A Unified Method for Generic Signal Parameter Estimation of Arbitrarily Distorted Single-Phase Grids With DC-Offset

Abstract

A unified method is presented which allows to estimate dc-offset, all harmonic components and fundamental frequency in arbitrarily distorted single-phase grids using a Frequency Adaptive Observer (FAO) consisting of modified Second-Order Generalized Integrators (mSOGIs), an adaptive DC-Integrator (DCI) and a modified Frequency Locked Loop (mFLL). DCI and mSOGIs are tuned by pole placement which allows for an arbitrarily fast detection of dc-offset and harmonic components if the fundamental frequency is known. If the fundamental frequency must be estimated as well, an mFLL with Gain Normalization (GN), Rate Limitation (RL), Anti-Windup (AW) strategy and low-pass filters (LPF) must be employed. The effectiveness of the proposed FAO is validated by experimental results and its enhanced performance is shown and compared to existing estimation methods. INDEX TERMS dc-offset estimation, frequency adaptive observer; frequency estimation; frequency locked loop; harmonics estimation; second-order generalized integrator.

One-Step-Prediction Discrete Observer Based Frequency-Locked-Loop Technique for Three-Phase System

“…where the output of the voltage is the superposition of the harmonics and DC component [28], [29]. Considering the harmonic property of three-phase system: the balanced condition harmonic sequences are …, −11, −5, +1, +7,…, 6n + 1, with n = …, -2, -1, 0, 1, 2, …, and the unbalanced condition harmonic sequences are …, −13, −7, −1, +5, +11, −13, ..., 6n − 1, hence, the order m can be deployed as −11, −5, −1, 0, +1, +7 [11].…”

“…can be used to estimate the harmonic sequence components with the structure shown in FIGURE 2 [29]. To make the figure more concise, the term ( 1)…”

3D-Modulation and PI State-Feedback Control for Voltage Source Inverters with Split DC-Link

“…With the grid voltage angle φ g estimated by a phase-locked loop or a frequency-locked loop [16], the Clarke-Park transformation can be applied to yield a representation in the synchronously rotating (d, q, γ)-reference frame for controller design, with (5) inserted, (4) becomes…”

Discrete-Time DC-Link Voltage and Current Control of a Grid-Connected Inverter with LCL-Filter and Very Small DC-Link Capacitance

“…The disadvantages of this scheme are the necessary implementation of a phase-locked loop (PLL) and the arising cross-coupling terms, which can be eliminated by an additional compensation method. By using the stationary (α, β)-reference frame, a PLL is not needed, as shown in [27], but a frequency-looked loop (FLL) is usually still required [28,29]. In this case, the references are sinusoidal and, therefore, a quasi proportional-resonant (QPR) controller must be implemented.…”

“…There are no cross-coupling terms, but existing harmonic distortion of the grid currents need to be suppressed by harmonic compensators separately. Each harmonic order requires an extra compensation [28,29]. In [9], also a continuous-time dc-link voltage droop controller for a single-phase GCI with LCL filter is proposed.…”