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In this article, a droop control algorithm is proposed for power distribution between sources in an island inverter-based microgrid without common central control. The analyses of the line impedance influence (resistive, inductive, and combined) are provided to show the impact on the power flow between a grid and a converter. Line impedance character influences the droop control algorithm performance. The impact of the accuracy of the setting, concerning line impedance, of the proposed droop control algorithm is then tested in a simulation. For the simulation, a microgrid model was built in the Simulink environment (MATLAB) with the PLECS toolbox. In the conclusion, the potential benefits and applications of the proposed droop control are discussed.

The Fortescue theorem is a well-known transformation technique for parameter identification in three-phase systems. It is a valuable tool that transforms an unbalanced system into symmetrical components. This method itself can not be used in a real-time system because it needs to identify individual vectors of the voltage. The solution proposed in this paper is to combine the Fortescue theorem with a second-order generalized integrator (SOGI). The SOGI algorithm provides two functions. Firstly, it identifies voltage vectors. Secondly, it works as a band-pass filter. This means it can deal with the systems containing multiple harmonics, processing them individually. This paper evaluates the performance of the proposed algorithm, with a focus on harmonic selectivity and speed of the reaction during transients.

In this paper we deal with predictive control of Interior Permanent Magnet Synchronous Motor (IPMSM) drive. The main goal of this paper is to improve produced torque quality by using precise mathematical model of IPMSM, which takes into account anisotropy of the motor construction. This phenomenon results in the effects such as nonlinear back EMF, high cogging torque etc. A conventional control algorithms deal with those effects by designing an optimal current references depending on some part of the motor non-linearity. The current reference design however may be quite complicated in the context of maintain high quality control performance with reasonable complexity of the control algorithm. In this paper we design a precise IPMSM model, which is based on measured characteristics of the real IPMSM. Furthermore a simple IPMSM model-based predictive controller using finite set of control actions with a simple cost function is presented. The cost function is designed to achieve tracking of required torque directly without the need for designing any current references. The proposed control algorithm is very simple and easy to implement, while achieving high quality torque control. The performance of the control is tested in experiments on a laboratory prototype of the 4.5kW IPMSM drive.

A cost-effective STATCOM is proposed and discussed in this paper. Its modular topology enables to scale the power to target systems. Besides reactive power, the proposed STATCOM enables to generate a zero-sequence component and compensate the voltage asymmetry, e.g., in widely spread medium-voltage distribution power grids with resonant grounding.

Converter losses play a crucial role in the process of power converter design. Especially semiconductor components and heat sink selection are strongly dependent on the total power converter losses and thus affect the power converter size and its price. The most popular techniques for determination of the losses are based on the computer simulation of the power converter. These kinds of simulations could be very time consuming, because on one side, the simulation needs very short steptime for differential equations calculation to model power converter switching. On the other side, the temperature dynamics of heat sink are commonly slow and depend on power cycles of converter. With the help of FPGAbased hardware in the loop (HIL), the simulation could run real-time and it is possible to test different scenarios, different modulation techniques and see their influences on converter losses. This approach can lead to reduction of losses to the state, when it is possible to reduce the size of converter. Furthermore, the HIL simulation could be used for testing and developing control algorithm in real time conditions. It also offers flexibility in the easy change of model parameters and monitoring values which are not or hardly obtainable in real machine. This paper presents the FPGA-based HIL simulator of induction motor drive with three phase voltage source inverter based on Semikron IGBT modules.

The paper is focused on the tram input LC traction filter stabilization by the super capacitor energy storage system. The input LC filter is almost undamped resonant circuit connected on the both sides to the sources of disturbances. On the input side, LC filter is connected by the tram pantograph to the dc-trolley overhead lines. The main disturbances are caused by the dc-trolley voltage drops, other vehicles, pantographs head arcs, etc. On the output side, the LC filter is connected to the traction drive. With the constant torque command, the tram during the voltage drops increase the current flow from the LC filter to hold constant torque and thereby further decrease the LC filter voltage, and vice versa. This could lead to unstable traction drive behavior. The super capacitor storage system, which is commonly used to accumulate energy during tram breaking, can be furthermore used to stabilize LC filter voltage. The paper describes the algorithm of the LC filter stabilization by the super capacitor storage system control.

Dual induction motor single inverter drives reduce installation space, weight and overall cost. On the other hand, complexity of the control increases significantly, since the condi­tion on each electric machine can vary in a wide range. Today, majority of control algorithms uses cascade structures of linear PI controllers. The consequences of parallel connection of induction motors are addressed by priorilizing of individual motors in the control by a weighting coefficient. The proper choice of the weigbting coefficient, which is generally state-depend ent time­ varying value, strongly affects the overall drive performance. In this paper, state of the art control techniques for dual motor drives are summarized. Based on the detailed analysis of the theoretical back ground , we formulate a control criteria which solve tbe whole control problem witbout additional cascades in a single loop by finite control set mod el predictive control (FCS-MPC). The extensive simulations are used to analyze and validate the designed control criteria.

The model predictive control is a set of algorithms which uses the dynamical model of controlled system to predict the future systems responses. Nowadays, the nonlinear finite control set model predictive control (FCS-MPC) is a popular technique for control of induction motor drives. The FCS-MPC enables accurate and high-dynamic control of the induction motor currents, rotational speed, torque etc. with respect to system constraints (e.g. urrent/voltage limitations). The main drawbacks of FCS-MPC algorithms are their computational requirements which reduce FCS-MPC prediction horizon and its applications. Our paper is focused on the FPGA accelerator of FCS-MPC of induction motor extended by the three phase inverter model with dead-times and voltage drops. These inverter nonlinear effects play important role especially in nonnominal drive conditions (e.g. low speeds).