Showing papers by "Luiz A. C. Lopes published in 2018"

Power Electronic Converter Based PMSG Emulator: A Testbed for Renewable Energy Experiments

Abstract: This paper presents a converter-based permanent magnet synchronous generator (PMSG) emulator as a testbed for designing, analyzing, and testing of the generator's power electronic interface and its control system. The PMSG model is formulated in a real-time digital simulator. A voltage type ideal transformer model combined with a virtual impedance is presented as an interface algorithm. The design procedure and implementation of the virtual impedance in a simulation platform is discussed. A six-switch voltage source converter is used as a power amplifier to mimic the behavior of the PMSG supplying linear and nonlinear loads. A proportional–integral plus resonant controller is proposed as a voltage loop controller for tracking a distorted output voltage reference signal. The accuracy of the proposed emulator is investigated for the fundamental and low-order voltage harmonics. Technical challenges of the PMSG emulator are considered and proper solutions are suggested. The performance of the proposed emulator is compared with an actual PMSG.

A novel 5-switch tapped-inductor multi-state bidirectional DC-DC converter

Abstract: DC distribution systems, common in transportation systems, are now being considered for residential and office buildings. Whatever the case, energy storage units with fast acting interfaces are of paramount importance for power balancing and power quality enhancement. The power electronics interfaces, usually centered on inductive elements, tend to present non-minimum phase characteristics and slow response. This issue can be mitigated with the use of multi-state switching techniques. The novel bidirectional DC-DC converter proposed in this paper is suitable for this technique and employs a tapped inductor in which the direction of the current does not have to change when the power flow through the converter is to be reversed, leading the system to a faster response.

Power balance technique for cascaded H-bridge multilevel cells in a hybrid power amplifier with wide output voltage range

Abstract: This paper discusses and extends the principle of a switching technique, called First-In First-Out (FIFO) and proposes a novel switching technique called Split Voltage First-In First-Out (SV-FIFO) for a wide output voltage variation, especially for lower output voltages. Both techniques enhance the power balance among the cells of a single-pulse/staircase Cascaded H-Bridge Multilevel Converter (CHBM) applied to a Hybrid Power Amplifier (HPA). These techniques are compared with the conventional First-In Last-Out (FILO) switching method for rated and lower output voltages. Mathematical equations are derived for a quantitative comparison of both methods, with the statistical analyses for various operating conditions.

Improved Dynamic Voltage Regulation in a Droop Controlled DC Nanogrid Employing Independently Controlled Battery and Supercapacitor Units

Abstract: DC bus voltage signaling (DBS) and droop control are frequently employed in DC nano and microgrids with distributed energy resources (DERs) operating in a decentralized way. This approach is effective in enforcing the desired contributions of power sources and energy storage systems (ESSs) in steady-state conditions. The use of supercapacitors (SCs) along with batteries in a hybrid energy storage system (HESS) can mitigate the impact of high and fast current variations on the losses and lifetime of the battery units. However, by controlling the HESS as a single unit, one forfeits the potential contribution of the SC and its high power capabilities to dynamically improve voltage regulation in a DC nanogrid. This paper discusses an approach where the SC interface is controlled independently from the battery interface, with a small droop factor and a high pass filter (HPF), to produce high and short current pulses and smooth DC bus voltage variations due to sudden power imbalances in the DC nanogrid. Experimental results are presented to show that, unlike in a conventional HESS, the SC unit can be used to improve the dynamic voltage regulation of the DC nanogrid and, indirectly, mitigate the high and fast current variations in the battery.

Proof-of-concept analysis of a supplemental solar power system for aircraft

Abstract: This paper aims to analyze the viability of a solar power system as a supplemental power source for commercial and business aircraft.,First, a model is established to estimate the potential available power from suitable aircraft surfaces for various meteorological conditions, ground and flight mission characteristics. A proposed aircraft system architecture and an associated parametric conceptual sizing model are presented. This supplemental solar power system sizing model is integrated into an aircraft multidisciplinary design optimization environment to evaluate the aircraft-level impact on mission fuel burn. A parametric study for a business jet aircraft is performed to analyze various solar cell types and power densities for converters. Trade-off studies are performed between efficiency and weight.,Considering today’s efficiency and power-to-weight ratio of the system components, overall fuel burn reduction can be achieved. Therefore, the technology development work can start now to target short to mid-term applications. In addition, promising system integration scenarios are identified, such as the use of solar power for autonomous operation of the air conditioning system on ground, which yield potential further benefit. In conclusion, a supplemental solar power system seems a promising candidate for more efficient aircraft operation.,The presented novel supplemental solar power system architecture concept and its foreseen aircraft integration show potential benefits for near term applications. The results show that the break even for this technology is already reached and therefore build the foundation to further investigate the technology integration challenges. Clear directions for future research and development are outlined enabling the advancement of the technology readiness level.

Virtual Synchronous Generator with Variable Inertia Emulation Via Power Tracking Algorithm

Abstract: This paper proposes the technique, variable inertia emulation of the virtual synchronous generator (VSG) fed from a photo voltaic (PV) source via power tracking algorithm. The virtual synchronous generator is tied to a three-phase distribution line at the point of common coupling (PCC). The operating point on the power - voltage characteristics of the PV source is suitability controlled to emulate the inertia in the input. The variable inertia is achieved through variation of inertia constant in the closed loop power control. This method of moving on the power - voltage characteristics requires a power tracking algorithm for the PV Source. The VSG is modeled using synchronous reference frame theory with a voltage oriented control scheme(VOC). We have chosen an improved version of phase locked loop(PLL) for the accurate estimation of the phase and extraction of the fundamental component from the voltage at PCC. The droop control characteristics determine the real power and reactive power to be supplied by the VSG. The simulation results support the analysis presented in this paper.

Design procedure for the LPF of a three-phase SPWM VSC operating with a wide range of output power, voltage and frequency with low harmonic distortion

Abstract: This paper proposes a design procedure for a Low Pass Filter (LPF) of a three-phase Voltage Source Converter (VSC) applied as a Power Amplifier (PA) intended for the emulation of a rotating AC machine. It operates with a wide range of output voltage, varying from 22 V to 220 V; frequency from 0 Hz to 1 kHz and is capable to maintain the output voltage with low value of Total Harmonic Distortion (THD). A design procedure is presented and discussed and its performance in steady state condition is verified by means of simulation with MATLAB software.