Active Power Flow Control Research Articles

The effect of smart transformers on the optimal management of a microgrid

This study examines the impact of smart transformers on the optimal management of microgrids within a combined heat and power framework. Utilizing a Genetic Algorithm for optimization, the research identifies optimal settings for control variables and resource capacities. The integration of smart transformers significantly enhances performance, improving voltage profiles and reducing electrical losses, while minimizing costs and pollution levels.Key gaps in existing literature include insufficient exploration of smart transformers' advantages and a lack of holistic approaches that integrate technical and economic objectives. This study proposes a comprehensive optimization framework that simultaneously addresses multiple goals, such as reducing power losses and environmental impacts.The contributions include the innovative application of smart transformers for accurate control of active power flow and the development of a robust optimization strategy. Comparative analyses with other techniques, such as Particle Swarm Optimization and Interior Point Method, demonstrate the superior performance of the Genetic Algorithm approach in achieving optimal microgrid management.

Active and reactive energy storage STATCOM distribution system power management

One of the critical factors influencing the overall development of modern power systems is the control of active and reactive power flows in distribution power systems. The static synchronous compensator (STATCOM) with storage energy is a powerful device that can control active and reactive power flow in a distribution system. A simulation model of power management using STATCOM with energy storage is presented in this paper. A fuzzy logic controller is proposed to manage the powers. The simulation results demonstrate STATCOM's ability to manage the active and reactive power flow in a controlled distribution line, and thus the powers regulated between feeders, by utilizing storage energy.

Experimental test performance for a comparative evaluation of a voltage source inverter: Dual voltage source inverter

Abstract This article proposes an adaptive Kernel-Hebbian least mean square (KHLMS) controller for a dual voltage source inverter (VSI). The recommended topology consists of a distributed energy resource (DER) supported VSI called main VSI (MVSI) and split capacitor supported VSI termed as auxiliary VSI (AVSI). Both the MVSI and AVSI are used to serve the shunt compensation when DER is not integrated with MVSI. The DER scenario is considered to suppress the active power flow shortage in the utility grid. Here, optimal active power flow control (OAPFC) is managed by MVSI and shunt compensation is achieved by AVSI during DER operated mode. Hence, a dual VSI based distribution static compensator (DSTATCOM) facilitates the configuration merits such as reduction in system downtime cost, filter rating switching stress etc. Supremacy of both the neural network (NN) based controller and topology is presented by comparing VSI (called AVSI) in the context of harmonic reduction in source side, voltage balancing, power factor (PF) enhancement, better voltage regulation and OAPFC. The experimental results are obtained through field programmable gate array (FPGA) based hardware units which exhibit radical improvement in the power quality (PQ) conferring as per the international standard grid code (IEEE-519-2017).

Advanced Doubly Fed Induction Machine Rotor Fault Diagnosis Based on Wavelet Analysis in Closed-Loop Operation Under Time–varying Condition

This paper introduces a new diagnostic technique for the detection of incipient electrical rotor faults in doubly fed induction Machine (DFIM) for wind power systems. In the considered application, the rotor is supplied by a static converter for the control of active and reactive power flows from the generator to the electrical grid. A new diagnostic method based on the rotor modulating signals pre-processing by Frequency Sliding (FS) and Discrete Wavelet Transform (DWT) thereby is here proposed to detect rotor faults dynamically over time. Experimental and simulation results demonstrate the effectiveness of the proposed approach under time-varying conditions.

Independent Control of Active and Reactive Power Flow for a Single-Phase, Unidirectional Onboard Power Converter Connecting the DC Power Bus to the AC Bus

The paper presents a proposed system that supplies a 400 Hz single-phase onboard grid from the DC onboard bus. This system enables independent compensation of reactive power in the AC grid. Independent control of active and reactive power flow requires the decomposition of current in the grid into active and reactive components. Independent control of active and reactive power requires the use of synchronizers that operate in the dq frame system. If synchronization is performed with a single-phase grid, the transformation of dq requires the virtual quadrature signals. Standard quadrature signal generation systems use a second-order generalized integrator. To improve the dynamics of the system, the paper proposes a new quadrature generator that operates on the basis of trigonometric calculations instead of a second-order integration system. The developed system was implemented in a proportional-resonant current control system. Tests carried out in steady state and in dynamic states related to typical grid disturbances proved significantly better dynamic properties than those of a standard integrator-based system.

DER integrated BTB-VSI based DSTATCOM for PQ enhancement

ABSTRACT This article demonstrates the performance of back-to-back connected voltage source inverter (BTB-VSI)-based distribution static compensator (DSTATCOM). In the proposed system, a three-phase three wire electrical utility system (EUS) is integrated with distributed energy resources (DER) through BTB-VSI. It has drawn more attention due to enhanced active power filtering, simple design procedure and performs reliable operation. The objectives of the research work is to provide clean power for weak EUS with improved power quality (PQ) such as, better voltage regulation, improved power factor (P.F), reduced total harmonic distortion (THD), balanced voltage at point of common coupling (PCC) and better optimal active power flow control (OAPFC), and so on. An artificial neurocontrol technique Kernel Hebbian Least Mean Square (KHLMS) is chosen to determine the accurate reference source current for operation of voltage source inverter (VSI). The BTB-VSI performance is investigated on both shunt compensation and OAPFC. The proposed system is converted to a simulation model and hardware unit using MATLAB/Simulink software and SPARTAN−6 field programmable gate arrays (FPGA) controller. Finally, the Simulation and experimental results illustrate that the shunt compensating ability with OAPFC of BTB-VSI performs better over VSI as per IEEE Std 1159–2019 grid code.

A Two-Stage Multi-Scenario Optimization Method for Placement and Sizing of Soft Open Points in Distribution Networks

The Soft Open Point (SOP) is an emerging power electronic device for active power flow control, reactive power compensation and post-fault service restoration in power distribution networks. In this paper, a novel two-stage multi-scenario optimization method for SOP placement and sizing is proposed to minimize power losses and active power curtailment of distributed generation (DG) in distribution systems. In Stage 1, the Loss Sensitivity Index (LSI) and Voltage Deviation Index (VDI) are used to identify candidate locations of SOPs, and a new method to estimate the LSI is proposed. In Stage 2, a mathematical optimization model is developed using AC power flow to optimally size each voltage source converter (VSC) of a SOP; the power factor constraint at the substation/grid interconnection is incorporated in this model to ensure security of the upstream grid. The proposed method is validated by a modified IEEE 33-node test system and a large 404-node unbalanced distribution system operated by Saskatoon Light and Power in Saskatoon, Canada.

Field Programmable Gate Array-Based Execution on a Distributed Energy Resource Supported Electrical Distribution System for Enhanced Power Quality with Optimal Active Power Flow Control

This paper explains the experimental study of a distributed energy resource (DER) integrated three-phase, three-wire electrical distribution system (EDS) under power quality (PQ) and optimal active power flow control (OAPFC). In this research, a back-to-back connected two-level VSI (BTB-TVSI) based distribution static compensator (DSTATCOM) for unbalanced non-linear load is designed. The aim is to provide better OAPFC in EDS with shunt compensation to maintain a round-the-clock quality power supply for end users. The improved neural network-based adaptive least mean square (ALMS) control algorithms are employed for DSTATCOM. The ALMS control strategy is realized using the SPARTAN-6 field programmable gate array (FPGA) evaluation kit. This research involves the comparative study of a two-level voltage source inverter (VSI) and a BTB-TVSI in terms of their OAPFC capability and robustness in mitigating power quality (PQ) against source current disturbances, low power factor (PF), poor voltage regulation, unbalanced voltage at the point of common coupling (PCC), high switching stress, and issues in the EDS operation. The experimental results demonstrate that the BTB-TVSI using an ALMS controller is able to achieve better dynamic performance and lower total harmonic distortion (THD) under selected/permissible limits in comparison to a conventional VSI.

Design and Implementation of a SiC-Based Multifunctional Back-to-Back Three-Phase Inverter for Advanced Microgrid Operation.

Because of the worldwide trend of microgrid (MG) and renewable energy (RE)-based distributed power generation (DG), advanced power flow control schemes with wide bandgap (WBG) semiconductor technologies to ensure high-level performance of grid-connected MGs is one of the crucial research topics. In grid-connected MGs, a static switch (SS) is commonly used at the point of common coupling (PCC) of two systems. In this paper, the role of SS is replaced by a SiC-based three-phase back-to-back (BTB) inverter system for seamless switching between grid-connected and standalone modes through advanced power flow control schemes. According to scenarios of different grid/load conditions and available DG capacities in an MG, various advanced control functions can be developed for both MG operating modes: bidirectional control of active and reactive power flows, seamless switching between operating modes, improvement of grid power quality (PQ), and voltage stabilization. In this paper, mathematical models of the BTB inverter in a synchronous reference frame (SRF) is first derived, and the required controllers are then designed. For functional testing, two typical cases are simulated and analyzed in a MATLAB/Simulink environment and then verified through 1kVA small-scale hardware implementation with Texas Instruments (TI) digital signal processor (DSP) TMS320LF2812 as the control core. Results show satisfactory performances of power flow control and PQ improvement of MG.

An adaptive active power rolling dispatch strategy for high proportion of renewable energy based on distributed deep reinforcement learning

In this article, an adaptive active power rolling dispatch strategy based on distributed deep reinforcement learning is proposed to deal with the uncertainty of high-proportioned renewable energy. For each agent, by using recurrent neural network layers and graph attention layers in its network structure, we aim to improve the generalization ability of the multiple agents in active power flow control. Furthermore, a regional graph attention network algorithm, which can effectively help agents aggregate the regional information of their neighborhood, is proposed to improve the information capture ability of agents. We adopt the structure of ‘centralized training, distributed execution’ to help agents improve the effectiveness of proposed methods in dynamic environments. The case studies demonstrate that the proposed algorithm can help multi-agents learn effective active power control strategies. Each agent has a strong generalization ability in terms of time granularity and network topology. We expect that such an approach can improve the practicability and adaptability of distributed AI method on power system control issues.

Combined Active and Reactive Power Flow Control Strategy for Flexible Railway Traction Substation Integrated With ESS and PV

This paper proposes a combined active and reactive power flow control strategy for the flexible traction substation (FTSS). It fully uses the active and reactive power flexibility of FTSS to maximize regenerative braking energy (RBE) and photovoltaic (PV) energy utilization and improve power quality comprehensively. First, the active power flow optimization layer coordinates the active power outputs of the back-to-back converter (BTBC) and energy storage system to maximize the utilization of the available RBE and PV energy and balance the active power outputs of the traction transformer. Meanwhile, it controls PV output to limit the surplus energy injected into the utility grid further. Then, the model predictive control (MPC)-based reactive power flow optimization layer employs the spare capacity of BTBC to optimize the reactive power flow to improve the multiple power quality issues further, including negative sequence current (NSC), effective power factor (EPF), and traction network voltage fluctuations. To establish the MPC optimization problem, the NSC, EPF, and traction network incoming voltage sensitivity matrices with respect to the reactive power outputs of the traction transformer are first derived. Finally, the hardware-in-the-loop experiments, based on the data measurement from a high-speed railway traction substation, verify the effectiveness of the proposed strategy.

A Robust Mixed-Integer Convex Model for Optimal Scheduling of Integrated Energy Storage—Soft Open Point Devices

Soft open points (SOPs) are power electronic devices which can replace conventional normally open points in distribution networks. SOPs enable full control of active power flow between the interconnected feeders and can inject reactive power at each node to which they are connected. SOPs integrated with energy storage (ES) have been recently proposed to realize both spatial and temporal flexibility in active distribution networks. The flexibility provided by integrated ES-SOP devices will allow network operators to run their networks closer to their limits, but only if there is appropriate management of the uncertainty arising from demand and renewable generation. The only existing model of an ES-SOP uses nonconvex nonlinear equations, neglects uncertainty, and represents converter losses in an oversimplistic manner. This paper presents a robust mixed-integer convex model for the optimal scheduling of integrated ES-SOPs to ensure a zero probability of constraint violation. Losses of the subsystems comprising the ES-SOP are modeled using a proposed binary-polynomial model, enabling efficient scheduling of the energization state of subsystems to reduce no-load losses. The ES-SOP is considered in this paper to be owned by the network operator to: 1) manage power flow constraints, 2) minimize cost of losses, and 3) maximize arbitrage profit.

SYNTHESIS OF AN AUTOMATED CONTROL SYSTEM FOR THE FLOW OF ACTIVE POWER ALONG A POWER LINE IN OVERLOAD CONDITION

Currently, there are practically no automated systems for controlling power flow within the specified limits when the power line is overloaded by active power. Regulation is assigned to the dispatchers of the power system or is carried out by means of emergency automation, which disconnects consumers. Therefore, an urgent task is to expand the arsenal of tools for automatic control of active power flow in overload mode. Relevance. A significant increase in electricity consumers leads to a complication of the electric power system. The workload for dispatching personnel is increasing. Maintaining the smooth operation of the elements of the power system is a very important and responsible task. In modern electric power industry, timely warning and elimination of overloads of network elements are relevant. The study aims are development and research of an intelligent automatic control system for the flow of active power along a power line based on the mathematical apparatus of fuzzy logic. The system is based on the use of the regulating effect of the load. Research methodology. Methods of calculating static load model during their actualization were used. The method of fuzzy sets was used in the construction of an intelligence control system for active power flows in overload condition. The effectiveness was estimated by expert methods. Results. The use of artificial intelligence methods for automatic regulation of transformer voltage under load allows up to 5–7 % reducing the flow of active power in overload mode.

SYNTHESIS OF AN AUTOMATED CONTROL SYSTEM FOR THE FLOW OF ACTIVE POWER ALONG A POWER LINE IN OVERLOAD CONDITION

Currently, there are practically no automated systems for controlling power flow within the specified limits when the power line is overloaded by active power. Regulation is assigned to the dispatchers of the power system or is carried out by means of emergency automation, which disconnects consumers. Therefore, an urgent task is to expand the arsenal of tools for automatic control of active power flow in overload mode. Relevance. A significant increase in electricity consumers leads to a complication of the electric power system. The workload for dispatching personnel is increasing. Maintaining the smooth operation of the elements of the power system is a very important and responsible task. In modern electric power industry, timely warning and elimination of overloads of network elements are relevant. The study aims are development and research of an intelligent automatic control system for the flow of active power along a power line based on the mathematical apparatus of fuzzy logic. The system is based on the use of the regulating effect of the load. Research methodology. Methods of calculating static load model during their actualization were used. The method of fuzzy sets was used in the construction of an intelligence control system for active power flows in overload condition. The effectiveness was estimated by expert methods. Results. The use of artificial intelligence methods for automatic regulation of transformer voltage under load allows up to 5–7 % reducing the flow of active power in overload mode.

Optimal Design of Solid State Transformer-Based Interlink Converter for Hybrid AC/DC Micro-Grid Applications

The conventional low-frequency transformer (LFT) in conjunction with power electronic converters is used as the conscientious device to provide galvanic isolation and voltage regulation for the hybrid micro-grid (HMG) applications. However, it may not be suitable for HMG applications where the high power density and active power flow control over a wide operating range are major concerns. This article presents the solid state transformer (SST)-based interlink converter (IC) used to provide high frequency (HF) galvanic isolation between the ac/dc micro-grid (MG) networks. The proposed structure of SST intends to meet out most of the aspects of HMG networks such as active control over the bidirectional power flow, high efficiency, high power density, and better voltage regulation. In SST, nonoptimal parasitic components of HF transformer (HFT) are used as a part of power transfer elements and are unable to assist soft-switching operation over the wide range of load variations that degrade its overall performance. In view of these concerns, the comprehensive design and analysis are carried out at different stages to decide the design constraints for the optimization of nonoptimal magnetizing components and their significant effect on the system performance. Furthermore, the influence of the system parameters is analyzed with analytical expression and graphical analysis. The proposed SST configuration is designed for minimum kVA rating and better voltage regulation at different buses by using the proposed dual degree control (DDC) scheme over the wide range of load variations. The 4-kW hardware prototype is built up in the laboratory which provides isolated dc dual-port output terminals. The design and testing are carried out under different loading conditions to validate the significant performance of the proposed SST structure.

Active Power Flow Control Using Phase Shifting Transformer and UPFC in AC Transmission Line

Electrical power system is huge interconnected power system to meet the consumer demand without interruption and to maintain the stability, to utilize existing system to their maximum limit within stability limit of the system, to solve the congestion problem and improve the power flow in the line. Phase shifting transformer (PST) is used to control the active power flow in transmission line. This active flow control is obtained by adjusting phase angle of voltages at PST terminal. Unified power flow controller (UPFC) is facts device, it can control both the active and reactive power in transmission line by controlling the line parameter like voltage, phase angle and line impedance there by adjusting the line reactance in real time. The power system simulation model for PST and UPFC are developed in MATLAB. By simulating the model without PST and UPFC and then model with PST and UPFC is simulated to obtain the results. Results are compared for different loading condition to analyze the performance of the system with both the model. Keyword – PST, UPFC, Power flow control, active and reactive power, MATLAB/SIMULINK

Generalized Active Power Flow Controller for Multiactive Bridge DC–DC Converters With Minimum-Current-Point-Tracking Algorithm

This article proposes a new active power flow controller for dc–dc multiactive bridge (MAB) converters with minimum current point tracking (MCPT) to minimize conductive losses. Unlike recent efforts in this area, the proposed controller does not require look-up table for implementation nor complex nonlinear converter modeling and is not circuit parameter dependent. The proposed control scheme is also generalized for MAB converters with any number of ports and is derived in per unit form to enable standard implementation for buck/boost/unity-gain operating modes. The proposed MCPT algorithm is based on an innovative adaptive perturb and observe tracking of the minimum current point (MCP) on the MAB converter current characteristic plane. This MCP is tracked while active power regulation is simultaneously achieved based on a new phase shift decoupler to enable direct regulation of individual port active power. Detailed design procedure of the proposed controller is presented and extensive simulation is carried out to validate the effectiveness of the proposed MCPT closed loop controller. Experimental implementation is also provided to substantiate the simulation results.

Active and reactive power control of grid‐connected single‐phase asymmetrical eleven‐level inverter

In recent times, multilevel inverters (MLIs) have become very popular for commercial and industrial applications. Here, an eleven-level inverter and its power flow control are presented. The presented topology has a lesser component count than other existing topologies, thus reducing the devices and overall cost of the inverter. This inverter comprises six bidirectional switches, two DC sources, one four-quadrant switch, and two capacitors for the voltage divider circuit. The conduction modes and corresponding switching states of the presented eleven-level inverter are shown in detail. Further, the apparent power control of the presented inverter under grid-connected operation is discussed, which provides simultaneous active and reactive power control over the power injected into the grid. Switching and conduction losses are calculated for 3 and 6 kVA grid injected power at 0.8 power factor lagging. The obtained results show that the total harmonic distortion (THD) of the inverter output voltage and grid current is 12.10% and 0.23%, respectively, under 6 kVA power transfer conditions. The real-time analysis is also carried out for 3 and 6 kVA power transfer conditions for the presented eleven-level inverter to validate the active and reactive power flow control.

Voltage Unbalance Compensation in Distribution Feeders Using Soft Open Points

Soft open points (SOPs) are power electronic devices that may replace conventional normally-open points in distribution networks. They can be used for active power flow control, reactive power compensation, fault isolation, and service restoration through network reconfiguration with enhanced operation flexibility and grid resiliency. Due to unbalanced loading conditions, the voltage unbalance issue, as a common problem in distribution networks, has negative impacts on distribution network operation. In this paper, a control strategy of voltage unbalance compensation for feeders using SOPs is proposed. With the power flow control, three-phase current is regulated simultaneously to mitigate the unbalanced voltage between neighboring feeders where SOPs are installed. Feeder voltage unbalance and current unbalance among three phases are compensated with the injection of negative-sequence and zero-sequence current from SOPs. Especially in response to power outages, three-phase voltage of isolated loads is regulated to be balanced by the control of SOPs connected to the feeders under faults, even if the loads are unbalanced. A MATLAB/Simulink model of the IEEE 13-bus test feeder with an SOP across feeder ends is implemented, and experimental tests on a hardware-in-the-loop platform are implemented to validate the effectiveness of the proposed control strategy.

An optimization method for operational efficiency of ADN with four-port SSOP

The soft open point (SOP) replaces the traditional feeder switch based on controllable electronic converter, it provides real-time and accurate active and reactive power flow control. To address the optimization effects of SOP on the operating efficiency of active distribution network(ADN), this paper firstly establishes the access topology and mathematical model of four-port SOP with energy storage (SSOP) considering the operating constraints of four-port SSOP converter and DC-side energy storage device; secondly, an optimization model of the operating efficiency of ADN based on four-port SSOP is established, where power loss reduction, feeder load balancing and voltage profile improvement were taken as objectives. Semi-definite programming is used to simplify the model and convert nonlinear constrains into linear quantities. Case studies of a four-port SSOP in a ADN are conducted to verify the effectiveness and efficiency of the proposed method.