风电变流器改进型断续脉宽调制策略

大功率风力发电变流器中,存在开关损耗和电流总谐波失真THD(total harmonic distortion)难以均衡的矛盾。如何优化调制方式,以提高系统效率,减小电流谐波,是大功率风电变流系统的核心技术之一。针对风电变流器宽频率、宽电压运行范围的特点,分析直驱风电变流器采用断续脉宽调制策略下的损耗和谐波性能,发现不同工况下主要关注指标不同,轻载时电能质量恶劣、开关损耗低,而重载时开关损耗严重、电能质量好;但是常用调制方式很难兼顾。为解决该问题,提出一种适用于永磁同步机直驱风电变流器的新型断续脉宽调制策略,该调制策略对开关损耗和THD的优化特性随变流器工作范围变化,实现不同工况下主要关注指标的优化。最后通过实验平台验证了该方案在重载时减小开关损耗,在轻载时降低电流谐波的有效性。

Improved Discontinuous Pulse Width Modulation Strategy for Wind Power Converters

For a high-power wind power converter, there is a contradiction between switching loss and the total harmonic distortion(THD) of current. How to optimize its modulation mode and thus improve the system efficiency and reduce the current harmonics is one of the core technologies of high-power wind power converter system. Considering the characteristics of wind power converters'' wide operating ranges of frequency and voltage, the loss and harmonic performance of direct-drive wind power converters under discontinuous pulse width modulation(DPWM) strategy is studied. It is found that the main indicators are different under different operating conditions:at light loads,the power quality is poor and the switching losses are small; at heavy loads,the power quality is good and the switching losses are large. However, common modulation methods are difficult to strike a balance between THD and switching losses. To solve this problem, a novel DPWM strategy is proposed for the direct-drive wind power converters of permanent magnet synchronous machines.Under this modulation strategy, the switching losses and optimal characteristics of THD vary with the operating range of the converter, which realizes the optimization of main indicators under different operating conditions. Finally, through an experimental platform, it was verified that the proposed scheme was effective to reduce the switching loss at heavy loads and reduce the current harmonics at light loads.