http://nova.newcastle.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:6066 Multilevel Converters (MCs) have emerged as a promising alternative to traditional two level converters. MCs use an arrangement of several semiconductors to synthesize high quality output voltage levels. Unfortunately, as a consequence of using more switching elements, MCs are, in general, more likely to be affected by faults, than their two level counterparts. In this paper, we propose a finite set constrained predictive control method for MCs, which is aimed at achieving robustness to failures in the semiconductors. We focus on three-phase multicell flying capacitor converters and show that, by carefully designing switching sequences, faults can be isolated from measurements provided by a single voltage sensor per phase. When faults occur, the proposed controller reconfigures the converter to provide to the load voltages which are similar to those obtained under normal, i.e., fault free, operating conditions. 2013-03-24T05:20:07.342Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:9161 Multilevel Converters (MCs) have emerged as a promising alternative to traditional two level converters. These topologies present a better output voltage quality due to the reduction of the voltage steps by increasing the voltage number levels. Within the MC family, flying capacitor converters present a special attraction due to the easy way to increase output voltage levels by adding cells. Recently model predictive control algorithms have reached a special interest in MCs applications. In particular, finite control set predictive control algorithms applied to flying capacitor converters have shown that it is possible to achieve a good performance in the control of capacitor voltages and output current. For that purpose, at each sample time the controller explores all the switching states and determines the optimal one to be applied. However, the number of switching states grow exponentially in relation to the number of cells. This increases the time that the algorithm takes to find the optimal switching state. In this paper we present an off-line strategy to reduce the number of switching states to be explored in a finite control set predictive algorithm by using only those which produce that the system state point towards to the reference. Moreover, a sampling period design is presented to guarantee that the system state remains inside of a positive invariant set. 2013-03-24T05:13:07.976Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:8678 Multilevel converters have emerged as a promising alternative to traditional two level converters, especially flying capacitor converters because of the fact that this topology requires only a main DC-link voltage and presents a easy way to increase the output voltage levels by increasing the number of cells. Unfortunately, a balancing of capacitor voltage is required. Recently, predictive control algorithms have been presented in order to control not only the output current but also to achieve good performance in the balancing of the capacitor voltages. For this purpose, it is necessary to know the state of these voltages generally taking a measurement of them, therefore the number of sensors required will be increased regarding the output voltage levels desired. This paper presents an estimation of the capacitor voltages using a discrete Kalman filter. This algorithm is employed to determinate correctly the system state and thus provides this information to the predictive controller in order to determinate the best switching combination to be applied in the next sample period. 2013-03-24T05:12:16.347Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:11254 Finite Control Set Model Predictive Control has emerged as a promising control technique for Power Converters due to the fact that the inherent non-linearity of these systems can be taken into account. In addition, this strategy directly provides the switching action to be applied to the converter; consequently, additional modulation stages are not required. Despite these advantages, stability for this class of predictive control technique remains as an open problem. In the present work, we provide insights into the closed-loop stability for the Finite Control Set Model Predictive Control. As an illustrative example, we apply these stability guidelines to a Multicell Converter. 2013-03-24T04:55:52.306Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:9217 This paper studies stability of Model Predictive Control for systems with a finite input alphabet. Since this kind of systems may present a steady-state error under closed-loop control, the forms is on stability in the sense of ultimate boundedness of solutions. To derive sufficient conditions for stability, two different approaches are presented. The first one approximates the finite input alphabet via saturation-control allowing us to analyze the problem from a robust control perspective. In the second approach, a direct analysis of the problem is carried out. The results thus obtained are shown to be less conservative regarding ultimate bounded set than those obtained via the robust control approach. 2013-03-24T04:51:24.405Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:10674 In the present work, we provide sufficient conditions for local practical stability for a specific class of power converters controlled via Finite Control Set Model Predictive Control which can be modeled as linear time-invariant systems with quantized input. In addition, we also establish bounds on the steady state behaviour of such systems. As illustrative examples, we apply our results to two converters, namely, a buck DC-DC converter, and a 2-level DC-AC inverter in a dq-coordinate frame. 2013-03-24T04:50:52.891Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:10678 In this paper, a finite control set model predictive controller for closed-loop control of an active front-end rectifier is presented. The proposed method operates in discrete time and does not require additional modulators. The key novelty of the control algorithm presented lies in the way dynamic references are handled. The control strategy is capable of providing suitable references for the source active power and the rectified voltage, without requiring additional control loops. Experimental results show that fast and accurate tracking of dynamic dc voltage and reactive power references can be achieved, while respecting the restrictions on maximum power levels of the rectifier. 2013-03-07T23:38:07.646Z ]]>