Research on Power Equalization of Three-Phase Cascaded H-Bridge Photovoltaic Inverter Based on the Combination of Hybrid Modulation Strategy and Zero-Sequence Injection Methods

2020 ◽  
Vol 67 (11) ◽  
pp. 9337-9347
Author(s):  
Wang Mao ◽  
Xing Zhang ◽  
Tao Zhao ◽  
Yuhua Hu ◽  
Fusheng Wang ◽  
...  
Keyword(s):  
Hybrid Modulation ◽  
Three Phase ◽  
Zero Sequence ◽  
Injection Methods ◽  
Power Equalization

scholarly journals Bearingless PM synchronous machine with zero-sequence current driven star point-connected active magnetic thrust bearing

2018 ◽  
Vol 4 (3) ◽  
pp. 5-25 ◽  
Author(s):  
Daniel Dietz ◽  
Andreas Binder
Keyword(s):  
Thrust Bearing ◽  
Lateral Force ◽  
Magnetic Bearing ◽  
Synchronous Machine ◽  
Active Magnetic Bearing ◽  
Three Phase ◽  
Zero Sequence ◽  
Force Ripple ◽  
Motor Operation ◽  
Modulation Degree

Common cylindrical bearingless drives require a separate thrust bearing, which is fed by a DC supply. Here, a technique is presented, which enables the feeding of the thrust bearing by an artificially generated zero-sequence current between the two star points of the two parallel windings in the bearingless PM synchronous machine. This way, no additional DC supply for an axial active magnetic bearing is needed. It is replaced by two three-phase inverters as stator winding supply, which are needed in any case to generate torque and lateral rotor force in the motor. This examination explains the technique of adapting the electric potential of the star points in two three-phase windings of the motor. The focus is on the determination of the operating area (maximum zero-sequence current and band width). It is constrained by the bearingless motor due to torque and lateral force ripple as well as additional eddy current losses. On the other hand, the DC link voltage and the modulation degree of the inverter for simultaneous motor operation as well as the bearing inductance limit the system dynamic. It is shown that the proposed technique is applicable for a modulation degree < 0.866, taking into account that other constraints by the bearingless machine and the inverter are mainly noncritical.

A Three-Phase Model Predictive Approach for Smooth Line-Switching in Islanded Microgrids

2021 ◽  
Author(s):  
Evangelos Pompodakis ◽  
Georgios C. Kryonidis ◽  
Minas Alexiadis
Keyword(s):  
Phase Model ◽  
Positive Sequence ◽  
Distributed Generators ◽  
Three Phase ◽  
Zero Sequence ◽  
Node Network ◽  
Switching Action ◽  
Switching Method ◽  
Line Switching ◽  
Distinct Features

This paper deals with a new line-switching method that facilitates the network reconfiguration of islanded microgrids. Its distinct features include the ability to handle network asymmetries and the minimization of the line current during the switching action. This is attained by developing a sensitive-based three-phase model predictive method to determine the operating set-points of the distributed generators (DGs) that minimize the current of the candidate line participating in the switching action. These set-points correspond to the positive-sequence powers as well as the negative- and zero-sequence currents of all DGs. Furthermore, the network constraints such as voltage limits and power limits of DGs are always satisfied. Simulations are performed in a balanced 33-bus islanded network as well as in the unbalanced IEEE 8500-node network to evaluate the performance of the proposed method.

scholarly journals Effects of the Selected Point of Voltage Reference on the Apparent Power Measurement in Three-Phase Star Systems

2020 ◽  
Vol 10 (3) ◽  
pp. 1036
Author(s):  
Vicente León-Martínez ◽  
Joaquín Montañana-Romeu ◽  
Elisa Peñalvo-López ◽  
Carlos M. Álvarez-Bel
Keyword(s):  
Reference Points ◽  
Power Measurement ◽  
Electrical Network ◽  
Entire System ◽  
Voltage Reference ◽  
Energy Principle ◽  
Conservation Of Energy ◽  
Three Phase ◽  
Zero Sequence ◽  
Power Component

The phenomenon responsible for the different apparent powers measured in a subsystem of a three-phase star-configured system, based on the voltage reference point, was identified in this paper using specific components of the instantaneous powers, as a result of applying the conservation of energy principle to the entire system. The effects of the phenomenon were determined using a proposed apparent power component referred to as the neutral-displacement power, whose square is the quadratic difference between the apparent powers of a subsystem, measured using two voltage reference points. The neutral-displacement power is a component of the apparent power, which is determined using the values of the zero-sequence voltages and the line currents in that subsystem. Expressions of the proposed power were derived using the Buchholz apparent power formulations. The validation of the derived expressions was checked in the laboratory and in a real-world electrical network, using a well-known commercial analyzer and a prototype developed by the authors.

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