Yaohua Luo

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.

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.

Advanced switching table for direct power control of a three-phase PWM rectifier

This paper presents a new switching table for direct power control (DPC) applied to a three-phase PWM rectifier. The conventional switching table for DPC is not satisfactory in the controlling of the active and reactive power. Based on the analysis on the change of active and reactive power, the optimal rectifier voltage can be selected. Consequently, the more effective switching table for DPC is obtained. Simulations and experiments are implemented to testify the validity of the proposed scheme.

The input characteristic and stability analyse of power converter in distribution power systems

The subsystems interaction and instability is a common issue in the distribution power systems (DPS). In order to improve the stability of DPS, the input characteristic of power converter and its impact on the system stability are studied. Then the effect of a resistance load to the system was detailed analysed and some inclusions useful to improve the stability were obtained. Simulation results demonstrate the correctness of the theoretical analysis.

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.

The input characteristic and stability analyse of inverter with induction motor

The connection of an inverter-motor-drive system and a rectifier may lead to instability of the DC-link voltage. As the small signal technology is an important method to the cascaded system, the input impedance of the inverter-motor-drive system and its impact on the system stability are studied. Then the effect of the input impedance was analysis from d-axis rotor flux, load torque and DC-link voltage and some conclusions useful to improve the input impedance and make the cascaded system stable were obtained. Simulation results demonstrate the correctness of the theoretical analysis.

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.

Simulation and analysis of ship electrical propulsion system in waves

For safe and cost effective operations, high performance vessel electrical propulsion systems are needed. However, limited attention has earlier been given to the effects of the propulsion system dynamics in waves. A propeller open water test has been finished to study the propeller characteristic in waves. A model of ship motion considered regular waves is introduced and the inverter-motor-drive system based on rotor magnetic field vector control is studied. Simulation results show the interaction between ship, inverter-motor-drive system and the propeller. The model presented can predict load variations of vessel electrical propulsion systems in waves.

H ∞ Controller Design for Induction Motor to Attenuate Rotor Resistance Perturbation and Torque Disturbance with Field Oriented

It is well known that the system performance of field oriented control induction motor drives degrades under the variation of rotor resistance and in the presence of external load torque disturbance. H infin state feedback method is employed to design controller for induction motor fed by a current controlled voltage source inverter in this paper. The proposed control law can achieve convergence to zero of both speed and flux tracking errors and ensure robustness with respect to torque disturbance and rotor resistance variation. In some sense, the proposed controller can be regarded as a PI controller by studying its structure, from the Hinfin, point of view, this result explains why PI controllers have been used successfully in field oriented control partially. Another important contribution of this result is that it presents a useful way to design robust PI controller. Simulation results are given to validate the proposed method