﻿ 基于快速排序法的MMC电容电压均衡控制策略 Capacitance-Voltage Balancing Control Method for the Submodule of Modular Multilevel Converter Based on the Rapid Sequencing Method

Smart Grid
Vol.07 No.02(2017), Article ID:20306,8 pages
10.12677/SG.2017.72011

Capacitance-Voltage Balancing Control Method for the Submodule of Modular Multilevel Converter Based on the Rapid Sequencing Method

Maolin Tang1, Chao Xiao2, Jinxin Ouyang2, Rui Yu1, Xi Zhang1, Xiaofu Xiong2

1State Grid Southwest Division, Chengdu Sichuan

2State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing

Received: Apr. 13th, 2017; accepted: Apr. 27th, 2017; published: Apr. 30th, 2017

ABSTRACT

With the improvement of the engineering capacity and the DC voltage level of FACTS based on modular multilevel converter (MMC), it is putting forward higher requirement for capacitor balance control issue of MMC sub-modules (SMs). In order to reduce the computational complexity of voltage balancing sorting of SMs and switching dissipation of MMC, a new voltage balancing control improved algorithm based on Quick Sort method and divided conquer was presented in this paper: dividing into groups twice according to the switching control instruction as well as charging and discharging active status of bridge arms in each control cycle; then choosing the SMs which have large difference with rated voltage within the minimum range on the basis of specific switching number; avoiding the prophecy of collating all SMs repeatedly. A MMC model has been set up on the PSCAD. Finally, the effectiveness of the design control method was verified. The results show that this voltage balancing method can be realized effectively under low switching dissipation and low ranking calculation.

Keywords:Modular Multilevel Converter (MMC), Sub-Module, Capacitance-Voltage Balancing Control, The Rapid Sequencing Method, Switching Frequency

1国家电网公司西南分部，四川 成都

2重庆大学输配电装备及系统安全与新技术国家重点实验室(重庆大学)，重庆

1. 引言

MMC-HVDC采用子模块级联型拓扑，具有模块化结构易于扩展、低次谐波含量低、损耗小的优点 [1] [2] ，使得基于模块化多电平换流器的柔性直流输电得到广泛的应用。

2. MMC直流输电基本结构

3. 基于快速排序法的电容电压均衡控制策略

3.1. 总体控制流程

① 定义两个数组A[xn − 1]、B[ym − 1]分别存放桥臂中未投入的N个以及处于投入状态的M个子模块电容电压值。

② 根据换流站控制层给出的下一个控制周期需投入或切除的子模块个数，判断以子模块电压额定值UN为分界元素进行第一轮初步排序的数组元素来源于已投数组还是待投数组。

(a) (b)

Figure 1. The topology of modular multilevel converter

Figure 2. Arithmetic flow chart of voltage balancing control

③ 最后，等待下一个控制周期，重复步骤1-步骤4。

3.2. 需投入子模块情况均压控制策略

Figure 3. Arithmetic flow chart of voltage balancing control when arm-current is charging

Figure 4. Arithmetic flow chart of voltage balancing control when arm-current is discharging

Figure 5. Arithmetic flow chart of voltage balancing control when ΔN < 0

3.3. 需切除子模块情况均压控制策略

4. 仿真结果分析

Figure 6. System construction drawing of MMC-HVDC

Figure 7. Switching frequency of submodules based on bubble sort algorithm

Figure 8. Switching frequency of submodules based on sort algorithm in this article

Table 1. Calculation contrast in normal conditions

5. 结论

Capacitance-Voltage Balancing Control Method for the Submodule of Modular Multilevel Converter Based on the Rapid Sequencing Method[J]. 智能电网, 2017, 07(02): 97-104. http://dx.doi.org/10.12677/SG.2017.72011

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