scholarly journals Investigation of Inertia Response and Rate of Change of Frequency in Low Rotational Inertial Scenario of Synchronous Dominated System

Electronics ◽  
2021 ◽  
Vol 10 (18) ◽  
pp. 2288
Author(s):  
Francisco Gonzalez-Longatt ◽  
Juan Manuel Roldan-Fernandez ◽  
Harold R. Chamorro ◽  
Santiago Arnaltes ◽  
Jose Luis Rodriguez-Amenedo
Keyword(s):  
Power Systems ◽  
Large Scale ◽  
Power Converter ◽  
Rate Of Change ◽  
Rotational Inertia ◽  
Distributed Energy ◽  
Inertial Response ◽  
System Frequency ◽  
Inertia Response ◽  
System Inertia

The shift to a sustainable energy future is becoming more reliant on large-scale deployment of renewable and distributed energy resources raising concerns about frequency stability. Rate of Change of Frequency (RoCoF) is necessary as a system inertia metric in order for network operators to perform control steps to preserve system operation. This paper presents in a straightforward and illustrative way several relevant aspects of the inertia response and RoCoF calculation that could help to understand and explain the implementation and results of inertial response controllers on power converter-based technologies. Qualitative explanations based on illustrative numerical experiments are used to cover the effects on the system frequency response of reduced rotational inertia in synchronous dominated power systems. One main contribution of this paper is making evident the importance of the governor action to avoid the synchronous machine taking active power from the system during the recovering period of kinetic energy in an under frequency event.

scholarly journals Emulating Rotational Inertia of Synchronous Machines by a New Control Technique in Grid-Interactive Converters

2020 ◽  
Vol 12 (13) ◽  
pp. 5346 ◽  
Author(s):  
Meysam Saeedian ◽  
Bahram Pournazarian ◽  
S. Sajjad Seyedalipour ◽  
Bahman Eskandari ◽  
Edris Pouresmaeil
Keyword(s):  
Power Systems ◽  
Large Scale ◽  
Renewable Energy Sources ◽  
Rate Of Change ◽  
Power Grids ◽  
Stable Region ◽  
Control Technique ◽  
Voltage Source ◽  
Rotational Inertia ◽  
Virtual Inertia

Integration of renewable energy sources (RESs) into power systems is growing due to eco-friendly concerns and ever-increasing electricity demand. Voltage source converters (VSCs) are the main interface between RESs and power grids, which have neither rotational inertia nor damping characteristics. Lack of these metrics make the power grid sensitive to frequency disturbances and thereby under frequency, to load shedding activation or even large-scale collapse. In this regard, the contribution of this paper is to develop a new control technique for VSCs that can provide virtual inertia and damping properties with the DC-link capacitors inhered in the DC-side of grid-tied VSCs. The applied VSC is controlled in the current controlled model, with the capability of injecting extra active power with the aim of frequency support during perturbations. The dynamics assessment of the proposed platform is derived in detail. It is revealed that the control scheme performs in a stable region even under weak-grid conditions. Finally, simulations are conducted in MATLAB to depict the efficacy and feasibility of the proposed method. The results show that frequency deviation is mitigated under step up/down changes in the demand, and the rate of change of frequency is improved by 47.37% compared to the case in which the synthetic inertia loop is canceled out.

scholarly journals Heterogeneous Inertia Estimation for Power Systems with High Penetration of Converter-Interfaced Generation

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5047
Author(s):  
Diala Nouti ◽  
Ferdinanda Ponci ◽  
Antonello Monti
Keyword(s):  
Power Systems ◽  
Estimation Algorithm ◽  
System Stability ◽  
Rotational Inertia ◽  
Heterogeneous Distribution ◽  
Proper Actions ◽  
High Penetration ◽  
System Operator ◽  
And Control ◽  
System Inertia

The increasing and fast deployment of distributed generation is posing challenges to the operation and control of power systems due to the resulting reduction in the overall system rotational inertia and damping. Therefore, it becomes quite crucial for the transmission system operator to monitor the varying system inertia and damping in order to take proper actions to maintain the system stability. This paper presents an inertia estimation algorithm for low-inertia systems to estimate the inertia (both mechanical and virtual) and damping of systems with mixed generation resources and/or the resource itself. Moreover, the effect of high penetration of distributed energy resources and the resulting heterogeneous distribution of inertia on the overall system inertia estimation is investigated. A comprehensive set of case studies and scenarios of the IEEE 39-bus system provides results to demonstrate the performance of the proposed estimator.

scholarly journals Wind Inertial Response Based on the Center of Inertia Frequency of a Control Area

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6177
Author(s):  
Alija Mujcinagic ◽  
Mirza Kusljugic ◽  
Emir Nukic
Keyword(s):  
Power System ◽  
Wind Power ◽  
Power Plants ◽  
Frequency Stability ◽  
Control Area ◽  
Rotational Inertia ◽  
Wind Power Plants ◽  
Inertial Response ◽  
Virtual Inertia ◽  
Inertia Response

As a result of the increased integration of power converter-connected variable speed wind generators (VSWG), which do not provide rotational inertia, concerns about the frequency stability of interconnected power systems permanently arise. If the inertia of a power system is insufficient, wind power plants’ participation in the inertial response should be required. A trendy solution for the frequency stability improvement in low inertia systems is based on utilizing so-called “synthetic” or “virtual” inertia from modern VSWG. This paper presents a control scheme for the virtual inertia response of wind power plants based on the center of inertia (COI) frequency of a control area. The PSS/E user written wind inertial controller based on COI frequency is developed using FORTRAN. The efficiency of the controller is tested and applied to the real interconnected power system of Southeast Europe. The performed simulations show certain conceptual advantages of the proposed controller in comparison to traditional schemes that use the local frequency to trigger the wind inertial response. The frequency response metrics, COI frequency calculation and graphical plots are obtained using Python.

scholarly journals Contribution of Wind Farms to the Stability of Power Systems with High Penetration of Renewables

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2207
Author(s):  
Jesus Castro Martinez ◽  
Santiago Arnaltes ◽  
Jaime Alonso-Martinez ◽  
Jose Luis Rodriguez Amenedo
Keyword(s):  
Power Systems ◽  
Power System ◽  
Wind Farms ◽  
Rate Of Change ◽  
System Stability ◽  
Droop Control ◽  
High Penetration ◽  
Controller Performance ◽  
The Stability ◽  
System Inertia

Power system inertia is being reduced because of the increasing penetration of renewable energies, most of which use power electronic interfaces with the grid. This paper analyses the contribution of inertia emulation and droop control to the power system stability. Although inertia emulation may appear the best option to mitigate frequency disturbances, a thorough analysis of the shortcomings that face real-time implementations shows the opposite. Measurement noise and response delay for inertia emulation hinder controller performance, while the inherently fast droop response of electronic converters provides better frequency support. System stability, expressed in terms of rate of change of frequency (ROCOF) and frequency nadir, is therefore improved with droop control, compared to inertia emulation.

scholarly journals Enhanced Inertial Response Capability of a Variable Wind Energy Conversion System

Energies ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 8132
Author(s):  
Jun Wang ◽  
Yien Xu ◽  
Xiaoxin Wu ◽  
Jiejie Huang ◽  
Xinsong Zhang ◽  
...  
Keyword(s):  
Control Strategy ◽  
Maximum Rate ◽  
Rate Of Change ◽  
Frequency Deviation ◽  
Control Coefficient ◽  
Maximum Frequency ◽  
Induction Generators ◽  
Inertial Response ◽  
System Frequency ◽  
Response Capability

An inertial response emulated control strategy of doubly-fed induction generators (DFIGs) is able to arrest their frequency decline following a severe frequency event. Nevertheless, the control coefficient is unchanged, so as to limit the benefit potentiality of improving the inertial response capability for various disturbances and provide less of a benefit for boosting the frequency nadir. This paper addresses an enhanced inertial response emulated control scheme for a DFIG to improve the maximum frequency deviation and maximum rate of change of frequency for various disturbances. To this end, the control coefficient is coupled with the system frequency deviation so as to regulate the control coefficient according to the system frequency deviation (i.e., sizes of the disturbance). Results clearly indicate that the proposed inertial response emulated control strategy provides better performance in terms of improving the maximum rate of change of frequency and maximum frequency deviation under various sizes of disturbance and random wind speed conditions.

Study of Multi-factor Coordinated Frequency Control Strategy by DFIG Wind Turbine

2019 ◽  
Vol 12 (1) ◽  
pp. 86-93
Author(s):  
Wang Yin-Sha ◽  
Li Wen-Yi ◽  
Li Zhi-Wen
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Frequency Response ◽  
Control Strategy ◽  
Large Scale ◽  
Frequency Control ◽  
Operating Conditions ◽  
Frequency Change ◽  
System Frequency ◽  
Inertia Response

Background: With the large-scale Doubly Fed Induction Generator (DFIG) wind turbine integrated into the power system, the DFIG inertia response of the wind turbine should be provided. Also, the frequency response should be similar to the conventional generation technologies. This paper investigated the influence of frequency response term and wind speed conditions on system frequency control. Methods: The specific operating conditions of four control strategies, including inertia control, droop control, over speed control and pitch angle control were researched in this paper. Multi-factor coordinated frequency control strategy of DFIG wind turbine was established based on the above researches. The strategy was composed of wind speed ranging from low to high. Results: According to the simulation results, the DFIG wind turbine, which was based on multifactor coordinated frequency control strategy, could respond to the system’s frequency change of power grid, effectively. Conclusion: It helps system frequency return to stable states better and faster than DFIG wind turbine and also could reduce the fluctuation of system frequency.

scholarly journals Reduced-Order-VSM-Based Frequency Controller for Wind Turbines

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 528
Author(s):  
Liang Lu ◽  
Oscar Saborío-Romano ◽  
Nicolaos A. Cutululis
Keyword(s):  
Power Systems ◽  
Wind Turbines ◽  
Rate Of Change ◽  
Reduced Order ◽  
Overcurrent Protection ◽  
Virtual Inertia ◽  
Grid Side ◽  
Grid Side Converter ◽  
Frequency Controller ◽  
System Frequency

Frequency support capability is becoming an important requirement for wind turbines, as wind power is increasingly integrated into power systems. In this paper, a frequency controller is implemented and validated. Such a controller allows wind turbines to help regulate the system frequency automatically and includes virtual inertia to help limit the rate of change of frequency. Compared with other methods, the controller achieves satisfactory frequency support capability with considerable simplicity. The controller is added to the grid-side converter controls, together with cascaded inner loops, which enables wind turbines to operate in grid-forming mode with overcurrent protection. The influence of the controller parameters on the frequency response is investigated.

scholarly journals Common-Mode Frequency in Inverter-Penetrated Power Systems: Definition, Analysis, and Quantitative Evaluation

2022 ◽  
Author(s):  
Huisheng Gao ◽  
Huanhai Xin ◽  
Linbin Huang ◽  
Zhiyi Li ◽  
Wei Huang ◽  
...  
Keyword(s):  
Power Systems ◽  
Power System ◽  
Test System ◽  
Mode Frequency ◽  
Rate Of Change ◽  
Synchronous Generators ◽  
Common Mode ◽  
Response Characteristics ◽  
Frequency Drop ◽  
System Frequency

<p>As synchronous generators (SGs) are extensively replaced by inverter-based generators (IBGs), modern power systems are facing complicated frequency stability problems. Conventionally, the frequency nadir and the rate of change of frequency (RoCoF) are the two main factors concerned by power system operators. However, these two factors heavily rely on simulations or experiments, especially in a power system with high-penetration IBGs, which offer limited theoretical insight into how the frequency response characteristics are affected by the devices. This paper aims at filling this gap. Firstly, we derive a formulation of the global frequency for an IBG-penetrated power system, referred to as common-mode frequency (CMF). The derived CMF is demonstrated to be more accurate than existing frequency definitions, e.g., the average system frequency (ASF). Then, a unified transfer function structure (UTFS) is proposed to approximate the frequency responses of different types of devices by focusing on three key parameters<a>, which dramatically reduces the complexity of frequency analysis. </a>On this basis, we introduce two evaluation indices, i.e., frequency drop depth coefficient (FDDC) and frequency drop slope coefficient (FDSC), to theoretically quantify the frequency nadir and the average RoCoF, respectively. Instead of relying on simulations or experiments, our method rigorously links the system’s frequency characteristics to the characteristics of heterogeneous devices, which enables an in-depth understanding regarding how devices affect the system frequency. Finally, the proposed indices are verified through simulations on a modified IEEE 39-bus test system. </p>

scholarly journals Assessment of Grid-Connected Wind Turbines with an Inertia Response by Considering Internal Dynamics

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1038 ◽  
Author(s):  
Callum Henderson ◽  
Dimitrios Vozikis ◽  
Derrick Holliday ◽  
Xiaoyan Bian ◽  
Agustí Egea-Àlvarez
Keyword(s):  
Wind Turbines ◽  
Power Converter ◽  
Current Control ◽  
Negative Effects ◽  
Industry Standard ◽  
Voltage Controller ◽  
External Frequency ◽  
Inertial Response ◽  
Grid Side ◽  
Inertia Response

This paper presents a small-signal analysis of different grid side controllers for full power converter wind turbines with inertia response capability. In real wind turbines, the DC link controller, the drivetrain damping controller and the inertial response might present contradictory control actions in a close bandwidth range. This situation might lead to reduced control performance, increased component stress and non-compliance of connection agreements. The paper presents an analysis of the internal wind turbine dynamics by considering different grid-side converter control topologies: standard current control used in the wind industry, standard current control with inertia emulation capabilities and virtual synchronous machines. Comments are made on the similarities between each topology and the negative effects and limits, and possible remedies are discussed. Finally, the conclusion poses that the inclusion of a DC link voltage controller reduces the ability of a converter to respond to external frequency events without energy storage. The degradation increases with the DC link voltage control speed.

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