Ignazio Marongiu

Second-order sliding-mode control of DC drives

One of the most recent topics in variable-structure systems theory is represented by the second-order sliding-mode control (2-SMC) methodology. This approach guarantees the same robustness and dynamic performance of traditional first-order SMC algorithms, and, at the same time, attenuates the chattering phenomenon, which is the main drawback in the actual implementation of this technique. In the present paper, a recently-proposed 2-SMC algorithm is used to synthesize a robust dc-drive control system which does not require current feedback and demands only rough information about the actual motor parameters. Stability and performance are analyzed, and an experimental comparison with a proportional-integral-based control scheme is reported.

Robust speed and torque estimation in electrical drives by second-order sliding modes

This paper presents the synthesis and practical implementation of a robust digital differentiator that provides the first and second derivative of a sampled smooth signal. The robustness of the proposed digital device, based on second-order sliding-modes (2-SMs), is analyzed with respect to measurement errors. Experimental results on an induction motor (IM) drive show that fast and accurate estimates of speed and torque can be obtained in several operating conditions by double differentiation of the encoder position measurement.

Real-Time Control Strategy of Energy Storage Systems for Renewable Energy Sources Exploitation

An optimal energy storage system (ESS) management procedure devoted to full renewable energy sources (RESs) exploitation is presented in this paper. It consists of an appropriate scheduling procedure and a real-time control strategy, which both aim to increase the RES penetration level as much as possible. In particular, the one-day-ahead scheduling procedure synthesizes the combined RES-ESS energy production profile with the aim of minimizing the RES energy production curtailments by means of ESS energy buffering. The real-time control strategy is developed in order to track the scheduled profile as well as possible by mitigating forecasting errors, thus improving RES reliability. The worth and effectiveness of the proposed management procedure is verified through a wide simulation study, which is carried out by means of the Matlab software package.

Operating Constraints Management of a Surface-Mounted PM Synchronous Machine by Means of an FPGA-Based Model Predictive Control Algorithm

A model predictive control algorithm (MPC) suitable for Surface-Mounted Permanent Magnet Synchronous Machines (SPMs) is presented in this paper. It is based upon an accurate discrete-time model of the drive, accounting for both voltage saturation and current limitation constraints. It aims to properly manage these constraints in order to guarantee a good exploitation of both transient and steady state SPM performances, especially over flux-weakening operation. The effectiveness of the proposed MPC is first validated by a simulation study, in which the sensitivity of the proposed MPC against un-compensated inverter un-idealities and parameter uncertainties is properly highlighted and discussed, as well as the effects of sudden load torque variations. Then, an experimental study is performed on a radial-flux SPM driven by a Field Programmable Gate Arrays (FPGA) control board. The performances achievable by the proposed MPC are compared with those obtained by a conventional PI-based control system in order to highlight the improvements, especially regarding transient and flux-weakening operation.

Discrete-Time Parameter Identification of a Surface-Mounted Permanent Magnet Synchronous Machine

A novel online discrete-time parameter identification algorithm suitable for surface-mounted permanent magnet synchronous machines (SPMs) is presented in this paper. It is developed by means of the model reference adaptive system technique and the Popov Hyperstability Criterion in order to identify SPM discrete-time model parameters. In particular, good accuracy of discrete-time parameters is required by digital control systems, particularly by predictive control algorithms, which present a low robustness against parameter mismatches. Hence, an extensive simulation study is first carried out in the Matlab Simulink environment with the aim of testing the effectiveness and robustness of the proposed identification algorithm against inverter unidealities. Then, the proposed identification procedure is experimentally validated on a predictive controlled radial-flux SPM, driven by a field programmable gate arrays control board.

Optimization of harmonic performances in multilevel converter structures

In recent years, multilevel power converters have been gaining more and more interest in high voltage and high power conversion applications. Within this scenario, a very interesting approach lies in the use of semiconductors with different voltage ratings and different switching characteristics. For this aim, both GTOs and IGBTs could be employed, but a better technological solution surely lies in the use of IGBTs only, with different voltage ratings. Optimized multilevel power converter structures, based on the multi-point-clamped (MPC) concept or on the series connection of H-bridge inverters, could then be developed, exploiting the possibilities arising from the use of different voltage levels. The authors have developed an optimal modulation strategy that uses the redundant switching configurations of the MPC converter structure to achieve an increment of the output voltage level number. The novel approach proposed permits a reduction of the harmonic content of the voltage/current waveforms and an interesting optimization of the switching stresses of power semiconductor devices.

Direct torque and flux control of induction motor drives

A general approach to direct torque and flux control of an induction motor fed by a VSI is presented in the paper. The inverter switching patterns are generated as a function of the reference values of both the electromagnetic torque and of the controlled flux. In particular, the proposed control algorithm is independent of which kind of flux is controlled-rotor or stator. The results obtained by means of a real-time simulation show that the proposed control strategy allows very fast and accurate response of the drive.

Vehicle-to-Grid Technology: State-of-the-Art and Future Scenarios

An overview of V2G (vehicle-to-grid) technology is presented in this paper. It aims to highlight the main features, opportunities and requirements of V2G. Thus, after briefly resuming the most popular charging strategies for PEVs (plug-in electric vehicles), the V2G concept is introduced, especially highlighting its potentiality as a revenue opportunity for PEV owners; this is mainly due to the V2G ability to provide ancillary services, such as load leveling, regulation and reserve. Such solutions have been thoroughly investigated in the literature from both the economic and technical points of view and are here reported. In addition, V2G requirements such as mobility needs, charging stations availability and appropriate PEV aggregative architectures are properly taken into account. Finally, future developments and scenarios have also been reported.

Electric Vehicle energy storage management for Renewable Energy Sources exploitation

A novel management strategy for Electric Vehicles (EVs) storage systems is proposed in this paper. It aims to enhance the Renewable Energy Sources (RES) exploitation hour by hour, but prioritizing the EV mobility requirements. A mathematical modelling of the mobility system is firstly developed in order to estimate, hour by hour, the amount of EVs available to exchange energy with the electric grid, together with the average state of charge of their corresponding batteries. Then, a management strategy is properly introduced in order to increase the RES hourly energy production as much as possible, providing ancillary services too. The proposed management system is properly validated by means of a simulation study referred to a weakly interconnected power system, which is characterized by a strong RES penetration level too. The simulation results highlight the effectiveness of the proposed management strategy and the potentiality of the EVs storage systems in enhancing the RES exploitation.

Predictive Control of Synchronous Reluctance Motor Drive

A predictive digital control algorithm, suitable for synchronous reluctance motor drives, is presented in the paper. The proposed algorithm, which is a direct digital control one, is implemented in rotor coordinates. It is a recursive algorithm which allows the imposition of the reference values of d and q current components. The digital control system directly synthesizes an output vector which imposes the timing control of the inverter by means of on/off state of the switches, thus avoiding the implementation of the traditional PI controllers and PWM technique. Due to the time required for the execution of the algorithm, the vector control has to be imposed with a delay of one sampling time. This drawback can be overcome by using very fast processors like FPGAs or by introducing the observed quantities instead of the measured ones in the recursive algorithm. Both the delayed control and the latter solution are considered in the paper. A computer simulation study, using the Matlab Simulink tool, is conducted on the drive. The simulation results are compared also with those obtained by simulating the traditional drive. The simulation study and the results comparison show the good performance of the proposed control algorithm.