Linash Kunjumuhammed

Bio: Linash Kunjumuhammed is an academic researcher from Mitsubishi Electric. The author has contributed to research in topics: Wind power & Electric power system. The author has an hindex of 13, co-authored 31 publications receiving 549 citations. Previous affiliations of Linash Kunjumuhammed include Indian Institute of Technology Madras & Mitsubishi.

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

Abstract: 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.

A control algorithm for single-phase active power filter under non-stiff voltage source

Abstract: The authors propose a control algorithm for a single-phase active-power filter working under a non-stiff voltage source. The method provides compensation for harmonics and reactive power and has an excellent dynamic performance. A detailed synchronization circuit is presented for proper sequencing of operation of the active power filter even when the source voltage contains multiple zero crossings. Experimental study has been carried out under a non-stiff voltage source to verify the proposed control scheme

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

Abstract: 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.

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

Abstract: 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.

Impact of Wakes on Wind Farm Inertial Response

Abstract: 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.

Definition and Classification of Power System Stability – Revisited & Extended

Abstract: Since the publication of the original paper on power system stability definitions in 2004, the dynamic behavior of power systems has gradually changed due to the increasing penetration of converter interfaced generation technologies, loads, and transmission devices. In recognition of this change, a Task Force was established in 2016 to re-examine and extend, where appropriate, the classic definitions and classifications of the basic stability terms to incorporate the effects of fast-response power electronic devices. This paper based on an IEEE PES report summarizes the major results of the work of the Task Force and presents extended definitions and classification of power system stability.

Enhanced power quality control strategy for single-phase inverters in distributed generation systems

Abstract: Power electronic converters are commonly used for interfacing distributed generation systems to the electrical power network. This paper deals with a single-phase inverter for distributed generation systems requiring power quality features, such as harmonic and reactive power compensation for grid-connected operation. The idea is to integrate the DG unit functions with shunt active power filter capabilities. With the proposed approach, the inverter controls the active power flow from the renewable energy source to the grid and also performs the non-linear load current harmonic compensation keeping the grid current almost sinusoidal. The control scheme employs a current reference generator based on Sinusoidal Signal Integrator (SSI) and Instantaneous Reactive Power (IRP) theory together with a repetitive current controller. Experimental results obtained on a 4 kVA inverter prototype demonstrate the feasibility of the proposed solution.

Single-Phase Back-To-Back Converter for Active Power Balancing, Reactive Power Compensation, and Harmonic Filtering in Traction Power System

Abstract: An active power compensator (APC) based on single-phase back-to-back power converter is proposed in this paper to solve problems of power quality of electric railway power supply system. This system adopts a single-phase feeding connection, which is called cophase power supply scheme. In this scheme, APC connects the balance transformer between feeding phase for power supply and another phase for compensation. It has some characteristics, such as active power balancing, reactive power compensating, and harmonics filtering. In order to achieve these characteristics, the control scheme requires seven combination models. In this paper, a multifunctional control algorithm is proposed to realize every conceivable model. A cophase system with APC based on field programmable gate array (FPGA) and YNvd balance transformer is also designed and evaluated. The experimental results obtained from this prototype illustrate that the compensating ability is extremely high in steady-state and dynamic responses, and the power quality of a substation with distorted loads can be improved integrally.

Generalised single-phase p-q theory for active power filtering: simulation and DSP-based experimental investigation

Abstract: The single-phase p-q theory for the purpose of active power filtering in the case of single-phase loads is dealt with here. A simple modification is proposed to develop a generalised single-phase p-q theory that can be utilised under the condition of distorted utility voltage. A systematic study is presented by realising both direct and indirect current control techniques. The simulation as well as the digital signal processor (DSP) (DS1104 of dSPACE) based experimental results are discussed. The developed single-phase shunt active power filter (APF) prototype is tested under different operating conditions with different loads to evaluate the full capabilities of the proposed generalised theory for practical uses. The shunt APF reduces the source current total harmonics distortion (THD) from 27.2 to 3.4% under a distorted supply voltage with a THD of 16.2%.

Feedback Linearization of a Single-Phase Active Power Filter via Sliding Mode Control

Abstract: The aim of this work is the application of the feedback linearization theory to a single-phase shunt active power filter, since this technique has been successfully applied to other areas of power electronic. The active filter is linearized by means of a nonlinear transformation of the system model, deduced from the application of Tellegen's theorem to the system. After that, a sliding mode controller is proposed to impose a desired dynamic behavior on the system, giving robustness and insensitivity to parameter variations. Moreover, the proposed controller ensures proper tracking of the reference signals and simplifies the overall control design. The controller was implemented into a low cost DSP. Experimental and simulation results are provided.