In recent years, dc microgrid (MG) is increasing rapidly in electric power grids and other isolated systems, integrating more efficiency and suite better some of the renewable energy sources, storage units, and dc loads. However, dc MG stability analysis becomes a challenge when constant power loads (CPLs) are applied to dc bus, which introduces destabilizing effects in the system due to its negative impedance characteristics. This paper presents a novel robust controller, based on linear programming based on the Chebyshev theorem as a robust control technique considering the Kharitonov’s theorem that ensures the minimization of the total deviation from the desired performance in a closed-loop system, specified by a family of characteristic polynomials. The purpose of the proposed controller is to tightly regulate the dc bus voltage, ensuring MG stability due to the effects of power variation on CPLs. The simulation and experimental tests are performed by using a MATLAB/Simulink simulator and a developed prototype of the DC MG system, respectively, to ratify the robustness and effectiveness of the proposed method of robust controller design.

Multi-converter electronic systems are becoming widely used in many industrial applications; therefore, the stability of whole system is a big concern to real-world power supplies applications. A multi-converter system comprised of cascaded converters has a basic configuration that consists of two or more converters in series connection, where the first is a source converter that maintains a regulated DC voltage on the intermediate bus while remaining are load converters that convert the intermediate bus voltage to tightly regulated outputs for the next system stage or load. Instability in cascaded systems may occur due to the constant power load (CPL), which is a behavior of the tightly regulated converters. CPLs exhibit incremental negative resistance behavior causing a high risk of instability in interconnected converters. In addition, there are other problems apart from the CPL, e.g., non-linearities due to the inductive element and uncertainties due to imprecision of mathematical model of DC-DC converters. Aiming to effectively mitigate oscillations effects in output of source converter loaded with a CPL, in this paper, an interval robust controller, by Linear Programming based on Kharitonov Rectangle, is proposed to regulate the output of source converter. Several tests were developed by using an experimental plant and simulation models, when the multi-converter buck-buck system is subjected to a variation of power reference. Both simulation and experimental results show the effectiveness of the proposed controller. Furthermore, the performance indices computed from experimental data show that the proposed controller outperforms classical control technique.

This study presents the design and evaluation of robust controllers, based on linear programming, Kharitonov's theorem and Chebyshev's theorem, in order to enhance the performance of a typical structure of multi-stage converters present in direct current (dc) systems. In such electric power distribution systems, point-of-load converters act as a constant power load (CPL), which introduces a destabilizing nonlinear effects to their supply bus voltage. The multi-stage converter system uses a simplified scheme based on cascaded converter, which is comprised of two dc-dc buck converter in series connection. The robust controllers evaluated overcome the negative incremental impedance instability problem due to CPL, which causes a high risk of instability in interconnected converters. Thereby, the robust controllers evaluated ensure robust control performance and stability with a minor performance degradation compared to a conventional controller when the cascaded converter system is subjected to parametric uncertainties. The control methodologies evaluated are applied in both dc-dc buck converters. Assessments on the performance of the control methodologies evaluated are conducted. Experimental validations on a 150-W dc-dc cascaded converter system test board are carried out to verify the theoretical claims.

This study presents the design and evaluation of a robust controller, based on frequency-domain, in order to enhance the performance of dc-dc power converters under parametric uncertainties. This robust control approach takes into account all possible uncertainties in the system such as load and input voltage variations. Thereby, the robust controller design is based on the constraints of the gain and/or phase margins delimited by these uncertainties in order to ensure robust performance and stability of the system. Assessments on the performance of the proposed robust control are conducted. Comparisons with other control methods are also provided. Experimental validations on a dc-dc buck converter system test board are carried out to verify the theoretical claims.

The abilities of Augmented Reality to overlay learning materials with contextual dynamic information and of software simulations to allow rapid and safe exploration of complex engineering concepts have already been established as beneficial in education. Access to both technologies in the classroom has been rather limited due to costs and hardware requirements. With the intention to bring these two technologies closer to engineering students, we created Virtual Circuits: a low-cost simulator app of electrical circuits designed for the classroom and autonomous study. Virtual Circuits requires only a smart-phone and a set of plastic tokens and, with the help of Augmented Reality and a simulation engine, it allows electrical engineering students to quickly explore complex concepts in their field. In this article we present the Virtual Circuits app and the results of our first field test in a real electrical engineering classroom at our university. The collected feedback from students was overwhelmingly positive hinting at tangible educational benefits and improvements in future versions of our app.

This paper presents a system designed to monitor at real-time the hydration index of patients suffering from renal diseases and that are forced to undergo regular dialysis sessions. The system comprises the smart electrode (SE)-skin interface and the SE stimulation and readout electronics. This medical system combines the tetra polar multi-frequency bioimpedance analysis with the four-electrode focused impedance measurement (FIM). When compared to the Keysight E4980A, the SE is able to measure impedances with 3% of maximal relative error. Measurements obtained by monitoring patients during dialysis sessions show the close correlation between the removed fluid and the hydration index H.