BPF-based Grid Voltage Feedforward Control of Grid-connected Converters for Improving Robust Stability

다국어 초록 (Multilingual Abstract)

Grid voltage feedforward is extensively used for controlling grid-connected converters. However, the conventional voltage feedforward control reduces the stability margins of the converter connected to a high-impedance grid. The effect mechanism of voltage feedforward on the grid-connected converter control under high-inductive conditions of the grid impedance is clearly explained in this study using the equivalent transformations of control block diagrams. Results show that the delay produced by the digital control is the root cause of this effect. An improved voltage feedforward strategy, in which a bandpass filter (BPF) is introduced into the feedforward path, is proposed to strengthen the converter’s robust stability against grid impedance variations. The selection method of the BPF’s bandwidth is also provided considering the tradeoff between the response speed to the grid voltage sag and the system’s robust stability. The converter can work stably over a wide range of the grid impedance through the proposed approach. Simulation and experimental results fully verify the effectiveness of the BPF-based voltage feedforward strategy.

목차 (Table of Contents)

• Abstract
• I. INTRODUCTION
• II. SYSTEM MODELING AND ANALYSIS OF THE EFFECT MECHANISM OF THE GRID VOLTAGE FEEDFORWARD ON THE CONTROL SYSTEM
• III. ROBUST STABILITY ANALYSIS OF THE CONVENTIONAL GRID VOLTAGE FEEDFORWARD METHOD
• IV. BPF-BASED GRID VOLTAGE FEEDFORWARD AND ITS ROBUST STABILITY ANALYSIS
• V. SIMULATION AND EXPERIMENTAL RESULTS
• VI. CONCLUSIONS
• REFERENCES

참고문헌 (Reference)

1 "Technical rule for photovoltaic power station connected to power grid"

2 Yang Han, "Stationary Frame Current Control Evaluations for Three-Phase Grid-Connected Inverters with PVR-based Active Damped LCL Filters" 전력전자학회 16 (16): 297-309, 2016

3 M. Liserre, "Stability of photovoltaic and wind turbine grid-connected inverters for a large set of grid impedance values" 21 (21): 263-272, 2006

4 T. -F. Wu, "Predictive current controlled 5-kW single-phase bidirectional inverter with wide inductance variation for DC-microgrid applications" 25 (25): 3076-3084, 2010

5 L. Zhang, "Power-synchronization control of grid-connected voltage-source converters" 25 (25): 809-820, 2010

6 D. Pan, "Optimized controller design for LCL-type grid-connected inverter to achieve high robustness against grid-impedance variation" 62 (62): 1537-1547, 2015

7 A. Alexander, "Modelling and analysis of modular multilevel converter for solar photovoltaic applications to improve power quality" 9 (9): 78-88, 2015

8 J. L. Agorreta, "Modeling and control of N-paralleled grid-connected inverters with LCL filter coupled due to grid impedance in PV plants" 26 (26): 770-785, 2011

9 S. Zhou, "LCL type grid-connected converter no startup inrush current control method based on capacitor branch voltage feedforward" 1471-1476, 2015

10 M. Zabaleta, "LCL grid filter design of a multimegawatt medium-voltage converter for offshore wind turbine using SHEPWM modulation" 31 (31): 1993-2001, 2016

11 L. Zhang, "Interconnection of two very weak ac systems by VSC-HVDC links using power-synchronization control" 26 (26): 344-355, 2011

12 J. Xu, "Improved control strategy with grid-voltage feedforward for LCL-filter-based inverter connected to weak grid" 7 (7): 2660-2671, 2014

13 J. Sun, "Impedance-based stability criterion for grid-connected inverters" 26 (26): 3075-3078, 2011

14 J. Zhou, "Impact of short-circuit ratio and phase-locked-loop parameters on the small-signal behavior of a VSC-HVDC converter" 29 (29): 2287-2296, 2014

15 "IEEE standard for interconnecting distributed resources with electric power systems"

16 X. Zhou, "High-frequency resonance mitigation for plug-in hybrid electric vehicles’ integration with a wide range of grid conditions" 27 (27): 4459-4471, 2012

17 Priyabrat Garanayak, "Harmonic Elimination and Reactive Power Compensation with a Novel Control Algorithm based Active Power Filter" 전력전자학회 15 (15): 1619-1627, 2015

18 S. Jiang, "Grid-connected boost-half-bridge photovoltaic microinverter system using repetitive current control and maximum power point tracking" 27 (27): 4711-4722, 2012

19 M. Liserre, "Grid impedance estimation via excitation of LCL-filter resonance" 43 (43): 1401-1407, 2007

20 R. W. Erickson, "Fundamentals of Power Electronics" Kluwer 330-410, 2001

21 G. F. Franklin, "Feedback Control of Dynamic Systems" Addison-Wesley Professional 2009

22 J. Xu, "Evaluations of current control in weak grid case for grid-connected LCL-filtered inverter" 6 (6): 227-234, 2013

23 Kun Yang, "Design and Research on High-Reliability HPEBB Used in Cascaded DSTATCOM" 전력전자학회 15 (15): 830-840, 2015

24 D. Dong, "Analysis of phase-locked loop low-frequency stability in three-phase grid-connected power converters considering impedance interactions" 62 (62): 310-321, 2015

25 B. Wen, "Analysis of D-Q small-signal impedance of grid-tied inverters" 31 (31): 675-687, 2016

26 E. M. Lightner, "An orderly transition to a transformed electricity systems" 1 (1): 3-10, 2010

27 X. Wang, "An active damper for stabilizing power-electronics-based AC systems" 29 (29): 3318-3329, 2014

28 J. Xu, "An LTCL filter for three-phase grid-connected converters" 29 (29): 4322-4338, 2014

29 W. Wu, "An LLCL power filter for single-phase grid-tied inverter" 27 (27): 782-789, 2012

30 Payam Alemi, "Active Damping of LLCL Filters Using PR Control for Grid-Connected Three-Level T-Type Converters" 전력전자학회 15 (15): 786-795, 2015

31 Jian-jun Sun, "A Resonant Characteristics Analysis and Suppression Strategy for Multiple Parallel Grid-connected Inverters with LCL Filter" 전력전자학회 16 (16): 1483-1493, 2016

32 Zhiqiang Wan, "A Modified Capacitor Current Feedback Active Damping Approach for Grid Connected Converters with an LCL Filter" 전력전자학회 15 (15): 1286-1294, 2015