Grid-connected PWM Converter Research Articles

The DC Inductor Current Ripple Reduction Method for a Two-Stage Power Conversion System

This paper proposes a method for minimizing the inductor current ripple of a DC–DC converter in a two-stage power conversion system consisting of a grid-connected PWM converter and an interleaved multiphase three-level DC–DC converter. To reduce the output voltage ripple, the three-level DC–DC converter is configured in parallel and operated interleaved. However, a circulating current generated by the interleaved operation increases the inductor current ripple of each DC–DC converter and causes system loss and inductor saturation. In this paper, the inductor and output current ripple of the interleaved three-phase three-level DC–DC converter is mathematically analyzed and the effect of the DC–DC converter’s duty ratio and output voltage on each current ripple is described. Based on this analysis, a method is proposed for controlling the optimal DC link voltage through the PWM converter, so that the DC–DC converter is controlled with the duty ratio that minimizes the inductor current ripple. The simulation and experimental results under various operating conditions are presented to verify the feasibility of the proposed control method.

Design of new robust backstepping control for three-phase grid-connected fourleg source voltage PWM converters

Design of new robust backstepping control for three-phase grid-connected fourleg source voltage PWM converters

Harmonic Current Suppression Strategy for Grid-Connected PWM Converters With LCL Filters

As for a grid-connected PWM converter with LCL filter, harmonic current can flow freely into the grid-side inductor and filter capacitor, when the connected power grid is harmonically distorted. The fact lies in that the conventional control scheme has a little ability to suppress the grid current harmonics. Though the harmonics can be suppressed by the capacitor current compensation method, it may lead to system stability issues. This paper proposes an improved harmonic suppression scheme with the partial capacitor current feedforward, which can effectively suppress the specified grid current harmonics on the premise of ensuring the system stability. Since the partial capacitor current is obtained as the differential output of a multi-second-order generalized integrator, no extra current sensors are needed. The effectiveness and feasibility of the proposed strategy are verified by detailed experimental results.

Performance evaluation of continuous and discontinuous pulse width modulation techniques for grid-connected PWM converter

Power quality has become an important issue as the number of nonlinear loads and power electronic equipment connected to the grid is continuously growing. Grid-connected PWM converters have been largely exploited in many industrial applications; they still present an interesting research subject in terms of improving current waveform quality and providing an accurate DC-link voltage. Besides the different control strategies proposed in the literature corresponded to a specific requirement performance, the modulation techniques also present a critical aspect in the design of the control system. In this paper, several modulation techniques including continuous and discontinuous modulations have been studied and analyzed for the control of grid-connected PWM converter. An extensive simulation and experimental tests have been carried out in order to investigate the influence of the studied modulation techniques on the harmonic current distortion delivered by the converter under different unbalanced grid conditions.

A Review on Direct Power Control for Applications to Grid Connected PWM Converters

A Review on Direct Power Control for Applications to Grid Connected PWM Converters

A Review on Direct Power Control for Applications to Grid Connected PWM Converters

The Direct Power Control strategy has become popular as an alternative to the conventional vector oriented control strategy for grid connected PWM converters. In this paper, Direct Power Control as applied to various applications of grid connected converters is reviewed. The Direct Power Control for PWM rectifiers, Grid Connected DC/AC inverters applications such as renewable energy sources interface, Active Power Filters, Doubly Fed Induction Generators and AC-DC-AC converters are discussed. Control strategies such as Look-Up table based control, predictive control, Virtual Flux DPC, Model based DPC and DPC-Space Vector Modulation are critically reviewed. The effects of various key parameters such as selection of switching vector, sampling time, hysteresis band and grid interfacing on performance of direct power controlled converters are presented.

Single-phase Grid-connected Photovoltaic System With Active Power Line Conditioning

This paper deals with an alternative current reference generator algorithm proposition, which is employed to inject active power into the grid and, simultaneously, performs reactive power compensation and load harmonic current suppression in single-phase grid-connected photovoltaic (PV) systems. The PV system reference current is computed based on synchronous reference frame method, which operates in conjunction with the dc-bus controller. In addition, by adopting a proper strategy, it is proposed criteria for establishing the priority on the power compensation by the PV system, in order that the power rating of the gridconnected PWM converter is not exceeded. The Perturband-Observe maximum power point tracking technique is employed to generate the dc-bus voltage reference for extracting the maximum power from the photovoltaic array and, therefore, maximizing its efficiency. Both simulation and experimental results are presented to verify the static and dynamic behaviors of the grid-tied photovoltaic system, as well as evaluate its performance.

A Capacitance Estimation of Film Capacitors in an LCL-Filter of Grid-Connected PWM Converters

A capacitor deterioration of LCL-filter grid-connected PWM converters is progressed by the self-healing mechanism. It leads to the degradation of the filter performance and drop of power factor. Thus, it is required to diagnose fault-point of capacitors and determine the replacement time. Typically, the fault of capacitors is determined when the capacitance is reduced up to 80% from initial value. This paper proposes algorithm to the determine capacitor replacement time of an LCL filter. The algorithm takes the advantage of change of the response on the injected resonant frequency corresponding to 80% value from the initial capacitance. The results of the algorithm are demonstrated through simulations and experiments.