Abstract
Researchers at the University of Central Florida have invented a robust DC link voltage control system that improves the performance, reliability and power density of two-stage microinverters used in solar photovoltaic (PV) energy conversion. The new, low-cost Phased-Locked-Loop (PLL)-Synchronized DC Link Voltage Control System enables microinverters to operate more efficiently by mitigating the effects of large voltage ripple and corresponding increases in total harmonic distortion (THD). Voltage ripple and THD in the output current of a microinverter may adversely affect an inverter's performance, such as its efficiency in transferring power from a solar cell and the ability to provide quality electrical power into the grid.
Technical Details
The unique PLL-Synchronized DC Link Voltage Controller regulates a two-stage microinverter in which the input couples a DC/DC converter to a PV panel and the output couples a DC/AC inverter to a power grid. The invention supports single-phase half-bridge, single-phase full-bridge, or three-phase half-bridge configurations. An example embodiment comprises an analog-to-digital converter (A/D), a loop compensator, and a PLL synchronized to the grid voltage.
Key to the invention is a synchronous control method that measures and tightly regulates the DC link average voltage.
Benefit
Reduces cost and circuit complexityIncreases reliabilityRemoves high voltage ripples from DC link capacitorDoes not require any modification, compared with similar state-of-the-art methodsMarket Application
InvertersMotor controllersPower electronic circuits that contain a DC link capacitor for energy storagePublications
Mitigation of Current Distortion in a Three-Phase Microinverter with Phase Skipping using a Synchronous Sampling DC Link Voltage Control, IEEE Transactions on Industrial Electronics, DOI 10.1109/TIE.2017.2760864
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