Research On Digital Filters Suitable For Wideband Synchronous Measurement Of Active Distribution Networks

In order to cope with the energy crisis and environmental pollution caused by the massive use of fossil energy,a series of new energy power generation methods such as photovoltaic and wind power have been gradually promoted and used.The extensive use of power electronic equipment in new energy power generation devices and the complexity of people’s electrical behaviors make electrical signals in distribution networks increasingly exhibit wideband characteristics,including harmonic and interharmonic components with large amplitudes.The existence of these components will not only interfere with the synchronous phasor measurement,deteriorate the power quality,but also cause resonance and other accidents in the power grid.Therefore,it becomes very important to improve the anti-interference ability of the fundamental wave component measurement and achieve high-precision measurement of harmonic and interharmonic components.However,most of the current wideband signal decomposition schemes are concentrated on the simulation verification level.Therefore,this paper proposes a digital filtering scheme suitable for hardware use,using digital filters to extract the fundamental,harmonic and interharmonic components,in order to improve the calculation accuracy of each component parameter.The main work of this article is as follows:1.In order to accurately retain the characteristics of the fundamental wave signal parameters and eliminate the phase shift,this paper proposes a fundamental wave component filtering scheme based on forward and reverse filtering.This scheme uses the principle of Chebyshev type 2 filter and forward and reverse filtering to remove the phase shift while extracting the fundamental time domain data.In order to reduce the amount of calculation and cache resource occupation,a scheme combining inverse filtering and least square fitting is proposed to shorten the filtering delay,and the parameters of the filtering scheme are determined through simulation.The hardware implementation scheme is explained.The calculation example shows that the filtering scheme has high accuracy and effectiveness when the signal is static or dynamic.2.A harmonic component filtering scheme based on amplitude characteristics is proposed.According to the harmonic content rate of each harmonic,select high-amplitude filtering scheme or low-amplitude filtering scheme to extract.For the cascaded filter neutron filter coordination and buffer resource allocation,this paper gives a hardware algorithm solution.Finally,a suitable phasor algorithm is selected,and a fundamental and harmonic component parameter identification scheme is proposed.The calculation example shows that when the signals with different characteristics are input,the scheme can effectively identify each component parameter,and has higher accuracy and stability.3.This paper proposes an adaptive detection and filtering scheme for the interharmonic components of the distribution network.First,combining the time and the adaptive threshold,an interharmonic initial frequency detection scheme is proposed.Secondly,according to the interharmonic content rate,adaptively select high-amplitude filtering scheme or low-amplitude filtering scheme to reduce the amount of calculation.In order to solve the problem that the initial frequency has errors and real frequency fluctuations that cause the interharmonic component to shift out of the passband,a passband expansion scheme is set up.Finally,an interharmonic component parameter identification scheme is proposed,and the hardware implementation process of the scheme is described.The static/dynamic simulation environment is set up to verify the accuracy and effectiveness of the scheme.4.Design a digital filter decomposition scheme for wideband signals,and integrate the scheme into the hardware program.Build a hardware test platform and set a wideband signal input environment for testing.The test results show that the filtering scheme proposed in this paper can run stably on the hardware platform and has high accuracy.