Robust Variable-Step Perturb-and-Observe Sliding Mode Controller for Grid-Connected Wind-Energy-Conversion Systems

In order to extract efficient power generation, a wind turbine (WT) system requires an accurate maximum power point tracking (MPPT) technique. Therefore, a novel robust variable-step perturb-and-observe (RVS-P&O) algorithm was developed for the machine-side converter (MSC). The control strategy was applied on a WT based permanent-magnet synchronous generator (PMSG) to overcome the downsides of the currently published P&O MPPT methods. Particularly, two main points were involved. Firstly, a systematic step-size selection on the basis of power and speed measurement normalization was proposed; secondly, to obtain acceptable robustness for high and long wind-speed variations, a new correction to calculate the power variation was carried out. The grid-side converter (GSC) was controlled using a second-order sliding mode controller (SOSMC) with an adaptive-gain super-twisting algorithm (STA) to realize the high-quality seamless setting of power injected into the grid, a satisfactory power factor correction, a high harmonic performance of the AC source, and removal of the chatter effect compared to the traditional first-order sliding mode controller (FOSMC). Simulation results showed the superiority of the suggested RVS-P&O over the competing based P&O techniques. The RVS-P&O offered the WT an efficiency of 99.35%, which was an increase of 3.82% over the variable-step P&O algorithm. Indeed, the settling time was remarkably enhanced; it was 0.00794 s, which was better than for LS-P&O (0.0841 s), SS-P&O (0.1617 s), and VS-P&O (0.2224 s). Therefore, in terms of energy efficiency, as well as transient and steady-state response performances under various operating conditions, the RVS-P&O algorithm could be an accurate candidate for MPP online operation tracking.     

高超音速飞行器鲁棒控制器设计

军事变革和信息化战场环境的变化,促使空天攻防作战成为未来作战的战场之一。临近空间高超音速飞机和导弹会对传统攻防体系带来颠覆性冲击。复杂环境对高超音速飞行器控制技术的发展提出了严峻的挑战,本文针对吸气式高超音速飞行器在飞行包线内动态特性易变、稳定性较差、不确定因素较多以及对外界扰动敏感以及整个执行机构控制能力弱和动态特性低等的控制问题,首次提出了一种能同时抑制扰动和模型不确定性的基于优化控制的鲁棒控制方法,保证飞行器能得到很好地控制,快速响应环境变化并很快回到稳定飞行的状态。采用线性矩阵不等式方法来设计飞行控制系统,给出了不确定系统稳定的条件, 将反馈稳定问题转化为了一个最优控制问题。同时将闭环极点在一定区域内参与优化,进一步提高优化效率。与文献方法仿真对比结果证实了本文方法的优越性。     

Robust and Secure Method for Transmitting Binary Message Using Binary Chaotic Sequence

Unlike masked with analog chaotic sequence, digital information is masked with binary chaotic sequence with a method proposed by U. Parfitz and 2. Ergezinger (Phys. Lett. 198A (1994) 146). It is demonstrated by numerical simulations that both security and robustness of this communication method are improved. When considered as digital communication, the method is very robust to transmission errors.     

LMI-Based Delayed Output Feedback Controller Design for a Class of Fractional-Order Neutral-Type Delay Systems Using Guaranteed Cost Control Approach

In this research work, we deal with the stabilization of uncertain fractional-order neutral systems with delayed input. To tackle this problem, the guaranteed cost control method is considered. The purpose is to design a proportional–differential output feedback controller to obtain a satisfactory performance. The stability of the overall system is described in terms of matrix inequalities, and the corresponding analysis is performed in the perspective of Lyapunov’s theory. Two application examples verify the analytic findings.