Simplified Space Vector Pulse Width Modulation Research Articles

Power Device Thermal Fault Tolerant Control of High-Power Three-Level Explosion-Proof Inverter Based on Holographic Equivalent Dual-Mode Modulation

It is necessary for three-level explosion-proof inverters to have high thermal stability and good output characteristics avoiding problems caused by power devices, such as IGBT, so it becomes a hot and difficult research point using only one control algorithm to guarantee both output characteristics and high thermal stability. Firstly, the simplified SVPWM (Space Vector Pulse Width Modulation) algorithm was illustrated based on the NPC (neutral-point-clamped) three-level inverter, and then the quasi-square wave control was brought in and made into a novel holographic equivalent dual-mode modulation algorithm together with the simplified SVPWM. The holographic equivalent model was established to analyze the relative advantages comparing with the two single algorithms. Finally, the dynamic output and steady power device losses were analyzed, based on which the power loss calculation and system simulation were conducted as well. The experiment proved that the high-power three-level explosion-proof inverter has good output characteristics and thermal stability.

Comparison of Sinusoidal and Space Vector PWM Control Techniques for Three-Level Inverter Drives

In recent years, inverters have been the most popular part of electrical drivers in variable voltage and frequency applications. Also multilevel inverters have gained interest in high power applications because of their advantages in high voltage and high power levels with low harmonic content. In this paper, basic structure of three-level inverter is introduced and its two modulation strategies are compared. One of the modulation algorithms is SPWM (Sinusoidal Pulse Width Modulation) technique where a sinusoidal modulation signal is compared with two triangle signals to obtain the three-level at the output phase voltage of the inverter. A simple SVPWM (Space Vector Pulse Width Modulation) algorithm is also realized. In this technique, three nearest vectors can be selected easily and switching sequence and switching times are calculated by using the vector position. Both techniques are simulated by using MATLAB/Simulink package program and applied to the RL and motor loads. Comparative results are given.

Simplified Three-Level Five-Phase SVPWM

A simplified space vector pulse width modulation (SVPWM) is proposed for a three-level five-phase inverter. The proposed method generates the duty cycle of the three-level inverter switches based on dwell times of the two-level inverter and carrier index. The proposed method automatically determines the eligible vectors, region, and switching sequence of optimized five vectors based on the modulation index. Out of 243 available vectors, 113 most eligible vectors are used for generation of desired voltage reference in main subspace, while zeroing the average voltage in the auxiliary subspace by using the proper switching sequence. This method also uses the redundant vectors in each subcycle thus balances the dc-link capacitor voltages and no additional algorithm or techniques are needed to balance the dc-link capacitor voltage. The identification of the reference location with the carrier index using the signum function simplifies the algorithm implementation. Thus, the proposed method eases the implementation of optimum five vectors to a greater extent. Based on only changing the carrier index, the proposed method can be easily extended for any multiphase multilevel (5, 7,…, n) inverter. The simulation and hardware results of the three-level five-phase inverter validate the proposed simplified method.

A Simple And Geometry Based Fast Space-Vector Pwm Technique For 15 Level Cascaded Multilevel Inverter With Reduction Of Switches

In this paper proposed a simple Space Vector Pulse Width Modulation (SVPWM) algorithm for medium voltage Multilevel Inverter (MLI) with reduced power semiconductor devices and triggering circuits. The result of its lower switching losses and synthesize the maximum output waveform. Conventional scheme and inverter structure incorporated more computational problem and to implement in hardware with increase of level. A new multilevel inverter and SVPWM scheme is much accurate with fast determination of vector location and dwell time calculation with simpler mathematical calculation. In order to minimize the harmonics, the effective switching state transition of SVPWM is computed and to compare with multi-carrier signals. The complexity of experimental digital implementation is simpler by this scheme. The proposed algorithm is simulated and experimentally results are validated with FPGA SPARTAN 6E. The proposed SVPWM and MLI can be easily extent the higher-level output waveform.

Simplified SVPWM that Integrates Overmodulation and Neutral Point Potential Control

A simplified and effective space vector pulse-width modulation (SVPWM) algorithm with two and three levels for three-phase voltage-source converters is proposed in this study. The proposed SVPWM algorithm only uses several linear calculations on three-phase modulated voltages without any complicated trigonometric calculations adopted by conventional SVPWM. This simplified SVPWM also avoids choosing the vector sector required by conventional SVPWM. A two-level overmodulation scheme is integrated into the proposed two-level SVPMW to generate the output voltage that increases from a linear region to a six-step state with a smoothly linear transition characteristic and a simple overmodulation process without a lookup table and complicated nonlinear functions. The three-level SVPWM with a proportional-integral controller effectively balances the neutral point potential of the neutral point clamped converter. Results from the simulation in MATLAB/Simulink and the experiment based on a digital signal processor are provided to clearly demonstrate the validity and effectiveness of the proposed strategies.

Simplified circuit and modulation scheme for five‐phase three‐level voltage source inverter

The simplified circuit and modulation scheme is presented for a five-phase three-level voltage source inverter (FPTL-VSI). The simplified FPTL-VSI is a concatenation of a dual-buck stage and a two-level VSI (TL-VSI), and the space vector pulse width modulation (SVPWM) is used as the modulation scheme. Owing to the merit of the dual-buck stage which uses only four controllable switching devices, the TL-VSI can produce a three-level voltage waveform. By simplification of the space voltage vectors, a simplified SVPWM scheme can be obtained. Thus, the simplified FPTL-VSI reduces the hardware costs and improves the quality of the output voltage waveforms. Furthermore, the hardware implementation of the simplified SVPWM scheme can be easily realised. The experimental results prove the feasibility and validity of the proposed inverter and the modulation scheme.

A New SVPWM Dead-Time Compensation Strategy for Low Speed Direct-Drive Motor

Traditional space vector pulse-width modulation (SVPWM) algorithm included complex calculations like triangle functions and square root, which increased execution time of the program. A novel SVPWM algorithm calculating modulation functions of three phases through stationary αβ components of reference voltage vectors was proposed here to solve the problem, which was composed of only simple four arithmeticoperations. The method simplified traditional SVPWM and improved real-time performance of digital control system. However, dead-time effect still existed in novel SVPWM algorithm. And it will lead to distortions of low speed direct-drive PMSM phase currents, brought increase of speed fluctuation, resulted in unstable operating of servo system. This paper analyzed details of error voltage vectors led by dead-time effect, researched relationship between error voltage vectors and polarities of three phase currents, and put forward a novel dead-time compensation strategy that decreased influence of zero current clamping. Simulation results showed that this strategy can effectively compensate effects of dead-time error voltage vector and improve wave forms of phase currents, which increased operating performance of low speed direct-drive PMSM.

Study and control of 5-level PWM rectifier-5-level NPC active power filter cascade using feedback control and redundant vectors

The purpose of this paper is to develop a control and regulation method for the input DC voltages of a 5-level neutral point clamping (NPC) active power filter (APF). This APF is applied for the enhancement of medium-voltage network power quality by compensation of harmonic currents produced by an induction motor speed variator. In the first part, the authors present a topology of a 5-level NPC voltage source inverter and its simplified space vector pulse width modulation (SVPWM) control strategy. In the second part, the control strategy of the 5-level pulse width modulation current rectifier is presented. In the third part, to remedy to instability problem of the input DC voltages of the APF, the authors propose the feedback control of the 5-level rectifier associated with a simplified SVPWM with the redundant vectors method for the 5-level APF. After that, the sliding mode regulator used to control the APF is developed. The application of the proposed control algorithm offers the possibility of stabilizing the DC voltages of the APF. The stable DC bus supply associated with the sliding regulator of the APF allows the obtainment of low-harmonic content network currents with unity power factor. The instability problem associated with the use of the multilevel APF is solved. The obtained results are full of promise for the use of the multilevel APF in medium-voltage and high-power applications.

A new simplified SVPWM algorithm based on modified carrier signal

This paper presents a simplified algorithm of space vector pulse width modulation (SVPWM) for a two-level three-phase inverter, which can operate in undermodulation and overmodulation modes. In other simplifications founded in literature, the reference voltages are modified and compared with a triangular carrier to estimate the switching states of the inverter. However, this paper proposes the modification of the carrier signal instead of the references. This procedure reduces the number of mathematical operations and increases the execution speed of SVPWM algorithm in DSPs or FPGAs. The reference voltages are sinusoidal, even for overmodulation mode. Simulation and experimental results proves that the proposed simplification produces the same switching patterns than conventional SVPWM, is simpler and is faster than other simplifications.

Novel Control Strategy for Multi-Level Active Power Filter without Phase-Locked-Loop

Active power filter (APF) using novel virtual line-flux-linkage oriented control strategy can not only realizes no phase-locked-loop (PLL) control, but also achieves a good inhibitory effect to interfere. However, there are some problems in the conventional method, such as the error of amplitude, the shift of phase angle and the non-determinacy of initial oriented angle. In this paper, two one-order low-pass filters are adopted instead of the pure integrator in the virtual line-flux-linkage observer, which can steady the phase and amplitude. Furthermore, an original scheme of harmonics detection under the rotating coordinate is advanced based on the simplified space vector pulse width modulation (SVPWM) strategy. Meanwhile, by using the new SVPWM algorithm, the voltage space vector diagram of the three-level inverter can be simplified and applied into that of two-level inverter, and this makes the control for Neutral Point potential easier.

Back-to-back three-level double-fed induction motor control system for mine hoist

The stator-flux-oriented vector control strategy for double-fed induction motor was investigated in this paper. Three phase three-level rectifier was used as AC/DC block. This rectifier worked with low harmonic distortion in the grid side. Besides, it maintained a high power factor while the energy flows in bidirectional way. For the DC/AC converter, three-level inverter was adopted. Using stator-flux oriented vector control, the double-fed induction gained a high dynamic performance when the stator side was controlled operating in a unite power factor condition. In this paper a novel simplified space vector pulse width modulation (SVPWM) method was proposed to simplify the calculation. The neutral-point potential balance can be easily realized with this method. The control strategy was verified by experiments.

A General Space Vector PWM Algorithm for Multilevel Inverters, Including Operation in Overmodulation Range

This paper proposes a simple space vector pulsewidth modulation algorithm for a multilevel inverter for operation in the overmodulation range. The proposed scheme easily determines the location of the reference vector and calculates on-times. It uses a simple mapping to generate gating signals for the inverter. A five-level cascaded inverter is used to explain the scheme. The scheme can be easily extended to a n-level inverter. It is applicable to neutral point clamped topology as well. Experimental results are provided for five-level and seven-level cascaded inverters

Space vector modulation strategy for an eight-switch three-phase NPC converter

A three-phase neutral point clamped (NPC) converter is presented for power factor correction and dc-link voltage regulation. A simplified space vector pulsewidth modulation scheme (SVPWM) is adopted to track line current commands. Using a simplified SVPWM algorithm, the calculated time for the time duration of voltage vector is reduced. The adopted NPC converter has less power switches compared with the conventional three-level NPC converter. Only eight power switches and four clamping diodes with voltage stress of half the dc bus voltage are used in the circuit configuration. Based on the proposed control algorithm, a reference voltage vector is generated on the ac terminal for drawing the sinusoidal line currents with unity power factor. Computer simulation and experimental results based on a laboratory prototype are presented to verify the validity and effectiveness of the proposed control strategy.

A new simplified space-vector PWM method for three-level inverters

In this paper, a new simplified space-vector pulse width modulation (SVPWM) method for a three-level inverter is proposed. This method is based on the simplification of the space-vector diagram of a three-level inverter into that of a two-level inverter. If simplified by the proposed method, all the remaining procedures necessary for the three-level SVPWM are done like conventional two-level inverter and the execution time is greatly reduced. The DC-link neutral-point potential control algorithms are implemented more easily. The proposed method can be applied to the multi-level inverters above three-level. The validity of the new SVPWM method is verified by experiment with a 1000 kVA three-level insulated gate bipolar transistor (IGBT) inverter.