Pub Date : 2024-08-07DOI: 10.1109/JESTIE.2024.3439716
Krishna Molli;P. Ajay D Vimal Raj
The demand for independent dc sources and switching components is increasing and turned to be the primary challenge with multilevel inverters (MLIs) for integrating renewable energy sources. As a result, the component reduction is crucial in these systems. The introduction of cascaded MLIs based on solid-state transformers (SSTs) has significantly reduced the requirement for dc sources. This article proposes a novel SST-based MLI with a single dc source and two capacitors to generate 25 levels at the output. Two medium-frequency isolation transformers with different rated voltages make up the proposed MLI. A cascaded H-bridge (CHB) connects the primary windings of each transformer, and the secondary windings are connected in series with the load. The proposed SST-based MLI uses a simple nearest level control switching methodology to generate the nearest level. A laboratory prototype was built to assess the proposed SST-based MLI performance. The power loss analysis of the system is also discussed. The proposed SST topology is also compared with other recent topologies of similar type.
{"title":"SST-Based 25-Level T-Type MLI for Integration of Microgrids","authors":"Krishna Molli;P. Ajay D Vimal Raj","doi":"10.1109/JESTIE.2024.3439716","DOIUrl":"https://doi.org/10.1109/JESTIE.2024.3439716","url":null,"abstract":"The demand for independent dc sources and switching components is increasing and turned to be the primary challenge with multilevel inverters (MLIs) for integrating renewable energy sources. As a result, the component reduction is crucial in these systems. The introduction of cascaded MLIs based on solid-state transformers (SSTs) has significantly reduced the requirement for dc sources. This article proposes a novel SST-based MLI with a single dc source and two capacitors to generate 25 levels at the output. Two medium-frequency isolation transformers with different rated voltages make up the proposed MLI. A cascaded H-bridge (CHB) connects the primary windings of each transformer, and the secondary windings are connected in series with the load. The proposed SST-based MLI uses a simple nearest level control switching methodology to generate the nearest level. A laboratory prototype was built to assess the proposed SST-based MLI performance. The power loss analysis of the system is also discussed. The proposed SST topology is also compared with other recent topologies of similar type.","PeriodicalId":100620,"journal":{"name":"IEEE Journal of Emerging and Selected Topics in Industrial Electronics","volume":"5 4","pages":"1519-1528"},"PeriodicalIF":0.0,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142438531","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In an era characterized by extensive use of and reliance on information and communications technology (ICT), cyber–physical power systems (CPPSs) have emerged as a critical integral of modern power infrastructures, providing vital energy sources to consumers, communities, and industries worldwide. The integration of ICT in these systems, while beneficial, introduces a rapidly evolving range of cybersecurity challenges that significantly threaten their confidentiality, integrity, and availability. To address this, our article offers a comprehensive and timely survey of the current landscape of cyber vulnerabilities in CPPS, reflecting the latest developments in the field up to the present. This includes an in-depth analysis of the diverse types of cyber threats to CPPS and their potential consequences, underscoring the necessity for a broad, multidisciplinary approach. Our review is distinguished by its thoroughness and timeliness, covering recent research to offer one of the most current overviews of cybersecurity in CPPSs. We adopt a holistic perspective, integrating technical, societal, environmental, and policy implications, thereby providing a more comprehensive understanding of cybersecurity in CPPSs. We delve into the complexities of cyberattacks, exploring sophisticated, targeted attacks alongside common threats, and emphasize the dynamic nature of cyber threats, providing insights into their evolution and future trends. Additionally, our review highlights critical yet often overlooked challenges, such as system visibility and standardization in security protocols, arguing their significance in enhancing CPPS resilience. Furthermore, our work gives special attention to the aspects of restoration and recovery postcyberattack, an area less emphasized in the existing literature. Through this comprehensive overview of the current state and evolving challenges of CPPS security, our article serves as an indispensable resource for research, practice, and policymaking dedicated to safeguarding the safety, reliability, and resilience of ICT-empowered energy systems.
{"title":"Cyber Vulnerabilities of Energy Systems","authors":"Alexis Pengfei Zhao;Shuangqi Li;Chenghong Gu;Xiaohe Yan;Paul Jen-Hwa Hu;Zhaoyu Wang;Da Xie;Zhidong Cao;Xinlei Chen;Chenye Wu;Tianyi Luo;Zikang Wang;Ignacio Hernando-Gil","doi":"10.1109/JESTIE.2024.3434350","DOIUrl":"https://doi.org/10.1109/JESTIE.2024.3434350","url":null,"abstract":"In an era characterized by extensive use of and reliance on information and communications technology (ICT), cyber–physical power systems (CPPSs) have emerged as a critical integral of modern power infrastructures, providing vital energy sources to consumers, communities, and industries worldwide. The integration of ICT in these systems, while beneficial, introduces a rapidly evolving range of cybersecurity challenges that significantly threaten their confidentiality, integrity, and availability. To address this, our article offers a comprehensive and timely survey of the current landscape of cyber vulnerabilities in CPPS, reflecting the latest developments in the field up to the present. This includes an in-depth analysis of the diverse types of cyber threats to CPPS and their potential consequences, underscoring the necessity for a broad, multidisciplinary approach. Our review is distinguished by its thoroughness and timeliness, covering recent research to offer one of the most current overviews of cybersecurity in CPPSs. We adopt a holistic perspective, integrating technical, societal, environmental, and policy implications, thereby providing a more comprehensive understanding of cybersecurity in CPPSs. We delve into the complexities of cyberattacks, exploring sophisticated, targeted attacks alongside common threats, and emphasize the dynamic nature of cyber threats, providing insights into their evolution and future trends. Additionally, our review highlights critical yet often overlooked challenges, such as system visibility and standardization in security protocols, arguing their significance in enhancing CPPS resilience. Furthermore, our work gives special attention to the aspects of restoration and recovery postcyberattack, an area less emphasized in the existing literature. Through this comprehensive overview of the current state and evolving challenges of CPPS security, our article serves as an indispensable resource for research, practice, and policymaking dedicated to safeguarding the safety, reliability, and resilience of ICT-empowered energy systems.","PeriodicalId":100620,"journal":{"name":"IEEE Journal of Emerging and Selected Topics in Industrial Electronics","volume":"5 4","pages":"1455-1469"},"PeriodicalIF":0.0,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142438502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The primary-parallel-secondary-series LCC resonant high voltage (HV) power supply with single-phase ac input has been widely applied for medical X-ray application. It requires extremely low ripple (<0.5%)>LCC converter at the same time. The dc-bus capacitance can, therefore, be remarkably reduced. This strategy has the advantages of no additional hardware costs, directly implemented in digital controller, and insensitive to accuracy of system parameters. Experiments are carried out on a practical 120 kV/900 W HV power supply and confirm the effectiveness of the proposed strategy. The peak–peak output voltage ripple is suppressed to only 0.36%, while the DC capacitance is significantly reduced to 1/12. Comparison of X-ray does prove that the image quality of X-ray machine is consequently greatly improved.
单相交流输入的初级-并联-次级-串联 LCC 谐振高压（HV）电源已广泛应用于医用 X 射线。它同时要求极低的纹波（LCC 转换器）。因此，直流母线电容可显著降低。该策略具有无需额外硬件成本、可直接在数字控制器中实现、对系统参数精度不敏感等优点。我们在一个 120 kV/900 W 高压电源上进行了实验，证实了所提策略的有效性。峰-峰输出电压纹波被抑制到仅 0.36%，而直流电容则显著降低到 1/12。X 射线对比证明，X 射线机的图像质量因此得到了极大改善。
{"title":"Output Voltage Ripple Suppression of PPSS-LCC Converter for Medical X-Ray Application Based on Repetitive Control","authors":"Chudi Lin;Liqun He;Mingdi Fan;Xiaohui Li;Shengfang Fan;Cheng Wang;Yaosuo Xue","doi":"10.1109/JESTIE.2024.3435005","DOIUrl":"https://doi.org/10.1109/JESTIE.2024.3435005","url":null,"abstract":"The primary-parallel-secondary-series \u0000<italic>LCC</i>\u0000 resonant high voltage (HV) power supply with single-phase ac input has been widely applied for medical X-ray application. It requires extremely low ripple (<0.5%)>LCC</i>\u0000 converter at the same time. The dc-bus capacitance can, therefore, be remarkably reduced. This strategy has the advantages of no additional hardware costs, directly implemented in digital controller, and insensitive to accuracy of system parameters. Experiments are carried out on a practical 120 kV/900 W HV power supply and confirm the effectiveness of the proposed strategy. The peak–peak output voltage ripple is suppressed to only 0.36%, while the DC capacitance is significantly reduced to 1/12. Comparison of X-ray does prove that the image quality of X-ray machine is consequently greatly improved.","PeriodicalId":100620,"journal":{"name":"IEEE Journal of Emerging and Selected Topics in Industrial Electronics","volume":"5 4","pages":"1688-1697"},"PeriodicalIF":0.0,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142434579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-26DOI: 10.1109/JESTIE.2024.3434422
Ranjan Kumar;Chandrashekhar N. Bhende
Power to the ac loads in a dc microgrid is mostly provided by point-of-load (POL) converters with integrated input LC filters. However, the interaction between the LC filter and POL converters may introduce instability and voltage oscillations across input dc capacitor. To address this issue, this article proposed an active damping stabilization control by incorporating a dc-side control stabilizing term into the finite control set model predictive control (FCS-MPC) algorithm. A new cost function is proposed in FCS-MPC control. The proposed method improves transient response and mitigates the voltage oscillations. Moreover, the proposed method requires fewer current sensors compared to alternative approaches, ensuring stability through an intrinsic and precise control strategy. Experimental and simulation results validate the effectiveness of the proposed stabilization control, offering a promising solution for POL converter applications.
{"title":"Model Predictive Control-Based Voltage Oscillations Stabilizer for Point-of-Load Converter With EMI Filter in DC Microgrids","authors":"Ranjan Kumar;Chandrashekhar N. Bhende","doi":"10.1109/JESTIE.2024.3434422","DOIUrl":"https://doi.org/10.1109/JESTIE.2024.3434422","url":null,"abstract":"Power to the ac loads in a dc microgrid is mostly provided by point-of-load (POL) converters with integrated input LC filters. However, the interaction between the LC filter and POL converters may introduce instability and voltage oscillations across input dc capacitor. To address this issue, this article proposed an active damping stabilization control by incorporating a dc-side control stabilizing term into the finite control set model predictive control (FCS-MPC) algorithm. A new cost function is proposed in FCS-MPC control. The proposed method improves transient response and mitigates the voltage oscillations. Moreover, the proposed method requires fewer current sensors compared to alternative approaches, ensuring stability through an intrinsic and precise control strategy. Experimental and simulation results validate the effectiveness of the proposed stabilization control, offering a promising solution for POL converter applications.","PeriodicalId":100620,"journal":{"name":"IEEE Journal of Emerging and Selected Topics in Industrial Electronics","volume":"6 1","pages":"215-223"},"PeriodicalIF":0.0,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dual-active-bridge series-resonant-converter (DAB-SRC) is widely applied due to its simple circuit structure. A lot of literature has proposed variety kinds of control strategies to ensure the soft switching realization. However, problems such as complex control algorithms, intricate parameter design processes, and a high number of feedback control variables still persist. This article introduced a variable frequency and single-phase-shifted (VF&SPS) control strategy based on the time-domain analysis, which employs only two control variables (frequency and phase-shifted angle) and only two frequently-used feedback variables (output voltage and current). The soft switching region and the gain model are presented by visualization method so the converter's operating region is clear. By establishing a linear function between normalized frequency f n and the quality factor Q ( f n = k * Q + b ), the operating track of the converter is restricted and the soft-switching is also ensured even with a constant switching dead-band time. The output is finally regulated by the phase-shifted angle ϕ, which is generated by a proportional integral compensator. The correctness of the theoretical analysis is verified by a 1.2-kW bidirectional prototype with a maximum efficiency of 97.9%.
双有源桥串联谐振变换器（DAB-SRC）因其电路结构简单而得到广泛应用。许多文献提出了各种控制策略来保证软开关的实现。然而，复杂的控制算法、复杂的参数设计过程和大量的反馈控制变量等问题仍然存在。本文介绍了一种基于时域分析的变频单移相（VF&SPS）控制策略，该策略只采用两个控制变量（频率和移相角）和两个常用的反馈变量（输出电压和电流）。采用可视化的方法给出了软开关区域和增益模型，使变换器的工作区域清晰可见。通过建立归一化频率fn与品质因子Q （fn = k * Q + b）之间的线性函数，限制了变换器的工作轨迹，即使开关死带时间不变，也能保证软开关。输出最终由相移角φ调节，由比例积分补偿器产生。通过1.2 kw双向样机验证了理论分析的正确性，最大效率为97.9%。
{"title":"A Simple Variable Frequency and Single-Phase-Shifted Control for the Dual Active Bridge Series Resonant Converter","authors":"Pengyu Jia;Kai Qiu;Mei Liang;Tiancong Shao;Yajing Zhang","doi":"10.1109/JESTIE.2024.3428651","DOIUrl":"https://doi.org/10.1109/JESTIE.2024.3428651","url":null,"abstract":"Dual-active-bridge series-resonant-converter (DAB-SRC) is widely applied due to its simple circuit structure. A lot of literature has proposed variety kinds of control strategies to ensure the soft switching realization. However, problems such as complex control algorithms, intricate parameter design processes, and a high number of feedback control variables still persist. This article introduced a variable frequency and single-phase-shifted (VF&SPS) control strategy based on the time-domain analysis, which employs only two control variables (frequency and phase-shifted angle) and only two frequently-used feedback variables (output voltage and current). The soft switching region and the gain model are presented by visualization method so the converter's operating region is clear. By establishing a linear function between normalized frequency \u0000<italic>f</i>\u0000<sub>n</sub>\u0000 and the quality factor \u0000<italic>Q</i>\u0000 (\u0000<italic>f</i>\u0000<sub>n</sub>\u0000 = \u0000<italic>k</i>\u0000 * \u0000<italic>Q</i>\u0000 + \u0000<italic>b</i>\u0000), the operating track of the converter is restricted and the soft-switching is also ensured even with a constant switching dead-band time. The output is finally regulated by the phase-shifted angle \u0000<italic>ϕ,</i>\u0000 which is generated by a proportional integral compensator. The correctness of the theoretical analysis is verified by a 1.2-kW bidirectional prototype with a maximum efficiency of 97.9%.","PeriodicalId":100620,"journal":{"name":"IEEE Journal of Emerging and Selected Topics in Industrial Electronics","volume":"6 1","pages":"308-326"},"PeriodicalIF":0.0,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article presents a super-capacitor energy storage system (SC-ESS)-based low-voltage ride-through (LVRT) scheme for the grid-interfaced permanent magnet vernier generator (PMVG)-based wind turbine system (WTS). The WTSs should be grid code compliant to ride through transient voltage faults by injecting required reactive power to maintain grid stability and reliability. To do this, the proposed unified super-capacitor and rotor speed control (USSC) scheme estimates the real-time wind speed and analyses the WTS power characteristic during grid faults. Then, the presented USSC identifies the optimal operating point that minimizes active power diverted to the SC-ESS. This is achieved by elevated rotor speed operation through WTS aerodynamic characteristics-specific conditional selection of $q$ -axis reference current to the generator. Simultaneously, E.ON grid code-compliant reactive current injection to the grid is performed by ensuring converter rating constraints. Therefore, an enhanced LVRT is achieved through the unified operation of grid side converter, machine side converter, and dc/dc converter, which leads to reduced SC-ESS capacity rating. Simulation comparison and laboratory experiments verify the applicability of the presented scheme for LVRT in a 5-kW-rated PMVG-based WTS.
{"title":"An Enhanced Low-Voltage Ride-Through for PMVG-Based WTS With Unified Super-Capacitor and Rotor Speed Control","authors":"Ganesh Mayilsamy;Seong Ryong Lee;Jae Hoon Jeong;Young Hoon Joo","doi":"10.1109/JESTIE.2024.3429379","DOIUrl":"https://doi.org/10.1109/JESTIE.2024.3429379","url":null,"abstract":"This article presents a super-capacitor energy storage system (SC-ESS)-based low-voltage ride-through (LVRT) scheme for the grid-interfaced permanent magnet vernier generator (PMVG)-based wind turbine system (WTS). The WTSs should be grid code compliant to ride through transient voltage faults by injecting required reactive power to maintain grid stability and reliability. To do this, the proposed unified super-capacitor and rotor speed control (USSC) scheme estimates the real-time wind speed and analyses the WTS power characteristic during grid faults. Then, the presented USSC identifies the optimal operating point that minimizes active power diverted to the SC-ESS. This is achieved by elevated rotor speed operation through WTS aerodynamic characteristics-specific conditional selection of \u0000<inline-formula><tex-math>$q$</tex-math></inline-formula>\u0000-axis reference current to the generator. Simultaneously, E.ON grid code-compliant reactive current injection to the grid is performed by ensuring converter rating constraints. Therefore, an enhanced LVRT is achieved through the unified operation of grid side converter, machine side converter, and dc/dc converter, which leads to reduced SC-ESS capacity rating. Simulation comparison and laboratory experiments verify the applicability of the presented scheme for LVRT in a 5-kW-rated PMVG-based WTS.","PeriodicalId":100620,"journal":{"name":"IEEE Journal of Emerging and Selected Topics in Industrial Electronics","volume":"6 1","pages":"115-125"},"PeriodicalIF":0.0,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905903","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-15DOI: 10.1109/JESTIE.2024.3428350
Biswajit Mandal;Partha Sarathee Bhowmik
The article presents a highly simplified novel intelligent approach to track the maximum power point (MPP) of a commercially available dye-sensitized solar panel with a deep neural network under uniform irradiance. The panel comprising dye-sensitized solar cell is a third-generation solar cell technology. It sustains its performance at low illumination levels unlike the conventional solar cell technologies. Therefore, it can eliminate the shading issue caused by the flying birds or cloud. The MPP tracking (MPPT) techniques extract maximum power from photovoltaic systems. The biologically inspired neural networks (NNs) are widely applied techniques, solve the numerous engineering and nonengineering problems. It includes the solution to the problems, associated with MPPT. NN-based MPPT methods have made tracking systems more straightforward and robust than conventional ones. These are the distinctive and better methods in terms of tracking speed, performance accuracy, and fewer oscillation near the MPP. This is the first research work, applied novel artificial intelligence based MPPT technique with a proposed scheme on a commercial dye-sensitized solar panel. The experimentation has found the scheme effective with lesser input feature than in the literature to the NN. The results, from the proposed method and the perturb and observe method, are compared for validation. The study has found less oscillation near MPP and faster tracking response.
{"title":"A Deep Neural Network-Based Highly Simplified Intelligent Approach for Maximum Power Point Tracking of Dye-Sensitized Solar Panel System","authors":"Biswajit Mandal;Partha Sarathee Bhowmik","doi":"10.1109/JESTIE.2024.3428350","DOIUrl":"https://doi.org/10.1109/JESTIE.2024.3428350","url":null,"abstract":"The article presents a highly simplified novel intelligent approach to track the maximum power point (MPP) of a commercially available dye-sensitized solar panel with a deep neural network under uniform irradiance. The panel comprising dye-sensitized solar cell is a third-generation solar cell technology. It sustains its performance at low illumination levels unlike the conventional solar cell technologies. Therefore, it can eliminate the shading issue caused by the flying birds or cloud. The MPP tracking (MPPT) techniques extract maximum power from photovoltaic systems. The biologically inspired neural networks (NNs) are widely applied techniques, solve the numerous engineering and nonengineering problems. It includes the solution to the problems, associated with MPPT. NN-based MPPT methods have made tracking systems more straightforward and robust than conventional ones. These are the distinctive and better methods in terms of tracking speed, performance accuracy, and fewer oscillation near the MPP. This is the first research work, applied novel artificial intelligence based MPPT technique with a proposed scheme on a commercial dye-sensitized solar panel. The experimentation has found the scheme effective with lesser input feature than in the literature to the NN. The results, from the proposed method and the perturb and observe method, are compared for validation. The study has found less oscillation near MPP and faster tracking response.","PeriodicalId":100620,"journal":{"name":"IEEE Journal of Emerging and Selected Topics in Industrial Electronics","volume":"6 1","pages":"196-203"},"PeriodicalIF":0.0,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-15DOI: 10.1109/JESTIE.2024.3427669
Chongbin Zhao;Qirong Jiang
Learning from two-level voltage-source converters, the existing impedance-based stability analyses of modular multilevel converters (MMCs) focus on system modes with finite closed-loop transfer functions, which consider perturbations of the current flowing into the interconnected ac/dc terminal as the input. However, this approach is insufficient for MMCs due to the actively controlled circulating current circuits, resulting from the distributed modulation of each arm and the circulating current control (CCC). To address this limitation, two cases that are not covered by the ac/dc terminal stability analysis are initially presented to support the conjecture. Subsequently, an inner-loop impedance involving the circulating circuit is established, which considers the dynamics of interconnected terminals and divides the injected voltage perturbation by the corresponding current perturbation. To avoid the right-half-plane pole check of the Nyquist criterion and improve the accuracy of mode identification, the optimization technique is integrated with the logarithmic derivative-based criterion. By utilizing the circulating current inner-loop impedance, it becomes possible to achieve CCC parameter tuning with stability constraints and conduct an internal stability analysis of MMC-based systems. In a nutshell, this work supportsthe integration of converter-dominated systems from the perspective of classical control theories.
{"title":"Complementing AC and DC Terminal Stability Analyses of MMC With Circulating Current Inner-Loop Impedance Model","authors":"Chongbin Zhao;Qirong Jiang","doi":"10.1109/JESTIE.2024.3427669","DOIUrl":"https://doi.org/10.1109/JESTIE.2024.3427669","url":null,"abstract":"Learning from two-level voltage-source converters, the existing impedance-based stability analyses of modular multilevel converters (MMCs) focus on system modes with finite closed-loop transfer functions, which consider perturbations of the current flowing into the interconnected ac/dc terminal as the input. However, this approach is insufficient for MMCs due to the actively controlled circulating current circuits, resulting from the distributed modulation of each arm and the circulating current control (CCC). To address this limitation, two cases that are not covered by the ac/dc terminal stability analysis are initially presented to support the conjecture. Subsequently, an inner-loop impedance involving the circulating circuit is established, which considers the dynamics of interconnected terminals and divides the injected voltage perturbation by the corresponding current perturbation. To avoid the right-half-plane pole check of the Nyquist criterion and improve the accuracy of mode identification, the optimization technique is integrated with the logarithmic derivative-based criterion. By utilizing the circulating current inner-loop impedance, it becomes possible to achieve CCC parameter tuning with stability constraints and conduct an internal stability analysis of MMC-based systems. In a nutshell, this work supportsthe integration of converter-dominated systems from the perspective of classical control theories.","PeriodicalId":100620,"journal":{"name":"IEEE Journal of Emerging and Selected Topics in Industrial Electronics","volume":"6 1","pages":"284-294"},"PeriodicalIF":0.0,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-12DOI: 10.1109/JESTIE.2024.3427363
Rahul Raj Kar;Rupesh Wandhare
Voltage source converters show considerable potential in integrating renewable energy sources with the power grid. The stability of LCL -type grid-connected converters is significantly affected by internal resonances within filters. The digital control delay can lead to instability with proportional capacitor current feedback-based active damping (AD). This instability emerges when the resonance frequency nears the critical frequency (fs/6) owing to fluctuations in grid impedance, in weak grid. To address this limitation, a hybrid damping comprising grid current feedback with a damping resistor is proposed to mitigate the effect of digital control delay. A feed-forward point of common coupling (PCC) voltage compensation is proposed without additional sensor requirements to enhance the phase margin (PM). The proposed hybrid damping compensates for the digital control delay, extending the critical frequency region to the Nyquist frequency (fs/2). The proposed design of PCC voltage feed-forward enhances the PM and strengthens the robustness against grid impedance variation. An open loop synchronization is implemented to mitigate the instability raised due to phase locked loop (PLL)-based synchronization (low-frequency instability). The hybrid damping and PCC voltage feedforward controller are designed using a graphical approach. The proposed control achieves a stable operation even when the short-circuit ratio is significantly low ( $leq 2$ ). An admittance-based stability analysis is performed followed by a closed-loop pole trajectory. To validate the proposed method and controller design, comprehensive simulation studies on a 100-kVA system and laboratory experiments on a 15-kVA prototype are conducted. The proposed methodology is tested for unbalanced voltage conditions and with an outer power loop control.
{"title":"Enhanced Stability and Control of Voltage Source Converters With LCL Filter in Weak Grid","authors":"Rahul Raj Kar;Rupesh Wandhare","doi":"10.1109/JESTIE.2024.3427363","DOIUrl":"https://doi.org/10.1109/JESTIE.2024.3427363","url":null,"abstract":"Voltage source converters show considerable potential in integrating renewable energy sources with the power grid. The stability of \u0000<italic>LCL</i>\u0000-type grid-connected converters is significantly affected by internal resonances within filters. The digital control delay can lead to instability with proportional capacitor current feedback-based active damping (AD). This instability emerges when the resonance frequency nears the critical frequency (fs/6) owing to fluctuations in grid impedance, in weak grid. To address this limitation, a hybrid damping comprising grid current feedback with a damping resistor is proposed to mitigate the effect of digital control delay. A feed-forward point of common coupling (PCC) voltage compensation is proposed without additional sensor requirements to enhance the phase margin (PM). The proposed hybrid damping compensates for the digital control delay, extending the critical frequency region to the Nyquist frequency (fs/2). The proposed design of PCC voltage feed-forward enhances the PM and strengthens the robustness against grid impedance variation. An open loop synchronization is implemented to mitigate the instability raised due to phase locked loop (PLL)-based synchronization (low-frequency instability). The hybrid damping and PCC voltage feedforward controller are designed using a graphical approach. The proposed control achieves a stable operation even when the short-circuit ratio is significantly low (\u0000<inline-formula><tex-math>$leq 2$</tex-math></inline-formula>\u0000). An admittance-based stability analysis is performed followed by a closed-loop pole trajectory. To validate the proposed method and controller design, comprehensive simulation studies on a 100-kVA system and laboratory experiments on a 15-kVA prototype are conducted. The proposed methodology is tested for unbalanced voltage conditions and with an outer power loop control.","PeriodicalId":100620,"journal":{"name":"IEEE Journal of Emerging and Selected Topics in Industrial Electronics","volume":"6 1","pages":"271-283"},"PeriodicalIF":0.0,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905776","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-11DOI: 10.1109/JESTIE.2024.3427009
Siqi Fu;Yao Sun;Xiaochao Hou;Shimiao Chen;Guangze Shi;Mei Su
Power, voltage, and frequency oscillation or instability of a multivoltage source converters (VSCs) system will threaten its stable operation. From a power system point of view, the four variables [ P Q ]-[ ω V ] are the key characteristic indicators that are paid attention to, which are usually used to describe the nodal dynamic characteristics, instead of the traditional impedance model. With that in mind, this article establishes a general [ P Q ] - [ ω V ] model of a hybrid GFM/GFL multi-VSC system for power oscillation analysis, where the system structure is not limited to a special star topology. The general [ P Q ] - [ ω V ] models of VSCs under typical grid-forming and grid-following control schemes are comprehensively built. As a result, it could serve as a standard model that provides a convenient and universal tool for both the low and medium frequency (a few tenths to tens Hz) power oscillation analysis and stability analysis. Moreover, the proposed model can locate the weak nodes with severe power oscillations and evaluate the effect of the oscillation suppression methods. To suppress the system medium frequency oscillation, a washout-filter coupling feedback control method is proposed with more control freedom and improved dynamic performance. Finally, the control-hardware-in-loop experiment results verify the theoretical analysis.
{"title":"A General [P Q]-[ω V] Model of Hybrid GFM/GFL Multi-VSC Systems: Power Oscillation Analysis and Suppression Method","authors":"Siqi Fu;Yao Sun;Xiaochao Hou;Shimiao Chen;Guangze Shi;Mei Su","doi":"10.1109/JESTIE.2024.3427009","DOIUrl":"https://doi.org/10.1109/JESTIE.2024.3427009","url":null,"abstract":"Power, voltage, and frequency oscillation or instability of a multivoltage source converters (VSCs) system will threaten its stable operation. From a power system point of view, the four variables [\u0000<italic>P Q</i>\u0000]-[\u0000<italic>ω V</i>\u0000] are the key characteristic indicators that are paid attention to, which are usually used to describe the nodal dynamic characteristics, instead of the traditional impedance model. With that in mind, this article establishes a general [\u0000<italic>P Q</i>\u0000]\u0000<italic>-</i>\u0000[\u0000<italic>ω V</i>\u0000] model of a hybrid GFM/GFL multi-VSC system for power oscillation analysis, where the system structure is not limited to a special star topology. The general [\u0000<italic>P Q</i>\u0000]\u0000<italic>-</i>\u0000[\u0000<italic>ω V</i>\u0000] models of VSCs under typical grid-forming and grid-following control schemes are comprehensively built. As a result, it could serve as a standard model that provides a convenient and universal tool for both the low and medium frequency (a few tenths to tens Hz) power oscillation analysis and stability analysis. Moreover, the proposed model can locate the weak nodes with severe power oscillations and evaluate the effect of the oscillation suppression methods. To suppress the system medium frequency oscillation, a washout-filter coupling feedback control method is proposed with more control freedom and improved dynamic performance. Finally, the control-hardware-in-loop experiment results verify the theoretical analysis.","PeriodicalId":100620,"journal":{"name":"IEEE Journal of Emerging and Selected Topics in Industrial Electronics","volume":"5 4","pages":"1362-1375"},"PeriodicalIF":0.0,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142438548","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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