Study Of Power System Probabilistic Optimal Dispatching

With the expansion and deregulation of the power system, which is confronting more operating uncertainties, thus the operation condition is becoming more and more complicated. Especially the introduction of market competition mechanism, which leads the operation of power system to the margin of security, coupling with the contingency of generator outage and transmission component failure, thus the power system operating risk is increasing much more. Traditional power system dispatching framework is based on the deterministic model and method, which can not reflect the real system operating risk, so the dispatching results may be either conservative or radical as it does not take into account of the possibility of the contingency. Because of the complicated operating condition and the economic interaction of market participants, the traditional deterministic pattern is not suitable for current situation and needs to be upgraded urgently. Therefore, the coordination of severity and probability of the contingency in power system operating condition, unfolding the risk essence and economic meaning, and presenting the optimal allocating direction of the resources, i.e.constructing the direction by the economics and probability theory, combining the consideration between operating risk and dispatching strategy, so the power system probabilistic optimal dispatching in the real-time operating condition has become a urgent research problem.This thesis has investigated the optimal dispatching by considering probabilistic disciplinarian and economic law under the real-time operating background. Based on the mathematical optimization theory, the research of probabilistic optimal dispatching has been carried out. The main research work and innovation of this thesis are shown as follows:(1) The concept and frame of power system probabilistic optimal dispatching have been established in this thesis. By analyzing the evolution of power system optimal dispatching model, it can be demonstrated that the probabilistic dispatching theory develops and integrates the traditional optimal dispatching, reliability evaluation and operating risk research. The intention of power system probabilistic optimal dispatching is to associate probability and outcome of the contingency, and giving the optimal decision-making of coordinating the security, economy and reliability. Based on the DC power flow model, the probabilistic optimal dispatching model and solution method have been investigated by considering the generator outage and transmission component failure. Therefore, the power system operating dispatching researching level has been promoted.(2) The power system probabilistic optimal dispatching model and it's solution arithmetic of considering generator outage has been established. This model has the objective function of the expected operating cost minimum, by considering the generator probabilistic outage characteristic and ramping rate, so the operating cost, corrective cost and the load interruption compensation have been taken into account altogether. Therefore, the economic relation has been coordinated in this mode for pre-contingency and post-contingency states, and the optimal allocation of spinning reserve, also the responsibility among the generators can be quantified for each other. With the comparison and analysis of three different dispatching modes, the basic probabilistic optimal dispatching model has been demonstrated effectively by the solution arithmetic.(3) The power system probabilistic optimal dispatching model and solution arithmetic of considering the transmission component failure has been established. With the power network security value factor, the power system operating economy and security have been compromisingly combined into one uniform expected objective function, thus the probabilistic optimal results can be obtained with the constraint-set of power network normal state and definite contingency states. Thereinto, the so-called dispatching economy has considered the power system expected operating cost, which has also included the security-corrective costs of generator ramping and load interruption at the contingency state. The so-called dispatching security has been represented by the power network expected loading severity of both the pre-contingency and post-contingency states. Therefore, the dispatching economy and security have been coordinated, and the operating risk of dispatching mode has been quantified. With the comparison and analysis of five different dispatching modes, the further evolutive probabilistic optimal dispatching model has been demonstrated effectively by the corresponding solution arithmetic.(4) The power system probabilistic optimal dispatching model and solution arithmetic of considering the compositive operating benefit has been established. This model has the objective function of power system expected operating benefit maximum, which has considered the generator operating cost and the redispatching costs, also the load normal benefit and interruption compensation in demand-side has been considered. With the forecasting probabilities of transmission conponent contingency states in future period by markov chain, the optimal dispatching results can be obtained with the constraint of both pre-contingency and post-contingency state. And for the possible security breaking case during the post-contingency state, the generator unit ramping, emergent load interruption and transmission component short-term overloading within the allowable time have been included in the constraint-set, also the cost of the corrective measures have been taken into account. Therefore, the forecasting probability of the power network operational tendency and active power optimal dispatching decision-making have been combined in this model, which can attain the curve of expected operating maximal benefit in different dispatching period, also the coordinated dispatching mode under the probabilistic framework of harmonizing risk with benefit corresponding to that period and the corrective strategies for emergent states. By contrasting the different dispatching modes, this progressive power system probabilistic optimal dispatching model has been demonstrated to be effectively.(5) Based on the complexity analysis of the probabilistic optimal dispatching model, an efficient solution pattern has been brought forward. For the huge dimension of probabilistic optimal dispatching, it is inefficient to solve it as a whole problem. Enlightened by the decomposing thought of the traditional optimal dispatching method, the probabilistic optimal dispatching model characteristic has been analysed. Thus, the decrescent model has been obtained by the critical contingency selecting in cyclical pattern. Therefore, the dimensions of the original model has been decreased ,and the calculation efficiency has been improved by this solution pattern, thus it may be feasible for the large power system.