Simulation Research on Integrated Hybrid PV- Wind Driven Generator Supplying AC/DC Micro-grid

AbstractElectricity demand in the current days is more compared to the power generated, the scarcity of power requirement is more for the day to day needs. In this paper, the modeling and simulation of a Permanent Magnet Synchronous Generator (PMSG) based wind power generation system under power system dynamic conditions are presented and also shows a simple method for converting wind energy and solar power hybrid system for AC/DC Micro-Grid application is introduced. Wind driven generator is coupled to tail vane by that energy is generated in all the directions which increases the total power and improves the efficiency of the system. A 3 bridge rectifier is used to supply AC micro-grid and BuckBoost DC-DC converter is used to supply the DC micro-grid. This algorithm is implemented using simple microcontroller to generate gate pulses to the converters and track the power generation and consumption. A simple control algorithm is used to supply power for the DC/AC micro-grid from the small/large scale power. The simulation is supported by using MATLAB/SIMULINK tool under different grid and load conditions and the corresponding simulated results are encouraged. The working model of the proposed methodology has been implemented with hardware and results are shown.

based wind power generation model Three-blade Horizontal Axis Wind Turbine (HAWT) with PMSG is used as the wind power generation unit. The turbine blade starts to rotate when the wind passes over the blade. The wind turbine produces the mechanical power by taking the input as wind speed. The shaft of the PMSG is connected with the Wind Turbine (WT) through the gearbox. The generated mechanical power is given as input to the PMSG, and it produces the electrical power with the help of permanent magnets. The generator terminal voltage is stepped-up to the suitable grid level using the step-up transformer, and it is connected to the power grid.

II. PROPSED WORKING DIAGRAM OF THE SYSTEM
The induction generator is operated in self-rotor excited system, the system can be operated over a wide range of speed for extracting Maximum Power available in the wind by rotating 360° as per the wind blows. Solar power is connected to the DC micro grid and battery is used to work in bidirectional to charge /discharge the power. The DC micro-grid supplies the power to the AC/DC loads depending on the requirement of the load with suitable converters to maintain constant voltage and frequency as shown in figure 1. Performance of the DC micro-grid system is presented to some researcher with different set of voltage and suitable electrical subsystem interface with grid, the voltage drop, based on efficiency, cost, thermal limits and protection issues. Considering various parameter, they came to conclusion the system which as low voltage (24V) will give maximum performance for the application which has low power. The power levels which are more than 3KW the level of dc voltage is 120V and it gives maximum operating efficiency as per the proposed windmill system and photovoltaic arrays generates 24V at DC grid and 230V at AC grid. By using suitable inverters, it changes the level of voltage along with energy storing system, like battery set. The whole control system has been implemented by using microcontroller.

III.
Model-Based development of the system A.
Photovoltaic Cell The silicon photocell is fabricated by forming a junction between two different materials in a single crystal of silicon, the silicon material by itself a poor conductor of electricity. By adding of a trace of another element, like arsenic or phosphorous, this contributes one electron to the silicon and makes it conducting. In this material, designated as n-type silicon, conduction is obtained by positive and the negative free electrons. The p-type silicon is formed by the addition of an element such as boron, or gallium that contains one less electron than silicon. The absence of electrons in p-type material creates positive charges or holes that also cause the silicon to become conductive. The boundary between the two regions, n-type and p-type in the single silicon crystal, establishes p-n junction.

B.
Mathematical modeling of PV array. The output current of the PV array is modeled by the following mathematical equations. Where, = reference temperature = 298.15 K are the photovoltaic, thermal voltage, photo generated current and saturation currents of the array

C. Wind Energy
Wind energy is one of the auspicious alternatives sources of energy. In the present crisis, the wind energy though not successful in large scale, will play a vital role in the rural areas, wind power can be successfully used for irrigation, lighting and running small scale industries. Winds on earth's surface are caused principally by unequal warming of the land and water by sun the variation in the thermal limits induce the course of air from one region to another region. Nearly 10 million MWs of wind energy are available in countries like USA, Netherlands and Denmark, strong and steady blow is there, and it can be successfully utilized through various mechanical conversions for power generation. Wind energy can supply economically a part of the power requirement. Where is the rotor rotational speed in rad/sec, and R is the radius of the rotor blade in m. Fig. 2 shows the vs λ curve. The power coefficient can be calculated with the help of tip speed ratio. The output power of the WT can be varied with the help of wind speed as shown in Fig. 3. The WT output power is zero when the wind speed is lower than the cut-in speed ( ). The turbine starts to operate once the wind speed goes more than the . The power output of the WT is a cubic relationship with the wind speed (it can be varied using the ) until the rated wind speed ( ) is reached. Then, the power output remains constant up to the cut-out wind speed ( ). The WT will go to shut down once the wind speed exceeds the cut-out wind speed. The WT designer sets the cut-in, rated and cut-out wind speed limits. The dynamic model of the WT is given by, where J is the inertia coefficient, B is the friction coefficient, is the turbine mechanical torque, and is the electromagnetic torque. and are the inductance of the d and q axis. and are the d and q axis stator currents. Substitute (15) and (16) in (13) and (14), we get, The electromagnetic torque is given by, Where, P= number of poles. The equivalent circuit of the PMSG which consists of the q and d axis circuit is shown in Fig. 4 (a) q-axis (b) d-axis can be calculated by using the equation (8) Power coefficient ( ) is calculated by using equation (9), = 0.37 Total power in the wind stream: Table I. Grid simulation parameters

Parameter Value
Simulated using MATLAB/SIMULINK tool under different grid & non-linear load conditions and the parameters used for simulation is tabulated in Table. I.

i. Power generation from PV & wind ( is greater than the load demand.
In this case, the hybrid PV/wind energy sources are interconnected with three phase bridge rectifiers in order to supply the power to the balanced linear & non-linear loads, the load current and load voltage is shown in Fig.  5(a) & 5(b). The output voltage of both PV and wind is boosted through DC-DC booster to the 800V at DC grid which is maintained constant by Interfacing Voltage Source Inverter (IVSI) control in order to control the real power is shown in Fig. 5(d). The total amount of power generated from both PV at 200W/m 2 & wind at 10m/s meets the total load demand and further the surplus power is injected to the grid as shown in Fig. 5(e) and the corresponding grid power factor is shown in Fig. 5(c).

ii. B. Power generation from PV & wind ( ) is less than the load demand
In this case, the hybrid PV/wind energy sources are interconnected with three phase bridge rectifiers in order to supply the power to the unbalanced linear & non-linear loads, the load current and load voltage is shown in Fig.  5(a) & 5(b). The output voltage of both PV and wind is boosted through DC-DC booster to the 800V at DC grid which is maintained constant by IVSI control in order to control the real power is shown in Fig. 5(c). The total amount of power generated from both PV at 800W/m 2 & wind at 5m/s is less than the total load demand and hence the remaining power received from the grid to fulfil the total load demand as shown in Fig. 5(e) and the corresponding grid power factor is shown in Fig. 5(d).    The above Figure 6 and 7 shows the Blade construction and tail construction of the wind turbine. The turbine blade is built with suitable composite materials such as carbon fiber and polyepoxide. Epoxy mixtures offer great performance and confirmed reliability in many challenging applications including components for aerospace and wind turbine blades and it has good mechanical properties like corrosion resistance, withstands high temperature and high stiffness and reduced weight on finished parts as shown in Figure 6 and 7.    The above Figure 10, 11 and 12 shows the Simulink model of bridge inverter for the AC operated loads. The input is given from DC micro-grid and output is given to the transformer. Inverter is controlled by Current Source Inverter and it is for the different AC load applications The charge controller is used to maintain the constant DC output voltage to the inverter and the control of inverter is done by using microcontroller PWM signals the voltage is maintained constant, using transformers to stepped up or down depending on application and solar system which establish the AC/DC off-gird or AC/DC micro-grid.

B. Simulation results of DC-DC converter and bridge inverter.
V. CONCLUSION In current situation, many nations support the consumers and private organization involved in energy sector, to producing electrical energy from using alternate resource like Non-Conventional Source of energy which moving forward to the establishment of AC/DC off-gird or AC/DC micro-grids. In this view, Dc micro-grid systems attract more focus on low voltage application which is provided from sustainable power sources. Especially, this voltage choice is best fit for domestic utilizations. The distribution network has been verified and validated through simulation studies for different cases. The work has been carried out for 2 cases, one with balanced undistorted grid & balanced non-linear load and the other with unbalanced distorted grid & unbalanced non-linear load. To ease operation and maintenance of DC micro-grid system operated by consumer, a simple circuit configuration and control algorithm are required. Windmill and solar photovoltaic cell produces the maximum power by rotating 360°. Hence, this is implemented by hardware module is presented a simple algorithm and circuit topology for DC/AC micro-grid applications supplied from a minor scale wind energy conversion system.