Adaptive Hybrid Generalized Integrator Based SMO for Solar PV Array fed Encoderless PMSM Driven Water Pump

 ABSTRACT:

The encoder influences reliability and cost of permanent magnet synchronous motor (PMSM) operated solar water pump (WP). It is even sensitive to electromagnetic noise and temperature, which thereby reduces its accuracy. To overcome these problems, an encoderless PMSM control by using adaptive hybrid generalized integrator (AHGI) based sliding mode observer (SMO) for the solar WP system is presented in this paper. The widely used low pass filter based SMO produces phase-shift, attenuation and dominant lower order harmonics (DLOH). This decreases the position estimation accuracy. Besides, the need for tracking dynamic system frequency further exacerbates its performance. The developed AHGI structure eliminates these drawbacks and provides an accurate estimate of position over a wide speed range. A harmonic decoupling network, a hybrid generalized integrator and an adaptive frequency tracker constitute AHGI, which respectively performs dominant harmonic signal generation, DLOH elimination and frequency tracking. The improvement in behavior of AHGI over the existing methods is analyzed by transfer functions, Bode plots and back electromotive force helices. Meanwhile an incremental conductance algorithm for PV array maximum power control is used. The developed structure is experimentally validated on a laboratory prototype and a comparison with the existing methods is also made.

 KEYWORDS:

1.      Solar water pump

2.      Solar photovoltaic (PV) array

3.      Encoderless control

4.      PMSM

5.      Adaptive hybrid generalized integrator (AHGI)

6.      Adaptive frequency tracker (AFT)

SOFTWARE: MATLAB/SIMULINK

SCHEMATIC DIAGRAM:

Fig. 1 Encoderless PMSM driven solar WP system with developed AHGI based SMO for rotor position estimation

 EXPECTED SIMULATION RESULTS:

Fig. 2 Experimental performance of the solar WP system with the developed AHGI based SMO (a) Starting at 1000 W/m2, (b) Starting at 500 W/m2, (c),(d) continuous running at 1000 W/m2, (e),(f) continuous running at 500 W/m2

 

Fig. 3 Experimental dynamic performance of solar WP system with the developed AHGI based SMO for irradiation variation from (a),(b),(c) 500 W/m2 to 1000 W/m2; (d),(e),(f) 1000 W/m2 to 500 W/m2

CONCLUSION:

An adaptive hybrid generalized integrator (AHGI) based SMO for encoderless operation of PMSM driving a solar WP has been presented here. It has been found that the developed AHGI structure has produced a satisfactory estimate of both the speed and rotor position through selective elimination of DLOH along with the removal of phase-shift and fundamental attenuation. The improved performance of AHGI structure over the LPF, SOGI and FOGI has been demonstrated by the transfer function and the frequency response. Besides, the superiority of AHGI has also been shown through both the simulated and experimental performances of back EMF and rotor position. Even the detailed experimental performance of system with the AHGI at continuous running and starting under dynamics of solar irradiation have been obtained. It has been found that the developed AHGI structure has produced a satisfactory estimate of αβ-components of back-EMF even under dynamics. It has also been shown experimentally that the developed AHGI successfully tracks the variations in the speed. A stable and reasonably satisfying performance of the system has been observed under all operating conditions. The developed AHGI structure can be used with any PMSM system for rotor position and speed estimation.

REFERENCES:

[1] M. Rezkallah, A. Chandra, M. Tremblay and H. Ibrahim, “Experimental Implementation of an APC With Enhanced MPPT for Standalone Solar Photovoltaic Based Water Pumping Station,” IEEE Trans. Sustain. Energy, vol. 10, no. 1, pp. 181-191, Jan. 2019.

[2] M. E. Haque, Y. C. Saw and M. M. Chowdhury, “Advanced Control Scheme for an IPM Synchronous Generator-Based Gearless Variable Speed Wind Turbine,” IEEE Trans. Sustain. Energy, vol. 5, no. 2, pp. 354- 362, April 2014.

[3] C. Lascu and G. Andreescu, “PLL Position and Speed Observer With Integrated Current Observer for Sensorless PMSM Drives,” IEEE Trans. Ind. Electron., vol. 67, no. 7, pp. 5990-5999, July 2020.

[4] S. Shukla and B. Singh, “Reduced Current Sensor Based Solar PV Fed Motion Sensorless Induction Motor Drive for Water Pumping,” IEEE Trans. Ind. Informat., vol. 15, no. 7, pp. 3973-3986, July 2019.

[5] A. Andersson and T. Thiringer, “Motion Sensorless IPMSM Control Using Linear Moving Horizon Estimation With Luenberger Observer State Feedback,” IEEE Trans. Transport. Electrific., vol. 4, no. 2, pp. 464- 473, June 2018.

Active Fault Current Limitation for Low-Voltage Ride-Through of Networked Microgrids

ABSTRACT:

With the continuously increasing penetration of networked microgrids (MGs) on the local utility grid (UG), MGs face the challenge to avoid increasing system fault currents during low-voltage ride-through (LVRT). To solve this challenge, an active fault current limitation (AFCL) method is proposed with three parts: 1) a novel phase angle adjustment (PAA) strategy is conducted to relieve the impact of MGs output fault current on system fault current; 2) the current injection (CI) strategy for LVRT is formulated to fit the function of PAA; 3) a novel converter current generation (CCG) strategy is developed to achieve a better voltage support ability by considering network impedance characteristics. The proposed AFCL method is applied to the back-to-back converter, as a connection interface between MGs and UG. Extensive tests and pertinent results have verified the improvements of proposed AFCL method with better LVRT performance, while the networked MGs output fault current does not increase the amplitude of system fault current.

KEYWORDS:

1.      Networked microgrids

2.      Back-to-back converter

3.      Low-voltage ride-through

4.      Fault current limitation

SOFTWARE: MATLAB/SIMULINK

 SCHEMATIC DIAGRAM:

Fig. 1. Structure of networked MGs and the corresponding fault current flow.

EXPECTED SIMULATION RESULTS:

Fig. 2. The PCC voltage of MG#1 and MG#2 with existing FCL method in [23]-[25].

Fig. 3. The PCC voltage of MG#1 and MG#2 with proposed AFCL method.

Fig. 4. The MG#1 and MG#2 fault current with existing FCL method in [23]-[25].

Fig. 5. The MG#1 and MG#2 fault current with proposed AFCL method.

Fig. 6. The MG#1 and MG#2 power injected by existing method in [23]-[25].

 

Fig. 7. The MG#1 and MG#2 power injected by proposed AFCL method.

Fig. 8. DC voltage of BTB converter with proposed/existing FCL in [23]-[25].

Fig. 9. The UG fault current with proposed/existing FCL in [23]-[25].

 

Fig. 10. The system fault current with existing FCL method in [23]-[25].

Fig. 11. The system fault current with proposed AFCL method.

 

CONCLUSION:

Under the UG fault condition, in view of the high-level system fault current during the LVRT of networked MGs, an AFCL method is proposed to avoid monotonically increasing system fault currents during the LVRT of networked MGs. In this method, in order to improve the voltage control ability of LVRT, the CCG strategy is proposed by embedding the network impedance characteristics. Then, in order to achieve a better fault current limitation by relieving the impact of MGs fault current, the PAA strategy is proposed with considering voltage’s phase angle difference from UG and MGs to fault branch. Meanwhile, the CI strategy is conducted to fit the feature of PAA. Numerous simulation results have validated the improvements of the proposed AFCL method with a successful LVRT, meanwhile, the networked MGs fault current does not increase the system fault current amplitude. Considering the fields with a high proportion of sensitive load, the BTB converter is widely used for the PCC connection point of DGs and MGs to provide high power quality. To reduce the fault current level, the AFCL method can be applied to the BTB converter, and can be also used to the other inverter products, such as wind and photovoltaic inverter, AC/DC microgrids, and HVDC transmission system.

REFERENCES:

[1] Q. Zhou, M. Shahidehpour, et al, “ Distributed Control and Communication Strategies in Networked Microgrids,” IEEE Communications Surveys & Tutorials, vol. 22, no. 4, pp. 2586-2633, Fourth quarter 2020.

[2] X. Zhao, J. M. Guerrero, et al, “Low-Voltage Ride-Through Operation of Power Converters in Grid-Interactive Microgrids by Using Negative-Sequence Droop Control,” IEEE Trans. Power Electron., vol. 32, no. 4, pp. 3128–3142, April 2017.

[3] I. Sadeghkhani, M. E. H. Golshan, A. Mehrizi-Sani, J. M. Guerrero, “Low-voltage ride-through of a droop-based three-phase four-wire grid-connected microgrid,” IET Gener. Transm. Distrib., vol. 12, no. 8, pp. 1906–1914, 2018.

[4] Y. He, M. Wang and Z. Xu, “Coordinative Low-Voltage-Ride-Through Control for the Wind-Photovoltaic Hybrid Generation System,” IEEE Journal of Emerging & Selected Topics in Power Electronics, vol. 8, no. 2, pp. 1503–1514, Jun. 2020.

[5] Y. Yang, F. Blaabjerg, and Z. Zou, “Benchmarking of grid fault modes in single-phase grid-connected photovoltaic systems,” IEEE Trans. Ind. Appl., vol. 49, no. 5, pp. 2167–2176, Sep./Oct. 2013.

A Sub-Synchronous Oscillation Suppression Strategy for Doubly Fed Wind Power Generation System

ABSTRACT:

During the power transmission of doubly-fed induction generator (DFIG), due to the influence of series compensating capacitance and long-distance transmission, DFIG is prone to sub-synchronous oscillation, which damages the stability of the system. By establishing the mathematical model of DFIG system, the cause of sub-synchronous oscillation and its influence on the control strategy of DFIG system are discussed. In order to solve the problem of performance degradation of traditional phase-locked loop (PLL) under sub-synchronous oscillation, an improved PLL is proposed to replace the traditional PLL. Aiming at the problem that the control of rotor side converter(RSC) and grid side converter(GSC) in doubly-fed wind power generation system under sub-synchronous oscillation is disturbed by harmonic signals, a control method of adding a quasi resonant controller in the control link of RSC and GSC to suppress sub-synchronous oscillation is proposed, and the feasibility of the method is verified by simulation and experiment. Finally, based on the research process of RSC direct resonance control, the sub-synchronous oscillation suppression strategy based on harmonic current extraction is proposed for the frequency adaptability of the quasi resonant controller. The actual performance of the sub-synchronous oscillation suppression strategy is verified through simulation and experiment. The experimental results show that the strategy is effective.

KEYWORDS:

1.      Doubly fed induction generator

2.      Sub-synchronous oscillation

3.      Rotor side converter

4.      Stator side converter

5.      Phase-locked loop

6.      Quasi resonance controller

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1. Structure Diagram Of Dfig Wind Power System Experimental Prototype. 

EXPECTED SIMULATION RESULTS:

Figure 2. Frequency Response Of F3(S).

Figure 3. Simulation Waveform Under Sub-Synchronous Oscillation.

Figure 4. Rsc Direct Resonance Control Simulation Waveform.

Figure 5. Gsc Direct Resonance Control Simulation Waveform.

Figure 6. Simulation Diagram Of Sub-Synchronous Oscillation Suppression Strategy Based On Harmonic Current Extraction.

Figure 7. The Resonant Controller Suppresses The Experimental Waveform Of The Ssci.

Figure 8. Waveforms Were Compared Before And After 10hz Synchronous Oscillation Suppression.

 

REFERENCES:

[1] C. Guoping, L. Mingjie, X. Tao, and L. Mingsong, ``Study on technical bottleneck of new energy development,'' Proc. CSEE, vol. 37, no. 1, pp. 20_26, 2017.

[2] C. Guoping, L. Mingjie, X. Tao, Z. Jianyun, and W. Chao, ``Practice and challenge of renewable energy development based on interconnected power grids,'' Power Syst. Technol., vol. 41, no. 10, pp. 3095_3103, 2017.

[3] O. P. Mahela, N. Gupta, M. Khosravy, and N. Patel, ``Comprehensive overview of low voltage ride through methods of grid integrated wind generator,'' IEEE Access, vol. 7, pp. 99299_99326, 2019.

[4] X. Xiaorong, H. Jingbo, M. Hangyin, and L. Haozhi, ``New issues and classi_cation of power system stability with high shares of renewables and power electronics,'' Proc. CSEE, vol. 41, no. 2, pp. 461_474.

[5] G. F. Gontijo, T. C. Tricarico, L. F. da Silva, D. Krejci, B. W. França, M. Aredes, and J. M. Guerrero, ``Modeling, control, and experimental verification of a DFIG with a series-grid-side converter with voltage sag, unbalance, and distortion compensation capabilities,'' IEEE Trans. Ind. Appl., vol. 56, no. 1, pp. 584_600, Jan. 2020.

A Novel Unified Controller for Grid-Connected and Islanded Operation of PV-Fed Single-Stage Inverter

 ABSTRACT:

 This paper presents a novel robust current droop controller (RCDC) using a single droop loop. This scheme is unified supporting dual mode of operation for micro-grids (MGs), including grid connected mode (GCM) and islanded mode (ISM) while ensuring seamless transition between the two modes with proportional power sharing maintained. The proposed controller is further incorporated with an improved maximum power point tracking (MPPT) technique presented for the parallel operation of single-stage inverters fed by multi-string PV array topology. In addition, an improved phase-locked-loop-less (PLL-less) method is presented supporting self-synchronization strategy of the parallel operation of PV-inverters with the main grid while maintaining the full capabilities of the unified control architecture. This obviates the usage of conventional PLLs, which are widely used with active synchronization techniques. The performance of the proposed control scheme is validated using real time simulations (RTS) developed by dSPACE MicroLabBox.

KEYWORDS:

1.      Smart Grid

2.      Distributed Generation

3.      Unified Droop Controller

4.      Self-Synchronization

5.      MPPT

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 Typical block diagram of the MG under study. 

EXPECTED SIMULATION RESULTS:

Fig. 2 Measured PV power under varied irradiation and temperature.

Fig. 3 Regulated DC-link voltage using the proposed MPPT algorithm.

Fig. 4 AC current set point controlled by DC voltage regulator under varied irradiation and temperature.

Fig. 5 Output active power under varied insolation and temperature level.

Fig. 6 Output reactive power under varied irradiation and temperature.

Fig. 7 Output peak currents proportionally shared between DG1 and DG2.

Fig. 8 Measured direct and quadrature axes voltages at the PCC.

 

CONCLUSION:

 This paper presents an enhanced RCDC with a simplified MPPT algorithm and PLL-less SSM for the parallel operation of single-stage inverters fed by multi-string PV arrays. The modified RCDC-QPR scheme efficiently operated in both ISM and GCM without observing any resonance effect. Only one AC current sensor has been used by the simplified P&O algorithm enhancing the design simplicity, while precisely tracking the MPP under varied insolation and temperature. Besides, good dynamic response has been resulted with tenuous perturbations owing to the adopted compromise between the P&O sampling rate and incremental voltage steps. Prominently, the design has been freely built with no regards to the operating mode, accepting the last current setpoint identified by the MPPT upon islanding with no need of setpoint manipulations thanks the flexibility of the proposed unified current controller. Depending on the proposed PLL-less SSM, the active synchronization has been successfully achieved without using dedicated PLLs or communication links between inverters. This offers a simpler design obviating the complex tuning and stability issues of normal PLLs. The general guidelines for tuning the PLL-less detector have been also outlined through quantitative analysis. The simplified MPPT and proposed PLL-less detector have both enriched the control flexibility of the original RCDC-QPR controller supporting dual mode of operation with seamless transition between these two modes, while exporting the extra PV power the main grid during GCM. Design competency has been validated using real time simulations developed by dSPACE MicroLabBox.

 REFERENCES:

 [1] A. K. Podder, N. K. Roy, and H. R. Pota, “MPPT methods for solar PV systems: a critical review based on tracking nature,” IET Renewable Power Generation, vol. 13, no. 10, pp. 1615–1632, 2019.

[2] R. Ahmad, A. F. Murtaza, and H. A. Sher, “Power tracking techniques for efficient operation of photovoltaic array in solar applications–A review,” Renewable and Sustainable Energy Reviews, vol. 101, pp. 82– 102, 2019.

[3] M. M. Hanif, “Investigation to Improve the Control and Operation of a Three-phase Photovoltaic Grid-tie Inverter,” PhD Thesis, Dublin Institute of Technology, 2011.

[4] H. Bounechba, A. Bouzid, H. Snani, and A. Lashab, “Real time simulation of MPPT algorithms for PV energy system,” International Journal of Electrical Power & Energy Systems, vol. 83, pp. 67–78, 2016.

[5] D. C. Huynh and M. W. Dunnigan, “Development and Comparison of an Improved Incremental Conductance Algorithm for Tracking the MPP of a Solar PV Panel,” IEEE Trans. Sustain. Energy, vol. 7, no. 4, pp. 1421–1429, Oct. 2016, doi: 10.1109/TSTE.2016.2556678.

A Model Predictive Control Method for Hybrid Energy Storage Systems

ABSTRACT:

The traditional PI controller for a hybrid energy storage system (HESS) has certain drawbacks, such as difficult tuning of the controller parameters and the additional filters to allocate high- and low- frequency power fluctuations. This paper proposes a model predictive control (MPC) method to control three-level bidirectional DC/DC converters for grid-connections to a HESS in a DC microgrid. First, the mathematical model of a HESS consisting of a battery and ultra capacitor (UC) is established and the neutral point voltage imbalance of a three level converter is solved by analyzing the operating modes of the converter. Secondly, for the control of the grid-connected converters, an MPC method is proposed for calculating steady state reference values in the outer layer and the dynamic rolling optimization in the inner layer. The outer layer ensures the voltage regulation and establishes the current predictive model, while the inner layer, using the model predictive current control, makes the current follow the predictive value, thus reducing the system current ripple. This cascaded topology has two independent controllers and is free of filters to realize the high-and low frequency power allocation for a HESS. Therefore, it allows two types of energy storage devices to independently regulate the voltage and realizes the power allocation of the battery and UC. Finally, simulation studies are conducted in PSCAD/EMTDC, and the effectiveness of the proposed HESS control strategy is verified in a case, such as a controller comparison and fault scenario.

KEYWORDS:

1.      Double layer control method

2.       Hybrid energy storage system (HESS)

3.      Model predictive control (MPC)

4.      Three-level DC/DC converter

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. The topology of a HESS.

EXPECTED SIMULATION RESULTS:

Fig. 2. Comparison under the proposed MPC method with the PI control method. (a) Bus voltage response under two methods. (b) UC voltage response under two methods.

 Fig. 3. The power response of the battery when the controller parameter _i is changed.

 Fig. 4. System voltage response in the case of short-circuiting of the UC.

(a) The response of the bus voltage during the short-circuit fault of the UC.

(b) The response of the UC voltage during the short-circuit fault of the UC.

Fig. 5. Photovoltaic module output power.

Fig. 6. Comparison between the proposed MPC method and the PI control method. (a) The bus voltage response under two methods. (b) The UC voltage response under two methods.

Fig. 7. The effectiveness under the proposed MPC method. (a) The voltage of capacitors C1 and C2. (b) Inductor L1 reference current iL1ref and actual current iL1.

 

CONCLUSION:

 In this paper, the advantages of a three-level bidirectional DC/DC converter for battery/UC HESS and the effectiveness of the proposed MPC method are discussed from both a theoretical analysis and simulation verification. At the same grid voltage level, the battery can suppress higher voltage level fluctuations after a two-stage boosting structure. Compared with the PI controller, the MPC controller doesn’t need a tedious step of adjusting parameters and various state variables are considered in each sampling instant. Moreover, the MPC algorithm based on the constant switching frequency achieves fast and accurate regulation of voltage and current with diminished ripples. Finally, the system does not need filters to allocate power fluctuations, and the control structure is optimized while the battery life is prolonged.

REFERENCES:

[1] D. Liang, C. Y. Qin, S. Y. Wang, and H. M. Guo, “Reliability evaluation of DC distribution power network,” in Proceedings of 2018 China International Conference on Electricity Distribution, Tianjin, 2018, pp. 654–658.

[2] Z. Huang, J. Ma, J. Zeng et al., “Research status and prospect of control and protection technology for DC distribution network,” in Proceedings of 2014 China International Conference on Electricity Distribution, Shenzhen, Sep. 2014, pp. 1488–1493.

[3] K. A. Joshi and N. M. Pindoriya, “Case-specificity and its implications in distribution network analysis with increasing penetration of photovoltaic generation,” CSEE Journal of Power and Energy Systems, vol. 3, no. 1, pp. 101–113, Mar. 2017.

[4] Y. Xu, T. Y. Zhao, S. Q. Zhao, J. H. Zhang, and Y. Wang, “Multiobjective chance-constrained optimal day-ahead scheduling considering BESS degradation,” CSEE Journal of Power and Energy Systems, vol. 4, no. 3, pp. 316–325, Sep. 2018.

[5] Y. Sun, Z. Zhao, M. Yang, D. Jia, W. Pei and B. Xu, “Overview of energy storage in renewable energy power fluctuation mitigation,” CSEE Journal of Power and Energy Systems, vol. 6, no. 1, pp. 160–173, Mar. 2020.