摘要
有源电力滤波器是一种新型的电力电子装置，可以对电力系统中的谐波进行补偿。和传统的谐波补偿方法相比，有源滤波器具有巨大的技术优势和良好的发展前景。由于有源滤波器具有实时性和准确性的工作特点，如果再结合信号处理和控制技术等学科的优点，就可在实现对有源电力滤波器功能优化的同时，提高有源电力滤波器的性能。瞬时无功功率理论在电力有源滤波器中获得了成功的应用。但在负载或者电网工作状态发生变化时，电路参数调整困难，且用模拟电路实现时需要大量的乘法器，成本较高。
本文首先介绍了电力系统的谐波以及谐波抑制技术，研究了有源电力滤波器在谐波抑制中的应用，由于瞬时无功方法存在的一些不足，本文研究了另一种畸变电流(基波无功电流和谐波电流的总和)检测方法——基于自适应线性神经网络的畸变电流检测方法。然后详细地介绍了自适应线性神经网络理论和核心算法——LMS算法，自适应噪声抵消技术的原理并提出了检测方法。在进行理论分析的基础上，本文对该方法进行了大量的仿真研究，仿真结果表明该方法具有很好的实时性和较好的畸变电流检测精度，对变化的负载电流可以很好地自适应跟踪检测，弥补了瞬时无功方法的不足，而且该检测方法算法简单，易于实现和调整。但该方法大约需要2～3个周期才能跟踪上实际波形的变化，动态响应速度较慢。
最后，本文提出了一种改进的基于自适应线性神经网络的畸变电流检测方法，该算法引入了变μ的思想，本文中它可以在两个值中变化，当系统处于快速响应过程中的时候μ取较大值，使系统响应速度加快；而当系统进入稳态调整阶段的时候取μ取较小值，保证检测的精度。仿真结果表明利用该方法比之改进前的方法无论是检测畸变电流、谐波电流，还是对变化的负载电流的自适应跟踪能力各方面都得到了很大的改善。
Active power filter is an advanced power electronic device, which can be used for integrated compensating harmonic. Compared with some conventional measures, active power filter has many advantages and favorable prospects. Because of the characteristics, real time and accurate compensation, it is possible to take full advantage of digital signal processing and control technologies. If so, not only can the functions of active power filters be optimized, but also the performances of active power filters can be improved significantly. But it is difficult to adjust circuit parameters when loads or power conditions are changed. And the realization of the instantaneous reactive power with analog circuit needs large numbers of multiplicative implements, which cause the cost very expensive.
Firstly, this paper discusses harmonic, harmonic control technologies and the application of active power filter in harmonic control, Because of the disadvantages of the instantaneous reactive power theory, the paper introduced another detecting method
of distortion currents-a detecting method of distortion currents based on adaptive
linear neural network.Secondly, the paper introduced adaptive linear neural network
theory , the nuclear algorithm-LMS algorithm, the theory of adaptive noise
counteracting and proposed detecting methods. On the base of theoretical analysis, a large number of simulations are developed, and the results show that the method has many advantages, such as real time, high accuracy, adaptability to load currents can make up the disadvantages of the instantaneous reactive power theory, the algorithm of this detecting method is also simple and easy to realize and modulate. But it needs two or three periods to follow the power system, the dynamic response is slow.
Finally, the paper proposed an improved detecting method of distortion currents based on adaptive linear neural network.In this method, "u" is variable, it can vary between two values, when the system is in the process of dynamic response we choose "u" the bigger value, which can expedite the dynamic response; but when the system is in the process of steady condition we choose "u" the smaller one, which can ensure the detecting precision. The simulation show that the improved method is much more improved than the general in many aspects such as detecting distortion currents, harmonic currents, or the adaptive following ability to load currents, it is indeed a good method in detecting distortion currents.
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