Journal ArticleDOI
Analysis of Control-Delay Reduction for the Improvement of UPS Voltage-Loop Bandwidth
TLDR
A small shift of the output-voltage sampling can significantly increase the UPS voltage-loop bandwidth while keeping the same stability margin, and less contribution comes from the delay minimization of the inductor-current sampling, so that current-ripple cancellation techniques are not needed.Abstract:
This paper investigates the effects of control-delay minimization in the dynamic performance of the output stage of uninterruptible power supplies (UPSs) by shifting the sampling time of inductor current and output voltage toward the duty-cycle update instant. This paper shows how a small shift of the output-voltage sampling can significantly increase the UPS voltage-loop bandwidth while keeping the same stability margin. Instead, less contribution comes from the delay minimization of the inductor-current sampling, so that current-ripple cancellation techniques are not needed. A detailed model based on the modified Z-transform, which accounts for different time delays in multiloop control, is proposed. The effectiveness of the proposed analysis is demonstrated by simulation and experimental results on a typical industrial three-phase/three-phase 8-kHz 30-kVA UPS prototype. By using two control designs based on the same phase margin, the output-voltage total harmonic distortion with the normalized distorting load is reduced from 6.8% to 5.7%, using a delay of the output voltage sampling equal to 25 mus.read more
Citations
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Journal ArticleDOI
Analysis of D-Q Small-Signal Impedance of Grid-Tied Inverters
TL;DR: In this article, the small-signal impedance of three-phase grid-tied inverters with feedback control and phase-locked loop (PLL) in the synchronous reference ( d-q ) frame is analyzed.
Journal ArticleDOI
Passivity-Based Stability Assessment of Grid-Connected VSCs—An Overview
TL;DR: In this article, the authors present an overview of passivity-based stability assessment, including techniques for space-vector modeling of VSCs whereby expressions for the input admittance can be derived.
Journal ArticleDOI
Impedance Shaping of the Grid-Connected Inverter with LCL Filter to Improve Its Adaptability to the Weak Grid Condition
TL;DR: In this paper, an impedance shaping method is proposed with virtual impedances, and the current control loop can be designed independently under the practical considerations, which can work stably over a wide range of the typical inductive resistive grid impedance and exhibit strong rejection ability of grid-voltage harmonics.
Journal ArticleDOI
Delay-Dependent Stability of Single-Loop Controlled Grid-Connected Inverters with LCL Filters
TL;DR: In this article, a systematic study on the relationship between the time delay and stability of single-loop controlled grid-connected inverters that employ inverter current feedback or grid current feedback (GCF) was carried out, and the ranges of time delay for system stability were analyzed and deduced in the continuous s-domain and discrete z-domain.
Journal ArticleDOI
Rotating-Sliding-Line-Based Sliding-Mode Control for Single-Phase UPS Inverters
TL;DR: The proposed method to the sliding-mode control of single-phase uninterruptible-power-supply inverters is capable of shortening the tracking and sliding times, resulting in a smaller total harmonic distortion in the output voltage.
References
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Book ChapterDOI
Computer Controlled Systems
TL;DR: The degree of success of a computer control application depends mainly on the effectiveness of the algorithm, which is generally designed from plant specifications and desired performance characteristics.
Journal ArticleDOI
Output impedance design of parallel-connected UPS inverters with wireless load-sharing control
TL;DR: This paper deals with the design of the output impedance of uninterruptible power system (UPS) inverters with parallel-connection capability, and proposes novel control loops to achieve both stable output impedance and proper power balance.
Book
Digital Control Systems
TL;DR: This chapter introduces the z-Transform, a new type of transform that combines Laplace Transforms, z-Transforms and Modified Z-TRANSFORMS with Convolution Integral to achieve state-of-the-art control of Discrete-Data Systems.
Journal ArticleDOI
Decentralized Control for Parallel Operation of Distributed Generation Inverters Using Resistive Output Impedance
TL;DR: The paper explorers the resistive output impedance of the parallel-connected inverters in an island microgrid and proposes a novel wireless load-sharing controller for islanding parallel invertes in an ac distributed system.