Showing papers by "Juan Carlos Balda published in 2008"

A Survey of Systems to Integrate Distributed Energy Resources and Energy Storage on the Utility Grid

Abstract: Renewable distributed energy resources (DERs) will play a large role in the future energy infrastructure because of advantages like lower carbon imprints, lower fuel costs, and reduced power flows on transmission lines. The unreliability of many renewable DERs due to the intermittent nature of their supply, especially in the case of solar and wind generators, can be mitigated with energy storage that brings a host of additional benefits including load leveling, frequency control, and power quality compensation. One barrier to adoption of these technologies is the need for interfaces between the different voltage levels and waveforms produced by the various systems. This paper, which is tutorial in nature, examines several possible interfaces presented in the literature and provides a comparison between their advantages and disadvantages.

High voltage, high power density bi-directional multi-level converters utilizing silicon and silicon carbide (SiC) switches

Abstract: This paper presents a bi-directional ac-dc isolated converter designed to be utilized within the US Navy's Integrated Fight Through Power (IFTP) concept. To demonstrate the proposed approach the authors have designed, fabricated, and tested a 20 kW power conversion module (PCM) prototype. The fabricated PCM module was used to demonstrate the proposed overall electrical design approach, high-frequency isolation, bi-directional power flow and soft-switching operation of the quasi-resonant topologies. Moreover, the 20-kW prototype allowed the verification of control methodologies as well as magnetic and thermal designs, and provides a test bed for future, higher power work.

Synthesis of Sinusoidal Waveform References Synchronized With Periodic Signals

Abstract: This paper proposes a novel method to generate a sinusoidal waveform synchronized with any measurable periodic signal whose frequency is within a given neighborhood. The synthesized sinusoidal signal could be used as a reference current for certain applications of parallel active power filters or any other where such synchronization would be necessary (e.g., ac/dc converters for renewable energy resources, power factor correctors, power supplies, UPS, etc.) The method is based on the behavior of a dynamical system and avoids employing the usual combination of phase-locked loop (PLL) and lookup table found in most parallel active filters synthesizing a sinusoidal source current (a table also means using significant storage memory). The novel method produces two high-quality sinusoidal waveforms that are in quadrature and is applicable to those parallel active filters whose control methodology is in the reference frame, or alternatively, it produces three sinusoidal waveforms shifted 120 degrees for designs that work in the frame. Here, a th order implementation is described, including a proof of convergence. For its most simple implementation , simulated and experimental results are included.

The modeling and characterization of silicon carbide thyristors

Abstract: The U.S. electric grid is moving down a path of modernization and SiC-based thyristor devices may play a role in that transformation. This paper reports two primary contributions - (a) accurate physics based modeling and characterization of a SiC p-type thyristor, and (b) developing and codifying a generalized parameter extraction strategy for the Lumped-Charge modeling method, making it feasible to apply this technique for any bipolar device - beyond the thyristor. The level-3 physics based model incorporating SiC material and device geometry is highly accurate, replicating device capacitances, lifetimes, and non-quasi-static effects present in the actual device. A 1 kV/36 A p-type SiC thyristor provided by Cree was used to validate the model. Special test jigs were also designed and used to fully characterize the dc and transient performance of the device, ensuring precise measurements and safety of the user.

Solid-state fault current limiters: Silicon versus silicon carbide

Abstract: As utilities face increasing fault currents in their systems as a result of increasing demand and/or deployment of new technologies, fault current limiters promise a solution that will mitigate the need for replacing existing breakers as well as being a general protective device for elements connected to the grid. This paper describes some recent advances in semiconductor-based fault current limiting technology including both the more mature silicon developments along with early developments using silicon carbide. The capabilities and limitations of these technologies are compared and contrasted. Some example scenarios of FCLs have been analyzed and are briefly described along with advanced features that semiconductor FCLs may bring to the solution space.

Fault Current Limiter Placement Strategies and Evaluation in Two Example Systems

Abstract: The growth of demand invariably lead to higher and higher fault currents, and as a consequence protection devices must have higher ratings The integration of distributed energy resources further complicates protection schemes, especially those that assume a radial distribution scheme and power flowing in only one direction These conditions generate an increasing demand for fault current limiters to keep fault currents within the ratings of existing protection equipment as well as to minimize the impact of distributed generation on the grid during faults However, placement of protection equipment must be carefully considered in order to keep them cost effective and to prevent the limiters themselves from disrupting existing protective measures This paper explores several placement and coordination guidelines, as well as provides simulations of fault current limiters placed in substations with ring bus and double bus configurations, respectively

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 grid interface for distributed energy resources with integrated energy storage using a high frequency AC link

Abstract: A multiport converter with a high frequency (hf) ac bus is proposed for use as a distributed energy resource (DER) to grid interface with an integrated energy storage system (ESS). The combination of DER and ESS allows the DER to provide load following, load leveling, power quality compensation, voltage and frequency control, and spinning reserve, as well as savings on deferred installation of new transmission lines and centralized power plants, reduced loads on existing transmission lines, increased grid security and reliability, and the potential to adjust power delivery to take advantage of the energy market. The use of the hf-ac bus allows the boost and dc-hf ac conversion functions to be combined into a single converter and reduces the size of the transformer and passives. The proposed design allows independent control of each of the DER and ESS inputs, allowing for modular design and ease of expansion for the system. The digest explores several of the challenges of the design and presents theoretical and simulated waveforms for one of the operating conditions. Seven possible operating conditions are identified, and the applicability of each operating condition is determined when the system is used for power generation, load leveling, and spinning reserve.

Testing of Power Electronic Modules for Distributed Systems at the National Center for Reliable Electric Power Transmission

Abstract: Testing of new technologies before field deployment is crucial to gain acceptance by electric utilities, in particular, of distributed generation based on high power electronic modules The NCREPT 138 kV 6 MVA Test Facility at the University of Arkansas offers an advanced test platform designed to meet the needs of complex high power electronics testing for several distributed energy applications NCREPT could be also employed as a test platform for compliance of IEEE 1547 and UL 1741 standards This paper describes the center capabilities and some potential test applications such evaluation of grid-connected inverters supporting energy storage systems