Mingyao Ma

Reconfiguration of Carrier-Based Modulation Strategy for Fault Tolerant Multilevel Inverters

This paper focuses on the fault-tolerance potential of multilevel inverters with redundant switching states such as the cascaded multilevel inverters and capacitor self-voltage balancing inverters. The failure situations of the multilevel inverters are classified into two types according to the relationship between output voltage levels and switching states. The gate signals can be reconfigured according to the failure modes when some of the power devices fail. The reconfiguration method is discussed for phase disposition PWM strategy (PDPWM) and phase shifted PWM strategy (PSPWM) in the paper and it can be extended for other carrier-based PWM strategies easily. Balanced line-to-line voltage will be achieved with the proposed method when device failure occurs. Furthermore, the circuit structures can be the same as the general ones and the voltage stress of the devices does not increase. Simulation and experimental results are included in the paper to verify the proposed method.

Reconfiguration of carrier-based modulation strategy for fault tolerant multilevel inverters

This paper focuses on the fault-tolerance of the multilevel inverters with the redundant switching states. The failure situations of the multilevel inverters are classified into two kinds of them according to relationship between the output voltage level and the switching states. When some of the power devices fail, the gate signals are reconfigured according to the failure types. The method is discussed for phase disposition PWM strategy (PDPWM) and phase shifted PWM strategy (PSPWM) in the paper and it can be extended for other carrier-based PWM strategies easily. The normal line-to-line voltage will be achieved with the proposed method when device failure occurs. At the same time, the circuit structures are the same as the generally used ones and the voltage stress of the devices does not increase. The simulation and experimental results are included in the paper to verify the proposed method

A non-isolated high step-up converter with built-in transformer derived from its isolated counterpart

In this paper, a non-isolated high step-up interleaved DC/DC converter is proposed for the photovoltaic and fuel cell grid-connected power applications. By employing the built-in transformer, the voltage gain is extended greatly without the extreme duty cycle and the voltage stress of the switches is reduced. The output diode reverse-recovery problem is alleviated by the leakage inductance of the built-in transformer, which reduces the reverse-recovery losses and the EMI noise. The active clamp scheme can suppress the surge voltage of the power switches and recycle the leakage energy. ZVS soft switching performance is realized for all the switches to reduce the switching losses. Finally, a 1 kW prototype with 40V input and 380V output is implemented and tested to show the performance of the presented converter.

An Improved ZVT PWM Three Level Boost Converter for Power Factor Preregulator

An improved ZVT PWM three level boost converter for power factor preregulator is proposed in this paper. Only one auxiliary switch is used in the active soft switching circuit. By using this ZVT converter topology, zero voltage turn-on and zero voltage turn-off of the main switches can be achieved and the reverse-recovery loss of boost diode can be reduced. In addition, the auxiliary switch is ZCS during the turn-on switching transition and zero voltage turn-off. A prototype of boost converter rated at 420 W has been built to confirm the effectiveness of the converter.

Interleaved boost converters with built-in voltage-doubler and current auto-balance characteristic

An interleaved boost converter with coupled inductors and switched capacitors is proposed in this paper. The switched capacitors are used to realize the inherent voltage-double function which increases the voltage gain and reduces the voltage stress of the switch greatly so that the low conduction resistance and low voltage rated switches can be applied. Moreover, according to capacitor charge balance, the load current can be auto-shared by each phase as a consequence of the switched capacitors adopted in the output stage. Active clamp circuits are applied for the interleaved two phases to recycle the leakage energy and absorb the voltage spikes caused by the leakage inductance. Both the main and the clamping switches are ZVT performances which reduce the switching losses during the whole switching transition. The current falling rate of the clamping and output diodes is controlled by the leakage inductance so that the diode reverse-recovery problem is alleviated. The experimental results based on a 48 V-to-380 V DC/DC prototype verify the effectiveness of the theoretical analysis.

Synchronization Analysis on Converters with Distributed Control

Converters built with integrated modules have many advantages such as increased power density, flexible distributed control, multi-functionality, increased reliability and short design cycles. However, the system performance will be affected due to the synchronization errors among each integrated modules. This paper analyzes the impact of the two kinds of synchronization errors on the whole system performance, as well as detailed synchronization implementation. Meanwhile, some valuable conclusions are derived from the theoretical analysis, simulations and experimental results

An improved PWM control method to reduce surge current through capacitors in hybrid-clamped multilevel inverter

An improved pulse width modulation (PWM) control method for three-phase hybrid-clamped multilevel inverters (HCMLI) is proposed in this paper. It can significantly reduce the surge currents through the DC link capacitors by changing the relative phase of the three-phase PWM carriers. The surge currents increase the capacitor losses and decrease the capacitor life, thus increasing the cost and reducing the reliability of inverters. The operating principle of the hybrid-clamped multilevel inverter, the generation mechanism of the surge currents, and the principle of the improved PWM method are given. The simulated and experimental results show that compared with the general PWM method, the improved PWM method can effectively reduce the voltage ripples on the DC link capacitors, consequently decreasing the surge currents through them.

Distributed control of phase leg cell in the full-bridge voltage source inverter

The distributed control within a power converter is studied in this paper. In the converter the integrated power electronics module of phase leg cell is used as the distributed part. Many topologies can be constructed flexibly in which the separated controllers replace the conventional concentrated controller. We focus on the distributed control strategies for single-phase full-bridge voltage source inverter in this paper. The characteristics of the new structures are discussed and the effects of the parameter dispersivity in the inverter are analyzed. The simulation and experimental results of each case are included.

An FPGA-based mixed-signal controller for switching mode converters

An FPGA-based mixed-signal voltage-mode controller for switching mode converters is investigated in this paper. The proposed control architecture contains an FPGA, a DAC and a comparator, where the FPGA is a control processor that implements DPWM generation and a PID control algorithm. The DAC in conjunction with the comparator operates in two operational modes: one is a conversion mode performing successive approximation A/D conversion, and the other is a modulation mode providing an instant pulse-width modulator in the analog domain. The fast response of this mixed-signal control architecture makes itself close in dynamic behavior to its analog counterpart. Furthermore, the proposed solution is also effective, since all components used are viable for power integration. Its features and performance are sufficient to promote itself for implementation in many industrial digital control systems.

Synchronization analysis of space vector PWM converters with distributed control

Synchronization effects and performance degradations of the distributed inverter built with several integrated modules for space vector modulation strategy are presented in the paper. Under the control of distributed SVPWM strategy, the building modules of the inverter generate their target output voltage vectors separately, and keep simultaneously working with the command of the synchronization signal sent by the master module. When the synchronization error exists, the output phase voltage of each module will not be influenced, but the l-l output voltage will contain some unanticipated harmonic components. This paper systemically analyzes the impact of the synchronization error on the whole system performance. Meanwhile, some valuable conclusions can be derived from the double Fourier analysis, Matlab simulation and experimental results.