Fernando Mancilla-David

A Transformer-less High-Gain Boost Converter With Input Current Ripple Cancelation at a Selectable Duty Cycle

This letter proposes a boost dc-dc converter topology with the novel capability of canceling the input current ripple at an arbitrarily preselected duty cycle. This is accomplished without increasing the count of the number of components in contrast to other solutions available in the literature. In addition, the converter features a high voltage gain without utilizing extreme values of duty cycle or boosting transformers. These features make the converter ideal to process electric power coming from low-voltage power-generating sources, such as renewables. This paper provides details on the principle of operation via topological considerations and a mathematical model. The key factor of reactive component sizing is also discussed in detail. The converter was validated in the laboratory through the construction of a hardware prototype.

A Comparative Evaluation of Series Power-Flow Controllers Using DC- and AC-Link Converters

This paper presents a comparative evaluation of direct AC-AC converters and multipulse voltage source DC-AC converters for providing series compensation of transmission systems. This paper provides a detailed discussion of power circuit design issues related to various performance considerations for both approaches. A benchmark case study is used to demonstrate the operation and performance of both designs in terms of steady-state and dynamic performance indices. It is shown through detailed computer simulations that both approaches are competitive with respect to each other in terms of their functional performance.

Achieving the Smart Grid through customer-driven microgrids supported by energy storage

This paper describes some of the aspects of the Smart Grid Initiative in the US and purports its realization through an emerging paradigm in microgrids, i.e., the customer-driven microgrids. Special attention is paid to the increasing role played by energy storage elements. Some existing technologies of energy storage are revisited in the perspective of their utilization in customer-driven microgrids.

A Neural Network-Based Low-Cost Solar Irradiance Sensor

Measuring solar irradiance allows for direct maximization of the efficiency in photovoltaic power plants. However, devices for solar irradiance sensing, such as pyranometers and pyrheliometers, are expensive and difficult to calibrate and thus seldom utilized in photovoltaic power plants. Indirect methods are instead implemented in order to maximize efficiency. This paper proposes a novel approach for solar irradiance measurement based on neural networks, which may, in turn, be used to maximize efficiency directly. An initial estimate suggests the cost of the sensor proposed herein may be price competitive with other inexpensive solutions available in the market, making the device a good candidate for large deployment in photovoltaic power plants. The proposed sensor is implemented through a photovoltaic cell, a temperature sensor, and a low-cost microcontroller. The use of a microcontroller allows for easy calibration, updates, and enhancement by simply adding code libraries. Furthermore, it can be interfaced via standard communication means with other control devices, integrated into control schemes, and remote-controlled through its embedded web server. The proposed approach is validated through experimental prototyping and compared against a commercial device.

Per-Sequence Vector-Switching Matrix Converter Modules for Voltage Regulation

This paper proposes a novel dynamic voltage restorer (DVR) topology based on reduced-order matrix converter modules. The topology utilizes two modules for selective and independent sequence voltage synthesis. As a result, the DVR proposed herein can compensate for balanced as well as unbalanced voltage sags/swells. Each module is realized using a vector-switching matrix converter. The entire topology is energy storage free, and each module is pulsewidth modulated using simple dc duty ratios. This paper provides details on the DVR modeling, equivalent circuit, and feedback controller design. Thorough computer simulations and experimental prototyping are used to validate the approach.

A review of AC choppers

AC choppers are a family of ac-to-ac power converters that can be derived from the traditional dc-to-dc converters. Research activity in this kind of converter has recently increased in applications for power conditioning—such as voltage control in the distribution system and power flow control in the transmission system—as an alternative for the dc-link approach compensators based on voltage source converters. The control is simpler and the power rating of the devices is smaller for compensators with the same power rating; the main drawback is they cannot control the output-voltage frequency as the matrix converter. This paper presents a state-of-the-art review on the development of ac-choppers. The principle of operation is explained by using the six switches three-phase buck converter as an example. The main applications used in power conditioning and power flow control are introduced along with emerging topologies.

Unbalanced Grid Fault Ride-Through Control for Single-Stage Photovoltaic Inverters

Integration of distributed generation (DG) such as photovoltaics (PV) represents a challenge for the traditional operation of distribution power systems. As the installed power of DGs grows, grid codes are being modified to involve DGs in the provision of ancillary services. This includes the ability to ride-through large disturbances. In this paper, the behavior of a single-stage PV system under unbalanced voltage conditions is studied, and a fault ride-through control scheme is proposed which is able to support the grid through the injection of reactive power. Furthermore, adjustable power quality is enabled as a tradeoff between power ripple and current harmonics. The control scheme makes use of a current controller based on the space vector Fourier transform concept. No rotational transformation is required, and zero steady-state error is ensured when tracking distorted current references. The controller was tested in detailed PSCAD/EMTDC computer simulations, and implemented in a real grid-connected PV system to demonstrate its performance under unbalanced voltage conditions.

An Estimator of Solar Irradiance in Photovoltaic Arrays With Guaranteed Stability Properties

Photovoltaic cells are characterized via a static relationship that describes their current-voltage relationship. This relationship is a complicated implicit algebraic equation that depends, in a nonlinear way, on two critical uncertain parameters: temperature and solar irradiance. The efficient operation of the panel relies on the knowledge of these key parameters. While it is technologically feasible to measure the former, a sensor for the latter is usually expensive and difficult to calibrate. In this paper, we propose a globally convergent estimator for solar irradiance which is developed using the principles of immersion and invariance recently reported in the control literature. To design the estimator, a suitable reparameterization of the current-voltage characteristic, which effectively exhibits a monotonic behavior, is introduced. The approach is validated through detailed computer simulations and experimental prototyping using real outdoor measurements.

A Dynamic Voltage Restorer based on vector-switching matrix converters

This paper introduces a novel Dynamic Voltage Restorer (DVR) based on a reduced-order matrix converter capable of compensating for balanced as well as unbalanced voltage sags. The DVR has the ability of independently and selectively generating positive as well as negative sequence voltages, and hence it can compensate for different kind of sags. Operating principles, equivalent circuits, and illustrative examples in terms of computer simulations are presented in order to validate the approach.

A Unified Single- and Three-Phase Control for Grid Connected Electric Vehicles

In order to reduce cost, size, weight, and volume of on board chargers in electric vehicles, it has been proposed to pursue integration for the dual usage of converters for both charging and propulsion. The solution here goes further in that it also supports the control of slow single-phase and fast three-phase charging through one and the same power electronic converter. A unified control methodology for the on-board chargers in electric vehicles is proposed. The control is distinguished in that it can perform four-quadrant operation while connected in single-phase or three-phase mode. The operation and network synchronization are automatically adjusted based on given terminal voltage and current measurements without the need for supplementary status signals. An analysis illustrates how the various measurements are processed for obtaining single- and three-phase flexibility while retaining compatibility with well-established methods of converter current mode control. The proposed control is validated via detailed simulation and demonstrated in a smart grid laboratory. The hardware implementation in the laboratory substantiates the claims of flexible single- and three-phase control.