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China's power system has entered the new stage of large-unit large-scale system, ultra-high-voltage, cross-regional networking. The emergence of ultra-large-scale power network is very beneficial to the overall network economic dispatch and emergency backup, but it also brings a series of new unfavorable factors. . In the case of power system networking becoming the mainstream of development, how to ensure the safe, stable and efficient operation of power systems, how to ensure adequate, reliable, high-quality and economical power has become a frontier topic in the field of power system control, although new control After the theory and scheduling strategy were introduced into the power system, some fruitful research results were indeed achieved. However, judging from the recent blackouts in various countries, the current power system is still relatively fragile. The emergency control of the hybrid power system is caused by large disturbances in the power system, and the system frequency and voltage are greatly deviated from the rated value or even beyond the allowable range. A series of correction controls to ensure stable operation and continuous power supply in the event of a system stability crisis. The measures can be applied to the power side (such as cutting machine, fast closing, etc.) load side (such as load shedding) or power grid (such as series compensation switching) for emergency control purposes to quickly suppress accidents and abnormal behavior states at a minimum cost. Develop and expand, minimize the duration of failures, reduce the impact of accidents on non-faulty parts of the power system, and keep the power system as safe and reasonable as possible.
However, the power system is essentially non-pure. 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 of power generation process, transmission and distribution. Algebraic logic constraints of electrical systems, as well as multi-objective optimal control with or driven by discrete events, make the emergency control problem of power systems necessarily have the characteristics common to hybrid control systems. This paper models hybrid control systems based on differential Petri nets. And an effective tool for analysis, a model for hybrid power system frequency emergency control is established, and simulation control is given.
1 Timing differential Petr 1.1 Time-differentiated differential Petri net definition Common Petri nets have unique advantages in the description and analysis of discrete event dynamic systems, but there is no way for a continuous variable dynamic system that exists in practical engineering practice. The hybrid control system is a unified body composed of three parts: an event-driven discrete operating mechanism, a continuous variable controlled process, and a conversion 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 sampling (hold) time period; k = int(t/Ts); from the continuous variable controlled process to the discrete event operating mechanism The event generation coupling amount V will be sampled with Ts as the period, and the holding time of the dominant coupling amount T(k) formed by the "internal control law" from the discrete event operating mechanism to the continuous variable controlled process should also be Ts; intC) Analysis of the modeling elements for the frequency control of the hybrid power system for the rounding function 2.2. Equation of motion: X: la 0.8Hz), low frequency automatic load shedding device action
Controllable event: 2c= = make the rotating standby full, so that the hydroelectric generating unit with phase modulation operation and pumped storage operation is changed to power generation operation, start the quick start unit, cut the load, and unwind the uncontrollable event: 2u==; continuous Partial input: u=: The results of simulation using MATLAB software are shown in the simulation results. In the case of 5%, 65%, and 10% overload of the system, the control method proposed in this paper can be used. It can be seen that in the case of 10% active power shortage, the system adopts the method of pre-cutting the load according to the frequency reduction rate proposed in this paper, and removes part of the load about 4s after the fault occurs, which accelerates the recovery process of the system frequency.
The differential Pet network model proposed in the 4 language language, because it can simultaneously process the evolution process of continuous variable dynamic system and discrete event dynamic system, makes the optimization strategy of frequency emergency control of hybrid power system can be started from the whole, thus achieving better control effect. However, due to the hybrid nature of modern large-scale power systems, the model built with the differential Pet network will have a problem of “state dimension explosion†when the system scale is large. This requires further improvement of the Pet network. To improve its ability to express and solve. These issues will be our future research priorities.
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