Chih-Lung Shen

A single-phase inverter system for PV power injection and active power filtering with nonlinear inductor consideration

This paper proposes a single-phase two-wire inverter system for photovoltaic (PV) power injection and active power filtering (APF) with nonlinear inductor consideration. The proposed system can fully or partially perform APF, process PV power, eliminate harmonic currents, improve power factor, and take into account the nonlinear effect of its output filter inductor. In the system, even though only the utility current is sensed, both APF and maximum power point tracking features can be still achieved, reducing the number of current sensors and cost significantly. To prevent output current from exceeding switch ratings, inverter current is properly controlled through a current estimator and a defined limit circle. A self-learning algorithm is also proposed to determine nonlinear inductance, which can increase the accuracy of the estimated current. Simulations and experimental results have verified the feasibility of the proposed PV inverter system and the algorithm.

PV Power Injection and Active Power Filtering With Amplitude-Clamping and Amplitude-Scaling Algorithms

This paper presents a half-bridge single-phase two-wire (1phi2W) photovoltaic (PV) inverter system that can perform both active power filtering and real power injection. In the proposed system, it needs only two active switches, reducing cost significantly. In addition, output current of the inverter can be controlled to prevent switches from exceeding their current ratings. Thus, power rating of the inverter can be effectively used and power quality can be improved. For controlling inverter output current, an amplitude-clamping algorithm and an amplitude-scaling algorithm are proposed, which can determine inverter current command without needs of complicated calculation. Simulations and experimental results have verified the feasibility of the proposed PV inverter system and the two current control algorithms

A 1/spl phi/3 W grid-connection PV power inverter with APF based on nonlinear programming and FZPD algorithm

This paper presents design and implementation of a single-phase three-wire (1/spl phi/3 W) grid-connection PV power inverter with active power filter which is based on nonlinear programming and fast-zero-phase detection (FZPD) algorithm. The proposed inverter system can not only transmit PV power but can compensate harmonic currents, supply reactive power, and balance power at source side even when the line voltages are highly distorted. Simulated and experimental results have verified the FZPD algorithm and demonstrated that when the voltage sources are highly distorted, the proposed inverter system can yield better power quality over that with zero-crossing detection.

Multi-Input Converter with MPPT Feature for Wind-PV Power Generation System

A multi-input converter (MIC) to process wind-PV power is proposed, designed, analyzed, simulated, and implemented. The MIC cannot only process solar energy but deal with wind power, of which structure is derived from forward-type DC/DC converter to step-down/up voltage for charger systems, DC distribution applications, or grid connection. The MIC comprises an upper modified double-ended forward, a lower modified double-ended forward, a common output inductor, and a DSP-based system controller. The two modified double-ended forwards can operate individually or simultaneously so as to accommodate the variation of the hybrid renewable energy under different atmospheric conditions. While the MIC operates at interleaving mode, better performance can be achieved and volume also is reduced. The proposed MIC is capable of recycling the energy stored in the leakage inductance and obtaining high step-up output voltage. In order to draw maximum power from wind turbine and PV panel, perturb-and-observe method is adopted to achieve maximum power point tracking (MPPT) feature. The MIC is constructed, analyzed, simulated, and tested. Simulations and hardware measurements have demonstrated the feasibility and functionality of the proposed multi-input converter.

A modified-forward multi-input power converter for solar energy and wind power generation

In this paper a modified-forward multi-input converter (MFMIC) for renewable energy is proposed, which can not only process solar energy but deal with wind power. The proposed converter is derived from series forward structure to step down voltage for charger systems or dc distribution applications. The MFMIC mainly contains an upper forward, a lower forward, a common output inductor, and a DSP-based system controller. The upper and lower forwards can operate separately or simultaneously to accommodate the variation of atmospheric conditions. When the MFMIC processes power at interleaving mode, better performance can be achieved and volume is reduced. To draw maximum power from PV panel and wind turbine, perturb-and-observe method is adopted for maximum power point tracking (MPPT). The MFMIC system is constructed, designed, analyzed and simulated. Simulations have demonstrated the feasibility of the proposed multi-input converter.

Interleaved soft-switching buck converter with coupled inductors

This paper presents an interleaved soft-switching buck converter with coupled inductors to extend duty ratio for high step-down voltage applications. In the proposed converter, a single-capacitor turn-off snubber is introduced to limit rising rate of active switches to reduce turn-off loss. To handle the energy trapped in the leakage inductance of the coupled inductors, simple passive-clamp circuits are added to the proposed converter, which can effectively recycle the energy and suppress voltage spike. To highlight the merits of the proposed converter, its performance indexes, such as voltage gain function and component stresses, are analyzed and compared with those of the conventional interleaved buck converter. In this study, the prototype of the proposed converter, input voltage of 150-200 Vdc, output voltage of 12 Vdc, and full load power of 240 W has been implemented and verified, from which experimental results have shown that 85% conversion efficiency can be achieved at the full load condition.

A single-phase two-wire grid-connection PV inverter with active power filtering and nonlinear inductance consideration

This paper proposes a single-phase two-wire (1/spl phi/2W) PV inverter system with power quality control and nonlinear inductance consideration. The proposed system can fully or partially perform active power filtering, process PV power, eliminate harmonic currents, improve power factor, and take into account nonlinear effect of its output filter. In the system, only is source current sensed to achieve power-quality control and maximum-power-point-tracking feature, reducing cost significantly. To prevent output current from exceeding switch ratings, inverter current is properly controlled through a current estimator and a defined limit circle. A self-learning algorithm is also proposed to determine nonlinear inductance, which can increase accuracy of the estimated current. Simulations and experimental results have verified the feasibility of the proposed PV inverter system and the algorithm.

Analysis and implementation of an interleaved ZVS buck converter with coupled-inductors

In this paper, an interleaved zero-voltage switching (ZVS) coupled-inductors buck converter with active-clamp circuits is study. Compared with passive-clamp circuits, the active-clamp circuits in the interleaved buck converter provided can have benefits of recycling the leakage energy, while minimum ringing voltage is across the active switches. Moreover, since both main and auxiliary switches can be turned on with ZVS, switching loss can be reduced and conversion efficiency therefore can be improved significantly. A 240W prototype of the proposed interleaved coupled-inductors buck converter was built and experimental results have shown that efficiency can reach as high as 90%. It is very suitable for non-isolation and high current density applications.

Development of a fuzzy-Q control for achieving robust inverter systems

This paper presents analysis and design control scheme including the nonlinear effects of the output-filter inductor and active switches of the inverter systems. Since the filter inductance will drop dramatically when the inverter system is operated at heavy loads, system dynamic performance will vary over a wide range. Q-parameter is selected as an input variable of the control scheme to improve the system performance. The dc link of the inverter system is a constant value, but the variation of the modulation will also affect the linear control of the system. The reference command of an inverter system is a sinusoidal wave. In the paper, a nonlinear controller is used to compensate the nonlinear results of the sine-modulated inverter during each cycle. Inverter systems with the proposed control scheme can compensate the influence due to variations of filter inductance and nonlinear effect of the active switches no matter it operated at the light loads or the heavy loads. Thus, a robust inverter system can be achieved.

Analysis, design, and practical considerations for 500 W power factor correctors

This paper presents analysis, design, and practical considerations for 500 W boost power factor correctors (PFCs). The boost PFCs with three active soft-switching cells, which are boost, forward and flyback, and a passive soft-switching cell are first discussed. The operating principle and performance characteristics of the PFCs are then presented in detail, from which the boost with a flyback soft-switching cell and that with a passive soft-switching cell are designed and implemented. Performance comparison among these PFCs is also presented. Hardware measurements are used to verify the theoretical discussion. The presented information can provide designers a good application reference.