Nikonenko Y. Control of electric vehicle electromechanical systems with battery- supercapacitor hybrid energy storage systems

The thesis is devoted to design methods development of traction electromechanical systems (EMS) based on AC vector-controlled electric drives (ED) with batteries-supercapacitors (SC) hybrid energy storage systems (HESS) aimed at improving static, dynamic, and energy characteristics through the development and implementation of nonlinear and adaptive control methods. The first section analyzes the existing traction EMS with HESS control methods to substantiate the importance to solve the scientific and applied problem considered in the thesis. Based on the results of the analytical review, it was found that the induction IM field-weakening systems do not ensure the full utilization of the primary source power. The batteries-only energy sources are typically applied to power modern electric vehicles (EV) which causes their accelerated aging. Typical HESS control systems which are based on linear proportional-integral controllers (PI-controllers) of currents and voltages with a low-pass filter (LPF) do not have a rigorous rationale, and the stability of significantly nonlinear systems has not been proven. As a result, the HESS and traction ED subsystems are interconnected and sensitive to coordinate and parametric disturbances. The main of which are variations of the IM active rotor resistance, PMSM and DC-DC converters electrical parameters. These perturbations lead to degradation of dynamic control quality indicators and reduction of energy efficiency of electromechanical energy conversion processes in existing systems. In the second section, new field-weakening algorithms in IM field-oriented control systems are developed, which provide a more complete usage of the source power. Also an adaptive observer of the IM active rotor resistance is designed, as well as identification algorithms of PMSM parameters, using the second Lyapunov method. They provide a globally stable estimation and are easier to use than existing analogues. In the third section, a theoretical study of the stability properties and characteristics of bidirectional DC-DC boost converters control systems were performed. Note that they are nonlinear non-minimum-phase control plants. The standard configuration with linear PI current and voltage controllers was considered. As a result of the theoretical analysis, it was found that: the resulting structure of the control system is in the form of a sequential connection of two linear asymptotically stable subsystems in a nonlinear feedback loop with bilinear properties. For the first time, the structure of the control system provides linearization with respect to a physically determined manifold, which is the power balance equation. The form of the linearized system allows the use of the theory of cascaded systems with the time-scale separation such that the internal (current) control loop is several times faster than the external (voltage) control loop. For the first time the mechanism of the load current affecting the structure of DC-DC converter control systems and their parameters is shown. It provides more robust tuning of the controllers to increase the converters load capacity. It is shown that the load current compensation in a controller improves the dynamic voltage stabilization accuracy. In the fourth section, for the first time, the structure of composite HESS control system is theoretically substantiated. It consists of coupled DC-link voltage, battery and SC currents subsystems, a frequency distribution filter (FDF), and a SC voltage control subsystem. It is proved, by considering the reduced-order system dynamics, that the SC current reference scaling as a function of the battery and SC voltages ratio in the FDF (feedback linearization), as well as the time-scale separation of control loops provide asymptotic DC link voltage control and the battery and SC currents components dynamic distribution. It has been shown that the load current compensation improves the dynamic quality indicators of DC-link voltage regulation. A new SC voltage controller has been developed. Tuning recommendations ensure that the SC charging process does not affect the DC-link voltage regulation. In the fifth section, a concept of EMS with HESS experimental studies is substantiated. It allows to develop unified experimental installations for full-scale testing of a wide range of control algorithms under conditions close to those existing in real EV. The rapid prototyping station for the study of traction EMS was designed, manufactured and commissioned. It consists of a 0.7 kW IM, a 3 kW PMSM, lithium-ion and lead-acid batteries, and a SC unit with DC-DC converters. The full-scale experimental testing of the developed control structures were performed on the rapid prototyping station to confirm the theoretical conclusions and identify effects that are not taken into account during design and in simulation. The setup is controlled by a controller based on TMS320F28335 DSP and designed software.