增强型半准Z源直驱永磁风电系统机侧谐波特性分析及抑制方法研究

Impedance source direct-driven permanent magnet wind power generation system (WPGS) with the advantage of single-stage control, allowing inverter shoot-through, without the need to insert the dead-time and so on. The impedance direct-driven permanent magnet WPGS provides a new way to further improve the reliability of the grid-connection and reduce the system cost. However, the generator stator current gets distorted with unacceptable levels of total harmonic distortion (THD), because impedance-source wind power generation system using the three-phase diode rectifier. In this project, a novel topology of enhanced half quasi-Z-source direct-driven permanent magnet WPGS will be proposed, considering two key issues of stator current harmonics and boosting capability. Then combined field - circuit coupled model and AC-DC mixture dynamic model will be built. The reason of the stator current’s high total harmonic distortion (THD) phenomenon will be analyzed in detail. The relationship between parameters of impedance source network, shoot-through duty cycle, equivalent switching frequency, capacitor voltage of impedance source network and THD of stator current will be researched. A novel stator current harmonic suppression method based on variable weight coefficient fitting shoot-through duty cycle control and new six-stage STSVPWM strategy will be proposed to improve the safety, stability and reliability of the enhanced half quasi-Z-source direct-driven permanent magnet WPGS. This project will provide theoretical and technical support for the development of the impedance source direct-driven permanent magnet WPGS, which is with important scientific significance and research value.

阻抗源直驱永磁风电系统具有单级控制、允许逆变桥臂直通、无需插入死区时间等优势，为进一步提高并网可靠性和降低系统成本提供了一种新思路。然而，该系统机侧常采用三相不可控整流器，由此产生的发电机定子电流谐波会增大发电机的损耗和转矩脉动。本项目综合考虑发电机定子电流谐波抑制可行性和系统升压能力，提出一种增强型半准Z源直驱永磁风力发电变流系统拓扑结构。建立该系统的交直流混合场路联合动态模型，分析变转速下发电机定子电流谐波的产生机理和不同调制策略对其的影响，研究阻抗源网络参数、直通占空比、等效直通开关频率、阻抗源网络电容电压与发电机定子电流谐波的量化关系，提出一种基于时变权重系数拟合直通占空比控制和新型六段式STSVPWM策略的发电机定子电流谐波抑制方法，提高增强型半准Z源直驱永磁风电系统的安全性、稳定性和可靠性。为阻抗源直驱永磁风电系统的发展提供理论指导与关键技术支撑，具有重要的科学意义和研究价值。

阻抗源逆变器具有单级控制、允许逆变桥臂直通、无需插入死区时间等优势，有望在直驱永磁风力发电系统中得到大规模应用。然而，该系统机侧常采用三相不可控整流器，由此产生的发电机定子电流谐波会降低系统的稳定性和可靠性。为此，本项目研究了以下内容：1) 提出了一种增强型半准Z源逆变器，并将其应用于直驱永磁风力发电变流系统，研究了该拓扑的升压能力、小信号模型、阻抗源网络器件应力及主要参数的设计。2) 提出了一种变直通占空比控制方法，对增强型半准Z源逆变器的直通占空比进行折中，使永磁同步风力发电机三相定子电流都尽可能接近正弦波，降低了发电机的定子电流谐波。3) 提出了一种高等效开关频率调制策略，每个周期内只用3个参考信号来生成栅极信号，开关信号在每个基频的部分周期内被钳位到正极或负极，提升了变流器的等效开关频率。4) 提出了一种变权重参数模型预测虚拟同步机控制策略，协调全局可行解和局部最优解在算法中的配比权重，确保阻抗源逆变器升压需求的同时充分发挥虚拟同步风电机组短时功率支撑作用。项目的实施将对推进直驱永磁风力发电变流技术的发展和完善具有重要的科学意义。