Marco Di Benedetto

Resonant Controllers With Three Degrees of Freedom for AC Power Electronic Converters

Grid-connected and stand-alone applications need inverters that accurately control the filter output voltages. Nowadays, resonant controllers (RCs) represent a good tradeoff between implementation issues and control performances. However, the unknown nature and size of supplied loads affect the dynamic control behavior and may reduce the effectiveness of the control system. A new structure of RC is introduced with the purpose of providing three degrees of freedom and allowing us to select independently the controllers magnitude, width, and phase. In order to fully take advantage of the proposed RC form, the online tuning procedure based on the output filter analysis is also proposed. According to that, several resonant compensators can be placed in the loop to achieve a better output voltage waveform (i.e., lower total harmonic distortion).

ISOP DC-DC converters equipped 5-level unidirectional T-Rectifier for aerospace applications

This paper deals with Input-Series Output-Parallel (ISOP) DC-DC converters to be used for capacitors voltage balancing in the 5-level unidirectional T-Rectifier for electric generating applications. The proposed generating unit is intended for aerospace applications, to this purpose the power electronic converter configuration is able to supply power to the electric loads at different voltage levels. The 5 level T-Rectifier output at ±270V feeds the ISOP DC-DC converters which output terminals are used to supply the 28V circuitry. Two different control strategies for the whole system are proposed, discussed and verified. First proposed architecture considers the AC-DC and DC-DC as coupled from the control point of view, introducing then the Couple Balancing Control Strategy (CBCS). A comparison is performed with respect to a completely decoupled regulation algorithm, where the AC-DC and DC-DC control loops are not nested, resulting in the Decoupled Balancing Control Strategy (DBCS).

Five-level back to back E-Type converter for high speed gen-set applications

Nowadays, high-speed turbines for electric power generation represent a good idea for commercial, industrial and military applications, where small size and lightweight, low maintenance, reliability in a wide range of environments and good efficiency are required. However, the main equipment in such power generating units are the electrical generator systems, the AC-DC power electronic converter and the output inverter, when AC output load is unavoidable. Multi-level power electronic topologies have been under research and development for more than one decade and have been found successful in variable-speed drive applications. The new power converter topology, called Five-Level E Type Inverter (5L E-Type Inverter), is presented and analyzed in this paper with reference to the back-to-back configuration with a multi-level rectifier. The thermal models of the IGBTs and diodes have been created taking into account the parameters provided by the manufactures and employing multi-dimensional look-up tables in Plexim/PLECS environment. Simulation results are performed through Matlab/Simulink in order to evaluate efficiency and losses distribution for switches and diodes of the proposed 5L E-Type inverter configuration.

Low frequency state-space model for the five-level unidirectional T-rectifier

This paper presents the analysis and the validation of the large signals model of a new five-level T-type unidirectional three-phase rectifier topology known as 5L T-RECT. Proposed modeling approach is mainly based on the well-known state-space averaging technique. Accordingly, to this technique, the averaging process is applied across one PWM sampling period TS, thus resulting in the basic 5L T-RECT mathematical model. Consequently, the AC-DC steady state operation is analyzed according to the achieved model. The large signals model of the 5L T-RECT has been verified through the direct comparison with the converter full digital-switching model, realized in the Matlab/Simulink environment. Simulation results exhibit a good matching with the proposed average model.

Analysis and design of LC filters for the 5-level 3-phase Back to Back E-Type Converter

This paper presents the analytical design procedure to select the inductance and the capacitance values of both the input and output filters for the 5-Level three-phase Back to Back E-Type Converter (5L3Φ BTB E-Type Converter). The 5L3Φ BTB E-Type Converter is used to accomplish the double conversion AC-DC/DC-AC in applications which include variable speed industrial electric drives and the interfacing of renewable energy sources with the utility grids. The filter topology consists of a two-cell structure in interleaving coupling through magnetic devices (inter-cell transformer — ICT) and it is able to connected in parallel two legs for each phase of the 5L3Φ BTB E-Type Converter. The use of the two-cells interleaved topology offers the advantages of reduction of size, losses and cost of the input and output filter, reduction of current stress of the DC-bus capacitors and enables better utilization of the power semiconductors. The preliminary results obtained with a 400V, 20kW 5L3Φ BTB E-Type Converter are presented to validate the analysis and the analytical design procedure of the filters.

Performance assessment of the 5-level 3-phase back to back E-type converter

An analytical approach for accurate calculation of the conduction and switching power losses associated with the switching devices in the 5-Level 3-Phase Back to Back E-Type Converter (5L3ϕ BTB E-Type Converter) has been proposed in this paper. The 5L3ϕ BTB E-Type Converter is composed by two different multilevel topologies: the 5-Level E-Type Inverter and the 5-Level E-Type Rectifier. The power losses analytical equations can be used to investigate the converters performance and efficiency as a function of the output power, the switching frequency and the modulation depth. Numerical results from the obtained analytical equations for calculation of conduction and switching losses of power devices have been compared with simulation results using Plexim/PLECS tool in Matlab/Simulink environment. The excellent match between analytic and simulation results validates the derived equations.

5-Level E-type back to back power converters—A new solution for extreme efficiency and power density

A novel solution to high efficiency and high specific power three-phase Back to Back Power Converters has been proposed and theoretically investigated in this paper. Target applications are variable speed gen-sets, electric drives and independent power supplies. The solution proposed is based on a novel 5-Level E-Type topology. Advantages of the new solution, such as significant reduction of the input/output filter size/weight and switching losses have been theoretically investigated. A typical 20kVA independent gen-set power supply application has been analyzed as a case study. An extraordinary double conversion efficiency of 98.6% and specific power of 5kVA/kg have been achieved. The design results has been confirmed by set of Plexim/PLECS simulations. This work is a part of an ongoing PhD Dissertation with Center for Power Electronics and Drives (C-PED) Roma-TRE University, Rome, Italy.

Variable speed generating unit for vehicle on-board applications

Variable speed operation has been proposed in literature as a solution to efficiency and pollution problems for diesel generating units, as well to improve efficiency and power conversion in rotating systems for renewable energy sources. In general, different topologies of prime-movers, like internal combustion engines, wind turbines and hydro turbines, etc. can be used to move an electric generator at variable speed. In variable speed generating systems, the electric output frequency is disengaged from the mover speed through a power electronic converter. This paper deals with a newly-conceived variable speed generating unit to be used in on-board vehicle applications. The control structure is discussed and experimentally verified by means of a 40kW rated power converter prototype. It is shown that the proposed voltage control allows simplifying the overall control configuration and fast compensation of load unbalances. Further to that, a complete current limiting strategy is described and tested under different load conditions.

Fault tolerance analysis for the 5-level unidirectional T-Rectifier

This paper deals with the fault tolerance analysis applied to the converter topology 5-level unidirectional T-Rectifier (5L T-RECT) to be used for electric generating applications. The proposed generating unit is intended for aerospace applications with high fundamental electric frequency, to this purpose the investigated power electronic converter configuration is able to supply power to the electric loads at different voltage levels. The depicted analysis has been performed to show the 5L T-RECT behavior in case of either switch or diode fault; identification and consequent action to be taken are shown in order to guarantee the converter continued operation.

Small-signal model for the ISOP DC-DC converters in the 5-level T-rectifier

A small-signal model for the Input-Series Output-Parallel (ISOP) DC-DC converters is developed in this paper. The proposed model is obtained applying the State-Space Averaging technique. The ISOP DC-DC converter consists of multiple DC-DC modules connected in series at the input and in parallel at the output. In this paper, the ISOP DC-DC converters are used in combination with the 5-level unidirectional T-Rectifier for electric generating units in More Electric Aircraft systems. The small-signal model for the ISOP DC-DC converters has been verified through the direct comparison with the converter full digital-switching model, realized in the Matlab/Simulink environment. Simulation results exhibit a good agreement between small-signal model and switching model.