Mandhir Sahni

General Methodology for Analysis of Sub-Synchronous Interaction in Wind Power Plants

This paper presents a general methodology for analysis of sub-synchronous interaction in wind power plants. These include appropriate frequency scanning method for the assessment of the sub-synchronous control interaction, and calculation of the electrical damping provided by the wind turbine generator for investigation of the sub-synchronous torsional interaction. A general formulation of both methods applicable to any given wind turbine and network is presented. A dynamic frequency scanning method for the turbine side is developed which takes account of the turbine nonlinearities and its active behavior. Various aspects that need to be considered when injecting a voltage or current signal into the system for dynamic frequency scanning are discussed in detail. The veracity of these methods is confirmed against electromagnetic transient analyses. The application of these tools and techniques is demonstrated on a practical power system comprising type 3 wind turbines and series compensated lines.

Sub-synchronous interaction in Wind Power Plants- part II: An ercot case study

This is the second part of a two-paper series. The first paper presented the tools and techniques for investigation of sub-synchronous control and torsional interaction in Wind Power Plants (WPPs). This paper presents a comprehensive Electro-Magnetic Transient (EMT) simulation based case study to investigate potential Sub-Synchronous Control Interaction (SSCI) issues. The Electric Reliability Council of Texas (ERCOT) transmission grid model is utilized for the case study. Implementation of the system and turbine side scans on the ERCOT grid model has been performed to identify conditions requiring further investigation. Detailed EMT simulations using specific turbine manufacturer models have been performed as part of further investigations. Scenarios around key aspects of the system and turbine model performance have been developed and investigated.

Dynamic Available AGC Based Approach for Enhancing Utility Scale Energy Storage Performance

With ever-increasing penetration of non-dispatchable intermittent generation resources in electric grids all over the world, the system operators are facing more challenges to meet the system AGC requirements which aim to maintain the target grid frequency and scheduled tie flows. The utility scale energy storage applications have been often referred to as one of the potential solutions for improving the system frequency response, especially the speed of response. A new concept relating to the use of Dynamic Available AGC (DAA) of the Battery Energy Storage System (BESS) is proposed in this paper and applied in conjunction with the priority and proportional AGC signal distribution strategies. Additionally, this paper proposes an independent AGC control strategy based on Area Control Error (ACE) signal distribution to further enhance the impact of the fast response capability of the BESS. The same is accomplished by means of implementing an independent Proportional Integral (PI) controller without low-order filter typically associated with the ACE signal distribution. The AGC simulation results based on generation trip and normal load variance events, as tested on the El Salvador system model, indicate significant benefits to the system AGC performance when using the concept of the DAA for the BESS and the independent AGC control strategy. The AGC simulation results also indicate that the utilization of 10 MW/3.66 MWh BESS can replace about 36 MW conventional AGC units on the tested system model without compromising on the AGC performance of the system for day-to-day variations experienced in the system load.

A Novel Approach for Arcing Fault Detection for Medium/Low-Voltage Switchgear

Switchgear arcing faults have been a primary cause for concern for the manufacturing industry and safety personnel alike. The deregulation of the power industry being in full swing and the ever-growing competitiveness in the distribution sector call for the transition from preventive to predictive maintenance. Switchgears form an integral part of the distribution system in any power system setup. Keeping in mind the switchgear arcing faults, the aforementioned transition applies, most of all, to the switchgear industry. Apart from the fact that it is the primary cause of serious injuries to electrical workers worldwide, switchgear arcing faults directly affect the quality and continuity of electric power to the consumers. A great amount of technological advancement has taken place in the development of arc-resistant/proof switchgears. However, most of these applications focus on minimizing the damage after the occurrence of the arcing fault. The problem associated with the compromise on the quality and continuity of electric power in such a scenario still awaits a technical as well as economically feasible solution. This paper describes the development of a novel approach for the detection of arcing faults in medium-/low-voltage switchgears. The basic concept involves the application of differential protection for the detection of any arcing within the switchgear. The new approach differs from the traditional differential concept in the fact that it employs higher frequency harmonic components of the line current as the input for the differential scheme. Actual arc-generating test benches have been set up in the Power System Simulation Laboratory at the Energy Systems Research Center to represent both medium- and low-voltage levels. Hall effect sensors in conjunction with data acquisition in LabVIEW are employed to record the line current data before, during, and after the arcing phenomenon. The methodology is first put to test via simulation approach for medium-voltage levels and then corroborated by actual hardware laboratory testing for low-voltage levels. The plots derived from the data gathering and simulation process clearly underline the efficiency of this approach to detect switchgear arcing faults. Both magnitude and phase differential concepts seem to provide satisfactory results. Apart from the technical efficiency, the approach is financially feasible, considering the fact that the differential protection is already being comprehensively employed worldwide.

General methodology for analysis of sub-synchronous interaction in wind power plants

Summary form only given. This paper presents a general methodology for analysis of sub-synchronous interaction in wind power plants. These include appropriate frequency scanning method for the assessment of the sub-synchronous control interaction, and calculation of the electrical damping provided by the wind turbine generator for investigation of the sub-synchronous torsional interaction. A general formulation of both methods applicable to any given wind turbine and network is presented. A dynamic frequency scanning method for the turbine side is developed which takes account of the turbine non-linearities and its active behavior. Various aspects that need to be considered when injecting a voltage or current signal into the system for dynamic frequency scanning are discussed in detail. The veracity of these methods is confirmed against electromagnetic transient analyses. The application of these tools and techniques is demonstrated on a practical power system comprising type 3 wind turbines and series compensated lines.

Dynamic equivalent model development to improve the operation efficiency of wind farm

An increasing number of wind turbine generators (WTGs) are being installed in modern power system networks. As a result, substantial achievements have been made in developing generic wind models to represent the dynamic behavior of WTGs on the grid. The Western Electricity Coordinating Council (WECC) has developed and proposed four generic models for positive sequence stability analysis of WTG. These models provide a good first step in terms of simulating the dynamic response of WTGs on the power system grid. Since it requires accurate parameters to predict the true response of the WTG, challenges associated with the simulation of dynamic response of WTGs in the field still remain. This paper proposes a procedure to estimate parameters of dynamic equivalent model of WTG by using the measurement data from phasor measurement units (PMUs). Hybrid dynamic simulation is used to reduce external system by employing input signal on PMU bus. Stochastic approximation is adopted in searching optimized model parameter values. A two-WTG subsystem in Electric Reliability Council of Texas (ERCOT) is presented as a case study to address the importance of correct model in system operation strategy. Two most commonly used generic WTG models have been utilized to demonstrate the effectiveness of the proposed approach.

Utilization of Low Voltage In-Line Power Regulator for reliable integration & performance of DER technologies

The increasing penetration of DER technologies is accompanied with challenges associated with changing system operation characteristics. Some of these challenges include load voltage regulation, reverse power flow issues, volt/VAR optimization and optimal use of sub-transmission and distribution facilities to reliably operate the system. This paper discusses the concept of a Low Voltage In-Line Power Regulator (LV-IPR) as a means to provide the necessary load voltage regulation and reactive compensation (under bi-directional power flow conditions) for reliable integration of DER technologies. A simplified dynamic model for the LV-IPR has been developed for the purposes of sub-transmission system studies and benchmarked with the detailed model. The performance of the LV-IPR has been evaluated on a sample utility distribution feeder in terms of its ability to provide load voltage regulation, reactive compensation and enhanced reliability for distributed PV integration. Finally, the capability of the LV-IPR to ensure no interference with the conventional protection schemes on the distribution system has also been established.

Benefits of upgrading protection schemes for hydroelectric power plants

The role played by various energy sources has undergone a sweeping change during the post-deregulation era in the power industry. In the wake of this transformation, hydroelectric power plants, primarily employed as peaking units, assume great opportunities in participating on load balancing and other ancillary services market. A comprehensive protection plan for hydroelectric power plants would be of great importance to improve their availability and security. This paper focuses on the benefits of elevating the existing hydrounit protection to microprocessor based protection schemes. Effects of this protection upgrade on the system reliability, availability and power market are discussed. These discussions are substantiated by an illustrative study carried out for a hydro-electric power plant in Central Texas. The paper concludes with generic recommendations on upgrade procedure for hydroelectric power plants

Arc Flash Study in large scale industrial plant with internal generation and complex interconnected network

This Poster present a comprehensive and hierarchical procedure for Arc Flash Study in complex large scale industrial plants with internal generation. All steps of study including Model development, Model validation, arc flash study and result analysis and debugging tips in each stage are discussed in details. In model development the equipment and important parameters which can affect the study are deliberated. In addition, significant points and challenges regarding load flow and short circuit study which are required to validate the developed model are covered. Then parameter, standards and setting which are necessary to be taken into account for the Arc Flash Study are introduced. Finally, the result analysis approaches and all the possible mitigation methodologies to decrease the incident energy in high category switchgears are presented.

An analytical approach for evaluating the risk of SSR for reciprocating engine based generation in series compensated networks

There has been limited focus on evaluation of Sub-synchronous Resonance (SSR) risk between reciprocating engine based generation and series compensated transmission networks. This paper aims to provide an analytical approach for investigating SSR issues associated with reciprocating engine based generators and series compensated transmission lines. Eigen value analysis is performed to determine the torsional modes and associated modal damping for the mechanical system. Transmission system side frequency scans in conjunction with generator electrical characteristics are used to derive the electrical damping at sub-synchronous frequencies. A comparison of electrical damping with the modal damping is used as a screening technique to identify potential conditions of SSR concerns. Detailed Electro-Magnetic Transient (EMT)-type simulations are conducted to evaluate potential SSR concerns for conditions shortlisted via the screening assessment. Sensitivity analysis around select transmission system and generator parameters is performed to comment on the impact of variations around the parameters on SSR risk.