Hybrid Modular Multilevel Converter with Redistributed Power to
Meanwhile, the SM capacitor voltage fluctuation of the upper and lower arms of MMC system can be suppressed by an optimal high-frequency injection method. Simulation and experiment results confirm
Suppression Strategy of Capacitor Voltage Fluctuation of MMC
In order to reduce the capacitance of the sub-module of modular multilevel converter (MMC), it is necessary to suppress the fluctuation of the capacitor voltage, thereby reducing the size and cost of the MMC. In order to realize the lightness of MMC, this article proposes a double-frequency circulation injection strategy. First, it analyzes the characteristics of sub-module capacitor
Module-capacitor voltage fluctuation optimization control for
Alternate arm converter (AAC) is a recently proposed promising modular multilevel converter. This paper presents a module-capacitor voltage fluctuation suppression strategy based on optimized zero-sequence voltage injection for the AAC. A mathematical analysis for the module-capacitor voltage fluctuation is presented first. Meanwhile, a set of control procedures is designed to
Comprehensive Analysis and Optimal Control for Capacitor
Due to possessing full-bridge submodules (FBSMs), hybrid modular multilevel converter (HMMC) can operate under over-modulation conditions. Meanwhile, the 2nd-order
Comprehensive Analysis of Capacitor Voltage Fluctuation and
Then the characteristics of capacitor voltage fluctuation in HBSMs and FBSMs are portrayed. Based on the characteristics, the runnable region for hybrid MMC is demonstrated, and the principles to
Analysis and optimization of hybrid modular multilevel converters
After that, the capacitor voltage fluctuation of FBSMs and HBSMs with regard to different modulation indices were comprehensively analyzed. The formula for calculating the
Hybrid Modular Multilevel Converter with Reduced Capacitor Voltage
The capacitors buffer power fluctuations at fundamental and second harmonic frequency, therefore the capacitor voltage ripple magnitude increases with decreasing phase current frequencies and will
Minimization of the capacitor voltage fluctuations of a modular
The modular multilevel converter (MMC) is one of the most potential converter topologies for medium/high power/voltage applications. One of the main technical challenges of an MMC is to eliminate/minimize the circulating currents within the legs. Circulating currents, if not properly controlled, increase the amplitude of capacitor voltage variations, rating values of the
Hybrid Modular Multilevel Converter with Reduced Capacitor Voltage
The operating principle and capacitor voltage fluctuation suppression method of hybrid MMC are analyzed in detail, which shows that the hybrid MMC can suppress the voltage fluctuation and eliminate the influence of injecting high-frequency components. Moreover, considering the feature of FC-SM, a novel hybrid capacitor voltage control is
Suppressing the Capacitor Voltage Fluctuations in Low
Finally, the proposed technique for suppressing the capacitor voltage fluctuations is experimentally validated on a 600-V three-level MMC feeding an inductive load. The voltage fluctuations are reduced by more than 50% (63.6%) when the proposed technique is applied with a high common-mode frequency.
A Control Strategy for Suppressing Submodule Capacitor Voltage
capacitor voltage fluctuation of the submodule, circulating current loss, and capacitor loss [8]-[10]. Among them, the capacitor voltage fluctuation of the submodule is a prominent
Control strategy for suppressing submodule capacitor voltage
Therefore, this paper proposes a method to suppress the SM capacitor voltage fluctuation of CHB-SST through fluctuating power control strategy. The control scheme passes the second order current component of the SM capacitor to the low-voltage side of the CHB-SST to reduce the voltage fluctuation of the SM capacitor, such that the capacitance can be optimized.
A Modified Modular Multilevel Converter With Reduced Capacitor Voltage
Moreover, a novel capacitor voltage fluctuation suppression scheme is also proposed to further reduce the second-order capacitor voltage ripples. Finally, both a three-phase prototype of M-MMC and traditional MMC have been built in the laboratory. The effectiveness of the proposed M-MMC topology and control methods is experimentally verified by
A novel capacitor voltage fluctuation suppression method for the
In order to suppress the low-frequency voltage fluctuation of the MMC sub-module capacitors, this paper proposes a charge channel topology including in-phase and
Optimal Second-Harmonic Current Injection for Capacitor Voltage
The capacitor voltage fluctuation under grid-side SLG faults can be reduced by suppressing the three-phase arm power fluctuations. A hybrid MMC model with the proposed scheme has been established in PSCAD/EMTDC to verify its effectiveness and feasibility. Simulation results show that the average voltage fluctuation reduction rate can reach 55.
Shared Capacitor Based Modular Multilevel Converter With
The capacitor voltage fluctuation suppression is essential for the reliable and safe operation of the modular multilevel converter (MMC). This article proposes a shared capacitor (SC) based MMC with suppressed capacitor voltage fluctuation, where the SC in each submodule is utilized as the power channel for three phases of the MMC. A multivariate sorting-based voltage balancing
A Control Strategy for Suppressing Submodule Capacitor Voltage
The submodule capacitor voltage fluctuation of the modular multilevel converter (MMC) leads to the increase of the size of the submodule capacitor, the increase of system cost, and the decrease of system reliability and stability. In order to solve the problem, the mathematical model of circulating current voltage drop is derived, and the mechanism of
using Capacitors to block variations in source voltage?
I''ve seen several circuit diagrams having a 0.1 microfarad capacitor connected to the supply voltage. How do capacitors work to prevent fluctuations in DC source voltage?
using Capacitors to block variations in source voltage?
I''ve seen several circuit diagrams having a 0.1 microfarad capacitor connected to the supply voltage. How do capacitors work to prevent fluctuations in DC source voltage? Why don''t they completely block DC and act as a sort of break in the circuit
Low-frequency suppression strategy based on MPC without
Modular multilevel converters (MMCs) have attracted a great deal of attention in medium-voltage motor drive applications. However, the excessive fundamental frequency submodule (SM) capacitor voltage ripple at low frequencies is a major technological challenge. In this paper, an SM capacitor voltage fluctuation suppression strategy based on model
ORCA – Online Research @ Cardiff
[10] and [11], mathematical models of the capacitor voltage fluctuation and energy storage requirements for HB-MMC have been developed. Reference [12] investigates how to reduce the capacitor voltage fluctuation using a third-harmonic voltage injection. The above methods all contribute to reducing the SM voltage fluctuation of HB-MMC.
DC-Link Voltage Fluctuation Suppression Method for
The zero-sequence component in the circulating current and the capacitor voltage fluctuation of the HBSM is strongly associated with the DC-link voltage fluctuations under an unbalanced grid. The traditional method of
Circulating Current Suppression Combined with APF Current
The advantage of APF-SM capacitors becomes even more evident, with their investment reducing to 18.03% of the traditional SM capacitors. It is evident that the method of using circulating current suppression combined with APF offers significant advantages in suppressing SM capacitor voltage fluctuations and saving capacitors.
Analysis and optimization of hybrid modular multilevel
After that, the capacitor voltage fluctuation of FBSMs and HBSMs with regard to different modulation indices were comprehensively analyzed. The formula for calculating the threshold value of m, which affects HBSM operating time, was also proposed. Furthermore, based on the relationship between the capacitor voltage ripple and modulation index
A novel capacitor voltage fluctuation suppression method for
It indicates that the capacitor voltage fluctuation under low-frequency operating state can be suppressed effectively by the proposed charge channel of the MMC. And compared with that of the MMC with in-phase charge channel, the capacitor voltage fluctuation of the MMC with inter-phase charge channel can be suppressed more effectively.
Capacitor Voltage Fluctuation Suppression Method Based on
capacitor voltage fluctuations are serious, influencing the system stability [6]. To cope with this issue, a common solution is the high-frequency injection method [7]. Injecting high-frequency voltages with opposite polarity into the three-phase upper arm and three-phase lower arm, and a high-frequency current into the circulating current, the
Suppression of DC-Link Voltage Fluctuation in the Motor
The Eq. () suggests that, when other conditions remain constant, C dc is proportional to the output power P. the larger the P is, the larger the required C dc is.And the smaller the fluctuation amplitude a is, the larger the required C dc is. Figure 3 shows the relationship between the capacitance variation ΔC dc and the voltage fluctuation variation Δa,
Capacitor Voltage Fluctuation Minimization for Four-Level Hybrid
Abstract: When a four-level hybrid clamped converter (4L-HCC) operates at low frequencies, the high load current causes significant voltage fluctuations among the
Comprehensive Analysis of Capacitor Voltage Fluctuation and
Hybrid modular multilevel converter (MMC) with half-bridge sub-modules (HBSMs) and full-bridge SMs (FBSMs) is considered as a promising topology for high-voltage direct current (HVDC) system to deal with dc fault due to its negative output from FBSMs. In
Suppression control strategy of MMC sub-module capacitor
The simulation and experimental results show that the MMC suppression control strategy proposed is suitable for use in variable-frequency applications, including the starting
Predictive Control of Modular Multilevel
To balance capacitor voltage and circulating current, a capacitor voltage fluctuation suppression outer loop controller and a circulating current suppression inner loop
Research on the mechanism of neutral-point voltage
In order to solve the neutral-point voltage fluctuation problem of three-phase three-level T-type inverters (TPTLTIs), the unbalance characteristics of capacitor voltages under different switching
DC‐link capacitor voltage balance strategy
Moreover, most objective functions of the capacitor voltage fluctuation focus on accurately predicting the midpoint current or capacitor voltage [21-24]. However, the
Specific sub-harmonic injection suppresses capacitor voltage
Suppressing capacitor voltage ripple of Modular multilevel converter (MMC) helps to reduce capacitor volume/weight and the cost of converter valve equipment. The ripple component and influence factors of the converter capacitor are deduced. The effects of the double frequency loop control and the third harmonic injection on the converter valve are analyzed. The proposed
6 FAQs about [Capacitor voltage fluctuation]
How to control a variable frequency capacitor voltage?
Therefore, for variable-frequency operation, it is necessary to remove the suppression method at higher frequencies and only use the balance control method of the MMC sub-module to control the fluctuation of the sub-module capacitor voltage.
How can circulating current and capacitor voltage fluctuation be improved?
If the control effects of secondary control objectives, such as circulating current, are poor, the proposed method can increase the output range of the PR controller, improve the adjustment ability for the candidate combinations, and thus enhance the control effect on the circulating current and capacitor voltage fluctuation.
What if capacitor voltage fluctuation is greater than circulating current deviation?
The reverse is also true. 1: If , it means that the capacitor voltage fluctuation is greater than the circulating current deviation, and the system is in a transient state; excessive deviation in the capacitor voltage fluctuation from the reference requires priority control.
What happens if the capacitor voltage is too low?
However, the fluctuation of the capacitor voltage of the MMC sub-module is inversely proportional to the working frequency of the MMC. When the MMC working frequency is too low, the MMC sub-module capacitor voltage fluctuates beyond the range allowed, that is, damage to the device affects the normal working.
What is sub-module capacitor voltage fluctuation?
It can be seen from the above waveforms that the sub-module capacitor voltage fluctuation is always controlled to less than 6% during the simulation process. When the working frequency of the MMC system is changed, the sub-module capacitor voltage fluctuations remain within a reasonable range, and there are no significant mutations. Fig. 11.
What is the maximum fluctuation amplitude of capacitor voltage?
Between 0.4 s and 0.7 s, the maximum fluctuation amplitude value of capacitor voltage is 108 V, and the fluctuation amplitude range is 8%. This is much smaller than the fluctuation amplitude value of the capacitor voltage without the suppression strategy.