Design and analysis of a feedforward control scheme for a three-phase voltage source pulse width modulation rectifier using sensorless load current signal

In this paper, the mathematical model and work principle of the three-phase voltage source pulse width modulation (PWM) rectifier (VSR) are analyzed. Then, the control strategies without feed-forward and with feed-forward are compared, which based on the power factor, the total harmonic distortion (THD) and DC voltage stability. Voltage-Oriented Control (VOC) and direct current control method were adopted to obtain current tracking control. Meanwhile, a simplified algorithm was presented for space vector PWM (SVPWM), which simplifies the arithmetic process. Contrastive analysis of two control strategy results show that without feed-forward control strategy exits the faults of low power factor, high THD and so on, although its model is simple. While feed-forward control strategy has been proved more effective.

The development of power electronics technology gives ample of opportunity for the grid integration of renewable in an efficient way. Commonly pulse width modulated voltage source inverter is widely used for this purpose. The control technique of grid integrated inverters plays a major role for the reduction of harmonic and improvement of power quality in the system. The most commonly used current control technique for the control of the inverter is hysteresis current controller strategies. But the main drawback hysteresis current controller is the uneven switching frequency and higher harmonic distortion. In this paper a hysteresis current controller with offset band for three phase grid integrated pulse width modulated voltage source inverter has been implemented for considerable reduction of harmonic distortion and better power quality. The MATLAB-Simulink environment is used to model, study and simulate the system.

This paper presents a discrete-time adaptive current controller for grid-connected pulse width modulation voltage source converters with LCL filter. The main attribute of the proposed current controller is that, in steady state, the damping of the LCL resonance does not depend on the grid characteristic since the adaptive feedback gains ensure a predefined behavior for the closed-loop current control. An overview of model reference adaptive state feedback theory is presented aiming to give the reader the required background for the adaptive current control design. The digital implementation delay is included in the model, and the stability concerning the variation of the grid parameters is analyzed in detail. Furthermore, current distortions due to the grid background voltage are rejected without using the conventional stationary resonant controllers or the synchronous proportional-plus-integral controllers. Simulation and experimental results are presented to validate the analysis and to demonstrate the good performance of the proposed controller for grid-connected converters subjected to large grid impedance variation and grid voltage disturbances.

This paper proposes the simplified pulse width modulation (PWM) strategy in the bidirectional ac/dc single-phase converter with the feed-forward control scheme. In this, the number of switching of the proposed simplified PWM strategy is reduced to one-fourth to that of the unipolar & bipolar PWM. The feed-forward control scheme is used to achieve better performance of the ac/dc converter in both the rectifier & inverter mode as compared with the conventional dual-loop control scheme. The simplified PWM strategy with feed-forward control scheme has higher efficiency than that of the unipolar PWM & bipolar PWM strategies. Also, the total harmonic distortion is less in this PWM strategy. The simulation & experiments are carried out to verify the validity of the proposed PWM strategy & control scheme.

A method of deriving the switching instants of different space vectors in the direct torque control of induction motor drives using pulse width modulated voltage source inverters is described in this paper. The switching instants of different space vectors are determined to reduce torque ripple compared to the commonly used space vector concept based on the sinusoidal pulse width modulation technique. The time durations of two adjacent voltage space vectors and the corresponding zero voltage space vectors are determined in this method depending on maximum and average switching frequency, allowable for the switching devices in the three-phase inverter. The sampling rate of the impressed reference voltage vector (in other words the switching frequency of the carrier wave) is varied to keep the torque ripple within the specified limit, determined by maximum allowable switching frequency. This paper also deals with the optimum switching pattern to reduce the average switching frequency of the switching devices. A simulation program is developed in order to verify the validity of the theory.

This paper presents a novel digital control scheme for the regulation of single-phase voltage source pulse width modulation (PWM) inverters used in AC power sources. The proposed scheme adopts two deadbeat controllers to regulate the inner current loop and the outer voltage loop of the PWM inverter. For the overhead of digital processing, the change of duty of PWM lags one carrier period behind the sampling signal, which is modeled as a first-order lag unit in a discrete domain. Based on this precise modeling, the deadbeat controllers make the inverter get a fast dynamic response, so that the inverter’s output voltage is obtained with a very low total harmonic distortion (THD), even when the load is fluctuating. The parameter sensitivity of the deadbeat control was analyzed, which shows that the proposed deadbeat control system can operate stably when the LC filter’s parameters vary within the range allowed. The experimental results of a 2kW inverter prototype show that the THD of the output voltage is less than 3% under resistive and rectifier loads, which verifies the feasibility of the proposed scheme. An additional advantage of the proposed scheme is that the parameter design of the controller can be fully programmed without the experience of a designer.

In this paper, an adaptive voltage-oriented control (VOC) for three-phase grid-connected pulse-width modulation (PWM) rectifier is developed. As the control loop behavior is affected by the PWM rectifier operating conditions, the effects associated to the PWM rectifier losses and uncertainty in the inductance should be inserted in the model. Thus, equivalent resistance and inductance are estimated online by means of an adaptive linear neuron (ADALINE). The proposed ADALINE estimator is inserted in the current control loop to perform an adaptive VOC scheme. Hence, an online updating of the decoupling terms and the current controller gains is achieved. The ADALINE capability to estimate accurately the equivalent inductance and resistance as well as the adaptive VOC scheme performances are finally evaluated by experiments. Experimental results show improved performances and accurate estimation.

This paper discusses dynamic stability and performance of current control scheme for parallel connection of pulse-width modulated (PWM) voltage source converters (VSCs) fed by distributed energy recourses (DERs) across the distribution level of power grid. The controller has feedback compensation and limits the current harmonics while featuring fast regulation for multi-converter system. The controller enables islanded and grid-connected operations of DERs, dynamically. The load dynamics will be included in the stable control loop to provide perfect regulation of the voltage at the point of common coupling (PCC). The current controller is tested under the considerations of system delays. In the islanded mode, one of the controllable units provides voltage and frequency control as a master controller and the other units operate based on the grid-connected control strategy. The stability assessment of the system is presented based on a detailed simulation. The simulation results show that the controller for the islanded two-parallel controllable DER can ensure the stability of the system when converters are tied together. In the other hand, the weakness of the current control based method is drawn out while mismatch coupling condition.

In this paper, Design and development of control circuit algorithm of 3-Φ Voltage Source Inverter (VSI) using Unipolar Sinusoidal Pulse Width Modulation (SPWM) techniques is proposed using STM32F407VGTx discovery board interfaced with MATLAB Simulink Environment. For implementing 3-Φ VSI, this method is most useful as it will eliminate complexity of control circuit algorithm occurred due to analog circuit, reduces cost, size of filter required, and improved overall inverter efficiency. Pulse width modulated voltage source inverter is preferred for high performance AC drives. The proposed control scheme and the result obtained by embedded simulations interfaced with STM32F4 microcontroller are presented and discussed. A simple hardware implementation is proposed and experimental results of SPWM based VSI are also shown. The Simulation results of the proposed scheme have excellent performance and compared with hardware results.

Due to the high stiffness, high dynamic performance, the parallel manipulator presents great advantages in the industrial manufacture. However in the machining process, the external low frequency disturbance, e.g. the varying cutting force, has a significant effect on the control system of parallel manipulator, which presents a chatter phenomenon on the end-effector of manipulator. In this paper, a feed forward control strategy is proposed to eliminate the effect of the random external disturbance on the control system of parallel manipulator. By applying the external disturbance force on the inverse dynamic model, the compensation torque is calculated and fed forward into the manipulator driving joints to cancel out the effect of the disturbance acting on the manipulator end-effector. The key issue herein is to be able to establish the accurate dynamic model for the parallel manipulator. Furthermore, in order to guarantee the position precision of the manipulator, a feed forward model-based control strategy combined with the feedback loop PV (position and velocity) control has been developed based on the reference trajectory, which could relatively simplify the highly nonlinear control system of the parallel manipulator and obtain a stable tracking error model. The whole research has been carried out on a parallel manipulator named CaPaMan which has been built in the laboratory of robotics and mechatronics in university of Cassino and South Latium. The results show that the chatter phenomenon could be utterly depressed by the force compensation from the feed forward path of the external disturbance; meanwhile the model-based controller can guarantee the trajectory tracking accuracy within a stable error by choosing the suitable PV gains.

The model predictive control (MPC) of voltage source pulse width modulation (PWM) rectififier is extremely dependent on system model in control process. System model mismatch will make the prediction results deviate from the actual value, seriously affect the system control results, even caused the system to be unstable. In addition, MPC is a control method based on state space model and predictive state of controlled system. In each control cycle, it performs an ergodic optimization to solve the online optimization, and thus determines optimal driving signal of the switching device. However, to obtain the optimal control variables online usually leads to a high amount of computation, which is one of the difficulties in the implementation of MPC on PWM rectifier. To solve these problems, neural network is used to approximate the unknown functions in system model. A finite set model predictive path integral control (FCS-MPPIC) based on neural network is proposed to effectively decrease computational complexity of control algorithm under premise of ensuring the distortion rate of the grid side current. At the same time, dynamic response speed of the system is improved. Finally, the availability of this method is verified through the simulation results.

The second-order ripple power of single-phase converter causes second-order ripple voltages on the DC bus. For eliminating second-order ripple components, passive power decoupling methods including DC bus electrolytic capacitors have some shortcomings, such as low power density and poor stability of converters. Thus, an active power decoupling method based on a single-phase converter is proposed in this paper. The control method, taking single-phase voltage source pulse width modulation (PWM) rectifier (single-phase VSR) as the basic converter and adopting a buck-boost power decoupling circuit, introduces second-order ripple of DC bus voltage into a power decoupling circuit. The ripple acts as compensation of the phase deviation between the command value and the actual value of the second-order ripple current. Therefore, estimation of the second-order ripple current is more accurate, the power decoupling circuit absorbs the second-order ripple power behind the H-bridge more completely, and the DC bus voltage ripple is effectively suppressed accordingly. Finally, experimental results of the single-phase VSR are given to verify the validity of the proposed method.

Partial Discharge (PD) is a critical threat to insulation reliability in rotating machines fed with Voltage Source Pulse Width Modulation (VS-PWM) motor drives. With the growing adoption of VS-PWM drives in electrified systems, driven by the fast-switching capability and efficiency benefits offered by Wide Band Gap (WBG) devices, it is imperative to design motor stator windings with robust and PD-free insulation. This comprehensive review focuses on elucidating the influence of PWM voltage waveform characteristics of VS-PWM motor drives on PD phenomena, exploring factors such as rise time, frequency, pulse width, voltage shape, and dead time. Additionally, the paper delves into potential reasons explaining the differences in results across various literature and emphasizes the need for a standardized test procedure and setup. Furthermore, the paper reviews various methods adopted in the literature to detect, separate, and quantify PD events under switching frequencies and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> environments. By examining these aspects, this paper contributes to understanding the intricate relationship between VS-PWM drive output voltage and PD-induced stator winding insulation degradation.

In order to alleviate the problems, such as the periodic fluctuations of reactive power, the poor quality of ac current and the long steady-state response time, caused by the traditional direct power control(DPC) in three-phase voltage source (Pulse Width Modulation)PWM rectifier, a novel DPC strategy of double hysteresis comparator bands and multiple switching tables (DM-DPC) is put forward in this paper. According to the instantaneous errors between the commanded and estimated active and reactive power, the different switching table and hysteresis comparator band are selected in the new strategy. The effect intensity table, which is used to increase/decrease active and reactive powers through switching state vectors in different sector, is summarized. Based on the effect intensity table, four switching tables are provided. The simulation model is constructed to compare the results obtained from both the proposed and the traditional direct power control strategy. The simulation results show that, by using the novel scheme, not only the reactive power becomes more stable, but the ac current harmonic total distortion rate (THD) and the time that the system takes to reach the steady-state are also reduced to 33.5%, 62.5% of the classical one respectively.

Most modern variable-speed motor drives are based on pulse width modulated voltage source inverters, supplied from a smooth DC link voltage. This is often obtained from a three-phase diode bridge mains rectifier with a large output capacitor to keep the DC link voltage essentially constant. The AC currents at the input of the bridge are often discontinuous and contain high levels of harmonics. Harmonic currents from non linear loads are unacceptable, as they penetrate the supply system and affect the voltage at the point of common coupling. In this paper a single stage, three-phase AC-to-DC converter topology, with new structure for high power applications is proposed. The principle features of the topology include continuous current operation of the input source inductors, inherent active wave shaping of the input currents, resulting in a high power factor operation. Only two active switches are required. Both the switches are soft-switched. The high frequency (HF) current injection technique is used. The diodes of rectifier also show soft-switching. The simulation results and experimental results for a laboratory prototype for 5 kW converter are presented.