Influence Of Phase-locked Loop Research Articles

Analysis of the influence of control parameters on the interaction between direct-driven wind turbines

In order to study the influence of control parameters on the interaction between direct-driven wind turbines, this paper presents the interaction model and analysis method of direct-driven wind turbines. Firstly, the harmonic linearization method is used to establish the interaction model of two direct-driven wind turbines, and the interaction mechanism between the two units is studied; secondly, the influence of phase-locked loop and DC voltage loop on the interaction between the two units is analyzed from the perspective of bandwidth and damping ratio of second-order closed-loop transfer function, and the interaction law of phase-locked loop and DC voltage loop on the interaction between the two units is studied and summarized; finally, the time-domain simulation of the two units grid-connected system is carried out, and the results are compared with the frequency domain analysis results to verify the rationality of the theoretical analysis.

Adverse Influence of PLL on the Bus Voltage Feed-Forward With Band Pass Filter Under Harmonic and Unbalance Condition

To improve the system performance, such as suppress the system harmonics, restrain the system resonance, etc., the bus voltage feed-forward (BVF) is often added in the control of three-phase inverter. Specially, under harmonic and unbalance condition, the band pass filter (BPF) is embedded in the path of BVF to control the selected frequency components. While, the influence of Phase-Locked Loop (PLL) on this control is ignored in the prior. In this letter, the multi-frequency model of the BVF with BPF considering the time-periodic trajectory of PLL is proposed. Afterwards, the adverse effect of PLL on BVF with BPF under harmonic and unbalance condition is explored and some new finds are given. Lastly, the theoretical analysis is verified by experimental results.

Small-Signal Dynamic DQ Model of Modular Multilevel Converter for System Studies

This paper presents three dynamic linear state-space models of the modular multilevel converter (MMC) which are suitable for small-signal dynamic studies and controller design. The three models differ by the number of states (two, six, and ten) and, therefore, are suitable for different applications based on the required accuracy. The 2nd- and 6th-order models ignore dynamics of the second harmonics and circulating current suppression control (CCSC). The main challenges of dynamic analytical modelling of MMC are the nonlinear multiplication terms in ABC frame equations for modulating oscillating signals. The multiplication nonlinear terms are therefore considered directly in the rotating DQ frame. This requires simultaneous modeling in zero sequence, fundamental frequency DQ and double fundamental frequency DQ2 frames. The proposed linear analytical models are implemented in state space in MATLAB. The validity and accuracy of the models are verified against a detailed 401-level MMC model in PSCAD/EMTDC in both time and frequency domains. The results show very good accuracy for the 10th-order model and decreasing accuracy for the lower order models. The influence of phase-locked loop and CCSC gains on the MMC dynamic is also studied using the proposed 10th model, and the results verify the suitability of the model for this purpose.