Power Quality Mitigation in Weak AC Grid with Low X/R Ratios using Distribution Static Compensator Controlled by LMF Algorithm
05 Jun 2020-
TL;DR: In this paper, a solution to mitigate power quality issues in the weak grid to minimize the effect of low X/R ratio at a higher level of WE penetration using distribution static compensator (DSTATCOM) controlled by a least mean fourth (LMF) algorithm is presented.
Abstract: Penetration of WE sources into the weak AC grid with low X/R ratio in the presence of unbalanced loads is a major cause of poor power quality (PQ). In such a scenario, WE penetration with higher levels becomes a significant challenge in the utility grid. This paper presents a solution to mitigate power quality issues in the weak grid to minimize the effect of low X/R ratio at a higher level of WE penetration using distribution static compensator (DSTATCOM) controlled by a least mean fourth (LMF) algorithm. This control algorithm extracting the active and reactive weight component of the unbalanced load current to estimate reference signals, which helps to generate gate pulses for DSTATCOM. The LMF algorithm has been tested successfully for maintaining voltage stability and PQ at a higher level of WE penetration in the weak grid.
Citations
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TL;DR: In this article , the frequency and voltage compliance capabilities of three grid-forming controls in an offshore wind farm are investigated and benchmarked, and it is concluded that the virtual synchronous machine is the most compliant grid-formation control and that DC-link modeling is of great importance when testing compliance during frequency disturbances.
Abstract: Weak grid conditions challenge the grid integration of offshore wind farms. Especially grids with low inertia and large grid impedance questions frequency and voltage compliance capabilities. Grid-forming wind turbines are a promising technology for weak grids due to the nature of their control strategy. This paper explains the difference in how weak grid conditions are described in the literature and shows how the voltage stability margin changes with the short-circuit ratio and X/R ratio. With that knowledge, the frequency and voltage compliance capabilities of three grid-forming controls in an offshore wind farm are investigated and benchmarked. These three controls are a droop control, a virtual synchronous machine, and a synchronverter. This was done by quantifying their performance during a frequency disturbance with sensitivity to the short-circuit ratio, X/R ratio, and the inertia constant, H. It is concluded that the virtual synchronous machine is the most compliant grid-forming control and that DC-link modeling is of great importance when testing compliance during frequency disturbances.
1 citations
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10 Dec 2022
TL;DR: In this paper , the authors used the existing distribution network for evacuating the surplus power from the micro-grids and also to deliver quality power to the last mile, and the proposed model establishes the improvements in the power quality and the reduction in power losses during peak loading condition even for the farthest loads.
Abstract: Integrating micro-grids for rural electrification as well as allowing bidirectional power flow in the existing distribution system is a huge challenge. Smart devices have made the system well monitored and controlled but the existing infrastructure is ageing. The main focus in this work is to use the existing distribution network for evacuating the surplus power from the micro-grids and also to deliver quality power to the last mile. In this work, computational algorithms developed in MATLAB have been validated by a real system simulated in PSCAD. The algorithm works both for planning and operating the distribution network at a desirable efficiency, benefitting the distribution system operators and the micro-grid agencies. The proposed model establishes the improvements in the power quality and the reduction in ohmic power losses during peak loading condition even for the farthest loads.
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04 Nov 2022
TL;DR: In this article , a virtual inductance control scheme is proposed to reduce the interaction between the d-axis and q-axes, which can improve system stability without sacrificing dynamic performances. But, the proposed scheme is not suitable for the DSTACOMs under weak grid conditions.
Abstract: Distributed static compensators (DSTATCOMs) are voltage source converter-based devices to support the voltage stability of power networks. Although the reactive-voltage droop curve is necessary for the DSTATCOMs to realize voltage regulation and reactive power compensation, it also creates an additional loop between the d-axis and q-axis current control of the DSTACOMs. As such, the interaction between the d-axis and q-axis current control may cause instability problems, especially under weak grid conditions. Such negative interaction effects can be alleviated by introducing damping resistances. However, the additional resistances may affect the dynamic performances. To solve this issue, a novel virtual inductance control scheme is proposed to reduce the interaction between the d- and q-axes. The coupling effects of the d- and q-axes can be alleviated by the introduced virtual inductor. Consequently, system stability can be improved without sacrificing dynamic performances. The effectiveness of the proposed control scheme is validated by MATLAB/Simulink simulation results.
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30 Aug 2022
TL;DR: In this article , the authors have shown that the virtual synchronous machine performs best regarding frequency and voltage compliance in weak grids under a frequency disturbance, where the frequency disturbance is scaled to 5% of the installed capacity.
Abstract: Grid-forming wind turbines are a promising technology for weak grids with a high penetration of converter-based power sources. The droop control, the synchronverter, and the virtual synchronous machine grid-forming control topologies are benchmarked by voltage and frequency stability performance from a frequency disturbance under different grid conditions (by varying short-circuit ratio, X/R ratio, and the inertia). The wind turbines are modelled in an offshore wind farm application and the frequency disturbance are scaled to 5% of the installed capacity. The study have shown that the virtual synchronous machine performs best regarding frequency and voltage compliance in weak grids under a frequency disturbance. DC-link modelling is essential for dynamic simulations of grid-forming converters, as grid perturbations can drain the link for energy.
References
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TL;DR: In this article, a mixed integer linear optimization model is proposed to simulate an integrated power and heating energy systems, including a CHP model capable of accounting for the commitment decisions and nonconvex energy generation constraints.
Abstract: With the largest installed capacity in the world, wind power in China is experiencing a ∼20% curtailment. The inflexible combined heat and power (CHP) has been recognized as the major barrier for integrating the wind source. The approach to reconcile the conflict between inflexible CHP units and variable wind power in Chinese energy system is yet unclear. This paper explores the technical and economic feasibility of deploying the heat storage tanks and electric boilers under typical power grids and practical operational regulations. A mixed integer linear optimization model is proposed to simulate an integrated power and heating energy systems, including a CHP model capable of accounting for the commitment decisions and nonconvex energy generation constraints. The model is applied to simulate a regional energy system (Jing–Jin–Tang) covering 100-million population, with hourly resolution over a year, incorporating actual data, and operational regulations. The results project an accelerating increase in wind curtailment rate at elevated wind penetration. Investment for wind breaks even at 14% wind penetration. At such penetration, the electric boiler (with heat storage) is effective in reducing wind curtailment. The investment in electric boilers is justified on a social economic basis, but the revenues for different stakeholders are not distributed evenly.
88 citations
"Power Quality Mitigation in Weak AC..." refers background in this paper
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TL;DR: In this paper, a combined wind farm controller based on Model Predictive Control (MPC) is proposed to improve the voltage control of wind farm collector systems, considering the significant impact of active power on voltage variations due to the low $X/R$ ratio.
Abstract: This paper proposes a combined wind farm controller based on Model Predictive Control (MPC). Compared with the conventional decoupled active and reactive power controls, the proposed control scheme considers the significant impact of active power on voltage variations due to the low $X/R$ ratio of wind farm collector systems. The voltage control is improved. Besides, by coordination of active and reactive powers, the Var capacity is optimized to prevent potential failures due to Var shortage, especially when the wind farm operates close to its full load. An analytical method is used to calculate the sensitivity coefficients to improve the computation efficiency and overcome the convergence problem. Two control modes are designed for both normal and emergency conditions. A wind farm with 20 wind turbines was used to verify the proposed combined control scheme.
49 citations
"Power Quality Mitigation in Weak AC..." refers methods in this paper
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TL;DR: In this paper, the effect of X/R ratio on reactive power requirements, voltage profile and stepvoltage variation at the Point of Common Coupling (PCC) of a wind farm connected to a distribution system was investigated.
Abstract: Existing technologies used for voltage regulation through reactive power control are mainly based on the reactance of the line while the line resistance is ignored. Hence, these solutions are appropriate for transmission networks where X/R ratio is high. However, this assumption does not hold for distribution systems as the value of line reactance is low, resulting in low X/R ratios. This paper investigates the effect of X/R ratio on reactive power requirements, voltage profile and step-voltage variation at the Point of Common Coupling (PCC) of a wind farm connected to a distribution system. The test distribution system has been modelled using different IEEE standard distribution systems. The results show that an increase in the X/R ratio increases the reactive power requirement and lowers the voltage at the PCC. However, lower X/R ratios increase the step-voltage variations as a function of wind power and adversely impact the power quality of the system.
14 citations
"Power Quality Mitigation in Weak AC..." refers background in this paper
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TL;DR: This paper presents a fuzzy logic based synchronous reference frame algorithm for distribution static compensator to enhance the power quality of a weak AC grid.
Abstract: This paper presents a fuzzy logic based synchronous reference frame algorithm for distribution static compensator to enhance the power quality of a weak AC grid. The proposed algorithm maintains constant DC-link voltage and extracts fundamental weighted values of load currents to es timate reference current. Thes e reference currents are utilized by DSTATCOM to mitigate the power quality. This control algorithm has been tested success fully in regulating the vol tage, mi tigating the harmonics, and load balancing for different types of loads at the point of common coupling.
8 citations
"Power Quality Mitigation in Weak AC..." refers background in this paper
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01 Jan 2017
6 citations
"Power Quality Mitigation in Weak AC..." refers background in this paper
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