Stability simulation and parameter optimization of a hybrid wind-diesel power generation system

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 an SMES unit for improvement of stability and system dynamic response is studied. Analysis of stability has further been explored using an eigenvalue sensitivity technique. The eigenvalues of the system with and without an SMES unit are studied and the effect of variation of the SMES unit parameters on eigenvalue locations are plotted. The dynamic response of the power system to random load changes with optimal gain setting is also presented.     

Dynamics and stability of a hybrid wind-diesel power system

Dynamic system analysis is carried out on an isolated electric power system consisting of a wind turbine generator (WTG) and a diesel engine generator (DG). The 150 kW wind turbine generator is operated in parallel with the diesel generator to serve an average load of 350 kW. A comprehensive digital computer model of a hybrid wind-diesel power generation system, including the diesel and wind power dynamics for stability evaluation, is developed. The dynamic performance of the power system and its control logic are studied, using the time domain solution approach. A systematic method of choosing the gain parameter of the wind turbine generator pitch control by the second method of Lyapunov that guarantees stability is presented. The response of the power system with the optimal gain setting to the random load changes has been studied. Analysis of stability has further been explored using the eigenvalue sensitivity technique.     

超导储能对并网型风电场运行性能影响的仿真分析

采用超导储能(SMES)可以改善风电场并网运行的稳定性,针对风电系统中出现的联络线短路故障和风电场的风速扰动,提出利用超导储能安装点的电压偏差信号作为超导储能有功控制器的控制策略。为了验证这种策略的有效性,建立了风电机组和超导储能装置的数学模型,并利用MATLAB/Simulink软件搭建了风电场接入电网后的仿真模型。仿真结果表明,采用该控制策略不仅可以在网络故障后有效地提高风电场的稳定性,而且能够在快速的风速扰动下平滑风电场的功率输出,降低风电场对电网的冲击。     

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 100 kJ/50 kW high-temperature superconducting magnet energy storage system in micro-grid

超导磁储能系统（superconducting magnetic energy storage,SMES）能够实现与电网之间的快速功率交换,对于增强电网稳定性,改善电能质量具有重要意义。本文针对一套100 kJ/50 kW高温超导磁储能系统,对其超导磁体设计与低温系统,功率调节系统的拓扑及控制策略设计、主监控系统的设计分别进行了阐述和分析。为了验证整个磁储能系统的性能,进行了相关的开环功率调节实验。实验结果表明,整套系统运行良好,SMES能够快速的响应主监控系统发出的功率指令,实现SMES与电网之间快速的功率交换。基于上述对SMES的分析和实验测试,结合云电科技园微电网的拓扑,给出了几种SMES在微电网中应用的试验方案,以验证SMES在微电网中应用的性能和作用。     

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 external fault of utility power system occurs. An actual external fault case and a simulated internal 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, an 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.     

Experimental evaluation of nonlinear robust control for SMES to improve the transient stability of power systems

This paper presents a new approach and corresponding experiments for the nonlinear robust control of a superconducting magnetic energy storage (SMES) unit to improve the transient stability of power systems. Based on the result of SMES prototype experience, a new dynamic model with disturbances of SMES is adopted, and transferred to the per unit system for simplifying the dynamic analysis and controller design. Then, feedback linearization scheme and linear H/sub /spl infin// control theory are applied to design a novel SMES nonlinear robust controller in a one-machine infinite bus (OMIB) power system. In order to confirm such positive effects of the proposed control strategy, experiments are carried on a laboratory setup of SMES comparing that with a conventional proportional-integral (PI) controller. The results of the experiments demonstrate that the proposed nonlinear robust controller has more excellent performance to improve the transient stability of power systems than that of conventional PI controllers.     

Hydrogen electronic injection system for a diesel power generator

This work presents an electronic control system developed for hydrogen injection in a diesel power generator. The full system is basically constituted by a gas fuel injection rail with injection valves, a speed sensor and an electronic control unit. The electronic injection system was installed and tested in a diesel power generator of 44 kW rated power. The tests were carried out with hydrogen injected in the intake manifold and diesel oil directly injected in the combustion chamber. The results show the injection valve opening periods necessary to obtain hydrogen mass flow rates equivalent to 5%, 10%, 15% and 20% of the diesel oil mass replaced. The measured hydrogen mass flow rate injected is presented as a function of load power demand and hydrogen concentration in the fuel.     

Application of simultaneous active and reactive power modulation ofsuperconducting magnetic energy storage unit to damp turbine-generatorsubsynchronous 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     

Dynamic Stability Enhancement and Power Flow Control of a Hybrid Wind and Marine-Current Farm Using SMES

This paper presents a control scheme based on a superconducting magnetic energy storage (SMES) unit to achieve both power flow control and damping enhancement of a novel hybrid wind and marine-current farm (MCF) connected to a large power grid. The performance of the studied wind farm (WF) is simulated by an equivalent 80-MW induction generator (IG) while an equivalent 60-MW IG is employed to simulate the characteristics of the MCF. A damping controller for the SMES unit is designed by using modal control theory to contribute effective damping characteristics to the studied combined WF and MCF under different operating conditions. A frequency-domain approach based on a linearized system model using eigen techniques and a time-domain scheme based on a nonlinear system model subject to disturbance conditions are both employed to validate the effectiveness of the proposed control scheme. It can be concluded from the simulated results that the proposed SMES unit combined with the designed damping controller is very effective to stabilize the studied combined WF and MCF under various wind speeds. The inherent fluctuations of the injected active power and reactive power of the WF and MCF to the power grid can also be effectively controlled by the proposed control scheme.      

The power regulation of a PWM type superconducting magnetic energystorage unit

This paper presents an analysis of the power regulation of a SMES unit under PWM switching control. The criteria for executing a power limit scheme to maintain power flows of the SMES unit within a controllable range are described. A general technique for design of power controllers based on the power limit scheme is developed. Two illustrative examples, being separate active and reactive power compensations of a model power system, are presented. The study indicates that active power priority control plays a dominant role in the power regulation of a SMES unit. Experimental results for two examples are also presented     

A 150 kJ/100 kW directly cooled high temperature superconducting electromagnetic energy storage system

高温超导磁储能系统（SMES）是一种功率型的储能装置,本文介绍了国内自主研发的150 kJ/100 kW直接冷却高温超导磁储能系统的总体结构和基本试验结果。高温超导磁体由Bi2223/Ag和YBCO两种超导带材绕制而成,通过直接冷却方式将储能磁体成功冷却到了17 K左右。经测试,储能磁体的直流临界电流达到180 A,临界储能量157 kJ,磁体中心场强4.7 T;该SMES能快速独立地在四象限进行有功功率和无功功率交换,响应速度小于10 ms;在电力系统动态模拟实验中,SMES有效抑制了电力系统中因发电机机端短路故障引起的功率振荡。     

Power flow control and damping enhancement of a large wind farm using a superconducting magnetic energy storage unit

A novel scheme using a superconducting magnetic energy storage (SMES) unit to perform both power flow control and damping enhancement of a large wind farm (WF) feeding to a utility grid is presented. The studied WF consisting of forty 2 MW wind induction generators (IGs) is simulated by an equivalent 80 MW IG. A damping controller of the SMES unit is designed based on the modal control theory to contribute proper damping characteristics to the studied WF under different wind speeds. A frequency-domain approach based on a linearised system model using eigen techniques and a time-domain scheme based on a nonlinear system model subject to disturbance conditions are both employed to validate the effectiveness of the proposed SMES unit with the designed SMES damping controller. It can be concluded from the simulated results that the proposed SMES unit combined with the designed damping controller is very effective in stabilising the studied large WF under various wind speeds. The inherent fluctuations of the injected active power of the WF to the power grid can also be effectively controlled by the proposed control scheme.     

Energetic and exergetic analyses of a dual-fuel diesel engine

The aim of this work is to investigate theoretically and experimentally the performance characteristics of a commercial diesel engine when operating in dual form: natural gas and diesel. The experimental facility (thermal system) is composed of a diesel engine coupled to an electronic generator with measuring sensor for temperature and pressure, air, natural gas and diesel flow meters, gas transducers, gas analyzer and power absorption system, constituted by an electric charge bank and its controlling system. For energetic and exergetic analysis of such dual engine, a mathematical model based on the thermodynamics concepts was developed. Numerical and experimental results concerning the effect of air conditions, the type and quantity of fuel used and the exhaustion gases over the engine performance and environmental impact are presented and analyzed. In this work, the diesel engine operated with powers ranging from 10 to 150 kW and replacement rates from 60% to 85%.     

Predictive control of an integrated PV-diesel water and power supply system using an artificial neural network

This paper discusses the development of a predictive artificial neural network (ANN)-based prototype controller for the optimum operation of an integrated hybrid renewable energy-based water and power supply system (IRWPSS). The integrated system, which has been assembled, consists of photovoltaic modules, diesel generator, battery bank for energy storage and a reverse osmosis desalination unit. The electrical load consists of typical households and the desalination plant. The proposed Artificial Neural Networking controller is designed to be implemented to take decision on diesel generators ON/OFF status and maintain a minimum loading level on the generator under light load and high solar radiation levels and maintain high efficiency of the generators and switch off diesel generator when not required based on predictive information. The key objectives are to reduce fuel dependency, engine wear and tear due to incomplete combustion and cut down on greenhouse gas emissions. The statistical analysis of the results indicates that the R² value for the testing set of 186 cases tested was 0.979. This indicates that ANN-based model developed in this work can predict the power usage and generator status at any point of time with high accuracy.     

Damping subsynchronous resonance using superconducting magneticenergy 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     

Application of superconductive magnetic energy storage in anasynchronous link between power systems

The concept that superconductive magnetic energy storage (SMES) can be incorporated into a back-to-back DC link is introduced. With an SMES-DC link, an SMES system can be shared between several neighboring power systems. This results in better economics for SMES usage for each participating power system. In addition to SMES operation, an SMES-DC link also allows asynchronous connection and interchange of power between the interconnected systems. It is demonstrated that an SMES-DC link can achieve significant economic benefits over pure power interchange or SMES operation alone. The basic principle of an SMES-DC link, which is able to interconnect any number of neighboring power systems with a single SMES unit, and various interconnected system operation modes are presented. A battery-DC link is discussed and compared with the SMES-DC link     

Improvement of synchronous generator damping throughsuperconducting magnetic energy storage systems

Stabilization of a synchronous generator through control of firing angle of the power converters in superconducting magnetic energy storage (SMES) systems is considered. An optimum strategy of the firing angle control is designed so as to eliminate the transients in minimum time. A nonlinear model of a synchronous generator, its governor and exciter systems, and an SMES system connected to the generator terminal is considered. The optimum firing angle control is derived retaining the nonlinearities of the system dynamics. Digital simulation results indicate that the proposed strategy controls the slowly growing as well as first swing instabilities very effectively     

超导储能系统提高风电场暂态稳定性研究

应用超导储能系统(SMES)对提高风电场的暂态稳定性进行了研究。在深入研究超导储能系统运行原理的基础上,建立了基于电压型换流器(VSC)的超导储能系统模型,实现了有功功率和无功功率的解耦控制,并提出了有功、无功功率综合控制策略。利用PSCAD/EMTDC软件进行了仿真计算,结果说明超导储能系统不但能够在风速波动时平滑风电场的功率输出,而且能够提高风电系统的暂态稳定性。