Luca Tarisciotti

Advanced Power Electronic Conversion and Control System for Universal and Flexible Power Management

The future electricity network has to be able to manage energy coming from different grids as well as from renewable energy sources (RES) and other distributed generation (DG) systems. Advanced power electronic converters can provide the means to control power flow and ensure proper and secure operation of future networks. This paper presents analysis, design, and experimental validation of a back-to-back three-phase ac-dc-ac multilevel converter employed for universal and flexible power management (UNIFLEX-PM) of future electrical grids and its advanced control technique. The proposed system has been successfully tested for bidirectional power flow operation with different grid operating conditions such as voltage unbalance, frequency variation, harmonic distortion, and faults due to short circuits.

Modulated Model Predictive Control for a Seven-Level Cascaded H-Bridge Back-to-Back Converter

Multilevel converters are known to have many advantages for electricity network applications. In particular, cascaded H-bridge converters are attractive because of their inherent modularity and scalability. Predictive control for power converters is advantageous as a result of its applicability to discrete system and fast response. In this paper, a novel control technique, named modulated model predictive control, is introduced with the aim to increase the performance of model predictive control. The proposed controller addresses a modulation scheme as part of the minimization process. The proposed control technique is described in detail, validated through simulation and experimental testing, and compared with dead-beat and traditional model predictive control. The results show the increased performance of the modulated model predictive control with respect to the classic finite control set model predictive control in terms of current waveform total harmonic distortion (THD). Moreover, the proposed controller allows a multi-objective control, with respect to dead-beat control that does not present this capability.

Modulated Model Predictive Control for a Three-Phase Active Rectifier

Model predictive control (MPC) has a number of desirable attributes which are difficult to achieve with classical converter control techniques. Unfortunately, the nature of power electronics imposes restriction to the method, as a result of the limited number of available converter states. This, combined with the spread spectrum nature of harmonics inherent with the strategy, complicates further design. This paper presents a method for removing this characteristic without compromising the desirable functionality of predictive control. The method, named modulated MPC, is applied to a two-level three-phase converter and compared with a number of similar approaches. Experimental results are used to support theoretical analysis and simulation studies.

Active DC Voltage Balancing PWM Technique for High-Power Cascaded Multilevel Converters

In this paper, a dedicated pulse width modulation (PWM) technique specifically designed for single-phase (or four wire three-phase) multilevel Cascaded H-Bridge Converters is presented. The aim of the proposed technique is to minimize the DC-Link voltage unbalance, independently from the amplitude of the DC-Link voltage reference, and compensate the switching device voltage drops and on-state resistances. Such compensation can be used to achieve an increase in the waveform quality of the converter. This is particularly useful in high-power low supply voltage applications where a low switching frequency is used. The DC-Link voltage balancing capability of the method removes the requirement for additional control loops to actively balance the DC-Link voltage on each H-Bridge, simplifying the control structure. The proposed modulation technique has been validated through the use of simulation and extensive experimental testing to confirm its effectiveness.

A new predictive control method for cascaded multilevel converters with intrinsic modulation scheme

Multilevel Converters are known to have many advantages for electricity network applications. In particular Cascaded H-Bridge Converters are attractive because of their inherent modularity and scalability. Predictive control for power converters is advantageous as a result of its applicability to discrete system and fast response. In this paper a novel control technique, named Modulated Model Predictive Control, is introduced with the aim to increase the performances of the Predictive control. The proposed controller is described in detail and validated through simulation and experimental testing, in comparison with Dead-Beat and Model Predictive Control.

Multiobjective Modulated Model Predictive Control for a Multilevel Solid-State Transformer

Finite control set model predictive control (FCS-MPC) offers many advantages over more traditional control techniques, such as the ability to avoid cascaded control loops, easy inclusion of constraint, and fast transient response of the control system. This control scheme has been recently applied to several power conversion systems, such as two, three, or more level converters, matrix converters, etc. Unfortunately, because of the lack of the presence of a modulation strategy, this approach produces spread spectrum harmonics which are difficult to filter effectively. This may result in a degraded power quality when compared to more traditional control schemes. Furthermore, high switching frequencies may be needed, considering the limited number of switching states in the converter. This paper presents a novel multiobjective modulated predictive control strategy, which preserves the desired characteristics of FCS-MPC but produces superior waveform quality. The proposed method is validated by experimental tests on a seven-level cascaded H-bridge back-to-back converter and compared to a classic MPC scheme.

A modulated model predictive control scheme for a two-level voltage source inverter

Traditional finite-set model predictive control (FS-MPC) techniques are characterized by a variable switching frequency which causes noise as well as large voltage and current ripple. In this paper a novel predictive control strategy with a fixed switching frequency for a voltage source inverter called as modulated model predictive control (M2PC) is proposed, with the aim of obtaining a modulated waveform at the output of the converter. The feasibility of this strategy is evaluated using simulation results to demonstrate the advantages of predictive control, such as fast dynamic response and the easy inclusion of nonlinearities. Finally, a modified strategy is proposed in order to naturally reduce the common mode voltage. The constraints of the system are maintained but the performance of the system in terms of power quality is improved when compared to FS-MPC.

Model Predictive Control for Shunt Active Filters With Fixed Switching Frequency

This paper presents a modification to the classical Model Predictive Control (MPC) algorithm and its application to active power filters. The proposed control is able to retain all the advantages of a finite control set MPC while improving the generated waveforms harmonic spectrum. In fact, a modulation algorithm, based on the cost function ratio for different output vectors, is inherently included in the MPC. The cost function-based modulator is introduced and its effectiveness on reducing the current ripple is demonstrated. The presented solution provides an effective and straightforward single loop controller, maintaining an excellent dynamic performance despite the modulated output and it is self-synchronizing with the grid. This promising method is applied to the control of a shunt active filter for harmonic content reduction through a reactive power compensation methodology. Significant results obtained by experimental testing are reported and commented, showing that MPC is a viable control solution for active filtering systems.

Modulated model predictve control (M 2 PC) for a 3-phase active front-end

One of the main issues with Model Predictive Control (MPC) applied to Power Electronics Converters is the ability to select only one output voltage vector which is applied during the whole sampling period. Such mode of operation requires, in order to improve the harmonic content, an increasing of the converter switching frequency which is variable depending on the operating conditions. In order to overcome these issues, whilst preserving all the advantages of MPC, this paper presents a novel Modulated Model Predictive Control, with the aim of obtaining a modulated waveform at the output of the converter without implementing an explicit modulation scheme. The proposed control technique is applied to the current control of a 2-Level, 3-Phase Active Rectifier, validated through simulation and experimental testing and compared to a traditional Model Predictive Control.

Grid Parameter Estimation Using Model Predictive Direct Power Control

This paper presents a novel finite-control-set model predictive control (FS-MPC) approach for grid-connected converters. The control performance of such converters may get largely affected by variations in the supply impedance, especially for systems with low short-circuit ratio values. A novel idea for estimating the supply impedance variation, and hence the grid voltage, using an algorithm embedded in the MPC is presented in this paper. The estimation approach is based on the difference in grid voltage magnitudes at two consecutive sampling instants, calculated on the basis of supply currents and converter voltages directly within the MPC algorithm, achieving a fast estimation and integration between the controller and the impedance estimator. The proposed method has been verified, using simulation and experiments, on a three-phase two-level converter.