PWM Algorithm Research Articles

Research on Energy Efficiency System of New Energy Vehicle Electric Drive

The motors of new energy vehicles adopt the built-in permanent magnet synchronous motor (PMSM) with high system efficiency. The mainstream control method of electric drive system is space vector PWM (SVPWM) algorithm. The SVPWM algorithm has higher low-order harmonic content in the low-speed segment voltage waveform, large asynchronous motor torque, and large motor iron loss, which makes the electric drive system less efficient in the low-speed segment system. This paper creatively proposes to change the modulation ratio M of the SVPWM waveform by adjusting the bus voltage, switching frequency and different control angles to reduce the harmonic content of the system to improve the overall efficiency of the electric drive system. In this paper, a theoretical model is established for the motor phase voltage harmonics, and various factors and components affecting the harmonic content are analyzed. Combined with the digital signal processor (DSP) based SVPWM vector control algorithm, the motor control SIMULINK simulation system is built. The voltage harmonic analysis of the simulation system is carried out by using the FFT tool in POWERGUI. The electric drive system bench is established for testing, the electric drive system simulation and the test bench test data are analyzed, and a clear method and means are proposed to reduce the harmonic content.

Improving of operation stability of frequency converters with active rectifiers in electric steel-making complex electrical equipment switching

Frequency converters with active rectifiers (FC-AR) are now used in rolling mill electric drives. Modern control systems of ARs are not adapted to voltage sags in power supply systems, which leads to converter tripping. The known methods of ensuring AR operation stability, such as kinetic buffering, correction signals based on negative sequence voltage and others, do not eliminate these emergency trips. As an additional measure the paper proposes the method of voltage sag compensation by using static var compensators (SVC) of electric arc furnaces (EAF) for parallel operation of frequency converters with active rectifiers and electric arc furnaces. However, it remains unknown how disturbances (such as overvoltages of switching of SVC harmonic filters (HF) and voltage sags during furnace transformer switching) affect operation stability of frequency converters with active rectifiers. All this makes it necessary to study the effect of these processes on the operation conditions of FC-AR and to improve the active rectifier control system. The authors used experimental arrays of instantaneous values of voltages and currents of the real-life complex «EAF-SVC» («Electric Arc Furnace – Statistic VAR Compensator») in this study. They also applied mathematical models of FC-AR with different PWM algorithms realized in Matlab-Simulink software. The main assumption of the model consists in using equivalent current sources modelling the operation of autonomous voltage invertors. An improved control system of AR has been developed. The main feature that distinguishes it from the known systems is the fact that it ensures operation stability during SVC harmonic filter and EAF transformer switching by using a signal conditioning unit for setting the active rectifier reactive current component as a function of power supply and AR input voltage difference. Implementation of the improved AR control system improves FC-AR stability during parallel operation with EAFs through reactive power consumption of the supply system. As a result, it reduces the amplitude of inrush current and voltage deviations in the DC-link of the FC-AR to the values lower than the setpoints of the AR protection system.

Interleaved Flyback Converter with Embedded Grid Interacting PV Cascaded MLI

The importance of extracting power from renewable energy sources are increasing in the modern world as the power demand is increasing day by day and the non renewable energy sources are getting dried up. Solar power is a domestic source of energy and its availability throughout the year makes it a primary target to solve this crisis. It will never produce any hazardous waste or pollution. But various issues like Power quality problems and Harmonic distortion seep in due to the intermittent nature of PV system. This paper proposes a cascaded H–bridge multilevel inverter for grid connected PV system with a flyback converter. This helps to achieve maximum power point tracking and also provides isolation which will further help to increase system efficiency. The DC–DC flyback converters are cascaded to generate multilevel output voltage. Then this multilevel dc output is given to H bridge inverter to generate multilevel output. A new control algorithm is used in this paper which combines voltage–hold Perturb and observe method and modified PWM algorithm which helps to achieve the best MPPT. The proposed topology is implemented in PSIM. The Simulation and Hardware results reveal that the suggested technique is highly.

Novel compound PWM strategy of a four-leg shunt active power filter

ABSTRACTThe currently used hysteresis method is of low control accuracy, and the PWM-based strategy fails to provide a high enough response speed; thus, there is always a trade-off between the performances of control accuracy and response speed for a four-leg shunt active power filter (APF) to cope with the large variation in the load harmonic profile. First, an improved SVPWM strategy is proposed in this paper; with the aim to increase the response speed of a four-leg APF by simplifying the implementation of current 3D-SVPWM methods, the principle and realisation of this strategy are explained in detail. Based on these works, a compound PWM algorithm that effectively integrates the improved SVPWM and a PI-based current hysteresis method is proposed to simultaneously guarantee a higher response speed and a higher control accuracy for a four-leg APF. The realisation and parameter tuning of the compound PWM are elaborated. The correctness and effectiveness of the improved SVPWM and the compound PWM strategy are verified by simulations using Matlab/Simulink software. Finally, experimental results on a four-leg APF implemented in a closed-loop real-time simulation platform are presented.

Circulating Current Reduction for Paralleled Inverters With Modified Zero-CM PWM Algorithm

Paralleled inverters are not only a suitable approach to increase the power capacity, but also have the capability of common mode voltage (CMV) reduction, or even elimination. The original zero CMV modulation scheme for paralleled inverters suffers from the current jump problem in phase-leg currents. This current jump phenomenon amplifies the peak values of differential-mode circulating current (DMCC) and zero-sequence circulating current (ZSCC), which is adverse for the design of coupled inductor and common-mode inductor. This paper introduces the modified modulation scheme, which can keep volt-seconds balance in whole fundamental period and mitigate the current jump in phase-leg currents. In addition, the reduction effect of the DMCC and ZSCC can be achieved. To verify the analysis, both the simulation and experimental results are presented, which validates the proposed methods and show that they are beneficial for DMCC and ZSCC reduction.

Level Shifted Discontinuous PWM Algorithms to Minimize Common Mode Voltage for Cascaded Multilevel Inverter Fed Induction Motor Drive

This paper presents combinations of level shifted pulse-width modulation algorithm with conventional discontinuous pulse-width modulation methods for cascaded multilevel inverters. In the proposed DPWM a zero sequence signal is injected in sinusoidal reference signal to generate various modulators with easier implementation. The analysis four various control strategies namely Common Carrier (CC), Inverted Carrier (IC), Phase Shifted (PS) and Inverted Phase Shift (IPS) for cascaded multilevel inverter fed induction motor drive has been illustrated. To validate the proposed work experimental tests has been carried out using dSPACE controller. Experimental study proves that using proposed algorithms reduction in common-mode voltage with fewer harmonics along with reduced switching loss for a cascaded multilevel inverter fed motor drive has been achieved.

Determining electrical losses of the traction drive of electric train based on a synchronous motor with excitation from permanent magnets

We have studied a traction drive based on the synchronous motor with excitation from permanent magnets for its electrical losses. A simulation model of the traction drive is synthesized, which employs the algorithm of a space-vector PWM. A special feature of the model is the application of parameters of actual IGBT-transistors and the possibility for obtaining instantaneous values of electric losses in transistors and snubbers of the inverter under different modes of operation. We have devised a procedure for calculating electric losses in the traction engine based on the shape of phase currents, geometrical and electrical parameters of the engine. Simulation of the traction drive and calculation of losses in the traction engine is integrated, which makes it possible to account for the impact of the inverter and engine on each other. We have simulated work of the reducer-free traction drive based on a synchronous motor with excitation from permanent magnets with a capacity of 80 kW. The dependences were constructed for losses in the traction inverter and engine on the clock frequency of a space-vector PWM and motion speed. The proposed procedure makes it possible to quantify the magnitude of electric losses in the traction drive elements depending on the types of transistors applied, clock frequency of the inverter, and parameters of the engine. This enables the optimization of the traction drive for the criterion of maximum performance efficiency, as well as thermal calculation of the elements of the drive.

Разработка усовершенствованного алгоритма ШИМ активного выпрямителя с адаптацией к резонансным явлениям во внутризаводской сети

Разработка усовершенствованного алгоритма ШИМ активного выпрямителя с адаптацией к резонансным явлениям во внутризаводской сети

A Novel Approach for Space Vector Based PWM Algorithm for Diode Clamped Three level VSI Fed Induction Motor Drive

<p>Performance of a voltage source inverter depends on pulse width modulation algorithms. Various algorithms exist for conventional space vector as well as space vector based bus clamped pulse width modulation for multilevel inverter in the literature. In this paper appropriate region selection algorithm for conventional space vector pulse width modulation (CSVPWM) and bus clamped pulse width modulation (BCPWM) techniques are proposed for diode clamped three level voltage source inverter. The proposed techniques are implemented on a three level voltage source inverter fed induction motor drive for open loop operation. The schemes are simulated in MATLAB/SIMULINK environments. The merit of proposed region selection algorithm is tested and verified through simulation result. Further performance comparisons between SVPWM and BCPWM for different modulation index are discussed. </p>

Technical approaches towards ultra-high power density SiC inverter in electric vehicle applications

Along with the rapid growth in electric vehicle (EV) market, higher power density and more efficient motor drive inverters are required. It is well known that silicon carbide (SiC) has advantages of high temperature, high efficiency and high switching frequency. It is believed that the appropriate utilization of these merits can pave the way to ultra-high power density inverters. This paper presents issues about SiC chip’s current-carrying capability enhancement which is crucial for a compact inverter of tens and hundreds of kilowatts. Technical approaches towards ultra-high power density EV inverter including SiC module packaging, dc-link capacitor function analysis and system level integration are discussed. Different PWM algorithms which may improve efficiency and help to reduce the inverter volume are also studied.

Modulated Predictive Control for Indirect Matrix Converter

Finite State Model Predictive Control (MPC) has been recently applied to several converter topologies as it can provide many advantages over other MPC techniques. The advantages of MPC include fast dynamics, multi-target control capability and relatively easy implementation on digital control platforms. However, its inherent variable switching frequency and lower steady state waveform quality, with respect to standard control which includes an appropriate modulation technique, represent a limitation to its applicability. Modulated Model Predictive Control (M2PC) combines all the advantages of MPC with the fixed switching frequency characteristic of PWM algorithms. The work presented in this paper focuses on the Indirect Matrix Converter (IMC), where the tight coupling between rectifier stage and inverter stage has to be taken into account in the M2PC design. This paper proposes an M2PC solution, suitable for IMC, with a switching pattern which emulates the desired waveform quality features of Space Vector Modulation (SVM) for matrix converters. The switching sequences of the rectifier stage and inverter stage are rearranged in order to always achieve zero-current switching on the rectifier stage, thus simplifying the current commutation strategy.

Maximum Power Point Tracking for Cascaded PV-Converter Modules Using Two-Stage Particle Swarm Optimization

The paper presents a novel two-stage particle swarm optimization (PSO) for the maximum power point tracking (MPPT) control of a PV system consisting of cascaded PV-converter modules, under partial shading conditions (PSCs). In this scheme, the grouping method of the shuffled frog leaping algorithm (SFLA) is incorporated with the basic PSO algorithm, ensuring fast and accurate searching of the global extremum. An adaptive speed factor is also introduced to improve its convergence speed. A PWM algorithm enabling permuted switching of the PV sources is applied. The method enables this PV system to achieve the maximum power generation for any number of PV and converter modules. Simulation studies of the proposed MPPT scheme are performed on a system having two chained PV buck-converter modules and a dc-ac H-bridge connected at its terminals for supplying an AC load. The results show that this type of PV system allows each module to achieve the maximum power generation according its illumination level without affecting the others, and the proposed new control method gives significantly higher power output compared with the conventional P&O and PSO methods.

Space vector based random pwm algorithms for acoustic noise and harmonics reduction for voltage source inverter fed ac drive

Conventional Space vector based Pulse Width Modulation (PWM) method is superior to Sinusoidal PWM technique in terms of its better DC bus utilization as well as harmonic reduction. But it doesn’t give solution to reduce acoustic noise which is more annoyance to the driver and the passenger or the human beings in certain applications such as electric propulsion or accessory drives. This paper presents space vector based random PWM techniques - a solution to reduce the acoustic noise as well spread spectrum resulting in low harmonic distortion as suppression of peak sound pressure levels. The techniques employed for a VSI fed Induction motor drive are 1) Random Zero vector PWM 2) Dual Zero Random PWM and 3) Variable Delay Random PWM. The spectrum plots of stator current demonstrate the effectiveness of the proposed PWM techniques. The feasibility of the proposed PWM techniques has been confirmed in terms of acoustical noise and harmonic distortion is presented in this paper.

Carrier Shifting Algorithms for the Mitigation of Circulating Current in Diode Clamped MLI fed Induction Motor Drive

Reduction of circulating current is one of the major considerations in inverter fed electrical drives. Diode clamped MLI enables higher output current per phase, thereby rating of the drive gets increased effectively. Various methods of triggering in the inverter legs creates better voltage profile and leads to the enabling of circulating current in the drive system. The induced circulating current flows through the apparatus neutral (N) and supply ground (G) is caused by the existence of parasitic capacitance. This circulating current may cause potential danger especially when parasitic capacitance poses large. In the past, different modulation techniques and conversion topologies have been introduced to minimize the flow of circulating current. However, these techniques lead to complexity, high cost, low voltage profile and efficiency due to lower modulation parameters. This paper proposes PS, POD, PD carrier shifting PWM algorithms for diode clamped MLI to tumbling the circulating current within the each phase of inverter legs. The performances of proposed algorithm, in terms of circulating current, THD, losses and efficiencies are analyzed theoreticallyand are validated via simulation and experimental results.

Control of a multilevel frequency converter of a power-efficient electric drive

The paper is devoted to an investigation of the control algorithms of a high-voltage electric drive, the converting part of which is represented by the well-known multilevel Series Connected H-Bridge Voltage Source Converter (SCHB VSC) topology. The control algorithm in the framework of the method forming a Space Vector Pulse-Width Modulation (SPWM) is based on the known principle of choosing the three nearest vectors on the voltage diagram of the converter and calculation of the durations of their switching per modulation cycle. A technique that is the same for all converters of creation of a switching algorithm of power valves based on this principle was proposed. The technique uses the principle of a “centered” SPWM with minimization of switching component of the losses in IGBT inverters of the converter cells. The technique of uniform distribution of the switching load by the cells in the phases of the converter and the method of estimation of the power efficient of a high-voltage electric drive and comparison of SPWM based on the results of the computer modeling were proposed. Results of the integrated simulating and modeling test of a 17-level SCHB VSC composed of a high-voltage variable-frequency electric drive, showing a decrease in the total power losses in the power modules of the converter with a modulator of the developed structure of the space-vector PWM by 43–46% compared to the traditional algorithm of sinusoidal PWM, were obtained.

A New Active Zero State PWM Algorithm for Reducing the Number of Switchings

To reduce common-mode voltage (CMV), various reduced CMV pulse width modulation (RCMV-PWM) algorithms have been proposed, including active zero state PWM (AZSPWM) algorithms, remote state PWM (RSPWM) algorithms, and near state PWM (NSPWM) algorithms. Among these algorithms, AZSPWM algorithms can reduce CMV, but they increase the number of switchings compared to the conventional space vector PWM (CSVPWM). This paper presents a new AZSPWM algorithm for reductions in both the CMV and total number of switchings in BLAC motor drives. Since the proposed AZSPWM algorithm uses only active voltage vectors for motor control, it reduces CMV by 1/3 compared to CSVPWM. The proposed AZSPWM algorithm also reduces the total number of switchings compared to existing AZSPWM algorithms by eliminating the switchings required from one sector to the next. The performance of the proposed algorithm is verified by analyses, simulations, and experimental results.

LCL Filter Design Method for Grid-Connected PWM-VSC

In recent years, several LCL filter design methods for different converter topologies have been published, many of which use analytical expressions to calculate the ideal converter AC voltage harmonic spectrum. This paper presents the LCL filter design methodology but the focus is on presentation and validation of the non-iterative filter design method for a grid-connected three-phase two-level PWM-VSC. The developed method can be adapted for different converter topologies and PWM algorithms. Furthermore, as a starting point for the design procedure, only the range of PWM carrier frequencies is required instead of an exact value. System nonlinearities, usually omitted from analysis have a significant influence on VSC AC voltage harmonic spectrum. In order to achieve better accuracy of the proposed procedure, the system nonlinear model is incorporated into the method. Optimal filter parameters are determined using the novel cost function based on higher frequency losses of the filter. An example of LCL filter design for a 40 kVA grid-connected PWM-VSC has been presented. Obtained results have been used to construct the corresponding laboratory setup and measurements have been performed to verify the proposed method.

Optimal control of a multilevel DC-link converter photovoltaic system for maximum power generation

This paper describes a new algorithm for optimal control of a PV system under partial shading. A multilevel DC-link is the essential part of the proposed system and its control engages a voltage-hold perturbation and observation (VH–P&O) method combined with a PWM algorithm with permutation of PV sources. The algorithm enables achieving the maximum power generation for any number of PV and converter modules. The main features of the control are: (i) a continual operation of all PV sources, shaded and non-shaded, at their maximum power points, (ii) delivery of all extracted power from PV sources to the load and (iii) generation of multilevel output voltage waveform with a low total harmonic distortion.

Realization of SVM Algorithm for Indirect Matrix Converter and Its Application in Power Factor Control

Compared with AC-DC-AC converter, matrix converter (MC) has several advantages for its bidirectional power flow, controllable power factor, and the absence of large energy storage in dc-link. The topology of MC includes direct matrix converter (DMC) and indirect matrix converter (IMC). IMC has received great attention worldwide because of its easy implementation and safe commutation. Space vector PWM (SVM) algorithm for indirect matrix converter is realized on DSP and CPLD platform in this paper. The control of the rectifier and inverter in IMC can be decoupled because of the intermediate dc-link. The space vector modulation scheme for IMC is discussed and the PWM sequences for the rectifier and inverter are generated. And a two-step commutation of zero current switching (ZCS) in the rectifier is achieved. Input power factor of IMC can be changed by adjusting the angle of the reference current vector. Experimental tests have been conducted on a RB-IGBT based indirect matrix converter prototype. The results verify the performance of the SVM algorithm and the ability of power factor correction.

A Simple Generalized PWM Algorithm for Three Phase Voltage Source Inverter Fed AC Drives

This paper presents a simple Generalized Pulse Width Modulation (GPWM) algorithm for Three Phase Voltage Source Inverter fed AC Drives. The conventional space vector approach requires angle and sector estimation for the calculation of gating times of the inverter and hence increases the complexity of the PWM algorithm. However, the proposed algorithm uses the concept of imaginary switching times to calculate the gating times. These imaginary switching times can be evaluated by using the instantaneous phase voltages only. To generate various PWM algorithms, generalized expression for the offset time is derived. In the derived offset expression, by varying a constant (k0) value from zero to one, various Discontinuous PWM (DPWM) algorithms can be generated along with the Space Vector PWM (SVPWM) algorithm. Thus, the proposed GPWM algorithm gives all the possible modulators for 3-phase, two-level inverters. To validate the proposed PWM algorithms, numerical simulation and experimental studies have been carried out and the results have been presented.