Showing papers by "Juan Carlos Balda published in 2016"

Power-Semiconductor Devices and Components for New Power Converter Developments: A key enabler for ultrahigh efficiency power electronics

Abstract: In a world with an increasing penetration of widebandgap (WBG) semiconductor technology, the FEPPCON 2015 Session on New Power Devices and High Temperature focused on power-semiconductor devices and passive components (magnetic and dielectric materials) up through integration, for the purpose of refining appropriate power-electronics converters by 2025. An important goal was to identify those markets and applications where silicon technology will remain the preferred choice. The semiconductors are rarely the predominant failure mechanisms even in silicon modules; the failure mechanisms are usually either the passive components or the packaging. Thus, higher power densities afforded by using WBG semiconductors require those passives capable of operating at high temperatures and having high reliabilities. Presenters addressed the state of the art and future directions for magnetic cores, dielectric materials, and electronic packaging/integration. Finally, potential additional frontiers that merit research in a WBG world (such as new markets, capabilities, circuit architectures, and applications) were evaluated. The session was divided into four main groups: "WBG Technologies," "Silicon Technologies," "Passive Technologies," and "Power-Integration Technologies."

Investigation of low-voltage solid-state DC breaker configurations for DC microgrid applications

Abstract: Among current research issues of dc microgrids, short-circuit protection is very challenging because of the high rate of rise for the fault currents. Slow-acting electromechanical circuit breakers lead to system overdimensioning resulting in additional costs. Circuit breakers based on power semiconductor devices have the potential of fast interruption of fault currents. Unfortunately, the energy stored in parasitic inductors or system inductive components have the potential of resulting in overvoltage across the solid-state circuit breaker (SSCB). Metal oxide varistor (MOV), snubber circuits and freewheeling diodes are used to protect the semiconductor devices against overvoltage. Six configurations for a voltage clamp for a SSCB are analyzed in this paper when inductive components are present on the load sides. Finally, the experimental results verified that series connected diode and MOV clamping provides better overvoltage protection for the SSCB.

Short-circuit protection for low-voltage DC microgrids based on solid-state circuit breakers

Abstract: Proper short-circuit protection in dc microgrids has provided a sturdy challenge to researchers as the development of commercially-viable equipment providing fast operation, coordination and reliability still continues. In this paper, issues associated with short-circuit protection of low-voltage dc (LVDC) microgrids are analyzed, a short-circuit protection methodology based on solid-state circuit breakers (SSCBs) that provides fault-current limiting (FCL) is evaluated, several fault-detection techniques are considered, and certain topics related to the SSCB design are addressed. Simulation results for a simple 1kV dc microgrid system illustrate that SSCB solutions based on integrated gate-commutated thyristors (IGCT) are feasible for low-voltage microgrids but requires connecting several devices in parallel to open fast-rising fault currents.

Simple and efficient low power photovoltaic emulator for evaluation of power conditioning systems

Abstract: Low power conditioning systems are required for photovoltaic (PV) applications in portable devices, small satellites, solar vehicles, etc. The research and development of the power conditioning unit for this application such as MPPT requires of controllable environment conditions, which are difficult to obtain due to weather variability. Thus, a photovoltaic emulator is developed to obtain a power source that presents the same current-voltage (I–V) relationship of PV cells according to the connected-load, irradiance and temperature. This paper presents the design of a PV system based on a synchronous buck converter, current and voltage sensors, and a microcontroller to control the PWM duty cycle to adjust the output voltage and current according to the I–V characteristic. The results show a good agreement between the output current of the emulator and the expected characteristic curve of the PV module; the achieved efficiency was between 80 % and 95 % over the entire operating range.

Analysis, modeling and control of an interleaved isolated boost series resonant converter for microinverter applications

Abstract: The analysis, modeling and control of an interleaved boost series resonant converter (IBSRC) is presented in this paper. The converter consists of an interleaved boost stage, a high-frequency transformer (HF-XFMR) and a voltage doubler rectifier. The HF-XFMR's leakage inductance and the voltage doubler bridge rectifier's capacitors form a resonant tank that allows zero-voltage switching (ZVS) of the main semiconductor devices and zero-current switching (ZCS) of the rectifier's diodes. This capability enables the IBSRC to operate at high switching frequencies leading to a compact design while keeping efficiency high. This makes the IBSRC suitable for the dc-dc converter stage of a dual-stage microinverter. The IBSRC dynamics are extensively investigated using the extended describing functions (EDF) methodology, whereas the converter small-signal model is derived to design the closed-loop control strategy. Experimental results on a 350-W prototype are presented to demonstrate the feasibility of the proposed model and the performance of the controller during input and output variations.

Passive integration using FMLF technique for integrated boost resonant converters

Abstract: In order to further increase the power density of the integrated boost resonant (IBR) converter, a novel passive integrated unit is proposed by combining three inductors, two capacitors and one transformer. For saving the these passive components, the Flexible Multi-Layer Foil (FMLF) integration technique is used. To avoid the coupling of two boost inductors and the transformer, the symmetry structure is used in the proposed unit. The electromagnetic analysis of the proposed unit is given, and the calculations of the circuit parameters are provided. Finally, a prototype for a 350-W IBR converter has been built to validate the feasibility of the proposed integrated unit.

Correcting current imbalances in three-phase four-wire distribution systems

Abstract: This paper presents the analysis and control of a current imbalance compensator designed to eliminate upstream negative- and zero- sequence current components caused by single-phase loads in three-phase four-wire systems. The proposed compensator significantly reduces the fundamental-frequency current component in the neutral conductor and can potentially be used to eliminate harmonic currents. The Matlab/Simulink™ simulations are based on a 3-MVA radial feeder case study and a scaled-down 10-kVA test setup used to validate the proposed ideas. Three TMS320F28335 DSPs are used to implement the control system and the results of both the simulations and the prototype testing are shown and discussed. Results from testing of the prototype demonstrate the ability of the compensator to reduce the current in the neutral conductor.

Ultracapacitor application and controller design in 400 V DC-powered green data centers

Abstract: The integration of solar power, batteries and ultracapacitors to increase the reliability of the power supply for dc-powered data centers and reduce carbon emissions is investigated in this paper. The availability of ultracapacitors that have very high power densities and charge/discharge cycling capability characteristics enable smoothing solar power intermittencies. Four typical weather conditions are simulated for solar power generation. A battery/ultracapacitor energy storage unit is controlled with the goal of improving battery lifetime. Simulation results verify the proposed ideas.

Resonance propagation modeling and analysis of AC filters in a large-scale microgrid

Abstract: Low-pass ac filters are frequently adopted in microgrid power electronic interfaces that convert distributed generators' dc power to ac power because most of today's distribution grids have ac voltages. Compared to a simple L filter, higher-order filters, such as LC or LCL filters, are preferred due to their more effective reduction of switching-frequency harmonics and smaller sizes. As the converter power ratings increase, resonance problems caused by the higher-order filters challenge microgrid stability. This paper investigates a microgrid resonance propagation circuit model, which includes paralleling multiple converters with their filters. Each converter has a power rating in the MW range. The converter control design is illustrated and hardware experimental results validate the design and modeling.

Design of a 2 MW DC-DC power supply using a medium frequency transformer

Abstract: In this paper a 2 MW dc-dc converter is presented and design criteria are carried out. It deals with the preliminary design for the hardware implementation. The power supply shall have multiple targets such as an PV emulator or supply for a dc-micro grid in the research facility National Center for Reliable Electric Power Transmission of the University of Arkansas. The converter is designed for an output current up to 1500A and a output voltage up to 1500V. The first part of the paper deals with the comparison of several topologies on the basis of simulations. Based on these results a topology is selected. The second part focus on the electrical layout, detailed simulation results and mechanical assembly of the converter. Additionally, the expected costs are derived.

Control of a flyback converter with parametric uncertainties operating in BCM Using the natural switching surface

Abstract: The derivation and implementation of the natural switching surfaces (NSS) considering parametric uncertainties for a flyback converter operating at boundary conduction mode (BCM) is the main focus of this paper. The NSS presents many benefits for the control of non-linear systems; for example fast transient response under load-changing conditions. However, the performance considerable worsens when real parameters of the converter are slightly different from the designed ones. Therefore, a novel control strategy that considers the effect of parameter uncertainties is presented. This control law can estimate and adapt the control trajectories in one switching action to obtain excellent performances even under extreme parameter uncertainties. The analytical derivation of the proposed adaptive switching surfaces are presented.