http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

This paper proposes a line current distortion compensation method, which is a fusion of the conventional variable on-time (VOT) control and the average current mode (ACM) control, for DCM/CRM boost PFC converter with zero current switching (ZCS)/zero voltage switching (ZVS)/valley switching (VS)/switching frequency limitation (SFL) functions. In this paper, the mathematical analyses of the line current distortion for the DCM/CRM boost PFC converter with ZCS/ZVS/VS/SFL functions are also derived to explain the causes of the line current distortion. In order to increase efficiency, the ZVS/VS/SFL functions are needed but the line current will be further distorted. To compensate the distorted line current, the ACM-based VOT (ABVOT) control for the DCM/CRM boost PFC converter is proposed. In addition, the constant-on-time-based noise-immunity S/H method is proposed to replace the multiplier, which is always needed for the conventional ACM-based control. The performance of the proposed ABVOT control with S/H method will be demonstrated by simulation and experiment results.

Line Current Distortion Compensation for DCM/CRM Boost PFC Converters

Continuous conduction mode power factor correction (PFC) without input current measurement is a step forward with respect to previously proposed PFC digital controllers. Inductor volt-second (vsL) measurement in each switching period enables digital estimation of the input current; however, an accurate compensation of the small errors in the measured vsL is required for the estimation to match the actual current. Otherwise, they are accumulated every switching period over the half-line cycle, leading to an appreciable current distortion. A vsL estimation method is proposed, measuring the input (vg) and output voltage (vo). Discontinuous conduction mode (DCM) occurs near input line zero crossings and is detected by measuring the drain-to-source MOSFET voltage vds. Parasitic elements cause a small difference between the estimated voltage across the inductor based on input and output voltage measurements and the actual one, which must be taken into account to estimate the input current in the proposed sensorless PFC digital controller. This paper analyzes the current estimation error caused by errors in the ON-time estimation, voltage measurements, and the parasitic elements. A new digital feedback control with high resolution is also proposed. It cancels the difference between DCM operation time of the real input current, (TDCMg) and the estimated DCM time (TDCMreb). Therefore, the current estimation is calibrated using digital signals during operation in DCM. A fast feedforward coarse time error compensation is carried out with the measured delay of the drive signal, and a fine compensation is achieved with a feedback loop that matches the estimated and real DCM time. The digital controller can be used in universal applications due to the ability of the DCM time feedback loop to autotune based on the operation conditions (power level, input voltage, output voltage...), which improves the operation range in comparison with previous solutions. Experimental results are shown for a 1-kW boost PFC converter over a wide power and voltage range.

/pdf/universal-digital-controller-for-boost-ccm-power-factor-47ej8ntsjf.pdf

Universal Digital Controller for Boost CCM Power Factor Correction Stages Based on Current Rebuilding Concept

The full-bridge converter is often connected between the ac grid and the dc bus. In the conventional multiloop control, the inner current control loop shapes the ac-side current waveform, and the outer voltage control loop regulates the dc-bus voltage. In this paper, the single-loop bidirectional current sensorless control (BCSC) for the full-bridge ac/dc converter with considering both the inductor resistance and conduction voltage is first proposed. The average-value behavior of the full-bridge ac/dc converter is analyzed and it is simplified to an equivalent single-switch model. Based on this developed equivalent model, BCSC is designed and implemented in the FPGA-based system. There is only voltage control loop in the proposed BCSC (i.e., no current control loop), but BCSC is able to regulate the dc-bus voltage and shape the ac-side current. The provided results in both the rectifier operation and the inverter operation demonstrate the effectiveness of the proposed BCSC.

/pdf/bidirectional-current-sensorless-control-for-the-full-bridge-1qg57t3s92.pdf

Bidirectional Current Sensorless Control for the Full-Bridge AC/DC Converter With Considering Both Inductor Resistance and Conduction Voltages

The three-level boost power factor correction (PFC) converter has advantages of lower inductor current ripple and lower switch withstanding voltage compared with the boost PFC converter. Interleaved pulsewidth modulation had been used in the multiphase boost PFC converter. In the literature, interleaved current sensorless control (ICSC) for the multiphase boost PFC converters had been proposed. In this paper, the behavior of the three-level boost PFC converter is first analyzed. The results show that three-level converter has the same average equation as the interleaved boost PFC converter. Then, ICSC is modified for the three-level boost PFC converter with considering the voltage imbalance and the zero-crossing current distortion. The proposed modified ICSC (MICSC) is implemented in a field-programmable gate array board. Simulation results and experimental results are also provided to validate the proposed MICSC.

Modified Interleaved Current Sensorless Control for Three-Level Boost PFC Converter With Considering Voltage Imbalance and Zero-Crossing Current Distortion

As is generally acknowledged, the main drawback of a fully digitalized power factor correction (PFC) rectifier is that too many analog-to-digital converters (ADCs) are used, and hence, the corresponding cost is high. Consequently, in this paper, the information on the desired signal is obtained from two paired saw-toothed waves compared with the sensed signal, without the use of any ADCs. For the PFC rectifier operating in the continuous conduction mode (CCM) under average current mode control, the two proposed formulas used to calculate the average inductor current, together with the strategy for changing sampling points, are applied to accurately sample the average inductor current of the PFC rectifier. At the same time, based on the slope value of the inductor current obtained from the proposed average current calculation formula, another related formula is derived to obtain the input voltage information used to feed the partial feedforward controller. As for the sinusoidal current command, it is generated by a sinusoid table along with a zero-crossing detector. Furthermore, the information on the output voltage is obtained by one simple approximate formula. Therefore, there is no ADC required to realize the full digital control of the PFC rectifier operating in CCM.

Fully Digitalized Implementation of PFC Rectifier in CCM Without ADC

As generally acknowledged, the main drawback of a fully-digitalized power-factor-correction (PFC) rectifier is that too many analog-to-digital converters (ADCs) are used, and hence the corresponding cost is high. Hence, in this paper, the information on the required signal is obtained via two paired sawtoothed waves compared with the sensed signal, without any ADC used. For the PFC rectifier operating in the continuous conduction mode (CCM), two proposed formulas used to figure out the average inductor current, together with the strategy for changing sampling points, are applied to accurately sampling the average inductor current of the PFC rectifier. At the same time, based on the slope value of the inductor current obtained from the first average current calculation formula, another formula used to calculate the input voltage is derived so as to obtain the input voltage information used to feed the partial feedforward controller. As for the sinusoidal current command, it is generated by a sinusoid table along with a zero crossing detector. On the other hand, the information on the output voltage is obtained by one approximate formula. Therefore, there is no ADC required to realize full digital control of the PFC rectifier operating in CCM. Furthermore, the feasibility and effectiveness of the proposed sampling topology are verified by experimental results.

H. W. Chen

Papers

Fully Digitalized Implementation of PFC Rectifier in CCM Without ADC

Fully-digitalized implementation of PFC rectifier in CCM without ADC