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In this paper, new steady-state analysis is proposed for a series resonant converter (SRC) that provides closed-form expressions for converter waveforms. Using the proposed analysis, explicit equations are obtained to design the converter components. It is shown that an SRC can be modeled through a nonlinear differential equation with discontinuous inputs. A Laplace-based theorem (LBT) is provided to obtain the steady-state analytic solution of the resonant converter differential equations. Using the LBT, a flowchart is proposed to analyze the converter where the nonlinearity of differential equation is removed by defining intermediate variables. The variable duty ratio SRC is analyzed using the proposed flowchart. Accurate, closed-form, and explicit equations for converter waveforms, voltage gain, current phase lag, zero voltage switching, and discontinuous conduction mode boundaries are derived. The proposed analysis is compared with conventional methods and its accuracy is validated through simulations and experimental results. Moreover, using the proposed method, a novel procedure is provided for the optimal design of the converter and is compared with conventional design approaches. [ABSTRACT FROM AUTHOR]

This paper presents an instantaneous torque control method for cascaded doubly fed induction machines (CDFIMs) with a rated torque-sharing ratio feature under steady-state operation. A CDFIM includes two coupled main and auxiliary doubly fed induction machines, and the rated torque-sharing ratio herein means that the machine torques are proportional to the machine ratings. The proposed method is established based on transferring the torque equations of the two machines into the rotor-flux reference frame of the auxiliary machine. Then, the instantaneous torque and the rated torque-sharing ratio are controlled via the stator current components of the auxiliary machine, while machine fluxes are within allowable ranges. To verify the method and evaluate its capabilities, the suggested method is used for the speed control of a CDFIM experimental setup including two 4-kW doubly fed induction machines and a 4-kW dc machine to apply a sudden mechanical load change to the CDFIM. Further, a case study including 12-kW and 4-kW DFIMs is also simulated to evaluate the performance of the torque control method for a CDFIM with different machine ratings. The test results confirm that the proposed control schemes achieve the desired performances without exceeding the ratings of the machines under various test scenarios. [ABSTRACT FROM AUTHOR]

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 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]