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The continuous integration of renewable energy sources into power systems has led to the construction of large power plants based on power electronics, with power ratings up to hundreds of megawatts, in order to accomodate technologies like solar PV and wind energy. Due to the size of these plants, they must provide support services for the grid and it is necessary to analyze the impact they have...
This paper presents a comparative study of direct power control (DPC) and model predictive control (MPC) for three-level neutral-point-clamped (NPC) AC/DC converters. The operating principle of DPC and MPC are introduced in detail, with focus on vector selection mechanism and suppression of neutral point voltage fluctuation. Special care is given to the avoidance of high voltage jumps in both phase...
A simplified analysis of influence of pole pairs on the steady-state behavior of induction motors is presented. The analysis makes simplifying assumptions to express relationship between key steady-state performance parameters of 2-pole reference motor compared to its multiple pole counterparts. The analysis is performed using considerations of fixed geometrical dimensions on one hand and fixed output...
This paper presents a two stage, three-phase grid interfaced SPV (Solar Photovoltaic) energy conversion system with an ANF (Adaptive Notch Filter) based control algorithm. The proposed SPV system is a multi-function grid-interfaced solar PV energy conversion system, which along with conversion of dc-power from SPV to AC mains, is capable of reactive power compensation, harmonics current elimination...
Photovoltaic power plants (PV) are equipped with anti-islanding algorithms, embedded in the converters controller, to avoid the island operation. However, the current trends in the development of the future electrical networks evidence that it is technically feasible and economically advantageous to keep feeding islanded systems under these situations, without cutting the power supply to the loads...
In this paper, an improvement in power sharing for Autonomous Microgrid is well established. All previous studies were based on voltage and frequency droop control to share power between distributed generators. This paper develops a new robust voltage and angle droop control to share power, where its advantage over the common frequency droop is in less frequency variation. The synchronization of Power...
Micro-grid should be able to operate in both islanding mode and grid-connected mode, but how to transfer smoothly between these two modes is a question. This paper presents a seamless transition strategy for droop-controlled inverters to operate in both islanding and grid-connected modes and transfer smoothly between these two modes. The control principle and pre-synchronization control strategy are...
In this paper, a control scheme to improve load sharing among inverters of different power ratings in an ac microgrid is proposed. The proposed control scheme shapes the output impedance of the inverters independent of the voltage controller parameters and minimizes the requirement of the virtual impedance for proper load sharing. Results show that system stability improves. Simulation and experimental...
This paper presents a novel control strategy to achieve unity power factor with an energy management system (EMS) in an AC microgrid. The digitally controlled, power electronics based EMS controls the microgrid in both grid-connected and islanding mode by making sure that energy is harvested from distributed resources, stored in batteries, and available at all times for critical loads. In this paper...
This paper presents a method to synchronize doubly-fed induction generators (DFIGs) to the grid using a virtual direct power control (DPC) scheme. The nonlinearity of the hysteresis-based controller in DPC approach causes variable switching frequency for rotor side converter, which complicates the filter design. Also, the large ripples in the stator active and reactive power calculations are the major...
Power converter operation on high-impedance grids can result in oscillatory behavior as a result of “self-synchronization” of an inverter's phase detection unit (PDU). This phenomenon is particularly of concern in renewable energy applications and it occurs when the converter's injected current changes the voltage angle at the point-of-common coupling (PCC) and synchronizes to itself through its PDU...
This paper presents a simple and efficient power control method of a cycloconverter-type high frequency link converter for vehicle-to-grid applications in single-phase power systems. It includes a simple current reference generator for the purpose of P-Q control and islanding operation detection, a feedforward controller and a feedback controller. Since the proposed method employs trigonometric angles...
In this paper, a transient control method is proposed to compensate the reactive currents when the resistive-inductive load is suddenly connected to the power winding of the brushless doubly-fed generator (BDFG). Under stand-alone situation, the waveform of stator power winding voltage is strongly affected because of reactive power component of load. To tackle this problem, the load-side converter...
This paper proposes a new control strategy for a single phase isolated-dual-active-bridge series resonant converter (IDBRC). The proposed strategy combines both frequency modulation and phase shifting between the two active bridges. The shifted phase is kept at a suitable value to maximize the average power factor of the system and to handle the direction of the power flow. Meanwhile, frequency modulation...
The concept of Double-Delta Sourced Transformer (DDST) had been proposed to eliminate passive filters in large-scale power conversion systems. For the grid connection, active and reactive powers in DDST must be under control. In this paper, the power modulation method is proposed for DDST through the current regulation. And, it is also considered when one of converters is disconnected from the transformer...
This paper presents a finite control set Model Predictive Control (FS-MPC) approach for a grid-connected converter, particularly suitable for non-stiff grids where under low Short Circuit Ratio (SCR) the performance of the controller may get affected by variations in supply impedance value. In order to avoid this problem, a novel supply inductance estimator that is based on the grid currents variations...
This paper presents a controller for three-phase DC/AC converters that is able to operate the converter in grid-connected and stand-alone modes and ensure seamless transition between these modes without reconfiguration of the control structure. The proposed controller provides control over real and reactive powers in grid-connected mode and it performs voltage support in the islanded mode. It integrates...
The direct power control (DPC) scheme for doubly-fed generator (DFIG) wind energy systems is known to have simple control structure and fast dynamic response in comparison with other well developed control approaches such as field oriented control (FOC). The simplicity of this method comes from employing hysteresis-based controls for the stator active and reactive powers. However, these controllers...
The increase of renewable energy sources and distributed generation may have a negative impact on power systems, specially on weak ones. Therefore, their control systems are acquiring growing importance, with new proposals that aim to contribute to the control and stability of the power system as conventional generating units. This paper studies the effect that a PV system using a synchronous power...
In this paper, a new approach for reactive power management based on inverter's capacity and sensitivity to the critical bus has been presented. The approach addresses the voltage rise and reverse power flow issue when residential renewable energy sources such as rooftop solar panels produce more energy than the local load demand. The overvoltage issues are controlled by active management of reactive...
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