Energy dispatching method and system for smart microgrid

Abstract

The present invention discloses an energy dispatching method and system for a smart microgrid, and relates to the field of electric energy dispatching. The energy dispatching method includes the following steps: judging whether an energy storage system is grid-connected and then controlling the working state of a PCS; if the energy storage system is grid-connected, the PCS operates in a P‑Q mode; if the energy storage system is off-grid, the PCS operates in a V / F mode, and after the diesel generator is started, the PCS switches from the V / F mode to the P‑Q mode; obtaining the working state of the energy storage system and the online state of the smart microgrid and the grid, the working state of the energy storage system includes shutdown, standby, discharge and charging; the online state of the smart microgrid and the grid is a grid-connected state or an off-grid state; adjusting the sending parameters of the EMS based on the working state of the energy storage system and the online state of the smart microgrid and the grid, and realizing energy dispatching based on the adjustment of the sending parameters of the EMS. The present invention can improve the utilization efficiency of photovoltaic power and ensure normal power supply in an off-grid situation by designing energy dispatching for the grid, energy storage, photovoltaic power generation, and diesel generation.

Description

Technical Field

[0001] The present invention relates to the field of electric energy dispatching, and in particular to an energy dispatching method and system for an intelligent microgrid. Background Art

[0002] With the advancement of renewable energy technology and the increasing demand for reducing greenhouse gas emissions, photovoltaic power generation has been widely used as a clean energy solution.

[0003] However, photovoltaic power generation is affected by weather and day-night changes, and power generation is unstable. Summary of the invention

[0004] To solve the above problems, the first aspect of the present invention provides an energy scheduling method for a smart microgrid, wherein the smart microgrid includes an energy storage system and a photovoltaic system, and the energy scheduling method includes the following steps:

[0005] Determine whether the energy storage system is grid-connected and then control the working state of the PCS; if the energy storage system is grid-connected, the PCS operates in PQ mode; if the energy storage system is off-grid, the PCS operates in V / F mode, and after the diesel generator is started, the PCS switches from V / F mode to PQ mode;

[0006] Acquire the working state of the energy storage system and the online state of the smart microgrid and the power grid, the working state of the energy storage system includes shutdown, standby, discharging and charging; the online state of the smart microgrid and the power grid is a grid-connected state or an off-grid state;

[0007] The parameters sent by the EMS are adjusted based on the working state of the energy storage system and the online state of the smart microgrid and the power grid, and energy scheduling is achieved based on the adjustment of the parameters sent by the EMS.

[0008] Among them, the EMS can set allocation priorities, and the allocation priorities include load priority, energy storage priority and electricity sales priority; when the allocation priority is load priority, the energy scheduling strategy is load>energy storage>electricity sales; when the allocation priority is energy storage priority, the energy scheduling strategy is energy storage>load>electricity sales; when the allocation priority is electricity sales priority, the energy scheduling strategy is load>electricity sales>energy storage.

[0009] Among them, when the smart microgrid is in a grid-connected state and the energy storage system is in a shutdown state, the energy storage battery stops charging and discharging, the PCS stops, the photovoltaic module stops generating electricity, and the electricity required by the load is provided by the grid.

[0010] When the smart microgrid is in grid-connected state and the energy storage system is in standby state, the battery stops charging and discharging, the PCS is in standby state, the photovoltaic module continues to generate electricity, and the electricity required by the load is provided by the grid and the photovoltaic module;

[0011] When the allocation priority is load priority, the EMS selects grid-side control and sets the maximum battery discharge power to 0 to ensure that the battery does not discharge; if the grid prohibits electricity sales, the constant power mode AC total active power is set to the load power; if the grid allows electricity sales, the constant power AC total active power is set to the load power + adjustment value, and the adjustment value is used to confirm the maximum photovoltaic power to prevent abnormal abandonment of light; when the maximum battery charging power is 0, the constant power mode AC total active power is adjusted to the PCS output upper limit;

[0012] When the allocation priority is energy storage priority, the EMS selects battery side control and sets the maximum battery discharge power to 0 to ensure that the battery does not discharge; the upper limit of the total inverter output power is the first threshold, and the lower limit of the total inverter output power is 0. The inverter is prohibited from purchasing electricity, but the load can be supplied with power at a value not exceeding the first threshold; if the power grid prohibits the sale of electricity, the first threshold is the load power; if the power grid allows the sale of electricity, the first threshold is the maximum power of the inverter;

[0013] When the allocation priority is electricity sales priority, the EMS selects grid-side control and sets the maximum battery discharge power to 0 to ensure that the battery does not discharge; if the grid prohibits electricity sales, the constant power AC total active power is set to the load power; if the grid allows electricity sales, the constant power mode AC total active power is set to the maximum power of the inverter.

[0014] Wherein, when the smart microgrid is in a grid-connected state and the energy storage system is in a discharging state;

[0015] When the photovoltaic power is greater than the load power, the power required by the load is fully provided by the photovoltaic system, and the energy storage system and the power grid do not supply power to the load; if the power grid allows electricity sales, the excess electricity will be transmitted to the grid; if the power grid prohibits electricity sales, the photovoltaic power cap is set to the load power;

[0016] When the photovoltaic power is less than the load power, if the power grid prohibits electricity sales, all the power generated by the photovoltaic system is transmitted to the load, and the energy storage discharge power is set to the difference between the photovoltaic power and the load power to ensure the normal operation of the load; if the power grid allows electricity sales, the energy storage discharge power is the maximum discharge power in the discharge stage. When the photovoltaic power + energy storage discharge power < load power, the remaining power is provided by the power grid.

[0017] Among them, when the allocation priority is load priority, the EMS selects the grid-side control and sets the maximum discharge power of the battery to the minimum of the actual value, the discharge stage set value and the load power to achieve energy storage protection; the actual value is the real-time value of the battery charging power; if the grid prohibits electricity sales, the constant power mode AC total active power is set to the smaller value of the discharge stage set value and the load power, so that the PCS can give priority to meeting the power demand of the grid side; if the grid allows electricity sales, the constant power AC total active power is set to the load power + adjustment value, and the adjustment value is used to confirm the maximum photovoltaic power to prevent abnormal abandonment of light; when the photovoltaic power is greater than the sum of the load power and the battery allowed charging power, the excess electric energy is transmitted to the grid;

[0018] When the allocation priority is electricity sales priority, the EMS selects grid-side control and sets the maximum discharge power of the battery to the minimum of the actual value, the discharge stage set value and the load power to achieve energy storage protection; if the grid prohibits electricity sales, the constant power mode AC total active power is set to the smaller value of the load power and the maximum power of the PCS inverter. When the photovoltaic power exceeds the constant power mode AC total active power, the excess electric energy flows to the battery; if the grid allows electricity sales, the constant power mode AC total active power is set to the maximum power of the PCS inverter, and all photovoltaic power flows into the load. If the photovoltaic power is greater than the load power, the excess photovoltaic power flows to the grid.

[0019] Among them, when the smart microgrid is in a grid-connected state and the energy storage system is in a charging state, the allocation priority can only be energy storage priority, EMS selects battery side control, sets the maximum battery discharge power to 0 to ensure that the battery is not discharged, and the upper limit of the inverter output total power is the first threshold value. The lower limit of the inverter output total power takes the larger value of the charging stage setting value and the demand control calculation value; if the power grid prohibits electricity sales, the first threshold value is the load power. At this time, photovoltaic power + grid power ≈ load power + charging power. According to the size of the load power and the charging power, the size of the grid power is dynamically adjusted; if the power grid allows electricity sales, the first threshold value is the maximum power of the inverter. At this time, photovoltaic power ≈ load power + charging power + electricity sales power.

[0020] Among them, the diesel generator is used to ensure power supply when the energy storage system is insufficient. When the remaining power ratio of the energy storage battery is lower than the second threshold, the EMS controls the diesel generator to start charging the energy storage battery; when the energy storage battery is charged to the third threshold or reconnected to the grid, the EMS controls the diesel generator to shut down.

[0021] Among them, when the energy storage battery fails, the EMS controls the diesel generator to directly power the load, and the diesel generator stops after being reconnected to the grid.

[0022] The second aspect of the present invention further provides an energy dispatching system, which can use the energy dispatching method of the smart microgrid as described in any one of the above items, and the system includes:

[0023] An STS module, wherein a first end of the STS module is connected to a power grid, a second end of the STS module is connected to a diesel generator, and a third end of the STS module is connected to a load, and the STS is used to implement switching between the power grid and the diesel generator;

[0024] The PCS module is connected to the photovoltaic system, the energy storage system and the load, and is used to convert the direct current generated by the photovoltaic system into the alternating current required by the load or the power grid.

[0025] Beneficial effects of the present invention: Different from the prior art, the present invention discloses an energy dispatching method and system for a smart microgrid, which relates to the field of electric energy dispatching. The energy dispatching method includes the following steps: judging whether the energy storage system is connected to the grid and then controlling the working state of the PCS; if the energy storage system is connected to the grid, the PCS operates in the PQ mode; if the energy storage system is off-grid, the PCS operates in the V / F mode, and after the diesel generator is started, the PCS switches from the V / F mode to the PQ mode; obtaining the working state of the energy storage system and the online state of the smart microgrid and the grid, the working state of the energy storage system includes shutdown, standby, discharge and charging; the online state of the smart microgrid and the grid is a grid-connected state or an off-grid state; adjusting the sent parameters of the EMS based on the working state of the energy storage system and the online state of the smart microgrid and the grid, and realizing energy dispatching based on the adjustment of the sent parameters of the EMS. The present invention can improve the utilization efficiency of photovoltaic power and ensure normal power supply in an off-grid situation by designing energy dispatching for the grid, energy storage, photovoltaic power generation and diesel generator. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of a flow chart of a first embodiment of an energy scheduling method provided by the present invention;

[0027] Figure 2 A schematic diagram of a flow chart of a second embodiment of the energy scheduling method provided by the present invention;

[0028] Figure 3 A schematic diagram of a flow chart of a third embodiment of the energy scheduling method provided by the present invention;

[0029] Figure 4 A schematic diagram of the structure of the first embodiment of the energy scheduling system provided by the present invention;

[0030] Figure 5 This is a schematic structural diagram of the second embodiment of the energy scheduling system provided by the present invention. DETAILED DESCRIPTION

[0031] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0032] In order to solve the problem that photovoltaic power generation in the prior art is affected by weather and day-night changes, resulting in unstable power generation; the present invention provides an energy scheduling method to balance supply and demand and ensure the stability of power supply. The energy storage system can store excess photovoltaic power and release it when power generation is insufficient. In addition, the diesel generator can be used as a backup power source to cope with the scenario of power outage in the power grid.

[0033] like Figure 1 As shown, Figure 1 The schematic flow chart of the first embodiment of the energy scheduling method provided by the present invention includes the following steps:

[0034] Step S11: Determine whether the energy storage system is grid-connected and then control the working state of the PCS (power conversion system); if the energy storage system is grid-connected, the PCS operates in PQ mode (active power and reactive power control mode); if the energy storage system is off-grid, the PCS operates in V / F mode (voltage and frequency control mode), and after the diesel generator is started, the PCS switches from V / F mode to PQ mode; the operating principles of the PQ operation mode and the V / F operation mode are described in detail below:

[0035] PQ operation mode, in which PCS is not responsible for regulating voltage and frequency, but relies on the rigid voltage and frequency support provided by the power grid. The main task of PCS is to control active power (P) and reactive power (Q), that is, how much actual available power (active power) is delivered to the power grid and how much power (reactive power) is used to improve the performance of the power grid. This mode is applicable when PCS is connected to the power grid. PCS participates in the power system as a power conversion device, but does not assume the responsibility for regulating the voltage and frequency of the power grid.

[0036] V / F operation mode: In this operation mode, the PCS is responsible for maintaining the voltage and frequency within the microgrid and acts as a power source in the microgrid. The PCS needs to generate and adjust the output voltage and frequency to ensure that the microgrid system can operate independently when a fault occurs in the large power grid, and provide appropriate voltage and frequency for the loads in the microgrid system.

[0037] It should be clear that after the diesel generator is started, the PCS switches from V / F mode to PQ mode. At this time, the diesel generator acts as the power grid, and the PCS only runs in V / F mode when the power grid is disconnected and the diesel generator is not started. The PCS can flexibly switch between on-grid and off-grid to ensure a stable power supply under any circumstances, especially when the power grid is unavailable. With the support of the diesel generator, the continuous power supply of important loads can be guaranteed.

[0038] Step S12: Obtain the working status of the energy storage system and the online status of the smart microgrid and the power grid. The working status of the energy storage system includes shutdown, standby, discharging and charging; the online status of the smart microgrid and the power grid is the grid-connected state or the off-grid state; in the grid-connected state, the energy storage system and the photovoltaic system are connected to the grid, and can obtain electricity from the grid or transmit electricity to the grid at the same time; in the off-grid state, it is no longer dependent on the power supply of the grid, and it may be necessary to start the diesel generator to ensure the power supply. It should be clear that the diesel generator will not run when it is placed in the off-grid state. Only when the remaining power ratio of the energy storage battery is insufficient and it is off-grid, the diesel generator will run to ensure the normal operation of the load.

[0039] Step S13: Based on the working state of the energy storage system and the online state of the smart microgrid and the power grid, the parameters sent by the EMS (energy management system) are adjusted, and energy scheduling is achieved based on the adjustment of the parameters sent by the EMS; the parameters sent by the EMS include the maximum charging power and discharging power of the battery, the total AC active power in the constant power mode, the upper and lower limits of the inverter output total power, and the inverter control mode in the grid-connected mode. The adjustment factors are as follows:

[0040] Adjust the maximum charging power and discharging power of the battery according to the working status of the energy storage system.

[0041] Depending on whether the power grid allows electricity sales, set the constant power mode AC total active power to meet load demand or sell electricity.

[0042] According to the energy storage priority and other factors, set the upper and lower limits of the inverter total output power to ensure stable system operation.

[0043] Smart microgrids can choose grid-side control or battery-side control mode to adapt to different working requirements; grid-side control refers to the flow of photovoltaic power to the grid side, and battery-side control refers to the flow of photovoltaic power to the battery side; it should be clear that both grid-side control and battery-side control are constant power modes, that is, the smart microgrid will maintain a constant power output without being affected by external conditions (such as grid voltage or frequency changes), thereby improving stability.

[0044] In summary, the energy scheduling method provided by the present invention includes the following steps: determining whether the energy storage system is grid-connected and then controlling the working state of the PCS; if the energy storage system is grid-connected, the PCS operates in PQ mode; if the energy storage system is off-grid, the PCS operates in V / F mode, and after the diesel generator is started, the PCS switches from V / F mode to PQ mode; obtaining the working state of the energy storage system and the online state of the smart microgrid and the grid, the working state of the energy storage system includes shutdown, standby, discharge and charging; the online state of the smart microgrid and the grid is a grid-connected state or an off-grid state; adjusting the sent parameters of the EMS based on the working state of the energy storage system and the online state of the smart microgrid and the grid, and realizing energy scheduling based on the adjustment of the sent parameters of the EMS. The present invention can improve the utilization efficiency of photovoltaics and ensure normal power supply in an off-grid situation by designing energy scheduling for the grid, energy storage, photovoltaics, and diesel generators.

[0045] In one embodiment, the EMS may set allocation priorities, which include load priority, energy storage priority and electricity sales priority; when the allocation priority is load priority, the energy scheduling strategy is load>energy storage>electricity sales; when the allocation priority is energy storage priority, the energy scheduling strategy is energy storage>load>electricity sales; when the allocation priority is electricity sales priority, the energy scheduling strategy is load>electricity sales>energy storage.

[0046] Through different priority settings, EMS can optimize energy use according to actual conditions and ensure the maximum utilization of renewable energy. In load priority mode, priority is given to meeting users' immediate needs and reducing the need to purchase electricity from the grid. In energy storage priority mode, priority is given to ensuring the charging of energy storage systems to reserve energy for subsequent needs. In power sales priority mode, economic benefits are increased by selling electricity to the grid.

[0047] In summary, by setting different priorities, EMS can implement the optimal energy scheduling strategy according to the current system status and needs, which not only improves the energy utilization efficiency and reliability of the system, but also optimizes the economic benefits.

[0048] In one embodiment, when the smart microgrid is in a grid-connected state and the energy storage system is in a shutdown state, the energy storage battery stops charging and discharging, the PCS stops, the photovoltaic module stops generating electricity, and the electricity required by the load is provided by the grid; that is, it is confirmed that the energy storage system has stopped running, which means that the energy storage battery is neither charged nor discharged, and the PCS is put into a shutdown state to ensure that the PCS does not perform energy conversion. When both the PCS and the energy storage system are shut down, the photovoltaic module also stops generating electricity, and the electricity required by the load is provided by the grid. At this time, the inverter control mode is set to grid-side control, and the EMS sets all power registers to 0, that is, all the parameters sent by the EMS are 0; it is ensured that the PCS will not automatically start running after it is turned on, and it will only start running after the LC confirms that the system is normal.

[0049] When the energy storage system needs to be temporarily shut down due to a fault or maintenance, the system will automatically switch to the above mode. At this time, all power needs are met by the power grid, ensuring the normal operation of the load. For example, during the period when the energy storage battery needs to be repaired or replaced, by shutting down and switching to power supply from the grid, the impact on users can be avoided. In this way, not only can the continuity and stability of power supply be ensured, but also the operating efficiency and economy of the system can be optimized to a certain extent.

[0050] In one embodiment, when the smart microgrid is in a grid-connected state and the energy storage system is in a standby state, the battery stops charging and discharging, the PCS is in a standby state, the photovoltaic module continues to generate electricity, and the electricity required by the load is provided by the grid and the photovoltaic module; Figure 2 As shown, Figure 2 A schematic flow chart of the second embodiment of the energy scheduling method provided by the present invention.

[0051] When the allocation priority is load priority, EMS selects grid-side control and sets the maximum battery discharge power to 0 to ensure that the battery does not discharge. The maximum battery charging power is set according to the actual value of the BMS (battery management system); if the grid prohibits electricity sales, the constant power mode AC total active power is set to the load power, so that PCS uses pure photovoltaic power, giving priority to meeting the power demand of the grid side, that is, meeting the power demand of the load. When the photovoltaic power exceeds the load power, the excess energy flows into the battery;

[0052] If the grid allows electricity sales, the constant power AC total active power is set to load power + adjustment value. The adjustment value is used to confirm the maximum photovoltaic power to prevent abnormal abandonment of light. In this embodiment, the size of the adjustment value is:

[0053] Battery real-time charging power - battery maximum charging power × 80%

[0054] If the adjustment value is less than 0, that is, the real-time charging power of the battery does not exceed 80% of the maximum charging power of the battery, the adjustment value is assigned 0; when the photovoltaic power is greater than the sum of the load power and the allowable charging power of the battery, the excess power is sold to improve the efficiency of electric energy utilization and economic benefits; when the maximum charging power of the battery is 0, the total AC active power in constant power mode is adjusted to the upper limit of PCS output; if demand control is turned on, the total AC active power value in constant power mode takes into account the reverse demand protection limit.

[0055] Through demand control, grid overload can be avoided during peak hours, ensuring the stable operation of the power system; through anti-reverse flow restriction, excess power generated by the photovoltaic system can be prevented from being fed back to the grid, avoiding interference with the normal operation of the grid.

[0056] In this embodiment, the adjustment value is obtained by comparing the real-time charging power of the battery with 80% of the maximum charging power of the battery. In other embodiments, the real-time charging power of the battery may be compared with 90% of the maximum charging power of the battery or other percentages of the maximum charging power of the battery. No limitation is made here.

[0057] When the allocation priority is energy storage priority, EMS selects battery side control and sets the maximum battery discharge power to 0 to ensure that the battery does not discharge. The maximum battery charging power is set according to the actual value of BMS, and the actual value can be set considering redundant protection; the upper limit of the total output power of the inverter is the first threshold, and the lower limit of the total output power of the inverter is 0. The inverter is prohibited from purchasing electricity, but it can supply power to the load at a value not exceeding the first threshold; if the power grid prohibits the sale of electricity, the first threshold is the load power; if the power grid allows the sale of electricity, the first threshold is the maximum power of the inverter; for example, in one embodiment, the load power is 50kW, the maximum power of the inverter is 100kW, and the power grid allows the sale of electricity. In this case, the inverter can supply power to the load, but the output power will not exceed 100kW; if the power generated by the photovoltaic system exceeds the load demand, the excess power can be sold back to the power grid; if the power grid does not allow the sale of electricity, the maximum output power of the inverter is 50KW. In this embodiment, the first threshold is 100KW. In other embodiments, the first threshold can also be taken as another value, and no limitation is made here.

[0058] When the allocation priority is electricity sales priority, EMS selects grid-side control and sets the maximum battery discharge power to 0 to ensure that the battery does not discharge, and the maximum battery charging power is set according to the actual value of BMS; if the grid prohibits electricity sales, set the constant power AC total active power as the load power; if the grid allows electricity sales, set the constant power mode AC total active power as the maximum inverter power. When electricity sales are allowed, by setting the constant power mode AC total active power as the maximum inverter power, the excess photovoltaic power can be fully utilized and sold back to the grid, thereby increasing economic benefits; when the grid prohibits electricity sales, by setting the constant power mode AC total active power as the load power, the excess power can be avoided from being sent back to the grid, thereby preventing the grid from being overloaded or unstable.

[0059] In one embodiment, when the smart microgrid is in a grid-connected state and the energy storage system is in a discharging state;

[0060] When the photovoltaic power is greater than the load power, the load power is fully provided by the photovoltaic system, and the energy storage system and the power grid do not supply power to the load; if the power grid allows electricity sales, the excess power will be transmitted to the grid; when the photovoltaic power exceeds the load demand and the power grid allows electricity sales, the excess power can be sold back to the grid to increase economic benefits. If the power grid prohibits electricity sales, the photovoltaic power cap is set to the load power. If the actual photovoltaic power is greater than the load power, the excess power is transmitted to the battery to maximize the use of the electricity generated by the photovoltaic system; by setting the battery charging power cap, the phenomenon of abandoned light due to excess photovoltaic power is avoided, ensuring the stable operation of the power system.

[0061] When the photovoltaic power is less than the load power, if the power grid prohibits the sale of electricity, all the power generated by the photovoltaic system is transmitted to the load, and the energy storage discharge power is set to the difference between the photovoltaic power and the load power to ensure the normal operation of the load; when the photovoltaic power is not enough to meet the load demand, the shortfall is supplemented by the discharge of the energy storage system to ensure the normal operation of the load. If the power grid allows the sale of electricity, the energy storage discharge power is the maximum discharge power in the discharge stage. When the photovoltaic power + energy storage discharge power < load power, the remaining power is provided by the grid, and the discharge power of the energy storage system is used first, which can reduce the cost of purchasing electricity from the grid.

[0062] like Figure 3 As shown, Figure 3 A flow chart of the third embodiment of the energy scheduling method provided by the present invention; in the discharging state of the energy storage battery, the EMS cannot set the allocation priority to energy storage priority; in this embodiment, when the allocation priority is load priority, the EMS selects the grid-side control and sets the maximum discharge power of the battery to the minimum of the actual value, the discharge stage set value and the load power to achieve energy storage protection, and the maximum charging power of the battery is set according to the actual value; the actual value is the real-time value of the battery charging power; if the power grid prohibits the sale of electricity, the constant power mode AC total active power is set to the smaller value of the discharge stage set value and the load power, so that the PCS prioritizes meeting the power demand on the grid side, and when the photovoltaic power exceeds the load power, it flows to the battery.

[0063] If the grid allows electricity sales, the constant power AC total active power is set to load power + adjustment value. The adjustment value is used to confirm the maximum photovoltaic power to prevent abnormal abandonment of light. When the photovoltaic power is greater than the sum of the load power and the allowable charging power of the battery, the excess electric energy is transmitted to the grid.

[0064] By giving priority to meeting load demand, we ensure that important loads always have sufficient power supply. By setting the maximum discharge power of the battery to the minimum of the actual value, the set value of the discharge stage and the load power, we avoid excessive discharge of the battery and extend the battery life. When electricity sales are allowed, by adjusting the total AC active power in constant power mode, we ensure that excess photovoltaic power can be sold back to the grid to increase economic benefits. By adjusting the value to confirm the maximum photovoltaic power, we can prevent the phenomenon of abandonment caused by excess photovoltaic power.

[0065] When the allocation priority is electricity sales priority, the EMS selects grid-side control and sets the maximum discharge power of the battery to the minimum of the actual value, the discharge stage set value and the load power to achieve energy storage protection; if the grid prohibits electricity sales, the constant power mode AC total active power is set to the smaller value of the load power and the maximum power of the PCS inverter. When the photovoltaic power exceeds the constant power mode AC total active power, the excess electric energy flows to the battery; if the grid allows electricity sales, the constant power mode AC total active power is set to the maximum power of the PCS inverter, and all photovoltaic power flows into the load. If the photovoltaic power is greater than the load power, the excess photovoltaic power flows to the grid. If the excess photovoltaic power is still greater than the maximum receiving power of the grid, after the grid receives the maximum power of electric energy, the electric energy flows to the battery.

[0066] Even when electricity sales are prioritized, it is ensured that photovoltaic power first meets load demand to prevent load power shortages caused by electricity sales; when the photovoltaic power exceeds the total AC active power in constant power mode, the excess electric energy flows to the battery to ensure the charge and discharge cycle of the energy storage system and improve the flexibility of the system.

[0067] In one embodiment, when the smart microgrid is in a grid-connected state and the energy storage system is in a charging state, the allocation priority can only be energy storage priority, the EMS selects battery side control, sets the maximum discharge power of the battery to 0 to ensure that the battery does not discharge, and the upper limit of the total inverter output power is a first threshold value, which is determined based on whether the power grid allows electricity sales; the lower limit of the total inverter output power is the larger value of the set value in the charging stage and the demand control calculation value, so as to ensure that the battery can be charged according to the planned power in the charging stage, and when there is excess photovoltaic power, full power flows to the battery, and then flows to the grid after exceeding the battery charging power upper limit.

[0068] By setting the upper limit of the inverter output total power to the first threshold value, and setting the lower limit of the inverter output total power to the larger value of the charging stage set value and the demand control calculation value, it is ensured that the energy storage system is charged first; the maximum discharge power of the battery is set to 0 to avoid battery discharge during the charging process, thereby protecting the battery.

[0069] If the power grid prohibits the sale of electricity, the first threshold is the load power. At this time, photovoltaic power + grid power ≈ load power + charging power. The grid power is dynamically adjusted according to the load power and charging power. By dynamically adjusting the grid power, it is ensured that photovoltaic power is fully utilized to meet load demand and charge the energy storage system. If the power grid allows the sale of electricity, the first threshold is the maximum power of the inverter. At this time, photovoltaic power ≈ load power + charging power + sales power.

[0070] In one embodiment, the diesel generator is used to ensure power supply when the energy storage system is insufficient. When the remaining power ratio of the energy storage battery is lower than the second threshold, the EMS controls the diesel generator to start charging the energy storage battery; when the energy storage battery is charged to the third threshold or reconnected to the grid, the EMS controls the diesel generator to shut down. For example, in one embodiment, the second threshold is 50% and the third threshold is 80%; in other embodiments, the second threshold and the third threshold may also take other values, which are not limited here, and it is only necessary that the second threshold is less than the third threshold.

[0071] When the energy storage battery is low on power, the diesel generator is started to charge the energy storage battery to ensure the continuity of power supply. The diesel generator is started in advance by setting the second threshold to prevent over-discharge of the energy storage battery and extend the battery life. The diesel generator is started only when necessary to avoid unnecessary fuel consumption, thereby saving costs.

[0072] In one embodiment, when the energy storage battery fails, the EMS controls the diesel generator to directly supply power to the load, and the diesel generator stops after reconnecting to the grid; when the energy storage battery fails, the diesel generator is started to supply power to the load to ensure that the power supply of the critical load is not affected. In this embodiment, when the energy storage battery fails, the diesel generator directly supplies power to the load; in another embodiment, when the energy storage battery fails, the diesel generator does not start and waits for manual operation, which is not limited here.

[0073] When the oil generator is working, the PCS runs in PQ mode. When it detects grid access, the PCS maintains the PQ operation mode, and the STS (static transfer switch) automatically switches from the oil generator to the grid. The EMS detects grid access from the STS communication, controls the shutdown of the oil generator, and enters the grid-connected operation mode. During the off-grid process, the EMS continues to send registers normally according to the policy template, and the PCS decides whether to respond to achieve seamless off-grid and grid-connected transition.

[0074] The present invention also provides an energy scheduling system, which can use any of the energy scheduling methods described above, such as Figure 4 As shown, Figure 4 This is a schematic diagram of the structure of the first embodiment of the energy scheduling system provided by the present invention. The energy scheduling system includes:

[0075] STS module, the first end of the STS module is connected to the power grid, the second end of the STS module is connected to the diesel generator, and the third end of the STS module is connected to the load. STS is used to realize the switching between the power grid and the diesel generator; the power grid and the first end of the STS module are connected through a transformer, and the transformer reduces the voltage of the power grid flowing into the smart microgrid to prevent damage to the smart microgrid caused by excessive voltage.

[0076] PCS module: The PCS module is connected to the photovoltaic system, energy storage system and load, and is used to convert the DC power generated by the photovoltaic system into the AC power required by the load or the power grid; the PCS module can convert the AC power of the power grid or diesel generator into DC power and store it in the energy storage system for use when needed.

[0077] In this embodiment, the power grid is connected to one smart microgrid. In other embodiments, the power grid may be connected to multiple smart microgrids, without any limitation. Figure 5 As shown, Figure 5 This is a schematic structural diagram of the second embodiment of the energy scheduling system provided by the present invention.

[0078] In summary, through the collaborative work of STS modules and PCS modules, the smart microgrid system can achieve efficient and reliable energy management and conversion. The STS module ensures the continuous power supply of the load during the power switching process, while the PCS module realizes the intelligent energy scheduling of the photovoltaic system and the energy storage system, improving the energy utilization efficiency. The introduction of these modules has greatly improved the reliability, flexibility and economy of the system.

[0079] The above description is only an implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. An energy dispatching method for a smart microgrid, wherein the smart microgrid includes an energy storage system and a photovoltaic system, characterized in that: The energy scheduling method comprises the following steps: Determine whether the energy storage system is grid-connected and then control the working state of the PCS; if the energy storage system is grid-connected, the PCS operates in PQ mode; if the energy storage system is off-grid, the PCS operates in V / F mode, and after the diesel generator is started, the PCS switches from V / F mode to PQ mode; Acquire the working state of the energy storage system and the online state of the smart microgrid and the power grid, the working state of the energy storage system includes shutdown, standby, discharging and charging; the online state of the smart microgrid and the power grid is a grid-connected state or an off-grid state; Adjust the parameters sent by the EMS based on the working state of the energy storage system and the online state of the smart microgrid and the power grid, and realize energy scheduling based on the adjustment of the parameters sent by the EMS; The EMS can set allocation priorities, which include load priority, energy storage priority and power sales priority; when the allocation priority is load priority, the energy scheduling strategy is load>energy storage>power sales; when the allocation priority is energy storage priority, the energy scheduling strategy is energy storage>load>power sales; when the allocation priority is power sales priority, the energy scheduling strategy is load>power sales>energy storage; When the smart microgrid is in grid-connected state and the energy storage system is in standby state, the battery stops charging and discharging, the PCS is in standby state, the photovoltaic module continues to generate electricity, and the electricity required by the load is provided by the grid and the photovoltaic module; When the allocation priority is load priority, the EMS selects grid-side control and sets the maximum battery discharge power to 0 to ensure that the battery does not discharge; if the grid prohibits electricity sales, the constant power mode AC total active power is set to the load power; if the grid allows electricity sales, the constant power AC total active power is set to the load power + adjustment value, and the adjustment value is used to confirm the maximum photovoltaic power to prevent abnormal abandonment of light; when the maximum battery charging power is 0, the constant power mode AC total active power is adjusted to the PCS output upper limit; When the allocation priority is energy storage priority, the EMS selects battery side control and sets the maximum battery discharge power to 0 to ensure that the battery does not discharge; the upper limit of the inverter output total power is the first threshold, and the lower limit of the inverter output total power is 0, the inverter is prohibited from purchasing electricity but can supply power to the load at a value not exceeding the first threshold; If the power grid prohibits the sale of electricity, the first threshold is the load power; if the power grid allows the sale of electricity, the first threshold is the maximum power of the inverter; When the allocation priority is electricity sales priority, the EMS selects grid-side control and sets the maximum battery discharge power to 0 to ensure that the battery does not discharge; if the grid prohibits electricity sales, the constant power AC total active power is set to the load power; if the grid allows electricity sales, the constant power mode AC total active power is set to the maximum power of the inverter.

2. The energy dispatching method of the smart microgrid according to claim 1, characterized in that: When the smart microgrid is in a grid-connected state and the energy storage system is in a shutdown state, the energy storage battery stops charging and discharging, the PCS stops, the photovoltaic module stops generating electricity, and the electricity required by the load is provided by the grid.

3. The energy dispatching method of the smart microgrid according to claim 1, characterized in that: When the smart microgrid is in a grid-connected state and the energy storage system is in a discharging state; When the photovoltaic power is greater than the load power, the power required by the load is fully provided by the photovoltaic system, and the energy storage system and the power grid do not supply power to the load; if the power grid allows electricity sales, the excess electricity will be transmitted to the grid; if the power grid prohibits electricity sales, the photovoltaic power cap is set to the load power; When the photovoltaic power is less than the load power, if the power grid prohibits electricity sales, all the power generated by the photovoltaic system is transmitted to the load, and the energy storage discharge power is set to the difference between the photovoltaic power and the load power to ensure the normal operation of the load; if the power grid allows electricity sales, the energy storage discharge power is the maximum discharge power in the discharge stage. When the photovoltaic power + energy storage discharge power < load power, the remaining power is provided by the power grid.

4. The energy dispatching method of the smart microgrid according to claim 3 is characterized in that: When the allocation priority is load priority, the EMS selects the grid-side control and sets the maximum discharge power of the battery to the minimum of the actual value, the set value in the discharge stage and the load power to achieve energy storage protection; the actual value is the real-time value of the battery charging power; if the grid prohibits electricity sales, the constant power mode AC total active power is set to the smaller value between the set value in the discharge stage and the load power, so that the PCS can preferentially meet the power demand on the grid side; if the grid allows electricity sales, the constant power AC total active power is set to the load power + adjustment value, and the adjustment value is used to confirm the maximum photovoltaic power to prevent abnormal abandonment of light; when the photovoltaic power is greater than the sum of the load power and the battery's allowed charging power, the excess electric energy is transmitted to the grid; When the allocation priority is electricity sales priority, the EMS selects grid-side control and sets the maximum discharge power of the battery to the minimum of the actual value, the discharge stage set value and the load power to achieve energy storage protection; if the grid prohibits electricity sales, the constant power mode AC total active power is set to the smaller value of the load power and the maximum power of the PCS inverter. When the photovoltaic power exceeds the constant power mode AC total active power, the excess electric energy flows to the battery; if the grid allows electricity sales, the constant power mode AC total active power is set to the maximum power of the PCS inverter, and all photovoltaic power flows into the load. If the photovoltaic power is greater than the load power, the excess photovoltaic power flows to the grid.

5. The energy dispatching method of the smart microgrid according to claim 1, characterized in that: When the smart microgrid is in a grid-connected state and the energy storage system is in a charging state, the allocation priority can only be energy storage priority, and the EMS selects battery-side control, sets the maximum battery discharge power to 0 to ensure that the battery does not discharge, and the upper limit of the inverter output total power is the first threshold value, and the lower limit of the inverter output total power is the larger value of the charging stage setting value and the demand control calculation value; if the power grid prohibits electricity sales, the first threshold value is the load power, at this time, photovoltaic power + grid power ≈ load power + charging power, and the size of the grid power is dynamically adjusted according to the load power and charging power; if the power grid allows electricity sales, the first threshold value is the maximum inverter power, at this time, photovoltaic power ≈ load power + charging power + electricity sales power.

6. The energy dispatching method of the smart microgrid according to claim 1, characterized in that: The diesel generator is used to ensure power supply when the energy storage system is insufficiently charged. When the remaining power ratio of the energy storage battery is lower than the second threshold, the EMS controls the diesel generator to start charging the energy storage battery; when the energy storage battery is charged to the third threshold or is reconnected to the grid, the EMS controls the diesel generator to shut down.

7. The energy dispatching method of the smart microgrid according to claim 6 is characterized in that: When the energy storage battery fails, the EMS controls the diesel generator to directly supply power to the load, and the diesel generator stops after being reconnected to the grid.

8. An energy dispatching system, using the energy dispatching method of the smart microgrid according to any one of claims 1 to 7, characterized in that: The system comprises: An STS module, wherein a first end of the STS module is connected to a power grid, a second end of the STS module is connected to a diesel generator, and a third end of the STS module is connected to a load, and the STS module is used to implement switching between the power grid and the diesel generator; The PCS module is connected to the photovoltaic system, the energy storage system and the load, and is used to convert the direct current generated by the photovoltaic system into the alternating current required by the load or the power grid.

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