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首页> 外文期刊>Journal of Engineering & Applied Sciences >Digital Current Sensing in Modular Multilevel Converter for HVDC Applications
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Digital Current Sensing in Modular Multilevel Converter for HVDC Applications

机译：用于HVDC应用模块化多电平转换器中的数字电流检测

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摘要

For long-distance transmission, HVDC (High-Voltage, Direct-Current) is proven to be less expensive and have lower electrical losses as compared to HVAC (High-Voltage, Alternating-Current). Now a days, the advancement of power electronic switches such as IGBT's and MOSFET enables the use of converters for HVDC applications. Among the well-known converters used for HVDC are Voltage Source Converter (VSC) Line Commutated Converter (LCC) and Modular Multilevel Converter (MMC). The MMC is still new and a promising technology for HVDC application. The MMC has many advantages such as controlling high amount of active/reactive power and possess lower losses as compared to other converters. To control the active/reactive power in a MMC, control scheme such as free-running hysteresis uses the reference voltage and the inductor current to produce the required switching pulses. This study proposed a technique in which a voltage sensor is use to measure the inductor current. Conventionally, the inductor current is sensed either with a resistor or Current Transformer (CT). This method is associated with some disadvantages; requires additional circuitry which introduces some power loss and requires higher bandwidth in order to sense accurately. This study instead, measures the current indirectly by using the information of the phase inductor voltage. As the voltage sensor is placed in parallel to the inductor, this measuring technique is immune to I~2R loss. The proposed technique will be investigated using MATLAB simulation to determine its current sensing capability in a MMC for HVDC applications. To design an improved current-less sensing method using a digital RC network. To extract the inductor current values from the phase inductor voltage an RC filter is required and placed in parallel across the inductor. In this way, all the high frequency harmonics will be filtered out and only the low frequency inductor current can be seen across the capacitor. The selection of RC values, however is dependent on the inductor value and inductor DC-Resistance (R_(DCR)). The main concern with this technique is that selection of RC values sometimes can be unavailable for hardware implementation. To further improve the implementation of RC network and eliminate the problems of selecting suitable RC values for hardware implementation. This paper proposed the used of digital filter based on the RC network concept. Instead of using the actual components for filtering the high frequency harmonics, this technique uses only the DSP for filtering to remove the high frequency harmonics. The proposed technique is able to convert the high frequency voltage V_(L1) measured from the phase inductor L_1 into the phase inductor current i_(L1) without any delay or difficulty. By comparing the signals of proposed method to the series sensing method and the conventional RC filter method the waveforms of both signals are almost identical. However, the proposed method eliminates the need for RC components as compared to the conventional RC filter method. This technique improves the efficiency of the system in terms of improve signal noise ratio and eliminates the need for passive component on the system.
机译：对于长距离传输，经过证明HVDC（高压，直流电流）且与HVAC（高压，交流电流）相比的电损耗较低。现在是一天，电力电子交换机等IGBT和MOSFET的进步使得能够使用转换器进行HVDC应用。在用于HVDC的众所周知的转换器中，用于HVDC的电压源转换器（VSC）线路换向转换器（LCC）和模块化多级转换器（MMC）。 MMC仍然是新的HVDC应用程序的有希望的技术。 MMC具有许多优点，例如控制高量的主动/无功功率并且与其他转换器相比具有较低的损耗。为了控制MMC中的主动/无功功率，诸如自由运行滞后的控制方案使用参考电压和电感器电流来产生所需的开关脉冲。该研究提出了一种技术，其中电压传感器用于测量电感器电流。传统上，电感电流用电阻器或电流互感器（CT）感测。该方法与一些缺点有关;需要额外的电路，该电路引入一些功率损耗，并且需要更高的带宽以准确地感知。该研究代替，通过使用相位电感电压的信息间接测量电流。由于电压传感器平行于电感器，因此该测量技术免于I〜2R损失。将使用MATLAB仿真研究所提出的技术，以确定其MMC的电流检测能力，用于HVDC应用。使用数字RC网络设计改进的电流传感方法。为了从相位电感电压从相电感电压提取电感器电流值，需要RC滤波器并在电感器上并联放置。以这种方式，所有高频谐波都将被滤出，并且只能在电容上看到低频电感电流。然而，RC值的选择取决于电感器值和电感器直流电阻（R_（DCR））。这种技术的主要关注点是RC值的选择有时可能无法用于硬件实现。为了进一步改进RC网络的实现，并消除为硬件实现选择合适的RC值的问题。本文提出了基于RC网络概念的数字滤波器使用的。该技术代替使用用于过滤高频谐波的实际组件，仅使用DSP进行过滤以删除高频谐波。所提出的技术能够将从相位电感器L_1测量的高频电压V_（L1）转换为相位电流I_（L1），而不会延迟或困难。通过将所提出的方法的信号与串联感测方法和传统的RC滤波器方法进行比较，两个信号的波形几乎相同。然而，与传统的RC滤波器方法相比，所提出的方法消除了对RC组分的需求。在提高信号噪声比方面，该技术提高了系统的效率，并消除了对系统上的无源组件的需求。

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