Impedance Analysis of Voltage Source Converter Using Direct Power Control

Gao, Shuning; Zhao, Haoran; Gui, Yonghao; Luo, Jia; Blaabjerg, Frede

doi:10.1109/tec.2020.3020181

Cited by 21 publications

(18 citation statements)

References 35 publications

(43 reference statements)

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“…Roughly speaking, the research works can be classified into two categories: those that view phase‐locked‐loop (PLL) dynamics as the major influencing factor 6‐11,15,16 and those that view outer control as the major influencing factor 12‐14,17‐20 …”

Section: Introductionmentioning

confidence: 99%

“…

italicdq

‐axis current errors are used as the feedback signals for the modulation blocks. To avoid the negative effect from PLL in the weak grid, References 15,16 propose the alternative control strategies which do not require the PLL for the synchronization. Reference 15 proposes a unified virtual synchronous control that can make the VSC emulate the rotor behavior of a synchronous generator to realize grid synchronization.…”

Section: Introductionmentioning

confidence: 99%

“…Reference 15 proposes a unified virtual synchronous control that can make the VSC emulate the rotor behavior of a synchronous generator to realize grid synchronization. The control strategy for the VSC in Reference 16 is the direct power control and it omits the inner current loop and PLL. Our prior research in Reference 21 indicates that PLL does influence stability, a finding documented in References 6,7.…”

Section: Introductionmentioning

confidence: 99%

“…A hardware testbed of a grid‐interfaced converter with the ability of demonstrating low‐frequency oscillations has not been seen in the literature. Among those references in Section 1.2, only References 15,16,19,20 validate the proposed control systems using hardware testbeds. References 15,16 actually use the control hardware‐in‐the‐loop (CHIL) testbed for the validation and there is no physical circuit and IGBT‐based inverter employed.…”

Section: Introductionmentioning

confidence: 99%

“…Among those references in Section 1.2, only References 15,16,19,20 validate the proposed control systems using hardware testbeds. References 15,16 actually use the control hardware‐in‐the‐loop (CHIL) testbed for the validation and there is no physical circuit and IGBT‐based inverter employed. So their real‐time results do not include the physical dynamics from the IGBTs and LC components.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Stability enhancement module for grid‐following converters: Hardware implementation and validation

Fan

Zhou

et al. 2021

Int Trans Electr Energ Syst

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Summary Low‐frequency oscillations limit power delivery of voltage‐source converter interfaced resources, for example, wind and solar, operating in grid‐following control mode. Our prior research identified the instability mechanism as the coupling between real power and voltage at point of common coupling. In turn, a stability enhancement control was proposed to weaken the coupling by introducing a simple voltage‐based feedback loop. The stability enhancement control has been validated via electromagnetic transient simulation testbeds. The objectives of this paper are (a) to provide a more insightful explanation of the enhancement module by examining the impedance of the grid‐following converter and (b) to verify the performance of the stability module using a hardware testbed. The theoretic examination demonstrates that stability enhancement module effectively reduces the negative resistance effect of Zqq and thus boosts stability. The experimental research leads to a hardware testbed of a grid‐following converter with the ability of demonstrating low‐frequency oscillations. The experimental results demonstrate the efficacy of the proposed stability enhancement control and the readiness of commercial realization of the stability enhancement unit.

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Section: Introductionmentioning

confidence: 99%

“…

italicdq

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Stability enhancement module for grid‐following converters: Hardware implementation and validation

Fan

Zhou

et al. 2021

Int Trans Electr Energ Syst

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Power quality improvement using 18 sector algorithm based direct power control

Rath

Kumar

Srungavarapu

et al. 2021

Int Trans Electr Energ Syst

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Predefined lookup table inspired direct power control techniques have been used mostly for active front end rectifiers. As an intransigent switching pattern is followed here, the effectiveness of the converter is hampered when the operating parameters change. Apart from that, the switching table design is attributed only to the sign of power demand. In this work, the magnitude of the power demand along with its sign is considered for the selection of the switching vector. The phase angle of the grid voltage vector is estimated using the virtual flux technique. The magnitude of active and reactive powers transferred from the grid to the converter depends on the switching vector of the converter and the phase angle of the grid voltage vector. Conventional methods of Direct Power Control have used 12 sector-based divisions. The switching vector is selected depending on the 30 slabs to which the grid voltage vector belongs. With the advent of high-speed microcontrollers, it is possible to improve the accuracy of the conventional DPC with increased resolution in the switching vector selection. So, in this work, one complete cycle of the grid voltage vector is divided into 18 sectors instead of 12 sectors to locate the grid voltage vector more accurately. Finally, a redesigned algorithm is customed to select the most suited vector that meets the power demands of the active front end rectifier at that particular phase angle. The feasibility of the proposed technique is verified with MATLAB simulations and experiments conducted in the laboratory.

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An adaptive phase‐locked loop‐less control strategy for LCL‐filtered grid‐connected inverter under complex grid conditions

Huang

Chen

et al. 2022

Circuit Theory & Apps

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The phase-locked loop, as a method to extract grid voltage phase angle, is commonly used for grid-connected inverter to synchronize the injected grid current with the grid. However, the phase-locked loop will also bring some problems. The current loop controller, the phase-locked loop, and the grid impedance are coupled together under the weak grid. Then, the phase angle of the inverter output impedance will be reduced, causing the system to be unstable. Moreover, the output phase angle of the phase-locked loop participates in the coordinate transformation under the unbalanced grid voltage condition, which degrades the quality of the injected grid current generated by the inverter with high harmonic content. Therefore, a vector current control strategy without phase-locked loop derived from direct power control is used in this paper. An adaptive linear Kalman filter algorithm is also applied to observe the voltage information and avoid the harmonic problems caused by power calculation. Finally, simulations and experiments are conducted to verify that the proposed method is effective, and the results are consistent with the theoretical analysis. K E Y W O R D Sgrid-connected inverter, Kalman filter, phase-locked loop, unbalanced grid voltage, weak grid | INTRODUCTIONDistributed generation systems, such as photovoltaic or wind energy, use power converter as an interface to the grid, so the performance of distributed power grid-connected converter directly affects the system reliability. 1,2 Aiming to achieve safe and efficient operation of grid connection, the synchronization of injected current with the voltage of the common coupling point (PCC) is one of the most important issues. 3 Especially, in the event of grid voltage distortion or imbalance, it is necessary to design a reliable synchronous algorithm with fast response and small error.At present, in order to synchronize grid-connected current with the grid voltage phase angle, the phase-locked loop (PLL) is commonly used. 4,5 However, PLL can also have some adverse effects on the system. Under the influence of PI controllers of PLLs connected to weak grids, phase information of the output will be disturbed by small signals disrupting the phase information. Due to this, the grid-connected inverter's coordinate system does not coincide with its

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Impedance Analysis of Voltage Source Converter Using Direct Power Control

Cited by 21 publications

References 35 publications

Stability enhancement module for grid‐following converters: Hardware implementation and validation

Stability enhancement module for grid‐following converters: Hardware implementation and validation

Power quality improvement using 18 sector algorithm based direct power control

An adaptive phase‐locked loop‐less control strategy for LCL‐filtered grid‐connected inverter under complex grid conditions

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