A novel analog maximum power point tracker for low‐cost and low‐power distributed PV systems

The main disadvantage of the voltage‐based maximum power point tracking (VMPPT) method is in the way the photovoltaic (PV) array is disconnected from the load when sampling open‐circuit voltage, which inevitably results in power loss. Another disadvantage is in case of rapid irradiance variation, where the duration between two successive samplings is too long, leading to considerable loss. To overcome these problems, this paper proposes a low‐cost analog VMPPT circuit that is designed on the basis of an ultralow‐power sample‐and‐hold circuit with the least hardware complexity, which has not been reported before. Furthermore, the method of determining the sampling frequency and time interval of the sampling mode is investigated. Experimental verification with a series of different PV power sources is likewise conducted. The experimental results confirm that the proposed MPPT circuit can operate over a wide range of PV power and can adapt quickly to the changing environment. The disconnection energy loss is reduced significantly, with a high system efficiency of up to 95.9%. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

On the terminal region of model predictive control for non‐linear systems with input/state constraints

This paper addresses the terminal region of model‐based predictive control (MPC) for non‐linear systems with control input and state constraints. Based on a stability condition of non‐linear MPC, a method to determine the terminal weighting term in the performance index and the terminal stabilizing control law to enlarge the terminal region and thus the domain of attraction of the non‐linear MPC is proposed. An LMI based optimization approach is developed to choose the terminal weighting item and fictitious terminal stabilizing control law so as to enlarge the terminal region of the non‐linear MPC method. The proposed method is illustrated by a numerical example and compares favourably with existing results. Copyright © 2003 John Wiley & Sons, Ltd.     

A transfer‐function approach to the analysis and design of zero‐power controllers for magnetic suspension systems

A transfer function approach is applied to the analysis and design of zero‐power controllers for magnetic suspension systems. The general structures of controllers achieving zero‐power control are derived for both current‐ and voltage‐controlled magnetic suspension systems. For the former type of system, there are two basic approaches: feeding back the velocity signal and introducing a minor feedback of the integral of the current. Both approaches are applicable to the latter type of system. In addition to them, the self‐sensing suspension also achieves zero‐power characteristics automatically. A direct synthesis method for zero‐power control is developed based on the analysis. Several experiments are carried out with a single‐degree‐of‐freedom model. The experimental results show the effectiveness of the proposed synthesis method. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(2): 67–75, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10049