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High proportion of distributed photovoltaic (PV) integration into distribution network can lead to power flow back feeding and node voltage exceeding its upper limit. To address this issue, a moment difference analysis theory (MDAT) for distribution network with high proportion of distributed PV is proposed. This theory transforms the PV accommodation problem into the problem of balancing moment difference equations. The critical moment difference represents the PV accommodation limitation of the distribution network, the PV moment is the object that needs to be accommodated, and the load moment serves as the resource to absorb the PV moment. Based on this, the distribution network with multiple branches is simplified into several single-branch lines, and the optimal energy storage configuration is obtained by solving a multivariate linear equation. The simulations are carried out on the single-branch Feeder 519 of the State Grid Shandong Electric Power Company and the IEEE 33-node distribution network with multiple branch feeders. The results show that, compared with the particle swarm optimization (PSO) algorithm, the proposed method improves the speed of energy storage optimization configuration by 47.87 to 2 371.37 times under an error margin of no more than 2 %, which verifies the accuracy and efficiency of the proposed method. Moreover, the proposed method considers factors such as energy storage charging and discharging, reducing the required energy storage capacity and improving battery utilization efficiency. [ABSTRACT FROM AUTHOR]

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In the current distribution network's energy structure, photovoltaic (PV) occupies a high proportion. However, the access of a high proportion of PV will lead to the phenomenon of reverse power flow in the distribution network, and then the problem of line overvoltage. When the reverse power flow increases, the problem of line overvoltage also worsens, which endangers the normal operation of power system. To solve this problem, this paper starts with the voltage rise theory of distribution network lines. Firstly, through strict mathematical derivation, it compares the influence of main network line parameters and distribution network line parameters on the voltage rise, and summarizes a simple calculation equation for the voltage rise of the distribution network with high proportion PV. Then, according to the mechanism of voltage rise and the principle of inverter control, considering the economy and practicability of the overvoltage suppression strategy, a reverse power flow overvoltage suppression strategy of a system with high proportion PV is proposed. Finally, a PV system model simulating a small village is used to verify the effectiveness of the proposed overvoltage suppression strategy. [ABSTRACT FROM AUTHOR]

In the current distribution network’s energy structure, photovoltaic (PV) occupies a high proportion. However, the access of a high proportion of PV will lead to the phenomenon of reverse power flow in the distribution network, and then the problem of line overvoltage. When the reverse power flow increases, the problem of line overvoltage also worsens, which endangers the normal operation of power system. To solve this problem, this paper starts with the voltage rise theory of distribution network lines. Firstly, through strict mathematical derivation, it compares the influence of main network line parameters and distribution network line parameters on the voltage rise, and summarizes a simple calculation equation for the voltage rise of the distribution network with high proportion PV. Then, according to the mechanism of voltage rise and the principle of inverter control, considering the economy and practicability of the overvoltage suppression strategy, a reverse power flow overvoltage suppression strategy of a system with high proportion PV is proposed. Finally, a PV system model simulating a small village is used to verify the effectiveness of the proposed overvoltage suppression strategy.

In a power system with highly proportional renewable energy integration, the power generated by photovoltaic (PV) of high permeability and high proportion needs to be connected to the distribution network through the power electronic inverter. The inverters can generate the low-order harmonic and high-order harmonic near the switching frequency. Harmonic power will be generated when the harmonic current flows through the power grid with the harmonic voltage of the same frequency, and the additional harmonic losses caused should not be neglected. To effectively analyze the voltage quality and calculate the harmonic loss of the low-voltage distribution network integrated with distributed PV, based on the harmonic loss factor of resistance proposed, the harmonic impedance modeling and harmonic loss calculation method for the key equipment of the power grid, such as lines and transformers, are introduced in this paper firstly. Next, a decoupling algorithm of harmonic power flow is proposed, and the influence of the access capacity of PV on voltage quality and line loss of the distribution network is analyzed. Finally, a harmonic loss calculation method based on measured harmonic data of the distribution network is proposed. It is found that the harmonic loss of the low-voltage distribution network accounts for about 0.6% of the total network loss. Therefore, voltage quality can be improved and line loss can be reduced effectively by reasonable access to PV and reducing harmonic order and the current harmonic distortion. [ABSTRACT FROM AUTHOR]