Oscillations in a power system are natural phenomena that occur due to the dynamic interaction of generators, loads, and transmission lines. However, if these oscillations are not properly damped, they can grow and threaten the stability and reliability of the system. In this article, you will learn how to damp oscillations in a power system using different methods and devices.
Oscillations are periodic variations of a physical quantity around an equilibrium point. In a power system, oscillations can be classified into three types: local, inter-area, and global. Local oscillations involve the swing of a single generator or a group of generators against the rest of the system. Inter-area oscillations involve the swing of two or more groups of generators across a weak transmission link. Global oscillations involve the swing of the entire system against a large disturbance.
Em suma, em um sistema elétrico trifásico ideal (G.T.D.) em corrente alternada, trata-se de três fases distintas (R-S-T) com ondas senoidais balanceadas, cuja defasagem angular entre elas é de 120°, proporcionando um equilíbrio entre elas. Academicamente, estudamos a sistemática de cálculo em sistemas trifásicos ideais, mas sabemos que na aplica??o real, nem sempre teremos um sistema harm?nico (fases equilibradas) devido as oscila??es oriundas de cargas lineares e n?o lineares acopladas no sistema trifásico. Oscila??es também podem ocorrer em sistemas monofásicos e de corrente contínua com suas particularidades. Essas oscila??es podem prejudicar a eficiência energética do sistema e impactar seu custos.
Oscillations are harmful because they can reduce the power transfer capability, degrade the power quality, and cause system instability. If the oscillations are not damped, they can amplify and lead to loss of synchronism, voltage collapse, or system separation. Oscillations can also trigger protective relays and circuit breakers, resulting in unnecessary tripping and outages. Therefore, it is important to damp oscillations in a power system to maintain a stable and secure operation.
O sistema elétrico n?o opera de forma ideal como nos livros acadêmicos mas pode coexistir com as oscila??es desde que estas n?o ultrapassem níveis mínimos aceitáveis ensaiados em laboratórios acadêmicos, de forma que a infraestrutura de gera??o, transmiss?o e/ou distribui??o desempenhe seu papel, entregando energia com o mínimo de perdas operacionais aos sub-sistemas dependentes desta energia. As oscila??es descontroladas s?o prejudiciais a qualquer sistema elétrico, pois podem comprometer a eficiência energética de G.T.D., causando altos custos, perdas operacionais e até falhas em alguma dessas etapas.
Oscillations cause system instability, compromise power quality and reduces/delay power transfer. Damping oscillations is a good solution to avoid their effects.
Oscillations can be measured by using different devices and techniques. Some of the common devices are phasor measurement units (PMUs), frequency meters, and power flow meters. PMUs can measure the voltage and current phasors at high sampling rates and provide synchronized data across the system. Frequency meters can measure the deviation of the system frequency from the nominal value. Power flow meters can measure the active and reactive power flows on transmission lines.
Some of the common techniques are modal analysis, spectral analysis, and time-domain analysis. Modal analysis can identify the mode shapes, frequencies, and damping ratios of the oscillations. Spectral analysis can decompose the oscillation signals into frequency components and show their magnitude and phase. Time-domain analysis can show the time history and trend of the oscillation signals.
Considerando estudos primordiais interativos de fen?menos físicos e elétricos de especialistas como Kirchhoff, Thévenin, Rogowski, Ampère, Maxwell, Gauss, Coulomb, Tesla, Faraday, Lenz, com contribui??es universais aceitáveis no meio acadêmico que nos proporcionaram o conhecimento do eletromagnetismo, por meio do qual temos a capacidade, através de instrumentos analógicos e/ou digitais, de aferir, mensurar, comparar e corrigir exatamente onde é ou s?o necessárias atenua??es de oscila??es que desequilibram o sistema. Atualmente, um exemplo de instrumentos completos para estas verifica??es s?o os analisadores de energia.
Oscillations can be damped by using different methods and devices. Some of the common methods are power system stabilizers (PSSs), flexible AC transmission systems (FACTS), and power oscillation damping (POD) controllers. PSSs are devices that modulate the excitation voltage of generators to provide damping torque. FACTS are devices that control the power flow and voltage on transmission lines by using power electronics. POD controllers are devices that use feedback signals from PMUs or other sensors to adjust the output of FACTS or other devices.
Some of the common devices are static VAR compensators (SVCs), static synchronous compensators (STATCOMs), thyristor-controlled series compensators (TCSCs), and unified power flow controllers (UPFCs). SVCs and STATCOMs are devices that inject or absorb reactive power to regulate the voltage on transmission lines. TCSCs and UPFCs are devices that vary the impedance or phase angle of transmission lines to control the power flow.
Uma vez feita a análise da qualidade da energia através de um analisador, é preciso verificar a característica das cargas envolvidas no sub-sistema. Identificadas as características, as oscila??es podem ser atenuadas por meio de filtros ativos, passivos ou mistos, em arranjos de geradores, transformadores, resistores, capacitores, inversores, etc., de acordo os princípios que s?o estudados em circuitos elétricos.
Damping devices can be designed by using different approaches and tools. Some of the common approaches are linear control theory, optimal control theory, and adaptive control theory. Linear control theory can design damping devices based on the linearized model of the power system and the desired damping performance. Optimal control theory can design damping devices that minimize a cost function that reflects the trade-off between damping and control effort. Adaptive control theory can design damping devices that adjust their parameters according to the changing system conditions and disturbances.
Some of the common tools are MATLAB, SIMULINK, and PSCAD. MATLAB is a software that can perform numerical computation, data analysis, and visualization. SIMULINK is a software that can model and simulate dynamic systems and control systems. PSCAD is a software that can simulate power systems and power electronics.
Para sistema elétricos mais robustos, todos estes dispositivos de amortecimento (filtros) podem ser projetados por meio de cálculos de circuitos elétricos ensaiados em situa??es ideais, através de estudo computadorizado (MatLab) e considerando normas nacionais (NBR) e internacionais (NEMA, IEC) quando n?o houver norma nacional vigente. Além de detalhes normativos, os profissionais envolvidos na concep??o deste projeto devem possuir habilita??o superior / técnica na área de Elétrica/Eletr?nica, anotando responsabilidade técnica (A.R.T.) pela solu??o a ser aplicada junto ao conselho de classe competente (no Brasil, CREA e CFT).
Excelente contenido adicionalmente, he tenido que equivocarme para enriquecer mi aprendizaje y además ense?ando a mis compa?eros aprendia más.
Damping devices can be tested by using different methods and scenarios. Some of the common methods are small-signal analysis, transient analysis, and field tests. Small-signal analysis can test the damping devices by applying small perturbations to the system and measuring the response. Transient analysis can test the damping devices by applying large disturbances to the system and measuring the response. Field tests can test the damping devices by installing them on the actual power system and observing the performance.
Some of the common scenarios are load changes, generator outages, line outages, and faults. Load changes can test the damping devices by changing the demand or supply of power in the system. Generator outages can test the damping devices by removing or adding generators in the system. Line outages can test the damping devices by opening or closing transmission lines in the system. Faults can test the damping devices by creating short circuits or open circuits in the system.