Space Vector PWM Algorithms for Three-level Inverter

This study presents a space vector pulse width modulation (PWM) method for a multilevel single-phase decentralized power converter (DPC) called MSPDPC. The proposed model is built by connecting half-bridge cells in series. The output voltage can be adjusted according to demand by adding or subtracting cells. Cells use communication protocols to transmit and receive information with two neighboring cells. The received data contains information for the decentralized space vector pulse width modulation (DSVPWM) method proposed in this paper. In the proposed DSVPWM method, cells set up links to exchange information such as cell position, total cells in a phase, reference voltage amplitude, and reference frequency. The PWM control signals of each cell are calculated based on the information received. The study also focuses on evaluating the ability to adjust the switching vector and the corresponding dwell time of the cells when the structure of the DPC changes. The ability to dynamically reconfigure the DPC is a crucial feature that ensures uninterrupted power supply in case of one or several cell failures. The system automatically establishes a new state with the active cells. The proposed configuration and communication method between cells provide very fast configuration times. The load voltage of the DPC is adjusted to 0.5 times the voltage per cell, which allows the modulation voltage amplitude to be adjusted best according to the load requirements. The study used Matlab/Simulink software to review the initial assessments. The proposed model and algorithms will be verified on the Digital Signal Processor (DSP) platform with a 220V/500W load.

The aim of this paper is to obtain the AC voltage from DC source with the help of Space vector based Inverter. In a space-vector PWM (Pulse Width Modulation) inverter, which is widely used, the voltage utilization factor can be increased to 0.906, normalized to that of the six step operation. Three phase voltage-source pulse width modulation inverters have been widely used for dc/ac power conversion since they can produce a variable voltage and variable frequency power. However, they require a dead time to avoid the arm-short and snubber circuits to suppress the switching spike. Apart from these ancillary aspects, the PWM inverters have an essential problem that they cannot produce voltages as large as the six-step inverters can. That is, the dc bus voltage cannot be utilized to the maximum. To increase the voltage utilization of the sinusoidal PWM inverter, a method of the addition of the third harmonics to the reference voltage was proposed by which the fundamental component can be increased by 15.5%. In a space-vector PWM inverter, which is widely used, the voltage utilization factor can be increased to 0.906, normalized to that of the sixstep operation. On the other hand, different discontinuous PWM strategies were analyzed, where the modulation waveform of a phase has at least one segment of 60 which is clamped to the positive and/or negative dc bus for, at most, a total of 120 in a fundamental period during which no switching in either inverter arm occurs. Recently, it is shown that discontinuous PWM schemes and the space-vector PWM can be obtained by properly adding a zero-sequence voltage to the original modulation waveform.

This paper investigates the effect of (voltage source) inverter's non-linearity on the space vector pulse width modulation (PWM) method and the discontinuous PWM methods, DPWM0, DPWM1, and DPWM2. The inverter's non-linearity of dead-time and minimum pulse-width are considered. These non-linearity's impose distortion regions where their effects cannot be properly compensated. The distortion regions are identified for the various PWM methods in space vector diagram format. A method to switch between DPWM methods to avoid the distortion regions while minimizing switching losses is proposed for the middle modulation indexes. At high modulation indexes, a method to modify the DPWM1 switching function is proposed which preserves the fundamental component while taking into consideration the inverter's non-linearity. The proposed methods are experimentally verified and shown to reduce the harmonics in the motor phase currents which would normally be induced due to the inverter non-linear effects. As a result, the proposed method allows for smoother torque production

Permanent magnet synchronous motor (PMSM) is the most widely used motor in electric vehicles (EV) due to its high power density and high efficiency. Conventional direct torque control (DTC) is developed to improve the performance of speed response of the PMSM drive but it suffers from higher torque ripples. Therefore a space vector modulation (SVM) based DTC has been developed to enhance the speed response. Due to the use of flux comparator and torque comparator conventional DTC has disadvantages such as higher torque and current ripples at steady state. To improve the performance of PMSM drive a space vector pulse width modulation is used with 3 level NPCI. To improve the performance of 2 level inverter in the PMSM drive is replaced with a neutral point clamped inverter (NPCI). Also, the switching selection strategy of SVM is modified using nearest three space vector pulse width modulation to reduce the total harmonic distortion (THD) in the inverter output. The simulation outcome proves that the SVM technique implementation in DTC for 3 level NPCI yields good performance for PMSM.KeywordsElectric vehicles (EV),voltage source inverter (VSI)Direct torque control (DTC)Neutral point clamped inverter (NPCI)Permanent magnet synchronous motor (PMSM)Space vector modulation (SVM)Total harmonic distortion (THD)

This paper proposes the modified space vector pulse width modulation (SVPWM) control algorithm for the three-phase voltage source inverter (VSI), which consists of traditional six switches VSI and three bidirectional switches for creating the ac decoupling circuit. This topology has some advantages such as the ability to reduce the leakage ground current from PV panel and therefore improve the efficiency of photovoltaic (PV) energy conversion based on the principle of decoupling when the zero space vectors occur. Likewise, no current flows through six traditional switches in zero space vectors, thus they operate at lower average temperature. In this case, the conduction losses are reduced. For avoiding shoot-through states between six traditional switches and three bidirectional switches, a delay time has been added to switching time and managed carefully to guarantee THD of output voltage. Operating of the inverter with the modified SVPWM method is simulated by using Matlab/Simulink software and implemented in the experimental prototype by using FPGA Virtex 5 (Xilinx).

Modulation techniques for current source inverters (CSIs) have traditionally been derived from those used for voltage source inverters (VSIs), with space vector modulation (SVM) and pulse width modulation (PWM) being the most popular. Among these, PWM is the preferred choice due to its simplicity and ability to offer the same benefits as SVM, such as increased phase voltage. Ideally, PWM from VSIs could be directly applied to CSIs, but this is not feasible because CSIs require a holistic consideration of all switches on the upper (positive) and lower (negative) rails. In contrast, VSIs allow for per-phase modulation, which enables the straightforward use of a PWM modulator. In this paper, a PWM method tailored specifically for CSIs without any requirements typical for SVM, such as sector identification, is proposed. Using linear algebra, a technique for generating duty cycles averaged over a switching frequency period is derived. These duty cycles are then fed into a specially for CSIs proposed multi-threshold pulse width modulator, which finally produces the gate signals. To validate our method, both simulation and extensive experimental results are presented. The proposed approach is general and applicable to CSIs with any number of phases.

Multilevel inverters are increasingly being used in high-power medium voltage industrial drive applications due to their superior performance compared to conventional two-level inverters. Thre are a number of Pulse width modulation (PWM) techniques applied in recent years. The most widely applied PWM techniques are Sine Pulse Width Modulation (SPWM) and Space Vector Pulse Width Modulation (SVPWM). SPWM is the most simple modulation technique that can realize easily in analog circuit. However, it has some drawbacks such as higher total harmonic distortion (THD), lower effective DC utilization and lower switching frequency. Space vector pulse width modulation (SVPWM) is widely used because of their easier digital realization and better DC bus utilization and lower THD. The complexity is due to the difficulty in determining the reference vector location, on times calculation, and switching states selection. This paper presents a simple SVPWM algorithm for diode clamped three level inverters based on standard two-level SVPWM which can easily determine the location of reference vector, calculate the on-times, the selection of switching states. Three level diode clamped inverter (3LDCI) using space vector modulation technique has been modeled and simulated using MATLAB/SIMULINK and Origin 6.1 with a passive R-L load that can be extended to any level. Simulation results are presented to verify the proposed SVPWM control in terms of THD. The results are compared with conventional sinusoidal pulse width modulation (SPWM) where SVPWM shows better performance than SPWM in terms of THD. DOI: http://dx.doi.org/10.11591/ijpeds.v5i1.6038

In this paper, a novel approach to realize the carrier-based pulse width modulation (CBPWM) method for indirect matrix converter (IMC) is presented. The advantage of the proposed CBPWM method is that only one triangular carrier signal with constant gradient falling and rising edges is used to generate the PWM to the power switches in both the rectifier and the inverter stages of IMC. The analysis of the proposed CBPWM method is based on the space vector approach and the relationship between CBPWM and space vector pulse width modulation (SVPWM) methods is provided. In this paper, four CBPWM methods called: sinusoidal PWM, third harmonic injection PWM, symmetrical PWM and discontinuous PWM are presented. These different CBPWM schemes are established according to the distribution of zero vectors and the switching pattern of the SVPWM method. The comparison of output voltage performance with different CBPWM schemes are investigated. Compared to the conventional method the calculation time of the proposed method is reduced around 50%. Concretely, the calculation time of the SVPWM method is 45 μs, while the calculation time of the proposed method is 22 μs. The experiments have been carried out to show the effectiveness of the proposed method.

Purpose This paper aims to present a modified space vector pulse width modulation (SVPWM) technique for six-phase induction motor drive based on common-mode voltage (CMV) and current losses which are two important issues affecting drive system behavior and quality. Design/methodology/approach It is shown that the presence of z-component currents and the presence of CMV in six-phase drive system are two major limiting factors in space vector selection. The behavior of several space vector selections in a two-level inverter considering minimum CMV and z-components is investigated. Then, the space vectors in a three-level inverter is analyzed and tried to explore an SVM technique with better behavior. Findings The analyses show that all the problems cannot be solved in a six-phase drive system with two-level inverter despite having 64 space vectors; this study tried to overcome the limitations by exploring space vectors in a three-level inverter. Originality/value The proposed pulse width modulation (PWM) strategy leads to minimum current distortion and undesired current components with zero CMV and modest torque ripple.

A voltage source inverter with variable frequency and variable voltage is applied for three-phase interior permanent magnet synchronous motor (IPMSM) drive for variable speed application. To obtain the required output voltage in the line side of the inverter a suitable pulse width modulation technique is used. The most prominent PWM techniques are Sinusoidal pulse width modulation (SPWM) and Space vector pulse width modulation (SVPWM). SPWM is simple and easy method to generate pulses for inverter, whereas SVPWM is an accurate method and generate less harmonic distortion compared to SPWM. However there is a lot of complexity involved in calculation of angle and sector as the level increases with SVPWM. To overcome this a similar and easy method known as unified pulse with modulation also know as carrier based space vector pulse width modulation technique(CBSVPWM is described using the concept of effective time. By using this method the inverter output voltage is directly synthesized by the effective times and the voltage modulation task can be greatly simplified. In this paper an IPMSM drive using CBSVPWM is simulated using MATLAB/SIMULINK software and its performance is compared with SPWM by varying modulation index (MI). The simulation study reveals that CBSVPWM simple and easy method which utilizes dc bus voltage more effectively and generates less THD compared to SPWM.

The Variable Frequency Drives (VFD) are a common type of controlling the speed of 3-phase induction motors which are based on two control modulation techniques of Voltage Source Inverter: Sinusoidal Pulse Width Modulation (SPWM) and Space Vector Pulse Width Modulation (SV-PWM). The SPWM control technique is known as an easier implementation, but the SV-PWM control technique can be distinguished by an easier digital realization and a better utilization of DC bus. All 3-phase PWM inverters produce a total harmonic distortion (THD) on its output, which causes electromechanical and thermal stresses. The aim of this paper is comparing the low order current harmonics while driving an unbalanced 3-phase induction motor (the case of deterioration of the insulation as a result of inter-turn short circuits between few turns of the same phase) using SPWM and SV-PWM two-level 3-phase Voltage Source Inverters (VSI). For this type of unbalanced 3-phase induction motor, the SVPWM and SV-PWM schemes are modeled and simulated using Matlab/Simulink software. A detailed comparative analysis of THD-phase currents is made for both modulation strategies at different switching frequencies while keeping the constant amplitude modulation index.

This paper presents a new switching algorithm for a five-phase voltage source inverter (VSI). In this method a space vector pulse width modulation (SVPWM) based on zero vector elimination is proposed to reduce voltage distortions. The new SVPWM has eight voltage levels to natural point in each phase. To verify the validity of the proposed method, a 2KW laboratory prototype with five-phase is implemented. The experimental result of the new method is compared with the conventional SVPWM for a same sampling time. The experimental results and simulation show that the new SVPWM has relatively lower THD and switching frequency.

This paper presents a modified space vector pulse width modulation (MSVPWM) technique for nine-level cascaded H-bridge (CHB) inverter. Based on a modular structure and absence of capacitor balancing problems, CHB inverter topology is preferred. Nowadays, space vector PWM (SVPWM) control scheme has achieved higher attention among different PWM techniques. In general, SVPWM method is realized based on disintegrating higher-level hexagons into a number of two-level hexagons. Compared to conventional SVPWM technique, the proposed MSVPWM technique reduces the computational burden and memory requirement involved in the realization of nine-level SVPWM. This is achieved by reducing the number of two-level hexagons without losing the inverter output voltage profile. Also a further modified space vector pulse width modulation technique is presented, which greatly reduces the computation efforts. The proposed SVPWM techniques are applied to a nine-level CHB inverter by using MATLAB/SIMULINK software tool and are compared with carrier-based sinusoidal pulse width modulation (SPWM) technique to validate the proposed techniques. The proposed SVPWM schemes produce lower harmonic distortion and higher DC bus utilization compared to SPWM technique. To verify the practicality of the proposed SVPWM techniques, experimental results are presented on nine-level CHB inverter.

Brushless doubly-fed machine (BDFM) is a new type of AC induction motor.It has a good applicable prospect as the variable frequency motors or the variable speed constant frequency generators. Although the advantage of the three-level inverter, there are also some problems of neutral point voltage balance in this method such as the unbalance of neutral point voltage. And the traditional principle of Three-level inverter space vector pulse width modulation method is to estimate the sectors and calculating a lot of trigonometric functions. To solve these problems, a novel method for the virtual space vector concept in G-H coordinate system is presented in this paper. The method proposed can omit the judging process of the sectors, reduce the calculating burden, and maintain the balance of neutral-point voltage between capacitances within a certain index modulation. The results of simulation are given to validate the improved virtual space vector modulation.

This paper is to present a new space vector pulse width modulation (PWM) algorithm for four switch three phase inverter (FSTPI) fed induction motor under DC-link voltage imbalance. By using reasonable mathematical transform, space vector PWM (SVPWM) technique for FSTPI under DC-link voltage imbalance or ripples have been solved, which is based on the establishment of basic space vectors and modulation technique in similarity with six-switch three-phase inverters. This approach has a very important sense to solve hard problems for FSTPI under DC-link voltage imbalance, for example ensuring the required voltage for undermodulation mode and overmodulation mode 1 and 2, extended to six-step mode. Matlab/Simulink is used for the simulation of the proposed SVPWM algorithm for undermodulation, overmodulation mode 1 and 2. This SVPWM approach is also validated experimentally using DSP TMS320LF2407a in FSTPI-IM system.