Multi-converter electronic systems are becoming widely used in many industrial applications; therefore, the stability of the whole system is a big concern to the 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 the 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 the imprecision of a mathematical model of dc-dc converters. Aiming to effectively mitigate oscillations effects in the 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 the experimental data show that the proposed controller outperforms a classical control technique. INDEX TERMS Constant power load (CPL), multi-converter buck-buck system, parametric uncertainties, robust control based on Kharitonov rectangle, mitigation oscillations in multi-converter buck-buck system.

[1] The objective of this paper is to analyze the improvement in the performance of the particle filter by including a resample-move step or by using a modified Gaussian particle filter. Specifically, the standard particle filter structure is altered by the inclusion of the Markov chain Monte Carlo move step. The second choice adopted in this study uses the moments of an ensemble Kalman filter analysis to define the importance density function within the Gaussian particle filter structure. Both variants of the standard particle filter are used in the assimilation of densely sampled discharge records into a conceptual rainfallrunoff model. The results indicate that the inclusion of the resample-move step in the standard particle filter and the use of an optimal importance density function in the Gaussian particle filter improve the effectiveness of particle filters. Moreover, an optimization of the forecast ensemble used in this study allowed for a better performance of the modified Gaussian particle filter compared to the particle filter with resample-move step.

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.INDEX TERMS Constant power load (CPL), Chebyshev theorem, DC microgrid (MG), Kharitonov stability theorem, microgrid stability, robust control design.

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