Yu-Shan Cheng

A novel asymmetrical FLC-based MPPT technique for photovoltaic generation system

In this paper, a novel asymmetrical fuzzy-logic-control (FLC) based maximum power point tracking (MPPT) algorithm for photovoltaic (PV) generation system (PGS) is proposed. The proposed method uses the power variation and voltage variation as the inputs, which significantly simplified the computation. Comparing with the conventional perturb and observe (P&O) method, the proposed asymmetrical FLC-based MPPT algorithm can improve the dynamic and steady state performance of the PGS simultaneously. Comparing with the proposed symmetrical FLC-based MPPT method, the transient time and the MPPT tracking accuracy are further improved by 38.1 % and 0.03 %, respectively.

Design and implementation of a high-efficiency bidirectional DC-DC converter

This paper studies the design and implementation of a non-isolated dual-half-bridge bidirectional DC-DC converter. Using the presented topology, high efficiency can be achieved under wide-range load variations by the zero voltage switching (ZVS) features. In this paper, dsPIC33FJ16GS502 digital signal controller (DSC) is utilized to implement the digital controller of the bidirectional DC-DC converter. According to the experimental results, a light-load efficiency over 92 % and a full-load efficiency over 97% can be achieved.

Development of wireless RGB LED dimming control technology using smart phone

In this paper, a LED lighting control system based on the Bluetooth wireless network is proposed. The presented system includes a RGB LED light bar, a lighting control APP for smart phones and a Bluetooth communication module for remote control. The hardware and software design will be presented in detail. The experimental results show that smart phone is a good candidate for home lighting control applications. Moreover, smart phone APPs enable easy connection; therefore offers advantages include product interoperability, vendor independence, and accessibility to broader markets.

A novel global maximum power point tracking method for photovoltaic generation system operating under partially shaded condition

Solar cells have nonlinear P-V curves that vary with insolation and temperature. Therefore, maximum power point tracking (MPPT) technique is used to operate and keep a solar cell at its maximum power output. In practical application, solar cells are usually influenced by partially shaded conditions (PSC). There is a bypass diode that prevents damage to the solar cell, which causes the P-V characteristic curve to have multiple peak values. As the traditional MPPT technology only tracks local maximum value, techniques which can find the global maximum value should be developed to maintain MPPT. This study proposed a new type of global maximum power point tracking (GMPPT) algorithm and experimentally proved that the global maximum power point (GMPP) could be tracked rapidly and successfully in different shaded conditions.

RGB LED backlight driving system with dynamic voltage regulation capability

Advantages including higher luminance efficacy, local dimming capability, wider color gamut, faster response, longer operation life and lesser environmental issues makes RGB LED backlight system suitable for high-end display units. For RGB LEDs, the forward voltages for the red, green and blue LEDs are different. Therefore, dynamic voltage regulation (DVR) can be applied to optimize the power stage design. In this paper, a RGB LED backlight driving system is proposed. The proposed system consists of a power factor correction pre-stage and a digitally-controlled LLC resonant converter. The output voltage of the presented LLC resonant converter is adjusted by a digital controller so that RGB LED maintains the desired string current; this will improve the efficiency of the driving system. According to the experimental results, the presented system can adjust the output voltage of the LLC resonant converter according to the requirements of the RGB LED string.

Design of a digitally-controlled LLC resonant converter with synchronous rectification

In this paper, a digitally-controlled LLC resonant converter with synchronous rectification is developed. The advantages of the LLC resonant converter include ability to operate over a wide input voltage range and the fact that zero voltage switching (ZVS) is achievable over the entire operating condition. Moreover, synchronous rectifier reduces conduction loss in LLC resonant converter; hence increases the efficiency further. Using a digital controller to replace its analog counterpart boasts the advantages such as components reduction and more flexible design. Experimental results show that the measured conversion efficiencies of the designed digital LLC resonant converter are all higher than 92% under all output voltage and load conditions.

Design and implementation of Li-ion battery charger using state-of-charge estimation with fuzzy temperature control

In this paper, a novel lithium-ion (Li-ion) battery charger is proposed; the proposed charger first takes the state of charge (SOC) information into account and adjusts the charging current accordingly. In order to further improve the charging efficiency, a fuzzy-logic-control-based (FLC-based) technique is also employed. The proposed FLC takes the temperature rise and the gradient of temperature rise of battery into account, and fine-tune the charging current accordingly. In this paper, the power stage is implemented using the synchronous-rectified buck converter. The digital compensator, digital filter and the SOC adaptive algorithm is implemented using the dsPIC digital signal controller from Microchip Corp; while the fuzzy logic controller is realized using the LabVIEW on a personal computer. In addition to the hardware, a graphical user interface is also presented. According to the experimental results, the charging efficiency of the proposed system can be increased and the performance of the proposed charger can be improved. Comparing to conventional constant-current constant-voltage (CC-CV) method, the proposed charging technique can reduce the average temperature rise for 23.2% while maintaining similar charging time.

A novel modulation technique with interleaved-and-shifted shoot-through state placement for quasi-Z-source inverters

Summary In this paper, a single-phase quasi-Z-source (qZS) inverter (qZSI), integrating the pulse width modulation (PWM) control with interleaved-and-shifted shoot-through state (STS) placement modulation technique, is proposed to simultaneously achieve both dc voltage boost and dc-ac inversion. Instead of placing the STS in both inverter legs simultaneously, the addressed method inserts the STS only in left/right inverter leg separately during the positive/negative half cycle of the output voltage to reduce switching losses and thermal stresses of the power devices. The STS shift is also studied to decrease the switching numbers of power devices and thus can improve the efficiency further. Theoretical analysis and design guidelines of the studied inverter are included. Improvement in effectiveness and performance of the devised scheme and modulation strategy are proved experimentally and compared with the previous studies on a built laboratory prototype.

Development of an 1.2 kW thermoelectric generation system for industrial waste heat recovery

In this paper, an 1.2 kW thermoelectric generation system (TEG) for industrial waste heat energy recovery is developed and implemented. To achieve better performance, a novel hybrid maximum power point tracking (MPPT) method is also proposed. Comparing with conventional perturb and observe (P&O) technique and variable-step P&O method, the presented MPPT method can improve the tracking speed by 85.0% and 78.6% when temperature differences is 180°C according to the simulated results. Also from the experimental results, the proposed MPPT method can improve the tracking speed for 42.8% and 86.2% comparing with the typically-utilized P&O technique when temperature differences are ΔT=60°C and ΔT=180°C, respectively. The proposed method boasts advantages such as fast tracking speed and no additional circuit.

A novel modulation control for quasi-Z-source inverters

In this paper, a single-phase quasi-Z-source (qZS) inverter (qZSI), integrating the pulse width modulation (PWM) control with interleaved placement shifted shoot-through state (STS) modulation technique, is developed to simultaneously achieve both dc voltage boost and dc-ac inversion. Instead of placing the shoot-through state in both inverter legs, the proposed method inserts the shoot-through state only in left/right inverter leg separately during the positive/negative half cycle of the output voltage to reduce switching losses and thermal stresses of the power devices. The shoot-through states shift is also studied to decrease the switching numbers of power devices and hence improve the efficiency further. The effectiveness and performance of the designed scheme and modulation strategy are proved experimentally and compared to the previous research on a built laboratory prototype.