大功率高精度快动态响应模块化多电平变换器研究

Higher energy, higher intensity, higher quality ion beam and higher beam transmission efficiency is the eternal goal of the development of heavy ion accelerator, which requires accelerator magnet excitation power supply has higher power level, higher control accuracy and faster response speed. The switch converter based on pulse width modulation (PWM) has gradually become the mainstream of ion accelerator excitation power supply, and the power level and response speed of excitation power mainly depend on power devices and topology. At present, there is still a contradiction between the power device capacity and the switching frequency, it is a good solution to realize the high power output through the series and parallel connection of the medium and small power converters. In this project, we will study a modular multilevel converter technology, which is highly integrated by multiple low power switching elements (not series parallel connection of small power converters) and can improve its power level of the converter without reducing the switching frequency, and various control and modulation strategies based on this technology will also be studied, all of these will make accelerator power supply power factor, net side current controllable and high power, high precision and fast response output to meet tens of thousands of amperes per second rising rate and less than ±1×10-4 high tracking precision of a new generation ions accelerator power supply. It will also do research and technical reserves for the future development of the ion accelerator at the same time.

更高能量、更高流强、更高品质的离子束以及更高的加速效率是离子加速器发展永恒的目标，这就要求加速器磁铁励磁电源具有更高的功率等级、更高的控制精度及更快的响应速度。基于脉冲宽度调制(PWM)的开关变换器已逐渐成为离子加速器励磁电源的主流，励磁电源的功率等级和响应速度主要取决于功率器件及拓扑结构。目前，功率器件容量和开关频率之间依然存在着矛盾，通过中小功率变换器的串并联实现大功率输出是一种很好的解决方案。本项目研究一种模块化多电平变换技术，该方法通过多个小功率开关元件（不是小功率变换器的串并联）进行高度集成化叠加，能够在不降低开关频率的同时提升变换器功率等级，并研究基于此技术的多种控制和调制策略，实现离子加速器电源网侧电流、功率因数可控，以及大功率、高精度、快响应输出，以满足新一代离子加速器电源每秒数万安培上升速率和小于±1×10-4高跟踪精度等要求，同时为未来离子加速器的发展做预研和技术储备。

离子加速器总是在追求更高的能量、束流品质和束流传输效率。这一趋势必然要求其电源子系统也向着更大电流、更高电压、更高精度、更快动态响应的方向发展。大电流、高电压、快电流变化率意味着电源功率等级、动态响应和宽电压范围下输出精度要求的提高，常规两电平电源设计已很难满足要求。磁铁负载具有阻感特性，其在脉冲电流波形上升段吸收的巨大感性无功会对电网造成周期性强冲击；下降段回馈的能量又需合理地存储或泄放，对电源的设计提出了新的挑战。. 为解决上述问题，在立项与研究之初，本项目以前级模块化多电平整流加后级模块化多电平逆变拓扑为研究对象。但研究过程中发现其只适用于输出为对称交流电流波形的工况，不适用于输出直流或单向脉冲电流波形。为此，调整研究方向为：非对称H桥级联多电平和悬浮型H桥多电平拓扑，以实现电源高压、大电流、快电流变化率输出。非对称H桥级联多电平采用高低压源H桥功率单元串联工作，可通过高低压源功率单元的模块化实现整机模块化设计；悬浮型H桥级联多电平采用单有源整流前级加多后级H桥串联拓扑，更方便电源进行模块化设计。. 目前，在非对称H桥级联多电平拓扑方面，利用近代物理研究所现有电源样机，开发了基于FPGA+DSP的整机控制算法；实现了电流峰值3900A、周期3Hz、40000A/s快脉冲波形输出，整周期跟踪误差小于±1×10-4。在悬浮型H桥级联多电平方面，搭建了小功率电源样机，实现该拓扑下200A快脉冲波形输出，正在进一步优化指标。. 本项目的研究成果为未来大电流、高电压、快电流变化率、快动态响应重离子加速器脉冲电源的设计与研制提供了参考。