analysis to determine locations for the Thyristor Controlled Series Capacitor (TCSC). We looked for locations that allow for large increases of Available Transfer Capability (ATC) and accounted for varying generation patterns. We also started to investigate the multi-path control of active power. This is important because in electricity markets it is highly desirable for TSOs to be able to transfer power in accordance with customer demands. Here, we propose to continue our research. We propose to investigate the effects of series power control on neighboring areas and the role of reactive power control for TSOs.
While series compensation FACTS and phase shift transformers can be of great use in controlling power flow over transmission paths, there are also concerns. Due to the nature of power electric networks, the control of power flow over one transmission path also affects the flow of power over other paths. This side effect can be undesirable and adversely affect the operation of TSOs in neighboring areas. We propose to study this problem and solutions.
We also want to consider issues of reactive power. It is known that adequate control of reactive power injections at busses can help avoid problems leading to voltage collapse and large-scale outages. Nonetheless, large-scale outages still occur. It is therefore proposed to revisit the procedures of reactive power planning of TSOs and to study ways to improve them. In this context, it is interesting to consider shunt compensation FACTS such as the Static Var Compensator (SVC) or the Static Synchronous Compensator (STATCOM).
The following tasks are proposed:
In 2003, we implemented a DC power flow program in MATLAB and integrated a TCSC model. With the increasing interest in issues of reactive power, we will extend our program. It will serve as a tool for further research. The extensions are twofold. First, we will include equations for reactive power and move to a full Newton-Raphson power flow. Second, we will study and implement models of reactive power compensators.
The discussion of multi-path control of active power using series compensators raised great interest last year. We propose to study this problem in more detail and research a solution. We will decompose our IEEE 30-bus system into three areas. The areas mark zones of responsibilities of the TSOs. We will investigate how the control of active power in one area affects the power flows in neighboring areas. We will then study methods of control that reduce this unwanted inter-area interaction while maintaining a high degree of ATC controllability in the original area of control. Following the advice from previous APT meetings, we will investigate deterministic for the purpose of optimization.
Large-scale outages have dominated the headlines of media in various countries including the USA and Italy. Inadequate provision of reactive power has been identified as one of the reasons that can contribute to such outages. It is therefore proposed here to revisit the issue of reactive power control. In particular we propose to investigate the current state of the art in this field. We plan to get in touch with utilities and TSOs and find out more about the current practice of reactive power control. The results will be summarized in written form. They will also serve as a good basis for further research.
Based on the outcome of Task 3, we will perform an analysis of the current practice. We will set up a test case using the IEEE 30-bus system and study the impact of various strategies of reactive power control. We will use our power flow program developed in Task 1. We will create scenarios that can result from inadequate reactive power control. We will then investigate means that allow improving the situation. Based on these investigations, we will issue recommendations for such improvement.
t0: Start
t0 + 2.5 months: Completion of Task 1
t0 + 6 months: Completion of Task 2
t0 + 9 months: Completion of Task 3
t0 + 12 months: Completion of Task 4
further schedule to be determined
[1] N. G. Hingorani, L. Gyugyi: Understanding FACTS: Concepts and Technology of Flexible AC Transmission Systems. IEEE Press, Piscataway, USA.