Impacts of Inverter Control Strategies on the Stability of Low-Inertia Power Systems

Faults in electrical power systems are among the key factors and sources to network disturbances, however control strategies are among key faults clearing techniques for the sake of safe operational mode of the system.Some researchers have shown various limitations of control strategies such as slow dynamic response,inability to switch Off and On network remotely and fault clearing time. For a system with wind energy technologies, if the power flow of a wind turbine is interrupted by a fault, the intermediate-circuit voltage between the machine-side converter and line-side converter will fall in unacceptably high values.To overcome the aforementioned issues, this paper used a Matlab simulations and experiments in order to analyze and validate the results.The results showed that fault ride through (FRT) with SCADA Viewer software are more adaptable to the variations of voltage and wind speed in order to avoid loss of synchronism. Therefore at the speed of 12.5m/s a wind produced a rated power of 750W and remained in synchronization before and after a fault created and cleared but worked as generator meanwhile at speed of 3.4m/s wind disconnected from grid and started working as a motor and consumed active power (P=-25watts) and voltage dip at 100% .For the protection purpose, the DC chopper and crowbar should be integrated towards management of excess energy during faults cases.

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Power Hardware-in-the-Loop-Based Performance Analysis of Different Converter Controllers for Fast Active Power Regulation in Low-Inertia Power Systems

Energies ◽

10.3390/en14113274 ◽

2021 ◽

Vol 14 (11) ◽

pp. 3274

Author(s):

Jose Rueda Torres ◽

Zameer Ahmad ◽

Nidarshan Veera Kumar ◽

Elyas Rakhshani ◽

Ebrahim Adabi ◽

...

Keyword(s):

Performance Evaluation ◽

Power Systems ◽

Real Time ◽

Control Strategies ◽

Active Power ◽

Power Electronic ◽

Hardware In The Loop ◽

Digital Controllers ◽

Power Regulation ◽

The Impact

Future electrical power systems will be dominated by power electronic converters, which are deployed for the integration of renewable power plants, responsive demand, and different types of storage systems. The stability of such systems will strongly depend on the control strategies attached to the converters. In this context, laboratory-scale setups are becoming the key tools for prototyping and evaluating the performance and robustness of different converter technologies and control strategies. The performance evaluation of control strategies for dynamic frequency support using fast active power regulation (FAPR) requires the urgent development of a suitable power hardware-in-the-loop (PHIL) setup. In this paper, the most prominent emerging types of FAPR are selected and studied: droop-based FAPR, droop derivative-based FAPR, and virtual synchronous power (VSP)-based FAPR. A novel setup for PHIL-based performance evaluation of these strategies is proposed. The setup combines the advanced modeling and simulation functions of a real-time digital simulation platform (RTDS), an external programmable unit to implement the studied FAPR control strategies as digital controllers, and actual hardware. The hardware setup consists of a grid emulator to recreate the dynamic response as seen from the interface bus of the grid side converter of a power electronic-interfaced device (e.g., type-IV wind turbines), and a mockup voltage source converter (VSC, i.e., a device under test (DUT)). The DUT is virtually interfaced to one high-voltage bus of the electromagnetic transient (EMT) representation of a variant of the IEEE 9 bus test system, which has been modified to consider an operating condition with 52% of the total supply provided by wind power generation. The selected and programmed FAPR strategies are applied to the DUT, with the ultimate goal of ascertaining its feasibility and effectiveness with respect to the pure software-based EMT representation performed in real time. Particularly, the time-varying response of the active power injection by each FAPR control strategy and the impact on the instantaneous frequency excursions occurring in the frequency containment periods are analyzed. The performed tests show the degree of improvements on both the rate-of-change-of-frequency (RoCoF) and the maximum frequency excursion (e.g., nadir).

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State-Space Model of Quasi-Z-Source Inverter-PV Systems for Transient Dynamics Studies and Network Stability Assessment

Energies ◽

10.3390/en14144150 ◽

2021 ◽

Vol 14 (14) ◽

pp. 4150

Author(s):

Lluís Monjo ◽

Luis Sainz ◽

Juan José Mesas ◽

Joaquín Pedra

Keyword(s):

Power Systems ◽

State Space ◽

State Space Model ◽

Pv System ◽

Pv Systems ◽

Renewable Power ◽

Ac Networks ◽

Transient Interactions ◽

The Stability ◽

Averaged Model

Photovoltaic (PV) power systems are increasingly being used as renewable power generation sources. Quasi-Z-source inverters (qZSI) are a recent, high-potential technology that can be used to integrate PV power systems into AC networks. Simultaneously, concerns regarding the stability of PV power systems are increasing. Converters reduce the damping of grid-connected converter systems, leading to instability. Several studies have analyzed the stability and dynamics of qZSI, although the characterization of qZSI-PV system dynamics in order to study transient interactions and stability has not yet been properly completed. This paper contributes a small-signal, state-space-averaged model of qZSI-PV systems in order to study these issues. The model is also applied to investigate the stability of PV power systems by analyzing the influence of system parameters. Moreover, solutions to mitigate the instabilities are proposed and the stability is verified using PSCAD time domain simulations.

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A Full-Newton AC-DC Power Flow Methodology for HVDC Multi-Terminal Systems and Generic DC Network Representation

Energies ◽

10.3390/en14061658 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1658

Author(s):

Leandro Almeida Vasconcelos ◽

João Alberto Passos Filho ◽

André Luis Marques Marcato ◽

Giovani Santiago Junqueira

Keyword(s):

Power Systems ◽

Direct Current ◽

Power Flow ◽

Large Scale ◽

Flow Problem ◽

Control Strategies ◽

Problem Formulation ◽

Expansion Planning ◽

Dc Power ◽

Power Flow Problem

The use of Direct Current (DC) transmission links in power systems is increasing continuously. Thus, it is important to develop new techniques to model the inclusion of these devices in network analysis, in order to allow studies of the operation and expansion planning of large-scale electric power systems. In this context, the main objective of this paper is to present a new methodology for a simultaneous AC-DC power flow for a multi-terminal High Voltage Direct Current (HVDC) system with a generic representation of the DC network. The proposed methodology is based on a full Newton formulation for solving the AC-DC power flow problem. Equations representing the converters and steady-state control strategies are included in a power flow problem formulation, resulting in an expanded Jacobian matrix of the Newton method. Some results are presented based on HVDC test systems to confirm the effectiveness of the proposed approach.

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Chaos Control for a Fractional-Order Jerk System via Time Delay Feedback Controller and Mixed Controller

Fractal and Fractional ◽

10.3390/fractalfract5040257 ◽

2021 ◽

Vol 5 (4) ◽

pp. 257

Author(s):

Changjin Xu ◽

Maoxin Liao ◽

Peiluan Li ◽

Lingyun Yao ◽

Qiwen Qin ◽

...

Keyword(s):

Time Delay ◽

Fractional Order ◽

Chaos Control ◽

Chaotic Behavior ◽

Control Strategies ◽

Feedback Controller ◽

Research Approach ◽

Controlling Chaos ◽

The Stability ◽

Jerk System

In this study, we propose a novel fractional-order Jerk system. Experiments show that, under some suitable parameters, the fractional-order Jerk system displays a chaotic phenomenon. In order to suppress the chaotic behavior of the fractional-order Jerk system, we design two control strategies. Firstly, we design an appropriate time delay feedback controller to suppress the chaos of the fractional-order Jerk system. The delay-independent stability and bifurcation conditions are established. Secondly, we design a suitable mixed controller, which includes a time delay feedback controller and a fractional-order PDσ controller, to eliminate the chaos of the fractional-order Jerk system. The sufficient condition ensuring the stability and the creation of Hopf bifurcation for the fractional-order controlled Jerk system is derived. Finally, computer simulations are executed to verify the feasibility of the designed controllers. The derived results of this study are absolutely new and possess potential application value in controlling chaos in physics. Moreover, the research approach also enriches the chaos control theory of fractional-order dynamical system.

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Dynamic Analysis for VSG-Based Power Flow Control Applied to DG Systems

10.53316/sepoc2021.037 ◽

2021 ◽

Author(s):

THIAGO FIGUEIREDO DO NASCIMENTO ◽

ANDRES ORTIZ SALAZAR

Keyword(s):

Power Systems ◽

Dynamic Analysis ◽

Power Flow ◽

Control Strategies ◽

Renewable Energy Sources ◽

Dynamic Performance ◽

Synchronous Generator ◽

Power Flow Control ◽

Grid Impedance ◽

Impedance Parameters

The integration of distributed generation (DG) systems based on renewable energy sources (RES) by using power converters is an emerging technology in modern power systems. Among the control strategies applied to this new configuration, the virtual synchronous generator (VSG) approach has proven to be an attractive solution due providing suitable dynamic performance. Thus, this paper presents a dynamic analysis of gridtied converters controlled by using VSG concept. This analysis is based on a dynamic model that describes the DG power flow transient characteristics. Based on this model, the grid impedance parameters variation effects on the VSG controllers dynamic performance are discussed. Simulation results are presented to evaluate the effectiveness of the theoretical analysis performed.

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Overview of Methods for Determining Parameters of Synchronous Generators

Bulletin of the South Ural State University series Power Engineering ◽

10.14529/power200412 ◽

2020 ◽

Vol 20 (4) ◽

pp. 103-113

Keyword(s):

Power Systems ◽

Computational Models ◽

Meta Analysis ◽

Measurement Data ◽

Synchronous Generator ◽

Adaptive Model ◽

Operational Control ◽

Synchronous Generators ◽

Computing Power ◽

The Stability

A synchronous generator is one of the key elements of any power system, having a significant impact on the stability and reliability of consumers’ power supply. Nowadays, the power systems emergency and operational control issues are being solved using computational models, the parameters whereof are determined using the reference data, or the data obtained during testing. High dependence of the models’ parameters on various external factors leads to a significant decrease in the accuracy of solving the issues of emergency and operational control. Identification based on the traditional telemetry systems or synchrophasor measurements is used to improve the accuracy of parameters of the power systems’ computational models. The purpose of this research lies in a meta-analysis of the available studies aimed at developing a methodology for determining parameters of a synchronous generator on the basis of measurement data. Russian and foreign studies were analyzed and grouped to achieve this goal. After that, for each group, advantages, disadvantages, and the area of application were identified. As a result, it is shown that the existing methods for determining parameters of synchronous generators based on measurement data cannot adapt to the source dataset and also require significant computing power. As a way to overcome these shortcomings, an adaptive model of a synchronous machine is proposed.

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Flexible Tranmission Elements for Grid Optimization

Bulletin of the South Ural State University series Power Engineering ◽

10.14529/power210206 ◽

2021 ◽

Vol 21 (2) ◽

pp. 53-61

Keyword(s):

Power Systems ◽

Electric Power ◽

Emergency Operation ◽

Power Losses ◽

Current Transmission ◽

Before And After ◽

Grid Optimization ◽

Flexible Alternating Current Transmission ◽

Active Power Losses ◽

The Stability

The article dwells upon optimizing, reduction of losses in, and improving the stability of grids by implementing devices that affect the parameters and power flows in a grid. State-of-the-art technology for better control is crucial for the development of electric power systems. FACTS technologies or flexible alternating current transmission systems, essentially transform the grid from a passive electricity transport into a device that actively controls the grid parameters. The article analyzes the development of a 500/220/110 kV grid that uses parameter-affective devices: SVC, BSK, LCD. Steady-state parameters, active power losses, and electric power losses were calculated for a year before and after the devices were deployed. Each device was therefore analyzed for effectiveness. The parameters of the SVC-equipped 500/220/110 kV grid were calculated for emergency operation with the 500 kV line being offline. Thus, the paper also analyzes the emergency performance of the SVC.

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A Review of Virtual Inertia Techniques for Renewable Energy-Based Generators

10.5772/intechopen.92651 ◽

2020 ◽

Author(s):

Ana Fernández-Guillamón ◽

Emilio Gómez-Lázaro ◽

Eduard Muljadi ◽

Ángel Molina-Garcia

Keyword(s):

Renewable Energy ◽

Power Systems ◽

Power System ◽

Power Plants ◽

Control Strategies ◽

Renewable Energy Sources ◽

Extensive Discussion ◽

Renewable Sources ◽

Virtual Inertia ◽

Alternative Sources

Over recent decades, the penetration of renewable energy sources (RES), especially photovoltaic and wind power plants, has been promoted in most countries. However, as these both alternative sources have power electronics at the grid interface (inverters), they are electrically decoupled from the grid. Subsequently, stability and reliability of power systems are compromised. Inertia in power systems has been traditionally determined by considering all the rotating masses directly connected to the grid. Thus, as the penetration of renewable units increases, the inertia of the power system decreases due to the reduction of directly connected rotating machines. As a consequence, power systems require a new set of strategies to include these renewable sources. In fact, ‘hidden inertia,’ ‘synthetic inertia’ and ‘virtual inertia’ are terms currently used to represent an artificial inertia created by inverter control strategies of such renewable sources. This chapter reviews the inertia concept and proposes a method to estimate the rotational inertia in different parts of the world. In addition, an extensive discussion on wind and photovoltaic power plants and their contribution to inertia and power system stability is presented.

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