Modeling and Simulation of a Hybrid Energy Storage System for Residential Grid-Tied Solar Microgrid Systems

Present-day power conversion and conditioning systems focus on transferring energy from a single type of power source into a single type of load or energy storage system (ESS). While these systems can be optimized within their specific topology (e.g. MPPT for solar applications and BMS for batteries), the topologies are not easily adapted to accept a wide range of power flow operating conditions. With a hybrid approach to energy storage and power flow, a system can be designed to operate at its most advantageous point, given the operating conditions. Based on the load demand, the system can select the optimal power source and ESS. This paper will investigate the feasibility of combining two types of power sources (main utility grid and photovoltaics (PV)) along with two types of ESS (ultra-capacitors and batteries). The simulation results will show the impact of a hybrid ESS on a grid-tied residential microgrid system performance under various operating scenarios.

Single-stage Five-level Common Ground Transformerless Inverter with Extendable Structure for Centralized Photovoltaics

The paper presents a five-level common ground type(5L-CGT),transformer-less inverter topology with double voltage boosting.The proposed inverter uses eight switches and two capacitors,charged at input voltage level.The inverter in its basic form acts as a string inverter for low-power PV applications.However,it can be extended to work as a scalable multi-level inverter with higher power handling capability to act as a centralized inverter.The working of the inverter with the sizing of the components is presented with mathematical analysis.The efficiency of the proposed PV inverter is found using thermal losses associated with switches using PLECS software.A prototype of 1 kW has been designed,and experimentation has been carried out.Various loads with a lagging power factor up to 0.6 have been tested with the inverter to establish the usability of the proposed inverter in a worst-case emulated homeuse scenario.The total harmonic distortion(THD)at the output has been recorded using a power quality analyzer with voltage and current THD values of 4.5%and 2.5%,respectively,which lies within the limits of IEEE 519 standards.The highest power conversion efficiency of the inverter has been recorded to be 96.20%.

Communication-less harmonic compensation in a multi-bus microgrid through autonomous control of distributed generation grid-interfacing converters

This paper proposes a novel approach to compensate buses voltage and current harmonics through distributed generation(DG)interfacing converter in a multibus microgrid.The control approach of each individual DG unit was designed to use only feedback variables of the converter itself that can be measured locally.In the proposed approach,the adjacent bus voltage is indirectly derived from the measured DG converter output voltage,DG line current and line impedance.A voltage closed-loop controller and a current closed-loop controller are designed to achieve both functions of DG real power generation and harmonics compensation.Therefore,the traditional harmonic measurement devices installed at the bus as well as the long distance communication between the bus and the DG converter are not required.The proposed approach can compensate the current harmonics,mitigate the buses voltage distortion and enable the customer devices to be operated in normal conditions within the multi-bus microgrid,and meanwhile relieve the burden of power quality regulator installed at the point of common coupling.Matlab simulations and experimental results are presented to show the operational effectiveness of the proposed approach.

Performance analysis of multiple gain boost converter with hybrid maximum power point tracker for solar PV connected to grid

This paper analyses the performance of a multiple gain boost converter(MGBC)connected to a solar photovoltaic(SPV)system with a grid-tied inverter.The capacitor inductor capacitor(CLC)-based MGBC is integrated to lift the output voltage of the SPV to the required level.The voltage lifts/levels in a boost converter(BC)are based on the number of CLC cells.The suggested MGBC is compared with various conventional BCs in terms of boost factor and component count.A hybrid fuzzy logic-perturb&observe maximum power point tracker(HFL-P&O MPPT)developed is used to monitor P_(max)(maximum power)generated by the SPV.Also,a comparative analysis of the suggested MPPT with a conventional P&O and fuzzy logic-based(FLB)MPPT for a CLC-based MGBC is presented.The comparison is made in terms of rise time,voltage ripples(%),steady-state time and boost factor.The output characteristics of the developed model for different irradiation conditions are analysed using the MATLAB/Simulink tool.The MPPT simulation result exhibits minimum oscillations at MPP and a significantly better rise time of 0.015 s when compared with a conventional MPPT and FLB MPPT.The proposed CLC-MGBC gives an appreciable boost factor of 4.The generated SPV power is supplied to the grid through a conventional inverter and synchronized using a phase-locked loop system.The total harmonic distortion of 1.66%obtained in the output current of the inverter is within the permissible range of the IEEE standards.