Recently, the first set of low-voltage DC power quality analyzer in China was put into use in Hebei Electric Power Research Institute of State Grid, and took the lead in conducting a number of low-voltage DC power quality test and analysis. At present, the construction of domestic DC power distribution projects has entered a rapid development stage. The DC power distribution system realizes the interconnection and regulation of source load storage in the form of DC through power electronic technology. It has the advantages of large power supply capacity, high reliability and strong source load adaptability. Unlike the AC power distribution system, the DC power distribution system is short of inertial elements, and the power disturbance generated by various power electronic devices spreads faster in the system, which is very easy to cause accident expansion. In addition, the DC distribution system does not have the concept of frequency and phase angle. The generation mechanism and evaluation index of power quality problems are quite different from those of the AC system, and the conventional test and analysis methods of AC power quality are no longer applicable. In order to solve the difficult problem of DC power quality test, the technicians of Hebei Electric Power Research Institute of State Grid analyzed the typical topology and operation mechanism of DC power system in depth. Starting from the key factors that affect the power supply quality of AC and DC distribution network, based on the voltage fluctuation and ripple coefficient, they proposed the test and analysis method of fast voltage change and ripple spectrum, and developed the DC power quality test technology that can characterize the characteristics of low-voltage DC, And a low-voltage DC power quality analyzer suitable for 1500V and below has been developed. In order to verify the effectiveness of the device, researchers selected typical DC application scenarios such as DC microgrid, distributed source network load and electric vehicle charging pile, and completed the power quality test of several low-voltage DC distribution systems such as ± 375 V, 400 V and ± 110 V respectively. The test results show that the device can not only monitor and analyze the steady-state parameters such as voltage deviation, ripple, flicker and imbalance in the DC system, but also capture and measure the transient parameters such as DC voltage rise and fall, short-time interruption, etc. with the ultra-high sampling frequency of 12.8 kHz, it can realize the accurate measurement of the total operating parameters of the DC distribution system. It is reported that the successful development of this device will meet the power quality test requirements of low-voltage DC distribution system, and provide a strong basis for the planning and design, operation and maintenance of DC distribution projects and the formulation of DC power quality standards. (news agency)