This paper investigates the use of a virtual synchronous generator(VSG) to improve frequency stability in an autonomous photovoltaic-diesel microgrid with energy storage. VSG control is designed to emulate inertial re...This paper investigates the use of a virtual synchronous generator(VSG) to improve frequency stability in an autonomous photovoltaic-diesel microgrid with energy storage. VSG control is designed to emulate inertial response and damping power via power injection from/to the energy storage system. The effect of a VSG with constant parameters(CP-VSG) on the system frequency is analyzed. Based on the case study, self-tuning algorithms are used to search for optimal parameters during the operation of the VSG in order to minimize the amplitude and rate of change of the frequency variations. The performances of the proposed self-tuning(ST)-VSG, the frequency droop method, and the CP-VSG are evaluated by comparing their effects on attenuating frequency variationsunder load variations. For both simulated and experimental cases, the ST-VSG was found to be more efficient than the other two methods in improving frequency stability.展开更多
In view of the problem of low self-service capability of the microgrid due to the high operating cost and low capacity of the traditional battery energy storage system.In this paper,an electrothermal hybrid energy sto...In view of the problem of low self-service capability of the microgrid due to the high operating cost and low capacity of the traditional battery energy storage system.In this paper,an electrothermal hybrid energy storage model based on electricity,hydrogen and thermal energy conversion and storage is introduced,and a microgrid autonomous operational strategy is proposed.First,the addition of the power to hydrogen transfer equipment in the traditional combined heat and power(TCHP)system without battery energy storage is studied,and a micro gas turbine,electric to hydrogen transfer equipment and electric boiler based electrothermal energy storage system(ETSS)model is established.Aiming at the lowest comprehen-sive operating cost of multiple energy sources in a microgrid and maximizing the consumption of curtailed wind,the multi-objective scheduling model of an electrothermal hybrid energy storage system is established,then the multi-energy autonomous operational strategy of a microgrid is proposed.Lastly,the simulation of a multi-energy microgrid in Northeast China is taken as an example.The results of the simulation showed that compared with a combined heat and power microgrid system considering conventiona battery energy storage,a multi-energy microgrid system using electrothermal hybrid energy storage has better flexibility and economy,and can improve wind power accommodation.展开更多
Frequency is a key issue for the stable operation of autonomous microgrid(AMG) with a large penetration of intermittent renewable energy resources.The fast development of demand-side response technology provides a new...Frequency is a key issue for the stable operation of autonomous microgrid(AMG) with a large penetration of intermittent renewable energy resources.The fast development of demand-side response technology provides a new solution for the frequency control of the AMG.In this paper,a novel decentralized demand control strategy(DDC) for family-friendly controllable refrigerators considering customer comfort level is proposed to regulate the frequency of AMG in coordination with the energy storage system(ESS).The refrigerator under DDC responds to the local frequency signals quickly and adjusts its operation cycle dynamically.Meanwhile,a customer participation degree which is proportional to the frequency deviation is introduced to evaluate the customer comforts when responding to the frequency of AMG.Finally,a benchmark low voltage AMG is established as a test system to verify the effectiveness of the proposed DDC strategy.Simulation results show that the DDC strategy can not only improve the frequency control effect of AMG effectively but also guarantee the customer comforts as well as reduce the capacity of ESS.展开更多
Growing application of distributed generation units at remote places has led to the evolution of microgrid(MG)technology.When an MG system functions independently,i.e.,in autonomous mode,unpredictable loads and uncert...Growing application of distributed generation units at remote places has led to the evolution of microgrid(MG)technology.When an MG system functions independently,i.e.,in autonomous mode,unpredictable loads and uncertainties emerge throughout the system.To obtain stable and flexible operation of an autonomous MG,a rigid control mechanism is needed.In this paper,a robust high-performance controller is introduced to improve the performance of voltage tracking of an MG system and to eliminate stability problems.A combination of a resonant controller and a lead-lag compensator in a positive position feedback path is designed,one which obeys the negative imaginary(NI)theorem,for both single-phase and three-phase autonomous MG systems.The controller has excellent tracking performance.This is investigated through considering various uncertainties with different load dynamics.The feasibility and effectiveness of the controller are also determined with a comparative analysis with some well-known controllers,such as linear quadratic regulator,model predictive and NI approached resonant controllers.This confirms the superi-ority of the designed controller.展开更多
This paper presents a comprehensive control scheme for the interlinking converter(ILC)in a hybrid AC/DC microgrid consisting of the outer loop flexible power sharing control and the improved robust inner loop control....This paper presents a comprehensive control scheme for the interlinking converter(ILC)in a hybrid AC/DC microgrid consisting of the outer loop flexible power sharing control and the improved robust inner loop control.The outer loop power control of ILC is presented to achieve flexible power sharing of distributed generations(DGs)in the hybrid microgrid,depending on different power management objectives,which is realized based on the deduced balance state equation,and regulating the frequency and DC voltage at the same time.The improved robust inner loop control of ILC is also presented to suppress external disturbance and system model uncertainties with the improved dynamic response.This improved inner loop control which includes a disturbance observer link,can force the converter current to track the reference value with no steady error and improve the dynamic stability of the microgrid・With the proposed outer loop power sharing control and improved inner loop control,the comprehensive control scheme for the ILC is presented・Simulations cases show the effectiveness and superiority of the proposed comprehensive control scheme.展开更多
基金supported by National High Technology Research and Development Program of China(863Program)(No.2015AA050607)the National key Research and Development Program of China(No.2016YFB0900300)the Science and Technology project of SGCC(No.NYB17201700151)
文摘This paper investigates the use of a virtual synchronous generator(VSG) to improve frequency stability in an autonomous photovoltaic-diesel microgrid with energy storage. VSG control is designed to emulate inertial response and damping power via power injection from/to the energy storage system. The effect of a VSG with constant parameters(CP-VSG) on the system frequency is analyzed. Based on the case study, self-tuning algorithms are used to search for optimal parameters during the operation of the VSG in order to minimize the amplitude and rate of change of the frequency variations. The performances of the proposed self-tuning(ST)-VSG, the frequency droop method, and the CP-VSG are evaluated by comparing their effects on attenuating frequency variationsunder load variations. For both simulated and experimental cases, the ST-VSG was found to be more efficient than the other two methods in improving frequency stability.
基金This work was supported by the National Key Research and Development Program of China(No.2017YFB0902100).
文摘In view of the problem of low self-service capability of the microgrid due to the high operating cost and low capacity of the traditional battery energy storage system.In this paper,an electrothermal hybrid energy storage model based on electricity,hydrogen and thermal energy conversion and storage is introduced,and a microgrid autonomous operational strategy is proposed.First,the addition of the power to hydrogen transfer equipment in the traditional combined heat and power(TCHP)system without battery energy storage is studied,and a micro gas turbine,electric to hydrogen transfer equipment and electric boiler based electrothermal energy storage system(ETSS)model is established.Aiming at the lowest comprehen-sive operating cost of multiple energy sources in a microgrid and maximizing the consumption of curtailed wind,the multi-objective scheduling model of an electrothermal hybrid energy storage system is established,then the multi-energy autonomous operational strategy of a microgrid is proposed.Lastly,the simulation of a multi-energy microgrid in Northeast China is taken as an example.The results of the simulation showed that compared with a combined heat and power microgrid system considering conventiona battery energy storage,a multi-energy microgrid system using electrothermal hybrid energy storage has better flexibility and economy,and can improve wind power accommodation.
基金supported by the Special Fund of the National Basic Research Program of China ("973" Project) (Grant Nos. 2009CB219701,2010CB234608)the National Natural Science Foundation of China (Grant No. 51277128)+1 种基金the Tianjin Municipal Science and Technology Development Program of China (Grant No. 09JCZDJC25000)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20090032110064)
文摘Frequency is a key issue for the stable operation of autonomous microgrid(AMG) with a large penetration of intermittent renewable energy resources.The fast development of demand-side response technology provides a new solution for the frequency control of the AMG.In this paper,a novel decentralized demand control strategy(DDC) for family-friendly controllable refrigerators considering customer comfort level is proposed to regulate the frequency of AMG in coordination with the energy storage system(ESS).The refrigerator under DDC responds to the local frequency signals quickly and adjusts its operation cycle dynamically.Meanwhile,a customer participation degree which is proportional to the frequency deviation is introduced to evaluate the customer comforts when responding to the frequency of AMG.Finally,a benchmark low voltage AMG is established as a test system to verify the effectiveness of the proposed DDC strategy.Simulation results show that the DDC strategy can not only improve the frequency control effect of AMG effectively but also guarantee the customer comforts as well as reduce the capacity of ESS.
文摘Growing application of distributed generation units at remote places has led to the evolution of microgrid(MG)technology.When an MG system functions independently,i.e.,in autonomous mode,unpredictable loads and uncertainties emerge throughout the system.To obtain stable and flexible operation of an autonomous MG,a rigid control mechanism is needed.In this paper,a robust high-performance controller is introduced to improve the performance of voltage tracking of an MG system and to eliminate stability problems.A combination of a resonant controller and a lead-lag compensator in a positive position feedback path is designed,one which obeys the negative imaginary(NI)theorem,for both single-phase and three-phase autonomous MG systems.The controller has excellent tracking performance.This is investigated through considering various uncertainties with different load dynamics.The feasibility and effectiveness of the controller are also determined with a comparative analysis with some well-known controllers,such as linear quadratic regulator,model predictive and NI approached resonant controllers.This confirms the superi-ority of the designed controller.
基金supported in part by the National Natural Science Foundation of China(52007050)by the Fundamental Research Funds for the Central Universities(B210202062).
文摘This paper presents a comprehensive control scheme for the interlinking converter(ILC)in a hybrid AC/DC microgrid consisting of the outer loop flexible power sharing control and the improved robust inner loop control.The outer loop power control of ILC is presented to achieve flexible power sharing of distributed generations(DGs)in the hybrid microgrid,depending on different power management objectives,which is realized based on the deduced balance state equation,and regulating the frequency and DC voltage at the same time.The improved robust inner loop control of ILC is also presented to suppress external disturbance and system model uncertainties with the improved dynamic response.This improved inner loop control which includes a disturbance observer link,can force the converter current to track the reference value with no steady error and improve the dynamic stability of the microgrid・With the proposed outer loop power sharing control and improved inner loop control,the comprehensive control scheme for the ILC is presented・Simulations cases show the effectiveness and superiority of the proposed comprehensive control scheme.
