J. Fernando Silva

Input filter design for sliding mode controlled matrix converters

This paper presents the input filter design for sliding mode controlled matrix converters. A global sliding mode control approach is considered for the converter with input filter to guarantee near unity input power factor operation and voltage or output current control. The sliding surfaces are directly obtained from the global system equations (matrix converter and input filter) written in the phase canonical form. The association of these sliding surfaces with the state-space vectors technique allows the choice of the most appropriate switching strategy. The proposed new input filter design considers the maximum allowed displacement factor introduced by the filter, as well as the ripple present at the capacitor voltages. Simulation results are obtained and discussed.This paper presents the input filter design for sliding mode controlled matrix converters. A global sliding mode control approach is considered for the converter with input filter to guarantee near unity input power factor operation and voltage or output current control. The sliding surfaces are directly obtained from the global system equations (matrix converter and input filter) written in the phase canonical form. The association of these sliding surfaces with the state-space vectors technique allows the choice of the most appropriate switching strategy. The proposed new input filter design considers the maximum allowed displacement factor introduced by the filter, as well as the ripple present at the capacitor voltages. Simulation results are obtained and discussed.

34 – Control Methods for Switching Power Converters

J. Fernando Silva, Ph.D. and Sonia Ferreira Pinto, Ph.D. Instituto Superior Tecnico, DEEC, A.C. Energia, Laboratorio de Maquinas Electricas e Electronica de Potencia, Centro de Automatica da Universidade Tecnica de Lisboa, AV. Rorisco Pais 1, 1049-001 Lisboa, Portugal 34.

Linear and Sliding-Mode Control Design for Matrix Converter-Based Unified Power Flow Controllers

This paper presents the design and compares the performance of linear, decoupled and direct power controllers (DPC) for three-phase matrix converters operating as unified power flow controllers (UPFC). A simplified steady-state model of the matrix converter-based UPFC fitted with a modified Venturini high-frequency pulse width modulator is first used to design the linear controllers for the transmission line active (P) and reactive (Q) powers. In order to minimize the resulting cross coupling between P and Q power controllers, decoupled linear controllers (DLC) are synthesized using inverse dynamics linearization. DPC are then developed using sliding-mode control techniques, in order to guarantee both robustness and decoupled control. The designed P and Q power controllers are compared using simulations and experimental results. Linear controllers show acceptable steady-state behavior but still exhibit coupling between P and Q powers in transient operation. DLC are free from cross coupling but are parameter sensitive. Results obtained by DPC show decoupled power control with zero error tracking and faster responses with no overshoot and no steady-state error. All the designed controllers were implemented using the same digital signal processing hardware.

Direct Power Control of Series Converter of Unified Power-Flow Controller With Three-Level Neutral Point Clamped Converter

A unified power-flow controller (UPFC) can enforce unnatural power flows in a transmission grid, to maximize the power flow while maintaining stability. Theoretically, active and reactive power flow can be controlled without overshoot or cross coupling. This paper develops direct power control, based on instantaneous power theory, to apply the full potential of the power converter. Simulation and experimental results of a full three-phase model with nonideal transformers, series multilevel converter, and load confirm minimal control delay, no overshoot nor cross coupling. A comparison with other controllers demonstrates better response under balanced and unbalanced conditions. Direct power control is a valuable control technique for a UPFC, and the presented controller can be used with any topology of voltage-source converters. In this paper, the direct power control is demonstrated in detail for a third-level neutral point clamped converter.

Advanced Control of Switching Power Converters

Publisher Summary This chapter provides basic and advanced skills to control electronic power converters, considering that the control of switching power converters is a vast and interdisciplinary subject. State-space models provide a general and strong basis for dynamic modeling of various systems including switching converters. State-space models are useful to design the needed linear control loops and can also be used to computer simulate the steady state and the dynamic behavior of the switching converter fitted with the designed feedback control loops and subjected to external perturbations. Current-mode control in switching power converters is the simplest form of state feedback. Closed-loop control of resonant converters can be achieved using the outlined approaches if the resonant phases of operation last for small intervals compared to the fundamental period. The first step in the fuzzy controller synthesis procedure is to define the input and output variables of the fuzzy controller. This is done accordingly with the expected function of the controller. There are no general rules to select those variables, although typically the variables chosen are the states of the controlled system, their errors, error variation, and error accumulation.

A new method to build a high-voltage pulse supply using only semiconductor switches for plasma-immersion ion implantation

Abstract A new method to obtain high voltage (kV) pulses suitable for a plasma immersion ion implantation (PIII) facility is presented. The circuit proposed is based on a step-up transformer with a constant flux reset clamp circuit that takes advantage of the low duty ratio required to reduce the voltage stress on all semiconductor switches. An initial prototype was assembled with 800-V semiconductor switches for an output pulse of −5 kV, 5-μs pulse width and 10-kHz pulse frequency. Theoretical and experimental results are presented and discussed.

Advanced control methods for power electronics systems

The application of modeling methods suitable for control and simulation of power electronic systems is outlined as a self-contained approach to solve the simulation and control problems of novel structures of power electronics converters. The straightforward non-linear modeling for controller design and simulation uses switched state-space models avoiding the averaging task, needs few linear control concepts, derives the stability study from geometric properties and leads to an integrated design of the control, modulators and simulation tasks. On-line sliding mode control techniques are well suited to power converters as they are inherently variable structure systems. Obtained controllers are robust concerning converter parameter variations, semiconductor non-ideal characteristics, load and line disturbances. Main modeling and design steps are summarized and some examples given. Results show fast dynamics, no steady-state errors and robustness against semiconductor non-idealities and dead times.

Backstepping Control of Smart Grid-Connected Distributed Photovoltaic Power Supplies for Telecom Equipment

Backstepping controllers are obtained for distributed hybrid photovoltaic (PV) power supplies of telecommunication equipment. Grid-connected PV-based power supply units may contain dc-dc buck-boost converters linked to single-phase inverters. This distributed energy resource operated within the self-consumption concept can aid in the peak-shaving strategy of ac smart grids. New backstepping control laws are obtained for the single-phase inverter and for the buck-boost converter feeding a telecom equipment/battery while sourcing the PV excess power to the smart grid or to grid supply the telecom system. The backstepping approach is robust and able to cope with the grid nonlinearity and uncertainties providing dc input current and voltage controllers for the buck-boost converter to track the PV panel maximum power point, regulating the PV output dc voltage to extract maximum power; unity power factor sinusoidal ac smart grid inverter currents and constant dc-link voltages suited for telecom equipment; and inverter bidirectional power transfer. Experimental results are obtained from a lab setup controlled by one inexpensive dsPIC running the sampling, the backstepping and modulator algorithms. Results show the controllers guarantee maximum power transfer to the telecom equipment/ac grid, ensuring steady dc-link voltage while absorbing/injecting low harmonic distortion current into the smart grid.

Space vector alpha-beta sliding mode current controllers for three-phase multilevel inverters

Robust sliding mode on-line space vector controllers, designed for output current control in multilevel three-phase power inverters are described. Capacitor voltage divider equalisation is included using the same approach. Using two four-level comparators, simulation and experimental results show no steady state-errors, very fast dynamics and robustness against power supply variations and load unbalances.

Predictive optimal matrix converter control for a Dynamic Voltage Restorer with flywheel energy storage

This paper presents a predictive optimal matrix converter controller for a flywheel energy storage system used as dynamic voltage restorer (DVR). The flywheel energy storage device is based on a steel seamless tube mounted as a vertical axis flywheel to store kinetic energy. The motor/generator is a permanent magnet synchronous machine driven by the AC-AC matrix converter. The matrix control method uses a discrete-time model of the converter system to predict the expected values of the input and output currents for all the 27 possible vectors generated by the matrix converter. An optimal controller minimizes control errors using a weighted cost functional. The flywheel and control process was tested as a DVR to mitigate voltage sags and swells. Simulation results show that the DVR is able to compensate the critical load voltage without delays, voltage undershoots or overshoots, overcoming the input/output coupling of matrix converters.