Linash P. Kunjumuhammed

Impact of Wakes on Wind Farm Inertial Response

Inertial response from wind generators is important since it limits the rate of change of frequency (RoCoF) during generation and load imbalance. It is automatically provided by synchronous machines due to their direct coupling with system frequency. When synchronous generators are replaced by asynchronous generators, the RoCoF deteriorates. The asynchronous generators can be made to offer inertial response through suitable control action. The amount of response is dependent on the wind speed at the turbine. The wind speed at a turbine blade is influenced by the upstream turbine known as the wake effect. This paper models and quantifies the impact of the wake on the inertial response of the wind farm. The modeled wake effect is compared with the measured data from a wind farm. The research contribution demonstrates that the wake effect has a significant influence on the actual inertial response capacity.

Electrical Oscillations in Wind Farm Systems: Analysis and Insight Based on Detailed Modeling

This paper presents modeling and analysis of electrical oscillations in a wind farm system. The detailed modeling and modal analysis of a wind farm system are presented in this paper. The approach to modeling uses detailed representation of a wind turbine generator and collection system including high-voltage direct-current (HVDC) power converter system control, facilitating a comprehensive analysis of the wind farm system. Various modes are classified according to the frequency of oscillation. The detailed modal analysis is used to characterize the critical modes. Time-domain simulation also confirms the presence of these modes. The effect of wind farm operating conditions and voltage source converter control tuning on critical oscillatory modes are also assessed and discussed in detail.

Effect of wind penetration on power system stability

The paper investigates the impact of large scale wind penetration on the inter-area mode damping of a power system. Simulation results using a two-area test system and a representative GB test system are used for the study. Different possible operating scenarios of the systems are generated and a qualitative behavior of the impact is presented.

Probability based control signal selection for inter area oscillations damping using TCSC

The residue analysis is primary basis for signal selection for damping the inter area oscillations employing flexible AC transmission system (FACTS) controller. The control signals should be selected to get the best residue possible under a large number of operating conditions. This ensures a high modal controllability and modal observability of the selected modes to be damped. The present work analyzes the variation of residues corresponding to different control signals for various operating conditions. A probabilistic approach is proposed to select the best control signal for the TCSC controllers, suitable for the majority of operating conditions. The results are presented using simulation studies in the NETS-NYPS test system.

The Adequacy of the Present Practice in Dynamic Aggregated Modeling of Wind Farm Systems

Large offshore wind farms are usually composed of several hundred individual wind turbines, each turbine having its own complex set of dynamics. The analysis of the dynamic interaction between wind turbine generators (WTG), interconnecting ac cables, and voltage-source converter (VSC)-based high voltage DC (HVDC) system is difficult because of the complexity and the scale of the entire system. The detailed modeling and modal analysis of a representative wind farm system reveal the presence of several critical resonant modes within the system. Several of these modes have frequencies close to harmonics of the power system frequency with poor damping. From a computational perspective, the aggregation of the physical model is necessary in order to reduce the degree of complexity to a practical level. This paper focuses on the present practices of the aggregation of the WTGs and the collection system, and their influence on the damping and frequency characteristics of the critical oscillatory modes. The effect of aggregation on the critical modes is discussed using modal analysis and dynamic simulation. The adequacy of aggregation method is discussed.

Selection of Feedback Signals for Controlling Dynamics in Future Power Transmission Networks

This paper deals with the selection of feedback signal(s) that retain the modal behavior of power system electromechanical dynamics under varying operating circumstances. The approach seeks signals that have relatively large magnitude of residue, less variation of the magnitude and phase angle, sufficient gap between the critical pole-zeros, and least sensitive to other modes. The methodology is tested in a 16-machine interconnected power system model with multiple wind farms.

A test system model for stability studies of UK power grid

The paper presents a test system model to study the effect of variable wind power output on the stability of future power systems. The test system is built upon a future UK transmission system model and it contains different types of generators, HVDC transmission lines, and interconnections. A poorly damped inter-area mode is present in the test system that closely resembles the Scotland-England inter-area mode existing in the UK transmission system. The study system will help to analyze the impact of increased variability in power system operating conditions on the oscillatory mode.

Stability Analysis of a PMSG-Based Large Offshore Wind Farm Connected to a VSC-HVDC

This paper presents modal analysis of a large offshore wind farm using permanent magnet synchronous generator (PMSG)-type wind turbines connected to a voltage source converter HVDC (VSC-HVDC). Multiple resonant frequencies are observed in the ac grid of offshore wind farms. Their control is crucial for the uninterrupted operation of the wind farm system. The characteristics of oscillatory modes are presented using modal analysis and participation factor analysis. Sensitivity of critical modes to wind turbine design parameters and their impact on closed loop stability of the system are discussed. A comparison between a full wind farm model and an aggregated model is presented to show differences in the characteristics of critical modes observed in the models, and implication of using the models for stability studies It is concluded that robust control design is important for reliable operation of the system.

Electrical oscillations in wind farm systems: Analysis and insight based on detailed modeling

Summary form only given. This paper presents modeling and analysis of electrical oscillations in a wind farm system. The detailed modeling and modal analysis of a wind farm system are presented in this paper. The approach to modeling uses detailed representation of a wind turbine generator and collection system including high voltage direct-current (HVDC) power converter system control, facilitating a comprehensive analysis of the wind farm system. Various modes are classified according to the frequency of oscillation.

Selection of feedback signals for controlling dynamics in future power transmission networks

This paper deals with the selection of feedback signal(s) that retain the modal behavior of power system electromechanical dynamics under varying operating circumstances. The approach seeks signals that have relatively large magnitude of residue, less variation of the magnitude and phase angle, sufficient gap between the critical pole-zeros, and least sensitive to other modes. The methodology is tested in a 16-machine interconnected power system model with multiple wind farms.