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Active power filter (APF) control is a natural area of application for vibrating reference frame (VRF) transformation due to the intentional occurrence of higher harmonics in the active filter current compensating load current harmonics. Due to the vibrating frame transformation, the APF current can be represented by the DC values, and thus proportional-integral (PI) controllers are sufficient to control the converter current. However, in the typical approach, it may be impossible to combine harmonic filtration with reactive power compensation features, due to the transformation constraints. The solution to this issue is decoupling of the fundamental harmonic and high harmonic components and a separate control for each of them. This paper presents a decoupled control system of an APF, which uses VRF transformation for accurate control of high-current harmonics. Decoupling is a groundbreaking improvement of the VRF method. Moreover, different current limitation scenarios are proposed, considering both harmonics compensation and fundamental frequency reactive current compensation. Theoretical considerations are supported by simulation and experimental tests.

The paper presents a control method for the three-phase power converter operating under unbalanced grid voltage conditions. The method uses a new transformation to the non-Cartesian frame, which makes the controlled current vector components balanced in this frame even if originally the three-phase current is referenced as unbalanced. Furthermore, Park’s transformation makes the controlled variables constant, which allows to apply proportional–integral terms as current controllers independent of the required control target. Several control targets known from literature have been analyzed with regard to the required new transformation parameters, and the transformation parameters for all targets have been found. Simulation results are shown to prove the theoretical analysis, and the experimental test results are presented as practical validation of the proposed use of the non-Cartesian frame in control.

One of the currently investigated problems in power electronics-based electrical energy conversion is proper operation of electronic converters during grid voltage imbalance and harmonics. In classic control methods, it introduces oscillations of variables, resulting in the necessity to improve control systems with signals filtration and usually by application of resonant terms as part of current controllers. The paper presents a new approach to grid-connected inverter control based on transformation to a non-Cartesian frame, the parameters of which are correlated with grid voltage asymmetry. The proposed method results in resignation from resonant terms used as controllers and their replacement with proportional–integral terms for which anti-wind-up structures are significantly simpler than for oscillatory terms. The paper presents new transformation principles, features and some simulation results showing the waveforms of signals transformed to the new non-Cartesian frame.

The paper presents the current development of the AOS-H2 electric motor-glider project. The project encompasses the design and manufacture of an electric propulsion system (EPS) and a CF/epoxy airframe to be used as a flying test platform for the designed EPS. A 40-kW electric motor is supplied by a 10-kW PEM fuel cell stack and a Li-ion battery during run-up and ascent and by the fuel cell stack alone during steady flight. The airframe and the EPS have been completed; the results of bench tests of the EPS have proved that it meets the established requirements..

This article concerns the connection process of a squirrel-cage induction generator to the grid/microgrid. Typically, the generator is unexcited, and its connection to the grid is made directly via a switch. This connection causes a high inrush current and grid voltage drop, which local consumers notice. This article proposes a robust power system consisting of the squirrel-cage induction generator, a power electronic converter, and a capacitor bank, all connected in parallel. The proposed configuration and a dedicated control system eliminate the inrush current and compensate for the generator's reactive power during grid-tied operation. The converter controls the generator voltage build-up to adjust the generator voltage to the grid voltage (controlled excitation) and connects the generator to the grid, minimising distortions. Moreover, the system is robust because the failure of the converter does not stop the power generation, unlike a system with a back-to-back converter, where the converter links the generator and the grid. Furthermore, the parallel-connected converter has a significantly reduced power rating because it is only rated for a part of the reactive generator power. The rest of the reactive generator power is delivered by the fixed capacitor bank. The article presents the system configuration, the control method, and laboratory results confirming the system's effectiveness in maintaining high-quality grid voltage during generator-to-grid connection and high-quality power supplied to the grid. [ABSTRACT FROM AUTHOR]

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The paper presents a multi-phase doubly fed induction machine operating as a DC voltage generator. The machine consists of a six-phase stator circuit and a three-phase rotor circuit. Two three-phase six-pulse diode rectifiers are connected to each three-phase machine section on the stator side and in parallel to the common DC circuit feeding the isolated load. The same DC bus is also common for the rotor side power electronics converter responsible for machine control. Two methods - direct torque control DTC and field oriented control FOC - were implemented for machine control and compared by means of simulation tests. Field oriented control was implemented in the laboratory test bench. [ABSTRACT FROM AUTHOR]

• Elaboration of the full and reduced order of state space model of cascaded brushless doubly fed induction generator. • Design of the full state feedback control of cascaded brushless doubly fed induction generator with rotor current estimator. • Design of the reduced state feedback control of cascaded brushless doubly fed induction generator designed. • Comparative study of full and reduced order state feedback control of cascaded brushless doubly fed induction generator using MW range model of cascaded brushless doubly fed induction generator. The cascaded brushless doubly-fed induction machine (CBDFIM) is the developed version of a classic slip-ring doubly-fed induction machine (DFIM). Deprived of the main DFIM disadvantage - the slip-ring connection, the cascaded brushless doubly-fed induction machine has better durability and lower maintenance costs. Structurally it is realized by the presence of control stator and main stator working with a common rotor shaft. However, this type of electrical machine is characterized by much higher control inertia and larger dq control axis coupling, in comparison to DFIM. This fact makes problematic obtainment good dynamic performance and stability of the controlled system for classic control schemes. In the paper presented cascaded brushless doubly-fed induction machine state-feedback control schemes, based on CBDFIM full and reduced state-space model. Proposed algorithms allow control of CBDFIM generated active and reactive power components in a grid-tied operation and offer great possibilities of obtaining the desired dynamics parameters and stability of the controlled system. The main paper goal is to prove that reduced order state feedback control can be equally effective than full state feedback control in terms of obtained closed loop system dynamics and reduces influence of the couplings between the controlled variables. [ABSTRACT FROM AUTHOR]