Carlos G. Montero

Basic Principles of MPC for Power Converters: Bridging the Gap Between Theory and Practice

This article presents the basic principles of operation for model predictive control (MPC), a control methodology that opens a new world of opportunities. MPC is a powerful technique that can fulfill the increased performance and higher efficiency demands of power converters today. The main features of this technique are presented as well as the MPC strategy and basic elements. The two main MPC methods for power converters [continuous-control-set MPC (CCS-MPC) and finite-control-set MPC (FCS-MPC)] are described, and their application to a voltage-source inverter (VSI) is shown to illustrate their capabilities. This article tries to bridge the gap between the powerful but sometimes abstract techniques developed by researchers in the control community and the empirical approach of power electronics practitioners.

POLAR LIPIDS OF NON-ALKALIPHILIC HALOCOCCI

Until recently, only one species of Halococcus has been recognized, namely, H. morrhuae, but a large number of extremely halophilic non-alkaliphilic cocci have now been isolated from hypersaline habitats in Spain and classified into four phenons (A-D); one of the phenon D strains has been classified as a new species, Halococcus saccharolyticus. Examination of the lipids of H. saccharolyticus and four strains of phenons A-C showed the presence in all of them of C20-C20 and C20-C25 diether molecular species of phosphatidylglycerophosphate (PGP), phosphatidylglycerol (PG) and phosphatidic acid (PA); a monounsaturated isoprenoid C20-C20 (phytanyl-phytenyl) species of PGP; a sulfated diglycosyl diphytanylglycerol (S-DGD) with structure 2,3-diphytanyl-1-(6-HSO3-mannosyl-1-2-glucosyl)-glycerol, which is identical to the S-DGD-1 in Haloferax mediterranei; a phosphoglycolipid (P-TGD) tentatively identified as a phytanyl-phytenyl-(H2PO3-galactosyl-mannosyl-glycosyl)-glyce rol, and two unidentified glycolipids present only in traces. No phosphatidylglycerosulfate (PGS) was detected in any of the strains examined. This pattern of lipids appears to be characteristic of the strains of Halococcus from salterns in Spain, but studies of a larger number and variety of Haloccus are necessary to establish this conclusion with certainty.

Halococcus saccharolyticus sp. nov., a New Species of Extremely Halophilic Non-alkaliphilic Cocci

Summary A representative of extremely halophilic non-alkaliphilic archaebacterial cocci, (strain P-423), recently described by Montero et al., (1988), was studied in detail. On the basis of phenotypic features, guanine plus cytosine content of the DNA, polar lipid composition and other molecular data, the new species Halococcus saccharolyticus sp. nov. is proposed. The type strain is strain P-423 (= ATCC 49257, DSM 5350, CCM 4147)

Taxonomic Study of Non-alkaliphilic Halococci

SUMMARY: Ninety-six extremely halophilic, non-alkaliphilic cocci were isolated from several salterns in different geographical areas of Spain. These strains, together with seven reference strains of the genus Halococcus, were characterized by means of 114 phenotypic features, the results being analysed by numerical techniques using the simple matching (SSM ) coefficient and the unweighted pair group clustering (UPGMA) algorithm. At the 70% similarity level, four phenons were obtained. Phenon A contained 87 strains, including all the reference strains, and was considered to comprise members of the only named species of the genus Halococcus, H. morrhuae. Phenons B and C, which included five and seven strains respectively, showed greater metabolic versatility than phenon A. The four strains belonging to phenon D were significantly different from the other phenons in that they produced acid from glucose and were able to use most of the organic compounds tested. The results indicate that there is phenotypic diversity among the members of the genus Halococcus and that phenon D may constitute a new taxon.

Toxicity of Heavy Metals to Archaebacterial Halococci

Summary The susceptibility of 77 archaebacterial halococci including 7 culture collection strains and 70 fresh isolates, to arsenate, cadmium, chromium, cobalt, copper, lead, mercury, nickel, silver, and zinc ions, was tested using an agar dilution method. Except for Halococcus morrhuae strain Delft, which showed the highest tolerance to lead and silver and the lowest tolerance to arsenate, all collection strain exhibited similar responses to the majority of the heavy metals tested. Only the response to lead was very heterogeneous. A high percentage of all the 77 halococci was tolerant to copper (90%), nickel (83%), chromium (82%), and lead (78%). However, only 33%, 30%, and 8% demonstrated tolerance to arsenate, cadmium, and cobalt, respectively. All the strains were susceptible against silver, mercury, and zinc. The sensitivity of these three metal ions seems to be a common feature of halophilic bacteria. Mercury showed the highest toxicity to the halococci tested.

Model predictive control of a VSI with long prediction horizon

This work presents a Model Predictive Control (MPC) strategy for a Voltage Source Inverter (VSI) used in a three-phase Uninterruptible Power Supply (UPS) for critical loads. An MPC using continuous variables is proposed for solving this problem and the output of the controller is used as the reference voltage to be generated by a PWM modulator. The solution of this unconstrained MPC gives rise to an explicit solution that can be computed beforehand, allowing the prediction horizon to be easily extended. Therefore, the effect of the length of the prediction horizon over the system performance is also evaluated in the paper. This study addresses how this parameter should be chosen to minimize the error between the actual and the desired output voltage. The proposed control strategy has been tested on a simulated model of a UPS supplying a three-phase resistor load. This model has been developed using MATLAB/Simulink with PSIM software. The simulation results show that proposed continuous MPC controller achieves high performance and high degree of robustness.

Design and experimental validation of a Model Predictive Control strategy for a VSI with long prediction horizon

This work presents the design and experimental validation of a Model Predictive Control (MPC) strategy for a Voltage Source Inverter (VSI) used in a three-phase uninterruptible power supply (UPS) for critical loads. The solution is obtained in two steps: first an unconstrained MPC problem is solved, which computes the continuous values of the voltage that must be provided by the converter. Then, a PWM modulation scheme is used to define the switching sequence of the switches that generate the desired input voltage to the LC filter. The first stage implies a dynamic optimization while the second one is just a static relationship. The solution of the unconstrained MPC problem gives rise to an explicit control law that can be computed beforehand, allowing the prediction horizon to be easily extended. This can improve the performance of other MPC formulation that use very short prediction horizons. The effect of the length of the prediction horizon and the control-weighting factor over the system performance is also evaluated experimentally in the paper. This study addresses how these parameters should be tuned to minimize the error between the actual and the desired output voltage. The proposed control strategy has been tested on a UPS supplying a three-phase RL load. The experimental results show that the proposed MPC controller achieves high performance of the overall system, even in the case of a model mismatch.

Fuel cell and power control for a hybrid vehicle. Experimental results

This work presents the design, implementation and experimental evaluation of the control system for a Fuel Cell Hybrid Vehicle (FCHV). The main objective of this paper is to develop control strategies for a real vehicle which has been designed in order to demonstrate the feasibility of the use of hydrogen as an energy source for automotive applications. The hybrid vehicle is driven by an array of batteries and a bank of two fuel cells. The control system is designed and tested in order to perform all the operations related to the coordinated operation of the fuel cells, the intermediate electrical storage and the power train. Real-time power management is done in order to satisfy the power demand of the electric motor taking into account the state of charge of the batteries and the operating regime of the fuel cells. An embedded controller has been installed to manage the power distribution between the fuel-cell bank and the batteries and a supervisor has also been designed and tested. An important contribution to be noticed is the development of a power management strategy devised to split the power between both fuel cells. Besides, a low-level controller has been implemented to regulate temperature and air excess ratio in the cells. Some experimental results are presented in order to show the vehicle performance. The proposed hybrid vehicle, tested under real driving conditions, has demonstrated a high robustness and reliability.

Physical map of a 257 kilobase-pairs region from the genome of the archaebacteriumHalococcus saccharolyticus

We report here the first available data on the genomic structure of an archaebacterial, extremely halophilic coccus. Thus, the physical map of a region of 257 kilobase-pairs (kbp) from the extremely halophilic aerobic archaebacteriumHalococcus saccharolyticus ATCC 49257 has been constructed. This DNA fragment could be ascribed to the FI fraction of the chromosome. Long repeated sequences were not detected, but, on the other hand, some losses of fragments in the recombinants were found. These data suggest that only a minor part of the chromosome ofH. saccharolyticus, which is not cccDNA, is accompanied by multiple rearrangements, while the other, which includes most of the chromosome, possesses more genetic stability. Our results indicate that there is a low degree of genomic variability in contrast to the high instability reported forHalobacterium salinarium.

Practical implementation of an hybrid electric-fuel cell vehicle

Electric vehicles are currently the focus of the researchers all over the world. High harmful gas emissions from conventional vehicles and the rising of new clean and competitive energy sources have leaded to an increasing interest of vehicle providers and consumers. In this paper, a practical example of an hybrid vehicle is addressed. The hybrid vehicle is driven by an array of batteries and a 5 kW fuel cell. The changes done in the vehicle chassis, the necessary power electronic converter and the control and monitoring systems are explained in this paper. Some experimental results are shown in order to show the vehicle performance. The vehicle range has been approximately doubled using the hybrid electric- fuel cell system. The proposed hybrid vehicle, tested under real weather conditions, has demonstrated a high robustness and reliability.