Volume 116 No. 19 2017, 79-85 ISSN: 1311-8080 (printed version); ISSN: 1314-3395 (on-line version) url: http://www.ijpam.eu ijpam.eu IMPLEMENTATION AND ANALYSIS OF HYBRID SMART ENERGY SYSTEM FOR DOMESTIC POWER SHARING S.P.Vijayaragavan Asst Prof, Dept of EEE, Bharath University, Chennai Vijayaragavan.eee@bharathuniv.ac.in Abstract: Power demand is increasing drastically in almost all developing countries due to sudden growth of population. The availability of fossil fuels is limited so that in most of the areas uninterrupted power supply is not possible. For meeting this requirement, this attempt have been made by investigating a cost effective micro hybrid inverter which can be operated as both off grid and grid tie hybrid inverter with change in load demand and available solar power. In this paper the controller for the hybrid inverter is designed with an Advanced Phase- Locked-Loop (APLL) technique in the feedback loop. The APLL can detect the phase and frequency of the grid voltage. The output of APLL is used to generate the SPWM signals to control the on and off states of MOSFET switches in the hybrid inverter. So whenever load demand exceeds the available solar IPV power, the grid will be switched on without disconnecting the solar IPV system. Index Terms: Integrated Photo Voltaic System, (IPV), APLL, SPWM, MOSFET are cheaper than the DC to controlled DC one, some demerits, such as discontinuous source current, large peak currents in power components, and improper transient response which reduces its efficiency. On the other hand, the DC to controlled DC converter has reduced transient losses and very high efficiency among other available isolated DC to DC converters. It can also provide a better output-current characteristic due to the inductor on the output stage. Thus, the DC to controlled DC configuration is a proper converter to be employed in designing the MPPT. A DC to controlled DC converter and its operating modes is shown below, which is used as the power stage interface between the Solar IPV Array and the hybrid inverter. The DC to controlled DC converter have two modes of operation. The first process is when the switch is in closed condition (ON), and it is conducting as a short circuit. In this mode, the capacitor releases energy to the output. The equations for the switch conduction mode are as follows: 1. Introduction The Integrated Solar as electrical energy source shows increasing growth in both in implementation on entire world and integrated installed capability of the plant. This technique is supported by many advantages such as the decreasing of fuel reserves cost and reduction of cost in the production value per kw electric from Integrated Solar and also technology development which results in the Integrated Solar power generating systems with more efficiency. IPV hybrid inverter will operate in maximum efficiency. Integrated Solar power converters and its control circuit have developed a lot. The conversion with high efficiency. 2. DC to Controlled DC Switching Regulator Among all the procedures available, both DC to controlled DC and other converters have properties like either higher or lower output voltage compared with the input voltage. Even the other configuration of converters Figure 1.Electrical circuit of the DC to controlled DC converter used as the IPV power-stage interface Figure 2.DC to controlled DC converter with (a) switch ON and (b) switch OFF 79
vl1 = Vg vl2 = -v1 v2 ic1= i2 ic2 = i2- v2/r The next operating mode occurs when the switch is open (OFF mode), the diode is forward bias condition and pass the energy to the output side. Capacitor C1 gets charge from the input volatge. The equations governing are given below vl1 = Vg v1 vl2 = -v2 ic1 = i1 ic2 = i2 v2/r The principles of DC to controlled DC converter operating conditions state that the required values of the voltage across the inductor and current in the capacitor waveforms are found to be zero when the converter is operated in steady state condition[11-15]. The relations between output and input currents and voltages are given in the following: with SPWM technique which is generated by the feedback loop by taking the reference from grid. The control strategy is developed by a feedback loop consists of a APLL to synchronize the hybrid inverter with grid. The hybrid inverter is operated with SPWM technique which is generated by the feedback loop by taking the reference from grid. The SRF APLL is the one with the best performance under distorted and non linear grid conditions. The control strategy is developed by a feedback loop consists of a APLL to synchronize the hybrid inverter with grid. The hybrid inverter is operated with SPWM technique which is generated by the feedback loop by taking the reference from grid[16-20]. The general rule used in this method, in which the curved slope of the IPV parabola at the MPP reaches zero. The components for the DC to controlled DC converter used in simulation were selected as follows: 1. Low value input inductor L1 =2.5mH 2. Low value capacitor C1 (IPV side) = 4.7 μf 3. Choke inductor L2 =2.5mH 4. An IGBT switch 5. A freewheeling diode 6. Capacitor C2 (filter side) = 0.1μF 7. Resistive load = 10Ω 8. switching frequency = 25000Hz The load circuit of the corresponding system contains of a DC to controlled DC converter and a gate circuit, and the control of the switching is done using the control circuit. 3. MPPT Algorithm This cannot compare the array terminal voltage with the actual MPP voltage, since the change in power is only considered to be a result of the array terminal voltage perturbation. Thus, there are some disadvantages with these methods, where they fail under rapidly changing atmospheric conditions. MPPT system produces an enhanced output signal which synchronizes in phavee and frequency with the input signal, using a negative feedback loop. The basic idea of the APLL control strategy is developed by a feedback loop consists of a APLL to synchronize the hybrid inverter with grid. The hybrid inverter is operated which is the basic idea of this algorithm. The error (e) determines the sensitivity of the system.it is suggested to choose a small and positive digit such that it can be rewritten as The value of steady state error was chosen as 0.02 depend on the trial error process. The flowchart is given below The Proposed MPPT Controller is designed to maintain the constant voltage at the hybrid inverter input terminals. The Solar IPV Array voltage is widely varies and depends on irradiation for the specified latitude. The DC to controlled DC DC/DC converter will acts as the switching regulator which can convert the widely changing voltage to the constant voltage with less switching losses and high efficiency as compared to usual buck-boost or boost regulators. The incremental conductance algorithm is implemented in Simulink environment to provide the necessary duty cycle to DC to controlled DC regulator. The IGBT Switch is triggered with pulse width modulation generator driven by the duty cycle. The Simulink implementation for the IncCond Conductance algorithm is shown in fig.4. The DC to controlled DC Regulator is combined with the developed solar IPV array model. The Controller for 80
the DC to controlled DC regulator is implemented with above mentioned algorithm to maintain the constant voltage at the hybrid inverter terminals. The Sim Power System Implementation of DC to controlled DC Regulator with the controller and Solar IPV Array model is shown in fig 5. 4. Power Controller The integrated power system is controlled by a control algorithm for the coupling of various system components. The system controller determines the availability of grid supply. Determining the best condition of operation is the key to achieve optimal operation the inputs of the controller are the parameters of control action. The inputs of the controller are the parameters such as unpredictable load power and renewable varying output solar energy[21-25]. A power control strategy is needed to control the flow of operational period continuously in the load. The fuzzy based technique/algorithm was designed based on the control procedure to get suitable desired operation to get power from the bus bar which saves huge cost. 4.1 Power Flow Control Algorithm: The Concept of Nero Fuzzy logic control have been used as an intelligent tool to integrate and create energy sources to flow in the system in such a way that it meets the load power requirement in best way under largely varying conditions. The entire system is comprised of IPV Array, Hybrid inverter and grid supply. The procedure while implementing are fixing the line grid constraints, choosing the fuzzy variables and the fuzzy rules for the fuzzy controller. Radiations and variable loads affect the performance of outputs and hence power demand are considered to be the input variables. The output variable of the controller is the duty cycle of operation i.e switching time (load sharing) period of the grid or generator at each sampling period of specified time depending on the solar IPV array voltage as decided by fuzzy control action.. 5. Design of Hybrid Inverter The hybrid inverter is the heart of IPV system and is the focus of all utility-interconnection. The IPV hybrid inverters are classified into off-grid and grid tie hybrid inverters. Line Off grid hybrid inverters are operated with battery and charge controller in a stand alone system. Grid tie hybrid inverters can feed the power generated by IPV array to grid with or without battery bank. It is not possible to connect the stand alone hybrid inverters to grid and grid hybrid inverters will not operate without taking reference signals from grid. To achieve the optimized power sharing by integrating the solar IPV system to the utility, it is very much necessary to design a new type of cost effective micro hybrid inverter suitable for low capacity residential loads. This type of hybrid inverter should handle the residential load when the load demand is less than the designed maximum solar IPV power. If the load demand is increased more than the available solar IPV power, the micro hybrid inverter will connects to the grid so that it can allow the load to take remaining power from grid without disconnecting from solar IPV system[26-30]. It is an attempt to introduce this kind of new feature to be implemented in the existing hybrid inverters such that two energy sources can co ordinate each other and share the load. With this it is possible to harvest optimized power from the cost effective solar IPV system and the grid can be connected to the output load whenever it is required. Control Strategy for Optimized Power Sharing Characteristic of IPV Hybrid inverter and Grid: Fig.7 shows the simplified diagram of hybrid energy system with proposed control terminologies and strategy. Integrated Initially IPV Hybrid inverter is connected to the load and supplies the power up to its maximum generating systems. If the load demand is increased beyond the maximum available IPV power then the IPV hybrid inverter will connects to the grid, so that load can draw the power from grid. The most optimum power sharing is possible in the grid as long as there is sufficient power generated by IPV plant. Fig.8 shows sim power system implementation of hybrid energy system. Initially IPV Hybrid inverter is connected to the load and supplies the power up to its maximum generating systems. If the load demand is increased beyond the maximum available IPV power then the IPV hybrid inverter will connects to the grid, so that load can draw the power from grid. 5.1 Advanced Phavee Locked Loop (Apll): A advanced phavee lock loop (APLL) produces an enhanced output signal which synchronizes in phavee and frequency with the input signal, using a negative feedback loop. The basic idea of the APLL control strategy is developed by a feedback loop consists of a APLL to synchronize the hybrid inverter with grid. The hybrid inverter is operated with SPWM technique which is generated by the feedback loop by taking the reference from grid. The control strategy is developed by a feedback loop consists of a APLL to synchronize the hybrid inverter with grid. The hybrid inverter is operated 81
with SPWM technique which is generated by the feedback loop by taking the reference from grid. The SRF APLL is the one with the best performance under distorted and non linear grid conditions. The control strategy is developed by a feedback loop consists of a APLL to synchronize the hybrid inverter with grid. The hybrid inverter is operated with SPWM technique which is generated by the feedback loop by taking the reference from grid[31-35]. 5.2 The Design of Main Controller: The control unit for the hybrid inverter is implemented with the three phase APLL by measuring the grid voltage and grid current. The output of APLL is phase and dq transformation of measured voltage and current of grid. They are given to the current controller to generate the SPWM signals.fig.9 shows the Simulink implementation of Main controller for hybrid inverter. Figure 4.SPWM signals from the main controller to trigger the IGBT switches of Hybrid inverter Figure 5.Three phavee Sinusoidal Voltage waveforms of Hybrid inverter with output LCL filter synchronized with grid voltage. Figure 3.The control unit of hybrid inverter with APLL and SPWM generator 5.3 Simulation Results of IPV Hybrid Inverter and Main Controller: The IPV Hybrid inverter is controlled by a main controller which is implemented with the proposed control strategy. It consists of advanced Phase locked loop, current controller and SPWM generator. The APLL is used to detect the phase and frequency of the grid voltage. In this the park transformation technique is used to extract the fundamental value of the voltage and current wave form from the grid. Six SPWM signals are generated to trigger the IGBT switches in the hybrid inverter. For simplicity only two signals are shown in fig.12. The generated three phase voltages from the Output LCL filter is shown in fig.13 This will follows the variation in the grid voltage and maintains the same phase and frequency as compared with grid voltage. 6. Results and Discussion Load Controller implemented with the sampled IPV power at regular intervals and the predefined load curve for a typical residence. The inputs for the controller are shown below. Figure 6.Output waveforms of both the energy systems for varying load demand Figure 7.Load sharing ofsolar IPV system with grid When the Load demand is increased more than the designed solar IPV capacity, the load sharing characteristics are shown in fig 14. and fig 15. 7. Conclusion The Hybrid Energy system is designed especially for Residential applications with a cost effective micro hybrid inverter which will have the capability to act as both off grid and grid tie hybrid inverter. Simulation 82
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