This paper investigates the problem of synchronization for offset quadrature amplitude modulation based orthogonal frequency division multiplexing(OFDM/OQAM) systems based on the genetic algorithm. In order to increas...This paper investigates the problem of synchronization for offset quadrature amplitude modulation based orthogonal frequency division multiplexing(OFDM/OQAM) systems based on the genetic algorithm. In order to increase the spectrum efficiency,an improved preamble structure without guard symbols is derived at first. On this basis, instead of deriving the log likelihood function of power spectral density, joint estimation of the symbol timing offset and carrier frequency offset based on the preamble proposed is formulated into a bivariate optimization problem. After that, an improved genetic algorithm is used to find its global optimum solution. Conclusions can be drawn from simulation results that the proposed method has advantages in the joint estimation of synchronization.展开更多
在五相永磁同步电机(permanent magnet synchronous motor,PMSM)中,传统无差拍直接转矩和磁链控制(deadbeat direct torque and flux control,DB-DTFC)策略存在定子磁链和转矩耦合、计算量大以及电流谐波大等问题。基于此,提出一种基于...在五相永磁同步电机(permanent magnet synchronous motor,PMSM)中,传统无差拍直接转矩和磁链控制(deadbeat direct torque and flux control,DB-DTFC)策略存在定子磁链和转矩耦合、计算量大以及电流谐波大等问题。基于此,提出一种基于定子磁链定向的新型DB-DTFC策略。首先,在基于定子磁链定向坐标系上建立电压分量与定子磁链和转矩的关系,以实现定子磁链和转矩的解耦控制,进而提高转矩的动态性能。其次,将电流谐波抑制技术和载波脉宽调制技术相结合,以抑制3次谐波电流,进而降低定子磁链和转矩的脉动。最后,对传统和新型DB-DTFC策略进行实验比较分析。结果表明,该策略能降低定子磁链和转矩脉动、电流谐波和CPU计算量。展开更多
在直驱风电系统中,为了提高变流器的性能,该文提出了外环采用PI控制,内环采用无源控制的混合控制策略。根据主电路拓扑结构分别建立了在dq坐标系下的欧格-拉格朗日EL(Euler-Lagrange)模型和端口受控耗散哈密顿PCHD(port control Hamilto...在直驱风电系统中,为了提高变流器的性能,该文提出了外环采用PI控制,内环采用无源控制的混合控制策略。根据主电路拓扑结构分别建立了在dq坐标系下的欧格-拉格朗日EL(Euler-Lagrange)模型和端口受控耗散哈密顿PCHD(port control Hamiltonian with dissipation)模型。基于EL模型,采用了注入阻尼的方法,得到无源控制律;而基于PCHD模型,采用能量成形的方法,利用IDA-PBC(injecting dampingpassivity-based contro)控制算法设计无源控制器。仿真结果表明机侧变流器能够实现对转速的控制;网侧变流器实现直流电压跟踪控制、单位功率因数并网。实验验证了所提控制策略的可行性。展开更多
基金supported by the National Natural Science Foundation of China(61671468)。
文摘This paper investigates the problem of synchronization for offset quadrature amplitude modulation based orthogonal frequency division multiplexing(OFDM/OQAM) systems based on the genetic algorithm. In order to increase the spectrum efficiency,an improved preamble structure without guard symbols is derived at first. On this basis, instead of deriving the log likelihood function of power spectral density, joint estimation of the symbol timing offset and carrier frequency offset based on the preamble proposed is formulated into a bivariate optimization problem. After that, an improved genetic algorithm is used to find its global optimum solution. Conclusions can be drawn from simulation results that the proposed method has advantages in the joint estimation of synchronization.
文摘在五相永磁同步电机(permanent magnet synchronous motor,PMSM)中,传统无差拍直接转矩和磁链控制(deadbeat direct torque and flux control,DB-DTFC)策略存在定子磁链和转矩耦合、计算量大以及电流谐波大等问题。基于此,提出一种基于定子磁链定向的新型DB-DTFC策略。首先,在基于定子磁链定向坐标系上建立电压分量与定子磁链和转矩的关系,以实现定子磁链和转矩的解耦控制,进而提高转矩的动态性能。其次,将电流谐波抑制技术和载波脉宽调制技术相结合,以抑制3次谐波电流,进而降低定子磁链和转矩的脉动。最后,对传统和新型DB-DTFC策略进行实验比较分析。结果表明,该策略能降低定子磁链和转矩脉动、电流谐波和CPU计算量。
文摘在直驱风电系统中,为了提高变流器的性能,该文提出了外环采用PI控制,内环采用无源控制的混合控制策略。根据主电路拓扑结构分别建立了在dq坐标系下的欧格-拉格朗日EL(Euler-Lagrange)模型和端口受控耗散哈密顿PCHD(port control Hamiltonian with dissipation)模型。基于EL模型,采用了注入阻尼的方法,得到无源控制律;而基于PCHD模型,采用能量成形的方法,利用IDA-PBC(injecting dampingpassivity-based contro)控制算法设计无源控制器。仿真结果表明机侧变流器能够实现对转速的控制;网侧变流器实现直流电压跟踪控制、单位功率因数并网。实验验证了所提控制策略的可行性。
