Fig 8 - uploaded by Marek Jasinski
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Simulated basic signal waveforms under step change of the load. From the top: line voltage, line current, and instantaneous active and reactive power.
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This paper proposes a novel and simple direct power control of three-phase pulsewidth-modulated (PWM) rectifiers with constant switching frequency using space-vector modulation (DPC-SVM). The active and reactive powers are used as the pulse width modulated (PWM) control variables instead of the three-phase line currents being used. Moreover, line v...
Context in source publication
Context 1
... line current 2.1%) as well for distorted (THD of line current 2.4%) line voltage. This is thanks to low-pass filter behavior of the integrators used in (5). Therefore, each of the th harmonics in power estimator (12) and the angle of VF vector are reduced by factor . The excellent dynamic behavior under a step change of the load is presented in Fig. 8. The coupling between active and reactive power is practically ...
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Citations
... In recent years, scholars have proposed several novel methods to enhance the performance of the DPC. In [10], a proportional integral (PI) based on the virtual flux DPC (VF-DPC) is proposed. However, it exhibits a slow dynamic response and poor anti-disturbance ability. ...
... In [22], an extended state observer (ESO) and second-order sliding-mode In recent years, scholars have proposed several novel methods to enhance the performance of the DPC. In [10], a proportional integral (PI) based on the virtual flux DPC (VF-DPC) is proposed. However, it exhibits a slow dynamic response and poor antidisturbance ability. ...
... Following (9), this article establishes an affine nonlinear model of the three-phase PWM rectifier, as shown in (10). ...
To effectively eliminate the impacts of both matched and mismatched power disturbances in a three-phase PWM rectifier, this paper proposes a robust direct power control (RDPC) method with a single-loop control structure. Firstly, a nonlinear power model of the three-phase PWM rectifier is established. Then, using the exact feedback linearization method, a linearized power model including matched and mismatched power disturbances is derived and achieves the decoupling of active and reactive power. Secondly, to regulate the DC bus voltage, a sliding-mode controller (SMC) combined with a nonlinear disturbance observer (NDO) is proposed. The proposed SMC combined with an NDO (SMC + NDO) method features a single-loop control structure, which enables a faster response and simpler structure compared to the dual-loop DPC method. By incorporating estimated mismatched power disturbance into the sliding-mode surface, it overcomes the SMC’s defect in incompletely suppressing mismatched disturbances and enables the simultaneous regulation of voltage and active power. Additionally, it effectively reduces sliding-mode chattering. To regulate reactive power, a sliding-mode controller based on the exponential convergence law is designed to suppress matched reactive power disturbances. Finally, the simulation and experimental comparative results demonstrate that the proposed controller exhibits stronger robustness against matched and mismatched power disturbances, as well as a better performance under the constant power load (CPL).
... The tuning method is used to adjust the parameters Kp, Ki of the PI controller. The DPC strategy utilizes direct control of the instantaneous active and reactive powers, rather than relying on internal current control loops (Malinowski et al. 2004). The rectifier's switching states are determined using the new switching table (Table 1), which considers the discrepancies between the calculated instantaneous powers P and Q and their respective references. ...
This chapter presents a control strategy for a standalone wind generation system based on a permanent magnet synchronous generator (PMSG), in order to extract the maximum electrical power under varying wind speed and apply the maximum power point tracking (MPPT) principle. This chapter is useful to simulate and model the wind energy conversion system (WECS) connected with DC load using MATLAB/Simulink environment. A direct power control (DPC) strategy is adopted for the generator side converter to rectify the PMSG voltage output. Also, a novel PI-control is presented to keep DC bus voltage constant. The results of the simulation presented show the effectiveness and the good reliability of the control strategy used for the power transfer.
... Force commutated three-level boost type of rectifier uses six switches with diode rectifier bridge, this topology is used for correction of displacement power factor (DPF) and reduction of THD in input current waveform [17]. Single-phase single-switch threelevel boost rectifier configuration in [18] offers additional features such as low cost of the power circuit. The singlephase three-level PWM rectifier operates in such a way that it reduces the AC harmonics and gives a high input PF. ...
We have previously proposed a hybrid rectifier that consists of a diode rectifier and a series chopper that operates at the line frequency with the input current total harmonic distortion (THD) of 16.4% and 28% at the primary and secondary side, respectively, of a balanced three-phase transformer. This paper focuses on further reduction of the input current THD using an input LC filter. Generally, an LC filter at the input of a diode rectifier reduces the input current THD, however, it introduces a lagging phase as well resulting in a reduced power factor. To mitigate the lagging power factor, the proposed rectifier can be operated with a leading phase controllable through the switching angle of the series chopper. Hence, an appropriate design of an input LC filter reduces the input current THD without degrading the input power factor. The proposed approach is presented with simulations and hardware results showing a significant reduction in the input current THD to 7% with a displacement factor close to unity.
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... Elimination of grid current distortion, understood as current unbalance and high content of higher harmonics, is a major area of interest in the field of control of power electronic converters operating under distorted voltage conditions [1][2][3][4][5][6][7]. Generally, the frequency spectrum of grid voltage disturbances is recognized. ...
... Ac.: Tech. 68(2) 2020 1 Considering the fact that the number of dominant grid voltage harmonics is limited, it is convenient to create a disturbance model with oscillatory terms selected for given pulsatances. The disturbance model applied in the controller structure allows to discard harmonics with the pulsatance of selected oscillators. ...
... To overcome the stability issues corresponding to the GFLIs, several PLL-less control strategies have been proposed to eliminate the PLL from the control structure. A new category known as direct power control (DPC) is proposed to directly control the output active and reactive power are without the need for an inner control loop [20]- [23]. However, DPCbased methods introduce a wide range of harmonics due to the variable switching frequency they employ [8]. ...
In the realm of modern power systems, grid-connected inverters are essential for integrating renewable energy resources. While grid-following inverters (GFLIs) currently dominate the market, grid-forming inverters (GFMIs) are pivotal for technology future power systems. Furthermore, recent research emphasizes the advantages of power-synchronized GFLIs (PSGFLIs), which combine the reliable operation of conventional GFLIs in strong grids with the stability of GFMIs in weak grids. This paper presents a comprehensive analysis of transient angle stability for a specific variant of PSGFLI, referred to as the linear parameter-varying control PSGFLI (LPV-PSGFLI). First, a nonlinear dynamic model suitable for transient stability analysis is derived. Then, the necessary and sufficient stability condition is obtained using Lyapunov's linearization stability analysis method. A method for estimating the required system variables for stability assessment is proposed, along with the static stability condition to identify the presence of an equilibrium point. Additionally, a Lyapunov energy function is proposed to determine the domain of attraction for the system's equilibrium point. The accuracy of the stability condition and the calculated domain of attraction is evaluated across multiple scenarios via simulations in MATLAB/Simulink and experimental tests performed on a scaled-down inverter experimentation platform.
... In direct power control schemes, the inner control loop controls the active power and the reactive power, which are estimated using the current and the voltage or the virtual flux [19]. The power estimation is based on the instantaneous power theory or p-q theory. ...
In this chapter, a current control scheme for grid-connected voltage source converters during unsymmetrical faults is presented. The method that is being given is based on a modification of direct power control with space vector modulation (DPC-SVM), which makes it ideal for controlling the converter during asymmetrical failures. The presented results show that the control scheme can maintain the magnitude of the current within its rated value and keep the distortion in the current minimal; as well as minimize the oscillations in the power caused by the negative-sequence components of voltage and current.
... To eliminate the net-side three-phase voltage sensor, the virtual flux concept was presented in [30]. Since the virtual flux vector ψ lags the grid-side voltage vector by 90°, it can get the virtual flux expression by integrating the grid-side voltage vector, neglecting the internal resistance R, as follows: ...
... As an alternative approach, DPC directly regulates instantaneous active and reactive power without using an inner current control loop and a PLL. There are different realization schemes, such as the look-up table-based DPC (LUT-DPC), model predictive DPC (MP-DPC) and space-vector modulation DPC (SVM-DPC) [3][4][5][6]. The main disadvantage of LUT-DPC is the variable switching frequency, resulting in difficulty in designing the grid-side filter and unexpected fluctuations in current and power. ...
... However, the computational burden required to solve the optimization problem underlying MPC-DPC with short sampling intervals constitutes a major challenge [4,5]. In [6], a DPC strategy involving SVM is proposed to achieve good performance at a steady state but stability was not proven. ...
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This paper presents the design and implementation of a Direct Power Control (DPC) based on virtual flux estimator and optimal Switching Table (VF-ST-DPC) for a three phase PWM rectifier. The proposed approach is based on the combination of the DPC technique principle, virtual flux estimator technique and an optimal switching table (ST) to select the optimal converter vector control. The objectives of approach are to solve the cross-coupling between the instantaneous active and the reactive power for each sector and improve the harmonic line currents. Thus, the proposed method is realized in the fixed coordinate frame, so, does not require Park’s transformation and the voltage grid synchronization is achieved by a virtual flux estimation method. Both, experimental results based on the dSPACE DS1104 card show that the VF-ST-DPC guarantees a smooth and decoupled control of instantaneous active and reactive power and provide a low harmonic (THD = 4.6%) by verifying the expected performances of the proposed method under steady-state and transient operation.
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This paper proposes a flat bottom driving method for a switched reluctance motor (SRM) by using a full-bridge power converter. Based on a ring structure, an SRM is able to be driven by a full-bridge inverter. With the proposed driving topology, by adding harmonics in the sinusoidal current waveform from the space vector PWM (SVPWM) driving method, the flat bottom current waveform can be generated for driving an SRM. According to the theoretical analysis and calculation, the flat bottom method reduces the copper loss, compared to the SVPWM driving method. The proposed driving topology and flat bottom method are tested by simulation and experimental system, of which the results are compared to that of the SVPWM driving method. The comparison shows that the flat bottom driving method contributes to the reduction of SRM copper loss, and the simulated results match the experimental results well.
