Amin Kargarian

System of Systems Based Security-Constrained Unit Commitment Incorporating Active Distribution Grids

In restructured power systems, the transmission and distribution grids are autonomously utilized by independent system operator (ISO) and distribution companies (DISCOs), respectively. As the operating condition of one grid influences the decisions made by operators of other grids, the ISO and DISCOs should collaborate and cooperate with each other in order to operate the entire power system in a secure and economic manner. According to the concept of system of systems (SoS) engineering, this paper presents a decentralized decision-making framework to determine a secure and economical hourly generation schedule for a transmission system encompassing numbers of active distribution grids. Taking into consideration the physical connections and shared information between ISO and DISCOs, an SoS-based SCUC framework is designed and a hierarchical optimization algorithm is presented to find optimal operating points of all independent systems in the SoS-based power system architecture. The numerical results show the effectiveness of the proposed SoS framework and solution methodology.

Distributed Security-Constrained Unit Commitment for Large-Scale Power Systems

Summary from only given. Independent system operators (ISOs) of electricity markets solve the security-constrained unit commitment (SCUC) problem to plan a secure and economic generation schedule. However, as the size of power systems increases, the current centralized SCUC algorithm could face critical challenges ranging from modeling accuracy to calculation complexity. This paper presents a distributed SCUC (D-SCUC) algorithm to accelerate the generation scheduling of large-scale power systems. In this algorithm, a power system is decomposed into several scalable zones which are interconnected through tie lines. Each zone solves its own SCUC problem and a parallel calculation method is proposed to coordinate individual D-SCUC problems. Several power systems are studied to show the effectiveness of the proposed algorithm.

Multiobjective optimal power flow algorithm to enhance multi-microgrids performance incorporating IPFC

The idea of connecting some adjacent microgrids and making a multi-microgrid (MMG) have recently attracted attention among power system researchers. It helps better operate, control and manage the power system. This paper presents a multiobjective optimal power flow (MOPF) algorithm for improving the performance of MMGs incorporating interline power flow controller (IPFC). The proposed MOPF simultaneously minimizes MMG operating cost and total energy loss, as well as voltage profile deviation of all buses in the system. The proposed multiobjective nonlinear constraint optimization problem is formulated considering the control variables of IPFC. Also, the proposed algorithm guarantees that the final system operating point has a suitable security margin from the voltage instability point. A typical MMG system is used to demonstrate the effectiveness and proficiency of the algorithm.

Reactive Power Provision in Electricity Markets Considering Voltage Stability and Transmission Congestion

Abstract This article presents a new algorithm for optimal reactive power procurement in pool electricity markets. Due to the significant impact of reactive power flow on the system voltage stability and transmission loss, the objective function of the proposed algorithm is minimization of the market payment for reactive power and system energy loss, simultaneously maximizing voltage stability margin. Moreover, as another object, the algorithm tries to decrease the probability of the transmission congestion during reactive power market clearing. A four-step multi-objective mixed-integer non-linear programming technique that uses the genetic algorithm in combination with a sequential quadratic programming method is implemented in MATLAB (The MathWorks, Natick, Massachusetts, USA) to solve the proposed problem. Numerical studies on the IEEE-RTS test system show the suitability of the proposed method.

Stochastic active and reactive power dispatch in electricity markets with wind power volatility

This paper proposes a stochastic multiobjective optimization algorithm for simultaneous active and reactive power dispatch in electricity markets with wind power volatility. Considering only economic issues during market clearing will achieve minimum system payment but may not yield an efficient and secure system operating point. Therefore, maximizing expected voltage security margin and minimizing transmission congestion probability are incorporated into the proposed multiobjective function. To demonstrate the effectiveness of the proposed algorithm, five average deviation indices and a spider diagram are introduced to evaluate the proposed algorithm.

Power flow calculation of hybrid AC/DC power systems

Multi-terminal HVDC systems have recently become an attractive option for interconnection of isolated AC systems such as offshore wind farms and oil platforms to asynchronous large AC systems. This paper deals with power flow calculation (PFC) of hybrid AC/DC power systems where several asynchronous AC systems are interconnected via a common multiterminal VSC-HVDC system. This paper proposes a unified AC-DC approach for PFC of a hybrid AC/DC power system. The proposed approach is then employed for two different analyses, namely a) the separated analysis where the entire hybrid AC/DC system is divided into two groups. The first group (named external AC system) comprises all asynchronous AC systems which are not directly connected to the slack convertor of the DC network, and the second group comprises an AC/DC system where the selected AC system is directly connected to the slack convertor. In this method, a PFC is firstly performed for the the first group, and its relevant obtained results will be used for PFC of the second group. b) the integrated analysis where the entire hybrid system is considered as a unit. Both a) and b) can be used in the practical analysis of the real-size power systems. However, due to practical issues and computational costs the separated analysis may be a more acceptable method. The simulations have been performed using MATLAB, and the obtained results have been compared with those obtained in SIMPOW.

Timeframe capacity factor reliability model for isolated microgrids with renewable energy resources

In recent decades, the integration of renewable energy resources in the power system has grown rapidly around the globe. Using renewable energy resources in microgrids is appropriate, especially where access to public power energy is impossible or costly. This paper presents a novel method for assessing the reliability of microgrids, taking into account the probabilistic behavior of solar and wind power. In this model, the study period is divided into different Timeframes (TFs), and for each TF, the timeframe capacity factor (TFCF) is considered for each renewable energy resource. To assess the microgrids reliability, the Loss of Load Expectation (LOLP) and Expected Energy Not Supplied (EENS) are calculated. Compared to existing probabilistic models, the prerequisites data and running time for reliability assessment is significantly reduced when using the proposed method. These two virtues suit the model well for optimization-based planning problems.

Optimal operation of distribution grids: A system of systems framework

There are many entities in the modern power systems that collaborate together to operate the system in a secure and reliable manner. Each of the entities is managed and operated autonomously and intends to increase its own benefit. This paper presents a system of systems (SOS) framework for optimal operation of distribution grids. The distribution grids are modeled as the SOS utilized by distribution companies (DISCOs) collaborating with different loads and microgrids. In this framework, the DISCO and microgrids are regarded as the individual systems which are independently managed and operated aiming at maximizing their own profit. Considering the correlation among the independent systems, the ORIGIN and CLIENT data are introduced and the relationship table is constructed to represent the correlated variables between the entities. The relationship table indicates the sequences of the optimization problems for the entities. The proposed framework is applied to a typical distribution grid and results are discussed.

Chance-Constrained System of Systems Based Operation of Power Systems

In this paper, a chance-constrained system of systems (SoS) based decision-making approach is presented for stochastic scheduling of power systems encompassing active distribution grids. Based on the concept of SoS, the independent system operator (ISO) and distribution companies (DISCOs) are modeled as self-governing systems. These systems collaborate with each other to run the entire power system in a secure and economic manner. Each self-governing system accounts for its local reserve requirements and line flow constraints with respect to the uncertainties of load and renewable energy resources. A set of chance constraints are formulated to model the interactions between the ISO and DISCOs. The proposed model is solved by using analytical target cascading (ATC) method, a distributed optimization algorithm in which only a limited amount of information is exchanged between collaborative ISO and DISCOs. In this paper, a 6-bus and a modified IEEE 118-bus power systems are studied to show the effectiveness of the proposed algorithm.

A system of systems engineering approach for unit commitment in multi-area power markets

In power systems, the main grid might be a group of several interconnected areas. The areas can be self-governing with their own polices and rules. According to the concept of system of systems (SoS) engineering, this paper presents a decentralized decision-making framework to determine an economical hourly generation schedule for a multi-area power system. Each self-governing area is modeled as an independent system, and the entire power system is modeled as a SoS. The proposed decentralized unit commitment algorithm takes into account the privacy of each independent system, and only a limited data information such as power exchange between the areas, needs to be exchanged between the systems. An iterative decentralized optimization model is presented to find the optimal operating point of all independent systems in the SoS-based power system architecture. The numerical results show the effectiveness of the proposed SoS framework and solution methodology.