Juan Carlos Balda

Bio: Juan Carlos Balda is an academic researcher from University of Arkansas. The author has contributed to research in topics: Power module & Converters. The author has an hindex of 29, co-authored 180 publications receiving 3468 citations. Previous affiliations of Juan Carlos Balda include Clemson University & University of Arkansas at Little Rock.

Wind farm layout for mitigating output power intermittency

Abstract: The placement of wind turbines (WTs) on a terrain to form a wind farm (WF) has significant impact on the total output power resulting from aggregating the WT powers at the point of common coupling (PCC). Output power intermittency is inherent in a WT as the wind speed invariably changes in intensity and direction. A combination of fast-acting energy storage (ES) and (relative) slow-acting spinning reserve may be used for smoothing the WF total output power when connected to the power grid. ES adds to the WF capital and operating costs. Thus, the main purpose of this paper is to present a simple methodology for evaluating the output power intermittency and ES requirements for a given WF layout. This methodology should minimize the number of WF layouts requiring more complex analysis before final siting. The methodology is illustrated by considering the spatial smoothing effects in three WF layouts having 16 WTs; namely, the straight-line, circular and square layouts. The total harmonic distortion (THD) of the total output power at the PCC when the wind direction varies from 0 to 90 degrees is used as a comparative figure of merit. For the direction with the worst THD, the amount of ES needed to limit the worst-case power ramp is calculated using a first-order approximation of the ES unit. The best layout is the one whose output power characteristic is least affected by changes in the wind direction, and thus, having the lowest THD and requiring the least amount of ES; this is the circular one for the analyzed layouts.

A comparison of selected silicon and silicon-carbide switching devices for PV microinverter applications

Abstract: Manufacturers of photovoltaic (PV) microinverters are seeking cost reductions with the goal of reaching grid parity. Wide bandgap semiconductor devices, such as silicon carbide (SiC) JFETs and MOSFETs, have technical advantages over silicon (Si) counterparts, in particular within the 200V~1200V range. Wide bandgap devices can operate at higher switching frequencies for comparable system efficiencies enabling reductions in component sizes leading to reduced system volume and cost. It is anticipated that SiC device costs and other wide bandgap devices will be competitive with Si devices in three to five years as manufacturers recoup R&D investments and reduce manufacturing costs. Thus, the main objective of this paper is to compare the performances of selected Si MOSFET, SiC JFET and SiC MOSFET for the utility interface of a dual-stage PV microinverter capable of injecting reactive power into the grid. The comparison is based on gate driver requirements, switching waveforms, thermal management needs, and efficiency.

Resonance propagation of ac filters in a large-scale microgrid

Abstract: Research into microgrids has become more promising during recent years. It has the potential of leading to a more resilient electric power delivery system in the face of system disturbances. Low pass ac filters are frequently adopted in microgrid power electronic interfaces that convert 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. However, the resonance problems caused by paralleling multiple converters with LCL filters, especially those converters having large power ratings (e.g., in the MVA range), must be accounted for when designing the entire microgrid. The analyses and designs should consider not only the resonant stability of a single converter but also the resonance propagation between multiple converters. A microgrid resonance propagation circuit model is built and investigated in this paper. Experimental waveforms validate the proposed analyses.

Active cancellation of common-mode voltages on drives rated 460-V and higher

Abstract: This paper presents a theoretical analysis of the "active circuitry" for a common-mode (CM) transformer to cancel CM voltages. The design methodology, and the practical Implementation issues are presented for motor drive systems rated 460 V or higher. An implementation example and experimental results for a 460-V motor drive system illustrate the feasibility of the proposed ideas.

An analysis of paralleled SiC bipolar devices

Abstract: SiC semiconductor devices are becoming more common in high power applications. This is largely due to higher blocking voltages and faster switching speeds. The development of SiC devices, specifically thyristors and GTOs, is still an evolving process [1]. There is not yet a single device capable of handling the magnitude of current typically seen in transmission and distribution systems and as a result these devices must be paralleled into a single switching position. SiC thyristors were used to carry out a study on paralleled SiC bipolar devices. Si bipolar devices are much better matched than SiC devices, but they exhibit much slower turn-on times [2]. Thus, the most suitable method of inducing current sharing in these devices is through gate control. However, SiC devices exhibit fast turn-on times while being poorly matched. Using various methods of gate control for SiC bipolar devices in parallel does not significantly affect the current sharing. The best way to improve current sharing is obtained using series resistors. These resistors should be chosen so that the voltage drop and power losses are minimized. The effects of thermal runaway are observed as well. As a device rises in temperature relative to the other devices, it conducts more current due to its negative temperature coefficient of on-state resistance. In order to maintain proper heat sharing, a design for a package is presented that includes three thyristors in parallel on a common substrate.

A Survey of Wide Bandgap Power Semiconductor Devices

Abstract: Wide bandgap semiconductors show superior material properties enabling potential power device operation at higher temperatures, voltages, and switching speeds than current Si technology. As a result, a new generation of power devices is being developed for power converter applications in which traditional Si power devices show limited operation. The use of these new power semiconductor devices will allow both an important improvement in the performance of existing power converters and the development of new power converters, accounting for an increase in the efficiency of the electric energy transformations and a more rational use of the electric energy. At present, SiC and GaN are the more promising semiconductor materials for these new power devices as a consequence of their outstanding properties, commercial availability of starting material, and maturity of their technological processes. This paper presents a review of recent progresses in the development of SiC- and GaN-based power semiconductor devices together with an overall view of the state of the art of this new device generation.

Overview of Dual-Active-Bridge Isolated Bidirectional DC–DC Converter for High-Frequency-Link Power-Conversion System

Abstract: High-frequency-link (HFL) power conversion systems (PCSs) are attracting more and more attentions in academia and industry for high power density, reduced weight, and low noise without compromising efficiency, cost, and reliability. In HFL PCSs, dual-active-bridge (DAB) isolated bidirectional dc-dc converter (IBDC) serves as the core circuit. This paper gives an overview of DAB-IBDC for HFL PCSs. First, the research necessity and development history are introduced. Second, the research subjects about basic characterization, control strategy, soft-switching solution and variant, as well as hardware design and optimization are reviewed and analyzed. On this basis, several typical application schemes of DAB-IBDC for HPL PCSs are presented in a worldwide scope. Finally, design recommendations and future trends are presented. As the core circuit of HFL PCSs, DAB-IBDC has wide prospects. The large-scale practical application of DAB-IBDC for HFL PCSs is expected with the recent advances in solid-state semiconductors, magnetic and capacitive materials, and microelectronic technologies.

Step-Up DC–DC Converters: A Comprehensive Review of Voltage-Boosting Techniques, Topologies, and Applications

Abstract: DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.

Energy Storage Systems for Transport and Grid Applications

Abstract: Energy storage systems (ESSs) are enabling technologies for well-established and new applications such as power peak shaving, electric vehicles, integration of renewable energies, etc. This paper presents a review of ESSs for transport and grid applications, covering several aspects as the storage technology, the main applications, and the power converters used to operate some of the energy storage technologies. Special attention is given to the different applications, providing a deep description of the system and addressing the most suitable storage technology. The main objective of this paper is to introduce the subject and to give an updated reference to nonspecialist, academic, and engineers in the field of power electronics.