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PV and inverter coupling induced system efficiency loss

The current PV inverter efficiency test is based on the ratio of the measured output AC active power to the measured input DC power (current and voltage RMS or average values). Because the majority of DC to AC inverters uses a switching topology, there are ripples in the input voltage and high-frequency harmonics in the output, which can affect the system efficiency in several ways: i) PV module or array does not work at its Pmax, but oscillating around Pmax due to the inverter maximum power tracking limit; ii) inverter input capacitor charging and discharging loss due to input voltage ripple; iii) AC output harmonics reduced system efficiency. To understand how these three factors affect the PV system efficiency, this study performed the analysis with simplified LTSPICE simulation, simplified analytical mathematical modeling and measured data from a PV array of 5kW.