a b s t r a c tThis paper aims at investigating the fuzzy adaptive control design for uncertain multivariable systems with unknown actuator nonlinearities and unknown control direction that possibly exhibit time-delay. The actuator nonlinearities involve dead-zone or backlash-like hysteresis, while the control direction is closely related to the sign of the control gain matrix. Two fuzzy adaptive controllers are proposed to deal with such an issue. The design of the first controller is mainly carried out in the free time-delay case, while the second control design is performed assuming that the system exhibits time-varying delays. Of practical interest, the adaptive compensation of the effects of the actuator nonlinearities requires neither the knowledge of their parameters nor the construction of their inverse. Furthermore, the lack of knowledge of the control direction is handled by incorporating in the control law a Nussbaum-type function. The effectiveness of the proposed fuzzy adaptive controllers is illustrated through simulation results.Crown
Abstract:In this paper, a new DC-link balancing method for a 7-level inverter fed by a photovoltaic system is proposed.The proposed redundant state technique is associated with selective harmonics elimination (SHE)-PWM instead of space vector (SV)-PWM. The switching angles related to the SHE are computed via the resultant theory method. Moreover, the study of this inverter is carried out on its equivalent matrix model. On the basis of this model, the link between the capacitor voltage, switching states, and load current is established. This allows understanding the switching redundancies' effect on the DC capacitor voltage balance. An algorithm is then developed to select the appropriate switching state, since there are 300 switching states and 720 unbalanced cases of the voltage capacitor. The proposed balancing method is tested in the case where the input DC inverter is provided by a photovoltaic generator (PVG) system and feeding an induction motor. The obtained results show that the 6 DC PVG capacitor voltages are kept balanced while cancelling the most undesirable harmonics row (5th, 7th, and 11th) in the inverter output voltage. Thus, using this cascade, photovoltaic supplying DC power can be amplified into high quality AC power.
SUMMARYThis paper concerns the development of a generalised algorithm of a novel space vector modulation (SVM) for N-level three-phase voltage source inverter. It is considering that the (NÀ1) DC input voltages of inverter are constant. The proposed method ensures initially the determination of the N 3 inverter switching states, the extraction of the redundancies to obtain 3N(N-1) þ 1 independent switching states and their organisation by sector in six distinct matrices W k with k ¼ (1, . . . ,6). After that, these matrices W k with k ¼ (2, . . . ,6) are ordered as the matrix W 1 related to the first sector. So, the research of the three closest vectors to the reference vector is carried out only in first sector and for this purpose, the equivalent reference vector is introduced which is resulting from the rotation by À(kÀ1)p/3 of the reference vector. The on-line choice of the three vectors (three switching states of the inverter) is based on the distances between the equivalent reference vector and some vectors located in its vicinity in the (a,b) plane of the first sector. Moreover, a simple method for the calculation of the duty cycles for these three switching states is proposed which exploits directly the three shortest distances associated to these three selected vectors. The sequence of these three switching states over a sampling period is investigated in view to reduce the harmonic contents of the voltage output. The application is carried out on an N-level three-phase voltage source inverter, where N is an arbitrary odd integer. Finally, the phase voltage and its harmonic spectrum provided by a three-phase N-level inverter with N ¼ (3,5,7,9,13,15) are presented to confirm the generalisation of this method.
In this paper, an observer-based adaptive feedback controller is developed for a class of chaotic systems. This controller does not need the availability of state variables. It can be used for tracking a smooth orbit that can be a limit cycle or a chaotic orbit of another system. This adaptive feedback controller is constructed with the aid of its H∞ control technique to achieve the H∞ tracking performance. Based on Lyapunov stability theorem, the proposed adaptive feedback control system can guarantee the stability of whole closed-loop system and obtain good tracking performance as well. To demonstrate the efficiency of the proposed scheme, two well-known chaotic systems, namely Chua's circuit and Lur'e system are considered as illustrative examples.
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