The Harmonic Detection Of Oilfield Power Network And The Research Of The APF's Control Technology

In order to increase the crude oil output and overall economic efficiency, we put in a lot of power-semiconductor devices in the oilfield distribution system. A growing number of energy-saving systems have caused the large harmonics to pollute the oilfield power networks. "Power Pollution" can not only cause a great loss of oil production, but also endanger the safe operation of power networks. Active Power Filter (APF) is an effective way for suppressing harmonics and improving the quality of power supply. The measurements and control methods of distorted current in the APF are not only the key factors which determine the compensation performances, but also affecting the application scope of APF. This paper mainly studies the new ways of measuring and controlling the distorted current of APF, to adapt to the modern power system's variability and the different applicational requirements for APF.First, on the basis of the necessary expositions and analysis of power harmonics generation, hazard and the current control measures, the paper analyzes and compares the four-phase and three-phase APF, and establishes the main circuit structure which is three-phase four-wire style of this system; to identify the main switch components by analyzing and computing the main circuit; to identify the specific protection circuit and design the buffer protection components by analyzing the protection circuits of the main switch components in detail; the paper analyses the switch frequency of main circuit of APF and discusses the interrelationship among many parameters; the paper proposes the estimated method of the capacitor voltage fluctuations based on the component method, and gets the relationship between the DC capacity and the fluctuation of capacitance voltage, we can design the value of the APF's DC capacitor based on this relationship, and verify its accuracy by simulation; at the same time, design the value of the inductance based on the current tracking performances.Secondly, this paper summarizes the current main methods of harmonic detection and puts forward a harmonic detection method based on wavelet neural network (WNN). Considering the real-time quality and accuracy of the harmonic current detection, this paper proposes a harmonic detection method of RBF neural network based on immune algorithm according to the principle of noise canceling, using neural network combined with adaptive detection algorithms on the basis of noise canceling. Simulation experiments show that RBF neural network based on immune algorithm has the characteristics of high convergence rate and accuracy, and power system harmonic current can be detected in real-time.Finally, the paper studies the control methods of APF. Through the specific analysis of the space vector PWM control, the current tracking control method based on space vector modulation is specifically analyzed, and then the simulation tests show the correctness and effectiveness of the algorithm; considering the adaptability of the changes of APF's circuit parameters and switch frequency, and the fluctuations of DC side voltage comprehensively, the paper proposes the vector one-cycle control method. The simulation results show that adopting this control method the APF can dynamically compensate the current harmonic and reactive power effectively, and it has a lot of advantages, such as simple, reliable, robust, high control precision, and high efficiency.These researches in a certain extent play a guiding and reference role in developing the experimental system for devices of harmonic suppression of oilfield power network.