Multi-energy micro-grid and off-grid and grid-connected energy management method thereof

Abstract

According to the off-grid energy management method, the real-time state of charge (SOC) of an energy storage battery is compared with a preset high electric quantity threshold value and a preset low electric quantity threshold value, and a diesel engine priority mode set by a user and real-time load and power conditions are combined; and dynamically selecting an optimal solution from a plurality of preset operation conditions. Through multi-source cooperation and intelligent scheduling, start-stop and working modes of the photovoltaic module, the diesel engine module and the inverter module can be intelligently controlled, seamless switching and optimal distribution among different energy sources are realized, power supply continuity and economy are ensured, and the service life of energy storage equipment is effectively prolonged.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power generation and energy storage, and specifically relates to a multi-energy micro-grid and an off-grid and on-grid energy management method thereof. BACKGROUND

[0002] For special application scenarios such as remote areas, islands, field exploration operations and emergency rescue, obtaining stable, reliable and clean power supply is the basis for ensuring normal operation. These scenarios are often accompanied by extreme physical environments such as high altitude, wide temperature difference, strong vibration or electromagnetic interference, which puts forward far more stringent requirements on the reliability, availability and safety of energy systems than conventional ones. However, the current power supply methods mainly relied on by these scenarios have limitations. Although traditional diesel generators can provide continuous power, their high energy consumption, high pollution, strong noise and high operating costs are increasingly prominent, which is contrary to the concept of green development. On the other hand, although independent renewable energy systems such as photovoltaic or wind power generation are clean and environmentally friendly, their power generation capacity is directly subject to natural conditions such as weather, light intensity and wind size, and the output power has significant intermittency and uncertainty, making it difficult to meet the uninterrupted power supply demand at all times.

[0003] Although there are some systems that simply combine multiple energy sources, they often lack an efficient and intelligent top-level energy management strategy. The energy switching logic of these systems is relatively rough, which may cause voltage fluctuations or even temporary power outages during energy switching, affecting power supply quality. At the same time, the energy utilization efficiency is low, and the charging and discharging process of the energy storage battery is not well managed, which easily leads to overcharging or overdischarging of the battery, thereby seriously shortening the service life of the battery. SUMMARY

[0004] The application provides a multi-energy micro-grid, which comprises an energy storage battery module, an energy storage battery switch S 电池 , a fan module, a fan switch S 风 , a photovoltaic module, a photovoltaic switch S 光 , an inverter switch S 逆 , a diesel engine module, a diesel engine switch S 柴 , a diesel engine input common-mode inductor L cm6 , an uncontrolled rectifier bridge circuit, a first interleaved parallel Boost circuit, a first output common-mode inductor Lcm3, a second input common-mode inductor L cm5 , a second interleaved parallel Boost circuit, a second interleaved parallel Boost circuit output common-mode inductor L cm2 , a three-phase inverter module input common-mode inductor L cm4 , a three-phase inverter module, a three-phase inverter module output common-mode inductor L cm1 .

[0005] The energy storage battery module is connected with the DC bus via an energy storage battery switch S 电池 The three-phase output end of the diesel engine module is connected with the DC bus via a diesel engine input common-mode inductor L cm6 The AC input end of the uncontrolled rectifier bridge is connected with the DC output end of the uncontrolled rectifier bridge, and the input end of the first interleaved parallel Boost circuit is connected with the DC output end of the uncontrolled rectifier bridge; the output end of the first interleaved parallel Boost circuit is connected with the DC bus via a first output common-mode inductor L cm3 The diesel engine switch S 柴 The output end of the photovoltaic module is connected with the DC bus via a second input common-mode inductor L cm5 The input end of the second interleaved parallel Boost circuit is connected with the DC bus; the output end of the second interleaved parallel Boost circuit is connected with the DC bus via a second output common-mode inductor L cm2 The photovoltaic switch S 光 The wind turbine module is connected with the DC bus via a wind power generation control unit and a wind turbine switch S 风 The DC bus is connected with the DC bus via an inverter switch S 逆 The three-phase inverter output common-mode inductor L cm1 The DC input end of the three-phase inverter module is connected with the DC bus; the AC output end of the three-phase inverter module is connected with the DC bus via a three-phase inverter input common-mode inductor L cm4 The A, B and C three-phase AC output ends are formed; when the A, B and C three-phase AC output ends are connected with the load, the off-grid state is formed; when the A, B and C three-phase AC output ends are connected with the power grid, the grid-connected state is formed.

[0006] The application further provides an off-grid energy management method of a multi-energy micro-grid, comprising:

[0007] S1: setting the multi-energy micro-grid to work in an initial state, and acquiring the operation parameters of the multi-energy micro-grid in the initial state in real time;

[0008] The initial state of the multi-energy micro-grid refers to that the photovoltaic switch S 光 is turned off, the diesel engine switch S 柴 is turned off, the wind turbine switch S 风 is turned off, and the inverter switch S 逆 is turned on, the high power threshold is set to 0.8, the low power threshold is set to 0.2, and the diesel engine is not prioritized;

[0009] S2: comparing the real-time state of charge SOC with the set threshold value, determining the interval of the multi-energy micro-grid according to the real-time state of charge SOC value, when SOC>t1, judging that the multi-energy micro-grid is in the high power threshold interval, when t2<SOC<t1, judging that the multi-energy micro-grid is in the medium power threshold interval, and when SOC<t2, judging that the multi-energy micro-grid is in the low power threshold interval, t1 is a first threshold value, and t2 is a second threshold value;

[0010] When the state of charge of the energy storage unit is monitored to be in the high power threshold interval, the multi-energy microgrid adopts the high power threshold interval working condition, specifically:

[0011] The user confirms whether the diesel engine is preferred, and when the diesel engine is preferred, it is judged whether the demand power P 负载 of the load is greater than the diesel engine power P 柴 , if yes, the photovoltaic constant voltage and the diesel engine constant power, the specific operation is: the photovoltaic switch S 光 is closed, and the upper computer gives a signal that the photovoltaic working mode is the constant voltage mode; the diesel engine switch S 柴 is closed, and the upper computer gives a signal that the diesel engine working mode is the constant power mode;

[0012] Otherwise, the photovoltaic is not connected, and the diesel engine constant voltage, the specific operation is: the photovoltaic switch S 光 is opened; the diesel engine switch S 柴 is closed, and the upper computer gives a signal that the diesel engine working mode is the constant voltage mode;

[0013] When the diesel engine is not preferred, it is judged whether the photovoltaic power P 光 is greater than or equal to the demand power P 负载 of the load, if yes, the photovoltaic constant voltage and the diesel engine is not started, the specific operation is: the photovoltaic switch S 光 is closed, and the upper computer gives a signal that the photovoltaic working mode is the constant voltage mode; the diesel engine switch S 柴 is opened;

[0014] Otherwise, the photovoltaic MPPT and the diesel engine is not started, the specific operation is: the photovoltaic switch S 光 is closed, and the upper computer gives a signal that the photovoltaic working mode is the maximum power point tracking mode; the diesel engine switch S 柴 is opened.

[0015] When the system monitors that the state of charge of the energy storage unit is in the medium power threshold interval, the multi-energy microgrid adopts the medium power threshold interval working condition, specifically:

[0016] The user confirms whether the diesel engine is preferred, and when the diesel engine is preferred, the photovoltaic MPPT and the diesel engine constant power, the specific operation is: the photovoltaic switch S 光 is closed, and the upper computer gives a signal that the photovoltaic working mode is the maximum power point tracking mode; the diesel engine switch S 柴 is closed, and the upper computer gives a signal that the diesel engine working mode is the constant power mode;

[0017] Otherwise, when the diesel engine is not preferred, the photovoltaic MPPT and the diesel engine is not started, the specific operation is: the photovoltaic switch S 光The upper computer gives a signal of photovoltaic working mode as maximum power point tracking mode when the switch S 柴 Open;

[0018] When the system monitors that the state of charge of the energy storage unit is in the low power threshold interval, the multi-energy micro-grid adopts a low power threshold interval working condition, specifically:

[0019] The user confirms whether the diesel engine is preferred, and when the diesel engine is preferred, it is judged whether the photovoltaic power P 光 and the diesel engine power P 柴 are greater than the demand power P 负载 of the load, if yes, start the diesel engine, diesel engine constant power, photovoltaic MPPT, the specific operation is: the photovoltaic switch S 光 is closed, the upper computer gives a signal of photovoltaic working mode as maximum power point tracking mode; the diesel engine switch S 柴 is closed, and the upper computer gives a signal of diesel engine working mode as constant power mode;

[0020] Otherwise, start the diesel engine, diesel engine constant power, photovoltaic MPPT, cut off the load, the specific operation is: the photovoltaic switch S 光 is closed, the upper computer gives a signal of photovoltaic working mode as maximum power point tracking mode; the diesel engine switch S 柴 is closed, and the upper computer gives a signal of diesel engine working mode as constant power mode; the inverter switch S 光 is opened;

[0021] When it is confirmed that the diesel engine is not preferred, the load is cut off, the photovoltaic MPPT is cut off, and the diesel engine is not started, and the specific operation is: the inverter switch S 光 is opened; the photovoltaic switch S 光 is closed, the upper computer gives a signal of photovoltaic working mode as maximum power point tracking mode; the diesel engine switch S 柴 is opened.

[0022] In another aspect, the application also provides a grid-connected energy management method of a multi-energy micro-grid, comprising:

[0023] S1: setting the multi-energy micro-grid in an initial state, and acquiring the running parameters and control signals of the multi-energy micro-grid in the initial state in real time; the initial state of the multi-energy micro-grid refers to that the photovoltaic switch S 光 is closed, the diesel engine switch S 柴 is closed, and the inverter switch S 逆 is closed;

[0024] S2: the multi-energy micro-grid is operated according to the mode selected by the user,

[0025] When the user selects the standby power mode, the specific operation process of the multi-energy micro-grid is:

[0026] When the state of charge of the energy storage unit is monitored to be higher than t1 and the inverter is not running at this time, the inverter remains off, the photovoltaic constant voltage, t1 is a set first threshold value;

[0027] When the state of charge of the energy storage unit is monitored to be higher than the standby power target value + 1%, the inverter discharges, and the photovoltaic MPPT is performed;

[0028] When the state of charge of the energy storage unit is monitored to be between the standby power target value - 1% and the standby power target value + 1%, it is continued to judge whether the photovoltaic power P 光 is greater than the power dead zone P 死区 , if yes, the inverter discharges, and the photovoltaic MPPT is performed;

[0029] Otherwise, the inverter charges, and the photovoltaic MPPT is performed;

[0030] When the state of charge of the energy storage unit is monitored to be lower than or equal to the standby power target value - 1%, it is continued to judge whether the photovoltaic power P 光 is greater than the system maximum charging power P max , if yes, the inverter discharges, and the photovoltaic MPPT is performed;

[0031] Otherwise, the inverter charges, and the photovoltaic MPPT is performed;

[0032] When the user selects the economic / peak valley charging mode, the specific operation process of the multi-energy microgrid is as follows:

[0033] When the state of charge of the energy storage unit is monitored to be greater than t1 and the inverter is not running at this time, the inverter remains off, and the photovoltaic constant voltage is performed;

[0034] When the state of charge of the energy storage unit is monitored to be higher than or equal to the charging upper limit value + 1%, the inverter discharges, and the photovoltaic MPPT is performed;

[0035] When the state of charge of the energy storage unit is monitored to be between the charging upper limit value - 1% and the charging upper limit value + 1%, it is continued to judge whether the photovoltaic power P 光 is greater than the power dead zone P 死区 , if yes, the inverter discharges, and the photovoltaic MPPT is performed;

[0036] Otherwise, the inverter charges, and the photovoltaic MPPT is performed;

[0037] When the state of charge of the energy storage unit is monitored to be lower than or equal to the charging upper limit value - 1%, it is continued to judge whether the photovoltaic power P 光 is greater than the system maximum charging power P max， , if yes, the inverter discharges, and the photovoltaic MPPT is performed;

[0038] Otherwise, the inverter charges, and the photovoltaic MPPT is performed;

[0039] When the user selects the economic / peak valley discharge mode, the specific operation process of the multi-energy micro-grid is as follows:

[0040] When the state of charge of the energy storage unit is monitored to be higher than or equal to t1, the inverter discharges and the photovoltaic constant voltage is applied;

[0041] When the state of charge of the energy storage unit is monitored to be higher than or equal to the discharge lower limit value + 1%, the inverter discharges and the photovoltaic MPPT is applied;

[0042] When the state of charge of the energy storage unit is monitored to be between the discharge lower limit value - 1% and the discharge lower limit value + 1%, the inverter discharges and the photovoltaic MPPT is applied;

[0043] When the state of charge of the energy storage unit is monitored to be lower than or equal to the discharge lower limit value - 1%, it is determined whether the photovoltaic power P 光 is greater than the power dead zone P 死区 , if yes, the inverter discharges and the photovoltaic MPPT is applied;

[0044] Otherwise, the inverter charges and the photovoltaic MPPT is applied.

[0045] Compared with the prior art, the present application has the following advantages:

[0046] The present application proposes a four-layer hierarchical energy management method based on "state acquisition-interval judgment-strategy execution-fault monitoring", which decouples the complex energy scheduling problem into three levels of logical layers, thereby realizing the adaptive optimal operation of the system under variable working conditions. The present application can be seamlessly applied to both grid-connected and off-grid modes through the configuration of grid-connected synchronous control. In the off-grid mode, the present application takes the guarantee of power supply reliability as the core target; in the grid-connected mode, the present application can further expand the implementation of peak clipping and valley filling, green power on-grid and other economic scheduling strategies, and has high universality and application flexibility.

[0047] The present application will be described in further detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 It is the overall topology structure of the multi-energy micro-grid system.

[0049] Figure 2 It is the topology structure of the three-phase inverter part of the multi-energy micro-grid.

[0050] Figure 3 It is the topology structure of the first interleaved parallel Boost part of the multi-energy micro-grid.

[0051] Figure 4 It is the topology structure of the second interleaved parallel Boost part of the multi-energy micro-grid.

[0052] Figure 5 Logic flowchart for off-grid mode of energy management method.

[0053] Figure 6 Logic flowchart for on-grid mode of energy management method.

[0054] Figure 7 Logic flowchart for system protection when photovoltaic fails.

[0055] Figure 8 Logic flowchart for system protection when diesel engine fails.

[0056] Figure 9 Logic flowchart for system protection when battery fails.

[0057] Figure 10 Waveform diagram for system switching from condition 5 to condition 1.

[0058] Figure 11 Waveform diagram for system switching from condition 5 to condition 6 or 7.

[0059] Figure 12 Waveform diagram for system switching from condition 6 to condition 4.

[0060] Figure 13 Waveform diagram for system switching from condition 4 to condition 6.

[0061] Figure 14 Waveform diagram for system switching from condition 6 to condition 3. DETAILED DESCRIPTION

[0062] As shown in Figure 1 , a multi-energy microgrid includes an energy storage battery module, an energy storage battery switch S 电池 , a fan module, a fan switch S 风 , a photovoltaic module, a photovoltaic switch S 光 , an inverter switch S 逆 , a DC bus, a diesel engine module, a diesel engine switch S 柴 , a diesel engine input common mode inductor L cm6 , a non-controlled rectifier bridge circuit, a first interleaved parallel Boost circuit, a first output common mode inductor L cm3 , a second input common mode inductor L cm5 , a second interleaved parallel Boost circuit, a second output common mode inductor L cm2 , a three-phase inverter input common mode inductor L cm4 , a three-phase inverter module, a three-phase inverter output common mode inductor L cm1 .

[0063] The energy storage battery module is connected with the DC bus via an energy storage battery switch S 电池 The three-phase output end of the diesel engine module is connected with the DC bus via a diesel engine input common-mode inductor L cm6 The AC input end of the uncontrolled rectifier bridge is connected with the AC input end of the first interleaved parallel Boost circuit, the DC output end of the uncontrolled rectifier bridge is connected with the input end of the first interleaved parallel Boost circuit, and the output end of the first interleaved parallel Boost circuit is connected with the DC bus via a first output common-mode inductor L cm3 and a diesel engine switch S 柴 The output end of the photovoltaic module is connected with the DC bus via a second input common-mode inductor L cm5 The input end of the second interleaved parallel Boost circuit is connected with the DC bus, and the output end of the second interleaved parallel Boost circuit is connected with the DC bus via a second output common-mode inductor L cm2 and a photovoltaic switch S 光 The wind turbine module is connected with the DC bus via a wind power generation control unit and a wind turbine switch S 风 The DC bus is connected with the DC bus via an inverter switch S 逆 and a three-phase inverter output common-mode inductor L cm1 The DC input end of the three-phase inverter module is connected with the DC bus, and the AC output end of the three-phase inverter module is connected with the DC bus via a three-phase inverter input common-mode inductor L cm4 , forming three AC output ends A, B and C, when the three AC output ends A, B and C are connected with the load, the micro-grid is in an off-grid state, and when the three AC output ends A, B and C are connected with the external power grid, the micro-grid is in a grid-connected state.

[0064] The multi-energy micro-grid has two operating modes of grid connection and off-grid. The A, B and C three-phase AC power output by the three-phase inverter module is the unified AC outlet of the micro-grid. When the micro-grid works in the off-grid mode, the A, B and C three-phase AC output ends are connected with the load to independently supply power to the off-grid load; when the micro-grid works in the grid-connected mode, the A, B and C three-phase AC output ends are connected with the external power grid to realize connection with the power grid and exchange of electric energy.

[0065] As shown in Figure 2 , the three-phase inverter module includes a first switch tube Q g1 , a first freewheeling diode D g1 connected in parallel with the first switch tube Q g1 , and a first buffer capacitor C g1 connected in parallel across the first switch tube Q g1 ; a second switch tube Q g2 , a second freewheeling diode D g2 connected in parallel with the second switch tube Q g2 , and a second buffer capacitor C g2 connected in parallel across the second switch tube Q g2 ; a third switch tube Q g3, and a third freewheeling diode D g3 parallelly connected to the third switch tube Q g3 , and a third buffer capacitor C g3 parallelly connected to the third switch tube Q g3 ; a fourth switch tube Q g4 , and a fourth freewheeling diode D g4 parallelly connected to the fourth switch tube Q g4 , and a fourth buffer capacitor C g4 parallelly connected to the fourth switch tube Q g4 ; a fifth switch tube Q g5 , and a fifth freewheeling diode D g5 parallelly connected to the fifth switch tube Q g5 , and a fifth buffer capacitor C g5 parallelly connected to the fifth switch tube Q g5 ; a sixth switch tube Q g6 , and a sixth freewheeling diode D g6 parallelly connected to the sixth switch tube Q g6 , and a sixth buffer capacitor C g6 parallelly connected to the sixth switch tube Q g6 .

[0066] The first switch tube Q g1 and the fourth switch tube Q g4 are connected in series to form a first bridge arm, the second switch tube Q g2 and the fifth switch tube Q g5 are connected in series to form a second bridge arm, and the third switch tube Q g3 and the sixth switch tube Q g6 are connected in series to form a third bridge arm; a direct current input end of the module is formed by the series-connected direct current side support capacitors C G1 and C G2 . Three-phase alternating current output ends after the switch tubes are connected with an LCL output filter. The LCL output filter is formed by an inverter side A-phase inductor L g1 , an inverter side B-phase inductor L g2 , an inverter side C-phase inductor L g3 , an A-phase filter capacitor C f1 , a B-phase filter capacitor C f2 , a C-phase filter capacitor C f3 , a network side A-phase inductor L g4 , a network side B-phase inductor L g5 , and a network side C-phase inductor L g6 .

[0067] As Figure 3 , Figure 4As shown, the first interleaved parallel Boost circuit and the second interleaved parallel Boost circuit are completely identical in structure, the first interleaved parallel Boost circuit comprises a first switch tube Q d1 , a first freewheeling diode D d1 connected in parallel with the first switch tube Q d1 , and a first buffer capacitor C d1 connected in parallel across the first switch tube Q d1 ; a second switch tube Q d2 , a second freewheeling diode D d2 connected in parallel with the second switch tube Q d2 , and a second buffer capacitor C d2 connected in parallel across the second switch tube Q d2 ; a third switch tube Q d3 , a third freewheeling diode D d3 connected in parallel with the third switch tube Q d3 , and a third buffer capacitor C d3 connected in parallel across the third switch tube Q d3 ; a fourth switch tube Q d4 , a fourth freewheeling diode D d4 connected in parallel with the fourth switch tube Q d4 , and a fourth buffer capacitor C d4 connected in parallel across the fourth switch tube Q d4 . The first switch tube Q d1 and the third switch tube Q d3 are connected in series to form a first bridge arm, the second switch tube Q d2 and the fourth switch tube Q d4 are connected in series to form a second bridge arm; the first bridge arm and the second bridge arm are connected in parallel. A midpoint of the first bridge arm is connected to one end of a first Boost inductor L d1 , and a midpoint of the second bridge arm is connected to one end of a second Boost inductor L d2 ; the other end of the first Boost inductor L d1 and the other end of the second Boost inductor L d2 are connected in parallel and then connected to a positive electrode of an output filter capacitor C D1 . A DC input end of the circuit is connected in parallel with an input filter capacitor C D2 .

[0068] The energy storage battery module as the core energy storage unit has an electric energy capacity of 147 kWh and a voltage range of 604 V to 766 V; the photovoltaic module as the main green energy input has a maximum power point tracking (MPPT) power of 32 kW and a maximum power point tracking (MPPT) voltage of 376 V; the diesel engine module as a backup or supplementary energy source has a rated power of 32 kW and outputs 400 V / 50 Hz alternating current; and the fan as another renewable energy source inputs a rated power of 5 kW.

[0069] The off-grid energy management method of the multi-energy micro-grid specifically comprises the following steps.

[0070] S1: Real-time acquisition of the operating parameters of the multi-energy micro-grid in the initial state, wherein the acquired operating parameters of the multi-energy micro-grid include the real-time state of charge SOC of the energy storage battery, the photovoltaic power P 光 , the fan power P 风 , the diesel engine power P 柴 , the load power P 负载 , and a diesel engine priority mode flag defined by a user.

[0071] The multi-energy micro-grid in the initial state refers to the photovoltaic switch S 光 being turned off, the diesel engine switch S 柴 being turned off, the fan switch S 风 being turned off, the inverter switch S 逆 being turned on, the high energy threshold being set to 0.8, the low energy threshold being set to 0.2, and the diesel engine not being prioritized.

[0072] S2: Comparison of the real-time state of charge SOC with the set threshold value, according to the real-time state of charge SOC value, when SOC>0.8, it is judged to be in the high energy threshold interval, when 0.2<SOC<0.8, it is judged to be in the medium energy threshold interval, and when SOC<0.2, it is judged to be in the low energy threshold interval.

[0073] When it is monitored that the state of charge (SOC) of the energy storage unit is in the high energy threshold interval, the multi-energy micro-grid adopts the high energy threshold interval working condition.

[0074] High energy threshold interval working condition: the user confirms whether the diesel engine is prioritized, when it is confirmed that the diesel engine is prioritized, it is judged whether the demand power P 负载 of the load is greater than the diesel engine power P 柴 , if yes, the photovoltaic constant voltage and the diesel engine constant power. The specific operation is as follows: the photovoltaic switch S 光 is closed, and the upper computer gives a signal that the photovoltaic working mode is the constant voltage mode; the diesel engine switch S 柴 is closed, and the upper computer gives a signal that the diesel engine working mode is the constant power mode.

[0075] Otherwise, photovoltaic constant voltage, diesel engine no start. The specific operation is: photovoltaic switch S 光 Open; diesel engine switch S 柴 Close, the upper computer gives the signal of diesel engine working mode as constant voltage mode.

[0076] When it is confirmed that diesel engine is not preferred, then continue to judge whether photovoltaic power P 光 is greater than or equal to the demand power P 负载 of the load, if yes, photovoltaic constant voltage, diesel engine no start. The specific operation is: photovoltaic switch S 光 Close, the upper computer gives the signal of photovoltaic working mode as constant voltage mode; diesel engine switch S 柴 Open.

[0077] Otherwise, photovoltaic MPPT, diesel engine no start. The specific operation is: photovoltaic switch S 光 Close, the upper computer gives the signal of photovoltaic working mode as maximum power point tracking mode; diesel engine switch S 柴 Open.

[0078] When the system monitors that the state of charge (SOC) of the energy storage unit is in the medium power threshold interval, the multi-energy microgrid adopts the medium power threshold interval working condition.

[0079] Medium power threshold interval working condition: the user confirms whether the diesel engine is preferred, when it is confirmed that the diesel engine is preferred, photovoltaic MPPT, diesel engine constant power. The specific operation is: photovoltaic switch S 光 Close, the upper computer gives the signal of photovoltaic working mode as maximum power point tracking mode; diesel engine switch S 柴 Close, the upper computer gives the signal of diesel engine working mode as constant power mode.

[0080] Otherwise, when it is confirmed that the diesel engine is not preferred, photovoltaic MPPT, diesel engine no start. The specific operation is: photovoltaic switch S 光 Close, the upper computer gives the signal of photovoltaic working mode as maximum power point tracking mode; diesel engine switch S 柴 Open.

[0081] When the system monitors that the state of charge (SOC) of the energy storage unit is in the low power threshold interval, the multi-energy microgrid adopts the low power threshold interval working condition.

[0082] Low power threshold interval working condition: the user confirms whether the diesel engine is preferred, when it is confirmed that the diesel engine is preferred, judge whether the sum of photovoltaic power P 光 and diesel engine power P 柴 is greater than the demand power P 负载 of the load, if yes, start the diesel engine, diesel engine constant power, photovoltaic MPPT. The specific operation is: photovoltaic switch S 光Close, the host computer gives the signal of photovoltaic working mode as maximum power point tracking mode; diesel engine switch S 柴 Close, the host computer gives the signal of diesel engine working mode as constant power mode.

[0083] Otherwise, start diesel engine, diesel engine constant power, photovoltaic MPPT, cut off load. The specific operation is: photovoltaic switch S 光 Close, the host computer gives the signal of photovoltaic working mode as maximum power point tracking mode; diesel engine switch S 柴 Close, the host computer gives the signal of diesel engine working mode as constant power mode; inverter switch S 光 Open.

[0084] When it is confirmed that diesel engine is not preferred, cut off load, photovoltaic MPPT, and do not start diesel engine. The specific operation is: inverter switch S 光 Open; photovoltaic switch S 光 Close, the host computer gives the signal of photovoltaic working mode as maximum power point tracking mode; diesel engine switch S 柴 Open.

[0085] A grid-connected energy management method of a multi-energy microgrid, specifically comprising:

[0086] S1: Real-time acquisition of the operating parameters of the multi-energy microgrid in the initial state, the acquired operating parameters of the multi-energy microgrid including the real-time state of charge SOC of the energy storage battery, the measured photovoltaic power P 光 , the user-defined backup SOC target value, the user-defined maximum battery charging power limit P max , the user-defined power dead zone P 死区 , and the user-defined backup or economic / peak-valley mode. The control signal includes a switch signal S 逆 for starting and stopping the inverter, and a photovoltaic mode for defining the photovoltaic working mode.

[0087] The multi-energy microgrid in the initial state refers to the photovoltaic switch S 光 is off, the diesel engine switch S 柴 is off, the inverter switch S 逆 is off.

[0088] S2: According to user selection, judge whether the system should execute backup mode, economic / peak-valley charging mode, or economic / peak-valley discharging mode, and compare the state of charge (SOC) of the energy storage unit with the set backup target value.

[0089] When the system works in backup mode, the multi-energy microgrid adopts backup mode working condition.

[0090] Standby mode working condition: when the state of charge (SOC) of the energy storage unit is higher than 0.8 and the inverter is not running at this time, the inverter is kept off and the photovoltaic constant voltage. The specific operation is that the upper computer gives a signal that the photovoltaic working mode is constant voltage mode.

[0091] When the state of charge (SOC) of the energy storage unit is higher than the standby target value + 1%, the inverter discharges and the photovoltaic MPPT. The specific operation is that the upper computer gives a signal that the inverter is in discharge mode; the upper computer gives a signal that the photovoltaic working mode is maximum power point tracking mode.

[0092] When the state of charge (SOC) of the energy storage unit is between the standby target value - 1% and the standby target value + 1%, it is judged whether the photovoltaic power P 光 is greater than the power dead zone P 死区 . If yes, the inverter discharges and the photovoltaic MPPT. The specific operation is that the upper computer gives a signal that the inverter is in discharge mode; the upper computer gives a signal that the photovoltaic working mode is maximum power point tracking mode.

[0093] Otherwise, the inverter charges and the photovoltaic MPPT. The specific operation is that the upper computer gives a signal that the inverter is in charge mode; the upper computer gives a signal that the photovoltaic working mode is maximum power point tracking mode.

[0094] When the state of charge (SOC) of the energy storage unit is lower than or equal to the standby target value - 1%, it is judged whether the photovoltaic power P 光 is greater than the maximum charging power of the system P max . If yes, the inverter discharges and the photovoltaic MPPT. The specific operation is that the upper computer gives a signal that the inverter is in discharge mode; the upper computer gives a signal that the photovoltaic working mode is maximum power point tracking mode.

[0095] Otherwise, the inverter charges and the photovoltaic MPPT. The specific operation is that the upper computer gives a signal that the inverter is in charge mode; the upper computer gives a signal that the photovoltaic working mode is maximum power point tracking mode.

[0096] When the system works in the economic / peak valley charging mode, the multi-energy microgrid adopts the economic / peak valley charging mode working condition.

[0097] Economic / peak valley charging mode working condition: when the state of charge (SOC) of the energy storage unit is greater than 0.8 and the inverter is not running at this time, the inverter is kept off and the photovoltaic constant voltage. The specific operation is that the upper computer gives a signal that the photovoltaic working mode is constant voltage mode.

[0098] When the state of charge (SOC) of the energy storage unit is monitored to be higher than or equal to the upper limit of charging + 1%, the inverter is discharged and the photovoltaic MPPT. The specific operation is: the upper computer gives a signal that the inverter is in the discharge mode; the upper computer gives a signal that the photovoltaic working mode is the maximum power point tracking mode.

[0099] When the state of charge (SOC) of the energy storage unit is monitored to be between the upper limit of charging - 1% and the upper limit of charging + 1%, it is judged whether the photovoltaic power P 光 is greater than the power dead zone P 死区 . If yes, the inverter is discharged and the photovoltaic MPPT. The specific operation is: the upper computer gives a signal that the inverter is in the discharge mode; the upper computer gives a signal that the photovoltaic working mode is the maximum power point tracking mode.

[0100] Otherwise, the inverter is charged and the photovoltaic MPPT. The specific operation is: the upper computer gives a signal that the inverter is in the charging mode; the upper computer gives a signal that the photovoltaic working mode is the maximum power point tracking mode.

[0101] When the state of charge (SOC) of the energy storage unit is monitored to be lower than or equal to the upper limit of charging - 1%, it is judged whether the photovoltaic power P 光 is greater than the maximum charging power of the system P max . If yes, the inverter is discharged and the photovoltaic MPPT. The specific operation is: the upper computer gives a signal that the inverter is in the discharge mode; the upper computer gives a signal that the photovoltaic working mode is the maximum power point tracking mode.

[0102] Otherwise, the inverter is charged and the photovoltaic MPPT. The specific operation is: the upper computer gives a signal that the inverter is in the charging mode; the upper computer gives a signal that the photovoltaic working mode is the maximum power point tracking mode.

[0103] When the system works in the economic / peak valley discharge mode, the multi-energy microgrid adopts the economic / peak valley discharge mode working condition.

[0104] Economic / peak valley discharge mode working condition: when the state of charge (SOC) of the energy storage unit is monitored to be higher than or equal to 0.8, the inverter is discharged and the photovoltaic constant voltage. The specific operation is: the upper computer gives a signal that the inverter is in the discharge mode; the upper computer gives a signal that the photovoltaic working mode is the constant voltage mode.

[0105] When the state of charge (SOC) of the energy storage unit is monitored to be higher than or equal to the lower limit of discharging + 1%, the inverter is discharged and the photovoltaic MPPT. The specific operation is: the upper computer gives a signal that the inverter is in the discharge mode; the upper computer gives a signal that the photovoltaic working mode is the maximum power point tracking mode.

[0106] When the state of charge (SOC) of the energy storage unit is monitored to be between the lower discharge limit value-1% and the lower discharge limit value+1%, the inverter discharges and the photovoltaic MPPT. The specific operation is: the upper computer gives a signal that the inverter is in discharge mode; the upper computer gives a signal that the photovoltaic working mode is the maximum power point tracking mode.

[0107] When the state of charge (SOC) of the energy storage unit is monitored to be lower than or equal to the lower discharge limit value-1%, it is judged whether the photovoltaic power P 光 is greater than the power dead zone P 死区 . If yes, the inverter discharges and the photovoltaic MPPT. The specific operation is: the upper computer gives a signal that the inverter is in discharge mode; the upper computer gives a signal that the photovoltaic working mode is the maximum power point tracking mode.

[0108] Otherwise, the inverter charges and the photovoltaic MPPT. The specific operation is: the upper computer gives a signal that the inverter is in charge mode; the upper computer gives a signal that the photovoltaic working mode is the maximum power point tracking mode.

[0109] In the specific implementation of the present application, the operation of the system depends on a series of key parameters and control signals. These parameters include: the real-time charge state SOC of the energy storage battery; the high and low power thresholds for dividing the high and low power intervals; and the diesel engine priority mode flag defined by the user. The control signals include the photovoltaic switch, diesel engine switch and inverter switch signals for starting and stopping each module, and the photovoltaic mode and diesel engine mode signals for defining the working mode of the module.

[0110] The energy management method described in the present application is characterized by the universality and universality of the scheduling algorithm, which can be seamlessly applied to both off-grid and grid-connected working modes. When the user selects the off-grid mode, the off-grid mode is entered, and different running strategies are configured to realize the optimization of the system in different scenarios.

[0111] In the off-grid running mode, the system is an independent power supply, and the stability and reliability of power supply are the highest priority. At this time, the energy management method will strictly implement the nine running conditions described later, and realize long-time off-grid autonomous operation through fine coordination and scheduling of photovoltaic, diesel engine and energy storage. In the grid-connected running mode, the method can support the connection of the system with the three-phase four-wire power grid to realize the main target of economic optimization and grid-friendly interaction. According to the configured intelligent switching and advanced grid synchronization control and island detection technology, the method can support seamless and rapid switching between on-grid and off-grid, and the switching time is less than 20ms, which can ensure uninterrupted power supply for critical loads during power grid failure or recovery.

[0112] In this mode, the system can actively charge the energy storage battery from the grid during the valley period of electricity price according to the peak-valley electricity price strategy, and supply power to the local load from the energy storage battery during the peak period of electricity price to achieve the economic operation of peak load shifting. When the photovoltaic power generation power is much higher than the local load demand and the energy storage battery is full, the system can also control the inverter to feed the excess clean power into the grid to realize green power on-grid and grid support. In addition, the method also supports cooperative charging management. In the standby power mode, if the photovoltaic power is insufficient, the system can actively take power from the grid to cooperate with the photovoltaic to perform constant power charging for the battery, so as to ensure that the battery is maintained in an optimal state.

[0113] The application constructs a set of off-grid and on-grid universal closed-loop control logic based on real-time state through the above method, which can intelligently optimize and seamlessly switch the energy among photovoltaic, diesel engine and energy storage battery according to the battery power and user demand, ensures the power supply reliability at critical moment and the economy of on-grid operation while giving priority to clean energy, significantly reduces the comprehensive operation cost of the system and effectively protects the core equipment, and has high technical advancement and wide application value.

[0114] The off-grid energy management strategy described above includes nine operating conditions, and the scheduling logic is as follows:

[0115] Condition 1 corresponds to the scenario that the energy storage battery is in the high power threshold interval and the diesel engine is not preferred, and the photovoltaic power is sufficient or exceeds the load demand. In this mode, the system controls the photovoltaic module to work in the constant voltage mode to stabilize power supply, and the diesel engine module is kept off to maximize the use of clean energy and prevent overcharging of the battery.

[0116] Condition 2 corresponds to the scenario that the energy storage battery is in a high power state and the diesel engine is not preferred, but the photovoltaic power is insufficient to independently meet the load demand. The system controls the photovoltaic module to switch to the maximum power point tracking (MPPT) mode to obtain maximum power generation, and the diesel engine module remains off, and the insufficient power is supplemented by the energy storage battery.

[0117] Condition 3 corresponds to the scenario that the energy storage battery is in a high power state, the diesel engine is preferred, and the load is heavy. The system starts the diesel engine and makes it work in the constant power mode, and commands the photovoltaic module to open in the constant voltage mode to cooperatively supply power to the heavy load.

[0118] Condition 4 corresponds to the scenario that the energy storage battery is in a high power state, the diesel engine is preferred, and the load is light. In order to follow the diesel engine priority principle and ensure economy, the system only starts the diesel engine and makes it work in the constant voltage mode to match the load, and the photovoltaic module remains off.

[0119] Case 5 is the standard green operation mode when the system is in normal power range and the diesel engine is not prioritized. The system will control the photovoltaic module to operate in the maximum power point tracking mode, and the power generated is prioritized to meet the load demand, and the remaining part is used to charge the energy storage battery, and the diesel engine module remains off.

[0120] Case 6 corresponds to the scenario that the system is in the normal power range and the diesel engine is prioritized. The system will start the diesel engine and operate cooperatively with the photovoltaic module operating in the maximum power point tracking mode. At this time, the output power of the diesel engine is precisely controlled, and the photovoltaic is combined to meet the load and charge the battery at the best rate.

[0121] Case 7 corresponds to the emergency scenario that the battery is in a low power state, the diesel engine is prioritized, and the total power generation capacity of the system is sufficient to support the load. The system will start the diesel engine and cooperate with the photovoltaic to generate power, while maintaining uninterrupted power supply to the load and charging the energy storage battery.

[0122] Case 8 corresponds to the severe scenario that the battery is in a low power state, the diesel engine is prioritized, but the total power generation capacity of the system is insufficient to support the load. In order to protect the entire system and prioritize the recovery of battery power, the system will perform load shedding operation, i.e. turn off the inverter, and then command the diesel engine and photovoltaic to use all the generated power to charge the battery.

[0123] Case 9 corresponds to the extreme scenario that the battery is in a low power state and the diesel engine does not intervene. In order to prevent the battery from being damaged by deep over-discharge, the system will turn off the inverter, cut off all loads, and at the same time command the photovoltaic module to operate in the maximum power point tracking mode, and use all the generated power to charge the battery.

[0124] The specific implementation steps of the energy management method in off-grid mode are as shown in Figure 5

[0125] ​In the high SOC threshold interval, when the SOC of the energy storage battery is in the high SOC interval, i.e. greater than or equal to the preset high SOC threshold, the system takes the priority of renewable energy consumption and the protection of the battery from overcharging as the primary goal. At this time, if it is judged that the diesel engine is not in the priority mode, the system will further compare the renewable energy power and the load power. In the case of sufficient renewable energy, i.e. the power is greater than or equal to the load power, the system will control the photovoltaic module to be turned on and work in the constant voltage mode to stabilize the power supply, while the diesel engine module is turned off. If the renewable energy is insufficient to supply power independently, the system will command the photovoltaic module to work in the maximum power point tracking mode to maximize the power generation, while the diesel engine is turned off, and the energy storage battery supplements the power difference. Conversely, if the diesel engine is in the priority mode in this high SOC interval, the system will make decisions according to the load. When the load is heavy, exceeding the rated power of the diesel engine, the system will start the diesel engine and make it work in the rated power mode, while commanding the photovoltaic module to be turned on in the constant voltage mode to cooperate to supply power for heavy load. If the load is light, only the diesel engine supplies power in the constant voltage mode, and the photovoltaic module is turned off to avoid the redundancy and waste of energy.

[0126] In the medium SOC threshold interval, when the SOC of the energy storage battery is in the normal SOC interval, i.e. between the set low SOC threshold and the high SOC threshold, the system enters the stable operation and economic dispatching mode. In this interval, if the diesel engine is not prioritized, this is the standard green operation mode of the system, and the system will command the photovoltaic module to generate power at full capacity in the maximum power point tracking mode, and after the load demand is met, the excess power will be charged to the energy storage battery. If the diesel engine is in the priority mode, the system will start the diesel engine and run cooperatively with the photovoltaic module working in the maximum power point tracking mode. At this time, the control unit will calculate an accurate diesel engine reference power according to the load and the battery state, to ensure that its output power exactly meets the load and can charge the battery at an appropriate rate, thereby avoiding power redundancy and impact on the battery.

[0127] In the low SOC threshold interval, when the SOC of the energy storage battery is in the low SOC interval, i.e. lower than or equal to the set low SOC threshold, the control strategy of the system will give the highest priority to guarantee the survival of the system and the emergency recovery of the power. In this severe working condition, if the diesel engine is not in the priority mode, in order to strictly protect the energy storage battery from being damaged by deep discharge, the system will perform a load shedding operation, i.e. turn off the inverter. At the same time, in order to recover the power as soon as possible, the system will command the photovoltaic module to be turned on and work in the maximum power point tracking mode to charge the battery with the maximum efficiency, and the diesel engine module remains off. If the diesel engine is in the priority mode in this low SOC interval, the system will first start the diesel engine and determine whether the combined output power of the diesel engine and the renewable energy source is sufficient to support the current load. If the total power is sufficient, the system will maintain the power supply to the load, and the diesel engine and the photovoltaic module will jointly supply power to the load and charge the battery. If the total power is still insufficient, the system will also preferentially perform a load shedding operation, i.e. turn off the inverter, and then command the diesel engine and the photovoltaic module to charge the battery with all the generated power.

[0128] When the system turns off the inverter due to the low battery power, the control unit does not stop working, but continues to monitor the change of the battery SOC, realizing an intelligent load recovery mechanism. Once the battery is charged to the preset recovery threshold, the system will automatically restart the inverter to restore the normal power supply to the load, thereby realizing high automation and operation continuity.

[0129] In addition to the nine off-grid working conditions, the on-grid energy management strategy includes eleven working conditions of standby power mode and peak-valley mode, which are selected by the user in the on-grid condition. The scheduling logic is as follows:

[0130] Working condition 10 corresponds to the scenario that the SOC of the energy storage battery is greater than 0.8 and the inverter stops running to protect the battery. In this mode, the system will command the photovoltaic module to work in the constant voltage mode to limit the generated power, and the inverter stops running to strictly prevent overcharging of the battery.

[0131] Working condition 11 corresponds to the scenario that the SOC of the energy storage battery is higher than the standby power target value + 1% and there is excess power available. The system will control the inverter to discharge to the grid, and the photovoltaic module will work in the maximum power point tracking mode to deliver the excess energy stored in the photovoltaic module and the battery to the grid. The inverter discharge power is the photovoltaic power P 光 .

[0132] Working condition 12 corresponds to the scenario that the SOC of the energy storage battery is in the float maintenance interval of the standby power target value, and the photovoltaic generated power is high. The system will accurately maintain the battery power, control the inverter to discharge, and deliver the photovoltaic power exceeding the required power for maintaining the battery to the grid. The inverter discharge power is the photovoltaic power P 光 - the power dead zone P 死区 .

[0133] Working condition 13 corresponds to the scenario that the energy storage battery power is in the float maintenance interval of the standby power target value, but the photovoltaic power is low. The system needs to ensure that the battery power is not lower than the standby power target, and control the inverter to take power from the grid to charge the battery at a small power to make up for the insufficient photovoltaic power. The inverter charging power is the power dead zone P 死区 - photovoltaic power P 光 .

[0134] Working condition 14 corresponds to the scenario that the energy storage battery power is lower than the standby power target value-1%, but the photovoltaic power is sufficient to meet other needs while charging the battery. The system will control the photovoltaic module to operate in the maximum power point tracking mode, and the generated power is preferentially used to charge the battery, and the excess part exceeding the upper limit of the battery charging power is delivered to the grid by the inverter. The inverter discharging power is the photovoltaic power P 光 - battery maximum charging power P max .

[0135] Working condition 15 corresponds to the scenario that the energy storage battery power is lower than the standby power target value, and the photovoltaic power is insufficient. In order to restore the battery to the standby state as soon as possible, the system will control the inverter to take power from the grid to charge the battery in cooperation with the photovoltaic power. The inverter charging power is the battery maximum charging power P max - photovoltaic power P 光 .

[0136] Working condition 16 corresponds to the scenario that in the economic / peak valley charging mode, the energy storage battery SOC>0.8, is in an extremely high power, and the inverter does not operate. The system will command the photovoltaic module to switch to the constant voltage mode to limit the power, and the inverter does not operate to ensure the safety of the system.

[0137] Working condition 17 corresponds to the scenario that in the economic / peak valley charging mode, the energy storage battery power is less than 0.8, but is still higher than the charging upper limit by 1%, which is suitable for participating in grid dispatching. The system controls the photovoltaic module to operate in the maximum power point tracking mode, and performs discharging operation by the inverter to sell photovoltaic and battery energy to the grid at a high price during peak time to make a profit. The inverter discharging power is the discharging target power set by the user.

[0138] Working condition 18 corresponds to the scenario that in the economic / peak valley charging mode, the energy storage battery power is lower than the charging upper limit+1%, but higher than the charging upper limit-1%, and the photovoltaic power is high. The system will command the photovoltaic to operate in the maximum power point tracking mode, and all the generated power together with part of the battery energy is delivered to the grid by the inverter. The inverter discharging power is the power dead zone P 死区 - photovoltaic power P 光 .

[0139] Condition 19 corresponds to a scenario where the energy storage battery SOC is lower than the upper limit of charging +1% but higher than the upper limit of charging -1% and the PV power is low. The system will command the inverter to take power from the grid and jointly charge the energy storage battery with the PV power to prepare for the peak period. The inverter charging power is the PV power P 光 - the power dead zone P defined by the user 死区 .

[0140] Condition 20 corresponds to a scenario where the energy storage battery SOC is lower than the upper limit of charging +1% but the PV power is sufficient. The system will command the PV to operate in the maximum power point tracking mode and its entire power generation, together with part of the battery energy storage, will be delivered to the grid by the inverter. The inverter discharging power is limited to the smaller one between the PV power P 光 and the discharging target power set by the user. The inverter discharging power is the PV power P 光 - the maximum charging power of the battery P max .

[0141] Condition 21 corresponds to a scenario where the energy storage battery SOC is lower than the upper limit of charging -1% and the PV power is insufficient. The system will command the inverter to take power from the grid and jointly charge the energy storage battery with the PV power to prepare for the peak period. The inverter charging power is the maximum charging power of the battery P max - the PV power P 光 .

[0142] Condition 22 corresponds to a scenario where the energy storage battery SOC is greater than 0.8, i.e. the battery is in a very high energy state. The system will command the PV module to switch to the constant voltage mode to limit the power, while the inverter discharges. The inverter discharging power is the maximum charging power limit corresponding to the current SOC.

[0143] Condition 23 corresponds to a scenario where the energy storage battery SOC is lower than 0.8 but higher than the lower limit of discharging +1%, i.e. the battery is suitable for participating in grid dispatching. The system controls the PV module to operate in the maximum power point tracking mode and performs discharging operation by the inverter to sell the PV and battery energy to the grid at a high price during the peak period to make a profit. The inverter discharging power is the maximum charging power limit corresponding to the current SOC.

[0144] Condition 24 corresponds to a scenario where the energy storage battery SOC is lower than the lower limit of discharging +1% but higher than the lower limit of discharging -1% and the PV power is high. The system will command the PV to operate in the maximum power point tracking mode and its entire power generation, together with part of the battery energy storage, will be delivered to the grid by the inverter. The inverter discharging power is the PV power P 光 .

[0145] Operating condition 25 corresponds to a scenario where the energy storage battery is below the upper limit of charging -1% and the photovoltaic power is sufficient. The system will command the photovoltaic to operate in maximum power point tracking mode, and all the generated power will be fed to the grid together with part of the battery energy storage. The inverter discharge power is the photovoltaic power P 光 - the power dead zone P defined by the user 死区 .

[0146] Operating condition 26 corresponds to a scenario where the energy storage battery is below the upper limit of charging -1% and the photovoltaic power is insufficient. At this time, the system will command the inverter to take power from the grid and charge the energy storage battery together with the photovoltaic power to prepare for the peak period of electricity price. The inverter charging power is the power dead zone P defined by the user 死区 - the photovoltaic power P 光 .

[0147] The specific implementation steps of the energy management method in grid-connected mode are shown in Figure 6 .

[0148] In the standby power mode, the system instructs the photovoltaic module and the inverter module to be turned on and ensures that the inverter is connected to the grid. The state of charge SOC of the battery is always maintained at the standby power target level set by the user in the standby power mode to cope with possible grid failures. The system dynamically adjusts the working state of the inverter by monitoring the difference between SOC and the standby power target value in real time and combining the photovoltaic power: if SOC exceeds the dead zone range of 1%, it indicates that the standby power reserve is sufficient, and at this time the inverter works in the discharge mode and feeds all the photovoltaic power to the grid. If SOC is lower than the standby power target value, the system will give priority to charging, and at this time it will compare the photovoltaic power with the maximum charging power allowed at present. If the photovoltaic power is insufficient, the inverter will take power from the grid to supplement the energy of the battery; if the photovoltaic power exceeds the required, the excess power will be fed to the grid. When SOC is within the ±1% dead zone of the standby power target, the system will make fine adjustments, and according to whether the photovoltaic power is higher than a very small power dead zone, it will decide whether to charge or discharge a small amount, so as to realize the accurate maintenance of the target. In this way, the system not only ensures that the battery is charged under safe and efficient conditions, but also feeds the excess clean energy to the grid, improving the comprehensive utilization rate of energy and the economy of the system.

[0149] In the economic charging mode, the system instructs the photovoltaic module and the inverter module to turn on and connect with the grid. This mode is usually used in periods of low electricity prices, and the goal is to charge the battery to the set upper limit of charging, in preparation for discharging during peak electricity prices. The total charging power is mainly limited in stages according to the SOC of the battery, and by monitoring the photovoltaic power in real time and combining the charging power upper limit in the current SOC interval, the working state of the inverter is dynamically adjusted: if the SOC is far below the upper limit of charging, the system will prefer to use the maximum power point tracking mode of photovoltaic to charge efficiently, and when the photovoltaic power is insufficient, the inverter will supplement power from the grid; if the photovoltaic power exceeds the current charging limit, the surplus energy will be fed into the grid. When the SOC reaches the ±1% dead zone of the upper limit of charging, the system will make a judgment based on a small dead zone to decide whether to fully charge the battery by taking a small amount of power from the grid or to send the weak photovoltaic surplus into the grid. Once the SOC exceeds the upper limit of charging, the charging task is completed, and the inverter switches to the discharging mode to feed all photovoltaic power into the grid. In this way, the system not only ensures that the battery is effectively supplemented during the economic period, but also maximizes the use of clean energy and improves the economy of the system.

[0150] In the economic discharging mode, the system instructs the photovoltaic module and the inverter module to turn on and connect with the grid. This mode is usually used in periods of high electricity prices, and the goal is to generate revenue by discharging into the grid until the SOC of the battery decreases to the set lower limit of discharging. When the SOC is far above the lower limit of discharging, the system instructs the inverter to work in the discharging mode, and all the energy stored in the battery and the photovoltaic generated power are fed into the grid. When the SOC is above 0.8, the photovoltaic will switch to the constant voltage mode to ensure system stability. As the discharging proceeds, when the SOC decreases to the ±1% dead zone of the lower limit of discharging, the system will stop taking power from the battery, and based on the comparison result of the photovoltaic power and the small power dead zone, it will decide whether to continue feeding the photovoltaic power into the grid or to take a small amount of power from the grid to maintain the SOC above the lower limit. This strategy ensures that the system can maximize power generation revenue during high electricity prices, while accurately controlling the depth of battery discharge and avoiding excessive discharge to prolong the service life of the battery.

[0151] In addition to the normal energy scheduling strategy described above, the system also designs strategies for photovoltaic, diesel engine and battery failure conditions to ensure that the system can respond promptly and operate safely and stably in the event of a system failure.

[0152] When the system detects a failure in the photovoltaic module, the control unit will immediately execute the protection logic, such as Figure 7The system will first shut down the PV module and disconnect it from the grid to prevent the fault from spreading. Then the system will assess the current operating condition and the status of other core components. In condition 1, condition 2, condition 3, condition 5, condition 6, the system will then check the health of the energy storage battery. If the battery is also in an abnormal state, the system will further shut down the inverter and cut off the load to ensure the core safety of the entire system. In condition 7, where the battery is low and relies on the diesel engine for power, if the PV fails, the system will shut down the PV and then check the status of the diesel engine. If the diesel engine is also faulty, or its rated power is insufficient to support the current load, the system will also shut down the inverter to protect the diesel engine and the stability of the grid. Since the diesel engine is prioritized and the load is light in condition 4, the PV module is always shut down under the control of the energy management strategy, so even if a PV failure is detected, it will not affect the normal execution of condition 4, so condition 4 is not within the scope of the PV failure handling logic. In condition 8, the system plans to start the PV to charge the battery, but before execution, it will perform a higher-level safety check in the main control program energy_management. If a fault is found in the PV, the start command will be intercepted to avoid running the faulty PV, and the original plan of PV + diesel dual charging scheme will be downgraded to a diesel single charging mode. In condition 9, the original plan of PV single charging mode will cause the system to have no available charging source temporarily due to the failure of the PV, and the system will enter a safe standby state until the PV failure is resolved.

[0153] When the system detects a fault in the diesel module, the system will also start the corresponding protection mechanism, such as Figure 8The control unit will first shut down the diesel module and stop its operation. In the diesel-priority normal operating conditions of Condition 3, Condition 4 and Condition 6, the system will immediately check the state of the energy storage battery after shutting down the diesel. If the battery also has an abnormality, the system will shut down the inverter to cut off the load. In Condition 7, the battery has low power, and the original plan is to supply power jointly by the diesel and the photovoltaic module. If the diesel fails, the system will evaluate the power supply capability of the photovoltaic module after shutting down the diesel. If the photovoltaic module also fails or its power alone cannot meet the load demand, the system will shut down the inverter to prevent the energy storage battery from being deeply discharged. If the photovoltaic module is normal and has sufficient power, the photovoltaic module will continue to supply power to the load. In Condition 1, Condition 2, Condition 5 and Condition 9, the diesel is not the preset energy source. Since the energy management strategy has instructed the diesel to remain shut down, its failure state will not affect the current operation mode dominated by the photovoltaic and battery, and thus no additional diesel switching operation needs to be performed. In Condition 8, the system plans to start the diesel to charge the battery, but before execution, a higher-level safety check will be performed in the main control program energy_management. If it is found that the diesel has a failure, the starting instruction will be intercepted to avoid running the failed diesel, and the original planned “photovoltaic + diesel” dual charging scheme will be downgraded to a mode relying only on the photovoltaic single charging.

[0154] The energy storage battery is the core of the microgrid system, and its failure is regarded as the highest level of safety event. As shown in Table 1, the system will first check the state of the battery in the main control program energy_management of the energy management. Once it is detected that the battery has a failure, regardless of the current state of the system in any of Conditions 1 to 9, the system will bypass all normal energy scheduling strategies and immediately execute the overall shutdown program, simultaneously shutting down the inverter, the photovoltaic module and the diesel module. Figure 9

[0155] To further verify the feasibility of the energy management method proposed in the present application in practice, we have tested some typical and representative condition switching scenarios on the hardware platform we have built, and recorded the dynamic change process of various waveforms when the system switches between different conditions. The experimental results show that all the switching processes are smooth and fast, and the system response meets the design expectation, proving that the control strategy is advanced and reliable for engineering application.

[0156] The waveform diagram of the system transitioning from Condition 5 to Condition 1 is as follows​Figure 10 As shown in the experimental waveform, the amplitude of the inductor current waveform on the photovoltaic side presents a smooth and continuous downward trend, accurately reflecting that the photovoltaic output power is actively and stably adjusted lower. The entire process has a rapid dynamic response, and the direct-current bus voltage and other key electrical quantities do not show severe oscillation, fully proving the stability and accuracy of the control algorithm of the application when adjusting the working mode of a single energy module.

[0157] The system seamlessly switches from working condition 5 to working condition 6 or working condition 7 when the energy needs to be supplemented, that is, the process of successfully starting the diesel engine module is as shown in Figure 11 In this scenario, the system decides to introduce the standby power source, the diesel engine, according to the normal or lower battery capacity and the diesel engine priority mode set by the user. In the waveform diagram, the amplitude of the inductor current waveform on the diesel engine side starts from zero and smoothly rises along a linear slope to finally reach the target value. It can be seen that the soft start process of the diesel engine module is accurately controlled, effectively avoiding the impact on the direct-current bus voltage caused by the sudden injection of power. This experimental result proves that the application has the ability to cooperatively schedule and seamlessly switch between multiple energy sources, ensuring the continuity of power supply and the overall stability of the system.

[0158] The dynamic process of the system switching from working condition 6 to working condition 4 is as shown in Figure 12 In the diesel engine priority mode, the system load decreases, and the control strategy is to improve fuel economy by instructing the diesel engine to switch from the high-power running mode to the constant voltage mode that matches the current light load. In the experimental waveform, the amplitude of the inductor current waveform on the diesel engine side smoothly decreases, accurately responding to the control instruction and adjusting the diesel engine output power to a new, lower stable level, verifying that the energy management strategy of the application has the ability to finely adjust power when pursuing the economic operation goal of the system.

[0159] The waveform diagram of the system switching from working condition 4 to working condition 6 is opposite to the previous scenario, which corresponds to the situation of load increase or battery charging demand enhancement, as shown in Figure 13 In this process, the diesel engine switches from the economic constant voltage mode to the constant power mode with higher performance. The experimental results show that the amplitude of the inductor current waveform on the diesel engine side is quickly and smoothly increased, accurately following the increase of the power instruction. Figure 8 This proves that the control method described in the application has excellent dynamic response performance and can quickly and stably increase the output of the standby energy source according to real-time demand, ensuring the power supply demand at critical moments.

[0160] The switching waveform from working condition 6 to working condition 3 is as shown in Figure 14At this time, the diesel engine module continues to operate, and the photovoltaic module is switched from the maximum power point tracking mode to the constant voltage mode according to the instruction. As can be seen in the waveform diagram, while the inductor current waveform on the diesel engine side remains basically stable, the amplitude of the inductor current waveform on the photovoltaic side can be smoothly adjusted. Therefore, the energy management system of the present application has the ability to independently and decoupled control multiple coexisting energy modules, and can flexibly optimize the output of each energy according to the complex system state, and realize the globally optimal energy distribution.

Claims

1. A multi-energy microgrid, characterized in that, Including energy storage battery modules and energy storage battery switches S 电池 Fan module, fan switch S 风 Photovoltaic modules, photovoltaic switches 光 Inverter switch S 逆 Diesel engine module, diesel engine switch S 柴 Diesel engine input common mode inductance L cm6 Uncontrolled rectifier bridge circuit, first interleaved parallel Boost circuit, first output common-mode inductor Lcm3, second input common-mode inductor L cm5 The second interleaved parallel Boost circuit and the common-mode inductor L of the second interleaved parallel Boost circuit output. cm2 Three-phase inverter module input common-mode inductor L cm4 Three-phase inverter module, three-phase inverter module output common-mode inductor L cm1 ; The energy storage battery module is connected to the energy storage battery switch S. 电池 Connected to the DC bus; the three-phase output terminals of the diesel engine module are connected to the diesel engine input common-mode inductor L. cm6 The AC input terminal of the uncontrolled rectifier bridge is connected to the AC input terminal, and the DC output terminal of the uncontrolled rectifier bridge is connected to the input terminal of the first interleaved parallel Boost circuit. The output terminal of the first interleaved parallel Boost circuit is connected to the first output common-mode inductor L. cm3 And diesel engine switch S 柴 Connected to the DC bus; the output of the photovoltaic module is connected via the second input common-mode inductor L. cm5 The second interleaved parallel Boost circuit is connected to the input terminal of the second interleaved parallel Boost circuit, and the output terminal of the second interleaved parallel Boost circuit is connected to the second output common-mode inductor L. cm2 and photovoltaic switch S 光 Connected to the DC bus; the wind turbine module is connected to the wind power generation control unit and the wind turbine switch S. 风 Connected to the DC bus; the DC bus is connected to the inverter switch S. 逆 and the common-mode inductor L of the three-phase inverter output cm1 The AC output of the three-phase inverter module is connected to the DC input terminal of the three-phase inverter module via the three-phase inverter input common-mode inductor L. cm4 This forms three AC output terminals A, B, and C. When the three AC output terminals A, B, and C are connected to the load, they are in an off-grid state. When the three AC output terminals A, B, and C are connected to the power grid, they are in a grid-connected state.

2. The multi-energy microgrid according to claim 1, characterized in that, The three-phase inverter module includes a first switching transistor Q. g1 , and the first switching transistor Q g1 The first freewheeling diode D connected in parallel g1 and connected in parallel to the first switch Q g1 The first buffer capacitor C at both ends g1 Second switch Q g2 , and the second switching transistor Q g2 The second freewheeling diode D connected in parallel g2 and connected in parallel to the second switch Q g2 The second buffer capacitor C at both ends g2 The third switch Q g3 , and the third switch Q g3 The third freewheeling diode D connected in parallel g3 and in parallel with the third switch Q g3 The third buffer capacitor C at both ends g3 Fourth switch Q g4 , and the fourth switch Q g4 The fourth freewheeling diode D connected in parallel g4 and in parallel with the fourth switch Q g4 The fourth buffer capacitor C at both ends g4 Fifth switch Q g5 , and the fifth switch Q g5 The fifth freewheeling diode D connected in parallel g5 and in parallel with the fifth switch Q g5 The fifth buffer capacitor C at both ends g5 The sixth switch Q g6 , and the sixth switch Q g6 The sixth freewheeling diode D connected in parallel g6 and in parallel with the sixth switch Q g6 The sixth buffer capacitor C at both ends g6 The first switching transistor Q g1 With the fourth switch Q g4 The first bridge arm is formed by series connection, and the second switch Q g2 With the fifth switch Q g5 The third switch Q is connected in series to form the second bridge arm. g3 With the sixth switch Q g6 The third bridge arm is formed by connecting them in series.

3. The multi-energy microgrid according to claim 1, characterized in that, The first interleaved parallel Boost circuit and the second interleaved parallel Boost circuit have the same structure. The first interleaved parallel Boost circuit includes a first switching transistor Q. d1 , and the first switching transistor Q d1 The first freewheeling diode D connected in parallel d1 and connected in parallel to the first switch Q d1 The first buffer capacitor C at both ends d1 Second switch Q d2 , and the second switching transistor Q d2 The second freewheeling diode D connected in parallel d2 and connected in parallel to the second switch Q d2 The second buffer capacitor C at both ends d2 The third switch Q d3 , and the third switch Q d3 The third freewheeling diode D connected in parallel d3 and in parallel with the third switch Q d3 The third buffer capacitor C at both ends d3 Fourth switch Q d4 , and the fourth switch Q d4 The fourth freewheeling diode D connected in parallel d4 and in parallel with the fourth switch Q d4 The fourth buffer capacitor C at both ends d4 The first switching transistor Q d1 With the third switch Q d3 The first bridge arm is formed by series connection, and the second switch Q d2 With the fourth switch Q d4 The first bridge arm is connected in series to form the second bridge arm; the second bridge arm is connected in parallel with the first bridge arm; the midpoint of the first bridge arm is connected to the first Boost inductor L. d1 One end is connected, and the midpoint of the second bridge arm is connected to the second Boost inductor L. d2 One end is connected; the first Boost inductor L d1 The other end is connected to the second Boost inductor L d2 The other end is connected in parallel to the output filter capacitor C. D1 The positive terminal of the circuit has an input filter capacitor C connected in parallel with the DC input terminal. D2 .

4. The off-grid energy management method for a multi-energy microgrid based on any one of claims 1 to 3, characterized in that, Including: S1: Set the multi - energy micro - grid to work in the initial state and obtain the operation parameters of the multi - energy micro - grid in real - time at the initial state; In its initial state, a multi-energy microgrid refers to a photovoltaic switch S 光 Off, diesel engine switch S 柴 Off, fan switch S 风 Off, inverter switch S 逆 Enabled, high battery threshold set to 0.8, low battery threshold set to 0.2, diesel engine not prioritized; S2: Compare the real - time state of charge (SOC) with the set threshold. According to the value of the real - time SOC, determine the interval where the multi - energy micro - grid is located. When SOC > t1, it is judged that the multi - energy micro - grid is in the high - charge - threshold interval. When t2 < SOC < t1, it is judged that the multi - energy micro - grid is in the medium - charge - threshold interval. When SOC < t2, it is judged that the multi - energy micro - grid is in the low - charge - threshold interval. t1 is the set first threshold, and t2 is the set second threshold; When it is monitored that the charge state of the energy storage unit is in the high - charge - threshold interval, the multi - energy micro - grid adopts the working condition of the high - charge - threshold interval, specifically: The user confirms whether diesel engine priority is required. If diesel engine priority is confirmed, the load's power demand P is determined. 负载 Is it greater than the diesel engine power P? 柴 If so, then the photovoltaic system operates at constant voltage, and the diesel engine operates at constant power. The specific operation is as follows: Photovoltaic switch S... 光 When closed, the host computer sends a signal indicating that the photovoltaic system is in constant voltage mode; diesel engine switch S 柴 When closed, the host computer sends a signal indicating that the diesel engine is operating in constant power mode. Otherwise, the photovoltaic system will not be connected, and the diesel engine will operate at constant voltage. The specific operation is as follows: Photovoltaic switch S... 光 Turn on; Diesel engine switch S 柴 When closed, the host computer sends a signal indicating that the diesel engine is operating in constant pressure mode. If it is confirmed that the diesel engine is not prioritized, then the photovoltaic power P is further evaluated. 光 Is it greater than or equal to the load's required power P? 负载 If so, the photovoltaic constant voltage switch and diesel engine will not start. The specific operation is as follows: Photovoltaic switch S 光 When closed, the host computer sends a signal indicating that the photovoltaic system is in constant voltage mode; diesel engine switch S 柴 Open; Otherwise, the photovoltaic MPPT and diesel engine will not start. The specific operation is as follows: Photovoltaic switch S 光 When closed, the host computer sends a signal that the photovoltaic operating mode is maximum power point tracking mode; diesel engine switch S 柴 Open; When the system monitors that the charge state of the energy storage unit is in the medium - charge - threshold interval, the multi - energy micro - grid adopts the working condition of the medium - charge - threshold interval, specifically: The user confirms whether diesel engine priority is enabled. If diesel engine priority is confirmed, the photovoltaic MPPT and diesel engine constant power are activated. The specific operation is as follows: Photovoltaic switch S 光 When closed, the host computer sends a signal that the photovoltaic operating mode is maximum power point tracking mode; diesel engine switch S 柴 When closed, the host computer sends a signal indicating that the diesel engine is operating in constant power mode. Otherwise, if it is confirmed that the diesel engine does not have priority, the photovoltaic MPPT and the diesel engine will not start. The specific operation is as follows: Photovoltaic switch S 光 When closed, the host computer sends a signal that the photovoltaic operating mode is maximum power point tracking mode; diesel engine switch S 柴 Open; When the system monitors that the charge state of the energy storage unit is in the low - charge - threshold interval, the multi - energy micro - grid adopts the working condition of the low - charge - threshold interval, specifically: The user confirms whether diesel engine priority is required. If diesel engine priority is confirmed, the photovoltaic power P is determined. 光 With diesel engine power P 柴 Is the sum greater than the load's required power P? 负载 If so, start the diesel engine, maintain constant power, and activate the photovoltaic MPPT. The specific operation is as follows: Photovoltaic switch S... 光 When closed, the host computer sends a signal that the photovoltaic operating mode is maximum power point tracking mode; diesel engine switch S 柴 When closed, the host computer sends a signal indicating that the diesel engine is operating in constant power mode. Otherwise, start the diesel engine, maintain constant power, activate the photovoltaic MPPT, and disconnect the load. The specific operation is as follows: Photovoltaic switch S... 光 When closed, the host computer sends a signal that the photovoltaic operating mode is maximum power point tracking mode; diesel engine switch S 柴 When closed, the host computer sends a signal indicating that the diesel engine is operating in constant power mode; inverter switch S 光 Open; When it is confirmed that the diesel engine is not prioritized, the load, photovoltaic MPPT, and diesel engine are disconnected. The specific operation is as follows: Inverter switch S 光 Turn on; Photovoltaic switch S 光 When closed, the host computer sends a signal that the photovoltaic operating mode is maximum power point tracking mode; diesel engine switch S 柴 Open.

5. The off-grid energy management method for multi-energy microgrids according to claim 4, characterized in that, The acquired operating parameters of the multi-energy microgrid include the real-time state of charge (SOC) of the energy storage batteries and the photovoltaic power (P). 光 Fan power P 风 diesel engine power P 柴 Load power P 负载 ; and the diesel engine priority mode flag defined by the user.

6. The grid-connected energy management method for a multi-energy microgrid based on any one of claims 1 to 3, characterized in that, Including: S1: Sets the multi-energy microgrid to its initial state, and acquires the operating parameters and control signals of the multi-energy microgrid in real time under the initial state; the multi-energy microgrid in the initial state refers to the photovoltaic switch S 光 Off, diesel engine switch S 柴 Off, inverter switch S 逆 Turn off; S2: The multi - energy micro - grid operates according to the mode selected by the user. When the user selects the backup power mode, the specific operation process of the multi - energy micro - grid is: When it is monitored that the charge state of the energy storage unit is higher than t1 and the inverter is in a non - operating state at this time, the inverter remains off and the photovoltaic operates at constant voltage. t1 is the set first threshold; When it is monitored that the charge state of the energy storage unit is higher than the backup power target value + 1%, the inverter discharges and the photovoltaic operates in the maximum power point tracking (MPPT) mode; If the state of charge of the energy storage unit is detected to be between -1% and +1% of the backup power target, then the photovoltaic power P is further determined. 光 Is it greater than the power dead zone P? 死区 If so, then the inverter discharges and the photovoltaic MPPT occurs; Otherwise, the inverter charges and the photovoltaic operates in the MPPT mode; If the state of charge of the energy storage unit is detected to be lower than or equal to the backup power target value of -1%, then the photovoltaic power P is further assessed. 光 Is it greater than the system's maximum charging power P? max If so, then the inverter discharges and the photovoltaic system undergoes MPPT. Otherwise, the inverter charges and the photovoltaic operates in the MPPT mode; When the user selects the economic / peak - valley charging mode, the specific operation process of the multi - energy micro - grid is: When it is monitored that the charge state of the energy storage unit is greater than t1 and the inverter is in a non - operating state at this time, the inverter remains off and the photovoltaic operates at constant voltage; When it is monitored that the charge state of the energy storage unit is higher than or equal to the charging upper limit value + 1%, the inverter discharges and the photovoltaic operates in the MPPT mode; If the state of charge of the energy storage unit is detected to be between -1% and +1% of the upper limit of charging, then the photovoltaic power P is further determined. 光 Is it greater than the power dead zone P? 死区 If so, then the inverter discharges and the photovoltaic MPPT occurs; Otherwise, the inverter charges and the photovoltaic operates in the MPPT mode; If the state of charge of the energy storage unit is detected to be lower than or equal to the upper limit of charging by 1%, then the photovoltaic power P is further judged. 光 Is it greater than the system's maximum charging power P? max， If so, then the inverter discharges and the photovoltaic MPPT occurs; Otherwise, the inverter charges and the photovoltaic operates in the MPPT mode; When the user selects the economic / peak - valley discharging mode, the specific operation process of the multi - energy micro - grid is: When it is monitored that the charge state of the energy storage unit is higher than or equal to t1, the inverter discharges and the photovoltaic operates at constant voltage; When it is monitored that the charge state of the energy storage unit is higher than or equal to the discharging lower limit value + 1%, the inverter discharges and the photovoltaic operates in the MPPT mode; When it is monitored that the charge state of the energy storage unit is between the discharging lower limit value - 1% and the discharging lower limit value + 1%, the inverter discharges and the photovoltaic operates in the MPPT mode; If the state of charge of the energy storage unit is detected to be lower than or equal to the discharge lower limit value of -1%, then the photovoltaic power P is further judged. 光 Is it greater than the power dead zone P? 死区 If so, then the inverter discharges and the photovoltaic MPPT occurs; Otherwise, the inverter charges and the photovoltaic operates in the MPPT mode.

7. The grid-connected energy management method for multi-energy microgrids according to claim 6, characterized in that, The operating parameters of the multi-energy microgrid obtained include: the real-time state of charge (SOC) of the energy storage batteries, and the measured photovoltaic power (P). 光 User-defined backup power SOC target value, user-defined maximum battery charging power limit P max User-defined power dead zone P 死区 User-defined backup power or economy / peak-valley mode; control signals include switching signals S for starting and stopping the inverter. 逆 And photovoltaic modes used to define how photovoltaics work.

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