Brushless DC electric motor (BLDC)

Brushless DC electric motor (BLDC motorsBL motors) also known as electronically commutated motors (ECMs, EC motors), or synchronous DC motors, are synchronous motors powered by DC electricity via an inverter or switching power supply which produces an AC electric current to drive each phase of the motor via a closed loop controller. The controller provides pulses of current to the motor windings that control the speed and torque of the motor.

The construction of a brushless motor system is typically similar to a permanent magnet synchronous motor (PMSM), but can also be a switched reluctance motor, or an induction (asynchronous) motor.[1]

The advantages of a brushless motor over brushed motors are high power to weight ratio, high speed, and electronic control. Brushless motors find applications in such places as computer peripherals (disk drives, printers), hand-held power tools, and vehicles ranging from model aircraft to automobiles.

Brushed DC motors were invented in the 19th century and are common. Brushless DC motors were made possible by the development of solid state electronics in the 1960s.[2]

An electric motor develops torque by alternating the polarity of rotating magnets attached to the rotor, the turning part of the machine, and stationary magnets on the stator which surrounds the rotor.[3] One or both sets of magnets are electromagnets, made of a coil of wire wound around an iron core. DC electric current run through the wire winding creates the magnetic field, providing the power which runs the motor. However, each time the rotor rotates by 180° (a half-turn), the position of the north and south poles on the rotor are reversed. If the magnetic field of the poles remained the same, this would cause a reversal of the torque on the rotor each half-turn, and so the average torque would be zero and the rotor wouldn’t turn.[4][5] Therefore, in a DC motor, in order to create torque in one direction, the direction of electric current through the windings must be reversed with every 180° turn of the rotor (or turned off during the time that it is in the wrong direction). This reverses the direction of the magnetic field as the rotor turns, so the torque on the rotor is always in the same direction.

Flexible AC transmission system (FACTS)

flexible alternating current transmission system (FACTS) is a system composed of static equipment used for the AC transmission of electrical energy. It is meant to enhance controll ability and increase power transfer capability of the network. It is generally a power electronics-based system.

FACTS is defined by the IEEE as “a power electronic based system and other static equipment that provide control of one or more AC transmission system parameters to enhance controll ability and increase power transfer capability.”

According to Siemens “FACTS Increase the reliability of AC grids and reduce power delivery costs. They improve transmission quality and efficiency of power

transmission by supplying inductive or reactive power to the grid.

In shunt compensation, power system is connected in shunt (parallel) with the FACTS. It works as a controllable current source. Shunt compensation is of two types:

Shunt capacitive compensation
This method is used to improve the power factor. Whenever an inductive load is connected to the transmission line, power factor lags because of lagging load current. To compensate, a shunt capacitor is connected which draws current leading the source voltage. The net result is improvement in power factor.
Shunt inductive compensation
This method is used either when charging the transmission line, or, when there is very low load at the receiving end. Due to very low, or no load – very low current flows through the transmission line. Shunt capacitance in the transmission line causes voltage amplification (Ferranti effect). The receiving end voltage may become double the sending end voltage (generally in case of very long transmission lines). To compensate, shunt inductors are connected across the transmission line. The power transfer capability is thereby increased depending upon the power equation

Static synchronous compensator (STATCOM) Projects

static synchronous compensator (STATCOM), also known as a static synchronous condenser (STATCON), is a regulating device used on alternating current electricity transmission networks. It is based on a power electronics voltage-source converter and can act as either a source or sink of reactive AC power to an electricity network. If connected to a source of power it can also provide active AC power. It is a member of the FACTS family of devices. It is inherently modular and electable.

A STATCOM is a voltage source converter (VSC)-based device, with the voltage source behind a reactor. The voltage source is created from a DC capacitor and therefore a STATCOM has very little active power capability. However, its active power capability can be increased if a suitable energy storage device is connected across the DC capacitor. The reactive power at the terminals of the STATCOM depends on the amplitude of the voltage source. For example, if the terminal voltage of the VSC is higher than the AC voltage at the point of connection, the STATCOM generates reactive current; conversely, when the amplitude of the voltage source is lower than the AC voltage, it absorbs reactive power.The response time of a STATCOM is shorter than that of a static VAR compensator (SVC), mainly due to the fast switching times provided by the IGBTs of the voltage source converter. The STATCOM also provides better reactive power support at low AC voltages than an SVC, since the reactive power from a STATCOM decreases linearly with the AC voltage (as the current can be maintained at the rated value even down to low AC voltage).

Design and Analysis of an On-Board Electric Vehicle Charger for Wide Battery Voltage Range  


The scarcity of fossil fuel and the increased pollution leads the use of Electric Vehicles (EV) and Hybrid Electric Vehicles (HEV) instead of conventional Internal Combustion (IC) engine vehicles. An Electric Vehicle requires an on-board charger (OBC) to charge the propulsion battery. The objective of the project work is to design a multifunctional on-board charger that can charge the propulsion battery when the Electric Vehicle (EV) connected to the grid. In this case, the OBC plays an AC-DC converter. The surplus energy of the propulsion battery can be supplied to the grid, in this case, the OBC plays as an inverter. The auxiliary battery can be charged via the propulsion battery when PEV is in driving stage. In this case, the OBC plays like a low voltage DC-DC converter (LDC). An OBC is designed with Boost PFC converter at the first stage to obtain unity power factor with low Total Harmonic Distortion (THD) and a Bi-directional DC-DC converter to regulate the charging voltage and current of the propulsion battery. The battery is a Li-Ion battery with a nominal voltage of 360 V and can be charged from depleted voltage of 320 V to a fully charged condition of 420 V. The function of the second stage DC-DC converter is to charge the battery in a Constant Current and Constant Voltage manner. While in driving condition of the battery the OBC operates as an LDC to charge the Auxiliary battery of the vehicle whose voltage is around 12 V. In LDC operation the Bi-Directional DC-DC converter works in Vehicle to Grid (V2G) mode. A 1KW prototype of multifunctional OBC is designed and simulated in MATLAB/Simulink. The power factor obtained at full load is 0.999 with a THD of 3.65 %. The Battery is charged in A CC mode from 320 V to 420 V with a constant battery current of 2.38 A and the charging is switched into CV mode until the battery current falls below 0.24 A. An LDC is designed to charge a 12 V auxiliary battery with CV mode from the high voltage propulsion battery.


  1. Bi-directional DC-DC converter
  2. Boost PFC converter
  3. Electric vehicle
  4. Low voltage DC-DC converter
  5. Vehicle-to-grid.



Fig 1 Block Diagram of Power distribution in EV











Fig 2 Simulated Results of Charging operation of the propulsion battery (a)Voltage and (b)Current in Beginning Point(c)voltage and (d)current in Nominal Point (e)voltage and (f)current in Turning Point(g)voltage and (h)current in End Point

Fig 3 DC link voltage and current during G2V operation (The current is multiplied by 100 for batter visibility)

Fig 4 Voltage and Current of Auxiliary battery during charging (Current is multiplied by 10 for better visibility)


An On-Board Electric Vehicle charger is designed for level 1 charging with a 230 V input supply. Different stages of an OBC is stated and the challenges are listed. The developments have been implemented to overcome key issues. A two stage charger topology with active PFC converter at the front end followed by a Bi-directional DC-DC converter is designed. The active PFC which is a Boost converter type produces less than 5 % THD at full load. Moreover, the PFC converter is applicable to wide variation in loads. The detailed design of the power stage, as well as the controller, is discussed with the simulated results.

A second stage DC-DC converter is designed and simulated for the charging current and voltage regulation. The converter performs very precisely by charging the propulsion battery in CC/CV mode over a wide range of voltage. A V2G controller has been developed for the DC-DC converter in order to supply power to the grid from the propulsion battery. A new Low-Voltage DC-DC converter is proposed to charge the Auxiliary battery via the propulsion battery utilizing the same OBC. The battery voltage and current waveforms are presented and the performance of the designed converter is verified.


[1] “No Title,” .

[2] S. S. Williamson, Energy management strategies for electric and plug-in hybrid electric vehicles. Springer, 2013.

[3] a. Emadi and K. Rajashekara, “Power Electronics and Motor Drives in Electric, Hybrid Electric, and Plug-In Hybrid Electric Vehicles,” IEEE Trans. Ind. Electron., vol. 55, no. 6, pp. 2237–2245, 2008.

[4] M. Yilmaz and P. T. Krein, “Review of charging power levels and infrastructure for plug-in electric and hybrid vehicles,” 2012 IEEE Int. Electr. Veh. Conf. IEVC 2012, vol. 28, no. 5, pp. 2151–2169, 2012.

[5] H. Wang, S. Dusmez, and A. Khaligh, “Design and analysis of a full-bridge LLC-based PEV charger optimized for wide battery voltage range,” IEEE Trans. Veh. Technol., vol. 63, no. 4, pp. 1603–1613, 2014.


Neuro-fuzzy current controller for three-level cascade inverter based D-STATCOM


Distribution STATCOM (D-STATCOM) is a custom power device connected in parallel to power system. In this paper, Neuro-Fuzzy Controller (NFC) which has robust structure is proposed for control of D-STATCOM’s dq-axis currents. Designed NFC is first order Mamdani type NFC structure and has two inputs, one output and six layers. DSTATCOM is based on three-level cascaded inverter and this inverter is controlled with Sinusoidal Pulse Width Modulation (SPWM) technique. dSPACE’s DS1103 control card is used for real-time implementation of D-STATCOM’s control algorithm. The performance of D-STATCOM using NFC is evaluated by changing of reference reactive current (iqref) as on-line. Under this condition, some experimental results obtained from experimental setup are given.


  2. Neuro-Fuzzy Current Controller
  3. SPWM
  4. Three-Level Cascade Inverter



Fig.1. Three-level cascaded inverter based D-STATCOM



Fig.2. Changing of dc link voltages

 Fig.3. iqref tracking performance of iq

Fig.4. Phase-a current and voltage waveforms of D-STATCOM


Fig.5. Changing of modulation index

Fig.6. Changing of phase angle


In this paper, NFC is developed to synthesize the current control loop of D-STATCOM. NFC which is a combination of ANN and FLC gives the D-STATCOM a good dynamic response and excellent tracking ability in changing of iqref. Experimental results show that Neuro-Fuzzy current controlled D-STATCOM can provide the desired reactive power exact and fast within own rated power limits even in the worst operating condition.


[1] S. Mohagheghi, “Adaptive Critic Designs Based Neuro-Controllers for Local and Wide Area Control of a Multimachine Power System with A Static Compensator,” Phd. Thesis, Georgia Institute of Technology, 2006.

[2] C. Schauder, H. Mehta, “Vector Analysis and Control of Advanced Static VAr Compensators,” Generation, Transmission and Distribution, IEE Proceedings C, vol.140, pp. 299-360, 1993.

[3] V. Blasko, V. Kaura, “A New Mathematical Model and Control of A Three-Phase AC-DC Voltage Source Converter,” IEEE Transactions on Power Electronics, vol.12, pp. 116-123, 1997.

[4] P. W. Lehn, M. R. Iravani, “Experimental Evaluation of STATCOM Closed Loop, IEEE Transactions on Power Delivery,” vol.13, pp. 1378-1384, 1998.

[5] P. Rao, M. L. Crow, Z. Yang, “STATCOM Control for Power System Voltage Control Applications,” IEEE Transactions on Power Delivery, vol.15, pp.1311-1317, 2000.

Cascaded Control of Multilevel Converter based STATCOM for Power System Compensation of Load Variation


The static synchronous compensator (STATCOM) is used in power system network for improving the voltage of a particular bus and compensate the reactive power.It can be connected to particular bus as compensating device to improve the voltage profile and reactive power compensation. In this paper, a multi function controller is proposed and discussed. The control concept is based on a linearization of the d-q components with cascaded controller methods. The fundamental parameters are controlled with using of proportional and integral controller. In closed loop method seven level cascaded multilevel converter (CMC) is proposed to ensure the stable operation for damping of power system oscillations and load variation.


  1. FACTS
  2. PWM
  3. CMC



 Figure 1.STATCOM network connection.


Figure 2. Load terminal dq0 Currents with Load variation

Figure 3. Source terminal dq0 Currents with Load variation.

Figure 4. Iqref output for load rejection.

Figure 5. Source Voltage for load rejection with AGC.

Figure 6. THD of output Voltage of Cascaded Multilevel converter.

Figure 7. THD of output Current of Cascaded Multilevel Converter

Figure 8.Source Active and Reactive power.

Figure 9. Power factor in Load and Source Bus

Figure 10.Three phase Supply Voltage of multilevel converter.


The cascaded controller is designed for seven level CMC based STATCOM. This control scheme regulates the capacitor voltage of the STATCOM and maintain rated supply voltage for any load variation with in the rated value. It has been shown that the CMC is able to reduce the THD values of output voltage and current effectively. The CMC based STATCOM ensures that compensate the reactive power and reduce the harmonics in output of STATCOM.


[1] N. Hingorani and L. Gyugyi, 2000, “Understanding FACTS: Concepts and Technology Flexible AC Transmission Systems”, New York: IEEE Press.

[2] P. Lehn and M. Iravani, Oct.1998, “Experimental evaluation of STATCOM closed loop dynamics”, IEEE Trans. Power Delivery, vol.13, pp.1378-1384.

[3] Mahesh K.Mishra and Arindam Ghosh, Jan 2003, ”Operation of a D-STATCOM in Voltage Control Mode”, IEEE Trans. Power Delivery, vol.18, pp.258-264.

[4] Arindam Ghosh, Avinash Joshi, Jan 2000, ”A New Approach to Load Balancing and Power Factor Correction in Power Distribution System”, IEEE Trans. Power Delivery, vol.15, No.1, pp. 417-422.

[5] Arindam Ghosh, Gerard Ledwich, Oct 2003,”Load Compensating DSTATCOM in Weak AC Systems”, IEEE Trans. Power Delivery, vol.18, No.4, pp.1302-1309.


A Five Level Cascaded H-Bridge Multilevel STATCOM

2015, IEEE

ABSTRACT: This paper describes a three-phase cascade Static Synchronous Compensator (STATCOM) without transformer. Lt presents a control algorithm that meets the demand of load reactive power and also voltage balancing of isolated dc capacitors for H-bridges. The control algorithm used for inverter in this paper is based on a phase shifted carrier (PSC) modulation strategy that has no restriction on the cascaded number. The performance of the STATCOM for different changes of loads was simulated.


  3. Cascaded Multilevel Inverter



Fig1.cascaded multilevel STATCOM.



Fig. 2 Source voltage, source current and inverter current far inductive load(sourece current gain-5 and Inverter current gain-8).

Fig. 3 Load & Inverter Reactive componenets of current for Inductive load.

F ig. 4 Response of DC link voltage for inductive load.

Fig. 5 Source voltage and inverter current for the change of inductive load to half of the load at I sec(lnverter current gain-8)

Fig. 6 Load & Inverter Reactive componenets of current for the change of Inductive load to half of the load at I sec.

Fig. 7 Source voltage and inverter current for the change of inductive load to standby at 1 sec (Inverter current gain-8).

Fig. 8 Load & Inverter Reactive componenets of current for the change of Inductive load to standby at 1 sec

F ig. 9 Inverter Output Voltage

Fig. 10 Harmonie spectrum ofInverter line voltage.

Fig. 11 Load & Inverter reactive component for the change of Inductive to

capacitive load at 1.5 Sec.

Fig. 12 Response of oe link voltage for change in mode of operation from

inductive to capacitive load at 1.5 Sec.

Fig. 13 Inverter reactive component for the change of Inductive to capacitive load at 2 Sec

Fig. 14 Response of OC link voltage for change in mode of operation from inductive to capacitive at 2 Sec


The cascaded H-bridge multilevel topology is used as one of the more suitable topologies for reactive-power compensation applications. This paper presents a new control strategy for cascaded H-bridge multilevel converter based STATCOM. By this control strategy, the dc-link voltage of the inverter is controlled at their respective values when the ST A TCOM mode is converted from inductive to capacitive. The dc link voltages of the inverter are kept balanced in all the circumstances, and the reactive power that is produced by the STATCOM is equally distributed among all the H-bridges.


[1] N. N. V. Surendra Babu, and B.G. Fernandes, ” Cascaded Two Level Inverter- Based Multilevel ST ATCOM for High-Power Applications,” IEEEE Trans. Power Delivery., vol. 29, no. 3, pp. 993-1001, lune. 2014.

[2] N.G. Hingorani and L. Gyagyi, “Understanding F ACTS”, Delhi, India: IEEE, 2001, Standard publishers distributors.

[3] B. Singh, R. Saha, A. Chandra, and K. AI- Haddad, ” Static synchronous compensators (ST A TCOM): A review, ” lET Power Electron., vol. 2, no. 4, pp. 297-324, 2009.

[4] Hirofumi Akagi, Shigenori Inoue and Tsurugi Yoshii, “Control and Performance of a Transformerless Cascade PWM ST A TCOM With Star Contiguration,” IEEE Trans. Ind. Appl., vol. 43, no. 4, pp. 1041-1049, July/ August 2007.

[5] H. Akagi, H. Fujita, S.Yonetaniand Y. Kondo, “A 6.6-kV transformerless ST ATCOM based on a tivelevel diode-clamped PWM converter: System design and experimentation of a 200-V 1 O-kV A laboratory model,” IEEE Trans. Ind. Appl., vol. 44, no. 2, pp. 672-680, Mar./Apr. 2008.

A Filterless Single-Phase AC-AC Converter Based on Coupled Inductors with Safe-Commutation Strategy and Continuous Input Current

2017, IEEE

ABSTRACT: A novel single phase ac-ac converter with no LC input/output filters is presented in this paper. The proposed converter has all the advantages of the previous single phase impedance source ac-ac converters; it can operate in buck/boost and in-phase/out-of phase with the input voltage, that makes it appropriate for voltage sags/swells compensator without any dc storage. A coupled transformer based on T-structure is utilized to give an opportunity to access desired output voltage with various duty cycles. In this topology snubber circuit is not required, because a safe commutation strategy enables to eliminate voltage and current spikes produced by short-circuit path. In addition, the converter performs in continuous current mode, so there is no inrush current. Also, the characteristic which the output voltage reverses or maintains phase angle with the input voltage is supported well, because the input and output share the same ground. Eventually, circuit analysis, operating principles and simulation results in MATLAB/SIMULINK are presented to verify the performance of the converter.


  1. Continuous input current
  2. T-source
  3. Safe commutaion strategy
  4. Ground sharing
  5. Dynamic voltage restorer (DVR)




Fig. 1. Filterless single-phase T-source ac-ac converter



Fig. 2. Simulation results of the proposed converter in boost in-phase mode at D = 0.9, R=10 Ω and n = 2, input/output voltage, c2 voltage, output current, input current.

Fig. 3. Simulation result of the proposed converter in boost in-phase mode at D = 0.9, R=20 Ω and n = 2, output current waveform

Fig. 4. Simulation results of the proposed converter in boost in-phase mode at D = 0.9, R=10 Ω and n = 3, input/output voltage, output current, input current

Fig. 5. Simulation results of the proposed converter in buck out-of-phase mode at D = 0.2, R=10 Ω and n = 2, input/output voltage, output current


In this study, a single phase T-source ac-ac converter has been introduced. The novel topology operates in continuous current mode and low THD, with no filters in input and output. With consider of this point, some privileges rise up such as declining in size and reducing in cost of the converter. Also, output voltage enables to reverse or sustain the phase angle relevant to input voltage greatly, because of the common ground. In addition, a safe commutation strategy is usedto prevent appearance of voltage spikes and current spikes, so it leads to the converter could be designed without any snubber circuits in bidirectional switches. The presence of a coupled transformer based on T- structure in the topology gives this permission to converter that operates in a wider range of duty cycles control. Furthermore, by using of T-source in this topology, desirable voltage gain has been obtained in small conducting duration, which leads to increase efficiency and decrease losses considerably. Moreover, this converter can be applied for DVR devices with utilizing buck-boost feature to compensate various voltage sags and voltage swells. Eventually, accuracy performance and theoretical results of the converter have been verified with consequences of the simulation.


[1] X. Liu, P.Wang, P. C. Loh, and F. Blaabjerg, “A three-phase dual-input matrix converter for grid integration of two AC type energy resources,” IEEE Trans. Ind. Electron., vol. 60, no. 1, pp. 20–30, Jan. 2013.

[2] Y. W. Li, F. Blaabjerg, D. M. Vilathgamuwa, and P. C. Loh, “Design and comparison of high performance stationary-frame controllers for DVR implementation,” IEEE Trans. Power Electron., vol. 22, no.2, pp.602-612, March 2007.

[3] T. Friedli, J.W. Kolar, J. Rodriguez, and P.W. Wheeler, “Comparative Evaluation of Three-Phase AC–AC Matrix Converter and Voltage DC-Link Back-to-Back Converter Systems,” IEEE Trans. Ind. Electron., vol. 59, no.12, pp. 4487 – 4510, Dec. 2012.

[4] L. Empringham, J.W. Kolar, J. Rodriguez, and P.W. Wheeler, “Technological Issues and Industrial Application of Matrix Converters: A Review, ” IEEE Trans. Ind. Electron., vol. 60, no. 10, pp. 4260-4271, May 2013.

[5] O. Ellabban, H. Abu-Rub, and Ge Baoming, “Field oriented control of an induction motor fed by a quasi-Z-source direct matrix converter, ” in Proc. IEEE 39th Ann. Conf. Ind. Electron. Society, pp. 4850-4855, Vienna, 2013.

A Superconducting Magnetic Energy Storage- Emulator/Battery Supported Dynamic Voltage Restorer

IEEE Transactions on Energy Conversion, 2016

ABSTRACT: This study examines the use of superconducting magnetic and battery hybrid energy storage to compensate grid voltage fluctuations. The superconducting magnetic energy storage system (SMES) has been emulated by a high current inductor to investigate a system employing both SMES and battery energy storage experimentally. The design of the laboratory prototype is described in detail, which consists of a series-connected three phase voltage source inverter used to regulate AC voltage, and two bidirectional DC/DC converters used to control energy storage system charge and discharge. ‘DC bus level signaling’ and ‘voltage droop control’ have been used to automatically control power from the magnetic energy storage system during short-duration, high power voltage sags, while the battery is used to provide power during longer-term, low power under-voltages. Energy storage system hybridisation is shown to be advantageous by reducing battery peak power demand compared with a battery-only system, and by improving long term voltage support capability compared with a SMES-only system. Consequently, the SMES/battery hybrid DVR can support both short term high-power voltage sags and long term under voltages with significantly reduced superconducting material cost compared with a SMES-based system.


  1. Dynamic Voltage Restorer (DVR)
  2. Energy Storage Integration
  3. Sag
  4. Superconducting Magnetic Energy Storage
  5. Battery



Figure 1. Hybrid energy storage DVR system configuration.


Figure 2. Simulated PLL Algorithm results: (a) Simulated voltage sag with phase jump (b) Phase jump angle (c) Blue trace: supply phase angle. Red trace: PLL output: ‘Pre-sag compensation’ with controller gains: kp = 0.5, ki = 5, (d) Blue trace: supply phase angle. Red trace: PLL output: ‘In phase compensation’ with controller gains kp = 200, ki = 50.

Figure 3. Hybrid System Experimental results: 0.1s Three phase sag to 35% of nominal voltage. (a) Supply voltages (b) Load voltages (c) DC Link Voltage (d) Battery Current (e) SMES-inductor current.

Figure 4. Battery System Experimental results: 0.1s Three phase sag to 35% of nominal voltage. (a) Supply voltages (b) Load voltages (c) DC Link Voltage (d) Battery Current.


Figure 5. Hybrid System Experimental results: Long-term three phase under voltage (a) RMS supply phase-voltage. (b) RMS load phase-voltage (c) DC Bus Voltage (d) Battery Current (e) SMES-inductor current.


The performance a novel hybrid DVR system topology has been assessed experimentally and shown to effectively provide voltage compensation for short-term sags and long-term under-voltages. A prototype system has been developed which demonstrates an effective method of interfacing SMES and battery energy storage systems to support a three phase load. The system has been shown to autonomously prioritise the use of the short-term energy storage system to support the load during deep, short-term voltage sags and a battery for lower depth, long-term under-voltages. This can have benefits in terms of improved voltage support capability and reduced costs compared with a SMES-based system. Additional benefits include reduced battery power rating requirement and an expected improvement in battery life compared with a battery-only system due to reduced battery power cycling and peak discharge power.


[1] P.K. Ray, S.R. Mohanty, N. Kishor, and J.P.S. Catalao, “Optimal Feature and Decision Tree-Based Classification of Power Quality Disturbances in Distributed Generation Systems,” Sustainable Energy, IEEE Trans., vol. 5, Sept. 2014, pp. 200-208.

[2] D. Novosel, G. Bartok, G. Henneberg, P. Mysore, D. Tziouvaras, and S. Ward, “IEEE PSRC Report on Performance of Relaying During Wide-Area Stressed Conditions,” Power Delivery, IEEE Trans., vol. 25, Jan. 2010, pp. 3-16.

[3] “IEEE Recommended Practice for Monitoring Electric Power Quality,” in IEEE Std 1159-1995, ed. New York, NY: IEEE Standards Board, 1995, p. i.

[4] S. Jothibasu and M.K. Mishra, “A Control Scheme for Storageless DVR Based on Characterization of Voltage Sags,” Power Delivery, IEEE Trans., vol. 29, July 2014, pp. 2261-2269.


Novel Back EMF Zero Difference Point Detection Based Sensorless Technique for BLDC Motor

2017, IEEE

ABSTRACT: In this paper a novel position sensorless scheme named Back EMF Zero Difference Point (ZDP) detection has been proposed for six-switch VSI converter fed permanent magnet BLDC motor. This technique is based on the comparison of back EMFs and detection of the points in the back EMF waveforms where they cross each other or in other words they are equal. Commutation point is achieved exactly at the same instant when the difference of back EMFs of any two phases becomes zero. The simulation study has been carried out for the proposed sensorless scheme. The proposed sensorless scheme has the excellent performance from zero to the extra high speed. The method needs no additional delay circuit as used for calculation of commutation point from back EMF ZCP and involves less calculation burden. The method is fault tolerant and accurate even in the case of noise in measurement (or estimation) of phase back EMFs. A nonzero threshold value proportional to input voltage (or reference speed) is used for overcoming the problem due to quantization and sampling for digital implementation. This method proves to be excellent substitute of hall sensing scheme as it also senses at zero speed.


  1. BLDC motor
  2. Back EMF ZDP
  3. Commutation
  4. Sensorless control
  5. Zero difference point.



Fig.1 VSI fed BLDC motor with indirect Back EMF detection scheme


Fig.2. Phase Back EMF ZDPs, switching signals, counter output and triggering sequence signals.

Fig.3. Steady state operation at the low speed of 600 rpm.

Fig.4. performance of proposed sensorless scheme at 17000 rpm

Fig.5. Noise immune performance during steady state operation for reference speed of 17000rpm.

Fig.6. sensing fault occurs at 0.5 second in the measurement of phase-B back EMF.

Fig.7. speed increases when sensing fault occurs (here phase-B sensing fault


In the proposed Back EMF Zero Difference Point (ZDP) detection method, the very first commutation signal is achieved at starting itself i.e. one step before the ZCP method, which proves the superiority of the method. The back EMF for the proposed scheme can be applied to various existing back EMF detection or estimation techniques. This technique is insensitive to the inherent noise in measurement (or estimation) of back EMF. This method does not need extra

Circuitry as needed for delay after ZCP for getting commutation point, thereby less computational complexity is involved. The speed (or input voltage) proportional threshold used for avoiding uncertainty in the zero difference of back EMF, sets its scope of wide usability in precise operation from zero to extra high speed. Operation at initial zero back EMF is the main strength of this method and it doesn’t necessitate separate starting techniques. Speed response at transient period is 0.15 ms faster than previous methods for identical motor parameters.


[1] M.V.Kesava Rao, Department of Electrical technology, IISc Bangalore, ‘‘Brush Contact Drops in DC machines’’, Accepted 25-6-1934, Bangalore Press.

[2] Y.S. Jeon, H.S. Mok, G.H. Choe, D.K. Kim, J.S. Ryu, “A New Simulation Model of BLDC Motor with Real Back EMF waveform”, 7 th workshop on Computers in power Electronics , 2000 (COMPEL 2000), page 217- 220.

[3] Padmaja yedmale, “Brushless DC (BLDC) Motor Fundamentals”, AN885, 2003 Microchip Technology.

[4] S. Tara , Syfullah Khan Md “Simulation of sensorless operation of BLDC motor based on the zero cross detection from the line voltage” International Journal of Advanced Research in Electrical Electronics and Instrumentation Engineering, vol 2, issue 12 , December 2013, ISSN 2320-3765.

[5] J. R. Frus and B. C. Kuo, “Closed-loop control of step motors using waveform detection,” in Proc. Int. Conf. Stepping Motors and Systems, Leeds, U.K., 1976, pp. 77–84.