| When calculating power flow according to conventional power flow model,power system usually only sets up a balancing node,corresponding to a balancing machine,to balance unbalanced power in the system.However,with the gradual increase of power system scale,single balancer has been difficult to meet the requirements of power balance.When the unbalanced power of the system is small,the conventional power flow calculation with only one balanced generator will not have a great impact on the power flow distribution of the system.When the unbalanced power of the system is large,the conventional power flow calculation with only one balanced generator is inappropriate,and the obtained power flow of the system may deviate from the actual state.Multi-balancer power flow calculation can make up for the shortcomings mentioned above.By setting up a group of balanced generators to share the unbalanced power of the system,the results of power flow calculation are more in line with the actual situation.The main work and innovation of this paper are as follows:(1)From the perspective of static voltage stability,an improved continuous power flow model is proposed to calculate the load margin considering voltage stability.The model is based on the prediction and correction technology of the continuation algorithm and Newton iteration format,and takes into account the reactive power reserve of generators and the automatic control scheme of step size.Finally,the calculation and solution of the continuous power flow are realized.In terms of power margin discrimination,the method identifies different types of system instability modes byjudging the saddle node bifurcation point or limit induced bifurcation point respectively.(2)The allocation scheme of balancer is mapped to multi-balanced nodes and continuous power flow calculation is introduced to realize the automatic allocation of unbalanced power.Because the improved formula of continuous power flow can produce different power margin results corresponding to various unbalanced power allocation schemes,the necessary optimization techniques are needed to search the allocation factors corresponding to the maximum(or minimum)power margin.Therefore,a hybrid optimization method is constructed by combining improved continuous power flow calculation with evolutionary mechanism-based particle swarm optimization through coordinate transformation.In addition,in order to achieve high performance computing on the premise of limited computing resources,parallel processing technology is used in algorithm programming.The validity of the proposed method is proved by a case study of a standard test case system.(3)In addition to maintaining power balance,the main tasks of the multi-zone balancing machine unit include adjusting the power exchange control between the zones.Under the general trend of energy interconnection,large-scale new energy needs to be transferred to the load center on a larger scale,and the power regulation problems between each region and within the region are closely related to the balancing machine unit.Therefore,this paper proposes a power flow analysis model based on multi-area balancing machine control.The model combines the balancing machines independently distributed in each sub-area through the distribution factor and the section power setting to realize the cooperative operation between the balancing machines..Starting from the active power flow equation of the tie line,the calculation formula of power exchange between sub-areas is derived,and the node parameters are introduced to represent the unbalanced power level and its distribution.Then,the node injection power formula is combined with the power exchange formula to establish an improved power flow model.At the same time,using the Newton iteration method based on the extended Jacobian matrix,the power flow variables in the integrated model can be adjusted simultaneously.(4)Through V-Q sensitivity analysis,the calculation results of traditional power flow model and improved power flow model with balancer parameters are compared.The results show that there are some errors in the analysis of multi-area system by traditional model.The improved power flow model is more accurate and has better convergence.In the case of large transmission power and heavy load,the error range may be extended to a considerable level,and the advantages of the new improved power flow model will be more prominent. |
