In the last decades the voltage regulation has been challenged by the increase of power variability in the electric grid,due to the spread of non-dispatchable generation sources.This paper introduces a Smart Transform...In the last decades the voltage regulation has been challenged by the increase of power variability in the electric grid,due to the spread of non-dispatchable generation sources.This paper introduces a Smart Transformer(ST)-based Medium Voltage(MV)grid support by means of active power control in the ST-fed Low Voltage(LV)grid.The aim of the proposed strategy is to improve the voltage profile in MV grids before the operation of On-Load Tap Changer in the primary substation transformer,which needs tens of seconds.This is realized through reactive power injection by the AC/DC MV converter and simultaneous decrease of the active power consumption of voltage-dependent loads in ST-fed LV grid,controlling the ST output voltage.The last feature has two main effects:the first is to reduce the active power withdrawn from MV grid,and consequently the MV voltage drop caused by the active current component.At the same time,higher reactive power injection capability in the MV converter is unlocked,due to the lower active power demand.As result,the ST increases the voltage support in MV grid.The analysis and simulation results carried out in this paper show improvements compared to similar solutions,i.e.the only reactive power compensation.The impact of the proposed solution has been finally evaluated under different voltage-dependence of the loads in the LV grid.展开更多
The Smart Transformer(ST)is a solid-state transformer with control and communication functionalities,interfacing medium voltage and low voltage grids.The ST can independently operate in a radial network configuration,...The Smart Transformer(ST)is a solid-state transformer with control and communication functionalities,interfacing medium voltage and low voltage grids.The ST can independently operate in a radial network configuration,and also in a meshed grid operation.The meshed operation has high potential to optimize the power flow in the network,avoiding or postponing the reinforcement of distribution grids.Nevertheless,the control and synchronization during the meshed operation are not trivial.The perturbation of the voltage in transition between the two operations is inevitable.This could lead to uncontrolled power flow and endanger the meshed operation.Moreover,the stability of the meshed grid has seldom been studied.To address these issues,this paper proposes a voltage control with power-based synchronization for the ST.This allows the universal operation of both radial and meshed grids,while ensuring smooth transition.Modeling and stability analysis of such a system are investigated to make sure of safe operation.Simulation and experimental results are provided to validate the effectiveness of the proposed control and theoretical analysis.展开更多
Solid-state transformer-based smart transformer(ST)can provide the dc connectivity and advanced services to improve the grid performance and to increase the penetration of the power electronics interfaced resources(e....Solid-state transformer-based smart transformer(ST)can provide the dc connectivity and advanced services to improve the grid performance and to increase the penetration of the power electronics interfaced resources(e.g.,distributed generators and electric vehicle charging stations)in modern electricity distribution grids.Since the ST is a new and effective paradigm of the electricity grid evolution to well understand the ST,this paper systematically presents the basic architecture and the typical control schemes of the ST and then the advanced services that ST can provide to improve the electricity grids performances in terms of the power flow control,power quality improvement,active damping and active contribution to improve distribution grid resilience by means of enabling autonomous microgrids operation as well as launching a restoration procedure following a general blackout.展开更多
The Smart Transformer (ST) is a solid-state transformer with control and communication functionalities, interfacing medium voltage and low voltage (LV) grids. The ST can work in both ways: it can operate in a radial n...The Smart Transformer (ST) is a solid-state transformer with control and communication functionalities, interfacing medium voltage and low voltage (LV) grids. The ST can work in both ways: it can operate in a radial network independently, and it also provides meshed operation. In particular, a meshed ST-fed grid is able to optimize the power flow of the network, therefore largely avoiding the reinforcement of utilities. Though the ST can address system-level issues, challenges in terms of control and stability are encountered. The modeling as well as stability analysis of ST converter and its control for meshed operation have rarely been studied. More importantly, the interactions between ST and grid-interfaced converters during meshed operation have not yet been investigated. To ensure reliable ST-fed grid, this paper develops a complete model of ST LV converter considering all the key elements for the meshed operation. System stability is assessed based on the developed model for different scenarios. The interactions between the ST and local grid converters are examined to provide comprehensive design guidelines for the meshed ST-fed grid. The control strategy and the theoretical analysis are validated by the simulation and experimental results.展开更多
基金the German Federal Ministry of Education and Research(BMBF)within the Kopernikus Project ENSURE“New ENergy grid StructURes for the German Energiewende”(03SFK1I0 and 03SFK1I0-2)the Ministry of Science,Research and the Arts of the State of Baden-Württemberg Nr.33−7533−30−10/67/1.
文摘In the last decades the voltage regulation has been challenged by the increase of power variability in the electric grid,due to the spread of non-dispatchable generation sources.This paper introduces a Smart Transformer(ST)-based Medium Voltage(MV)grid support by means of active power control in the ST-fed Low Voltage(LV)grid.The aim of the proposed strategy is to improve the voltage profile in MV grids before the operation of On-Load Tap Changer in the primary substation transformer,which needs tens of seconds.This is realized through reactive power injection by the AC/DC MV converter and simultaneous decrease of the active power consumption of voltage-dependent loads in ST-fed LV grid,controlling the ST output voltage.The last feature has two main effects:the first is to reduce the active power withdrawn from MV grid,and consequently the MV voltage drop caused by the active current component.At the same time,higher reactive power injection capability in the MV converter is unlocked,due to the lower active power demand.As result,the ST increases the voltage support in MV grid.The analysis and simulation results carried out in this paper show improvements compared to similar solutions,i.e.the only reactive power compensation.The impact of the proposed solution has been finally evaluated under different voltage-dependence of the loads in the LV grid.
基金supported by the National Natural Science Foundation of China under Grant 52377171.
文摘The Smart Transformer(ST)is a solid-state transformer with control and communication functionalities,interfacing medium voltage and low voltage grids.The ST can independently operate in a radial network configuration,and also in a meshed grid operation.The meshed operation has high potential to optimize the power flow in the network,avoiding or postponing the reinforcement of distribution grids.Nevertheless,the control and synchronization during the meshed operation are not trivial.The perturbation of the voltage in transition between the two operations is inevitable.This could lead to uncontrolled power flow and endanger the meshed operation.Moreover,the stability of the meshed grid has seldom been studied.To address these issues,this paper proposes a voltage control with power-based synchronization for the ST.This allows the universal operation of both radial and meshed grids,while ensuring smooth transition.Modeling and stability analysis of such a system are investigated to make sure of safe operation.Simulation and experimental results are provided to validate the effectiveness of the proposed control and theoretical analysis.
基金the German Federal Ministry of Education and Research(BMBF)within the Kopernikus Project ENSURE"New ENergy grid StructURes for the German Energiewende"(03SFK1I0-2)。
文摘Solid-state transformer-based smart transformer(ST)can provide the dc connectivity and advanced services to improve the grid performance and to increase the penetration of the power electronics interfaced resources(e.g.,distributed generators and electric vehicle charging stations)in modern electricity distribution grids.Since the ST is a new and effective paradigm of the electricity grid evolution to well understand the ST,this paper systematically presents the basic architecture and the typical control schemes of the ST and then the advanced services that ST can provide to improve the electricity grids performances in terms of the power flow control,power quality improvement,active damping and active contribution to improve distribution grid resilience by means of enabling autonomous microgrids operation as well as launching a restoration procedure following a general blackout.
基金supported in part by the National Natural Science Foundation of China under Grant 52377171in part by the Fundamental Research Funds for the Central Universities under Grant 2242024K40030.
文摘The Smart Transformer (ST) is a solid-state transformer with control and communication functionalities, interfacing medium voltage and low voltage (LV) grids. The ST can work in both ways: it can operate in a radial network independently, and it also provides meshed operation. In particular, a meshed ST-fed grid is able to optimize the power flow of the network, therefore largely avoiding the reinforcement of utilities. Though the ST can address system-level issues, challenges in terms of control and stability are encountered. The modeling as well as stability analysis of ST converter and its control for meshed operation have rarely been studied. More importantly, the interactions between ST and grid-interfaced converters during meshed operation have not yet been investigated. To ensure reliable ST-fed grid, this paper develops a complete model of ST LV converter considering all the key elements for the meshed operation. System stability is assessed based on the developed model for different scenarios. The interactions between the ST and local grid converters are examined to provide comprehensive design guidelines for the meshed ST-fed grid. The control strategy and the theoretical analysis are validated by the simulation and experimental results.
