Fast Voltage-Balancing Control and Fast Numerical Simulation Model for the Modular Multilevel Converter

There is no common accepted way for calculating the valve power loss of modular multilevel converter (MMC). Valve power loss estimation based on analytical calculation is inaccurate to address the switching power loss and valve power loss estimation based on detailed electro-magnetic simulation is of low speed. To solve this problem, a method of valve power loss estimation based on the detailed equivalent simulation model of MMC is proposed. Results of valve power loss analysis of 201-level 500MW MMC operating at 50Hz~1000Hz are presented. It is seen that the valve power loss of a MMC increased by 12, 40 and 93 % under 200Hz, 500Hz and 1000Hz operating frequency. The article concludes that in a device with isolated inner AC system, MMC operating at higher frequency will be more competitive than typical 50Hz/60Hz MMC with moderate increase of operating power loss and significant reduction of the size of the AC components.

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“…Thus, a fast simulation model of MMC is proposed as a substitution to obtain the above variables for valve power loss. [18].…”

Section: Methodsmentioning

confidence: 99%

Fast valve power loss evaluation method for modular multi-level converter operating at high-frequency

Fen

Xie

Cheng

et al. 2016

Prot Control Mod Power Syst

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“…A PSCAD implementation from Manitoba HVDC described in [16] was validated in [17]. Further simplifications have been suggested in [18] and improved representations of the blocking state were introduced in [19], [20] and [21]. In [20] the impact of the level of detail in MMC modeling on the simulation results is investigated.…”

Section: A Model Reviewmentioning

confidence: 99%

On the electromagnetic coupling of AC and DC circuits on hybrid transmission towers

Herre

Wouters

Steennis

et al. 2016

2016 IEEE International Energy Conference (ENERGYCON)

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“…In [1][2][3], the balance strategy of the capacitor voltages for sub-modules is proposed, but the influence of the circulating current on the capacitor voltages of sub-modules is ignored. In [4], the arm inductance is used to suppress the circulating current.…”

Section: Introductionmentioning

confidence: 99%

“…But in the application of MMC, it is still urgent for MMC to solve the stability of sub-module capacitor voltages and the suppression of circulating current due to the interaction between the sub-module capacitor voltages and the circulating current. So a lot of literature has done a number of studies on it.In [1][2][3], the balance strategy of the capacitor voltages for sub-modules is proposed, but the influence of the circulating current on the capacitor voltages of sub-modules is ignored. In [4], the arm inductance is used to suppress the circulating current.…”

mentioning

confidence: 99%

Improved Model Predictive Control Strategy for Modular Multilevel Converter

Jiang

Zhang

2018

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract. For reducing switching frequency and decrease computation of the traditional model predictive control (MPC) for modular multilevel converter, an improved MPC strategy is proposed. The control of AC current, circulating current and capacitor voltages are realized synchronously by building multi-objective functions. Combining with capacitor voltage sorting method, MPC calculation is decreased. The switch frequency was lowered by introducing weighting factors. Capacitor voltage difference among the sub-modules is lessened through the allowable value of capacitor voltage deviation between sub-modules. The simulation results verify its correctness. IntroductionModular multilevel converter (MMC) is widely applied to high-voltage direct current, power quality control, AC drive and other high-voltage and high-power applications due to its prominent features such as modularity and cascade. But in the application of MMC, it is still urgent for MMC to solve the stability of sub-module capacitor voltages and the suppression of circulating current due to the interaction between the sub-module capacitor voltages and the circulating current. So a lot of literature has done a number of studies on it.In [1][2][3], the balance strategy of the capacitor voltages for sub-modules is proposed, but the influence of the circulating current on the capacitor voltages of sub-modules is ignored. In [4], the arm inductance is used to suppress the circulating current. The method not only increases the equipment cost of the system, but also has limited effect on the suppression of the circulating current. In order to suppress double frequency circulating current in MMC, a circulating current suppressor is proposed in [5] based on double frequency negative sequence coordinate transformation. But it is more complex because of double frequency negative sequence coordinate transformation and interphase current decoupling. Model predictive control (MPC) is used to control MMC in [6,7].However, it is necessary to predict all possible switch state combinations of the upper and lower arms for the next cycle in each control cycle to achieve multi-objective optimization control. For a 5-level MMC, the number of sub-modules per arm is 4, and the number of switch states to be considered for each control cycle is . With the increase of the number of MMC level and the number of sub-modules, the computational complexity of the switch state combinations is obviously increased, which puts forward higher requirements for the controller.For realizing AC / DC power conversion and safe and stable operation, a MPC strategy based on n+1 level MMC is proposed with the control targets of AC current, interphase circulating current and capacitor voltage of sub-modules. In this strategy, the weight accumulation factors are used to fuse the multiple control objectives and to construct the multi-objective optimization functions. The strategy can reduce the calculation of MPC by combining the capacitor voltage sorting method and lower

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Fast Voltage-Balancing Control and Fast Numerical Simulation Model for the Modular Multilevel Converter

Cited by 56 publications

References 17 publications

Fast valve power loss evaluation method for modular multi-level converter operating at high-frequency

Fast valve power loss evaluation method for modular multi-level converter operating at high-frequency

On the electromagnetic coupling of AC and DC circuits on hybrid transmission towers

Improved Model Predictive Control Strategy for Modular Multilevel Converter

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