【作者】 王毅；

【导师】 赵建国； 孙树敏；

【作者基本信息】 山东大学 ， 电气工程， 2011， 硕士

【摘要】 由于无功功率在电网中传输会造成网络损耗以及受电端电压下降,因此大量的无功功率在电网中传输必然使电能利用率大大降低且严重影响供电质量。在电网中的适当位置装设无功补偿装置成为满足电网无功需求的必要手段。近年来,无功补偿对电力系统的重要性越来越被人们广泛认同。从低压无功补偿装置的构成而言,主要由电容器、投切开关元件和控制器3部分组成。其中,投切开关元件性能的好坏对低压无补偿装置的可靠性起着非常重要的作用。在低压无功补偿装置中,单独使用交流接触器进行投切,存在涌流大、触点易损坏和响应慢等问题；而单独使用电力电子器件,则存在功耗大、抗干扰弱和易产生谐波等问题。为了克服以上两种投切开关的不足,本文设计了一种以单片机AT89S51为核心的低功耗电容投切复合开关,装置以晶闸管和磁保持继电器并联为主回路开关,电容投切可以通过晶闸管和继电器配合工作,晶闸管在电压过零时导通,投合后电流由磁保持继电器单独承担,具有功耗低、浪涌小、抗谐波强和响应速度快等优点。本文首先系统地阐述了无功补偿的相关原理和复合开关的工作原理、补偿方式及实现方法,为本文设计的复合开关奠定了一定的理论基础。然后设计以AT89S51为核心的复合开关的硬件系统,其中主要包括过零检测电路、晶闸管触发电路、电源电路、复位电路和显示电路等几部分。而且提出复合开关的一种保护电路,能有效地解决晶闸管由于单片机受强干扰失控造成晶闸管应关断而又未关断引起短路故障发生的问题。其次对软件程序进行了设计,实现了复合开关的基本功能。另外,针对各种干扰对复合开关的影响,设计了各种抗干扰措施,提高了该复合开关的可靠性和稳定性。本文设计的复合开关的重要特性之一就是可以过零投入,避免投切瞬间的过电压和涌流,通过机械开关投入和晶闸管过零投入的仿真波形比较,证明了过零投入的必要性。并在现有实验条件的基础下,对本文设计的复合开关投切电容器一个月,工作效果良好,验证了其可行性。最后在低压复合开关原理的基础上,对复合开关在高压方面做了初步展望,构建了基本结构,并在投入电容器和短路故障方面做了相关仿真,并预见它有着广泛的应用前景。更多还原

【Abstract】 Because transmission of reactive power in electric network can lead to network loss and step-down voltage, and a lot of transmission of reactive power in electric network must make the electricity utilization greatly reduced and seriously affect the quality of power supply. It becomes necessary means to meet the demand of the grid reactive power that reactive power compensation devices are installed in proper position of electric network. In recent years, the importance of reactive power compensation in power system is widely recognized by people. The low-voltage reactive power compensation device is mainly comprised of capacitance, throwing cut switch component and controller. Among them, the performance of the throwing cut switch plays a vital role to the reliability of the low-voltage reactive power compensation device.In the low-voltage reactive power compensation device, the problems are large inrush current, contacts easy to be damaged and slow reaction by using AC contactor alone, besides, the problems are big power, low capability of the anti-interference and harmonic easy to be produced by using power electronic device alone. In order to overcome the shortages of the above two kinds of throwing cut switches, a kind of low-power compound switch with AT89S51 as the core has been designed in this paper. The device uses the parallel connection of thyristor and magnetic latching relay in the main loop. The throwing cut process is the cooperation action between the thyristor and the magnetic latching relay. The thyristor works when the voltage is zero. During the device is switch-on, the electric current is taken on by the magnetic latching relay alone. The compound switch has the advantages of low power consumption, small inrush current, strong capability of the anti-interference to harmonic and high speed responsibility.This paper firstly expounds systematically the relevant principles of the reactive power compensation, the working principle, the compensation mode and the realization method of the compound switch, which lay theoretical basis for the compound switch.Secondly the hardware system of the compound switch which puts AT89S51 as the core is designed. The hardware system mainly includes zero detection circuit, thyristor trigger circuit, power supply circuit, reset circuit and show circuit. And a protection circuit of the compound switch has been designed, which can effectively solve the problem caused by the thyristor that can not been cut off due to the strong interference of the single-chip microcomputer, otherwise it will cause short-circuit.Then the software programs have been designed to realize the basic function of the compound switch. In addition, according to various interferences on the influence of the compound switch, the anti-interference measures have been studied to improve the reliability and the stability.One of the important characteristics of the compound switch is zero input, which can avoid overvoltage and inrush current, and the necessity of zero input has been proved by the simulation waveform. In the existing test conditions, the feasibility of the compound switch has been proved by working properly one month.Finally, on the basis of the low-voltage compound switch, this paper makes a preliminary outlook in high-voltage aspects of the compound switch, and constructs the basic structure. And through the simulation about the input capacitors and short-circuit fault aspects, a broad prospect of application of the compound switch has been foreseen.更多还原