**1. Introduction**

By 2050 the demand for energy could double or even triple as the global population grows and developing countries expand their economies. Energy prices, supply uncertainties, and environmental concerns are driving many countries to rethink their energy mix. The Inter‐ national Energy Agency's Energy Technology Perspectives2008publication projects that en‐ ergy sector emissions of greenhouse gases (GHGs) will increase by 130% over 2005 levels, by 2050, in the absence of new policies (IEA, 2008).

Renewable energy is part of the solution for the energy problem, and wind energy is one of the cost-effective options for the generation of electricity. The main applications are the gen‐ eration of electricity and water pumping.

By the end of 2007, in the world, there were around 100,000 wind turbines installed in wind farms, with an installed capacity of 94,000 megawatts, which generated around 300 TWh/ year. Wind energy is now part of national policies for generation of electricity in many coun‐ tries (Vaughn Nelson, 2009).

In 2007, in Europe there were 57,000 MW installed wind power, which generated 3.7% of the electrical demand. The European goal is 20% of electricity generated by renewables by 2020, of which 12–14% would be from wind. In 2010, wind energy provided for nearly 26% of electricity consumption in Denmark, more than 15% in Portugal and Spain, 14% in Ireland and nearly 9% in Germany, over 4% of all European Union (EU) electricity, and nearly 2.9% in the United States (US Department of Energy, 2011). In the future, many countries around the world are likely to experience similar penetration levels as wind power is increasingly considered not only a means to reduce CO2 emissions but also an interesting economic alter‐

native in areas with appropriate wind speeds. Since 2000, cumulative installed capacity has grown at an average rate of around 30% per year. In 2008, more than 27 GW of capacity were installed in more than 50 countries, bringing global capacity onshore and offshore to 121 GW. Wind energy in 2008 was estimated by the Global Wind Energy Council to have generated some 260 million megawatt hours of electricity. Applications for generation of electricity are divided into the following categories: utility-scale wind farms and small wind turbines (less than 100 kW).

Numerical modelling is an important part of the design, assessment, implementation and

Wind Diesel Hybrid Power System with Hydrogen Storage

http://dx.doi.org/10.5772/52341

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This chapter is devoted to a large scale wind-diesel Hybrid Power System (HPS) applica‐ tions. It presents theoretical analysis, modelling and control of Wind Energy Conversion Systems (WECS) connected to an autonomous power system with hydrogen storage. The wind generator under study is a Doubly Fed Induction Generator (DFIG) type. The models of the main components (mainly wind turbine, generator, diesel genset, electrolyzer) will be derived. The wind turbine's maximum power point tracking technique will be presented and a power transfer strategy in the interconnected system will be analysed. Performance of the control method is validated to maintain the hybrid power system's frequency. The effec‐ tiveness of the proposed hybrid system is validated by simulation using Matlab/ Simulink/ SimPowerSystems environment. The Hybrid Power System (HPS) is composed of a 600 kW diesel genset, three 190 kW wind turbines, three 80 kW alkaline electrolyzers and a 610 kW

The structures of Hybrid Power System (HPS) can be classified into two categories: AC cou‐

In an AC-coupled HPS, all sources are connected to a main AC-bus before being connected to the grid. In AC-coupled structure, different sources can be located anywhere in the micro‐ grid with a long distance from each other. However, the voltage and the frequency of the main AC bus should be well controlled in order to ensure the stability of the system and the

In a DC-coupled HPS, all sources are connected to a main DC-bus before being connected to the grid through a main inverter. In a DC-coupled structure, the voltage and the frequency

However, not all HPSs can be classified into AC or DC-coupled system, since it is possible to have both coupling methods, then a Mixed HPS is obtained. In this case, some advantages

Wind turbines come in different sizes and types, depending on power generating capaci‐ ty and the rotor design deployed. Small wind turbines with output capacities below 10 kW are used primarily for residences, telecommunications dishes, and irrigation water pumping applications. Utility-scale wind turbines have high power ratings ranging from 100 kW to 5 MW. Current wind farms with large capacity wind turbine installations are

The wind-diesel HPS configuration studied in this work is represented in Fig. 1.

evaluation of autonomous power systems with wind power.

**2. Wind-diesel power system with hydrogen storage**

maximum load.

pled and DC-coupled (T. Zhou, 2009).

compatibility with the utility network.

can be taken from both structures.

**2.1. Wind turbine**

of the grid are independent from those of each source.

Currently, for remote communities and rural industry the standard is diesel generators. Re‐ mote electric power is estimated at over 11 GW, with 150,000 diesel gensets, ranging in size from 5 to 1,000 kW. In Canada, there are more than 800 diesel gensets, with a combined in‐ stalled rating of over 500 MW in more than 300 remote communities (Vaughn Nelson, 2009). Diesel generators are inexpensive to install; however, they are expensive to operate and maintain, and major maintenance is needed from every 2,000 to 20,000 hours, depending on the size of the diesel genset.

Wind–diesel is considered because of the high costs for generating power in isolated sys‐ tems. In near future, the market of wind–diesel systems will grow up because of the high cost of diesel fuel. Wind–diesel power systems can vary from simple designs in which wind turbines are connected directly to the diesel grid, with a minimum of additional features, to more complex systems.

There are a number of problems in integrating a wind turbine to an existing diesel genset: voltage and frequency control, frequent stop–starts of the diesel, utilization of surplus ener‐ gy, and the use and operation of a new technology. These problems vary by the amount of penetration. Wind turbines at low penetration can be added to existing diesel power with‐ out many problems, as it is primarily a fuel saver. However, for high wind penetration, stor‐ age is needed. Moreover, one of the major drawbacks of wind energy is its unpredictability and intermittency. So, to supply better consumers' energy needs, wind systems have to op‐ erate with storage devices. Several energy storage methods have been in development over the past several years. This includes compressed air, pumped hydro, flow battery flywheel, hydrogen storage, etc. It has been proved (E.I. Zoulias, N. Lymberopoulos, 2008; Nelson et al., 2006) that hydrogen can be effectively used as storage medium for intermittent renewa‐ ble energy sources (RES)-based autonomous power systems. More specifically, excess of RES energy produced from such systems at periods of low demand can be stored in the form of hydrogen, which will be used upon demand during periods when the wind energy is not available.

For many years, Hydrogen Research Institute (HRI) has developed a renewable photovolta‐ ic/wind energy system based on hydrogen storage(M. L. Doumbiaet al., 2009; K. Agbossou et al., 2004). The system consists of a 10 kW wind turbine generator (WTG) and a 1 kW solar photovoltaic (PV) array as primary energy sources, a battery bank, an 5 kW electrolyzer, a 5 kW fuel cell stack, different power electronics interfaces for control and voltage adaptation purposes, a measurement and monitoring system. This renewable energy system is scaled for residential applications size and can be operated in stand-alone or grid-connected mode and different control strategies can be developed.

Numerical modelling is an important part of the design, assessment, implementation and evaluation of autonomous power systems with wind power.

This chapter is devoted to a large scale wind-diesel Hybrid Power System (HPS) applica‐ tions. It presents theoretical analysis, modelling and control of Wind Energy Conversion Systems (WECS) connected to an autonomous power system with hydrogen storage. The wind generator under study is a Doubly Fed Induction Generator (DFIG) type. The models of the main components (mainly wind turbine, generator, diesel genset, electrolyzer) will be derived. The wind turbine's maximum power point tracking technique will be presented and a power transfer strategy in the interconnected system will be analysed. Performance of the control method is validated to maintain the hybrid power system's frequency. The effec‐ tiveness of the proposed hybrid system is validated by simulation using Matlab/ Simulink/ SimPowerSystems environment. The Hybrid Power System (HPS) is composed of a 600 kW diesel genset, three 190 kW wind turbines, three 80 kW alkaline electrolyzers and a 610 kW maximum load.
