In this study, an improvement method for double‐fed asynchronous motor‐generators (DFAMG) design with open slots is proposed to reduce the capacity demand of rotor converter for the first time. The proposed method is achieved by decreasing the air‐gap length (AGL) and applying conductive and magnetic rotor slot wedges. The design method of magnetic slot wedges and AGL in large DFAMG is presented. The mechanical analysis of a large DFAMG prototype reveals the necessity of using metal rotor wedges. To precisely investigate the influence of magnetic wedges in DFAMG, a two‐dimensional field‐circuit coupled model is proposed to consider the effects of rotor converter. Several wedge configurations of commercially available products are designed and analysed. The relationships between the electromagnetic properties of rotor wedges and prototype performance are investigated. The feasibility and advantage of the proposed method in DFAMG design are verified. A guidance for applying the proposed method in design improvement of large DFAMG is developed.

This paper presents a novel method for calculating the transient parameters of a saturated salient-pole synchronous machine (SPSM) with damper cage using finite element analysis. All detailed leakage inductances in a modified d-q model are discussed and separately extracted. In addition; the frozen permeability method is used in a 2-D finite element analysis to consider saturation and skin effects for determining the inductances. The terminal reactance parameters are obtained from all elements of the d- and q-axis equivalent circuits in all the chosen time constants during the transient process. The variation of leakage inductances of the SPSM in transient processes is also investigated and discussed. To determine transient time constant parameters; the Prony algorithm is applied in the presented method. A program developed to automatically solve the simulation and computation with the proposed method is described. This method is applied to a prototype and validated by experimental results. Some discussion about the relationship between rotor geometric design and the transient parameters of SPSMs is provided. The variation of leakage magnetic field of SPSMs in transient processes is also investigated. This method can be applied in transient parameter estimation and optimization of SPSMs in the design stage.

The full-size converter-based variable-speed pumped storage unit (FSC-VSPSU) is widely regarded as the future direction of variable-speed pumped storage technology due to its wide operating range and fast switching capabilities. However, previous studies often assume a constant DC-link voltage, which is not applicable to FSC-VSPSU, as fluctuations in grid-side active power can affect the DC-link voltage, thereby threatening system stability. To address this issue, this article proposes a crowbar-less low-voltage ride-through (LVRT) control strategy for FSC-VSPSU. The proposed approach effectively mitigates the elevated system costs inherent in conventional crowbar circuit implementations by harnessing the significant energy storage potential of the rotor to absorb power imbalances during LVRT. Furthermore, a novel parameter design methodology for the DC-link voltage controller is introduced to guarantee that the DC-link voltage consistently remains within the allowable threshold range during LVRT. The effectiveness of the proposed control strategy and the accuracy of the parameter design methodology have been validated through MATLAB(R2023a)/Simulink.

Active disturbance rejection control is implemented in a LC-filtered surface-mounted permanent magnet synchronous motor (SPMSM) drive system to enhance current control dynamics. However, the combined effects of computation one-beat delay and the pulse-width modulation zero-order hold (ZOH) effect significantly degrade system stability and dynamic performance. To address these limitations, an improved predictive extended state observer (ESO) with an accurate ZOH discretization method is proposed to ensure fast and robust dynamic performance. The predictive ESO predicts one beat to compensate for the delay effect, while the ZOH discretization yields a more precise discrete dynamic model of the system. These combined improvements substantially enhance the system’s phase and gain margins, leading to superior dynamic performance. Furthermore, a discrete-domain transfer function of the control system is analytically derived, with the control parameters systematically designed using frequency-domain analysis to guarantee robust performance. Experimental validation on a LC-filtered SPMSM drive system demonstrates remarkable enhancement in current control dynamics while maintaining sufficient robustness.