CN108390409A - The forest zone microgrid energy management control method of biomass energy and solar energy complementation - Google Patents

Abstract

The invention discloses the forest zone microgrid energy management control methods of a kind of biomass energy and solar energy complementation, solar energy resources can maximumlly be utilized, ensure entire forest zone micro-grid system uninterrupted power supply using biomass energy power supply in the case of giving full play to its real-time power regulation ability under the premise of ensureing service lifetime of accumulator and considering forest zone micro-capacitance sensor operating cost.

Description

Energy management and control method of forest area microgrid based on biomass energy and solar energy complementarity

technical field

The invention relates to the technical field of micro-grid control, in particular to an energy management and control method for micro-grids in forest areas in which biomass energy and solar energy are complementary.

Background technique

At present, ecological observation stations and forest fire prevention monitoring stations have been built in forest areas, and most of them use photovoltaic-battery power supply systems, which make up for the inability to use traditional large power grids for power supply due to geographical conditions. However, the power output of existing photovoltaic and battery power supply systems is easily affected by light conditions. For example, when there is a long period of rainy weather in summer or short sunshine hours in winter, the photovoltaic cell-battery system is often unable to provide continuous power for the connected load. This will cause the ecological observation station or the forest fire monitoring station to fail to work normally due to insufficient power supply.

In order to solve the above problems in the photovoltaic-battery power supply system, it is one of the feasible ways to ensure the continuous supply of electric energy by using other energy sources in the forest area. In fact, there are usually abundant biomass energy in forest areas, including the residues of forest tending operations, wood processing residues, and discarded fungus bags, which create conditions for the development of biomass power generation. Different from photovoltaic power generation, biomass power generation has the advantages of continuous stability, but under the current technical conditions, the use of biomass power generation alone has the problem of low operating efficiency (increased operating costs).

When there are many different types of distributed power sources in the microgrid, according to the characteristics of the distributed An important means of grid power supply reliability.

In terms of micro-grid energy management control strategy, through the retrieval of existing technical literature, Xu Siqin et al. proposed an energy management control strategy for independent photovoltaic power generation DC grid, which uses battery packs and isolated bidirectional DC/DC converters as energy sources. The main control unit is used to ensure the stability of the DC bus voltage of the system, but this strategy requires high battery capacity; Sun Tengchao et al. comprehensively analyzed the working mode of the microgrid under different operating conditions for the optical storage microgrid system, and carried out load control It is proposed that the common load will be cut off when the output of solar energy storage is insufficient; the energy management strategy of the independent wind and solar hybrid power generation system proposed by Chen Xuanyi et al. compares the sum of the output power of wind energy and solar energy with the load power, and compares the output power of the system The operating status is divided into 6 modes, and the strategy is also susceptible to weather conditions.

Contents of the invention

The purpose of the present invention is to provide an energy management and control method for forest area micro-grids in which biomass energy and solar energy are complementary, which can improve the power supply reliability of forest area micro-grids in isolated grid operation.

The purpose of the present invention is achieved through the following technical solutions:

A method for energy management and control of microgrids in forest areas that complements biomass energy and solar energy, including:

Photovoltaic cells, storage batteries and biomass power sources are all connected to the DC bus; according to the intermittent and random fluctuation factors of photovoltaic cells, and on the basis of taking into account the service life of batteries and the operating cost of biomass energy, priority is given to using solar energy to use batteries Mainly, ensure real-time balance of power, and finally use the energy management control method of biomass energy.

It can be seen from the above-mentioned technical solution provided by the present invention that it can maximize the use of solar energy resources, give full play to its real-time power adjustment ability under the premise of ensuring the service life of the battery, and use biomass under the condition of considering the operating cost of the forest area micro-grid. The energy source ensures the uninterrupted power supply of the micro-grid system in the entire forest area.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those of ordinary skill in the art can also obtain other drawings based on these drawings on the premise of not paying creative efforts.

Fig. 1 is the power supply topology diagram of the forest area micro-grid system that biomass energy and solar energy are complementary provided by the embodiment of the present invention;

Fig. 2 is a schematic diagram of an energy management and control method for forest area micro-grids complementary to biomass energy and solar energy provided by an embodiment of the present invention;

Fig. 3 is a simulation result diagram of the energy management and control method of the microgrid in the forest area provided by the embodiment of the present invention that biomass energy and solar energy are complementary;

Fig. 4 is a control block diagram of each distributed power source of the biomass-solar complementary forest area micro-grid provided by the embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

An embodiment of the present invention provides an energy management and control method for a micro-grid in a forest area in which biomass energy and solar energy are complementary. The role of biomass power supply can effectively reduce the operating cost of forest area micro-grid under the condition that the load can continue to supply power.

In the embodiment of the present invention, photovoltaic cells, storage batteries, and biomass power sources are all connected to the DC bus; specifically, as shown in Fig. The battery and storage battery are respectively connected to the DC bus through the buck chopper circuit and the boost/buck bidirectional chopper circuit; while the micro gas turbine powered by biomass energy is connected to the DC bus through the AC/DC rectifier.

The dynamic power balance equation satisfied between the power supply and the load in the energy management optimization strategy designed by the present invention is shown in the following formula:

P _pv +P _bat +P _biomass =P _load .

In the above formula, P _pv represents the actual output power of the photovoltaic cell, which is mainly affected by the illuminance, battery capacity and actual load; P _bat represents the actual output power of the battery, and the value of P _bat during the actual operation of the forest area microgrid The value is dynamically changing; P _biomass represents the power provided by biomass energy, and its value is also dynamically changing; P _load is the load power, and its value is mainly determined by the actual load in the forest area microgrid.

In order to ensure that the micro-grid system in the forest area can provide uninterrupted power supply for the load under any circumstances, in the embodiment of the present invention, according to the intermittent and random fluctuation factors of photovoltaic cells, taking into account the service life of the battery and the operating cost of biomass energy On the basis of solar energy, it adopts the energy management and control method of giving priority to the use of solar energy, using batteries as the mainstay to ensure real-time power balance, and finally using biomass energy.

In the embodiment of the present invention, for the photovoltaic cell part, it is mainly judged whether the photovoltaic cell is turned on or off by comparing its actual output voltage (Upv) with the minimum operating voltage (Upv-min); According to the power demand, the working mode of photovoltaic cells is divided into maximum power tracking mode and constant voltage mode. In the maximum power tracking mode, the output power of the photovoltaic cell is affected by the light intensity; while in the constant voltage mode, the output power of the photovoltaic cell is affected by the actual load in the forest microgrid.

For the battery part, in order to ensure its service life, the over-discharge and over-charge protection of the battery is set. That is, by comparing the actual output voltage (Ubat) of the battery with the overcharge voltage (Ubat-max) or over-discharge voltage (Ubat-min), it is determined whether the battery is working or not. When the battery output voltage is greater than the overcharge voltage or less than the overdischarge voltage, the battery part does not work. In the energy management control strategy designed in the present invention, the working modes of the storage battery are divided into three types: shutdown mode, charging mode and discharging mode.

For the part of biomass power generation, in order to minimize the increase in the operating cost of the micro-grid in the forest area caused by the operation of the biomass power source, the biomass power source is only put into operation when the output power of the optical storage system does not meet the load demand. Thus, in the energy management control scheme designed in the present invention, the working modes of the biomass power generation part are divided into three types: shutdown mode, constant voltage control and power control. In the constant voltage mode, the output power of the biomass power supply is mainly determined by the actual load in the forest microgrid; while in the power control mode, the output power of the biomass power supply is not only affected by the actual load in the forest area, but also It is affected by the actual output power of photovoltaic cells or batteries in the forest microgrid.

By combining the different working states of the above-mentioned photovoltaic cells, storage batteries and biomass power sources, combined with the actual operation of the micro-grid in the forest area, in order to achieve multiple complementarities and optimize the use of solar energy, the micro-grid system is coordinated and controlled, and the specific division There are eight working modes:

Mode Ⅰ: Powered solely by biomass energy.

Assuming that there is no light for a long time due to weather conditions and the output voltage of the battery has reached the over-discharge voltage, in order to protect the battery at this time, the battery should be cut off from the microgrid. The load in the microgrid system in the forest area depends on the constant voltage power supply from the biomass power source to maintain the stability of the DC bus voltage under the condition of load fluctuation. In this mode, the corresponding dynamic power balance equation is:

P _biomass =P _load .

Mode II: Powered by photovoltaic cells and biomass energy at the same time.

Assuming there is sunlight, but the output power of the photovoltaic can not meet the demand of the load, and the output voltage of the battery has reached its over-discharge voltage, the biomass power supply will be put into operation, and should work in the power control mode to supplement the output power of the photovoltaic battery Insufficient parts, photovoltaic work should work in the mode of maximum power tracking. In this mode, the corresponding dynamic power balance equation is:

P _pv +P _biomass =P _load .

Mode Ⅲ: Powered solely by the photovoltaic cell and charging the battery at the same time.

Assuming that there is enough light, that is, when the output power of the photovoltaic cell is greater than the load power, and the battery voltage is less than or equal to the overcharge voltage, the biomass power supply will not be put into operation, and the photovoltaic will work in the maximum power tracking mode to supply power to the load while charging the battery. In this mode, the corresponding dynamic power balance equation is:

P _pv =P _load +P _bat ;

Mode Ⅳ: Powered solely by photovoltaic cells.

The system works in mode Ⅲ, if the battery voltage reaches the overcharge voltage, it will switch to mode Ⅳ. At this time, in order to ensure the power balance of the system, the maximum power tracking mode of the photovoltaic battery is switched to the constant voltage mode, and the biomass power supply and the battery do not work. In this mode, the corresponding dynamic power balance equation is:

P _pv =P _load .

Mode Ⅴ: Powered by photovoltaic cells and batteries at the same time.

Assuming there is sunlight, but the output power of the photovoltaic can not meet the demand of the load, and the actual output voltage of the battery has not reached its over-discharge voltage, the photovoltaic works in the maximum power tracking mode, the battery works in the discharge mode, and the biomass power supply does not work , the actual load in the microgrid system is mainly powered by photovoltaics and batteries. In this mode, the corresponding dynamic power balance equation is:

P _pv +P _bat =P _load .

Mode Ⅵ: Powered by photovoltaic cells, batteries and biomass energy at the same time.

The system works in mode V. When the sum of the output power of photovoltaic cells and batteries cannot meet the actual load, photovoltaics, batteries and biomass supply power to the load at the same time. Photovoltaics work in maximum power tracking mode, batteries work in constant voltage discharge mode, and biomass The power generation part performs power control. In this mode, the corresponding dynamic power balance equation is:

P _pv +P _bat +P _biomass =P _load .

Mode VII: Powered by battery alone.

When the system works in mode V, the illuminance suddenly decreases to 0 due to cloud cover and other reasons, and the actual output voltage of the battery has not yet reached its over-discharge voltage, the load in the forest area microgrid will be powered by the battery alone, and the biomass power supply will not work. In this mode, the corresponding dynamic power balance equation is:

P _bat =P _load .

Mode Ⅷ: Powered by batteries and biomass energy at the same time.

The system works in mode VII. When the battery output power is less than the load power, the battery and biomass supply power to the load together. The battery works in constant voltage discharge mode, the biomass power supply works in constant power control mode, and the photovoltaic cells do not work. In this mode, the corresponding dynamic power balance equation is:

P _bat +P _biomass =P _load .

When the battery voltage reaches the over-discharge voltage, switch to mode I. In mode I, if the biomass fuel is insufficient, in order to ensure the continuous power operation of the micro-grid system in the entire forest area, some non-important loads will be cut off (the specifics can be determined according to the actual situation).

For the introduction of these eight modes above, the following Figure 2 introduces the process of selecting the corresponding mode in combination with specific strategies.

As shown in Figure 2, the main process is as follows:

First, detect and calculate various parameters.

Then, compare the actual output voltage of the photovoltaic cell with its minimum operating voltage. If the actual output voltage is higher, the photovoltaic cell is in the working mode; otherwise, it is in the shutdown mode.

1. Photovoltaic cells are in working mode

1. When the photovoltaic cell is in working mode, and the actual output power of the photovoltaic cell is greater than the load power:

1) If the battery voltage is greater than its overcharge voltage, the photovoltaic cell works in constant voltage mode, neither the biomass energy nor the battery works, and the forest area microgrid system is in mode IV.

2) If the battery voltage is less than or equal to its overcharge voltage, the photovoltaic battery works in the maximum power tracking mode, the battery works in the charging mode, and the forest microgrid system is in mode III.

2. When the photovoltaic cell is in working mode, and the actual output power of the photovoltaic cell is less than the load power:

1) If the battery voltage is greater than the over-discharge voltage, and the sum of the actual output power of the photovoltaic cell and the actual output power of the battery is greater than the load power, the photovoltaic cell works in the maximum power tracking mode, and the battery works in the discharge mode. The system is in mode V.

2) If the battery voltage is greater than the over-discharge voltage, and the sum of the actual output power of the photovoltaic cell and the actual output power of the battery is less than or equal to the load power, the photovoltaic cell works in the maximum power tracking mode, the battery works in the discharge mode, and the biomass energy Working in power control mode, the microgrid system in the forest area is in mode VI.

3) If the battery voltage is less than or equal to the over-discharge voltage, the photovoltaic cell works in the maximum power tracking mode, the biomass energy works in the power control mode, and the forest microgrid system is in mode II.

2. The photovoltaic cell is in shutdown mode.

1. When the photovoltaic cell is in shutdown mode and the battery voltage is lower than the over-discharge voltage, the biomass energy works in the constant voltage control mode, and the forest microgrid system is in mode I.

2. When the photovoltaic cell is in shutdown mode:

1) If the actual output power of the battery is equal to the load power, the forest area microgrid system is in mode VII.

2) If the actual output power of the battery is less than the load power, the battery works in the discharge mode, the biomass energy works in the power control mode, and the microgrid system in the forest area is in mode VIII. After that, when the battery voltage reaches the over-discharge voltage, the forest The micro-grid system in the district is converted to mode I. In mode I, if the biomass energy is insufficient, the scheduled non-important load is cut off.

In order to verify the energy management and control strategy of a forestry microgrid that complements biomass energy and solar energy proposed in the present invention, simulation analysis is performed using PSCAD, assuming that the initial operating voltage of the battery in the microgrid system is greater than the overdischarge voltage and less than the overcharge voltage. The over-discharge voltage Ubat-min is 40V, the overcharge voltage Ubat-max is 60V, the photovoltaic minimum operating voltage Upv-min is 120V, and the DC bus voltage Ubus is 100V.

In order to simulate different seasons, different light conditions, and consider the biomass characteristics of forest areas in different seasons, the following three working conditions are simulated:

Working condition 1: Simulate the working conditions of the micro-grid system all day and night under the condition of good sunlight in summer:

The initial light intensity is 0, the system is in working mode VIII, and the light intensity is gradually increased to 800W/m ² in 5s. With the continuous increase of photovoltaic output, the output of biomass power generation and battery keeps decreasing, and the working mode is first switched from VIII to VI is converted to V again. When the photovoltaic output power is greater than the load power, switch to working mode III. Reduce the light intensity at 15s. When the light intensity is reduced to make the photovoltaic output power less than the load power, the photovoltaic and battery supply power to the load at the same time, and the system operates in mode V. At 19.5s, the light intensity decreases to 0. At this time, the system is powered by the battery alone to the load, and the system runs in mode VII until the simulation ends at 24s. The simulation results are shown in Fig. 3(a).

Working condition 2: Simulate the working conditions of the microgrid system all day and night under the condition of rainy summer, poor light conditions and insufficient biomass fuel:

The initial light intensity is 0, and the light intensity gradually increases to 350W/ ^m2 in 7s. With the continuous increase of photovoltaic output, the output of biomass power generation and storage battery is continuously reduced, and the working mode is first switched from Ⅷ to Ⅵ and then to Ⅴ. When the battery reaches the over-discharge voltage, the battery is turned off, and the photovoltaic and biomass parts supply power to the load, and the system operates in mode II. Gradually reduce the light to 100W/m ² in 10s, until the light disappears, the system has been working in mode II. The light is reduced to 0 in 18s, powered by biomass alone, and the system works in working mode I. Considering the lack of forest biomass in summer, part of the load is cut off at 20.5s to ensure the power supply reliability of the system. The simulation ends at 24s. The simulation results are shown in Fig. 3(b).

Working condition 3: Simulate the working conditions of the microgrid system throughout the day and night when the sunshine time is short, the light intensity is weak, and the biomass fuel is sufficient in winter:

The initial light intensity is 0, and the system is in working mode VIII. When the battery voltage reaches the over-discharge voltage, the battery is disconnected, and the biomass part supplies power to the load, and the system operates in working mode I. At 7.5s, the light intensity gradually increases to 450W/m ² , and the photovoltaic and biomass supply power to the load at the same time, and the system operates in working mode II. When the photovoltaic output power is greater than the load power, the photovoltaic power supply supplies power to the load while charging the battery, and the system operates in working mode III. 14s began to gradually reduce the light intensity, when the photovoltaic output power is less than the load power, the battery and photovoltaic power supply to the load at the same time, the system runs in working mode V. The light fall is 0 at 16.6s. Powered by batteries and biomass at the same time, the system operates in working mode VIII. When the battery reaches the over-discharge voltage, it will stop running, and the biomass will supply power to the load alone, and the system will run in working mode I. The simulation ends at 24s. The simulation results are shown in Fig. 3(c).

On the other hand, the control principle of each distributed power source of the biomass-solar complementary forest area microgrid can be seen in Figure 4; where: Figure 4(a) is the MPPT control block diagram of photovoltaic power generation; Figure 4(b) is the constant voltage control block diagram of photovoltaic power generation ; Fig. 4(c) is the block diagram of battery constant voltage control; Fig. 4(d) is the block diagram of biomass power generation constant voltage control.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person familiar with the technical field can easily conceive of changes or changes within the technical scope disclosed in the present invention. Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (4)

1. A forest area micro-grid energy management control method complementary to biomass energy and solar energy, characterized in that it comprises: Photovoltaic cells, storage batteries and biomass power sources are all connected to the DC bus; according to the intermittent and random fluctuation factors of photovoltaic cells, and on the basis of taking into account the service life of batteries and the operating cost of biomass energy, priority is given to using solar energy to use batteries Mainly, ensure real-time balance of power, and finally use the energy management control method of biomass energy. 2. a kind of forest area micro-grid energy management control method that biomass energy and solar energy are complementary according to claim 1, is characterized in that, forest area micro-grid system has following eight kinds of operating modes under the described energy management control mode: Mode Ⅰ: Powered solely by biomass energy; Mode II: Powered by photovoltaic cells and biomass energy at the same time; Mode Ⅲ: Powered solely by the photovoltaic cell while charging the battery; Mode Ⅳ: powered by photovoltaic cells alone; Mode Ⅴ: Powered by photovoltaic cells and batteries at the same time; Mode VI: Powered by photovoltaic cells, storage batteries and biomass energy at the same time; Mode VII: Powered by battery alone; Mode Ⅷ: Powered by batteries and biomass energy at the same time. 3. A kind of biomass energy and solar energy complementary forest area micro-grid energy management control method according to claim 2, is characterized in that, Compare the actual output voltage of the photovoltaic cell with its minimum operating voltage. If the actual output voltage is larger, the photovoltaic cell is in the working mode; otherwise, it is in the shutdown mode; When the photovoltaic cell is in the working mode, and the actual output power of the photovoltaic cell is greater than the load power: if the battery voltage is greater than its overcharge voltage, the photovoltaic cell works in constant voltage mode, neither the biomass energy nor the battery works, and the forest area microgrid The system is in mode IV; if the battery voltage is less than or equal to its overcharge voltage, the photovoltaic cell works in the maximum power tracking mode, the battery works in the charging mode, and the forest microgrid system is in mode III; When the photovoltaic cell is in the working mode, and the actual output power of the photovoltaic cell is less than the load power: if the battery voltage is greater than the over-discharge voltage, and the sum of the actual output power of the photovoltaic cell and the actual output power of the battery is greater than the load power, the photovoltaic cell The battery works in the maximum power tracking mode, the battery works in the discharge mode, and the forest area microgrid system is in mode V; if the battery voltage is greater than the over-discharge voltage, and the sum of the actual output power of the photovoltaic battery and the actual output power of the battery is less than or equal to Load power, photovoltaic cells work in maximum power tracking mode, batteries work in discharge mode, biomass energy works in power control mode, forest area microgrid system is in mode VI; if the battery voltage is less than or equal to the over-discharge voltage, photovoltaic cells work in the maximum In the power tracking mode, the biomass energy works in the power control mode, and the forest microgrid system is in mode II; When the photovoltaic cell is in shutdown mode and the battery voltage is lower than the over-discharge voltage, the biomass energy works in the constant voltage control mode, and the forest microgrid system is in mode I; When the photovoltaic cell is in shutdown mode: if the actual output power of the battery is equal to the load power, the forest area microgrid system is in mode VII; if the actual output power of the battery is less than the load power, the battery works in discharge mode, and the biomass energy Working in the power control mode, the forest area micro-grid system is in mode VIII. Afterwards, when the battery voltage reaches the over-discharge voltage, the forest area micro-grid system switches to mode I. If the biomass energy is insufficient in mode I, the predetermined non-important load. 4. according to claim 2 or 3 described a kind of biomass energy and solar energy complementary forest area microgrid energy management control method, it is characterized in that, In mode I, the corresponding dynamic power balance equation is: P _biomass = P _load ; In mode II, the corresponding dynamic power balance equation is: P _pv +P _biomass =P _load ; In mode III, the corresponding dynamic power balance equation is: P _pv =P _load +P _bat ; In mode IV, the corresponding dynamic power balance equation is: P _pv = P _load ; In mode V, the corresponding dynamic power balance equation is: P _pv +P _bat =P _load ; In mode VI, the corresponding dynamic power balance equation is: P _pv +P _bat +P _biomass =P _load ; In mode VII, the corresponding dynamic power balance equation is: P _bat = P _load ; In mode VIII, the corresponding dynamic power balance equation is: P _bat + P _biomass = P _load ; Among them, P _pv represents the actual output power of the photovoltaic cell, P _bat represents the actual output power of the storage battery, P _biomass represents the power provided by biomass energy, and P _load represents the load power.