In this paper a non-isolated high step-up DC/DC converter, belonging to the family of Reduced Redundant Power Processing Converters (R2P2), is investigated for high power applications. The selection of this topology as the most suitable for such applications among those belonging to the R2P2 family is justified. Emphasis is given on the theoretical analysis of the real step-up voltage ratio of the converter, and voltage and current stresses under continuous and discontinuous conduction modes of operation, taking into account the non-ideality of the topology components, namely the parasitic resistances of semiconductor devices and inductors and the voltage drop of diodes. The theoretical analysis and the behavior of the selected converter are experimentally validated through a 2kW prototype. Moreover, the overall efficiency of the chosen converter is experimentally investigated for various step-up voltage ratios and for a high-power range, considering a waste heat recovery system for a maritime application.

In this paper, an effective procedure for broken rotor bar (BRB) fault detection in a three-phase squirrel-cage induction machine (SCIM) is proposed. This approach relies on a motor current signature analysis (MCSA) by observing the specific fault-related current component generated by applying the DC injection braking method. Unlike the traditional MCSA, which is commonly focused on the detection of BRB sidebands around the fundamental current component, the proposed methodology introduces a new BRB feature in the current spectrum which makes it much easier for identification. The distinctive time-frequency evolution pattern of this feature provides the reliable identification of BRBs, even under no-load operating conditions, thus overcoming the major drawback of traditional MCSA-based methods. Fault severity classification is easily performed through the magnitude inspection of the BRB fault-related current component. In addition, the proposed approach does not require high-complexity signal processing algorithms to achieve reliable results. The proposed concept is presented theoretically, assisted by a magnetically coupled multiple circuit model of the SCIM, both with healthy and faulty rotor bars. Finally, the experimental tests validate the proposed methodology and demonstrate its effectiveness and usefulness.

With the increase in power installed from distributed generation sources (DGS), many problems have appeared following the utilisation of novel topologies and structures. Higher-level controllers for the safe operation of power grids with a high penetration of DGS must be developed. This task becomes difficult as the size and complexity of modern power systems have increased. The development and testing of these systems under strict human supervision controlling each step of the testing procedure is no longer viable. This paper presents a comprehensive integrated platform based on an HIL emulator for the development and testing of electric power systems rich in DGS. Essentially, DGS is considered a controllable black-box system. A detailed calculation of the power references for an arbitrary DGS is shown. The paper also describes the utilisation of enhanced Python scripting which was designed to load all network-related data, start the emulation, collect the data, and generate reports. Furthermore, fully developed controller built-in oscilloscope functionality is introduced. The incorporated oscilloscope facilitates non-intrusive DGS controller data acquisition and analysis, reducing the need for external measurements. The proposed framework was verified by a case study in which a grid topology consisting of 26 nodes was emulated on parallel CHIL infrastructure. Four active and twenty-two passive nodes were instantiated and their reaction to a distribution network grid faults was examined. DGS converter control was executed in external controllers outside of the dedicated HIL environment. All DGSs were governed by different control strategies, regarding maximisation of active/reactive power production, minimisation of the active/reactive power oscillations, adjustable positive/negative components ratio, or without any limitations under voltage disturbances. Real-time experiments confirmed the usefulness and flexibility of the proposed framework concept.

This paper examines the control strategy adopted for six-phase machines that have been designed as double three-phase machines without a displacement between the magnetic axes of the two sets of three-phase windings (6PH-ZS). The approach is based on vector control principles, enabling the independent control of direct- and quadrature-current components in both three-phase windings. The advantages of such an approach stem from the flexibility of the current distribution between windings, which aims to achieve the required flux and torque. The proposed control strategy is considered for both motor and generator operating regimes. However, an additional quasi-transformer regime is also addressed. While the classic operation regime requires the machine to produce either driving or generating/braking torque, the quasi-transformer regime enables the control of electric power flow between two three-phase windings. A theoretical analysis of the machine model and control algorithm for the flow of electric power through machines is presented for the three aforementioned operating regimes. Verification of the proposed control algorithm is performed through extensive experimental verification.

Hardware-in-the-Loop (HIL) emulation is poised to become unsurpassed design tool for development, testing, and optimization of real-time control algorithms for grid connected power electronics converters for distributed generation, active filters and smart grid applications. It is strongly important to examine and test how grid connected converters perform under different operating conditions including grid disturbances and faults. In that sense, converter?s controller is a key component responsible for ensuring safe and high-performance operation. This paper demonstrates an example how ultra-low latency and high fidelity HIL emulator is used to easily, rapidly and exhaustively test and validate standard control strategy for grid connected power electronics converters, without need for expensive hardware prototyping and laboratory test equipment.