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In industrial microgrids with medium power rating photovoltaic systems, the low-voltage ride-through capability should be incorporated to help keep power system stability. The goal of this paper is to present a control strategy that allows taking advantage of the maximum capability of the inverters to support the most dropped phase in a photovoltaic-based industrial microgrid during voltage sags....
The growing interests in industrial microgrid and its high power rating, have made it as a good candidate for voltage support purposes. The aim of this paper is to present a reactive current injection control strategy for a photovoltaic-based industrial microgrid during voltage sags. During the sag, depending on the grid code requirements, the maximum rated reactive current should be injected by the...
This paper presents a networked control scheme for a photovoltaic-based industrial microgrid to adaptably operate in both grid-connected and islanded modes, and even to transfer smoothly between these two modes. The control scheme is mainly based on the droop method for active and reactive power sharing by means of voltage and frequency regulation. In addition, to get a smooth transfer between islanded...
This paper presents a detailed analysis of a voltage source inverter with vector operation technique allowing to derive a transformation from natural-frame to a new frame called from heron γθ-frame. This transformation leads to obtain a dynamic model for the voltage source inverter in γθ-frame in order to apply an sliding mode control to the system. Due to the behavior of the vector operation, the...
Microgrid increases the reliability and quality of supply of industrial and commercial buildings. The operation in islanding mode is a challenging issue due to the limited energy available and the lack of a main grid for synchronizing purposes. This paper presents both the design of a small-scale industrial microgrid and a hierarchical control strategy for islanding mode operation. The control scheme...
This paper presents a non-linear control scheme for power-factor-correction rectifiers. Based on the dynamic model of a power-factor-correction boost rectifier, a control algorithm is deduced by imposing a desired linear dynamics in the output-voltage. The proposed scheme has shown its fast dynamic response of the output-voltage, excellent voltage regulation, insensitive to load variations and the...
This paper presents a sliding mode control for a three-phase grid-connected voltage source inverter with vector operation. The design of closed-loop system is based on the sliding-mode theory, and it is carried out with the help of a converter large-signal dynamic model. The closed-loop system improves the transient response and minimizes the steady-state error. Essentially, the contribution of this...
This paper presents an active damping method in natural frame for a three-phase voltage source inverter with LCL filter. The proposed method is based on the pole placement technique via Ackermann's formula. This approach is used to obtain the proper sliding surface vector coefficients to emulate a virtual resistor in series with the capacitor filter. Besides a well-known method in the literature have...
This paper present a sliding mode control operating at fixed switching frequency for a three-phase unity power factor rectifier using the vector operation technique. The proposed method allows to find a large-signal converter dynamic model in order to transform a tree-phase system into two decoupled subsystems. With this technique only two sliding-mode controllers are needed and the neutral point...
This paper presents an improved variable hysteresis-band current-control in natural frame for a three-phase shunt active power filter. The proposed control algorithm is based on three decoupled sliding-mode controllers combined with three independent Kalman filters. The use of Kalman filters instead of a non-adaptive state observer improves the quality of the estimated signals in presence of noise,...
This paper proposes a new active damping method based on virtual resistors for three-phase grid connected voltage source inverters (VSI) with LCL filter. The use of this filters is a standard solution to provide the proper attenuation to the sideband voltage harmonics of the modulation signal. However these grid filters can introduce an unstable dynamics if a passive or active damping is not properly...
Unbalanced voltages in three-phase power systems is a common perturbation propagated along the grid. Distributed Generation plants have gained widespread attention due to their capability to improve power quality in a distributed manner, including voltage unbalance mitigation. A conventional control strategy to command power plants during balanced grid voltages, is the use of power factor to inject/absorb...
Grid faults are one of the most severe perturbations to deal with in grid connected systems. To support the grid under voltage-sags (dips), different reactive power control strategies are needed depending on the type of grid fault. One of the possible objectives when supporting the grid voltage under type C voltage sags could be to avoid undervoltage in the faulted phases and over-voltage in the non-faulted...
Unbalanced voltage sags strongly deteriorate the performance of power converters and electrical machines connected to the distribution network. In particular, a reduction of the power quality is noticed in these equipments, which is caused by a ripple in the output power and an increase of the current harmonic distortion. Several solutions based on reactive power compensation have been introduced...
This paper proposes a new structure for grid synchronization based on generalized integrators (GI) that lead to fast detection of positive and negative components of the grid voltage. The GI are used as a band pass filter (GI-BPF) mainly to provide in-phase and quadrature components of grid voltage. The proposed structure consists in the cascaded connection of multiple GI-BPF to achieve a faster time...
A Voltage Sourced Inverter (VSI) intended to inject active power to the grid is presented. The VSI is designed with an LCL output filter. This objective is done by means of a sliding mode control, which is a widely used technique to control systems where a fast dynamic response, robustness and accuracy are required. However, variable switching frequency appears when the sliding mode control is implemented...
In this paper, a novel droop control scheme applied to distributed UPSs forming a microgrid is proposed. The control architecture consists of two levels of hierarchy: 1) the P/Q droop control method of every UPS unit and 2) the management of the microgrid through the control of the setpoints of the units and the intelligent switch connected to the strong grid. This second level of control let us to...
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