Solar H8 inverter to reduce leakage currents in grid connected applications
ABSTARCT :
Solar energy is a promising alternative energy source for a sustainable pollution-free future. But certain factors such as solar irradiation, lack of sunlight during night hours etc. degrade or diminish the scope of solar power. To address with this problem MPPT technique is used here. Due to the requirements of high efficiency, reliability, power density and low cost and reduced size, transformer less PV inverters can be utilized in a grid-connected solar energy system. But the presence of transformer less system will lead to leakage currents, which is not at all acceptable in the case of grid connected applications. So to reduce leakage currents the modified version of H6 inverters ie an H8 inverter is used in this paper. In order to synchronize H8 inverter and grid PI controllers are used. This paper aims to utilize solar energy and reduce the leakage currents produced by transformer less inverter for grid connected applications. This is done by the integration of solar, transformer lessstep-up converter and h8 inverter. The concept is to utilize renewable sources effectively which helps in reducing the grid demand.
EXISTING SYSTEM :
? The existing modulation-based mitigation methods are not appropriate for Z-source family inverters due to the shoot-through states.
? Moreover, the highfrequency harmonics of the leakage currents are eliminated by adding a notch filter to the qZSI.
? The existing solutions based on modified topologies adopt a relatively large number of extra components, which lead to higher cost and potentially low reliability, and thus the new modified topologies using fewer components is a promising solution to reduce the cost and improve the reliability of the system.
? In addition, it is necessary to propose new modulation techniques, which are easy to be implemented in the digital control system compared with the existing complicated modulation methods.
DISADVANTAGE :
? Due to the requirements of high efficiency, reliability, power density and low cost and reduced size, transformer less PV inverters can be utilized in a grid-connected solar energy system.
? In order to deal with this problem, MPPT (Maximum Power Point Tracking) technique is introduced, which is nothing but an algorithm to extract the maximum power from the solar panels.
? The generation of leakage currents is the major problem faced by a grid connected PV system.
? The leakage current should be strictly limited, since it can lead to safety issues, increased the total harmonic distortion (THD) of the injected currents, and also electromagnetic interference (EMI) problems; all of which, may violate the grid standards.
PROPOSED SYSTEM :
• To address this, various mitigation strategies were proposed by modifying the topologies or modulation methods to maintain a constant common mode voltage (CMV) and decrease the common mode current (CMC).
• In , a topology derived from the single-phase zero-voltage state rectifier was proposed, which can achieve a constant CMV to eliminate the leakage current.
• In , the active zero state pulse-width modulation (PW) was proposed based on two active vectors replacing the traditional zero states in opposite directions, where the peak value of the CMV is reduced.
• In , the remote state PWM was proposed where only the even vectors or odd vectors are used. Thus, the CMV remains constant.
ADVANTAGE :
? The proposed new carrier based modulation technique ensures good performance in terms of output current with low THD.
? This paper reviewed and investigated the performance of 3- phase transformer less PV inverters combined with PWM techniques to reduce the leakage currents.
? The voltage obtained from the PV panels with the help of MPPT is the fed to a step up converter to boost the voltage level.
? Boost converter is used here because of its simple structure and ease of control. H8 inverter is used here because of its ability to suppress the leakage currents.
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