Available Transmission Capacity Research Articles

Calculation and optimization of inter-regional available transfer capability considering wind power uncertainty and system improvement measures

The intermittency and uncertainty of wind energy make transmission congestion management increasingly complex. In this paper, we investigate the impact of wind energy on available transmission capacity (ATC) and then explore ways to mitigate transmission congestion from the grid and load side, respectively. The impact of a stochastic variable is considered by applying Latin Hypercube Sampling (LHS) and backward curtailment techniques to generate typical scenarios. ATC is improved by the optimal allocation of Thyristor Controlled Series Compensation (TCSC) on the grid side and the use of Demand Response (DR) on the load side. The source-grid-load cooperative optimisation model for ATC is solved by an improved particle swarm optimisation (PSO) algorithm. Based on the IEEE-30 bus system, an experimental scheme is designed and analytical calculations are performed. The results show that the joint application of TCSC and DR can help to improve ATC in a comprehensive way. The work done in this paper can achieve the purpose of promoting renewable energy consumption by improving the utilisation efficiency of the transmission network without changing the network structure.

An Effective Method to Determine the Available Transmission Capacity with Variable Frequency Transformer

Available transmission capacity (ATC) is a top priority and lucrative solution for electricity market players. Fast and accurate ATC solutions enable participants to gain a competitive advantage in the marketplace. In order to procure a competitive solution, we propose the differential power flow equation-based static ATC. Using the proposed method, the entire time-domain trajectory of a dynamic system can be solved along with a differential equation based on a fictional time. In this paper, a variable frequency transformer (VFT) was used to control and increase the transmission power, which made the calculations more complex. In addition, the proposed method was used in seven different systems and 50% of the time was saved on small systems. It also enjoyed a much better performance (up to 90%) on large systems. It can be concluded that the proposed static ATC introduces promising results and is suitable for online applications.

Coordinated generation and transmission expansion planning approach considering probabilistic available transfer capability

The available transmission capacity of the network has a great impact on the safety and reliability of the whole system. After the reform of electricity market, the grid is required to have the highest available transmission capacity (ATC) based on the existing load due to the uncertain factors. Therefore, it is necessary to consider the growing demand for available transmission capacity from the grid planning stage. Meanwhile, considering the uncertain factors have a great influence on the available transmission capacity (ATC), this paper first models the three uncertain factors and introduces the solving method of probabilistic available transfer capability, then proposes a grid expansion planning model considering the probabilistic available transmission capacity under the influence of uncertainties, which is applied to the six-node test system. Finally, the genetic algorithm is used to solve the final planning scheme. Compared with other planning schemes, this method can consider the comprehensive investment cost and the probability available transmission capacity. The case study shows that the method is effective and can achieve good results.

Available transfer capacity model and algorithm of the power grid with STATCOM installation

The optimization of the available transmission capacity (ATC) was considered in the power systems integrated with static synchronous compensator (STATCOM). A calculation method of ATC second-order cone programming (SOCP) based on Benders decomposition was proposed, aiming at the non-convexity and non-linearity in the optimization of the ATC of the power grid. The proposed method was divided into three stages. Firstly, the mathematical model of ATC considering the integration of the STATCOM is established. Secondly, the non-convex tidal current model is approximately converted into a convex optimization model by SOCP. Finally, the solution obtained by transforming the ATC model into two-stage models with basic state power flow constraints and N-1 power flow constraints using Benders decomposition method. The simulation results obtained from the IEEE-118 node system show that the proposed method can guarantee the feasibility of effectively regulating the grid transmission capacity of the power grid. It is also demonstrated that the installation of STATCOM can improve the system transmission capacity.

Production efficiency of nodal and zonal pricing in imperfectly competitive electricity markets

Electricity markets employ different congestion management methods to handle the limited transmission capacity of the power system. This paper compares production efficiency and other aspects of nodal and zonal pricing. We consider two types of zonal pricing: zonal pricing with Available Transmission Capacity (ATC) and zonal pricing with Flow-Based Market Coupling (FBMC). We develop a mathematical model to study the imperfect competition under zonal pricing with FBMC. Zonal pricing with FBMC is employed in two stages, a day-ahead market stage and a re-dispatch stage. We show that the optimality conditions and market clearing conditions can be reformulated as a mixed integer linear program (MILP), which is straightforward to implement. Zonal pricing with ATC and nodal pricing is used as our benchmarks. The imperfect competition under zonal pricing with ATC and nodal pricing are also formulated as MILP models. All MILP models are demonstrated on 6-node and the modified IEEE 24-node systems. Our numerical results show that the zonal pricing with ATC results in large production inefficiencies due to the inc-dec game. Improving the representation of the transmission network as in the zonal pricing with FBMC mitigates the inc-dec game.

Production Efficiency of Nodal and Zonal Pricing in Imperfectly Competitive Electricity Markets

Electricity markets employ different congestion management methods to handle the limited transmission capacity of the power system. This paper compares production efficiency and other aspects of nodal and zonal pricing. We consider two types of zonal pricing: zonal pricing with Available Transmission Capacity (ATC) and zonal pricing with Flow-Based Market Coupling (FBMC). We develop a mathematical model to study the imperfect competition under zonal pricing with FBMC. Zonal pricing with FBMC is employed in two stages, a day-ahead market stage and a re-dispatch stage. We show that the optimality conditions and market clearing conditions can be reformulated as a mixed integer linear program (MILP), which is straightforward to implement. Zonal pricing with ATC and nodal pricing is used as our benchmarks. The imperfect competition under zonal pricing with ATC and nodal pricing are also formulated as MILP models. All MILP models are demonstrated on 6-node and the modified IEEE 24-node systems. Our numerical results show that the zonal pricing with ATC results in large production inefficiencies due to the inc-dec game. Improving the representation of the transmission network as in the zonal pricing with FBMC mitigates the inc-dec game.

Available Transmission Capacity Analysis for the Receiving-End Grid of UHV-DC Transmission System

UHV-DC transmission system presents certain adverse reactive characteristics to its receiving-end grid. Based on the approach of P-V curve and V-Q curve, this paper presents a method of voltage stability analysis for the receiving-end grid of UHV-DC transmission system, which gives its available transmission capacity (ATC), voltage limit and reactive power margin, with the consideration of the normal, N-1 and N-2 operation situations and the situation of the commutation failure. Different with traditional ATC analysis, the characteristics of UHV-DC transmission system is included here. With the real UHV-DC project of ±800kV HaZheng in China, the effectiveness and efficiency of the proposed mothed are verified.

Impact of Wind Power on the ATC Values in Hydro- Dominated Power System

The wind power generation is increasing in many countries as a result of decreasing technology costs, active government policies for renewable energy sources, environmental concerns, etc.. This paper investigates the impact of wind power generation on ATC (available transmission capacity) calculation. In order to determine the maximum incremental MW transfer possible between two parts of a power system without violating any specified limits, ATCs are calculated. When calculating ATC values, it is necessary to assume production and consumption pattern in power system. Production of wind power depends on the wind speed, which is a random variable and it is impossible to forecast exactly the production of wind power that is needed for the ATCs calculation. In order to investigate influence of the stochastic wind power production on the ATCs value, computer model of Croatian electric power system is made in Power World Simulator. ATCs are calculated for southern part of Croatian power system in which besides wind power, hydro power plants are only type of power generation. Available wind speed measurements are used as input data for wind power production. The results of the ATC calculation for different scenario of wind power production and location in the Southern Croatian power system are presented and discussed in the paper.

Available transmission capacity (ATC) and its value under open access

Strictly engineering aspects of available transmission capacity (ATC) are analyzed first. Nonlinear network theory is used to provide several key conditions under which one could define a notion of ATC and specific novel algorithms for its evaluation. Next, the fundamental problem which prevents one from developing an economically efficient distributed transmission market based on the ATC is identified. It is suggested that for an electric power network of an arbitrary topology it is not possible to map the computed ATC onto its market value. All findings are illustrated using examples of small power systems.