非理想电网状态下三相并网变换器的谐波抑制策略

发布时间：2018-04-30 03:13

本文选题：并网变换器 + 可再生能源　；参考：《哈尔滨工业大学》2014年硕士论文

【摘要】：为了解决全球范围内的能源短缺和环境污染应运而生的可再生能源发电系统发展势头迅猛。并网变换器负责可再生能源与电网之间的能量交换，在整个可再生能源发电系统中居于核心地位。鉴于电力电子器件的广泛应用，电网污染问题越来越严重。因此，有必要在非理想电网状态下，对并网变换器的控制策略进行深入地研究。本文针对并网变换器进行研究关键问题有：电网正序电压同步，并网电流谐波抑制，系统有功功率和直流电压波动。电网正序电压矢量角是可再生能源发电系统能够正常接入电网所需具备的最基本也是最重要的信息，锁相环是得到此信息的有效方式。本文首先分析了锁相环的基本原理，然后分析了锁相环的改进方式，根据分析结果提出了两相静止坐标系下的改进复数滤波器和基于滑动戈泽尔变换的锁相环。通过仿真验证了改进复数滤波器能够快速准确地分离出电网三相电压的正负序分量，并能够在一定程度上对电网电压的谐波进行衰减；验证了基于滑动戈泽尔变换的锁相环能够在电网电压畸变时快速、准确地锁相，并在电网电压的频率在小范围偏移时仍然能够有效地工作。并网变换器流入（出）电网的电流谐波含量需要满足标准，而并网电流的谐波大多来自于周期性的扰动。本文首先分析了三相PWM并网变换器电流谐波来源，，介绍了适用于抑制周期性扰动的重复控制；然后针对实际的硬件系统参数，设计了重复控制器；最后仿真验证了在两相静止坐标系下使用重复控制的确能够有效地抑制电网电压谐波带来的周期性扰动。当三相并网变换器工作在整流状态时，稳定的直流母线电压既能保证直流负载稳定工作，又能确保直流侧电容的安全。对三相电压源型PWM整流器，首先在αβ轴下计算交流侧的瞬时复功率，根据功率分析直流母线电压波动的原因；然后推导出系统功率控制的基本方程，分析系统在不同的电流及功率要求下指令电流的计算表达式，并将此表达式应用于控制系统中；仿真和实验结果说明根据推导出的功率表达式的确能够有效地控制系统中的功率波动及直流侧电压。为了验证理论分析的实际可行性，搭建了一套15kW的三相PWM并网变换器实验平台。在此平台上完成了锁相环、并网电流谐波抑制及有功功率和直流电压波动抑制实验，并给出了实验结果和分析，证实了理论分析的正确性。
[Abstract]:In order to solve the global energy shortage and environmental pollution, the renewable energy power generation system is developing rapidly. Grid-connected converter is responsible for the energy exchange between renewable energy and power grid, and plays a key role in the whole renewable energy generation system. In view of the wide application of power electronic devices, the problem of power grid pollution is becoming more and more serious. Therefore, it is necessary to study the control strategy of grid-connected converter in non-ideal power grid. In this paper, the key problems of grid-connected converter are as follows: positive sequence voltage synchronization, harmonic suppression of grid-connected current, active power and DC voltage fluctuation. The positive sequence voltage vector angle is the most basic and important information needed for the renewable energy generation system to be able to access the grid normally. Phase locked loop is an effective way to obtain this information. In this paper, the basic principle of PLL is analyzed, and then the improved PLL is analyzed. Based on the analysis results, an improved complex filter in two-phase stationary coordinate system and a PLL based on sliding Gozel transform are proposed. The simulation results show that the improved complex filter can quickly and accurately separate the positive and negative sequence components of the three-phase voltage, and can attenuate the harmonics of the grid voltage to a certain extent. It is verified that the phase-locked loop based on sliding Gozel transform can be used quickly and accurately when the voltage is distorted, and can work effectively even when the frequency of the grid voltage is shifted in a small range. The harmonic content of current in and out of grid-connected converters needs to meet the standard, and the harmonics of grid-connected current mostly come from periodic disturbances. In this paper, the source of current harmonics in three-phase PWM grid-connected converter is analyzed, and the repetitive control which is suitable for suppressing periodic disturbance is introduced, and then the repetitive controller is designed for the actual hardware system parameters. Finally, the simulation results show that using repetitive control in two-phase stationary coordinate system can effectively suppress the periodic disturbance caused by voltage harmonics. When the three-phase grid-connected converter is in the rectifying state, the stable DC bus voltage can not only guarantee the steady operation of the DC load, but also ensure the safety of the DC side capacitance. For three-phase voltage source type PWM rectifier, the instantaneous complex power of AC side is first calculated under 伪尾 axis, the reason of DC bus voltage fluctuation is analyzed according to power, and the basic equation of system power control is deduced. The calculation expression of instruction current under different current and power requirements of the system is analyzed and applied to the control system. The simulation and experimental results show that the power fluctuation and DC side voltage can be effectively controlled by the derived power expression. In order to verify the feasibility of theoretical analysis, an experimental platform of 15kW three-phase PWM grid-connected converter is built. The experiments of phase-locked loop, grid-connected current harmonic suppression and active power and DC voltage fluctuation suppression are carried out on this platform. The experimental results and analysis are given, and the correctness of the theoretical analysis is verified.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM46

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