Tennesse Technological University MODELING/SIMULATION OF COMBINED PEM FUEL CELL AND MICROTURBINE DISTRIBUTED GENERATION PLANT Rekha .T. Jagaduri Department of Electrical and Computer Engineering Tennessee Technological University Tennesse Technological University

Tennesse Technological University OUTLINE Overview of Distributed Generation Plant. Micro turbine as a DG. PEM Fuel Cell as a DG. Modeling of micro turbine. Modeling of fuel cell. Control Systems of micro turbine and fuel cell. Grid connected micro turbine and fuel cell. Simulation results. Conclusion. Future work. Tennesse Technological University

OVERVIEW OF A DISTRIBUTED GENERATION Distributed Generation (DG) is the use of small-scale power generation technologies located close to the load being served. It includes, for example, photovoltaic systems, fuel cells, natural gas engines, industrial turbines, micro turbines, energy-storage devices, wind turbines, and concentrating solar power collectors. These technologies can meet a variety of consumer energy needs including continuous power, backup power, remote power, and peak shaving. They can be installed directly on the consumer’s premise or located nearby in district energy systems, power parks, and mini-grids. Tennesse Technological University

ECONOMIC ADVANTAGES OF DG Economic advantages include one or more of the following: Load management Reliability Power quality Fuel flexibility Cogeneration Deferred or reduced T&D investment or charge Increased distribution grid reliability/stability Tennesse Technological University

Tennesse Technological University MICRO TURBINE AS A DG Micro turbine made its commercial debut in 1998. Micro turbines belongs to an emerging class of small-scale distributed power generation Basic components: compressor, combustor, turbine, and generator. Typically in the 30-400 kW size. Tennesse Technological University

Tennesse Technological University MICRO TURBINE Tennesse Technological University

MODELING OF MICRO TURBINE Mechanical Equations: Electrical Equations: Tennesse Technological University

TWO AXIS MODEL OF A MICRO TURBINE Phasor diagram of Micro turbine Tennesse Technological University

MICRO TURBINE CONTROLS Overall block diagram of Micro turbine control Tennesse Technological University

FREQUENCY CONTROL OF MICRO TURBINE Frequency control block Tennesse Technological University

VOLTAGE CONTROL OF MICRO TURBINE Voltage control block Tennesse Technological University

Tennesse Technological University FUEL CELL AS A DG First fuel cell was developed in 1839 by Sir William Grove. Practical use started in 1960’s when NASA installed this technology to generate electricity on Gemini and Apollo spacecraft. Types of fuel cells: phosphoric acid, proton exchange membrane, molten carbonate, solid oxide, alkaline, and direct methanol. Typically 5-1000+ kW in size, A number of companies are close to commercializing proton exchange membrane fuel cells, with marketplace introductions expected soon. Tennesse Technological University

BASIC PRINCIPLE OF A FUEL CELL A fuel cell consists of two electrodes separated by an electrolyte. Hydrogen fuel is fed into the anode of the fuel cell. Oxygen (or air) enters the fuel cell through the cathode. With the aid of a catalyst, the hydrogen atom splits into a proton (H+) and an electron. The proton passes through the electrolyte to the cathode and the electrons travel in an external circuit. As the electrons flow through an external circuit connected as a load they create a DC current. At the cathode, protons combine with hydrogen and oxygen, producing water and heat. Fuel cells have very low levels of NOx and CO emissions because the power conversion is an electrochemical process. Tennesse Technological University

Tennesse Technological University PEM FUEL CELL Anode side reaction: H2 2H+ + 2e- Cathode side reaction: 0.5O2+2H++2e-H20 +Heat ------------------------------------ Overall reaction: H2 + 0.5O2  H20 +Heat Tennesse Technological University

OVERALL CHEMICAL REACTION OF PEMFC Component balance Equation Energy balance Equation Nernst Equation Tennesse Technological University

POWER CONDITIONING UNIT AC Voltage of the fuel cell: Vac = m . VFC where m is the modulation index,  is the firing angle Block diagram of fuel cell with PCU Tennesse Technological University

Tennesse Technological University FUEL CELL CONTROLS Power Control scheme Tennesse Technological University

FUEL CELL CONTROLS Voltage Control Scheme Tennesse Technological University

INTERFACING DG WITH POWER GRID The machine side characteristics of micro turbine are transformed to the system side frame of reference using the transformation matrix The current injected into the system I = Y. V Which could be further written as Ire+ jIim = (G + jB). Vre + jVim Tennesse Technological University

Tennesse Technological University NUMERICAL ANALYSIS Test System Tennesse Technological University

Tennesse Technological University CASE STUDY Case 1: Assuming 10% increase in input power of the micro turbine Case 2: Assuming 20% increase in input power of the fuel cell Case 3: Assuming a 10% increase in micro turbine power (with and without governor) Case 4: Assuming a 1% increase in micro turbine voltage reference ( with and without voltage regulator) Tennesse Technological University

SIMULATION RESULTS – CASE 1 Tennesse Technological University

SIMULATION RESULTS – CASE 2 Tennesse Technological University

SIMULATION RESULTS – CASE 3 Tennesse Technological University

SIMULATION RESULTS – CASE 4 Tennesse Technological University

Tennesse Technological University CONCLUSION A combined micro turbine and PEM fuel cell plant connected to a power system was modeled and simulated. Both the fuel cell and micro-turbine were assumed to be equipped with power and voltage control loops. The micro-turbine was modeled using the d-q frame of reference and it was interfaced with the power system using transformation between this frame of reference and the system frame of reference. A test system with typical numerical values was used to determine the accuracy of the model. Tennesse Technological University

Tennesse Technological University FUTURE WORK The same procedure may be extended to the case of several DG’s connected to a power system. Tennesse Technological University

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