Computer Controlled Systems: Theory and Design

The dual frequency radio signals of the Global Positioning System (GPS) allow measurements of the total number of electrons, called total electron content (TEC), along a ray path from GPS satellite to receiver. We have developed a new technique to construct two-dimensional maps of absolute TEC over Japan by using GPS data from more than 1000 GPS receivers. A least squares fitting procedure is used to remove instrumental biases inherent in the GPS satellite and receiver. Two-dimensional maps of absolute vertical TEC are derived with time resolution of 30 seconds and spatial resolution of 0.15° × 0.15° in latitude and longitude. Our method is validated in two ways. First, TECs along ray paths from the GPS satellites are simulated using a model for electron contents based on the IRI-95 model. It is found that TEC from our method is underestimated by less than 3 TECU. Then, estimated vertical GPS TEC is compared with ionospheric TEC that is calculated from simultaneous electron density profile obtained with the MU radar. Diurnal and day-to-day variation of the GPS TEC follows the TEC behavior derived from MU radar observation but the GPS TEC is 2 TECU larger than the MU radar TEC on average. This difference can be attributed to the plasmaspheric electron content along the GPS ray path. This method is also applied to GPS data during a magnetic storm of September 25, 1998. An intense TEC enhancement, probably caused by a northward expansion of the equatorial anomaly, was observed in the southern part of Japan in the evening during the main phase of the storm.

A new technique for mapping of total electron content using GPS network in Japan

Hybrid systems are presented as a viable, safe and effective solution to minimize the associated problems of the dependence on renewable energies with the environmental resources. In this way different renewable systems such as photovoltaic, wind, hydrogen and so on, can work together to configure hybrid renewable systems. However, to make them work properly in a holistic way by creating synergies among them is not an easy task. Recently hydrogen technology has appeared as a promising technology to hybridize renewable energy systems, since it allows the generation (by electrolyzers) and storage of hydrogen when there is a surplus of energy in the system, and at a later time (e.g. when there are insufficient renewable resources available) using the stored hydrogen to generate electrical energy by fuel cells. The choice of a correct energy management strategy should guarantee an optimum performance of the whole hybrid renewable system; therefore, it is necessary to know the most important criteria in order to define a management strategy that ensures the best solution from a technical and economic point of view. This paper presents a critical review and analysis of different energy management strategies for hybrid renewable systems based on hydrogen backup. In the same way, a review is also presented of the most important technical and economic optimization criteria, as well as problems and solutions studied in the scientific literature.

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A review of energy management strategies for renewable hybrid energy systems with hydrogen backup

DC microgrids encounter the challenges of constant power loads (CPLs) and pulsed power loads (PPLs), which impose the requirements of fast dynamics, large stability margin, high robustness that cannot be easily addressed by conventional linear control methods. This necessitates the implementation of advanced control technologies in order to significantly improve the robustness, dynamic performance, stability and flexibility of the system. This article presents an overview of advanced control technologies for bidirectional dc/dc converters in dc microgrids. First, the stability issue caused by CPLs and the power balance issue caused by PPLs are discussed, which motivate the utilization of advanced control technologies for addressing these issues. Next, typical advanced control technologies including model predictive control, backstepping control, sliding-mode control, passivity-based control, disturbance estimation techniques, intelligent control, and nonlinear modeling approaches are reviewed. Then the applications of advanced control technologies in bidirectional dc/dc converters are presented for the stabilization of CPLs and accommodation of PPLs. Finally, advanced control techniques are explored in other high-gain nonisolated (e.g., interleaved, multilevel, cascaded) and isolated converters (e.g., dual active bridge) for high-power applications.

Review on Advanced Control Technologies for Bidirectional DC/DC Converters in DC Microgrids

High step-up converters are required for distributed photovoltaic generation systems, due to the low voltage of the photovoltaic source. In this paper, a new hybrid high voltage gain dc–dc converter is created by merging the standard boost converter with a coupled inductor and different switched-capacitor techniques. With a single switch and no requirement of higher duty cycle values, the proposed converter achieves a high voltage gain and high efficiency, in addition to lowered voltage and current stresses of the components. A 200-W prototype was implemented experimentally to evaluate the converter, which reached a maximum efficiency of 97.6%.

Analysis and Design of High-Efficiency Hybrid High Step-Up DC–DC Converter for Distributed PV Generation Systems

A synthesis methodology for developing a set of very high step-up dc–dc converters is presented and discussed in this paper. The proposed method makes use of a boost converter as basic topology in which three step-up techniques are combined and incorporated. The studied techniques are the switched capacitors voltage multipliers (VM), the diode VMs, and the coupled-inductors. With the proposed methodology, many well-known converters are identified and two novel converters are proposed. In addition to a detailed analysis of the synthesis of each topology, a comparative analysis among of some important converters is presented. This comparison involves aspects such as voltage gain, voltage stress, component stress factor, component count, and relative cost. By means of these comparisons, the main characteristics and constraints of the analyzed converters are identified. Results from 250 W prototypes, designed according to photovoltaic ac-module specifications, are obtained experimentally to validate the theoretical analyses and point out advantages and limitations of each converter. The results demonstrate that the combination of the three studied techniques provides the best trend off on the comparative analysis carried out in this work.

Synthesis and Comparative Analysis of Very High Step-Up DC–DC Converters Adopting Coupled-Inductor and Voltage Multiplier Cells

https://link.springer.com/content/pdf/10.1007/s40313-021-00835-5.pdf

Feasibility Assessment of Adaptive Sliding Mode Controllers for Grid-Tied Inverters with LCL Filter

The proposal of this paper is to present and analyze a charging station PV system of battery (PV-CS) with a wide range of output voltage buses, where is possible to make the charge of the batteries at the maximum power point tracking (MPPT), which increases the PV utilization. In this paper, a complete analysis of the Zeta converter applied as a photovoltaic battery charger is carried out. The solar battery charger includes a Constant Current/Constant Voltage charging method with inherent MPPT. The battery pack is properly charged as well as the maximum power is harvest from the solar module. Experimental results prove the feasibility of the design.

Design and implementation of PV power zeta converters for battery charger applications

This paper provides an automated design to provide robust PIDs with fixed control gains, suitable to be applied in power converters whose parameters belong to real intervals. Differently from conventional PIDs which use only a nominal model to obtain the fixed control gains and, a posteriori, verify robustness, the proposed approach ensures, a priori (i.e. during the design stage), robust performance for a set of plant parameters. To illustratethe proposed procedure, two conventional PID controllers are given, to achieve phase margin and crossover frequency for a nominal model of a buck converter. An objective function based on frequency domain specifications is proposed. A particle swarm optimization algorithm is then used to find PIDs, in a large search space that include stable and unstable controllers, allowing to optimize this function for all cases of combinations of plant parameters. A case study for the buck converter illustrates the improvements of performance with the proposed method when compared to the conventional PID controllers. Additionally, the design is used in a more challenging application, for a buck-boost converter suitable for small satellites application, becoming a simple alternative for benchmarks for robust control of power converters.

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Robust PID Controllers Optimized by PSO Algorithm for Power Converters

Often, for simplicity, it is adopted for boost converter inductor and capacitor design the inductor current variation (∆IL), defining it as an output current percentage.However, this kind of methodology does not guarantee the inductor and capacitor minimum values that assure the converter working on continuos mode operation, discontinuos mode operation, or when it is desired to operate the converter at the boundary between these modes. The aim of this paper is to present a theoretical study of the no-losses boost converter. The principle of operation and static analysis are developed in detail for operation on the following modes: continuos mode operation, discontinuos current mode operation and at the boundary between these modes. During this analyses, all four variables (input and output currents and voltages) are considered as design choices for independent variables that determine the boundary between continuos and discontinuos modes. In addition, a design methodology is presented to ilustrate the theoretical procedures, which guarantee the inductor and capacitor minimum values according to the desired operation mode. Finally, the simulation results proof the theroretical analysis.

Everson Mattos

Papers

Synthesis and Comparative Analysis of Very High Step-Up DC–DC Converters Adopting Coupled-Inductor and Voltage Multiplier Cells

Feasibility Assessment of Adaptive Sliding Mode Controllers for Grid-Tied Inverters with LCL Filter

Design and implementation of PV power zeta converters for battery charger applications

Robust PID Controllers Optimized by PSO Algorithm for Power Converters

A review of boost converter analysis and design in aerospace applications