To ensure low harmonic pollution in power systems, the restrictions on total harmonic distortion (THD) produced by AC/DC converters are being made more stringent by utilities. Single-phase active rectifiers are among the power electronic conditioning devices used to ensure that loads meet the utility THD limits. Linear control schemes based on proportional-integral (PI) controllers are commonly used in single-phase active rectifiers due to ease of tuning. However, linear controllers do not provide global asymptotic stability. Lyapunov-based nonlinear control strategy enables converters to have global asymptotic stability. However, most models of Lyapunov-based single-phase active rectifiers in the literature appear in a detailed form. Detailed models require relatively large computational effort to give accurate results. In this paper, a single-phase active rectifier based on Lyapunov inner current and load current feedforward control schemes is modeled with dynamic phasors (DPs). The Lyapunov function is derived from the most dominant harmonic in each state variable. Simulation results show that the DP model is about 220 times faster than a detailed switching model. There is a close match between the DP and detailed model results. The proposed DP model is useful for the fast-paced study of multi-active-rectifier-converter systems.

To design efficient and reliable direct current-based energy systems, telecommunication equipment, transportation systems, and healthcare devices, accurate DC-DC converter models are required. In addition, computationally efficient models are required to expeditiously simulate large DC systems (with multiple converters). In this paper, the dynamic phasor (DP) method is used to develop computationally efficient multi-frequency average models of dual-loop controlled DC-DC converters (buck, boost, and buck-boost) which are suitable for accurate modeling and analysis of ripples. By recognizing that high frequency components of inductor current and capacitor voltage are small compared to DC components, in addition to being equal to zero over a switching cycle, the control system is designed to target the average value of current and voltage. This simplifies the control process compared to existing DP-based closed-loop models of DC-DC converters. Small-signal modeling technique is used to obtain suitable control gains. The DP-based DC-DC converter models built on MATLAB/Simulink are validated against detailed models built on Simulink/Simscape. Simulation results confirm the effectiveness of the proposed control strategy as well as the huge computational advantage of DP-based DC-DC converter models over detailed models.

The increasing deployment of inverter-based sources in power systems and microgrids, and the concomitant reduction in system inertia, have made the study of system dynamic interactions and stability, essential. Detailed inverter models are accurate but computationally inefficient for such studies. This paper presents a dynamic phasor (DP) based model of a single-phase single-stage photovoltaic (PV) inverter. Compared to the existing DP-based PV inverter models in literature, the proposed DP-based PV inverter model includes the PV model and maximum power point tracking (MPPT) dynamics. The DP-based PV inverter model is then linearized around an equilibrium point and the resulting small-signal model is used to develop equations required for obtaining suitable control gains. The DP-based model is built on MATLAB/Simulink and then validated against a detailed model developed in Simulink/Sim-scape. Simulation results confirm the high efficacy of the DP model in predicting dominant harmonics in the AC/DC sides of the inverter, using a simulation step size 50 times larger than the detailed model’s step size. The DP-based PV inverter model is well-suited for system-level study of inverter-based microgrids.

The accurate study of an inverter-based energy source is usually performed with the detailed inverter model. However, to perform system-level studies in microgrids, the time to simulate the system increases exponentially as more de-tailed inverter models are added. This paper presents a computationally efficient model of a single-phase PQ inverter based on the dynamic phasor (DP) method. By using the PQ theory and establishing a relationship between the direct-quadrature axis components of the synchronous reference frame and the DP real and imaginary components, independent control of the active and reactive power is realized. The fidelity of the DP-based single-phase PQ inverter model is verified by validating it against a detailed single-phase PQ inverter model implemented in Simulink/Simscape (SS). Simulation results reveal that the DP model can predict transients accurately, using a step size 125 times larger than the detailed SS model’s step size. The proposed DP-based PQ inverter model is suitable for fast-paced system-level studies of a multiple inverter based single-phase microgrid.

Modeling and simulation of DC-DC converters are essential in the design of efficient and robust energy systems, telecommunication equipment, transportation infrastructure, and healthcare devices. This paper presents computationally efficient frequency-dependent average models (FDAMs) of voltage-controlled DC-DC converters (buck, boost, and buck-boost) developed using the dynamic phasor (DP) method. By recognizing that in a DC-DC converter, the DC component dominates in the circuit variables, this paper neglects the pulse-width modulation (PWM) stage in developing control algorithms used in generating time-varying duty cycle unlike in the existing FDAMs. Rather, the time-varying duty cycle is produced by using the output voltage zeroth DP component as feedback signal while neglecting the high frequency components. This approximation simplifies the control process thereby enabling faster simulations of the FDAM models. Comparative studies involving step changes in output voltage reference and the load resistance are conducted using the detailed DC-DC converter models implemented in Simulink/Simscape (SS) platform, and the DP-based FDAMs developed in MATLAB environment in order to validate the proposed DP model's control scheme. Simulation results obtained reveal that the DP-based models are capable of accurately depicting the switching transients and steady-state conditions as the fully detailed switched models developed in SS while being more computationally efficient than the SS models. Thus, the DP-based FDAM is suitable for conducting a detailed system-level study of DC-DC converter-based power systems.

Dynamic Thermal Line Rating (DTLR) incorporates weather conditions prevailing on line ampacity to calculate actual current-carrying capacity of transmission lines. These weather variables include ambient temperature, wind speed, wind direction, and solar intensity. In this paper, probability and fuzzy techniques are adopted to model the existing uncertainties in weather variables and their performances are compared. A transmission line in Alberta's electric system is considered as a case study. Weather data are available at nine towers along the transmission line. Line sectional ampacities are estimated using conductor thermal equations. Results indicate that fuzzy model is able to estimate DTLR as efficient as probabilistic model and due to its low computational cost can be used for real-time applications. Modeling uncertainties in DTLR calculation would enable system operators to make decisions on DTLR considering the degree of risk that power utilities are willing to accept.

A methodology is described to conservatively predict the behavior of DC capacitor voltage for floating capacitor H-bridge converters, which are located in each phase between the utility grid and a squirrel cage induction motor. Under the proposed methodology, an algorithm is developed to predict the DC voltage level before motor starting. In this way, DC capacitor voltage overshoot problem can be avoided, which greatly improves the safety and reliability of the proposed power electronics. The paper presents the theory necessary to understand how to model AC bridge voltage trend under various motor loading conditions and how to conservatively predict the behavior of DC capacitor voltage before motor starting. Hardware experimental results show that the voltage level of DC capacitor for the proposed system can be accurately predicted.

This paper presents the predicted performance of an interior permanent magnet synchronous machine (IPMSM) operating in wide speed range. The predictions are carried out with material properties obtained using from Epstein tests on samples that have undergone different treatments together with stress released annealing. Results of the Epstein frame tests for permeability and core loss density are presented, together with hysteresis B-H curves. Finite element analysis is used to investigate the variation of torque, power, saliency ratio, and core losses, after the different heat treatments have been applied.