#### 期刊菜单

An Overview of Modeling and Control Methods for Microgrids
DOI: 10.12677/AEPE.2021.93018, PDF, HTML, XML, 下载: 456  浏览: 1,278

Abstract: The microgrid is attracting more and more attention and it is considered as the development trend of low-carbon smart grid, which will gradually change the traditional power supply mode. Based on the modeling and control of smart microgrid, this paper expounds the fundamental structure and operation condition of AC microgrid, DC microgrid and AC/DC hybrid microgrid. The comprehensive modeling principle and operation characteristics of clean wind, photovoltaic and energy storage power generation are analyzed. This paper particularly reviews the control strategies of hierar-chical control, decentralized control and master-slave control for microgrid under different operat-ing modes. Finally, the prospects of microgrid in energy management and project, power quality improvement and operation protection, as well as interconnection and coordinated operation of multi-microgrid are also forecasted.

1. 引言

2. 微网的建模

(a) (b) (c)

Figure 1. Microgrid structure based on photovoltaic-battery energy storage system. (a) AC microgrid structure; (b) DC microgrid structure; (c) AC/DC microgrid structure

Figure 2. Microgrid structure based on photovoltaic-battery energy storage system

$\begin{array}{l}{P}_{PG}+{P}_{bat}={P}_{DC}^{load}+{P}_{AC}^{load}+{P}_{grid}\\ {P}_{PG}+{P}_{bat}={P}_{DC}^{load}+{P}_{AC}^{load}\end{array}$ (1)

$\begin{array}{l}{P}_{load}\left(t\right)={P}_{PG}\left(t\right)+{P}_{ESS}\left(t\right)+{P}_{grid}\left(t\right)\\ {{P}^{\prime }}_{load}\left(t\right)={P}_{load}\left(t\right)-{P}_{PG}\left(t\right)-{P}_{ESS}\left(t\right)\\ {P}_{out}\left(t\right)={P}_{PG}\left(t\right)+{P}_{ESS}\left(t\right)-{P}_{load}\left(t\right)\end{array}$ (2)

Figure 3. Microgrid structure of wind-PV-battery hybrid system

$\begin{array}{l}{P}_{m}=\frac{\text{1}}{\text{2}}\cdot {C}_{P}\cdot \rho \cdot A\cdot {V}_{w}^{\text{3}}\\ {T}_{m}\text{=}\frac{{P}_{m}}{{\omega }_{m}}=\frac{\frac{1}{2}\cdot {C}_{P}\cdot \rho \cdot A\cdot {V}_{w}^{3}}{{\omega }_{m}}\end{array}$ (3)

${C}_{P}\left(\lambda ,\beta \right)={k}_{1}\left({k}_{2}\frac{1}{{\lambda }_{i}}-{k}_{3}\beta -{k}_{4}{\beta }^{{k}_{5}}-{k}_{6}\right)\mathrm{exp}\left(-{k}_{7}\frac{1}{{\lambda }_{i}}\right)$ (4)

$J\frac{\text{d}{\omega }_{m}}{\text{d}t}={T}_{e}-{T}_{m}-B\cdot {\omega }_{m}$ (5)

Figure 4. Dynamic model of wind turbine

(a)(b)

Figure 5. Single diode and double diode equivalent circuit. (a) Single diode equivalent circuit; (b) Double diode equivalent circuit

${I}_{pv}={N}_{pp}\left\{{I}_{pv,n}-{I}_{o}\left[\mathrm{exp}\left(\frac{{V}_{pv}+{I}_{pv}{R}_{s}}{{V}_{T}{N}_{ss}}-1\right)\right]\right\}-\left(\frac{{V}_{pv}+{I}_{pv}R}{{R}_{p}}\right)$ (6)

${I}_{pv}={N}_{pp}\left\{{I}_{pv}-{I}_{o1}\left[\mathrm{exp}\left(\frac{{V}_{pv}+I{R}_{s}}{{a}_{1}{V}_{t}{N}_{ss}}\right)-1\right]-{I}_{o2}\left[\mathrm{exp}\left(\frac{{V}_{pv}+I{R}_{s}}{{a}_{2}{V}_{t}{N}_{ss}}\right)-1\right]\right\}-\left(\frac{{V}_{pv}+{I}_{pv}{R}_{s}}{{R}_{p}}\right)$ (7)

${E}_{g}={E}_{go}-K\frac{Q}{Q-\int {i}_{batt}dt}+A\mathrm{exp}\left(B\int {i}_{batt}dt\right)$ (8)

Figure 6. Battery equivalent circuit model

3. 微网控制

Figure 7. Power distribution between DG converter and the grid

$Q=\frac{{V}_{grid}}{{X}_{s}}\left[{E}_{gen}\mathrm{cos}\left({\theta }_{gen}-{\theta }_{grid}\right)-{V}_{grid}\right]$ (9)

3.1. 锁相环技术

PLL的基本框图如图8所示，相位检测用以确定相角与输入电压之间的变化，再进入环路滤波，利用环路滤波器的输出触发电压控制振荡器(Voltage Controlled Oscillator, VCO)，产生电压相位角。

Figure 8. Basic block diagram of a phase locked loop

Figure 9. Grid-connected inverter structure

Figure 10. Basic block diagram of PQPLL

SRFPLL适用于三相系统，其不提供相位、频率和振幅的具体值，而只提供平均值，该方法的主要目的是检测逆变器之间公共耦合点的电压幅值和频率 [28]，SRFPLL线性化小信号模型框图如图11所示。

Figure 11. Linearized small signal model of SRFPLL

Figure 12. Linearized small signal model of SRFPLL

EPLL的状态方程如下式所示 [28]：

$\begin{array}{l}A={x}_{1}{\epsilon }_{\mu }\mathrm{cos}\phi \\ {\omega }^{\prime }={x}_{2}{\epsilon }_{\mu }\mathrm{sin}\phi \\ {\phi }^{\prime }=\omega +{x}_{3}\mathrm{sin}{\omega }^{\prime }\end{array}$ (10)

Figure 13. Basic block diagram of SSIPLL

Table 1. Compare of PLL technology

3.2. 微网的协调控制策略

Figure 14. Block diagram of a microgrid model with microgrid central controller

Figure 15. A new control architecture of DC microgrid

Figure 16. Control architecture of multi-microgrid system

4. 结论与展望

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