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In the grid-connected inverter based on the deadbeat current control, the filter inductance variation and single update PWM affect the distortion of the grid current, stability, and dynamic of the system. For this, a double update PWM method for the deadbeat current controller in three-phase grid-connected system is proposed, which not only effecti...
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Citations
... In this compensation technique, the measured state variables are fed into the controller through a filter, or a filter is placed in the cascade with the main controller or is connected to filter the voltage reference to the modulator. In either of the modes, the filter can compensate for the phase lag caused by the time-delay without the need for an additional sensor, and this method was adopted in [14,[17][18][19][20]. However, this method has drawbacks in terms of noise amplification, complexity in tuning the filter parameters, sensitivity of the filter to parameter variations and high sensitivity to grid impedance variation. ...
... It is a common practice to sample the state variables at the middle of every turn-on or turn-off time of pulse width modulation (PWM). This way, the average value of variables such as inductor current, capacitor current or grid current is sampled, as shown in Figure 3(a), where m s is the single-update PWM wave, the single-update PWM wave m s (K − 1) of the (K − 1) th carrier cycle is loaded at the peak of the (K − 1) th triangular carrier and the duty cycle is expressed as M (K ) = m s (K − 1), where m s (K − 1) is the duty cycle calculated by sampling values at the peak of the (K − 1) th triangular carrier [20]. In a single update, as shown in Figure 3(c). ...
Abstract The control of grid‐connected inverters is recently executed with digital microprocessors due to the advances in digital signal processing technology. However, the digital realisation has a drawback of the phase lag induced by the time‐delay. This phase lag challenges the stability and robustness of the controller of the inverters. In view of the challenge, this paper presents a comprehensive review of time‐delay compensation techniques employed in both model‐free (MF), and model‐based (MB) controls of an inverter in grid connection. MF techniques mainly use proportional‐integral, and proportional resonance controllers with some techniques to reduce time‐delay. Meanwhile, for MB, this paper discusses the commonly used control techniques, which are the Smith predictor, modified Smith predictor, deadbeat controller and model predictive controller. Several related techniques from the literature that have been adopted to mitigate the delays are tabulated comprehensively, and critical issues regarding the MF and MB techniques are also discussed. Finally, this paper presents a hypothesis on which technique is superior at present and suggests a hybrid technique from the MF and MB techniques to give readers a direction for further research.
... However, the traditional deadbeat algorithm relies on high-precision model parameters, and there is a problem of control delay in engineering applications [13,14]. e PWM duty updating method proposed in document [15] is different in the modulation wave. But the work we do differently is sampling twice in one period. ...
Aiming at the problem of control delay and inductance deviation, which exist in the traditional deadbeat control of the full-bridge circuit, an improved deadbeat control strategy was proposed. An improved Newton interpolation prediction algorithm was proposed to compensate the delay problem of deadbeat control, and an on-line inductance identification algorithm based on double frequency sampling was proposed to correct the inductance deviation. A mathematical model of deadbeat control for full-bridge inverter was established; besides, the performance of different interpolation prediction algorithms was analyzed. An online inductor identification model is established, on the basis of which the online inductance identification compensation formula is derived. It is indicated that an output constant current of 10 A is available with the deadbeat control relative error of only 0.2%, the grid-connected power factor up to 0.999, and the output current’s total harmonic distortion of only 2.37%. The prototype experiment shows that the output current’s total harmonic distortion is as low as 2.403% and the power factor is as high as 0.998. The results show that the improved deadbeat control strategy can effectively improve the control accuracy and the quality of grid-connected power.
... Inverters produce higher order harmonics at the switching frequency and its multiples. In order to minimise the influence of previously mentioned aliasing effect, sampling techniques such as single update pulse width modulation (PWM) [3], double update PWM [4] and multisampling PWM [5][6][7] are used. These sampling methods can put various technical requirements on the hardware used for sampling. ...
The purpose of this paper is to describe common problems that influence accurate current sampling in the case of power inverters. The current sampling is observed for nominal and low load of the inverter. Considered problems include dead time of power switches and small load time constant. Techniques considered for minimization of the influence of these problems are synchronized sampling method, multisampling method and antialiasing filter. The common algorithms for obtaining a single current value in the multisampling method are also considered. Effects of reviewed techniques on current sampling are examined in the case of one power inverter that supplies passive load in isolated grid. The results confirm the necessity of careful current sampling method consideration with respect to the application. Model of the inverter with all considered techniques for accurate current sampling is built using MATLAB/Simulink.
The control of voltage source converters (VSCs) is now implemented on digital microprocessors. This digitalization has the drawback of time delay in the control loop. The goal of this research work was to investigate improvements that can be obtained from the combination of model-based and model-free time-delay compensation approaches. Deadbeat control (DBC) from model-based techniques and the method of moving the control variable’s sampling instants, or the pulse-width modulation (PWM) updating instants, from model-free time-delay compensation techniques, were put together as the proposed new method of time-delay compensation in this study. These controllers were thoroughly examined in terms of control algorithm design, system stability analysis, and sensitivity analysis of plant parameter perturbations. In addition, thorough Simulink-based computer simulations were conducted in this work to assess the performance of each controller. The proposed method compensated about 80 μs as compared with the time delay compensated by the conventional single-sampling method. This research work was limited to simulations only; hence, conducting experiments to further validate this research work could be a direction for further research.
