Abstract
The primary frequency modulation (PFM) performance of a power control system (PCS) is an important factor affecting the security and stability of a power grid. The traditional control method is proportional integral (PI) control. In order to improve its dynamic control performance, a control method based on the combination of internal model control (IMC) and PI is proposed. Using the method of theoretical assessment and system identification, a simple simulated model of the typical PCS is established. According to the principle of system identification and the least square estimation (LSE) algorithm, the mathematical models of a generator and a built-in model are established. According to the four dynamic performance indexes, the main and auxiliary assessment index of the PCS are defined, and the benchmark and the result of the performance assessment are given. According to three different structures, the PFM dynamic performance of the PCS is analyzed separately. According to the dynamic performance assessment index of PFM, the structure of the control system and the influence of different parameters on the performance of the PCS are analyzed under ideal conditions. The appropriate control structure and controller parameters are determined. Secondly, under the non-ideal condition, the influence of the actual valve flow coefficient on the performance of the control system is studied under two different valve control modes. The simulation results show that the internal model combined with PI has better dynamic control performance and stronger robustness than the traditional PI control, and it also has better application prospects for thermal power plants.
Highlights
Power grid frequency is an important index of power quality that reflects the balance relation between active power and load
Frequency control of the power grid consists of three stages according to execution order, namely primary frequency modulation (FM), secondary FM, and triple FM
Because the thermal power units occupy a very important position in China’s energy structure proportion, this paper mainly studies the effect of thermal units on the primary frequency modulation (PFM) performance of a power grid
Summary
Power grid frequency is an important index of power quality that reflects the balance relation between active power and load. Establishing a simplified PCS model with certain accuracy has become the primary task in studying the dynamic performance of PFM of generating units. As PFM is an important function of thermal power units related to the power grid, its performance has a direct impact on the security and stability of the power system [13,14,15,16]. According to two kinds of steam turbine valve control modes, the actual valve local flow coefficient is calculated, and the dynamic characteristics and robustness of a PCS under different control strategies are analyzed. Under the simulation environment, when the valve local flow coefficient is different, the performance of the PCS in PI and IMC mode is compared and analyzed, the root locus is plotted, and the robustness of the system is analyzed.
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