This paper proposes a novel multi-pulse flexible-topology thyristor rectifier(FTTR) that can operate over a large voltage range while maintaining a low total harmonic distortion(THD) in the input current.The proposed multi-pulse FTTR has two operating modes:parallel mode and series mode.Irrespective of the mode in which it operates,the multi-pulse FTTR maintains the same pulses in the load current.To mitigate the harmonic injection into the AC mains,the topology-switching mechanism is then proposed.In addition,predictive current control is employed to achieve fast current response in both the transience and the transitions between modes.To verify the effectiveness of the multi-pulse FTTR as well as the control scheme,performance analysis based on an 18-pulse FTTR is investigated in detail,including fault tolerance evaluation,current THD analysis based on IEEE standard,and potential applications.Finally,a simulation model and the corresponding laboratory setup are developed.The results from both simulation and experiments demonstrate the feasibility of the proposed multi-pulse FTTR as well as the control scheme.
详细推导了中点钳位型三电平并网逆变器的状态空间模型,并在此基础上提出了一种有限集最优预测(finite set optimal predictive,FSOP)控制方法。该方法将三电平并网逆变器的27个开关矢量组成一个有限集,然后在有限集中选择使罚函数最优的开关矢量,其中的罚函数是由输出电流误差、中点不平衡电压和器件开关次数组成的加权和。文中给出了FSOP控制方法的流程图,并通过仿真和实验评估了该方法的控制性能。仿真和实验结果表明:与传统方法相比,FSOP控制方法的控制目标灵活,通过调整罚函数的加权系数就可以灵活方便地优化逆变器的综合性能;FSOP控制方法避免了传统方法中控制器加调制器的级联结构,在跟踪输出电流参考信号、平衡中点电压方面具有较快的响应速度。
等效瞬时电感算法是区分励磁涌流和故障电流的有效方法,但220 k V及以下电压等级的Y/△接线三相变压器多采用三相一体式结构,△侧环流难以获取,因而限制了该算法在此类变压器中的应用。提出一种计算环流的新方法。首先利用变压器等效电路的微分方程,推导出△侧环流和Y侧零序电流的比例关系。在磁通不饱和区域,Y侧对应相电流和环流相等,因而也和零序电流成比例。然后利用波形相关度理论,分别求取Y侧三相电流与零序电流的相关系数以区分磁通不饱和区域,证明至少可以获取一相长度足够的磁通不饱和区域。利用该段区域内的电流求出比例系数,进而可由Y侧零序电流求得△侧环流。最后通过MATLAB仿真验证了该方法求取△侧环流的准确性。该方法无需已知变压器参数,也无需控制合闸角,在一个工频周期内就能准确求取环流。
High pressure sodium （HPS） lamp has been widely used in street lighting applications because of its maturity, reliability, high lighting efficiency, long life-time, and low cost. Light emitting diode （LED） is expected as the next generation lighting source due to its continuously improving luminous efficacy, better color characteristic, and super long life-time. The two lighting sources may coexist in street lighting applications for a long time. A novel HPS and LED compatible driver is proposed which is rather suitable and flexible for driving HPS and LED in street lighting applications. The proposed driver combines the LLC and LCC resonant circuits into a flexible resonant tank. The flexible resonant tank may change to LLC or isolated LCC circuit according to the lighting source. It inherits the traditional HPS and LED drivers＇ zero voltage switching （ZVS） characteristics and dimmable function. The design of the proposed flexible resonant tank considers the requirements of both HPS and LED. The experiments of driving HPS and LED on a prototype driver show that the driver can drive the two lighting sources flexibly with high efficiency.
