Research On Frequency Bias Coefficient In Automatic Generation Control

In interconnected power systems, it's required frequency and tie-line power interchanges should operate at scheduled frequency and scheduled interchanges. Automatic generation control (AGC) is the main technical means to actualize the above function. AGC calculate area control error (ACE) on different control modes, and regulate area AGC units' output power to keep ACE in the required bound. So frequency and interchanges could return to the scheduled values, and it could actualize the balance between system generation and load demand at scheduled frequency.In tie-line frequency bias control mode, the setting of area frequency bias coefficient in ACE formula has an important effect on controlling system frequency stability, AGC's dynamic response characteristic, and the fair distribution of area frequency support obligation. Aiming at frequency bias coefficient' different functions, some correlative problems, which have no good solution as yet, like frequency bias coefficient' ascertained method,setting mode, and distributed principle, are analyzed and studied in this paper.Firstly, based on the elementary principle of selecting frequency bias coefficient, under different system operation modes, it presented an all-day multi-period frequency bias coefficient setting method in Chapter 2. For actualizing power assistance between control areas, it could modify ample reserve area's frequency bias coefficient to B_dp+â–³B. Meanwhile, combining our country's AGC hierarchical control mode, it also presented another frequency bias coefficient setting method, which adjust grid area and province areas' frequency bias coefficients according to |â–³f| grade.On this basis, using multi-target optimum technology and super-short-term load forecasting (SSTLF), it presented an object-controllable and ahead frequency bias coefficient setting method to ascertainâ–³B in Chapter 3. In the algorithm, control factors are introduced, which could control each object's importance artificially according to areas' characteristics and decision-makers' intentions. Using the results of SSTLF, it could calculate each area's frequency bias coefficient ahead to actuliaze AGC's ahead control.Based on the theoretical analysis and model simulation, in different system technical conditions, it compared the influence of system control performence for using variable or fixed frequency bias coefficient setting mode. Thus it presented that the influence of frequency and tie-line power interchange are small for using variable or fixed frequency bias coefficient under the existing system technical condition. And as long as sysem total frequency bias coefficient is fixed, under the condition of enough reserve capacity and available transfer capability, it doesn't impact frequency quality for distributing area's frequency bias coefficient in different proportion. On the existing system technical condition and the intending developmental tendency, some reasonable proposals for setting area's frequency bias coefficient are put forward.In order to guarantee frequency quality and fairly distribute area secondary frequency regulation obligation, through properly setting system's and area's frequency bias coefficients, it could arrange a more reasonably desired secondary frequency regulation characteristic to each area from above to below. Meanwhile, in order to improve area primary frequency control ability, it required each area's natural frequency characteristic coefficient must achieve the arranged this area's frequency bias coefficient. Thus it presented the fair distribution mode of area primary and secondary frequency support obligation in Chatper 5. Hence frequency bias coefficient is endued with a new function: according to the proposed frequency bias coefficient setting method, area's frequency bias coefficient not only could restrict area secondary frequency regulation characteristics, but also be a baton for leading and improving area primary frequency control ability to the required target.Aiming at the existing problems in control performance assessment criteria, the concept of area frequency control responsibility error and the corresponding transaction mechanism are presented in the regional layered electricity market in Chapter 6. The introduction of this transaction mechanism could inspirit area to actively accomplish its frequency regulation responsibility through market means, and improve system's frequency quality and opertiaon efficiency.Because the existing power system simulation software can't satisfy our research requirement, for verifying the correctness of the proposed theory and method, by using MATLAB/Simulink, a dynamic simulation system for studying short-, mid- and long-term frequency control in interconnected power systems is built in Chapter 7. By several cases, it showed the results of theory calculation and the simulation is accordant. And it verified the validity and rationality of the simulation system in mid- and long-term frequency control dynamic processes by using field data.In conclusion, the paper studied the setting of frequency bias coefficient in AGC. Based on summarizing and using the research achievements both at home and abroad, it presented new setting method,new control function and assessment function of frequency bias coefficient. On the proposed frequency bias coefficient setting method, it could guarantee and improve frequency quality, harmonize grid and province dispatchs' AGC action of, distribute area frequency regulation obligation fairly. The study of the paper could provide theory basis for interconnected power system operating more safely,economically and in high quality.