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Due to a limitation in the magnitude of the three-phase output inverter currents, the output active power of the photovoltaic (PV) unit has been de-rated during low voltage ride through, which brings great instability risk to the power system. With the increase in the penetration rate of new energy, the impact of the power shortage on the system transient stability increases. It is of great significance to analyze the impact of this transient power shortage on system stability. This article explores methods to improve the active power output capability of photovoltaic units during low-breakthrough periods. A transient simulation model of a grid-connected PV generator with low-voltage ride-through (LVRT) capability is presented, under the condition of meeting the overcurrent capacity of the PV inverter and the requirement of dynamic reactive power support supplied by the PV generator specified in the China grid codes (GB/T 19964-2012) during grid fault. An example system with high PV penetration is built. The change principle and influencing factors of PV transient active power output are analyzed. The simulation model is designed in PowerFactory/DIgSILENT, and several types of three-phase voltage sags are performed in simulation to assess the impact of the active current reference calculation method and the maximum inverter output current (Imax) limit value on the PV active power output. According to the three indexes, namely the maximum active power of PV unit during the fault, the power improvement gradient and the power surge after the fault is cleared. Simulation results showed that using the orthogonal decomposition method to calculate the active current reference can make full use of the current capacity of the converter. Setting Imax to 1.1 rated current of photovoltaic inverter (IN) can reduce the cost-effectiveness ratio of the transient active power output of the PV unit. Therefore, we aim to improve the unit’s transient active power output capacity and realize the optimal effect of improving the transient active power shortage of the system.
Xiangwu Yan; Baixue Liang; Jiaoxin Jia; Waseem Aslam; Chenguang Wang; Shizheng Zhang; HongBin Ma. Strategies to Increase the Transient Active Power of Photovoltaic Units during Low Voltage Ride Through. Energies 2021, 14, 5236 .
AMA StyleXiangwu Yan, Baixue Liang, Jiaoxin Jia, Waseem Aslam, Chenguang Wang, Shizheng Zhang, HongBin Ma. Strategies to Increase the Transient Active Power of Photovoltaic Units during Low Voltage Ride Through. Energies. 2021; 14 (17):5236.
Chicago/Turabian StyleXiangwu Yan; Baixue Liang; Jiaoxin Jia; Waseem Aslam; Chenguang Wang; Shizheng Zhang; HongBin Ma. 2021. "Strategies to Increase the Transient Active Power of Photovoltaic Units during Low Voltage Ride Through." Energies 14, no. 17: 5236.
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.
Xiangwu Yan; Chenguang Wang; Ziheng Wang; HongBin Ma; Baixue Liang; Xiaoxue Wei. A United Control Strategy of Photovoltaic-Battery Energy Storage System Based on Voltage-Frequency Controlled VSG. Electronics 2021, 10, 2047 .
AMA StyleXiangwu Yan, Chenguang Wang, Ziheng Wang, HongBin Ma, Baixue Liang, Xiaoxue Wei. A United Control Strategy of Photovoltaic-Battery Energy Storage System Based on Voltage-Frequency Controlled VSG. Electronics. 2021; 10 (17):2047.
Chicago/Turabian StyleXiangwu Yan; Chenguang Wang; Ziheng Wang; HongBin Ma; Baixue Liang; Xiaoxue Wei. 2021. "A United Control Strategy of Photovoltaic-Battery Energy Storage System Based on Voltage-Frequency Controlled VSG." Electronics 10, no. 17: 2047.
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.
Xiangwu Yan; HongBin Ma; Jiaoxin Jia; Waseem Aslam; Chenguang Wang; Shizheng Zhang; Baixue Liang. Precise Reactive Power-Voltage Droop Control of Parallel Virtual Synchronous Generators That Considers Line Impedance. Electronics 2021, 10, 1344 .
AMA StyleXiangwu Yan, HongBin Ma, Jiaoxin Jia, Waseem Aslam, Chenguang Wang, Shizheng Zhang, Baixue Liang. Precise Reactive Power-Voltage Droop Control of Parallel Virtual Synchronous Generators That Considers Line Impedance. Electronics. 2021; 10 (11):1344.
Chicago/Turabian StyleXiangwu Yan; HongBin Ma; Jiaoxin Jia; Waseem Aslam; Chenguang Wang; Shizheng Zhang; Baixue Liang. 2021. "Precise Reactive Power-Voltage Droop Control of Parallel Virtual Synchronous Generators That Considers Line Impedance." Electronics 10, no. 11: 1344.
With the increasing penetration level of wind turbine generators (WTGs) integrated into the power system, the WTGs are enforced to aid network and fulfill the low voltage ride through (LVRT) requirements during faults. To enhance LVRT capability of permanent magnet synchronous generator (PMSG)-based WTG connected to the grid, this paper presents a novel coordinated control scheme named overspeed-while-storing control for PMSG-based WTG. The proposed control scheme purely regulates the rotor speed to reduce the input power of the machine-side converter (MSC) during slight voltage sags. Contrarily, when the severe voltage sag occurs, the coordinated control scheme sets the rotor speed at the upper-limit to decrease the input power of the MSC at the greatest extent, while the surplus power is absorbed by the supercapacitor energy storage (SCES) so as to reduce its maximum capacity. Moreover, the specific capacity configuration scheme of SCES is detailed in this paper. The effectiveness of the overspeed-while-storing control in enhancing the LVRT capability is validated under different levels of voltage sags and different fault types in MATLAB/Simulink.
Xiangwu Yan; Linlin Yang; Tiecheng Li. The LVRT Control Scheme for PMSG-Based Wind Turbine Generator Based on the Coordinated Control of Rotor Overspeed and Supercapacitor Energy Storage. Energies 2021, 14, 518 .
AMA StyleXiangwu Yan, Linlin Yang, Tiecheng Li. The LVRT Control Scheme for PMSG-Based Wind Turbine Generator Based on the Coordinated Control of Rotor Overspeed and Supercapacitor Energy Storage. Energies. 2021; 14 (2):518.
Chicago/Turabian StyleXiangwu Yan; Linlin Yang; Tiecheng Li. 2021. "The LVRT Control Scheme for PMSG-Based Wind Turbine Generator Based on the Coordinated Control of Rotor Overspeed and Supercapacitor Energy Storage." Energies 14, no. 2: 518.
With the development of electric vehicles in China, the fault monitoring and warning systems for the charging process of electric vehicles have received the industry’s attention. A method for the monitoring and warning of electric vehicle charging faults based on a battery model is proposed in this paper. Through online estimation of the state of charge of the power battery model and battery electromotive force, parameters such as battery state of charge, voltage, and temperature can be adjusted in real time to simulate the charging response of the power battery, which can simulate power batteries of different types, specifications, and parameters. During the charging process, CAN (Controller Area Network) bus monitoring technology is used to receive and analyze the charging information of the charger, as well as the battery charging information and battery charging demand information. The charging response information simulated by the battery model is compared with the battery charging state information, and the charging state information of the charger is compared with the battery charging demand information to determine whether the charging process is normal. When it is judged that a charging fault occurs, a fault warning signal is sent. This method can identify more than 10 types of faults, including the failure of the BMS (Battery Management System) function. The comparison and analysis of actual charging accident data and power battery model data verifies the feasibility of the charging fault monitoring method proposed in this paper.
Yuanxing Zhang; Taoyong Li; Xiangwu Yan; Ling Wang; Jing Zhang; Xiaohong Diao; Bin Li. Electric Vehicle Charging Fault Monitoring and Warning Method Based on Battery Model. World Electric Vehicle Journal 2021, 12, 14 .
AMA StyleYuanxing Zhang, Taoyong Li, Xiangwu Yan, Ling Wang, Jing Zhang, Xiaohong Diao, Bin Li. Electric Vehicle Charging Fault Monitoring and Warning Method Based on Battery Model. World Electric Vehicle Journal. 2021; 12 (1):14.
Chicago/Turabian StyleYuanxing Zhang; Taoyong Li; Xiangwu Yan; Ling Wang; Jing Zhang; Xiaohong Diao; Bin Li. 2021. "Electric Vehicle Charging Fault Monitoring and Warning Method Based on Battery Model." World Electric Vehicle Journal 12, no. 1: 14.
The large-scale application of wind power eases the shortage of conventional energy, but it also brings great hidden danger to the stability and security of the power grid because wind power has no ability for frequency regulation. When doubly-fed induction generator (DFIG) based wind turbines use rotor kinetic energy to participate in frequency regulation, it can effectively respond to frequency fluctuation, but has the problems of secondary frequency drop and output power loss. Furthermore, it cannot provide long-term power support. To solve these problems, a coordinated frequency control strategy based on rotor kinetic energy and supercapacitor was proposed in this paper. In order to ensure the DFIG provides fast and long-term power support, a supercapacitor was used to realize the droop characteristic, and rotor kinetic energy was used to realize the inertia characteristic like synchronous generator (SG). Additionally, the supercapacitor is also controlled to compensate for the power dip of the DFIG when rotor kinetic energy exits inertia support to avoid secondary frequency drop. Additionally, a new tracking curve of DFIG rotor speed and output power was adopted to reduce the power loss during rotor speed recovery.
Xiangwu Yan; Xuewei Sun. Inertia and Droop Frequency Control Strategy of Doubly-Fed Induction Generator Based on Rotor Kinetic Energy and Supercapacitor. Energies 2020, 13, 3697 .
AMA StyleXiangwu Yan, Xuewei Sun. Inertia and Droop Frequency Control Strategy of Doubly-Fed Induction Generator Based on Rotor Kinetic Energy and Supercapacitor. Energies. 2020; 13 (14):3697.
Chicago/Turabian StyleXiangwu Yan; Xuewei Sun. 2020. "Inertia and Droop Frequency Control Strategy of Doubly-Fed Induction Generator Based on Rotor Kinetic Energy and Supercapacitor." Energies 13, no. 14: 3697.
Renewable generation brings both new energies and significant challenges to the evolving power system. To cope with the loss of inertia caused by inertialess power electronic interfaces (PEIs), the concept of the virtual synchronous generator (VSG) has been proposed. The PEIs under VSG control could mimic the external properties of the traditional synchronous generators. Therefore, the frequency stability of the entire system could be sustained against disturbances mainly caused by demand changes. Moreover, as the parameters in the emulation control processes are adjustable rather than fixed, the flexibility could be enhanced by proper tuning. This paper presents a parameter tuning method adaptive to the load deviations. First, the concept and implementation of the VSG algorithm performing an inertia response (IR) and primary frequency responses (PFR) are introduced. Then, the simplification of the transfer function of the dynamic system of the stand-alone VSG-PEI is completed according to the distributed poles and zeros. As a result, the performance indices during the IR and PFR stages are deduced by the inverse Laplace transformation. Then, the composite influences on the performances by different parameters (including the inertia constant, the speed droop, and the load deviations) are analyzed. Based on the composite influences and the time sequences, an adaptive parameter tuning method is presented. The feasibility of the proposed method is verified by simulation.
Weichao Zhang; Xiangwu Yan; Hanyan Huang. Adaptive Performance Tuning for Voltage-Sourced Converters with Frequency Responses. Applied Sciences 2020, 10, 1884 .
AMA StyleWeichao Zhang, Xiangwu Yan, Hanyan Huang. Adaptive Performance Tuning for Voltage-Sourced Converters with Frequency Responses. Applied Sciences. 2020; 10 (5):1884.
Chicago/Turabian StyleWeichao Zhang; Xiangwu Yan; Hanyan Huang. 2020. "Adaptive Performance Tuning for Voltage-Sourced Converters with Frequency Responses." Applied Sciences 10, no. 5: 1884.
In converter-based AC microgrids, the frequency-droop is widely applied. As a considerable share of installed capacity is replaced by renewable generation, the virtual synchronous machine (VSM) algorithm is presented to address stability issues caused by low-inertia converter interfaces. Recently, droop control loops are also modified to improve stability. The VSM and the frequency-droop are both derived from the property imitation of synchronous generators (SGs) while researched independently. In this paper, by simplifications in the steady state, the expression of the inertia emulation of the VSM algorithm based on the second-order SG model is linearized as a first-order ordinary differential equation. In frequency-droop loops, as the instantaneous power components are commonly passed through a low-pass filter for disturbance rejection, the system function of the droop control can also be transformed into a first-order ordinary differential equation, which is equivalent to that of the VSM under certain conditions. In terms of the inertia constant, the swing equation is normalized under per unit representation. By the same simplification in the VSM linearization, the equivalence between the linearized VSM and the SG is also demonstrated. Therefore, the equivalence among SGs, the VSM, and the frequency-droop are summarized, which provides insights for coordinative control of power converters integrated into current SG dominating power systems. For a specific synchronous generator, the equivalence conditions are verified by simulation.
Weichao Zhang; Xiangwu Yan. Equivalence Analysis of Virtual Synchronous Machines and Frequency-Droops for Inertia Emulation in Power Systems with Converter-Interfaced Renewables. Journal of Electrical Engineering & Technology 2020, 15, 1167 -1175.
AMA StyleWeichao Zhang, Xiangwu Yan. Equivalence Analysis of Virtual Synchronous Machines and Frequency-Droops for Inertia Emulation in Power Systems with Converter-Interfaced Renewables. Journal of Electrical Engineering & Technology. 2020; 15 (3):1167-1175.
Chicago/Turabian StyleWeichao Zhang; Xiangwu Yan. 2020. "Equivalence Analysis of Virtual Synchronous Machines and Frequency-Droops for Inertia Emulation in Power Systems with Converter-Interfaced Renewables." Journal of Electrical Engineering & Technology 15, no. 3: 1167-1175.
As the increasing penetration of inverter-based generation (IBG) and the consequent displacement of traditional synchronous generators (SGs), the system stability and reliability deteriorate for two reasons: first, the overall inertia decreases since the power electronic interfaces (PEIs) are almost inertia-less; second, renewable generation profiles are largely influenced by stochastic meteorological conditions. To strengthen power systems, the concept of the virtual synchronous generator (VSG) has been proposed, which controls the external characteristics of PEIs to emulate those of SGs. Currently, PEIs could perform short-term inertial and primary frequency responses through the VSG algorithm. For renewable energy sources (RES), deloading strategies enable the generation units to possess active power reserves for system frequency responses. Additionally, the deloading strategies could provide the potential for renewable generation to possess long-term frequency regulation abilities. This paper focuses on emulation strategies and economic dispatch for IBG units to perform multiple temporal frequency control. By referring to the well-established knowledge systems of generation and operation in conventional power systems, the current VSG algorithm is extended and complemented by the emulation of secondary and tertiary regulations. The reliability criteria are proposed, considering the loss of load probability (LOLP) and renewable spillage probability (RSP). The reliability criteria are presented in two scenarios, including the renewable units operated in maximum power point tracking (MPPT) and VSG modes. A LOLP-based economic dispatch (ED) approach is solved to acquire the generation and reserve schemes. The emulation strategies and the proposed approach are verified by simulation.
Weichao Zhang; Xiangwu Yan; Hanyan Huang. Emulation Strategies and Economic Dispatch for Inverter-Based Renewable Generation under VSG Control Participating in Multiple Temporal Frequency Control. Applied Sciences 2020, 10, 1303 .
AMA StyleWeichao Zhang, Xiangwu Yan, Hanyan Huang. Emulation Strategies and Economic Dispatch for Inverter-Based Renewable Generation under VSG Control Participating in Multiple Temporal Frequency Control. Applied Sciences. 2020; 10 (4):1303.
Chicago/Turabian StyleWeichao Zhang; Xiangwu Yan; Hanyan Huang. 2020. "Emulation Strategies and Economic Dispatch for Inverter-Based Renewable Generation under VSG Control Participating in Multiple Temporal Frequency Control." Applied Sciences 10, no. 4: 1303.
With the development of electric vehicles in China, the impact of the electrical performance of electric vehicle charging equipment on electric vehicle battery can not be ignored. A test system for the field test of off-board charger electrical performance is presented in this paper. The test system is composed of hardware devices and control system. The hardware devices include a power module, a load module, a measurement module, and a protection module. The load module uses a lightweight controllable charging load to reduce the weight and volume of test system for field test needs. The control system can control the test process and analysis test data. Taking the stabilized voltage precision test as an example, an off-board charger is tested and the test results are analyzed in this paper.
Ling Wang; Zisheng Liu; Shuaishuai Zhao; Zhichao Chai; Xiangwu Yan. Test System for the Field Test of Off-Board Charger Electrical Performance. IOP Conference Series: Materials Science and Engineering 2019, 677, 052044 .
AMA StyleLing Wang, Zisheng Liu, Shuaishuai Zhao, Zhichao Chai, Xiangwu Yan. Test System for the Field Test of Off-Board Charger Electrical Performance. IOP Conference Series: Materials Science and Engineering. 2019; 677 (5):052044.
Chicago/Turabian StyleLing Wang; Zisheng Liu; Shuaishuai Zhao; Zhichao Chai; Xiangwu Yan. 2019. "Test System for the Field Test of Off-Board Charger Electrical Performance." IOP Conference Series: Materials Science and Engineering 677, no. 5: 052044.
An electric vehicle power battery simulation system simulating different power battery packs for the field test of the off-board charger is designed, which can be used to test the performance of an off-board charger. Specifically, the improved power battery model is combined with the improved lightweight charging load and the online estimation of the state of charge as well as the electromotive force of the battery model are used to adjust charging load parameters in real time to simulate the charging response. An acceleration coefficient is introduced into the traditional battery model to improve test efficiency, and the type, specification, temperature and voltage parameters of the battery can be set online according to the test requirements. An improved charging load scheme is proposed, in which a DC converter cascaded power battery pack of the mobile test vehicle is used to form a lightweight charging load with the mode of constant voltage, constant current, constant power and constant resistance and the ability to be adjusted continuously within the rated range. As a result, the size and weight of the charging load are reduced and the autonomous test of the off-board charger is realized. The performances of the proposed battery simulation system are validated through the various experimental results.
Xiangwu Yan; Ling Wang; Zhichao Chai; Shuaishuai Zhao; Zisheng Liu; Xuewei Sun. Electric Vehicle Battery Simulation System for Mobile Field Test of Off-Board Charger. Energies 2019, 12, 3025 .
AMA StyleXiangwu Yan, Ling Wang, Zhichao Chai, Shuaishuai Zhao, Zisheng Liu, Xuewei Sun. Electric Vehicle Battery Simulation System for Mobile Field Test of Off-Board Charger. Energies. 2019; 12 (15):3025.
Chicago/Turabian StyleXiangwu Yan; Ling Wang; Zhichao Chai; Shuaishuai Zhao; Zisheng Liu; Xuewei Sun. 2019. "Electric Vehicle Battery Simulation System for Mobile Field Test of Off-Board Charger." Energies 12, no. 15: 3025.
In view of the fact that the electronic load used in the on-site detection of the electric vehicle off-board charger is large and heavy, and it would be limited by some external factors such as the space and load of the detection vehicle and the height of the underground garage. In addition, considering that if using the power batteries of mobile detection vehicle as charging load directly, it's charging modes and parameters are unitary, the state of charge (SOC) and electromotive force also cannot be flexibly set, which would result in long charging time, low efficiency, limited test range and items. This paper proposes a topological scheme that the lightweight controllable charging load consists of a vehicle-mounted power battery pack and a cascaded DC/DC converter, researches the double-closed loop control methods such as constant input voltage, constant load resistance as well, further comes true the typical working modes: constant input voltage, constant load resistance. Moreover the operating modes have the ability to continuously adjust in the rated range. In a word, the proposed scheme can achieve self-test of the off-board charger while reducing the weight of the charging load. Finally, the simulation model in Matlab/Simulink is established to verify the feasibility of the proposed topology and the effectiveness of the control methods.
Yan Wang; Haowen Wu; Zhichao Chai; Ling Wang; Xianwen Zhu; Yong Xiao; Xiangwu Yan; Jia He. Lightweight Controllable Charging Load for Motion Detection of Off-Board Charger. IOP Conference Series: Earth and Environmental Science 2019, 252, 032172 .
AMA StyleYan Wang, Haowen Wu, Zhichao Chai, Ling Wang, Xianwen Zhu, Yong Xiao, Xiangwu Yan, Jia He. Lightweight Controllable Charging Load for Motion Detection of Off-Board Charger. IOP Conference Series: Earth and Environmental Science. 2019; 252 (3):032172.
Chicago/Turabian StyleYan Wang; Haowen Wu; Zhichao Chai; Ling Wang; Xianwen Zhu; Yong Xiao; Xiangwu Yan; Jia He. 2019. "Lightweight Controllable Charging Load for Motion Detection of Off-Board Charger." IOP Conference Series: Earth and Environmental Science 252, no. 3: 032172.
Performance status evaluation is essential for the safe running of electric vehicle (EV) charging infrastructure. With the development of the EV industry, the EV charging infrastructure industry has advanced considerably. Safe and reliable operation of the charging infrastructure is important for the development of EVs. As such, we propose a comprehensive evaluation method to assess the performance condition of an EV charging infrastructure. First, based on the analysis of the existing EV charging principles, we established an evaluation index system for EV charging infrastructure. Second, the subjective weight, objective weight, and comprehensive weight of the index system were determined through analytic hierarchy processes (AHP) and the entropy weight method. Then, we used fuzzy comprehensive evaluation to appraise the performance of the charging infrastructure through expert investigation. Finally, based on the actual data from an EV charger, the performance conditions of the EV charging infrastructure were evaluated to demonstrate the feasibility of the method and the reliability of the index system.
Qiushuo Li; Yong Xiao; Shuaishuai Zhao; Xianwen Zhu; Zongyi Wang; Zisheng Liu; Ling Wang; Xiangwu Yan; Yan Wang. Performance Status Evaluation of an Electric Vehicle Charging Infrastructure Based on the Fuzzy Comprehensive Evaluation Method. World Electric Vehicle Journal 2019, 10, 35 .
AMA StyleQiushuo Li, Yong Xiao, Shuaishuai Zhao, Xianwen Zhu, Zongyi Wang, Zisheng Liu, Ling Wang, Xiangwu Yan, Yan Wang. Performance Status Evaluation of an Electric Vehicle Charging Infrastructure Based on the Fuzzy Comprehensive Evaluation Method. World Electric Vehicle Journal. 2019; 10 (2):35.
Chicago/Turabian StyleQiushuo Li; Yong Xiao; Shuaishuai Zhao; Xianwen Zhu; Zongyi Wang; Zisheng Liu; Ling Wang; Xiangwu Yan; Yan Wang. 2019. "Performance Status Evaluation of an Electric Vehicle Charging Infrastructure Based on the Fuzzy Comprehensive Evaluation Method." World Electric Vehicle Journal 10, no. 2: 35.
Due to the irreversible energy substitution from fossil fuels to clean energy, the development trend of future power systems is based on renewable energy generation. However, due to the incompatibility of converter-based non-dispatchable renewable energy generation, the stability and reliability of traditional power systems deteriorate as more renewables are introduced. Since conventional power systems are dominated by synchronous machines (SM), it is natural to utilize a virtual synchronous generator (VSG) control strategy that intimates SM characteristics on integrated converters. The VSG algorithm developed in this paper originates from mimicking mathematic models of synchronous machines. Among the different models of implementation, the second-order model is simple, stable, and compatible with the control schemes of current converters in traditional power systems. The VSG control strategy is thoroughly researched and case studied for various converter-interfaced systems that include renewable generation, energy storage, electric vehicles (EV), and other energy demands. VSG-based integration converters can provide grid services such as spinning reserves and inertia emulation to the upper grids of centralized plants, distributed generation networks, and microgrids. Thus, the VSG control strategy has paved a feasible way for an evolutionary transition to a power electronics-based future power grid. By referring to the knowledge of traditional grids, a hierarchical system of operations can be established. Finally, generation and loads can be united in universal compatibility architecture under consolidated synchronous mechanisms.
Xiangwu Yan; Weichao Zhang. Review of VSG Control-Enabled Universal Compatibility Architecture for Future Power Systems with High-Penetration Renewable Generation. Applied Sciences 2019, 9, 1484 .
AMA StyleXiangwu Yan, Weichao Zhang. Review of VSG Control-Enabled Universal Compatibility Architecture for Future Power Systems with High-Penetration Renewable Generation. Applied Sciences. 2019; 9 (7):1484.
Chicago/Turabian StyleXiangwu Yan; Weichao Zhang. 2019. "Review of VSG Control-Enabled Universal Compatibility Architecture for Future Power Systems with High-Penetration Renewable Generation." Applied Sciences 9, no. 7: 1484.
The penetration of renewable energy sources (RES) into a grid via inverters causes a stability issue due to the absence of an inertia. A virtual synchronous generator (VSG) is designed to provide an artificial inertia and droop control to the grid-connected inverters. The different power ratings of multiple VSGs create complications in the coordination due to unequal droop or damping coefficient ‘ D ’. The dependency of a factor ‘ D ’ on P − ω droop control under static state and a damping behavior during power oscillation under dynamic state is analyzed by considering three cases on multi-VSGs microgrid system and the equivalent equations of P − ω droop control are derived for all three cases to see the effect of a load on the overall system’s frequency. A master–slave configuration of a VSG is proposed to deliver maximum power during static state, but provides P − ω control during the dynamic state. Simulation results verify the improvement introduced by the proposed VSG control.
Xiangwu Yan; Aazim Rasool; Farukh Abbas; Haaris Rasool; Hongxia Guo. Analysis and Optimization of the Coordinated Multi-VSG Sources. Electronics 2018, 8, 28 .
AMA StyleXiangwu Yan, Aazim Rasool, Farukh Abbas, Haaris Rasool, Hongxia Guo. Analysis and Optimization of the Coordinated Multi-VSG Sources. Electronics. 2018; 8 (1):28.
Chicago/Turabian StyleXiangwu Yan; Aazim Rasool; Farukh Abbas; Haaris Rasool; Hongxia Guo. 2018. "Analysis and Optimization of the Coordinated Multi-VSG Sources." Electronics 8, no. 1: 28.
Large-scale wind farms connect to the grid and deliver electrical energy to the load center. When a short-circuit fault occurs on the transmission line, there will be an excess of electric power, but the power demand will increase instantaneously once the fault is removed. The conventional additional frequency control strategies of wind farms can effectively reduce the frequency fluctuation caused by load mutation, but still there are some limitations for the frequency fluctuation caused by the whole process of occurrence, development and removal of a short-circuit fault on the transmission line. Therefore, this paper presents an improved additional frequency control strategy for wind farms. According to the variation law of system frequency during the whole process of a short-circuit fault, the proposed strategy revises the parameters in conventional additional frequency control of the doubly-fed induction generator (DFIG) to have effective damping characteristics throughout the entire process from failure to removal, thereby the output power of DFIGs could respond to frequency fluctuation rapidly. MATLAB/ Simulink is used to build a four-machine two-area model for simulation analysis. The results show that the control strategy can effectively reduce the frequency fluctuation of DFIGs, and enhance the stability of the system.
Xiangwu Yan; Zijun Song; Yun Xu; Ying Sun; Ziheng Wang; Xuewei Sun. Study of Inertia and Damping Characteristics of Doubly Fed Induction Generators and Improved Additional Frequency Control Strategy. Energies 2018, 12, 38 .
AMA StyleXiangwu Yan, Zijun Song, Yun Xu, Ying Sun, Ziheng Wang, Xuewei Sun. Study of Inertia and Damping Characteristics of Doubly Fed Induction Generators and Improved Additional Frequency Control Strategy. Energies. 2018; 12 (1):38.
Chicago/Turabian StyleXiangwu Yan; Zijun Song; Yun Xu; Ying Sun; Ziheng Wang; Xuewei Sun. 2018. "Study of Inertia and Damping Characteristics of Doubly Fed Induction Generators and Improved Additional Frequency Control Strategy." Energies 12, no. 1: 38.
Renewable energy sources are integrated into a grid via inverters. Due to the absence of an inherent droop in an inverter, an artificial droop and inertia control is designed to let the grid-connected inverters mimic the operation of synchronous generators and such inverters are called virtual synchronous generators (VSG). Sudden addition, removal of load or faults in the grid causes power and frequency oscillations in the grid. The steady state droop control of VSG is not effective in dampening such oscillations. Therefore, a new control scheme, namely bouncy control, has been introduced. This control uses a variable emergency gain, to enhance or reduce the power contribution of individual VSGs during a disturbance. The maximum power contribution of an individual VSG is limited by its power rating. It has been observed that this control, successfully minimized the oscillation of electric parameters and the power system approached steady state quickly. Therefore, by implementing bouncy control, VSGs can work in coordination to make the grid more robust. The proposed controller is verified through Lyapunov stability analysis.
Aazim Rasool; Xiangwu Yan; Haaris Rasool; Hongxia Guo; Mansoor Asif. VSG Stability and Coordination Enhancement under Emergency Condition. Electronics 2018, 7, 202 .
AMA StyleAazim Rasool, Xiangwu Yan, Haaris Rasool, Hongxia Guo, Mansoor Asif. VSG Stability and Coordination Enhancement under Emergency Condition. Electronics. 2018; 7 (9):202.
Chicago/Turabian StyleAazim Rasool; Xiangwu Yan; Haaris Rasool; Hongxia Guo; Mansoor Asif. 2018. "VSG Stability and Coordination Enhancement under Emergency Condition." Electronics 7, no. 9: 202.
This paper investigates how to develop a two-stage voltage-type grid-connected control method for renewable energy inverters that can make them simulate the characteristics of a synchronous generator governor. Firstly, the causes and necessities of the failure zone are analyzed, and thus the traditional static frequency characteristics are corrected. Then, a novel inverter control scheme with the governor’s failure zone characteristics is proposed. An enabling link and a power loop are designed for the inverter to compensate fluctuations and regulate frequency automatically. Outside the failure zone, the inverter participates in the primary frequency regulation by disabling the power loop. In the failure zone, the droop curve is dynamically moved to track the corrected static frequency characteristic by enabling the power loop, resisting the fluctuation of grid frequency. The direct current (DC) bus voltage loop is introduced into the droop control to stabilize the DC bus voltage. Moreover, the designed dispatch instruction interface ensures the schedulability of the renewable energy inverter. Finally, the feasibility and effectiveness of the proposed control method are verified by simulation results from MATLAB (R2016a).
Xiangwu Yan; Xueyuan Zhang; Bo Zhang; Zhonghao Jia; Tie Li; Ming Wu; Jun Jiang. A Novel Two-Stage Photovoltaic Grid-Connected Inverter Voltage-Type Control Method with Failure Zone Characteristics. Energies 2018, 11, 1865 .
AMA StyleXiangwu Yan, Xueyuan Zhang, Bo Zhang, Zhonghao Jia, Tie Li, Ming Wu, Jun Jiang. A Novel Two-Stage Photovoltaic Grid-Connected Inverter Voltage-Type Control Method with Failure Zone Characteristics. Energies. 2018; 11 (7):1865.
Chicago/Turabian StyleXiangwu Yan; Xueyuan Zhang; Bo Zhang; Zhonghao Jia; Tie Li; Ming Wu; Jun Jiang. 2018. "A Novel Two-Stage Photovoltaic Grid-Connected Inverter Voltage-Type Control Method with Failure Zone Characteristics." Energies 11, no. 7: 1865.
The lack of inertia and damping mechanism of photovoltaic (PV) grid-connected systems controlled by maximum power point tracking (MPPT) poses a challenge for the safety and stability of the grid. Virtual synchronous generator (VSG) technology has attracted wide attention, since it can make PV grid-connected inverter present the external characteristics of a synchronous generator (SG). Nevertheless, traditional PV-VSG is generally equipped with an energy storage device, which leads to many problems, such as increased costs, space occupation, and post-maintenance. Thus, this paper proposes a two-stage improved PV-VSG control method based on an adaptive-MPPT algorithm. When PV power is adequate, the adaptive-MPPT allows the PV to change the operating point within a stable operation area to actualize system supply-demand, matching in accordance to the load or dispatching power demand; when PV power is insufficient, PV achieves traditional MPPT control to reduce power shortage; simultaneously, improved VSG control prevents the DC bus voltage from falling continuously to ensure its stability. The proposed control approach enables the two-stage PV-VSG to supply power to loads or connect to the grid without adding additional energy storage devices, the effectiveness of which in off-grid and grid-connected modes is demonstrated by typical simulation conditions.
Xiangwu Yan; Jiajia Li; Ling Wang; Shuaishuai Zhao; Tie Li; Zhipeng Lv; Ming Wu. Adaptive-MPPT-Based Control of Improved Photovoltaic Virtual Synchronous Generators. Energies 2018, 11, 1834 .
AMA StyleXiangwu Yan, Jiajia Li, Ling Wang, Shuaishuai Zhao, Tie Li, Zhipeng Lv, Ming Wu. Adaptive-MPPT-Based Control of Improved Photovoltaic Virtual Synchronous Generators. Energies. 2018; 11 (7):1834.
Chicago/Turabian StyleXiangwu Yan; Jiajia Li; Ling Wang; Shuaishuai Zhao; Tie Li; Zhipeng Lv; Ming Wu. 2018. "Adaptive-MPPT-Based Control of Improved Photovoltaic Virtual Synchronous Generators." Energies 11, no. 7: 1834.
This study introduces a three-phase virtual synchronous motor (VSM) control and its possible application for providing fast-charging service from off-board chargers of electric vehicles (EVs). The main circuit of the off-board charger consists of a three-phase voltage source PWM rectifier (VSR) and a resonant LLC zero-voltage-switching converter. In the proposed control approach, VSM-controlled pre-stage VSR emulates the external characteristics of a synchronous motor (SM), simultaneously, droop control based on charging mode in the VSM can satisfy the demand of the EVs constant-current fast-charging; The post-stage DC–DC converter is responsible for stabilizing the DC bus voltage. The feature of this control strategy is that VSM and fast charging control are implemented by the pre-stage converter, which has better coordination. In the MATLAB, the equivalent synchronous grid of the distribution network supplies to the power battery through the off-board charger, and the effectiveness of the presented control is demonstrated by typical working conditions.
Xiangwu Yan; Jiajia Li; Bo Zhang; Zhonghao Jia; Yang Tian; Hui Zeng; Zhipeng Lv. Virtual Synchronous Motor Based-Control of a Three-Phase Electric Vehicle Off-Board Charger for Providing Fast-Charging Service. Applied Sciences 2018, 8, 856 .
AMA StyleXiangwu Yan, Jiajia Li, Bo Zhang, Zhonghao Jia, Yang Tian, Hui Zeng, Zhipeng Lv. Virtual Synchronous Motor Based-Control of a Three-Phase Electric Vehicle Off-Board Charger for Providing Fast-Charging Service. Applied Sciences. 2018; 8 (6):856.
Chicago/Turabian StyleXiangwu Yan; Jiajia Li; Bo Zhang; Zhonghao Jia; Yang Tian; Hui Zeng; Zhipeng Lv. 2018. "Virtual Synchronous Motor Based-Control of a Three-Phase Electric Vehicle Off-Board Charger for Providing Fast-Charging Service." Applied Sciences 8, no. 6: 856.