In this article, a new bidirectional single-stage interleaved totem-pole electrolytic capacitorless ac–dc converter with high-frequency isolation and low components count is proposed. The proposed converter is constructed using nonregulating two-phase interleaved totem-pole converter switched with a fixed 50% duty on the grid side and a full-bridge on the dc-side for active power and dc output regulation. This switching method results in a ripple-free grid current regardless of the magnitude of the input inductances. Consequently, a proper design of input inductance secures soft switching for all switches under wide voltage and load ranges without an auxiliary circuit or resonant tank. Hence, the proposed topology overcomes the reverse recovery issue, thereby enabling the use of Si devices in CCM. Moreover, the current spike around the ac main zero-crossing is avoided in the CCM operation due to small rectified voltage around zero-crossing. Furthermore, the instantaneous powers at the grid side and dc-side are identical since the proposed topology is electrolytic capacitorless with inherent second harmonic ripple current at the dc-side. PFC is inherently performed in the proposed converter without a current shaping control loop, and the phase-shift angle is the only control variable. Hence, the control system is simple and reliable. A 3.3 kW prototype of the proposed converter is built and tested in order to verify the performance and the theoretical claims.

Interleaved Totem-Pole ZVS Converter Operating in CCM for Single-Stage Bidirectional AC–DC Conversion With High-Frequency Isolation

The Swiss-type rectifier (SR) uses a three-phase unfolder circuit to convert the ac voltage into two time-varying positive voltages. The power factor correction of ac sides and the stable dc voltage output can be realized by using two dc–dc topologies without any bulky decoupling capacitors. By applying the phase-shifted full-bridge topology into the dc structure, both the soft-switching and the high-frequency electrical isolation can be achieved. However, the power coupling between two full bridges using the traditional modulation method will affect the zero-voltage switching (ZVS) condition of lagging legs. Then, the duty cycle loss caused by the transformer leakage inductance will affect the input and output performance. Therefore, a new method using the up-counting mode modulation is proposed to implement the ZVS for both the lagging switches. Then, the relationship between the duty cycle loss and the extra 6 N  ± 1 harmonics added into the input current is theoretically analyzed. Hence, to suppress the low-order harmonics, a novel compensation strategy is proposed. The proposed modulation method and control strategy have been successfully verified by the experiments. 95% efficiency under half-rated power and 3% input current total harmonic distortion (THD) under rated power have been achieved under a 10-kW 380 Vac input/400 Vdc output prototype with 90-kHz switching frequency.

Modulation Method and Control Strategy for Full-Bridge-Based Swiss Rectifier to Achieve ZVS Operation and Suppress Low-Order Harmonics of Injected Current

The Swiss-type rectifier (SR) uses harmonic injection circuit and two dc–dc converters to help three-phase uncontrolled rectifier bridge to achieve better power factor correction (PFC). By applying the full-bridge topology to the dc structure, both the soft switching and the high-frequency galvanic isolation can be achieved. However, two full-bridge structures are required to realize the PFC principle of SR. That means the current flows through at least four switches and two transformers during the power conduction or freewheeling period. There are improvements in both conduction loss and core utilization. Thus, an optimized single-stage isolated Swiss-type ac/dc converter based on a single full-bridge with midpoint-clamper is proposed. Only one full-bridge structure is used to improve the conduction loss and core utilization. Two bidirectional voltage clampers are used to implement the PFC principle of the SR. The performance of the proposed converter has been verified by experiments. A total of 95.4% efficiency under half rated power and 5% input current THD under rated power have been achieved under a 10-kW 380 Vac input/400 Vdc output prototype with 90 kHz switching frequency.

An Optimized Single-Stage Isolated Swiss-Type AC/DC Converter Based on Single Full-Bridge With Midpoint-Clamper

This paper presents a novel single-stage bidirectional isolated AC-DC converter with power factor correction (PFC). The proposed converter integrates the interleaving and the Dual Active Bridge converter, using the phase-shift control to regulate the power flow and to minimize power decoupling. A theoretical analysis is presented and validated through simulation.

A Bidirectional Single-Stage Isolated AC-DC Converter for Electric Vehicle Chargers

A dual three-phase active bridge (D3AB) power factor correction (PFC) rectifier features two dc ports, i.e., one on the primary side, which is not isolated from the mains, and the second, which is galvanically isolated dc port on the secondary side. A model for calculating the conducted electromagnetic interference (EMI) noise of a 7.5-kW D3AB PFC rectifier operating from a 400 V<inline-formula><tex-math notation="LaTeX">$_\mathrm{rms}$</tex-math></inline-formula> line-to-line mains and generating dc output voltages of <inline-formula><tex-math notation="LaTeX">$V_{\mathrm{dc,1}} =$</tex-math></inline-formula> 800 V and <inline-formula><tex-math notation="LaTeX">$V_{\mathrm{dc,2}} =$</tex-math></inline-formula> 400 V is presented in this article. The EMI model takes into account the implications of the power levels provided at the primary- and secondary-side dc ports, i.e., <inline-formula><tex-math notation="LaTeX">$P_{1}$</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">$P_{2}$</tex-math></inline-formula>, respectively, on the conducted EMI noise and is used to design an EMI filter for a hardware prototype of the D3AB converter topology, which is volume-optimized for the considered specifications. The designed filter has a volume of <inline-formula><tex-math notation="LaTeX">$0.17\,\text{dm}^{3} = 10.\text{4}\;\text{ in}^{3}$</tex-math></inline-formula> (<inline-formula><tex-math notation="LaTeX">$0.09\text{ dm}^{3} = 5.5\text{ in}^{3}$</tex-math></inline-formula> for the differential mode filter and <inline-formula><tex-math notation="LaTeX">$0.08\text{ dm}^{3} = 4.9\text{ in}^{3}$</tex-math></inline-formula> for the common mode filter part). As part of the experimental verification of the model, the conducted EMI noise of the hardware prototype is measured under two different workload scenarios, i.e., <inline-formula><tex-math notation="LaTeX">$P_{1} = \text{4}\;\text{ kW}$</tex-math></inline-formula>, <inline-formula><tex-math notation="LaTeX">$P_{2} = \text{2.5}\;\text{ kW}$</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">$P_{1} = 0$</tex-math></inline-formula>, <inline-formula><tex-math notation="LaTeX">$P_{2} = 6.5\text{ kW}$</tex-math></inline-formula>. Measurements show that the level of conducted EMI noise increases with increasing load on the secondary side, which is consistent with the predictions of the noise model. The complete hardware prototype achieves sinusoidal mains currents with a power factor of <inline-formula><tex-math notation="LaTeX">$\lambda = 0.994$</tex-math></inline-formula> and a total harmonic distortion of currents lower than <inline-formula><tex-math notation="LaTeX">$5.6\%$</tex-math></inline-formula> at the considered loads and complies with the CISPR 11 class A quasi-peak conducted EMI limit.

EMI Filter Design for the Integrated Dual Three-Phase Active Bridge (D3AB) PFC Rectifier

This paper presents a novel single-stage ac/dc rectifier with high-frequency isolation and bidirectional power flow capability, which is feasible to connect dc grids to ac ones. A thorough analysis is performed based on the development of an actual model as well as a fundamental one using the double-sideband amplitude modulation equations. The derived models allow the determination of the active and reactive power flow through the transformer as well as defining the operating regions for which soft commutation is achieved. Besides, the current stresses of the semiconductors devices are analyzed in detail. Experimental results obtained from a 5 kW prototype are presented and discussed in order to validate the proposed model as well as demonstrate the converter's performance and claimed advantages. The proposed concept can also be extended to dc/dc, ac/ac, and multilevel topologies.

A Single-Stage Three-Phase Bidirectional AC/DC Converter With High-Frequency Isolation and PFC

This paper shows the experimental validation of a basic module from a single-stage ac-dc bidirectional power converter, which is feasible for solid-state transformer applications. The proposed converter is based on the dual active bridge (DAB) using an interleave technique. The converter can be modularized and applied at high voltage in a three phase system operating as rectifier or inverter. The topology is briefly presented and experimental results from a small-scale prototype are discussed to validate its operation principles and control strategy. The results show that the control strategy is able to operate the converter properly maintaining all DC bus on reference value. The converter is also capable of operate with a high power factor and a low harmonic distortion. Simulation results are shown from a prototype that is under construction with a higher power and magnetic integration.

Experimental validation of a basic module based on a single-stage AC-DC converter, feasible to solid-state transformer applications

This paper compares the classic bidirectional boost converter with the interleaved boost one using an interphase transformer. A loss analysis considering the use of silicon carbide switches is performed considering two different scenarios: same number of commutations for both converters and same volume of magnetic cores. In both cases, the total silicon area is considered to be equal. The study shows that the structure using the interleave technique presents smaller losses, even when the same magnetic volume is maintained.

Jose W. M. de Araujo

Papers

A Single-Stage Three-Phase Bidirectional AC/DC Converter With High-Frequency Isolation and PFC

Experimental validation of a basic module based on a single-stage AC-DC converter, feasible to solid-state transformer applications

On the study of the interleaving technique using an interphase transformer considering the use of SIC