Development Of Remote Power Quality Monitoring Software System Based On LabVIEW

Ideally, power energy provided to consumer should be a sine wave with constant voltage frequency, and its three-phase voltages have the same amplitude, phase difference of 120 degree between each other. However, due to the existence of various nonlinear, concussive and asymmetrical loads in power system, and all sorts of factors including incomplete regulatory methods, faults and interferences, harmonic currents and negative-sequence currents are generated and injected into the power grid. And the so-called ideal state actually does not exist, so it brings the power quality problem. Power quality problem is related to the healthy long-term development of national economy and the normal production and life of society and people, and it is a very important and worthy of study subject we have to face. The new electric power system reform requires establishing electric power market, opening power sale side and introducing market competition. The main point to all of these is that, in the future, power energy will return to its commodity properties, and circulate in the form of commodity in the market. As a commodity, the basic market characteristics are high-quality, safe and cheap. The key is high-quality among them. If the power quality can’t be guaranteed, it will eventually be eliminated by the market. Therefore, this puts forward higher requirements to power quality and brings challenges to power quality monitoring.The rapid development of remote networked virtual intelligent equipments in recent years prompts developers to use the hardware device as simple as possible and software with complete functional structure to make up a complete set of equipment. The complex mathematical operations are embedded into software and performed by powerful computers instead of hardware. At the same time, realizing remote network transmission, reducing the size of hardware device and labor cost, realizing full automatic unattended, all above is to maximize the economic benefits and to meet the requirements of the equipment in the information age. The power quality monitoring system studied in this paper is also in accordance with the idea. The on-site hardware device consists of voltage and current sensors, adjusting and amplifying circuits, data acquisition card and industrial tablet computer. The circuits are very simple without microprocessor for complex operations, so it is not regarded as the main research content of this paper. The main research content is power quality monitoring software system.The software system is based on Lab VIEW platform. The overall structure of the software system uses C/S(Client/Server) mode, modular programming idea, and one server communicates with several on-site node equipments through one-to-many TCP communication mode. The software system includes two main pieces of software, the on-site monitoring software in the industrial tablet computer and the server monitoring software in the remote data management center. The on-site monitoring software is primarily responsible for reading the data acquisition file every 5 minutes, and then calculating the data to get power quality parameters, displaying the results and uploading them to the remote server through 4G or WIFI network. The calculation part is based on Producer/Consumer mode and queue technology, realizing the multi-threaded parallel execution for calculating several parameters to improve the efficiency of calculation. The server monitoring software can orderly receive the calculation results uploaded by several on-site node equipments, write the results into database, display the results to realize remote real-time monitoring, query the database and playback the original data.In this paper, the measurement methods of power quality parameters were well studied, including voltage deviation, frequency deviation, harmonics in public supply network, three-phase voltage unbalance, voltage fluctuation and flicker, voltage dips and short interruptions. The measurement method of flicker was studied emphatically and the Simulink model of flicker was established for simulation verification, verifying correctness and feasibility of the model and measurement method, laying the foundation for realizing the flicker calculation module in the software system.In the end, the software system was simulated and tested. Parameters calculation modules were simulated emphatically through simulation input signals. Most of the errors are within ±0.01% and very small, proving the correctness of parameters calculation modules. In the laboratory, the single and three phase power frequency voltages were collected and the power quality parameters were calculated. The database capacity was tested, and it can meet the requirement of continuous monitoring for 365 days. The operation of the software system and the realization of each function were tested in detail. The whole power quality monitoring software system is stable and reliable, all functions including acquisition data calculation and processing, real-time display and monitoring, one-to-many network communication, database storage, database query and original data playback are realized, proving the system can effectively carry out remote real-time online monitoring for power quality.