Sharif Digital Repository

In this paper the impact of Static Synchronous Series Compensator (SSSC) on the impedance calculated by distance relay is investigated. Analytical results are presented and verified by detailed simulations. Six different phase to phase and phase to ground measuring units of the distance relay are simulated to resemble the behavior of the relay. It is shown in this paper that zero sequence of the injected voltage by 48 pulse SSSC converter has the most impact on the apparent impedance seen by the phase to ground fault measuring unit and cause under reaching of distance relay. It can be concluded from the results that SSSC located in the middle of the transmission line cause to divide trip... 

Today, the interest on distributed generation has been increasing, especially due to technical development on generation systems that meet environmental and energy policy concerns. One of the most important distributed energy technologies is Combined Heat and Power (CHP). CHP is small and self-contained electric generation plan that can provide power for household applications, commercial or industrial facilities and hence its applications are overtly increasing. It can reduce power loss and enhance service reliability in distribution systems. One of the influential factors for the users is the purchasing cost of CHP which is largely dependent on its type, capacity and efficiency. Therefore... 

Lack of demand response has always been the main reason for price increasing, shortage of production capacity and system risk increasing as the electricity markets have been greatly involved during the past years. In Electricity market, the exchanges are profitable for producers and consumers when both can participate freely. Based on this new environment, we are currently facing with a new concept as demand-side participation or demand response. There are several demand response programs that accurate pricing of each them is the major challenge that retailers and market operators are facing with. In this article the day-ahead real time pricing contract (DA-RTP) based on two different... 

The continuous spread of distributed energy resources (DERs) such as combined heating and power (CHP), diesel generators, boilers and renewable energy sources provide an effective solution to energy related problems to serve the power and heat demands with minimum cost. Moreover, the DERs may play a significant role for supplying power and heat in rural areas, where grid electricity is not available. Also, some dry areas may face water scarcity and salinity problems. So, one important solution is the use of DERs to drive desalination units in order to solve water scarcity and salinity problems. In this study, the optimal scheduling of DERs and reverse osmosis (RO) desalination unit that feed... 

Doubly-fed induction generator (DFIG) is the most commonly used technology for wind power generation due to the variable speed performance, decoupled control of active and reactive powers, and high efficiency. However, the DFIG originally cannot participate in damping of power system oscillations since it is not synchronously connected to the power system. This paper proposes an optimal and robust additional damping controller for the DFIG wind turbine to contribute it to damp power system oscillations. It is a fuzzy logic controller that its parameters are optimally tuned using the genetic algorithm (GA). The proposed controller modifies the DFIG active power output by using feedback from... 

Doubly-fed induction generator (DFIG) based wind turbines with traditional maximum power point tracking (MPPT) control provide no inertia response under system frequency events. Recently, the DFIG wind turbines have been equipped with virtual inertia controller (VIC) for supporting power system frequency stability. However, the conventional VICs with fixed gain have negative effects on inter-area oscillations of regional networks. To cope with this drawback, this paper proposes a novel adaptive VIC to improve both the inter-area oscillations and frequency stability. In the proposed scheme, the gain of VIC is dynamically adjusted using fuzzy logic. The effectiveness and control performance of... 

Under voltage load shedding is one of the most important tools to avoid voltage instability. In this paper an optimal load shedding algorithm is developed. This approach is based on the concept of the static voltage stability margin and its sensitivity value at the maximum loading point or the collapse point. The traditional load shedding objective is extended to incorporate both technical and economical effects of load shedding. The voltage stability criterion is modeled as a soft constraint into load shedding scheme. The proposed methodology is implemented over the IEEE14 bus system and solved using a mathematical (GAMS/CONOPT) and two heuristic (P.S.O & GA) methods. © 2006 IEEE  

Islanding detection methods are divided into three main groups as remote, active and passive. Although passive schemes have larger Non Detection Zones (NDZ) relative to other schemes, they are more used in utilities due to their low costs and less PQ problems than other schemes. Passive Schemes are based on the measurements of passive system parameters. These parameters are measured at the point of common coupling (PCC). A new approach in passive techniques is the use of data-mining to classify the system parameters. In this paper, massive indices are collected by simulation of a practical distribution system in PSCAD/EMTP environment. These indices include voltage, frequency, current,... 

Passive islanding detection schemes are more used in utilities due to their low costs and less harmonic problems although having larger Non Detection Zones (NDZ) relative to other schemes. Passive system measurements at the point of common coupling (PCC) are the basis of this scheme. A new approach in passive techniques is the use of intelligent based methods in data-mining to classify the system parameters which affect the islanding detection. As a result, by finding an efficient and robust data-mining algorithm, the passive schemes problem, which is their relatively large NDZ, will be minimized. In this paper, massive measurements are collected by simulation of IEEE standard distribution... 

In this paper, the impact of demand response programs (DRPs) on reliability improvement of the restructured power systems is quantified. In this regard, the demand response (DR) model which treats consistently the main characteristics of the demand curve is developed for modeling. In proposed model, some penalties for customers in case of no responding to load reduction and incentives for customers who respond to reducing their loads are considered. In order to make analytical evaluation of the reliability, a mixed integer DCOPF is proposed by which load curtailments and generation re-dispatches for each contingency state are determined. Both transmission and generation failures are... 

Recently in electricity markets, a massive focus has been made on setting up opportunities for participating demand side. Such opportunities, also known as demand response (DR) options, are triggered by either a grid reliability problem or high electricity prices. Two important challenges that market operators are facing are appropriate designing and reasonable pricing of DR options.In this paper, time-of-use program (TOU) as a prevalent time-varying program is modeled linearly based on own and cross elasticity definition. In order to decide on TOU rates, a stochastic model is proposed in which the optimum TOU rates are determined based on grid reliability index set by the operator. Expected... 

In this paper a new algorithm for allocating energy and determining the optimum amount of network active power reserve capacity and the share of generating units and demand side contribution in providing reserve capacity requirements for day-ahead market is presented. In the proposed method, the optimum amount of reserve requirement is determined based on network security set by operator. In this regard, Expected Load Not Supplied (ELNS) is used to evaluate system security in each hour. The proposed method has been implemented over the IEEE 24-bus test system and the results are compared with a deterministic security approach, which considers certain and fixed amount of reserve capacity in... 

This paper presents a novel approach to optimal placement of Phasor Measurement Units (PMUs) for state estimation. At first, an optimal measurement set is determined to achieve full network observability during normal conditions, i.e. no PMU failure or transmission line outage. Then, in order to consider contingency conditions, the derived scheme in normal conditions is modified to maintain network observability after any PMU loss or a single transmission line outage. Observability analysis is carried out using topological observability rules. A new rule is added that can decrease the number of required PMUs for complete system observability. A modified Binary Particle Swarm Optimization... 

This study presents a passive model to detect islanding conditions of synchronous distributed generation resources in a distribution network or a microgrid. The proposed approach uses the classification and regression tree algorithm for distinguishing between islanding and non-islanding situations. It utilises the rate of change of frequency (ROCOF) and harmonic content of the equivalent reactance seen at the location of distributed generation as input features for decision tree construction. Indeed the thresholds of the proposed input features are extracted by the decision tree algorithm. The output if-then rules of the decision tree algorithm are then utilised to make a new relay logic for... 

Portfolio theory has found its model in numerous engineering applications for optimizing the electrical generation mix of an electricity area. However, to have better performance of this theory, this paper presents a new heuristic method as known modified artificial bee colony (MABC) to portfolio optimization problem. Moreover, we consider both dis-patchable and non-dis-patchable constrains variables and energy sources. Note that the proposed MABC method uses a Chaotic Local Search (CLS) to enhance the self searching ability of the original ABC algorithm. Resulting, in this paper a portfolio theory-based MABC model that explicitly distinguishes between electricity generation (energy),... 

No-one likes being confined to a hospital bed. Children particularly can feel lonely, bored or frightened in these conditions. Hours feel like days, and they may not be able to fully comprehend why they are there. Among kids hospitalized because of distinct diseases, children with cancer have incomparable status and needs. They experience physical and mental problems caused by cancer and medications. Cancer treatment may cause distress which can lessen the effectiveness of the treatment. Utilizing social robots to interact with children in clinical environments has been verified to both diminish their distress level and enhance the effectiveness of the treatment process. To improve the... 

The complex structure of the power system and the pivotal role of electrical energy in determining the socio-economic indicators of any countries lead the policy makers of power industry to take into account the expansion planning of generation system with high priority. Considering the intense fluctuations of costs in electrical energy generation (particularly due to variation of fuel prices within the recent years in the Middle East), finding an optimal generation portfolio, regardless of the costs variations risk looks impossible. The portfolio theory, as an efficient tool for risk management, provides a proper solution to materialize the optimal generation portfolios with the following... 

In this paper resilience oriented water and energy hub scheduling for a remote area is presented. The optimal operation scheduling considering maintenance programming and reliability indices are presented. Demands which include electricity, heat and drinking waters are supplied by diesel generators, boilers, combined heat and power units, and drinking water sources such as desalination units and transferring water. The considered system contains renewable energy resources such as wind turbine and photovoltaic arrays as well as electrical storage units. In order to enhance resiliency of system against forced outages of components and regular maintenance programs, maintenance constraints and... 

A system protection scheme is proposed to mitigate cascaded voltage collapses. Based on the post-contingency conditions of either existence or non-existence of an equilibrium solution, and with regard to the stability and security criteria, the proposed scheme finds the optimal set of remedies. The proposed stabilising scheme brings the non-equilibrium post-contingency operating point back inside a stable region, and then passes this point to the securing scheme. Also, to enhance the performance of the stabilising scheme, a sensitivity analysis method is presented to detect the most effective remedies. The proposed securing scheme converts the stable, but insecure operating point, to a... 

In this paper, a system wide scheme is proposed to arrest voltage instability. This scheme consists of two stabilizing and securing parts. For post- contingency situations, where there are no equilibrium solutions, first, the stabilizing scheme finds the closest solvable operating point, and then passes this point to the securing scheme. The securing scheme brings the solvable, but insecure operating point, back to a secure and stable one. Also, a voltage stability indicator is proposed to monitor the available margin to the collapse point. The proposed stabilizing and securing model are solved using the sequential quadratic programming technique. ©2009 IEEE