BY TNAVEEN SNEELIMA PS SUBRMANYAM Asstprofessor Assosprofessor Professor DEPARTMENT OF EEE VBIT LAY OUT KEY WORDS OBJECTIVES GRID CO ORDINATION ID: 815379
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Slide1
A NOVEL CONTROL STRATEGY FOR HYBRID AC/DC MICRO GRID SYSTEMS
BY
T.NAVEEN
S.NEELIMA
P.S SUBRMANYAM
Asst.professor
Assos.professor
Professor
,
DEPARTMENT
OF
E.E.E,
V.B.I.T
Slide2LAY OUTKEY WORDSOBJECTIVESGRID CO ORDINATIONEXISTING SYSTEM
PROPOSED SYSTEM
HYBRID AC/DC POWER SYTEMS
SIMULATION RESULTS
CONCLUSION
REFERENCES
SCOPE FOR FUTURE WORK
Slide3KEY WORDSHybrid AC/DC power systems: The combination of AC/DC networks connected to a gridMicro grid : Collects power from various small energy sources and connects it to grid.
AC micro grids
: facilitate connection of renewable power sources to conventional ac systems
dc power from photovoltaic (PV) panels or fuel cells - converted into ac using dc/dc boosters and dc/ac inverters to connect to ac grid.
AC/DC/AC converters
: commonly used as drives to control the speed of ac motors in industrial plants.
Slide4OBJECTIVESTo reduce the processes of multiple dc–ac–dc or ac–dc–ac conversions in an individual ac or dc grid.To have stable operation in grid-tied or autonomous mode. To implement Grid coordination and control algorithms
To achieve smooth power transfer between ac and dc links for stable system operation under various generation and load conditions.
To maintain stable operation for grid switching from one operating condition to another.
Slide5GRID CO ORDINATIONThe coordination -control schemes among various converters to harness maximum power from renewable power sources .Minimization of power transfer between ac and dc networks.Stable operation of both ac and dc grids under variable supply and demand conditions in both grid and islanding modes
.
Avoids multiple reverse conversions in individual ac or dc grids which cause additional power loss .
Slide6EXISTING SYSTEMIndividual AC/DC grids.Requires multiple reverse conversions.For long distance transmission HVDC is required.
Poor quality of electricity.
Less reliable.
Difficult to interface for DC loads.
Less operational efficiency.
Interfacing of different sources is difficult
Slide7PRPOSED SYSTEMA hybrid system with minimal reverse conversions. Co ordination-control schemes for optimal operation under all conditions.Improved operational efficiency.Integration of various AC/DC sources with energy storage systems.
DC micro grids to integrate various distributed generators.
Slide8A HYBRID AC/DC MICROGRID:
Slide9GRID OPERATIONThe hybrid grid can operate in two modes. GRID-TIED MODE :The main converter provides stable dc bus voltage
Required power is exchanged between the ac and dc buses.
The boost converter and WTG are controlled to provide the maximum power.
Converter acts as an inverter or converter based on total power generation
Isolated Mode
Power is not balanced by the utility grid.
MPPT on or MPPT off based on system power constraints.
Slide10CONSIDERED HYBRID GRIDForty kW PV arrays connected to dc bus through a dc/dc boost converter. A capacitor Cpv to suppress high frequency ripples of the PV output voltage.
A 50 kW wind turbine generator (WTG) with doubly fed induction generator (DFIG) is connected to an ac bus.
The rated voltages for dc and ac buses are 400 V and 400 V
rms
respectively.
A three phase bidirectional dc/ac main converter with R-L-C filter connects the dc bus to the ac bus through an isolation transformer.
Slide11Modeling of PV PanelFig. 3. Equivalent circuit of a solar cell.
The current output of the PV panel is modeled by the following three equations
Slide12MODELING OF WIND TURBINE GENERATORPower output Pm from a WTG is determined from following equation
Where ρ is air density, A is rotor swept area,
V
ω
is wind speed, and is the power coefficient, which is the function of tip speed ratio and pitch angle .
The voltage equations of an induction motor in a rotating
d-q
coordinate are as follows
Slide13COMPACT REPRESENTATION OF HYBRID GRID
Slide14A. Grid-Connected Mode Boost converter tracks the MPPT of the PV array by regulating its terminal voltage.The dc/dc converter of the battery can be controlled as the energy buffer in this techniqueThe main converter operates bidirectional
Variable characteristic of wind and solar sources are compensated .
Buck or boost operations are performed accordingly.
Slide15CONTROL STRATEGIES FOR GRID-CONNECTED MODEThe control block diagram for boost converter and main converter
Slide16B. Isolated ModeThe converter may operate in the MPPT on or MPPT off based on power balance The dc-link voltage is maintained by either the battery or the boost converter based on system operating conditionState of charging battery is observed
Net power is calculated and compared with reference
Powers under various conditions balanced as follows:
Slide17CONTROL STRATEGIES FOR ISOLATED MODE
Slide18Operation of main converter in grid connected mode
Grid-Connected Mode simulation circuit and results
Slide19Terminal voltage of the solar panel
Slide20PV output power VS solar irradiation
Slide21Ac side voltage and current of the main converter with variable
solar irradiation level and constant DC load
Slide22Ac side voltage and current of the main converter with constant solar irradiation level and variable DC load
.
Slide23DC bus voltage transient response
Slide24Dynamic response of main converter in isolated connected mode
Isolated Mode simulation circuit and results
Slide25ISOLATED MODE:
B
attery charging current (upper) for the normal case
Slide26B
attery SOC for the normal case
Slide27O
utput power of the DFIG
Slide28AC side voltage VS current
Slide29DC bus voltage transient response in isolated mode
.
Slide30DC bus voltage when MPPT is mode.
Slide31PV output when MPPT is
on
Slide32Battery current when MPPT
is
on
mode
Slide33SCOPE FOR FUTURE WORKThe future objective of constructing a smart gird is to provide reliable high quality electric power in eco friendly and sustainable way. With the advancement in power electronics technology plays a most important role to interface different sources and loads to a smart grid.Robust control can be applied to meet the uncertainties in controller design due to uncertain parameters or disturbances in the renewable energy sources The hybrid grids can be implemented for some small customers want to install their own PV systems on the roofs
Feasible for some small isolated industrial plants with both PV system and wind turbine generator as the major power supply.
Slide34REFERENCES[1] R. H. Lasseter, “Micro Grids,” in Proc. IEEE Power Eng. Soc. Winter Meet., Jan. 2002, vol. 1, pp. 305–308.[2] Y. Zoka, H. Sasaki, N. Yorino, K. Kawahara, and C. C. Liu, “An interaction problem of distributed generators installed in a Micro Grid,” in Proc. IEEE Elect. Utility Deregulation, Restructuring. Power Technol., Apr. 2004, vol. 2, pp. 795–799.[3] R. H. Lasseter and P. Paigi, “Micro grid: A conceptual solution,” in Proc. IEEE 35th PESC, Jun. 2004, vol. 6, pp. 4285–4290.
[4] C. K. Sao and P. W. Lehn, “Control and power management of converter fed Micro Grids,” IEEE Trans. Power Syst., vol. 23, no. 3, pp. 1088–1098, Aug. 2008.
[5] T.
Logenthiran
, D.
Srinivasan
, and
D.Wong, “Multi-agent coordination for DER in Micro Grid,” in Proc. IEEE Int. Conf. Sustainable Energy Technol., Nov. 2008, pp. 77–82.[6] M. E. Baran and N. R.
Mahajan
, “DC distribution for industrial systems: Opportunities and challenges,” IEEE Trans. Ind. Appl., vol. 39, no. 6, pp. 1596–1601, Nov. 2003.
Slide35THAN Q…