Active Power Flow Control Research Articles

Wireless Power Supply Design for Precharging Circuit of SST in Railway Vehicles

Frequency modulation control-based wireless power supply (WPS) system adopted for the operating signals of a precharging circuit in solid-state-transformer (SST) is proposed in this article. To guarantee high voltage insulation capability between trolley line and railway vehicle and to decrease the voltage level of railway feeder, a large and heavy main transformer (MTr) operating at 50/60 Hz is conventionally used in railway vehicles. The SST, operating at high frequency for compact size and active control of bidirectional power flow, is an emerging technology in order to substitute a conventional MTr. At initial start of the SST, it is important to slowly charge the capacitor voltages by a precharging circuit connected in series with the trolley line. To operate a precharging circuit in the SST, the proposed WPS system can be utilized for high voltage insulation capability in this article. To transfer operating signals wirelessly through the air, long slim dipole coils for transmitter (Tx) and receiver (Rx) are adopted to fabricate a small size of the whole WPS system. The proposed WPS can be operated at a maximum power efficiency point w.r.t. the wide ranges of the coil distance and load conditions by the proposed frequency modulation control method in the primary side. A 3-30 W prototype of the Tx and Rx coils for the proposed WPS were fabricated and verified by simulation and experiments, showing that 84.0% and 80.2% of high dc-dc efficiencies for P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> = 30 and 12 W at d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> = 30 mm, respectively. As a result, the proposed control method without communication circuits between Tx and Rx sides has been successfully verified when coil distance and load resistance are widely varied.

Testing Photovoltaic Power Plants for Participation in General Primary Frequency Control under Various Topology and Operating Conditions

The energy transition is accompanied by developing a digital decentralized low-carbon energy infrastructure with renewable-based generating plants as its main elements. In 2020, 15 photovoltaic power plants (PVPs) with an installed capacity of 364 MW were commissioned in Russia, which is 21.08% of the total installed PVP capacity of Russia. The findings of an analysis of Russia’s current regulatory and technical documents (RTD) concerning the frequency and active power flow control are presented. They indicate that all PVPs must participate in the general primary frequency control (GPFC). This requirement is due to large frequency deviations of transient processes resulting from an emergency active power shortage, which can shut down frequency-maintaining generating plants by relay or process protection devices and industrial consumers with significant damage to them. The requirements suggest full-scale tests of PVP to confirm their readiness for participation in GPFC. The program and results of checking the algorithm of change in the PVP active power, depending on frequency, are demonstrated with an example of one PVP. The full-scale tests confirmed the compliance of the certified PVP with this requirement. The plans for involving PVPs in the power flow control under various topology and operation conditions are considered.

Integration of Voltage Source Converters in Steady-State RMS Short-Circuit Analysis

Voltage source converters (VSCs) are self-commutated converters able to generate AC voltages with or without the support of an AC connecting grid. VSCs allow fast control of active and reactive powers in an independent way. VSCs also have black start capability. Their use in high-voltage direct current (HVDC) systems, comparative to the more mature current source converter (CSC)-based HVDC, offers faster active power flow control. In addition, VSCs provide flexible reactive power control, independent at each converter terminal. It is also useful when connecting DC sources to weak AC grids. Steady-state RMS analysis techniques are commonly used for early-stage analysis, for design purposes and for relaying. Sources interfaced through DC/AC or AC/DC/AC converters, opposite to conventional generators, are not well represented by electromotive forces (E) behind impedance models. A methodology to include voltage source converters (VSCs) in conventional RMS short-circuit analysis techniques is advanced in this work. It represents an iterative procedure inside general calculation techniques and can even be used by those with only basic power electronics knowledge. Results are compared to those of the commercial software package PSS®CAPE to demonstrate the validity of the proposed rmsVSC algorithm.

A Riemannian optimization approach to the radial distribution network load flow problem

The Load Flow (LF) equations in power networks are the foundation of several applications on active and reactive power flow control, distributed and real-time control and optimization. In this paper, we formulate the LF problem in radial electricity distribution networks as an unconstrained Riemannian optimization problem, consisting of two manifolds, and we consider alternative retractions and initialization options. We introduce a Riemannian approximate Newton method tailored to the LF problem, as an exact solution method guaranteeing monotonic descent and local superlinear convergence rate. Extensive numerical comparisons on several test networks illustrate that the proposed method outperforms standard Riemannian optimization methods (Gradient Descent, Newton’s), and achieves comparable performance with the traditional Newton–Raphson method (in Euclidean coordinates), albeit besting it by a guarantee to convergence. We also consider an approximate LF solution obtained by the first iteration of the proposed method, and we show that it significantly outperforms other approximants in the LF literature. Lastly, we derive an interesting analogy with the well-known Backward–Forward Sweep (BFS) method showing that BFS iterations move on the power flow manifold, and highlighting the advantage of our method in converging under high constant impedance loading conditions, whereas BFS may diverge.

D-q Control Scheme for Unified Power Flow Controller

Unified Power Flow Controller (UPFC) is the most prominent versatile FACTS controller applied in power system providing dynamic control of transmission line parameters. It can achieve Voltage regulation, series compensation and phase shifting independently. It provides combined advantages of STATCOM and SSSC by connecting two VSC’s with common dc coupling. Active power and reactive power can be directly controlled using UPFC. This paper presents UPFC for active power flow control through transmission lines. Control scheme based on d-q transformation is demonstrated. System studies are presented in MATLAB Simulink to present the active power flow control in the line.

Eight‐switch CHB‐based three‐level three‐phase shunt active power filter

This study presents a reduced switch three-phase three-level H-Bridge-based shunt active power filter (SAPF) for the mitigation of current harmonics, the reduction of current unbalance and the injection of reactive power. This recommended SAPF is developed by using two H-bridge and two DC-link capacitors. Compared to the conventional three-level H Bridge-based SAPF, the eight-switch cascaded H bridge (ES-CHB)-based topology saves four semiconductor switches and one DC-link capacitor. The ES-CHB-based SAPF saves the power electronic components and reduces voltage stress across each switch by introducing a small AC capacitor in series with coupling inductor in each phase. This LC circuit also reduces the harmonic stress of SAPF by tuning at the sixth order of current harmonics. The only drawback of the suggested SAPF is the DC link voltage unbalances. To address this problem, a modified feedback control strategy is proposed in this study. The modified controller regulates the DC link voltage at the desired voltage and mitigates the DC link voltage unbalances, by using reactive power flow control and active power flow control, respectively. The performance of the suggested eight-switch three-level CHB-based SAPF is evaluated through MATLAB simulation and experimentally verified through the hardware implementation.

Technical Constrained Power Flow Studies for IDC-PFC Integrated Into the MT-HVDC Grids

Power flow (PF) flexibility in the multi-terminal HVDC (MT-HVDC) grids is a thought-provoking issue. It leads to employing the active DC power flow controller (DC-PFC)s. Hence, this paper examines the static average model (AM) and power injection model (PIM) of an interline DC-PFC (IDC-PFC). It is to provide a suitable base for DC PF studies and easy embedding of the DC-PFCs into MT-HVDC grids’ PF equations. In this regard, this paper proposes a new DC PF solver (DC-PFS) for the IDC-PFC compensated MT-HVDC grids within the well-accepted Newton-Raphson (NR) framework. It requires a few modifications in the main structure of the system's Jacobin (J) matrix compared to the uncompensated MT-HVDC grid. Also, the system's admittance matrix and its symmetry are preserved. In the proposed concept, the IDC-PFC cooperates with other MT-HVDC grid's state variables to satisfy the predetermined control objective(s). Furthermore, this paper proposes a new solution procedure (SP) to handle various system's limitations during the processes of solving the DC PF problem. Meanwhile, there is no need to modify the related J matrix. The effective and accurate performance of the IDC-PFC's models, as well as presented NR-based DC-PFS and SP, are verified by performing several simulations on the 8-bus CIGRE MT-HVDC grid.

Enhancement of active and reactive power flow control over the transmission line using unified power floe controller. (Dept. E.)

Enhancement of active and reactive power flow control over the transmission line using unified power floe controller. (Dept. E.)

Power flow control in parallel transmission lines based on UPFC

The power flow controlled in the electric power network is one of the main factors that affected the modern power systems development. The unified power flow controller (UPFC) is a FACTS powerful device that can control both active and reactive power flow of parallel transmission lines branches. In this paper, modelling and simulation of active and reactive power flow control in parallel transmission lines using UPFC with adaptive neuro-fuzzy logic is proposed. The mathematical model of UPFC in power flow is also proposed. The results show the ability of UPFC to control the flow of powers components "active and reactive power" in the controlled line and thus the overall power regulated between lines.

RETRACTED ARTICLE: Use of neural network based DVR for the reduction of power quality issues in composite micro-grid

Most of today’s every power system networks deals with a serious scenario of Power quality. This problem had ever more observed with the advent of practical hardware, in which it will carry out serious impact in the eminence of power supply in to the micro-grid networks. Matter by reason of power quality, it is produced and critical to a non-common normal current and voltage re-emergence. It takes with reference to the distress of sophisticated electronic gadgets and renewable vigor sources. The predominant matter is centers to the voltage enlargements and dips. In this paper the instigator introduces a precise method for the bulge of voltages and dips. In the direction of revise the topic pointed out above for modified power types of electronic cog is embraces. Solitary, dynamic voltage restorer (DVR), is a leading progressed control hardware that can be utilized in micro-grids. If any uncertainty produced in the micro-grid DVR act as most favorably to ease the power quality problems. This job clarifies the MATLAB consequences of a dynamic voltage restorer (DVR) demonstrating with investigation. Particular form of controller’s similar to PI and NN controller like (proportional integral and neural network) is utilized in this DVR system. In this system procedure, DVR NN controller actualizes modified through the conventional PID-controller can be used examine a builded Composite micro grid system with Renewable sources. The newly developed controller is faster than traditional process initiated controller. By the use of MATLAB replication tools, presentation of the system shall be considered. To find the performance of the suggested NN based DVR which is simulated for the power loss reduction, power factor correction, and active and reactive power flow control. From the simulation results, NN based DVR is better compared to PI based DVR.

A control strategy for soft open points based on adaptive voltage droop outer-loop control and sliding mode inner-loop control with feedback linearization

A soft open point (SOP) is a flexible power electronic device that can enable accurate active and reactive power flow control to balance the power flow in a distribution network. Due to the inclusion of renewable energy resources with intermittent characteristics in distribution networks, frequent power adjustments and parameter perturbations present great challenges for the control systems of SOPs. Thus, to fully use the regulatory capabilities of the converters in SOP systems and avoid reaching the voltage limits, an adaptive voltage droop control scheme for the outer control loop that considers both a power sharing factor and a DC voltage deviation factor is proposed. Subsequently, a sliding mode control strategy with feedback linearization of the modular multilevel converters (MMCs) is introduced to the inner control loop, thereby improving the robustness of the system and reducing the difficulty of parameter tuning relative to proportional-integral (PI) control. In addition, this paper investigates the zero-dynamics stability of the proposed controller. By combining the two parts of the control system, a control strategy for SOPs based on adaptive voltage droop outer-loop control and sliding mode inner-loop control with feedback linearization is proposed. Case studies of a three-port SOP in a distribution network are conducted to verify the effectiveness and efficiency of the proposed controller.

Solid State Transformers: Concepts, Classification, and Control

Increase in global energy demand and constraints from fossil fuels have encouraged a growing share of renewable energy resources in the utility grid. Accordingly, an increased penetration of direct current (DC) power sources and loads (e.g., solar photovoltaics and electric vehicles) as well as the necessity for active power flow control has been witnessed in the power distribution networks. Passive transformers are susceptible to DC offset and possess no controllability when employed in smart grids. Solid state transformers (SSTs) are identified as a potential solution to modernize and harmonize alternating current (AC) and DC electrical networks and as suitable solutions in applications such as traction, electric ships, and aerospace industry. This paper provides a complete overview on SST: concepts, topologies, classification, power converters, material selection, and key aspects for design criteria and control schemes proposed in the literature. It also proposes a simple terminology to identify and homogenize the large number of definitions and structures currently reported in the literature.

Use of Hybrid Phase Shifter for Congestion Management in A Grid with RESs and EVs: Transmission Efficiency Benefit in Comparison with Phase Shifting Transformer

Integration of renewable energy sources (RESs) and electric vehicles (EVs) to electric power grids is increasing. These RESs and EVs may introduce major problems to grid such as transmission lines congestion. Owing to the causative factors nature, congestion may regularly happen and continue forlong commulative time. Thus, transmission efficiency (TE) is a major factorwhen relieving congestion. Congestion can be relieved by using phase shifting transformers (PSTs), hybrid phase shifters (HPSs), or flexible AC transmission system (FACTS) devices. However, PSTs have technical drawbacks such as their large steps, which may result in increased losses, and FACTS devices cost is high. This paper investigates benefits of using an HPS rather than a PST in terms of TE. As HPS operates continuously, it provides more precise control of active power flow than PST. A modified IEEE-14 bus test system is used and a security margin is kept in each simulated case with HPS/PST. Results revealed higher TE when an HPS is used. Thus, RESs and EVs can be more optimally hosted with HPSs.

Novel Implementation and Comparison of Active and Reactive Power Flow Control Methods in a Single Phase Grid-Connected Microgrid

Grid-connected inverters are essential microgrid components that interface a common dc bus, fed by several distributed resources, to the ac loads. This article presents different methods to control active and reactive power flow from the ac source in a single phase microgrid when it operates in grid-connected mode. A novel mixed-frame control strategy is presented and its performance evaluated using different methods to produce the orthogonal axis components. The different strategies are presented and compared with respect to their performance in the presence of harmonics in the main ac grid. Physics-based models and simulated plots are presented and validated by experimental waveforms measured on a laboratory prototype.

Analysis of Active Power Flow Control with Phase Shifting Transformer in AC Transmission Line

Analysis of Active Power Flow Control with Phase Shifting Transformer in AC Transmission Line

Active and reactive power flow management in parallel transmission lines using static series compensation (SSC) with energy storage

&lt;p&gt;The power flow controlled in the electric power network is one of the main factors that affected the modern power systems development. The Static Series Compensatior with storage energy, is a FACTS powerful device that can control the active power flow control of multiple transmission lines branches. In this paper, a simulation model of power control using static series compensator with parallel transmission lines is presented. The control system using adaptive neuro-fuzzy logic is proposed. The results show the ability of static series compensator with storage energy to control the flow of powers components "active and reactive power" in the controlled line and thus the overall power regulated between lines. &lt;/p&gt;

An Energy Management Platform for the Optimal Control of Active and Reactive Powers in Sustainable Microgrids

This paper presents an energy management platform based on a receding-horizon scheme for the optimal control of active and reactive power flows in microgrids, including small-size photovoltaic, combined heat and power, wind generation, mini-hydro, and energy storage. The objective function to be minimized can be set both on the daily operational costs (economic indicator) and on the global CO2 emissions of the system (environmental indicator), whereas decision variables are the production schedules of the generators and the power flows across the grid. The tool includes the technical constraints characterizing low voltage/medium voltage (LV/MV) microgrids and gives the user the possibility to select different models for the electrical network (nonlinear power flow equations, linear approximation, and single bus-bar) and different optimization ranges. The energy management system has been validated through an experimental campaign on the smart polygeneration microgrid of the University of Genoa, which provides electricity and thermal energy to the Savona Campus, an “open-air” demo-site of an environmentally sustainable urban district with a population of about 2200 people. The results of the tests on the field highlight the robustness of the developed platform and the capability of the receding-horizon algorithm at the core of it of successfully treating data uncertainties.

A Robust Active and Reactive Power Control Scheme With Multiloop Disturbance Rejection for a Wind Energy Conversion System

In this paper, a new control scheme is proposed to regulate the active power and reactive power of a permanent magnet synchronous generator (PMSG) based wind energy conversion system (WECS). Due to uncertainties in the internal dynamics of PMSG, modeling error in WECS and external disturbances, such as wind speed variation, control of active power, and reactive power, of a WECS becomes a challenging task. To address the above-mentioned problem, we propose a multiloop active disturbance rejection control (MADRC) approach to achieve efficient control of active and reactive power flow between the WECS and grid. The performance of this proposed control scheme is verified first by simulation and then, through experimentation on a 1-kW PMSG-based WECS developed in our laboratory. From the obtained simulation and experimental results, it is observed that the proposed MADRC provides excellent active and reactive power controls in the face of parametric variations and disturbance with satisfactory steady-state and dynamic performances. Further, on comparing its performance with that of a single-loop active disturbance rejection control and H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> controller, it is found that MADRC exhibits superior active and reactive power control performances amongst aforesaid controllers.

Enhanced operation of ‘Sen’ transformer with improved operating point density/area for power flow control

In flexible AC transmission systems, conventional transformers with tap changing mechanism in ‘Sen’ transformer configuration is a cost effective approach for independent active and reactive power flow control compared to voltage source converter-based solutions. ‘Sen’ transformer regulates the power flow by injecting a series voltage in the transmission line with a specific magnitude and phase angle with respect to the line current flowing through it. The accuracy of such injected voltage depends on the number of available taps in the transformer. However, with limited number of taps the conventional ‘Sen’ transformer results in a limited number of operating points, leading to large steady state error for a given design. This study discusses different types of ‘Sen’ transformer configurations, tap control schemes and proposes an improved tap selection technique with tap reversal arrangement for enhanced operation of ‘Sen’ transformer for power flow control. The proposed method increases the number of operating points, which leads to smaller steady state error with improved copper utilisation and increased tap changing complexity. The new tap changing algorithm and its implementation techniques are described in detail. The proposed configuration is analysed against similar configurations and is verified through a 160 MVA Simulink model.

AC load flow based model for transmission expansion planning

This paper proposes an accurate model to solve the transmission network expansion planning (TNEP) problem. The TNEP problem is solved using a linear DC model, a mixed integer linear DC model, and the proposed accurate exact mixed integer non-linear AC model. A 19 bus system which is a part of the 220 kV Egyptian transmission network is used for the verification of the proposed load flow models. The proposed exact non-linear AC load flow based model that considered control of active and reactive power flow in the network and considered the power losses in the system yielded promising results when compared to DC load flow based linear and mixed integer linear models. It provided a planned network with least number of added lines and consecutively with the least cost.