Beniamino Guida

Buck-boost DC/DC converter for aeronautical applications

In this document a DC/DC converter for power conversion between +28V/+270V voltage levels is presented, and the main characteristics of the converter are discussed. The topological structure is first introduced, outlining the hardware components used and the modular approach. The step-down (or Buck) and step-up (or Boost) modulations are then discussed, focusing on the switching signals to drive the low-voltage and high-voltage bridges of the single modules. The description of the control phase follows, justifying the controller used to steer the output voltage towards the desired value. The firmware realized for the converter management is equipped also with a supervision and protection logic, realized as a composition of finite state machines. Finally, simulative results and real measurements are provided to evidence the correctness of the overall topological choices and of the control system realized for the bidirectional converter, focusing also on the comparison between the expected results and those obtained.

Sliding mode control for DC/DC converters

In this paper, different sliding mode controls for DC/DC converters control are considered. Classical Buck, Boost and bidirectional Buck/Boost plants are presented for control application. A unified approach is adopted based on the mathematical tools of first- and second-order sliding mode output control. Set-up and ancillary conditions, as condenser pre-charging, are discussed and justified on a rigorous mathematical basis. Numerical simulations show the effectiveness of the proposed novel control strategy in terms of disturbance rejection and fast tracking of the output reference. Direct implementation with hysteretic controllers or PWM are possible.

A Petri net application for energy management in aeronautical networks

In this paper, the implementation of an Intelligent Load Power Management (I-LPM) strategy for an aeronautical electrical network using a Petri net based approach will be discussed. The control strategy for I-LPM implementation will be presented following a step-by-step approach. In details, a rigorous method for translating the requirements that describe the desired energy management logic in a formal Petri net will be discussed. Next, in order to verify the Petri net correctness in terms of qualitative properties, a number of reduction techniques steps will be applied, eventually deriving a straightforward net where some basic properties will be verified by direct inspection. Finally, simulation results will evidence how the first Petri net so far derived can be applied, as a consequence of the successful verification of its basic properties, as a supervisory control strategy for the I-LPM of a basic aeronautical electrical network, as well as the obtained advantages over a traditional energy management strategy.

Implementation of control and protection logics for a bidirectional DC/DC converter

In this paper, a control strategy for a bidirectional DC/DC power converter is discussed, and the logics to guarantee the operation correctness in various operative modes and for safety requirements are considered. In Buck (or step- down) mode, a voltage PI regulator is proposed, whereas in Boost (or step-up) mode an inner current control loop is introduced to guarantee a more effective current tracking, and to avoid damages due to overcurrents. Furthermore, a Finite State Machine (FSM) approach has been adopted to model the converter behavior and, in particular, to describe the protection logics for both Buck and Boost working modes, along with a special configuration called “Buffer control”, easily described using the FSM approach as composition of states. Numerical simulations results and real measurements show the effectiveness of the control strategy combined with a FSM logic description, rising up as a flexible approach to control a power converter device and to define its behavior in a desired working mode, as for buffer control.

Smart Buck-Boost Converter Unit operations for aeronautical applications

In this paper, sliding mode control for DC/DC Buck/Boost bidirectional converters (BBCU, Buck-Boost Converter Unit) is considered. The approach stems from aeronautic applications, and aims to produce an intelligent device able to autonomously switch from buck mode, where the battery pack onboard is recharged, to boost mode, where some energy from the battery is required to supply critical loads.Two levels of control are detailed: low-level switching, based on the sliding mode mathematical theory, and supervisory control of the device, based on hybrid control. Proofs of stability are provided. A scenario with standard operating conditions, then an overload and finally a return to standard condition is presented, and numerical simulations show the effectiveness of the proposed novel control strategy in terms of stability and performance of the smart converter. Direct implementation with hysteretic controllers or PWM are possible, and also finite-time stability considerations are given.

Supervised control of buck-boost converters for aeronautical applications

Recent MEA (More Electric Aircraft) concepts require new approaches to design and management of the electric system onboard. Bidirectional Buck-Boost Converter Units (BBCUs) used like bridges between power buses with different voltage require intelligent supervisory control for autonomous selection of operating modes. In this paper at low-level, sliding manifold-based strategies are employed to track desired current references, or to recover from overload within a prescribed time. At a higher level, three working modes are defined, (Buck-, Boost- and Intermediate-Mode), and scheduled by a high-level supervisory strategy. Stability proofs of the overall strategy require estimates of the Region of Attraction (ROA) for each controller, that are discussed in the paper. A typical aeronautic scenario is presented, with standard operating conditions followed by two types of overloads (the second more severe than the first) and finally a return to standard condition. Detailed numerical simulations show the effectiveness of the proposed novel control strategy in terms of stability and performance of the smart converter.

Boost Full Bridge Bidirectional DC/DC Converter for Supervised Aeronautical Applications

The More Electrical Aircraft concept requires electronic devices able to efficiently and safely convert electrical power between different voltage levels. The entire realization of a bidirectional DC/DC converter, from design to validation phase, is here discussed in detail. First, a boost full bridge electrical structure is selected, adopting a Parallel Input Parallel Output (PIPO) interleaving technique and an optimal turns ratio selection for the transformers in order to reduce both weight and size of the equipment. Next, modulation schemes in both step-down and step-up modes are discussed. Successively ad hoc PI regulators for both operative modes are presented. A key idea of the paper is that the converter behavior must be related not only to the control strategy but also to a global supervision logic able to safely conduct the converter operations and to react from external stimuli. Thus, a finite state machine (FSM) approach is employed. An innovative strategy called buffer mode is presented, defined as an intelligent combination of buck and boost modes. Extensive simulations and experimental results are shown, in order to confirm the effectiveness of the proposed approach.

Power management of DC aeronautical electrical networks including supercapacitors

This paper focuses on a novel energy management strategy for aeronautical electrical networks, including supercapacitors for fast energy charge/discharge cycles. Considering a simplified but representative architecture for a DC aeronautical electrical network, the bidirectional DC/DC converter equipment acts as a bridge between the HVDC network and the LVDC network, operating in Buck or Boost with respect to the current flight conditions and flight phase. The main idea of the paper is to let the DC/DC converter, connected between the DC bus and the supercap, being supervised in order to autonomously decide the conversion mode (i.e. Buck or Boost), in order to cope with generator overloads and reduce its overload capacity, hence its dimensions. The supervision is based on sliding mode for the converter control, whose stability proofs are given. Simulation results are shown in order to give evidence about the effectiveness of the proposed approach.

Intelligent power regulation using innovative modules for energy supervision

This paper focuses on the application of a new load power management concept called Intelligent Load Power Management (I-LPM) for aeronautical electrical networks, requiring the development of specific electrical modules, and of a related supervisory control strategy. Each phase required for the I-LPM equipment implementation is discussed, including requirements collection, design and implementation tasks. Simulations and experimental results are illustrated and commented, focusing on the power management benefits obtained with the I-LPM approach.

Supervised bidirectional DC/DC converter for intelligent Hybrid Electric Vehicles energy management

In this paper, an innovative supervisory control strategy for application on HEV energy management has been presented. An implementation for a basic DC/DC converter has been discussed, where a configuration composed by a LV battery and an HV bus fed by a battery has been arranged. The Recovery mode, discussed at length in this paper as an innovative method to overcome high-voltage bus drops due to sudden power peak demands from a traction motor, has been implemented by using a control structure based on a sliding inner current loop and an outer voltage loop, whose stability has been demonstrated by resorting to control theory results. Reported simulation results demonstrate the effectiveness of the proposed approach, considering the ability of the supervisory strategy to automatically switch from Buck to Boost, when an additional power supply is required from the secondary battery source, and return back from Boost to Buck, when the HEV is in normal cruise conditions. Experimental results will shortly follow in order to finely validate the intelligent strategy here discussed. The outlined approach is fully applicable to different DC/DC converter types, because it regulates the duty cycle value, common variable for each converter despite the effective adopted modulation strategy. Besides, an extension of the supervisory control strategy for braking energy recovery is currently under study.