Lluis Monjo

Study of the Steinmetz Circuit Influence on AC Traction System Resonance

Traction systems are single-phase, nonlinear loads, which can unbalance and pollute supply voltages. To reduce voltage unbalance, reactances are usually connected in delta configuration with traction systems. This setup is called the Steinmetz circuit. Parallel and series resonances can occur between the Steinmetz capacitor and system inductors, increasing voltage distortion. Thus, it is important to analyze the parallel resonance “observed” from the traction system to avoid harmonic problems due to its injected harmonic currents. This paper studies this resonance analytically and presents simple expressions to locate it. Experimental measurements are also provided to validate the obtained analytical results. These expressions are also used to analyze resonance in several power systems in the literature.

Resonance-Based Procedure for Locating Failed Luminaires in AGL Systems

Aeronautical ground lighting (AGL) systems provide a visual reference for aircraft during airport operations. Fast detection and location of failed luminaires is an important safety concern in AGL systems. In the event of luminaire failure, AGL transformers introduce harmonic currents. Resonances can increase harmonics, worsening the problem. This paper presents analytical expressions for determining resonance frequencies in AGL systems, as well as a simple procedure based on these expressions for locating failed luminaires from measurements.

Positive-Net-Damping Stability Criterion in Grid-Connected VSC Systems

Resonance instabilities in power systems can be assessed with the positive-net-damping stability criterion. This criterion is a review of the complex torque coefficients method, but it does not provide the frequency of the closed-loop oscillatory modes. This paper presents an alternative approach of the positive-net-damping stability criterion to analyze electrical resonance instability. In this approach, resonance instabilities are identified in feedback systems derived from impedance-based equivalent circuits. The proposed approach is used to characterize the frequency of closed-loop oscillatory modes and identify the physical and control parameters of the system that increase or reduce the damping of these modes. The extension of the proposed approach to study the stability of single-input single-output and multiple-input multiple-output feedback systems is analyzed, and the approach is also compared with other stability methods in the literature. An example of an offshore wind power plant illustrates the theoretical study and compares the proposed approach with different methods to evaluate stability. Time-domain simulations in Power System Computer Aided Design/Electro Magnetic Transient Design and Control (PSCAD/EMTDC) are shown to validate the stability study.

Electrical resonance instability study in wind power plants

Wind power plant stability can be affected by the interaction between the wind turbine and the resonances in the collector grid. This paper presents an electrical resonance instability study applied to wind power plants. The influence of feedforward low pass filter bandwidth and converter filter inductance on wind power plant stability is analyzed with examples. An impedance-based representation of the wind power plant is used to identify the resonances and analyze stability problems. PSCAD/EMTDC time-domain simulations are also shown to validate the stability study.

Electrical resonance instability study in traction systems

Traction system stability can be affected by the interaction between the traction load and resonances in the railway traction grid. This paper presents an electrical resonance instability study applied to traction systems. The influence of traction section length and converter time delay on traction system stability is analyzed with examples. An impedance-based representation of the traction system is used to identify the resonances and analyze stability problems. PSCAD/EMTDC time-domain simulations are also shown to validate the stability study.