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In this paper, a Backstepping Global Integral Terminal Sliding Mode Controller (BGITSMC) with the view to enhancing the dynamic stability of a hybrid AC/DC microgrid has been presented. The proposed approach controls the switching signals of the inverter, interlinking the DC-bus with the AC-bus in an AC/DC microgrid for a seamless interface and reg...
In a stand‐alone microgrid, voltage control is an important issue to keep the grid balanced under unbalanced load conditions. The other important challenges in microgrids include handling the neutral to the ground voltage (NGV) as well as total harmonic distortion (THD) under its limits due to the IEEE standards. A four‐leg inverter is the best cho...
The control of load frequency is an important
power system area. This paper proposes a
higher order sliding mode (HOSM) controller for load
frequency control (LFC) of two area thermal interconnected
power system with nonlinearities. The proposed
second order sliding mode controller (SMC) utilizes
twisting algorithm. When a disturbance occurs on sys...
Citations
... However, a change in the system that is far from this operational point causes method inefficiency. In order to mitigate the negative effects of CPL, many nonlinear techniques including the backstepping method [11], Sliding Mode (SM) [12,13], synergetic control [14], Passivity-Based Control (PBC) [4,[15][16][17], and Model Predictive Control (MPC) [18,19] have been introduced. In [11], an adaptive backstepping SM strategy was proposed. ...
... However, an additional current sensor was required to measure the load current. In [13], an SM controller was used to eliminate CPL instability. Besides the appropriate dynamic response and superior performance for sudden and big changes in output, the switching frequency was variable and caused output capacitor voltage ripple due to the use of hysteresis modulation. ...
This paper proposes an adaptive nonlinear control strategy to eliminate the instability problem of buck converters in DC microgrids (DCMG) considering constant power load (CPL). The strategy includes an Adaptive Passivity-Based Controller (PBC) and an Adaptive Extended Kalman Filter (AEKF). The proposed AEKF performs faster and more accurately than the conventional EKF and adjusts the covariance matrices adaptively. Furthermore, this AEKF directly estimates the unknown CPL power supplied by the converter and prevents the number of measurement sensors from increasing. Hence, PBC ensures system stability alongside AEKF. The controller guarantees Lyapunov stability and fast dynamic response in the presence of uncertainties and perturbations compared to other nonlinear methods. MATLAB simulations and laboratory implementation are provided to confirm the performance and robustness of the proposed control strategy and validate the analysis.
... Therefore, total of eight operation modes are expected to be considered as a finite-set constraint. The switching state vector and the AFE rectifier voltage are expressed in (3), and the resulting voltage vector of the AFE with v dc is determined by the states of the switches as in (4). ...
Although onboard dc power systems bring values for the power and propulsion system of the future hybrid ships, the main barrier for the development of such systems for large-scale vessels is the technical operational issues, such as stability and power quality and how to satisfy the related standards and regulations. In the advanced ship power systems, the conventional diode rectifiers are being replaced with active front-end (AFE) rectifiers providing the control flexibility but at a higher cost. However, to make such devices more profitable, the ship control system can be reconfigured to unlock the potentials of AFEs for the general system stability. This article is dealing with the stability issue of hybrid dc power systems proposing a predictive control approach to improve the voltage regulation and better use of converters. The proposed method replaces the conventional direct power control (DPC) of AFE rectifiers with a model predictive control (MPC) and integrates the dc–dc converters in the same control platform. In this method, optimal control commands for the rectifiers and the dc–dc converter are calculated by the predictive control to minimize the dc bus voltage fluctuations, especially under the fast load changes. The controller is then extended to regulate the load sharing between the different energy units. The effectiveness of the proposed method is evaluated in simulation with a typical shipload profile, as well as a real ship profile, which has several operating modes, such as steep load increase & decrease, high speed, and maneuvering operation. The performance of the proposed control strategy is compared with conventional controllers, and the results show that the new method can provide significant advantages in terms of fast and stable control performance, as well as the steady-state voltage regulation and enhancing the power smoothing function of the battery. Laboratory experimental data are also used for validation.
The Super-Twisting Algorithm is employed to control the voltage of a Bidirectional DC-to-DC Converter of an on-board propulsion system in presence of large load variations. The Bidirectional DC-to-DC Converter is modeled using average value modeling, and it is shown by an alternative approach that the zero dynamics for the converter topology supplying a Constant Power Load are unstable with the DC bus voltage as output, and stable for the inductor current as output. Here, a derivation of the controller gains is presented based on the average model of the system. The gains are described with respect to the inductor current and its bounded perturbations. The performance of the proposed controller is compared to a conventional cascaded PI controller, and exhibits strong robustness with respect to external system variations.
