MIMO-Identification Techniques for Rapid Impedance-Based Stability Assessment of Three-Phase Systems in DQ Domain

Roinila, Tomi; Messo, Tuomas; Santi, Enrico

doi:10.1109/tpel.2017.2714581

Cited by 113 publications

(78 citation statements)

References 20 publications

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“…Moreover, it suits a practical implementation due to its small disturbance amplitude and immunity against background noise in the system [19,20]. Recently, the advantages of the PRBS have motivated researchers to adopt it for impedance estimation purpose while using power electronics converters [8,[21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

“…The implementation of the PRBS identification technique into 3-phase grid-connected inverters controlled in the synchronous reference frames (dq-axis) for grid impedance estimation purpose has been reported in several studies [8,[21][22][23]. The injection point of the PRBS in the control loop of the inverters differs between studies.…”

Section: Introductionmentioning

confidence: 99%

“…The injection point of the PRBS in the control loop of the inverters differs between studies. For instance, it is injected into the carrier frequency of PWM [21], inner current controller references at dq-axis [22,23], and several locations (hybrid injection) simultaneously [8]. The second approach has the advantage of more control of the PRBS, and it provides more accurate results for a frequency range within the controller bandwidth.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, it becomes necessary to explore online grid impedance estimation using grid-connected inverters in unbalanced low-voltage networks. Applications of the estimated impedance may include (1) online stability assessment based on generalised nyquist criteria to extend previous studies that considered the PRBS estimation technique only for balanced systems [7,[21][22][23] and (2) the use of the fundamental grid impedance to improve, for example, low-voltage ride-through capability of grid-connected inverters. In recent studies [11,31], it was shown that the fundamental grid impedance components (R g and L g ) are required to obtain optimal or suboptimal dq-axis current references of both the positive-and negative sequences' control loops.…”

Section: Introductionmentioning

confidence: 99%

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Online Parametric Estimation of Grid Impedance Under Unbalanced Grid Conditions

2019

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Whereas power-electronics-based power systems are expected to enable more integration of renewable energy sources, they could pose crucial challenges including stability issues due to the Thévenin impedance seen by inverters. Such problems could be mitigated by enabling the inverters to estimate the grid impedance by including a grid impedance estimation technique into their control loop. However, one aspect which has been overlooked thus far is that the accuracy of such grid impedance estimation techniques is significantly affected by various grid conditions. For instance, the unbalance in three-phase power systems causes unwanted oscillations at double the fundamental frequency in the inverters control loops. Therefore, this paper proposes a simple and reliable online estimation of the grid impedance under unbalanced conditions. The technique is based on wide-band impedance estimation incorporated into the control loop of the positive sequence of a three-phase grid-connected inverter equipped with a positive-and negative-sequence control (PNSC) strategy. Additionally, complex curve fitting is utilized to obtain parametric models of the grid impedance. To demonstrate the efficacy of the proposed grid impedance estimation technique, extensive case studies are performed. These include: (1) unbalanced operations of both resistive-inductive (RL) and resistive-inductive-capacitive (RLC) models of the grid, (2) background harmonics, and (3) asymmetrical impedances of the network.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Online Parametric Estimation of Grid Impedance Under Unbalanced Grid Conditions

2019

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“…It is also worth noting studies on the stability in high voltage direct current (HVDC) systems [20,21] or multiple grid-connected inverters [18,24]. When the converter and grid impedance characteristics are unknown, it is possible to measure the converter and grid impedance online for the stability assessment and adaptive control [25,26]. However, these studies have not fully incorporated the harmonic stability concerns observable in grid operations.…”

Section: Introductionmentioning

confidence: 99%

Impedance-Based Stability Analysis in Grid Interconnection Impact Study Owing to the Increased Adoption of Converter-Interfaced Generators

et al. 2017

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This study investigates the emerging harmonic stability concerns to be addressed by grid planners in generation interconnection studies, owing to the increased adoption of renewable energy resources connected to the grid via power electronic converters. The wideband and high-frequency electromagnetic transient (EMT) characteristics of these converter-interfaced generators (CIGs) and their interaction with the grid impedance are not accurately captured in the typical dynamic studies conducted by grid planners. This paper thus identifies the desired components to be studied and subsequently develops a practical process for integrating a new CIG into a grid with the existing CIGs. The steps of this process are as follows: the impedance equation of a CIG using its control dynamics and an interface filter to the grid, for example, an LCL filter (inductor-capacitor-inductor type), is developed; an equivalent impedance model including the existing CIGs nearby and the grid observed from the point of common coupling are derived; the system stability for credible operating scenarios is assessed. Detailed EMT simulations validate the accuracy of the impedance models and stability assessment for various connection scenarios. By complementing the conventional EMT simulation studies, the proposed analytical approach enables grid planners to identify critical design parameters for seamlessly integrating a new CIG and ensuring the reliability of the grid.

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Signal Design for Multi-input System Identification

Tan

Godfrey

2019

Industrial Process Identification

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MIMO-Identification Techniques for Rapid Impedance-Based Stability Assessment of Three-Phase Systems in DQ Domain

Cited by 113 publications

References 20 publications

Online Parametric Estimation of Grid Impedance Under Unbalanced Grid Conditions

Online Parametric Estimation of Grid Impedance Under Unbalanced Grid Conditions

Impedance-Based Stability Analysis in Grid Interconnection Impact Study Owing to the Increased Adoption of Converter-Interfaced Generators

Signal Design for Multi-input System Identification

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