Shahzad Ebrahim, Khan Adnan Umar, Iqbal Muhammad, Saeed Ahmad, Hafeez Ghulam, Waseem Athar, Albogamy Fahad R, Ullah Zahid
Department of Electrical Engineering, FET, International Islamic University, Islamabad 44000, Pakistan.
Research and Innovation Centre of Excellence (KIOS CoE), University of Cyprus, P.O. Box 20537, Nicosia 1678, Cyprus.
Sensors (Basel). 2022 Mar 25;22(7):2524. doi: 10.3390/s22072524.
This work investigates sensor fault diagnostics and fault-tolerant control for a voltage source converter based microgrid (model) using a sliding-mode observer. It aims to provide a diagnosis of multiple faults (i.e., magnitude, phase, and harmonics) occurring simultaneously or individually in current/potential transformers. A modified algorithm based on convex optimization is used to determine the gains of the sliding-mode observer, which utilizes the feasibility optimization or trace minimization of a Ricatti equation-based modification of H-Infinity (H∞) constrained linear matrix inequalities. The fault and disturbance estimation method is modified and improved with some corrections in previous works. The stability and finite-time reachability of the observers are also presented for the considered faulty and perturbed microgrid system. A proportional-integral (PI) based control is utilized for the conventional regulations required for frequency and voltage sags occurring in a microgrid. However, the same control block features fault-tolerant control (FTC) functionality. It is attained by incorporating a sliding-mode observer to reconstruct the faults of sensors (transformers), which are fed to the control block after correction. Simulation-based analysis is performed by presenting the results of state/output estimation, state/output estimation errors, fault reconstruction, estimated disturbances, and fault-tolerant control performance. Simulations are performed for sinusoidal, constant, linearly increasing, intermittent, sawtooth, and random sort of often occurring sensor faults. However, this paper includes results for the sinusoidal nature voltage/current sensor (transformer) fault and a linearly increasing type of fault, whereas the remaining results are part of the supplementary data file. The comparison analysis is performed in terms of observer gains being estimated by previously used techniques as compared to the proposed modified approach. It also includes the comparison of the voltage-frequency control implemented with and without the incorporation of the used observer based fault estimation and corrections, in the control block. The faults here are considered for voltage/current sensor transformers, but the approach works for a wide range of sensors.
本文研究了基于滑模观测器的电压源变换器型微电网（模型）的传感器故障诊断与容错控制。其目的是对电流/电压互感器中同时或单独出现的多种故障（即幅值、相位和谐波）进行诊断。采用一种基于凸优化的改进算法来确定滑模观测器的增益，该算法利用基于H无穷（H∞）约束线性矩阵不等式的Riccati方程修正的可行性优化或迹最小化。对故障和干扰估计方法进行了修正和改进，对先前工作中的一些内容进行了校正。还给出了所考虑的故障和受扰微电网系统观测器的稳定性和有限时间可达性。对于微电网中出现的频率和电压骤降所需的常规调节，采用基于比例积分（PI）的控制。然而，同一个控制模块具有容错控制（FTC）功能。这是通过引入一个滑模观测器来重构传感器（互感器）的故障实现的，这些故障在校正后被馈送到控制模块。通过给出状态/输出估计、状态/输出估计误差、故障重构、估计干扰和容错控制性能的结果，进行了基于仿真的分析。针对正弦、恒定、线性增加、间歇、锯齿和随机等常见的传感器故障类型进行了仿真。然而，本文包括了正弦型电压/电流传感器（互感器）故障和线性增加型故障的结果，而其余结果是补充数据文件的一部分。与所提出的改进方法相比，对先前使用的技术估计的观测器增益进行了比较分析。它还包括在控制模块中，有无基于所使用的观测器的故障估计和校正的情况下，对实施的电压 - 频率控制的比较。这里的故障是针对电压/电流传感器互感器考虑的，但该方法适用于广泛的传感器。
