Grid Voltage Synchronization for Unbalanced Voltages Using the Energy Operator

Abstract

Abstract--This paper presents a novel synchronization technique which can identify the grid voltage frequency and phase angle under unbalanced grid voltage conditions. The method combines the features of two different energy operator schemes: the basic one for estimating the frequency of the grid voltages and the cross-energy operator for phase tracking. Using a moving data window of five samples the algorithm can track the fundamental frequency and phase angle quickly and accurately. The paper discusses the fundamental principles of the method, highlights its features and filter requirements in implementation. An experimental implementation of this method is presented which validates its performance for practical operation. The ability of the proposed method to enable a STATCOM riding-through unbalanced grid voltage condition is verified by the results from a power network simulation study.

Amplitude-Phase Detection for Power Converters Tied to Unbalanced Grids with Large X/R Ratios

“…The three-phase parameters after the disturbance are shown in Table II. The DDC component during transient is determined by (6). On this basis, comparative experiments on amplitudephase detection are conducted when ignoring and considering the influence of DDC components.…”

“…Among them, fast and accurate amplitude-phase detection is the basis for the subsequent works [4], and is crucial for highperformance control of converters [5], [6]. Indeed, with the wide application of converters, the grid code requires grid-tied converters to equip with fault ride-through capabilities [7]- [9], making it necessary to study effective amplitude-phase detection methods when considering DDC components associated with large grid X/R ratios.…”

Phase locked-loop with decaying DC transient removal for three-phase grids

“…Fast and accurate detection of grid amplitude and phase is of paramount importance for power system applications, including the control of electrical machines [1], measuring power quality phenomena and indices [2], islanding detection [3], and especially, high-performance control of grid-tied converters [4]. This is usually done by means of phase locked-loops (PLLs), [5,6], either in the form of open-loop or closed-loop schemes. Over the past decades, there has been a rapid development of PLL techniques.…”