Standard Space Vector Pulse Width Modulation Research Articles

Analysis and Control for Wind Energy Conversion System with Five-Level Neutral-Point Clamped Inverter

Multi-level neutral point clamped inverters allow for higher resolution AC outputs and increase the overall efficiency, but higher-level inverters also increase cost exponentially with level and control of the neutral point voltage becomes more difficult through processor capability. The method used within this paper seeks to reduce algorithm complexity by using a two-level space-vector pulse width modulation algorithm-based method while simultaneously implementing a neutral point voltage control embedded within to ensure signal integrity to drive a five-level neutral-point clamped inverter. The increased level of the neutral-point clamped inverter will allow for higher switching efficiency by reducing voltage stress on the switching devices and more stability through reduction of harmonics in the AC output waveform. Results from simulation show the increase in resolution of the AC outputs to both the utility grid and the permanent magnet synchronous generator when compared to a three-level neutral-point clamped inverter using a standard space-vector pulse width modulation switching scheme.

Parallel connected GaN E‐HEMT VSI‐based servo drives for PMSMs

The operation of parallel-connected servo drives has the advantages of increasing the torque (hence the power) capacity, reliability, redundancy and modularity. However, smaller discrepancies of the system clocks of the independent microcontrollers, asynchronous pulse width modulation (PWM) carrier signals and hardware differences can make the output voltages of the parallel modules non-identical, which results in circulating currents. These circulating currents limit the parallel operation, introduce additional power dissipation, cause unbalanced power distribution and degrade the control performance. To eliminate the circulating currents separated DC supplies, coupled inductors (CIs), PWM techniques, modified control techniques etc. are proposed in the literature. In this study, a fault-tolerant parallel-connected gallium nitride enhancement-mode high electron mobility transistor voltage source inverter-based servo drive scheme that eliminates the need for CIs and separate DC supplies and also enables the use of a standard proportional-integral current control and a standard space vector PWM approach is proposed and tested. To evaluate the performances of the proposed scheme, up to six servo drives (limit-6 × 7 Arms) are connected in parallel and tested under various conditions with a 24 V permanent magnet synchronous motor (nominal-61.9 Arms). The results show that the parallel operation not only increases the torque capacity of the system but also increases modularity, flexibility, reliability and also redundancy.

Common-Mode Voltage Reduction in VSI-Fed Motor Drives With an Integrated Active Zero-State Switch

Common-mode voltage (CMV) produced by voltage source inverters (VSI) is of great concern in motor drive systems. A significant amount of conducted common-mode/bearing current will be induced and will interfere with system operation. As an alternative to inserting bulky passive filters to combat the adverse effect by CMV, this article proposes a new topology of integrated active zero-state switch (IAZS). Minor adjustment to the standard space vector pulsewidth modulation (SVPWM) is proposed to facilitate the use of IAZS, which enables CMV reduction in VSI-fed motor drives. Simulation and experimental results on a commercial VSI are presented as proof of concept to validate the effectiveness of the proposed design in CMV reduction.

Active Broken Rotor Bar Diagnosis in Induction Motor Drives

A new active fault diagnosis strategy for broken rotor bars (BRBs) in induction motor (IM) drives is proposed. The active scheme consists of injecting a zero-sequence signal online with a standard space vector pulsewidth modulation (PWM). The injected signal is obtained by applying the null vectors of the PWM, when the star point of the IM is connected to the dc-link midpoint. The response to the injected signal is acquired by using current derivative sensors, from which the diagnostic signals are obtained. BRB faults produce new components in the spectral distribution of the diagnostic signals, which are used as a fault indicator. These components are extracted by using a proposed algorithm, based on a simple reference frame transformation. Experimental results demonstrate the validity of our proposal not only at steady state, but also at transient conditions of speed and load. This is possible because a methodology to convert the diagnostic signals to a stationary ones by resampling it as a function of the rotor position is proposed.

Saliency-Based Permanent Magnet Machine Position Sensorless Drive Using Proposed PWM Injection and Shunt-Based Current Sensing for Position Estimation

For saliency-based position sensorless drives, the switching frequency pulsewidth modulation (PWM) voltage injection can achieve noise-free position estimation which is suited for high-performance motion systems. However, considering the switching frequency injection, multiple phase currents should be sampled per PWM cycle instead of single average current. It leads to the implementation issue on the space-vector PWM (SVPWM) inverter using shunt resistor current sensing for machine control. In this article, a modified PWM injection instead of SVPWM injection is proposed for the saliency-based drive using shunt current sensing. It is concluded that at least two transient currents can be sampled per PWM cycle based on the proposed PWM control. More importantly, the field-oriented control is maintained when the saliency-based drive is applied. A 2 kW permanent magnet (PM) machine is used for the experimental verification. This article includes the position estimation comparison using either the proposed PWM injection with shunt resistors or standard SVPWM with Hall-effect sensors.

PWM‐based Flux linkage estimation for permanent magnet synchronous machines

Monitoring of rotor temperature in permanent magnet synchronous machines (PMSM) is of great importance as high temperature could cause partial or even irreversible demagnetisation of the permanent magnets (PMs). Rotor temperature measurement unfortunately is particularly difficult in practice, since it is difficult to access temperature sensors on a rotating shaft. Nevertheless, rotor temperature can be obtained indirectly with the information of rotor magnet flux linkage, as PM remanence decreases with rotor temperature. Here, a simple and relatively accurate method for online estimation of PM flux linkage is presented, based on the measurement of current response to the standard space-vector pulse width modulation (SV-PWM). This method uses the already-existing PWM voltage as the excitation signal in order to avoid any form of signal injection which produces undesirable disturbance to the system. Knowledge of machine parameters, such as inductances which may vary due to saturation, is not required. The proposed methodology has been verified in real-time simulation.