Carrier-based Discontinuous Pulse Width Modulation Research Articles

A RANDOMIZED CARRIER-BASED DISCONTINUOUS PULSE WIDTH MODULATION STRATEGY FOR NEUTRAL POINT CLAMPED THREE-LEVEL INVERTER

This article introduces a novel approach called randomized carrier-based discontinuous pulse width modulation (RCDPWM) to address the challenge of mitigating both low-order and high-order harmonics concentrated at the switching frequency and its integer multiples in the output voltage and current of a three-level inverter. The proposed strategy reduces switching losses and a wide dispersion of voltage and current harmonics with significantly smaller amplitudes by integrating features from discontinuous and randomized PWM methods. This characteristic proves beneficial for enhancing efficiency and electromagnetic compatibility. The RCDPWM strategy involves three schemes: two simple schemes (one random parameter), randomized pulse position modulation (RPP-DPWM) and randomized carrier frequency modulation (RCF-DPWM), and a dual scheme combining the two previous ones (RPPRCF-DPWM). Power spectral density (PSD) is used to assess the effectiveness of the proposed strategy in quantitatively analyzing the harmonic dispersion degree. The results demonstrate that the proposed RCDPWM strategy significantly expands harmonic clusters around the switching frequency, reducing its intensity. The spectrum analysis revealed that the RPPRCF-DPWM scheme is the most effective in spreading the output voltage and current spectrum compared to simple schemes (RPP-DPWM and RCF-DPWM).

Enhanced Carrier-Based Discontinuous PWM for Three-Level Inverters With Unbalanced Neutral-Point Voltage

Enhanced Carrier-Based Discontinuous PWM for Three-Level Inverters With Unbalanced Neutral-Point Voltage

Optimized Carrier-Based Discontinuous PWM Without Regulating NP Voltage for Three-Level Vienna Rectifier

Optimized Carrier-Based Discontinuous PWM Without Regulating NP Voltage for Three-Level Vienna Rectifier

A Bidirectional Grid-Tied ZVS Three-Phase Converter Based on DPWM and Digital Control

In this paper, a bidirectional grid-tied ZVS three-phase converter is proposed. The circuit operation principle in both the rectifier and inverter modes was analyzed. The proposed topology could achieve zero-voltage switching in the six main switches and the auxiliary switch both in the rectifier mode and inverter mode. In addition, the reverse recovery current of body diodes in the main switches was also suppressed. Furthermore, in order to realize the ZVS control scheme under the grid-tied bidirectional power flow condition and reduce the number of switchings, a modified carrier-based discontinuous PWM was proposed to fit the bidirectional switching sequence. Finally, a 3 kW prototype was constructed. Some simulation and experimental results are presented to verify the validity of the proposed circuit topology and PWM control scheme.

A Carrier-Based Discontinuous PWM for an 80 Kw PV Inverter With the Reduction of the DC-Link Voltage Ripple and Common Mode Current

Discontinuous pulse width modulation (DPWM) method is broadly used in three-phase inverter to achieve high efficiency through the reduction of the switching loss. The high-power rating photovoltaic (PV) inverter with DPWM has its intrinsic issues such as large DC-link voltage ripple and high-frequency resonant current due to the large stray capacitance proportional to the power rating. To extend the application of DPWM from 10 kW to 80 kW PV inverter, a new DPWM method (DPWMn) which divides the clamping period into <i>n</i> intervals is proposed to achieve the three objectives simultaneously: 1) reduction of the DC-link voltage ripple; 2) suppression of the high-frequency current oscillation; 3) improve the efficiency compared to the continuous space vector PWM (SVPWM). The proposed DPWMn is validated by an 80 kW three-phase T-type PV inverter. Compared to the SVPWM, the DPWMn has reduced 30&#x0025; switching loss while maintaining the similar power quality and the common mode current. Compared to the existing DPWM methods, DPWMn reduces the voltage ripple by 52&#x0025; and has the minimum energy ripples. Furthermore, the carrier-based DPWMn only utilizes the measured voltage and can be easily implemented.

A Carrier-Based Discontinuous PWM Method for a Five-Level Flying Capacitor Rectifier With Unbalanced DC-Link Voltages

Unbalanced dc-link voltages occur when five-level flying capacitor (5L-FC) rectifier has dual dc loads of different rated voltages. Compared with traditional continuous pulsewidth modulation (CPWM) strategies, discontinuous PWM (DPWM) methods have more advantages in high-frequency and high-power applications for less commutation and higher efficiency. Therefore, this article proposes a carrier-based DPWM method for 5L-FC rectifiers with unbalanced dc-link voltages. The proposed method is first analyzed in the revised space vector diagram considering unbalanced dc voltages to divide subsectors and find available clamping modes, then it is implemented by applying carrier-based PWM with injecting clamping compensation component, which greatly reduces the implementation complexity. There is a pair of redundant clamping modes with opposite effects on the neutral-point (NP) in each subsector. Thus, the NP voltage can be actively controlled by selecting suitable clamping mode in each subsector. In addition, the allowable ranges of unbalanced voltage degree and unbalanced power degree are investigated in detail. Simulations and experiments verified the effectiveness and performance of the proposed method.

A Discontinuous PWM Strategy to Control Neutral Point Voltage for Vienna Rectifier With Improved PWM Sequence

Vienna rectifier is a boost-type rectifier with unidirectional energy flow, which is widely used in industrial applications. To improve the power density of the Vienna rectifier, the high switching frequency is seen as an inevitable cause of larger switching losses. To reduce switching losses, discontinuous pulsewidth modulation (DPWM) is usually used. But this will cause dc offset and ac ripple on neutral point (NP) voltage. To overcome these problems, a carrier-based DPWM (CB_DPWM) method suitable for a Vienna rectifier with simple implementation is proposed to simultaneously reduce switching losses and control NP voltage. By selecting the proper clamping mode, NP voltage can be well controlled. To avoid unnecessary switching actions while switching clamping mode, an improved PWM sequence based on carrier type is given. The comparisons among space vector PWM, DPWM 1–3 presented by Zhang <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> , and the proposed CB_DPWM are presented with the corresponding simulation and experimental results, and the superiority of the proposed strategy is verified in terms of reducing switching loss and controlling NP voltage.

Hierarchical carrier-based discontinuous PWM strategy for hybrid-switch current source rectifier

Hierarchical carrier-based discontinuous PWM strategy for hybrid-switch current source rectifier

A Carrier-Based Discontinuous PWM Strategy of NPC Three-Level Inverter for Common-Mode Voltage and Switching Loss Reduction

For the conventional carrier-based pulse width modulation (CBPWM) strategies of neutral point clamped (NPC) three-level inverters, the higher common-mode voltage (CMV) is a major drawback. However, with CMV suppression strategies, the switching loss is relatively high. In order to solve the above issue, a carrier-based discontinuous PWM (DPWM) strategy for NPC three-level inverter is proposed in this paper. Firstly, the reference voltage is modified by the twice injection of zero-sequence voltage. Switching states of the three-phase are clamped alternatively to reduce both the CMV and the switching loss. Secondly, the carriers are also modified by the phase opposite disposition of the upper and lower carriers. The extra switching at the border of two adjacent regions in the space vector diagram is reduced. Meanwhile, a neutral-point voltage (NPV) control method is also presented. The duty cycle of the switching state that affects the NPV is adjusted to obtain the balance control of the NPV. Still, the switching sequence in each carrier period remains the same. Finally, the feasibility and effectiveness of the proposed DPWM strategy are tested on a rapid control prototype platform based on RT-Lab.

A Carrier-Based Discontinuous PWM for Single and Parallel Three-Level T-Type Converters With Neutral-Point Potential Balancing

The three-level converters have an inherent problem of the neutral-point (NP) voltage unbalance due to the split dc-link capacitors. This NP voltage unbalance degrades the output voltage/current waveform quality. A carrier-based discontinuous pulsewidth modulation (CB-DPWM) with NP voltage balancing strategy-that involves the injection of calculated zero-sequence voltages to the original modulation signal-is implemented for the three-level T-type converter in this article. The zero-sequence voltages are determined from the space-vector synthesis of the converter output voltages. This method allows the determination of the zero-sequence voltages with few judgment conditions. Unlike the space-vector-based discontinuous pulse width modulation, the CB-DPWM is easier to realize in practical applications. Moreover, the proposed CB-DPWM can also be directly used in parallel systems, which can suppress NP voltage ripples and circulating currents simultaneously by a coordinated strategy. The efficacy of the proposed method in balancing the NP voltage in single and parallel systems is demonstrated by simulations and experiments.

A Carrier-Based Discontinuous PWM Strategy for T-Type Three-Level Inverter with Reduced Common Mode Voltage and Neutral Point Voltage Control

A novel carrier-based discontinuous pulsewidth modulation (CB_DPWM) strategy for T-type three-level converter is proposed in this article. Because one significant advantage of the proposed CB_DPWM is the reduction of common mode voltage (CMV), it is named as RCMV_CB_DPWM hereafter. It also can reduce switching loss and remove dc offset from the neutral point voltage (NPV) simultaneously. RCMV_CB_DPWM has two design freedoms, one is modulation wave and the other is carrier wave. By injecting zero sequence voltage properly, the corresponding clamping mode can be acquired. Moreover, reduced CMV can be achieved by arranging carrier wave flexibly. The integrity of RCMV_CB_DPWM is analyzed as well as its NPV self-equilibrium ability, and an active NPV control method is then introduced. Moreover, its realization is discussed briefly. Finally, the experiments are carried out to verify the effectiveness of the proposed method.

Carrier-Based Discontinuous PWM Method for Five-Leg Inverter

This paper proposes a rotation carrier-based discontinuous pulse width modulation (CB-DPWM) method for the five-leg inverter (FLI). The FLI based on two-level topology consists of 10 switching devices for driving dual motors. Therefore, two switching devices can be reduced to compare the configuration using two three-leg inverters for driving dual motors. The proposed pulse width modulation (PWM) method is based on the reference signals which are used in existing carrier-based continuous pulse width modulation (CB-CPWM) method for FLI. In the proposed rotation CB-DPWM method, one of five-leg is periodically clamped to V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> /2 or - V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> /2 by adding the offset voltage to the reference voltages of the existing CB-CPWM method. The five reference voltages for all legs are considered to calculate the offset voltage of the proposed rotation CB-DPWM method. Consequently, since the proposed rotation CB-DPWM method has less switching than the existing CB-CPWM, the switching loss can be reduced and it results in the efficiency improvement. Simulation and experimental results confirm the effectiveness and feasibility of the proposed method.

A Carrier-Based Discontinuous PWM Method With Varying Clamped Area for Vienna Rectifier

The three-level Vienna rectifier is an attractive topology for power factor correction applications. However, for practical high-frequency applications, the nonlinearity caused by snubber circuit and parasitic capacitance of Vienna rectifier's switching device will distort input current. This paper proposes a carrier-based discontinuous space-vector modulation (CB-DSVM) method with varying clamped area for Vienna rectifier in high switching frequency applications. The equivalent circuit of Vienna rectifier considering the nonlinear factors is built and the effect of pulse shaping around current zero-crossing point is investigated. The voltage errors caused by the nonlinearity of switching device will distort terminal voltage, which mainly appears at the zero-crossing time. A DSVM method with the fixed clamped area around the zero-crossing point is proposed to reduce the voltage errors and then the simplified CB-DSVM method with varying clamped area by adding a clamped factor to the judging conditions is further studied, which will reduce low-order harmonics of the CB-DSVM method. Simulations and experiments are carried out in a 600 W Vienna rectifier platform, which demonstrates the validity of the proposed method. Compared with the CB-SVM method, the proposed CB-DSVM method with varying clamped area has comparative neutral-point voltage balancing ability and better input current quality.

Performance Analysis of Carrier-Based Discontinuous PWM Method for Vienna Rectifiers With Neutral-Point Voltage Balance

The nongenerative-boost type rectifier, which is called the Vienna rectifier, is advantageous in terms of efficiency and current total harmonic distortion. Therefore, the Vienna rectifier is used in grid-connected applications such as telecommunication systems and wind turbine systems. Owing to the structural characteristics of the Vienna rectifier, various switching methods exist. Among these methods, a carrier-based discontinuous pulse-width modulation (CB-DPWM) method guarantees high efficiency compared to continuous pulse-width modulation methods; moreover, it is simple compared to a DPWM method based on space vectors. In this paper, the performance of the CB-DPWM method, its applicable region depending on the power factor and modulation index ( $M_{a}$ ), and its efficiency are analyzed in detail. Then, based on the analysis, a neutral-point voltage balancing method for the CB-DPWM method is proposed. The effectiveness and performance of the proposed neutral-point voltage balancing method are verified by simulation and experiment.

Carrier-Based Discontinuous PWM Method for Vienna Rectifiers

Vienna rectifiers, which are nongenerative-boost types of rectifiers, are used in grid-connected applications with a unity power factor such as telecommunication systems and wind turbine systems. These rectifiers are advantageous in that they have low total harmonic distortion and efficiency. There are many switching methods, which are different from those of threelevel topologies, for Vienna rectifiers. In this paper, we propose a carrier-based discontinuous pulse width modulation (CB-DPWM) method. This method is simple compared to the discontinuous PWM (DPWM) method for Vienna rectifiers based on space vectors and guarantees normal rectifier operation for all modulation index (M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> ) values. We perform experiments to verify the suitability and performance of the proposed CB-DPWM method.

An Optimized Discontinuous PWM Method to Minimize Switching Loss for Multilevel Inverters

This paper presents a novel approach to analyze carrier-based discontinuous pulse width modulation (DPWM) method for multilevel inverters. The separation of the offset into the main and additional components shows the use for analyzing PWM control characteristics of multilevel inverters. The results are then applied to propose a novel minimized loss DPWM method by varying the offset depending on peak values of three-phase load currents. As results of avoiding commutations at high currents, the switching loss can be reduced. The proposed method is theoretically analyzed and verified by experimental results.