There are issues with flexible DC transmission system such as a lack of control freedom over power flow.In order to tackle these issues,a DC power flow controller(DCPFC)is incorporated into a multi-terminal,flexible D...There are issues with flexible DC transmission system such as a lack of control freedom over power flow.In order to tackle these issues,a DC power flow controller(DCPFC)is incorporated into a multi-terminal,flexible DC power grid.In recent years,a multi-port DC power flow controller based on a modular multi-level converter has become a focal point of research due to its simple structure and robust scalability.This work proposes a model predictive control(MPC)strategy for multi-port interline DC power flow controllers in order to improve their steady-state dynamic performance.Initially,the mathematical model of a multi-terminal DC power grid with a multi-port interline DC power flow controller is developed,and the relationship between each regulated variable and control variable is determined;The power flow controller is then discretized,and the cost function and weight factor are built with numerous control objectives.Sub module sorting method and nearest level approximation modulation regulate the power flow controller;Lastly,theMATLAB/Simulink simulation platformis used to verify the correctness of the establishedmathematicalmodel and the control performance of the suggestedMPC strategy.Finally,it is demonstrated that the control strategy possesses the benefits of robust dynamic performance,multiobjective control,and a simple structure.展开更多
To realize effective utilization of renewable energy sources,a novel polymorphic topology with hybrid control strategy based LLC resonant converter was analyzed and designed in this paper.By combining the merits of a ...To realize effective utilization of renewable energy sources,a novel polymorphic topology with hybrid control strategy based LLC resonant converter was analyzed and designed in this paper.By combining the merits of a full bridge LLC resonant converter,three-level half bridge LLC resonant converter,and variable frequency control mode,the converter realizes an intelligent estimation of input voltage by automatically changing its internal cir-cuit topology.Under this control strategy,different input voltages determine different operation modes.This is achieved in full bridge LLC mode when the input voltage is low.If the input voltage rises to a certain level,it operates in three-level half bridge LLC mode.These switches are digital and entirely carried out by the DSP(Digi-tal Signal Processor),which means that an auxiliary circuit is unnecessary,where a simple strategy of software modification can be utilized.Experimental results of a 500W prototype with 100V~600V input voltage and full load efficiency of up to 92%are developed to verify feasibility and practicability.This type of converter is suitable for applications with an ultra-wide input voltage range,such as wind turbines,photovoltaic generators,bioenergy,and other renewable energy sources.展开更多
A time-inconsistent linear-quadratic optimal control problem for stochastic differential equations is studied.We introduce conditions where the control cost weighting matrix is possibly singular.Under such conditions,...A time-inconsistent linear-quadratic optimal control problem for stochastic differential equations is studied.We introduce conditions where the control cost weighting matrix is possibly singular.Under such conditions,we obtain a family of closed-loop equilibrium strategies via multi-person differential games.This result extends Yong’s work(2017) in the case of stochastic differential equations,where a unique closed-loop equilibrium strategy can be derived under standard conditions(namely,the control cost weighting matrix is uniformly positive definite,and the other weighting coefficients are positive semidefinite).展开更多
Multilevel unified power flow controllers(ML-UPFCs)aim to improve grid stability,power quality,and fault management.This approach is particularly beneficial for renewable energy systems connected to a grid,where effic...Multilevel unified power flow controllers(ML-UPFCs)aim to improve grid stability,power quality,and fault management.This approach is particularly beneficial for renewable energy systems connected to a grid,where efficient power flow and robust fault handling are crucial for maintaining system reliability.However,current grid-integrated systems face challenges such as inefficient fault management,harmonic distortions,and instability when dealing with nonlinear loads.Existing control strategies often lack the flexibility and optimization required to handle these issues effectively in dynamic grid environments.Therefore,the proposed methodology involves a multistep control strategy to optimize the integration of solar photovoltaic(SPV)systems with MLUPFCs.Initially,the SPV array generates direct current(DC)power,which is optimized using a perturb and observe maximum power point tracking controller.The DC-to-DC boost converter then steps up the voltage for input to a voltage source inverter(VSI)or voltage source converter(VSC).The VSI/VSC,enhanced by greedy control-based monarch butterfly optimization,converts DC to AC while minimizing harmonic distortion.The power is then fed into the grid,which supplies sensitive critical and nonlinear loads.Three-phase fault detection mechanisms and series transformers manage the power flow and fault conditions.Furthermore,the ML-UPFC,controlled by a random forest cuckoo search optimization algorithm,enhances the fault ride-through capabilities and power regulation.Additional transformers and a shunt transformer optimize the voltage levels and reactive power management,ensuring stable and high-quality power delivery to both sensitive and nonlinear loads.Finally,the proposed approach addresses power flow optimization,fault mitigation,and nonlinear load management with the aim of enhancing grid stability and efficiency.展开更多
基金funded by National Natural Science Foundation of China (52177074).
文摘There are issues with flexible DC transmission system such as a lack of control freedom over power flow.In order to tackle these issues,a DC power flow controller(DCPFC)is incorporated into a multi-terminal,flexible DC power grid.In recent years,a multi-port DC power flow controller based on a modular multi-level converter has become a focal point of research due to its simple structure and robust scalability.This work proposes a model predictive control(MPC)strategy for multi-port interline DC power flow controllers in order to improve their steady-state dynamic performance.Initially,the mathematical model of a multi-terminal DC power grid with a multi-port interline DC power flow controller is developed,and the relationship between each regulated variable and control variable is determined;The power flow controller is then discretized,and the cost function and weight factor are built with numerous control objectives.Sub module sorting method and nearest level approximation modulation regulate the power flow controller;Lastly,theMATLAB/Simulink simulation platformis used to verify the correctness of the establishedmathematicalmodel and the control performance of the suggestedMPC strategy.Finally,it is demonstrated that the control strategy possesses the benefits of robust dynamic performance,multiobjective control,and a simple structure.
文摘To realize effective utilization of renewable energy sources,a novel polymorphic topology with hybrid control strategy based LLC resonant converter was analyzed and designed in this paper.By combining the merits of a full bridge LLC resonant converter,three-level half bridge LLC resonant converter,and variable frequency control mode,the converter realizes an intelligent estimation of input voltage by automatically changing its internal cir-cuit topology.Under this control strategy,different input voltages determine different operation modes.This is achieved in full bridge LLC mode when the input voltage is low.If the input voltage rises to a certain level,it operates in three-level half bridge LLC mode.These switches are digital and entirely carried out by the DSP(Digi-tal Signal Processor),which means that an auxiliary circuit is unnecessary,where a simple strategy of software modification can be utilized.Experimental results of a 500W prototype with 100V~600V input voltage and full load efficiency of up to 92%are developed to verify feasibility and practicability.This type of converter is suitable for applications with an ultra-wide input voltage range,such as wind turbines,photovoltaic generators,bioenergy,and other renewable energy sources.
基金supported by National Natural Science Foundation of China (Grant Nos.12025105, 11971334 and 11931011)the Chang Jiang Scholars Program and the Science Development Project of Sichuan University (Grant Nos. 2020SCUNL101 and 2020SCUNL201)。
文摘A time-inconsistent linear-quadratic optimal control problem for stochastic differential equations is studied.We introduce conditions where the control cost weighting matrix is possibly singular.Under such conditions,we obtain a family of closed-loop equilibrium strategies via multi-person differential games.This result extends Yong’s work(2017) in the case of stochastic differential equations,where a unique closed-loop equilibrium strategy can be derived under standard conditions(namely,the control cost weighting matrix is uniformly positive definite,and the other weighting coefficients are positive semidefinite).
文摘Multilevel unified power flow controllers(ML-UPFCs)aim to improve grid stability,power quality,and fault management.This approach is particularly beneficial for renewable energy systems connected to a grid,where efficient power flow and robust fault handling are crucial for maintaining system reliability.However,current grid-integrated systems face challenges such as inefficient fault management,harmonic distortions,and instability when dealing with nonlinear loads.Existing control strategies often lack the flexibility and optimization required to handle these issues effectively in dynamic grid environments.Therefore,the proposed methodology involves a multistep control strategy to optimize the integration of solar photovoltaic(SPV)systems with MLUPFCs.Initially,the SPV array generates direct current(DC)power,which is optimized using a perturb and observe maximum power point tracking controller.The DC-to-DC boost converter then steps up the voltage for input to a voltage source inverter(VSI)or voltage source converter(VSC).The VSI/VSC,enhanced by greedy control-based monarch butterfly optimization,converts DC to AC while minimizing harmonic distortion.The power is then fed into the grid,which supplies sensitive critical and nonlinear loads.Three-phase fault detection mechanisms and series transformers manage the power flow and fault conditions.Furthermore,the ML-UPFC,controlled by a random forest cuckoo search optimization algorithm,enhances the fault ride-through capabilities and power regulation.Additional transformers and a shunt transformer optimize the voltage levels and reactive power management,ensuring stable and high-quality power delivery to both sensitive and nonlinear loads.Finally,the proposed approach addresses power flow optimization,fault mitigation,and nonlinear load management with the aim of enhancing grid stability and efficiency.
