Guilherme Bonan

Multiple Resonant Controllers for Uninterruptible Power Supplies—A Systematic Robust Control Design Approach

This paper deals with the synthesis problem of multiple resonant controllers for uninterruptible-power-supply systems in a robust control framework. The controller parameters aiming the tracking of sinusoidal reference signals (with zero steady-state error) and the rejection of harmonic components of the output voltage (when supplying energy to time-varying nonlinear loads) are determined by means of a convex optimization problem subject to a set of linear-matrix-inequality constraints. Results from a 5.0-kVA experimental setup are considered to illustrate and validate the proposed approach.

Robust control design of multiple resonant controllers for sinusoidal tracking and harmonic rejection in Uninterruptible Power Supplies

This paper presents a robust control strategy for tracking sinusoidal reference signals with zero steady state error and harmonic compensation in Uninterruptible Power Supplies - UPS. Multiple resonant controllers are derived for DC-AC inverters when supplying energy to (uncertain) nonlinear loads to obtain a nice tradeoff between transient response and disturbance rejection regardless possible load variations. The controller parameters are determined by means of a convex optimization problem subject to a set of linear matrix inequalities (LMIs). Real time experiments demonstrate the potentials of the proposed approach for controlling UPS systems.

Repetitive controller design for uninterruptible power supplies: An LMI approach

This paper proposes a semidefinite programming approach for designing repetitive controllers applied to uninterruptible power supplies. Considering a state space realization of a standard repetitive controller, Lyapunov-Krasovskii stabilization design conditions are cast in terms of linear matrix inequalities which are numerically solved by standard software packages. These conditions ensure the closed-loop stability for a set of admissible loads which is supposed known a priori. Experimental results are presented to demonstrate the effectiveness of the proposed design conditions.

Small renewable hybrid systems for stand alone applications

To provide renewable energy to stand alone applications the generation system should be composed of different types of energy sources to make better use of the natural resources in these applications. A common practice is to combine wind and solar PV energies in the so called hybrid renewable systems. Due to the long distance, and difficult access the overall system used in these applications must be reliable. And the reliability of the system, specially the inverter used to regulate the AC voltage, is one of the main problems associated to these systems, and is responsible for the lack of confidence in renewable systems at several locations in Brazil. This paper shows the initial results of using renewable hybrid systems specially designed for isolated areas, focusing attention on reliability, efficiency and expansion flexibility. It presents the system description, mode of operation, inverter design, and experimental results measured in a pilot plant located in Lençóis Island, a small isolated community in the northeast region of Brazil.

Robust PSC control design for sinusoidal tracking in uninterruptible power supplies

This paper proposes an alternative strategy to track sinusoidal reference signals with zero steady state error for uninterruptible power supplies - UPS. A robust proportional-sinusoidal-cosinusoidal (or in short PSC) controller is derived for sinusoidal voltage regulation subject to load variations. The controller parameters are determined by means of a convex optimization problem subject to a set of linear matrix inequalities (LMIs). Simulations and practical experiments demonstrate the potential of the proposed approach for controlling UPS systems.

Parallel-connected inverters applied in renewable energy systems

This paper presents the results of inverter development for standalone renewable energy systems used in isolated communities. One of the main problems of such systems, located in isolated areas of difficult access, is the inverters. The mean time before failure of these equipments has been shown smaller than expected. In these applications the inverters should have the following features: expansion flexibility and robustness; high efficiency; and adequacy to operate in adverse environmental conditions. The results presented in this paper are related to inverters development taking into account these requirements. The paper will present the mode of operation of the system, showing its robustness and viability for utilization of the inverters in standalone renewable energy systems.

Power transference to AC voltage sources

This paper presents a simple approach of a topology already known in the literature, applied in active power transference from DC source to any AC voltage source, whether the utility power or a voltage inverter that is forming an isolated AC grid. Simulation results of this application are presented and experimental results validate this topology.

Simplifying the design of parallel-connected UPS inverters by means of the per unit system

Parallel UPS inverters provide redundancy and scalability to energy backup systems and the main design challenge is to guarantee that each unit will supply the same power to a common load. Therefore, the key of a good design is the study of the active and reactive powers unbalance. In this paper, the unbalance of a drooping parallelism method is analyzed and practical simplifications are applied in the exact equations. These equations are then rewritten in the per unit system, making the study even more intuitive and generalizing the design. The design method is first tested with a research association of two analog based UPS inverters and then with an entire line of commercial DSP based UPS inverters.