Showing papers by "Marco Liserre published in 2003"
19 Feb 2003
TL;DR: In this paper, a new active damping method that does not need the use of more sensors and that can be tuned using genetic algorithms is presented, which is used only for the optimum choice of the parameters of the filter and an on-line implementation is not needed.
Abstract: The use of a LCL-filter mitigates the switching ripple injected in the grid by a three-phase active rectifier. However stability problems could arise in the current control loop. In order to overcome them a damping resistor can be inserted, at the price of a reduction of the efficiency. On the contrary the use of the active damping seems really attractive but it is often limited by the use of more sensors respect to the standard control and by the complex tuning procedure. This paper introduces a new active damping method that does not need the use of more sensors and that can be tuned using genetic algorithms. It consists of adding a filter on the reference voltage for the converter's modulator. The tuning process of this filter is easily done, for a wide range of sampling frequencies, with the use of genetic algorithms. This method is used only for the optimum choice of the parameters of the filter and an on-line implementation is not needed. Thus the resulting active damping solution does not need new sensors or complex calculations. Moreover, in the paper particular attention is devoted to the dynamics of the system due to the introduction of the active damping.
310 citations
12 Oct 2003
TL;DR: The design of an active rectifier that does not need damping whether passive or active is described, which allows obtaining stability without the decrease of the efficiency typical for the passive damping methods or the increase of cost due to more sensors or more complex control algorithms.
Abstract: Industrial-LCL-based grid converters using an active rectifier need to be designed in view of robustness, stability and high efficiency In this paper the design of an active rectifier that does not need damping whether passive or active is described This allows obtaining stability without the decrease of the efficiency typical for the passive damping methods or the increase of cost due to more sensors or more complex control algorithms that is typical for the active damping methods This has been achieved with a careful choice of sensor position and of the passive elements in the LCL-filter In fact if the current sensors are on the grid side, rather than on the converter side, the current loop is much more near to the stability Moreover, if the grid side inductance is a fraction of the converter side one, the current loop is again much more near to the stability Thus, with a proper design the system can be made stable at some switching frequencies even without any damping
142 citations
TL;DR: In this article, the use of a passivity-based controller for a single-phase multilevel H-bridge rectifier suitable for traction applications is investigated, which achieves stability, unity power factor, good balancing between the two DC links, and satisfactory behavior even in the presence of load changes.
Abstract: The control of a single-phase multilevel H-bridge rectifier suitable for traction applications is considered. Such a converter often presents instability problems making difficult its design and uncertain its behavior. In this paper the use of a passivity-based controller is experimentally investigated. Such a controller achieves stability, unity power factor, good balancing between the two DC links, and satisfactory behavior even in the presence of load changes. A right choice of the damping parameters allows the fulfilling of system requirements in terms of DC-link voltage error and grid current distortion.
123 citations
23 Jun 2003
TL;DR: In this article, an overview of the three-phase voltage source active rectifiers and their applications is given, the basic control methods like phase and current controls are described, advanced control such as two-axis based, feedforward and active damping if an LCL-filter is used are also described.
Abstract: In this paper an overview of the three-phase voltage source active rectifiers and their applications is given. The basic control methods like phase and current controls are described. Advanced control such as two-axis based, feedforward and active damping if an LCL-filter is used are also described. The use of emerging control technologies such as direct power control, fuzzy control and soft computing like genetic algorithm are investigated. Particular attention is also paid to industrial problems such as cost, reduction of the number of sensors, non- ideal conditions, such as grid unbalance, LCL-filter design and EMI-issues. Finally, some tests results are presented and discussed in order to provide the theoretical analysis with a solid experimental basis.
65 citations
TL;DR: The results show that even without current sensors, the low-frequency distortion of the line currents and the DC voltage oscillations produced by the proposed system are very limited, ensuring performance similar to those of PI-based closed loop active rectifiers.
Abstract: This paper presents a current-sensorless active rectifier specifically designed for low-cost applications. Both the control and the modulation use fuzzy logic. A simple model of the system is given in order to explain the current feedforward control using fuzzy logic and the fuzzy-logic-based modulation, then, the new algorithm is analyzed looking for high performance even using small passive elements and low switching frequency. Performance are compared with those of a closed-loop proportional-plus-integral (PI)-based rectifier with space-vector modulation (SVM). This comparison has been carried out either considering the whole systems or a combination of their components (PI control + fuzzy modulation or fuzzy feedforward control + SVM). The results show that even without current sensors, the low-frequency distortion of the line currents and the DC voltage oscillations produced by the proposed system are very limited, ensuring performance similar to those of PI-based closed loop active rectifiers.
52 citations
15 Jun 2003
TL;DR: In this paper, a single phase AC/DC/AC converter feeding an induction motor for traction applications is described with the help of theoretical analysis and simulations, moreover some first partial experimental results are also shown.
Abstract: This paper deals with the design of a single phase AC/DC/AC converter feeding an induction motor for traction applications. A cascade of H-bridge cells has been used to obtain a multilevel conversion structure. The front-end rectifier should absorb current with low harmonic content to eliminate disturbances on the communication equipments and, more in general, to reduce electromagnetic pollution. Additional specification is the elimination of the transformer such as to reduce encumbrance and cost. A similar H-bridge cascade has been used in the motor side. In fact, supplying the motor by multilevel voltages greatly reduce the current harmonic distortion, enhancing induction motor performance, and the switching frequency, improving efficiency and extending component life. In this paper the design of the converter has been described with the help of theoretical analysis and simulations, moreover some first partial experimental results are also shown.
21 citations
09 Jun 2003
TL;DR: In this paper, the experimental results of an LCL-filter-based three-phase active rectifier are analyzed with the circuit theory approach, and a virtual circuit is synthesized in role of the digital controller and of the feedback filters to have a homogenous model that allows a sensitivity analysis, which is rigorous and straightforward for the industry.
Abstract: Three-phase active rectifiers based on the voltage source converter topology can successfully replace traditional thyristor based rectifiers or diode bridge plus chopper in interfacing dc-systems to the grid. However, if the application in which they are employed has a high safety issue or if there are other loads connected to the same point of common coupling (PCC), and sensitive to the harmonics produced by the switching of the converter, an LCL-filter has to be used. This kind of solution has been studied in theory but its sensitivity to the values of the LCL-filter passive elements employed, to the grid side stiffness and to the parameters of the controller has never been detailed. In this paper the experimental results of an LCL-filter-based three-phase active rectifier are analyzed with the circuit theory approach. A "virtual circuit" is synthesized in role of the digital controller and of the feedback filters to have a homogenous model that allows a sensitivity analysis, which is rigorous and straightforward for the industry.
18 citations
12 Oct 2003
TL;DR: The objective is to establish a link between the dead-beat control and the fuzzy logic control so as to provide dead- Beat control with more intelligence and to reduce the trial and error attempts for the fuzzy controller tuning.
Abstract: The half-bridge converter can be successfully employed as active filter in single-phase systems. The reduced number of semiconductor switches together with the need of balancing the capacitor voltages makes its control challenging especially if the aim is to have a simple digital algorithm easy to be implemented on an industrial microcontroller. Thus it has been chosen to adopt a fuzzy logic control the design of which is based on the dead-beat theory. The objective is to establish a link between the dead-beat control and the fuzzy logic control so as to provide dead-beat control with more intelligence and to reduce the trial and error attempts for the fuzzy controller tuning. The analysis developed and the consequent control include all the phenomena using no knowledge of the load, of the coupling filter or of the grid parameters thanks to the fuzzy logic computing. The proposed single phase active filter is controlled by the 7045F Hitachi microcontroller. Three techniques have been implemented in order to have a comparison: a classical hysteresis control and two predictive ones. The experimental results are discussed to better appreciate the impact of fuzzy logic in the design of controllers for low cost applications.
14 citations
09 Jun 2003
TL;DR: The problem of the balancing of the voltages of the two capacitors is investigated, aiming to do not use a separate controller but only a simple combination logic that exploits the redundancies of the configuration.
Abstract: The half-bridge converter can be successfully employed as an active filter in single-phase systems. The impact of this configuration becomes particularly relevant if the power level is limited and the cost reduction becomes a key point. In fact the half-bridge is made by only two bi-directional switches and two capacitors, being anyway able to ensure proper compensation even of the low order harmonics generated by a diode bridge. In this paper, the problem of the balancing of the voltages of the two capacitors is investigated, aiming to do not use a separate controller but only a simple combination logic that exploits the redundancies of the configuration. The simulation and the experimental results show that the voltages can not be controlled in all the conditions but this lack of performance does not affect very much the behavior of the active filter; the compensation of the selected harmonic currents is still good.
8 citations
02 Nov 2003
TL;DR: In this article, two passivity-based control (PBC) algorithms for the H-bridge-based multilevel rectifier are analyzed and compared, and the use of the passivitybased control properly fits stability problems related to this type of converter.
Abstract: This paper deals with a multilevel H-bridge based front-end rectifier to be used in high voltage high power applications The main control issue for such type of converter is stabilization In fact, voltage unbalancing across the distinct DC links can lead to system instability In this paper two passivity-based control (PBC) algorithms for the H-bridge-based multilevel rectifier are analysed and compared The use of the passivity-based control properly fits stability problems related to this type of converter Two approaches for the PBC design have been considered: the first one is developed considering the overall multilevel converter; the second one is developed by splitting the system into n subsystems and controlling them independently The partition of the multilevel converter is done on the basis of energy considerations The main advantage of the second approach is the separate control of the different DC-links and a more flexible loading capability
19 Feb 2003
TL;DR: In this paper, a passivity-based controller for a high voltage, high power single phase rectifier suitable for traction applications is proposed, which allows stability, unity-power factor, good balancing of the two DC links and a satisfactory transient behaviour even in presence of sudden load changes.
Abstract: This work addresses the control of a high voltage, high power single phase rectifier suitable for traction applications. A multilevel H-bridge single phase configuration has been considered. Such a converter often presents instability problems making difficult its design and uncertain its behaviour. This paper proposes a new controller based on the passivity-based approach. Such a controller allows stability, unity-power factor, good balancing of the two DC links and a satisfactory transient behaviour even in presence of sudden load changes. A different choice of the damping parameters allows fulfilling the system requirements in terms of reduced DC link voltage error or low grid current distortion or to find an optimum trade-off between them. The better performance in comparison with a PI are demonstrated.
23 Jun 2003
TL;DR: The design of the controller for a single phase rectifier, which represents the last generation interface between utility and DC power systems, has been fully investigated with the help of theoretical analysis and experimental results are shown.
Abstract: This work is focused on the design of the controller for a single phase rectifier, which represents the last generation interface between utility and DC power systems. Such kind of front-end converter allows mitigating harmonic power quality problems caused by traditional diode bridge rectifiers. This converter should absorb current with low harmonic and near unit power factor, moreover it should allow power reversal. In this paper, the design has been fully investigated with the help of theoretical analysis and experimental results are shown.
02 Nov 2003
TL;DR: In this article, two different predictive controllers are compared for active filtering, the first controller aims to lower the switching frequency and the second one aims to the minimum possible current error and is based on a simpler algorithm.
Abstract: Predictive controllers can be successfully adopted for active filter due to their fast response and simple algorithm that allows a short execution time In this paper two different predictive controllers are compared The first controller aims to lower the switching frequency; the second one aims to the minimum possible current error and is based on a simpler algorithm The two controllers are analyzed taking into consideration their digital implementation, via simulation and experimental results