New MPPT algorithm for bidirectional inverter design


Researchers from the University of Science and Technology of China have designed a novel topology for a bidirectional inverter for uninterruptible power supply (UPS).

The proposed inverter design, with battery backup, relies on a maximum power point tracking (MPPT) solar charge controller based on an artificial fish-swarm algorithm, which is inspired by the collective movement of fish and their instinctive behaviors. This algorithm is said to offer high convergence speeds, flexibility, fault tolerance, and accuracy. The scientists said the perturb and observe (P&O) algorithm, which is most commonly used for PV applications, has a number of drawbacks.

The newly developed algorithm works according to a two-step process. The first step involves a variable perturbation observation method to find the maximum power point of the system. In the second step, the proposed device makes use of the fish-swarm algorithm to rapid-search and track the global maximum power point.

The PSpice software was used for the model simulation, which was aimed at obtaining the volt-ampere characteristic curve of PV system output. “The solar array simulator was used to verify the effect of maximum power point tracking at different light intensities,” the researchers said.

The open circuit voltage of the simulator was 193.785 volts, while the short circuit current was 2.6786 ampere. The ambient temperature was 27 C and the lighting power density was 1,000 W/m2. The simulation showed that the MPPT tracking has an average efficiency of 99.5% and a maximum efficiency of 99.9%.

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“According to the curves of the output power, voltage and current of the solar panel in 60 seconds and the Boost circuit can track the maximum power point around 10 seconds,” the researchers said.

The inverter is suitable for uninterrupted power supply in case of grid failure.  “The distortion rate of the grid-connected current waveform was within 2% and the DC current component was less than 0.5%,” the scientists said. “The full bridge inverter can be reverse rectified by connecting the reverse diode in parallel with the full-bridge switch. It provides the possibility for the power generation to charge the battery.”

They presented the new inverter topology in “Bidirectional energy storage photovoltaic grid‐connected inverter application system,” which was recently published in the International Journal of Energy Research.

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