This article reveals parasitics-induced current distortion (PCD) effect in discontinuous conduction mode boost power factor (PF) correction (PFC) converter. With consideration of parasitics, accurate inductor current is derived through total differential functions of line voltage, output voltage and duty cycle. Furthermore, the proposed current model is used to analyze PFC converter under conventional sensorless average current mode (SACM) control, which is achieved by a variable duty cycle. It is found that parasitics have considerable influence to the input current, and PCD leads to a degraded PF. In order to solve this issue, a current reshaping strategy is proposed to reduce the PCD phenomenon. Based on the damped current equations, a compensation gain is derived to reshape the input current, which reduces the current damping and distortion caused by parasitics. Both the PCD phenomenon and the current reshaping strategy are verified by simulations and experiments.

This article proposes a unified pulsewidth-cycle (UPWC) control strategy to achieve mixed-mode operation and consistent valley switching (VS) for boost power factor correction converter. Compared with conventional single-mode controllers, it has a unified scheme to achieve single discontinuous conduction mode (DCM), single critical conduction mode (CRM), or mixed DCM/CRM operations in each half-line cycle. To regulate the input current as a sinusoid, the UPWC controller adopts a variable pulsewidth and a near-constant switching cycle under DCM, while adopts a constant pulsewidth and a variable switching cycle under CRM. To facilitate analysis, normalized mapping of operation modes is provided, along with the final pulsewidth and switching cycle. Furthermore, to ensure consistent VS, a controlled zero current detection method is proposed to fix the turn-on point of the power switch. No matter in DCM or CRM, consistent VS reduces both the switching loss and current distortion caused by parasitic resonance. To further reduce the current distortion caused by fixing the turn-on point, a compensation gain is provided that reshapes the input current as a sinusoid. Finally, through mixed DCM/CRM operation and consistent VS, the proposed UPWC controller achieves preferable performances in the power range, efficiency, power factor, and current distortion.

This article presents an optimal duty ratio assisted pulse frequency modulation control for very high frequency isolated class E dc–dc converter to achieve both continuous power flow and optimal switch timing. The continuous power flow significantly reduces output ripple of the converter, while the optimal switch timing guarantees consistent zero-voltage-switching (ZVS) and minimized reverse conduction loss. To pave the way for the proposed control, a resonant fitting model is established for deriving the optimal duty ratio and output power under dynamic switching frequency. The optimal duty ratio is calculated according to zero-crossing points of the switching node voltage ( v_ds ), and it aims to turn on the power switch once v_ds reaches zero. This ensures consistent ZVS while preventing reverse conduction of gallium nitride (GaN) high electron mobility transistor (HEMT) when the switching frequency changes. Furthermore, the proposed control is integrated with on/off modulation to extend load range of the converter. A 10–18 MHz prototype is built to verify effectiveness of the proposed control. Compared with conventional PFM control, the proposed control reduces the power loss by 35.9% at 40% load while maintains continuous power flow.

Nonideal switching characteristics of voltage source inverter (VSI) will result in distortions in both phase currents and reference voltages of a permanent magnet synchronous machine (PMSM) drive system, which will also consequently introduce ripples into the output speed and shaft torque, and result in a performance deterioration in the state observation control. To solve this issue, a method of directly extracting and compensating the nonlinear voltage disturbance due to VSI nonlinearity employed in PMSM drives is proposed in this paper. Firstly, the distorted voltage due to VSI nonlinearity is directly extracted via a harmonic separation scheme, which can be easily compensated by a proportional integral controller afterwards. Since both 6th harmonic and DC terms of dq -axis distorted voltages due to VSI nonlinearity are well compensated, the proposed method shows sufficiently good performance under both $i_{d}=0$ and maximum torque per ampere controls ( $i_{d} < 0$ ), as verified on two prototype PMSMs being salient pole and non-salient pole, respectively, both developed for a low-speed rotary actuator. In addition, the application of proposed method to state observation controls such as the model-based sensorless control and the deadbeat predictive current control, is finally investigated. Test results manifest that the proposed method can effectively improve the accuracy of observed rotor position/speed, and the ability of current tracking.

For very high frequency (VHF) class 2 inverter, conventional design method requires complex tuning for parameters. Without fully quantitative calculations, the tuning highly depends on experience that cannot achieve optimal design. In this paper, a target function design strategy is proposed based on quantitative harmonic weighting, which simplifies the design procedures and minimizes the switch voltage stress. Firstly, the target switch voltage with minimized peak value is derived by optimizing the harmonic weighting. With the result, the power switch is modeled as a voltage source to simplify the calculations, where the branch currents are solved to provided fully quantitative analysis. Based on the analysis, optimal features of switching node impedance are derived to achieve the target switch voltage. Additionally, basic constrains of the resonant tank are analyzed to reduce circling currents. Combining the optimal features and basic constrains of the resonant tank, the circuit parameters are calculated directly, which minimizes the switch voltage stress and improves power efficiency. Compared with conventional design, a 27.12MHz prototype demonstrates 10.2% reduction in average switch voltage stress and 7.2% improvement in average efficiency.

The permanent magnet synchronous motor (PMSM) has been widely used in the field of ship electric propulsion due to its advantages of a small size, light weight, low loss, and high efficiency. In this paper, a 100 kW ship-side thruster motor was taken as the research object, and the problem of the high harmonic content of the air gap magnetic flux density in the motor was addressed by designing a rotor eccentricity. On this basis, the hybrid Taguchi method of genetic algorithm was used to optimize the rotor structural parameters with increasing the efficiency and reducting the cost of the motor as the optimization objectives. The results show that the performance and economy of the motor have been greatly improved after optimization. Finally, the motor weight reduction hole was designed, and a prototype was manufactured and tested. The test data are within the allowable range compared with the simulation data, verifying the effectiveness of the multiobjective optimization algorithm proposed in this paper.