For the status of rapidly increasing distributed photovoltaic (PV) penetration in low voltage distribution network (LVDN), several strategies that enhance the PV consumption ability in LVDN are researched and analyzed in detail. Distributed PV and distributed energy storage system (ESS) in LVDN are modeled in Matlab/Simulink platform. Moreover, control effectiveness on voltage deviation, power loss and power factor under the two strategies that are based on PV inverter reactive power and ESS active power respectively is analyzed and compared. The research results indicate that the voltage regulation ability under reactive power control strategy based on PV inverter is limited in LVDN, and the power loss and power factor are negatively affected under the strategy; the active power control based on ESS can regulate voltage relative effectively and optimize power loss, but the active power control require ESS has a large capacity, and it is not conducive to optimizing power factor. Based on this, a coordinated control strategy with inverter reactive power and ESS active power is proposed. The simulation results show that the coordinated control strategy can regulate voltage efficiently and has the better comprehensive optimal results. Meanwhile, it can maximize the use of PV inverter reactive power capability, and reduce the ESS capacity requirements.

When a large-scale distributed photovoltaic power supply is connected to a distribution network, it may cause line overload, harmonic pollution, and voltage over-limitation. This paper mainly studies the influence of different penetration rate of distributed photovoltaic power supply on the voltage of typical rural distribution network, builds a rural distribution network model with distributed photovoltaic power supply by ETAP simulation software, simulates the power flow of the distribution network with photovoltaic power supply at different times in sunny days, and analyzes the influence of different photovoltaic power supply access on the voltage of rural distribution network at different times. In order to solve the problem of voltage beyond limits, this paper proposes a voltage regulation measure based on the central point, which is putting reactors in the central point of the distribution network, absorbing the excess reactive power of the grid by adjusting reactors when the bus voltage exceeds the limit, thus reducing the bus voltage. Finally, the effectiveness of this method is verified by a simulation example.

The LCL grid-connected inverters have become an important topology structure for eliminating high-order harmonics, and become a research hotspot for scholars at home and abroad. When the topology and modulation strategy are determined, the decoupling control of the system becomes the decisive factor for the stability and performance of the system. This paper discusses the limitations of traditional single control strategy in LCL grid-connected inverters, the advantages of compound control strategy and the advantages and disadvantages of different combinations of two kinds of compound control. The internal control mechanism of parallel compound control proportion-integral (PI) ＋ repeat-control (RC) is analyzed, and the influence of coupling degree on the system is reduced by adjusting the parameters of PI control.

With the increasing of wind power penetration in the power system, the phenomenon that wind power cannot be connected to the grid becomes more and more serious, and the problem of wind abandonment needs to be solved urgently. Aiming at the problem of how the energy storage system cooperates with the abandonment of wind in the power grid, this paper builds up an optimal scheduling model including multi source and energy storage power station. The proposed model aims at the minimum running cost of the system. Compared with other scheduling models, the improvement of the model is to increase the cost of wind abandonment and battery operation, and quantify the economic loss of wind abandonment and battery loss. Matlab/Simulink simulation software is used to optimize the scheduling model through improved particle swarm optimization algorithm, and the economy of the system before and after energy storage device configuration is compared and analyzed. Simulation results show that after the energy storage battery is configured, each generator set can flexibly participate in the power system scheduling, effectively improve the wind power consumption capacity of the system, and reduce the abandoned wind power, which has good economic benefits.

This paper puts forward a island division method based on the bubble algorithm to restore the power supply of distribution network with distributed generation (DG). Firstly, the distribution network is transformed into an undirected connection diagram. Then, the weights of all nodes in distribution network are given, and the set of nodes satisfying the conditions is searched by using the bubble algorithm. Finally, the load switches of the nodes outside the set are cut off. The simulation results show that the bubble algorithm can maintain the integrity of the distribution network to the greatest extent, and only the load switch is used to restore the power supply after fault removal. Moreover, the proposed island division method is applicable not only to the radial network but also to the ring network.

Aiming at the problems caused by the current indirect methods for ultra-short-term wind speed prediction which used the same model for each frequency sequence, this paper proposed a combined ultra-short-term wind speed prediction method using a hybrid model based on wavelet decomposition. The proposed method is based on three basic methods, which are autoregressive differential moving average model, back propagation (BP) neural network and support vector machine. The appropriate method is selected and the corresponding model is created according to the characteristics of each frequency sequence after wavelet decomposition, then the results of ultra-short-term wind speed prediction can be obtained through wavelet reconstruction. The proposed method can consider the difference and predictability among each frequency sequence fundamentally, therefore the prediction accuracy can be improved. The proposed method has higher prediction accuracy under different time horizons. When mean absolute error is used as the evaluation index, the prediction accuracy of the proposed method can be improved by 64.2% and 61.4% under 1 h and 4 h time horizons respectively compared with the persistence method, 7.2% and 5.7% under 1 h and 4 h time horizons respectively compared with the minimum prediction error method in traditional single model combination prediction method.

With the development of flexible DC technology, hybrid AC/DC distribution networks based on voltage source converter (VSC) has become the future trend of urban areas. This paper compares different types of converters, the results show that VSC has greater advantages in control flexibility. The VSC control method are analyzed, and the maximum transmission capacity of DC line based on the VSC unipolar symmetric wiring method is proposed. A power flow calculation method through decoupling between AC system and DC system is proposed, which can be applied to a complex AC/DC hybrid distribution network with multi-terminal DC, and can ensure the simplicity and rapidity of power flow calculation. Through the comparison between the commercial power flow solving software DIgSILENT and the proposed method, the correctness of the proposed method is verified.

With the fast development of distributed generation (DG) and demand response (DR), the issue of distribution network planning becomes increasingly important. The mathematical model of integrated resource planning for distribution network considering DG and DR is established. The stochasticity of wind power is considered, and a hybrid intelligent algorithm is used to solve the problem, aiming to obtain the distribution network planning scheme with the highest system reliability and economy. When choosing the optimal objective function, many factors are considered at the same time, including the network loss cost of power system, the investment cost and operating cost of DG, the interruptible load compensation cost considering DR, the saving of electricity purchase after introduction of DG, the environmental benefits after optimization, etc. The hybrid intelligent algorithm based on support vector machine and particle swarm optimization algorithm are adopted for the DG planning. Finally, an actual distribution network in China is taken as an example to verify the improvement effect of the proposed algorithm on system reliability and economy.

To cope with the unstable output power of distributed generation systems, it is necessary to configure an energy storage device with a suitable capacity in the microgrid, and adopt appropriate control methods to achieve the output power of the smooth distributed power generation, so as to achieve the effect of peaking and filling the valley of the microgrid load. This paper proposes the method of applying the upper and lower limit constraint method and the weighted moving average control method to meet the access requirements of the microgrid, targeting the minimum energy storage configuration capacity, and optimizing the configuration of the hybrid energy storage device. The optimized configuration of the energy storage device can be effectively realized by verifying the two methods.

In view of the problems of long line, low terminal voltage and poor reliability in remote mountainous areas, an effective way is to make full use of local renewable energy and build microgrid. In this paper, the existing problems of Liannan power grid and pilot line are analyzed, and the reconstruction scheme of microgrid with photovoltaic and energy storage is proposed. In the process of practice, the ‘three-phase unbalance governance’，the ‘accurate fault location of overhead line’，and the ‘intelligent inspection of power channel and power equipment’，are further adopted to improve power supply quality. The investment estimation and effect analysis of the proposed scheme are carried out. The results show that the proposed scheme can significantly improve the power quality and supply reliability, and deal with the disordered access of distributed generation, which has the value of popularization and application.