Valuation of reactive power support services based on sensitivity and risk analysis
Introduction
In a deregulated power system reactive power support is regarded as an important ancillary service which is used to maintain the voltage profile and keep the voltage stability of the system. In order to operate the system in a secure manner a system operator (SO) has to procure adequate amount of reactive power from various reactive resources in the system, e.g. generators, synchronous condensers and shunt capacitors. Due to the local nature, reactive power produced by suppliers at different locations will have different contributions to the system security. Reactive output from remote generators usually has little contribution to the improvement of system security. Hence, it is not preferable for a SO to procure a large amount of reactive power from remote reactive resources even though they have relatively low production costs.
In the past two decades researches on reactive power problems in the deregulated environment have been carried out. The focuses were on reactive power pricing methods which mainly concerned the cost of reactive power production and transportation [1], [2], [3], [4]. Attention paid to the cost of reactive power resource is much more than that paid to the value of reactive power resource. However, as mentioned above the contributions of reactive power from different resources are not homogeneous and this will have a negative impact on the efficiency of reactive power dispatch and reactive capacity investment. Hence, evaluations of the values of reactive power support services from different resources become important and necessary. Xu et al. [5], [6] introduce the concept of “Equivalent Reactive Compensation (ERC)” and use it to evaluate the dynamic reactive power support services. Pirayesh et al. [7] makes a valuation of reactive power service based on MW transaction reduction. Staniulis [8] summarizes and compares some existing methods of reactive power valuation, viz. voltage sensitivity (VS)-based method, PV curve method, ERC method and back-up generation method. It also finds that different results will come up from different perspectives. Integrating voltage sensitivity and risk analysis, a new reactive valuation method from the perspective of voltage regulation is proposed in this paper.
Section snippets
Sensitivity analysis method
Sensitivity-based method is widely used in power system analysis. In the area of reactive power valuation net loss sensitivity (LS) and voltage sensitivity have been adopted [9]. The former emphasizes the economical value of reactive power while the latter emphasizes the technical value of reactive power.
Generally, voltage sensitivity is a value that describes the marginal reactive power injection or absorption needed for nodal voltage control. Mathematically it can be described as:where Q
Numerical example
The IEEE 14-bus system depicted in Fig. 3 is used to illustrate the proposed methodology and examine its features. G1 and G2 are generators while G3, G6 and G8 are synchronous condensers. In the power flow calculation bus 1 is chosen as the slack bus.
Based on the VS method the value of reactive power support service from each resource is shown in Fig. 4. Reactive power output of G6 is most valuable because G6 is close to the load area while the remote resources G1, G2, G3 have relatively low
Discussions
In this paper, a method integrating voltage sensitivity and risk analysis is proposed to assess the value of reactive power support services from the perspective of voltage regulation. The following are some discussions on the method.
Conclusion
In this paper, a method based on voltage sensitivity and risk analysis is proposed to evaluate the reactive power support services from different resources. The major difference between the VS method and the proposed method is that the former is based on the voltage control ability of each reactive resource while the latter is based on the low voltage risk alleviation ability of each reactive resource. In the proposed method a network-parameter-based severity function is adopted which reflects
Acknowledgements
Supports from the Research Grants Council of Hong Kong (5215/03E) are gratefully acknowledged.
References (12)
- et al.
Real-time pricing of reactive power: theory and case study results
IEEE Trans. Power Syst.
(1991) - et al.
OPF for reactive pricing studies on the ngc system
IEEE Trans. Power Syst.
(1996) - et al.
A simulation based approach to pricing reactive power
- et al.
Reactive power pricing: a conceptual framework for remuneration and charging procedures
IEEE Trans. Power Syst.
(2000) - et al.
Assessing the value of generator reactive power support for transmission access
IEE Proceedings: Generation, Transmission and Distribution
(2001) - et al.
Valuation of dynamic reactive power support services for transmission access
IEEE Trans. Power Syst.
(2001)
Cited by (13)
A comprehensive survey on reactive power ancillary service markets
2021, Renewable and Sustainable Energy ReviewsCitation Excerpt :Loss sensitivity and voltage sensitivity are the factors that determine the economic and technical value of reactive power source. Based on these factors along with risk assessment, a formulation for the value of reactive power source was proposed by Ref. [89]. It has been observed that the value of reactive power source during maximum permissible loading and during voltage instability are different [87].
Dynamic voltage support planning for receiving end power systems based on evaluation of state separating and transferring risks
2010, Electric Power Systems ResearchSimplified reactive power management strategy for complex power grids under stochastic operation and incomplete information
2009, Energy Conversion and ManagementCongestion Cost and Risk Assessment Cost Evaluation in Transmission Pricing Wheeling
2019, Proceedings of the 3rd International Conference on Inventive Systems and Control, ICISC 2019Reactive power planning under conditional-value-atrisk assessment using chance-constrained optimisation
2015, IET Generation, Transmission and DistributionAllocating the cost of reactive power by using modified value based approach and tracing method
2012, 2012 IEEE 5th Power India Conference, PICONF 2012