针对目前国内冶炼行业矿热炉功率因数普遍偏低的问题，研制了一种基于PLC与触摸屏的矿热炉二次低压无功自动补偿测控系统，实现了并联电容器补偿无功功率的自动控制，提高了矿热炉的功率因数。 本文首先分析了矿热炉冶炼过程中功率因数低带来的问题，阐明了对其进行无功补偿的意义；然后对比了现有各种无功补偿装置的优缺点，并在此基础上针对矿热炉冶炼低电压、大电流的特点提出了矿热炉低压无功补偿测控系统的总体方案；最后完成了系统的硬件设计、软件设计和运行调试。 系统硬件设计分为三个部分：电源部分、控制部分和监测部分。电源部分采用交流稳压器向控制柜和电容柜提供稳定电源，并采用智能电压表监测稳压器输出电压。控制部分以PLC为主机，采集现场各仪表数据并控制电容器投切；上位机触摸屏完成电量参数值显示、系统参数设置和手动控制等功能。监测部分由智能温度表和温度传感器组成，监测电容柜中补偿导线内冷却水的温度，若温度超限则触发系统急停动作，对系统进行保护。 系统软件设计分为下位机PLC软件设计和上位机触摸屏软件设计。下位机PLC软件主要实现与各仪表通信采集各仪表数据，自动控制电容器投切功能。PLC程序还可接收触摸屏控制命令实现电容器的手动投切和系统急停动作。触摸屏程序主要包括三类界面：数据显示界面、控制界面和参数设置界面。数据显示界面将电网参数以数字和图形的方式显示出来，方便现场工作人员查看；控制界面实现补偿电容器的手动投切，系统手动/自动工作模式切换和系统急停功能；参数设置界面将自动控制参数通过串行数据线写入PLC数据寄存器，作为PLC自动控制的依据。 在完成了系统各部分设计之后，对系统的三个主要功能：电量参数采集、手动控制和自动控制进行了测试，结果表明该测控系统达到了设计要求，且运行稳定，目前该系统已交付用户使用。

Contraposing the problem that the power factor of submerged arc furnaces is generally low in domestic refining industry, we develop a test control system of low voltage reactive power compensation for submerged arc furnace based on PLC and HMI. The system achieves the automatic control of reactive power compensation with shunt capacitors and improves the power factor of submerged arc furnace. First this article analyzes the problem brought by low power factor in a submerged arc furnace smelting process and clarifies the significance of reactive power compensation for a submerged arc furnace. Then it compares the advantages and disadvantages of the existing reactive power compensation devices. On this basis, it advances the general scheme of the submerged arc furnace low voltage reactive power compensation control system contraposing the characteristics of low-voltage and high-current. Finally it completes the design of system hardware, system software and system debugging. The system hardware design is divided into three parts: the power part, the control part and the monitoring part. The power part use two AC voltage regulators to provide a stable power supply to the control cabinet and the capacitor cabinet and intelligent voltmeter to monitor the output voltage of voltage regulators. PLC is the master controller of the system, it collects data from instruments and controls capacitors switching. HMI completes many functions such as the power parameters display, the system parameters settings, and manual control. The monitoring part consists of smart thermometers and temperature sensors, monitors the cooling water temperature of the copper pipe wire. If the temperature is too high, the system will trigger emergency stop to protect the system. System software design is divided into software design of PLC and software design of HMI. PLC software completes the functions such as communication with the instruments to collect the data of each instrument and automatic control of capacitors switching. The PLC program can also receive HMI control commands to manually switch capacitors and trigger emergency stop. HMI program includes three types of interface: data display interface, control interface and parameters settings interface. The data display interface displays the power parameters in numerical and graphical way, facilitates staffs to view. The control interface completes many functions such as manual capacitors switching, system manual / automatic mode switching and triggering emergency stop. The parameters settings interface will write automatic control parameters to PLC data registers through the serial data line, as the basis for the PLC automatic control. After completion the design of the system, three main functions of the system: power data collection, manual control and automatic control were tested. The results showed that the control system meets the design requirements and runs stably and reliably. At present the system has been delivered to users.