Abstract
Harmonic interference is a major hazard in the current power system that affects power quality. How to extract harmonics quickly and accurately is the premise to ensure the sustainable operation of power system, which is particularly important in the field of new energy power generation. In this paper, a harmonic extraction method based on a time-varying observer is proposed. Firstly, a frequency estimation algorithm is used to estimate the power grid current frequency, which can estimate the frequency in real time. Then, applying the zero-crossing detection method to convert the frequency into a phase variable. Finally, using the phase variable and integral current signal as input, a observer is modeled to extract each order harmonic component. The proposed method is evaluated on a FGPA test platform, which shows that the method can extract the harmonic components of the grid current and converge within 80 ms even in the presence of grid distortions. In the verification case, the relative errors of the 1st, 5th, 7th and 11th harmonics are 0.005%, −0.003%, 0.251% and 0.620%, respectively, which are sufficiently small.
Highlights
The development and utilization of solar energy, wind energy and tidal energy will gradually replace the traditional fossil fuels to build an environment-friendly human society [1,2]
The harmonic caused by the increase in nonlinear load [4,5] will lead to a decline in power quality (PQ), which will damage the equipment with strict requirements for power quality [6]
This paper proposes a method with good robustness against frequency changes to extract every order harmonics for distorted grid
Summary
The development and utilization of solar energy, wind energy and tidal energy will gradually replace the traditional fossil fuels to build an environment-friendly human society [1,2]. Real-time, fast and accurate harmonic extraction is the premise of harmonic control and power system sustainable operation, especially in the field of renewable energy. In terms of harmonic extraction methods, traditional methods can be roughly divided into two kinds: frequency-domain methods and timedomain methods [13]. For frequency-domain methods, the Fast Fourier Transform (FFT) is a typical harmonic analysis method, which requires one cycle of sampling and analysis of the original signal before harmonic information can be obtained [14].
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