Evaluation of Economic Impact of Renewable Energy Sources in Multi-period Optimal Operation of Power Systems

Abstract

In order to operate the electrical network economically and effectively, generation from various sources must be appropriately scheduled. Integrated systems are more common today because of the increase in the cost of fossil fuels and the technological advancements made in the field of renewable energy Resources. To be able to determine the best settings, the optimal power flow problem is posed with all relevant system characteristics, including generator outputs. The network might include conventional fossil fuel generators and renewable energy sources like wind power generators and solar photovoltaic. The classic problem of optimal power flow is a complex non-linear problem with non-linear constraints. In this research, it is suggested how thermal plants with wind and solar integration operate economically using General Algebraic Modeling System (GAMS) software\\\'s which has used Non-linear programming to resolve the Dynamic Economic Dispatch (DED) which is a part of optimal power flow problem. The impact of wind and solar integration on the cost-effective operation of thermal units while taking into considering IEEE-24 bus test system has been researched. In this paper, the reduction of a thermal plant\\\'s fuel consumption with the integration of wind and solar power is the primary focus of study.

Introduction

I. INTRODUCTION

Electric utilities now have to comply with stricter regulations, and modern power systems include numerous interconnections and are built to handle both actual and reactive power demand. This trend has made it imperative to achieve system design and operations with increased security levels and greater sophistication. A lot of research has been done on the "optimum power flow" (OPF) as a potent way to solve this class of operations. The goal of a typical OPF optimization is to dispatch active (P) and/or reactive (Q) power while maintaining the feasibility in considering the power system limits [12]. Deregulation and increased competition have given electric companies new reasons to cut costs. The cost of fuel used to power generator turbines makes up a significant portion of operating costs, hence the electric industry has demonstrated a growing interest in fuel cost reduction. By determining the best distribution of the electric load among the available generation units, a strategy is suggested to reduce these costs. The Economic Load Dispatching (ELD) problem exactly what this is. ELD's primary goal is to save fuel costs while still meeting load demand. However, it's also crucial to be aware of additional factors that, in addition to running costs, can have an impact on critical system characteristics like security and stability. Here, the idea of of optimal flow rises to take care about all those mentioned above. The best active and reactive power dispatch is provided by an optimized power flow solution. It is a non-linear problem with numerous variables with limit constraints of the equality and inequality kind. The operating performance of a power generation-transmission system is optimized using the OPF calculation.

The primary goals of optimal power flow are to:

• Ensure static security and quality of service by placing restrictions on the operation of the generation-transmission system;

• Improve reactive-power/voltage scheduling. To increase operational efficiency by making full use of the system's spectrum of possible operation and by precisely coordinating transmission losses during the scheduling process.

The OPF has traditionally been thought of as the minimizing of an objective function that represents the cost of production. The physical rules regulating the power systems are the limiting factors [6].

Fossil fuels are the main fuel of thermal power, but there is a fear that they will get exhausted eventually with time. So, alternative sources of energy that is the renewable energy sources are very important aspect now-a-days. Renewable energy sources are energy sources that derive their power from the continuous and natural flow of energy that surrounds us. Bioenergy, direct solar energy, geothermal energy, hydropower, wind, and ocean energy are a few of them [9].

Typically, private operators are the owners of wind or solar PV farms. A contract for the purchase of scheduled power from these private operators is signed by the grid operator or independent system operator (ISO) [4,5]. The power output from these renewable resources, however, can occasionally exceed the planned power, which results in an underestimating of the available energy [6]. As surplus power is wasted if it fails to be utilized, ISO will be responsible for the fine.

In this study, the dynamic economic dispatch (DED) solution of thermal generators with wind and solar power integration is taken into consideration. DED stands for the dispatch of generating units over a 24-hour period. The goal of cost-based dynamic economic dispatch is to reduce operational costs while satisfying technological limitations on equality, inequality, and other factors. With regard to equality, inequality, and other technical limitations, generation and demand are matched at each interval of time [2].

The organization of paper as follows : At first, IEEE-24 bus test system consists of ten thermal generating units each with their own cost coefficients, ramp limitations, and maximum and minimum power constraints are considered. Secondly, wind and solar power integrated to test system individually. Finally thermal units with both wind and solar power integration to 24 bus test system is analysed and results are shown.

II. PROBLEM FORMULATION

The objective functions of the problem and its constraints are as follows:

A. Objective Function

The costs associated with producing power using g thermal units over a time period of t, representing the entire cost of electricity generation over a 24-hour period considering  thermal units with wind and solar integration as shown in equation below. The objective junction is to minimize the fuel cost of thermal units including wind and solar curtailments.

It can be seen that reduction in total active power generation by thermal units in all cases when integration of renewable energy sources like wind and solar is employed to IEEE-24 bus system as shown in figure 15 represents variations in active power generation in 24 hour time period. Renewable purchase costs are calculated by directly multiplying purchase tariffs to how much active power purchased. Table 8 indicates reduction in fuel cost for generating power in thermal power units while considering four cases like presence of only thermal, wind integration with thermal, solar integration with thermal and both wind and solar connected to thermal in IEEE- 24 bus reliability test system. All results are optimal values obtained using CONOPT solver in GAMS.

Conclusion

In this research work, lowering the system\\\'s generation costs was the ultimate objective. Since fossil fuel reserves are currently running low, it is crucial to reduce fossil fuel consumption, which will also lower the cost of electricity generation by using renewable energy sources in which absence of fuel and its transportation is main advantage. Thus, it can be inferred that the integration of renewables can lower the cost of power generation, which makes the system more affordable by solving the optimal power flow problem taking into consideration all the system constraints. It is always preferred to rise the system\\\'s active power generation when generation costs are reduced. A suitable dynamic multi-objective AC optimal power flow with wind and solar integration to IEEE-24 bus system has been presented out in this study. The CONOPT solver is used in GAMS to solve the multi-period AC optimal power flow problem, which has been described as a non-linear problem. In a 24-hour period, the generators must maintain a balance between generation and load every hour. The 24-hour DED findings and comparison data show the effectiveness of the suggested methodology when all constraints are followed properly. Optimal schedule of thermal plants with wind and solar integration for 24 hours shows the reduction in thermal fuel cost.

References

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Copyright

Copyright © 2023 Yamini Gompa, Vaisakh K. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.