Effective low‐cost solution using cascaded connection of two modified notch filters to mitigate the second and third harmonic currents in single‐phase dual‐stage half‐bridge microinverter

Abstract

On the grid side, the half-bridge topology of the microinverter is of interest for solar rooftop applications because of its high efficiency, low component count, and cost-effectiveness. However, it has an inherent double-line frequency ripple voltage on the dc-link, which causes the injection of a third-order harmonic current when the voltage control loop is closed. Furthermore, in practice, different average voltages or different capacitances of the two capacitors at the dc-link produce a second-order harmonic current that flows into the grid. In this paper, the analytical details of these harmonics are comprehensively described, and a simple and effective low-cost technique using the cascaded connection of two modified notch filters is proposed in the voltage control loop to mitigate their effects. The simulation and experimental results of a 300 W microinverter indicate that the proposed filters represent an effective low-cost solution and perform well in accordance with the IEEE 1547 standard, even if the capacitances at the dc-link are mismatched by 20%. Besides, the prototype is tested when occurring of the changing +1% of the line frequency, or appearing of the distorted waveform of grid voltage with the composition of 6% of fifth-order harmonic. Nomenclature Capital boldface italic letters such as V, represent phasors. Capital italic letters such as C 1 , represent constant variables. Small italic letters such as v dc (t), represent instantaneous variables depending on time. Small italic letters such as ṽ dc (t), represent small ac signals in the time domain. Capital italic letters such as G vp (s), represent transfer functions in the s-domain. Small italic letters such as v dc (s), represent signal variables in the s-domain.

High performance current control of single‐phase grid‐connected converter with harmonic mitigation, power extraction and frequency adaptation capabilities

“…The DQH control scheme uses a large number of mathematical operations which have an execution time of 9.08 μs for the TMS320F28069 microcontroller running at 90 MHz. The calculation of sine and cosine at the harmonic grid-tied photovoltaic inverters [18], and PWM rectifiers. The DQMR control scheme is a good alternative to the DQH control technique, requiring only a slightly greater computation time than the PMR controller, while retaining the power extraction capability as the DQH technique.…”

“…The current signals i ′ d (t ) and i ′ q (t ) are not available for the PMR controller. The instantaneous active and FIGURE 18 Experimental results of the DQMR control scheme under the distorted PCC voltage reactive powers can be controlled through the power references p ref (t ) and q ref (t ) which become correct once the grid current error to reach zero. In other words, the PMR control has an indirect power control capability.…”

“…However, there is an inherent current error due to a finite regulator gain at the grid frequency [15]. Among the stationary frame controllers, the proportional-resonant (PR) regulator is widely adopted in the grid current control loop of the VSCs [6,[16][17][18]. The PR regulator has a relatively large gain at the grid frequency which enforces the current error to zero.…”

Energetiškai efektyvaus fotovoltinio mikroinverterio kūrimas

“…Antruoju etapu nuolatinė įtampa, naudojant sinusinės impulsų pločio moduliacijos metodą SIPM (angl. SPWM -sine pulse width modulation), inverteriu keičiama į kintamąją (Vongkoon et al 2019). Dalyje publikacijų pristatomi taip vadinami grįžtamieji (angl.…”

“…In the first stage, the voltage of the photovoltaic module is raised by a DC/DC converter to a value close to the amplitude of the electrical grid voltage. In the second stage, the DC voltage is converted to a variable by an inverter using the sinus PWM technique (Vongkoon et al 2019).…”