Under Frequency Load Shedding Techniques for Future Smart Power Systems

2019 ◽  
pp. 188-202
Author(s):  
H. H. Alhelou
Keyword(s):  
Power Systems ◽  
Power System ◽  
Active Power ◽  
Load Shedding ◽  
System Stability ◽  
Special Focus ◽  
Power Demand ◽  
Synchronous Generators ◽  
Smart Power ◽  
System Frequency

It is critical for today's power system to remain in a state of equilibrium under normal conditions and severe disturbances. Power imbalance between the load and the generation can severely affect system stability. Therefore, it is necessary that these imbalance conditions be addressed in the minimum time possible. It is well known that power system frequency is directly proportional to the speed of rotation of synchronous machines and is also a function of the active power demand. As a consequence, when active power demand is greater than the generation, synchronous generators tends to slow down and the frequency decreases to even below threshold if not quickly addressed. One of the most common methods of restoring frequency is the use of under frequency load shedding (UFLS) techniques. In this chapter, load shedding techniques are presented in general but with special focus on UFLS.

scholarly journals WAMS-Based Online Disturbance Estimation in Interconnected Power Systems Using Disturbance Observer

2019 ◽  
Vol 9 (5) ◽  
pp. 990 ◽  
Author(s):  
Hassan Haes Alhelou ◽  
Mohamad Hamedani Golshan ◽  
Takawira Njenda ◽  
Pierluigi Siano
Keyword(s):  
Power Systems ◽  
Power System ◽  
Disturbance Observer ◽  
Load Shedding ◽  
System Stability ◽  
Main Stage ◽  
Estimation Errors ◽  
Disturbance Estimation ◽  
System Frequency ◽  
Swing Equation

In the event of a generator loss or disturbance, the power system frequency declines quickly and overall system stability is at risk. During these scenarios, under frequency load shedding is triggered to restore the power system frequency. The main stage of modern adaptive under frequency load shedding techniques is disturbance estimation. However, the swing equation is widely used in disturbance estimation but has some critical estimation errors. In this paper, instead of using the swing equation we proposed the use of a disturbance observer to estimate the curtailed power. By making use of wide area measurements, a system frequency response model, which is a representative of the whole power system, can be realized in real time. Using different power system states of the developed model, a disturbance observer can be designed as well. The main advantage of the disturbance observer is that it can accurately estimate the disturbance magnitude and its location in a very short time. Further investigations show that by using the disturbance observer disturbances, which occur at the same time or at different times in different areas regardless of the magnitude or size, accurate estimations can be made. To ascertain the efficiency of the proposed scheme, simulations are done for a four-area power system using Matlab/Simulink.

scholarly journals An approach for a multi-stage under-frequency based load shedding scheme for a power system network

2020 ◽  
Vol 10 (6) ◽  
pp. 6071
Author(s):  
Mkhululi Elvis Siyanda Mnguni ◽  
Yohan Darcy Mfoumboulou
Keyword(s):  
Decision Making ◽  
Power Systems ◽  
Power System ◽  
New England ◽  
Operating Conditions ◽  
Load Shedding ◽  
Power Network ◽  
Load Demand ◽  
Multi Stage ◽  
System Frequency

The integration of load shedding schemes with mainstream protection in power system networks is vital. The traditional power system network incorporates different protection schemes to protect its components. Once the power network reaches its maximum limits, and the load demand continue to increase the whole system will experience power system instability. The system frequency usually drops due to the loss of substantial generation creating imbalance. The best method to recover the system from instability is by introducing an under-frequency load shedding (UFLS) scheme in parallel with the protection schemes. This paper proposed a new UFLS scheme used in power systems and industry to maintain stability. Three case studies were implemented in this paper. Multi-stage decision-making algorithms load shedding in the environment of the DIgSILENT power factory platform is developed. The proposed algorithm speeds-up the operation of the UFLS scheme. The load shedding algorithm of the proposed scheme is implemented as a systematic process to achieve stability of the power network which is exposed to different operating conditions. The flexibility of the proposed scheme is validated with the modified IEEE 39-bus New England model. The application of the proposed novel UFLS schemes will contribute further to the development of new types of engineers.

scholarly journals Enhancement of Power System Transient Stability by the Coordinated Control between an Adjustable Speed Pumping Generator and Battery

2020 ◽  
Vol 10 (24) ◽  
pp. 9034
Author(s):  
Junji Tamura ◽  
Atsushi Umemura ◽  
Rion Takahashi ◽  
Atsushi Sakahara ◽  
Fumihito Tosaka ◽  
...  
Keyword(s):  
Power Systems ◽  
Power System ◽  
Wind Farm ◽  
Transient Stability ◽  
Wind Farms ◽  
System Stability ◽  
Synchronous Generators ◽  
Adjustable Speed ◽  
The Stability ◽  
Network Fault

The penetration level of large-scale wind farms into power systems has been increasing significantly, and the frequency stability and transient stability of the power systems during and after a network fault can be negatively affected. This paper proposes a new control method to improve the stability of power systems that are composed of large wind farms, as well as usual synchronous generators. The new method is a coordinated controlling method between an adjustable-speed pumping generator (ASG) and a battery. The coordinated system is designed to improve power system stability during a disconnection in a fixed-rotor-speed wind turbine with a squirrel cage-type induction generator (FSWT-SCIG)-based wind farm due to a network fault, in which a battery first responds quickly to the system frequency deviation due to a grid fault and improves the frequency nadir, and then the ASG starts to supply compensatory power to recover the grid frequency to the rated frequency. The performance of the proposed system was confirmed through simulation studies on a power system model consisting of usual synchronous generators (SGs), an ASG, a battery, and an SCIG-based wind farm. Simulation results demonstrated that the proposed control system can enhance the stability of the power system effectively.

scholarly journals Power System Stability Study on Multi Machine Systems having DFIG Based Wind Generation System

2020 ◽  
Vol 6 (3) ◽  
pp. 27-30
Author(s):  
Pramod Kumar Mehar ◽  
Mrs. Madhu Upadhyay
Keyword(s):  
Steady State ◽  
Power Systems ◽  
Power System ◽  
Power Plants ◽  
Transient Stability ◽  
Power System Stability ◽  
Stability Study ◽  
System Stability ◽  
Synchronous Generators ◽  
The Impact

Power system stability is related to principles of rotational motion and the swing equation governing the electromechanical dynamic behavior. In the special case of two finite machines the equal area criterion of stability can be used to calculate the critical clearing angle on the power system, it is necessary to maintain synchronism, otherwise a standard of service to the consumers will not be achieved. With the increasing penetration of doubly fed induction generators (DFIGs), the impact of the DFIG on transient stability attracts great attention. Transient stability is largely dominated by generator types in the power system, and the dynamic characteristics of DFIG wind turbines are different from that of the synchronous generators in the conventional power plants. The analysis of the transient stability on DFIG integrated power systems has become a very important issue. This paper is a review of three types of stability condition. The first type of stability, steady state stability explains the maximum steady state power and the power angle diagram. There are several methods to improve system stability in which some methods are explained.

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>

Stability Enhancement in Multi-Machine Power Systems by Fuzzy-based Coordinated AVR-PSS

2015 ◽  
Vol 4 (2) ◽  
pp. 36-50 ◽  
Author(s):  
Rahmat Khezri ◽  
Hassan Bevrani
Keyword(s):  
Fuzzy Logic ◽  
Power Systems ◽  
Power System ◽  
Coordinated Control ◽  
System Stability ◽  
Test Case ◽  
Synchronous Generators ◽  
System Stabilizer ◽  
Stability Enhancement ◽  
Logic Unit

This paper presents performance of intelligent fuzzy-based coordinated control for Automatic Voltage Regulator (AVR) and Power System Stabilizer (PSS), to prevent losing synchronism after major sudden faults and to achieve appropriate post-fault voltage level in multi-machine power systems. The AVR and PSS gains can adaptively change to guarantee the power system stability after faults. For change in AVR and PSS gains, at least one significant generator in each area of a multi-area power system is equipped with fuzzy logic unit. The fuzzy logic unit accepts normalized deviations of terminal voltage and phase difference of synchronous generators as inputs and generates the desirable gains for AVR and PSS. The construction of appropriate fuzzy membership functions and rules for best tuning of gains is described. The proposed fuzzy control methodology is applied to 11-bus 4-generator power system test case. Simulation results illustrate the effectiveness and robustness of the proposed fuzzy-based coordinated control strategy.

Stability Enhancement in Multi-Machine Power Systems by Fuzzy-Based Coordinated AVR-PSS

Fuzzy Systems ◽  
2017 ◽  
pp. 235-249
Author(s):  
Rahmat Khezri ◽  
Hassan Bevrani
Keyword(s):  
Fuzzy Logic ◽  
Power Systems ◽  
Power System ◽  
Coordinated Control ◽  
System Stability ◽  
Test Case ◽  
Synchronous Generators ◽  
System Stabilizer ◽  
Stability Enhancement ◽  
Logic Unit

This paper presents performance of intelligent fuzzy-based coordinated control for Automatic Voltage Regulator (AVR) and Power System Stabilizer (PSS), to prevent losing synchronism after major sudden faults and to achieve appropriate post-fault voltage level in multi-machine power systems. The AVR and PSS gains can adaptively change to guarantee the power system stability after faults. For change in AVR and PSS gains, at least one significant generator in each area of a multi-area power system is equipped with fuzzy logic unit. The fuzzy logic unit accepts normalized deviations of terminal voltage and phase difference of synchronous generators as inputs and generates the desirable gains for AVR and PSS. The construction of appropriate fuzzy membership functions and rules for best tuning of gains is described. The proposed fuzzy control methodology is applied to 11-bus 4-generator power system test case. Simulation results illustrate the effectiveness and robustness of the proposed fuzzy-based coordinated control strategy.

scholarly journals A Developed Graphical User Interface for Power System Stability and Robustness Studies

2015 ◽  
Vol 15 (3) ◽  
pp. 458
Author(s):  
Ghouraf Djamel Eddine ◽  
Naceri Abdellatif ◽  
Abid Mohamed ◽  
Kabi Wahiba
Keyword(s):  
User Interface ◽  
Power Systems ◽  
Power System ◽  
Graphical User Interface ◽  
Operating Time ◽  
Stability Study ◽  
System Stability ◽  
Synchronous Generators ◽  
Analysis And Synthesis ◽  
Dynamic Performances

This paper present the realization and development of a graphical user interface (GUI) to studied the stability and robustness of power systems (analysis and synthesis), using Conventional Power System Stabilizers (CPSS - realized on PID scheme) or advanced controllers (based on adaptive and robust control), and applied on automatic excitation control of powerful synchronous generators, to improve dynamic performances and robustness. The GUI is a useful average to facilitate stability study of power system with the analysis and synthesis of regulators, and resolution of the compromise: results precision / calculation speed. The obtained Simulation results exploiting our developed GUI realized under MATLAB shown considerable improvements in static and dynamic performances, a great stability and enhancing the robustness of power system, with best precision and minimum operating time. This study was performed for different types of powerful synchronous generators.

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 Voltage Stability of Power Systems with Renewable-Energy Inverter-Based Generators: A Review

Electronics ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 115
Author(s):  
Nasser Hosseinzadeh ◽  
Asma Aziz ◽  
Apel Mahmud ◽  
Ameen Gargoom ◽  
Mahbub Rabbani
Keyword(s):  
Renewable Energy ◽  
Power Systems ◽  
Voltage Stability ◽  
Reactive Power ◽  
Power Grid ◽  
Renewable Energy Sources ◽  
Electrical Power ◽  
System Stability ◽  
Special Issue ◽  
Synchronous Generators

The main purpose of developing microgrids (MGs) is to facilitate the integration of renewable energy sources (RESs) into the power grid. RESs are normally connected to the grid via power electronic inverters. As various types of RESs are increasingly being connected to the electrical power grid, power systems of the near future will have more inverter-based generators (IBGs) instead of synchronous machines. Since IBGs have significant differences in their characteristics compared to synchronous generators (SGs), particularly concerning their inertia and capability to provide reactive power, their impacts on the system dynamics are different compared to SGs. In particular, system stability analysis will require new approaches. As such, research is currently being conducted on the stability of power systems with the inclusion of IBGs. This review article is intended to be a preface to the Special Issue on Voltage Stability of Microgrids in Power Systems. It presents a comprehensive review of the literature on voltage stability of power systems with a relatively high percentage of IBGs in the generation mix of the system. As the research is developing rapidly in this field, it is understood that by the time that this article is published, and further in the future, there will be many more new developments in this area. Certainly, other articles in this special issue will highlight some other important aspects of the voltage stability of microgrids.

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