矩阵整流式大电流磁铁电源拓扑特性及调制策略的研究

Field system, as a vital part of synchrotron, is composed of magnet and magnet power supply. During the development process of particle accelerator, superconducting magnet and power technology are crucial for the magnetic fields system. The accelerator field system is required to have lower ripple level and higher precision of the magnetic field, such indicators are directly depended on current ripple and tracking error of magnet power supply. However, there are some problems such as low input power factor and high THD (total harmonics distortion) in input current for accelerator magnet power supplies which use traditional phase-controlled or uncontrolled three-phase bridge rectifier to carry out AC/DC converting. Moreover, for superconducting power supply, how to feedback energy to grid is also need to be carried out related research. In view of the above problems existing in accelerator power supply technology, as a solution of topology of the main circuit, matrix converter is applied to magnet power supply and the feasibility of solution will be discussed in this project. As to modulation strategy of matrix converter, the control strategy of bidirectional current of accelerator power is presented. While the frequency instability of hysteresis current control is discussed in depth and some constructive results are obtained. Three topologies of matrix rectifier (MR) of accelerator power, direct type MR, magnetic coupling type MR and pre-stage voltage regulating type MR, are proposed, furthermore, characteristics of various topologies and corresponding modulation strategies are studied. With the researched project, not only a novel feasible implementation for special power supplies of accelerators be provided, but also technical preparation for future development of the accelerator be made.

磁场系统作为加速器的重要部分，由磁铁电源与磁铁共同组成。超导磁铁和电源技术是粒子加速器发展过程中磁场系统的关键技术。磁场系统要求低纹波和高精度，而这取决于磁铁电源的电流纹波和跟踪误差。加速器磁铁电源中交流/直流环节一般采用成熟的相控整流或不控整流原理，但是这种整流模式使得磁铁电源的网侧功率因数不高且给电网带来谐波污染。此外，对超导磁铁电源实现能量回馈电网的问题也亟需开展相关研究。本项目针对目前加速器电源技术存在的上述问题，拟采用矩阵变换器作为加速器电源主电路拓扑的解决方案并对其可行性进行研究；提出适用于加速器电源的双向电流控制策略，对其中滞环控制的频率不稳定问题进行深入探讨，得到有建设性的结果；提出三种加速器电源可用的矩阵整流器拓扑结构，并对各种拓扑的特性及相应调制策略进行研究。通过本项目的研究，为加速器特种电源技术提供一种新颖的可行的实现方案，也可为今后加速器的进一步发展做技术储备。

电源技术和超导磁铁是重离子加速器发展过程中磁场系统的关键技术。磁场系统的性能取决于磁铁电源的相关参数如电流纹波和跟踪误差等。加速器磁铁电源中一般采用成熟的相控整流或不控整流技术来完成交流/直流变换环节，但是这种整流模式使得磁铁电源的网侧功率因数不高且给电网带谐波污染。此外，对超导磁铁脉冲电源能量回馈电网的问题也亟需开展相关研究。矩阵式变换器可以运行于整流或脉冲输出状态，直流侧无需大容量储能元件，装置体积较小，可以实现输入电流正弦化，从而达到较高的功率因数。矩阵式变换器由于采用双向开关，可实现能量双向流动，利用这一特性可将磁铁多余能量回馈给电网。.　　本项目研究了一种全新的三相/一相矩阵式变换器（31MC）调制策略，即采用输入电流空间矢量调制和准固定频率输出电流滞回跟踪相结合的方式。既可改善网侧电流谐波情况，也可保证负载侧电流跟踪给定电流波形的同时修正开关频率的不稳定。对该策略进行了仿真研究，仿真结果验证了开关频率和滞环的环宽之间的负相关特性，通过给误差乘环宽调节因子，可以调节滞环比较器的环宽，从而实现对开关频率的调节。本项目进而提出了三种将矩阵整流器应用于加速器电源的拓扑方案：直接耦合型矩阵式整流器、磁耦合型矩阵式整流器、前级调压型矩阵式整流器。以方案二为例，建立了相应的主电路和控制策略的原理模型并进行仿真实验，结果验证了　该拓扑方案可以实现稳流输出，并且输入功率因数较为理想。为进一步研究矩阵式整流器的拓扑及性能，对三种拓扑方案进行了样机测试，并对实验结果和性能进行分析。.　　由于加速器电源的性能很大程度上取决于主电路拓扑和控制策略的选择，将矩阵变换器应用于重离子加速器磁铁电源是其中一个有力的、潜在的解决方案。矩阵变换器通用性和扩展性非常好，略作改动就可以应用于不同场合的磁铁电源。在强流重离子加速器装置（HIAF）超导磁铁电源项目中，矩阵变换技术有望大展身手。