(1) Power system static var compensator (DSTATCOM)
In the power system, high frequency furnace, large capacity motor, high sensitivity half load fast impact load current (such as sudden start) will produce a lot of voltage flicker, which leads to the imbalance of current and voltage in the distribution system. Traditionally, static variable compensator (SVC) is used to suppress voltage flicker, but the response speed of SVC is very slow (tens of milliseconds), and the flicker suppression rate is difficult to reach more than 50%. Compared with the power system, PWM control is used in parallel. The voltage source converter of distribution system, namely static reactive power compensation device (DSTATCOM), has the advantages of fast dynamic response, compensation voltage independent of system voltage, powerful harmonic suppression function, good suppression effect on voltage flicker effect and small active power loss. As a result, DSTATCOM devices become more and more popular, replacing SVC devices.
(2) Active power filter (APF)
The uncontrolled harmonic voltage and current are the key factors affecting power quality in power system. First, harmonic measurement is performed by periodically measuring the instrument and the middle line with the correct RMS value. Strengthen the measurement and inspection of power line power quality, and regularly test and compare the distribution system, especially the medium and low voltage system, in order to find the law of harmonic generation and development. According to the working principle of the equipment, the suppression and prevention measures of harmonic pollution are divided into passive and active filters composed of power electronic equipment. Passive filters consist of passive components (such as resistors) to form low impedance paths to specific harmonics or even more to suppress capacitors, reactors, and sometimes harmonics.
(3) Timely monitoring of power system data (SCADA)
In the power system, the dynamic power quality problem is recently exposed by the development of advanced technology. The research on the sensitivity and pressure of power users can provide an important basis for the selection of appropriate compensation methods. The establishment of power quality standards provides an important reference. SCADA system used for on-site dynamic data quality monitoring is the research direction of distribution management system. Field data includes measurement data (e.g., power, voltage, and current) and event data generated by tasks (e.g., closing, overcurrent, and fast braking). If an accident occurs and a trip occurs, the fault record data of the station will also be recorded, and you will see that the amount of data to be communicated is not consistent with that in the normal industrial control. Because the field data of the power system changes very fast, the over-current may last more than 10 milliseconds, and the data will stop, so the demand for real-time data and communication speed is very high. The stable basic data in the monitoring system is the key to the stability of the system, and it is also the focus of the monitoring software design. Some existing software uses data communication, processing and monitoring in one software. Intuitive and compact, but it's very inconvenient to upgrade and improve the system, so you have to reconfigure some changes for each system. Modular structure is adopted.