This article is presented by:
S. N. Singh
A. K. Singh
FPGA Based Sinusoidal Pulse Width
Modulated Waveform Generation for Solar
(PV) Rural Home Power Inverter
With the increasing concern about global environmental protection and energy demand due to rapid growth of population in developing countries and the diminishing trend of resources of conventional grid supply, the need to produce freely available pollution free natural energy such as solar/wind energy has been drawing increasing interest in every corner of the world. In an effort to utilize these energies effectively through Power converter, a great deal of research is being carried out by different researchers / scientist and engineers at different places in the world to meet the increasing demand of load . The study presents methodology to integrate solar (PV) energy (which is freely available in every corner of the world) with grid source and supplement the existing grid power in rural houses during its cut off or restricted supply period. In order to get consistency in supply a DG is also added as a standby source in the proposed integration of network. The software using novel Direct PWM modulation strategy and its soft control features extend the flexibility to control converter (inverter) parameters like voltage, frequency, number of samples of PWM pulses constituting sine-wave without changing any hardware configuration in the circuit. The system simulation of PWM Pulse generation has been done on a XILINX based FPGA Spartan 3E board using VHDL code. The test on simulation of PWM generation program after synthesis and compilation were recorded and verified on a prototype sample.
HE basic need of an electrical energy is increasing with the rapid growth of population in urban, sub-urban and rural sectors. On the other end, the conventional grid supply in a grid connected area has become standstill due to diminishing trend of raw material resources and its further extension is not possible due to various technical, political and economic reasons. To meet the excess energy demand, alternative renewable energy sources like solar/wind etc with energy storage device i.e. Battery are being used to work as a standalone power source or in sharing mode with Grid or DG power source. Among these two sources solar energy is preferred as it is easily available in every part of the country in the world where as wind energy is restricted to the coastal area only. A purely solar power converter, if used alone, may become very expensive as far as initial investment is concerned. Further, due to varying solar insolation, the battery barely gets time to fully charge from a single PV source due to varying sun radiation or from the limited available grid source especially in rural sector to its full extent. Hence the solar power system needs to be integrated with supplementary additional DG back up sources in order to deliver 24 hour power. The system can also work as a standalone power source in a grid deprived area in remote rural sectors by adding more number of PV modules and battery bank. The optimal utilization of these sources is possible with efficient smart adaptive Power converter and adopting optimal load management. In the present study, the Pulse width modulated (PWM) adaptive intelligent Power converter (inverter) has been designed and developed where the input DC power stored in the battery bank, obtained through PV and /or Grid sources, has been digitized to produce a sequence of PWM pulses (approximated to a sine wave) at the output of power converter and deliver power to the load. The traditional analog Sine-Triangular method for generating PWM pulses adopt the technology where a high frequency carrier signal is compared with sinusoidal wave as reference signal, set at desired output frequency , and thus needed two signals to produce PWM signal In the present scheme, the PWM pulses are directly generated using a new technique through software program coded with VHDL and downloaded in FPGA Spartan 3E starter kit to produce base drive signals for inverter power device switches. The FPGA VLSI technology offers a fast system with many more advantages as compared to other conventional technology including DSP based controller etc. The software program can easily be changed to optimize and control the inverter parameters like frequency, voltage amplitude, number of PWM pulses in half cycle etc. without changing the hardware circuit. The PWM output waveform designed with high number of PWM pulses in a half cycle can produce a low value of THD content (less than 3-5% THD) and approximate very near to a sine wave which is comparable with the quality of the sine wave of the grid supply.
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