Research and Implementation of High-Speed Traveling Wave Data Acquisition Based on ZYNQ Processor

The original article was published in “Power Capacitors and Reactive Power Compensation”, 2024, Issue 5.

https://www.chndoi.org/Resolution/Handler?doi=10.14044/j.1674-1757.pcrpc.2024.01.011

Research and Implementation of High-Speed Traveling Wave Data Acquisition Based on ZYNQ Processor

Du Lei, Zhou Dongjie, Hao Huizhen, Mu Tao

(XJ Electric Co., Ltd., Xuchang, Henan 461000)

Introduction

This paper proposes a high-speed data acquisition system for traveling wave distance measurement based on ZYNQ by studying a distributed traveling wave distance measurement system based on electronic transformers, focusing on key technologies for its implementation. First, the principles and system architecture of the high-speed acquisition unit are introduced, and a method for high-speed AD data DMA interaction between CPU and FPGA using the AXI bus inside ZYNQ is described. Secondly, a remainder sharing algorithm is designed to address the issue of uneven AD sampling intervals affecting the accuracy of traveling wave distance measurement. Finally, a phase adjustment algorithm implemented in FPGA is proposed, which effectively eliminates traveling wave phase errors while significantly reducing CPU computational load. The product has been tested and operated in a network, achieving precision and reliability at a leading domestic level.

Main Content

The distributed high-speed traveling wave distance measurement device is responsible for high-speed data acquisition of the small signals output from electronic transformers, data storage, and sending the recorded waveforms of fault moments to the distance measuring host upon request, cooperating with the distance measuring host to locate fault points, widely used in fault diagnosis and location of smart substations. Research on high-speed acquisition units is of great significance for traveling wave distance measurement.

The distributed high-speed acquisition unit is used to collect small signals converted from Rogowski coils and record the fault waveforms, sending the recorded signals to the host for distance measurement calculations. The higher the acquisition speed of the high-speed acquisition unit, the higher the measurement accuracy. The traveling wave propagation speed is related to line parameters and the main frequency components of the line’s traveling wave, with the actual speed approaching the speed of light. Assuming a value of 300 m/μs for calculations, if the sampling interval of the acquisition unit is 1 μs (sampling rate of 1 MHz), the minimum resolution for distance measurement accuracy is 300 m. According to the requirements of the State Grid, for line lengths under 300 km, the two-end distance measurement error should not exceed 500 m; for line lengths over 300 km, the two-end distance measurement error should not exceed 1,000 m. To improve measurement accuracy considering various error factors, the sampling rate of the high-speed acquisition unit needs to be at least 2 MHz, achieving a minimum resolution of 150 m for distance measurement accuracy.

ZYNQ stands for Zynq-7000 All Programmable SOC (System on Chip). The Zynq-7000 series is an all-programmable system-on-chip (APSoC) launched by Xilinx, comprising a processing system (PS) and programmable logic (PL). The Zynq SOC integrates an ARM dual-core Cortex-A9 processor and Xilinx 7 series FPGA architecture, meaning that ZYNQ is essentially a system-on-chip (SOC), thus possessing the advantages of application-specific integrated circuits (ASIC) in terms of power consumption, performance, and compatibility, while also featuring the programmability of field-programmable gate arrays (FPGA). It perfectly integrates the software programmability of the processor with the hardware programmability of FPGA, offering unparalleled system performance, flexibility, and scalability. The programmable logic part of this new device is based on Xilinx’s 28 nm process 7 series FPGA.

The advantages of using ZYNQ chips as the main control chip for distributed traveling wave signal high-speed acquisition devices include:

1) The ZYNQ chip has low power consumption, integrating FPGA and ARM onto a single chip, which helps to reduce the area of the printed circuit board (PCB), allowing the acquisition device to be miniaturized and conveniently installed on-site.

2) Due to the localized installation of the acquisition unit, the surrounding electromagnetic environment is complex, and electromagnetic compatibility (EMC) requirements are high. The SOC architecture integrating FPGA and ARM into a single chip significantly enhances the electromagnetic compatibility of the acquisition unit.

3) The ZYNQ chip features a high-bandwidth direct memory access (DMA) channel between FPGA and ARM, facilitating rapid data transfer between FPGA and the central processing unit (CPU), enabling the acquisition unit to achieve high sampling rates and process large amounts of data.

1) Basic Architecture of Distributed Traveling Wave Distance Measurement

2) Implementation Principles of High-Speed Acquisition Unit

2.1 System Architecture of High-Speed Acquisition Unit

2.2 Implementation of FPGA-based DMA High-Speed Data Channel

2.3 High-Speed ADC

3) Remainder Sharing Algorithm for High-Speed Data Acquisition

4) Phase Restoration Algorithm for High-Speed Traveling Waves

Conclusion

This paper proposes a solution for the implementation of a high-speed acquisition unit for traveling wave distance measurement. It fully utilizes the good dynamic characteristics of electronic transformers and Rogowski coils, with the high-speed acquisition unit installed on-site, distributed data collection, and centralized computation, allowing for more accurate collection and restoration of high-frequency traveling waves. The acquisition unit adopts the ZYNQ chip ARM+FPGA SOC architecture, achieving high-bandwidth data transmission between CPU and FPGA through an innovative DMA data transfer mode. Coupled with high-speed AD, it realizes high-precision and high-speed acquisition of traveling waves, and through remainder sharing and phase compensation algorithms, eliminates sampling errors, significantly improving the accuracy of traveling wave distance measurement. Verification shows that the ZYNQ multi-core processor combined with the FPGA acquisition unit architecture can effectively measure and locate fault nodes, demonstrating high application value.

Author Information

Du Lei (1983—), female, engineer, engaged in relay protection work in power systems.

Zhou Dongjie (1983—), male, senior engineer, mainly engaged in research on embedded hardware platforms in the field of relay protection. E-mail: [email protected].

Hao Huizhen (1982—), female, senior engineer, mainly engaged in relay protection work in power systems. E-mail: [email protected].

Mu Tao (1981—), male, senior engineer, mainly engaged in relay protection work in power systems. E-mail: [email protected].

Article Index

Du Lei, Zhou Dongjie, Hao Huizhen, et al. Research and implementation of high-speed traveling wave data acquisition based on ZYNQ processor. Power Capacitor & Reactive Power Compensation, 2024, 45(5): 69-75.

DU Lei, ZHOU Dongjie, HAO Huizhen, et al. Research and implementation of high-speed traveling wave data acquisition. Power Capacitor & Reactive Power Compensation, 2024, 45(5): 69-75.