Francisco Freijedo

Real time grid-synchronization techniques are studied in this dissertation. The synchronization block is a crucial part of the controller in grid-connected power converters. The phase-angle of the voltage/current vector fundamental component at the point of common coupling (PCC) should be tracked online in order to control the energy transfer between the power converter and the ac mains. Synchronization algorithms have been evolving since the first analog zero-cross detectors to current high performance digital implementations. An in-depth review of the state-of-art in grid synchronization is contributed in the Chapter 2 of this PhD dissertation. In some ways, it could be said that the grid synchronization state-of-art has been evolving to avoid malfunctions due to power quality phenomena. The Ainsworth proposal of using a voltage controlled oscillator (VCO) inside the control loop of a High Voltage Direct Current (HVDC) successfully dealt with the novel, at that time, harmonic inst...

Abstract—Phase locked loop (PLL) algorithms for grid syn-chronization are a very important part of the control in most of the grid-connected power converters applications. The perfor-mance of the PLL should not be much affected under distorted grid conditions: the presence of ...

This paper analyzes the tuning of the phase locked loops (PLLs) employed in the control of power converters when there is distortion in the AC mains. The pros and cons of different optimization approaches are studied. In a general way, PLLs with a low bandwidth (low-gain PLLs) are required when handling with distorted. This paper proves that the tuning of

ABSTRACT Harmonic detection is very important in the control of active power filters (APFs). This paper presents a technique for harmonic identification, based on moving average filters (MVAs) and heterodyning, very suitable for digital implementation. The approach of fundamental component identification is contributed both for single-phase and three-phase voltage/current systems. Selective harmonic identification is also feasible. Due to the rapid step-response, good harmonic/noise cancellation of MVAs, and good frequency adaptation of the proposed algorithms, they have a very good performance compared with other alternatives. Experimental results of digital implementation in a rapid prototyping platform (dSpace DS1103), including an APF prototype are contributed proving the theoretical approaches. Details and experimental results of FPGA implementation, a clear trend in the field of digital control, are also contributed.

Reference generation is very important in the control of power line conditioners. This paper presents some algorithms both for single-phase and three-phase systems very suitable for reference generation and digital implementation. The key of the proposed algorithm is the implementation and tuning of Moving Average FIR filters (MVAs). Thanks to the rapid step-response and good harmonic/noise cancellation of MVAs, proposed

The power grid in most of the countries is aging and under increasing stress. The modern industrial infrastructure demands increasing amounts of affordable and reliable electricity. Solutions based on flexible AC transmission systems (FACTS) can be used to control power flow on the grid. Shunt VARs compensators provide grid voltage support, while series VARs compensators are required to control active