Adaptive backstepping approach for dc‐side controllers of Z ‐source inverters in grid‐tied PV system applications

Abstract

Z-source inverters (ZSIs) are single-stage power converters with both voltage buck and boost capabilities provided by the unique impedance network and the ability to operate during shoot-through states. This study proposes a novel non-linear adaptive backstepping method for dc-side controllers in a multi-loop control scheme of the ZSI in grid-tied photovoltaic (PV) systems. Despite the variability of the capacitor and inductor values in the ZSI impedance network, the proposed controller guarantees robust and stable operation under varying levels of PV irradiance and temperature. The shoot-through duty ratio of the ZSI is obtained directly from the output of an MPPT algorithm and the measured PV and inductor currents. This strategy overcomes the disadvantages of the conventional approach such as the non-minimum phase at the dc side of the ZSI. It also eliminates the need to linearise the voltage/current characteristics of the PV arrays and ZSI model. The ac-side controllers consist of an outer proportionalâȂŞintegral voltage controller and an inner deadbeat current controller to achieve unity power factor and stable capacitor voltage in spite of grid voltage fluctuations. The efficacy of the proposed adaptive backstepping controller and the multi-loop control scheme is validated by offline and hardware-in-the-loop real-time simulations.

Impact of optimum power factor of PV‐controlled inverter on the aging and cost‐effectiveness of oil‐filled transformer considering long‐term characteristics

“…where Y wdn is attribution of the winding losses to the total, losses of the transformer, Y fe is attribution of the core losses to the total losses of the transformer, Y st is attribution of the stray losses to the total losses of the transformer, m wdn is winding material weight (kg), m fe is core weight (kg), m mp is tank and fittings weight (kg), m oil is the oil weight (kg), c wdn is winding material specific heat capacity (c Cu = 0.11 and c Al = 0.25 Wh/kg°C ), c fe is core specific heat capacity, (c fe = 0.13 Wh/kg°C ), c mp is tank and fitting specific heat capacity, (c mp = 0.13 Wh/kg°C ), c oil is the oil specific heat capacity, (c oil = 0.51 Wh/kg°C ) and O oil is the oil correction factor for the ONAF and OFAF cooling modes, (O oil = 0.86 Wh/kg°C ), The transformer oil thermal capacitance without external cooling is formulated as [21] C th − oil = m wdn × c wdn + m fe × c fe + m mp × c mp + m oil × c oil (10) Equation (7) is used to simulate TOT variations all day long for different scenario of PVI operation. Fig.…”

“…In fact, various studies in the literature are targeting unity PF operation for PVI [9][10][11]. In [9], the authors utilised PVI at unity PF for the optimal design of secondary distribution system.…”

Design and implementation of an optimal switching controller for uninterruptible power supply inverters using adaptive dynamic programming

“…Suitable number of random samples for x k s and t k are fed to (11) and least square is utilised for solving the equation for each W j . Interested readers are referred to [32] for further discussion on finding weights with least square.…”

“…There are many control approaches for this inverter such as proportional–resonant control [3], dead beat control [4], and hysteresis control [5] in the literature. Also, there has been investigations on more complicated designs to have a better quality output voltage such as sliding mode control [2, 6], repetitive control, [7], multi‐loop control, [8, 9], dq ‐frame current control [10], and adaptive control, [11]. Most of the control approaches in the literature are based on pulse‐width modulation (PWM) technique.…”

LMI‐based robust controller design and implementation for Z‐source inverters

“…To deal with these limitations, two‐stage VSIs and CSIs have been proposed, thereby yielding higher cost, lower efficiency and more complexity [2]. Both VSIs and CSIs are susceptible to open/short circuit problems of electromagnetic interference noise across the source [3], which can be managed using time delays for VSIs and overlap delays for CSIs at the expense of a slight distortion in output waveforms [4]. All these drawbacks have led to the emergence of various single‐stage inverters.…”