Sebastian Gomez Jorge

Current Controller Based on Reduced Order Generalized Integrators for Distributed Generation Systems

This paper presents a current controller based on a stationary reference frame implementation of an integrator in the synchronous reference frame [called here reduced order generalized integrator (ROGI)], suitable for three-phase distributed generation systems. The proposed controller is compared with the traditional second-order generalized integrator (SOGI)-based current controller. It is confirmed that, in normal operation conditions, both controllers have similar performance, requiring the ROGI-based controller much less computational burden than the SOGI counterpart. The proposed controller injects sinusoidal currents synchronized with the grid voltage, without requiring any dedicated synchronization algorithm. Three different current injection strategies are realizable with the same controller structure: balanced current injection, constant instantaneous active power injection, and maximum instantaneous active power injection. A state-variable-based control methodology in the discrete-time domain is presented. It ensures the stability and performance of the closed-loop system, even for high-order controllers and large digital signal processor processing delay. Moreover, it is confirmed that the proposed controller works satisfactorily even on faulty grid conditions.

Full-State Feedback Equivalent Controller for Active Damping in

This paper presents a method for the active damping of a grid-tie LCL inverter. This method is based solely on the feedback of the injected current into the grid and is applicable to any linear current controller. It requires a low additional computational load over that required to control a grid-tie L inverter and the same measurements. A general design methodology for the current controller, which allows positioning all of the closed-loop poles of the system at arbitrary locations (even unstable modes of the LCL filter), is proposed. Stability and robustness of the resulting system are analyzed. Simulation and experimental results that validate the proposal are presented.

LCL

This paper presents a frequency adaptive discrete-time-domain nonlinear filter for three-phase grid synchronization. Due to the discrete time nature of the proposal, all the analysis performed here is valid for a DSP implementation, and this implementation is straightforward. The proposed algorithm has very low computational burden, as in its basic form it only requires three states.

-Filtered Grid-Connected Inverters Using a Reduced Number of Sensors

This paper analyzes the behavior of a non-frequency-adaptive reduced-order-generalized-integrator-based current controller when the grid frequency is subject to variations and proposes a simple method for making it frequency adaptive. The proposed frequency adaptation scheme allows to keep the good performance of the current controller even in the presence of frequency variations. The resulting frequency-adaptive controller has very low computational burden, and it is therefore suitable for low-cost digital-signal-processor implementation.

Frequency Adaptive Discrete Filter for Grid Synchronization Under Distorted Voltages

This paper proposes a grid voltage sensorless controller for single-phase voltage source converters. The controller is composed of an observer and a current control scheme. The proposed observer replaces the grid voltage measurement and is used to generate the current references and to compensate the perturbation effect of the actual grid voltage on the coupling inductor. This allows us to implement a simple proportional resonant current control algorithm. The proposed observer also estimates the grid frequency, allowing us to immunize the controller to grid frequency variations.

Frequency-Adaptive Current Controller for Three-Phase Grid-Connected Converters

In this paper, a nonlinear control strategy for controlling a dc/dc buck converter feeding a constant power load is proposed. The main objective of the proposed controller is to improve the transient performance when in presence of unknown power disturbances. A feedback controller is combined with a feedforward strategy. A nonlinear reduced order observer is used for estimating the value of the power load and its time derivative. These estimated values are fed forward to the nonlinear feedback controller whose design is based on feedback linearization method. The proposed controller is tested via simulation and experimental results.

Control Scheme for a Single-Phase Grid-Tied Voltage Source Converter With Reduced Number of Sensors

This paper presents a globally convergent nonlinear observer capable of recovering the positive and negative sequences of an unbalanced grid voltage. The proposed algorithm has frequency adaptation, and is therefore, in steady state, immune to grid frequency variations. Another feature is that since it is a reduced-order observer, only three states are needed to implement it. The validity of the proposed scheme is verified through mathematical analysis, simulation, and experimental results.

Nonlinear Control of a Buck Converter Which Feeds a Constant Power Load

In this paper a nonlinear control strategy for controlling a dc/dc Buck converter feeding a constant power load is proposed. A feedback controller is combined with a feedforward strategy. A nonlinear reduced order observer is used for estimating the value of the power load and its time derivative. These estimated values are fed forward to the nonlinear feedback controller whose design is based on feedback linearization method. The proposed controller is tested via simulations and also, experimental results are presented.