An Improved Voltage Ripple Control Algorithm for Modular Multilevel Converter Based Variable Speed Drive
03 Nov 2018-pp 968-973
TL;DR: This paper proposes an improved balancing approach based on Space Vector Pulse Width Modulation (SVPWM), which uses only one SVPWM, which not only simplifies the calculation but also reduces the sub modules capacitor fluctuation and the circulating current in the MMC, thereby allowing the operation of MMC - based variable speed drive over the entire operating speed range and improve the converter efficiency.
Abstract: Modular Multilevel Converter (MMC) is one of the most promising topologies for high power- medium voltage application. However, the use of MMC in variable speed drive applications is still limited. This is due to the fact that the fluctuation of the submodules capacitor voltage is large at low speed constant torque operation. This paper proposes an improved balancing approach based on Space Vector Pulse Width Modulation (SVPWM). The proposed method uses only one SVPWM, which not only simplifies the calculation but also reduces the submodules capacitor fluctuation and the circulating current in the MMC, thereby allowing the operation of MMC - based variable speed drive over the entire operating speed range and improve the converter efficiency. The closed loop operation of the MMC - based variable speed drive is verified through extensive simulations.
Citations
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TL;DR: A novel speed observer for MMC-based VSD suitable for low-speed operation is proposed and a discrete model where the rotor parameters do not change during a short sampling time is considered.
Abstract: Modular Multilevel Converter (MMC) is widely known as one of the most promising topologies for high power medium voltage application. However, MMC is still limited when it comes to Variable...
3 citations
Cites background from "An Improved Voltage Ripple Control ..."
...These ripples are directly proportional to the output current amplitude and inversely proportional to the output frequency (Hagiwara, Nishimura, and Akagi 2010; Bashir, Zidan, and Valtchev 2018)....
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References
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15 Jun 2008
TL;DR: In this article, a novel concept of high voltage direct current converter (HVDC) employing the modular multilevel converter (M2C) is presented employing the M2C.
Abstract: In this paper a novel concept of high voltage direct current converter (HVDC) is presented employing the modular multilevel converter (M2C). Converters using IGBT-power devices, are getting increased importance in order to meet the global needs for reliable and environment friendly power supply and distribution. The new topology is compared to HVDC-transmission based on two level (2level) converters with direct series connected IGBT- devices or known multilevel converters. Main design aspects, concerning the rating of the power devices, the power losses and achievable efficiencies are investigated. For this purpose, a new computation method is presented and applied. This enables clear insight into the influence of various design parameters in a generalized form. Additionally, the characteristics and the differences of the topologies, with respect to passive filters, the necessary pulse frequencies and the arm currents are examined. As an example of the results, a comparison of the semiconductor losses and the efficiencies of the different topologies are given.
800 citations
TL;DR: In this article, the authors describe the control and operating performance of a modular multilevel PWM inverter for a transformerless medium-voltage motor drive, where the inverter is prominent in the modular arm structure consisting of a cascaded stack of multiple bidirectional choppercells.
Abstract: This paper describes the control and operating performance of a modular multilevel PWM inverter for a transformerless medium-voltage motor drive. The inverter is prominent in the modular arm structure consisting of a cascaded stack of multiple bidirectional chopper-cells. The dominant ac-voltage fluctuation with the same frequency as the motor (inverter) frequency occurs across the dc capacitor of each chopper-cell. The magnitude of the voltage fluctuation is inversely proportional to the motor frequency. This paper achieves theoretical analysis on the voltage fluctuation, leading to system design. A downscaled model rated at 400 V and 15 kW is designed and built up to confirm the validity and effectiveness of the nine-level (17-level in line-to-line) PWM inverter for a medium-voltage motor drive.
653 citations
"An Improved Voltage Ripple Control ..." refers background in this paper
...These voltages ripples are directly proportional to the output current amplitude and inversely proportional to output frequency [9]....
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TL;DR: Two new control strategies to reduce the magnitude of the SM capacitor voltage ripple in the MMC-based adjustable-speed drive systems under constant-torque low-speed operation are proposed.
Abstract: The modular multilevel converter (MMC) is increasingly becoming popular for multi-MW drive systems. One of the main technical challenges associated with the operation of MMC for adjustable-speed drives is the large magnitude of submodule (SM) capacitor voltage ripple under constant-torque low-speed operation. This paper proposes two new control strategies to reduce the magnitude of the SM capacitor voltage ripple in the MMC-based adjustable-speed drive systems under constant-torque low-speed operation. The proposed control strategies are based on injecting a square-wave common-mode voltage at the ac-side and a circulating current within the phase-legs to attenuate the low-frequency components of the SM capacitor voltages. The frequency spectrum of the injected circulating current consists of components in the vicinity of either the common-mode frequency or the common-mode frequency and third harmonic of the common-mode frequency. This paper also provides: i) a theoretical comparison of the proposed control strategies with the existing ones; ii) a controller design methodology to systematically determine the controller gains of the proposed control strategies; and iii) a theoretical proof of stability of the proposed control strategies and their design methodology based on Lyapunov analysis of singularly perturbed nonlinear non-autonomous systems. A set of experimental results for various case studies on a laboratory-scale prototype are provided to support the theoretical proof of stability of the proposed control strategies and their design methodology, and to show the superior performance of the proposed strategies over the existing strategy.
143 citations
"An Improved Voltage Ripple Control ..." refers methods in this paper
...The proposed solutions [10-13] are mainly based on the injection of a common mode voltage at the AC side and a circulating current within the MMC, in order to reduce the low-frequency component of SM voltage....
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TL;DR: In this article, a fault-tolerant control of MMC with the hot reserved SMs based on the carrier phase shift modulation is proposed, where a rotating sliding choice box is adopted to select the operating SMs and the corresponding phase shift angles, which enables the equal burden of each SM.
Abstract: Reliability is one of the most important challenges for the modular multilevel converter (MMC), which is composed of a large number of power electronics submodules (SMs). In order to increase the system reliability, the reserved SMs are often utilized. A novel strategy is proposed in this paper to implement the fault-tolerant control of MMC with the hot reserved SMs based on the carrier phase shift modulation. All the SMs, including the hot reserved SMs, work in the operating mode and the standby mode in turns. A rotating sliding choice box is adopted to select the operating SMs and the corresponding phase-shift angles, which enables the equal burden of each SM. Once the faults are detected and localized, the reserved SMs can simultaneously replace the bypassed failed SMs, which guarantees the fault-tolerant operation with a nearly seamless transition and very short recovery time. Furthermore, the line cycle is set as the rotating period in the control strategy, without increasing much switching loss. The mismatch pulses are greatly reduced as well. This technique can also be easily implemented in a DSP or microcontroller. Simulations in MATLAB/Simulink and experiments based on a downscaled MMC prototype have verified the feasibility and effectiveness of the proposed control strategy.
102 citations
"An Improved Voltage Ripple Control ..." refers background in this paper
...This is due to it is salient features such as transformerless operation modular realization, scalability and voltage waveform with less harmonic distortion [1-3]....
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TL;DR: In this paper, the authors proposed a novel topology for a PV power generation system by connecting a PV module to the capacitor in each submodule of a modular multilevel converter parallel.
Abstract: In the case of partial shading, the output power of the unshaded PV modules will be decreased by the influence of the shaded PV modules in one branch. In order to solve this problem, this paper proposes a novel topology for a PV power generation system by connecting a PV module to the capacitor in each submodule of a modular multilevel converter parallel. As partial shading occurs, the maximum power can be extracted by regulating the capacitor voltage to the maximum power point voltage. With this proposed topology, the maximum power tracking controller, the redundancy module controller, the voltage stability controller, and the grid-connected controller are studied. Simulation and experiment results show that comparing to the traditional topology, the proposed topology can greatly improve the output power of the PV system under the conditions of partial shading and features with low-voltage stress and high efficiency.
97 citations
Additional excerpts
...Tremendous research effort was given to the use of MMC in HVDC applications, which helped in widespread of MMC in these applications[4-8]....
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