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Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems
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Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems

A special issue of Electronics (ISSN 2079-9292). This special issue belongs to the section "Power Electronics".

Deadline for manuscript submissions: closed (28 February 2022) | Viewed by 41769

Special Issue Editor

Dr. Jingyang Fang

E-Mail Website
Guest Editor
Department of Electrical and Computer Engineering, Duke University, Durham, NC 27708, USA
Interests: power electronics; power systems; digital control; energy storage; renewable energies
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

As the trend of the massive integration of power electronics-coupled renewable energies, electric vehicles, and energy storage continues, modern power grids are experiencing a revolutionized transition to more-electronics power systems. Along with the large-scale employment of power converters, power quality issues (e.g., harmonics, reactive power, and imbalances) and stability problems (e.g., converter-level instabilities and system-level loss of synchronization) are emerging and evolving. Despite being major trouble sources, grid-tied power converters are promising solutions to such problems mostly due to their flexible and strong control. This Special Issue focuses on the enhancement of power quality and stability of modern power systems through power-electronic-based solutions. It aims to lay a foundation for the further integration of renewable energies in future renewable-dominated power systems. The topics of presentations and research papers include, but are not limited to, the following:

 

  • Modeling, control, and design of grid-forming power conversion systems;
  • Inertia emulation and fast frequency control via power converters and energy storage;
  • Synchronization of multiple grid-tied converters;
  • Smart converters with stability enhancement and power quality conditioning;
  • Virtual synchronous machines (VSMs) and virtual oscillators;
  • Real-time control and optimization of 100% power-electronic-coupled power systems;
  • Next-generation grid codes and standards.

Dr. Jingyang Fang
Guest Editor

Manuscript Submission Information

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Keywords

  • power electronics
  • power systems
  • grid-tied power converters
  • modeling and control
  • Inertia
  • Stability
  • Synchronization
  • Power quality
  • Virtual synchronous machines (VSMs)
  • Real-time optimization

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Published Papers (17 papers)

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Research

17 pages, 6048 KiB  
Article
Weak Grid-Induced Stability Problems and Solutions of Distributed Static Compensators with Voltage Droop Support
by Fan Feng and Jingyang Fang
Electronics 2022, 11(9), 1385; https://doi.org/10.3390/electronics11091385 - 26 Apr 2022
Cited by 5 | Viewed by 2156
Abstract
Distributed static compensators (DSTATCOMs) are grid-connected power electronic equipment dedicated to compensating reactive power as well as improving voltage regulation in distribution networks. They eclipse conventional compensation approaches, such as capacitor banks, in terms of flexibility and effectiveness. Despite their identified advantages, STATCOMs [...] Read more.
Distributed static compensators (DSTATCOMs) are grid-connected power electronic equipment dedicated to compensating reactive power as well as improving voltage regulation in distribution networks. They eclipse conventional compensation approaches, such as capacitor banks, in terms of flexibility and effectiveness. Despite their identified advantages, STATCOMs with voltage droop are subject to weak grid-induced stability problems, as first revealed by this paper. Specifically, the voltage droop controller that couples the amplitude of point of common coupling (PCC) voltages to the reactive current reference creates a local control loop. Such a loop greatly deteriorates system stability in weak grids, which feature large and variable grid impedances. To address such stability problems, we propose a novel virtual resistance control scheme, which improves system stability through mitigation of local control loop gains in the low-frequency band. Experimental results obtained from a DSTATCOM prototype clearly demonstrate the correctness of stability analysis and the effectiveness of stability improvement. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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26 pages, 14300 KiB  
Article
Detection and Diagnosis of Stator and Rotor Electrical Faults for Three-Phase Induction Motor via Wavelet Energy Approach
by Ameer M. Hussein, Adel A. Obed, Rana H. A. Zubo, Yasir I. A. Al-Yasir, Ameer L. Saleh, Hussein Fadhel, Akbar Sheikh-Akbari, Geev Mokryani and Raed A. Abd-Alhameed
Electronics 2022, 11(8), 1253; https://doi.org/10.3390/electronics11081253 - 15 Apr 2022
Cited by 8 | Viewed by 3028
Abstract
This paper presents a fault detection method in three-phase induction motors using Wavelet Packet Transform (WPT). The proposed algorithm takes a frame of samples from the three-phase supply current of an induction motor. The three phase current samples are then combined to generate [...] Read more.
This paper presents a fault detection method in three-phase induction motors using Wavelet Packet Transform (WPT). The proposed algorithm takes a frame of samples from the three-phase supply current of an induction motor. The three phase current samples are then combined to generate a single current signal by computing the Root Mean Square (RMS) value of the three phase current samples at each time stamp. The resulting current samples are then divided into windows of 64 samples. Each resulting window of samples is then processed separately. The proposed algorithm uses two methods to create window samples, which are called non-overlapping window samples and moving/overlapping window samples. Non-overlapping window samples are created by simply dividing the current samples into windows of 64 samples, while the moving window samples are generated by taking the first 64 current samples, and then the consequent moving window samples are generated by moving the window across the current samples by one sample each time. The new window of samples consists of the last 63 samples of the previous window and one new sample. The overlapping method reduces the fault detection time to a single sample accuracy. However, it is computationally more expensive than the non-overlapping method and requires more computer memory. The resulting window samples are separately processed as follows: The proposed algorithm performs two level WPT on each resulting window samples, dividing its coefficients into its four wavelet subbands. Information in wavelet high frequency subbands is then used for fault detection and activating the trip signal to disconnect the motor from the power supply. The proposed algorithm was first implemented in the MATLAB platform, and the Entropy power Energy (EE) of the high frequency WPT subbands’ coefficients was used to determine the condition of the motor. If the induction motor is faulty, the algorithm proceeds to identify the type of the fault. An empirical setup of the proposed system was then implemented, and the proposed algorithm condition was tested under real, where different faults were practically induced to the induction motor. Experimental results confirmed the effectiveness of the proposed technique. To generalize the proposed method, the experiment was repeated on different types of induction motors with different working ages and with different power ratings. Experimental results show that the capability of the proposed method is independent of the types of motors used and their ages. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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15 pages, 5819 KiB  
Article
Intelligent Design of Multi-Machine Power System Stabilizers (PSSs) Using Improved Particle Swarm Optimization
by Sohaib Latif, Sadaf Irshad, Mehrdad Ahmadi Kamarposhti, Hassan Shokouhandeh, Ilhami Colak and Kei Eguchi
Electronics 2022, 11(6), 946; https://doi.org/10.3390/electronics11060946 - 18 Mar 2022
Cited by 47 | Viewed by 2479
Abstract
In this paper, an improved version of the particle swarm optimization algorithm is proposed for the online tuning of power system stabilizers in a standard four-machine two-area power system to mitigate local and inter-area mode oscillations. Moreover, an innovative objective function is proposed [...] Read more.
In this paper, an improved version of the particle swarm optimization algorithm is proposed for the online tuning of power system stabilizers in a standard four-machine two-area power system to mitigate local and inter-area mode oscillations. Moreover, an innovative objective function is proposed for performing the optimization, which is a weight function of two functions. The first part of fitness is the function of the angular velocity deviation of the generators, and the other part is a function based on the percentage of undershoot and maximum overshoot, and also the damping time of the power system oscillations. The performance of the proposed stabilization method is compared with the genetic algorithm and bacteria foraging algorithm results. Simulations are made in three different power system operation conditions by changing the system load. The simulation results indicate the superiority of the proposed method over the genetic algorithm and bacteria foraging algorithm. In all the scenarios, power system oscillations are damped faster and with lower amplitude when the power system stabilizers coordinate with the proposed optimization method. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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18 pages, 6182 KiB  
Article
Digital Implementation of Harmonic and Unbalanced Load Compensation for Voltage Source Inverter to Operate in Grid Forming Microgrid
by Xiu-Hua Guo, Che-Wei Chang and Le-Ren Chang-Chien
Electronics 2022, 11(6), 886; https://doi.org/10.3390/electronics11060886 - 11 Mar 2022
Cited by 4 | Viewed by 2502
Abstract
Voltage source inverter (VSI) is a good candidate for grid forming microgrid because it provides constant amplitude, frequency, and sinusoidal shape voltage at point of common coupling (PCC). As the microgrid is separated from utility grid, voltage quality of the PCC is easily [...] Read more.
Voltage source inverter (VSI) is a good candidate for grid forming microgrid because it provides constant amplitude, frequency, and sinusoidal shape voltage at point of common coupling (PCC). As the microgrid is separated from utility grid, voltage quality of the PCC is easily affected by the type of load. To ensure power quality in grid operation, a three-phase VSI providing automatic voltage compensation for unbalanced or nonlinear load is presented in this paper. To maintain voltage quality at a certain level, the Fast Fourier Transform (FFT) algorithm is embedded in a proportional-resonant (PR) controller to mitigate the total harmonic distortion (THD) at PCC. In the meantime, any change of voltage magnitude that is caused by the unbalanced load could be reduced as well. To further enhance the transient response with the change of load, a predictive current (PC) controller is integrated into the PR controller. All the control strategies are implemented by digital approach. The effectiveness of proposed controls is verified through experiments on a testbed of the three-phase stand-alone system. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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13 pages, 2188 KiB  
Article
A New Approach for the Incorporation of the End-User’s Smart Power–Electronic Interface in Voltage Support Application
by Reza Etemad, Mohammad Sadegh Ghazizadeh, Mehrdad Ahmadi Kamarposhti, Ilhami Colak and Kei Eguchi
Electronics 2022, 11(5), 765; https://doi.org/10.3390/electronics11050765 - 2 Mar 2022
Viewed by 1418
Abstract
Technology advancement in power–electronic interfaces and their evolution open an opportunity to end-users to benefit from their newfound capability. For the end-users, power–electronic interfaces can act as Distributed Energy Resources (DERs) for reactive power injection and absorption. If these power–electronic interface capabilities can [...] Read more.
Technology advancement in power–electronic interfaces and their evolution open an opportunity to end-users to benefit from their newfound capability. For the end-users, power–electronic interfaces can act as Distributed Energy Resources (DERs) for reactive power injection and absorption. If these power–electronic interface capabilities can be properly integrated into traditional utility system operations, they can be used as beneficial tools for distribution management and voltage profile enhancement. Considering the present distribution system, it is not possible to communicate to all DERs. In this paper, we considered two proposed residential-control and droop-control methods. The multi-criteria decision-making technique (MCDM), along with fuzzy theory, was used to prioritize candidate buses for their participation in the Volt-VAR program. In this paper, the contribution of active DERs in reactive power compensation was evaluated. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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18 pages, 4887 KiB  
Article
Control and Optimization of Lattice Converters
by Zhiting Mei, Jingyang Fang and Stefan Goetz
Electronics 2022, 11(4), 594; https://doi.org/10.3390/electronics11040594 - 15 Feb 2022
Cited by 2 | Viewed by 1664
Abstract
Multilevel converters continue their upward trend in renewable generation, electric vehicles, and power quality conditioning applications. Despite having satisfactory voltage capabilities, mainstream multilevel converters suffer from poor current sharing performances, thereby leading to the development of lattice converters, i.e., a strong and versatile [...] Read more.
Multilevel converters continue their upward trend in renewable generation, electric vehicles, and power quality conditioning applications. Despite having satisfactory voltage capabilities, mainstream multilevel converters suffer from poor current sharing performances, thereby leading to the development of lattice converters, i.e., a strong and versatile type of future multilevel power converters. This article addresses two problems faced by lattice converters. First, we propose and detail how to optimize the efficiency of a given lattice converter by controlling the on/off states of H-bridge submodules. Second, we introduce the method that determines the voltage at each node of the converter in order to satisfy output voltage and current requirements. Design and analysis of lattice converters need a different mathematical toolbox than routinely exercised in power electronics. By use of graph theory, this article provides control methods of 3 × 3 and 4 × 4 lattice converters, satisfying various control objectives such as input/output terminals and output voltages. We further validate the methods with simulation results. The methodologies, algorithms, and special cases described in the article will aid further design and refinement of more efficient and easy-to-control lattice converters. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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12 pages, 13626 KiB  
Article
Adaptive Droop Coefficient and SOC Equalization-Based Primary Frequency Modulation Control Strategy of Energy Storage
by Gaojun Meng, Yang Lu, Haitao Liu, Yuan Ye, Yukun Sun and Wenyi Tan
Electronics 2021, 10(21), 2645; https://doi.org/10.3390/electronics10212645 - 29 Oct 2021
Cited by 10 | Viewed by 2066
Abstract
In order to efficiently use energy storage resources while meeting the power grid primary frequency modulation requirements, an adaptive droop coefficient and SOC balance-based primary frequency modulation control strategy for energy storage is proposed. Taking the SOC of energy storage battery as the [...] Read more.
In order to efficiently use energy storage resources while meeting the power grid primary frequency modulation requirements, an adaptive droop coefficient and SOC balance-based primary frequency modulation control strategy for energy storage is proposed. Taking the SOC of energy storage battery as the control quantity, the depth of energy storage output is adaptively adjusted to prevent the saturation or exhaustion of energy storage SOC. The balanced control strategy is introduced to realize the rational utilization of resources and the fast balance of SOC in the process of primary frequency modulation of energy storage battery under different charge states. Then, four evaluation indexes are proposed to evaluate the effect of primary frequency modulation and SOC maintenance. Taking a regional power grid as an example, a simulation analysis is carried out under step load disturbance and continuous load disturbance. According to the simulation results, the proposed control strategy is effective in power system frequency regulation and battery SOC maintenance. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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24 pages, 4286 KiB  
Article
Performance Improvement of Reluctance Synchronous Motor Using Brain Emotional Learning Based Intelligent Controller
by Mehrdad Ahmadi Kamarposhti, Hassan Shokouhandeh, Ilhami Colak and Kei Eguchi
Electronics 2021, 10(21), 2595; https://doi.org/10.3390/electronics10212595 - 24 Oct 2021
Cited by 4 | Viewed by 1860
Abstract
In this paper, intelligent control of a reluctance synchronous motor by an emotional controller, considering the effect of magnetic saturation on implementation, is analyzed; the maximum torque per ampere (MTPA) strategy is provided. According to the application of the proposed control scheme, the [...] Read more.
In this paper, intelligent control of a reluctance synchronous motor by an emotional controller, considering the effect of magnetic saturation on implementation, is analyzed; the maximum torque per ampere (MTPA) strategy is provided. According to the application of the proposed control scheme, the structure adequately performs the control of speed and magnetic flux of the reluctance synchronous motor drive. Additionally, the application of intelligent control based on an emotional learning system has provided adequate results to create a proper control process. The control function of a SynRM drive based on vector control in a rotor machine was compared with another based on emotional controllers and a PI controller regulated by genetic algorithms. The result of this comparison was the improvement of control functions by the controller based on the emotional controller. In addition, the MTPA based on search algorithms was well implemented in different situations. Due to its simplicity and independence from system parameters, the emotional controller can be considered as a potential operational method in the industry. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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14 pages, 4153 KiB  
Article
Transient Stability Enhancement of a Grid-Connected Large-Scale PV System Using Fuzzy Logic Controller
by Md. Rifat Hazari, Effat Jahan, Mohammad Abdul Mannan and Narottam Das
Electronics 2021, 10(19), 2437; https://doi.org/10.3390/electronics10192437 - 8 Oct 2021
Cited by 16 | Viewed by 3294
Abstract
This paper presents a new intelligent control strategy to augment the low-voltage ride-through (LVRT) potential of photovoltaic (PV) plants, and the transient stability of a complete grid system. Modern grid codes demand that a PV plant should be connected to the main power [...] Read more.
This paper presents a new intelligent control strategy to augment the low-voltage ride-through (LVRT) potential of photovoltaic (PV) plants, and the transient stability of a complete grid system. Modern grid codes demand that a PV plant should be connected to the main power system during network disturbance, providing voltage support. Therefore, in this paper, a novel fuzzy logic controller (FLC) using the controlled cascaded strategy is proposed for the grid side converter (GSC) of a PV plant to guarantee voltage recovery. The proposed FLC offers variable gains based upon the system requirements, which can inject a useful amount of reactive power after a severe network disturbance. Therefore, the terminal voltage dip will be low, restoring its pre-fault value and resuming its operation quickly. To make it realistic, the PV system is linked to the well-known IEEE nine bus system. Comparative analysis is shown—using power system computer-aided design/electromagnetic transients including DC (PSCAD/EMTDC) software—between the conventional proportional–integral (PI) controller-based cascaded strategy and the proposed control strategy to authenticate the usefulness of the proposed strategy. The comparative simulation results indicate that the transient stability and the LVRT capability of a grid-tied PV system can be augmented against severe fault using the proposed FLC-based cascaded GSC controller. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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14 pages, 5922 KiB  
Article
Research on Direct Power Control Strategy Based on Voltage Controlled Virtual Synchronous Generator
by Haizhen Xu, Changzhou Yu, Fubin Mao, Taotao Hu, Zelin Wu and Qinglong Wang
Electronics 2021, 10(19), 2415; https://doi.org/10.3390/electronics10192415 - 3 Oct 2021
Cited by 3 | Viewed by 1990
Abstract
To support the “carbon peak and carbon neutrality” goal, new energy is poised to explode, and new energy power generation converter is simultaneously facing new challenges. The conventional current-controlled new energy converter can quickly transmit active power on the DC bus to the [...] Read more.
To support the “carbon peak and carbon neutrality” goal, new energy is poised to explode, and new energy power generation converter is simultaneously facing new challenges. The conventional current-controlled new energy converter can quickly transmit active power on the DC bus to the power grid. However, for the weak grid, the stability margin of the converter grid-connected system is reduced on the one hand, which can easily cause resonance oscillation; on the other hand, the current controlled converter cannot actively respond to system frequency and voltage fluctuation to offer support. The voltage controlled virtual synchronous generator (VVSG) is used to improve system small signal stability and frequency stability; however, its power response speed is too slow to meet the requirements of fast following power command. Although a voltage/current dual-mode switching control scheme is put forward to achieve characteristics complementary of current controlled converter and voltage-controlled converter, the control structure switching and intermediate variable following is required to realize mode switching, which is prone to large power shocks and switching failures. In view of the problem, a direct power control strategy based on VVSG is proposed. The control structure is raised based on a conventional VVSG outer active power control loop, and the output active power and frequency characteristics are analyzed. Compared with the voltage and current dual-mode control, VVSG with direct power control can perform large inertia characteristic in the weak grid and fast power following characteristics in the strong grid by adjusting λ, and without control structure switching and intermediate variable following. Moreover, the two characteristics can be smoothly transited. In addition, the active support ability of voltage source can be maintained under both characteristics. Finally, the effectiveness of the proposed control strategy is verified through simulation results. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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15 pages, 3665 KiB  
Article
A Novel Inductor for Stabilizing the DC Link of Adjustable Speed Drive
by Qian Wang, Bingyang Luo, Jun Wang, Zhe Kong and Feng Liu
Electronics 2021, 10(19), 2401; https://doi.org/10.3390/electronics10192401 - 1 Oct 2021
Viewed by 2611
Abstract
The DC-link filter which includes a magnetic inductor and a storage capacitor is one of the key parts of adjustable speed drives in the market. It significantly affects the stability, reliability, and power density of the motor-drive system. This paper proposes a novel, [...] Read more.
The DC-link filter which includes a magnetic inductor and a storage capacitor is one of the key parts of adjustable speed drives in the market. It significantly affects the stability, reliability, and power density of the motor-drive system. This paper proposes a novel, variable active inductor to improve the performance of DC links in terms of stability, reliability, size, and cost. In contrast to conventional DC-link magnetic inductors, the variable active inductor is made of power electronic circuits, including active switches, passive filters, and smart controllers, which no longer rely on magnetic material. The demonstration shows that the inductor can emulate the electrical characteristics of the magnetic inductor for filtering harmonics and stabilizing the DC link, meanwhile representing a smaller size, lighter weight, and lower cost compared with a conventional one. Furthermore, this paper proposes a variable inductance control method which is able to adaptively tune the inductance value with the operating conditions of the drive system. The DC link can be stabilized, and high performance can be maintained in both balanced and unbalanced grid voltage conditions. A case study of the proposed variable inductor in a motor drive with a three-phase diode-bridge rectifier as the front end is discussed. Experimental results are given to verify the functionality and effectiveness of the proposed variable inductor. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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16 pages, 6508 KiB  
Article
Unified Graph Theory-Based Modeling and Control Methodology of Lattice Converters
by Jingyang Fang
Electronics 2021, 10(17), 2146; https://doi.org/10.3390/electronics10172146 - 3 Sep 2021
Cited by 6 | Viewed by 2428
Abstract
Lattice converters combine the merits of both cascaded-bridge converters and multi-paralleled converters, leading to infinitely large current and voltage capabilities with modularity and scalability as well as small passive components. However, lattice converters suffer from complexity, which poses a serious threat to their [...] Read more.
Lattice converters combine the merits of both cascaded-bridge converters and multi-paralleled converters, leading to infinitely large current and voltage capabilities with modularity and scalability as well as small passive components. However, lattice converters suffer from complexity, which poses a serious threat to their widespread adoption. By use of graph theory, this article proposes a unified modeling and control methodology for various lattice converters, resulting in the satisfaction of their key control objectives, including selected inputs/outputs, desired voltages, current sharing, dynamic voltage balancing, and performance optimization. In addition, this article proposes a plurality of novel lattice converter topologies, which complement state-of-the-art options. Simulation and experimental results verify the effectiveness and superiority of the proposed methodology and lattice converters. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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17 pages, 16047 KiB  
Article
A United Control Strategy of Photovoltaic-Battery Energy Storage System Based on Voltage-Frequency Controlled VSG
by Xiangwu Yan, Chenguang Wang, Ziheng Wang, Hongbin Ma, Baixue Liang and Xiaoxue Wei
Electronics 2021, 10(17), 2047; https://doi.org/10.3390/electronics10172047 - 24 Aug 2021
Cited by 11 | Viewed by 2593
Abstract
At present, the installed capacity of photovoltaic-battery energy storage systems (PV-BESs) is rapidly increasing. In the traditional control method, the PV-BES needs to switch the control mode between off-grid and grid-connected states. Thus, the traditional control mode reduces the reliability of the system. [...] Read more.
At present, the installed capacity of photovoltaic-battery energy storage systems (PV-BESs) is rapidly increasing. In the traditional control method, the PV-BES needs to switch the control mode between off-grid and grid-connected states. Thus, the traditional control mode reduces the reliability of the system. In addition, if the system is accidentally disconnected from the grid or the energy storage battery fails to work normally, the DC voltage of the inverter increases or decreases rapidly. To address these two problems, in this paper, a united control strategy is proposed. In the case of grid connection, based on the voltage-frequency controlled VSG strategy, the strategy adjusts the output power of the VSG by changing the position of the primary frequency modulation curve. This method can ensure that, after the system is connected to the grid, excess PV power can be sent to the grid, or power can be absorbed from the grid to charge energy storage. In the off-grid state, the strategy uses FPPT technology and superimposes a voltage component onto the voltage loop to quickly balance the DC power and AC power of the inverter. This strategy can improve the reliability of the system’s power supply if the energy storage fails to work normally. Finally, a PV-BES model was built using MATLAB-Simulink, and the simulation results proved the effectiveness of the proposed strategy. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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15 pages, 6387 KiB  
Article
An Improved Droop Control Strategy for Grid-Connected Inverter Applied in Grid Voltage Inter-Harmonics and Fundamental Frequency Fluctuation
by Wanwan Xu, Bin Wang, Jiang Liu and Da Li
Electronics 2021, 10(15), 1827; https://doi.org/10.3390/electronics10151827 - 30 Jul 2021
Viewed by 2780
Abstract
This paper presents a current suppression method based on a droop control strategy under distorted grid voltage with inter-harmonics and fundamental frequency fluctuation. In this proposed strategy, the current incomplete derivation controller is employed to decrease the negative impact caused by harmonic and [...] Read more.
This paper presents a current suppression method based on a droop control strategy under distorted grid voltage with inter-harmonics and fundamental frequency fluctuation. In this proposed strategy, the current incomplete derivation controller is employed to decrease the negative impact caused by harmonic and inter-harmonic grid voltage. This method provides a good dynamic response and has low complexity against the inter-harmonics with unfixed fundamental frequency. Based on a mathematical model of the grid-connected inverter, we designed novel instantaneous frequency detection and feed-forward methods to suppress the grid fundamental frequency fluctuation impacts. Then the main parameters were analyzed. The simulation and experimental results verified the feasibility and effectiveness of the proposed method. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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19 pages, 30633 KiB  
Article
Precise Reactive Power-Voltage Droop Control of Parallel Virtual Synchronous Generators That Considers Line Impedance
by Xiangwu Yan, Hongbin Ma, Jiaoxin Jia, Waseem Aslam, Chenguang Wang, Shizheng Zhang and Baixue Liang
Electronics 2021, 10(11), 1344; https://doi.org/10.3390/electronics10111344 - 3 Jun 2021
Cited by 6 | Viewed by 2729
Abstract
Problems such as high power coupling, low distribution accuracy, and insufficient reactive power-voltage droop accuracy occur when distributed generators are operated in parallel due to the influence of line impedance. The precise control of output reactive power and voltage is difficult to achieve [...] Read more.
Problems such as high power coupling, low distribution accuracy, and insufficient reactive power-voltage droop accuracy occur when distributed generators are operated in parallel due to the influence of line impedance. The precise control of output reactive power and voltage is difficult to achieve using traditional virtual synchronous generator (VSG) control. Taking this into consideration, this study proposes a virtual synchronous generator reactive power-voltage integrated control strategy that considers line parameters to solve this problem. First, the impedance voltage drop of the line is compensated for in accordance with local information control to ensure the consistency of the control voltage in parallel operation of distributed generators and to realize the precise droop control of reactive power and the voltage of the point of common coupling (UPCC). Second, virtual negative impedance control is added to change the equivalent output impedance characteristics of the system and achieve power decoupling. On this basis, the active frequency and reactive voltage decoupling control effect of the improved control strategy is quantified and analyzed using the relative gain matrix. The accuracy of reactive power distribution and droop control is theoretically derived and analyzed by establishing a small-signal model of a two-machine parallel system. Finally, the accuracy and effectiveness of the proposed integrated control strategy are verified via a simulation model and an experimental platform for parallel operation. Results show that the proposed integrated control strategy can effectively solve the problems of power decoupling and accurate distribution, reduce system loop current, and realize accurate reactive power-voltage droop. Compared with the traditional VSG control strategy, the dynamic deviation of UPCC is reduced by at least 40% when a large-scale load disturbance occurs. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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19 pages, 6238 KiB  
Article
The Strategy of Active Grid Frequency Support for Virtual Synchronous Generator
by Lingfang Yang, Junpeng Ma, Shunliang Wang, Tianqi Liu, Zihao Wu, Ruogu Wang and Lutian Tang
Electronics 2021, 10(10), 1131; https://doi.org/10.3390/electronics10101131 - 11 May 2021
Cited by 4 | Viewed by 2038
Abstract
Virtual synchronous generator (VSG) control is a promising control approach for voltage source converters as an interface between new energy sources and the power grid. VSG is a grid-friendly control scheme, which can imitate the mechanical inertia of the synchronous generator (SG) and [...] Read more.
Virtual synchronous generator (VSG) control is a promising control approach for voltage source converters as an interface between new energy sources and the power grid. VSG is a grid-friendly control scheme, which can imitate the mechanical inertia of the synchronous generator (SG) and the power droop characteristics. Yet, the droop characteristics imitation of SG induces the frequency variation of the grid-connected inverter along with the droop characteristic curve, which will deteriorate the performance of the grid frequency support during the transient process. In this paper, a control scheme, which shapes the droop curve during the disturbance, is proposed for active grid frequency support. First, a load disturbance extraction strategy with a high-pass filter is applied in the proposed method, and the disturbance component is effectively extracted to compensate for the frequency reference variation in traditional VSG control. The grid frequency is actively supported by shaping the droop curve of active power to the frequency of VSG during the disturbance. Afterward, H∞ and H2 norms are used as the objective function to quantify the control performance of the proposed method, and the particle swarm optimization (PSO) algorithm is applied to optimize the control parameters of the proposed method. With a well-optimized high-pass filter, the active support performance is further improved. Finally, the simulation results and hardware in the loop (HIL) tests verify the effectiveness of the proposed method. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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15 pages, 11420 KiB  
Article
Modeling and Analysis of N-Branch Hybrid Switched Inductor and Capacitor Converter
by Lei Yang, Li Ma, Xiaojie Li, Liansong Xiong, Xinghua Liu, Hui Cao and Junkang Ni
Electronics 2021, 10(8), 891; https://doi.org/10.3390/electronics10080891 - 8 Apr 2021
Viewed by 1772
Abstract
This paper proposes a family of N-Branch hybrid switched inductor and capacitor (SLC) converters. With the single circuit, the multi-level output voltage or current could be generated. The proposed converter is suitable both for the voltage source and the current source. The same [...] Read more.
This paper proposes a family of N-Branch hybrid switched inductor and capacitor (SLC) converters. With the single circuit, the multi-level output voltage or current could be generated. The proposed converter is suitable both for the voltage source and the current source. The same LC network is reused for different LC branches. The proposed converter is controlled by the phase shift control method with a time domain multiplexing concept. The N level circuit is operated with the same frequency. One cycle period is divided into N small time cycles for each branch. The phase shift for each branch is 360°/N. The load voltage could be changed by modifying the duty cycle of the transistor. When the SLCs work in the resonant condition, the soft switching will be acquired. The power loss of transistors could be sharply reduced. In this paper, a 300 W SLC converter is constructed to verify the theoretical analysis and operation mechanism in the resonant condition and hard switching condition. With the experimental and simulated verification, the soft switching and the stable multi-level output voltage or current are achieved. The proposed SLC converter could be used for the multi-level voltage power supply system, such as the electric vehicle, the electric aircraft, autonomous underwater vehicles (AUVs) and a new energy generation system. Full article
(This article belongs to the Special Issue Power Quality Conditioning and Stability Enhancement of More-Electronics Power Systems)
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