Performance analysis of 1ϕ T/4 PLLs with secondary control path in current sensorless bridgeless PFCs

New power factor correction (PFC) stages such as bridgeless converters and the associated current shaping techniques require grid synchronization to ensure unity Displacement Power Factor (DPF). Sensorless line current rebuilding algorithms also need synchronization with the line voltage to compensate at least for part of the current estimation error. The application of a secondary control path to reach faster and more robustly the proper operation point previously applied in single/three-phase PLLs in grid connected converters is here proposed for the current sensorless bridgeless PFCs. This work analyzes the performance of three single-phase T/4 PLL structures, first without secondary control path, and later with feedforward and feedback secondary control paths, both in simulation and experimentally, and evaluates their applicability to current sensorless digitally controlled single phase bridgeless PFCs based on the current rebuilding technique.This work has been supported by the Spanish Ministry of Economy and Competitiveness under grant TEC2014-52316-R ECOTREND Estimation and Optimal Control for Energy Conversion with Digital Devices

Estudio comparativo para PLL monofásico

La sincronización entre convertidores de potencia, con la red eléctrica, es un tema importante de investigación, debido a la integración masiva de fuentes renovables y de cargas basadas en componentes de electrónica de potencia (EDP), por lo cual, muchos investigadores se han dedicado a proponer y mejorar diversas técnicas que permiten vincular redes entre sí [1] [2]. Para lograr la coordinación de sistemas monofásicos es necesario determinar la fase, amplitud y frecuencia de la señal de la red. El manejo de la amplitud es sencillo ya que puede medirse con el valor pico de la señal o utilizando métodos de detección de voltaje rms, por el contrario, la detección de fase se hace critica ya que una pequeña variación entre la señal entregada por los dispositivos basados en EDP y la señal generada por la red puede producir corrientes circulantes ocasionando daños en los elementos del sistema [3]

Two-sample PLL with improved frequency response applied to single-phase current sensorless bridgeless PFCs

A new implementation of the recently proposed fixed-frequency two-sample (2S) quadrature generation subsystem (QSG) digital Phase Locked Loop PLL, applicable to single-phase Power Factor Correction (PFC), is proposed. Its characteristics are high accuracy and low computational burden. The proposed PLL includes a frequency feedback loop to improve the synchronization under line frequency variations. Its performance within a digital controller of a current sensorless bridgeless PFC is evaluated by simulations and experimentally. The obtained results are compared with previously published PLLs in the literature.This work has been supported by the Spanish Ministry of Economy and Competitiveness under grant TEC2014-52316-R ECOTREND Estimation and Optimal Control for Energy Conversion with Digital Devices

A Frequency-Fixed SOGI-Based PLL for Single-Phase Grid-Connected Converters

© 1986-2012 IEEE. Second-order generalized integrator (SOGI) based phase-locked loops (PLLs) are widely used for grid synchronization in single-phase grid-connected power converters. Previously, the estimated frequency of the PLL stage is fed back to the front-end SOGI block to make SOGI-PLLs frequency-Adaptive, which increases the implementation complexity, and makes the tuning sensitive, thus reducing stability margins. Alternatively, a frequency-fixed SOGI-based PLL (briefly called FFSOGI-PLL) is proposed to ensure stability and simple implementation in this letter. It is commonly known that the in-phase and quadrature-phase signals generated by the frequency-fixed SOGI are of different amplitudes in the presence of frequency drifts, which causes second-harmonic ripples in the estimated parameters of the PLL loop. To deal with this issue, a simple yet effective method is developed in FFSOGI-PLL. The standard SOGI-PLL is first introduced, followed by the working principle and small-signal model of FFSOGI-PLL. The FFSOGI-PLL is then compared with the SOGI-PLL in terms of stability and transient performance. Finally, experimental results are presented to demonstrate the effectiveness of FFSOGI-PLL

Modulated model predictive control for a 7-level cascaded h-bridge back-to-back converter

Multilevel Converters are known to have many advantages for electricity network applications. In particular Cascaded H-Bridge Converters are attractive because of their inherent modularity and scalability. Predictive control for power converters is advantageous as a result of its applicability to discrete system and fast response. In this paper a novel control technique, named Modulated Model Predictive Control, is introduced with the aim to increase the performance of Model Predictive Control. The proposed controller address a modulation scheme as part of the minimization process. The proposed control technique is described in detail, validated through simulation and experimental testing and compared with Dead-Beat and traditional Model Predictive Control. The results show the increased performance of the Modulated Model Predictive Control with respect to the classic Finite Control Set Model Predictive Control, in terms ofcurrent waveform THD. Moreover the proposed controller allows a multi-objective control, with respect to Dead-Beat Control that does not present this capability

Observer-Based Quadrature Signal Generator for UPQC in a Single-Phase Distribution System

This paper presents a control algorithm for generation of reference voltage and current based on Observerbased QSG (Quadrature Signal Generator) for UPQC (Unified Power Quality Conditioner) in a Single-Phase Distribution System. The proposed UPQC is a combination of DSTATCOM and DVR used for load and source compensation such as voltage sag and swell, voltage and current harmonics etc. The proposed control algorithm is capable of generating reference signals from the distorted voltages and currents. In this paper, an improved OQSGbased PLL (Phase-Locked Loop) is utilized over OQSG to enable and operate with increased bandwidths that will improve the dynamic response, tracking accuracy and faster detection of reference signal under all varying load and grid conditions. The control algorithm is tested and evaluated using MATLAB / Simulink