The high potentiality of integrating renewable energies,such as photovoltaic,into a modern electrical microgrid system,using DC-to-DC converters,raises some issues associated with controller loop design and system sta...The high potentiality of integrating renewable energies,such as photovoltaic,into a modern electrical microgrid system,using DC-to-DC converters,raises some issues associated with controller loop design and system stability.The generalized state space average model(GSSAM)concept was consequently introduced to design a DC-to-DC converter controller in order to evaluate DC-to-DC converter performance and to conduct stability studies.This paper presents a GSSAM for parallel DC-to-DC converters,namely:buck,boost,and buck-boost converters.The rationale of this study is that modern electrical systems,such as DC networks,hybrid microgrids,and electric ships,are formed by parallel DC-to-DC converters with separate DC input sources.Therefore,this paper proposes a GSSAM for any number of parallel DC-to-DC converters.The proposed GSSAM is validated and investigated in a time-domain simulation environment,namely a MATLAB/SIMULINK.The study compares the steady-state,transient,and oscillatory performance of the state-space average model with a fully detailed switching model.展开更多
Modelling of bidirectional full bridge DC-DC converter as one of the most applicable converters has received significant attention. Mathematical modelling reduces the simulation time in comparison with detailed circui...Modelling of bidirectional full bridge DC-DC converter as one of the most applicable converters has received significant attention. Mathematical modelling reduces the simulation time in comparison with detailed circuit response;moreover it is convenient for controller design purpose. Due to simple and effective methodology, average state space is the most common method among the modelling methods. In this paper a bidirectional full bridge converter is modelled by average state space and for each mode of operations a controller is designed. Attained mathematical model results are in a close agreement with detailed circuit simulation.展开更多
This paper delineates a conventional buck converter controlled by optimized PID controller where Genetic Algorithm (GA) is employed with a view to enhancing the performance by analyzing the performance parameters. Gen...This paper delineates a conventional buck converter controlled by optimized PID controller where Genetic Algorithm (GA) is employed with a view to enhancing the performance by analyzing the performance parameters. Genetic Algorithm is a probabilistic search algorithm which is substantially used as an optimization technique in power electronics. A bunch of modifications have already been introduced to enhance the performance depending upon the applications. However, in this paper, modified genetic algorithm has been used in order to tune the key parameters in the converter. Hence, an analysis is carried out where the performance of the converter is illustrated in terms of rise time, settling time and percentage of overshoot by deploying GA based PID controller and the overall comparative study is presented. Responses of the overall system are accumulated through rigorous simulation in MATLAB environment.展开更多
基于广义状态空间平均法,利用脉冲频率调制-脉冲宽度调制(pulse frequency modulation-pulse width modulation,PFM+PWM)调制提供的双自由度提出一种可以同时调节输出电压以及实现开关器件主动软开关的控制策略,可以根据器件主体损耗情...基于广义状态空间平均法,利用脉冲频率调制-脉冲宽度调制(pulse frequency modulation-pulse width modulation,PFM+PWM)调制提供的双自由度提出一种可以同时调节输出电压以及实现开关器件主动软开关的控制策略,可以根据器件主体损耗情况“主动”切换软开关模式,兼顾整体效率提升与负载调节范围的扩展。分析全桥型串联谐振直流变换器工作频率高于谐振频率时的3种运行模式,并通过谐振腔参数设计避免特殊断续电流模式的发生;通过广义状态空间平均法建立包含调制环节在内的系统基波截断小信号模型,其数值扫频结果与物理模型展现出极高的精确度,并能精确反映拍频极点;定义反映多输入多输出系统能控程度的灵敏度矩阵,依据此设计实现输出电压调节及主动软开关的双链路线性控制策略。MATLAB/Simulink仿真及样机实验验证表明,所提控制相比传统脉冲频率调制具备更高的整体效率以及更宽的负载调节范围。展开更多
LLC谐振变换器在航空航天领域中广泛应用,但LLC谐振变换器固有的非线性特性及输出“小纹波”易造成系统失稳。为准确分析LLC谐振变换器非线性特性及输出“小纹波”问题,引入广义状态空间平均(generalized state space averaging, GSSA)...LLC谐振变换器在航空航天领域中广泛应用,但LLC谐振变换器固有的非线性特性及输出“小纹波”易造成系统失稳。为准确分析LLC谐振变换器非线性特性及输出“小纹波”问题,引入广义状态空间平均(generalized state space averaging, GSSA)理论对LLC谐振变换器进行建模,将时域非线性状态空间模型转化为GSSA模型。并推导基于GSSA理论的闭环系统小信号模型。通过特征值分析法及Nyquist曲线对元件参数、控制参数及参数耦合对系统稳定性影响进行分析,再利用仿真对模型及理论分析进行验证。仿真结果表明,建立的广义状态空间平均模型可以考虑到系统中“小纹波”因素,具有更高的精度。稳定性理论分析结果与稳定性分析仿真验证结果一致。展开更多
High voltage fracturing technology was widely used in the field of reservoir reconstruction due to its advantages of being clean, pollution-free, and high-efficiency. However, high-frequency circuit oscillation occurs...High voltage fracturing technology was widely used in the field of reservoir reconstruction due to its advantages of being clean, pollution-free, and high-efficiency. However, high-frequency circuit oscillation occurs during the underwater high voltage pulse discharge process, which brings security risks to the stability of the pulse fracturing system. In order to solve this problem, an underwater pulse power discharge system was established, the circuit oscillation generation conditions were analyzed and the circuit oscillation suppression method was proposed. Firstly, the system structure was introduced and the charging model of the energy storage capacitor was established by the state space average method. Next, the electrode high-voltage breakdown model was established through COMSOL software, the electrode breakdown process was analyzed according to the electron density distribution image, and the plasma channel impedance was estimated based on the conductivity simulation results. Then the underwater pulse power discharge process and the circuit oscillation generation condition were analyzed, and the circuit oscillation suppression strategy of using the thyristor to replace the gas spark switch was proposed. Finally, laboratory experiments were carried out to verify the precision of the theoretical model and the suppression effect of circuit oscillation. The experimental results show that the voltage variation of the energy storage capacitor, the impedance change of the pulse power discharge process, and the equivalent circuit in each discharge stage were consistent with the theoretical model. The proposed oscillation suppression strategy cannot only prevent the damage caused by circuit oscillation but also reduce the damping oscillation time by77.1%, which can greatly improve the stability of the system. This research has potential application value in the field of underwater pulse power discharge for reservoir reconstruction.展开更多
文摘The high potentiality of integrating renewable energies,such as photovoltaic,into a modern electrical microgrid system,using DC-to-DC converters,raises some issues associated with controller loop design and system stability.The generalized state space average model(GSSAM)concept was consequently introduced to design a DC-to-DC converter controller in order to evaluate DC-to-DC converter performance and to conduct stability studies.This paper presents a GSSAM for parallel DC-to-DC converters,namely:buck,boost,and buck-boost converters.The rationale of this study is that modern electrical systems,such as DC networks,hybrid microgrids,and electric ships,are formed by parallel DC-to-DC converters with separate DC input sources.Therefore,this paper proposes a GSSAM for any number of parallel DC-to-DC converters.The proposed GSSAM is validated and investigated in a time-domain simulation environment,namely a MATLAB/SIMULINK.The study compares the steady-state,transient,and oscillatory performance of the state-space average model with a fully detailed switching model.
文摘Modelling of bidirectional full bridge DC-DC converter as one of the most applicable converters has received significant attention. Mathematical modelling reduces the simulation time in comparison with detailed circuit response;moreover it is convenient for controller design purpose. Due to simple and effective methodology, average state space is the most common method among the modelling methods. In this paper a bidirectional full bridge converter is modelled by average state space and for each mode of operations a controller is designed. Attained mathematical model results are in a close agreement with detailed circuit simulation.
文摘This paper delineates a conventional buck converter controlled by optimized PID controller where Genetic Algorithm (GA) is employed with a view to enhancing the performance by analyzing the performance parameters. Genetic Algorithm is a probabilistic search algorithm which is substantially used as an optimization technique in power electronics. A bunch of modifications have already been introduced to enhance the performance depending upon the applications. However, in this paper, modified genetic algorithm has been used in order to tune the key parameters in the converter. Hence, an analysis is carried out where the performance of the converter is illustrated in terms of rise time, settling time and percentage of overshoot by deploying GA based PID controller and the overall comparative study is presented. Responses of the overall system are accumulated through rigorous simulation in MATLAB environment.
文摘基于广义状态空间平均法,利用脉冲频率调制-脉冲宽度调制(pulse frequency modulation-pulse width modulation,PFM+PWM)调制提供的双自由度提出一种可以同时调节输出电压以及实现开关器件主动软开关的控制策略,可以根据器件主体损耗情况“主动”切换软开关模式,兼顾整体效率提升与负载调节范围的扩展。分析全桥型串联谐振直流变换器工作频率高于谐振频率时的3种运行模式,并通过谐振腔参数设计避免特殊断续电流模式的发生;通过广义状态空间平均法建立包含调制环节在内的系统基波截断小信号模型,其数值扫频结果与物理模型展现出极高的精确度,并能精确反映拍频极点;定义反映多输入多输出系统能控程度的灵敏度矩阵,依据此设计实现输出电压调节及主动软开关的双链路线性控制策略。MATLAB/Simulink仿真及样机实验验证表明,所提控制相比传统脉冲频率调制具备更高的整体效率以及更宽的负载调节范围。
文摘LLC谐振变换器在航空航天领域中广泛应用,但LLC谐振变换器固有的非线性特性及输出“小纹波”易造成系统失稳。为准确分析LLC谐振变换器非线性特性及输出“小纹波”问题,引入广义状态空间平均(generalized state space averaging, GSSA)理论对LLC谐振变换器进行建模,将时域非线性状态空间模型转化为GSSA模型。并推导基于GSSA理论的闭环系统小信号模型。通过特征值分析法及Nyquist曲线对元件参数、控制参数及参数耦合对系统稳定性影响进行分析,再利用仿真对模型及理论分析进行验证。仿真结果表明,建立的广义状态空间平均模型可以考虑到系统中“小纹波”因素,具有更高的精度。稳定性理论分析结果与稳定性分析仿真验证结果一致。
基金financially supported by the National Science and Technology Major Project(No.2016ZX05034004)。
文摘High voltage fracturing technology was widely used in the field of reservoir reconstruction due to its advantages of being clean, pollution-free, and high-efficiency. However, high-frequency circuit oscillation occurs during the underwater high voltage pulse discharge process, which brings security risks to the stability of the pulse fracturing system. In order to solve this problem, an underwater pulse power discharge system was established, the circuit oscillation generation conditions were analyzed and the circuit oscillation suppression method was proposed. Firstly, the system structure was introduced and the charging model of the energy storage capacitor was established by the state space average method. Next, the electrode high-voltage breakdown model was established through COMSOL software, the electrode breakdown process was analyzed according to the electron density distribution image, and the plasma channel impedance was estimated based on the conductivity simulation results. Then the underwater pulse power discharge process and the circuit oscillation generation condition were analyzed, and the circuit oscillation suppression strategy of using the thyristor to replace the gas spark switch was proposed. Finally, laboratory experiments were carried out to verify the precision of the theoretical model and the suppression effect of circuit oscillation. The experimental results show that the voltage variation of the energy storage capacitor, the impedance change of the pulse power discharge process, and the equivalent circuit in each discharge stage were consistent with the theoretical model. The proposed oscillation suppression strategy cannot only prevent the damage caused by circuit oscillation but also reduce the damping oscillation time by77.1%, which can greatly improve the stability of the system. This research has potential application value in the field of underwater pulse power discharge for reservoir reconstruction.
