Tárcio André dos Santos Barros

Performance of a Direct Power Control System Using Coded Wireless OFDM Power Reference Transmissions for Switched Reluctance Aerogenerators in a Smart Grid Scenario

This paper presents a performance analysis of a wireless direct power control system for switched reluctance aerogenerators. Aiming at a smart grid scenario, the utilization of wireless technologies for transmitting control information requires a powerful modulation and error-correction coding schemes to avoid any serious problems to the energetic plant. These transmission errors can cause permanent damages in the components of the turbine and converters, and they can also compromise the quality of the energy delivered to the grid. The performance of the proposed system is investigated in a frequency-selective fading channel, thus enabling a deeper study of the impact of the use of wireless communications for reference signal transmissions. This research demonstrates the operational viability of wireless systems for this type of application, when an appropriate digital modulation and coding techniques are applied.

Design methodology of P-res controllers with harmonic compensation for three-phase DC-AC grid-tie inverters with LCL output filter

This paper describes the modeling, control and operation of a grid-tie DC-AC inverter with LCL output filter. The proposed control system mitigates the impact caused by grid harmonic voltages. A current control approach with active damping based on the P-resonant controller with a cascaded notch filter is analyzed. In this approach the aim is to mitigate the effects of the resonance peak of the LCL filter and mains harmonics on the operation of the converter and on the quality of the electrical current injected into the power grid. The proposed P-resonant controller is designed and its parameters are obtained with an analytical methodology based on frequency response.

Evaluation of active frequency drift anti-islanding methods with a single-phase grid-tie photovoltaic inverter

The increasing number of distributed generators connected to the distribution grids requires islanding detection methods that guarantee the disconnection of generators during grid faults and unintentional island situations. Many anti-islanding techniques have been developed to satisfy this necessity. This paper evaluates two frequency-drift anti-islanding methods used with a single-phase grid-tie photovoltaic (PV) inverter.

Design, optimization and analysis of the axial C-core Switched Reluctance Generator for wind power application

Switched reluctance generator (SRG) has been covered in several researches in the last two decades. These kind of machine is very promising for wind power application due to their low cost, high efficiency and high power density per volume. On the other hand, lots of researches are dedicated to the study and project of traditional SRG (radial flux). This article presents the electromagnetic design and optimization of the Axial Switched Reluctance Generator with C Core (C-SRG) using finite element method. Moreover, in order to better analyze the dynamic behavior of the C-SRG, a co-simulation was developed using the software Maxwell 3D and Simplorer. The simulation results indicate that the methodology adopted was suitable and can be applied to C-SRG electromagnetic design.

Direct Power Control for Switched Reluctance. Generator in Wind Energy

This paper proposes a direct power control for switched reluctance generator for wind energy systems directly connected to electric system, microgrid or system isolated. The controller process the power error directly and manipulates the turn-off angle of the converter in order to the generator power reach the reference. Simulations results are presented to validate the controller operation.

Design of Computational Experiment for Performance Optimization of a Switched Reluctance Generator in Wind Systems

This paper presents as a new contribution a proposal to optimize the performance of a switched reluctance generator (SRG) in a variable wind energy conversion system. An approach based on the design of computational experiment is applied to determinate the optimal firing angles and the optimal dc link voltage that guarantee the best system behavior for each rotor speed. A third-order response surface model based on space-filling designs is applied to build a multiobjective function considering efficiency improvement and torque ripple reduction. An interior point method is applied to find the minimum of the surface, optimizing the process. Direct power control is used to obtain the maximum power as a function of the rotor speed, employing the optimal parameters. Hysteresis and single-pulse current control are applied for low- and high-speed operation, respectively. Simulation and experimental results have shown that the proposed approach returned a good compromise between SRG high efficiency and low torque ripple. Moreover, the presented technique reduces computational effort and provides a clear massive data simulation framework.

An Approach for Switched Reluctance Generator in a Wind Generation System With a Wide Range of Operation Speed

This paper presents a complete approach for switched reluctance generator (SRG) in variable wind energy conversion systems. Two forms of direct power control (DPC) and a commutative system that allows SRG performance at a wide range of speed variations are proposed. Thus, more mechanical energy can be captured in wind generation. In the proposed structure, the SRG operates in a self-excited mode using a common dc bus system of a voltage source inverter connected to an electrical grid. DPCs are proposed by hysteresis of the SRG phase current for low-speed operation (DPC-LS) and by a single pulse of current for high-speed operation (DPC-HS). The low-pass filter employed to obtain the average power generated may slow down the response of the control system of the DPC applied to SRG. To improve the system performance, sliding mode controllers in DPCs were used. For operation throughout a wide speed range, the DPC-LS and DPC-HS controls should be joined. Therefore, a commutative system with smooth transition between DPC modes is proposed. Finally, simulations and experimental tests were conducted to verify the behavior of the proposed arrangement. The results confirmed correct operation of the proposed system.

Strategy for modeling a 3-phase grid-tie VSC with LCL filter and controlling the DC-link voltage and output current considering the filter dynamics

This work presents an analytical and detailed design methodology of the output current controller and DC link voltage controller of the three-phase VSC (voltage source converter) with output LCL filter. Most of inverter-based grid-tie systems use L filters, which present structural simplicity and are easy for modeling and controlling. However, the 3rd order LCL filter mitigates switching harmonic currents and increases bandwidth. Despite its advantages, the LCL filter introduces a resonant peak and reduces damping. This problem can be addressed with active damping techniques. This paper presents an accurate modeling and controlling analysis of the grid-tie VSC taking into account the influence of the dynamic behavior of the LCL filter.

Evaluation of active anti-islanding methods based on the ABNT NBR IEC 62116 and IEEE STD 929-2000 standards

In this paper two active anti-islanding methods are evaluated and compared according to the ABNT NBR 62116 and IEEE STD 929-2000 standards. These standards specify voltage and frequency trip time settings and trip magnitudes. The first method is the active frequency drift with positive feedback and the second one is the active frequency jump that is based on phase-locked loop perturbation. The latter distorted less the power injected into the utility grid and had a better time response to detect grid faults. Besides, it was able to obey the two standards, different from the first one that was able to follow just the second standard.

Modeling and digital control of a high-power full-bridge isolated DC-DC buck converter designed for a two-stage grid-tie PV inverter

This paper describes a grid-tie photovoltaic (PV) inverter composed of an isolated full-bridge buck DC-DC converter with high-frequency transformer and a cascaded DC-AC full-bridge inverter connected to the grid. Emphasis is given on the modeling and digital control design of the DC-DC converter with the polynomial pole placement method. Simulation results are presented and a inverter prototype is currently being built.