Yuxi Wang

Resonance Analysis and Soft-Switching Design of Isolated Boost Converter With Coupled Inductors for Vehicle Inverter Application

The comprehensive resonance analysis and soft-switching design of the isolated boost converter with coupled inductors are investigated in this paper. Due to the resonance participated by the voltage doubler capacitor, clamping capacitor, and leakage inductance of coupled inductors, the reverse-recovery problem of the secondary diodes is restrained within the whole operation range. By choosing appropriate magnetic inductance of the coupled inductors, zero-voltage switching on of the main mosfets is obtained collectively at the same working conditions without any additional devices. Moreover, the range of duty ratio is enlarged to achieve soft switching and an optimal operation point is obtained with minimal input current ripple, when duty ratio approaches 0.5. Additionally, two kinds of resonances are analyzed and an optimized resonance is utilized to achieve better power density. The prototype is implemented for the vehicle inverter requiring a 150 W output power, input voltage range varying from 10.8 to 16 V, and 360 V output voltage. Experiment results verify the design and show that the minimum efficiency is about 93.55% and 90.53% at low load and full load, respectively.

A new ZVCS resonant voltage-fed push-pull converter for vehicle inverter application

In this paper, a new zero voltage current switching (ZVCS) resonant voltage-fed push-pull converter for vehicle inverter application is proposed. It achieves ZCS off of the secondary diodes with using secondary leakage inductance as resonant element. By selecting appropriate dead time, the proposed circuit can also feature ZVS on of MOSFETs. The proposed topology can achieve satisfying performance in terms of voltage conversion ratio, efficiency, cost and volume, compared with four different secondary structures. Burst mode is used to guarantee the bus voltage under 500V in the whole input voltage range. At last, a 150W prototype with 10.8V-16Vdc input voltage, 220Vac, 50Hz output voltage is implemented to validate the operation, features, and burst mode characteristic. The measured efficiency is more than 95.6% and 93.3% in the whole input voltage range when output power is 150W and 60W, respectively.

Design methodology of LLC converters based on simplified mode analysis for wide output range

In this paper, an LLC resonant converter design methodology for wide output voltage range based on simplified operation mode analysis is presented. A new method to calculate the magnetizing inductance is developed based on the LLC mode analysis, which can ensure soft-switching operation when a maximum constant output power is implemented. The parameters, resonant frequency, maximum frequency and dead time, are swept to achieve the optimal design. The proposed design procedure is simple to handle yet can achieve satisfactory performance and is applied to a 1 kW converter. The experimental results are given to verify this methodology.

Comparison of two diagnosis methods based on switching voltage pattern for IGBTs open-circuit faults in voltage-source inverters

This paper investigates two diagnosis methods based on switching voltage pattern for IGBTs open-circuit faults in voltage-source inverters. One is based on bridge arm pole voltage, and the other is based on bridge arm line voltage. With extra simple circuit, these two diagnosis methods can detect and identify single and multiple open-circuit faults of the inverter IGBTs effectively. The comparison of diagnosis time and anti-interference feature between these two methods has been presented. The simulation results are carried out to show the effectiveness and differences of these two methods.

A Comparative Study of Two Diagnostic Methods Based on the Switching Voltage Pattern for IGBT Open-Circuit Faults in Voltage-Source Inverters

This paper reports an investigation conducted on two diagnostic methods based on the switching voltage pattern of IGBT open-circuit faults in voltage-source inverters (VSIs). One method was based on the bridge arm pole voltage, and the other was based on bridge arm line voltage. With an additional simple circuit, these two diagnostic methods detected and effectively identified single and multiple open-circuit faults of inverter IGBTs. A comparison of the times for the diagnosis and anti-interference features between these two methods is presented. The diagnostic time of both methods was less than 280ns in the best case. The diagnostic time for the method based on the bridge arm pole voltage was less than that of the method based on the bridge arm line voltage and was 1/2 of the fundamental period in the worst case. An experimental study was carried out to show the effectiveness of and the differences between these two methods.

A novel two stage LED driver compatible with electronic transformers for MR16 lamp

In this paper, a novel two stage LED driver scheme used in the MR16 system is proposed. A peak current control boost converter is adopted in the front stage to avoid the capacitive load problem. By adding a low pass filter (LPF) unit in the front stage control loop, the inrush current problem is solved. The proposed approach is well compatible with the electronic transformers (ETs). The second stage can be a buck or buck-boost converter depending on the output voltage of LED lamps. The effect of the dc link voltage ripple is eliminated by adding the second stage circuit. The proposed LED driver presents a considerably good compatibility with different kinds of electronic transformers. Moreover multi LED drivers can be parallel in the system without the over current problem. Furthermore, the power factor can be significantly improved with the proposed two stage scheme. 3W LED drivers are built and tested. The experimental results verify the theoretical analysis.

A fixed-frequency quasi sliding-mode repetitive control (QSMRC) for voltage source inverters

In this paper, a hybrid quasi sliding-mode repetitive control (QSMRC) method with fixed-frequency modulation is proposed. By employing the equivalent control approach, the quasi sliding-mode control (QSMC) is first derived and implemented. The repetitive control strategy is embedded in the derived QSMC to reduce the steady-state tracking error and the total harmonic distortion (THD). The proposed QSMRC successfully combine the inherent robustness of sliding-mode control (SMC) and the harmonic suppression capability of RC. Further improved THD performance is realized compared with RC. Moreover, the proposed QSMRC provides similarly excellent transient response as SMC. It significantly improves the system robustness and dynamic performance. The theoretical analysis and the promising features are verified by simulation comparisons based on PSIM models. The proposed QSMRC method performs high steady-state precision, fast dynamic response and low THD for voltage source inverters.

An evolutionary approach based on ant colony system to system-level fault diagnosis

Ant colony system is a novel simulated evolutionary algorithm, which provides a new method for complicated combinatorial optimization problems such as traveling salesman problem, sequential ordering problem, generalized assignment problem, etc. In this paper, an evolutionary approach based on ant colony system is applied to system-level fault diagnosis. It only needs a small amount of communication data with the host controller, while avoids circuit-level fault diagnosis which usually takes up hardware and software resources. Firstly, characteristics of each power module in the multi-modular system are collected up to the host controller and form a circular graph. Then ant colony algorithm (ACA) is applied to the circular graph combining with symmetric comparison model. Finally, experimental results from simulation study and theoretical analysis demonstrate the effectiveness of the ACA-based diagnosis approach for multi-modular system, making it a viable addition to system-level fault diagnosis.

Open-transistor faults diagnosis in voltage-source inverter based on phase voltages with sliding-window counting method

This paper presents a diagnosis method for open-transistor faults in voltage-source inverter (VSI) based on output phase voltages. When fault occurs, the faulty phase voltage will vanish during certain half periods, which can be utilized for diagnosing. In order to reduce calculation and improve noise resistance, the sliding-window counting method with first-in-first-out algorithm are introduced to detect the vanishment which indicates the faulty phase. Afterwards, the faulty transistor can be located by observing which half period the vanishment is in. Only output phase voltages are utilized and no complex algorithm is needed, thus this method can be easily embedded in existing voltage-loop or dual-loop controlled system without extra hardware circuits. Based on the time-domain characteristic of the faulty phase voltage, this method can achieve relative short detection time. Furthermore, it is capable of diagnosing simultaneous two-transistor faults. To validate the effectiveness of this method, experiments are carried out and discussed.

Modeling and research of three-phase inverter powering nonlinear load

Three-phase inverter has been widely applied in various applications, and lots of control schemes are investigated for the inverter powering nonlinear load, aiming to achieve favorable performance. However, the model currently proposed for inverter is based on linear load, which is not suitable for condition with nonlinear load. In this paper, a novel modeling method for three-phase inverter powering nonlinear load is proposed. Then, the mathematical derivation and performance analysis of the proposed model are presented in detail. Based on the proposed model, a control scheme is further presented, incorporating PI control and capacitor current feedback. In addtion, the second-order system damping theory and phase-plane analysis method are well developed to describe the steady-state and dynamic performance of the proposed model and control scheme. Compared with conventional dual-loop control, low THD of the ouput voltage could be acheived by means of the proposed scheme, which is perfectly validated by the simulation results.