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Dual-comparison one-cycle control for the bidirectional power flow in single-phase grid-connected converters is proposed in this paper. Advantages of dual-comparison one-cycle control when compared to conventional one-cycle control is that it does not give any steady-state dc offset, no light-load instability, and implements unipolar pulsewidth modulation without having to sense the grid voltage. Addition of a fictitious current term, which is generated from the gating signal of one of the active devices, using a bandpass filter, enables the bidirectional power flow. The quality factor of the bandpass filter is shown to impact the total harmonic distortion in current, fundamental displacement angle, and steady-state dc offset. The optimal value of a quality factor, obtained with aid of simulations, gives a superior performance. The current drawn or injected into the grid is seen to lag the grid voltage. The reason for a nonunity displacement power factor is analyzed and a compensation to achieve a unity displacement power factor is also proposed in this paper. Detailed simulation and experimental studies are carried out to validate the proposed control and the high performance that can be obtained. [ABSTRACT FROM AUTHOR]

Widely distributed single-phase power electronic rectifier loads are an increasing source of harmonics in the power distribution system. These harmonics have many well-known adverse impacts on the power system, so it is necessary to improve the power quality of the rectifiers. This paper presents a novel single-phase rectifier in which capacitors are used in parallel with diodes in one leg of the rectifier. A general analytical model of the proposed topology is obtained. The closed-form expressions for the rectifier waveforms are utilized in parameter selection that leads to optimal performance in terms of input current total harmonic distortion (THD). Different topologies of rectifiers are compared in terms of the input voltage, current waveform distortion, output dc voltage ripple, and desired target for the dc output voltage. The proposed topology reduces the THD from 145% in a normal rectifier to 63% while maintaining voltage ripple less than 0.3%. The proposed topology keeps dc bus ripple small while simultaneously providing better THD. The passive components considered for improving harmonic injection are two small capacitors. The additional cost required for the proposed rectifier is low, and the proposed rectifier also has a higher efficiency than the other commonly used diode rectifier topologies. [ABSTRACT FROM AUTHOR]

Resistance emulation using one cycle control (OCC) has been used extensively in single-phase full-bridge boost rectifiers. This paper proposes a new control strategy called dual comparison OCC (DC-OCC), which eliminates the limitations of OCC. The advantages of the proposed control strategy is that it ensures the average current is equal to grid voltage scaled by emulated resistance, in each switching cycle. This eliminates issues such as dc offset due to the peak current comparison in OCC. It also ensures that there is no distortion in current when the converter is lightly loaded. It is analytically shown that the proposed DC-OCC does not have the light load instability concerns of conventional OCC. The proposed method is also shown to achieve unipolar pulse-width modulation without sensing the grid voltage resulting in lower effective switching frequency. The proposed control requires only one additional comparator and additional logical elements for implementation. Detailed simulation and experimental studies are carried to validate the proposed control and the high performance that can be obtained. [ABSTRACT FROM PUBLISHER]