| At present, the vast majority of metering instruments are designed for the premise that voltage and current are sinusoidal signals. However, with the wide application of non-linear loads (such as electrified railway, electric arc furnace, rolling mill and high power rectifier equipment, etc.) in the electrical network, and renewable energy integration. These not make electrical network signal distortion, but also add decreasing DC component, so the voltage and current signal are no longer sinusoidal. The operating environment (engineering steady-state) of metering instrument has changed in this case, relative to the design environment (ideal steady-state), so the accuracy of electric energy metering is worthy of further study in engineering steady-state environment. Many aspects are involved about electric energy metering, synchronous sampling signal is chosen as the main research aspect in this paper. It is researched that the influence of operating environment changes to synchronous sampling signal, thus the impact of sampling signal on electric energy metering is revealed.Firstly, composition of the voltage signal is analyzed in engineering steady-state environment, it is pointed out that this signal contains sinusoidal component and decreasing DC component, and the influence of decreasing DC component on zero crossing is explained. Secondly, engineering steady-state signal is analyzed mathematically by using zero-crossing detection theory, its phase expression is obtained. Then this phase as the input of PLL, its output quality is analyzed according to its mathematical model, and its operating behavior is obtained in engineering steady-state, so it is comprehended that the characteristics of synchronous sampling signal based on phase-locked technology. Thirdly, the characteristics of electric energy metering is analyzed mathematically in engineering steady-state environment, and the influence that synchronous sampling based on phase-locked technology on electric energy metering, is explained from the same measuring point and different measuring points. It is pointed out that electric energy is not conserved at this time, there may be a negative line loss phenomenon in some region, where disturbance is changed dramatically. Finally, the main factors that affects electric energy based on phase-locked technology, is analyzed by Matlab/Simulink simulation experiment. At the same time, it is verified that electric energy non-conservation and negative line loss, and corresponding solutions are propounded. |
