Zero-crossing Distortion Research Articles

A Modulation Method With Current Zero-Crossing Distortion Elimination and Voltage Balance Control for the RSHMC Converter

A Modulation Method With Current Zero-Crossing Distortion Elimination and Voltage Balance Control for the RSHMC Converter

High-performance front end PFC controller design for light electric vehicle charger application

Power factor correction (PFC) boost converters operating in CCM (continuous conduction mode) typically utilize average current mode (ACM) control alongside a LPF (low-pass filter) to reduce the impact of double line frequency ripple on the current loop. However, the LPF limit the voltage loop bandwidth in ACM-regulated converters, resulting in sluggish dynamic response. Additionally, zero-crossing distortion (ZCD) often occurs in the current control loop due to inaccuracies in tracking the reference current at the zero crossing point of the waveform. To address these challenges, this paper proposes a feed-forward control strategy that utilizes supply voltage and output current, effectively eliminating the need for an LPF and enhancing transient response. The voltage loop is tuned using the conventional Z-N method, while the Grey Wolf Optimization (GWO) technique is employed to optimally tune the gain parameters of the current controller (KPi and KIi). This approach effectively reduces reference tracking errors and mitigates ZCD, offering a balance between simplicity and performance. The proposed method is simple, offering fast transient and steady-state response, low THD, near-unity PF, and tight voltage regulation under fluctuating conditions. The effectiveness of this approach is validated through MATLAB/Simulink simulations, and hardware verification is conducted using a 500 W laboratory prototype controlled by a dSPACE 1104 digital controller.

A Low Distortion Collaborative Modulation for Zero-Crossing Distortion Pseudo DC Link Single-Stage Isolated Inverter

A Low Distortion Collaborative Modulation for Zero-Crossing Distortion Pseudo DC Link Single-Stage Isolated Inverter

A Novel Suppression Method for Input Current Zero-Crossing Distortion of the Vienna Rectifier Based on Negative-Sequence Current Regulation Under the Unbalanced Grid

A Novel Suppression Method for Input Current Zero-Crossing Distortion of the Vienna Rectifier Based on Negative-Sequence Current Regulation Under the Unbalanced Grid

A Novel Modulation Method to Decouple Output Power and Suppress Current Zero-Crossing Distortion for Vienna Rectifiers in Bipolar Output Mode

A Novel Modulation Method to Decouple Output Power and Suppress Current Zero-Crossing Distortion for Vienna Rectifiers in Bipolar Output Mode

A Novel Single-Stage AC/DC Converter Integrated Interleaved DCM Boost PFC and LLC DC–DC With Reduced Bus Voltage

Due to the applied pulse frequency modulation (PFM) control and switch integration, single-stage Boost-LLC AC/DC converters suffer from high bus voltage which makes them difficult to operate for high voltage input. To solve this issue, a novel single-stage AC/DC Converter by incorporating the interleaved DCM boost cell and an LLC cell is proposed. Different from the existing topology, in the proposed converter, two capacitors employed for splitting the ac input voltage into two parts are placed before the rectifier bridge. Thus, the voltage across each PFC cell is halved and the bus voltage can be significantly reduced. Furthermore, two high-frequency diodes and one filter capacitor are omitted, which helps improve the zero-crossing distortion of the input current. More importantly, the circuit efficiency is thus increased. Hence, low bus voltage, low component count, and high efficiency are the main advantages of the proposed converter. Simulations and experimental results are presented to prove the above features of the proposed converter.

A Novel Modulation Method to Suppress the Current Zero-Crossing Distortion for Vienna Rectifier With Different Control Methods Under Unbalanced Grid

Vienna rectifier is a boost type rectifier with unidirectional energy flow, which is widely used in many applications. Under unbalanced grid, there will be even harmonics in dc-link voltage and odd harmonics in input current if traditional control methods are used. Therefore, two control methods for Vienna rectifier under unbalanced grid are introduced, which are balanced positive-sequence current control (BPSC) and instantaneous active power control (IAPC). The current zero-crossing distortion (CZCD) is an inherent issue for Vienna rectifier due to its special circuit topology. The displacement angle between the input current and the voltage is revealed, which is the essence of CZCD. The issue of CZCD is more complex under unbalanced grid than that under balanced grid, and CZCD cannot be addressed well under existing suppression method. A novel method that can minimize CZCD under unbalanced grid is also proposed. The proposed method works well under both balanced and unbalanced grid. Finally, an experimental platform is built, and the feasibility and superiority of the proposed method is verified by comprehensive experiments.

Dead-Time Compensation Method in Cascaded HBridge Inverter to Mitigate Zero-Crossing Distortion by Reflecting the Ratio of Current Polarity

Dead-Time Compensation Method in Cascaded HBridge Inverter to Mitigate Zero-Crossing Distortion by Reflecting the Ratio of Current Polarity

Decoupled Unipolar Hysteresis Current Control for Single-Phase Grid-Tied Inverter Without Current Zero-Crossing Distortion

Decoupled Unipolar Hysteresis Current Control for Single-Phase Grid-Tied Inverter Without Current Zero-Crossing Distortion

An Improved Modulation Strategy Without Current Zero-Crossing Distortion and Control Method for Vienna Rectifier

An Improved Modulation Strategy Without Current Zero-Crossing Distortion and Control Method for Vienna Rectifier

Optimization of Zero-Crossing Distortion for Unipolar BCM Grid-Tied Inverter

Optimization of Zero-Crossing Distortion for Unipolar BCM Grid-Tied Inverter

O Splines-Based Fixed-Frequency Integral Sliding-Mode Controller for PFC Rectifier

This paper proposes a fast-response sliding mode controller (SMC) for a semi-bridgeless boost converter under large and quick load fluctuations to ensure tight output voltage regulation and unity power factor correction (PFC) at the line side. In this sense, a novel approach for estimating the reference current profile is presented focusing on the real-time phasor estimation via the O-splines of the discrete-time Taylor-Fourier transform (DTTFT). This method allows for improving the computational efficiency and dynamic performance of the estimations of amplitude, frequency and phase of the network voltage used for the generation of the reference current profile. Several aspects of the controller design are discussed, including the choice of the sliding surface, the existence and stability conditions, and the implementation of an adaptive hysteresis band to fix the switching frequency and reduce zero-crossing distortion. Experimental results of a GaN-based prototype validate the theoretical predictions, exhibiting a PF close to 1 and a total harmonic distortion lower than 3.2% in presence of load changes of up to 50% and changes in the output voltage set point. Several comprehensive experimental comparisons between the proposed framework and the most widely used methods recently reported in the literature are accomplished in terms of transitory and steady-state responses. The robustness of the proposed control approach is experimentally demonstrated under sag conditions and a wide operating range of the input voltage.

A modulation strategy for eliminating zero-crossing distortion of dual buck high-precision resonant converter

Due to no current distortion caused by blanking time, the resonant pole dual buck soft-switching power converter (RPDBSPC) can be applied to ultra-precision motor drive. The soft-switching operation can expand the switching frequency and improve the current response. Based on the resonant pole soft-switching topology, this paper proposes an in-phase modulation strategy. By analyzing the output voltage characteristics of switching nodes under different inductance current states, it reveals the mechanism of in-phase modulation to achieve nonlinear voltage suppression by adjusting the common conduction region. According to the correlation of modulated signals, the mathematical model of modulation algorithm is established, then the strategy feasibility and system stability are researched. Finally, the total harmonic distortion of output current can reach to 0.134% by applying the in-phase modulation when the bus voltage is 500V and the switching frequency is 100 kHz.

A Novel Modulation Method Based on Model Prediction Control With Significantly Reduced Switching Loss and Current Zero-Crossing Distortion for Vienna Rectifier

Finite control set model predictive control (FCS-MPC) is widely used in rectifiers due to its fast response. When there are multiple control objectives, the optimal switching sequence is selected by minimizing the cost function with weighting factors. However, the reduction of current ripple caused by output error and switching loss is in conflict to a certain extent for FCS-MPC. In addition, when multiple objectives are controlled, the selection of weighting factor is a serious challenge. Therefore, a modulation method based on continuous control set model predictive control is proposed in this article. Two phases are clamped and one phase is modulated, which not only can significantly reduce the switching loss without increasing the computational burden, but also can control the neutral point voltage without using weighting factors. In addition, when the proposed method is adopted, current zero-crossing distortion can be suppressed over the full range of modulation index. The effectiveness of the proposed method is verified by simulation and experimental results.

Hybrid-Modulation Hysteresis Scheme Based Decoupled Power Control of Grid-Connected Inverter

Most existing power control methods for grid-connected inverter are implemented in synchronous reference frame. In order to achieve soft-switching operation, those methods usually need additional design considerations, which could introduce complex computation. This article presents a control strategy for single-phase grid-connected inverter system with LCL filter that can be used for grid-connected battery/photovoltaic (PV) system, with the target to implement decoupled active and reactive power control capability in stationary frame and achieve soft-switching behavior for higher efficiency. In order to improve system efficiency, a new hybrid-modulation-based hysteresis current scheme is used to achieve soft-switching while improving the inherent zero-crossing distortion issue existing in traditional unipolar hysteresis current control. Multiproportional and resonant compensators are utilized to mitigate output low-frequency distortions further, together with a capacitor current feedback-based active damping design embedded in an inner loop. The proposed controller also demonstrates good robustness and immunity to distorted grid conditions. Simulation and experimental results are presented in this article with essential theoretical analysis to verify the validity of the proposed control strategy.

A Hybrid DPWM for Vienna Rectifiers Based on the Three-Level to Two-Level Conversion

In view of the large neutral-point (NP) voltage fluctuation and the high low-frequency harmonics in the input current of conventional discontinuous pulse width modulation (DPWM) for the Vienna rectifier, a hybrid DPWM (HDPWM) is proposed on the basis of three-level to two-level conversion. The proposed HDPWM combines the modulation degree of freedom, namely the vector synthesis direction and the equivalent zero vector distribution coefficient. Under the two-level modulation unit, the shift angles that satisfy the predefined NP balance requirement for HDPWM are accurately calculated. Compared with the continuous PWM and conventional DPWM, the proposed HDPWM could effectively suppress the zero-crossing distortion, reduce the NP fluctuation and the switching losses. Simulation and experiment results demonstrate that the proposed HDPWM could reduce the NP voltage fluctuation to 1/2 of the conventional DPWM with reduced input current low-frequency harmonics and no zero-crossing distortion.

Stability Analysis of PFC Converters Under Different Source Impedances and Its Consequences on Zero-Crossing Distortion

In the presence of multiple power converters in a power system the total current may exhibit zero-crossing distortion in the form of recurrent damped oscillations with high magnitude. These oscillations are synchronized with the power system frequency. This paper presents a comprehensive analysis of the input current of single-phase ac-dc converters fitted with power factor correction (PFC) controllers. Emphasis is given on the impacts of the source impedance, and on how the number of converters connected to a common coupling point (PCC) impacts the PFC controller’s performance. A system model is developed followed by simulation and measurements in a real installation with electronic ballasts used to drive fluorescent lighting tubes. Results show that the recurrent damped oscillations originating from PFC controllers are close to the harmonic range and with a very low level of cancellation between devices. The magnitude therefore increases proportionally with the number of devices. As the source impedance increases, instability may occur. Possible explanations for these observations are discussed.

Improved Control Strategy for Zero-Crossing Distortion Elimination in Totem-Pole PFC Converter with Coupled Inductor

Coupled inductors can effectively optimize the THD, loss, current ripple, and power density of multiphase interleaved totem-pole PFC converters. However, a coupled inductor will also worsen the zero-crossing distortion process. This paper first introduces the working principle of the interleaved totem-pole PFC converter with a coupled inductor based on a detailed analysis of modes, and then analyzes the influence on the zero-crossing process caused by the coupled inductor. To eliminate the zero-crossing distortion caused by the coupled inductor, an improved control strategy and its digital realization method of the totem-pole PFC converter is presented through the system model. Finally, the validity and correctness of the proposed circuit and control are verified in the 7.7 kW interleaved totem-pole PFC converter.

Research on control strategy of grid-connected inverter based on three-loop structure

A grid-connected inverter system is deeply researched based on the two-stage single-phase PV grid-connected inverter. Full bridge structure is adopted in the backend inverter circuit. In order to realise the balanced flow of power, to improve the system's response speed and to eliminate the influence of the resonance peak of LCL filter, the three loop control strategy is adopted in the inverter system. At the same time, the reason of generation of the dead-time and its influence on the output of the grid-connected inverter are analysed in detail. And an improved dead-time compensation method is proposed for zero-current clamping phenomenon. The output voltage error of inverter is extended from two to seven in this method, which effectively solves the problems, such as zero-crossing distortion of the grid-connected current, additional odd harmonic content, higher distortion rate and lower amplitude of fundamental wave.

An Improved Sliding Mode Direct Power Control Strategy Based on Reactive Power Compensation for Vienna Rectifier

Vienna rectifiers are widely used in electric vehicle charging systems, wind power generation systems and other fields due to their excellent high-voltage resistance, small size and high efficiency. Aiming at the problems of the Vienna rectifier’s long response time, low anti-disturbance ability, and current zero-crossing distortion, a new sliding mode direct power control strategy based on disturbance compensation is proposed. Firstly, a model considering the uncertainty is established, and the neural network is used to estimate and compensate the uncertain disturbance. Secondly, aiming at the slow approach speed and slow system convergence of traditional control methods, a new approaching law sliding mode direct power control strategy is designed. Aiming at the current zero-crossing distortion, the reason is analyzed and a compensation method is proposed. Finally, simulations and experiments show that the proposed method has no voltage overshoot and converges faster, effectively improving the problem of different phases of voltage and current. The rectifier operates at unit power, has better steady-state performance and stronger anti-load disturbance ability. The current total harmonic distortion is controlled below 2%, and the current quality is effectively improved.