جستجوی مقالات مرتبط با کلیدواژه « stability analysis » در نشریات گروه « برق »

Solar energy, as an unlimited, clean and cost-effective source of energy, can be converted into electrical energy using photovoltaic arrays. In this paper, design, control and stability analysis of inverter-based power conditioner, which is connected to the low voltage grid via LCL filter, are presented to manage power injection of the photovoltaic system. Since the PV arrays generated voltage is lower than the grid voltage, DC-DC converter is utilized to increase the PV output voltage. The LCL filter is employed to improve injected current quality and to reduce interface inverter output voltage distortions. This filter can cause to occur resonance and system instability. Current double feedback control method, which is used inverter side and grid side currents as feedback current, is proposed to damp the resonance and to improve harmonic eliminations. The systematic design procedure of the proposed control strategy parameters is presented considering resonance damping, stability margin and grid-connected features to ensure the system stability in a non-ideal and weak grid. The proposed power conditioner system is simulated in MATLAB/Simulink to verify model performance and proposed control method. The simulation results show good performance of the proposed system in managing PV power flow into the grid, high quality of the injected current, and system stability against the grid impedance change disturbances.

This paper deals with the optimal state observer of non-linear systems based on a new strategy. Despite the development of state prediction in linear systems, state prediction for non-linear systems is still challenging. In this paper, to obtain a future estimation of the system states, initially Taylor series expansion of states in their receding horizons was achieved to any specified order and then an analytic solution was developed for the prediction error problem, which resulted in a closed-form for non-linear optimal observer. In the proposed observer, the observer gain was optimally chosen among gains obtained from the analytic solution of the prediction error problem and satisfied the stability condition. Finally, the qualitative simulation results showed the effectiveness of the proposed method in the state observation.

In this paper a modified adaptive robust composite control scheme for fully-constrained cable-driven robots with elastic cables is presented here. At first, an adaptive control algorithm based on sliding mode control method is introduced for rigid robots using internal force concept to ensure that all cables are remained in tension through the whole workspace. Then, the dynamic equations are turned into singularly perturbed form to develop the adaptive controller of rigid robots to be used for robots with elastic cables. To improve the stability and robust performance of the system as an achievement of the paper, a correction term is added to the adaption law of rigid robots and the stability analysis of the system is conducted using the Lyapunov theory. Finally, while the simulation results are given for intended robot with elastic cables, performance of the proposed algorithm against the uncertainty of dynamic parameters is proved and by comparing the performance of the proposed control scheme in this paper with those related to the initial robust adaptive controller a remarkable improvement in the accuracy of the desired path tracking confirmed.

In this paper, a new algorithm in order to increase the satisfaction of terminal constraints in the predictive control problem is presented. In this algorithm, by extracting mathematical relations, the terminal constraints are transferred from the final moment to the current moments. In each iteration, this transformation takes place in the optimization problem. At each moment of optimization, a new expression is obtained in terms of control inputs in each of the finite prediction control horizons. The equation of this transfer constraint is derived based on the variable discrete equations with the time of the controlled process and its execution at any moment fulfills the final constraints of the problem. This new algorithm, after extracting its mathematical relationships, is used to track the path of a robot with terminal constraints, and its performance is demonstrated using robot dynamics simulations. Also, the stability analysis of the proposed controller is performed by writing an appropriate cost function and applying Lyapunov theorem.

According to the global prevalence of coronavirus (COVID-19) pandemic, mathematical models can predict and control the dynamic behavior of the pandemic. Therefore, in this study, a comprehensive model is considered to examine the trend of COVID-19 based on Susceptible, Exposed, Infected (Symptomatic and Asymptomatic), and Recovered individuals. In the absence of a curative treatment or vaccination campaign, the group of "quarantined people" is added to the model. Then, a positivity analysis of states is examined, and the threshold criterion is determined. The equilibrium points (disease-free and endemic) are also calculated, and their stability is investigated using the Jacobin matrix. The quarantine rate is regulated as the only control input using the fuzzy sliding mode controller. The efficiency of the controller is also investigated in the presence of uncertainty in model parameters. Also, the impact of the infected community on other communities, considering the controller, will be examined. Finally, the performance and efficiency of the proposed controller are evaluated.

Wind turbines as a renewable energy are installed and operated as wind farms in various locations with windy climates.  Connecting micro grids to wind turbines can lead to improved power generation and transmission to distribution networks. Therefore, formulating and configuring the micro-grid connected to the wind turbine requires accurate examination of the configuration of the micro-grid with wind power generation system along with variable speed with wind energy determination and error estimation for stability analysis and control by means of error detection. The aim of this study is to use fuzzy logic control systems and then identify the faulty areas for stability analysis with the Extended Kalman Filter (EKF). In fact, I can provide our services to our users by using consulting services and providing linear services, and we can do it using fuzzy logical services. Simulation results represented improved error estimation and stability analysis and other evaluation criteria.

Optoelectronic oscillators (OEOs) use a long optical fiber delay line as a very high-Q resonator to produce very low phase noise RF/microwave oscillations. Computing all the oscillation modes and stability analysis of them in the frequency domain, in case of having wide band RF/microwave filters in their oscillation loops, is addressed in the current paper. Such a large bandwidth can be used to produce harmonic components of the oscillation or to give the possibility of sweeping the oscillation frequency in a large bandwidth by using a phase shifter and a small fiber. It is shown that in the case of OEOs with wideband RF filters, considering only the fundamental harmonic, instead of adequate number of them, may result in noticeable error in steady state computations as well as erroneous judgment about the stability of the modes. A relaxation algorithm is introduced for computing the oscillation modes. Stability analysis is performed by implementing the Nyquist stability test on a spectral domain system of equations governing the perturbations. The validity of the analysis approaches of this paper are verified by comparing their results against the time-consuming time-domain integrations.