This paper introduces a design of the sensorless brushless DC motor control process based on the characteristics of the PMD(Programmable Motor Driver)of TMP88PH40 single chip.Analyses the process of start-up,position detection of rotor and speed control of the sensorless brushless DC motor.Introduces the pivotal parts of the PMD: position detection unit and timer unit.The debugging and running of the control system was passed,and the experiments testified that the system can achieve the start-up,smooth drive and variable-frequency control of the sensorless brushless DC motor.

This paper tries to investigate the effects of sinusoidal pulse width modulation (SPWM) dead-time on the common-mode voltage (CMV) in high-voltage adjustable speed drive (ASD) system with three-level neutral point clamped (NPC) inverter. Firstly, the relationship of the CMV between the motor and the three-level NPC inverter is analyzed and the correlative expression is derived. Secondly, the CMV expressions of the NPC inverter without snubbers and load under different dead-time inserted modes are deduced and analyzed using the dual-Fourier method. Then, the impacts of the SPWM dead-time on the output voltage and the CMV of the inverter with RC snubbers and inductance load are studied. Finally, Simulations are carried out to research above problems based on MATLAB. Some useful outcomes can be gained by observing the deduced expressions. When the inverter has not snubbers and load, the output CMV of the inverter comprises the odd time of triple-harmonic mainly, inserting dead-time does not generate the magnitude change of first-harmonic and the new low order harmonic, and the dead time change provokes the magnitude change of the same time harmonic, whether inserting dead-time or not and also regardless of the dead-time inserted modes. When the inverter has RC snubbers and inductance load and adopts the asymmetric dead-time inserted mode, the forward load current makes the output voltage reduced and the negative-going load current makes the voltage raised. This may bring the change of the output CMV of the inverter. Simulation study verifies the above outcomes. Results indicate that: The direction and magnitude of load current and the structure and parameter of the switches' snubbers influence the output voltage and may further influence the output CMV of the inverter. Analyzing the mathematic relation between the SPWM dead-time and the output CMV of the inverter is very difficult.

On the base of roundly analyzing and studying the running mode of the sensorless BLDCM,introduced the theories of detecting back electromotiveforce,phase verdict and the startup of BLDCM.Introduced the hardware circuits and the software flow chart.TMP80PH40 is the system's core.The power MOSFETs were drived by IR2103.The PMD(progammbale motor driver) carryed out detecting back electromotiveforce,phase verdict and the startup of BLDCM.The results showed the system realizes the DC variable-frequency controlling.

EPT (Electronic Power Transformer) is a new type of transformer,which realizes voltage trans-formation and power delivery in power system through power electronic conversion. The main principle of EPT is described and simulation of a new EPT scheme is carried out,in which its steadystate characteristic and dynamic characteristic in four conditions are involved. Simulative results show that EPT guarantees good voltage and current waveforms in both primary and secondary sides and has good control performance. It can be used as a new regulating device of power quality for its regulating function.