International Journal of Advanced Engineering Application

Design and Performance Analysis of a High-Efficiency Single-Phase Transformerless Grid-Tied Photovoltaic Inverter with Active Leakage Current Suppression and Enhanced MPPT Under Partial Shading Conditions

Author(s):V. M. Venkateswara Rao

Affiliation: Independent Researcher

Page No: 34-39

Volume issue & Publishing Year: Volume 3, Issue 5, 2026/05/06

Journal: International Journal of Advanced Engineering Application (IJAEA)

ISSN NO: 3048-6807

DOI: https://doi.org/10.5281/zenodo.20055679

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Abstract:
The rapid adoption of rooftop photovoltaic (PV) systems in Indian residential and commercial sectors has amplified the demand for single-phase grid-tied inverters that simultaneously achieve high conversion efficiency, low leakage ground current, compliance with IEEE 1547-2018 and IEC 62109-1 safety standards, and reliable Maximum Power Point Tracking (MPPT) under the non-uniform irradiance conditions produced by partial shading. Transformerless inverter topologies eliminate the galvanic isolation provided by the line-frequency transformer — reducing weight, volume, and core losses — but introduce a common-mode voltage (CMV) variation path through the parasitic capacitance between PV panel frames and the protective earth, generating leakage currents that constitute shock hazards and accelerate PV module insulation degradation. This paper proposes a modified H5 inverter topology with an active clamping branch that maintains constant CMV at half the DC-link voltage throughout all switching states, suppressing leakage current to below 20 mA peak — the IEC 62109-1 threshold — without the efficiency penalty associated with passive LC filters. A variable-step Incremental Conductance (InC) MPPT algorithm with shadow detection capability is implemented to recover power from shaded sub-strings by scanning the voltage-power characteristic for global maxima, preventing tracker lock-in at local maxima that afflicts conventional Perturb-and-Observe (P&O) methods. The complete system is simulated in MATLAB/Simulink with a validated PV array model (SunPower SPR-305E WHT-D, 5 series × 4 parallel) and implemented on a 1 kW hardware prototype using STM32F407 microcontroller and SiC MOSFET switches (Cree C3M0065090D). Simulation results confirm peak efficiency of 98.1% at rated power, leakage current of 14.3 mA peak under worst-case switching transients, and Total Harmonic Distortion (THD) of injected grid current of 1.8% at full load. Hardware prototype measurements yield efficiency of 97.6% at 1 kW, leakage current of 17.2 mA peak, and grid current THD of 2.3% — within IEEE 1547 limits. Under partial shading (one of four parallel strings fully shaded), the proposed variable-step InC-MPPT recovers 94.7% of the theoretical global maximum power within 2.4 seconds, compared to 78.3% recovery by conventional P&O after 8.1 seconds. European weighted efficiency reaches 97.4%.

Keywords: transformerless inverter, photovoltaic, leakage current, MPPT, partial shading, H5 topology, common-mode voltage, SiC MOSFET, grid-tied, THD

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