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This article proposes a controller for dc–dc converters to achieve fast load-transient responses. The controller is developed for both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) of operation. The main idea is developed for buck converters, but it is shown that the proposed controller can be applied to other topologies, such as the noninverting buck–boost converter. The controller derivation, analysis, and experimental verifications are provided in both CCM and DCM, and its performance is compared with other methods. The main advantage of the proposed controller is that it minimizes the recovery times associated with load-transient responses in dc–dc converters while maintaining component sizes and other system parameters within the acceptable range. The proposed controller can be used to minimize load transients in electronic portable devices and electric vehicle charging. [ABSTRACT FROM AUTHOR]

A new inverter control approach, called enhanced virtual synchronous machine (eVSM), is proposed based on the VSM concept. Unlike existing VSM approaches, the eVSM does not emulate the rotating inertia based on an assumption of the unlimited energy storage, but it deploys the physically existing inertia of the dc-link element. The eVSM adopts an innovative way of enlarging the inertia utilization range, which obviates the need for having a large dc-link element or a dedicated battery storage system, while still providing the same inertia response of an equivalent synchronous machine. Theoretical developments and numerical results presented in this paper confirm that the proposed eVSM can present a stabilizing support to the grid similar to a synchronous machine despite the small size of its dc-link element. Moreover, its transient responses can be improved beyond those of conventional synchronous machines thanks to the possibility of more flexibly adjusting damping and governor functions. [ABSTRACT FROM AUTHOR]

This paper presents a model and a control strategy for a doubly-fed induction generator (DFIG) wind energy system in an unbalanced microgrid based on instantaneous power theory. The proposed model uses instantaneous real/reactive power components as the system state variables. In addition to the control of real/reactive powers, the controllers use the rotor-side converter for mitigating the torque and reactive power pulsations. The control scheme also uses the grid-side converter for partial compensation of unbalanced stator voltage. The main features of the proposed control method are its feedback variables are independent of reference frame transformations and it does not require sequential decomposition of current components. These features simplify the structure of required controllers under an unbalanced voltage condition and inherently improve the robustness of the controllers. A power limiting algorithm is also introduced to protect power converters against over rating and define the priority of real/reactive power references within the control scheme. The performance of the proposed strategy in reducing torque ripples and unbalanced stator voltage is investigated based on the time-domain simulation of a DFIG study system under unbalanced grid voltage. [ABSTRACT FROM PUBLISHER]

This paper presents a fast and robust $DQ$ current controller to regulate the output power of single-phase grid-connected inverters. The proposed method generates the grid current orthogonal component without introducing any additional dynamics or distortions to the control loop. Moreover, its operation does not depend on the system parameters. The proposed method exhibits improved steady-state and dynamic performances in comparison with the inverters equipped with the conventional orthogonal signal generation techniques. Its improved characteristics make the proposed controller suitable for smart inverter applications, to provide advanced grid functionalities as demanded by recently revised standards. Simulation and experimental results show the feasibility and performance of this control structure. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive investigation of various reference frames and their relative speeds in cascaded doubly-fed induction machines (CDFIMs). Then, a compact space-phasor model of CDFIMs in the natural and arbitrary reference frames is presented that is useful for performance analysis of CDFIMs based on rotating phasors. The merits of the proposed model compared with existing models are using a common (single) reference frame for all machines and parts of CDFIMs, and the model formulation is independent of the rotor angle position. The reference frames in the suggested model can be fixed on the common rotor of the CDFIM machines for dynamic analysis or it can be fixed on the stator/rotor flux of each cascaded machines useful for CDFIMs controller design. A two-axes equivalent circuit for a CDFIM is also presented, which enables analysis of CDFIMs in commercially available power circuit simulation software tools. The validity of the model is verified via the investigation of an experimental setup and consists of two mechanically coupled 4-kW DFIMs and a 4-kW dc machine as a load. The setup is investigated under various test scenarios, including free acceleration, load (torque) change, and frequency step change conditions. [ABSTRACT FROM AUTHOR]