Simulation and control of a supercapacitor supercapacitor fuel cell hybrid power generation system to feed a direct current electric motor

Dissertation for Master's Degree in Power Electrical Engineering

Abstract

In this thesis, a combined power generation system using fuel cell/battery/supercapacitor to feed a light electric vehicle with independent excitation electric motor drive system was studied and simulated. The electric vehicle system consists of a feed and control system, multiple sources, power control unit and energy management system, independent excitation DC machine and electric vehicle load. The system speed reference is selected according to the ECE-47 drive. In other words, a model including several energy sources, based on logical rules, control algorithm and energy storage system for a light three-wheeled electric vehicle has been presented. The main feature of the light electric vehicle comes from its control strategy, which supports the energy management system for the battery, fuel cell and supercapacitor under different loads. The simulation results show that the control algorithm can manage the multi-source system in a completely planned way. An important application of the energy management system is the compromise between fuel storage along with a clean drive as well as helping the engine and battery in terms of cost. In this thesis, proportional-integral controllers are used in the power control system. The simulation results have shown that the use of fuzzy controllers compared to proportional-integral fixed gain controllers increases the capability of the studied system in tracking the reference speed. Fuzzy controllers update their parameters compared to proportional-integral controllers, which are fixed against the speed fluctuations of their parameters, which are called self-adjusting controllers. Therefore, they perform better against speed changes.

Key words: combined power generation system, battery, fuel cell, supercapacitor, control algorithm of energy management system, fuzzy controller

Introduction

Transportation industry is one of the industries that are always the attention of experts and craftsmen. Scientists have always been trying to produce cars that have better performance, lower fuel consumption and less pollution than conventional cars. In this regard, a significant effort has been made to improve the quality of fuel used in cars from gasoline to other forms. For example, extensive research has been done on hydrogen fuels and fuel cells [1]. However, due to the high production cost and also the problems caused by the nature of these types of fuels (high flammability and difficult storage conditions), their consumption has not been possible [1].

Today, the use of electric cars in which the electric motor alone produces the driving force is not customary. The first factor is the very high cost of producing these cars, which increases their prices. In addition, these cars travel a small distance per charge. On the other hand, the time required to charge the battery in these cars is very long, which has limited the use of these cars compared to combustion cars [1]. According to the statistics obtained in 1980, about 30 percent of the total carbon pollution produced in the United States was due to the use of combustion engines[2], which increased to 40 percent in 2000. A combustion engine usually has an efficiency of about 32% in the best conditions. Normally, the efficiency of a normal combustion engine is about 18% in the city and about 26% on highways [2]. One of the solutions used to increase the efficiency of combustion engines is to reduce their fuel consumption. In this way, the pollution of cars can be reduced.

Among the disadvantages of combustion cars, the following can be mentioned [2]:

The size of the combustion engine is such that they can provide the necessary power for the desired acceleration for the car. Therefore, these engines are usually bulky and heavy.

The thermal efficiency of these engines depends a lot on their working point and constantly changes during the movement of the car depending on the conditions. In addition, because these engines must be designed in such a way that they meet the needs of the car during acceleration, they have very low efficiency under normal conditions.

The entire kinetic energy of the car is converted into heat during braking and wasted.

With the research conducted by the researchers, they have realized that the use of electric hybrid cars can be the answer to the stated content. A hybrid car[3] is a car that uses two or more energy generators and an energy converter to produce power. Today, the use of new energy sources in hybrid cars has been greatly welcomed. The most common source of new energy used in these cars is the fuel cell. Batteries are also used in these cars. By using hybrid cars, it is possible to use the capabilities of both types of combustion and electric cars. Therefore, with the use of hybrid cars, environmental pollution is reduced, and the acceleration power of the car is also strengthened [3]. Considering the use of two main sources of fuel cell and auxiliary battery, the control of these two sources is a complex problem. By controlling these two sources, it is possible to determine the amount of vehicle fuel consumption, the level of pollution produced, and also the amount of charge of the batteries.

According to the above, the purpose of using hybrid cars is to use the advantages of both combustion and electric engines and eliminate their disadvantages. Some of the weak points of combustion engines are presented below [2].

By using the electric propulsion system along with the combustion propulsion system, a major part of the car's power is provided by the electric system during acceleration and downhill travel. Therefore, the size of the combustion engine is reduced.

The working conditions of the combustion engine are completely or partially the working conditions of the car such as speed, acceleration, torque and power, and as a result, the combustion engine works in the range of its maximum efficiency. This energy is returned to the car during acceleration.

Regarding hybrid cars, many studies have been conducted on the design and construction of this type of car in recent years.

1-2 New structures in the car

One of the important issues in using cars with combustion engines is environmental pollution. The use of combustion vehicles has caused serious damage to the environment and, as a result, to humans. There is a close relationship between environmental pollution, especially in urban areas, and how cars work. By examining the types of pollution caused by cars and the effects of each of them in damaging the environment, they have determined specific standards and limits for each of the pollutants. Hydrocarbons, nitrogen oxides, carbon monoxide and suspended particles are the most important parameters that have been considered in all the proposed standards. Carbon dioxide and sulfur dioxide are the products of combustion of fossil fuels in internal combustion engines [4]. Considering the decreasing trend of fossil fuels and the extreme fluctuations of the oil market, the evolution of the usual technologies used in the automobile industry seems necessary. Also, energy consumption is increasing every day, which can be seen in the reduction of oil reserves in warehouses of industrialized countries and the global price of oil. On the other hand, the number of cars in use is increasing day by day. Therefore, according to the discussed topics, the existing resources are not able to meet the energy needs of human society. So far, some problems of using combustion vehicles have been discussed. Therefore, in order to overcome the mentioned problems, cars with less fuel consumption and pollution should be used. This car was able to travel 40 miles with only a battery. In 1903, a gasoline-electric car was designed and built by the English company Krieger [5]. In 1905, a hybrid car was built by an American engineer named Piper [6]. In this car, the electric motor was used as an auxiliary motor because the gasoline engines of that time did not have high power. The built car was able to accelerate from zero to 40 kilometers per hour in 10 seconds. After that, in 1964, the Canadian Galt Motor Company introduced a new low-consumption hybrid car to the market. This car had a small two-stroke combustion engine that produced 10 horsepower with two pistons. The output axis of the combustion engine in this car was connected to a generator that had two outputs.