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Analysis of the Acceptance Ability of Distribution Network to Distributed PV
DOI: 10.12677/AEPE.2017.56022, PDF, HTML, XML, 下载: 1,641  浏览: 4,810  国家科技经费支持

Abstract: In this paper, the impact of distributed photovoltaic (PV) access on the power quality and fault current of distribution network is studied. First of all, the constant power output of photovoltaic power model is adopted and the influence of the access of distributed photovoltaic on distribution network voltage deviation and voltage harmonic are analyzed; Secondly, the change of fault current is analyzed considering fault at the upstream, downstream and adjacent feeder of the distributed PV access location, respectively; Finally, practical example is calculated based on above theoretical analysis, and the maximum penetration of PV is calculated in comprehensive consideration of power quality and existing protection setting value.

1. 引言

2. 分布式光伏接入对配电网电能质量的影响

2.1. 分布式光伏接入后对配电网的电压偏差的影响

Figure 1. Multi node constant power distribution network

$\begin{array}{c}\Delta {{U}^{\prime }}_{i}=\frac{{V}_{i}-{V}_{N}}{{V}_{N}}=\frac{{V}_{0}-\Delta {V}_{0,i}-{V}_{N}}{{V}_{N}}\\ =\frac{{V}_{0}}{{V}_{N}}-\frac{i\left(2N-i+1\right)}{2}×\frac{{P}_{l}×R+{Q}_{l}×X}{{V}_{N}^{2}}-1\end{array}$ (1)

$\Delta {V}_{pvj}=\left\{\begin{array}{l}-\frac{j\left(R{P}_{pv}+X{Q}_{pv}\right)}{{V}_{N}},j\in \left[1,i\right]\\ -\frac{i\left(R{P}_{pv}+X{Q}_{pv}\right)}{{V}_{N}},j\in \left[i+1,N\right]\end{array}$ (2)

$\Delta {V}_{j}=\left\{\begin{array}{l}\frac{j\left(2N-j+1\right)}{2}×\frac{R{P}_{l}+X{Q}_{l}}{{V}_{N}}-\frac{j\left(R{P}_{pv}+X{Q}_{pv}\right)}{{V}_{N}},j\in \left[1,i\right]\\ \frac{j\left(2N-j+1\right)}{2}×\frac{R{P}_{l}+X{Q}_{l}}{{V}_{N}}-\frac{i\left(R{P}_{pv}+X{Q}_{pv}\right)}{{V}_{N}},j\in \left[i+1,N\right]\end{array}$ (3)

${V}_{j}=\left\{\begin{array}{l}{V}_{0}-\frac{j\left(2N-j+1\right)}{2}×\frac{R{P}_{l}+X{Q}_{l}}{{V}_{N}}+\frac{j\left(R{P}_{pv}+X{Q}_{pv}\right)}{{V}_{N}},j\in \left[1,i\right]\\ {V}_{0}-\frac{j\left(2N-j+1\right)}{2}×\frac{R{P}_{l}+X{Q}_{l}}{{V}_{N}}+\frac{i\left(R{P}_{pv}+X{Q}_{pv}\right)}{{V}_{N}},j\in \left[i+1,N\right]\end{array}$ (4)

$\Delta {U}_{j}=\left\{\begin{array}{l}\frac{{V}_{0}}{{V}_{N}}-\frac{j\left(2N-j+1\right)}{2}×\frac{R{P}_{l}+X{Q}_{l}}{{V}_{N}^{2}}+\frac{j\left(R{P}_{pv}+X{Q}_{pv}\right)}{{V}_{N}^{2}}-1,j\in \left[1,i\right]\\ \frac{{V}_{0}}{{V}_{N}}-\frac{j\left(2N-j+1\right)}{2}×\frac{R{P}_{l}+X{Q}_{l}}{{V}_{N}^{2}}+\frac{i\left(R{P}_{pv}+X{Q}_{pv}\right)}{{V}_{N}^{2}}-1,j\in \left[i+1,N\right]\end{array}$ (5)

2.2. 新能源系统接入对谐波电压畸变量的影响

2.2.1. 分布式光伏系统接入容量对谐波电压畸变量的影响

$|{I}_{pv}|=|\frac{{P}_{pv}}{{V}_{pv}\ast dp{f}_{pv}}|$ (6)

$\begin{array}{c}\Delta {V}_{h}=|{V}_{h,2}|-|{V}_{h,1}|=\sqrt{{r}^{2}+{h}^{2}{x}^{2}}\ast \left(|{I}_{pvh}|G+|{I}_{lh}|L\right)-L\ast \sqrt{{r}^{2}+{h}^{2}{x}^{2}}\ast |{I}_{lh}|\\ =\sqrt{{r}^{2}+{h}^{2}{x}^{2}}*|{I}_{pvh}|G>0\end{array}$ (7)

2.2.2. 分布式光伏系统接入位置对谐波电压畸变量的影响

1) 分布式光伏系统接入线路 ${G}_{1}$ 之前 $Z$ ( $Z<{G}_{1}$ )位置的谐波电压幅值可表示为： $|{V}_{h}|=|\left(r+jhx\right)\ast Z|\ast |{I}_{pvh}+{I}_{lh}|=Z\sqrt{{r}^{2}+{h}^{2}{x}^{2}}\ast \left(|{I}_{pvh}|+|{I}_{lh}|\right)$ 。由于分布式光伏系统采用电压控制的运行模式，则 ${V}_{pv}$ 基本保持不变， ${P}_{pv}$ 不变时，由方程式(2)可知，在分布式光伏系统的接入节点分别为 ${G}_{1}$${G}_{2}$ 时， $|{I}_{pvh}|$ 几乎相同。而 $G$ 越大，线路末端节点电压 $V$ 就越高，在分布式光伏系统的接入节点为 ${G}_{2}$ 时的 $|{I}_{lh}|$ 比接入节点为 ${G}_{1}$ 时的 $|{I}_{lh}|$ 小。因此，随着接入位置 $G$ 的增大，分布式光伏系统接入点 ${G}_{1}$ 之前 $Z$ ( $Z<{G}_{1}$ )位置的谐波电压幅值 $|{V}_{h}|$ 减小，谐波电压畸变水平降低。

2) 分布式光伏系统接入线路 ${G}_{2}$ 之后 $Z$ ( $Z>{G}_{2}$ )位置的谐波电压幅值可表示为：当分布式光伏系统接入位置为 ${G}_{1}$ 时， $|{V}_{h\left({G}_{1}\right)}|=\sqrt{{r}^{2}+{h}^{2}{x}^{2}}\ast \left[{G}_{1}\left(|{I}_{pvh}|+|{I}_{lh}|\right)+\left(Z-{G}_{1}\right)|{I}_{lh}|\right]$ ；当分布式光伏系统接入位置为 ${G}_{2}$

Figure 2. Distribution network for harmonic analysis

3. 分布式光伏接入对配电网电流保护的影响

${I}_{k,R1}=\frac{{E}_{s}}{a{Z}_{1-2}}$ (8)

$\left(\frac{1}{{Z}_{L}}+\frac{1}{\left(1-a\right){Z}_{1-2}+{Z}_{2-3}}\right)\stackrel{˙}{U}=\left(\frac{S}{\stackrel{˙}{U}}\right)$ (9)

Figure 3. Distribution network for relaying protection analysis

Figure 4. Equivalent circuit diagram for short circuit at f1

$\left(1+\frac{|{Z}_{L}|}{\left(1-a\right)|{Z}_{1-2}|+|{Z}_{2-3}|}\right){U}^{2}=P|{Z}_{L}|\mathrm{cos}\beta$ (10)

$U=\sqrt{\frac{P{R}_{L}\left(\left(1-a\right)|{Z}_{1-2}|+|{Z}_{2-3}|\right)}{\left(1-a\right)|{Z}_{1-2}|+|{Z}_{2-3}|+|{Z}_{L}|}}$ (11)

${I}_{k,R2}=\frac{U}{\left(1-a\right)|{Z}_{1-2}|+|{Z}_{2-3}|}=\sqrt{\frac{P{R}_{L}}{{\left(\left(1-a\right)|{Z}_{1-2}|+|{Z}_{2-3}|\right)}^{2}+|{Z}_{L}|\left(\left(1-a\right)|{Z}_{1-2}|+|{Z}_{2-3}|\right)}}$ (12)

4. 算例分析

4.1. 考虑电能质量的分布式光伏准入容量

4.1.1. 电压偏差

4.1.2. 电压谐波

Figure 5. A typical distribution network

Table 1. Node voltage deviation when the PV capacity changes

Table 2. Node voltage deviation when the PV location changes

Table 3. Node voltage deviation when the PV capacity changes

4.2. 考虑电流保护的分布式光伏准入容量

Table 4. Node voltage deviation when the PV location changes

Table 5. Feeder current protection setting value without considering distributed PV

Table 6. Short circuit current effective value of each protection when the PV capacity changes

Table 7. Short circuit current effective value of each protection when the PV location changes

Table 8. PV access capacity

4.3. 综合考虑电能质量与电流保护的分布式光伏准入容量

5. 结论

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