Design of Power Quality Analysers

Client 

A European power sector company. 

Challenge 

To develop a power quality analysers with the following characteristics: 

• Basic measurements: voltage (V), current (A), frequency (Hz), phase rotation indicator. 
• Power: active power (W), apparent power (VA), non-active power, (var), power factor. 
• Fundamental power: fundamental active power (W), apparent fundamental power (VA), fundamental reactive power (VAR), DPF (Cos Φ). 
• Energy: active energy (Wh), apparent energy (VAh), non-active energy (VARh). 
• Harmonics: harmonic components up to and including the 50th and total harmonic distortion of voltage and current. 
• Advanced power quality analysis: monitoring, statistics, and reports according to the EN50160 specifications, event statistics complimented by waveform recording, harmonics and interharmonics according to IEC 61000-4-7, directional power harmonics, voltage and current THD coefficients, flicker according to IEC 61000-4-15, event/data log, power quality event/data logging, logging capability for more than 100 parameters, logging parameters with real-time stamps. 

Solution 

We used OpenAMP to develop the device, which combines AMP (asymmetric multiprocessing) Linux with RTOS. We also used Qt to develop the user interface, data visualisation, logs, and events.  

For the build system, our engineers employed the Yocto Project. Additionally, we implemented the device management business logic on the Linux side while the RTOS side handled the power quality measurement. All mathematical analyseis were carried out using CMSIS DSP. 

There are two versions of the device. In the first version, an external front-end microcircuit is responsible for the entire analysis process. This microcircuit transmits data via SPI to the power quality analysers, which have already calculated the data. Data collection, processing, and aggregation are performed on the RTOS side.  

The second version of the device uses ADCs for the front end. It implements the entire process with a DSP coprocessor and mathematical analysis on RTOS according to IEC 61000-4-30, IEC 61000-4-7, and IEC 61000-4-15. We used FreeRTOS as the RTOS in CMSIS RTOS 2 (CMSIS-RTOS API v2). 

Business Value 

Power quality analysers help improve energy efficiency, extending equipment lifespan, reducing downtime, ensuring compliance with standards and regulations, and providing a competitive advantage.  

The power quality analysers designed at Promwad for our client have the following features:  

• IEC 61000-4-30 Class A voltage measurement accuracy ±0.1%;  
• current measurement accuracy ±1%;  
• voltage and current rms calculation half-cycle steps;  
• frequency measurement accuracy ±10 mHz;  
• 150/180-cycle aggregation no gaps permitted;  
• synchronised with UTC 10 min tick;  
• measurements of harmonics up to order 50th;  
• time-clock uncertainty per 24 hours ±1 second;  
• time synchronisation GPS receiver;  
• radio timing signals or network timing signals.