The permanent magnet synchronous motor (PMSM) driven by an inverter is widely used in the industrial field, but the inverter has a significant impact on the operational stability of the PMSM. The torque ripple of the PMSM is directly affected by the coupling of multiple harmonic voltages in the motor windings. In order to analyze its influence, a water-cooled PMSM with 20 kW 2000 r/min is taken as an example to establish the finite element model of the prototype, and the correctness of the model is verified by experiments. Firstly, based on the finite element method, the electromagnetic field of the PMSM is numerically solved in different operating states, and the performance parameters of the PMSM are obtained. Based on these parameters, the influence of the harmonic voltage amplitude on the torque ripple is studied, and the influence law is obtained. Secondly, combined with the decoupling analysis method, the influence of harmonic voltage coupling on the torque ripple is compared and analyzed, and the variation law of harmonic voltage coupling on the torque ripple is obtained. In addition, the influence of different harmonic voltage coupling on the average torque of the PMSM is studied, and the influence degree of different harmonic voltage amplitude on the torque fluctuation is determined. The conclusion of this paper provides reliable theoretical guidance for improving motor performance.
A novel in-phase disposition (IPD) SPWM pulse allocation strategy applied to a cascaded H-bridge (CHB) converter is presented in this paper. The reason causing the power of the CHB converter imbalance is analyzed according to the traditional structure, the conception of power imbalance degree is introduced and the principle of the novel in-phase disposition SPWM allocation strategy is deduced in detail. The new pulse allocation scheme can ensure the power balance in 3/4 cycles through interchanging the PWM pulse sequence of the different CHB cell, meanwhile it makes the full advantage of the IPD control strategy, lower the total harmonic distortion (THD) of line voltage compared to a carrier phase shifted (CPS) control strategy, which is verified by theoretical derivation. A seven-level cascaded inverter composed by three H-bridge cells is taken as the exam- ple. The simulation and experiment is performed. The results indicate the validity of the analysis and verify the effectiveness of the proposed SPWM allocation strategy.
The paper presents the theoretical background, computer model, laboratory measurements and SPICE simulation results of a 323 W, 1 MHz Class E inverter operating with an efficiency of 97%. The inverter is built around a CoolMOS transistor from Infineon Technologies. The transistor belongs to a new generation of high quality, optimized for low conduction losses and high speed switching power MOSFET-s. The presented computer model of Class E inverter is based on a state-space description and allows computing the inverter parameters for the optimum operation. Its validity has been confirmed experimentally. The SPICE simulation of the inverter has been also carried out in order to obtain better agreement between measurement and calculation results.
In this survey paper, resonant and quasiresonant dc link inverters are reexamined for ac motor drive applications. Critical evaluation of representative topologies is based on simulation and waveform analysis to characterize current/voltage stress of components, control timing constraints and feasibility. A special concern over inverter common-mode voltage and voltage gradient du/dt limitation capacity is discussed for motor bearing and winding insulation safety. Experimental records of the laboratory developed parallel quasiresonant dc link inverter feeding induction motor confirm results of analysis. Comparative tables and simulation results demonstrate characteristic features of various schemes.
An integrated Z-source inverter for the single-phase single-stage grid-connected photovoltaic system is proposed in this paper. The inverter integrates three functional blocks including maximum-power-point-tracking, step-up/down DC-side voltage and output grid-connected current. According to the non-minimum-phase characteristic presented in DC-side and the functional demands of the system, two constant-frequency sliding-mode controllers with integral compensation are proposed to guarantee the system robustness. By using two controllers, the effects caused by the non-minimum-phase characteristic are mitigated. Under the circumstance of that the input voltage or the grid-connected current changes suddenly, the notches/protrusions following the over-shoot/ under-shoot of the DC-bus voltage are eliminated. The quality of grid-connected current is ensured. Also, a small-signal modelling method is employed to analyze the close-loop system. A 300W prototype is built in the laboratory. A solar-array simulator (SAS) is used to verify the systematic responses in the experiment. The correctness and validity of the inverter and proposed control algorithm are proved by simulation and experimental results.
The paper presents an induction generator connected to the power grid using the AC/DC/AC converter and LCL coupling filter. In the converter, both from the generator and the power grid side, three-level inverters were used. The algorithm realizing pulse width modulation (PWM) in inverters has been simplified to the maximum. Control of the induction generator was based on the indirect field oriented control (IFOC) method. At the same time, voltage control has been used for this solution. The MPPT algorithm has been extended to the variable pitch range of the wind turbine blades. The active voltage balancing circuit has been used in the inverter DC voltage circuit. Synchronization of control from the power grid side is ensured by the use of a PLL loop with the system of preliminary suppression of undesired harmonics (CDSC).
This paper proposes a new dc-side active filter for wind generators that combines 12-pulse polygon auto-transformer rectifier with dc-side current injection method and dual-buck full-bridge inverter having not the “shoot-through” problem in conventional bridge-type inverters, and therefore this system with the character low harmonic distortion and high reliability. The proposed dc-side active filter is realized by using dual-buck full bridge converter, which directly injects compensation current at dc-side of two six-pulse diode bridges rectifiers. Compared with the conventional three-phase active power filter at ac-side, the system with the dc-side active filter draws nearly sinusoidal current by shaping the diode bridges output current to be triangular without using the instantaneous reactive power compensation technology, only using simple hysteretic current control, even though under load variation and unbalanced voltage disturbances, and while an acceptable linear approximation to the accurate waveform of injection current is recommended. The perfor- mance of the system was simulated using MATLAB/Simulink, and the possibility of the dc-side active filter eliminating current harmonics was confirmed in steady and transient states. The simulation results indicate, the system has a total harmonic distortion of current reduced closely to 1%, and a high power factor on the wind generator side.