Microgrid Economic Operation Research Based on Improved Particle Swarm Optimization Algorithm

Abstract

This paper presents a new optimization approach for solving the economic operation with consideration of wind, solar, micro-turbine, fuel cells, battery and load in an energy system. Mathematical models of each micro source and the system model of the microgrid economic operation are established, and the system model is solved by improved particle swarm optimization (PSO) algorithm. The best output of each micro source and energy storage unit and the lowest operating cost comparing by improved PSO is compared with the traditional PSO. The MATLAB simulation indicates the high speed and accuracy of the improved PSO, and verifies the effectiveness of the model. Introduction In recent years, clean energy and distributed generation is attracting extensive attention all over the world [1,2]. People begin to put forward the application of distributed generation, and the microgrid also arises. Microgrid economic operation is one of the most important problems of microgrid research. Through scheduling the output of distributed power and energy storage unit in microgrid, the energy efficiency can be improved a lot and the power generation cost and system discharge can be reduced in some degree under the demand of enough electric power [3]. Literature [4] analyzed microgrid economic operation models of different constraint conditions. Literature [5] studied the optimal allocation of energy according to various distributed energy resources (DER). Literature [6] studied microgrid economic operation models in island and calculated the model by generic algorithm. Microgrid optimal operation is a kind of dynamic multidimensional nonlinear optimization problems, and it needs for quick search to the global optimal point. The commonly methods including mathematics analytic method, particle swarm optimization (PSO) algorithm, ant colony algorithm, genetic algorithm (GA), evolutionary algorithms, etc. [7-10]. This article made a research for a microgrid system which contains windturbine (WT), photovoltaic (PV), fuel cell (FC), micro-turbine (MT), storage battery (SB) and electrical load. And it built a microgrid economic operation model in meeting the constraint conditions of energy balance between supply and demand, power quality and more. Each micro source output and the optimal object under the parallel operation considering the real-time electric price is calculated by using improved PSO. And the optimization results is compared with the traditional PSO. Micro Source Modeling In this section this paper did not analyze windturbine (WT) and photovoltaic (PV) because of its characteristics of randomness and intermittent. And the distribution characteristics of WT and PV are analyzed according to historical data. Fuel Cell. The daily cost calculation formula of fuel cell is formulated as follows: 1 FC FC FC FC P C c T LHV η = ⋅ ⋅∑ (1) 3rd International Conference on Machinery, Materials and Information Technology Applications (ICMMITA 2015) © 2015. The authors Published by Atlantis Press 290 0.0023 0.6735 J J P η = − + (2) where CFC is the operation cost of fuel cell; T is the fuel operation time; LHV is the low calorific value of gas; c is the fuel price; PFC is the static power output; ηFC is the efficiency of fuel cell. Micro Gas Turbine. Its daily cost calculation formula is similar to fuel cell. 1 MT MT MT MT P C c T LHV η = ⋅ ⋅∑ (3) 3 2 0.0753( ) 0.3095( ) 0.4174( ) 0.1068 65 65 65 MT MT MT MT P P P η = − + + (4) where CMT is the operation cost of micro gas turbine; PMT is the micro gas turbine power output; ηMT is the efficiency of micro gas turbine. Storage Battery. The charging and discharging of storage battery under the parallel operation is not only restricted by the performance requirements, but also affected by electricity peak and valley. Battery only works in electricity peak and valley. Microgrid Economic Operation Modeling This paper mainly analyzed the optimization of the lowest costs on conditions of the active power balance, the limitation of distributed power output and the limitation of battery storage capacity. Objective Function. Microgrid as an independent whole under the parallel operation can purchase power from the external grid when its internal power is not enough to meet the requirements of the internal loads, and it also can send power to the grid. The economic operation problem can be formulated as follows: