Unified Current Control Research Articles

Unified Fault-tolerant Control Strategy with Torque Ripple Compensation for Five-phase Permanent Magnet Synchronous Motor Based on Normal Decoupling

In this paper, the decoupling matrix in a five-phase permanent magnet synchronous motor (FPMSM) is rebuilt and changed, according to different open-phase conditions, which complicate the switch and control algorithm. This paper proposes a unified fault-tolerant control strategy with decoupling transformation matrix, effectively suppressing the torque ripple for several open-phase faults. The current algorithms for different open-phase faults are demonstrated; torque ripple, especially, is analyzed with third harmonic magnetomotive force (MMF). The unified current control law is expressed with two adjustable coefficients, which are regulated for torque ripple compensation. As the current control equation remains unchanged, the fault-tolerant can smoothly switch from normal to fault condition, only with different coefficients. The proposed method with torque compensation (TC) can realize effective suppression of torque ripple. The decoupling relationship between open-phase control laws and fault-tolerant current is verified by simulation. The torque ripple of fault-tolerant and effect of torque compensation (TC) under all fault-tolerant conditions are simulated by finite element simulation. The stability of switching and correctness of torque compensation are verified by experiments.

Disturbance Rejection Control Method of Double-Switch Buck-Boost Converter Using Combined Control Strategy

Since it has strong ability to realize a conversion to adapt to a wide variation of input voltage, the double-switch buck-boost (DSBB) converter is usually employed as a front-end converter in two-stage power converter systems, where conversion efficiency is always highly valued. Because there is only one switch in the Pulse Width Modulation (PWM) state in the buck or boost work mode, the combined control scheme was investigated for its advantages in inductor average current and conversion efficiency. However, in this method, the operation mode should be determined by additional logic according to the change of input voltage. Moreover, different control systems should be designed for different operation modes to guarantee dynamic control performance and smooth transition between different work modes. To address these issues, the linear active disturbance rejection control (LADRC) method is introduced to develop an inner current control loop in this paper. In this method, the model deviations in different work modes are considered as a generalized disturbance, and a unified current control plant can be derived for current controller design. Furthermore, the duty cycle limitations in practice are considered, an additional mode for transitional operation is produced, and the corresponding control scheme is also developed. Simulation and experimental test results are provided to validate the correctness and effectiveness of the proposed control scheme.

A Unified Current Control Scheme for Voltage Source Converter High Voltage Direct Current Under Unbalanced Grid Conditions

This paper presents a novel unified dynamic model and vector current control strategy to improve voltage source converter (VSC) based high voltage direct current (HVDC) (VSC-HVDC) transmission system performance under unbalanced system conditions. Both the AC- and DC-side models are developed in the unique positive synchronously rotating reference (dq-p) frame with respect to both the positive- and negative-sequence components. Based on the model, the active power (or DC voltage) control is schemed with a proportional-integral regulator plus a resonant integrator, intended to eliminate the 2ω ripple in the DC-link, and reactive power control resorts to a resonant filter to mitigate the current harmonic distortion due to the ripple component. To prevent the sequential component decomposition, the current control of both the positive- and negative-sequence components is designed in a unified way in the stationary αβ frame. The proposed strategy can maintain rather low level AC current harmonics along with the DC-link 2ω ripple elimination, enhancing the VSC-HVDC operational ability under AC unbalanced conditions. The PSCAD/EMTDC simulation results verify the validity of the proposed strategy.

A unified current control scheme for voltage source converter high voltage direct current under unbalanced grid conditions

This paper presents a novel unified dynamic model and vector current control strategy to improve voltage source converter (VSC) based high voltage direct current (HVDC) (VSC-HVDC) transmission system performance under unbalanced system conditions. Both the AC- and DC-side models are developed in the unique positive synchronously rotating reference (dq-p) frame with respect to both the positive- and negative-sequence components. Based on the model, the active power (or DC voltage) control is schemed with a proportional-integral regulator plus a resonant integrator, intended to eliminate the 2ω ripple in the DC-link, and reactive power control resorts to a resonant filter to mitigate the current harmonic distortion due to the ripple component. To prevent the sequential component decomposition, the current control of both the positive- and negative-sequence components is designed in a unified way in the stationary alphabeta frame. The proposed strategy can maintain rather low level AC current harmonics along with the DC-link 2ω ripple elimination, enhancing the VSC-HVDC operational ability under AC unbalanced conditions. The PSCAD/EMTDC simulation results verify the validity of the proposed strategy.