Theoretical Research On Real Power Balancing Control Performance Assessment Method Of China Power Grid

The current real power balancing control performance assessment method applied in China power grid follows the index and form of the assessment standard in North American grid.For China grid's operation principle and structure are different from North American grid's,the theoretical basis of the current method should be improved.In addition,the development of ultra-high voltage alternating current/direct current(UHV AC/DC)transmission and large-scale renewable energy integration has changed the concept and process of real power balancing control.The change causes the decline of applicability of the current method.Therefore,there is a need to design a new assessment method which has a defensible theoretical basis and can meet operation requirements of China grid.This thesis is to propose a new assessment method,the purpose of which is to maintain the overall reliable operation of grid.Based on the national standard document on grid operation,the scope of application of the new method is mainly aimed at normal operation and I level disturbances.Considering the definition of reliability,providing overall normal power supply has become the basis to design control requirements which include the requirement for maintaining power supply quality,security and adequacy requirements for maintaining power supply quantity.Taking the national standard document on power quality into account,the requirement for power quality has been translated into maintaining long-term frequency quality.According to the national standard document on grid operation,the requirements for power quantity have been described that under-frequency load shedding and over-frequency unit shortage would not be triggered under I level disturbances.The above real power balancing control requirements for overall grid can be meet by frequency and emergency reserve control and convert into assessment requirements for control areas with Tie-line Bias Frequency Control(TBC)mode.Then,three assessment indexes including long-term index,security index and adequacy index have been obtained.Long-term index can reflect area's long-term ACE control performance.Security index and adequacy index can reflect area's short-term ACE and emergency reserve control performance.In designing the latter two indexes,normal operation and I level disturbance are differentiated.For the influence on real power balancing control by new characteristics of grid,the appropriate frequency control modes have been proposed.State-network-provincial dispatcher should respectively adopt 'FFC-FFC-(n+1)TBC" and "FFC-TBC-(n+1)TBC" mode when regional networks interconnected by UHVAC and UHVDC tie-lines.This thesis discusses that cooperation control philosophy should replace the traditional regional autonomy philosophy and puts forward three new cooperation control concepts.For the operation principle of "Unified Dispatch and Hierarchical Management"',a three-level assessment structure in which network and provincial dispatchers are both the objects to be inspected is established.Assessment indexes are designed for different interconnection conditions and cooperation control concepts.To implement the proposed method,a new automatic generation control(AGC)strategy in which fuzzy control logic and dynamic threshold coefficients are used is raised.The strategy can reconcile requirements for operation security and frequency quality.Test results show that the proposed method,comparing with the current methods,has the more reasonable assessment results and the function to lead areas'performance to meet requirements for overall reliable operation of grid and decreases the number of orders to regulate AGC units.