Search

This paper proposes an integrated common and differential mode filter with passive damping for single-phase grid-connected transformerless photovoltaic (PV) microinverters, employing the full-bridge voltage source inverter (VSI) topology with continuous unipolar modulation. This strategy achieves low current distortion, low leakage current and high efficiency. A design procedure for the proposed filter is presented including the passive damping components. The effectiveness of the proposed solution is confirmed by simulation and experimental results. Additionally, discussions about safety standards, analysis of leakage current production mechanism and some common mode (CM) filter implementations found in the literature are presented.

This paper presents an optimized tuning method of Proportional Resonant (PR) current controllers implemented in the stationary frame. The approach consists of defining three operation regions based on behavior of the closed loop poles, and of determining simplified tracking and disturbance transfer functions for each of these regions. Charts of proportional and resonant normalized gains versus settling time and overshoot are then built, allowing the designer to easily visualize the influence of these gains on the transient response. It is shown that the disturbance response performance is more significant than the tracking one, and that minimum settling time and overshoot for this case are obtained if the resonant gain is set equal to the controller resonant frequency, providing a simple and efficient rule-of-thumb for the designer. Simulation and experimental results are presented to validate the method.

The Dynamic Voltage Restorer (DVR) is a solution for protection of sensitive loads from voltage sags and swells. Its basic function is to inject voltages in the grid line in order to mitigate voltage sags and/or swells. Typically the controller structure for a DVR is composed by an inner current loop and an outer voltage loop. Usually a proportional or proportional integral controller is used for the current loop and a resonant controller is used for the voltage loop. This paper presents the design of a robust controller for the voltage tracking loop of a DVR that guaranties the robust stability against load parameters variation, and assures the tracking of a sinusoidal voltage waveform and the rejection of the non linear load current influence with a pre specified error. The voltage controller design is based on H8 parameter specification approach. All the performance and robustness requirements are specified and analyzed based on the frequency response plot of closed loop transfer function. The proposed controller performance is validated by using PSIM software simulation and by experiments carried out on a DVR.

The ability to individually extract the many disturbances of the AC line currents or voltages is desirable for reference signal calculation algorithms employed in power conditioners, allowing improved utilization of the power converter. This paper proposes a novel algorithm based on the dot product of three dimensional space vectors in the abc coordinate system, for real time calculation of the instantaneous positive, negative and zero sequence components for each individual harmonic. It is presented the functionalities for compensating fundamental reactive power, selected current harmonics and current unbalances. This method is computationally simple and requires no coordinate transformation. The proposed algorithms are validated by simulation and experiments.