Reactive Power Generation Research Articles

Photovoltaic systems and yearly net self-sufficient electricity supply in distribution networks

The paper deals with distributed photovoltaic (PV) systems capable of accepting reference values for the reactive power generation and active power curtailment. The aim of the performed research is to analyze to what extent can the use of controllable PV systems increase the total share of PV systems in electric grids and to what extent can controlled PV systems increase the yearly net self-sufficient electricity supply. In the case study the analysis is performed from the viewpoint of the distribution grid, considering the voltage profile, conductor loading and grid losses. Problems related to the power system stability are not discussed.

Impact of OLTC equipped transformer operation on PV installation in urban distribution network

Presented paper addresses the problem of proper large-scale integration of photovoltaic (PV) systems in urban area distribution network (DN). A methodology for minimization of annual energy losses in DN by optimal placement of PV systems, which simultaneously considers rooftop PV potential and time dependent network operation, is presented. Optimal reactive power generation of PV systems and optimal setting of on-load tap changer (OLTC) equipped transformer in secondary substation are determined as well. Furthermore, proposed methodology enables evaluation of the impact of OLTC equipped transformer on the share of PV installation that urban DN can accommodate. Proposed methodology is based on the optimization tool called differential evolution, with the objective function set to minimize network’s annual energy losses, while preventing the voltage violations and thermal overloading of lines. Results of the case study performed on a real urban low voltage distribution network, with consideration of different scenarios of OLTC operation are presented. The results indicate that simultaneous consideration of chosen variables yields greater benefits to DN operation in terms of reduction of annual energy losses and greater PV penetration.

Generation and absorption of reactive power by wind farms – consequences of implementation of EU regulation 2016/631

Generation and absorption of reactive power by wind farms – consequences of implementation of EU regulation 2016/631

Hybrid Wind-Solar System with UPQC

The hybrid wind-solar system is a combination of renewable energy sources, specifically wind and solar, that is utilized for power generation. While wind power has historically been used for various purposes such as sails, windmills, and wind pumps, it is now predominantly used for electricity generation. This system incorporates solar panels and small wind turbine generators to produce electricity. The advantage of hybrid systems is that they can generate electricity as needed, taking into account the varying peak working hours of solar and wind systems throughout the year. To ensure a stable power system, UPQC (Unified Power Quality Conditioner) is employed. This multipurpose power conditioner serves multiple functions, including preventing harmonic load current from entering the power system, rectifying voltage fluctuations, and compensating for voltage disturbances from different power sources. It is specifically designed to minimize interference with sensitive or critical loads. With its series and shunt compensation capabilities, UPQC effectively manages power flow, reactive power, harmonics, and voltage disturbances. In this paper, the work addresses the issue of electricity quality that arises from the installation of wind turbines in the grid. To get over this issue, the suggested course of action demonstrates how to install a BESS and a unified power quality conditioner (UPQC) at the connection point. Even though wind power fluctuates, the use of battery energy storage technology helps to provide a constant power supply. With the power system block established in MATLAB/SIMULINK, one can simulate the UPQC control method of a grid-connected wind energy generating plant. As a result, the power's quality will increase. When the recommended approach lowers the load's and the induction generator's reactive power requirements, it is successful. Furthermore, the plan for raising the grid's power quality criteria and developing the grid coordination rule are also provided.

Application of Covariance Matrix Adaptation‐Evolutionary Strategy for Modified Constrained Optimal Power Flow Problem Incorporating Valve Point and Emission Effect

A prevailing problem in power and energy subsystems is the smooth operation of electric energy systems. This work presents recent, efficient, and reliable evolutionary algorithm for solving the optimal power flow (OPF) analysis. All various practical complex equality and inequality constraints, namely, bus voltages, real powers of the generator buses, tap settings of the transformers and the reactive power generations, shunt compensation, and emission, are considered for the real‐world scenario. Primary feature in a gas power plant that raises a lot of computational shortcomings with nonlinear structure in fuel cost is valve point effect. The existing research works have not factored the valve point effect and lack the accuracy in the fuel cost minimization and do not reflect the various practical complexities such as valve point and emission effects in the OPF problem formulation. This paper, for the first time, introduces modified OPF problem formulation incorporating valve point effect and applies covariance matrix adaptation‐evolution strategy (CMA‐ES) for solving the modified OPF problem. The algorithm is scrutinised and tested on a modified IEEE‐30‐bus platform for various OPF objectives such as cost minimization, transmission loss, and total voltage deviation, subjected to practical constraints. Load flow analysis has been carried out using the Newton–Raphson method. This work aims to lay the foundation in such a way that it can be applicable in a real‐world scenario for any number of buses.

Grey Wolf Optimizer Algorithm for Multi-Objective Optimal Power Flow

This article introduces the Grey Wolf Optimizer (GWO) algorithm, a novel method aimed at tackling the challenges posed by the multi-objective Optimal Power Flow (OPF) problem. Drawing inspiration from the foraging behavior of grey wolves, GWO stands apart from traditional approaches by enhancing initial solutions without relying on gradient data collection from the objective function. In the domain of power system optimization, the OPF problem is widely acknowledged, involving constraints related to generator parameters, valve-point loading, reactive power, and active power. The proposed GWO technique is applied to IEEE 14-bus and 30-bus power systems, targeting four case objectives: minimizing cost with quadratic cost function, minimizing cost with inclusion of valve point, minimizing power loss, and minimizing both cost and losses simultaneously. For the IEEE-14 bus system, which requires meeting a power demand of 259 MW, GWO yields optimal costs of 827.0056 $hr, 833.4691 $hr, 1083.2410 $hr, and 852.2255 $hr across the four cases. Similarly, for the IEEE-30 bus system aiming to satisfy a demand of 283.4 MW, GWO achieves optimal costs of 801.8623 $hr, 825.9321 $hr, 1028.6309 $hr, and 850.4794 $hr for the respective cases. These optimal results are then compared with existing research outcomes, highlighting the efficiency and cost-effectiveness of the GWO algorithm when juxtaposed with alternative methods for solving the OPF problem.

Maximum Reactive Power Generation Method Based on Limitation of Output Capacity for Star-Connected Cascaded H-Bridge STATCOM Under Voltage Sag

Star-connected cascaded H-bridge (SCHB) STATCOM is being widely used in medium and high voltage to support grid by injecting positive and negative sequence current. Under balanced conditions, the rated reactive power is usually utilized to calculate the required reactive current reference based on instantaneous power theory. However, under grid voltage sag, the rated reactive power changes due to the introduced negative sequence current and extra zero sequence voltage for cluster voltage balancing, which may increase overcurrent and overmodulation risk. Therefore, how to derive the maximum compensable reactive power is required for SCHB STATCOM under the grid voltage sag. In this paper, the quantitative relationship between the imbalanced degree of grid voltages and reactive power reference is fully explored. On this basis, the maximum reactive power is calculated under voltage sags by considering current and voltage limitation. In this calculation, a new geometrical analysis method is proposed, which makes the calculation speed faster for online calculation. Therefore, a new grid support control strategy is proposed for the SCHB STATCOM under grid voltage sag, which can effectively support the grid with the maximum output reactive power. Finally, the proposed method is verified by experimental results on a 400V/7.5kVar SCHB STATCOM prototype.

Improvement of the cooling system of reactive power compensating devices used in railway power supply

This article analyzes the reactive power generation and compensation solutions in the "Uzbekistan Railways" electrical supply system operating at 25kV, 50Hz frequency. It examines the efficiency and economic analysis of the cooling system connected to the control components (thyristors) of the device compensating reactive power under various operating conditions. The study compares the conventional cooling system approach with the newly researched cooling system for the controlling components of reactive power compensation. It proposes specific systematic solutions regarding the electric locomotive's load current, environmental conditions, reliability of the cooling system, maintenance capabilities of the cooling system, and real-time monitoring and control analysis delivery to the service provider. Additionally, conclusions are drawn regarding the economic and energy efficiency.

Analysis of unified power quality conditioner errors

This article is devoted to error analysis of the unified power quality regulator. In the context of the growing importance of reliable and high-quality power supply, power quality regulators are becoming key devices to ensure the stability of networks and meet the needs of domestic consumers. The paper proposes a comprehensive approach to error analysis of the unified power quality conditioner, the main purpose of which is to compensate for the impact of rapidly changing loads on power quality. At the same time, indicators of general harmonic distortion of the quality of electricity are analyzed, and factors such as the magnitude and duration of loads are also taken into account. A large part of the article is devoted to the study of the sources of errors in unified power quality conditioner. A comparison of the parallel-serial and series-parallel topologies of unified power quality conditioner is performed. The influence of the unified power quality conditioner control algorithm on the formation of errors of each topology is analyzed. Using Matlab/Simulink computer simulation tools, the article proposes a framework for error quantification, which allows accurate estimation of errors at various stages of unified power quality conditioner operation. This framework covers the Fourier series transformation of voltage and power for comprehensive estimation of error magnitudes. To confirm the effectiveness of the proposed error analysis and compensation strategies, the article presents graphs of simulation results in the time and frequency domains. Active and reactive power generation errors and voltage setpoint errors are described. These findings emphasize the ability of unified power quality conditioner to improve the quality of electricity, despite measurement errors. The main results include the analysis of deviations of voltage quality indicators, the establishment of a connection between compensation errors and deficiencies in the functioning of the system, as well as the development of recommendations for improving the efficiency of compensation devices.

FACTS placement for reactive power planning with weak node constraints using an improved symbiotic search algorithm

In this paper, an economically feasible and reliable operation of the IEEE 57 bus system for Optimal Power Flow (OPF) is proposed. The Improved Symbiotic Organisms Search (ISOS) algorithm is proposed for effective reactive power planning as an OPF issue. Further, the optimal position of Flexible AC Transmission Systems (FACTS) is taken into consideration, by including the existing system controlling variables like reactive power generators output, transformer tapping and capacitors connected at shunt. The objective of the work is two-fold; i.e., to reduce the energy loss and to enhance the voltage profile within the prescribed limit by ensuring the economic operation and investment cost of FACTS in the system. In this work, two FACTS devices like Static Var Compensator (SVC) and Thyristor-Controlled Series Controller (TCSC) have been taken into consideration. Voltage sensitivity indicator and reactive power flow are two tools that are utilised in order to locate weak nodes for the implementation of FACTS. Finally, the performance of the ISOS algorithm is compared with that of three other state- of-the -art optimization techniques, such as, Symbiotic Organisms Search (SOS), Differential Evolution (DE) and Teaching Learning Based Optimization (TLBO). A Non-parametric statistical analysis is also performed to investigate the dominance of the ISOS algorithm over others.

РОЗПОДІЛЕНЕ РЕГУЛЮВАННЯ НАПРУГИ РОЗПОДІЛЬЧОЇ ЕЛЕКТРОМЕРЕЖІ З ВІДНОВЛЮВАНИМИ ДЖЕРЕЛАМИ ЕЛЕКТРОЕНЕРГІЇ

The problems of distributed voltage control in electrical grids (EGs) with renewable sources of electric energy with converter-interfaced generation (CIG). It is proposed to control the EGs modes by controlling the reactive power of converter-interfaced generation. It is proposed to use the mean square deviation of the voltage in the converter inter-faced generation (CIG) installation nodes as the criterion of the target function. The extremum seeking control method was used to solve the problem of dynamic optimization with daily changes in the parameters of the electric network, namely the loads and active power of renewable sources. The examples provided have shown the improvement of the voltage in the EG at different levels of reactive power generation limitation according to the norms of the standard EN50549-1:2019. The optimal values of the average daily value of the rms deviation of the voltage of the ieee33 test EM were obtained with a significant penetration of the RES power. Bibl. 12, fig. 4, table. Keywords.: distributed voltage control, converter interfaced generation, extremum seeking control method.

An AC optimal power flow framework for active–reactive power scheduling considering generator capability curve

AbstractThis paper presents a simplified optimal power flow (OPF) framework to facilitate co‐optimised active and reactive power scheduling for synchronous generators and price‐sensitive demands. The proposed framework creates an opportunity for generators and loads to simultaneously participate in a combined market for active and reactive power. The co‐optimisation of active and reactive power generation is constrained by the interdependence of the active and reactive power capacities, which is represented by the generator capability curve. Thus, a detailed mathematical derivation of the opportunity costs across various regions of the generator capability curve is presented. This study considers a detailed generator capability curve that considers the armature, field, under‐excitation, and prime mover limits. The interdependence of active and reactive power consumption for demand is modelled using the concept of power‐factor. The OPF problem for generator and load scheduling is formulated as a non‐linear optimisation task, leveraging the inherent properties of the generator capability curve, that is, piecewise smoothness, continuity, and the monotonically increasing slope magnitudes. Furthermore, to simplify the OPF formulation, the non‐linear capability curve is represented as a combination of the linear curves. To demonstrate the effectiveness of the proposed OPF methodologies, suitable case studies are conducted using different test systems.

A survey on voltage stability indices for power system transmission and distribution systems

Voltage stability is a critical aspect of power system operation, ensuring the reliable and efficient delivery of electrical energy to consumers. Recently, voltage stability in the power system has received much attention. The primary cause of voltage instability is the lack of real and reactive power generation to cope with the continuous demand increment. Maintaining voltage stability while planning, controlling, and assessing the system’s security is a difficult task for power system engineers. From knowledge of past incidents, a lack of reactive power is identified as the primary cause of voltage instability, which may further lead to the total collapse of the system. The importance of voltage stability assessment is essential to maintain the integrity of power systems. It helps prevent voltage instability, which can lead to cascading failures and widespread outages. This paper uses various parameters, including load demand, generator capacity, and system impedance, to develop voltage stability indices (VSIs). The paper mainly focuses on the idea of VSIs that have been developed in order to monitor and control the criticality of the power system. The voltage stability indices for transmission and distributed systems, as well as their subclasses, are thoroughly reviewed in this study. Furthermore, traditional voltage stability methods, as well as various software tools for monitoring the voltage stability problems, are also discussed. In addition, the development of VSIs and its related concepts are clearly described in this paper. This comprehensive survey provides a decent groundwork for future work in this area, and assists professionals in selecting the optimal VSI for various applications. Moreover, it provides a concise overview of methods and the importance of voltage stability assessment in both transmission and distribution systems.

Secondary control with reduced communication requirements for accurate reactive power sharing in AC microgrids

AbstractA secondary control method is proposed for accurate reactive power sharing as well as frequency and voltage restoration in islanded AC microgrids (MGs). The proposed method consists of an MG secondary controller, local secondary controllers for distributed energy resources (DERs), and a low‐bandwidth communication link for broadcasting common data from the MG secondary controller to DERs. The broadcasted data includes the MG point of common coupling voltage magnitude and a common vertical shift for frequency and voltage restoration. Local secondary controllers calculate specific shifts for the Q‐V droop characteristic of each dispatchable DER and the V‐Q reverse droop characteristic of each photovoltaic (PV) system, aligning their operating points with the Q‐VPCC and VPCC‐Q droop characteristics, respectively. By employing VPCC as a common global variable, coordination of reactive power generation of all dispatchable DERs and PV systems is achieved, enabling accurate reactive power sharing. Importantly, in the proposed scheme, the required communication bandwidth and the communication burden are minor and are not increased with the number of DERs. Additionally, the DERs are relieved of the need for data transmission capability. The small signal stability of the proposed method is examined and its effectiveness is validated through Hardware‐in‐the‐Loop (HIL) experimental results.

Research on the Optimization of Synchronous Switch Energy Harvesting Circuit Based on Capacitor

As advanced systems continue to advance and fuse functions expand, the demand for higher power supply requirements for fuses has increased. Consequently, researchers have turned their attention to the recovery of energy from the environment. Piezoelectric energy harvesting has gained significant popularity due to its advantageous characteristics, such as high energy density, ease of implementation, and compact size. However, the presence of various component types within the energy harvesting circuit inevitably results in the generation of reactive power, leading to a reduction in the circuit’s power factor. To address this issue, this paper introduces the adoption of the third-order valley-fill circuit as the power factor correction circuit. The implementation process involves the utilization of Multisim software to simulate the double-limit zero-crossing detection circuit, pulse signal generation circuit, and power factor correction circuit. Furthermore, the aforementioned circuits were subjected to plate-level welding, followed by individual tests to evaluate the effectiveness of the double-limit zero-crossing detection, pulse signal test, and load voltage measurement. These findings unequivocally exemplify the successful accomplishment of the intended objective of augmenting the output power by the third-order valley-fill circuit.

Incorporating photovoltaic inverter capability into stochastic optimal reactive power dispatch through an enhanced artificial gorilla troops optimizer

AbstractThis study addresses the challenging task of solving optimal reactive power dispatch (ORPD) while incorporating renewable energy resources (RERs), considering their stochastic and time‐varying nature. Specifically, the focus is on solving the stochastic optimal reactive power dispatch (SORPD) problem, taking into account uncertainties in load demand and generated power, as well as the reactive power generation capability of photovoltaic (PV) systems. To tackle this problem, an enhanced Artificial Gorilla Troops Optimizer (EGTO) is proposed, which utilizes multiple strategies. The objective is to minimize power loss and improve voltage profile and system stability under uncertain conditions. The algorithm is applied and tested on the IEEE 30‐bus system, both with and without the STATCOM functionality of the PV system. A comparison is conducted against other well‐known optimization algorithms. The results demonstrate the significant improvement achieved by incorporating the PV unit. The inclusion of the PV system leads to reduced expected power losses, voltage deviations, and improved voltage stability. Specifically, without and with the STATCOM functionality, the expected power loss decreases from 5.9218 MW at the base case to 1.1419 MW and 1.1197 MW, respectively. Similarly, the expected voltage deviation decreases from 1.9320 p.u. to 0.0909 p.u. and 0.0893 p.u., respectively, and the expected voltage stability decreases from 0.1336 p.u. to 0.07199 p.u. and 0.07142 p.u., respectively.

Integrated Reactive Power Optimisation for Power Grids Containing Large-Scale Wind Power Based on Improved HHO Algorithm

Large-scale wind power grid integration will greatly change the system current distribution, making it difficult for the reactive power regulator to adjust to the optimal state. In this paper, an integrated reactive power optimisation method based on the improved Harris Hawk (HHO) algorithm is proposed. Firstly, a reactive power regulation model is constructed to solve the reactive power regulation interval of wind turbines, and the reactive power margin of wind turbines is used to participate in the system’s reactive power optimisation. Finally, a reactive power compensation capacity allocation optimisation model considering nodal voltage deviation, line loss and equipment investment cost, is established, and a reactive power optimisation scheme is obtained using the Harris Hawk optimisation algorithm on the basis of considering the constraints of the wind turbine reactive power output interval. The improved HHO algorithm is used to solve the reactive power optimisation scheme considering the constraints of tidal power, machine end voltage, a conventional generator and wind farm reactive power. In the simulation, the effects of the improved Harris Hawk optimisation algorithm and the particle swarm optimisation algorithm are compared, and the experimental results prove that compared to the particle swarm algorithm, the optimisation result of the improved Harris Hawk optimisation algorithm reduces the average loss of the system by 42.6% and reduces the average voltage deviation by 30.3%, which confirms that the improved Harris Hawk intelligent optimisation algorithm is effective in proving its superiority and solving the multi-objective model for reactive power optimisation.

Reactive power management: Comparison of expert‐based and optimization‐based approaches for dispatcher training

AbstractReactive power management (RPM) in electric power systems is usually based on a rule‐based control derived from the transmission system operator's (TSO) experience. This approach faces challenges as the number of decisions and the complexity of the system operation is increasing. With the increasing generation from renewables and the evolution of electricity markets, the available resources must be optimally utilized. This paper compares the optimization‐based approach (OBA) and the experience‐based expert approach (EBA) for RPM. The OBA is based on security‐constrained optimization with minimum redispatch cost as the objective function for a reference contingency. In contrast, the EBA's actions are based on the system operator's experience. Comparison is made in terms of the generator redispatch cost, active and reactive power redispatch volume, active power losses, nodal voltages, and the number of actions to ensure secure operation. The analysis using a reduced model of an actual transmission system shows that OBA is more beneficial than EBA, with up to 22% and 42% reduction in redispatch cost and volume, respectively. Moreover, the control decisions from both approaches are seen to be similar. This study aims to show the usefulness of the OBA and motivate TSOs to move towards optimization‐based reactive power management.

Artificial Intelligence Approach for the Control of SPMSG Based Grid Connected WECS

In India, power plant requirement is rapidly increasing as non-conventional sources are in current need. Government financial aid plays important role for generator plant execution because of its tedious procedure. If the utilization of wind power production has to be doubled, then machines, turbines and converters are essential in two numbers. The research work includes parallel connection of two machines using star-delta-star transformer fashion resulting in six-phase permanent synchronous machine. This arrangement is more economical as the number of converters are reduced thereby increasing the efficiency by minimizing the switching losses. Initially rectifier setup is used wherein high frequency AC is converted to low frequency and maximum power point tracking is done with the aid of a converter. It is DC-DC conversion by decoupled DQ strategy. Later, it is again converted back to three phase AC so as to synchronize it to the grid. The system response is analysed by conventional PI controller by reducing the noise in the real & reactive power generation. Further, ANFIS-PI controller is implemented to improve the response of PI controller which is much essential for wind power generation. The MATLAB simulated results of PI controller system response and ANFIS-PI controller is presented in this paper.

Improving the quality of electricity in power supply systems with reservation from diesel generator plants

Subject of research: substantiation of the parameters and application of FACTS-devices of the STATCOM type for improving the quality of electricity in power supply systems with redundancy from diesel generator sets.
 Purpose of research: is to substantiate technical solutions based on semiconductor devices with reactive and active power generation aimed at improving the quality of electricity in remote power supply systems powered in backup mode from diesel generator sets.
 Methods and objects of research: fast Fourier transform, instantaneous power theory, simulation in Matlab Simulink. The object of research is the power supply system with a complete transformer substation 10/0.4 kV and redundancy from diesel generator sets.
 Main results of research: the article presents the features of ensuring the redundancy of the considered power supply system, taking into account the quality of electricity and the rationale for technical solutions to improve it when supplying the household loads of the village in the backup mode from the DGU based on simulation modeling. A spectral analysis of a sharply variable load curve was performed. It is proposed to use a three-level STATCOM at a voltage of 0.4 kV with a supercapacitor storage, which requires less storage energy than a buffer storage, to ensure the quality of electricity when powered by a diesel generator set. The results of the studies carried out testify to the prospects of using STATCOM with a storage device to improve the quality of electricity in low-voltage networks.