Frequency Modulation Method and System of Photovoltaic Virtual Synchronous Generator Based on Computer Technology

As an important part of electric multiple units (EMU), the auxiliary power supply system plays an important role in the normal operation of the vehicle. In order to improve the reliability of the auxiliary power supply system, the virtual synchronous generator (VSG) technology is applied to the parallel control system of auxiliary inverter. The essence of VSG technology is to control the inverter to simulate the working principle of synchronous generator, so as to obtain similar operation characteristics of synchronous generator. The auxiliary inverter controlled by VSG technology can avoid the disadvantage of hard external characteristics of power electronic devices. Its rotating inertia can obviously prevent frequency fluctuation, and the system has high stability and reliability. In this paper, the frequency and voltage of the auxiliary inverters are controlled independently with VSG technology, so that the output voltage can be controlled stably and the power quality can be improved. Finally, the MATLAB simulation results show that the parallel control of auxiliary inverter based on VSG achieves the expected goals.

In recent years, virtual synchronous generator (VSG) technology has been more and more used in grid-connected inverters of PV power generation systems. Photovoltaic inverter based on VSG can improve the voltage support capacity of the power grid, but it increases the difficulty of the power grid elaborate modeling and simulation. This paper researched the modeling and parameter identification of the PV inverter based on VSG. In this paper, the PV inverter simulation model based on VSG technology was set up in PSCAD and the effective voltage support capability of VSG technology for the power grid was verified. The mathematical model of the inverter based on VSG was established in MATLAB and important parameters were identified based on the improved differential evolution algorithm. Finally, the performance of the modeling method and parameter identification method used in this paper were tested by considering various perturbations.

Estimating the system efficiency of the multifunctional hydrogen complex at nuclear power plants

In order to improve the friendliness of the grid connection of new energy power generation, the new energy photovoltaic (PV) unit is equivalent to a synchronous generator in the power system and a virtual synchronous generator (VSG)-controlled PV energy storage complementary grid-connected power generation system model is established and studied to analyze the VSG. When power is supplied to the load together with the power grid, the energy storage unit inside the VSG will release and store the electrical energy according to the fluctuation of the PV output, which plays the role of the adjustment of the prime mover; in the case of load power fluctuations, and power grid assume the corresponding active power regulation according to their capacity. The amount of active power adjustment to jointly and maintain the power balance inside the system under the condition of fluctuating load power. The overall system architecture and control strategy of PV grid-connected inverter based on VSG algorithm are proposed. The PV-VSG proposed here not only takes into account the maximum power point tracking control but also has independent participation in the power supply. A series of characteristics of synchronous generators, such as network frequency modulation voltage regulation and inertia damping, can effectively improve the new energy PV power generation system and promote the new energy consumption. The results of system simulation and field demonstration operation fully show the effectiveness and correctness of the proposed control strategy based on VSG algorithm.

A large number of distributed generations (DGs) connected to the distribution network have a significant impact on the stability of the power system due to their low inertia. Meanwhile the DGs are generally linked to the end of the distribution network, where power quality problems are very common. This paper applies virtual synchronous generator (VSG) technology in three-phase four-leg inverter. A strategy of harmonics compensation is utilized to reduce the harmonic pollution caused by unbalanced and nonlinear load. A parameter selection method based on the dynamic response characteristics of VSG control is proposed. The inner current control loop is used so that the inverter output current could track the reference value accurately. The validity and correctness of the control strategy are proved by the simulation results.

Virtual synchronous generator (VSG) is a promising control strategy of an inverter-interfaced distributed generator, owing to its ability to provide inertia support and primary frequency regulation after a grid disturbance. These new features, however, require extra transient energy, which is generally released/absorbed by energy storage (ES). To optimize the design of the ES of a VSG, it is necessary to establish a modeling and calculation method of the transient energy demand (TED) of a VSG and the corresponding maximum grid frequency deviation (MGFD) under a given grid disturbance condition. This method should take the dynamic models of both the grid and the VSG into consideration, including nonlinearity such as droop deadband. Hence, a systematical modeling method and calculation algorithm for the TED and MGFD is presented in this paper. The numerical results obtained by the proposed algorithm are well verified by simulation results from PSCAD/EMTDC. Based on this algorithm, we investigate the influence of VSG parameters on TED and MGFD, and will propose a VSG parameter optimization method to minimize the TED with a given MGFD constraint in our future work.

A novel grid-forming technology for transient stability enhancement of power system with high penetration of renewable energy

This study constructs a novel virtual synchronous generator system based on a transfer function, and optimizes the parameters of the model by using the improved whale algorithm to improve the frequency control ability of virtual synchronous generator. Virtual synchronous generator technology helps to solve the problem that the integration of large-scale renewable energy generation into the power system leads to the deterioration of system frequency stability. It can maintain the symmetry of grid-connected scale and system stability. The virtual synchronous generator technology makes the inverter to have the inertia and damping characteristics of a synchronous generator. The inverter has the inertia characteristics and damps to reduce the frequency instability of high penetration renewable energy power system. The improved whale algorithm is efficient to find the best combination of control parameters and the effectiveness of the algorithm is verified by microgrid and power system. The results show that the proposed frequency coordination control scheme suppresses the frequency deviation of power system and keep the system frequency in a reasonable range.

In order to meet the quality requirement of primary frequency regulation and AGC (Automatic Generation Control) for power plants in China Southern Power Grid "two rules", the paper designs a AGC and primary frequency regulation monitoring and management system for power plant by analyzing the system requirements and combining with the actual situation of the power plant. Based on data acquisition and processing module and real-time database, the system has realized many functions such as automatic collecting, calculating and dealing with the data of the AGC and primary frequency regulation, giving a warning and analyzing the reason when the AGC and primary frequency regulation service are disqualification. After a period of trial running, it shows that the monitoring and management system can improve the quality of the AGC and primary frequency regulation services provided by the power plant. At the same time, the system can also provide guarantee for the safety, stability and economy of the generators.

Aiming at the difference between conventional power electronic interface converter and traditional synchronous generator in microgrid, it cannot provide inertial support and damping effect for microgrid. In this paper, a converter based on virtual synchronous generator technology is used to design the power outer loop and the electromagnetic equation, so that the power electronic converter has some external characteristics of the synchronous generator while providing some damping and inertia for the microgrid, It is clarified that sag control is essentially a kind of virtual synchronous generator control. Finally, the feasibility and correctness of the method are verified by MATLAB simulation.

Virtual synchronous generator (VSG) technology for integration of distributed energy resources attracts increasing attentions for its enabling inverters to simulate the inertia and damping characteristics of synchronous generators and improve the stability of the system. In this paper, a decentralized VSG-based adaptive coordinated control strategy is proposed for islanding microgrids consisting of photovoltaic generators combined with battery energy storages in DC side (PV/BES-VSG). By the proposed method, the droop characteristics of VSGs can be adaptively adjusted according to the DC bus voltage. In this way, the local controllers of PV/BES-VSG units can switch operating modes automatically without the need of a central controller, so that the power sharing among PV/BES-VSG units is allocated according to the maximum output power of PVs and the limit of charging/discharging power of BES instead of merely rated capacity of the inverters. To test the proposed method, an islanding model of microgrid with two PV/BES-VSG units in parallel is built in Matlab/Simulink. The simulation results show that by the proposed control strategy, the coordination control between PV and BES, and between PV/BESVSG units can be effectively realized with maximum use of PV power under the premise of the rational distribution of power.

Battery storage configuration for multi-energy microgrid considering primary frequency regulation and demand response

Aiming at the problem that the power supply quality of the microgrid needs to be improved and the large impact of grid connection, a new type of virtual synchronous generator (VSG) control strategy is proposed to control the microgrid inverter. The VSG model based on stator voltage model and rotor motion model is established by deformation and vector decomposition of the hidden-pole synchronous generator second-order equation. The virtual frequency regulation module and the virtual voltage regulation module are also obtained by improving the principle of generator frequency and voltage regulation, and the grid-connected control module with voltage phase angle double feedback is also designed. By constructing relevant models, compare the performance of voltage, frequency and power before and after grid connection. The simulation results show that the VSG control strategy can better adjust load changes under the premise of less impact on the grid, and verify the effectiveness of the proposed control strategy.

By adopting the virtual synchronous generator (VSG) scheme with the inertia emulation controller and droop controller, wind power plants (WPPs) can participate in inertial response (IR) and primary frequency regulation (PFR). According to the analysis in this article, besides the well-known dynamic coupling between the wind turbine operating point (WTOP) controller and the inertia emulation controller, there is a static coupling between the WTOP controller and the droop controller. These couplings would impair the IR and PFR characteristics of the VSG controlled WPPs (VSG-WPPs). The equivalent droop coefficient of the VSG-WPPs is no longer equal to the setting value and changes under different operation conditions. To eliminate these adverse impacts, a decoupling control scheme is proposed. According to the MATLAB simulations and real-time hardware-in-loop testing results provided in this article, under the same power disturbance, the frequency response characteristics of the WPPs with the proposed scheme are much better than the WPPs with the original scheme.

Challenges of investment and financing for developing photovoltaic power generation in Cameroon, and the countermeasures