Superconducting Magnetic Energy Storage Unit Research Articles

Enhancement of Transient Stability of an Industrial Cogeneration System with Superconducting Magnetic Energy Storage Unit

This paper has developed the coordination of load shedding scheme and superconducting magnetic energy storage (SMES) unit to enhance the transient stability of a large industry cogeneration facility. The load-shedding scheme and the tie-line tripping strategy by using the frequency relays have been designed to prevent the power system from collapse when an extemal fault of utility power system occurs. An actual extemal fault case and a simulated intemal fault case have been selected to verify the accuracy of the load shedding scheme by executing the transient stability analysis. To improve the frequency and voltage responses, an SMES unit with various control modes has been installed in the cogeneration system. The sensitivity analysis of the SMES unit with different parameters is applied to achieve better system responses. Besides, a SMES unit with active power deviation as feedback signal is also considered to improve the electric power fluctuation of the study plant with rolling mills. It is found that the SMES system will enhance the electric power quality and minimize the economic losses of the cogeneration facility due to unnecessary load shedding.

The Transient Stability Enhancement of Synchronous Machine with SMES by Using Adaptive Control

In this study, Parameter Adaptive Control algorithm is applied to a system consisting of the synchronous machine and SMES (superconducting magnetic energy storage) unit for maintaining stability. The control scheme is based on the autoregressive moving average (ARMA) model, which gives explicit identification of the system. Simulation results obtained by using a nonlinear model of the system showed that the application of adaptive control scheme to the system with SMES considerably improves the damping of system post fault.

Dynamic performance assessment of an isolated wind-diesel power system with superconducting magnetic energy storage unit under turbulent wind and load disturbances

This paper presents modelling and control aspects of an isolated wind–diesel system equipped with a superconducting magnetic energy storage (SMES) unit. The SMES unit is located at the induction generators' terminal bus, for exchanging real and reactive powers in four quadrants, with the wind–diesel system. The system components are modelled by non-linear equations for accurate dynamic performance assessment and the SMES unit is modelled as a controllable current source. The control of the SMES unit is exercised through a multi-input–multi-output (MIMO) self-tuning regulator (STR). The STR uses the local voltage and frequency measurements and generates appropriate signals for the control of the SMES unit. The SMES coil current deviation forms a part of one of the regulated variables of the STR for achieving a continuous control. The complete model of the hybrid system is developed and the parameters of the STR are adjusted for quality improvement of the power supply under turbulent wind. The scheme is then tested for load disturbances. The simulation results show the positive impact of the proposed scheme on the quality of the power supply both under turbulent wind as well as load disturbances. Copyright © 2002 John Wiley & Sons, Ltd.

Application of Superconducting Magnetic Energy Storage unit in multi-machine power systems

The use of Superconducting Magnetic Energy Storage (SMES) units to improve the dynamic stability of a multi-machine power system is investigated. The SMES unit is equipped with two independent controllers which ensures the effective management of its active and reactive power capabilities. The parameters of these controllers are determined once off-line. The simulation results show that the SMES unit is able to restore system stability even for disturbances of large magnitude. The control algorithms for SMES unit are simple and implementation will require very little hardware.

Application of simultaneous active and reactive power modulation of SMES unit under unequal α-mode for power system stabilization

A simple and novel control strategy for damping electromechanical oscillations through control of power converter firing angles /spl alpha//sub 1/ and /spl alpha//sub 2/ of a superconducting magnetic energy storage (SMES) unit is proposed. Both active and reactive power modulations are used under unequal /spl alpha/-mode of operation. The choice of unequal mode is discussed in detail. The gains of the proposed SMES controller are determined once offline depending on the power system and the rating of the SMES unit. Simulation results show that the SMES unit can effectively suppress power system oscillations by utilizing its active and reactive power modulation capabilities. The control algorithm is simple and its realization will require very little hardware.

Application of superconducting magnetic energy storage unit for damping of subsynchronous oscillations in power systems

A novel strategy for suppressing subsynchronous resonance (SSR) in power systems using a superconducting magnetic energy storage (SMES) unit is presented. The energy transfer between the power system and the SMES unit is based on simultaneous control of active and reactive power modulation of the SMES unit. The active power is controlled by an artificial neural network (ANN) based controller, while the reactive power is controlled by a conventional regulator. The gains of the controllers are determined from the power system operating conditions and the rating of the SMES unit. Unequal α-mode of firing angle control of the converters is utilized to enforce zero energy transfer in the SMES unit under steady state conditions. The proposed scheme is tested using the IEEE first benchmark model for subsynchronuos oscillations, and it is found that, with the proposed mode of control, the SMES unit can effectively restore power system stability.

Multi-mode wide range subsynchronous resonance stabilization using superconducting magnetic energy storage unit

This paper presents a novel strategy to stabilize the torsional oscillations due to subsynchronous resonance (SSR) of a capacitor compensated power system through control of firing angles of superconducting magnetic energy storage (SMES) unit. The control strategy of SMES is based on artificial neural network (ANN). The gain of the controller is generated on-line depending on the operating conditions and the type of the disturbance. The proposed method of control of SMES for power system stabilization has been tested on the IEEE first benchmark model for subsynchronous resonance studies. Dynamic simulations are performed using the non-linear system model. It has been found that the SMES unit is very effective to eliminate the slowly growing transients resulting from the unstable modes.

An adaptive fuzzy controlled superconducting magnetic energy storage unit for power systems

This paper presents the development of an adaptive fuzzy controller to improve the dynamic stability of an electric power system with a Superconducting Magnetic Energy Storage (SMES) unit. The d.c. voltage applied to the SMES unit is generated from the fuzzy controller. The premise variables chosen for the fuzzy membership functions are speed error and its derivative. The rules in fuzzy cells are adapted according to the performance feedback of the closed loop system. The effectiveness of the proposed controller in restoring energy balance is demonstrated by simulation studies for different types of disturbances.

Augmentation of transient stability using a superconducting coil and adaptive nonlinear control

The very nonlinear nature of the generator and system behaviour following a severe disturbance precludes the use of classical linear control techniques. In this paper, a nonlinear adaptive excitation and a thyristor-controlled superconducting magnetic energy storage (SMES) unit is proposed to enhance the transient stability of a power system with unknown or varying parameters like equivalent reactances of the transmission lines. The SMES unit is located near the generator bus terminal in a power system. A nonlinear feedback control law is found which linearizes and decouples the power system. An adaptive control law is used to design the controller for the generator excitation and SMES system. Simulation results demonstrate that the proposed controller can ensure transient stability of a single-machine-infinite-bus system under a large sudden fault which may occur near the generator bus terminal.

Simultaneous frequency and voltage control of wind-diesel power systems using energy storage

This paper presents a new scheme for smoothing out the voltage and frequency fluctuations simultaneously in a hybrid wind-diesel system using a super conducting magnetic energy storage (SMES) unit. The SMES unit located at induction generators' terminal bus, uses local measurements for exchanging real and reactive powers simultaneously in four quadrants. Complete model of the hybrid wind-diesel-SMES system is developed and is used for eigenvalue analysis and design of controllers. Computer simulation results illustrate the positive impact of the SMES unit on the quality of the supply and furthermore some modifications of the controller design are proposed. © 1998 John Wiley & Sons, Ltd.

Dynamic simulation of hybrid wind-diesel power generation system with superconducting magnetic energy storage

In this paper, a systematic method of choosing the gain parameter of the wind turbine generator pitch control is presented, using the Lyapunov technique, that guarantees stability. A comprehensive digital computer model of a hybrid wind-Diesel power generation system, including the Diesel and wind power dynamics with a superconducting magnetic energy storage (SMES) unit, for stability evaluation is developed. The effect of introducing the SMES unit for improvement of stability and system dynamic response is studied. Analysis of the stability has been further explored using an eigenvalue sensitivity technique. The eigenvalues of the system with and without the SMES unit have been studied, and the effects of variation of the SMES unit parameters or eigenvalue locations are plotted. The dynamic response of the power system to random load changes with optimal gain setting is also presented.

A fuzzy set theory based control of superconductive magnetic energy storage unit to improve power system dynamic performance

At present fuzzy logic control is receiving increasing emphasis in process control applications. The paper describes the application of fuzzy logic control in a power system that uses a 12-pulse bridge converter associated with superconductive magnetic energy storage (SMES) unit. The fuzzy control is used in both the frequency and voltage control loops, replacing the conventional control method. The control algorithms have been developed in detail and simulation results are presented. These results clearly indicate the superior performance of fuzzy control during the dynamic period of energy transfer between the power system and SMES unit.

Exploratory assessment of the dynamic behavior of multimachine system stabilized by a SMES unit

A new linear model of superconducting magnetic energy storage (SMES) system is designed for dynamic stability analysis in multimachine power system. An equivalent current source for the SMES unit is assumed. The linear model includes voltage, active power and energy regulators. On a sample network, eigenanalysis using the QR algorithm shows that the proposed model increases the damping of slow oscillation modes. Step-response simulations illustrate the positive impact of the SMES regulator as a power system stabilizer. Performing the component connection method (CCM), the approach is attractive in case one or more additional SMES units should be considered. >

AUTOMATIC GENERATION CONTROL WITH SUPERCONDUCTING MAGNETIC ENERGY STORAGE IN POWER SYSTEM

ABSTRACT This paper describes the development of a digital computer model for a two area interconnected power system which includes the governor deadband nonlinearity, steam reheat constraints and boiler dynamics. The improvement in automatic generation control (AGO with the addition of a small capacity Superconducting Magnetic Energy Storage (SMES) unit is studied. Time domain simulations are used to study the performance of the power system and the controller. Parameter optimization of the controller are carried out by the second method of Lyapunov, which ensures the stability of the system. Suitable methods for the control of SMES unit are also described.

DAMPING TORSIONAL OSCILLATIONS BY A SUPERCONDUCTING MAGNETIC ENERGY STORAGE UNIT

ABSTRACT This paper investigates the effect of a superconducting magnetic energy storage (SMES) unit on the repressing of torsional oscillations in a capacitor compensated power system. The IEEE Second Benchmark Model is employed. To increase the damping of torsional modes, an auxiliary controller, proportional-integral-derivative (PID) or lead-lag, is employed to control the power modulation of the SMES unit according to generator speed deviation. The gains of the proposed auxiliary controller are determined by a pole assignment method where the eigenvalues of the torsional modes are placed at a prespecified position. Eigenvalue analysis and computer simulations of the studied system show that the SMES unit provides adequate damping torque over a wide range of operating conditions. Stability investigation shows that the PID controller is better than the lead-lag controller. The SMES unit also ensures a stable system when one of the parallel lines is out of service.

Power oscillation damping by superconducting magnetic energy (SMES) storage unit

With the increase in the size and capacity of electric power systems and the growth of widespread interconnections, the problem of power oscillations due to the reduced system damping has become increasingly serious. Since a Superconducting Magnetic Energy Storage (SMES) unit with a self-commutated converter is capable of controlling both the active (P) and reactive (Q) power simultaneously and quickly, increasing attention has been focused recently on power system stabilization by SMES control. This paper describes the effects of SMES control on the damping of power oscillations. By examining the case of a single generator connected to an infinite bus through both theoretical analyses and experimental tests (performed with a SMES unit with maximum stored energy of 16 kJ and an artificial model system), the difference in the effects between P and Q control of SMES is clarified as follows: 1 In the case of P control, as the SMES unit is placed closer to the terminal of the generator, the power oscillations will decay more rapidly. 2 In the case of Q control, it is most effective to install the SMES unit near the midpoint of the system. 3 By comparing the P control with Q control, the former is more effective than the latter based on the conditions that the SMES unit location and the control gain are the same.

Damping subsynchronous resonance using superconducting magnetic energy storage unit

A novel damping scheme using superconducting magnetic energy storage (SMES) unit is proposed in this paper to damp subsynchronous resonance (SSR) of the IEEE Second Benchmark Model, system-1 which is a widely employed standard model for computer simulation of power system SSR. The studied system contains a turbine-generator set connected to an infinite bus through two parallel transmission lines, one of which is series-capacitor compensated. In order to stabilize all SSR modes, simultaneous active and reactive power modulation and a proportional-integral-derivative (PID) damping controller designed by modal control theory are proposed for the SMES unit. A frequency domain approach based on eigenvalue analysis and time-domain approach based on nonlinear model simulations are performed to validate the effectiveness of the damping method. It can be concluded from the simulation results that the proposed damping scheme can effectively suppress SSR of the studied system. >

Dynamics and stability of a wind stand-alone power system

A simulation and digital computer model of a wind stand-alone power generation system, including wind turbine generator pitch control and a Superconducting Magnetic Energy Storage (SMES) unit, is developed for dynamic and stability evaluation. The effect of introducing the SMES unit for improvement of stability and system dynamic response is studied. The wind turbine generator pitch control gain is optimized by actual integration of squared errors in the response. The frequency deviation due to load perturbation is reduced using the SMES unit. Analysis of system stability has been explored using an eigenvalue sensitivity technique. The response of the power system with optimal gain setting to random load changes due to the random nature of the wind has then been studied.

Application of simultaneous active and reactive power modulation of superconducting magnetic energy storage unit to damp turbine-generator subsynchronous oscillations

An active and reactive power (P-Q) simultaneous control scheme, which is based on a superconducting magnetic energy storage (SMES) unit, is designed to damp out the subsynchronous resonant (SSR) oscillations of a turbine-generator unit. In order to suppress unstable torsional mode oscillations, a proportional-integral-derivative (PID) controller is used to modulate the active and reactive power input/output of the SMES unit according to speed deviation of the generator shaft. The gains of the proposed PID controller are determined by pole assignment approach based on modal control theory. Eigenvalue analysis of the studied system shows that the PID controller is quite effective over a wide range of operating conditions. Dynamic simulations using the nonlinear system model are also performed to demonstrate the damping effect of the proposed control scheme under disturbance conditions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

On the design of superconducting magnetic energy storage systems

With respect to the available technology and the total costs a first significant step in developing superconducting magnetic energy storage (SMES) plants will be to design a device that is characterized by a small content of stored energy as well as by a high charging power, which is called a small fast-acting SMES unit. It is shown that a small fast-acting SMES unit should be designed as a toroidal coil operating at low induction and high current. The effects of the SMES design and the operating cycle on the cryogenic AC losses are investigated. The quench pressure and cooling concept are discussed. >