Modified Phase-Shifted PWM Scheme for Reliability Improvement in Cascaded H-Bridge Multilevel Inverters

ABSTRACT:

The cascaded H-bridge multilevel inverter (CHMI) is a modular structure that consists of many

power semiconductor switches.With this increase in the number of power semiconductor switches, it is hard to predict and handle the failure of the devices, and hence reliability of CHMI decreases. The major cause of power semiconductor switch failure is junction temperature that is produced by power losses. The study proposes a multi-carrier pulse-width modulation (PWM) scheme for reduction in switching losses of CHMI. In the proposed modulation scheme, the two legs conduct switching operation at different frequencies for switching reduction. One leg conducts switching operation with high frequency, while the other leg conducts switching operation with fundamental frequency. The switching operations with different frequencies cause unbalanced switching loss to each leg. Therefore, the junction temperature that is based on power losses leads to different life-times for the power semiconductor switch. Additionally, the switching frequency of the two legs is alternated to evenly distribute switching losses and junction temperature. Simulation and experimental results verify the performance of the proposed PWM scheme.

KEYWORDS:

  1. Cascaded H-bridge multilevel inverter
  2.  Phase-shifted pulse-width modulation scheme
  3. Reliability of power semiconductor switch
  4. Switching loss reduction

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1. Circuit Configuration of Three-Phase CHMI.

EXPECTED SIMULATION RESULTS:

Figure 2. Simulation of Conventional PS-PWM Scheme.

Figure 3. Simulation of Proposed PS-PWM Scheme In 5-Level CHMI.

Figure 4. Simulation of Proposed PS-PWM Scheme In 9-Level CHMI.

CONCLUSION:

This paper proposes a modulation method for a 5-level three phase CHMI to extend the life-time and improve reliability of power semiconductor switches. The proposed method is based on the PS-PWM scheme and decreased power losses via the clamped modulation period. The existing reference voltage waveform is modified into two-type reference voltage waveforms to inject the clamped modulation period. The clamped signal reduces power loss, and other signal is reconfigured to maintain the quality of output waveforms such as the level of output voltage. Reduced power losses decrease the temperature of the power semiconductor switch, and thus the expected life-time of the power semiconductor switch is extended by using the proposed modulation method. Additionally, the proposed modulation scheme considers the power loss balance among the switches in the same cell to improve the reliability of the CHMI. The rotation method with 1/4 period is applied to proposed scheme for even switching loss and temperature among switches. Therefore, the all switches in proposed method are decreased temperature and increased life-time evenly. The performance of the proposed method is verified via simulation and experimental results.

REFERENCES:

[1] B.Wu, High-Power Converter and AC Drives. Hoboken, NJ, USA:Wiley, 2006.

[2] D. Karwatzki and A. Mertens, “Generalized control approach for a class of modular multilevel converter topologies,” IEEE Trans. Power Electron., vol. 33, no. 4, pp. 2888_2900, Apr. 2018.

[3] S. Kouro, M. Malinowski, K. Gopakumar, J. Pou, L. G. Franquelo, B.Wu, J. Rodriguez, M. A. Pérez, and J. I. Leon, “Recent advances and industrial applications of multilevel converters,” IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2553_2580, Aug. 2010.

[4] J. Rodriguez, S. Bernet, B. Wu, J. O. Pontt, and S. Kouro, “Multilevel Voltage-Source-Converter topologies for industrial medium-voltage drives,” IEEE Trans. Ind. Electron., vol. 54, no. 6, pp. 2930_2945, Dec. 2007.

[5] G. P. Adam, I. A. Abdelsalam, K. H. Ahmed, and B.W.Williams, “Hybrid multilevel converter with cascaded H-bridge cells for HVDC applications: Operating principle and scalability,” IEEE Trans. Power Electron., vol. 30, no. 1, pp. 65_77, Jan. 2015.

The Study of Single-phase PWM Rectifier Based on PR Control Strategy

ABSTRACT:

Synchronous PI controller is usually used to track current in three-phase PWM rectifier with zero steady-state error which is difficult to achieve in the single-phase system. A novel proportional-resonant (PR) control scheme for single-phase PWM rectifier is proposed in the paper. Compared with traditional PI control and current hystereis control (CHC) methods, the PR control structure is simple and can reduce control time delay Significantly. The simulation results verify the feasibility of the proposed control scheme in the disturbance rejection. In addition, sinusoidal current zero static error control can be achieved without a coordinate transformation and the DC voltage can automatically adjust to changes of grid voltage, load value and frequency which contributes to energy conversion and bidirectional flow of electricity.

KEYWORDS:

  1. Single-phase rectifiers
  2. CHC control
  3. PR-based control

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

(a) The topological structure

(b) The current control dynamic block diagram

Fig 1. The topological structure and the current control dynamic block diagram of PWM rectifiers.

EXPECTED SIMULATION RESULTS:

(a) The value of DC voltage.

(b) The value of AC current.

(c) Comparison between the feedback current and the referent current

Fig.2. The simulation waves based on CHC control scheme.

(a) The value of DC voltage.

(b) The value of grid voltage and AC current

(c) The value of actual voltage and predictive error.

(d) Comparison between the feedback current and the referent current

Fig 3.The simulation waves based on PR control scheme.

(a) Current Hystereis Control(CHC)

(b) Proportional-Resonant (PR) based control.

Fig 4. The AC current spectrum.

CONCLUSION:

From the above conducted studies, one can conclude that PR-based Control strategy for single-phase PWM rectifier presents better steady-state and can successfully achieve accurate regulation with fast dynamic response with minimum harmonic distortions. The simulation results show that sinusoidal current zero static error control can be achieved without a coordinate transformation and the DC voltage could automatically adjust to changes of grid voltage, load value and frequency which contributes to energy conversion and bidirectional flow of electricity. The control algorithm is easy to be realized while the robustness and power quality is improved. The highlight of paper lies in applying PR regulator to the adjustment of sinusoidal AC current zero static error , building the system model of single-phase PWM rectifier in MATLAB/Simulink with CHC and PR control scheme respectively and giving proper comparisons to some degree.

REFERENCES:

[1] Song H.S, Nam K, Instantaneous Phase-angle Estimation Algorithm Under Unbalanced Voltage-sag Condition, IEEE Proc Generation, Transmission, and Distribution, Vol.147, No.6, 409-415, 2000.

[2] Zmood D.N, Holmes D.G, Stationary Frame Current Regulation of PWM Inverters with Zero Steady-state Error, IEEE Transactions on Power Electronics, Vol.18, No.3, 814-822, 2003.

[3] Yuan X, Merk W, Stemmler H, Stationary-frame Generalized Integrators for Current Control of Active Power Filters with Zero Steady-state Error for Current Harmonics of Concern Under Unbalance and Distorted Operating Conditions, IEEE Trans on Industry Applications, Vol.38, No.2, 523-532, 2002.

[4] ZHAO Qinglin, GUO Xiaoqiang, WU Weiyang, Research on Control Strategy for Single-phase Grid-connected Inverter, Proceedings of the CSEE, 60-64, 2007.

[5] JIANG Jun-feng, LIU Hui-jin, CHEN Yun-ping, A Novel Double Hystersis Current Control Method of Active Power Filter with Voltage Space Vector. Proceedings of the CSEE, Vol.24, No.10, 82-86, 2004.

Sensorless Start-Up Strategy for a 315 kW High-Speed Brushless DC Motor with Small Inductance and Non-ideal Back-EMF

ABSTRACT:

This paper presented a novel sensorless start-up strategy for a 315kW high-speed magnetic suspension brushless DC (BLDC) motor with small inductance and non-ideal back electromotive force (back-EMF). Two key strategies on the sensorless start-up strategy of BLDC motor were presented: (1) small current start-up strategy for the high-speed BLDC motor with small inductance, and (2) self-adaption control strategy to compensate the commutation error for the BLDC motor with non-ideal back-EMF in the start-up stage. A hybrid pulse width modulation (PWM) strategy based on the load torque was proposed to limit the start-up current. An optimal motor start-up curve based on the system parameters was presented, and a self-adaption control strategy was proposed to solve the synchronous switching problem. The effectiveness and feasibility of the proposed method were verified by a series of experiments on the 315 kW-20000 rpm magnetic suspension blower platform.

KEYWORDS:

  1. BLDC motor
  2. Small inductance
  3. Non-ideal back-EMF
  4. Sensorless
  5. Start-up strategy
  6. Self-adaption control strategy

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. The block diagram of novel sensorless start-up strategy.

EXPECTED SIMULATION RESULTS:

Fig. 2. The comparisons experiment results of sensorless start-up strategy. (a) The start-up stage based on traditional sensorless “three-step” start-up method. (b) The start-up stage based on the sensorless start-up strategy proposed in this paper.

Fig. 3. The phase current and line-to-line voltages in the start-up stage without commutation compensation. (a) The synchronous error angle caused the waveform distortion in the start-up stage. (b) The synchronous error angle caused the motor out of step in the start-up stage.

Fig. 4. The comparisons experiment results of sensorless strategy under heavy load. (a) The start-up stage based on traditional sensorless “three step” start-up strategy. (b) The start-up stage based on the sensorless start-up strategy proposed in this paper

Fig.5. The curves of electromagnetic torque and the motor speed when the load torque changed in the start-up stage. (a) The curves under traditional sensorless start-up strategies. (b) The curves under sensorless start-up strategies proposed in this paper.

CONCLUSION:

This paper analyzed the main factors that influence the sensorless start-up performance of the high-power high-speed BLDC motor with small inductance and non-ideal back-EMF. A reliable start-up strategy was proposed by improving the detection of the initial rotor position, the closed-loop acceleration, and the synchronous switching process. The important conclusions were listed as follows.

(1) The rotor initial position can be positioned by the “two step” detection strategy. The start-up current can be adjusted according to the load torque in real time. Therefore, the method proposed in this paper ensured that the motor can start-up successfully under the load condition.

(2) The speed-up curve in the external-synchronization stage was optimized by analyzing the relationship between the motor speed and the terminal voltage. The rotor rotating time from the stationary position to a specify position was obtained by analyzing the average torque in 1/6 cycle and the rotor inherent characteristic.

(3) The synchronous switching process was improved by estimating the commutation error angle and the free decelerating. The influence of the back-EMF shape was analyzed by Eq. (28) and (29). The problems of high frequency noise and the rotor position error were solved by the free decelerating.

REFERENCES:

[1] A. Boglietti, C. Gerada, A. Cavagnino, “High-speed electrical machines and drives,” IEEE Trans. Ind. Electron., vol. 61, no. 6, pp. 2943-2945, Jun. 2014.

[2] W. Li, J. Fang, H. Li, J. Tang, “Position sensorless control without phase shifter for high–speed BLDC motors with low inductance and non-ideal back EMF,” IEEE Trans. Power Electron., vol. 31, no. 2, pp. 1354–1366, Feb. 2016.

[3] S. Chen, G. Liu, S. Zheng, “Sensorless control of BLDCM drive for a High-Speed maglev blower using a low pass filter,” IEEE Trans. Power Electron., vol. 32, no. 11, pp. 8845–8856, Nov. 2017.

[4] S. Shinnaka, “New “D-state-observer”-based vector control for sensorless drive of permanent-magnet synchronous motors,” IEEE Trans. Ind. Appl., vol. 41, no. 3, pp. 825–833, Jun. 2005.

[5] G. Liu, C. Cui, K. Wang, B. Han, S. Zheng, “Sensorless control for high–speed brushless DC motor based on the line–to–line back EMF,” IEEE Trans. Power Electron., vol. 31, no. 7, pp. 4669–4683, Jul. 2016.

Sensor-Less Five-Level Packed U-Cell (PUC5) Inverter Operating in Stand-Alone and Grid-Connected Modes

ABSTRACT:

In this paper a new mode of operation has been introduced for Packed U-Cell (PUC) inverter. A sensor-less voltage control based on redundant switching states is designed for the PUC5 inverter which is integrated into switching process. The sensor-less voltage control is in charge of fixing the DC capacitor voltage at half of the DC source value results in generating symmetric five-level voltage waveform at the output with low harmonic distortion. The sensor-less voltage regulator reduces the complexity of the control system which makes the proposed converter appealing for industrial applications. An external current controller has been applied for grid-connected application of the introduced sensor-less PUC5 to inject active and reactive power from inverter to the grid with arbitrary power factor while the PUC auxiliary DC bus is regulated only by sensor-less controller combined with new switching pattern. Experimental results obtained in stand-alone and grid-connected operating modes of proposed PUC5 inverter prove the fast response and good dynamic performance of the designed sensorless voltage control in balancing the DC capacitor voltage at desired level.

KEYWORDS:

  1. Multilevel Inverter
  2. Packed U-Cell
  3. Sensor-Less Voltage Regulator
  4. PUC5
  5. 5-Level Inverter
  6. Power Quality

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1: PUC inverter topology

EXPECTED SIMULATION RESULTS:

Fig. 2: start-up capacitor charging, 5-level voltage generating and FFT Analysis

Fig 3: adding single-phase rectifier (as nonlinear load) paralleled with the RL load to the output of PUC5

Fig. 4: DC source voltage changes and capacitor voltage is tracking the reference value

Fig. 5: switches gate pulses

Fig. 6: grid-connected PUC5 with change in current reference amplitude

Fig. 7: THD, and Crest factor computation of injected grid current

Fig. 8: PUC5 inverter operation at different power factors a) PF = 0.86, _ = 30° b) PF = 0.86, _ = 60°

CONCLUSION:

The PUC5 inverter has been proposed in this paper while the capacitor voltage is balanced without involving any external controller and voltage feedback sensors. The proposed sensor-less voltage controller has been integrated into switching technique to work as open-loop system with reliable results. Moreover, another controller has been designed for the PUC5 inverter to work as unity power factor grid-connected inverter. Low harmonics components in both voltage and current waveforms generated by PUC5, no need to bulky output filters, reliable and good dynamic performance in variable conditions (including change in DC source, load, power amount injected to the grid), requiring no voltage/current sensor in stand-alone mode, low manufacturing costs and miniaturized package due to using less components and etc are interesting advantages of the introduced PUC5 topology which have been proved by experimental results in both stand-alone and grid-connected modes. The presented PUC5 inverter can be a challenging candidate for conventional photovoltaic application inverters.

REFERENCES:

[1] H. Abu-Rub, M. Malinowski, and K. Al-Haddad, Power electronics for renewable energy systems, transportation and industrial applications: John Wiley & Sons, 2014.

[2] L. G. Franquelo, J. Rodriguez, J. I. Leon, S. Kouro, R. Portillo, and M. A. M. Prats, “The age of multilevel converters arrives,” IEEE Ind. Electron. Mag., vol. 2, no. 2, pp. 28-39, 2008.

[3] C. Cecati, F. Ciancetta, and P. Siano, “A multilevel inverter for photovoltaic systems with fuzzy logic control,” IEEE Trans. Ind. Electron., vol. 57, no. 12, pp. 4115-4125, 2010.

[4] M. Seyedmahmoudian, S. Mekhilef, R. Rahmani, R. Yusof, and E. T. Renani, “Analytical modeling of partially shaded photovoltaic systems,” Energies, vol. 6, no. 1, pp. 128-144, 2013.

[5] H. Mortazavi, H. Mehrjerdi, M. Saad, S. Lefebvre, D. Asber, and L. Lenoir, “A Monitoring Technique for Reversed Power Flow Detection With High PV Penetration Level,” IEEE Trans. Smart Grid, vol. 6, no. 5, pp. 2221-2232, 2015.

Sensorless BLDC Motor Commutation Point Detection and Phase Deviation Correction Method

ABSTRACT:

 Phase-to-neutral voltage or neutral-to-virtual neutral voltage zero-crossing points (ZCPs) detection method is usually used for sensorless BLDC motor commutation control. Unfortunately, neither of them can be realized in lower speed range. In this paper, a simple commutation point detection method is proposed based on detecting inactive phase terminal to dc-link midpoint voltage. It eliminates the requirement of neutral wire or virtual neutral voltage and provides an amplified version of back electromotive force (EMF) at the ZCPs which makes the lower speed range detection possible. As the speed increasing, commutation point error is enlarged due to the low pass filter (LPF) et al. Utilizing the symmetry of the terminal to midpoint voltage the phase error can be corrected. However, due to the nonlinear relationship between the detected voltage difference and phase error, it is difficult to regulate the error fast and robustly. Therefore, a novel phase regulator based on fuzzy neural network (FNN) is proposed in this paper with simple structure and learning ability. The validity of the proposed ZCPs detection method and commutation instant shift correction method are verified through experimental results.

KEYWORDS:

  1. Brushless dc (BLDC) motor
  2. Commutation signal
  3. Fuzzy neural network
  4. Sensorless motor
  5. Zero-crossing points (ZCPs) detection

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1Buck converter based BLDC motor drive system topology

EXPECTED SIMULATION RESULTS:

Fig. 2 Three kinds of ZCPs detection methods comparison.

Fig. 3 Convergence speed comparison between PI controller and FNN-based controller at 18000rpm.

Fig. 4 Performance comparisons between PI controller and FNN-based controller during 10000rpm~13000rpm.

Fig. 5 Performance comparisons between PI controller and FNN-based controller during 3000rpm~7000rpm.

Fig. 6 Performance comparisons between direct calculation method and FNN-based controller at 5000rpm.

Fig. 7 Speed range tests for the terminal to virtual neutral voltage-based method and the proposed method.

Fig. 8 Transient performances of the proposed method.

CONCLUSION:

In this paper, a novel commutation point detection method is proposed. It is realized based on detecting the ZCPs of inactive phase terminal to dc-link midpoint voltage. Since it provides an amplified version of back-EMF at the ZCPs, this method makes the sensorless driving in lower speed range possible. Then, the relationship between the phase shift and the sampled terminal to midpoint voltage difference is derived, and its influencing factors are analyzed in detail. Based on this relationship, a robust and fast commutation point phase deviation correction method is proposed based on the FNN controller. The experiments show that the proposed controller is effective in both steady-speed control and variable-speed control. It exhibits fast convergence behavior in the whole speed range compared with the PI controller, and it presents strong robustness compared with the direct calculation method even if motor parameters have large fluctuations.

REFERENCES:

[1] W. Jiang, H. Huang, J. Wang, et al, “Commutation Analysis of Brushless DC Motor and Reducing Commutation Torque Ripple in the Two-Phase Stationary Frame,” IEEE Trans. Power Electron., vol. 32, no. 6, pp. 4675–4682, Jun. 2017.

[2] W. Chen, Y. Liu, X. Li, et al, “A Novel Method of Reducing Commutation Torque Ripple for Brushless DC Motor Based on Cuk Converter,” IEEE Trans. Power Electron., vol. 32, no. 7, pp. 5497–5508, Jul. 2017.

[3] S.Zheng, B.Han, L.Guo. Composite Hierarchical Antidisturbance Control for Magnetic Bearing System Subject to Multiple External Disturbances [J]. IEEE Transactions on Industrial Electronics, 2014, 61(12): 7004-7012.

[4] S.Zheng, H.Li, B.Han, J.Yang. Power Consumption Reduction for Magnetic Bearing Systems during Torque Output of Control Moment Gyros [J]. IEEE Transactions on Power Electronics, 2017, 32(7): 5752-5759.

[5] T. Chun, Q. Tran, H. Lee, “Sensorless Control of BLDC Motor Drive for an Automotive Fuel Pump Using a Hysteresis Comparator,” IEEE Trans. Power Electron., vol. 29, no. 3, pp. 1382–1391, Mar. 2014.

Novel Single Stage Power Factor Corrected LED Driver Topology for Space Constrained Applications of Aircraft Exterior Lighting System

ABSTRACT:

This paper proposes a novel converter topology based on a single stage LED driver with Power Factor Correction (PFC) which is optimized for weight, volume and cost, for space constrained environments such as Aerospace exterior lighting product. The proposed topology utilizes a single switch to harmonize the input current as well as control the intensity of lighting system. A typical Power Factor Pre-regulator (PFP) uses a bulk energy storage capacitor, which is subjected to wear out at higher altitudes due to low pressure conditions and freezes at negative temperatures, resulting in poor reliability converter for Aerospace applications. Unlike a regular Power Factor Pre-regulator (PFP), the proposed topology avoids the use of bulk energy storage capacitor which results in a fast transient response with enhanced reliability, reduced board real estate and weight. The proposed LED driver topology can control the LED current with both Buck and Boost mode of control, making it a good choice for applications with wide input voltage variation. A 110 W prototype based on proposed converter was built to verify the operation of proposed topology. The experimental results are in line with the predicted performance. The proposed converter is able to achieve a power factor of 0.988 with an input current THD of < 10%.

SOFTWARE: MATLAB/SIMULINK

CONVENTIONAL DIAGRAM:

Figure 1. Conventional two stage active PFC based LED driver topology

EXPECTED SIMULATION RESULTS:

Figure 2. Measured waveforms at 90V AC input (a) Input Voltage (Red) (b) Input current (Blue) (c) Average Voltage drop across LED current sense resistor (green) (Equivalent to LED average current as the sense resistor value is 1ohm.

Figure 3. Measured Linear FFT of input current

Figure 4. Start-up transient at 90V AC input (a) Input Voltage (Red) (b) Input current (Blue) (c)  Average Voltage drop across LED current sense  resistor (Green)(Equivalent to LED average current  as the sense resistor value is 1ohm.

Figure 5. Current profiles through various power circuit components (a) LED Current (Green) (b) Current through MOSFET M1 (Red) (c) Current through inductor L2 (Blue) (d) Current through Inductor L1 (Purple)

Figure 6. Current profiles through various power circuit components (a) LED Current (Green) (b) Current through MOSFET M1 (Red) (c) Current through inductor L2 (Blue) (d) Current through Inductor L1 (Purple)

Figure 7. Measured waveforms at 132V AC input (a) Input Voltage (Light Blue) (b) Input current (Blue) (c) Average Voltage drop across LED current sense resistor (Red).

CONCLUSION:

This paper presents a novel LED driver topology, capable of input power factor correction, for space constrained applications, such as Aerospace exterior lighting product line. Due to the compact design of the proposed LED driver topology, it can be of great advantage for an integrated power supply solution for Aerospace exterior lighting product offerings. The proposed LED driver topology can control the LED current with both Buck and Boost mode of control, making it a good choice for applications with wide input voltage variation. The proposed LED driver topology has been verified by mathematical analysis, circuit simulation and performance has been demonstrated experimentally as well. The proposed LED driver topology promises an appreciable amount of savings in term of real estate, power loss, and heat sink requirements while enhancing the power density of the converter and its reliability. Typically, it’s the bulk output capacitor that wears out with pressure variation (wear out phenomenon accelerates at altitudes more than 8000m due to the reduced pressures); which can be avoided with the proposed topology. Depending upon the load (number of LEDs) and input voltage; in order to protect LEDs, a reverse blocking diode may be required during the Buck operation. For Boost application, reverse blocking diode will not be required even with today’s technology. Authors have been granted a U.S. Patent 9363291 [8] against the proposed novel LED driver topology.

REFERENCES:

[1] L. H. Dixon, “High Power Factor Preregulators for Off- Line Power Supplies,” Unitrode Power Supply Design Seminar Manual SEM600, 1988. (Republished in subsequent Manuals)

[2] Spiazzi, G., and Mattavelli, P. (1994) “Design criteria for power factor preregulators based on SEPIC and Cuk converters in continuous conduction mode,” IEEE IAS Conference Record, 1994, 1084-1089.

[3] Z. Ye, F. Greenfeld, and Z. Liang, “Single-stage offline SEPIC converter with power factor correction to drive high brightness LEDs,” in Proc. IEEE Appl. Power Electron. Conf., 2009, pp. 546–553.

[4] C.Zhou and M.Jovanovic, “Design Trade-offs in Continuous Current-Mode Controlled Boost Power-Factor Correction Circuits”, HFPC Cod. Proc., 1992, pp. 209-220

[5] L. H. Dixon, “Average Current Mode Control of Switching Power Supplies,” Unitrode Power Supply Design Seminar Manual SEM700, 1990

Initial Rotor Position Detection for Brushless DC Motors Based on Coupling Injection of High-Frequency Signal

ABSTRACT:

In applications where motor inversion is forbidden, it is important to detect the initial rotor position of the motor. For this reason, based on coupling injection of high-frequency signal, a novel method of initial rotor position detection for brushless DC motors (BLDCM) is proposed in this paper. Firstly, the proposed method detects the relationship between three-phase winding inductances by injecting the high-frequency detection signal into motor windings in a coupling way, and the initial rotor position is determined into two sectors with 180 degrees electric angle difference. Then, the polarity of the permanent magnet rotor is determined by applying two opposite voltage vectors to motor windings, so that the initial rotor position is determined into a unique sector, and the positioning accuracy is 30 degrees electric angle. The proposed method significantly reduces the amplitude of the detection signal while increases its frequency by the way of coupling injection, thus reducing the response current and electromagnetic torque generated by the high-frequency signal and reducing the possibility of rotor inversion. Finally, the effectiveness of the proposed method is verified by experimental results.

KEYWORDS:

  1. Brushless DC motor
  2.  Initial rotor position
  3. High-frequency signal
  4. Coupling injection

SOFTWARE: MATLAB/SIMULINK

BLOCK DOAGRAM:

Figure 1 Equivalent Circuit Of System When The High-Frequency Detection Signal Is Injected Into Phase A And B.

EXPECTED SIMULATION RESULTS:

Figure 2. Experimental Waveforms With The Rotor Located At 195 Degree. (A) Step I. (B) Step Ii.

Figure 3. Experimental Waveforms With The Rotor Located At 52 Degree. (A) Step I. (B) Step Ii.

Figure 4. Result Of Rotor Position Detection Based On The Proposed Method.

Figure 5. Electromagnetic Torque Of Two Methods When The Rotor Locates At 195 Degree. (A) Method In [13]. (B) Proposed Method.

Figure 6. Electromagnetic Torque Of Two Methods When The Rotor Locates At 52 Degree. (A) Method In [13]. (B) Proposed Method.

Figure 7. Maximum Electromagnetic Torque Of Two Methods When The Rotor Locates At Different Positions.

CONCLUSION:

In this paper, the relationship between winding inductances and the rotor position of BLDCM is analyzed in detail, and a novel method of initial rotor position detection based on high-frequency signal coupling injection is proposed. The initial rotor position can be determined into a sector with 30 degrees electric angle. The proposed method overcomes the limitations of fixed DC-link voltage and limited switching frequency of the inverter by the way of coupling injection, and significantly reduces the amplitude of the detection signal while increases its frequency. Experimental results show that, compared with traditional methods, the method proposed in this paper can accurately detect the initial rotor position and effectively reduce the electromagnetic torque, thus reducing the possibility of rotor inversion in the process of initial position detection.

REFERENCES:

[1] K. Liu, Z. Zhou, and W. Hua, “A novel region-re_nement pulse width modulation method for torque ripple reduction of brushless DC motors,” IEEE Access, vol. 7, pp. 5333_5342, 2019. doi: 10.1109/ACCESS.2018.2888630.

[2] C. Xia, G. Jiang,W. Chen, and T. Shi, “Switching-gain adaptation current control for brushless DC motors,” IEEE Trans. Ind. Electron., vol. 63, no. 4, pp. 2044_2052, Apr. 2016. doi: 10.1109/TIE.2015.2506144.

[3] C. Xia, Y. Wang, and T. Shi, “Implementation of _nite-state model predictive control for commutation torque ripple minimization of permanent- magnet brushless DC motor,” IEEE Trans. Ind. Electron., vol. 60, no. 3, pp. 896_905, Mar. 2013. doi: 10.1109/TIE.2012.2189536.

[4] B. Tan, X. Wang, D. Zhao, K. Shen, J. Zhao, and X. Ding, “A lag angle compensation strategy of phase current for high- speed BLDC motors,” IEEE Access, vol. 7, pp. 9566_9574, 2019. doi: 10.1109/ACCESS.2018.2887106.

[5] J. Shao, “An improved microcontroller-based sensorless brushless DC (BLDC) motor drive for automotive applications,” IEEE Trans. Ind. Appl.,vol. 42, no. 5, pp. 1216_1221, Sep. 2006. doi: 10.1109/TIA.2006.880888.

Front-End Buck Rectifier With Reduced Filter Size and Single-Loop Control

ABSTRACT:

This paper presents a transformerless solution for front-end rectification, which is particularly suitable for traction applications, requiring high voltages to be stepped down to appropriate dc voltage. The proposed topology is based on pulse width modulation buck rectifier (current source inverter topology) and is capable of rectification and stepping down of single-phase ac supply, in a single stage. A new control scheme is proposed to achieve constant dc output voltage and sinusoidal source current, irrespective of large ripples in the dc inductor current. The proposed scheme is configured in single-loop voltage control mode. The relevant small-signal model is derived from the large-signal model using multi order decomposition. An elaborate procedure of dc filter design is discussed, for circuit operation with minimum energy storage. All analytical results are validated by numerical simulation for sinusoidal and distorted source voltage. Experimental verification is achieved through a 1.2-kW grid-connected laboratory prototype.

KEYWORDS:

  1. Buck rectifier (BR)
  2. Single-loop control
  3. Single phase
  4. Traction
  5. Transformerless

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Basic BR circuit.

EXPECTED SIMULATION RESULTS:

Fig. 2. (a) Simulation results: Steady-state operation. vs (160 V/div); is (5 A/div); idc (5 A/div); vo (160 V/div); time (5 ms/div). (b) Harmonic spectrum of is (percentage of fundamental).

Fig. 3. (a) Simulation results: Steady-state operation at boundary condition. vs (160 V/div); is (5 A/div); idc (5 A/div); is1 (5 A/div); time (5 ms/div). (b) Harmonic spectrum of is (percentage of rated fundamental).

Fig. 4. Simulation results: Dynamic performance with step change in vo reference. idc (8 A/div); vo (25 V/div); vo (25 V/div); time (40 ms/div).

Fig. 5. Simulation results: Dynamic performance with step change in vs. vs (200 V/div); is (10 A/div); idc (5 A/div); vo (100 V/div); time (20 ms/div).

Fig. 6. Simulation results with distorted source. (a) vs (120 V/div); is (5 A/div); time (5 ms/div). (b) Harmonic spectrum of is (percentage of fundamental).

CONCLUSION:

In this paper, a single-loop control scheme for single-phase BR has been presented. A nonlinear modulation scheme is proposed, and its effect is analyzed using a multi order system decomposition. The effectiveness of the proposed scheme is proved by simulation and experimental results. From experimental results, it is clear that the proposed control scheme is capable of maintaining sinusoidal source current and near-UPF operation with optimum filter volume, even under distorted grid conditions. Generalized design of the dc inductor, which is the most critical element, is presented in detail. Since source current wave shape is maintained despite ripples in dc current, requirement of an inner current loop is rendered superfluous. Apart from justifying the single-loop control scheme, this also entails greatly simplified controller design and realization.

REFERENCES:

[1] M. Brenna, F. Foiadelli, and D. Zaninelli, “New stability analysis for tuning PI controller of power converters in railway application,” IEEE Trans. Ind. Electron., vol. 58, no. 2, pp. 553–543, Feb. 2011.

[2] M. Carpita, M. Marchesoni, M. Pellerin, and D. Moser, “Multilevel converter for traction applications: Small-scale prototype test results,” IEEE Trans. Ind. Electron., vol. 55, no. 5, pp. 2203–2212,May 2008.

[3] P. Drabek, Z. Peroutka, M. Pitterman, and M. Cedl, “New configuration of traction converter with medium-frequency transformer using matrix converters,” IEEE Trans. Ind. Electron., vol. 58, no. 11, pp. 5041–5048, Nov. 2011.

[4] A. Rufer, N. Schibli, C. Chabert, and C. Zimmermann, “Configurable front-end converters for multicurrent locomotives operated on 16 2/3 Hz and 3 kV DC systems,” IEEE Trans. Power Electron., vol. 18, no. 5, pp. 1186–1193, Sep. 2003.

[5] S. Dieckerhoff, S. Bernet, and D. Krug, “Power loss-oriented evaluation of high voltage IGBTs and multilevel converters in transformerless traction applications,” IEEE Trans. Power Electron., vol. 20, no. 6, pp. 1328–1336,Nov. 2005.

Performance Analysis of Grid Connected PV/Wind Hybrid Power System during Variations of Environmental Conditions and Load

ABSTRACT:

This paper investigates a dynamic modeling, simulation and control of Photovoltaic (PV)-wind hybrid system connected to electrical grid and feeds large plant with critical variable loads. The technique of extracting maximum power point is applied for the hybrid power system to capture maximum power under varying climatic conditions. Moreover, Control strategy for power flow is proposed to supply critical load demand of plant. Modeling and simulation of the proposed hybrid system is performed using matlab-Simulink software. The Dynamic performance of the proposed hybrid system is analyzed under different environmental conditions. The simulation results have proven the effectiveness of the proposed maximum power point tracking (MPPT) strategies in response to rapid variations of weather conditions during the day. Moreover, the results show that when the injected power from hybrid system is larger than critical load power, the excess power will be injected to electrical grid. Otherwise, when injected power is lower than critical power demand, electrical utility grid in cooperated with hybrid power system will supply the critical load power. Moreover, when the injected power from hybrid system is unavailable, load demand is entirely fed by electrical utility.

KEYWORDS:

  1. PV
  2. Wind
  3. Hybrid system
  4. MPPT control
  5. DFIG
  6. Load

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Hybrid power system model.

EXPECTED SIMULATION RESULTS:

(a) Solar irradiance.

(b) Injected active power and reactive power.

(c) Injected current from PV station side (A).

(d) Grid voltage and injected current.

Fig. 2. Performance of PV station (A).

(a) Solar irradiance.

(b) Injected active power and reactive power.

(c) Injected current from PV station side (B).

(d) Power factor of DC/AC converter.

Fig. 3. Performance of PV station (B).

(a) Wind speed profile.

(b) Injected active power and reactive power.

(c) Injected current from Wind farm side (C).

(d) DC link voltage.

Fig. 4. Performance of wind farm

(a) Power delivered to grid side (PCC-bus).

(b) Voltage of PCC-bus.

Fig. 5. Performance of PV-wind hybrid system at PCC-bus.

(a) power flow between hybrid system, grid and load.

(b) Load current side (D).

(c) Load voltage bus-B1.

Fig. 6. Injected power from hybrid system greater than load demand for case 1.

(a) Real power flow between hybrid system, grid and load.

(b) Load current side (D).

Fig. 7. Injected power from hybrid system lower than load demand for case 2.

Fig. 8. Real power flow between hybrid system, grid and load when hybrid power is unavailable.

CONCLUSION:

In this paper, modeling, simulation and control of grid connected photovoltaic-wind hybrid power system have been successfully investigated. The proposed hybrid system consists of two Photovoltaic (PV) stations placed at different locations and one wind farm are integrated into main AC bus and supply large plant with critical variable loads. The incremental conductance MPPT technique is applied for both PV stations to extract maximum power under variations of solar irradiance. Also, an improved MPPT control strategy based on measurement of mechanical power is applied for wind farm to capture the maximum power under changes of wind speed. Moreover, control strategy for power flow is proposed to supply critical load demand of plant. The Dynamic performance of the proposed hybrid system is tested under different environmental conditions such as changes of solar irradiance and wind speed. In addition, the validation of the proposed power flow is evaluated under variation of the critical load demand. The simulation results have proven the robustness of the MPPT control strategies in response to rapid variations in weather conditions during the day. Moreover, the power flow control strategy successfully meets the critical load demand of the plant.

REFERENCES:

[1] R. Benadli and A. Sellami, “Sliding mode control of a photovoltaic-wind hybrid system,” in Electrical Sciences and Technologies in Maghreb (CISTEM), 2014 International Conference on, 2014, pp. 1-8.

[2] J. Hossain, N. Sakib, E. Hossain, and R. Bayindir, “Modelling and Simulation of Solar Plant and Storage System: A Step to Microgrid Technology,” International Journal of Renewable Energy Research (IJRER), vol. 7, pp. 723-737, 2017.

[3] U. Choi, K. Lee, and F. Blaabjerg, “Power electronics for renewable energy systems: Wind turbine and photovoltaic systems,” in Renewable Energy Research and Applications (ICRERA), 2012 International Conference on, 2012, pp. 1-8.

[4] A. B. Oskouei, M. R. Banaei, and M. Sabahi, “Hybrid PV/wind system with quinary asymmetric inverter without increasing DC-link number,” Ain Shams Engineering Journal, vol. 7, pp. 579-592, 2016.

[5] H. Laabidi and A. Mami, “Grid connected Wind- Photovoltaic hybrid system,” in Energy (IYCE), 2015 5th International Youth Conference on, 2015, pp. 1-8.

Voltage Sag Enhancement of Grid Connected Hybrid PV-Wind Power System Using Battery and SMES Based Dynamic Voltage Restorer

ABSTRACT:

Renewable energy sources; which are abundant in nature and climate friendly are the only preferable choice of the world to provide green energy. The limitation of most renewable energy sources specifically wind and solar PV is its intermittent nature which are depend on wind speed and solar irradiance respectively and this leads to power fluctuations. To compensate and protect sensitive loads from being affected by the power distribution side fluctuations and faults, dynamic voltage restorer (DVR) is commonly used. This research work attempts to withstand and secure the effect of voltage fluctuation of grid connected hybrid PV-wind power system. To do so battery and super magnetic energy storage (SMES) based DVR is used as a compensating device in case of voltage sag condition. The compensation method used is a pre-sag compensation which locks the instantaneous real time three phase voltage magnitude and angle in normal condition at the point of common coupling (PCC) and stores independently so that during a disturbance it used for compensation. Symmetrical and asymmetrical voltage sags scenario are considered and compensation is carried out using Power System Computer Aided Design or Electro Magnetic Transient Design and Control (PSCAD/EMTDC) software.

KEYWORDS:

  1. Dynamic voltage restorer (DVR)
  2.  Energy storage
  3. Intermittent
  4. Power quality
  5. Voltage sag compensation

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1. Wind turbine system and its power curve

EXPECTED SIMULATION RESULTS:

Figure 2. Simulation results and DVR response for 25% symmetrical voltage sag case (a) load voltage without DVR, (b) DVR injected voltage and (c) load voltage with DVR

Figure 3.Simulation results and DVR response for 12% symmetrical voltage sag case (a) load voltage without DVR, (b) DVR injected voltage and (c) load voltage with DVR

Figure 4. Simulation results and DVR response for 25% asymmetrical voltage sag case (a) load voltage without DVR, (b) DVR injected voltage and (c) load voltage with DVR

Figure 5. Simulation results and DVR response for 35% asymmetrical voltage sag case (a) load voltage without DVR, (b) DVR injected voltage and (c) load voltage with DVR

CONCLUSION:

In this paper, a voltage sag enhancement of sensitive load which gets power from grid connected PV-wind power system is demonstrated using HES based DVR. The proposed DVR targets to protect the sensitive load from being affected by any voltage fluctuation which arise either from fault condition or unstable power output of PV-wind system. The control and operations of BES and SMES devices is developed by observing voltage condition of the grid at the PCC and the SOC levels of battery and SMES. In addition to this, for full realization of the proposed DVR system the control and operation of the VSC is developed by observing the voltage level at the PCC. The pre-sag compensation strategy is selected based on the capability of both magnitude and phase jump restoration. Based on the conditions, three operating states of the HES based DVR are defined, which are normal (idle state), charging state and discharging state. The effectiveness of the proposed operating states has been demonstrated in realistic cases. In the simulation, different voltage sag depth scenarios are considered for both symmetrical and asymmetrical voltage imbalances and the HES based DVR works well. A combination of voltage sag, voltage swell and harmonics scenarios will be demonstrated in the future works.

REFERENCES:

[1] BP Statistical Review of World Energy, 68th ed. 2019.

[2] M. R. Banaei and S. H. Hosseini, “Verification of a new energy control strategy for dynamic voltage restorer by simulation,” vol. 14, pp. 112–125, 2006.

[3] IRENA, Future of wind: Deployment, investment, technology, grid integration and socio-economic aspects (A Global Energy Transformation paper). International Renewable Energy Agency, Abu Dhabi, 2019.

[4] IRENA, Future of Solar Photovoltaic: Deployment, investment, technology, grid integration and socio-economic aspects (A Global Energy Transformation: paper). International Renewable Energy Agency, Abu Dhabi, 2019.

[5] H. M. Al-masri, S. Member, M. Ehsani, and L. Fellow, “Feasibility Investigation of a Hybrid On-Grid Wind Photovoltaic Retrofitting System,” IEEE Trans. Ind. Appl., vol. 52, no. 3, pp. 1979–1988, 2016.