Decoupled Double Synchronous Reference Frame PLL for Power Converters Control

Abstract

This paper deals with a crucial aspect in the control of grid-connected power converters, i.e., the detection of the fundamental-frequency positive-sequence component of the utility voltage under unbalanced and distorted conditions. Specifically, it proposes a positive-sequence detector based on a new decoupled double synchronous reference frame phase-locked loop (DDSRF-PLL), which completely eliminates the detection errors of conventional synchronous reference frame PLL's (SRF-PLL). This is achieved by transforming both positive-and negative-sequence components of the utility voltage into the double SRF, from which a decoupling network is developed in order to cleanly extract and separate the positive-and negative-sequence components. The resultant DDSRF-PLL conducts then to a fast, precise, and robust positive-sequence voltage detection even under unbalanced and distorted grid conditions. The paper presents a detailed description and derivation of the proposed detection method, together with an extensive evaluation using simulation and experimental results from a digital signal processor-based laboratory prototype in order to verify and validate the excellent performance achieved by the DDSRF-PLL.Index Terms-Grid-connected converters, phase locked loop (PLL), positive sequence signals detection, synchronous reference frame (SRF).

Power quality improvement of single-phase photovoltaic systems through a robust synchronization method

“…4, where a PI controller is used in the synchronous reference frame to extract the phase angle of the fundamental voltage. The tuning process of such a PLL is based on the linearized small signal analysis of the PLL as presented in [6], [33], [35]. In the case where the transfer function of the PI controller is given by K p +1/(T i .…”

Operation of a hybrid modular multilevel converter during grid voltage unbalance

“…Techniques for extracting the reference frame components during unbalance [34] are used to obtain the unbalance factor (β) in the grid and the proportion of asymmetric third harmonic voltage ( x  ) required for sustainable operation is evaluated using the control concept discussed in the Section 4. Table 1 lists the main parameters used in the simulation model.…”

“…The decoupled double synchronous reference frame (DDSRF) concept presented in [34] is adopted to extract the positive and negative sequence voltages and transform to the positive and negative reference frames.…”

Phase-locked loops for grid-tied inverters: comparison and testing

“…If the positively rotating components are decoupled and extracted from the negatively rotating components, then the performance of the traditional SRF-PLL can be improved based on the decoupled positive components. This idea is discussed in detail in [2] and [9].…”