为了改善传统的电力电子变压器(power electronic transformer,PET)不适用于高电压、大功率电力系统的不足,提出将模块化多电平换流器(modular multilevel converter,MMC)应用于PET的输入级,以提高PET的电压和功率等级;输出级由三相全桥逆变器组成,且在输出级连接永磁同步电机,并提出基于(port controlled Hamiltonian with dis?sipation,PCHD)模型的无源性控制(passivity-based control,PBC)策略,可进一步应用于列车牵引、风力发电等系统.最后在仿真实验平台进行了电机空载运行、恒速运行、变速运行和负载转矩突变4种不同工况情况的实验分析,结果表明所提控制策略具有鲁棒性强和动态性能好等特点.
模块化多电平变流器(MMC)用于高压直流输电(HVDC)系统中时,通常采用PI控制方法,但这种策略存在参数选取繁杂、动态性能较差的缺点.为了提高高压直流输电(HVDC)系统的动态性能、简化参数选取,提出背靠背(B2B)型模块化多电平变流器-高压直流输电(MMC-HVDC)系统的Lyapunov控制策略.首先,建立B2B型MMC-HVDC数学模型;然后,设计Lyapunov函数控制策略;其次,在控制部分加入环流抑制、移相载波调制等,以完整地实现系统功能;最后,在Matlab/Simulink平台上验证了Lyapunov控制策略具有参数选择容易、动态性能优良的特点.
The Modular Multilevel Matrix Converter can realize the three-phase AC-AC transformation. Its outstanding advantages are easy to modularize, high reliability and low harmonic content, which can be used in high-voltage and large-capacity driven system. Aiming at the shortcomings of traditional PI control, such as slow stability, easy overshoot and poor dynamic performance, this paper proposes a new nonlinear Flatness-Based-Control strategy based on Differential Flatness theory, which has the advantages of fast response, no overshoot, no static error in tracking and high dynamic performance. It can greatly improve the control effect of M3C input-side and output-side current. And under the operating conditions of input-side frequency changes, the Flatness-Based-Control strategy can still maintain the extremely low impact of the system, and the overall control effect is better. At last, the correctness and superiority of this method are verified by experiments under different working conditions.
MMC-DVR combined with dynamic voltage regulator（DVR）and modular multilevel converter（MMC）can be used to solve the problem of sag/swell compensation for medium and high voltages. Since MMC-DVR is a non-linear system，the compensation effect of linear control methods such as PID commonly used in DVR systems is not satisfactory. To this end，this paper proposes a passive nonlinear control method for the MMC-DVR system，which can be deeply integrated in the wind farm grid-connected system，and can solve the negative problems such as power quality degradation. First，the circuit topology and working principle of MMC-DVR are introduced，and the mathematical model under the static and rotating coordinate system is established. Then，the passive control method is proposed to solve the problem. Finally，the MMC-DVR control system is built on Matlab/Simulink software experimental platform， and the experimental results verify the feasibility and superiority of the passive nonlinear control strategy proposed in this paper .
