Fanrong Meng

High Performance Repetitive Controller for Eliminating Periodic Disturbance of Inverter with Unbalance Load

The paper has researched on the control of three-phase inverter with unbalanced load. Based on the analysis output characteristic of inverter with unbalanced loads, the method of restrain the unbalance output voltage was researched, and then the models of inverter respectively in dq-frame and αβ-frame were established. According to the models and the characteristics of traditional dual-loop control and repetitive control, a new control strategy in which the dual-loop control in dq-frame was in parallel with repetitive control in αβ-frame was proposed. Based on the model in dq-frame, the dual-loop control of inverter was designed; and based on the model in αβ-frame, the repetitive controller of inverter was designed. The results of simulation in MATLAB and the experiment based on DSP - TMS320F28335 have compared the control effects of dual-loop control, repetitive control and the compound control proposed in this paper. And it has proved to be a correct and available control strategy.

Analysis of current sharing and controller design fundamental for paralleled DC/DC power converters

The key technology for multi power converters paralleled is active current sharing. In this paper, out loop current sharing scheme is used as an example to investigate the relationship between output impedance and current balance. It is induced that the deviation of output impedance is the essential reason that degrades the performance of current sharing, and the bandwidth of current sharing loop must exceed the frequency area where exist obvious output impedance deviation to obtain perfect current sharing. Simulation results validate the proposed analysis and design method.

The Research on the Zero Sequence Circulating Current Suppression in Parallel Inverters

That inverters work in direct parallel would increase the reliability and capacity, and also reduce the cost and volume for tidal current generation system, but the zero sequence circulating current will be generated. The state model of the parallel connected inverters is constructed in synchronous rotating coordinates, the mechanism of circulating current is analyzed based on the state model, and a zero sequence circulating current suppression method is proposed. The zero sequence voltages of the inverters are regulated in real time to suppress the circulating current. The model of zero sequence circulating current closed-loop control is constructed, and the constraint of the method is analyzed. The experiment results show that the circulating current is suppressed effectively.

A novel phase-locked loop for power converters of ocean current power generation system

This paper presents a novel phase-locked loop (PLL) system suitable for ocean current power generation system. It can provide phase angle for power converters to implement Park transformation accurately and timely. The electricity coming from the ocean current generator has low and variant frequency, together with harmonics. Due to the frequency-locked loop (FLL), the proposed structure is frequency adaptive. Moreover, the system employs multiple second order generalized integrators (MSOGI) and a decoupled network to isolate the positive and negative sequence components of fundamental voltage as well as the third, fifth, seventh and eleventh harmonics from the original input voltage. Simulation and experimental results validate the effectiveness of the proposed method.

A comparative study on switching tables of direct power control for voltage source rectifier

In this paper, a comparative study is carried out on the six new switching tables and the conventional switching table of the direct power control (DPC) for voltage source rectifier (VSR). On the basis of the mathematical model for VSR, the expressions for variation of active and reactive power are obtained. In order to minimize the errors between the command and the estimated values of active and reactive power, the appropriate rectifier voltage vectors are selected. Six new switching tables are constructed accordingly. Compared to the conventional DPC, significant power ripple reduction and more sinusoidal line input current can be observed in the six new DPCs. A further comparative investigation is conducted among the six DPCs. Simulation and experimental results validate the effectiveness of the presented DPCs.

DC bus voltage feedforward analysis and regulation for interconnected power converters with CPL

Power electronics based distributed power systems are more and more used in different situations. In these systems, with tight regulation, the load converters may exhibit constant power load (CPL) behavior with negative impedance, and the system stability would be degraded severely. In this paper, an active method using DC bus voltage feedforward is proposed to overcome these problems. A typical DC distributed power system is employed to analysis the design method by using small signal linearization around the operating point. Furthermore, least mean square (LMS) based adaptation is used to enhance the design. The simulation results show the validation of the proposed analysis and design method.

Digital repetitive controller design for periodic disturbance attenuation in high performance inverters

In the paper, a digital repetitive control scheme is proposed for the single-phase inverters to achieve the high-quality sinusoidal output voltages and the minimum total harmonics distortion. In the proposed control scheme, the repetitive controller is plugged into the stable state feedback controlled single-phase inverter system. The repetitive controller is designed to eliminate the periodic disturbance and track the periodic or dc reference signal with zero tracking error. The design method of the controller is described systematically, besides the stability of system is analysed. Simulation results illustrate the availability of the proposed scheme.