Download modeling/simulation of combined pem fuel cell

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
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OUTLINE
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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.
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OVERVIEW OF A DISTRIBUTED GENERATION
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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.
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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
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MICRO TURBINE AS A DG
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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.
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MICRO TURBINE
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MODELING OF MICRO TURBINE
Pm
Mechanical
Equations
Vf
Mechanical Equations:
Electrical Equations:

Electrical
Equations
Pe
H d
 D  Pe  Pm
f o dt
d
   0
dt
E ' Vq  rI q  X d ' I d
0 Vd  rI d  X q I q
Tdo'
dE '
 E '  ( X d  X d ' ) I d  E fd
dt
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TWO AXIS MODEL OF A MICRO TURBINE
Phasor diagram of Micro turbine
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MICRO TURBINE CONTROLS
GOVERNOR

GENERATOR
Pref
Vt
TURBINE
EXCITER
Vref
AVR
Overall block diagram of Micro turbine control
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FREQUENCY CONTROL OF MICRO TURBINE
Pmo
Pm
Pm ,ref +
GOVERNOR
+
+
Pm
TURBINE
-
1
R

Frequency control block
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VOLTAGE CONTROL OF MICRO TURBINE
Vrefo
VF
Ve
V ref +
+
AMPLIFIER
EXCITER
-
+
Vtref
V
t
Voltage control block
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FUEL CELL AS A DG
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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.
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BASIC PRINCIPLE OF A FUEL CELL
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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.
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PEM FUEL CELL
Anode side reaction:
H2 2H+ + 2eCathode side reaction: 0.5O2+2H++2e-H20 +Heat
-----------------------------------Overall reaction:
H2 + 0.5O2  H20 +Heat
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OVERALL CHEMICAL REACTION OF PEMFC
Component balance Equation
dxi
PV
TS
 Wi in  Wi Out  Ri
RT
dt
Energy balance Equation
M s Cs
Nernst Equation
dTs
dCs
 M sTs
 Qgenerated  Qlosses
dt
dt
RTS xH2 2 xO 2
VFC  N cell [ E 
ln 2
]  Elosses
4F
xH 2O
o
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POWER CONDITIONING UNIT
AC Voltage of the fuel cell: Vac = m . VFC
where m is the modulation index,  is the firing angle
FUEL
CELL
INVERTER
PCU
GRID
GRID
BATTERY
BATTERY
INTERFACE
INTERFACE
BATTERY
Block diagram of fuel cell with PCU
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FUEL CELL CONTROLS
o
Pfc , ref+
PI
CONTROLLER

+
+

-
Pfc , actual
Power Control scheme
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FUEL CELL CONTROLS
mo
V fc,ref
+
PI
CONTROLLER
m
+
+
m
-
Vfc,actual
Voltage Control Scheme
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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
Vq   cos  sin  
  


sin

cos

V

 d 
Vre 
V 
 im 
The current injected into the system
I = Y. V
Which could be further written as
Ire+ jIim = (G + jB). Vre + jVim
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NUMERICAL ANALYSIS
jXLN
MICRO
TURBINE
jXgt
POWER
SYSTEM
jXfc
FUEL
CELL
SLD=PLD+jQLD
ZLD
Test System
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CASE STUDY
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Case 1: Assuming 10% increase in input power of the micro turbine
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Case 2: Assuming 20% increase in input power of the fuel cell
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Case 3: Assuming a 10% increase in micro turbine power (with and without
governor)
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Case 4: Assuming a 1% increase in micro turbine voltage reference ( with
and without voltage regulator)
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SIMULATION RESULTS – CASE 1
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SIMULATION RESULTS – CASE 2
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SIMULATION RESULTS – CASE 3
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SIMULATION RESULTS – CASE 4
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CONCLUSION
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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.
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FUTURE WORK
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The same procedure may be extended to the case of several DG’s
connected to a power system.
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THANK YOU
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