Electric utility expansion planning with generation transmission interactions : implications for transmission pricing | |
| Author | Samarakoon, H. M. D. R. H. |
| Call Number | AIT Diss. no. ET-99-4 |
| Subject(s) | Electric power transmission Electric utilities--Costs |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | A generation expansion planning model considering transmission system cost and a transmission expansion planning model considering power plant location selection are developed in this study in order to consider the interactions between generation plant locations and transmission network development. The treatment of generation and transmission expansion planning in two separate models facilitates more technical considerations including probabilistic production cost simulation, transmission network security constraints and load flow analyses. These two ·models are used iteratively to improve the solution till convergence is achieved. The generation expansion planning problem is formulated as a dynamic programming model that has three sub-models for calculating (i) generating capacity cost, (ii) electricity production cost and (iii) transmission cost for each state (i.e., a combination of generation plants) of each stage (i.e., a period of the planning horizon). Such a model formulation helps to consider the variations of transmission cost with regards to location, size and time of commissioning of power plants, while retaining more sophisticated technical features in the existing generation . planning models (e.g., probabilistic production cost simulation). The transmission expansion planning model considering power plant location selection is a single period mixed integer linear programming model. The non-linearity of the DC load flow equations of the model for)llulation is avoided by using a new state enumeration technique that reduces the size of the formulation. Line outage distribution factors (LODFs) are used in order to identify the critical contingencies of the network and to formulate security constraints of the model. Such approci.ch reduces the problem size considerably. The proposed planning approaches for generation and transmission are applied in the Sri Lan.lean power system in order to compare planning and cost implications of the approaches with that of the sequential generation and transmission planning approach (i.e., without consideration of interactions between generation and transmission). Results of the case study show that the power plants capacity mix and plant locations under the proposed planning approaches are quite different from that under the sequential planning approach. These proposed approaches are resulted in a net reduction in the total cost of the power system with considerable reduction in costs of transmission, but a higher cost of generation. The transmission planning solutions obtained in these proposed approaches are further· improved with the consideration of reactive power flows in the network. A separate transmission planning model is developed for this purpose. Sensitivity factors (COSFs) of the voltage magnitude and phase angle for a circuit outage are derived using decoupled load flow in order to formulate security constraints, which do not incorporate any additional variable. A method for identifying critical contingencies is developed using COSFs. Such approach helps to reduce number of constraints considerably. 111 '· The study further examines (i) the importance of voltage stability aspect in transmission planning; (ii) the voltage stability implication of the proposed planning approach and (iii) the planning implications of the consideration of power cables in urban areas as a technical option in order to reduce long term health hazards in power transmission. It shows that the system voltage stability is quite improved under the proposed planning approach. However, it shows the criticality of the system in terms of voltage stability in the cases studied. The consideration of power cables in urban areas results in a change of generation schedule as well as a slight increase in the total cost of generation and transmission of the system. The study also analyzes the implications of the proposed generation and transmission planning approach for transmission pricing. A transmission pricing approach is developed for this purpose. The proposed pricing approach stipulates transmission price to have variable and fixed charge components. The variable charge is based on the marginal variable cost. The fixed charge at a node is determined on the basis on marginal capacity cost at the node and taking into account for the expected return on h·ansmission capital. It is charged according to the operating capacity and the location of individual suppliers and independent of their operating patterns. The node based fixed charge approach is then extended to a long term contract structure which makes contracts between transmission utility and the power suppliers to access the network from a specified location up to a specified capacity. The proposed contracts allow the suppliers to access any consumer in the network without making any restriction on their transmission paths. The case study of the Sri Lankan power system using the proposed transmission pricing approach shows that the revenues from variable and fixed charges and expected return on capital investments in transmission significantly vary with the system expansion planning criteria. |
| Year | 1999 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Energy Technology (ET) |
| Chairperson(s) | Shrestha, Ram M.; |
| Examination Committee(s) | Fujiwara, Okitsugu ;Thukaram, D. ;Surapong Chirarattananon ;Rahman, Saifur; |
| Scholarship Donor(s) | The Government of Japan; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1999 |