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The modular multilevel converters (MMCs) are composed of many sub-modules(SMs) connected in series. Module control unit is key components of the SMs, and a auxiliary power supply is needed to energize the module control unit. However, Many MMCs projects require the voltage of IGBT to be higher than 3300V, which means the input voltage of auxiliary power supply used in MMCs should be higher than 2500V...
This paper proposed four stability improvement methods by source-side PWM rectifier for More Electric Aircrafts (MEAs). These stabilization methods are based on injecting compensation signals into the control loop of the source-side PWM rectifier which can omit remote sensor and compensation signal of each load. Besides, they overcome the drawback that load-side active damping methods do harm to load...
Explored in this paper is the grid impedance effect on the stability of a single-phase grid connected inverter with an LC filter based on the analysis of inverter output impedance. For a single-phase grid connected inverter, a PI controller is often used to regulate the current injected into the grid. However, the control performance can be influenced when the inverter is connected to a weak grid...
This paper investigates the impacts of the load subsystem on stability and performance of the upstream converter in multi-stage dc-to-dc power conversion systems. The paper demonstrates that an appropriate load subsystem could offer both stability and predictable performance for the upstream converter that was at the brink of instability before being coupled with the load subsystem. This stabilizing...
This paper discusses the effect of Constant Power Loads (CPLs) on the stability of a Smart Transformer (ST). The main characteristic of a CPL is that its current decreases when its voltage increases and vice versa. Therefore, in small signal analysis a CPL behaves as a negative impedance, and as a consequence it can impact the system stability. The aim of this work is to establish how it is possible...
This paper compares three current control methods for LCL-filtered grid-connected inverters, they are single-loop control based on inverter current feedback, that based on grid current feedback, and dual-loop control with capacitor current feedback active damping. The virtual impedance introduced by each method is identified, which comprises frequency-dependent resistance and reactance. The reactance...
With high power Virtual Synchronous Generator (VSG)-based Voltage Source Converter (VSC) and low switching frequency, time delay has become a big issue affecting VSC stability and dynamic response in islanded mode. In this paper, effect of time delay on output impedance is analyzed and a hybrid derivative feedback control is proposed to improve system stability and dynamic response. First step, derivative...
This paper discusses the dynamic interaction of multi active power filters (APFs) paralleled with a weak power grid. In order to analyze the dynamic interaction from multi APFs, the output impedance of an APF is solved. The influences of both circuit and control parameters on the output impedance are analyzed. Based on the output impedance of an APF, the dynamic influences of an APF on the other APF...
In some practical situations multi APFs are located far from each other, paralleled through the long cables. In this system the stability of one APF is influenced by the other APF paralleled with it. In this paper stability of the multi-parallel APF system is analyzed. Moreover, the improvement methods for stability of the system are given.
This paper establishes the criteria to ensure stable operation of two-stage, bidirectional, isolated AC-DC converters. The bi-directional converter is analyzed in the context of a building block module (BBM) that enables a fully modular architecture for universal power flow conversion applications (AC-DC, DC-AC and DC-DC). The BBM consists of independently controlled AC-DC and isolated DC-DC converters...
Class D amplifiers are becoming the most feasible solution for embedded audio application. However, distortions due to the non-linear nature of switching stage are the main drawback for this amplifier topology. This paper discusses the design and implementation of high fidelity audio class D using sliding mode control scheme. This design method proves to be a cost effective solution for industrial...
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