摘要：With large-scale use of kinds of motors, oilfield drilling electrical system always accompanied by serious power quality problem, including reactive current, harmonics current and grid voltage distortion, which would greatly threaten the safety and proper working of the whole system. This paper focuses on a power quality improvement project to solve these problems. A hybrid compensating scheme, including an active compensator and a passive compensator, is carried out. Because of the specificity of oilfield drilling electrical system, compensators are redesigned against features of this application background. And then the current detection point arrangement of this hybrid system is also taken into consideration to build the whole system much more effective and reliable. Now the improvement project is already implemented in application field, and the power quality of the system is greatly improved.

摘要：Static, passive, filters present an economic and simple solution to the harmonic distortion at the distribution level and at the same time supply the required reactive power for voltage support and/or power factor correction. Applying these filters to a distribution network, if not properly designed, may have an adverse effect on the network. This paper presents analysis of the effects of using passive harmonic filters in a power distribution networks. The driving point impedance at the node where the filter installed, as a measure of how harmonic currents would produce harmonic voltages, is determined as function of the filter parameters. Hence, effects of filter parameters on the system impedance, parallel resonant frequency and impedance at resonance are illustrated. The effects of using more than one filter are also examined. A method for the optimal design of a passive filter considering the component limits, harmonic distortion limits and parameter tolerances is also presented. The proposed optimization model has proved its effectiveness through application to measurements at a real distribution feeder.

摘要：The purpose of the paper is to develop a solution for application of PV （photovoltaic） generators in MV （medium voltage） distribution system without unacceptable voltage changes due to drops of PV power output. The proposed solution includes operation of PV with predetermined leading power factor and addition of a capacitor bank in parallel to PV plant in order to compensate the reactive power absorbed by the PV inverters. The analytical expression of required power factor angle is derived. Adding a capacitor bank in parallel to PV power plant may pose a problem because of space limitations. The dimensions and cost of small MV capacitor banks depend significantly on the capacitor bank protection against internal faults. Application of the developed negative-sequence current difference method for the unbalance protection of the capacitor banks enables to achieve a compact and cost-reduced design of the banks connected in parallel to PV power plants. A real-world example of operation of the PV plant in parallel to the capacitor bank with the novel protection scheme is described.