Ting Qian

Coupled Input-Series and Output-Parallel Dual Interleaved Flyback Converter for High Input Voltage Application

This paper proposes an integrated magnetic dc-dc converter suitable for high input voltage application. The converter is based on a coupled input-series and output-parallel dual interleaved Flyback converter concept. All the center and outer legs are gapped, and the transformers are integrated into one magnetic core with not so tight coupling. The gap is beneficial for suppressing current spike caused by the voltage mismatch between the windings. The two transformers are inversely coupled, and current ripple reduction can be achieved with suitable coupling design. A prototype with 350-450-V input and 24-V/4-A output is built. Experimental results verify the performance of the new topology.

Dual Interleaved Active-Clamp Forward With Automatic Charge Balance Regulation for High Input Voltage Application

This paper proposes a new dual interleaved active-clamp forward topology suitable for high input voltage and high-density application. Two interleaved forward circuits are connected in series on the primary side and in parallel on the secondary side. Therefore, only two high-voltage MOSFETs are needed for the primary switches. Also, the two interleaved parts utilize auxiliary windings to share one capacitor to fulfill active-clamp. Charge balance of the two channels is, thus, regulated by the shared clamping capacitor without demand for extra control schemes. Through the resonance between the magnetizing inductors and the equivalent capacitors of the switches during the transition time, switching loss of the primary switches can be reduced. Interleaved operation reduces the size of the output filter inductor. Based on detailed analysis, a prototype with 220-400-V input and 5-V/30-A output is built. Experimental results verify the performance of the new topology.

Self-Driven Synchronous Rectification Scheme Without Undesired Gate-Voltage Discharge for DC-DC Converters With Symmetrically Driven Transformers

This paper proposes a new self-driven synchronous rectification scheme for dc-dc converters with symmetrically driven transformers and wide input voltage range. The driving signals are obtained from the output inductor. Two auxiliary switches are utilized to turn off the main switches properly. Two extra auxiliary switches, which are controlled by a delayed signal from the inductor, are added to avoid the undesired gate discharge. This approach can achieve high efficiency and is suitable for practical applications. Experimental results based on a 36-75 V input, 2.5 V/30 A output prototype are shown to verify the proposed scheme.

Adaptive saturation scheme to limit the capacity of a shunt active power filter

When the current reference of a shunt active power filter (SAPF) changes quicker than the output current can change, the output of the APF cannot precisely track the current reference. Undesired harmonics will be generated by the APF due to the controller saturation. Based on detailed analysis of the reason and consequences of the controller saturation problem, this paper proposes an adaptive saturation scheme to suppress the effect of saturation by using the feedback of the current error signal. The proposed scheme can adaptively adjust the capacity of the APF according to different load conditions. The adjusted reference is still in phase with the original calculated harmonics and contains no extra undesired harmonics. Also, this algorithm has no risk of affecting the reference when there is no saturation. Simulation results show that the proposed scheme can operate effectively and the effect of saturation is greatly reduced

Parallel operation of shunt active power filters for damping of harmonic propagation in electric shipboard power systems

For modern navy electric ship, the application of multiple shunt active power filters (SAPF) has become an attractive choice to mitigate the current distortion of the nonlinear loads. Multiple SAPF has the advantage of high power capacity and high reliability. Based on the introduction of SAPF, this paper analyzes the importance of paralleling SAPF in electric ship systems. A new paralleling approach is proposed and compared with several known paralleling/cascading methods. The proposed method separates the tasks of compensating for reactive power and harmonic currents. It has fast response and is suitable for redundancy design. Simulation results verify the analyses.

Self-driven synchronous rectification scheme for wide range application of DC/DC converters with symmetrically driven transformers

Synchronous rectifiers are widely used in low voltage and high current DC/DC converters to reduce conduction power loss. For popular and reliable topologies, such as Half-bridge, Push-pull and Phase-shifted Full-bridge, the application of self-driven synchronous rectification has design challenges due to the existence of dead times. Existing solutions are not suitable for wide input voltage ranges. This paper presents a new self-driven scheme which properly combines the signal from the transformer and output inductor to drive the MOSFETs. This method provides a suitable solution for wide range input application, since the risk of exceeding the gate voltage rating is greatly reduced. The synchronous rectifier is driven during all the conduction period, and thus greatly reduces the power loss. The influence of the leakage inductance in practical application is also analyzed. Experimental results based on a 36–75V input, 2.5V/30A output prototype are shown to verify the proposed scheme.

Adaptive phase adjustment synchronization method for source voltage distortion in electric ship application

In any distributed power system where the impedance of the generator is non-negligible compared to the impedance of its nonlinear loads, the source voltage typically contains some distortion. Specifically, US Navy ship power generators experience a significant amount of voltage distortion. Since shunt active power filters (SAPFs) normally use the waveform of the source voltage for their reference generator, a significant voltage distortion can create undesired harmonics in the current reference, thus inject undesired harmonics into the line. This paper proposes a phase adjusting algorithm that is robust to source voltage distortion. Low pass filter (LPF) is utilized to suppress the distortion; phase shift caused by LPF or other factors is adaptively adjusted to zero by closed loop control. This approach can be implemented in either instantaneous reactive power theory based control or synchronous reference frame theory based control and no predictive estimations are needed for precise synchronization

Coupled Dual Interleaved Flyback Converter for High Input Voltage Application

This paper proposes an integrated magnetic DC-DC converter suitable for high input voltage application. The converter is based on a coupled input-series and output-parallel dual interleaved Flyback converter concept. All the center and outer legs are gapped, and the transformers are integrated into one magnetic core with not so tight coupling. The gap is beneficial for suppressing current spike caused by the voltage mismatch between the windings. The two transformers are inversely coupled, and current ripple reduction can be achieved with suitable coupling design. A prototype with 350-450V input and 24V/4A output is built. Experimental results verify the performance of the new topology.

Self-Balanced Input-Series Two-Stage DC-DC Converter and Ripple Match Design

This paper proposes a new self-balanced input-series, two-stage scheme suitable for high input voltage DC-DC converters. Series connection is applied for the first stage to reduce voltage stress, while a single second stage is used to regulate the charge balance of the first stage. Also, this research proposes a new ripple match concept to choose optimized first stage inductance value to reduce the voltage ripple across the intermediate capacitors, and thus, significantly suppress the current ripple of the second stage. A prototype with 500-700V input and 5V/30A output is built. Experimental results verify the principle and performance of the new topology.

Self-Balanced Dual Interleaved Active-Clamp Forward for High Input Voltage Application

This paper proposes a new Dual Interleaved Active-Clamp Forward topology suitable for high input voltage and high density application. Two interleaved forward circuits are connected in series on the primary side and in parallel on the secondary side. The two interleaved parts utilize auxiliary windings to share one capacitor to fulfill active-clamp and charge balance regulation. Interleaved operation reduces the size of the output filter inductor. A prototype with 220-400V input and 5V/30A output is built. Experimental results verify the performance of the new topology.