A Control Strategy for the Grid-Side Converter of the Directly-Driven Wind Turbine with PM Synchronous Generator under Unbalanced Grid Voltage

2013 ◽  
Vol 816-817 ◽  
pp. 669-677
Author(s):  
Wei Cai ◽  
Hui Min He ◽  
Jian Wei Wang ◽  
Shao Ze Su
Keyword(s):  
Control Strategy ◽  
Synchronous Generator ◽  
Active Power ◽  
Current Control ◽  
Frequency Oscillation ◽  
Dc Voltage ◽  
Negative Sequence ◽  
Double Frequency ◽  
Grid Side ◽  
Unbalanced Grid

A mathematical model of the full power grid-connecting converter at grid side for permanent magnet synchronous generator (PMSG) under unbalanced grid conditions is built, double-frequency oscillation mechanism on DC voltage is analyzed, and the influence of active power ripple of grid-connecting impedance on dual current control is discussed. To suppress the double-frequency oscillation on DC voltage, and take the grid-connected impedance on active power into account, a dual current control strategy, which based on respectively orientating positive-and negative-sequence voltages,is proposed, and introduced the correction value of active power ripple of grid-connecting impedance to correct reference current of proposed control strategy. Simulation results show that the proposed control strategy can effectively control positive and negative-sequence currents,eliminate the DC voltage double-frequency oscillation,and improve harmonic characteristic of grid-connected current.

Dual-Current Loops Control Strategy of PWM Rectifier under Unbalanced Grid Voltage Conditions

2014 ◽  
Vol 556-562 ◽  
pp. 2114-2118
Author(s):  
Yi Feng Ni ◽  
Yong Qiang Zhu
Keyword(s):  
Control Strategy ◽  
Active Power ◽  
Current Control ◽  
Pwm Rectifier ◽  
Current Harmonics ◽  
Dc Voltage ◽  
Grid Voltage ◽  
Instantaneous Power ◽  
Sequence Components ◽  
Unbalanced Grid

The unbalanced grid voltage causes the current harmonics, the fluctuation of the active power in AC side and the fluctuation of the DC voltage. The dual-current loops control strategy can slove those problems. The positive and negative sequence components of grid voltages and currents were calculated based on the symmetrical component method and were used to calculate the instantaneous power in double dq rotate coordinate, which ratate at positive and negative synchronous angular velocity respectively. The dual-current loops control strategy was finally verified in simulation by comparing with the conventional synchronous PI current control. The simulation results show the dual-current loops control strategy is effective on eliminating the fluctuation of the active power in AC side and the fluctuation of the DC voltage.

Some Controlling Strategies of DFIG to the Grid Turbulence

2013 ◽  
Vol 291-294 ◽  
pp. 541-543
Author(s):  
Huan Wang ◽  
Lei Pan
Keyword(s):  
Control Strategy ◽  
Tracking Control ◽  
Dynamic Performance ◽  
Synchronous Generator ◽  
Active Power ◽  
Current Control ◽  
Grid Turbulence ◽  
Dynamic Adjustment ◽  
Stator Current ◽  
Speed Fluctuation

The paper introduces several methods about controlling strategies of DFIG to the gird turbulence. They could reduce the torque pulsation. They have better dynamic adjustment performance than the positive, negative sequence dual current control strategy. Stator current THD is well controlled. The experimental results show that it can smooth the DFIG active power output comparing with the traditional maximum wind energy tracking control strategy, significantly reduces the speed fluctuation of synchronous generator. The dynamic performance is improved.

scholarly journals Research and improvement of current control strategy of active power filter

2020 ◽  
Vol 619 ◽  
pp. 012069
Author(s):  
Huajun Wu ◽  
Yupeng Wang ◽  
Bo Liu ◽  
Lidong Chen ◽  
Gen Pei
Keyword(s):  
Control Strategy ◽  
Active Power Filter ◽  
Active Power ◽  
Current Control ◽  
Power Filter

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.

Comparison of two control strategies for VSC-MTDC with wind farm

2021 ◽  
Vol 14 ◽  
Author(s):  
Congshan Li ◽  
Pu Zhong ◽  
Ping He ◽  
Yan Liu ◽  
Yan Fang ◽  
...  
Keyword(s):  
Power Control ◽  
Control Strategy ◽  
Voltage Stability ◽  
Wind Farm ◽  
Control Strategies ◽  
Wind Farms ◽  
Active Power ◽  
Stable Operation ◽  
Active Power Control ◽  
Dc Voltage

: Two VSC-MTDC control strategies with different combinations of controllers are proposed to eliminate transient fluctuations in the DC voltage stability, resulting from a power imbalance in a VSC-MTDC connected to wind farms. First, an analysis is performed of a topological model of a VSC converter station and a VSC-MTDC, as well as of a mathematical model of a wind turbine. Then, the principles and characteristics of DC voltage slope control, constant active power control, and inner loop current control used in the VSC-MTDC are introduced. Finally, the PSCAD/EMTDC platform is used to establish an electromagnetic transient model of a wind farm connected to a parallel three-terminal VSC-HVDC. An analysis is performed for three cases of single-phase grounding faults on the rectifier and inverter sides of a converter station and of the withdrawal of the converter station on the rectifier side. Next, the fault response characteristics of VSC-MTDC are compared and analyzed. The simulation results verify the effectiveness of the two control strategies, both of which enable the system to maintain DC voltage stability and active power balance in the event of a fault. Background: The use of a VSC-MTDC to connect wind power to the grid has attracted considerable attention in recent years. A suitable VSC-MTDC control method can enable the stable operation of a power grid. Objective: The study aims to eliminate transient fluctuations in the DC voltage stability resulting from a power imbalance in a VSC-MTDC connected to a wind farm. Method: First, the topological structure and a model of a three-terminal VSC-HVDC system connected to wind farms are studied. Second, an analysis is performed of the outer loop DC voltage slope control, constant active power control and inner loop current control of the converter station of a VSC-MTDC. Two different control strategies are proposed for the parallel three-terminal VSC-HVDC system: the first is DC voltage slope control for the rectifier station and constant active power control for the inverter station, and the second is DC voltage slope control for the inverter station and constant active power for the rectifier station. Finally, a parallel three-terminal VSC-HVDC model is built based on the PSCAD/EMTDC platform and used to verify the accuracy and effectiveness of the proposed control strategy. Results: The results of simulation analysis of the faults on the rectifier and inverter sides of the system show that both strategies can restore the system to the stable operation. The effectiveness of the proposed control strategy is thus verified. Conclusion: The control strategy proposed in this paper provides a technical reference for designing a VSC-MTDC system for wind farms.

scholarly journals An Autonomous Power-Frequency Control Strategy Based on Load Virtual Synchronous Generator

Processes ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 433 ◽  
Author(s):  
Jiangbei Han ◽  
Zhijian Liu ◽  
Ning Liang ◽  
Qi Song ◽  
Pengcheng Li
Keyword(s):  
Power Systems ◽  
Dynamic Stability ◽  
Control Strategy ◽  
Load Capacity ◽  
Frequency Control ◽  
Synchronous Generator ◽  
Active Power ◽  
Power Oscillation ◽  
Power Frequency ◽  
Virtual Synchronous Generator

With the increasing penetration of the hybrid AC/DC microgrid in power systems, an inertia decrease of the microgrid is caused. Many scholars have put forward the concept of a virtual synchronous generator, which enables the converters of the microgrid to possess the characteristics of a synchronous generator, thus providing inertia support for the microgrid. Nevertheless, the problems of active power oscillation and unbalance would be serious when multiple virtual synchronous generators (VSGs) operate in the microgrid. To conquer these problems, a VSG-based autonomous power-frequency control strategy is proposed, which not only independently allocates the power grid capacity according to the load capacity, but also effectively suppresses the active power oscillation. In addition, by establishing a dynamic small-signal model of the microgrid, the dynamic stability of the proposed control strategy in the microgrid is verified, and further reveals the leading role of the VSG and filter in the dynamic stability of microgrids. Finally, the feasibility and effectiveness of the proposed control strategy are validated by the simulation results.

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