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The output voltages of renewable energy resources are relatively low for practical applications. Hence, a converter with high voltage gain is needed. This article proposes a high voltage gain nonisolated three-port converter for a renewable energy source with energy storage applications. A coupled inductor with three windings is used for transferring energies among photovoltaic (PV), battery, and the load. When the battery provides energy to the load, two primary windings with opposite polarities are connected in series. Thus, the effective primary turns is reduced for improving the voltage gain. In addition, the energy stored in the leakage inductor is recycled to the output so as to suppress voltage stress on the power switches and improve system efficiency for energy transference from either PV or battery to the load. Both PV and the battery can provide power to the load independently, thus sharing the load power coordinately. The operation principles, steady-state analyses and key parameter design of the proposed topology are then described in detail. Finally, an experimental prototype is implemented to verify the theoretical analyses with PV, battery, and load voltages of 48 V, 24 V, and 200 V, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a novel multilevel dc–ac inverter is proposed. The proposed multilevel inverter generates seven-level ac output voltage with the appropriate gate signals’ design. Also, the low-pass filter is used to reduce the total harmonic distortion of the sinusoidal output voltage. The switching losses and the voltage stress of power devices can be reduced in the proposed multilevel inverter. The operating principles of the proposed inverter and the voltage balancing method of input capacitors are discussed. Finally, a laboratory prototype multilevel inverter with 400-V input voltage and output 220\ \textV\text{rms}/2\,{\text{kW}} is implemented. The multilevel inverter is controlled with sinusoidal pulse-width modulation (SPWM) by TMS320LF2407 digital signal processor (DSP). Experimental results show that the maximum efficiency is 96.9% and the full load efficiency is 94.6%. [ABSTRACT FROM AUTHOR]

This paper presents a novel dc–dc converter configuration, which successfully integrates two technologies, including a switched capacitor and a switched coupled inductor, into one converter. By adopting a coupled inductor to charge a switched capacitor, the voltage gain can be effectively increased, and the turns ratio of the coupled inductor can be also reduced. Not only lower conduction losses but also higher power conversion efficiency is benefited from a lower part count and lower turns ratios. The proposed converter is simply composed of six components, which can be further derived to varied converters for different purposes, such as a bidirectional converter. The operating principle and steady-state analysis are discussed in this paper. A 250-W laboratory hardware prototype is completed and verified. The voltage gain is up to 11. The highest efficiency is 97.2%, and the full-load efficiency is kept at 93.6%. [ABSTRACT FROM AUTHOR]

This paper presents a new bidirectional dc–dc converter with a high conversion ratio for renewable energy systems. The coupled-inductor technique is used to achieve a high conversion ratio with very simple control circuits. In discharging mode, the converter acts as a two-stage boost converter, controlling one power switch to achieve high-voltage step-up conversion. In charging mode, the converter acts as two cascaded buck converters that control two power switches simultaneously to achieve high-voltage step-down conversion. The operating principles and analysis of the steady-state characteristics are discussed in great detail. Finally, a 24-V/200-V prototype circuit with output power of 200 W is implemented to verify the feasibility of the proposed converter. The maximum efficiency levels in discharging and charging modes are about 94.3% and 91.6%, respectively. [ABSTRACT FROM AUTHOR]

This paper proposes a novel balancing method for series-connected batteries applications. The proposed method uses a transformer to couple the energy from charger or discharger to batteries for energy balancing. The proposed method has the advantages of high efficiency, compact size, suitable for any type of switching converter, load-related balancing energy, and extremely simple structure without any active switch for voltage balance function. Three converters, including a CLL converter, an interleaved noninverting buck–boost (BB) converter, and a noninverting BB converter, with voltage balancing function and state-of-charge balancing function are built to verify the feasibility of the proposed balancing methods. [ABSTRACT FROM AUTHOR]

This paper presents an algorithm for implementing the nonlinear-carrier (NLC) control method for a single-phase power factor correction (PFC) rectifier without an input voltage-sensing circuit, an error amplifier in the current shaping loop, or other external control components. Unity power factor and low harmonic distortion are achieved by adapting NLC control with a variable slope ramp. This ramp is created through a slope comparison without any dividers. The proposed method not only achieves a high power factor, but also efficiently simplifies complexity of integrated circuit realization. A 400-W PFC boost rectifier is implemented to verify the performance of the proposed NLC control. The highest power factor reaches to 99.9% with input voltage of 120 V/60 Hz, and the lowest input current harmonic distortion is 4.267%. [ABSTRACT FROM PUBLISHER]

In this study, a probabilistic neural network (PNN) is used to estimate the state of health (SOH) of Li-ion batteries. The accurate prediction of SOH can help avoid inconveniences or fatal accidents from the sudden malfunction of the battery. A total of 110 pieces of Li-Co batteries are used. Constant current/voltage recharging and constant current discharging are performed for the life-cycle test of the battery. The data obtained from the recharging and discharging electric characteristics as well as the life-cycle test of the battery are used to estimate the SOH of the battery. The test data show that the constant current charging time, the instantaneous voltage drop at the start of discharging, and the open circuit voltage are the most important characteristics for estimating the SOH of the battery. The PNN is trained using 100 pieces of batteries. The remaining 10 pieces are used to verify the feasibility of the proposed method. The effectiveness of the PNN training using a number of samples is discussed and analyzed. The results show that the average error of the prediction is 0.28% and the standard deviation is 1.15%. The computation time of the PNN is 62.5 ms. Thus, the proposed method can accurately estimate the SOH of the battery in a short period. [ABSTRACT FROM PUBLISHER]

This paper proposes a high step-up solar power optimizer (SPO) that efficiently harvests maximum energy from a photovoltaic (PV) panel then outputs energy to a dc-microgrid. Its structure integrates coupled inductor and switched capacitor technologies to realize high step-up voltage gain. The leakage inductance energy of the coupled inductor can be recycled to reduce voltage stress and power losses. A low voltage rating and low-conduction resistance switch improves system efficiency by employing the incremental conductance method for the maximum power point tracking (MPPT) algorithm. Because of its high tracking accuracy, the method is widely used in the energy harvesting of PV systems. laboratory prototypes of the proposed SPO that have an input voltage range of 20 to 40 V and a maximum PV output power of 400 V/300 W are applied. The highest PV power conversion efficiency is 96.7%. The maximum MPPT accuracy is 99.9%, and the full load average MPPT accuracy is 97.8%. [ABSTRACT FROM AUTHOR]

The grid-connected AC module is an alternative solution in photovoltaic (PV) generation systems. It combines a PV panel and a micro-inverter connected to grid. The use of a high step-up converter is essential for the grid-connected micro-inverter because the input voltage is about 15 V to 40 V for a single PV panel. The proposed converter employs a Zeta converter and a coupled inductor, without the extreme duty ratios and high turns ratios generally needed for the coupled inductor to achieve high step-up voltage conversion; the leakage-inductor energy of the coupled inductor is efficiently recycled to the load. These features improve the energy-conversion efficiency. The operating principles and steady-state analyses of continuous and boundary conduction modes, as well as the voltage and current stresses of the active components, are discussed in detail. A 25 V input voltage, 200 V output voltage, and 250 W output power prototype circuit of the proposed converter is implemented to verify the feasibility; the maximum efficiency is up to 97.3%, and full-load efficiency is 94.8%. [ABSTRACT FROM PUBLISHER]

A novel two-switch high-step-up isolated converter with voltage lift is proposed in this paper. The proposed isolated converter utilizes a transformer with low turn ratio to achieve high step-up gain. The secondary winding charges two boosting capacitors in parallel as switches during the switch-on period, and two boosting capacitors are discharged in series during the switch-off period. Thus, the converter has high voltage gain with appropriate duty ratio. In addition, by using two clamping diodes and a capacitor on the primary side, leakage energy is recycled, and the voltage spikes of the two active switches are clamped, thereby improving conversion efficiency. Finally, experimental results based on a prototype implemented in the laboratory with an input voltage of 24 V, an output voltage of 200 V, and an output power of 200 W verify the performance of the proposed isolated converter; full-load efficiency is nearly 93%. [ABSTRACT FROM PUBLISHER]

CuO is doped into (Na0.5K0.5)NbO3 (NKN) ceramics to improve the piezoelectric properties and thus obtain a piezoelectric transformer (PT) with high output power. In X-ray diffraction patterns, the diffraction angles of the CuO-doped NKN ceramics shift to lower values because of an expansion of the lattice volume, thus inducing oxygen vacancies and enhancing the mechanical quality factor. A homogeneous microstructure is obtained when NKN is subjected to CuO doping, leading to improved electrical properties. PTs with different electrode areas are fabricated using the CuO-doped NKN ceramics. Considering the efficiency, voltage gain, and temperature rise of PTs at a load resistance of 1 kΩ, PTs with an electrode with an inner diameter of 15 mm are combined with the circuit design for driving a 13-W T5 fluorescent lamp. A temperature rise of 6°C and a total efficiency of 82.4% (PT and circuit) are obtained using the present PTs. [ABSTRACT FROM PUBLISHER]

This paper proposes a new high step-up dc–dc converter designed especially for regulating the dc interface between various microsources and a dc–ac inverter to electricity grid. The figuration of the proposed converter is a quadratic boost converter with the coupled inductor in the second boost converter. The converter achieves high step-up voltage gain with appropriate duty ratio and low voltage stress on the power switch. Additionally, the energy stored in the leakage inductor of the coupled inductor can be recycled to the output capacitor. The operating principles and steady-state analyses of continuous-conduction mode and boundary-conduction mode are discussed in detail. To verify the performance of the proposed converter, a 280-W prototype sample is implemented with an input voltage range of 20–40 V and an output voltage of up to 400 V. The upmost efficiency of 93.3% is reached with high-line input; on the other hand, the full-load efficiency remains at 89.3% during low-line input. [ABSTRACT FROM AUTHOR]