Impact of DG Configuration on Maximum Use of Load Supply Capability in Distribution Power Systems

Traditional distributed generators (DGs) planning methods take network loss minimization as the main objective to optimize DG sites in feeders. The use of load supply capability (LSC) in DG planning will precisely answer the questions how many DGs should be integrated, which transformer they should be connected to, and which type of DGs should be adopted. The main work of this paper is to analyze the impact of DGs on LSC so as to answer the three key questions. It resolves the planning problem through three steps: (i) two LSC models considering DGs’ access are developed, in which two different transfer strategies are considered: direct load transfer and indirect load transfer; (ii) the method of combined simple method and point estimate method is proposed. At last, based on a base case, when the configuration of DGs is changing, the impact of DGs on system LSC is studied. After the case study, the conclusion concerning the impact of load transfer strategy, DG capacities, and DG types on LSC is reached

Flexibility evaluation of active distribution networks considering probabilistic characteristics of uncertain variables

The flexibility evaluation of distribution networks has attracted significant research attention with the increasing penetration of renewable energy. One particular gap in existing studies is that little attention has been paid to the probabilistic characteristics of uncertain regions. In this study, a novel sequential flexibility evaluation method is proposed based on the feasibility analysis of the uncertain region of photovoltaic active power and load demand. The model features the uncertain region with probabilistic characteristics, which is essential for analysing the impact of probabilistic characteristics of uncertain variables (PCUVs) on flexibility evaluation. The sequential direction matrix is adopted to reflect the major factor of flexibility shortage. The evaluation procedure is modelled as a bi-level optimisation problem. Demonstrated by the simulation results, the flexibility index is larger by considering the PCUV. Furthermore, the elements in the sequential direction matrix indicate that the photovoltaic power during midday is the major cause of flexibility shortage.</p

Research on unit commitment optimization of high permeability wind power generation and P2G

As an important form of future energy utilization, the operation of combined electricity-gas energy systems is also threatened by high-level penetration intermittent renewable energy. The application of power to gas (P2G) technology has deepened the coupling between the concerned power system and the natural gas system, and hence, bidirectional energy flow between the power system and the natural gas system can be implemented. P2G technology provides an alternative solution for the optimal operation of the combined electricity-gas energy systems to accommodate intermittent renewable energy, particularly, wind power. In this new environment, the unit commitment optimization of high permeability wind power and P2G is addressed, where the objective is to minimize the total operating cost of combined electricity-gas energy systems. First, the P2G technology and the application and supportive policies are introduced. Second, considering the characteristics of P2G devices and the combined system, a two-level economic dispatch model of the combined system with security constraints is proposed. Third, based on the Karush Kuhn Tucker optimality condition, the two-level optimization model is transformed into a mixed integer linear programming. Finally, the case study shows that the proposed unit commitment model is effective and accurate in optimizing the combined energy systems with high penetration level wind power.</p

Load carrying capability of regional electricity-heat energy systems:Definitions, characteristics, and optimal value evaluation

Evaluating the load carrying capability of regional electricity-heat energy systems is of great significance to its planning and construction. Existing methods evaluate energy supply capability without considering load characteristics between various users. Besides, the impact of integrated demand response is not fully considered. To address these problems, this paper builds a load carrying capability interval model, which uses reliability as a security constraint and considers integrated demand response. An evaluation method for the optimal load carrying capability considering uncertainties of load growth is proposed. First, this paper defines energy supply capability, available capacity, and load carrying capability. Interval models are built to achieve the visualization display of these indices. Their characteristics are studied and the impact factors of interval boundary are analyzed. Secondly, a two-layer optimization model for the evaluation of optimal load carrying capability is constructed, considering the uncertainties of load growth. The upper-layer model aims at optimizing the sum of load carrying capability benefit, integrated demand response cost, and load curtailment penalty. The lower-layer model maximizes energy supply capability. Thereafter, the lower-layer model is linearized based on piecewise linearization and the least square method. The computation efficiency is greatly enhanced. In the case study, a real regional electricity-heat energy system is used to validate the proposed model and method.</p

Reliability Assessment of Active Distribution System Using Monte Carlo Simulation Method

In this paper we have treated the reliability assessment problem of low and high DG penetration level of active distribution system using the Monte Carlo simulation method. The problem is formulated as a two-case program, the program of low penetration simulation and the program of high penetration simulation. The load shedding strategy and the simulation process were introduced in detail during each FMEA process. Results indicate that the integration of DG can improve the reliability of the system if the system was operated actively