State Feedback Reshaping Control of Voltage Source Converter

Abstract

Admittance reshaping is a widely used strategy to address the converters low-frequency stability issues in weak grid, caused by the PLL and its interaction with the dc and ac voltage control. However, the asymmetric control of the d-and q-axis current references and the coupling between the converter ac and dc side restricts the damping capability of Single-Input-Single-Output feedbacks. This phenomena gets even worse in presence of nearby converters. This paper extends the concept of admittance reshaping to Multi-Input-Multi-Output (MIMO) control. A full state-feedback is added to the current reference of the converter to increase the damping of the conventional multi-loop control. A systematic offline algorithm is delegated to design the feedback, and a scalar coefficient is employed to activate/deactivate online the reshaping feedback, making the proposed solution user-friendly. The proposed control is analyzed both in time-and frequencydomain and tested in parallel-operation with other converters, and shows higher damping capability than conventional solutions and good robustness with respect to grid impedance and operating point variations. Experimental tests under ac and dc disturbances are conducted both in lab setup and in Hardware-In-the-Loop.

Interaction Dynamics and Active Suppression of Instability in Parallel Photovoltaic Voltage-and Current-Source Converters Connected to a Weak Grid

“…The above survey shows that the movement of the PVG from the CVR to the CCR affects the dc-link stability for both VSC and CSC systems. However, up to the authors' insight, how the changing PVG dynamics and grid strength affect the stability of parallel VSC and CSC systems is not reported [7], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32]. This shortcoming is addressed in this article.…”

“…In this section, the stability of the parallel VSC-CSC system is carried out using the placement of the eigenvalues in the s-plane with the changing operating point (i.e., PVG source dynamics, converters active power injection, grid strength, and PLL bandwidth) [26], [34]. The steady-state values of the converter inputs define the operating points.…”

“…However, the study did not consider the weak grid system. The authors in [26] proposed a state feedback reshaping method by adding full state feedback to the VSC current reference when connected to a weak grid, resulting in a 50% higher damping capability than the virtual admittance-based solution. However, the source dynamics and the effect of the developed method on the power injection level were not considered.…”

“…It is apparent from the above survey that the current literature did not address the following: 1) dynamic interactions in a parallel PV-based VSC and CSC system connected to a weak grid, and 2) active stabilization methods to facilitate reduced interaction, stability, and rated power injection [18], [19], [20], [21], [22], [23], [24], [25], [26]. Motivated by these shortcomings, this article provides, for the first time, a dc-links interactions and stability study of a parallel PVbased VSC and CSC system connected to a weak grid.…”

Enhanced Frequency Stability of SAW Yarn Tension Sensor by Using the Dual Differential Channel Surface Acoustic Wave Oscillator

“…At present, the commonly used sensors for detecting yarn tension are based on phase detection systems [ 6 ], amplitude detection systems [ 7 ], the phase lock loop (PLL) detection method [ 8 ], direct digital synthesizer (DDS) scanning detection [ 9 ], and mixing detection method [ 10 ]. Among them, phase detection and amplitude detection systems are used in the largest amounts; however, both of them are low sensitivity [ 11 ].…”