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- A new real time Lyapunov based controller for power quality improvement in unified power flow controllers using direct matrix convertersPublication . Monteiro, Joaquim; Pinto, Sonia; Martins, Aranzazu Delegado; Silva, José FernandoThis paper proposes a Direct Matrix Converter operating as a Unified Power Flow Controller (DMC-UPFC) with an advanced control method for UPFC, based on the Lyapunov direct method, presenting good results in power quality assessment. This control method is used for real-time calculation of the appropriate matrix switching state, determining which switching state should be applied in the following sampling period. The control strategy takes into account active and reactive power flow references to choose the vector converter closest to the optimum. Theoretical principles for this new real-time vector modulation and control applied to the DMC-UPFC with input filter are established. The method needs DMC-UPFC dynamic equations to be solved just once in each control cycle, to find the required optimum vector, in contrast to similar control methods that need 27 vector estimations per control cycle. The designed controller's performance was evaluated using Matlab/Simulink software. Controllers were also implemented using a digital signal processing (DSP) system and matrix hardware. Simulation and experimental results show decoupled transmission line active (P) and reactive (Q) power control with zero theoretical error tracking and fast response. Output currents and voltages show small ripple and low harmonic content.
- Using metaheuristics-based methods to provide sustainable market solutions, suitable to consumer needsPublication . Santos, Ricardo; Abreu, António; Monteiro, JoaquimNowadays the buildings sector is one of the key sectors to achieve sustainability, with the correspondent consumers, in particular, the household consumers, having the need to perform sustainable choices every day, regarding the appliances to be acquired from the market. This is not only due to government’s growing concerns about sustainability but also with the consumers on having sustainable solutions, given the different economic, social (including their comfort) and environmental needs. However, the existence of several electrical appliances on market, with all their different issues, brands and models, together with the several tradeoffs referred before, difficult the consumer’s choices, on having sustainable solutions in the market. Therefore, this work, presents an approach, by using Multi-Attribute Value Theory (MAVT), integrated with metaheuristics, which uses Evolutionary Algorithms (EA) to provide suitable and sustainable market solutions to a consumer, according to its own needs. Based on the achieved solutions and considering the relative importance, given to each consumer, and regarding each dimension of sustainability, it’s possible to achieve several savings, namely electrical and water consumption, CO2 emissions, among others. A case study shall be shown, to demonstrate the applicability of the proposed approach.
- Surgical correction of scoliosis: numerical analysis and optimization of the procedurePublication . Madeira, JFA; Pina, H. L.; Pires, E. B.; Monteiro, JoaquimA previously developed model is used to numerically simulate real clinical cases of the surgical correction of scoliosis. This model consists of one-dimensional finite elements with spatial deformation in which (i) the column is represented by its axis; (ii) the vertebrae are assumed to be rigid; and (iii) the deformability of the column is concentrated in springs that connect the successive rigid elements. The metallic rods used for the surgical correction are modeled by beam elements with linear elastic behavior. To obtain the forces at the connections between the metallic rods and the vertebrae geometrically, non-linear finite element analyses are performed. The tightening sequence determines the magnitude of the forces applied to the patient column, and it is desirable to keep those forces as small as possible. In this study, a Genetic Algorithm optimization is applied to this model in order to determine the sequence that minimizes the corrective forces applied during the surgery. This amounts to find the optimal permutation of integers 1,..., n, n being the number of vertebrae involved. As such, we are faced with a combinatorial optimization problem isomorph to the Traveling Salesman Problem. The fitness evaluation requires one computing intensive Finite Element Analysis per candidate solution and, thus, a parallel implementation of the Genetic Algorithm is developed. Copyright q 2010 John Wiley & Sons, Ltd.
- Matrix converter-based active distribution transformerPublication . Pinto, S. F.; Alcaria, P.; Monteiro, Joaquim; Silva, J.F.This paper proposes a matrix converter-based active distribution transformer (MC-ADT) with enhanced control functionalities to be used in smart grids (SG). The proposed MC-ADT uses a matrix converter (MC) connected to a transformer inserted in series with the grid, and allows: 1) real-time voltage regulation of the low-voltage side of the MC-ADT, based on an adjustable reference value defined by the SG requirements and bounded by the standard values; 2) capability to regulate the LV grid voltage even in case of sags, voltage rises, and overvoltages in the transformer medium-voltage side; and 3) contribution to power factor correction in the MV side. The MC-ADT grid voltage regulators are synthesized, establishing the MC reference currents. To guarantee the tracking of the MC input and output reference currents, the space vector representation, together with sliding-mode direct control techniques, are used. The obtained experimental and simulation results show that the proposed system is able to regulate the LV grid voltages even for sags and overvoltages up to 20% in the MV side, and contributes to power factor correction in MV, while presenting fast dynamic response, without overshoot and almost zero steady-state error.
- Matrix Converter-Based Unified Power-Flow Controllers: Advanced Direct Power Control MethodPublication . Monteiro, Joaquim; Silva, J. Fernando; Pinto, S. F.; Palma, João Carlos Pires daThis paper presents a direct power control (DPC) for three-phase matrix converters operating as unified power flow controllers (UPFCs). Matrix converters (MCs) allow the direct ac/ac power conversion without dc energy storage links; therefore, the MC-based UPFC (MC-UPFC) has reduced volume and cost, reduced capacitor power losses, together with higher reliability. Theoretical principles of direct power control (DPC) based on sliding mode control techniques are established for an MC-UPFC dynamic model including the input filter. As a result, line active and reactive power, together with ac supply reactive power, can be directly controlled by selecting an appropriate matrix converter switching state guaranteeing good steady-state and dynamic responses. Experimental results of DPC controllers for MC-UPFC show decoupled active and reactive power control, zero steady-state tracking error, and fast response times. Compared to an MC-UPFC using active and reactive power linear controllers based on a modified Venturini high-frequency PWM modulator, the experimental results of the advanced DPC-MC guarantee faster responses without overshoot and no steady-state error, presenting no cross-coupling in dynamic and steady-state responses.
- Dual 3-phase bridge multilevel inverters for AC drives with voltage sag ride-through capabilityPublication . Fernao Pires, Vitor; Monteiro, Joaquim; Silva, José FernandoOne of the main power quality issues that can affect variable speed drives (VSDs) is the occurrence of voltage sags on their AC power supply. Voltage sags can affect the inverter nominal operation, leading to a malfunction of the AC motor. This paper presents an inverter with resilient capability to voltage sags. The topology consists of two conventional three-phase bridge inverters arranged to require just a single DC source. This inverter is also characterized by a voltage multilevel operation, providing the full advantages of multilevel converters without the need for level balancing. Associated with this AC motor driver, a control system based on a field-oriented controller with a vector voltage modulator that will enable voltage sag ride-through capability is proposed. The proposed control system does not require any changes in the occurrence of voltage sags. To verify the characteristics of the proposed drive and control system, simulation tests are provided. Simulation results confirm the voltage sag resilient capability of the proposed multilevel converter.
- Integrated battery charger for electric vehicles based on a dual-inverter drive and a three-phase current rectifierPublication . Fernao Pires, Vitor; Monteiro, Joaquim; Cordeiro, Armando; Silva, José FernandoThis paper presents a new three-phase battery charger integrated with the propulsion system of an electric vehicle. The propulsion system consists of a dual-inverter topology connected to an induction motor via open windings. The electrical vehicles (EV) batteries are divided by two inverters. This will result in a drive with multilevel characteristics reducing the total harmonic distortion (THD) of the voltage applied to the motor. The modularity of the multilevel inverter will be maintained since two classical three-phase inverters are used. The charger will be fed by a three-phase high power factor current source rectifier. The motor windings will take the role of the DC-inductor required by the rectifier. In this way, an intermediate storage element between the grid and the batteries of the vehicle exist. For the control system of the battery charger, we propose the use of the instantaneous power theory and a sliding mode controller for the three-phase charger input currents. Finally, to verify the behavior and characteristics of the proposed integrated battery charger and control system, several tests are be presented.
- Inverse dynamics based predictive control for unified power flow controllers without DC busPublication . Monteiro, Joaquim; Silva, Fernando José; Pinto, Sónia Ferreira; Palma, João Carlos Pires daThis paper presents a new predictive digital control method applied to Matrix Converters (MC) operating as Unified Power Flow Controllers (UPFC). This control method, based on the inverse dynamics model equations of the MC operating as UPFC, just needs to compute the optimal control vector once in each control cycle, in contrast to direct dynamics predictive methods that needs 27 vector calculations. The theoretical principles of the inverse dynamics power flow predictive control of the MC based UPFC with input filter are established. The proposed inverse dynamics predictive power control method is tested using Matlab/Simulink Power Systems toolbox and the obtained results show that the designed power controllers guarantees decoupled active and reactive power control, zero error tracking, fast response times and an overall good dynamic and steady-state response.
- A single-switch DC-DC converter with a high voltage gain capability and reduced voltage stress of the switch for renewable energy applicationsPublication . Fernao Pires, Vitor; Cordeiro, Armando; Foito, Daniel; Monteiro, Joaquim; Silva, J. F.The growing trend toward high-efficiency, high gain converters that minimize component count, has spurred the development of many new step-up topologies. In this context introduces a new single-switch, non-isolated DC-DC step-up converter topology specifically designed for renewable energy applications. Key advantages of this topology include a high boost factor, continuous input current, reduced voltage stress on the switch, and a suitable number of elements relative to the achieved boost factor. These features address many of the critical design objectives. The steady-state analysis of the proposed converter is presented and discussed. Simulation and experimental results are presented to verify the theory and performance of the converter.
- Linear and sliding-mode control design for matrix converter-based unified power flow controllersPublication . Monteiro, Joaquim; Silva, José Fernandes Alves da; Pinto, Sónia Ferreira; Palma, João Carlos Pires daThis paper presents the design and compares the performance of linear, decoupled and direct power controllers (DPC) for three-phase matrix converters operating as unified power flow controllers (UPFC). A simplified steady-state model of the matrix converter-based UPFC fitted with a modified Venturini high-frequency pulse width modulator is first used to design the linear controllers for the transmission line active (P) and reactive (Q) powers. In order to minimize the resulting cross coupling between P and Q power controllers, decoupled linear controllers (DLC) are synthesized using inverse dynamics linearization. DPC are then developed using sliding-mode control techniques, in order to guarantee both robustness and decoupled control. The designed P and Q power controllers are compared using simulations and experimental results. Linear controllers show acceptable steady-state behaviour but still exhibit coupling between P and Q powers in transient operation. DLC are free from cross coupling but are parameter sensitive. Results obtained by DPC show decoupled power control with zero error tracking and faster responses with no overshoot and no steady-state error. All the designed controllers were implemented using the same digital signal processing hardware.