Seven-Level Inverter with Reduced Switches for PV System Supporting Home-Grid and EV Charger

ABSTRACT:

This paper proposes a simple single-phase new pulse-width modulated seven-level inverter architecture for photovoltaic (PV) systems supporting home-grid with electricvehicle (EV) charging port. The proposed inverter includes a reduced number of power components and passive elements size, while showing less output-voltage total harmonic distortion (THD), and unity power factor operation. In addition, the proposed inverter requires simple control and switching strategies compared to recently published topologies. A comparative study was performed to compare the proposed inverter structure with the recent inverter topologies based on the number of components in the inverter circuit, number of components per output-voltage level, average number of active switches, THD, and operating efficiency as effective parameters for inverter performance evaluation. For design and validation purposes, numerical and analytical models for a grid-tied solar PV system driven by the proposed seven-level inverter were developed in MATLAB/Simulink environment. The inverter performance was evaluated considering grid-integration and stand-alone home with level-2 AC EV charger (3–6 kW). Compared with recently published topologies, the proposed inverter utilizes a reduced number of power components (7 switches) for seven-level terminal voltage synthesis. An experimental prototype for proposed inverter with the associated controller was built and tested for a stand-alone and grid-integrated system. Due to the lower number of ON-switches, the inverter operating efficiency was enhanced to 92.86% with load current THD of 3.43% that follows the IEEE standards for DER applications.

KEYWORDS:

1.      DC-AC converter

2.      Electric vehicles

3.      Home grid

4.      Maximum power point tracking (MPPT)

5.      Multilevel inverter

6.      Photovoltaic (PV) system

7.      Seven-level inverter

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:  

Figure 1. Circuit configuration of solar PV system in integrated with the grid and EV loads via the proposed 7level-inverter.

EXPECTED SIMULATION SYSTEM:

(a) Solar irradiation

(b) PV current

(c) PV voltage

Figure 2. Cont

time(s)

(d)PV power

Figure 3. the pv panel current, voltage, and power.

 

Figure 4. multi- Level inverter output voltage.

Figure 5. the injected current, voltage, and power variation. (a) Grid voltage and current; (b) Grid injected power.

 

Figure 6. The reference and actual injected currents of the seven-level inverter at irradiance variation.

 

Figure 7. Simulation results of the proposed 7-level inverter as level-2 EV charger (240 V, 3:6 kW); (a) loading profile, (b) multilevel output voltage, and (c) inverter voltage/pulsating current

Figure 8. Simulation results of the proposed 7-level inverter for house loads voltage control (2 kW). (a) Load reference and actual voltages, (b) Load voltage and current

CONCLUSION:

This paper has presented a new topology of a single-phase seven-level inverter as an interface for grid-integrated and stand-alone solar PV systems. The circuit configuration This paper has presented a new topology of a single-phase seven-level inverter as an interface for grid-integrated and stand-alone solar PV systems. The circuit configuration This paper has presented a new topology of a single-phase seven-level inverter as an interface for grid-integrated and stand-alone solar PV systems. The circuit configuration and operation principle of the proposed inverter have been presented in detail a long with    the switching patterns and control strategy. A comparative study between the proposed inverter structure and the recent MLI topologies is enriched to reveal the features of the proposed inverter. The proposed MLI structure considers a reduced number of power switches, NC/L, and NAVG/Pole, which enhances the inverter operating efficiency and decreases its cost. Only seven switches have been utilized to synthesis voltage waveform of seven levels at the output terminals. The performance of the proposed inverter and associated control was investigated for grid-integrated and stand-alone PV systems based on simulation and experimental tests. The test platform includes a boost converter with MPPT control, which feeds the front-end of the proposed MLI. The results show that the proposed inverter exhibits an improved steady state response, and minimum settling time (i.e., 5 ms). THD of both voltage and current waveforms during grid-integration and stand-alone operations is 3.43%, which follows the IEEE-1547 harmonic standards for DER applications. In addition, the inverter offers a high operating efficiency of 92.86%, compared to most of the recently published topologies surveyed in this paper.

REFERENCES:

1. Solangi, K.; Islam, M.; Saidur, R.; Rahim, N.; Fayaz, H. A review on global solar energy policy. Renew. Sustain. Energy Rev. 2011, 15, 2149–2163. [CrossRef]

2. Ali, A.I.; Sayed, M.A.; Mohamed, E.E. Modified efficient perturb and observe maximum power point tracking technique for grid-tied PV system. Int. J. Electr. Power Energy Syst. 2018, 99, 192–202. [CrossRef]

3. Sayed, M.A.; Mohamed, E.; Ali, A. Maximum Power Point Tracking Technique for Grid tie PV System. In Proceedings of the 7th International Middle-East Power System Conference, (MEPCON’15), Mansoura University, Dakahlia Governorate, Egypt, 15–17 December 2015.

4. Ali, A.I.; Mohamed, E.E.; Sayed, M.A.; Saeed, M.S. Novel single-phase nine-level PWM inverter for grid connected solar PV farms. In Proceedings of the 2018 International Conference on Innovative Trends in Computer Eng. (ITCE), Aswan, Egypt, 19–21 February 2018; IEEE: Piscataway, NJ, USA, 2018; pp. 345–440.

5. Youssef, A.-R.; Ali, A.I.; Saeed, M.S.; Mohamed, E.E. Advanced multi-sector P&O maximum power point tracking technique for wind energy conversion system. Int. J. Electr. Power Energy Syst. 2019, 107, 89–97.

 

Sensorless Control of Permanent Magnet Synchronous Motor in Full Speed Range*

ABSTRACT:

 Aiming at resolving the limitation of the speed regulation range of sensorless control technology, a new composite sensorless control strategy is proposed to realize a control method for a permanent magnet synchronous motor (PMSM) in full speed range. In the medium- and high-speed range, the improved new sliding mode observer method is used to estimate the motor speed and rotor position information. In the zero and low speed range, in order to avoid the defects of the sliding mode method, the rotating high-frequency voltage signal injection method is used. When switching between low, medium, and high speed, the fuzzy control algorithm is adopted to achieve smooth transitions. The simulation experiment results show that the hybrid mode combining the sliding mode observer and rotating high-frequency voltage injection methods, can effectively reduce the jitter in the algorithm switching process, and realize the smooth control of a PMSM in full speed range.

KEYWORDS:

1.      PMSM

2.      Full speed range

3.      Rotating high-frequency voltage signal injection method

4.      Sliding mode observer method

5.      Fuzzy Control

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

                                       

Fig. 1 Schematic diagram of improved sliding mode observer

 EXPECTED SIMULATION RESULTS:

Fig. 2 The full range sensorless control waveform under the traditional weighting algorithm

 

 Fig. 3 Full range sensorless control waveform based on fuzzy control

Fig. 4 Comparison of the speed waveforms of the two control algorithms in the switching interval

 Fig. 5 Comparison of the rotor position waveforms of the two control algorithms in the switching interval

 

CONCLUSION:

 In this paper, the overall scheme design and control strategy of the PMSM sensorless control system, are studied, and the control method of motor running in the full-speed range, is analyzed in detail. The simulation results and experiments show that the high-frequency signal injection method in the low-speed range, and the sliding mode observer method in the medium and high speed range, can accurately estimate the rotor position and speed, and the tracking speed is fast. In the estimation process, the robustness improves. At the same time, using fuzzy control in the low-speed to medium and high-speed range, can make the PMSM switch smoothly, which has a certain application value.

REFERENCES:

[1] H Lin, H Guo, H Qian. Design of high-performance permanent magnet synchronous motor for electric aircraft propulsion. Proc. 21st Int. Conf. Electrfic. Mach. Syst. (ICEMS), 2018: 174-179.

[2] S Kim, J I Ha, S K Sul. PWM switching frequency signal Injection sensorless method in IPMSM. IEEE Transactions on Industry Application, 2012, 48(5): 1576-1587.

[3] Y P Zhou, G Yang, J H Yang. Speed control strategy of permanent magnet synchronous motor based on adaptive backstepping. Chinese Journal of Electrical Engineering, 2020, 15(3): 38-43.

[4] Y P Zhou , G Yang , J H Yang. PMSM speed control using adaptive sliding mode control based on an extended state observer. High Technology Letters, 2018(4): 422-433.

[5] S Q Peng , Y Y Song . Sensorless vector control of PMSM based on adaptive fuzzy sliding mode observer. Control and Decision, 2018, 33(4): 644-648.

Investigating The Ability Of Shunt Hybrid Power Filter Based On SRF Method Under Non-Ideal Supply Voltage

 ABSTRACT:

This study presents the capacity of a self-tuning filter based on the synchronous reference frame method with a fuzzy logic controller for the improvement of the efficiency of harmonic suppression of a shunt hybrid active power filter in an unbalanced distorted and undistorted voltage supply conditions. The simulation results indicated that the filter with a fuzzy logic controller had a good filtering performance in steady and transient states, irrespective of whether the voltage supply is distorted or unbalanced.

SOFTWARE: MATLAB/SIMULINK

CONTROL DIAGRAM:

Figure 1. SRF control strategy with STF based on SHAPF.

EXPECTED SIMULATION RESULTS:

Figure 2. SHAF response under ideal voltage situation (a) Source voltage (Vs), (b) Load current (IL),

(c) load current with filter, (d) Filter compensation current ( If) , and (e) DC link voltage of system

(Vdc).

Figure 3. THD of current (Is)under ideal voltage supply.

Figure 4. SHAF response under non ideal voltage situation (a) Source voltage (Vs), (b) Load current (Il), (c) load current with filter, (d)Filter compensation current ( If), and (e) DC link voltage of system (Vdc).

 CONCLUSION:

 This paper investigated the effectiveness of a synchronous reference frame (SRF) with a self-tuning filter (STF) control strategy in controlling the performance of a three-phase SHAPF system under conditions of non-ideal and balanced supply voltage. The fuzzy logic controller was utilized for the adjustment of the DC voltage. The performance of the SHAPF system was investigated under a dynamic and steady state and under different load operating conditions. The simulation results showed the SAPF to have successfully reduced current harmonics to about 1.7 and 2.7 % for both cases of source voltages.

REFERENCES:

 [1] Eltawil, M.A. and Zhao, Z., 2010. Grid-connected photovoltaic power systems: Technical and potential problems—A review. Renewable and Sustainable Energy Reviews, 14(1), pp.112- 129.

[2] Bhat, A.H. and Agarwal, P., 2008. Three-phase power quality improvement ac/dc converters. Electric Power Systems Research, 78(2), pp.276-289.

[3] Wagner, V.E., Balda, J.C., Griffith, D.C., Mceachern, A., Barnes, T.M., Hartmann, D.P., Phileggi, D.J., Emannuel, A.E., Horton, W.F., Reid, W.E. and Ferraro, R.J., 1993. Effects of harmonics on equipment. IEEE Transactions on Power Delivery, 8(2), pp.672-680.

[4] Mohamed, M.A., 2015. Design of shunt active power filter to mitigate the harmonics caused by nonlinear loads (Doctoral dissertation, Universiti Tun Hussein Onn Malaysia).

[5] Soomro, D.M. and Almelian, M.M., 2015. Optimal design of a single tuned passive filter to

mitigate harmonics in power frequency.

Fuzzy Logic Controller-based Synchronverter in Grid-connected Solar Power System with Adaptive Damping Factor*

ABSTRACT:

 In recent years, renewable energy sources, specifically solar power systems, have developed rapidly owing to their technological maturity and cost effectiveness. However, its grid integration deteriorates frequency stability because of insufficient rotating masses and inertial response. Hence, a synchronverter, which is an inverter that mimics the operation of a synchronous generator, is crucial to interface solar power in a power grid. It stabilizes the power grid by emulating a virtual inertia. However, a conventional proportional-integral(PI)-based synchronverter is not equipped with an adaptive damping factor (Dp) or a digitalized smart controller to manage fast-responding solar inputs. Hence, a novel fuzzy logic controller (FLC) framework is proposed such that the synchronverter can operate in a grid-connected solar power system. In this study, Dp is controlled in real time using an FLC to achieve balance between speed and stability for frequency error correction based on frequency difference. Results of four case studies performed in Matlab/Simulink show that the proposed FLC-based synchronverter can stabilize the grid frequency by reducing the frequency deviation by at least 0.2 Hz (0.4%), as compared with the conventional PI-based synchronverter.

KEYWORDS:

1.      Fuzzy logic controller (FLC)

2.      Synchronverter

3.      Renewable energy system (RES)

4.      Grid stability

5.      Solar power system

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 Power section of synchronverter

EXPECTED SIMULATION RESULTS:

                                       

Fig. 2 Active power for varying resistive loads (RL)

Fig. 3 Outputs of synchronverter for first case study

Fig. 4 Testing environment for second case study

 

Fig. 5 Outputs of synchronverter for second case study

 

Fig. 6 Testing environment for third case study

 

Fig. 7 Outputs of synchronverter for third case study

 

Fig. 8 Testing environment for fourth case study

 

 

Fig. 9 Outputs of synchronverter for fourth case study

CONCLUSION:

 Herein, a novel FLC-based framework was proposed to control a synchronverter in a grid- connected solar power system under dynamic weather conditions. Four case studies were simulated in Matlab/Simulink, and the results validated the ability of the proposed controller in stabilizing fg by reducing the frequency deviation by at least 0.2 Hz (0.4%), as compared with the conventional PI-basedsynchronverter. The performance of the FLC-based synchronverter was optimal even under sudden load changes or varying irradiances and temperatures. P was injected or absorbed whenever the frequency decreased or increased, respectively. The Dp controlled by the FLC was able to balance between transient speed and stability, whereby a larger Dp afforded a more prominent dampening effect, and vice versa.

 REFERENCES:

[1] H Zsiborács, N H Baranyai, A Vincze, et al. Intermittent renewable energy sources: The role of energy storage in the European Power System of 2040. MDPI Electronics, 2019, 8(7): 729.

[2] M Z Saleheen, A A Salema, S M M Islam, et al. A target-oriented performance assessment and model development of a grid-connected solar PV (GCPV) system for a commercial building in Malaysia. Renewable Energy, 2021, 171: 371-382.

[3] Y Wang, V Silva, A Winckels. Impact of high penetration of wind and PV generation on frequency dynamics in the continental Europe interconnected system. IET Renewable Power Generation, 2014, 10(1): 10-16.

[4] F Li, C Li, K Sun, et al. Capacity configuration of hybrid CSP/PV plant for economical application of solar energy. Chinese Journal of Electrical Engineering, 2020, 6(2): 19-29.

[5] G Perveen, M Rizwan, N Goel. Comparison of intelligent modelling techniques for forecasting solar energy and its application in solar PV based energy system. IET Energy Systems Integration, 2019, 1(1): 34-51.

Evaluation of High Step-up Power Conversion Systems for Large-capacity Photovoltaic Generation Integrated into Medium Voltage DC Grids*

 ABSTRACT:

 With the increase of dc based renewable energy generation and dc loads, the mediumvoltage dc (MVDC) distribution network is becoming a promising option for more efficient system integration. In particular, large-capacity photovoltaic (PV)-based power generation is growing rapidly, and a corresponding power conversion system is critical to integrate these large PV systems into MVDC power grid. Different from traditional ac grid-connected converters, the converter system for dc grid interfaced PV system requires large-capacity dc conversion over a wide range of ultra-high voltage step-up ratios. This is an important issue, yet received limited research so far. In this paper, a thorough study of dc-dc conversion system for a medium-voltage dc grid-connected PV system is conducted. The required structural features for such a conversion system are first discussed. Based on these features, the conversion system is classified into four categories by series-parallel connection scheme of power modules. Then two existing conversion system configurations as well as a proposed solution are compared in terms of input/output performance, conversion efficiency, modulation method, control complexity, power density, reliability, and hardware cost. In-depth analysis is carried out to select the most suitable conversion systems in various application scenarios.

KEYWORDS:

1.      Photovoltaic generation

2.      Dc-dc conversion

3.      Medium voltage dc grid

4.      Large-capacity

5.      Ultra-high voltage transfer ratio

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 Topology of PDSR system solution

EXPECTED SIMULATION RESULTS:

Fig. 2 Cycle waves in steady state of the solution of PDSR

Fig. 3 Power step response of the solution of PDSR

Fig. 4 Cycle waves in steady state of the solution of PDDS

Fig. 5 Power step response of the solution of PDDS

Fig. 6 Cycle waves in steady state of the solution of PPDS

Fig. 7 Power step response of the solution of PPDS

 CONCLUSION:

 In this paper, the emerging conversion systems for large-scale PV plants integrated into MVDC grid are studied. The required structural features for such a conversion system are discussed. The conversion system can be classified into four categories by series-parallel connection scheme of power modules: PDSR, PPSR, PDDS and PPDS. Features of each connection-scheme are qualitatively analyzed. A solution of PDDS is also proposed in this paper. Through comparison of the proposed solution with the existing solutions of PDSR and PPDS are conducted through module topology analysis, simulation verification, and estimates of efficiency and cost. The system-connection schemes PDDS and PPDS are most promising. Usually, the PDDS scheme leads to high PWM frequency, good response, high power density and high efficiency, but it has a high cost for active switches and has common reliability. On the other hand, the PPDS scheme leads to low PWM frequency, slow response, low power density, and common efficiency. But it has a low cost of active switches and is highly reliable

 REFERENCES:

[1] A Q Huang, M L Crow, G T Heydt, et al. The future renewable electric energy delivery and management (FREEDM) system: The energy internet. Proceedings of the IEEE, 2011, 99(1): 133-148.

[2] E Rodriguez-Diaz, J C Vasquez, J M Guerrero. Intelligent dc homes in future sustainable energy systems: When efficiency and intelligence work together. IEEE Consumer Electronics Magazine, 2016, 5(1): 74-80.

[3] M Starke, L M Tolbert, B Ozpineci. AC vs. DC distribution: A Loss comparison. 2008 IEEE/PES Transmission and Distribution Conference and Exposition, 2008, Chicago, IL, USA.

[4] M Ding, Z Xu, W Wang, et al. A review on China’s large-scale PV integration: Progress, challenges and recommendations. Renewable and Sustainable Energy Reviews, 2016, 53(9): 639-652.

[5] F Li, C Li, K Sun, et al. Capacity configuration of hybrid CSP/PV plant for economical application of solar energy. Chinese Journal of Electrical Engineering, 2020, 6(2): 19-29.