Voltage Angle Research Articles

Comparison amongst Lagrange, Firefly, and ABC Algorithms for Low-Noise Economic Dispatch and Reactive Power Compensation in Islanded Microgrids

For the microgrids to operate securely, distributed generators must be able to interact with one another without experiencing any communication delays or noise. To develop a more effective economic dispatch strategy, this research focuses on noise’s effect on the performance of an islanded microgrid. Three different strategies, Lagrange, firefly, and artificial bee colony algorithms, are compared for optimal solutions of economic dispatch. Their performance is compared based on stability during noise interference and faster response time with and without the virtual synchronous generator-STATCOM strategy. The virtual synchronous generator is used as a voltage source to regulate active power and reactive power with the grid. A STATCOM controller is introduced in the system for reactive power compensation. Reactive power compensation is the process of controlling reactive power to enhance the efficiency of alternating current power systems. By boosting the active power, reactive power compensation in the transmission system will increase the stability of microgrids. The voltage, output power, power factor, and phase angle of the microgrid benefit from the stability provided by the controller. As a result, the performance and resilience of the microgrid is improved.

Loop Analysis and Angle Recovery Based Reactive Power Optimization for Three-Phase Unbalanced Weakly-Meshed Active Distribution Networks

This paper presents a loop analysis and angle recovery (LAAR) based reactive power optimization for three-phase unbalanced and weakly-meshed active distribution networks (ADNs). For each loop, the width first search (WFS) method is used to find the breakpoint bus of each tie line, and then all loops are broken up at these breakpoint buses by disconnecting tie lines, placing added buses, and adding compensation powers, so that the original weakly-meshed ADN can be precisely converted into an equivalent radial ADN. Furthermore, the traditional second-order cone programming can be employed for the equivalent radial networks to find the global optimal solution. However, the compensation powers are not constant values but related to the bus voltages, which are unknown before opening the loops. To address this problem, we design an iterative method to dynamically update the values of compensation powers until the convergence criterion is met. Moreover, the voltage angles are recovered for all loops at each iteration. The effectiveness of the proposed LAAR method is demonstrated by 9 cases, and the results show that the LAAR method can achieve a better convergence performance than the traditional method.

Experimental Validation of a Phase Lead-Lag Synchronous Frame Phase-Locked Loop Under Different Voltage Conditions

Due to the rapid increase in single-phase inverters tied to the grid, fast and robust phase-locked loop algorithms have become indispensable. In previous work, a phase lead-lag synchronous reference frame phase-locked loop (PLL) was proposed. The method makes use of two single-tuned filters that perform as a phase detector. They are capable of shifting the phase of the grid voltage to be advanced or delayed by 45∘ with respect to the grid voltage phase. The generated orthogonal signals are transformed by Park transformation. The quadrature voltage is regulated to zero by means of a PI controller, while its output determines the frequency of the grid voltage and the phase angle obtained by integrating the estimated frequency. In this paper, deficiencies in the previous work are addressed. A small signal model of the method which takes into account frequency variation, voltage variation, and harmonic distortion is derived and presented. The design guidelines are discussed and an example illustrated. The method is validated through simulations and experiments under various voltage conditions while the algorithm is implemented on a rapid prototyping MicroLabBox. It is tested under different voltage scenarios, generated by a programmable AC source. The experimental results show that the method can track the phase angle of the grid voltage with nearly zero phase error under normal voltage conditions. It can track the phase of the grid voltage under 45∘ step phase jumps in 2.75 cycles, achieve harmonic attenuation of -15 dB under 15% third harmonic distortion, and attain an adequate phase margin near 45∘. This confirms that the method is fast and robust under adverse voltage conditions.

A non-PMU-based WAN protection scheme for swing detection and stability enhancement in power systems

This paper presents a scheme for power swing detection and stability assessment for multi-machine power systems in addition to a brief survey on that topic. The scheme adopts smart grid perception. It is an asynchronous scheme that uses the rate of change of the angle of the generator bus voltage instead of synchronously estimating the absolute rotor angle value for stability assessment. Therefore, it does not require phasor measurement units (PMUs). Instead, it uses commercially available intelligent electronic devices (IEDs). It introduces a new application of the multicast Generic Object Oriented Substation Event (GOOSE) protocol or its routable version (R-GOOSE) to reflect the disturbance in the power grid on the transmission pattern of data packets over the grid data network. In this scheme, the angle change information is transmitted in the form of GOOSE packets simultaneously from the IEDs that readily measure the angles of the affected generators. On the other hand, the detecting device identifies the stability status of each affected generator. The proposed scheme is validated by simulating disturbances on the IEEE 39-bus system. The results show that the scheme can discriminate between stable and unstable swings. In addition, the loss of synchronism of the unstable generator is predicted ahead of its occurrence by enough time to take an appropriate action.

Optimization for position and rating of distributed generating units using bacteria foraging algorithm to reduce power losses

Distributed generation (DG) units, which include solar panels, wind turbines, and fuel cells, are gaining in popularity as a result of the fact that they are dependable and produce no harmful emissions when they generate electricity. However, the integration of these new power sources into the current power grid may result in several technical difficulties, including voltage fluctuations, power imbalances, and increased power losses. The use of optimization methods may assist to solve these difficulties by determining the best position and size of DG units. This will help to reduce the amount of power that is lost and will enhance the power system's overall performance. Therefore, the Bacteria Foraging Optimization (BFO) method was used for DG in this study. This approach helps to decrease phase jump during symmetrical and unsymmetrical faults, as well as power losses, controls voltage magnitude and angle, and regulates voltage magnitude. In addition, nonlinear restrictions that are regarded to be forward factors include voltage limitation, DG capacity limitation, and phase jump limitation. On the IEEE 69 bus radial distribution scheme, both single and double DGs are taken into consideration for the allocation process. Because of its worldwide convergence and decreased calculation liability, the BFO algorithm is used in the optimization process for both position and rating. The suggested procedure is tested on the IEEE 69 bus radial distribution system in a MATLAB environment; the results demonstrate the efficiency of the suggested approach. In this case, the proposed system was successful in achieving the triple line-to-ground fault-based phase jump of 26.3° without DG and 0.52° with DG; the line-to-line (AB) fault-based phase jump of 0.01° without DG and 0.001° with DG; the single line (A) to ground fault-based phase jump of 0.0027° without DG and 0.001° with DG; and the line to ground fault-based phase jump of 0.001° with DG.

Method of static stability dominant identification

AbstractTwo extreme cases of static stability are voltage stability and power angle stability. The general stability analysis only focuses on one of the voltage stability or power angle stability. The stability limit and state change are studied for a certain kind of stability characteristics. In this paper, the stability limits of static voltage and power angle are derived, respectively. Therefore, different stability characteristics and their interrelationships can be further studied. The index to judge the dominant stability characteristic is defined. The proposed index only needs the system wide‐area measurement information to quickly and accurately judge the dominant static stability characteristics. The dominant instability (DI) characteristic index proposed in this paper is equal to 1 or −1, which can help to quickly identify whether the power angle stability or voltage stability is dominant. The effectiveness of the method is proved by a simple system.

The Propagation of VSC Damping Effect to Exploit AC Transmission Limit

In this paper, the propagation of active damping and its implication of sizing a VSC stabilizer in AC transmission is investigated. In the context of PLL-based grid-following Voltage Source Converter (VSC) based AC transmission, the enabling design of stabilizer to exploit transmission limit of active power is presented. After analyzing the boundary of active transmission from VSC side, the effect is showcased by EMT time domain simulations, which reflects the coupling effect between the reach of effect and the magnitude of transient response. With frequency domain analysis, it reveals that the effect of stabilization diminishes when electrical distance from the stabilizer grows, whereas the required size of VSC stabilizer to withstand the transient current decreases. It is found that transient response of VSC stabilizer can be approximated with small signal impedance with the large-signal voltage angle corrected. This principle is numerically verified with time domain simulations. As an implication, this paper once again proves that PLL-based grid-following VSC is not fundamentally flawed in a low-SCR grid.

Generating performance of a tubular permanent magnet linear generator for application on free-piston engine generator prototype with wide-ranging operating parameters

This paper proposes a tubular permanent magnet linear generator (TPMLG) applied to the free-piston engine generator and establishes a test rig of the TPMLG. A large amount of experimental data was obtained under unfired conditions and a 2D finite element model of the TPMLG was developed and validated. Then, the electromagnetic characteristics were analyzed under no-load and load conditions. The effects of motion profile, operating frequency, velocity, stroke length, oscillation center position and load resistance on the output performance and generating efficiency (η) of TPMLG were investigated. Results show that the phase angle and distortion rate of the output voltage and current will vary under different motion profiles. As the operating frequency, velocity and stroke length increase, the output voltage, current, power and loss power increase gradually, while η increases at first and subsequently plateaus. When peak velocity is fixed and stroke length increases, both output power and copper loss rapidly increase and then remain steady. Meanwhile, there is only a slight change in generating efficiency. There is an optimal load resistance of approximately 6 Ω needed to achieve maximum output power. When load resistance is greater than 40 Ω, changes in load voltage, current and η become insignificant and the η reaches a maximum of 92.54%. Furthermore, the OCP changes the load voltage and current curves but has little effect on output power in terms of the RMS value.

Optimal low voltage ride through of wind turbine doubly fed induction generator based on bonobo optimization algorithm

The large-scale wind energy conversion system (WECS) based on a doubly fed induction generator (DFIG) has gained popularity in recent years because of its various economic and technical merits. The fast integration of WECS with existing power grids has caused negative influence on the stability and reliability of power systems. Grid voltage sags produce a high overcurrent in the DFIG rotor circuit. Such these challenges emphasise the necessity of the low voltage ride through (LVRT) capability of a DFIG for ensuring power grid stability during voltage dips. To deal with these issues simultaneously, this paper aims to obtain the optimal values of injected rotor phase voltage for DFIG and wind turbine pitch angles for all operating wind speeds in order to achieve LVRT capability. Bonobo optimizer (BO) is a new optimization algorithm that is applied to crop the optimum values of injected rotor phase voltage for DFIG and wind turbine pitch angles. These optimal values provide the maximum possible DFIG mechanical power to guarantee rotor and stator currents do not exceed the rated values and also deliver the maximum reactive power for supporting grid voltage during faults. The ideal power curve of a 2.4 MW wind turbine has been estimated to get the allowable maximum wind power for all wind speeds. To validate the results accuracy, the BO results are compared to two other optimization algorithms: particle swarm optimizer and driving training optimizer. Adaptive neuro fuzzy inference system is employed as an adaptive controller for the prediction of the values of rotor voltage and wind turbine pitch angle for any stator voltage dip and any wind speed.

Experimental investigation of synthetic jet control of wing rock for a flying wing aircraft

Flying wing aircraft easily experience wing rock due to the lack of lateral-directional stability, which causes serious challenges to flight control and safety. Thus, it is necessary to reduce the wing rock amplitude or reduce the mean roll angle by additional control. For a flying wing model with a 65° leading-edge sweep, we propose a strategy using an array of synthetic jet actuators to control the wing rock. The control effect and mechanism are studied by attitude measurement and particle image velocimetry measurement in a wind tunnel; the results confirm that the synthetic jet can effectively change the trim position of the wing rock. The control effect is affected by the angle of attack, Reynolds number, actuation position, actuation voltage, and frequency. In general, downstream actuators perform better at low angles of attack, while upstream actuators perform better at high angles of attack; the actuators positioned at the downward rolling side have a better effect than those positioned at the upward side. Furthermore, continuously variable control of the trim position can be achieved by changing the actuation voltage or modulation frequency, which provides a base for attitude manipulation by using active flow control instead of a mechanical control surface. Quantitative analysis of the flow field indicates that the leading-edge vortex on the upward side provides a rolling moment, while the recirculation zone on the downward side also contributes to the wing rock. This is a dynamic process, causing the flying wing to balance at a nonzero mean roll angle. The synthetic jet positioned at the downward rolling side can transport high-momentum fluids to the near-wall region, thereby suppressing flow separation and reducing the size of the recirculation zone. This enhances the lift on the control side and thus reduces the mean roll angle of the wing rock.

Improvement of Power Quality in Primary Distribution Systems Based on Static-Var Compensators

A flexible AC Transmission Systems (FACTS) is a new technology offers a fast and reliable control over the transmission and distribution parameters like voltage and phase angle between the sending end voltage and receiving end voltage. Distribution static synchronous compensator (DSTATCOM) is a second generation member of the (FACTS) controllers. Reactive power compensation is an important aspect in the control of distribution systems. Reactive current in addition to increasing the distribution system losses, introduces voltage drop at lead point and finally it causes poor power quality in power systems. Primary radial distribution feeders have high resistance to reactance ratio, which causes voltage drop and high power loss in radial distribution systems. providing high demanding power to entire load while maintaining voltage magnitude at acceptable range is one of the major system constraints, using of capacitor banks to improve the reactive power have not quite enough at high reactive power feeder, because it have more slow in step by step response and have not capable to generate continuously variable reactive power. In some primary distribution feeders at the state of Khartoum, it is observed that there are some appropriate drops in voltage and quality service at high reactive power loads although some individual capacitor banks have been connected at these feeders, from here we researched for a new technology to overcome this problem. A steady-state model of (DSTATCOM) is proposed and developed to compensate the reactive power by using a Voltage Source Converter (VSC) with Pulse Width Modulation (PWM) and cascade control of four direct proportional integral controllers (PI) in synchronous reference frame. The detailed modeling and control design of (DSTATCOM) with specific typical radial primary distribution feeders (industrial, commercial, residential) are presented and implemented along necessary mathematical model equations in the Matlab software. Simulation schemes of (DSTATCOM) are done with help of control block diagrams and stability analysis. Load flow is an important method for analysis, operation and planning studies of any power system in a steady-state condition. In this research backward forward sweeps load flow method (Kirchhoff’s Laws) has been proposed rather than Newton-Raphson and Fast decoupled methods because the distribution feeders have a high R/X ratio which make the systems are ill-conditioned iterations analysis. (DSTATCOM) was installed on specific typical radial feeders at the (DSTATCOM) which using for distribution lines and load compensation has been the subject of considerable interest beside it is a new technology for a good power quality solution. Keywords: Power System, Flexible AC Transmission Systems (FACTS) Devices, STATCOM, PI Controller DOI: 10.7176/ISDE/13-1-05 Publication date: May 31 st 2023

Dynamic State Estimation of Nonlinear Differential Algebraic Equation Models of Power Networks

This paper investigates the joint problems of dynamic state estimation of algebraic variables (voltage and phase angle) and generator states (rotor angle and frequency) of nonlinear differential algebraic equation (NDAE) power network models, under uncertainty. Traditionally, these two problems have been decoupled due to complexity of handling NDAE models. In particular, this paper offers the first attempt to solve the aforementioned problem in a coupled approach where the algebraic and generator states estimates are simultaneously computed. The proposed estimation algorithm herein is endowed with the following properties: <i>(i)</i> it is fairly simple to implement and based on well-understood Lyapunov theory; <i>(ii)</i> considers various sources of uncertainty from generator control inputs, loads, renewables, process and measurement noise; <i>(iii)</i> models phasor measurement unit installations at arbitrary buses; and <i>(iv)</i> is computationally less intensive than the decoupled approach in the literature.

Improving the efficiency of mode automation using synchrophasor measurements to identify stability disturbance

The paper presents new approaches and principles for identifying the conditions of stability disturbance based on detecting dangerous disturbances in the early stages using information about changes in regime parameters and their Rate of Change. As a mode parameter, the mutual voltage angle between the controlled 500 kV substation and its Rate of Change was selected in the study. It is suggested to take the values of the mentioned parameters from the Wide Area Measurements System (WAMS). The relevance of the research is due to the need to improve the efficiency and eliminate the drawbacks of existing revealing devices of regime automatics, which will reduce the number of accidents due to disturbances of the power system stability. The proposed principle of predicting stability violation is based on using the provision of Lyapunov’s stability theory, according to which the assessment of stability is carried out by the total system energy consisting of kinetic and potential. In contrast to the existing principles of detecting stability violation, where the exit from the stability area is determined by the main parameter (potential energy), the prediction principle allows evaluating stability by its rate of change (kinetic energy), which provides the early detection of stability disturbance. Calculations were performed on modeling power surges in the North-South interconnection of the Kazakhstan Unified Energy System in the «DigSILENT Power Factory» software on the model, which was verified by real perturbations in the power system according to the WAMS data. The calculations confirmed the effectiveness of the proposed principles and the possibility of using WAMS data for detecting emergency power surges on transit power networks in the initial stage

Optimization of CMT Welding Parameters of Stellite-6 on AISI316L Alloy Using TOPSIS Method

Thisarticle discusses the welding parameters optimization to find the quality of stellite-6 cladding on AISI304L austenite alloy using a new optimization method called Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). The experiments(31 nos.) were carried out with the cold metal arc transfer welding method (CMT) based on the central composite design (CCD). The cladding material is the stellite-6 alloy which is appreciated for its corrosion and wear resistance. Four factors (welding current, voltage, welding speed and torch angle) and five levels were considered for the experiment and the optimization. It is necessary to find the optimized parameters for the industrial applications as a huge number of experiments are not recommended. The optimization results showed that the 2nd experiment had the 1st rank with high relative closeness and the 19th experiment was in the last rank. Higher current and low welding speed yielded good results and a low corrosion rate of 0.004582 mm/yr. Furthermore, the Micro-structural, Corrosion study and the SEM-EDS of the specimen produced by the 2nd experiment are discussed here. Cr and Co elements were most abundant, according to an EDS study, in the cladding region.

A Robust Open-Circuit Fault Diagnosis Method for Three-Level T-Type Inverters Based on Phase Voltage Vector Residual Under Modulation Mode Switching

This article proposes a new phase voltage vector residual-based fault diagnosis method to distinguish the similar open-circuit (OC) fault features of different switches in the three-level T-type inverter. The fault feature based on phase voltage residual can be generated with the designed expected phase voltage model considering different modulation strategies and modes. Under the zero-crossing (ZC) and non-ZC conditions of the faulty phase, the voltage vector residual characteristics caused by OC faults can be summarized. An adaptive residual vector amplitude threshold is designed based on uncertainty propagation using parameter error, dead time, and delay time as system error inputs. In addition, a hierarchical fault diagnosis scheme is proposed, which involves two steps. First, the group-level fault can be located according to voltage residual vector amplitude and angle. Next, the three-level modulation mode of all phase legs is switched to the two-level mode to further identify the faulty switch from the faulty group. The proposed method can achieve a reasonable balance between robustness and rapidity. Meanwhile, complexity and adaptability are also considered. Experimental results under various conditions sufficiently verify the robustness and effectiveness of the proposed fault diagnosis method.

Suppression to concurrent commutation failure of UHVDC with hierarchical connection mode based on improved dc current prediction

AbstractFor the ultra high‐voltage dc (UHVDC) transmission with hierarchical connection mode (HCM) at the inverter side, local commutation failure (LCF) at one layer after the ac fault may cause concurrent commutation failure (CCF) at the non‐fault layer. The inter‐layer couplings at the ac and dc sides add the difficulty to suppress the CCF. The fault instant may decide the dc current variation during the commutation, which affects the suppression effect. This paper shows the mechanism of the CCF including the inter‐layer ac and dc coupling, and proposes a control method for the inverter at the fault and non‐fault layers. First, an analytical expression among the dc current, ac voltage, and extinction angle of both layers is newly derived to find the dominant factors to the CCF. Second, to improve the calculation accuracy, a three‐point sampling function using Newton interpolation is newly proposed to predict the dc current. Finally, a coordinated control strategy based on the constant extinction area, the overlap‐arc area, and the dominant factor of the CCF is proposed to adjust the firing angle and suppress the CCF. The simulation results using the PSCAD/EMTDC software are given to verify the control effect of the proposed method against the CCF.

The Concept and Understanding of Synchronous Stability in Power Electronic-Based Power Systems

Synchronous stability in power systems is of essential importance for system safety and operation. For the phase-locked loop (PLL)-based synchronous stability in power electronic-based power systems, which has recently stimulated interest in researchers in the field of electrical power engineering, but is still controversial, this paper divides the topic into two aspects, including the PLL device stability and the system stability. It is found that the PLL device is always stable and the error between the PLL output angle θpll and the terminal voltage angle θt is always finite. Therefore, the synchronization of power electronic-based power systems should be understood as the output synchronization between the electrical rotation vectors (θt or θpll) from each item of grid-tied equipment, rather than the synchronization of the PLL device itself. In addition, it is found that θpll plays an active role in the system synchronization dynamics not only in electromagnetic timescales but also electromechanical timescales and it could be selected as a dominant observable. In this paper, the concept of synchronous stability is well clarified. These findings are well supported by theoretical analyses and MATLAB/Simulink simulations, and thus could provide insights on the synchronous stability mechanism.

An Electrical Power System Reconfiguration Model Based on Optimal Transmission Switching under Scenarios of Intentional Attacks

Currently, operating electrical power systems (EPS) is a complex task that relies on the experience of the operators or the strength of algorithms developed for autonomous operation. The continuous operation of EPS is vulnerable to intentional cybernetic and physical attacks. With the most significant extension and distribution in the EPS, the transmission lines are most exposed to potential attacks. Before this, the entire behavior of the EPS changes, and, on occasions, a blackout can even be generated. The present investigation focused on developing a methodology for reconfiguring the power system against intentional attacks, considering the topology change through optimal switching of transmission lines (OTS) based on optimal DC flows and quantifying the contingency index, which allows for the identification of the weaknesses of the EPS. The methodology was applied to the IEEE 30−bus system, and contingencies were randomly generated, as is typical with intentional attacks. The study successfully identified the reconfiguration strategy of EPS based on OTS-DC, mitigating potential problems such as line loadability and voltage angle deviation in the nodes.

Integrated Microgrid Islanding Detection with Phase Angle Difference for Reduced Nondetection Zone

Microgrids with distributed generation (DG) are rapidly coming into distribution networks to supply load demand in order to preserve ecological balance and reduce greenhouse gas emissions. Power electronic advancements are making renewables dispatchable to loads while turning passive networks to active with bidirectional power flow. The IEEE-1547-2018 regulations enforced certain standards on microgrids, including the ability to detect unintended failures, island the microgrid in less than 2 seconds, and feed connected loads while maintaining voltage, frequency, and power quality. There are numerous islanding techniques accessible, including passive, active, hybrid, and communication techniques. The active techniques degrade power quality due to injection of deviations, passive type leaves larger nondetection zone (NDZ), and communication type are costly. The hybrid type combines both passive and active methods. To get away from all these issues, a passive technique is formulated in this paper, which measures the differential phase angle of voltage and current at DG output, to detect islanding. This approach reliably identifies islanding in 20 ms at nearly zero NDZ. This approach is also stable during transient conditions such as load switching and throwing off. There is also no power quality issue because there are no injections during testing. This method is tested in MATLAB/Simulink and evaluated using the differential frequency technique to get performance indices in accordance with UL-1741 testing standards.

A Novel Anti-Offset Interdigital Electrode Capacitive Coupler for Mobile Desktop Charging

This article proposes a novel antioffset interdigital electrode capacitive wireless power transfer system for mobile desktop applications. The coupler consists of two pairs of series connected interdigital electrodes at transmitter side and two copper plates at receiver side, and a detailed generalized design methodology is provided. To realize antioffset at transverse direction, switch array is adopted at series connected interdigital electrodes side, and coupling coefficient can be kept stable at any misalignment distance. When misalignment occurs, changes of switch array are decided by voltage and current phase angle detection at transmitter side, and the system resonance frequency does not need to be tuned with the changes of misalignment distance. No additional position detection sensors are required, which simplifies the system and reduces the production cost. System energy transfer efficiency can be kept stable between 81.18% and 86.77% at any misalignment distance. When rotational misalignment occurs, the receiver can maintain voltage gain of more than 1.95 with stable 5 W output at −45°∼45° offset. Experimental results at 2.28 MHz show great agreement with theoretical analysis.