Abstract
The ongoing transition of the energy system towards being low-carbon, digitized and distributed is accelerating. Distributed Energy Resources (DERs) are playing a major role in this transition. These DERs can be aggregated and controlled by Virtual Power Plants (VPPs) to participate in energy markets and make full use of the potential of DERs. Many existing VPP models solely focus on the financial impact of aggregating DERs and do not consider the technical limitations of the distribution system. This may result in technically unfeasible solutions to DERs operations. This paper presents an expanded VPP model, termed the Technical Virtual Power Plant (TVPP), which explicitly considers the technical constraints of the network to provide operating schedules that are both economically beneficial to the DERs and technically feasible. The TVPP model is formulated as a bi-level sto-chastic mixed-integer linear programming (MILP) optimization model. Two objective functions are used, the upper level focuses on minimizing the amount of power imported into the TVPP from the external grid, while the lower level is concerned with optimally scheduling a mixture of DERs to increase the profit of the TVPP operator. The model considers three TVPPs and allows for energy trading among the TVPPs. The model is applied to several case studies based on the IEEE 119-node test system. Results show improved DERs operating schedules, improved system reliability and an increase in demand response engagement. Finally, energy trading among the TVPP is shown to further reduce the costs of the TVPP and power imported from the upstream electrical network.

Abstract
This study presents a planning model for utilizing emergency transmission capacity in the power system reserve market with renewable energy sources. To this end, first, the effects of the operation of a transmission line at higher power than rated power are described. The lifetime reduction of transmission lines caused by operation under these conditions is then measured, and finally, the price is determined based on the rate of lifetime reduction. This surplus capacity is then entered into a two-stage model of the energy and reserve market as a function of price offer, while also taking renewable energy sources into account. The numerical results of a 6-bus network indicates that the introduction of renewable energy sources reduced energy costs while increasing reserve market costs due to uncertainty. Despite the emergency capacity, such costs are reduced due to the network's utilization of low-cost resources.

Abstract
In this paper, Emission Controlled Security Constrained Unit Commitment (ECSCUC) model is proposed in power system. This model consists of a closed-loop modified Unit Commitment (UC) and Security-constrained Optimal Power Flow (SCOPF). An emission controlled formulation is developed to improve the economic-environment conditions of operation of power system. The objective of this ECSCUC model is to obtain the maximum social welfarebased system operating cost while maintaining the system security also considering the environmental impacts. This paper proposed a multi-stage multi-objective mixed-integer nonlinear programming (MINLP) to minimize system operation cost. In this paper, multi-reservoir cascaded hydro plant with time delay and thermal plants are considered for maintaining the demand. The presented formulation treats emission controlled security constrained unit commitment of hydrothermal power system which attempts to optimize both cost and emission simultaneously. The numerical examples exhibit the effectiveness of the proposed model in recent competitive electricity markets.

Abstract
In large scale power systems, PSS is not sufficient to damp inter-area oscillations; therefore, FACTS devices, such as SVC, which is one of the most important these devices, are typically used with PSSs. In this paper, the parameters of a power system stabiliser (PSS) and static VAR compensator (SVC) with help of a combination of a Differential Evolution algorithm (DE) and Local Search Algorithm (called the DELSA (Memetic DE algorithm)) are introduced, which are designed independently, converge to the correct and optimal solution in a small number of iterations and are attuned to damping low frequency oscillations, such as local mode oscillations, inter-area mode oscillations, other controllers modes, and modes of the generator excitation system. Suppose that the DE algorithm searches in a wide-ranging area, whereas the local search focuses on the attraction area, which probably has the optimal solution. We studied the three-area power system that was simulated in the time domain by MATLAB. © 2011 Praise Worthy Prize S.r.l. - All righs reserved.

Abstract
In this paper, economic analysis of gas-fired generator, biomass unit and wind turbine is carried out in different scenarios based on gas price, energy selling price, and load factor in Iran and the payback period and rate of return are determined. Then, the participation of the Distributed Generations (DGs) in a day-ahead energy and reserve market is simulated for scheduling from the view point of ISO. The ISO target in this model is minimizing total system producing cost considering system security constraints and technical limitation of all units. Finally, the simulation results demonstrate the reserve market as an apt place for DGs.

Abstract
Conventional second harmonic current restriction approach is an adopted method which has been implemented to transformer differential protection schemes. Because of unreliable nature of this approach in discrimination between inrush current, internal faults and external faults and due to the saturation of current transformers, we present new features of the differential protection scheme. This helps to determine the feasibility and applicability of the proposed approach in differential protective scheme for power transformer. The Current Transformer Saturation (CTS) phenomenon issue and its revelation is one of the most significant problems in power system protection particularly in the differential protection. In this paper, the saturation phenomenon and its effects on the differential protection are analyzed. Prevalent algorithms in digital signal processing which are implemented in power system cannot correctly recognize this phenomenon. Mal-operation of differential protection relay takes place when saturation in CT is appeared. This paper presents a Third-Difference Algorithm (TDA) for CTS recognition. In order to make comparison between the presented approach and prevalent digital protective algorithm, an identical case study is simulated. Simulation results also show that the TDA is both satisfactory and consistent with expectation. © Indian Society for Education and Environment (iSee).