Research Of The Implementation Mode Of Tie-line Power Control Performance Assessment Standard

With the rapid economic development of our country, the power load is growing very fast. But the distribution of the source and the power load is imbalanced. The ultra-high voltage (UHV for short) alternating current (AC for short) transmission which can transmit large capacity of electric energy remotely is the development tendency. The power control of the UHV tie-line is very important in the UHV AC transmission. The excessive power fluctuation of the UHV tie-line makes the power flow exceed the steady state limit and leads to the voltage fluctuation of the two side500kV power grid. This causes the difficulty of voltage regulation and threats the safe operation of the power grid seriously.At present, the tie-line power control performance assessment standard (standard T for short) is put forward to suppress the power fluctuation of the UHV tie-line. It has received favorable effects in practical use. However, our analyses prove that the implementation mode of only standard T or the parallel implementation mode of CPS and standard T cannot balance the control of the UHV tie-line power deviation and the frequency deviation. The two implementation modes of standard T reduce the quality of operation and make the power system unsafe.To solve the above problems, firstly this paper analyses the rationale of CPS and standard T. Their control methods are both the ACE, but they have different control objectives. The control objectives of CPS and standard T are the frequency deviation and the UHV tie-line power deviation. Because of the different control objectives, the control areas will have regulation contradictions in the parallel implementation mode of CPS and standard T. This will reduce the control efficiency and threaten the safety of the power grid. The serial implementation mode of CPS and standard T is put forward to solve the regulation contradiction. The basic theory is that the control area changes their control performance assessment standard in different running state. The whole UHV interconnected power grid implements only one control performance assessment standard, CPS or standard T. The control objective is the same in all control areas at the same time. So, the regulation contradiction will not be appeared. This can improve the control effect. According to the thought of grabbing the principal contradiction, this paper has designed four control modes in four running state of the UHV interconnected power grid. These control modes can balance the control of the frequency deviation and the UHV tie-line power deviation. At last, the numerical simulation of the serial implementation mode of CPS and standard T proves that the serial mode can control both the frequency deviation and the UHV tie-line power deviation. So, the serial mode has rationality and validity.