Study Of Control Strategy Of Tie-Line Power Between Areas Considering ACE Constraint

China has a vast territory, the regional disparity of economic development is obvious. The distribution of resource center and load center is uneven. Electricity demands mainly concentrate in the south-east coast areas, while energy resources mainly concentrate in the north-west areas. So large scale of cross-region transmission is needed. Meanwhile, the commission and operation of UHV AC/DC power grid makes the operation of interconnected power grid more complicated. The transmission power of tie-lines between areas should be in accordance with the tie-line plan. A deviation between tie-line actual exchange power and planed exchange power may cause the over-load of the tie-line which is a serious threat to system security, especially for the UHV tie-line. The transmission capacity of a UHV line is 5 times of an EHV line. If the UHV tie-line break down duing to the over-load, large scales of power transfer will be caused, which have much more serious effects on power system.Measures should be taken to eliminate the over-load when the tie-line power exceeds its limits. These measures are known as TLR (Transmission Loading Relief). The most widely used TLR method is the method based on sensitivity. Regulate the most sensitive generators so that the over-load of tie-line power can be eliminated efficiently. The method is flexible and its physical meaning is very simple. But, the responsibility of control areas is not considered. It may cause the areas which lead to the tie-line over-load do nothing to eliminate the off-limit yet the areas which shouldn’t be responsible for the over-load have to regulate for other areas. It’s very unfair.Aiming at the above problems, the paper puts forward a new TLR method considering ACE constraint. The new method distribute regulation to control areas. Only the responsible control areas take the regulation task, and the greater responsibility, the more regulation. ACE reflects the balance between generation and load in a control area. The size of responsibility of each control area can be reflected by ACE. The new method allocates regulation to control areas according to ACE. It effectively solves the fairness problem of the TLR method based on the sensitivity and is good for the reasonable and safe operation of power grid.The paper uses 118 nodes test system to simulate the new TLR method considering ACE constraint and the traditional method based on sensitivity. The results show that the number of generators and control areas take part in regulation of traditional method is less than the new TLR method, but the adjusting time is not necessarily shorter because of the ramp rate limits. Also, the traditional method can’t embody the fairness. The essence of the new TLR method is an optimization problem. The objective function can be different according to the actual demand. And the indicators can be controlled within an acceptable range using multi-objective optimization. The new method allocates regulation task to control areas according to the ratio of ACE, so it is conducive to the recovery of ACE.