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Variable switching frequency pulse width modulation (VSF PWM) has been proposed in the past to optimize the total harmonic distortion (THD) performance and switching losses of an inverter. Nevertheless, such VSF PWMs give rise to switching harmonics which vary across a wide frequency spectrum, where the lower frequencies could resonate with the filter while the upper frequency could exceed the maximum switching frequency. This complicates VSF PWM design, restricting their practical uses. In this paper, a confined band VSF PWM (CB-VSF PWM) for a single-phase inverter with an LCL filter is presented. By confining the switching frequencies within a practical band, the design of the filter becomes easier while maintaining low current THD with low switching losses. The choices of the upper and lower bands of the proposed VSF are defined and the design criterion is introduced. It is found that the proposed method allows reduction in switching losses as well as reduction in current THD when the effect of the LCL filter is taken into consideration. The performance analysis is validated through simulation and experimental results in a 1 kW inverter. [ABSTRACT FROM AUTHOR]

Increased penetration of distributed energy resources into conventional power systems increases control challenges. These can be suitably met by microgrids. This paper examines the architecture of microgrids and reviews their classifications and the literatures discussing their control objectives during islanded mode. It finds the use of microgrids enhancing the conventional power system's grid smartness. It also summarizes microgrid control objectives and their most common problems and solutions. [ABSTRACT FROM PUBLISHER]

This paper presents a dc-to-dc converter, which offers continuous input and output energy flow and low input current ripple, applicable and mandatory for photovoltaic (PV) arrays and maximum power tracking applications. The PV array yields exponential curves for current and voltage where maximum power occurs at the curve's mutual knee. Conventional dc-to-dc converters have a relatively high input current ripple which causes high power losses when connected to nonlinear sources like PV arrays. The proposed converter maximizes the power that can be sourced from the PV array, without the need of any electrolytic filtering capacitance. The effect of current ripple can be significant and decreases PV system efficiency. Converter simulations and experimental results support and extol the system concept. [ABSTRACT FROM PUBLISHER]

This paper presents a fuzzy logic controller (FLC)-based single-ended primary-inductor converter (SEPIC) for maximum power point tracking (MPPT) operation of a photovoltaic (PV) system. The FLC proposed presents that the convergent distribution of the membership function offers faster response than the symmetrically distributed membership functions. The fuzzy controller for the SEPIC MPPT scheme shows high precision in current transition and keeps the voltage without any changes, in the variable-load case, represented in small steady-state error and small overshoot. The proposed scheme ensures optimal use of PV array and proves its efficacy in variable load conditions, unity, and lagging power factor at the inverter output (load) side. The real-time implementation of the MPPT SEPIC converter is done by a digital signal processor (DSP), i.e., TMS320F28335. The performance of the converter is tested in both simulation and experiment at different operating conditions. The performance of the proposed FLC-based MPPT operation of SEPIC converter is compared to that of the conventional proportional–integral (PI)-based SEPIC converter. The results show that the proposed FLC-based MPPT scheme for SEPIC can accurately track the reference signal and transfer power around 4.8% more than the conventional PI-based system. [ABSTRACT FROM AUTHOR]

This study presents an optimisation technique for proportional-integral-derivative (PID) controller to achieve maximum-power-point tracking (MPPT) of single-ended primary-inductor converter (SEPIC). A new weight function is developed to optimise the PID parameters based on gradient-descent (GD) method by adding low-pass filter term. The proposed optimisation method does not stick in the local minima, which happens frequently with the traditional weight function used in GD method, where the low-pass filter term suppresses the noise and smooths the iteration process. The prototype of the proposed optimised PID-based SEPIC converter for photovoltaic inverter applications is built using DSP-based TMS320F28335. The performance of the proposed optimised PID-based MPPT scheme is tested in both simulation and experiment at different operating conditions. A performance comparison of the proposed GD method with the conventional GD PID is also made in real-time. It is found that the proposed optimised PID-based SEPIC converter is superior to the conventional GD PID controller in terms of power transfer and efficiency. Furthermore, the proposed optimised PID controller for two-level inverter can achieve a better total harmonic distortion (THD) level as compared to the multi-level inverter frequently used by researchers for the same purpose. [ABSTRACT FROM AUTHOR]

The theme of this paper is a novel MPPT converter for battery charger. The converter combines both cuk and buck converters topologies to extract maximum power from photovoltaic arrays while supplying a controlled constant current/voltage to the battery simultaneously. The new topology uses two control signals instead of one control signal; one for maximum power point tracking, another for battery charger control providing constant current/voltage to the battery. The Advantage of this converter is to exploit the maximum power of the PV array avoiding battery damage caused by variable MPPT voltage. As a matter of fact, the tracking voltage that tracks the maximum power is variable according to weather irradiation conditions. However, batteries need constant voltage and current for charging to avoid the damage and to extend its lifetime. Therefore, it is reliable to combine the battery charger control and the maximum power exploitation using two control signals simultaneously. The real-time implementation of the cuk-buck converter was carried in TMS320F28335 DSP. A 4kW prototype system was built and four 12V 100Ah batteries were used. The effectiveness of the proposed converter was tested in both simulation and experiment in various operating conditions. The experiment results verified that the PV power obtained of the two control signal converter was exploited better than that of one control signal and that battery's full charging state was reached in a relatively short time. [ABSTRACT FROM AUTHOR]