Resonant Mode Microinverter for grid-tied PV applications
A novel single-stage LCL resonant microinverter is proposed, that reduces installation and maintenance costs in solar systems. The topology achieves partial ZVS on the primary FETs, full ZVS on the secondary FETs, low reactive power, and current source output characteristics. It is compatible with bidirectional GaN FETs and validated through 500 kHz, 380 W simulations and experiments. Additionally, a method for determining the validity of the fundamental harmonic approximation (FHA) in resonant circuits and wireless power transfer (WPT) systems is introduced. The method, demonstrated with series-series and double-sided LCC topologies, expands the FHA’s applicability range and is validated through a 600 W setup.
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Switch-Mode & Synchronously Switched Active EMI Filters
Electromagnetic interference (EMI) in the 0.15-30 MHz frequency range is a key challenge. While passive LC filters can occupy up to 1/3 of the power supply’s volume, active EMI filters (AEFs) are effective in reducing filter size and current. Traditional AEFs use linear amplifiers to counteract ripple voltage or current, leading to limited bandwidth and high power consumption. We investigate switch-mode and synchronously switched AEFs as alternatives, which use high-frequency (30-300 MHz) amplifiers to achieve near-100% efficiency and avoid introducing additional interference in the regulated range. Additionally, the design and implementation of ultra-fast isolated gate drivers with 2-8 ns propagation delays (and very high on/off slew rates) is proposed, helping achieve super high control bandwidths for such AEFs.
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Differential Power Processing Architecture for On-Vehicle Photovoltaics
On-vehicle integration of photovoltaics can extend the range of electric vehicles by a useful amount each day. However, partial shading can significantly limit PV power production even in stationary installations, and this is expected to be more severe in vehicles. Differential power processing (DPP) approaches can maximize PV output power despite partial shading. A PV-to-isolated-bus DPP architecture using extensible and inexpensive converter modules can leverage the vehicle’s existing low voltage battery as the common bus and reuse the existing onboard charger to interface the solar string to the high-voltage battery. The proposed converter module achieves maximum power point tracking (MPPT) for the cell(s) it is connected to without requiring any communication or power transfer across the isolation barrier while allowing bidirectional power with synchronous rectification. This offers high system efficiency, and simple control that scales easily to large numbers of DPP units.
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