Hybrid Wind-PV System Simulation
Hybrid energy system is the combination of
two energy sources for giving power to the load.
Now a day’s electricity is most needed facility for the human being. All the conventional energy resources are depleting day by day. So we have to shift from conventional to non-conventional energy resources. In this the combination of two energy resources is takes place i.e. wind and solar energy. This process reviles the sustainable energy resources without damaging the nature. We can give uninterrupted power by using hybrid energy system. Basically this system involves the integration of two energy system that will give continuous power. Solar panels are used for converting solar energy and wind turbines are used for converting wind energy into electricity. This electrical power can utilize for various purpose. Generation of electricity will be takes place at affordable cost. This paper deals with the generation of electricity by using two sources combine which leads to generate electricity with affordable cost without damaging the nature balance. This whole system works at 50 Hz frequency.
Electricity is most needed for our day-to-day life. There are two ways of electricity generation either by conventional energy resources or by non-conventional energy resources. Electrical energy demand increases in word so to fulfill demand we have to generate electrical energy. Now a day’s electrical energy is generated by the conventional energy resources like coal, diesel, and nuclear etc. The main drawback of these sources is that it produces waste like ash in coal power plant, nuclear waste in nuclear power plant and taking care of this wastage is very costly and is also harmful for the environment. The nuclear waste is very harmful to human being also. The conventional energy resources are depleting day- by- day. Soon it will be completely vanishes from the earth so we have to find another way to generate electricity. The new source should be reliable, pollution free and economical. The non- conventional energy resources should be good alternative energy resources for the conventional energy resources. There are many non-conventional energy resources like geothermal, tidal, wind, solar etc. the tidal energy has drawbacks like it can only implemented on sea shores. While geothermal energy needs very lager step to extract heat from earth. Solar and wind are easily available in all condition. The non-conventional energy resources like solar, wind can be good alternative source. Solar energy has drawback that it could not produce electrical energy in rainy and cloudy season so we need to overcome this drawback we can use two energy resources so that any one of source fails other source will keep generating the electricity and in good weather condition we can use both sources combine. This whole system works at 50 Hz frequency.
HYBRID ENERGY SYSTEM
Hybrid energy system is the combination of two energy sources for giving power to the load. In other word it can defined as “Energy system which is fabricated or designed to extract power by using two energy sources is called as the hybrid energy system.” Hybrid energy system has good reliability, efficiency, less emission, and lower cost. In this proposed system solar and wind power is used for generating power. Solar and wind has good advantages than other than any other non- conventional energy sources. Both the energy sources have greater availability in all areas. It needs lower cost. There is no need to find special location to install this system.
Solar energy is that energy which is gets by the radiation of the sun. Solar energy is present on the earth continuously and in abundant manner. Solar energy is freely available. It doesn’t produce any gases that mean it is pollution free. It is affordable in cost. It has low maintenance cost. Only problem with solar system it cannot produce energy in bad weather condition. But it has greater efficiency than other energy sources. It only need initial investment. It has long life span and has lower emission.
Wind energy is the energy which is extracted from wind. For extraction we use wind mill. It is renewable energy sources. The wind energy needs less cost for generation of electricity. Maintenance cost is also less for wind energy system. Wind energy is present almost 24 hours of the day. It has less emission. Initial cost of the system is also less. Generation of electricity from wind is depend upon the speed of wind flowing. The major disadvantages of using independent renewable energy resources are that unavailability of power for all time. For overcoming this we use solar and wind energy together. So that any one source of power fails, other will take care of the generation. This proposed system consist of both energy sources. Another way is that we can use any one source and keep another source as a stand by unit. This will leads to continuity of generation. This will make system reliable. The main disadvantages of this system are that it needs high initial cost. Except that it is reliable, it has less emission. Maintenance cost is less. Life span of this system is more. Efficiency is more.
The micro grid is divided into three important parts: A Three phase synchronous generator, acting as the base power generator. A Pv farm with mppt combined with a wind farm (DFIG) 1500 w. Wind farm some specification- Generator data for wind turbine (nom.power =1500/0.9, L-L Vrms=400, fz=50 Hz, resistance=0.006) Turbine data (nominal output power=2*10^6, wind speed at nominal speed and at Cpmax=11m/s, initial wind speed=11m/s). Dump resistor protection is used to detect fault.
THREE PHASE SYNCHRONOUS GENERATOR
which is connected to the grid Power from this generator is used when there is insufficient generation of power from the combined system of renewable energy sources such as power from PV farm with mppt and wind farm (DFIG).
RENEWABLE ENERGY SOURCES
There is combined system of PV farm (with mppt) and wind farm (DFIG) which is connected to the grid with the help of some main components such as VSC controller and PWM generator.
WIND ENERGY CONVERSION SYSTEM
To date, there have been a variety of WECS’ designs; however by far the most popular and widely used is the horizontal axis wind turbine (HAWT). As made clear in the Introduction, the design of interest is the low-cost, low-power HAWT design common in rural and urban applications. Such systems are becoming increasingly popular and consist of following 4 main components:-
This consists of the blades of the turbine, along with the hub; upon which the blades are mounted. The performance of a wind turbine is greatly affected by blade geometry, and in many designs, this component is also the most expensive part of the turbine unit.
connecting the rotor to the generator is the drive train. In larger wind turbine systems, the drive train includes gearing to increase the speed of rotation from the rotor into the generator. Small turbines do not have this feature; the drive train for these systems is simply a connecting shaft.
The generator converts the mechanical rotation of the drive train into electricity. Small turbine generators are commonly of the 3- phase, permanent magnet type; however other generator types have been used.
To protect the system, in addition to converting the output of the generator to domestic voltages, a power electronic interface converter is necessary.
There are two ways in which we can divide the complete control strategies of the machine, one is the scalar control and the other one is the vector control. The limited use of scalar control makes way for the vector control. Although it is easy in executing the scalar control strategies, but the inherent coupling effects present give very slow response. This problem is overcome by the vector control. An Induction machine can be executed like a dc machines with the help of vector control strategy. Vector control is employed for achieving a decoupled control for both active and reactive powers. The base on which the vector control theory is based is d-q axis theory.
D-q axis transformation (reference frame theory)
Direct-quadrature zero conversion is a mathematical conversion employed to make easy the analysis of a three phase circuits, where three AC quantities are converted to two DC quantities. Various mathematical calculations are performed on the imaginary DC quantities and the AC quantities are again recovered by performing an inverse transformation on the DC quantities. It is very similar to Park’s transformation, and it solves the problem of AC parameters that are varying with time. Employed to simplify the analysis of three phase circuits, where three AC quantities are converted to two DC quantities. Owing a smooth air-gap in the induction machine, the self-inductances of both the stator and rotor coil is constant, but the mutual inductances vary with the rotor movement with respect to that of the stator. Therefore the analysis of the induction machine in real time becomes very complex because of varying mutual inductances, as the voltage is nonlinear. Change of variables are therefore employed for the stator and rotor parameter to remove the effect of varying mutual inductances. This conversion leads to imaginary magnetically decoupled two phase machine. The orthogonally placed balanced windings are called d and q windings that can be considered as stationary or rotating relative to that of the stator. In the stationary reference frame, the ds and sq. axes are fixed on the stator, with either ds or qs axis coinciding the phase axis of the stator. In the rotating frame, the rotating d-q axes may be either fixed on the rotor or made to move with synchronous speed.
Modeling of DFIG in synchronously rotating frame
The equivalent circuit diagram of an induction machine is shown in picture below. In this picture the machine is represented to have two phase, it has been discussed before that a three phase machine can be represented by following some basic rules as a two phase machine. For the modeling of DFIG’S in the synchronously rotating frame of reference we have to represent the two phase of stator (ds-qs) and that of rotor (dr qr) circuit variable in a synchronously rotating (d-q) frame of reference.
Here hybrid system of wind farm (DFIG) and PV farm with mppt are synchronized with grid system. Mppt is used to maximize the power output of the PV farm. Protection system which is consist of dump resistor which is connected with the DFIG system of wind turbine. This protection system works when fault occurs between (0.1 to 0.3 sec).Dump resistors is used to disconnect synchronous generator from faulty line and the current of the synchronous generator goes to earth.
This paper presented the modeling, simulation and Control of a grid connected PV and Wind Hybrid Power System. The system is simulated in Matlab/Simulink environment. It is observed that the extraction of the maximum power from PV array is obtained using MPPT system. The P and O MPPT algorithm has been implemented. In Wind Energy Conversion system DFIG based wind turbine used. The PV output and the wind output after converting to dc by the help of PWM,VSC controller and Universal bridge is given to the inverter and then the combination of PV and Wind is given to the grid.