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Current controlled inverters need to be dynamic and robust even under grid disturbances and different grid faults. Besides a robust control method the requirements for synchronization of the system become more and more important especially when multilevel inverter topologies are used. The combination of direct current control methods and advanced grid synchronization techniques promise excellent working...
This paper is focused on the optimal design of the controllers in an active filtering and regeneration system for DC railway traction substation. The control algorithm of the system is based on the indirect current control method and uses two closed loops with PI controllers: an outer one for the DC voltage control and the other for the grid current control. In order to perform the energy regeneration...
In this paper, a model predictive control strategy for a five level cascaded H bridge multilevel inverter used in a grid connected photovoltaic system is presented. Finite Control Set Model Predictive Control (FCS-MPC) is used here due to its simple and flexible nature to adapt with the discrete nature of power electronic circuits. Its digital implementation is also made easier with the advancement...
This paper proposes a novel seamless transfer control strategy of three-phase grid-connected inverter between grid-connected (GC) and stand-alone (SA) modes which can cover from no load to full load, even in non linear (NL) loads. The three-phase grid-connected inverter which uses in distributed generation (DG) system can be operated in both GC and SA control modes, especially for energy storage systems...
This paper describes a theoretical with experiment study on a control strategy for the parallel operation of three-phase voltage source inverters (VSI), to be applied to uninterruptible power systems (UPS). A circulating current suppression strategy for parallel VSIs is proposed in this paper based on circulating current control loops used to modify the reference currents by compensating the error...
This paper discusses the emulation of an active RLC load by means of an inverter. To this purpose, a suitable current control strategy is analyzed and developed. The limitations of this approach are explored, highlighting the requirements of the adopted regulator in order to avoid instability issues. The proposed analysis and model of the controlled system are verified by means of simulations and...
Cascaded H-Bridge (CHB) inverter is the most widely used topology for Medium Voltage (MV) drive system due to the high degree of modularity, easier implementation of medium output voltage, and ability to continuous operation under the cell fault condition. Because each power cell of CHB should have isolated DC source, multi-winding input transformer and three phase Active Front-End (AFE) are generally...
In this paper, it is described how the circulating current flows between inverters which have isolated DC-link such as Cascaded H Bridge (CHB) topology, when they operating in parallel. In this case, Zero Sequence Circulating Current (ZSCC) flowing through shared DC-link cannot flow between inverters in parallel. However, circulating current is provoked by asynchronous switching instant of devices...
In this paper, a 25-kW Wireless Power Transfer (WPT) system is considered for in-motion charging of an electric bus. The goal of this research is to derive a control strategy for the primary side of a wireless Electric Vehicle (EV) charger, with the objective to achieve fast dynamics and full control over the primary coil current and the amount of transferred power. To this aim, a dual-loop controller...
Voltage control strategy has been observed as being more advantageous than current control strategy for microgrid applications where grid-connected and standalone operation of grid-supporting inverters are desired. Voltage control, however, limits the ability to directly control the inverter current. As a result, the fault ride-through or the low-voltage ride-through (LVRT) capability becomes more...
For the LCL-filtered grid-connected inverter, it has been reported that the digital time delays will narrow the stable region of current control loop when the inverter-side current is used for implementing the feedback control. A sufficient stable condition is that the filter resonance frequency should be designed under one-sixth of sampling frequency. However, the low resonance frequency leads to...
An Anti-Windup (AW) scheme is developed in this paper for Proportional Resonant (PR) controllers in the current control loop of a voltage source converter with an LCL filter. The innovation of this scheme lies in the fact that the anti-windup feedback signal is distributed to each input of the integrator. By controlling the percentage of this distribution, one can effectively adjust the phase shift...
The dynamic impacts of controlling zero sequence current in a three-phase four-wire low voltage (LV) distribution network with a four-leg voltage source inverter (VSI) and PV installations are investigated in this paper. The PV VSI is designed to control active power at unity power factor (p.f) with additional neutral and zero sequence current controls. Inherently, most of the three-phase four-wire...
Virtual synchronous machine (VSM) can be used in micro-grids (MGs) for supporting virtual inertia to mitigate frequency fluctuations in the system. The performance of VSM depends on the performance of the current controlled voltage source inverter. Generally used proportional-integral (PI) controller has limited transient performance in current control. Adaptive dynamic programming (ADP) controller...
This paper proposed a decoupling predictive current control method for the application of traction line-side converter in high-speed railway. The method adopts a decoupled discrete-time model of the system to predict the future value of input current for all possible voltage vectors generated by the converter. Considering the calculation time, two-step prediction is taken in the scheme. The voltage...
This paper describes a current control of the three-phase inverter in a stand-alone wind energy system using model predictive control (MPC). The system includes a wind turbine without the use of a gearbox, a permanent magnet synchronous generator (PMSG), a pure diode based three-phase rectifier and a three-phase voltage-source two-level inverter. The simulation results obtained by using MATLAB/Simulink...
This paper presented Proportional Resonant (PR) current control of single phase grid connected inverter for PV energy conversion to the utility grid. The synchronization mechanism is Second-Order Generalized Integrator (SOGI) phase locked loop (PLL). The PR current control is regulator in stationary reference frame and an advantage is reduce current distortion. The implemented software using Real...
In this paper, the topology and the control scheme of the photovoltaic three-phase grid connected inverter based on voltage-oriented control (VOC) is analyzed. In VOC, a current control loop is used. The currents are controlled in a synchronous rotating dq-frame using a decoupled feedback control. The reference current of d-axis controller is extracted from instruction which comes from the former...
This paper proposes a novel on-line inductance identification method to account for inductance saturation in current controller design for single-phase grid-connected inverter with single inductor filter. The predictive control method with delay compensation is used which has wide bandwidth and reaches steady state within one switching period in current control loop. A multiple-sampling method is...
The article shows the concept of the control system with output currents trajectory correction to circular form in case of the voltage source inverter. The discussed solution presents the concept of control system using the principle of double-modulation to adjust the trajectory of the currents in the cases of load asymmetry. The controller with double-modulation, proposed in the paper, has been verified...
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