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With the rapid development of renewable energy resources, harmonics in modern distribution systems have become more serious owing to the wide adoption of power electronic devices. Today, distribution-level phasor measurement units (D-PMUs), which can provide synchronized harmonic data with high-time resolution, are being rapidly developed. To utilize the D-PMUs, a hierarchical harmonic contribution (HC) determination method is proposed in this paper for systems with multiple harmonic sources. The HCs were determined using a widely linear complex partial least squares (WL-CPLS) method, which is both accurate and efficient. In an actual power system, the D-PMUs are not fully installed at all buses and the harmonics monitored by each D-PMU are actually the aggregate effects of multiple harmonic sources in the subarea. Based on the above consideration, a hierarchical HC strategy is proposed to locate the main harmonic contributors, layer by layer. The proposed method can be applied to a radial distribution system with any number of D-PMU placements. The methodologies are explained and verified using the IEEE 37-bus system. The real case study results based on the demonstration project are also analyzed in this paper.

Due to the access of a large number of distributed energy sources and power electronic equipment, the power quality problems caused by harmonics have attracted widespread attention. Under the premise of grasping power quality monitoring data, it is urgent to determine the source of harmonics, in order to take targeted measures at the source and improve the power quality problems that occur in the system. This paper proposes a method to determine the harmonic contribution of each harmonic source in a multi-harmonic source system based on data selection method considering regression coefficient fluctuation. Firstly, an index factor for evaluating the harmonic contribution based on partial least squares of each harmonic source is established. Then the data selection method based on coefficient fluctuations in the regression model is used to select valid data segments. Finally, by analyzing the harmonic voltage and harmonic current data, the quantitative magnitude of the harmonic responsibility of each harmonic source is determined. The proposed method is convenient in calculation and strong in engineering practice. Simulation analysis and actual case verifies the effectiveness of the proposed method.

one of the qualities of a good high voltage direct current (HVDC) system is robustness. The system should produce the output with very minimum harmonics distortion, and it should be stable against both small and large disturbances. In this paper, to determine the better model configuration of voltage source converter (VSC) that has both minimum harmonic distortion at the output and strong resistance to disturbances, the average model (AVM) and Switch Function based model were compared using dynamic behaviour validation. For analysis purposes, two point-to-point VSC-HVDC systems connecting two asynchronous high voltage alternate current (HVAC) systems which include two VSC terminals and the dc-link were developed base on the selected models. And two-level-VSC topology was used for simplifying calculations. The Vector control technique was proposed to control active and reactive power flow on the rectifier (sending end) and to control the dc voltage and reactive power flow at the inverter (receiving end). Using MATLAB SIMULINK the systems were simulated and the result was obtained and discussed. The results were good and accurate for both models but the only difference is that the high-frequency harmonics generated by the switching pulse cannot be presented by AVM since it can only present the fundamental component of ac currents and voltages.

With the generalization and application of PMUs, the approach of the measurement and calculation for the electrical parameters in power grid are greatly enriched. But at present, PMU can only calculate the fundamental phasor and the utilization ratio of hardware resources is low. Firstly, based on the calculation principle of PMU for fundamental phasor calculation, the algorithm of PMU to calculate harmonic phasor is proposed. Secondly, the accuracy of harmonic phasor calculated by PMU and harmonic phasor calculated by conventional Fast Fourier Transform (FFT) is compared when the signal frequency deviates from the rated frequency. Thirdly, the harmonic phasors calculated by PMU and conventional FFT are used for harmonic contribution determination (HCD). The feasibility of harmonic phasor calculated by PMU on improving the accuracy of HCD is analyzed based on the case study results. Finally, the effectiveness of the proposed method is verified based on 18-bus distribution system. The case-study results show that the accuracy of the proposed method is good. The harmonic phasor data calculated by PMU is of great value for improving the accuracy of HCD.