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Stability is a great concern for power systems with relatively small sources and multiple regulated power converters. Addressing this need, this paper presents the experimental verification of the Generalized Nyquist stability Criterion (GNC) for balanced three-phase ac systems. This criterion, developed by MacFarlane and Postlethwaite in the 1970's, was proposed as a stability analysis tool for ac...
This paper discusses an improved design procedure considering the impacts from the noise propagation paths and noise load/source. These impacts influence the choices of filter topology and filter components parasitic control. The paper proposes a step-by-step design procedure combining the traditional design method and the considerations from the impedance mismatching.
Predictive current mode control is one of the promising digital current mode control method featuring fast dynamic response and low cost implementation. To understand the benefit and the limitation of each implementation, choose the modulation scheme and design the control loop, this paper proposes small signal Laplace-domain models for a family of digital predictive current mode controls, including...
This paper presents the islanding detection algorithms for three-phase (3Ф) grid-interface converters based on the grid synchronization small-signal stability. To study the grid synchronization behavior at the islanded condition, a low-frequency small-signal phase-locked-loop (PLL) model is proposed by considering the converter interaction with the system impedances. Many of the frequency-related...
A small signal model for average current mode control based on equivalent circuit is proposed. The model uses the three-terminal equivalent circuit model based on linearized describing function method to include the feedback effect of the side-band frequency components of inductor current. It extends the results obtained in peak-current model control to average current mode control. The proposed small...
This paper proposes a control system to widen the bandwidth of piezoelectric transducers (PZTs) for vibration energy harvesting while extracting near maximum power. A straightforward complex conjugate match achieves maximum power transfer only at a single frequency while requiring an impractically large inductance. The proposed system intends to address the problem. It incorporates a bi-directional...
Smart micro-grids offer a new and challenging application environment for modern power electronics. In fact, smart micro-grids are populated by a plethora of distributed energy resources (DERs), which interface with the distribution grid by means of electronic power processors (EPPs). This scenario enables the distributed control of the active and reactive currents flowing in the power lines, with...
This paper focuses on the conducted electromagnetic interference (EMI) noise suppression solution at the ac output terminal of PWM motor drives. Dc-fed voltage source inverter (VSI) is selected as one typical topology. A practical output EMI filter design procedure is proposed. To ensure design accuracy, the procedure includes the system impedance characterization with offline measurement. Meanwhile,...
More attention to the electromagnetic interference (EMI) issues arises in grid-interface converter system where the radio frequency (RF) conducted emissions have to be considered on both dc and ac-side, such as in the application of photovoltaic (PV) system, dc distribution system, and charging system in electric vehicles (EVs). This paper presents a brief overview of the recent EMI research activities...
This paper initiated a discussion on the motor drive switching frequency and its impact on EMI filter design for power density point of view. The paper analyses EMI noise characteristics with increasing switching frequency in DC-fed three-phase motor drive systems, which result in different filter parameters. Nevertheless increasing switching frequency also brings in differences on volt-second across...
This paper presents a state-feedback model to predict the frequency behavior of the grid-interface converter which uses phase-locked loop (PLL) techniques to synchronize with the grid. The frequency positive-feedback mechanism in the converter system is proposed and quantified in the model. The nonlinear behavior of the PLL under the weak grid condition can be accurately predicted and the large-signal...
This paper presents complete Verification, Validation, and Uncertainty Quantification (VV&UQ) procedures that are applied to a two-level boost rectifier. The goal of this VV&UQ study is the improvement of the modeling procedure for power electronics systems, and the full assessment of the boost rectifier model (as an example) predictive capabilities. Modeling and simulation of large systems...
This paper presents a novel anti-islanding (AI) detection algorithm for three-phase (3Φ) grid-interface converters in distributed generation systems. A generic phase-locked loop (PLL) model by considering the converter interaction with grid is proposed. And the frequency positive-feedback mechanism is proposed to predict the frequency behavior of the grid-interface converter system, especially under...
A novel transformer assisted three-level zero-voltage switching (ZVS) converter is proposed in this paper. The proposed topology features simple structure and good ZVS performance. The auxiliary circuit structure and the modulation method are as simple as in the two-level converter. Only two auxiliary switches, four auxiliary diodes and a two-winding transformer are needed to achieve the soft-switching...
This paper discussed improving EMI design based on propagation path impedance. The way conventionally used in EMI filter design barely includes information on propagation path impedances, although this information is well known as important to filter topology selection and its in-circuit attenuation; besides, filters attenuation is usually measured by small signal insertion gain, which is different...
In this paper, a Simplified Optimal Trajectory Control (SOTC) for the LLC resonant converters is proposed. During the steady state, linear compensator like PI or PID is used, controlling the switching frequency (fs) to eliminate the steady error. However, during load transients, the Simplified Optimal Trajectory Control (SOTC) method takes over, controlling the pulse widths of the driving signals...
This paper presents the multi-phase hybrid ripple-based adaptive on-time control architecture for VRMs. Due to the ripple cancellation effects with multi-phase operations, ripple-based control may suffer from large jitter issues and instability issues when applying to VRMs with ceramic output capacitors. By utilizing the hybrid ripple concept, both inductor current ripple and compensated external...
This paper presents insertion gain predictions for both the differential mode (DM) and the common mode (CM) of an EMI filter. The proposed approach, essentially based on measurements, allows prediction of EMI filter performance for high-complexity converters without time-consuming simulations. The key idea is to use direct measurements to represent the complex system by an equivalent circuit in the...
A compact EMI filter becomes one of the critical issue for a high power density converter design especially in transportation applications. This paper proposed a design procedure for a more compact EMI filter with consideration of both the low frequency and high frequency attenuation requirement. For simplicity purpose, EMI filter transfer gain is utilized to conduct the analysis. With the proposed...
Different current mode controls are widely adopted in commercial PWM controllers for Point-of-Load converter application. To understand the unique properties of various current mode control schemes and study the subtle differences between them, this paper investigates and compares four current mode control schemes (peak-current control, valley-current control, constant on-time control and constant...
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