Grid-connected photovoltaic micro-inverter with new hybrid control LLC resonant converter

A dual-output LLC resonant converter using pulse frequency modulation (PFM) and asymmetrical pulse width modulation (APWM) can achieve tight output voltage regulation, high power density, and high cost-effectiveness. However, an improper resonant tank design cannot achieve tight cross regulation of the dual-output channels at the worst-case load conditions. In addition, proper magnetizing inductance is required to achieve zero voltage switching (ZVS) of the power MOSFETs in the LLC resonant converter. In this paper, voltage gain of modulation methods and steady state operations are analyzed to implement the hybrid control method. In addition, the operation of the hybrid control algorithm is analyzed to achieve tight cross regulation performance. From this analysis, the design methodology of the resonant tank and the magnetizing inductance are proposed to compensate the output error of both outputs and to achieve ZVS over the entire load range. The cross regulation performance is verified with simulation and experimental results using a 190 W prototype converter.

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PV Micro-Inverter Topology Using LLC Resonant Converter

Energies ◽

10.3390/en12163106 ◽

2019 ◽

Vol 12 (16) ◽

pp. 3106 ◽

Cited By ~ 4

Author(s):

Hiroki Watanabe ◽

Jun-ichi Itoh ◽

Naoki Koike ◽

Shinichiro Nagai

Keyword(s):

Conversion Efficiency ◽

Power Converter ◽

Electrolytic Capacitor ◽

Resonant Converter ◽

Double Line ◽

Line Frequency ◽

Point Tracking ◽

Llc Resonant Converter ◽

Frequency Power ◽

Micro Inverter

In this paper, a DC–single-phase AC power converter with an LLC resonant converter is presented for a photovoltaic (PV) micro-inverter application. This application requires the leakage current suppression capability. Therefore, an isolated power converter is usually combined for DC/AC systems. The LLC resonant converter is the one of the isolated power converter topologies, and it has good performance for conversion efficiency with easy control. On the other hand, a double-line frequency power ripple has to be compensated for in order to improve the performance of the maximum power point tracking (MPPT). Therefore, a bulky electrolytic capacitor is usually necessary for the power converter. However, the electrolytic capacitor may limit the lifetime of the micro-inverter. This paper introduces the PV micro-inverter with a LLC resonant converter. In addition, the active power decoupling circuit is applied in order to compensate the double-line frequency power ripple by the small capacitor in order to eliminate the electrolytic capacitor. Finally, the transformer design is considered in order to reduce the transformer losses. As a result, the conversion efficiency of the LLC converter is improved by 1% when the litz wire has many strands.

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Variable Mode Hybrid Control Based on Half-bridge LLC Resonant Converter for Stabilize The Voltage

2020 International Conference on Electrical Engineering (ICEE) ◽

10.1109/icee49691.2020.9249776 ◽

2020 ◽

Author(s):

Lingzhi Yi ◽

Huan Liao ◽

Peng Jiang ◽

Wang Li ◽

Junyong Sun

Keyword(s):

Hybrid Control ◽

Resonant Converter ◽

Llc Resonant Converter ◽

Variable Mode

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A Phase-Shift-Modulated LLC-Resonant Micro-Inverter Based on Fixed Frequency Predictive-MPPT

Energies ◽

10.3390/en13061460 ◽

2020 ◽

Vol 13 (6) ◽

pp. 1460

Author(s):

Omar Abdel-Rahim ◽

Nehmedo Alamir ◽

Mohamed Abdelrahem ◽

Mohamed Orabi ◽

Ralph Kennel ◽

...

Keyword(s):

High Efficiency ◽

Harmonic Distortion ◽

Maximum Power ◽

Switching Frequency ◽

Resonant Converter ◽

Fixed Frequency ◽

Pv System ◽

Partial Shading ◽

Llc Resonant Converter ◽

Micro Inverter

Maximum Power Point Tracking (MPPT) control is an essential part of every photovoltaic (PV) system, in order to overcome any change in ambient environmental conditions and ensure operation at maximum power.. Recently, micro-inverters have gained a lot of attention due to their ability to track the true MPP for each individual PV module, which is considered a powerful solution to overcome the partial shading and power mismatch problems which exist in series-connected panels. Although the LLC resonant converter has high efficiency and high boosting ability, traditional MPPT techniques based on Pulse Width Modulation (PWM) do not work well with it. In this paper, a fixed frequency predictive MPPT technique is presented for the LLC resonant converter to be used as the first-stage in a PV micro-inverter. Using predictive control enhances the tracking efficiency and reduces the steady state oscillation. Operation with fixed switching frequency for the LLC resonant converter improves the total harmonic distortion profile of the system and ease the selection of circuit magnetic component. To demonstrate the effectiveness of the proposed MPPT technique, the system is simulated using MATLAB/Simulink platform. Furthermore, a 150 W hardware prototype is developed and tested. Both simulation and experimental results are consistent and validate the proper operation of the developed system.

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