In this paper, different types of synergetic controllers (SCs), such as simple SC, piecewise linear function form of SC, linear synergetic controller, improved synergetic controller with terminal SC, and fast terminal SC have been designed and applied to an islanded DC microgrid. To be able to make the design of the controllers independent from system component values, a generalized mathematical method has been derived for all power electronics-based subsystems of the microgrid system. A small-scale DC microgrid has been designed and implemented to verify experimentally the robustness of the control law from the different synergetic controllers. Moreover, a generalized synergetic controller design approach has been derived in this paper for the islanded DC microgrids. The obtained results from both simulation and experiment tests have been compared and included in this paper. It is concluded that definition of macro variables is affecting robustness and tracking performance of the designed controllers.
The cyclic variations in spark ignition engines occurring especially under specific engine operating conditions make the maximum pressure variable for successive in-cylinder pressure cycles. Minimization of cyclic variations has a great importance in effectively operating near to lean limit, or at low speed and load. The cyclic variations may reduce the power output of the engine, lead to operational instabilities, and result in undesirable engine vibrations and noise. In this study, spark timing is controlled in order to reduce the cyclic variations in spark ignition engines. Firstly, an ARMAX model has developed between spark timing and maximum pressure using system identification techniques. By using this model, the maximum pressure of the next cycle has been predicted. Then, self-tuning minimum variance controller has been designed to change the spark timing for consecutive cycles of the first cylinder of test engine to regulate the in-cylinder maximum pressure. The performance of the proposed controller is illustrated in real time and experimental results show that the controller has a reliable effect on cycle to cycle variations of maximum cylinder pressure when the engine works under low speed conditions.
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