Overloading is a major problem as there is no any system to ensure the consumer power usage. For example, weather conditions can change the consumer usage and extreme weather conditions can cause overloading. So when there is no way to determine consumer usage, the one alternative is load balancing.
Load balancing is very important feature that keeps the system safe from overloading. When one area is overloaded, the loads can be transferred to the less loaded areas using switches. And load balancing provides how much load has to be transferred to maintain system within limits. The other way is to control using automatic generation control (AGC).
Load balancing is implemented at the substation side at the power distribution level, while AGC is implemented at power station side at power generation level. Because implementation of AGC is very costly, load balancing provides good alternative.
In this project, the design and implementation of Power Load Balancing will be done using Fuzzy logic toolbox of MATLAB. Fuzzy logic provides easy way using graphical user interface to implement fuzzy system. A set of rules can determine the fuzzy system.
My focus in this project is on understanding the background of power system and importance of load balancing in power system. The designing part will give the hands on experience on MATLAB fuzzy logic toolbox.
TOOL USED FOR LOAD BALANCING
In this project, I have used fuzzy logic toolbox provided by MATLAB. MATLAB is an abbreviation of matrix laboratory. It was developed in late 1970s by the MathWorks Incorporation and provided to users. MATLAB covers different areas of real time implementation like matrix manipulation, data algorithms, user interfaces with languages like C and C++, data analysis and graphical implementations.
MATLAB provides separate tools for applications. For example, it provides toolboxes for signal processing, fuzzy logic, neural networks and many other real time applications. In this project, I am using fuzzy logic for load balancing. So how to build a simple fuzzy logic system and how to simulate it, is explained in details below.
Fuzzy Logic Toolbox:
MATLAB provides inbuilt fuzzy logic toolbox that provides Graphical User Interface (GUI) based implementation of fuzzy systems. In this project, this inbuilt function of MATLAB is used for load balancing.
BACKGROUND OF POWER SYSTEM AND LOAD BALANCING
In this chapter, the basics of power system like power generation at power station, power transmission to the subsystem and power distribution to the user are discussed. The other alternative of load balancing that is automatic generation control is also discussed.
None of us can ever imagine a world without electricity. The very first step is the generation of power. Companies generally use load curve to measure the approximate amount of power that has to be generated at a given time. This provides only an approximate value and to make it precise automatic generation control or load balancing is implemented for power control. But these curves give good information for selection of generator units.
Power is generated at power stations with the generators running by heat, nuclear, gas, water flow, wind or other natural source of energy. Generators convert one form of energy into electrical energy that is transmitted over the lines. Most of the commercial power is generated from electromagnetic induction that uses mechanical energy to produce electrical energy.
Power transmission and power distribution are two totally different scenarios. Power transmission deals with the bulk transfer of electricity from power plants to the power substations located near consumer’s place. And power distribution deals with the affective distribution of the power within all consumers to avoid overloading or less loading conditions.
Once power is generated at the power station, and reaches to the substations, the next thing comes is the proper distribution network to different areas. The effective distribution uses load profile technique. Depending upon the load profile values, the transformers and power carrying conductors are designed. Many countries uses single phase 220-230 V, and few regions also use split phase. Split phase provides both 120 V and 240 V power. Small transformers are used to downgrade the voltage to 120V for household use and 240V is used for heavy appliances in industry.
Load profile is a graphical representation of the electrical usage versus time. It gives the approximate load usage for a given area. Direct meter can be used to determine load profile, however easy way is to use customer billing for the usage. For example evaluating all energy bills from a given area determines the load usage and put it as a graphical representation gives load balancing that will be used as reference for the power generation.
LOAD BALANCING USING FUZZY LOGIC
As we discussed in previous chapter, load balancing refers to the release of power or maintaining of power as per consumer demand. In this project, I have used fuzzy logic technique to determine load balancing. In this chapter, I will discuss basics of fuzzy logic, how fuzzy logic is used for load balancing and steps to design and implement of load balancing.
Introduction of Fuzzy Logic:
Fuzzy control was introduced in 1970s and it is classified as intelligent controller. Fuzzy logic is derived from fuzzy set theory to deal with reasoning that is approximate rather than precise. But in many scenarios, rough practical answer comes out as more effective than complex precision. It was developed for control operations to develop knowledge based systems and allows values to be defined like true/false and yes/no. It is simple to implement and hence it is becoming more favorite for knowledge based system implementations.
Implementation of Load Balancing Using Fuzzy Logic:
Let us consider in our case, the distribution feeder is a three phase structure. Each feeder is connected to specific amount of loads. So, to analyze the load balancing using fuzzy logic, it is considered that each feeder is connected to 100 domestic loads. So, 300 loads are connected to three feeders. In this project, I have kept loads constant to 300 but as for future expansion of this project, load balancing can also be designed for variable loads.
The results for the load balancing are shown below. We can adjust the input load value by moving the red line shown in figure and we can also apply input value in the box named input.
Load balancing is a critical requirement of the power system to ensure that entire system works without overloading. This project gives us a good understanding of load balancing.
Fuzzy logic toolbox provided by MATLAB is used in this project for design and development of load balancing. MATLAB is provided by MathWorks Incorporation and it covers areas of applications like data algorithm, matrix manipulation and data manipulation. Fuzzy logic is a toolbox that provides graphical user interface based implementation of fuzzy system.
Before consumer usage of power, it has to be properly generated, transmitted and distributed. Power stations generate the power by converting one form of energy into electrical energy. Once power is generated, it should be transmitted to the subsystems near consumers. So proper power transmission network is required to reduce transmission losses.
Transmission can be overhead or underground depending upon requirements. The critical stage is power distribution. Depending upon the consumer usage, the distribution should be such that it can avoid over loading situation. Load profile gives the graphical representation of the customer power usage.
Automatic generation control is the one way to control the continuously changing load. It is implemented at the power station side and it controls the generation of power depending upon the change in load. It is good alternative to load balancing, but it is very costly. So for rural areas where load fluctuations are not large, load balancing is employed.
Fuzzy logic is the easy way to design load balancing. Using basic fuzzy rules and fuzzy blocks like normalized, Fuzzification, Defuzzification and Denormalized, we can design a load balancing system. In this project, the load balancing using 3-phase with 100 loads per phase system is designed successfully. But the fuzzy system balances the load with some error value that keep changing the final load. So to avoid that error value, error calculations are required.
Hence this project elaborates the need of load balancing and provides the design concepts for the same.
In this project, it is assumed that for a 3-phase system, each phase has maximum of 100 loads. So, entire system can have total of 300 loads. Here, number of loads are assumed fix. And for load balancing, load can be transferred from overloaded system to less loaded system keeping total loads same. But this project can be expanded to design and implement of load balancing system for variable loads in future. Each subsystem can have some amount of buffer to store the electrical energy and when overloading occurs, it can provide power for balancing the load.
Source: California State University
Author: Saumil Navalbhai Patel