Description:FIELD OF INVENTION
User's field of interest involves the study of steady-state voltage stability, focusing on the interplay between the dynamics of generators and shunt compensators. This includes analyzing how these elements affect voltage levels and stability in power systems, ensuring reliable and efficient operation. This research aims to enhance the resilience and performance of electrical grids under various operating conditions.
BACKGROUND OF INVENTION
Steady-state voltage stability is a crucial aspect of power system operation, ensuring that the system can maintain acceptable voltage levels under normal and disturbed conditions. It involves the ability of a power system to control voltage following a disturbance, such as a sudden increase in load or a generator outage. Voltage instability can lead to voltage collapse, causing widespread blackouts and significant economic losses. The dynamics of generators and shunt compensators play a pivotal role in maintaining voltage stability. Generators, as primary power sources, are equipped with automatic voltage regulators (AVRs) and excitation systems that adjust the field voltage to control the terminal voltage and reactive power output. This dynamic response is essential for maintaining voltage levels and supporting the system during disturbances. Shunt compensators, including capacitors and reactors, provide reactive power support to the system. Their dynamic behavior is critical in counteracting voltage drops by either absorbing or injecting reactive power as needed. Static Var Compensators (SVCs) and Static Synchronous Compensators (STATCOMs) are advanced shunt devices that offer fast and precise voltage regulation by dynamically adjusting reactive power output in response to system conditions. The integration of these dynamic elements into steady-state voltage stability analysis enhances the accuracy and reliability of stability assessments. Traditional methods often overlook the transient behavior of generators and compensators, potentially leading to underestimation of stability margins. By considering their dynamics, the power system can be more effectively managed, ensuring robust voltage profiles and mitigating the risk of voltage collapse. This approach is vital for the modern, complex power grid, characterized by high penetration of renewable energy sources and varying load patterns.
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SUMMARY
Steady-state voltage stability is a critical aspect of power system operation and planning, ensuring that the voltage levels within the network remain within acceptable limits under normal and disturbed conditions. This study focuses on evaluating voltage stability by incorporating the dynamic behaviors of generators and shunt compensators, which are essential elements in maintaining voltage control. Generators, with their automatic voltage regulators (AVRs) and excitation systems, play a pivotal role in voltage stability. The dynamic response of these components affects how quickly and effectively a generator can adjust its output to maintain stable voltage levels. Understanding the interactions between generator dynamics and voltage stability helps in predicting system behavior under various loading conditions and disturbances.
Shunt compensators, including static VAR compensators (SVCs) and static synchronous compensators (STATCOMs), provide reactive power support to the system, enhancing voltage stability. The dynamics of these compensators, characterized by their response times and control strategies, are crucial for rapid voltage adjustment and stabilization following disturbances. By analyzing the performance of shunt compensators, the study aims to determine their effectiveness in supporting steady-state voltage stability. The integration of generator and shunt compensator dynamics into voltage stability analysis provides a more comprehensive understanding of the system's stability margins and potential vulnerabilities. This approach facilitates the development of more robust control strategies and optimization of reactive power resources, ensuring a reliable and stable power system. The study's findings can inform the design and operation of power systems, contributing to enhanced stability and resilience against voltage instability phenomena.
DETAILED DESCRIPTION OF INVENTION
Voltage stability in power systems is a critical issue that has been addressed through various means, including the use of shunt compensators and FACTS (Flexible Alternating Current Transmission Systems). As the demand for reliable and high-quality power supply grows, advancements in reactive power compensation and voltage control technologies have become increasingly important.
Shunt compensators like SVC (Static Var Compensators) and STATCOM (Static Synchronous Compensators) play a pivotal role in maintaining voltage stability. These devices are designed to provide fast and reliable reactive power compensation, which helps to control voltage levels within the desired range.
Shunt Compensators: SVC and STATCOM
1. SVC (Static Var Compensator):
o Functionality: SVCs are devices used for controlling voltage by providing fast-acting reactive power compensation. They achieve this by adjusting the reactive power output to stabilize the voltage.
o Operation: SVCs can absorb or generate reactive power, thereby maintaining the voltage within the set limits. They are typically used in high-voltage networks to enhance voltage stability.
o Historical Use: The world's first SVC for voltage control over 100 kV was implemented in the United States in 1977. It was used on 138 kV busbars to address significant voltage stability issues.
2. STATCOM (Static Synchronous Compensator):
o Functionality: STATCOMs are advanced reactive power compensation devices considered to be more efficient and faster than SVCs. They use power electronics to generate or absorb reactive power, thus stabilizing the voltage.
o Operation: STATCOMs operate similarly to SVCs but offer higher control dynamics and faster response times due to their power electronic nature.
o Historical Use: The first STATCOM was developed in Japan in 1991. Its innovative design has made it one of the best devices for voltage and reactive power control in power systems.
Combined Systems: SVC Based on STATCOM
• These hybrid systems integrate the functionalities of both SVC and STATCOM, offering enhanced performance in terms of voltage control and reactive power compensation. Although not yet implemented in some national power systems, the increasing demand for improved voltage safety and energy quality is driving interest in these advanced systems.
Importance of Reactive Power Compensation
• Voltage Control: Maintaining voltage levels within the specified range is crucial for the stable operation of power systems. Reactive power compensation directly impacts voltage stability.
• Energy Quality: Ensuring high-quality power supply involves controlling voltage fluctuations and maintaining consistent voltage levels, which reactive power compensators effectively manage.
• System Stability: By providing rapid and reliable reactive power compensation, devices like SVC and STATCOM help to prevent voltage collapse and improve overall system stability.
Advancements in FACTS Technology
• The development of FACTS technology has significantly contributed to the progress in voltage stability solutions. FACTS devices are distinguished by their high-speed operation and dynamic control capabilities, making them essential for modern power systems.
Criteria for Control in FACTS Shunt Compensators
1. Voltage Control:
o Objective: Maintain the reference voltage at the connection node.
o Purpose: This is the fundamental criterion for the operation of these types of compensators.
2. Power Factor Control:
o Objective: Ensure the power factor remains within a specified range.
o Application: This criterion is mainly used in industrial plants.
3. Reactive Power Control:
o Objective: Maintain reactive power at a specified level.
o Application: Although possible to implement, this criterion is not commonly used in practice.
4. Damping of Power Oscillations:
o Objective: Eliminate power oscillations, such as those occurring after short circuits.
Types of Shunt Compensators
1. Electromechanical
2. Static
3. Conventional
These shunt compensators serve different purposes and have specific applications depending on the control criteria they are designed to meet.
Static compensators (STATCOMs) and Synchronous Voltage Compensators (SVCs) play crucial roles in modern power systems, offering advanced and flexible control of reactive power, which is essential for maintaining voltage stability and improving power quality. Here’s a detailed breakdown of these technologies:
Electromechanical Compensators
Electromechanical compensators, primarily regulated synchronous machines, are designed to either supply or absorb reactive power. Despite their effective regulation capabilities, they are less commonly used today due to the advent of more advanced static solutions.
Static Compensators
Static compensators can be divided into two main categories: conventional and power compensators.
Conventional Compensators
Conventional compensators include:
• Mechanically Switched Capacitors (MSC)
• Mechanically Switched Reactors (MSR)
These devices use mechanical switches, which present several disadvantages:
• Discrete Control Method: Limited to on/off switching, lacking smooth control.
• Mechanical Wear: Mechanical components and contacts wear out over time, limiting the number of switch operations.
• Slow Switching Times: Mechanical switches are not suited for fast-changing states, making them less responsive in dynamic situations.
Power Compensators
Power compensators, also known as shunt power compensators, are more modern and capable of continuous control in both steady and fast-changing states.
SVC Compensators
Shunt power compensators mainly include various types of SVC (Static Var Compensators). SVCs have a modular structure, allowing for different configurations and components based on specific requirements. SVC types include:
Thyristor Switched Capacitor (TSC)
• Configuration: Consists of capacitors and thyristor switches.
• Operation: Switches capacitors on or off to adjust the total reactive power supplied.
• Control: Offers discrete control of capacitive reactance.
Thyristor Switched Reactor (TSR) and Thyristor Controlled Reactor (TCR)
• TSR:
o Configuration: Composed of induction reactors and thyristor switches.
o Operation: Switches reactors on or off based on required reactive power.
o Control: Discrete control of inductive reactance.
• TCR:
o Configuration: Similar to TSR but with thyristor-controlled reactors.
o Operation: Allows smooth control of inductive reactance.
o Control: Continuous control of inductive reactance.
TCR-FC (Thyristor Controlled Reactor - Fixed Capacitor)
• Configuration: Combines TCR modules (inductive) and Fixed Capacitors (capacitive), which also serve as higher harmonic filters.
• Operation: TCR modules absorb reactive power, while FCs supply reactive power and filter harmonics.
• Control: Provides a balanced approach to reactive power compensation and harmonic filtering.
TCR-TSC-FC
• Configuration: Integrates TCRs, TSCs, and Fixed Capacitors.
o TCR: Absorbs reactive power.
o TSC: Supplies primary reactive power.
o FC: Provides additional reactive power and harmonic filtering.
• Operation: Offers comprehensive control over reactive power compensation and harmonic mitigation.
• Control: Combines discrete and continuous control methods for optimal performance.
While electromechanical compensators have limitations in terms of switching speed and durability, static compensators, especially SVCs, offer significant advantages. These include modular design, continuous and discrete control capabilities, and improved performance in dynamic states. The various configurations of SVCs (TSC, TSR, TCR, TCR-FC, and TCR-TSC-FC) provide tailored solutions for reactive power management and voltage stability in modern power systems.

Figure 1: Structure of SVC compensator
STATCOM
A STATCOM (Static Synchronous Compensator) is a type of shunt compensator used in electrical power systems to regulate voltage and improve stability. It functions as a key component in Flexible AC Transmission Systems (FACTS). Here's a brief explanation of its components, working principle, and benefits:
Components
1. Voltage Source Converter (VSC): Converts DC voltage to AC voltage and vice versa.
2. DC Capacitor: Provides the DC voltage for the VSC.
3. Coupling Transformer: Connects the STATCOM to the AC network.
4. Controller: Manages the operation of the STATCOM by adjusting the VSC output.

Working Principle
• Voltage Regulation: The STATCOM operates by generating or absorbing reactive power to regulate the voltage at the point of connection to the AC grid. It can inject or absorb reactive current almost instantaneously to control the voltage.
• Reactive Power Control: By varying the output voltage of the VSC relative to the grid voltage, the STATCOM can either absorb reactive power (if the VSC voltage is lower) or generate reactive power (if the VSC voltage is higher).
Benefits
1. Improved Voltage Stability: Helps maintain voltage levels within desired limits, reducing the risk of voltage collapse.
2. Enhanced Power Quality: Mitigates issues like voltage sags, flickers, and unbalances.
3. Dynamic Response: Provides fast response to changing grid conditions, making it suitable for dynamic voltage regulation.
4. Reduced Transmission Losses: Optimizes reactive power flow, minimizing losses in the transmission network.
5. Scalability and Flexibility: Can be used in various voltage levels and adapted to different network conditions.
Applications
• Load Centers: Ensuring stable voltage for industrial and commercial consumers.
• Renewable Integration: Enhancing the stability of networks with high penetration of renewable energy sources.
• Transmission Lines: Increasing the transfer capacity and reliability of long transmission lines.

Figure 2: Structure of STATCOM compensator constructed on the basis of voltage converter
A hybrid compensator is a device or system used in electrical power systems to enhance voltage stability, power quality, and overall system performance by combining the benefits of different types of compensators. Hybrid compensators often integrate both static and dynamic compensation methods to achieve optimal results. Here's an overview:
Types of Compensators
1. Static Compensators (STATCOM):
o Static Var Compensators (SVC): Uses inductors and capacitors to provide reactive power compensation.
o Static Synchronous Compensators (STATCOM): Uses power electronics to provide rapid and continuous reactive power compensation.
2. Dynamic Compensators:
o Dynamic Voltage Restorers (DVR): Protects sensitive loads from voltage sags and swells.
o Unified Power Flow Controllers (UPFC): Controls voltage, impedance, and phase angle in transmission lines.
Hybrid Compensator Concept
Hybrid compensators combine the features of both static and dynamic compensators to leverage their strengths and mitigate their weaknesses. Here are some common hybrid compensator configurations:
1. Combination of STATCOM and SVC:
o Objective: Provide continuous and rapid reactive power support.
o Advantage: STATCOM provides fast response, while SVC offers high capacity and cost-effectiveness.
2. Combination of STATCOM and Shunt Capacitors/Reactors:
o Objective: Maintain voltage stability and improve power quality.
o Advantage: STATCOM handles dynamic changes, while shunt capacitors/reactors manage steady-state reactive power needs.
3. Integration with Energy Storage Systems (ESS):
o Objective: Enhance grid reliability and support peak load demands.
o Advantage: Energy storage provides backup power and smooths out fluctuations, while STATCOM/SVC provides reactive power compensation.
4. Combination of DVR and STATCOM:
o Objective: Protect sensitive loads from voltage disturbances and provide reactive power support.
o Advantage: DVR addresses voltage sags and swells, while STATCOM ensures voltage stability and reactive power compensation.
Benefits of Hybrid Compensators
1. Enhanced Voltage Stability: By combining fast-acting and steady-state compensators, hybrid systems can maintain voltage stability more effectively under varying load conditions.
2. Improved Power Quality: Hybrid compensators can mitigate voltage sags, swells, flicker, and harmonic distortion, leading to better power quality.
3. Increased System Reliability: Integration with energy storage and other dynamic components ensures a reliable power supply, even during peak loads or disturbances.
4. Cost-Effectiveness: By optimizing the use of different compensators, hybrid systems can achieve high performance without the need for expensive upgrades to existing infrastructure.
Applications of Hybrid Compensators
• Renewable Energy Integration: Hybrid compensators help manage the intermittent nature of renewable energy sources like wind and solar, ensuring stable grid operation.
• Industrial Power Systems: Ensuring stable voltage and power quality for sensitive industrial equipment.
• Transmission and Distribution Networks: Enhancing the capacity and stability of transmission and distribution lines, reducing losses, and improving efficiency.
Hybrid compensators are an essential part of modern power systems, offering a versatile and efficient solution to the challenges of voltage stability and power quality in increasingly complex electrical networks.

Figure 3: Structure of STATCOM-based SVC
Voltage control using shunt devices is a crucial technique for maintaining voltage stability and quality in power systems. Shunt devices are used to manage voltage levels by injecting or absorbing reactive power. Here's an overview of key shunt devices used for voltage control:
1. Shunt Capacitors
• Function: Shunt capacitors are used to provide reactive power support, which helps to raise the voltage level in a power system. They are commonly installed in distribution networks to improve voltage profiles and reduce losses.
• Operation: By adding reactive power to the system, capacitors counteract the effects of inductive loads, helping to maintain or increase voltage levels.
• Benefits: Improved voltage regulation, reduced losses, and enhanced system efficiency.
2. Shunt Reactors
• Function: Shunt reactors absorb reactive power, which can help to lower the voltage in the system. They are typically used in high-voltage transmission lines to mitigate overvoltage conditions caused by line capacitance.
• Operation: By absorbing reactive power, shunt reactors help to stabilize the voltage and prevent excessive voltage rise, especially during light load conditions.
• Benefits: Reduced overvoltage risk, improved voltage stability, and system protection.
3. Static VAR Compensators (SVCs)
• Function: SVCs are advanced devices that use a combination of capacitors and reactors to provide dynamic reactive power compensation. They can adjust reactive power output quickly to maintain voltage stability.
• Operation: SVCs consist of a thyristor-controlled reactor (TCR) and a thyristor-switched capacitor (TSC) to regulate reactive power dynamically.
• Benefits: Fast response to voltage fluctuations, enhanced voltage control, and improved system stability.
4. Static Synchronous Compensators (STATCOMs)
• Function: STATCOMs are voltage source converters that provide reactive power compensation and voltage support. They can both absorb and supply reactive power, making them versatile for voltage control.
• Operation: STATCOMs use a voltage source inverter to generate a controllable AC voltage, which can be adjusted to regulate reactive power flow.
• Benefits: Fast dynamic response, flexible voltage control, and improved system reliability.
5. Unified Power Flow Controllers (UPFCs)
• Function: UPFCs are advanced FACTS (Flexible AC Transmission System) devices that can control voltage, power flow, and system stability by combining the functions of series and shunt compensation.
• Operation: UPFCs use voltage source converters to inject or absorb reactive power at multiple points, allowing for comprehensive control over power flow and voltage levels.
• Benefits: Multifunctional control, enhanced power system flexibility, and improved overall stability.
Key Considerations
• Location: Proper placement of shunt devices is essential for effective voltage control and stability. They should be strategically positioned based on load patterns and voltage profiles.
• Coordination: Integration of shunt devices with other voltage control equipment (like tap-changing transformers) requires careful coordination to avoid conflicts and ensure optimal performance.
• Dynamic Response: Devices like STATCOMs and SVCs offer fast dynamic responses, which are crucial for managing sudden voltage fluctuations and maintaining system stability.
Effective voltage control using shunt devices helps maintain voltage within desired limits, enhances system performance, and ensures reliable operation of electrical grids.

Figure 4: Static voltage and power characteristics: a) SVC – with voltage controller, b) STATCOM – with voltage controller

Voltage Control Characteristics of Power Compensators

Figure 5: Effect of various installed types of compensators on the shape of the curves

Figure 6: Magnified fragment
Overview
Power compensators, such as Static Var Compensators (SVC) and Static Synchronous Compensators (STATCOM), are essential for maintaining voltage stability in power systems. Their performance is especially notable in dynamic and emergency conditions, where they play a crucial role in ensuring voltage security.
Voltage Response of Compensators
• SVC (Static Var Compensator):
o Capacitive Part: Reactive power Q varies with the square of the voltage, following the equation: Q=Bmax×U2 Bmax represents the maximum capacitive susceptance when all capacitor bank components are active and reactors are off.
o Inductive Part: Reactive power Q also follows the voltage square but with a different parameter: Q=Bmin×U2 Bmin denotes the minimum inductive susceptance when all capacitors are off and reactors are on.
• STATCOM (Static Synchronous Compensator):
o Current-Based Control: Reactive power Q is directly proportional to the voltage and described by the equation: Q=I×U Here, I is the constant current, which remains fixed until voltage limits Umax and Umin are reached.
Practical Behavior
1. Linear Range: Both SVC and STATCOM behave similarly when operating within the control range, characterized by a low-gradient voltage characteristic (usually 1-10% of the nominal voltage).
2. Voltage Extremes:
o At voltages significantly above or below the rated conditions, the performance diverges:
 SVC: Reactive power changes in a quadratic relationship with voltage, which leads to differing behaviors in capacitive and inductive modes.
 STATCOM: Reactive power changes linearly with voltage, offering better performance at lower voltage levels.
Comparative Analysis
• Curves Analysis: Example curves for a 400 kV node show that:
o Without compensators, voltage variations are more pronounced.
o With compensators (MSC, SVC, and STATCOM), voltage control is improved. The SVC and MSC (which includes TSC-type compensators) show similar characteristics, while STATCOM exhibits advantages at lower voltages.
• Effectiveness:
o Above 85% of Reference Voltage: SVC, STATCOM, and MSC demonstrate similar control effectiveness.
o Below 85% of Reference Voltage: STATCOM performs better due to its linear dependence on voltage, compared to the quadratic dependence in MSC and SVC.
Power compensators like SVC and STATCOM provide rapid automatic voltage control, enhancing voltage stability, particularly in fast-changing states. While more costly than conventional systems, their advanced properties make them valuable for enhancing voltage security in both national power systems (NPS) and distribution networks, such as those with a high penetration of wind farms.

DETAILED DESCRIPTION OF DIAGRAM
Figure 1: Structure of SVC compensator
Figure 2: Structure of STATCOM compensator constructed on the basis of voltage converter
Figure 3: Structure of STATCOM-based SVC
Figure 4: Static voltage and power characteristics: a) SVC – with voltage controller, b) STATCOM – with voltage controller
Figure 5: Effect of various installed types of compensators on the shape of the curves
Figure 6: Magnified fragment. , Claims:1. Steady state voltage stability considering dynamics of generators and shunt compensators claims that incorporating generator and shunt compensator dynamics into steady-state voltage stability analysis provides a more accurate representation of system behavior under various operational conditions, leading to improved stability assessments.
2. Dynamic modeling of generators and shunt compensators enables better management of load variations and system disturbances, ensuring that the system remains stable during sudden or gradual changes in load.
3. By accounting for the dynamics of shunt compensators, voltage regulation can be optimized, enhancing the system’s ability to maintain voltage levels within desired limits despite fluctuations in load and generation.
4. Dynamic models of generators and shunt compensators facilitate real-time monitoring of voltage stability, allowing for proactive measures to be taken before stability margins are breached.
5. Understanding the impact of generator dynamics on voltage stability helps in designing more reliable power systems that can withstand various operational stresses and prevent voltage collapse.
6. Including dynamic effects in stability analysis provides more precise estimates of stability margins, which are crucial for ensuring the system's capability to handle contingencies and prevent voltage instability.
7. Dynamic modeling allows for the development of more effective control strategies for shunt compensators and generators, improving their response to voltage stability challenges and reducing the risk of system instability.
8. By integrating generator and compensator dynamics into voltage stability studies, potential risks of voltage collapse can be better identified and mitigated through targeted interventions.
9. Detailed dynamic analysis supports informed planning and operational decisions, aiding in the design of robust systems that can effectively manage voltage stability under various scenarios.
10. Dynamic models of generators and shunt compensators improve the accuracy of simulations used to predict system behavior, ensuring that stability analyses reflect real-world conditions and responses.