The emergence of super-large-scale power networks in the new phase of the large-scale system, ultra-high voltage, and cross-regional networking of China’s power systems has greatly benefited the entire network in terms of economic dispatch and emergency backup, but it has also brought a series of new unfavorable factors. . Under the circumstance that power system networking becomes the mainstream of development, how to ensure the safety, stability, and efficient operation of electric power systems and how to ensure sufficient, reliable, high-quality, and economical electric power have become frontier topics in the field of power system control. Although, new controls After the theories and scheduling strategies were introduced into the power system, they have indeed achieved some fruitful research results. However, judging from the blackouts that have occurred in various countries in recent years, the current electric power system is still relatively brittle. The emergency control of hybrid electric power systems is caused by large disturbances in the electric power system, and the frequency and voltage of the system deviate greatly from the rated values ​​and even exceed the allowable range. When a stable crisis occurs, a series of calibration controls are performed to ensure the stable operation and continuous power supply of the system. Its measures can be applied to the emergency side of the power supply side (such as cutting machine, fast off, etc.) on the load side (such as load shedding) or the power grid (such as series compensator switching) to quickly suppress accidents and abnormal behavior status with minimum cost. Develop and expand, minimize the duration of failures, reduce the impact of accidents on the non-failure part of the power system, and maintain the power system at a safe and reasonable level of operation.
However, the power system is inherently non-pure in nature. In addition to the characteristics of high dimensionality, strong nonlinearity, multi-distribution parameters, and randomness of interference, the most important property is the dynamic continuity and transmission and distribution of its power generation process. The algebraic logic constraints of electrical systems, and the multi-objective optimization control driven by discrete events or the like, make the emergency control problems of power systems necessarily have the features common to hybrid control systems. This paper models hybrid control systems based on differential Petri nets. With the analysis and effective tools, the model of frequency emergency control of hybrid power system was established and the simulation control was given.
1 timed differential Petr 1.1 The definition of timed differential Petri nets The ordinary Petri nets have unique advantages in the description and analysis of discrete event dynamic systems, but they are incapable of doing a great deal of continuous variable dynamic systems in practical engineering practice. The hybrid control system is a unity of three parts composed of an event-driven discrete operating mechanism, a continuous variable controlled process, and a transition interface between the two. The open-loop model can be represented by a nine-tuple. That is, the equation of motion that determines the dynamic behavior of the hybrid control system is: 0, TsGR+ is the given sample (hold) time period; k = int(t/Ts); from continuous variable controlled process to discrete event operator The event generation coupling quantity V will be sampled in cycles of Ts, and the holding time of the dominant coupling quantity T(k) formed by the “internal control law†from the discrete event operating mechanism to the continuous variable controlled process shall also be Ts; intC) For the rounding function 2.2 Analysis of the modeling elements of the frequency power control of hybrid power systems f. Equation of motion: X introduced: la 0.8Hz), low-frequency automatic load-reducing device operation Load removal (removal take multistage, differential take 0.2Hz ~ 0.3Hz); s5: restore the operating state (A /> 1.2Hz), according to actual conditions splitting system, to try to ensure the operation of the system after splitting.
Controllable event: 2c = = full rotation reserve, so that the phase-shifting operation and the pumped-storage-powered hydroelectric generating unit are changed to the power generation operation, the quick-starting unit is started, the load is cut, and the uncontrolled events are resolved: 2u ==; consecutive Partial input: u=: The result of simulating the system with MATLAB software can be seen from the simulation results. Under the condition that the system overloads 5%, 65%, and 10% respectively, the control method proposed in this paper can be used. It can be seen that, in the case of active power shortage of 10%, the system adopts the method of cutting load in advance according to the frequency reduction rate proposed in this paper. A part of the load is removed in about 4s of the fault, which accelerates the recovery process of the system frequency.
The differential Pet network model proposed in the 4-junction language can handle the evolution process of continuous-variable dynamic systems and discrete-event dynamic systems at the same time, making the optimization strategy of frequency-emergency control of hybrid power systems possible from a global perspective, thereby achieving better control effects. However, due to the promiscuity of modern large-scale power systems, the model built with the differential Petnet network will have the problem of “state-dimension explosion†when the system is large-scale, which requires further improvement of the Pet network. To improve its ability to express and solve problems. These issues will be the focus of our future research
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