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Taking micro-grid hierarchical control as the object, aiming at the synchronization of amplitude and phase of the voltage in micro-grid point of common coupling with the grid side voltage in the process switching islanding mode into grid connected mode, the relationship between the voltage phase difference, the magnitude difference of fundamental wave in network switch and error voltage magnitude was set up, and the grid-synchronization control strategy for the minimum value searching of double disturbance was proposed based on the Fourier transformation to eliminate effectively the voltage difference between the micro-grid point of common coupling with the fundamental wave voltage in grid side, reduce the impact to micro-grid in moment closing network switch. Eventually, the algorithmic was verified through simulation and experiment.

The principle of injected fundamental and harmonic current of grid-connected inverter with droop controller is analyzed firstly in this paper, and a compound harmonic current suppression strategy of GC-VCI with distorted grid voltage is proposed. A notch filter is firstly designed for the separation of different frequency components of the PCC voltage. Then the fundamental component of the inverter's output is controlled by the droop controller solely. A PIR complex controller is adopted for enhancing the tracking ability for harmonic component. As a result, the difference of harmonic voltage between PCC and the output point of inverter is reduced, and the injected harmonic current is decreased. These theoretical findings are verified through simulations and experiments on the laboratory platform.

Aiming at the low-power operation of PV power generation system(PVPGS), the output current distortion of PV power generation system was discussed by theoretically analyses and experimental investigations. An effective solution was presented for suppressing the harmonic distortion of grid current. Finally, the experimental validation was carried out. The results reveal that the proposed solution can effectively suppress the low-order grid current harmonics of on-grid inverter in the low-power operation and enable total harmonic distortion of grid current in the low-power operation meet the grid codes of IEEE Std.1547-2003.

This paper addresses the low-frequency relative stability problem of the grid-connected voltage source inverter (VSI) based distributed generation (DG) unit in microgrid, in which the conventional active power-frequency (P-ω) and reactive power-voltage (Q-E) droop controllers are commonly used to share the loads. In the sense of the characteristic equation and eigenvalues, the relative stability and the transient response are remarkably affected by the change of the droop gains and/or stable operating points, resulting in the poor damping and eventually instability. An improved P-ω and Q-E droop scheme based on the static droop characteristics combined with a derivative term is presented to preserve the system stability and obtain an improved damping performance. Subsequently, the dynamic performance of the system can be adjusted without affecting the static droop gains to damp the oscillatory modes of the power sharing controllers. Finally, the desired transient and steady-state responses can be obtained.

This book provides a comprehensive and consistent introduction to the Internet of Things. Hot topics, including the European privacy legislation GDPR, and homomorphic encryption are explained. For each topic, the reader gets a theoretical introduction and an overview, backed by programming examples. For demonstration, the authors use the IoT platform VICINITY, which is open-source, free, and offers leading standards for privacy. Presents readers with a coherent single-source introduction into the IoT;Introduces selected, hot-topics of IoT, including GDPR (European legislation on data protection), and homomorphic encryption;Provides coding examples for most topics that allow the reader to kick-start his own IoT applications, smart services, etc.