Boyang Hu

180-Degree Commutation System of Permanent Magnet Brushless DC Motor Drive Based on Speed and Current Control

Abstract—To drive Brushless dc motor, each coil of conventional 120-degree commutation rotates only 120-degree with current to generate torque, and wait for next excitation in the other 60 degree without torque generated. However, each coil of 180-degree commutation works for the entire electrical period, which is expected to deliver more power. Analysis, modeling and simulation of 180-degree commutation have not been addressed in previous publications. In this paper, 180-degree commutation theory is analyzed. A 180-degree square-waveform inverter method is designed. A novel 180-degree commutation system is proposed with initial condition, speed and current control. Simulation results prove that the proposed 180-degree system works properly with greater maximum torque than conventional 120-degree system.

Interleaving technique of series connected module-integrated converters for PV systems: Novel approach and system analysis

Conventional interleaving techniques are widely used for parallel connected dc-dc converters. Series connection of dc-dc converters are getting more concerned recently to create a high voltage low current string. However, the interleaving technique of series dc-dc converters has never been addressed. This paper proposes a low cost high performance interleaving technique based on series connection dc-dc converters to reduce the output voltage ripples. The proposed technique is capable for photovoltaic (PV) with mismatched operating conditions. Each PV panel is able to track its own maximum power point (MPP) which simultaneously delivers the maximum power for the system. The proposed technique is mathematically investigated based on both buck-derived and boost-derived converters and proved by Simulink/Matlab simulations and experiment results. Maximum power point tracking (MPPT) algorithm is also tested for a PV/battery charging system with satisfactory performances in both steady-state and transient responses with reduced voltage ripples.

Sensorless drive of brushless DC motor with 180-degree commutation

To drive trapezoidal back-emf type of brushless dc motor, for 120-degree commutation, the winding without phase current in each conduction interval can be considered as a sensor for back-emf detection. However, in the case of 180-degree commutation, the back-emf detection can not be realized because all the three windings are driven with current. Sensorless algorithm of indirect back-emf determination is necessary to be used. In this paper, 180-degree commutation gate switching pattern is analysed. An enhanced sensorless algorithm is developed for 180-degree commutation. PWM soft chopping tehcnique is carried out for supplied voltage adjustment. The simulation results based on Matlab/Simulink prove that the proposed sensorless drive of 180-degree commutation works properly.

A NEW INTERLEAVING TECHNIQUE FOR VOLTAGE RIPPLE CANCELLATION OF SERIES-CONNECT PHOTOVOLTAIC SYSTEMS

The research into series connection of dc–dc converters has been concentrating more recently on creating a high voltage low current string. However, the interleaving technique of series-connect photovoltaic (PV) module integrated converters (MICs) has not been sufficiently addressed so far. This paper proposes a low cost high performance interleaving technique based on series PV MICs to reduce the output voltage-ripples. With the reduced voltage-ripples, the size and cost of capacitors at grid connected inverters can be reduced. The proposed technique is capable of solving the problem for PV panels with mismatched operating conditions. Each PV panel is able to track its own maximum power point (MPP) which simultaneously delivers the maximum power for the system. The proposed technique is mathematically investigated based on boost (step-up) converters and validated by Simulink/Matlab simulation and experiment results. The MPP tracking (MPPT) algorithm is tested for a PV/battery charging system with satisfactory performances in both steady-state and transient responses with reduced voltage-ripples.

Modeling of a new multiple input converter configuration for PV/battery system with MPPT

For renewable sources, such as wind and solar energy, the generated voltages often vary because of environmental changes. When the input voltage drops to the value lower than the battery, it will fail to recharge. The cascaded buck-boost converters are conventionally used to step-up or step-down the input voltage, however it is relatively complex and costly. In this paper, a new battery charging system is proposed based on the noninverting buck-boost converters. The converter requires one less inductor and capacitor compared with the conventional buck-boost converters, thus the cost and loss are reduced significantly. The model is validated through the simulation results of one and multiple sources with constant and variable input voltages. Test results show stable operating performances on both steady-state and transit conditions. Maximum Power Point Tracking (MPPT) algorithm is also successfully applied to the proposed multiple input converter configuration. The proposed system is suitable for both low-voltage portable charging devices and grid-based battery bank systems.

Sensorless drive of permanent magnet brushless DC motor with 180 degree commutation

The three-phase wye connected permanent magnet brushless dc motor is conventionally driven by 120 degree commutation. Two phases are conducting current and the other one is always floating without any torque produced in each conduction interval. Rather than the conventional 120 degree drive, all three phases of 180 degree commutation are expected to conduct current in all sectors, which results in more power delivered from inverter side to the motor side for the same power supply voltage. In this paper, a recently proposed sensorless algorithm is highlighted with well performance in low speed operation. Based on dSPACE, comparison of different dynamic conditions between 120 and 180 degree commutation is presented and analyzed comprehensively. Extensive experiment tests show excellent results on dynamic performance of 180 degree commutation, which matches the simulation results from Simulink/Matlab. 180 degree commutation is verified to work properly with the ability to deliver more power when compared with conventional 120 degree commutation.

A new interleaving technique based on current ripple reduction of paralleled converters for renewable systems

Conventional interleaving switching techniques are widely used to minimise the output current ripples of one input source with several paralleled DC-DC converters. The method of minimising the output current ripples of different paralleled renewable sources working with different duty cycles has never been considered and conventional interleaving techniques are no longer practical to meet requirements. This paper proposes a novel interleaving switching technique for multi-input sources using a novel phase shift method to reduce the current ripples, and further reduce the size/cost of inductors and capacitors needed for filtering. It has favourable advantages such as low cost and fast dynamic response. It is able to accommodate variable input voltages and duty cycles from each converter and the failures of one or more cells. The proposed switching technique is applicable to any type of buck-derived or boost-derived DC-DC converters integrated with renewable sources. It can be used to implement maximum power point tracking applications for integrating renewable sources to the grid. In this paper, photovoltaic systems are adopted for analysis. The proposed technique is validated through detailed mathematical analysis, simulation and implementation.

A NOVEL 180-DEGREE SENSORLESS SYSTEM OF PERMANENT MAGNET BRUSHLESS DC MOTOR

For the conventional 120-degree sensorless drive of a permanent magnet brushless dc (PMBLDC) motor, the winding without phase current in each conduction interval can be considered to be a sensor for back-EMF detection. However, in the case of 180-degree commutation, back-EMF detection is impossible due to all three phases conduct current in each interval and no back-EMF signals are available on stator terminals. This paper proposes a novel 180-degree sensorless system for a PMBLDC motor. The position and speed information are estimated based on the back-EMF signals, which are estimated from the simple sensing of the stator terminal voltage and phase current signals. Furthermore, the proposed 180-degree sensorless system is able to generate up to 33% more torque than the conventional 120-degree system for the same given power supply voltage. The validity of the proposed system is verified through both simulation and implementation.

A novel sensorless algorithm of the trapezoidal back-electromagnetic force brushless DC motors from near-zero to high speeds

Abstract This paper proposes a novel sensorless drive method for the brushless DC (BLDC) motors. It provides an accurate and robust position and speed estimation from the near-zero speed to the rated speed. The proposed sensorless algorithm uses a trapezoidal waveform of the back- electromotive force (EMF) signal with speed information. The back-EMF signals are estimated based on the three-phase current and terminal voltage signals. The validity of the proposed method is verified through both simulation and experimental results.

A novel sensorless method of brushless DC motor based on 180-degree commutation

In this paper, a novel sensorless-drive method of 180-degree commutation is proposed. Inverter gate signals are generated by using the zero-crossing points of estimated back-emf signals, also by comparing the polarities of the estimated back-emf signals. The estimated trapezoidal back-emf signals are obtained by sensoring the three phase-current of motor and the inverter output voltage. Rather than the conventional estimation methods, the proposed method cancels the complicated calculation-steps, which can burden DSP in practical experiments. The simulation under Matlab/Simulink environment shows that the proposed method works properly to make the sensorless drive easy, without estimation of speed and position information.