Comparison of Impedance Model and Amplitude–Phase Model for Power- Electronics-Based Power System

Yang, Ziqian; Mei, Cong Li; Cheng, Shijie; Zhan, Meng

doi:10.1109/jestpe.2019.2927109

Cited by 28 publications

(19 citation statements)

References 28 publications

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“…The small-signal stability of this impedance model is consistent with that of the state space models and amplitude-phase models established in [23], [34], [35]. Compared with Z a,f ull and Z b,f ull in (2), the dynamic behaviors of the current inner controllers and the line inductance are neglected, and the line currents are equal to the current references.…”

Section: A Impedance Model Of Slow Timescalesupporting

confidence: 77%

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Fast-Slow-Scale Interaction Induced Parallel Resonance and its Suppression in Voltage Source Converters

Qiu

Kurths

et al. 2021

IEEE Access

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Multi-timescale interaction of power electronics devices, including voltage source converter (VSC), has made the stability and analysis of high penetrating renewable power systems very complicated. In this paper, the impedance model is used to analyze the multi-timescale characteristics and interaction of the VSC. Firstly, the multi-timescale impedance characteristics of VSC are investigated based on the Bode plots. It is found that the slow-timescale (within the DC-link voltage control scale) and fast-timescale (within the AC current control scale) models are separately consistent with the full-order model perfectly within their low-and high-frequency ranges. In addition, there exists a high impedance peak within the intermediate frequency range (roughly from 10 Hz to 100 Hz). Then, the impedance peak is theoretically estimated and explained by the slow-fast-scale impedance parallel resonance through transfer-function diagram analysis. Moreover, it is found that the impedance peak is more related to some outer controllers, such as the alternative voltage control and active power control. Specifically, larger proportional coefficients can greatly suppress the resonance peak. Finally, simulations and experiments are conducted to verify the generality of the multi-timescale characteristics and interaction of the VSC. Hence these findings are not only significant to provide a physical insight into the inner key structure of the impedance of VSC, but also expected to be helpful for controller and parameter design of the VSC.INDEX TERMS Small-signal stability, multiple time-scale analysis, interaction, parallel resonance, parameter design.

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Section: A Impedance Model Of Slow Timescalesupporting

confidence: 77%

“…Referring to [22], [23], [35], the slow-scale (voltagetimescale) state space model can be established by considering the dynamics of the DVC, AVC, capacitor, and PLL. The state variables can be chosen as follows:…”

Section: State Space Model Of Slow-scale Modelmentioning

confidence: 99%

Fast-Slow-Scale Interaction Induced Parallel Resonance and its Suppression in Voltage Source Converters

Qiu

Kurths

et al. 2021

IEEE Access

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“…In particular, they are the state space time‐domain method [14], and the impedance [15–18] and amplitude‐phase methods [19], which are frequency‐domain ones. Recently some papers [20, 21] have successfully uncovered possible connection or equivalence of these methods.…”

Section: Introductionmentioning

confidence: 99%

Sustained oscillations and bifurcations in three‐phase voltage source converter tied to AC grid

Yang

Cheng

et al. 2020

IET Renewable Power Generation

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Recently large‐scale integration of power‐electronic‐based devices has made system‐level oscillations occur frequently, which posed a big challenge for modern power grids. Previous studies mainly treated sustained oscillations under the framework of (linear) small‐signal stability and/or by incorporating the impact of current saturation, but seldom considered system non‐linearity like phase‐locked‐loop. In this study, the authors established a sixth‐order non‐linear model for a three‐phase voltage‐source converter tied to AC grid, and studied its dynamics completely from non‐linear system theory and signal analysis technique, with all parameters including current controllers, phase‐locked‐loop, line inductance, and grid voltage. They found that the operation point usually becomes unstable by Hopf bifurcation, and the sustained oscillations are possible only for super‐critical Hopf bifurcation. Based on these observations, sustained periodic oscillation should be treated as a limit cycle even without saturation. With saturation, some other phenomena have also been found, such as saturation‐induced instability and saturation‐restricted oscillation. In addition, they discovered that for sustained oscillations, the usual purely sinusoidal three‐phase currents exhibit the form of sin⁡false[2πf1t+csin⁡false(2πfdqtfalse)false] or cos⁡false[2πf1t+csin⁡false(2πfdqtfalse)false], where f1 (fdq) denotes basic (modal oscillation) frequency with c a constant. This work could provide an improved understanding of sustained oscillations and associated system dynamics in an overall perspective manner.

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“…Now we have obtained the restricted relations between the impedances (Z dd , Z dq , Z qd , and Z qq ), the operating point vectors x, and the system parameters (a k and b k ). These equations in (22) would become the basis for the parameter identification of a k and b k .…”

Section: Identification Methods In the Fdimmentioning

confidence: 99%

“…As the black-box or gray-box is more realistic, the IM/AM measurement has been widely used under various practical conditions and has become a dominant method in electric power engineering. In addition, the method of amplitudephase motion equations has been proposed [20], and the equivalence and relation of all these important methods have been investigated very recently [21], [22].…”

mentioning

confidence: 99%

Black-Box Impedance Prediction of Grid-Tied VSCs Under Variable Operating Conditions

Qiu

Huang

et al. 2022

IEEE Access

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Impedance/admittance models (IM/AMs) have been widely used to analyze the small-signal stability of grid-tied power electronic devices, such as the voltage source converter (VSC). They can be either derived from theoretical analysis under white-box conditions, where all parameters and control structures are fully known, or measured based on experiments under black-box conditions, where the topology and parameters of the controllers are completely unknown. As the IM/AMs depend on specific operating conditions, it is highly desirable to develop fast algorithms for IM/AM prediction (or estimation) under the black-box and variable-operating-point conditions. This article extends the nearly-decoupled AM method for sequence AMs proposed recently by Liu et al to fit any unknown control structure, including not only grid-following VSC, but also grid-forming VSC. It is, therefore, referred to as the fully-decoupled IM (FDIM) method. Furthermore, a curve fitting method for the transfer function is proposed to expedite the algorithm, based on the information of a few disturbance frequencies only. Finally, the algorithm is verified by wide simulations and experiments under different situations, including the direct-drive wind turbine generator. The whole approach is expected to be broadly applicable to the stability analysis of power-electronic-based power systems under variable operating conditions.

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Comparison of Impedance Model and Amplitude–Phase Model for Power- Electronics-Based Power System

Cited by 28 publications

References 28 publications

Fast-Slow-Scale Interaction Induced Parallel Resonance and its Suppression in Voltage Source Converters

Fast-Slow-Scale Interaction Induced Parallel Resonance and its Suppression in Voltage Source Converters

Sustained oscillations and bifurcations in three‐phase voltage source converter tied to AC grid

Black-Box Impedance Prediction of Grid-Tied VSCs Under Variable Operating Conditions

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