Seven-phase Voltage Source Inverter Research Articles

An improved seven-phase SVPWM modulation strategy based on virtual voltage vectors

Seven-phase motors are usually powered by seven-phase voltage source inverter. The traditional seven-phase SVPWM algorithm produces a large common-mode voltage (CMV), while harmonic currents in the harmonic subspace can also produce large harmonic losses in motor. The CMV is usually reduced by deprecating the zero-vector method, but the complexity of the computation is complicated by increasing the number of phases. In order to reduce the amount of computation while reducing the harmonic currents and weakening CMV, an improved seven-phase SVPWM algorithm based on virtual voltage vector method to weaken CMV was proposed. First, the time of action of each vector was calculated by adding one constraints. Then, the virtual voltage vectors were constructed by the outermost vectors in the fundamental subspace by comparing the advantages and disadvantages of each voltage vector group. Finally, the reference voltage vectors were constructed by the virtual voltage vectors. Simulation models were built to compare and verify accuracy of proposed SVPWM algorithm.

Fuzzy Logic Decoupling Control of Real and Reactive Power in Grid-Connected Photovoltaic Power System based a Seven Levels Inverter Linked to a Three-Stage Boost Circuit

ABSTRACT The paper presents a detailed modelling, simulation, and control of the real and reactive power flows in the Grid-Connected Photovoltaic Power system (GCPV) based on seven-phase voltage source inverter linked to a three-stage boost circuit interfacing a photovoltaic (PV) generation system to the power grid. Synchronisation of the inverter and grid AC waveforms is achieved using a phase-locked-loop (PLL) circuit. An effective decoupling strategy based on fuzzy logic controllers (DFLC) is designed to eliminate the interaction between the two current components. The DC-link voltage is controlled using a closed loop scheme based on a clamping bridge and an adaptive fuzzy logic PI controller (AFLC-PI). The overall model is implemented in Matlab and Simulink/SimPowerSystems toolboxes. Simulations results with the PV system operating with real irradiance data are presented to demonstrate the performance of the proposed decoupling and control strategies under different conditions of the power grid.

Comparative Analysis of Control Methods with Model Reference Adaptive System Estimators of a Seven-Phase Induction Motor with Encoder Failure

This article presents a comparative analysis of the direct torque control with space vector modulation method for seven-phase squirrel-cage induction motor during the encoder failure. The direct torque control with space vector modulation method with model reference adaptive system with current model and current estimator and model reference adaptive system—flux based estimator applied in the control loop of the motor speed have been analyzed. The mathematical model of the seven-phase induction motor and model reference adaptive system-type estimators have been described. The method of space vector modulation applied to the seven-phase voltage source inverter, controlled seven-phase induction motor, has been described. The operation of direct torque control with space vector modulation has been verified via simulation tests, and the results of performed simulation studies have been analyzed and presented. The authors’ original contribution and work novelty includes comparison studies of the performance of the direct torque control method with space vector modulation of a seven-phase induction motor with two estimators: model reference adaptive system—flux based estimator and the novel model reference adaptive system with current model and current estimator.

Space Vector vs. Sinusoidal Carrier-Based Pulse Width Modulation for a Seven-Phase Voltage Source Inverter

The paper presents an extensive comparison between two pulse width modulation (PWM) control schemes, namely carrier-based and space vector based PWM for a seven-phase voltage source inverter. Sinusoidal carrier-based PWM and space vector PWM techniques are employed to control multiphase power converters supplying variable speed multiphase motor drive systems. Implicit relationships that exist between the two PWM techniques are comprehensively explored; this paper, reveal the underlying relationship between the two PWM techniques in terms of several parameters such as modulating signals and space voltage vectors, modulating signals and space voltage vector sectors, switching pattern of space vector and type of carrier. Furthermore, sharing of zero vectors among different chosen space vectors is elaborated that leads to the formulation of different types of modulation. Digital implementation of the two modulation schemes is elaborated. Simulation results are validated using experimental investigation.

Generalized Minimum Common-Mode Voltage PWM for Two-Level Multiphase VSIs Considering Reference Order

A minimum common-mode voltage (CMV) pulse-width modulator (MCMV_PWM) is proposed for generalized two-level N -phase voltage-source inverters (VSIs) with odd phase numbers. The CMV engenders the breakdown of winding insulation, electromagnetic interference, and leakage currents. Recently, many CMV reduction/elimination PWMs have been widely discussed, but those discussions have mainly focused on the topologies of multilevel inverters or dual-inverter drives for open-ended windings. Therefore, in this study, a two-level multiphase VSI that can be applied to multiphase motor drives, in general, is considered. The relation between switching states and the CMV is derived first. Subsequently, the CMV is minimized using two different leg distributions: double-sided and central distributions. Consequently, for an N -phase VSI, the proposed method reduces the maximum CMV to V dc/(2 N ); that CMV is lower than the maximum CMV of the conventional space-vector PWM (SVPWM), namely V dc/2. In experiments, five-phase and seven-phase VSIs were constructed. The waveforms of the CMV, phase voltage, and phase current produced by the SVPWM and the proposed MCMV_PWM confirm the practicality of CMV minimization.

Finite State Predictive Current and Common Mode Voltage Control of a Seven-phase Voltage Source Inverter

<p class="abstract">The paper elaborate finite set model based predictive current control of a seven-phase voltage source inverter. The current control is carried out considering a finite set of control actions. The space vector model of a seven-phase voltage source inverter (VSI) yields 2<sup>7</sup> = 128 space voltage vectors, with 126 active and two zero vectors. The control method described in this paper discard some switching states from the whole set and employs reduced number of switching states to track the commanded current. Three sets of space vectors are used for switching actuation, in one case only 15 vectors are used (14 active and one zero), in second case 29 vectors are used (28 active and one zero) and finally 43 vectors (42 active and one zero) are employed. Optimal algorithm is employed to find the vector which minimizes the chosen cost function. The effect of selecting the cost function, the number of space vectors and the sampling time is investigated and reported. The developed technique is tested for RL load using simulation and experimental approaches.</p><br /><p class="Papertitle"> </p>

FPGA Implementation of SVPWM Technique for Seven-Phase VSI

This paper presents the performance investigation of FPGA implementation of SVPWM technique for seven-phase voltage source inverter (VSI). Seven-phase voltage source inverters are dominantly used to supply the seven-phase drives which are used for high power applications. In the SVPWM technique a large space vectors are detailed. A voltage source inverter with the proposed SVPWM is simulated in Matlab/Simulink. The performance of the 7-phase VSI is analyzed in terms of fundamental voltage and THD. In the proposed work, SVPWM algorithm is described in high-speed integrated circuit hardware description language coding and implemented in an XILINX Spartan 3A FPGA processor. The selection of zero and active space vector sequence are discussed and the possibilities of realization on FPGA are analyzed.

Analysis of Discontinuous Space Vector PWM Techniques for a Seven-Phase Voltage Source Inverter

This paper presents discontinuous space vector PWM (DPWM) techniques for a seven-phase voltage source inverter (VSI). Space vector model of a seven-phase VSI shows that there exist 128 space vectors with different lengths and maps into fourteen sided polygons. A number of possibilities could arise to implement modulation of inverter legs due to large number of available space voltage vectors. Two strategies are adopted here; one utilising large and two middle sets of space vectors to implement discontinuous space vector PWM. Clamping of legs of inverter to either positive or negative dc bus leads to discontinuity in the switching and consequently offers reduced switching loss modulation strategy. A significant reduction in switching losses can be achieved while employing DPWM in a seven-phase VSI. A generalised method is also proposed to realize the DPWM in a seven-phase VSI. Comparison of continuous and discontinuous PWM is presented in terms of switching current ripple. The experimental set-up is illustrated and the experimental results are presented. DOI: http://dx.doi.org/10.11591/ijpeds.v2i2.244

Space Vector Pulse Width Modulation Scheme for a Seven-Phase Voltage Source Inverter

This paper analyses a simple space vector PWM (SVPWM) scheme for a seven-phase voltage source inverter. At first the conventional method of producing sinusoidal output voltage by utilizing six active and a zero space vectors are used to synthesis the input reference and then new PWM scheme called time equivalent space vector PWM is presented. A comparison of the proposed scheme with the conventional scheme is presented based on various performance indices. Extensive Simulation results are provided to validate the findings DOI: http://dx.doi.org/10.11591/ijpeds.v1i1.72

Analytical Determination of DC-Bus Utilization Limits in Multiphase VSI Supplied AC Drives

Two-level multiphase voltage source inverters (VSIs) are typically used as the supply for multiphase machines. Such machines are often with concentrated winding in which case, certain low-order stator current harmonics are injected to provide torque enhancement. Also, a multimotor drive system can be realized by connecting a number of multiphase machines in series, using phase transposition while supplying the whole system from a single multiphase VSI. In both situations, it is important to know the limits of the inverter operation in the linear modulation region. This paper develops a simple method that enables analytical determination of the boundaries of the linear modulation region for all multiphase inverters with a prime number of phases. The limits are independent of the actual pulse width modulation (PWM) method utilized, and are equally applicable to both carrier-based and space vector PWM techniques. Theoretical considerations are verified experimentally using the five-phase and seven-phase VSI rigs.