Series Capacitor Compensation Research Articles

Wind conversion systems effects on power grid and ability of thyristor controlled series capacitor and static synchronous series compensator devices for dynamic performance enhancing

Wind conversion systems effects on power grid and ability of thyristor controlled series capacitor and static synchronous series compensator devices for dynamic performance enhancing

Сравнение характеристик линий высокого и сверхвысокого напряжений при выборе параметров управляемого устройства продольной компенсации

The use of series compensation devices leads to an increase of the transmission line capacity. However, it also increases the risk of an oscillatory violation of the stability of the electric power system. Cumulative hunting and self-excitation of the system is observed in the systems with controlled series compensation devices with a high degree of capacitive compensation. It is known that automatic excitation control of generators partially eliminates the negative effect of series capacitive compensation on oscillatory stability. Therefore, when choosing the tuning parameters of controlled devices, it is necessary to consider their combined effect on the system modes. The developed methods to study steady-state stability make it possible to analyze the modes of power systems with controlled power transmission of various voltage levels. Thus, it is advisable to conduct a comparative analysis of the influence of the adjustable parameters of the series compensation device on the steady-state stability of systems of various voltage levels, considering synchronous generators automatic excitation control. Methods of mathematical modeling of the electric power system, the theory of long-distance power lines and electromechanical transients, methods of analyzing the stability of electric power systems are used. The original software in the C ++ programming language has been used as a modeling tool. The choice of controlled series compensation device and the automatic excitation control regulation laws parameters is made, provided that steady-state stability is maintained. The stability regions of the studied electric power-engineering system are constructed depending on the tuning parameters of the considered devices of various voltage levels. A comparative analysis of the characteristics of the modes of high and extra-high voltage lines has been carried out. The regulation coefficients values of controlled series compensation device and automatic excitation of generators have been determined, under which there is no violation of oscillatory stability for different voltage levels. The conducted comparative analysis of the characteristics of high and extra-high voltage power lines demonstrates the need to consider the power transmission rated voltage when comprehensively selecting the tuning parameters of the controlled series compensation device and the automatic excitation control regulator.

Combined Rotor-Side and Grid-Side Suppression of Sub-Synchronous Oscillation in Doubly-Fed Wind Turbines

Abstract In the field of wind power generation, the significant geographical separation between wind farms and load centers often necessitated the long-distance and large-scale transmission of wind energy, which was typically achieved through transmission lines equipped with series compensation capacitors. However, this setup led to interactions between the series compensation capacitors and the control systems of doubly-fed induction generators (DFIGs), potentially causing sub-synchronous oscillations in grid-connected systems. To address this issue, our study focused on a DFIG-based wind farm interconnected via a series-compensated line. We proposed an innovative suppression strategy that incorporated additional virtual damping on the grid side. This strategy was effectively combined with an ancillary approach of adding virtual inductance on the rotor side, offering a robust solution to mitigate sub-synchronous oscillations. The simulation results showed that the joint application of these two strategies was more effective than implementing them individually. Notably, the strategy involving additional virtual damping on the grid side outperformed the approach of adding virtual inductance on the rotor side.

Transmission Expansion Planning Considering Storage, Flexible AC Transmission System, Losses, and Contingencies to Integrate Wind Power

To meet future load projection with the integration of renewable sources, the transmission system must be planned optimally. Thus, this paper introduces a comparative analysis and comprehensive methodology for transmission expansion planning (TEP), incorporating the combined effects of wind power, losses, N-1 contingency, a FACTS, and storage in a flexible environment. Specifically, the optimal placement of the FACTS, known as series capacitive compensation (SCC) devices, is used. The intraday constraints associated with wind power and energy storage are represented by the methodology of typical days jointly with the load scenarios light, heavy, and medium. The TEP problem is formulated as a mixed-integer nonlinear programming (MINLP) problem through a DC model and is solved using a specialized genetic algorithm. This algorithm is also used to determine the optimal placement of SCC devices and storage systems in expansion planning. The proposed methodology is then used to perform a comparison of the effect of the different technologies on the robustness and cost of the final solution of the TEP problem. Three test systems were used to perform the comparative analyses, namely the Garver system, the IEEE-24 system, and a real-world Colombian power system of 93 buses. The results indicate that energy storage and SCC devices lead to a decrease in transmission requirements and overall investment, enabling the effective integration of wind farms.

Power frequency shunting property of whole group 500kV UHV Series compensated MOVs containing 10 Served and 1 New MOVs

Metal OxideVaristors(MOV) are widely used as protective devices of series compensation capacitor banks for Extra-High Voltage and UHV (Ultra High Voltage) large capacity long-distance transmission lines. As MOVs work in the strong nonlinear part of the V-I curve, the aging and deterioration degree of different MOVs in parallel connection are different, leading to one or two MOVs in the entire heavy-duty group being the first to be damaged. The uniformity of current is an important criterion for how to control the power frequency shunting of multiple parallel MOVs for series compensation capacitor banks. In order to investigate whether replacing damaged MOVs with newly manufactured MOVs of the same specifications can meet the uniformity requirements, the power frequency reclosure tests are carried out with an average voltage peak of 166.3 kV on MOV group with 10 served and 1 new MOV for the first time with actual 500 kV MOVs. Research finds that when the DC (Direct Current) U2mA mean absolute error of MOVs is 0.2%, the current mean absolute error is about 6%. After testing, the temperature rise of each MOV ranges from 22.9 to 36.3 °C. The test results in this paper provide a direct data basis for confirming the criterion of DC reference voltage and shunt uniformity at large power frequency current on actual 500 kV series compensation MOVs apparatus.

Analysis of Factors Affecting Sub-Synchronous Oscillation in Doubly-Fed Wind Power Grid-Connected System Based on Impedance Sensitivity and Research on Suppression Strategy

Aiming at the matter of sub-synchronous oscillation (SSO) of the doubly-fed induction generator (DFIG) series compensation capacitors grid connection, a SSO suppression strategy based on adding damping controllers in rotor-side converter (RSC) is put forwarded. Considering the control parameters of power and current control loops of RSC, the equivalent impedance model of DFIG series compensation grid connection (SCGC) is established, and then combined with the equivalent RLC resonant circuit of the system, the mechanism and factors of SSO are analyzed by impedance method. Calculating the impedance sensitivity of the system impedance to parameters by sensitivity analysis method, so as to identify the leading factor affecting the SSO characteristics of wind power system. Combined with the stability criterion of system impedance characteristics, the parameters are adjusted to meliorate system stability. Based on the leading factor affecting the SSO and the mechanism of the SSO, the damping controllers are added in the RSC to supply positive damping for the system to eliminate the negative damping brought by the RSC and rotor resistance, thus suppressing the SSO of the system. The validity of the put forwarded suppression strategy is proved through PSCAD/EMTDC simulation.

A Protection for Loss of Field in Synchronous Generator in Presence of Series Compensation Capacitor

A Protection for Loss of Field in Synchronous Generator in Presence of Series Compensation Capacitor

Optimal location of multiple FACTS devices in N-1 contingency conditions using traditional genetic algorithm

<span lang="EN-US">Transmission systems are prone to contingency conditions that would either occur using a generator outage or line outage. Placing and sizing the flexible ac transmission systems (FACTS) devices appropriately can reduce the effects of the contingency condition. This paper optimally locates FACTS devices in a transmission system under the N-1 contingency condition. The genetic algorithm (GA) technique is used to locate different, multiple FACTS devices (thyristor-controlled series capacitor and static VAR compensator) optimally in a power system. This optimization technique is used to locate FACTS devices on the IEEE 9 bus system. MATLAB simulation is developed and checked for both single and multiple FACTS placements. Simulation results obtained for generator outage and line outage are tabulated with the type of FACTS device/rating, location, and generation cost with line loss reduction. The optimized results observed for the cost-optimized FACTS placement problem are found to be satisfactory. The results obtained in the IEEE 9 bus system have shown improvement in a decrease of generation cost and system loss component while placement and sizing of both the FACTS devices.</span>

Power flow management and LVRT enhancement by using multi-functional capacitive bridge-type fault current limiter in DFIG system

This paper proposes a new concept of the fault current limiter (FCL) named multi-functional capacitive bridge-type fault current limiter (MCBFCL). It acts as a variable capacitor to manage active power flow under normal operating condition and enhances the low-voltage ride-through (LVRT) performance of wind farms (WFs) under fault operating conditions. The MCBFCL have been presented based on the capacitive bridge-type fault current limiter (BFCL) and is modified to compensate the transmission line impedance in order to manage power flow, while it is not bypassed under normal operating conditions unlike the conventional FCLs. In this paper, first, the power circuit and principle performance of the MCBFCL are discussed. Then time domain simulations are conducted in PSCAD/EMTDC environment to check the MCBFCL performance under both normal and fault operating conditions. Also, the MCBFCL performance is compared to the resistive and inductive BFCLs in transmission lines with series capacitive compensation. In this work doubly fed induction generator (DFIG)-based wind turbines have been utilized. Simulation results showed that the MCBFCL can manage the power flow under normal operating condition and enhances the LVRT performance of the WF under both symmetrical and asymmetrical fault operating conditions. Also, it has a superior performance in terms of LVRT indices values compared to the resistive and inductive BFCLs.

Research and Improvement of Electromechanical Transient Performance of Power System Based on SIMULINK

The research on electromechanical transient stability of power systems is of great significance. Analyzing the parameters of the simulation system and its improved system with typical short-circuit faults, this paper studies the transient stability of power systems and its improvement. Firstly, based on the SIMULINK of MATLAB, a double-loop simulation with the single-machine-infinite-bus system is built. The simulation experiments of the system under the circumstances of three-phase short circuit and single-phase grounding short circuit faults are then carried out to analyze the parameters such as limit cutting time and voltage. Besides, this paper explores how the controllable series capacitor compensation device and reducing mechanical power output by prime mover improve the transient stability of the system. Experiments show that the stability after fault is under conditions where the fault is removed before the critical clearing time, which can increase the threshold to gain more response time for relay protection devices. Thus, the value of researching and improving system transient stability is proved.

Series Capacitive Compensation to Increase the Railway Traction Power Supply System Transmission Capacity

The article addresses the problem of improving the numerical analysis and operation of series capacitive compensation (SCC) units in the return wire of 25 kV power supply system traction substations to increase the railway capacity. Numerical analyses of the SCC impedance for two versions are considered: according to the condition of voltage equalization in the traction substations power supply arms and according to the condition of minimizing the negative sequence voltage. It is shown that the existing regulatory documents correctly place focus on the SCC impedances determined from the condition of ensuring equal power supply arm voltages. It is also shown that for numerical analyses of SCC impedance, the connection of the 110(220) kV power supply line impedances should be taken into account. To this end, it is proposed to connect, in the equivalent analysis circuit diagrams, two adjacent substations to the external power supply system through an equivalent delta of the impedances of 110(220) kV power lines. To effectively increase the voltage in the traction network while maintaining the minimum equalizing current values, it is advisable to connect the SCCs at both adjacent substations. In so doing, the no-load voltage values should be kept at the same level to reduce the equalizing current first component, which is determined by the difference of the transformers’ no-load voltages. It is shown that the connection of the SCC does not entail a growth in the equalizing current second component, which is determined by the difference of voltage losses at adjacent substations, including the voltages across the SCCs. If the SCC is connected at only one substation of the inter-substation zone, it is advisable to introduce automated control of the transformer OLTC at the substation without an SCC with a limited number of switching operations (up to 10 per day) with increased loads in the traction network.

Method for Assessing the Risk of Subsynchronous Oscillations in DFIG-Based Wind Parks

The risk of unstable subsynchronous oscillations (SSO) in DFIG-based wind parks radially connected to transmission lines with series capacitive compensation is typically assessed with numerous electromagnetic transient (EMT) simulations, which is a time-consuming process. However, not all operating scenarios present risk of SSO and require such a detailed investigation. This paper proposes two charts based on impedance equivalents of wind generators obtained through frequency scans to quickly map which combinations of parameters can create unstable SSOs and which combinations are risk-free. With the information, engineers can immediately filter out scenarios with no risk of instability and conduct detailed studies on fewer scenarios that are truly critical. These charts can be obtained with simple equations that use only information readily available in practice to engineers, without the need to run any computer simulation. The charts also reveal the key operating conditions that can increase the risk of an unstable SSO and provide real-time quantitative insights into how close a wind park is to an instability. Application examples are provided to illustrate how this approach can help engineers speed up studies to identify the risk of SSO.

Domestic Induction Heating System With Standard Primary Inductor for Reduced-Size and High Distance Cookware

In this article, a hybrid wireless power transfer system, which combines induction heating (IH) and inductive power transfer functionalities, is proposed to improve the performance of a domestic IH application with small loads weakly coupled to distant inductors. Considering the basic single-inductor domestic IH application, the proposed system adds a secondary inductor with a series compensation capacitor directly attached to the small ferromagnetic cookware. The extended distance can be used to implement the glassless induction concept, where the ceramic glass of typical cooktops is substituted by the kitchen surface itself. The design of the secondary coil is carried out by means of a combination of finite-element and electrical simulations. A design process, including the housing of the resonant capacitors and the selection of the secondary winding number of turns and cabling, is presented. As a result, a prototype is implemented and tested under working conditions up to 1500 W at several distances. Experimental results validate the electrical modeling and simulation. Moreover, thermal results confirm the feasibility of the proposal and validate the adopted strategies for the capacitor housing.

A 1-kW and 100-cm Distance Magnetically Coupled Resonant WPT System Achieving 80% Efficiency

For the magnetically coupled resonant wireless power transfer (MCR WPT) applications with high-power level and medium-range distance, the low coupling coefficient brings severe challenges to the system efficiency and reliability, as the coil loss and the voltage/current stress on compensation components are both considerable; meanwhile, the high operating frequency that contributes to improve the power density will result in high switching loss and related electromagnetic interference. In this article, a parameter design methodology for high-power and medium-range-distance MCR WPT applications was proposed to achieve high system efficiency. The accurate time-domain system model was built to obtain the relationship among voltage/current stresses on the compensation components, zero-voltage-switching (ZVS) conditions of power switches and system parameters. The key parameters, including the switching frequency, the coil self-inductance, and the compensation inductance, are designed to realize wide-range ZVS and reduce voltage/current stresses. Double-layer coil configuration was adopted instead of the traditional single-layer coil to reduce coil losses, and the series compensation capacitors in TX and RX coils were split to achieve current sharing between double-layer coils. Meanwhile, the LCCL-TT compensation network was used to achieve the optimal load and maximize the system efficiency. Finally, a 1-kW MCR WPT prototype within 100-cm transmission distance was implemented in the laboratory for experiments, and the system efficiency under the rated condition is 80.62%.

Investigation of Distribution System Stability with Incorporation of Capacitor Switching: A Case Study of Monatan 11 Kv Distribution System

Effectiveness of an electrical distribution system depends on the stability of its voltage profile. Several methods such as Static Compensator (SC), Thyristor Controlled Series Compensation (TCSC) and Series Capacitor have been applied for the stability of the system. However, these methods have been characterized by harmonic variation and low efficiency. Therefore, this research paper applied Shunt Switching Capacitor (SSC) on 11 kV distribution system located at Monatan, Ibadan, Oyo State in order to investigate the stability of the system during outages. Hourly data on bus voltage of the system were collected to determine the average bus voltage and voltage drop of the distribution system for stability evaluation using IEEE statutory limits method. Load Flow Model (LFM) of the distribution system was developed with incorporation of Capacitor Switching Compensation (CSC). This was solved using Kirchoff’s Current Law( KCL) analysis to improve the average bus voltage and voltage drop of the distribution system while simulation was done using MATLAB R2015a. The results of the average bus voltage and voltage drop of the distribution system were 10.5 and 4.2 , respectively. The CSC model improved the average bus voltage and voltage drop by 6 % and 33 % respectively. The research showed that incorporating capacitor switching as a compensation technique enhanced the stability of the distribution systems. The research is useful in the planning and optimization of electrical distribution systems. Keywords: Electrical Distribution System, Voltage, Capacitor Switching Compensation, Load Flow Models, Monatan 11 kV Distribution System, Voltage Drop, MATLAB. DOI: 10.7176/NCS/14-02 Publication date: August 31 st 2022

Multiphase Interleaved IPT Based Current-Source Converter for High-Current Application

This article proposes a multiphase interleaved inductive power transfer (IPT) based dc–dc converter for high-current applications. There are three main contributions. First, the proposed converter is designed based on a loosely coupled IPT system with series compensation capacitors, which permits large leakage inductance and avoids magnetic saturation. Second, series capacitors are used to compensate the magnetic coupler, which achieves load-independent output current, namely a current-source converter. Third, a scalable multiphase converter is achieved with an input-parallel output-parallel structure for high current. Meantime, an interleaved control strategy is implemented to an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> -phase system with an angle shift of 360°/(2× <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> ), reducing output current ripples. A 2-kW/100-A three-phase converter prototype is implemented with zero-voltage switching and harmonic loss suppression. Experimental results show a load-independent output current, which is linearly regulated by input dc voltage. With an input voltage of 480 V, the output current reaches 101.5 A with a small peak-peak ripple of 2.4 A. Output power reaches 2.07 kW with a 91.39% dc–dc efficiency. A steady-state test for a solid-state circuit breaker (SSCB) is conducted using the proposed high-current converter, showing its application in evaluating the steady-state efficiency and thermal performance of SSCB.

An improved strategy for out-of-step oscillation separation devices based on apparent impedance angle applied to a series compensated line

AbstractOut-of-step oscillation separation devices based on apparent impedance angle trajectory are widely used in the power grid in China, and their reliability is of great importance. In this paper, the influence mechanism of series compensation on apparent impedance angle trajectory is analyzed. It reveals that series compensation capacitors reduce the equivalent impedance angle and consequently the apparent impedance angle cannot pass through all four zones, resulting in the risk of failure for the separation devices. A revised method of apparent impedance angle based on compensation principle is discussed, and then an improved out-of-step oscillation detection criterion is proposed. In view of the fact that the apparent impedance angle at the moment of maximum current is equal to the equivalent impedance angle during an oscillation process, a practical algorithm based on the compensated apparent impedance angle is proposed. RTDS tests are conducted to verify the effectiveness of the new criterion, considering transmission lines with a high series compensation level.

An Intelligent Self Healing System for Congestion Management in Smart Grid Using Genetic Algorithm

Power transfer to the load through transmission and distribution network is the major role of a power system operator. Transmission line congestion management is essential for satisfactory delivery of power to the customers. In this paper, a mathematical computational algorithm is developed using Genetic Algorithm (GA) based optimization which relieves congestion in the transmission lines. GA is able to remove congestion by proposing the appropriate change required in line reactance to relieve transmission line congestion. The proposed algorithm considers series capacitance compensation thereby increasing the line loading ability. The proposed method removes congestion automatically in any line, considering its line load limit and makes the grid smart through this self-healing property. This automated technique is able to propose the change in line reactance value required to remove congestion without changing the generation and load. To validate the effectiveness of the algorithm, it is tested in 5 bus IEEE, 14 bus IEEE, and 30 bus IEEE test systems. This algorithm is also verified in scaled down laboratory model of 5 bus IEEE system available in the laboratory. The testing results prove that the proposed GA based congestion management algorithm can relieve congestion in any line of any network automatically.

Research on identifying parameter of DFIG-based wind farm based on mathematical mechanization analysis

In order to obtain precise running parameters which are the intrinsic cause resulting in sub-synchronous resonance (SSR) in transmission line with series compensation capacitor, an approach that can be used to identify the dynamic equivalent parameters of DFIG (doubly-fed induction generator) -based wind farm has been proposed based on the mechanized mathematics theory. Core work is to derive the analytical expressions of the stator resistance, inductance and the rotor resistance, inductance and the mutual inductance which are expressed by the sampling voltage, current and active power based on polynomial modelling and characteristic set of the mathematical mechanization. Simulation results which are associates with the actual sampled data of a wind farm show that, the equivalent parameters consist of 32 DFIGs have been given and verified by proposed approach. Also, the maximum identifying error of corresponding resistance and inductance of the stator and rotor was lower than 5% based on sampling an actual DFIG farm. This work can provide a reference for analysing and suppressing SSR which is a bottleneck for a wind farm stable running.

Transmission Network Expansion Planning Considering Optimal Allocation of Series Capacitive Compensation and Active Power Losses

This paper presents a modeling and solution approach to the static and multistage transmission network expansion planning problem considering series capacitive compensation and active power losses. The transmission network expansion planning is formulated as a mixed integer nonlinear programming problem and solved through a highly efficient genetic algorithm. Furthermore, the Villasana Garver’s constructive heuristic algorithm is implemented to render the configurations of the genetic algorithm feasible. The installation of series capacitive compensation devices is carried out with the aim of modifying the reactance of the original circuit. The linearization of active power losses is done through piecewise linear functions. The proposed model was implemented in C++ language programming. To show the applicability and effectiveness of the proposed methodology several tests are performed on the 6-bus Garver system, the IEEE 24-bus test system, and the South Brazilian 46-bus test system, presenting costs reductions in their multi-stage expansion planning of 7.4%, 4.65% and 1.74%, respectively.