The power grid containing wind farms is analyzed by AC probabilistic load flow. By using the method of the combination concept of Cumulants and Gram-Charlier series expansion theory, the DC probabilistic model is extended into AC probabilistic model, in which a three-parameter Weibull distribution is adopted to describe the random variation of wind speed, meanwhile the asynchronous wind turbine generator is treated as PQ node, then a probabilistic model of wind turbine generator is built. Based on the built model the calculation of IEEE 118-bus system is carried out, and then the probabilistic distributions of nodal voltages as well as the probabilistic distribution of branch load flow are obtained. The variation of nodal voltages and branch load flow before and after the connection of wind farms with power grid is compared.

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In this paper, a novel scheme for error current compensation of current transformers (CTs) is presented. The method is to apply Hall current transducers (HCTs) based on magnetic force balance to detect and compensate the error current so as to eliminate the error of CT caused by its exciting current. Theoretical analysis and experimental tests clearly illustrate the performance of the proposed scheme. After compensation, the accuracy of the common CT is increased 500 times from 0.5% (5000 ppm) to 0.001% (10 ppm) at the condition of burden Z b = 1 cos = 1. A self-calibrating method is adopted for a current transformer with the wind ratio of 1:1. Index Terms-Current compensation, current transformer (CT), Hall effect.

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