Optimization of FACTS Devices Using Modern Artificial Intelligence Methods

Optimization of FACTS Devices Using Modern Artificial Intelligence Methods.

By Eng. Ayman Ehab Lutfy Master student, Electrical Power Engineering Department, Faculty of Engineering, Cairo University Under supervision: Associate Prof. Dr. Heba Ahmed Hassan Prof. Mohamed Ahmed Hassan Elsayed Electrical Power Engineering Department, Faculty of Engineering, Cairo University.

Contents. Power Systems: Objectives and Aspects. system integrity. Power system stability. Control Subsystem. FACTS devices. System modelling and limits. FACTS devices modelling. Load flow solution. Evaluating indices and objective function formulation. stochastic algorithms for optimization and search techniques. Particle swarm optimization (PSO) Flow chart of the algorithm. System input data, conditions and limits. Results and simulation. Conclusion ..

The interconnected nature of the grid, the presence of diverse generator types, fluctuating load profiles, unique transmission line properties,.

Complexity of Power Systems. Power systems can extend across extensive geographical regions, incorporating numerous interconnected substations and components. Load demands exhibit variations throughout the day, week, and across seasons, necessitating continual adjustments in generation and distribution. Diverse generator types (thermal, hydro, wind, solar) introduce complexities in control and coordination. Transmission line characteristics, losses, and reactive power compensation influence system behavior. The risk of contingencies, such as faults, equipment failures, or natural disasters..

Power system stability. Power system stability is a significant challenge for the secure operation of modern large interconnected systems. Recent major blackouts worldwide, occurring in sophisticated and secure systems, underscore the difficulties in maintaining power system stability. Stability refers to the system's ability to return to normal or stable operation after experiencing disturbances, particularly in terms of synchronous operation. Power system stability is analyzed under two main categories Steady state stability. Transient stability. Steady-state stability relates to the system's ability to regain synchronism after minor, gradual disturbances, such as gradual power changes. Transient stability , an extension of steady-state stability, deals with the effects of sudden, large disturbances like faults or line outages. Transient stability studies focus on the system's ability to maintain synchronous operation when subjected to large disturbances, with the loss of synchronism typically occurring within seconds of the disturbance..

system integrity. system integrity entails continuous monitoring of real-time system parameters through comprehensive AC load flow calculations, accounting for all potential outage events, including generator and transmission line outages. It is important to note that power systems can never be entirely secure at all times, as it is possible to devise sequences of events leading to either partial or complete system collapse..

Power system operation and control. Effectively coordinating preventive, emergency, and corrective controls in such a complex environment requires advanced monitoring approaches and control systems. These systems are instrumental in ensuring power supply stability, reliability, and safety. Preventive, emergency, and corrective controls represent strategies employed to uphold the stability, reliability, and safety of the system. These controls address various issues such as voltage stability, frequency control, and fault protection. Preventive controls encompass measures taken to avert potential issues and maintain the power system's normal operating conditions. These measures are implemented during regular operating conditions to ensure the system stays within safe and reliable limits. Emergency controls entail actions triggered by sudden disturbances or faults that endanger the system's stability or reliability. These controls are automatically activated when the system encounters abnormal conditions. Corrective controls involve actions taken to restore the power system to stability and its normal operating conditions following a disturbance. These controls are utilized to rectify system parameters that deviate from acceptable limits..

Power system operation and control. In all three types of controls, striking a balance between load and generation constraints is crucial. Preventive measures help maintain a stable operating point by anticipating potential imbalances, while emergency and corrective measures address sudden imbalances that could lead to system instability or blackouts. Regarding voltage stability, required actions may include: Generator and Load Management: Initiating generator or load tripping or rapidly adjusting generated or load power to relieve system stress and prevent voltage collapse. Utilization of FACTS Devices: FACTS devices play a pivotal role in voltage and power flow control. These devices can be deployed automatically or manually to modify system parameters such as voltage and impedance, enhancing voltage stability and averting a transition to an emergency state. FACTS devices serve as a proactive measure to maintain voltage stability even when confronted with unexpected disturbances..

Flexible AC Transmission System Controllers. fid.

Flexible AC Transmission System Controllers. FACTS devices are primarily employed for corrective and preventive control in electrical power systems, contributing to optimized power flow and system stability under normal operating conditions and expected contingencies. FACTS devices are classified into three categories: Series devices, such as the thyristor-controlled series compensator (TCSC) and static synchronous series compensator (SSSC). Shunt devices, such as the static var compensator (SVC) and static synchronous compensator (STATCOM). Combined series-shunt devices, exemplified by the unified power flow controller (UPFC)..

Types of FACTS Devices. Static Var Compensator (SVC) SVCs are shunt-connected devices that regulate reactive power by adjusting susceptance. They are often used to control voltage levels and improve power factor at specific locations in the power network. Static Synchronous Compensator (STATCOM) Similar to an SVC, STATCOM is shunt-connected but utilizes power electronics to generate or absorb reactive power. STATCOMs offer rapid response times and enhanced controllability..

Types of FACTS Devices. Thyristor-Controlled Series Capacitor (TCSC) TCSCs are series-connected devices that adjust impedance using thyristor-controlled reactors, facilitating control over power flow by modifying line reactance. Unified Power Flow Controller (UPFC) UPFCs combine shunt and series compensation capabilities, providing simultaneous control over voltage and power flow, enhancing power flow management flexibility..

Types of FACTS Devices. Static Synchronous Series Compensator (SSSC) SSSCs are series-connected devices that introduce voltage in quadrature with line current. They enable enhanced power flow control and mitigate transmission line oscillations. Interline Power Flow Controller (IPFC) IPFCs are designed to control power flow between parallel transmission lines, enhancing control over power transfer between lines..

Load flow solution. The need for power flow studies arises for several reasons, including: Line Flows: Understanding the power flows within transmission lines, ensuring they remain within operational limits. Bus Voltages and System Voltage Profile: Analyzing the voltage levels at different buses and maintaining an acceptable voltage profile across the system. Effect of Configuration Changes: Assessing how alterations in the network's configuration, including the addition of new circuits, impact system loading. Handling Temporary Losses: Evaluating the effects of temporary loss of transmission capacity or generation on system loading and its associated consequences. In-Phase and Quadrature Boost Voltages: Studying the effects of voltage control mechanisms in both magnitude and phase on system loading. Economic Operation: Ensuring efficient and cost-effective system operation, including optimizing power generation and minimizing operating costs..

Load flow solution. System Loss Minimization: Minimizing power losses within the system to enhance efficiency. Transformer Tap Settings: Determining optimal settings for transformer taps to achieve economic operation. System Improvement: Exploring possibilities to enhance existing systems by changing conductor sizes, system voltages, or other components. Power flow analysis is a mathematical approach that systematically calculates various parameters such as bus voltages, phase angles, active and reactive power flows, and system stability under steady-state conditions. This analysis is crucial for both power system planning and operation..

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System Model for Load Flow Studies. Figure1: The schematic diagram of two bus power system.

System Model for Load Flow Studies.

System Model for Load Flow Studies.

System Model for Load Flow Studies.

Flexible AC Transmission System Controllers model for load flow studies..

Flexible AC Transmission System Controllers model for load flow studies..

Voltage Source Converter Based Controllers. VSC. Figure2: The schematic diagram of a Static Synchronous Compensator (STATCOM).

Voltage Source Converter Based Controllers. Figure4: the diagram of a Unified Power Flow Controller.

Voltage Source Converter Based Controllers. V2 i2 i e V1.

Voltage Source Converter Based Controllers.

Voltage Source Converter Based Controllers. Controller Constraint Equations Control Variable(s) SVC TCSC STATCOM STATCOM with energy source SSSC SSSC with energy source.

Thyristor Controlled Series Compensator (TCSC). Figure7: Single line diagram of two buses of a distribution system with Thyristor Controlled Series Compensator (TCSC).

Thyristor Controlled Series Compensator (TCSC).

Thyristor Controlled Series Compensator (TCSC).

The Static Var Compensator (SVC). the SVC employs back-to-back connected thyristor valves to regulate the flow of current through a reactor. Initially, the SVC found application in load compensation for rapidly fluctuating loads like those found in steel mills and arc furnaces. In transmission scenarios, the SVC's role involves regulating grid voltage. When the reactive load of the power system leans towards being capacitive (leading), the SVC utilizes thyristor-controlled reactors to absorb vars, thereby reducing the system voltage. By combining the continuously variable thyristor-controlled reactor with capacitor bank steps, the SVC provides the capability for dynamic adjustment of leading or lagging power. The primary objective is to enhance dynamic power factor control and balance source-side currents as needed. There exist two types of SVCs:: Fixed Capacitor-Thyristor Controlled Reactor (FC-TCR) Thyristor Switched Capacitor - Thyristor Controlled Reactor (TSC-TCR). The latter type, TSC-TCR, offers greater flexibility than the former and demands a smaller reactor rating, thereby generating fewer harmonics. Analysis of SVC The effectiveness of an SVC greatly depends on its placement. Ideally, it should be situated at the electrical center of the system or at the midpoint of a transmission line. In industrial settings, SVCs are commonly positioned near high-demand, rapidly changing loads, such as arc furnaces, to mitigate voltage flicker. SVCs play a crucial role in minimizing variations through precise control..

The Static Var Compensator (SVC). A D B O C slope of (OA) = slope of (OBC) = slope of (AB) = CAPACITIVE MODE INDUCTIVE MODE.

The Static Var Compensator (SVC).

The Static Var Compensator (SVC). TCR TSR TSC SWITCHED RESISTOR FC control STEPDOWN TRANSFORMER PT.

The Static Var Compensator (SVC).

The Static Var Compensator (SVC). INDUCTIVE REGION CAPACITIVE REGION RESONANCE REGION.

The Static Var Compensator (SVC).

The Static Var Compensator (SVC).

Applications of Static Var Compensators (SVC).

Static Synchronous Compensator (STATCOM). The Static Synchronous Compensator (STATCOM) represents an advanced form of static VAR compensator, employing a voltage source converter (VSC) in place of controllable reactors and switched capacitors. Unlike variable impedance-type Static VAR Compensators (SVC) that rely on thyristor devices, VSCs necessitate self-commutated power semiconductor devices such as GTO, IGBT, IGCT, and MCT, which may involve higher costs and losses. Nonetheless, STATCOM offers several technical advantages over SVC:.

Static Synchronous Compensator (STATCOM). Swift response. Requires less physical space since bulky passive components like reactors are eliminated. Exhibits inherent modularity and relocatability. Can be seamlessly integrated with real power sources, such as batteries, fuel cells, or SMES (superconducting magnetic energy storage). Maintains superior performance in low-voltage conditions, as it can keep reactive current constant. In contrast, an SVC exhibits a linear drop in capacitive reactive current as voltage approaches its limit, determined by passive component ratings – reactors and capacitors. Initially, the STATCOM was known as an advanced SVC..

Principle of Operation of STATCOM.

Principle of Operation of STATCOM. A D B 0 C CAPACITIVE MODE INDUCTIVE MODE.

Principle of Operation of STATCOM.

Principle of Operation of STATCOM. The characteristic of a STATCOM reveals another noteworthy aspect of this technology its ability to provide nearly full capacitive output independently of the system voltage, offering a constant-current output at lower voltages. This feature proves particularly valuable when the STATCOM is required to support system voltage during and after faults, where voltage collapse might otherwise be a limiting factor..

Principle of Operation of STATCOM. VOLTAGE SOURCE CONEVERTER.

Principle of Operation of STATCOM.

Applications of STATCOM. Given that a STATCOM is an advanced form of Static VAR Compensator (SVC) employing Voltage Source Converter (VSC) technology, its applications are motivated by reasons similar to those for SVC deployment. However, a STATCOM offers distinct advantages over an SVC, including: Enhanced performance in low-voltage scenarios. Rapid response independent of system conditions. Reduced space requirements with a smaller footprint..