Abstract
The paper presents a nonlinear continuous mathematical model of a current driver based on a closed-loop DC-DC boost converter. This converter represents a subsystem of a load simulator for ground testing of power supplies for autonomous low power (up to several tens of kW) objects implemented for various purposes. We consider the current value of 180 A as a center of expansion. The load current must vary within the range of ±10% with respect to this center. The model of the current driver is implemented in both continuous and discrete forms in Matlab Simulink, taking into account parametric disturbances in the form of a change in the equivalent output resistance of the converter. The adequacy of the developed models was confirmed. The current transfer function of the DC-DC boost converter is obtained with the assumption that its parameters are constant. This function is used in the form of a block diagram and applied as a linearized model of an open loop current driver. This makes it possible to implement the model for adjusting the current regulator. The adjustments for modular, linear and symmetric optima are tested on the nonlinear continuous model. This model makes it possible to identify the features of the current driver performance during design stage, taking into account the parameter spread of the power circuit components. It also allows us to optimally adjust the regulators and readjust them taking into account the generated load current waveform. To perform a soft start of the closed current driver loop tuned to the symmetric optimum and to prevent a controller from limiting its output at zero level, a ramp function reference generator was implemented. Its parameters were calculated. The tuned controller provides the desired current of the load simulator within the range 10% around the center of expansion corresponding to 180 A. The proposed approach makes it possible to significantly reduce the time and cost for the process of designing a current driver as part of a load simulator for power supplies of autonomous objects. Numerical experiments carried out on a continuous nonlinear model confirm the correctness of the assumptions made. This suggests that the nonlinear model can be implemented to develop various structures of load simulators while the linearized model may serve as a reliable entity to adjust the current controller.
Keywords
Current driver, load simulator, electrical complex, ground tests, power supply system, autonomous object, DC-DC boost voltage converter, controller adjustment, center of expansion, simulation model.
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