Soubhik Auddy

Mitigation of Subsynchronous Resonance in a Series-Compensated Wind Farm Using FACTS Controllers

The rapid growth of wind power systems worldwide will likely see the integration of large wind farms with electrical networks that are series compensated for ensuring stable transmission of bulk power. This may potentially lead to subsynchronous-resonance (SSR) issues. Although SSR is a well-understood phenomenon that can be mitigated with flexible ac transmission system (FACTS) devices, scant information is available on the SSR problem in a series-compensated wind farm. This paper reports the potential occurrence and mitigation of SSR caused by an induction-generator (IG) effect as well as torsional interactions, in a series-compensated wind farm. SSR suppression is achieved as an additional advantage of FACTS controllers which may already be installed in the power system for achieving other objectives. In this study, a wind farm employing a self-excited induction generator is connected to the grid through a series-compensated line. A static var compensator (SVC) with a simple voltage regulator is first employed at the IG terminal in addition to the fixed shunt capacitor for dynamic reactive power support. The same SVC is shown to effectively damp SSR when equipped with an SSR damping controller. Also, a thyristor-controlled series capacitor (TCSC) that is actually installed to increase the power transfer capability of the transmission line is also shown to damp subsynchronous oscillations when provided with closed-loop current control. While both FACTS controllers-the SVC and TCSC-can effectively mitigate SSR, the performance of TCSC is shown to be superior. Extensive simulations have been carried out using EMTDC/PSCAD to validate the performance of SVC and TCSC in damping SSR.

Mitigation of subsynchronous oscillations in a series compensated wind farm with Thyristor Controlled Series Capacitor (TCSC)

Wind power penetration is rapidly growing all over the world as the alternative, renewable and environment friendly resource of energy production. With this rapid growth of wind power, the power systems of future will likely see the integration of large wind farms with electrical networks that are series compensated for ensuring stable transmission of bulk power. This may potentially lead to subsynchronous resonance (SSR) issues. Although SSR is a well-understood phenomenon that can be mitigated with FACTS devices, scant information is available on the SSR problem in a series compensated wind farm. This paper reports the occurrence and mitigation of SSR caused by induction generator (IG) effect as well as torsional interactions (TI), in a series compensated wind farm. SSR suppression is achieved as an added advantage of a thyristor controlled series capacitor (TCSC) actually installed to increase the power transfer capability of the transmission line. In this study, a wind farm employing self-excited induction generator (SEIG) is connected to the grid through a series compensated line. A thyristor controlled series capacitor (TCSC) is shown to damp subsynchronous oscillations when provided with closed loop current control. Extensive simulations have been carried out using EMTDC/PSCAD to validate the performance of TCSC in damping SSR.

Mitigation of subsynchronous oscillations in a series compensated wind farm with static var compensator

Subsynchronous resonance (SSR) is a potential problem in a series compensated power system. A wind farm employing self-excited induction generator (SEIG) connected to the grid through a series compensated transmission line may experience the same problem. This paper presents a study of subsynchronous oscillations resulting from torsional interactions as well as induction generator self-excitation effects in such a wind energy conversion system (WECS). It is shown that these two phenomena may cause system instability if proper preventive measures are not taken. A static var compensator (SVC) with a voltage controller has been employed at the induction generator terminal to damp the subsynchronous oscillations. It is also found that an auxiliary subsynchronous damping controller (SSDC) improves the damping of torsional oscillations. Extensive time domain simulations have been carried out using EMTDC/PSCAD to validate the performance of the SVC in preventing SSR

Bibliography of HVDC Transmission: 2005-2006 IEEE Working Group Report

This paper presents a Bibliography of HVDC transmission technology from August, 2005 to present. It provides a listing of various journal and conference papers in this area.

Mitigation of subsynchronous resonance by SVC using PMU-acquired remote generator speed

Subsynchronous resonance (SSR) is a potential problem in power systems having series compensated transmission lines. Flexible AC transmission systems (FACTS) controllers are widely applied to mitigate subsynchronous oscillations (SSO). With the advent of wide area measurement (WAM) technology, it is possible to measure the states of a large interconnected power system with synchronized phasor measurement units (PMU). In this paper the concept of using remote signals acquired through PMU has been proposed to damp SSR. An auxiliary subsynchronous damping controller (SSDC) for a static VAr compensator (SVC) using the remote generator speed as the stabilizing signal has been designed to damp subsynchronous oscillations. The IEEE first benchmark model is used to show the effectiveness of the controller. Extensive simulation results in EMTDC/PSCAD show that an SVC already installed in a transmission system with the primary objective of improving power transfer capability can also damp SSR with the auxiliary controller using remote generator speed. Finally, the effect of signal transmission delay is discussed

Field Validation of a Doubly Fed Induction Generator (DFIG) Model

With the increased penetration of wind power it is important to carefully asses the impact of grid integration of wind turbine generators. Accurate wind turbine generator models are required for this purpose. Variable speed wind turbine generators are widely being interconnected to the grid to ensure optimum power capture from the wind energy. In this paper, an attempt is made to validate a variable speed doubly fed induction generator model with the field test results. The GE 1.5 MW wind turbine generator is a good example of doubly fed induction generator configuration which is already implemented in PSS/E software. These wind turbine generators are actually installed in the AIM Erie Shore Wind Generating Station of Hydro One Network Inc. A series of tests were performed in this wind farm in 2006 winter. A few of the tests are simulated in PSS/E to validate the existing models. Simulation results are found to be in good agreement with the field test results confirming the accuracy of the GE 1.5 MW wind turbine generator (WTG) models of PSS/E wind. The reasons for the mismatch between the simulation and actual results are also pointed out.

Bibliography of HVDC Transmission 2001-2003 Part: II IEEE Working Group Report

This paper presents a continuation of the Bibliography of HVDC transmission technology for the year 2001-2003.

Damping of Inter-Area Oscillation in Power Systems by Static Var Compensator (SVC) Using PMU-Acquired Remote Bus Voltage Angles

This paper presents a novel concept of Static Var Compensator (SVC) damping control using a weighted sum of bus voltage angles of remote generators that are responsible for causing inter-area oscillations in power systems. These remote bus voltage angle signals are acquired through Phasor Measurement Units (PMUs). A time domain simulation study on a 39-bus New England multi-machine system is utilized to show that an SVC auxiliary damping control, based on the derivative of these remote bus voltage angles, is superior to the conventionally employed local signals in damping inter-area oscillations. The effect of transmission delay in the acquisition of remote signals is also presented and a simple mechanism to compensate this delay is proposed and validated. The robustness of the delay compensator is finally shown for a wide range of signal transmission delays. The designed SVC controller shows a superior performance in damping the inter-area oscillations despite the signal transmission delays.

Bibliography of HVDC Transmission: 2006–2007 IEEE Working Group Report

This paper presents a bibliography of HVDC transmission technology for 2006-07. It provides a listing of various journal and conference papers in this area.

An Alternative Method to Build DC Switchyard With Hybrid DC Breaker for DC Grid

In this paper, a new dc switchyard structure for a multiterminal dc (MTDC) grid is proposed. Fast fault current breaking capability, which is essential for a dc grid, can be achieved with available HVDC breaker solutions (e.g., ABBs hybrid HVDC breaker). However, the hybrid HVDC breaker concept also opens up possibilities for unconventional (relative to ac) switchyard solutions which may be more cost effective. The main aim of this paper is to expound how the proposed dc switchyard can be built with hybrid HVDC breakers in a configuration where the number of components is much less compared to a conventional switchyard structure. After that, the switchyard operation, fault current handling flexibility, and actions against component failure are described conceptually. Finally, the performance of the proposed switchyard is validated and compared with that of a conventional double breaker double busbar switchyard structure for selected cases through time-domain simulations