Power Flow Calculation Of Distribution Network With Distributed Generation

Power flow calculation is an important basis for power planning and design,fault diagnosis and protection of power grid safety operation.However,the traditional power flow calculation methods are lack of consideration of the uncertain factors in power system,or only consider single uncertainty(randomness and fuzziness,etc),which makes it difficult to accurately reflect the real situation of power grid.The actual power grid has many uncertain factors,the reasons of uncertainty including the change of the load and distributed generation(DG)which may be influenced by the weather changes.On the other hand,with the wide application of power electronic equipment required for the grid connected of distributed generation it produces a large number of harmonic due to current(voltage)distortion,which results in the decrease of power quality and causes a series of harmonic harm,Therefore,uncertain harmonic power flow calculation is one of research contents in this paper.By studying the existing research on the uncertain flow algorithm at home and abroad,an uncertainty power flow algorithm based on cloud model(hereinafter referred to as Cloud Flow algorithm)was proposed,and it can be applied to harmonic power flow calculation.The proposed method is more inclusive of volatility information and realizes the unity of fuzziness and randomness in information.It is a kind of new method for power flow calculation,which has advantages of high efficiency and accuracy.The main work of this paper is as follows:(1)As for the uncertainty output power of distributed generation and fluctuating load in distribution network,existing modeling methods only consider single uncertainty and ignore the correlation between fuzziness and randomness.In view of the shortcomings of the existing modeling methods,the theory of cloud model in the modeling is introduced.According to Beta distribution(approximation of the sun's light intensity probability distribution)and Weibull distribution(approximate wind speed probability distribution),a new modeling method which considers the influence of randomness and fuzziness and comprehensively descripts their link,so as to make up for the deficiency of the existing modeling methods is presented.(2)Considering the influence of uncertain factors on power flow distribution,a new method of power system uncertainty calculation based on cloud model is proposed.Cloud model theory is used to calculate the output power fluctuation range of fluctuating load and intermittent distributed generation,which makes the current results can more accurately reflect the influence of uncertainty factors on the system trend,therefore,the power flow algorithm can be applied in power system containing uncertain nodes.Compared the proposed method with probability method and the Monte Carlo method,it can be proved that the proposed algorithm has a higher accuracy and computational efficiency by an example of IEEE 33-node.(3)According to the operating characteristic of electronics inverter as harmonic source,the Cloud Flow algorithm is applied to harmonic power flow calculation,an uncertainty harmonic power flow algorithm based on cloud model is proposed.Through the IEEE 33-node distribution system,it is proved that the proposed algorithm is more reasonable,with high accuracy and computational efficiency,and it helps to avoid the harm caused by harmonic distortion rate exceeding the limit.