Dead-time Compensation Method Research Articles

A New Dead-time Compensation Method Based on LMS Algorithm for PMSM

This paper presents a new dead-time compensation method for permanent-magnet synchronous motor (PMSM) at low speed. Based on least-mean-square (LMS) algorithm and combined with the traditional average voltage compensation method, the proposed method can determine the current polarity through extracting the fundamental current. Compared with traditional compensation methods, the proposed method can detect current polarity more accurately at low speed due to the narrower notch bandwidth. Moreover, this method is robust to motor parameters and easy to implement. The proposed method is simulated in a voltage-source inverter PMSM drive controlled by I/F and the results show that it meets the requirement of dead-time compensation and eliminates the influence of dead-time effect.

Current Reduction Method for Dual Active Bridge Converter in Non-linear Dead-time Compensation Method

Current Reduction Method for Dual Active Bridge Converter in Non-linear Dead-time Compensation Method

Dead-time Compensation Method Based on Field Oriented Control Strategy

This paper analyzed a dead-time effect and zero-current clamping phenomenon in FOC control strategy, and then proposed corresponding compensation measures. The Field Oriented Control (FOC) strategy of brushless motor is improved according to this Dead-time Compensation measure. On the basis of the existing FOC control theory, a dead-time hysteresis loop is added near the current zero-crossing point to prevent current fluctuation and zero-point clamping from causing errors. The dead-time compensation is carried out in each PWM cycle according to the principle that the actual volt-second area is equal. Finally, the feasibility of the method was verified by experiments, the results showed that the compensation method effectively improves the current waveform and improves the stability of the motor operation, and it proved to be of good use value.

Online Feedback Dead Time Compensation Strategy for Three-Level T-Type Inverters

The insertion of dead time will lead to the distortion of output waveforms, which seriously affects the characteristics of the ac induction motor control system. In order to reduce the output distortion of three-level T-type inverters caused by dead time insertion, an online feedback dead time compensation method is developed. In this method, the compensation time is obtained and further corrected by the online feedback of duty cycle. Meanwhile, current polarity judgment is accurately realized by sampling the neutral point (NP) potential and three-phase output terminal voltage potentials. In addition, in this article, we take the NP potential fluctuation into account to approximate the true situation. The developed method can be applied to both open-loop and closed-loop motor drive systems. To verify the effectiveness of the method, essential simulation and experiments are carried out. Compared with the traditional methods, the developed method can prominently reduce the output waveform distortion. Simulation results emphasize that the proposed scheme can significantly improve the performance of three-level inverters, and the identical conclusion is obtained on 210 V/2.24 kW motor platform.

Switching State Sequences-Based Modulation Scheme for T-Type 5L-ANPC Converter

A switching state sequences (SSSs)-based modulation scheme along with a dead-time effect compensation method is proposed in this paper. In the proposed modulation scheme, the converter’s switching states changing sequence in one carrier period, i.e., the SSS, is treated as the basic unit to control the T-type 5L-ANPC converter. Because there are only two possible voltage levels in each SSS, the converter can be controlled as a traditional two-level converter within each SSS. Thus, a switching pulse modification-based method is proposed to compensate the dead-time effect within each SSS. Moreover, an SSS transition rule and the transition diagram are furtherly presented to avoid the dead-time effect between different SSSs. Consequently, both the output voltage delay and the unwanted voltage glitches that caused by the dead-time effect are avoided in the whole modulation range. Besides, a balancing strategy is proposed to balance the flying capacitor voltage based on the charging abilities of SSSs. The performance and effectiveness of the proposed modulation scheme are validated by both simulation and experimental results.

Dead-Time Effect Compensation Method Based on Current Ripple Prediction for Voltage-Source Inverters

In voltage-source inverters (VSIs), dead time is used to prevent shoot-through over switching devices. However, the existence of the dead time will distort the output phase current, which degrades the performance of the inverter as well as influences the common-mode voltage (CMV), particularly in CMV elimination relevant modulation schemes, such as zero-common-mode (CM) pulsewidth modulation (PWM)-based paralleled inverters. In the light of the situation that the normal sampling-based dead-time compensation (DTC) methods are often disturbed by the current ripple, this paper introduces a novel DTC method for the VSI, which can mitigate the impact of the current ripple and improve the accuracy of DTC. The proposed method deduces the real-time current ripple, which can reconstruct the actual trajectory of phase-leg currents, and the peak values corresponding to rising and falling edges for PWM signals can be predicted. In this way, DTC can be implemented based on the direction of relevant instantaneous switching currents and finally improves the accuracy. Especially, the current-ripple-prediction-based DTC can help to improve the CMV distortion caused by the dead time for paralleled inverters with zero-CM PWM. Simulation and experimental results are provided to validate that the proposed method can be applied to different topologies and modulation schemes with good performance.

New Dead-Time Compensation Method of Power Inverter using Carrier Based Sinusoidal Pulse-Width Modulation

<p>A new dead-time compensation method of power inverter circuits is suggested and presented in this paper. The proposed method utilizes carrier based sinusoidal pulse width modulation technique to produce driving signals of the inverter power switches with dead-time correction capability. The proposed method able to eliminate dead-time effects such as reducing the waveform distortion of the inverter output current, and increasing the fundamental component amplitude of output current. An analysis of the proposed method is presented. Some computer simulations were carried out to investigate the principle operation, and to test performance of the new method. The developed method was validated through experimental test of H-bridge voltage source inverter circuits. The data obtained from the computer simulation and prototype experiments have confirmed that that the proposed method worked well compensating the dead-time in the voltage source power inverter circuits.</p>

Dead-time Compensation Method for Dual Active Bridge Converter with Three-level Operation

Dead-time Compensation Method for Dual Active Bridge Converter with Three-level Operation

A New LMS Algorithm Based Deadtime Compensation Method for PMSM FOC Drives

This paper presents a new least-mean-square (LMS) algorithm based deadtime compensation method to suppress the current distortion in permanent-magnet synchronous motor (PMSM) field-oriented control (FOC) drives. Compared to conventional average value compensations, the proposed method is robust to switching device parameter variations thanks to the online adaptation capability of the LMS algorithm. Similarly, the disturbance observer compensators are also immune to switching device parameter variations; however, varying motor parameters degrade their compensation performance. Without prior knowledge of switching device or motor parameters, the proposed method can directly reduce the deadtime current harmonics by generating compensation voltage references. In addition, the proposed method is easy to implement since it does not require voltage errors estimation or current harmonics extraction, which are necessary for disturbance observer and adaptive filter based methods. The proposed method is tested on a 2.5-kW voltage-source inverter PMSM drive controlled by an FOC algorithm. Its effectiveness is validated by both experimental results and spectrum analysis.

Suppression of Dead-Time Distortion Through Revised Repetitive Controller in PMSM Drives

This paper proposes a new dead-time compensation method for voltage-source inverters (VSIs) used in permanent-magnet synchronous motor (PMSM) drives. The proposed technique is developed based on the revised repetitive controller (RRC) to reduce current harmonics and distortion, which is essential to improve efficiency, rotor position observer performance at very low speed, and self-commissioning accuracy. This method significantly suppresses the sixth-order harmonics and its multiples in synchronous reference frame and reduces the current total harmonic distortion (THD) without depending on the precise current sampling especially in the zero-crossing region. Unlike in most average value theory or pulse based compensations, it does not require additional hardware. It is also shown that RRC-based compensation has better robustness against motor parameter variations than disturbance observer based methods and requires very low computational effort. Compared to other repetitive controllers (RC), the proposed RRC is dedicated for dead-time compensation and can easily be integrated because of its simpler structure. In addition, it can be conveniently activated or deactivated on the fly, which adds more flexibility to the control overall algorithm. The effectiveness of the proposed method is validated by theoretical analysis, spectrum analysis, as well as simulation and experimental results.

Current sensor fault diagnosis and adaptive fault-tolerant control of PMSM drive system based on differential algebraic method

As the key sensor of Electric Vehicle Permanent Magnet Synchronous Machine (PMSM) drive system, the current sensor usually occurs gain and offset fault, and the fault will directly affect the performance and stability of PMSM drive system. Therefore, the inverter nonlinearity dead-time compensation method is first investigated allowing for parasitic capacitor effect, and the proposed method are compared with the traditional dead-time compensation method, moreover, the technical advantages are all validated via experimental results, the fault diagnosis accuracy problem of current sensor caused by the inverter nonlinearity induced offset voltage between inverter reference and output voltage are cleverly solved. Then, the differential algebraic based fault diagnosis method and adaptive fault-tolerant control strategy are presented. An integrated solution of PMSM drive system is innovatively proposed integrated the proposed dead-time compensation method with proposed differential algebraic based fault diagnosis method and adaptive fault-tolerant control strategy together. At last, system simulation and dSPACE based experimental test are implemented to validate the feasibility and effectiveness of proposed integrated solution of PMSM drive system and the conclusions are shown.

Analysis and Compensation of Dead-Time Effect of a ZVT PWM Inverter Considering the Rise- and Fall-Times

The dead-time effect, as an intrinsic problem of the converters based on the half-bridge unit, leads to distortions in the converter output. Although several dead-time effect compensation or elimination methods have been proposed, they cannot fully remove the dead-time effect of blanking delay error, because the output current polarity is difficult detect accurately. This paper utilizes the zero-voltage-switching (ZVT) technique to eliminate the blanking delay error, which is the main drawback of the hard-switching inverter, although the technique initially aims to improve the efficiency. A typical ZVT inverter—the auxiliary resonant snubber inverter (ARSI) is analyzed. The blanking delay error is completely eliminated in the ARSI. Another error source caused by the finite rise- and fall-times of the voltage is analyzed, which was not considered in the hard-switching inverter. A compensation method based on the voltage error estimation is proposed to compensate the rise- and fall-error. A prototype was developed to verify the effectiveness of the proposed control. Both the simulation and experimental results demonstrate that the qualities of the output current and voltage in the ARSI are better than that in the hard-switching inverter due to the elimination of the blanking delay error. The total harmonic distortion (THD) of the output is further reduced by using the proposed compensation method in the ARSI.

Adaptive-Linear-Neuron-Based Dead-Time Effects Compensation Scheme for PMSM Drives

This paper presents an adaptive-linear-neuron (ADALINE)-based dead-time compensation method for vector-controlled permanent-magnet synchronous motor drives. The proposed strategy is achieved by suppressing the sixth-order current harmonics in the dq-axes synchronous reference frame. Four ADALINEs are employed in the proposed algorithm. Two ADALINEs are used for estimating the sixth-order harmonic components of dq-axes currents and the other two are used for generating the dq-axes compensation voltages. The voltage compensators are self-tuned by minimizing the estimated current distortion by means of the least mean square algorithm. The proposed compensation algorithm does not require any additional hardware or complicated signal processing algorithms. Experimental results validating the proposed compensation method are also presented.

Accuracy Enhancement of Parameter Estimation and Sensorless Algorithms Based on Current Shaping

Dead time is typically incorporated in voltage source inverter systems to prevent short circuit cases. However, dead time causes an error between the output voltage and reference voltage. Hence, voltage equation-based algorithms, such as motor parameter estimation and back electromotive force (EMF)-based sensorless algorithms, are prone to estimation errors. Several dead-time compensation methods have been developed to reduce output voltage errors. However, voltage errors are still common in zero current crossing areas, and an effect of the error is much worse in a low speed region. Therefore, employing voltage equation-based algorithms in low speed regions is difficult. This study analyzes the conventional dead-time compensation method and output voltage errors in low speed operation areas. A current shaping method that can reduce output voltage errors is also proposed. Experimental results prove that the proposed method reduces voltage errors and improves the accuracy of the parameter estimation method and the performance of the back EMF-based sensorless algorithm.

A Dead-Time Compensation Method for Parabolic Current Control With Improved Current Tracking and Enhanced Stability Range

Hysteresis current control is an attractive nonlinear current-control method for voltage source inverters when a fast system response is required. A well-known disadvantage of hysteresis current control is that the system has to operate over a wide switching frequency range. This causes an increase in the switching losses of the system and increases the difficulty in designing the output filter. The recently proposed parabolic current control solves this problem by employing a pair of parabolic carriers as the control band. Through the use of parabolic current control, constant switching frequency can be achieved. In the implementation of parabolic current control, dead time is employed to prevent shoot through of the inverter leg. The employment of dead time impacts the current-tracking precision and the stability range of the parabolic current-control method. Another side effect of using dead time is that the switching frequency deviates from the desired value. In this paper, the effects of dead time on parabolic current control are analyzed, and a compensation method is proposed for voltage source inverters that use parabolic current control. Using the output current direction of the voltage source inverter, a new pair of improved parabolic carriers is derived. As a result, the current error can be well controlled and the effects of dead time can be eliminated. The improvement in the current tracking of the system comes with an added benefit where the duty cycle range is extended. The effectiveness of the proposed dead-time compensation method is experimentally verified by the use of a full-bridge voltage source inverter.

Dead-Time Effect Compensation Based on Additional Phase Current Measurements

This paper proposes a new method of dead-time effect compensation. The proposed solution is based on additional phase current measurements realized by analog-to-digital converters. These measurements are carried out at the time instants specified by a pulsewidth-modulation (PWM) strategy. This makes it possible to estimate inverter currents at the commutation instants and, finally, to estimate the voltage error caused by dead time. This voltage error is compensated during the next switching period by modification of a reference voltage. The proposed solution can be used to compensate the voltage error in multilevel multiphase voltage source inverters. The experimental research studies were carried out on three-phase two-level and three-level neutral-point-clamped inverters supplying 55- and 160-kW motors, respectively. The results of the experimental investigations are presented in this paper.

불평형부하 시 독립형 인버터의 데드타임 보상기법

Stand-alone inverter supplies constant voltage to loads. However, when a three-phase stand-alone inverter supplies unbalanced load, the generated output voltages also become unbalanced. The nonlinear characteristics of inverter dead time cause a more serious distortion in the output voltage. With unbalanced load, voltage distortion caused by dead time differs from voltage distortion under balanced load. Phase voltages in the stationary reference frame include unbalanced odd harmonics and then, d-q axis voltages in the synchronous reference frame have even harmonics with different magnitude, which are mitigated by the proposed multiple resonant controller. This study analyzes the voltage distortion caused by unbalanced load and dead time, and proposes a novel dead time compensation method. The proposed control method is tested on a 10-kW stand-alone inverter system, and shows that total harmonic distortion (THD) is reduced to 1.5% from 4.3%.

CPLD-Based Circuit Design of IGBT Dead-Time Compensation

IGBT (insulated-gate bipolar transistors) dead-time compensation circuit has a very important significant for improving the output voltage waveform of the inverter, reducing the harmonic output current. Thus, many compensation strategies are reported in literatures and have been implemented in industrial drives recently. Overall, the method of dead-time compensation can be divided into hardware compensation and software compensation. Hardware compensation method needs additional hardware circuits, which means additional space and cost. Still more, the additional circuit is easy to interfere with others, which can reduce the compensation accuracy. While the software compensation method takes up a lot of memory space and additional input-output ports of processor, which often result to the added operation and heat dissipation of controller. In this paper, CPLD (complex programmable logic device)-based circuit design of dead-time compensation is presented to solve these existed drawbacks. It is verified that not only can the circuit simplify existed inverter dead-time compensation design, but also it has the advantages of small volume, strong anti-interference ability, and high compensation precision. The simulation results validate that this method is feasible and effective.

Vector based dead-time compensation for three-level T-type converters

This paper proposes a new vector-based dead-time compensation method for three-level T-type converters. The origins and effects of the dead-time voltage errors are analyzed in detail for different switching commutations and load conditions. In order to eliminate the dead-time distortion in each phase, a dead-time error voltage vector is introduced to adjust the reference voltage vector depending on load current polarity. The proposed vector-based dead-time compensation scheme has several advantages. First, it can be applied to multilevel converters with any number of voltage levels using any modulation schemes. Second, the pulse loss issue which is common in conventional pulse-based compensation strategies can be eliminated. In addition, the pulse saturation can be mitigated by operating the converters in overmodulation regions. All of these advantages and effectiveness of the proposed vector-based dead-time compensation method are verified through both simulation and experimental studies.

Online adaptive parameter identification of PMSM based on the dead-time compensation

This paper presents a method of online identification of the parameters of permanent magnet synchronous motors (PMSM) by model reference adaptive identification based on Popov Super Stability Theory. Firstly, the relations of parameters in the Field Orientation Control (FOC) system are analysed. Secondly, the proposed identification method of PMSM concerns two parts. In the case of high-speed operation of the motor, the method can accurately identify the inductance in dq-axis and the permanent magnet (PM) flux linkage. On the other hand, in the case of low speed, it can accurately identify the winding resistance of the stator. The method does not require additional excitation signals, but only makes use of motor voltage, current and their deviations. Thirdly, a simple and effective dead-time compensation method has been applied to inhibit the dead-time effects on the parameter identification. At last, the simulation and experiment results clearly demonstrate the validity and feasibility of the method.