Carlos Giron

A DSP- and FPGA-Based Industrial Control With High-Speed Communication Interfaces for Grid Converters Applied to Distributed Power Generation Systems

New energy concepts such as distributed power generation systems (DPGSs) are changing the face of electric distribution and transmission. Power electronics researchers try to apply new electronic controller solutions with the capacity of implementing new and more complex control algorithms combined with internal high-speed communication interfaces. Thus, it is possible to monitor, store, and transfer a large number of internal variables that can be sent online to local or remote hosts in order to take new set points of different generation units. With this objective, this paper presents the design, implementation, and test of an industrial multiprocessor controller based on a floating-point digital signal processor (DSP) and a field-programmable gate array, which operate cooperatively. The communication architecture, which has been added to the proposed electronic solution, consists of a universal serial bus (USB), implemented with a minimum use of the DSP core, and a controller area network (CAN) bus that permits distributed control. Although the proposed system can be readily applied to any DPGS, in this paper, it is focused on a 150-kVA back-to-back three-level neutral-point-clamped voltage source converter for wind turbine applications.

LQG Servo Controller for the Current Control of

This paper presents a current control scheme for a voltage-source converter connected to the grid through an LCL filter. The proposed current control is based on the linear quadratic (LQ) Gaussian (LQG) servo controller technique, which combines the LQ regulator and the Kalman filter (KF). The use of the KF instead of a Luenberger estimator improves the quality of the estimation of state variables in noisy environments, increasing the noise immunity of the control loop. This paper focuses on giving some criteria and practical hints to choose both the KF and LQ design parameters to achieve null steady-state tracking error, channel decoupling, and noise immunity. Furthermore, this paper analyzes the steady-state KF approximation that allows a significant decrement in the computational complexity of the algorithm at nearly no cost in accuracy. Simulation and experimental results prove the correct operation of the proposed LQG current control and the possible advantages of using KF to estimate the state vector.

LCL

The aim of this paper is to propose a multivariable current controller of voltage source converters (VSC) connected to the grid through an LCL filter. The proposal is a linear quadratic (LQ) servocontroller, which uses a fullorder estimator to obtain the full state vector. Two kinds of estimators are proposed and compared: prediction estimator and Luenberger estimator. The behavior and robustness of the controller is tested in presence of grid disturbances and mismatches in the model parameters.

Grid-Connected Voltage-Source Converters

This paper describes a communication architecture for a digital controller based on DSP-FPGA to be used in power electronic systems. For high rate transmissions, the proposed architecture has an USB bus implemented with a minimum use of the DSP core, using enhanced direct memory access and external memory interface modules of a TMS320C6713 high performance DSP and Cypress EZ-USB SX2trade high-speed USB interface device. Moreover, this architecture has CAN-bus communications to expand system with others subsystem, and a compact flash interface to storage data and DSP program, improving platform to boot alone. Host side has an application interface programmed in C with multithreading to process all data due high speed transfers.

Control of grid-connected voltage source converters with LCL filter using a Linear Quadratic servocontroller with state estimator

This paper describes the hardware and software modules of a remote Internet-based laboratory for experimentation with a 120-kVA multilevel power converter. The key feature of this laboratory is the utilization of a multilevel converter that can be controlled and supervised remotely in a secured way. A wide variety of laboratory experiments are supported, from grid connection to AC motor control. Users can choose the control structure, the control parameters, and the kind of load and get the graphical results of the measurements, all in real time.

Implementing high speed communication buses for a FPGA-DSP architecture for digital control of power electronics

The aim of this paper is to propose and compare two multivariable current controllers of voltage source converters (VSCs) connected to the grid through an LCL filter. The first proposal is a linear quadratic (LQ) servocontroller, which uses a full-order estimator to obtain the full state vector. The second proposal is based on the internal model control (IMC). The behavior of both controllers is tested in presence of grid disturbances and mismatches in the model parameters.

Remote Laboratory for Experimentation With Multilevel Power Converters

The importance of Wind Turbines based on Permanent Magnet Synchronous Generators (PMSG) has been increasing over the last years due to, fundamentally, its high efficiency. Fulfilling low voltage ride-through (LVRT) requirements is mandatory to guarantee the stability of the power systems under voltage dips, especially, in scenarios with high penetration of wind energy like Spain, Denmark, Germany, etc. This paper is focused on satisfying LVRT restrictions controlling both active and reactive powers delivered to the grid according to the more relevant grid codes. To achieve these requirements, this work proposes a method where kinetic energy storage in the turbine blades is carried out. DC active crowbar (braking chopper) is added in the converter, and, lastly, pitch angle control is used under long voltage dips. A control scheme, which emphasizes the regulation of the DC-link voltage, is designed and simulated in a Wind Turbine (WT) based on PMSG of 1MW with sensorless control.

Control of voltage source converters with LCL filter using state-space techniques

In this paper, two current controller schemes, based on repetitive controllers and proportional+resonant controllers using second order generalized integrators connected in parallel, are proposed and compared for shunt active power filters. Both controllers are well suited due to their optimum tracking and harmonic rejection capability. The objectives of this paper are: to analyze both controllers in the continuous and discrete time-domains; to study how to tune the parameters of the controllers and other auxiliary elements like PI controller in the case of repetitive-based controller; to show questions related to real-time implementation for the two cases; and, finally, to present some experimental and comparative results.

Low voltage ride-through of wind turbine based on interior Permanent Magnet Synchronous Generators sensorless vector controlled

Due to the intensive use of power converters and other non-linear loads in industry and by consumers in general, it can be observed an increasing deterioration of the power quality. The presence of harmonics in power lines results in greater power losses in the distribution system, interference problems in communication systems and, sometimes, operation failures of electronic equipments. Owing to these problems, active filters are used for harmonic elimination and they need a reliable identification method to operate efficiently. Many algorithms have been developed to estimate the harmonic parameters such as magnitude and phase. In this work, it is reported a comparison of identification techniques for single-phase systems, moreover, improvements on these methods and a new algorithm based on correlators are proposed. This comparison can guide in choosing a suitable technique in each application. Simulation and experimental results (obtained with digital signal processor TMS320C6713) validate the proposed comparison

Comparison of current controllers based on repetitive-based control and second order generalized integrators for active power filters

The future concept of universal operation embraces those distributed power generation systems (DPGS) capable of getting disconnected from the main grid to start operating within an island. Once the cause of disconnection is solved, the DPGS is able to resynchronize and reconnect with the grid. In these conditions, the universal operation can be successfully implemented through a voltage control. Voltage control is manly adopted in uninterruptible power supply (UPS) and island applications. However, a study that solely focused on the universal operation is missing. The goal of this work is to help in the selection of the most suitable control structure as function of: 1) power dynamics, power quality, and robust stability in grid-connected; 2) voltage regulation and performance under local load steps in island mode; and 3) behavior during the reconnection with the grid. For that purpose, five architectures have been reviewed within a general mathematical framework and with experimental results.