Dynamic Reactive Power Compensation Research Articles

Dynamic compensation of active and reactive power in distribution systems through PV-STATCOM and metaheuristic optimization

This article presents a heuristic methodology to address the operation problem of PV-STATCOMs, focusing on the dynamic compensation of active and reactive power to minimize daily energy losses and costs associated with purchasing energy in distribution networks. The methodology is developed using a master-slave type optimization approach. In the master stage, potential solutions are generated using an optimization algorithm based on the salp swarm. In contrast, the slave stage evaluates these solutions using the power flow method by successive approximations. The methodology was evaluated in two test systems, with 33 and 69 nodes, varying the power factor of each PV-STATCOM. The results demonstrate a significant reduction in both energy losses in the network and the cost of purchasing energy at the substation. Furthermore, the efficiency of the salp swarm algorithm for effective resolution of the problem is confirmed. This approach contributes to optimizing the operation of PV-STATCOMs and highlights the proposed algorithm's applicability and effectiveness in practical distribution network environments.

Research on intelligent auxiliary regulation technology of large power grid section based on artificial intelligence

In the modern era, large-scale renewable energy systems are integrated with advanced power systems and provide efficient operations. Also, optimized power systems require accurate energy generation and effective control systems to manage and ensure a stable power supply. Nevertheless, uncertainties are the intermittent balance of supply and high electricity demand. In addition, conventional power sources are not applicable for this challenging task and increase electricity costs. Therefore, an efficient Neuro Fuzzy Single phase Unified Power Quality Conditioner with Maximum Power Point Tracking (NF-SP UPQC -MPPT) strategy is developed for enhancing the grid-connected power systems. Here, Neuro-fuzzy logic is used as dynamic reactive power compensation in the grid. Also, this logic can efficiently handle the Energy storage system (ESS). Then SP UPQC was used to enhance power quality in electrical distribution systems. It combines both series and shunt compensators to mitigate various power quality issues such as voltage sags, harmonics, and unbalance. After that MPPT was utilized to extract the maximum power from the grid system. Model Predictive Control (MPC) controller to determine the overall stability and performance of the system. Moreover, the developed model was implemented on the MATLAB platform and performance is analyzed in terms of voltage deviation, grid current, reactive power fluctuations and Total Harmonic Distortion (THD).

Dynamic Reactive Power Allocation Method of Power Grid with High-Permeability PV Considering Transient Voltage Stability

Dynamic Reactive Power Allocation Method of Power Grid with High-Permeability PV Considering Transient Voltage Stability

Design and Verification of Cascaded Multilevel STATCOM Active Filter Function

STATCOM can be used as both dynamic reactive power compensation device and active power filter to improve the power quality of a power grid. This paper describes the active filter function implemented into an existing STATCOM control. The paper explains firstly the filtering control system of the STATCOM, starting from the introduction of active power filter principle, harmonic current detection and tracking control. After that, the parameter design, open-loop characterization and simulation verification of the proposed filtering control scheme are carried out. The PSCAD simulation results show that the active filtering control scheme proposed in this paper can effectively reduce the harmonic content in the system and has good stability.

Dynamic active and reactive power compensation in distribution networks using PV-STATCOMs: A tutorial using the Julia software

This document presents a tutorial regarding the use of PV-STATCOMs for dynamic active and reactive power compensation in AC distribution networks. The main idea is to guide the reader from the classical power flow formulation for AC distribution networks in the complex domain to a multi-period power flow problem using the optimization tools available in the Julia programming software. The use of PV-STATCOMs as dynamic active and reactive power compensation tools allows considering different power factors, i.e., they can work as a PV generation plant with a unitary power factor, as a purely reactive power compensator (capacitive or inductive), or as a dynamic active and reactive power compensator with a variable power factor. The Julia software was selected as a programming environment due to its excellent performance in terms of its programming interface and the use of specialized solvers for nonlinear programming problems in the complex domain, which helps introduce some concepts for the efficient operation of distribution networks while focusing on the mathematical model instead of on the solution technique. Numerical results confirm that the proposed approach, which uses the Ipopt solver, yields excellent numerical solutions in comparison with optimization methodologies recently reported in the scientific literature. A version of the IEEE 33-bus grid adapted for multi-period optimal power flow studies was employed as a test feeder. All numerical results were obtained using Julia, with the help of the JuMP optimization environment and the Ipopt solver.

Startup control strategies for pre-fabricated synchronous condensers using static frequency converters

In ultra-high voltage transmission systems, a considerable number of dynamic reactive power compensation devices must be equipped. Synchronous condensers are capable of providing substantial amounts of dynamic reactive power. Therefore, distributed prefabricated synchronous condensers can be deployed in ultra-high voltage transmission systems to supply reactive power support to the power grid. The start-up of synchronous condensers can only be achieved through external means. Currently, there are multiple start-up methods available for small-capacity prefabricated synchronous condensers. With the rapid advancements in frequency conversion technology and power electronics, static frequency converters (SFCs) can be utilized to initiate synchronous condensers. This paper investigates the principles of SFC start-up and coordinated control while also configuring protective devices for SFCs based on their structural characteristics and operational principles. A validation platform consisting of one SFC starting two synchronous condensers was established to analyze their start-up time, yielding results demonstrating the ability of SFC-driven distributed small-capacity synchronous condensers to rapidly adjust the power quality of the power grid.

Dynamic Reactive Power Compensation Optimization Strategy for Distribution Networks with Distributed Generators and Energy Storage Systems

To balance the output and load dynamic changes of distributed power generators (DG) and energy storage systems (ESS), a demand-side response-based dynamic reactive power optimization (RPO) strategy for distribution networks (DN) is proposed. This strategy adopts a phased optimization method to coordinate and optimize different types of reactive variables within the same period. By adjusting the states of parallel capacitor banks (SCBs) on load voltage transformers (OLTC), DGs, and ESS inverters, the RPO of the DN is carried out. Based on the characteristics of the model, an improved particle swarm optimization algorithm (IPSO) is used to solve different types of variables, and an IPSO based on tent chaotic mapping and levy flight strategy is proposed to improve the efficiency of collaborative solving. The simulation results show that the proposed strategy, considering the change of new energy output and demand side response, can reduce the solution scale while obtaining high satisfaction RPO results.

Research on Reactive Power Coordination Control Strategies of Multi-Infeed Line-Commutated Converter–High-Voltage Direct Current Systems

For a receiving-end power grid with multi-infeed LCC-HVDC systems, simultaneous commutation failures may seriously threaten the safe and stable operation of the system. To evaluate the impact of commutation failure and improve the voltage stability of the commutation buses in multi-infeed HVDC systems, this paper proposes a method for evaluating the voltage stability of commutation buses and a reactive power coordination control (RPCC) method for commutation failure of multiple HVDC systems. Firstly, three indicators and the entropy weight method are adopted to comprehensively evaluate the voltage stability of commutation buses. Then, an RPCC method is proposed to resist commutation failure. The proposed RPCC method uses the voltage interaction factor (VIF) to screen out DC systems that are strongly related to dynamic reactive power compensation devices and activates the devices to provide RPCC to the DC systems through an auxiliary controller. Finally, the effectiveness of the proposed method is verified through a practical example of the Jiangsu power grid.

Analysis of transient electromagnetic force on end windings of 300 Mvar synchronous condenser during dynamic reactive power compensation process

The uneven distribution of renewable energy supply and demand promotes the development of high-voltage direct current transmission. As the critical reactive power compensation equipment for high voltage direct current transmission, the synchronous condenser must have a strong overload capability. One of the critical factors limiting the improvement of its overload capacity is the reliability of the end winding, which depends on the magnitude of the force on end windings during dynamic large reactive power output. Therefore, this paper proposes a coupling model of transient electromagnetic force for the high voltage direct current transmission system and the end zone of the synchronous condenser. The transient response of the synchronous condenser under different fault degrees is calculated, analyzed, and verified by experiments. Based on the current response of the synchronous condenser, the transient electromagnetic force on end windings is calculated. The distribution law of the force on end windings of the synchronous condenser under different degrees of dynamic reactive power compensation process is revealed. Further, the regions on end windings with larger force during strong overload are indicated. The optimizing fixation scheme for end windings is proposed according to the distribution features of the force, which can improve the operational reliability of end windings.

A New Control Strategy of Hybrid Reactive Power Compensation System in Distribution Network

Reactive power compensation is an important measure to improve the power quality of distribution networks, especially with the increasing connection of distribution transformers, heavy industrial electrical equipment, and asynchronous motors, which generate a large amount of reactive power demand. Traditional reactive power compensation devices, such as fixed capacitors (FC) and thyristor switched capacitors (TSC), have some drawbacks, such as low response speed, harmonic generation, and switching shock. A static synchronous compensator (STATCOM) is a flexible AC transmission system (FACTS) device that can provide fast and continuous reactive power compensation, but it also has some limitations, such as high cost, large capacity requirement, and low utilization rate. Therefore, hybrid reactive power compensation systems that combine FC or TSC with STATCOM have attracted much attention in recent years. Many researchers have proposed and studied different topologies and control methods of hybrid systems to overcome the disadvantages of single devices and achieve better performance. However, most of the existing hybrid systems are designed for low or medium-voltage distribution networks, and their performance under high-voltage distribution networks is still unclear. Moreover, the coordination control strategy of the hybrid system and its subsystems is also a key issue that affects the effectiveness and efficiency of reactive power compensation. In view of this, this paper aims to propose a TSC+STATCOM hybrid reactive power compensation system for high-voltage distribution networks, which optimizes the shortcomings of traditional reactive power compensation devices. The system uses the synergistic effect of TSC and STATCOM to achieve large-scale static reactive power and small-scale dynamic reactive power compensation and adopts a switching strategy based on an expert decision system. This paper introduces the working principle of each subsystem of the hybrid reactive power compensation system in detail and builds a simulation model of the hybrid reactive power compensation system under a high voltage distribution network on Matlab/Simulink platform. The simulation results verify the feasibility and excellent performance of the system control method in reactive power compensation and improving power quality.

A Differentiated Dynamic Reactive Power Compensation Scheme for the Suppression of Transient Voltage Dips in Distribution Systems

At present, with the construction of new power systems, the uncertainty of the system is increasing and the transient voltage stability of the power grid is becoming more and more complicated. For this reason, this paper proposes a differentiated dynamic reactive power compensation configuration method for suppressing transient voltage dip instability. The method first establishes a dynamic reactive power device configuration indicator system based on multiple-two-element notation, and then establishes a differentiated dynamic reactive power compensation device configuration model based on the node instability risk characteristics. The model takes the investment cost and suppression effect as the optimization objectives, and flexibly adjusts the optimization weights of its cost and suppression effect according to the high or low risk of the transient voltage instability of the compensation node, so as to realize the differentiated dynamic reactive power compensation. Compared with traditional compensation methods, differentiated compensation can significantly improve the economic benefits of reactive power compensation configuration. Finally, taking the IEEE39 node test system as an example, the improved TLBO algorithm is used to solve the model. The cost of differentiated compensation is reduced by 22.13%, with a similar suppression effect, which verifies the validity of the method proposed in this paper.

Stability simulation and improvement of typical phase-locked loop of STATCOM with different equivalent grid R/L ratios

Transient synchronization stability is the precondition for dynamic reactive power compensation of STATCOMs in the event of a grid fault, which might be so serious that their neighboring distributed power generators lose their synchronization stability. However, there are very limited research publication in this area. This paper focuses on STATCOM synchronization stability and its improvement. The proposed adaptive phase locked loop (PLL) is based on the estimated phase error rather than the estimated frequency error, which is an innovative approach not yet been seen in published papers. Moreover, the impacts of short-circuit ratio and the ratio of equivalent grid R to X are also investigated. Both steady-state analysis and time-domain simulation results are presented in this paper. The results show good consistency between steady-state analysis, simulation with a controlled current source model and with a detailed STATCOM model, and the differences are within reasonable range. Compared with the typical PLL, the proposed adaptive PLL demonstrates improved performance of transient synchronization stability.

Optimal dynamic reactive power compensation in power systems: Case study of Ecuador-Perú interconnection

Dynamic reactive compensation using Flexible AC Transmission Systems (FACTS) in power systems allows for regulation of the voltage within limits defined by the grid operator. Optimization algorithms that solve the optimal power flow (OPF) problem can be used to determine the operating range of a FACTS device. In this paper, we compare, in terms of total solve time, the solutions of two optimization algorithms for dynamic reactive power compensation, using the Branch Flow Model (BFM) and the Bus Injection Model (BIM) to represent the power flow equations. The algorithms to solve both problems have been compared using four cases: the adapted IEEE 14-Bus System, New England IEEE 39-Bus System, IEEE 118-Bus Test System, and the authors' proposed 20-Bus SNI-500 kV Ecuadorian System. The results allow us to identify that the convergence of BFM is achieved in less solve-time concerning BIM. Furthermore, both algorithms were applied to the case study of the future Ecuador-Perú 500 kV Interconnection, obtaining that the operating range of the SVC to be installed on the Peruvian side should supply between 58 MVAr and 209 MVAr.

Online Adaptive Parameter Estimation of a Finite Control Set Model Predictive Controlled Hybrid Active Power Filter

This paper presents a novel strategy for online parameter estimation in a hybrid active power filter (HAPF). This HAPF makes use of existing capacitor banks which it combines with an active power filter (APF) in order to dynamically compensate reactive power. The equipment is controlled with finite control set model predictive control (FCS-MPC) due to its already well-known fast dynamic response. The HAPF model is similar to a grid-connected LCL-filtered converter, so the direct control of the HAPF current can cause resonances and instabilities. To solve this, indirect control, using the capacitor voltage and the inverter-side current, is applied in the cost function, which creates high dependency between the system parameters and the equipment capability to compensate the load reactive power. This dependency is evaluated by simulations, in which the capacitor bank reactance is shown to be the most sensitive parameter, and, thus, responsible for inaccuracies in the FCS-MPC references. In order to minimize this problem without increasing the complexity of the FCS-MPC algorithm, an estimation technique, based on adaptive notch filters, is proposed. The proposed algorithm is tested in a laboratory prototype to demonstrate its ability to follow variations in the HAPF capacitor reactance, effectively correcting the reactive power reference and providing dynamic reactive power compensation. During the tests, the proposed algorithm was capable of keeping the supplied reactive power within a 1% error, even in a situation with 33% variation in the HAPF capacitor reactance.

Nonlinear Transient Mathematical Model of Large-Capacity Synchronous Condenser Based on Time-Varying Reactance Parameters

Large-capacity synchronous condenser (SC) is an essential dynamic reactive power compensation device in an Ultra-high voltage direct current (UHVDC) transmission system. The particular transient operating state and structural characteristic of SC lead to a severe magnetic saturation effect during transient operation. To accurately describe the dynamic characteristics of SC, it is urgent to establish a transient mathematical model considering the magnetic saturation effect. Therefore, this paper proposes a nonlinear transient mathematical model for SC based on time-varying reactance parameters and gives a calculation method for time-varying reactance parameters. The mathematical model proposed in this paper is verified by taking a 300MVar SC as the research object. This condenser is connected to the power grid at the sending end of the UHVDC transmission system. The proposed mathematical model, the traditional fixed-parameter transient mathematical model, and the saturated standard SG model used in the power system were used to simulate the voltage generated by dynamic reactive power compensation characteristics of SC during a drop failure. Compared with the fault test results, the accuracy of the proposed mathematical model is verified. The effect of magnetic saturation on the dynamic reactive power compensation characteristics was analyzed, respectively. In addition, the accuracy of the proposed mathematical model is closer to the actual motor state, which is helpful for further research on the operation analysis and state monitoring of SC.

Application of Dynamic Reactive-power Compensator Based on SVG in Coal Mines

With the improvement of automation degree of coal mine mechanical and electrical equipments, such as conveyors, crushers, mining motors, inverters, and a large number of non-linear loads, cause large reactive power consumption, power factor of coal mine power grid, power supply quality and stability, and bring greater influence to coal mine safety production and economic benefits. As a new generation of high voltage dynamic reactive power compensator, SVG (Static Var Generator) has fast response and compound functions, such as compensating reactive power, suppressing harmonic and imbalance with FC(Filter Capacitor), which plays a good role in improving the power quality of coal mine. This paper designs the system parameters of SVG in coal mine and introduces its application.

Full-Scale Electromagnetic Transient Modeling and Oscillation Suppression of a Wind Farm with SVG

With the gradual depletion of the earth’s resources and people’s attention to environmental issues, the access of renewable energy has been paid more and more attention by countries around the world. Wind is one of the pollution-free energy sources, and wind power generation is forming a boom in the world, because wind power generation does not need to use fuel, nor does it produce radiation or air pollution. The power of wind power generation is characterized by volatility and intermittence. When there is disturbance in the system, the wind farm is likely to oscillate and challenge the stability of the power grid. Therefore, the wind turbine generator must be connected to SVG system to realize dynamic reactive power compensation function, so as to ensure the stability of its operation in case of fault. In addition, the cause of wind turbine oscillation needs to be analyzed in detail to ensure its stability.

Reactive Power Compensation Configuration of Offshore Wind Power Based on Economic Differential Pressure Theory

The conventional reactive power balance analysis method for offshore wind power transmission projects can be used to obtain many feasible solutions for reactive power compensation configuration, which requires a large number of simulation calculations to eliminate unreasonable schemes. The work is tedious and lacks theoretical guidance. In this paper, the main influencing factors, such as the current carrying capacity of offshore wind power and submarine cable, the mode of real-time power generation, and the reactive power output regulation of the wind turbine itself, are considered. The reactive power balance of offshore wind power transmission projects is derived. Combined with the economic differential pressure theory, the sea-side and land-side configuration methods of high reactance and dynamic reactive power compensation are put forward. On the basis of realizing real-time reactive power balance, the recommended reactive power compensation configuration scheme effectively reduces the active power loss of the transmission project, and at the same time, lowers the bus voltage of each node at sea, thus reducing the high risk of the excessive voltage of offshore wind farm. This project is supported by the Science and Technology Project of State Grid Corporation of China under “Research on multiple temporal and spatial coordinated optimal control theory for medium and long-distance large-scale offshore wind power transmission system” (No. 5100-202155305A-0-0-00).

Research on novel var compensator based on dual-rotary phase-shifting transformers and its control strategy

With the continuous increase in the penetration of distributed power with random output, the acceleration of the urban cableization rate and the rapid development of supergrid, the active distribution network puts forward higher requirements for the performance of dynamic reactive power compensation. A topology of novel rotary VAR compensator (NRVC) is proposed by integrating the current source static synchronous compensator with the continuous regulation characteristics of dual rotary phase-shifting transformers. The NRVC compensation principle is analyzed by establishing the steady-state mathematical model of dual rotary phase-shifting transformers and NRVC. The dynamic response performance and universal applicability are improved by considering its compensation capacity constraints, applying the instantaneous reactive power theory, and constant power factor control. A dual closed-loop decoupling control strategy of power outer-loop and current inner-loop is also presented to prevent internal overcurrent. Finally, the simulation and experimental results are performed to verify the effectiveness of the proposed system and control strategy, which realized bidirectional and continuous regulation of compensated reactive power, and has manifold advantages: low cost, strong shock resistance, large heat capacity, simple control, and no harmonic pollution.

Complete operational voltage assessment of Shandong pilot offshore wind project

AbstractThis article presents a thorough methodology for the voltage assessment of pilot offshore wind project in Shandong province, China. The results presented in this paper can be considered as the milestone of the offshore wind research in Shandong Province since there is still no grid codes for offshore wind power plant grid connection in the local electrical power grid. It mainly consists of three parts. In the first part, a detailed model of the offshore wind farm created in the DIgSILENT PowerFacotry simulation platform is presented, including wind turbines, power converters, transformers, submarine cables and relevant control schemes. In the second part, nonlinear time‐domain simulations were performed to analyze the wind farm's active power, reactive power, and voltage conditions under different wind scenarios. Based on the simulations results, a dynamic reactive power compensation system was proposed, and the consequence of the reactive power compensation was also demonstrated using nonlinear time‐domain simulations.