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A DQ-frame Asymmetrical Virtual Impedance Control for Enhancing Transient Stability of Grid-Forming Inverters

IEEE TRANSACTIONS ON POWER ELECTRONICS 2022年第4期37卷 4535-4544页

作者： Jin, Zheming Wang, Xiongfei Beijing Jiaotong Univ Sch Elect Engn Beijing Peoples R China Aalborg Univ Dept Energy Technol DK-9220 Aalborg Denmark

This article proposes a dq-frame asymmetrical virtual impedance control scheme for preventing grid-forming (GFM) inverters from the loss of synchronization with the grid under large disturbances. The approach exploits the two degrees of freedom in the dq-frame virtual impedance synthesis of GFM inverters, and introduces a virtual transient impedance (VTI) scheme to improve the power transmission capability and, thus, restoring equilibrium points of GFM inverters during the large disturbances. The transient stability of GFM inverters with the different kinds of virtual impedance setting is analyzed to formulate the design guideline of VTI method. Simulations and experimental tests are presented to validate the effectiveness of the approach.

关键词： Inverters Transient analysis Power system stability Stability criteria Impedance Voltage control Circuit stability Grid-forming (GFM) inverters synchronous reference frame transient stability virtual impedance

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Extensive Application of UPQC-L for a Dual Point of Common Coupling System with Multiple Loads under Unbalanced Source Condition

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ELECTRIC POWER COMPONENTS AND SYSTEMS 2017年第15期45卷 1653-1666页

作者： Patnaik, Nishant Panda, Anup Kumar Natl Inst Technol Dept Elect Engn Rourkela India

This paper presents a synchronous reference frame (SRF)-based power angle control (PAC) approach for a specific unified power quality conditioner (UPQC) arrangement, termed as UPQC-L for dual point of common coupling system under unbalanced source voltage condition. In contrast to a conventional configuration of UPQC, the static compensator (STATCOM) part is on left side of UPQC-L, while dynamic voltage restorer (DVR) is on the right side. The UPQC-L configuration is specifically adapted for protection of sensitive and critical load types from voltage disturbances. Along with its basic compensation capability of current harmonic compensation and voltage compensation, it efficiently handles reactive power demand from sensitive load. This is achieved with the introduction of PAC concept for effective sharing of reactive power between STATCOM and DVR. The extraction of instantaneous power angle faces difficulty with unbalanced voltage and UPQC-L configuration. Thus, the control algorithm for UPQC-L is designed based on SRF and numerical analysis approach with equal reactive power sharing phenomena by STATCOM and DVR of UPQC-L. UPQC-L with the proposed control approach is successfully implemented in MATLAB/SIMULINK (The Mathworks, Inc. USA) and verified experimentally for mitigation of voltage disturbances (such as sag/swell, unbalancing, and harmonics), current harmonics, and high-reactive power demand.

关键词： unified power quality conditioner power angle control harmonic compensation reactive power compensation synchronous reference frame unbalanced voltage

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Enhanced method of rotor speed and position estimation of permanent magnet synchronous Machine based on stator SRF-PLL

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ENGINEERING SCIENCE AND TECHNOLOGY-AN INTERNATIONAL JOURNAL-JESTECH 2017年第5期20卷 1450-1459页

作者： Vijayapriya, R. Raja, P. Selvan, M. P. Natl Inst Technol Dept Elect & Elect Engn Tiruchirappalli 620015 Tamil Nadu India

A stator flux oriented synchronous reference frame - phase locked loop (SRF-PLL) is proposed for the precise computation of rotor speed and position of permanent magnet synchronous machine (PMSM). A direct method of rotational speed computation based on the stator electromotive force (EMF) is initially formulated. Using the speed as a reference to the inverse Park and Clarke transformation blocks, the three-phase positive sequence stator flux is derived. A pre-stage low pass filter (LPF) is implemented to cancel out the ripples in the d-q components of the stator flux introduced by the dynamic operating conditions of inverter non-linearities and grid disturbances. The estimated three-phase positive sequence stator flux is used to compute the rotor position by aligning the total stator flux along the direct axis through a PLL block. Provision of the frequency amendment and ripple cancellation outside the PLL block results in a fast-dynamic response with an enhanced frequency adaptable capability. To validate the effectiveness of the proposed method, the sensorless vector control of grid integrated PMSM based wind-driven generator (WG) is analytically verified using the PSCAD/EMTDC simulation tool under various dynamic operating conditions such as wind speed variation and grid disturbances. (C) 2017 Karabuk University. Publishing services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.

关键词： Low pass filter synchronous reference frame Phase locked loop PMSM Stator flux Speed and position estimation

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A study on the dynamic model of a three-phase grid-connected inverter and an innovative method for its verification

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INTERNATIONAL JOURNAL OF SYSTEM ASSURANCE ENGINEERING AND MANAGEMENT 2022年第3期13卷 1508-1522页

作者： Esfandiari, Arash Hashemnia, Mohammad Naser Islamic Azad Univ Mashhad Fac Engn Mashhad Razavi Khorasan Iran

The ever-increasing use of renewable energy sources has underlined the role of power electronic converters as an interface between these resources and the power grid. One application of these converters is in three-phase inverters utilized in a solar power plant to inject active/reactive power to the grid. The dynamic model of power electronic converters is necessary for investigating the overall system stability and the design of the controller for the converters. Generally, the inverter dynamic model is needed to investigate the dynamic behavior of inverters in different applications. This paper is a study of the dynamical model of the grid-connected voltage source inverter, which is extracted by the state-space averaging (SSA) method. This model is verified by applying the values of the operating point to the inverter in Matlab (R) Simulink environment. To attain the steady-state operating point, the zero component of the duty ratio of the converter is required. To obtain this component, the matrix form of the converter's average equations is used. Overally, using the above methods provides a more efficient and clear understanding of the dynamic model of the converter.

关键词： Dynamic model Grid-connected inverter Operating point PWM State-Space Averaging (SSA) synchronous reference frame Transfer function

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Design and performance of dynamic voltage restorer using genetic algorithm

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INTERNATIONAL JOURNAL OF ELECTRONICS 2018年第1期105卷 88-103页

作者： Kassarwani, Neelam Ohri, Jyoti Singh, Alka NIT Dept Elect Engn Kurukshetra Haryana India DTU Dept Elect Engn Delhi India

In the present scenario, sensitive loads suffer nearly 80% of power quality problems especially due to voltage sag. Dynamic voltage restorer (DVR) finds its perfect application as a compensator to mitigate the voltage sag problem. In this paper, source voltage suffers voltage sag of 30% and load terminal voltage is regulated using proportional and integral (PI) controllers. synchronous reference frame algorithm is adopted to generate reference load voltage for voltage source converter switching. Optimised values of the gains of PI controllers are achieved using genetic algorithm. Control strategy of the DVR is simulated using MATLAB software and performance of DVR is studied.

关键词： Power quality voltage sag dynamic voltage restorer synchronous reference frame genetic algorithm

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DQ-reference-frame based impedance and power control design of islanded parallel voltage source converters for integration of distributed energy resources

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ELECTRIC POWER SYSTEMS RESEARCH 2019年第Mar.期168卷 67-80页

作者： Ramezani, Malek Li, Shuhui Sun, Yang Univ Alabama Dept Elect & Comp Engn Tuscaloosa AL 35487 USA

This paper investigates dq-reference-frame (dq-RF) self and cross-coupling output impedances of the islanded voltage source converter (VSC), by considering the controller impacts. The dq-RF impedances for the closed-loop system are designed to exhibit the desired resistive, inductive, or capacitive characteristics, and are employed in the power control of VSC. The effects of these impedances and connecting lines impedances on the power control of islanded parallel connected VSCs, for different impedance characteristics, are also studied. It is shown in this paper that the unbalanced impedance significantly affects the performance and power control of these parallel converters. Besides, virtual impedance based active and reactive power control of the parallel converters in the dq-RF, for resistive, inductive, and capacitive cases, are designed and implemented. The numerical and experimental results verify the analysis presented in this paper about the dq-output impedance and the virtual impedance based power sharing control.

关键词： synchronous reference frame Distributed energy resources Voltage source converter

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Proportional complex integral based control of distributed energy converters connected to unbalanced grid system

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CONTROL ENGINEERING PRACTICE 2020年 103卷 104574-104574页

作者： Meral, Mehmet Emin Celik, Dogan Van Yuzuncu Yil Univ Inst Nat & Appl Sci Dept Elect & Elect Engn Van Turkey

The high penetration of distributed energy resources (DERs) consisting of photovoltaic and fuel cell and wind power plants into the modern power grid results in several challenges such as stability and reliability. In this regard, this paper proposes proportional complex integral (PCI)-based control scheme of distributed energy inverter (DEI) connected to the utility grid to overcome limitations of synchronous rotating coordinate systems based control schemes. The dynamic performance, power quality and stability of the grid connected DEI are enhanced in contrast to proportional integral (PI)-based control scheme during unbalanced and distorted grid voltages. A noteworthy contribution of this paper is that the third-order (3rd) current harmonic stemmed from the DC-link voltage (DC-LV) oscillations is eliminated at the grid side. Elimination of the DC-LV oscillations contributes to reducing the size of the DC capacitance and increasing the lifetime of the power conversion system. Active power reference is calculated in a closed-loop control system based on the DC-LV controller or based on maximum allowable active power injection according to the control objectives. Another contribution to previous studies is to eliminate the need for a phase locked loop (PLL). The complexities and additional hardware requirement for phase estimation are reduced. The performance comparison for two control schemes has been evaluated in terms of dynamic response, removing active power oscillations (APOs) for the DC-side voltage stability, removing reactive power oscillations (RPOs) for the AC side voltage stability, reducing the DC-LV oscillations for the elimination of third-order current harmonic and protection of the inverter from overcurrent. The effectiveness and availability of the proposed control scheme are confirmed through a set of case studies.

关键词： Distributed energy converters DC-link voltage oscillations Proportional complex integral Third-order current harmonic Stationary reference frame synchronous reference frame

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Hardware in the loop implementation of wavelet based strategy in shunt active power filter to mitigate power quality issues

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ELECTRIC POWER SYSTEMS RESEARCH 2019年第Apr.期169卷 92-104页

作者： Kumar, Ravinder Bansal, Hari Om Birla Inst Technol & Sci Dept Elect & Elect Engn Power Elect & Drives Lab Pilani Rajasthan India

This paper presents a Wavelet Transform (WT) based control algorithm for a shunt active power filter (SAPF), mainly to mitigate harmonic distortions in power distribution system modeling. Wavelet transforms are being used extensively for signal analysis and processing for fast and accurate identification of transients in power systems. In this work, SAPF has been modeled with a three-phase voltage source inverter using WT based schemes, resulting in minimizing of harmonic distortions and improvement in power factor for balanced, unbalanced & nonlinear loads. The system response for different types of WTs is compared and it is found that Haar WT provides minimum Total Harmonic Distortion (THD) and maximum power factor. OPAL-RT 4510 controller with microsecond step on its FPGA based computational engine is used for Hardware in the loop testing (HIL).

关键词： Wavelet transform Hardware in the loop Power quality synchronous reference frame Shunt active power filter

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Improving the SRF method to compensate low-order harmonics under nonsinusoidal network voltages

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TURKISH JOURNAL OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCES 2016年第2期24卷 412-U648页

作者： Modarresi, Javad Fallah, Mehdi Gholipour, Eskandar Tavakoli Bina, Mohammad Univ Isfahan Dept Elect Engn Esfahan Iran KN Toosi Univ Technol Fac Elect & Comp Engn Tehran Iran

Increasing the application of power in electronic devices has increased the harmonics in power systems. Numerous methods like the synchronous reference frame (SRF) and the p-q-based method have been suggested to overcome the effects of these harmonics. The conventional SRF method provides acceptable results in harmonic compensation of high-order harmonics (higher than the fourth order), but the transient response time will be drastically increased in the presence of low-order harmonics due to the existence of a conventional low-pass filter. Furthermore, if the load terminal voltages are distorted, then the conventional SRF method will become unable to implement load current compensation. This research has used wavelet transform to overcome these difficulties. The proposed method is not only faster than conventional SRF, but it can also compensate the load currents if the load terminal voltages are also distorted. The simulation and experimental results are performed using MATLAB/Simulink and digital signal processor TMS320F28335 to verify the proposed method.

关键词： Active filter digital signal processor harmonic synchronous reference frame wavelet transform

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Behaviour of the doubly fed induction generator exposed to unsymmetrical voltage sags

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IET ELECTRIC POWER APPLICATIONS 2012年第8期6卷 561-574页

作者： Rolan, A. Corcoles, F. Pedra, J. ETSEIAT UPC Dept Elect Engn Terrassa Barcelona 08222 Spain ETSEIB UPC Dept Elect Engn Barcelona 08028 Spain

This study analyses the dynamic behaviour of the doubly fed induction generator exposed to unsymmetrical voltage sags, providing insights into wind turbine fault ride-through capability. The sags are assumed to be caused by faults. An analytical approach assuming that the rotor-side converter can keep constant the rotor current in the synchronous reference frame during the event is used. The voltage limit of the rotor-side converter is also considered in order to determine the situations where the rotor current can be controlled. The effects of sags on grid-connected equipments depend on the sag characteristics (duration and depth), but also on the fault clearing process. In this process, the fault is not cleared instantaneously, as in the case of abrupt sags (which is the usual approach in the literature), but in the successive natural fault-current zeros, leading to a voltage recovery in several steps known as discrete sags. The effects of both abrupt and discrete sags on the doubly fed induction generator behaviour are compared. This comparison reveals that the discrete clearing process smoothes the sag effects on the generator.

关键词： rotor current synchronous reference frame voltage sags double-fed induction generator voltage recovery non-symmetric Induction generators

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