Alben Cardenas

Development of a FPGA Based Real-Time Power Analysis and Control for Distributed Generation Interface

Energy coming from renewable sources has become very important nowadays, mainly because of their negligible contribution to greenhouse gas generation. A problem that then arises is how to integrate these new sources into a traditional power grid, in such a manner as to maximize the efficiency and reliability of this new distributed generation (DG) system. The hardware to do that is generally a voltage source inverter (VSI) that supplies a common load, as in single-phase residential and commercial applications. The optimizing process requires, of course, the usual power analysis. This paper presents the development and the experimental evaluation of a power control system for a single-phase grid-connected VSI including the power analysis using as processor for the control implementation a field-programmable gate array (FPGA) circuit. New hardware structures of adaptive linear neural networks (ADALINE) allow the implementation of power control algorithms and have also permitted the real-time analysis of the high-order harmonics without increasing the implementation area of the FPGA circuit. These features are ideal for novel DG power electronics interfaces that could be used not only for active power dispatch but also for harmonics and reactive power compensation. Simulation and experimental results of the proposed fixed and variable frequency schemes are included to confirm their validity.

Real-time evaluation of power quality using FPGA based measurement system

Real-time evaluation of power quality is a desired feature in research and industrial projects, especially when embedded systems are employed and/or studied. Fast Fourier Transforms FFT is commonly used to evaluate the harmonic content of electric signals. Artificial Neural Networks (ANN) are also employed for harmonics estimation with short processing time and low implementation complexity. Commercial power quality measurement systems are available and offer good performance, communication and storage capabilities, and other special features, however in most of them the real-time information is not available or it is offered with important communication delays. This paper presents the implementation of a measurement system using Xilinx FPGA target and the Adaptive Linear Neuron (ADALINE) algorithm for real-time evaluation of power quality. Experimental results show that the implemented system can be employed for power quality monitoring and embedded control applications.

Load Sharing Strategy for Autonomous AC Microgrids Based on FPGA Implementation of ADALINE&FLL

Paralleled operation of voltage-source inverters (VSIs) is currently achieved by using voltage/frequency droop control techniques which requires the knowledge of the system parameters. Otherwise, centralized control techniques with robust communication among VSIs controllers are also used. This paper presents a new control strategy which allows the load sharing between the power sources of an ac microgrid without centralized controller or any communication among the VSIs; only local measurements of voltage and output current are used. The dispatchable sources (e.g., fuel cells) of the microgrid are operated using voltage control with a direct droop scheme, and the nondispatchables or intermittent ones (e.g., wind turbine generators) are operated using power control with a complementary inverse droop scheme (D-Droop + I-Droop). The number of operating sources can be changed online without any modification needed on the VSI controllers. The proposed VSI controllers are based on the variable frequency adaptive linear neuron with frequency-locked loop for the VSIs system synchronization, voltage/power and signal estimation. Experimental results using field-programmable gate array devices for the implementation of each VSI control in the microgrid test bench demonstrated the validity of the proposition.

Experimental Evaluation of Voltage Positive Feedback Based Anti-Islanding Algorithm: Multi-Inverter Case

The novel scenario of power systems with massive utilization of distributed generation (DG) imposes that islanding detection methods for voltage source inverter (VSI)-interfaced DGs must be evaluated taking into account multi-inverter configurations. This paper presents the experimental validation of an active islanding detection algorithm for multi-inverter systems proposed by the authors in previous work. Field programmable gate array implementation of power control and islanding detection algorithms has been used to test this proposition in a multi-inverter system based on grid-connected insulated gate bipolar transistor VSIs. The proposed islanding detection algorithm offers a very low impact on power quality and rapid and efficient islanding confirmation which is demonstrated by simulation and experimentation. The performance of the algorithm was tested under critical conditions as resonant load with high quality factor and unity power factor and also for cases where load and VSI powers are matched.

Towards Smart Integration of Distributed Energy Resources Using Distributed Network Protocol Over Ethernet

The Distributed Network Protocol (DNP3) is the communication protocol standardized by IEEE for electric power systems (EPS) and it is a promising communication standard in the context of Smart Grids. This paper presents the Distributed Network Protocol over Ethernet (E-DNP3) using field programmable gate array (FPGA) technology as the first step to the EPS automation. The communication architecture improves the delivery time comparing with previous works and provides an adaptable solution for real-time information exchange in electrical applications such as management, control, and protection of power systems. The developed work allows the analysis of the feasibility of the proposed communication architecture in a real microgrid scenario. This implementation accomplishes a new technique for the communication architecture in order to integrate the distributed energy resources (DERs) to the local power system. The experimental results prove that the proposed architecture satisfies the communication requirements for real-time monitoring and control of EPS towards Smart Grid applications.

Development of Power Interface With FPGA-Based Adaptive Control for PEM-FC System

This paper presents the development of a power interface for a fuel cell (FC) system supplying an ac load. The proposed system comprises a two stages conditioning system, including a switched capacitor dc-dc boost converter and a full bridge insulated-gate bipolar transistor (IGBT) single-phase inverter (dc-ac converter). A fully digital control structure is proposed to manage both power converters using the same control device. The control strategy takes advantage of the parallelism of the field programmable gate arrays (FPGA) technology to share in real-time the controllers information addressing the common problem of low-frequency ripple of FC current when supplying ac loads. The control system has been implemented and evaluated by co-simulation, and by experimentation with a proton exchange membrane fuel cell (PEM-FC) system. The results show that the proposed system allows a safe operation of the FC by limiting the current ripple under 3%. These results also confirm that the transient response of the conversion system permits to correctly supply the ac load.

FPGA implementation of fixed and variable frequency ADALINE schemes for grid-connected VSI synchronization

Grid-connected Voltage Source Inverter (VSI) are essentials to integrate the Distributed Energy Resources (DER) with the utility power systems. This integration allows the increasing of the reliability and the efficiency of power systems. However, the massive utilization of VSI can generates problems into the power quality indices of power systems, especially if the power control algorithm has a poor synchronization. Therefore, a good synchronization of power control algorithm helps to keep acceptable power quality indices. This paper presents the FPGA implementation of synchronization and power control of VSI using a variable frequency ADALINE structure. The proposed ADALINE implementation is used for amplitude, frequency and phase detection of the fundamental utility voltage and its harmonics. Fundamental signal information is then employed for the synchronization and power control scheme. The fundamental and harmonics information is employed to evaluate the power flow and the power quality of VSI output current. This evaluation is very useful for power quality problems mitigation. Experimental results, using low power VSI and Xilinx FPGA system, demonstrate the validity of proposition.

An Active Anti-Islanding Algorithm for Inverter Based Multi-Source DER Systems

Islanding detection is an essential function for safety and reliability in grid connected distributed generation (DG) systems. Several methods for islanding detection are proposed, but most of them are not efficient for multi-source configurations, or they may produce important power quality degradation getting worst with DG penetration increasing. This paper presents an active islanding detection algorithm for voltage source inverter (VSI) based multi-source DG systems. The proposed method is based on voltage positive feedback theory. Simulations by MATLAB/Simulink/SimPowerSystems were used to evaluate its performance and its advantages concerning time response and power quality effects under critical conditions as loads unity power factor and high quality factor.

Frequency Locked Loop for grid-connected VSI synchronization and power analysis

Future power systems will include the massive utilization of distributed generation mainly based on renewable energy resources. These renewable energy resources can be interconnected to the utility grid by means of power electronics converters working as Voltage Source Inverters (VSIs) which must be synchronized with the utility voltage. Synchronization methods are mandatory to make possible a correct power control and to keep an acceptable power quality. The Field Programmable Gate Array (FPGA) has been introduced in recent years as a promising target device for embedded applications especially when the parallel implementation of multiple algorithms is needed. This paper presents a new structure of the Adaptive Linear Neuron (ADALINE) with Frequency Locked Loop (ADALINE-FLL), its FPGA implementation and its experimental evaluation. The proposition has been implemented in a Xilinx FPGA device and experimentally validated using low power VSI connected to a low voltage utility.

Hardware implementation of droop control for isolated AC microgrids

Lately the integration of Distributed generation systems privileging renewable sources for offshore regions is growing to view a reduction of air pollutant emissions. Due to the intermittency of Renewable Energy Sources (RES) it must be necessary to develop a quality advanced control of the involved power interfaces to warrant the frequency and voltage required by ac off-shore loads taking into account the absence of grid connection. The droops control is a well known control strategy used for load sharing using local information of the inverters active and reactive powers. This paper presents the experimental validation of droop control strategy, using ADAptive LInear NEuron (ADALINE) signal decomposition technique for the VSI synchronization, and within a realistic scenario representing an autonomous microgrid. The advantages of the real-time operation and parallel multi task operation have been exploited using the FPGA devices, which have been employed for the hardware implementation of each VSI (Voltage Source Inverter) control. Simulation, co-simulation and experimental results are provided to verify the validity of the proposed implementation.