Modular multilevel converter for large-scale photovoltaic generation with reactive power flow and unbalanced active power extraction capabilities

2019 ◽  
Vol 162 ◽  
pp. 135-154
Author(s):  
Mario González ◽  
Víctor Cárdenas ◽  
Homero Miranda ◽  
Ricardo Álvarez-Salas
Keyword(s):  
Power Flow ◽  
Large Scale ◽  
Reactive Power ◽  
Active Power ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Photovoltaic Generation ◽  
Power Extraction ◽  
Reactive Power Flow

scholarly journals Behaviour of Distribution Grids with the Highest PV Share Using the Volt/Var Control Chain Strategy

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3865 ◽  
Author(s):  
Daniel-Leon Schultis ◽  
Albana Ilo
Keyword(s):  
Power Flow ◽  
Large Scale ◽  
Reactive Power ◽  
Low Voltage ◽  
Information And Communications Technology ◽  
Optimal Arrangement ◽  
Reactive Power Flow ◽  
Voltage Limit ◽  
Scale Integration ◽  
Distribution Grids

The large-scale integration of rooftop PVs stalls due to the voltage limit violations they provoke, the uncontrolled reactive power flow in the superordinate grids and the information and communications technology (ICT) related challenges that arise in solving the voltage limit violation problem. This paper attempts to solve these issues using the LINK-based holistic architecture, which takes into account the behaviour of the entire power system, including customer plants. It focuses on the analysis of the behaviour of distribution grids with the highest PV share, leading to the determination of the structure of the Volt/var control chain. The voltage limit violations in low voltage grid and the ICT challenge are solved by using concentrated reactive devices at the end of low voltage feeders. Q-Autarkic customer plants relieve grids from the load-related reactive power. The optimal arrangement of the compensation devices is determined by a series of simulations. They are conducted in a common model of medium and low voltage grids. Results show that the best performance is achieved by placing compensation devices at the secondary side of the supplying transformer. The Volt/var control chain consists of two Volt/var secondary controls; one at medium voltage level (which also controls the TSO-DSO reactive power exchange), the other at the customer plant level.

scholarly journals Interphase Power Flow Control via Single-Phase Elements in Distribution Systems

2021 ◽  
Vol 3 (1) ◽  
pp. 37-58
Author(s):  
Piyapath Siratarnsophon ◽  
Vinicius C. Cunha ◽  
Nicholas G. Barry ◽  
Surya Santoso
Keyword(s):  
Power Consumption ◽  
Power Systems ◽  
Power Flow ◽  
Distribution Systems ◽  
Single Phase ◽  
Reactive Power ◽  
Active Power ◽  
Real Power ◽  
Power Flow Control ◽  
Reactive Power Flow

The capability of routing power from one phase to another, interphase power flow (IPPF) control, has the potential to improve power systems efficiency, stability, and operation. To date, existing works on IPPF control focus on unbalanced compensation using three-phase devices. An IPPF model is proposed for capturing the general power flow caused by single-phase elements. The model reveals that the presence of a power quantity in line-to-line single-phase elements causes an IPPF of the opposite quantity; line-to-line reactive power consumption causes real power flow from leading to lagging phase while real power consumption causes reactive power flow from lagging to leading phase. Based on the model, the IPPF control is proposed for line-to-line single-phase power electronic interfaces and static var compensators (SVCs). In addition, the control is also applicable for the line-to-neutral single-phase elements connected at the wye side of delta-wye transformers. Two simulations on a multimicrogrid system and a utility feeder are provided for verification and demonstration. The application of IPPF control allows single-phase elements to route active power between phases, improving system operation and flexibility. A simple IPPF control for active power balancing at the feeder head shows reductions in both voltage unbalances and system losses.

scholarly journals Flexible power flow contol [i.e. control] for brushless doubly fed induction generator

2021 ◽  
Author(s):  
Kostyantyn Protsenko
Keyword(s):  
Power Flow ◽  
Reactive Power ◽  
Experimental System ◽  
Power Converter ◽  
Maintenance Cost ◽  
Induction Generator ◽  
Doubly Fed Induction Generator ◽  
Power Extraction ◽  
Reactive Power Flow ◽  
Doubly Fed

This thesis presents the brushless doubly fed induction generator (BDFIG) system for wind energy conversion. The system is proposed as an advanced solution to the traditional doubly fed induction generator (DFIG) to reduce the maintenance cost and improve the system reliability of the wind turbine system. The proposed BDFIG employs two cascaded induction machines to eliminate the brushes and copper rings in DFIG. The dynamic model of BDFIG with two machines' rotors electromechanically coupled in the back-to-back converter is developed. The independent control of the active and reactive power flow is achieved by means of a four-quadrant power converter under the closed-loop stator flux oriented control scheme. In the proposed control strategy, the generator speed tracks well the reference speed, thus the maximum power extraction is achieved. The experiment was done on a 2kW BDFIG system. Simulations and experimental results from the experimental system verify the proposed system model and control design.

scholarly journals Reactive Power Injection to Mitigate Frequency Transients Using Grid Connected PV Systems

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1998
Author(s):  
Yujia Huo ◽  
Simone Barcellona ◽  
Luigi Piegari ◽  
Giambattista Gruosso
Keyword(s):  
Power Systems ◽  
Power Flow ◽  
Reactive Power ◽  
Active Power ◽  
Ancillary Service ◽  
Synchronous Generators ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Reactive Power Flow ◽  
Virtual Inertia

The increasing integration of renewable energies reduces the inertia of power systems and thus adds stiffness to grid dynamics. For this reason, methods to obtain virtual inertia have been proposed to imitate mechanical behavior of rotating generators, but, usually, these methods rely on extra power reserves. In this paper, a novel ancillary service is proposed to alleviate frequency transients by smoothing the electromagnetic torque of synchronous generators due to change of active power consumed by loads. Being implemented by grid-tied inverters of renewables, the ancillary service regulates the reactive power flow in response to frequency transients, thereby demanding no additional power reserves and having little impact on renewables’ active power generation. Differently from the active power compensation by virtual inertia methods, it aims to low-pass filter the transients of the active power required to synchronous generators. The proposed ancillary service is firstly verified in simulation in comparison with the virtual inertia method, and afterwards tested on processor by controller-hardware-in-the-loop simulation, analysing practical issues and providing indications for making the algorithm suitable in real implementation. The ancillary service proves effective in damping frequency transients and appropriate to be used in grid with distributed power generators.

scholarly journals Electromechanical Transient Modeling of Line Commutated Converter-Modular Multilevel Converter-Based Hybrid Multi-Terminal High Voltage Direct Current Transmission Systems

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2102 ◽  
Author(s):  
Liang Xiao ◽  
Yan Li ◽  
Huangqing Xiao ◽  
Zheren Zhang ◽  
Zheng Xu
Keyword(s):  
High Voltage ◽  
Direct Current ◽  
Power Flow ◽  
Large Scale ◽  
Transient Stability ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Hvdc System ◽  
High Voltage Direct Current ◽  
Current Transmission

A method for electromechanical modeling of line commutated converter (LCC)-modular multilevel converter (MMC)-based hybrid multi-terminal High Voltage Direct Current Transmission (HVDC) systems for large-scale power system transient stability study is proposed. Firstly, the general idea of modeling the LCC-MMC hybrid multi-terminal HVDC system is presented, then the AC-side and DC-side models of the LCC/MMC are established. Different from the conventional first-order DC-side model of the MMC, an improved second-order DC-side model of the MMC is established. Besides considering the firing angle limit of the LCC, a sequential power flow algorithm is proposed for the initialization of LCC-MMC hybrid multi-terminal HVDC system. Lastly, simulations of small scale and large scale power systems embedded with a three-terminal LCC-MMC hybrid HVDC system are performed on the electromechanical simulation platform PSS/E. It is demonstrated that if the firing angle limit is not considered, the accuracy of the power flow solutions will be greatly affected. Steady state calculation and dynamic simulation show that the developed LCC-MMC hybrid MTDC model is accurate enough for electromechanical transient stability studies of large-scale AC/DC system.

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