Analysis and Compensation of the System Time Delay in an MMC System

Wang, Chuyang; Xiao, Lan; Jiang, Huijie; Cai, Tingting

doi:10.1109/tpel.2018.2791573

Cited by 17 publications

(12 citation statements)

References 31 publications

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“…which is primarily caused by the sampling circuit, analogdigital converter, calculation process in the digital signal processor, modulation and submodule balancing of the MMC [25]. The time delay D(s) is defined as an exponential function e −sT d with a duration of T d .…”

Section: Mathematical Modelingmentioning

confidence: 99%

Stability Analysis of High-Frequency Interactions Between a Converter and HVDC Grid Resonances

Lekić

Alam

Beerten

2021

IEEE Trans. Power Delivery

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Section: Mathematical Modelingmentioning

confidence: 99%

Stability Analysis of High-Frequency Interactions Between a Converter and HVDC Grid Resonances

Lekić

Alam

Beerten

2021

IEEE Trans. Power Delivery

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“…5, k ( n ) is obtained by subtracting Δ U max from U cm ( n − 1) and using the controller in the dashed box, and this controller makes U cm ( n − 1) track its command value Δ U max , where Δ U max can be calculated by (21). I z _dc is the dc reference value of the circulating current and can be obtained by the method in [25]. On the basis of (9) and (10), i z _ac can be rewritten as

i_{z_ac} = \frac{u_{normals} i_{normals}}{U_{dc}} - I_{z_dc}

i z _ac can be calculated by substituting I z _dc , i s , u s and U dc into (26).…”

Section: Methods 1 and Methods 2 For Reducing The Extra Loss From Injmentioning

confidence: 99%

“…On the basis of the circuit topology shown in Fig. 1 and the Kirchhoff's voltage law, equations of the MMC are obtained as follows [21]:

({, \begin{matrix} right leftthickmathspace.5em \\ L \frac{d i_{p}}{d t} = \frac{U_{dc}}{2} - u_{p} - u_{normals} \\ L \frac{d i_{n}}{d t} = \frac{U_{dc}}{2} - u_{n} + u_{normals} \\ i_{normals} = i_{p} - i_{n} \end{matrix})

The circulating current i z is given by [21]

i_{z} = 0.5 false(i_{p} + i_{n} false)

u x and u y are defined by [25]

({, \begin{matrix} right leftthickmathspace.5em \\ u_{x} = L \frac{d false(i_{normals} false)}{d t} \\ u_{y} = 2 L \frac{d false(i_{z} false)}{d t} \end{matrix})

On the basis of (1)–(3), u p and u n can be rewritten as

({, \begin{matrix} right leftthickmathspace.5em \\ u_{p} = \frac{U_{dc} - 2 u_{normals} - false(u_{x} + u_{y} false)}{2} \\ u_{n} = U_{dc} + 2 u_{normals} \end{matrix})

…”

Section: Control Of the MMCmentioning

confidence: 99%

“…1, the instantaneous output power p o and input power p in can be obtained as

({, \begin{matrix} right leftthickmathspace.5em \\ p_{normalo} = u_{normals} i_{normals} \\ p_{i n} = U_{dc} i_{z} \end{matrix})

i z _ref in Fig. 2 is set to be I z _dc when the control strategy of suppressing circulating current harmonics is used to ensure that i z is controlled as the direct current I z _dc [24, 25]. When the internal power loss of the MMC is neglected, the active powers of the input and that of the output are equal, so the dc components of p in and p o are equal.…”

Section: Control Of the MMCmentioning

confidence: 99%

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Adaptive loss and capacitance‐reduction control strategy based on second‐harmonic circulating current injection for MMC

Jiang

Xiao

Wang

2019

IET Power Electronics

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The submodule (SM) capacitance value of a modular multilevel converter (MMC) is so large that the reliability and cost of the MMC are affected. By existing methods of second-harmonic circulating current injection with a closed-loop control strategy, the SM capacitance value can be greatly reduced. However, the design of the SM capacitance value is not given, and extra loss is brought in. This study gives the design of the SM capacitance value when the second-harmonic circulating current is injected with a closed-loop control strategy. Then, an adaptive control method based on SM capacitor voltage fluctuation feedback is proposed to reduce the extra loss caused by the second-harmonic circulating current injection. In addition, for the case without SM capacitor voltage sensors, a method based on real-time calculation of the injected second-harmonic circulating current is proposed to reduce the extra loss without SM capacitor voltage sensors. Finally, the accuracy of the design and the validity of the proposed methods are verified by simulation and experimental results.

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“…The components that contribute to total time delay T d of the control system in an MMC are [45] the following:…”

Section: Analysis Of Latency In Wireless Controlmentioning

confidence: 99%

Wireless Control of Modular Multilevel Converter Submodules

Ciftci

Schiessl²,

Gross

et al. 2021

IEEE Trans. Power Electron.

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Wireless control of modular multilevel converter (MMC) submodules offers several potential benefits to exploit, such as decreased converter costs and ease in converter installation. However, wireless control comes with several challenging engineering requirements. The control methods used with wired communication networks are not directly applicable to the wireless control due to the latency and reliability differences of wired and wireless networks. This article reviews the existing control architectures of MMCs and proposes a control and communication method for wireless submodule control. Also, a synchronization method for pulsewidth modulation carriers is proposed suitable for wireless control. The imperfections of wireless communication, such as higher latency and packet losses compared to wired communication, are analyzed for the operation of MMCs. The latency is fixed with a proper controller and wireless network design. The converter is rendered immune to the packet losses by decreasing the closed-loop control bandwidth. The functionality of the proposal is verified, for the first time, experimentally on a laboratory-scale MMC using a simple wireless network. It is shown that wireless control of MMC submodules with the proposed approach can perform comparably to the wired control.

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Analysis and Compensation of the System Time Delay in an MMC System

Cited by 17 publications

References 31 publications

Stability Analysis of High-Frequency Interactions Between a Converter and HVDC Grid Resonances

Stability Analysis of High-Frequency Interactions Between a Converter and HVDC Grid Resonances

Adaptive loss and capacitance‐reduction control strategy based on second‐harmonic circulating current injection for MMC

Wireless Control of Modular Multilevel Converter Submodules

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