A Transient Stability Preventive Control Strategy Of Power System Basing On Risk

Currently, with the rapid development of long-distance power grid interconnection, fardistance and large power transmission have formed the scale between regional powergrid;at the meantime, the power industry also have entered into the era of large power grid,high pressure, heavy duty,(super) long-distance. With the continuous development andgrowth of the electricity market, the operators of power system are not only in the pursuit ofstability, but also increasingly want to be able to obtain greater economic benefits.Therefore, how to balance the operation safety and economy of power system by usingvarious control strategies, and result in the most rational economic benefits, while ensuringthe stable of power system, which is of great significance for the long-term operation anddevelopment of large-scale power system. The transient stability preventive control ofpower system is the most effective way to achieve this goal. Furthermore, how to realizereal-time react is a problem needed to be solved basing on the currently running state (suchas real-time failure probability of power system). Meanwhile, power system should makequick react in the early or medium period after the occurring of transient accidents, which isthe key requirements of transient stability preventive control of power system, hence thereal-time calculation’s requirements of transient stability preventive control strategies isquite high. Based on on-line monitoring data of transmission lines and currentmeteorological data, this paper propose a real-time fault probability evaluation model oftransmission line considering meteorological factors; further more, this paper proposes acontrol strategy to balance the security and economy of power system basing on extendedequal area criterion theory and the real-time fault probability of transmission lines.Firstly, the real-time fault probability model of the transmission line are deeplydiscussed. In order to calculate the real-time fault probability value of transmission line,first of all, according to the online monitoring data of the transmission line’s insulator,conductor, lightning arrester, tower, and ground line, the quantitative model of eachmonitoring parameter is established respectively. Then the theory of unascertained rationalnumbers is used to determine the weight coefficient of each layer, and combining with fuzzy assessment method, finally a real-time and hierarchical fault probability assessmentmodel of transmission line is established. Through analyzing the failure statistics data ofsouthern power grid, it is found that bad weather has become an important factor causingthe fault of transmission line. Considering the effects of bad weather on transmission line’sfault probability, this paper puts forward and sets up a real-time evaluation model oftransmission line’s fault probability considering both transmission line’s on-line monitoringdata and the current meteorological conditions. The example shows that the proposedassessment model of transmission line’s real-time fault probability is reasonable andeffective.Then, the transient risk assessment of power system mainly involve the failureprobability and consequences, in order to make reasonable assessment of risk basing on thereal-time running state (including meteorological factors) of power system, this article willmake the calculation using the real time fault probability of transmission line. In order toachieve a reasonable quantification of the value of transient risk assessment, this article hasproposed a normalized severity index and normalized transient risk index, basing on theaccelerating area and deceleration area of contingencies calculated by EEAC algorithm.At last, basing on risk assessment theory and extend equal area criterion, a newtransient stability control strategy of power system is proposed. According to theacceleration area and deceleration area and fault probability of contingency, a normalizedtransient risk index is defined, the system’s overall transient acceptable risk index and thetransient acceptable risk index of a single contingency are also defined according to theproposed rule.Based on these indices a preventive transient risk control strategy of powersystem is proposed. The control strategy can identify the contingencies of instability withlow risk which should be ignored. Hence, it can effectively prevent excessive control, inother words, it can guarantee the transient security of the system and reduces the cost ofcontrol. Simulation results on New England10-machine and39-bus system verified therationality and effectiveness of the control strategy.