Research on household energy efficiency management strategy based on integrated photovoltaic/storage intelligent inverter

With the rapid development of the new energy industry and the continuous practice of smart grid technology, distributed power generation technology has been vigorously developed. In order to promote the application of distributed power generation, the National Development and Reform Commission issued the "Interim Measures for the Management of Distributed Power Generation" in 2013, proposing that for distributed power generation, power grid companies should provide grid connection services and the government should provide certain subsidies.

The home power supply network is no longer a single power load, but also a power generation role. The home load is not only powered by the AC power grid, but also by local distributed power sources. Home energy efficiency management and energy consumption are no longer simple electricity management. Smart grid and home energy efficiency management are a two-way interactive method with a strong correlation.

Household energy efficiency management will actively participate in the comprehensive control of the smart grid, so that the grid can provide users with more economical and better services. At the same time, household loads can ensure safer and more efficient operation of the grid by avoiding operation during peak hours.

The combination of smart grid and distributed power generation has led to the concept and development of energy efficiency management for household microgrids. In recent years, there have been a lot of research and practice, and the continuous application of distributed power generation in households has led to changes in the development model of the entire industry. Photovoltaic power generation is the most widely used in household distributed power generation. The combination of distributed photovoltaic power generation and energy storage can achieve the optimal utilization of household energy efficiency.

The integrated photovoltaic/storage smart inverter can connect photovoltaic panels and energy storage batteries to the grid at the same time, and through the coordinated management of the panels and batteries, it can achieve three working modes: maximum power grid-connected power generation, power dispatchable grid-connected power generation, and off-grid operation. Combining the smart home energy efficiency management strategy with the integrated photovoltaic/storage smart inverter system can achieve optimized control of household electricity consumption and improve the economic efficiency of household electricity consumption.

This paper proposes a household energy efficiency management strategy based on a photovoltaic/storage integrated intelligent inverter, gives the overall architecture of the household microgrid system, and makes a detailed introduction. Through the analysis of the mathematical model of household energy efficiency management, an energy efficiency management strategy for time-of-use electricity prices is proposed to achieve the goal of minimizing household electricity costs. The correctness of the control algorithm is verified through Matlab/Simul ink simulation analysis.

1 System overall architecture model of home microgrid based on smart inverter

A collection of distributed power sources, energy storage units, loads, and monitoring and protection devices, with flexible operation modes and dispatchable performance, can switch between grid-connected and off-grid operation modes. This is the definition of a microgrid. A household microgrid can be understood as a household electricity network that has the functions and characteristics in the above definition, so we can call it a household microgrid.

This paper designs a home microgrid system based on smart inverter, which can realize the relevant functions of the microgrid and uses a small number of devices, making it easy to apply to user homes that install distributed power generation.

1.1 Introduction to the functions of the integrated photovoltaic/storage smart inverter

The grid-connected inverter used in distributed power generation is characterized by a small power level, but more integrated functions, and is smarter than traditional grid-connected inverters. The integrated photovoltaic/storage intelligent inverter can be connected to two independent photovoltaic power generation units and one energy storage unit. The specific structural diagram is shown in Figure 1.

Figure 1 Smart inverter system structure

In the system designed here, the voltage of the photovoltaic panel is generally around 150V to 300V, and the voltage of the energy storage battery system is generally around 45V to 65V. The inverter mainly consists of four parts: two BOOST boost DC/DC converters, which are used to connect two independent photovoltaic power generation channels, and can realize functions such as boost and MPPT; a bidirectional DC/DC conversion circuit, which adopts the DAB topology structure, can realize boost, buck and charge and discharge of the battery, and can stabilize the DC BUS voltage by charging and discharging the battery; a single-phase inverter circuit, which adopts the H-bridge structure, can realize inverter grid-connected, off-grid, PQ adjustable and other functions.

1.2 Home Microgrid System Architecture

Figure 2 is a system cabinet diagram of a household microgrid. As can be seen from the system in the figure, the household microgrid system designed in this paper can be connected to distributed photovoltaic power generation and energy storage batteries, and the application of intelligent inverters can realize two working modes: grid-connected operation mode and off-grid operation mode. When working in grid-connected mode, the output active power and reactive power can accept the control instructions of the upper layer. The bidirectional metering device can realize bidirectional metering of power exchange between users and the grid [6].

If the power of photovoltaic power generation is greater than the power consumption of the local load and the battery has sufficient power, the excess power can be sent to the grid. In remote mountainous areas or areas with unstable power grids, there may be grid failures or grid instability. At this time, the system can disconnect the grid-connected switch and work in independent mode. The photovoltaic power generation and battery provide power, and the smart inverter works in voltage source mode.

The microgrid monitoring system and energy management system can monitor and control the equipment in the system. According to the specific goals and actual conditions, energy management strategies will be added to the microgrid monitoring platform [7]. LabVIEW has been increasingly used in China due to its advantages such as easy entry, short development cycle and low development cost [8]. The monitoring system in this paper is developed using LabVIEW software.

The smart inverter is connected to the data acquisition card through a 485 communication line, the local load or the switch that controls the local load is connected to the data acquisition card through a 485 communication line, and the energy efficiency management system directly transmits data with the acquisition card, ultimately achieving comprehensive management of the entire system.

Figure 2 Block diagram of home microgrid system

2 Mathematical model of household electricity consumption (omitted)

3 Home Energy Efficiency Management and Control Strategies (Omitted)

4 Simulation results and analysis (omitted)

in conclusion

This paper gives a detailed description of the construction of the home system and introduces the composition and functions of the smart inverter. On this basis, through in-depth analysis of the home power supply and load, a mathematical model is obtained. And in the form of a mathematical model, a control strategy for energy efficiency management is given. Finally, Matlab/Simulink is used to simulate the actual data to verify the correctness and feasibility of the energy management algorithm.

In this article, in order not to affect the user's use of the load, the load is not managed. The next step is to further classify the load, adjust the working power and working period of the load, and implement a more optimized energy efficiency management strategy.