Power Control of Photovoltaic Inverter under Unbalanced Grid Faults Considering Limits of Its Current Harmonics

2014 ◽  
Vol 960-961 ◽  
pp. 1356-1360 ◽  
Author(s):  
Yu Zhou ◽  
Zhi Yong Dai ◽  
Qiang Gang Wang ◽  
Ling Ye ◽  
Nian Cheng Zhou
Keyword(s):  
Power Control ◽  
Control Strategy ◽  
Reactive Power ◽  
Harmonic Distortion ◽  
Optimal Parameters ◽  
Current Harmonics ◽  
Power Characteristics ◽  
Active And Reactive Power ◽  
Fluctuation Amplitude ◽  
Unbalanced Grid

This paper studies the instantaneous output power characteristics of photovoltaic inverters and its flexible power control strategy under unbalanced grid faults. Then the optimal parameters model of the power control is established with minimum integrated fluctuation amplitude of the active and reactive power as a goal when the constraint of the output current harmonic distortion of photovoltaic inverters is taken into account. Finally, the optimal power control of photovoltaic inverters based on dead-beat current tracking is realized and the feasibility of the proposed control strategy is verified with the power system transient software PSCAD/EMTDC.

Decoupled Control Strategy of Grid Interactive Inverter System with Optimal LCL Filter Design

2013 ◽  
Vol 14 (5) ◽  
pp. 477-486 ◽  
Author(s):  
B. Chitti Babu ◽  
Anup Anurag ◽  
Tontepu Sowmya ◽  
Debati Marandi ◽  
Satarupa Bal
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Filter Design ◽  
Dynamic Performance ◽  
Harmonic Distortion ◽  
Voltage Source ◽  
Lcl Filter ◽  
Current Harmonics ◽  
Switching Losses ◽  
Active And Reactive Power

Abstract This article presents a control strategy for a three-phase grid interactive voltage source inverter that links a renewable energy source to the utility grid through a LCL-type filter. An optimized LCL-type filter has been designed and modeled so as to reduce the current harmonics in the grid, considering the conduction and switching losses at constant modulation index (Ma). The control strategy adopted here decouples the active and reactive power loops, thus achieving desirable performance with independent control of active and reactive power injected into the grid. The startup transients can also be controlled by the implementation of this proposed control strategy: in addition to this, optimal LCL filter with lesser conduction and switching copper losses as well as core losses. A trade-off has been made between the total losses in the LCL filter and the Total Harmonic Distortion (THD%) of the grid current, and the filter inductor has been designed accordingly. In order to study the dynamic performance of the system and to confirm the analytical results, the models are simulated in the MATLAB/Simulink environment, and the results are analyzed.

scholarly journals Predictive Direct Power Control for Dual-Active-Bridge Multilevel Inverter Based on Conservative Power Theory

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2951 ◽  
Author(s):  
Azuwien Aida Bohari ◽  
Hui Hwang Goh ◽  
Agustiono Kurniawan Tonni ◽  
Sze Sing Lee ◽  
Sy Yi Sim ◽  
...  
Keyword(s):  
Power Control ◽  
Reactive Power ◽  
Direct Power ◽  
Direct Power Control ◽  
Current Harmonics ◽  
Dual Active Bridge ◽  
Active And Reactive Power ◽  
Unbalanced Grid ◽  
Conservative Power Theory ◽  
Conservative Power

This paper explores the feasibility of multilevel dual-active bridge-inverter (DABMI) applications for grid-connected applications of a modern Model of Predictive Direct Power Control (MPDPC) based on the conservative power theory (CPT). In the case of unbalanced grid voltages, the objective of the study is to promote continued active and reactive energy in MPDPC without reducing efficiency such as transient response and current harmonics. The nature of the instantaneous p-q theory permits only one out of three control targets to be fulfilled. The proposed control approached directly regulates the instantaneous active and reactive power to achieve three particular control objectives namely sinusoidal and symmetrical grid current, cancelling twice of fundamental grid frequency reactive power ripples, and removing twice grid frequency active power ripple. The techniques of complicated Grid part sequence extraction are unnecessary and improved at no extra expense, as is the case with current MPDPC fault-tolerant approaches. The instantaneous power at the next sampling instant is predicted with the newly developed discrete-time model. Each possible switching state will then be evaluated in the cost function defined until the optimal state which lead to the minimum power errors is determined. In MATLAB/Simulink simulation, the proposed CPT-based MPDPC measures reliability and performance at balanced and unbalanced grid voltages then compared with the conventional and existing MPDPC The proposed method manages to achieve all of three control targets which generates sinusoidal grid currents and attenuates active and reactive power ripple of twice the grid frequency exactly at the same time without losing its critical efficiency including transient reaction and current harmonics.

scholarly journals Active and Reactive Power Compensation Control Strategy for VSC-HVDC Systems under Unbalanced Grid Conditions

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3140 ◽  
Author(s):  
Weiming Liu ◽  
Tingting Zheng ◽  
Ziwen Liu ◽  
Zhihua Fan ◽  
Yilong Kang ◽  
...  
Keyword(s):  
Control Strategy ◽  
Disturbance Observer ◽  
Reactive Power ◽  
Operating Conditions ◽  
Voltage Source ◽  
Double Frequency ◽  
Compensation Control ◽  
Active And Reactive Power ◽  
Passivity Based Control ◽  
Unbalanced Grid

This paper presents a power compensation strategy to suppress the double frequency power ripples of Voltage source converter high-voltage direct current (VSC-HVDC) systems under unbalanced grid voltage conditions. The mathematical control equations of the double frequency ripple power of VSC under unbalanced operating conditions are firstly derived and established, where the dynamic behaviors of the double frequency ripples in active and reactive power are regarded as being driven by current-relevant components and voltage-relevant components, respectively. Based on the equations, a power compensation control strategy of VSC-HVDC is proposed via the passivity-based control with disturbance observer to suppress both the current-relevant and voltage-relevant components in the power ripples. With this control strategy, the double frequency ripples in active and reactive power are suppressed simultaneously and system performance is significantly enhanced with the implementation of the disturbance observer in the passivity-based control. Theoretical stability analysis and simulation cases show the effectiveness and superiority of the proposed strategy.

Analysis on Power Output Capability and its Power Control Strategy of DFIG Wind Turbine under Unbalanced Grid Voltage

2013 ◽  
Vol 448-453 ◽  
pp. 1819-1824
Author(s):  
Shu Ju Hu ◽  
Ling Ling Wang ◽  
Ya Deng
Keyword(s):  
Power Control ◽  
Wind Turbine ◽  
Control Strategy ◽  
Power Output ◽  
Reactive Power ◽  
Maximum Output ◽  
Voltage Sags ◽  
Active And Reactive Power ◽  
Unbalanced Voltage ◽  
Power Limit

Wind turbines are required by gird codes that active and reactive power should be fed into power grid during gird faults such as voltage sags. Power output capability is important for DFIG wind turbine to provide active and reactive power support. Constraints of stator, rotor maximum current and maximum output voltage of rotor-side converter (RSC) of DFIG are considered to analyze stator power output limit of the DFIG under unbalanced voltage sags, and newton-raphson method is used to solve the power limits, then the power control strategy based on power limit analysis is proposed. Simulation, calculation and comparison are carried out by a 1.5MW DFIG wind turbine model, and the effectiveness of the analysis and the proposed control strategy is verified.

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