A multi-port intelligent microgrid energy exchanger and a control method and system thereof

Abstract

The application discloses a kind of multi-port intelligent micro-grid energy exchange and its control method and system, the energy exchange includes: photovoltaic chopper, at least two energy storage chopper, output chopper, host inverter, slave inverter and control chip;The one end of the photovoltaic chopper and the one end of host inverter are connected, and the one end of one energy storage chopper and the one end of slave inverter are connected, and the one end of another energy storage chopper and the one end of output chopper are connected;The other end of the host inverter and the other end of slave inverter are connected to generate three-way ac port and first dc port, and the other end of the output chopper generates second dc port;The other end of the photovoltaic chopper is connected with photovoltaic power station, and the other end of two energy storage choppers is connected with an external energy storage respectively.The application realizes new energy grid connection, reduces system land occupation, reduces investment cost, and facilitates the construction work of energy internet.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of micro-grid and energy exchange, and particularly relates to a multi-port intelligent micro-grid energy exchanger and a control method and control system thereof. BACKGROUND

[0002] The energy internet is a network that comprehensively uses advanced power electronic technology, information technology and intelligent management technology, interconnects a large number of new power networks, oil networks, natural gas networks and other energy nodes composed of distributed energy collection devices, distributed energy storage devices and various types of loads, to realize energy equal exchange and sharing network with bidirectional energy flow. The energy internet has developed rapidly in recent years. Different researchers have developed the energy internet from different angles, and are committed to establishing a new generation of intelligent network with power as the core and deep integration of energy and information. The micro-grid is a basic component unit of the regional energy internet. The traditional micro-grid construction scheme is based on a photovoltaic converter, an energy storage converter, a fan converter and other special power electronic grid-connected interfaces to realize new energy grid connection. The system occupies a wide area and has large investment, which is not conducive to the construction of the energy internet. SUMMARY

[0003] In order to solve the above-mentioned deficiencies in the prior art, the present application provides a multi-port intelligent micro-grid energy exchanger, comprising: a photovoltaic chopper, at least two energy storage choppers, an output chopper, a master inverter, a slave inverter and a control chip.

[0004] One end of the photovoltaic chopper is connected to one end of the master inverter, one end of one energy storage chopper is connected to one end of the slave inverter, and one end of the other energy storage chopper is connected to one end of the output chopper.

[0005] The other end of the master inverter is connected to the other end of the slave inverter to generate three AC ports and a first DC port, the other end of the output chopper generates a second DC port, the first AC port is connected to the power grid, and the remaining AC ports and the first DC port and the second DC port are connected to the load.

[0006] The other end of the photovoltaic chopper is externally connected to a photovoltaic power station, and the other ends of the two energy storage choppers are respectively connected to an external energy storage.

[0007] Preferably, the first DC port is connected to a 48V DC load.

[0008] Preferably, the second DC port is connected to a 400V DC load.

[0009] Preferably, the first AC port is connected to the power grid through an inverter side grid-connected switch and a grid side grid-connected switch in sequence.

[0010] The application also provides a control method of a multi-port intelligent micro-grid energy exchanger based on the same inventive concept, comprising:

[0011] S1, detecting the voltage of each energy storage connected to each energy storage chopper through each energy storage chopper, when the voltage of any energy storage is greater than the energy storage threshold, the energy storage chopper corresponding to the energy storage voltage greater than the energy storage threshold is started to run in the constant DC bus voltage mode and S2 is executed; otherwise, detecting whether the photovoltaic power station has power through the photovoltaic chopper, when the photovoltaic power station has power, charging any energy storage, and continuing to detect the voltage of the energy storage;

[0012] S2, setting the operation mode of the output chopper and judging whether the grid-side voltage has power, when the grid-side voltage has power, starting to run in the grid-connected mode, executing S3 to send the photovoltaic power to the grid side in the maximum output mode, otherwise, starting to run in the off-grid mode, executing S4 to send the photovoltaic power to the load side in the maximum output mode;

[0013] S3, setting the grid-connected operation mode of the master inverter and the slave inverter, and determining whether the photovoltaic power station charges each energy storage based on the state of charge of each energy storage;

[0014] S4, setting the off-grid operation mode of the master inverter and the slave inverter, and determining the operation mode of the photovoltaic chopper and the operation state of each energy storage based on the relationship between the photovoltaic power and the load power and the state of charge of each energy storage.

[0015] Preferably, the energy storage chopper corresponding to the energy storage voltage greater than the energy storage threshold is started to run in the constant DC bus voltage mode and S2 is executed, comprising:

[0016] When the energy storage chopper corresponding to the energy storage voltage greater than the energy storage threshold is started to run in the constant DC bus voltage mode, judging whether the DC bus-side voltage reaches a control target value, if the DC bus voltage is greater than the control target value, closing the grid-connected switch on the inverter side to execute S2, otherwise, continuing to detect the voltage of each energy storage.

[0017] Preferably, the setting of the operation mode of the output chopper comprises:

[0018] setting a low voltage value of the output chopper running as a charging pile;

[0019] The low voltage is 400V.

[0020] Preferably, when the grid-side voltage has power, starting to run in the grid-connected mode, executing S3 to send the photovoltaic power to the grid side in the maximum output mode, otherwise, starting to run in the off-grid mode, executing S4 to send the photovoltaic power to the load side in the maximum output mode, comprising:

[0021] When the grid voltage is on, the grid-side grid-connected switch is closed to start the grid-connected mode, and the photovoltaic power is sent to the grid side in the maximum output mode, otherwise the grid-side grid-connected switch is opened to start the off-grid mode, and the photovoltaic power is sent to the load side in the maximum output mode.

[0022] Preferably, the grid-connected operation mode of the master inverter and the slave inverter is set, comprising:

[0023] The master inverter is set to operate in the PQ mode of a given grid-connected power, and the slave inverter automatically follows the master inverter.

[0024] Preferably, the determination of whether the photovoltaic power station charges each energy storage based on the state of charge of each energy storage comprises:

[0025] When the state of charge of the energy storage that has been put into the fixed DC bus mode operation is lower than 90%, the grid-connected power given value is changed, the photovoltaic power station charges the corresponding energy storage until it is charged to 90%, otherwise the photovoltaic power is all grid-connected;

[0026] When the state of charge of the energy storage that has not been put into the fixed DC bus mode operation is lower than 90%, the power distribution coefficient is changed according to the proportion of the state of charge of each energy storage, so that the photovoltaic power station charges each energy storage, and when the state of charge of each energy storage is 90%, the charging is stopped, and the photovoltaic power is all grid-connected.

[0027] Preferably, before the off-grid mode is started, comprising:

[0028] The state of charge of each energy storage is determined, and when the state of charge of any energy storage is greater than 30%, the off-grid mode is started, otherwise the voltage of each energy storage is continuously detected.

[0029] Preferably, the off-grid operation mode of the master inverter and the slave inverter is set, comprising:

[0030] The master inverter is set to operate in the VF mode under the condition of an AC voltage of 380V, and the slave inverter automatically follows the master inverter.

[0031] Preferably, the operation mode of the photovoltaic chopper and the operation state of each energy storage are determined based on the relationship between the photovoltaic power and the load power, and the state of charge of each energy storage, comprising:

[0032] When the photovoltaic power is greater than the load power, the remaining photovoltaic power in the photovoltaic chopper charges the energy storage with a state of charge less than 90%, and when the state of charge of the energy storage reaches 90%, the remaining photovoltaic power raises the DC bus voltage, then the photovoltaic chopper enters the limited power operation mode, and the given value of the limited power is equal to the load power.

[0033] When the photovoltaic power < load power and the state of charge of each energy storage > 30%, the photovoltaic chopper runs at maximum power and each energy storage enters the fixed DC bus mode, and each energy storage discharges according to the droop control to the load;

[0034] When the photovoltaic power < load power and the state of charge of any energy storage is lower than 30%, the energy storage with the state of charge lower than 30% is on standby;

[0035] When the photovoltaic power < load power and the state of charge of each energy storage is lower than 30%, each energy storage is on standby and returns to S1.

[0036] Preferably, the grid-connected operation mode of the master inverter and the slave inverter further comprises:

[0037] The multi-port intelligent micro-grid energy exchanger performs island detection in the grid-connected operation control, and if islanding occurs, the multi-port intelligent micro-grid energy exchanger is transferred to the VF mode according to overvoltage or undervoltage or overfrequency or underfrequency.

[0038] Preferably, the off-grid operation mode of the master inverter and the slave inverter further comprises:

[0039] The multi-port intelligent micro-grid energy exchanger is transferred to the grid-connected operation mode if the grid recovers to normal in the off-grid operation mode.

[0040] Based on the same inventive concept, the application further provides a control system of a multi-port intelligent micro-grid energy exchanger, comprising:

[0041] The detection voltage module is used to detect the voltage of each energy storage connected with each energy storage chopper respectively through each energy storage chopper, and when the voltage of any energy storage > the energy storage threshold, the energy storage voltage > the energy storage chopper corresponding to the energy storage threshold starts the fixed DC bus voltage mode operation and executes the judgment module; otherwise, the photovoltaic chopper is used to detect whether the photovoltaic power station has power, and when the photovoltaic power station has power, any energy storage is charged, and the voltage of the energy storage is continuously detected;

[0042] The judgment module is used to set the operation mode of the output chopper and judge whether the grid-side voltage has power, and when the grid-side voltage has power, the grid-connected mode is started and the grid-connected module is called to send the photovoltaic power to the grid side in the maximum output mode, otherwise the off-grid mode is started and the off-grid module is called to send the photovoltaic power to the load side in the maximum output mode;

[0043] The grid-connected module is used to set the grid-connected operation mode of the master inverter and the slave inverter, and determine whether the photovoltaic power station charges each energy storage based on the state of charge of each energy storage;

[0044] The off-grid module is used for setting off-grid operation modes of the master inverter and the slave inverter, and determining operation modes of the photovoltaic chopper and operation states of the storages based on a relationship between the photovoltaic power and the load power and states of charge of the storages.

[0045] Preferably, the judging module comprises:

[0046] The on-grid judging unit is used for closing the grid-side on-grid switch to start the on-grid mode and executing the on-grid module to send the photovoltaic power to the grid side in the maximum output mode when the grid-side voltage has power.

[0047] The off-grid judging unit is used for opening the grid-side on-grid switch to start the off-grid mode and executing the off-grid module to send the photovoltaic power to the load side in the maximum output mode when the grid-side voltage has no power.

[0048] Preferably, the on-grid module comprises:

[0049] The first on-grid unit is used for changing the on-grid power given value when the state of charge of the storage in the fixed DC bus mode is lower than 90%, so that the photovoltaic power station charges the corresponding storage until the state of charge is 90%, otherwise the photovoltaic power is totally on-grid.

[0050] The second on-grid unit is used for changing the power distribution coefficient according to the proportion of the state of charge of each storage when the state of charge of the storage not in the fixed DC bus mode is lower than 90%, so that the photovoltaic power station charges each storage, and stops charging when the state of charge of each storage is 90%, and the photovoltaic power is totally on-grid.

[0051] Preferably, the off-grid module comprises:

[0052] The first off-grid unit is used for charging the storage with the state of charge lower than 90% with the remaining photovoltaic power in the photovoltaic chopper when the photovoltaic power is greater than the load power, and the photovoltaic chopper enters the limited power operation mode when the state of charge of the storage reaches 90% and the remaining photovoltaic power raises the DC bus voltage, and the given value of the limited power is equal to the load power.

[0053] The second off-grid unit is used for operating the photovoltaic chopper with the maximum power and each storage entering the fixed DC bus mode when the photovoltaic power is less than the load power and the state of charge of each storage is greater than 30%, and each storage discharges to the load according to the droop control.

[0054] The third off-grid unit is used for making the storage with the state of charge lower than 30% standby when the photovoltaic power is less than the load power and the state of charge of any storage is lower than 30%.

[0055] The fourth off-grid unit is used for making each storage standby and calling the detection voltage module when the photovoltaic power is less than the load power and the state of charge of each storage is lower than 30%.

[0056] Preferably, the control system is disposed on a control chip, and the control chip is connected with the photovoltaic chopper, the energy storage choppers, the output chopper, the master inverter and the slave inverter respectively.

[0057] Compared with the prior art, the energy exchange machine has the following beneficial effects:

[0058] (1) The energy exchange machine comprises a photovoltaic chopper, at least two energy storage choppers, an output chopper, a master inverter, a slave inverter and a control chip. One end of the photovoltaic chopper is connected with one end of the master inverter, one end of one energy storage chopper is connected with one end of the slave inverter, and one end of another energy storage chopper is connected with one end of the output chopper. The other end of the master inverter is connected with the other end of the slave inverter to generate three AC ports and a first DC port. The other end of the output chopper generates a second DC port. The first AC port is connected with a power grid, and the remaining AC ports and the first DC port and the second DC port are connected with loads. The other end of the photovoltaic chopper is connected with a photovoltaic power station, and the other ends of the two energy storage choppers are respectively connected with external energy storages. The energy exchange machine realizes grid connection of new energy, reduces system occupation and investment cost, and facilitates construction of an energy internet.

[0059] (2) The energy exchange machine realizes flexible interconnection of AC and DC sides in a microgrid, can directly access photovoltaic, energy storage, electric vehicles, electric bicycles and other DC loads, and 220V / 380V AC loads. The energy exchange machine can realize autonomous control of the DC side photovoltaic, energy storage and AC / DC loads, form a flexible and coordinated AC / DC microgrid, and realize coordinated and optimized operation of distributed power sources, energy storage and AC / DC loads.

[0060] (3) The energy exchange machine adopts integrated design, can reduce the initial investment of microgrid construction, and integrates energy storage bidirectional AC / DC conversion, photovoltaic AC / DC conversion and other primary power conversion modules, and self-adaptive local control software, so that the total equipment investment in the initial stage of microgrid construction is reduced.

[0061] (4) The energy exchange machine has high reliability and low operation and maintenance cost. During operation, the microgrid energy exchange machine can improve safety, is stable in operation, and has low operation failure rate. At the same time, the reduction of operation and maintenance equipment reduces the labor cost of inspection, and the reduction of maintenance links also effectively reduces the maintenance cost.

[0062] (5) The energy exchanger provided by the application has the inherent characteristics of droop characteristics, and the DC bus voltage changes with the change of the system operation state, the energy exchanger has a double energy storage structure, the double energy storage power droop control is used to maintain the DC bus voltage together, the voltage and power deviation are inhibited, and the AC side is more conducive to grid-connected and off-grid switching. BRIEF DESCRIPTION OF DRAWINGS

[0063] Figure 1 Fig. 1 is a structural schematic diagram of a multi-port intelligent micro-grid energy exchanger in the application;

[0064] Figure 2 Fig. 2 is a control method flow chart of the multi-port intelligent micro-grid energy exchanger in the application;

[0065] Figure 3 Fig. 3 is a specific control method flow chart of the multi-port intelligent micro-grid energy exchanger in the application. DETAILED DESCRIPTION

[0066] In order to better understand the application, the content of the application will be further described below in combination with the drawings and examples in the specification.

[0067] Embodiment 1

[0068] Based on the ideas of intensification and primary and secondary fusion, the application provides a multi-port intelligent micro-grid energy exchanger, which can be integrated to access photovoltaic, AC power supply, energy storage, multi-voltage grade DC load and AC load. Meanwhile, a multi-energy complementary operation control strategy for the energy exchanger is provided, the strategy is integrated in the energy exchanger, realizes primary and secondary fusion of the whole machine, and can realize the coordinated control of source, load and storage and the energy optimization management function between AC / DC power supply and AC / DC load; a double energy storage structure is adopted, and the DC bus voltage is maintained together through power droop control, which is convenient for the AC side to realize seamless grid-connected and off-grid switching, and provides technical support for the construction of future regional energy internet.

[0069] As shown in Figure 1 Fig. 1, the application provides a multi-port intelligent micro-grid energy exchanger, which comprises a photovoltaic chopper, at least two energy storage choppers, an output chopper, a master inverter, a slave inverter and a control chip.

[0070] One end of the photovoltaic chopper is connected with one end of the master inverter, one end of one energy storage chopper is connected with one end of the slave inverter, and one end of another energy storage chopper is connected with one end of the output chopper.

[0071] The other end of the master inverter and the other end of the slave inverter are connected to generate three AC ports and a first DC port, the other end of the output chopper generates a second DC port, the first AC port is connected to a power grid, and the remaining AC ports and the first DC port and the second DC port are connected to loads;

[0072] The other end of the photovoltaic chopper is externally connected to a photovoltaic power station, and the other ends of the two energy storage choppers are respectively connected to one external energy storage;

[0073] The control chip is connected with the photovoltaic chopper, each energy storage chopper, the output chopper, the master inverter and the slave inverter, and is used for sending control signals.

[0074] The application provides a multi-port energy exchange rack, which generates three DC inputs, one of which is a photovoltaic input, and two of which are energy storage inputs; provides 48 / 400V two-way DC outputs, which can be directly connected to DC loads such as electric vehicles and electric bicycles; and simultaneously provides 220 / 380V three-way AC power supply interfaces, one of which is connected to a 380V three-phase power grid, one of which is connected to a single-phase 200V local load, and one of which is connected to a 380V three-phase local load. In summary, the energy exchange rack comprises five DC ports and three AC ports.

[0075] As shown in Figure 2 The application provides a control method for a multi-port intelligent micro-grid energy exchange rack, which comprises the following steps:

[0076] S1, the control chip detects the voltage of the energy storage connected with each energy storage chopper through each energy storage chopper, and when the voltage of any energy storage is greater than an energy storage threshold, the energy storage chopper corresponding to the energy storage voltage greater than the energy storage threshold starts a fixed DC bus voltage mode and executes S2; otherwise, the control chip detects whether the photovoltaic power station has power through the photovoltaic chopper, and when the photovoltaic power station has power, any energy storage is charged, and the voltage of the energy storage is continuously detected;

[0077] S2, the operation mode of the output chopper is set, and it is judged whether the grid-side voltage has power; when the grid-side voltage has power, the grid-connected mode is started, S3 is executed to send the photovoltaic power to the grid side in the maximum output mode, otherwise, the off-grid mode is started, and S4 is executed to send the photovoltaic power to the load side in the maximum output mode;

[0078] S3, the grid-connected operation mode of the master inverter and the slave inverter is set, and whether the photovoltaic power station charges each energy storage is determined based on the state of charge of each energy storage;

[0079] S4, the off-grid operation mode of the master inverter and the slave inverter is set, and the operation mode of the photovoltaic chopper and the operation state of each energy storage are determined based on the relationship between the photovoltaic power and the load power and the state of charge of each energy storage.

[0080] In Figure 3 The control method of the multi-port intelligent micro-grid energy exchanger is specifically explained as follows:

[0081] S1, the control chip detects the voltage of the energy storage connected to each energy storage chopper through each energy storage chopper. When the voltage of any energy storage is greater than the energy storage threshold, the energy storage chopper corresponding to the energy storage threshold greater than the energy storage voltage is started to operate in the constant DC bus voltage mode and S2 is executed. Otherwise, the photovoltaic chopper detects whether the photovoltaic power station has power. When the photovoltaic power station has power, any energy storage is charged, and the voltage of the energy storage is continuously detected, which specifically includes:

[0082] 1) The voltage of any one of the two batteries is greater than a certain value, then the constant DC bus voltage mode is started to operate, and the second step is performed. If the voltages of the two batteries do not meet the starting conditions, it is judged whether the photovoltaic has power: the photovoltaic has power, then the photovoltaic charges any battery, and when the voltage of the battery is greater than a certain value, the constant DC bus voltage mode is started to operate, and the second step is performed; the photovoltaic generator has no power, and the standby state is maintained.

[0083] 2) The energy storage chopper that has started to operate in the constant DC bus voltage mode is started to operate in the constant DC bus mode, and it is judged whether the voltage on the DC bus side reaches the set control target value. If the DC bus voltage is equal to the control target value, the grid-connected switch on the inverter side is closed, that is, KM1 in Figure 1 , and the third step is performed. If the DC bus voltage cannot reach the control target value, return to step (1). In this embodiment, the set control target value is 750V. The DC bus voltage is the voltage of DD2 and DD3.

[0084] S2, set the operation mode of the output chopper and judge whether the grid voltage has power. When the grid voltage has power, the grid-connected mode is started to operate, S3 is executed, and the photovoltaic power is sent to the grid side in the maximum output mode. Otherwise, the off-grid mode is started to operate, S4 is executed, and the photovoltaic power is sent to the load side in the maximum output mode, which specifically includes:

[0085] 3) After the 750V DC bus voltage is established, DD4 is started to operate in the constant low voltage mode of 400V to charge the battery.

[0086] 4) Judge the grid voltage. If the grid voltage is normal, the grid-connected switch on the grid side is closed, that is, QF14 in Figure 1 , and the inverter starts to operate in the grid-connected mode. The power given value is the photovoltaic output power value. If the grid voltage is abnormal, the grid-connected switch on the grid side is disconnected, and the device starts to operate in the VF mode. The constant voltage given value is 220V, and then the next step is performed.

[0087] S3, set the grid-connected operation mode of the master and slave inverters, and determine whether the photovoltaic power station charges the energy storage based on the state of charge of each energy storage, specifically comprising:

[0088] 5) If the device starts the grid-connected operation mode in step 4), the power of the photovoltaic is sent to the grid side in the maximum output mode. First, set DA1 to run in the PQ mode to give a given grid-connected power, and DA2 automatically follows DA1, wherein the PQ mode startup power is given and the DSP has been set; then control according to the SOC of the two battery paths in two cases:

[0089] If the SOC of the battery group put into the fixed DC bus mode operation is lower than 90%, change the given value of the grid-connected power so that a part of the power charges the battery until it is charged to 90%; if the SOC of the other battery group is lower than 90%, put its battery into the fixed DC bus mode operation, and change the power distribution coefficient according to the proportion of the SOC to achieve the purpose of "more charging if less", and when the SOC of the two battery paths is 90%, stop the standby battery.

[0090] S4, set the off-grid operation mode of the master and slave inverters, and determine the operation mode of the photovoltaic chopper and the operation state of each energy storage based on the relationship between the photovoltaic power and the load power and the state of charge of each energy storage, specifically comprising:

[0091] 6) If the device starts the off-grid VF operation mode in step 3), the power of the photovoltaic is sent to the load side in the maximum output mode. First, determine whether the battery SOC at the startup time is greater than 30%, if the battery SOC at the startup time is greater than 30%, set DA1 to run in the VF mode to fix the AC voltage at 380V; DA2 automatically follows A1, wherein the PQ mode startup power is given and the DSP has been set. This embodiment considers that the connected load power is less than 60kW, i.e. DA1 does not run in the step-down current limiting mode, and then controls in the following two cases:

[0092] ① If the power of the photovoltaic is greater than the load power, set the remaining part to charge the battery, and after the battery SOC reaches 90%, the remaining power of the photovoltaic will raise the DC bus voltage, then the photovoltaic enters the power limiting operation mode, the given value of the power limiting is equal to the load power, and the charging conditions and methods in this process are the same as in the grid-connected state.

[0093] ② If the power of the photovoltaic is less than the load power, start another battery to fix the DC bus, and the two batteries discharge to the load according to the droop control, if the SOC of one battery is lower than 30%, stop the branch of this battery, and if the SOC of both batteries is lower than 30%, the device is in standby state and returns to step 1) to wait for the grid voltage to be normal and grid-connected. In this process, 1) one battery group works, and only one battery discharges; 2) two battery groups work, and the discharge power is equally divided.

[0094] Note: ① The battery SOC is greater than 30% when the fixed value mother link works, and the VF mode can run (when only one group of batteries works, one group is judged, and when two groups of batteries work, two groups are judged); ② If the battery SOC is less than 30% at the moment of starting, the VF mode cannot run, and only the grid can be charged by entering the PQ mode.

[0095] 7) The device performs island detection in grid-connected operation control, and if islanding occurs, it is transferred to the VF mode according to overvoltage or undervoltage or overfrequency or underfrequency.

[0096] 8) If the grid recovers normally in off-grid operation control, the device starts synchronization and is transferred to the grid-connected operation mode.

[0097] The switches QF10, QF11 and QF12 on the load side in the application are opened and closed according to actual needs.

[0098] Example 2

[0099] The application proposes a specific structure of an energy exchanger as shown in the figure. Figure 1 The device is composed of six single converters in a double plus structure, wherein DD1, DD2, DD3 and DD4 are photovoltaic choppers, first energy storage choppers, second energy storage choppers and 400V output choppers respectively, DA1 and DA2 are master and slave inverters respectively, and are three-phase three-wire, which are changed into three-phase four-wire through a transformer, and can be connected to a single-phase load. The 48V DC module input is a single-phase AC 220V input. The switches QF1 and QF2 are input and output switches of the photovoltaic chopper, the switches QF2 and QF5 are input and output switches of the first energy storage chopper, the switches QF3 and QF6 are input and output switches of the second energy storage chopper, the switches QF9 and QF10 are input and output switches of the 400V output chopper, the switch QF7 is a DC input switch of the master inverter, the switch QF8 is a DC input switch of the slave inverter, QF11 is a three-phase four-wire AC load switch, QF12 is a single-phase AC load switch, QF13 is a DC 48V output switch, QF14 is a grid-side grid switch, and the switch KM1 is an inverter-side grid-connected switch for grid-connected and off-grid switching.

[0100] The application proposes an eight-port intelligent microgrid energy exchanger architecture for regional energy internet, which can be directly connected to a 380V grid, access photovoltaic, two-way energy storage, electric vehicles (400V), electric bicycles (48V) and other DC loads, 220V / 380V AC loads; highly integrated photovoltaic inverters, energy storage bidirectional converters and other primary conversion devices, which can quickly build AC / DC interconnected microgrids and reduce the initial investment of engineering construction.

[0101] The application provides an operation control strategy of an AC-DC hybrid micro-grid based on an energy exchanger.

[0102] Embodiment 3

[0103] The application also provides a control system of a multi-port intelligent micro-grid energy exchanger based on the same inventive concept, which comprises:

[0104] The detection voltage module is used for detecting the voltage of the energy storage connected to each energy storage chopper through each energy storage chopper, and when the voltage of any energy storage is greater than the energy storage threshold, the energy storage voltage greater than the energy storage threshold is used to open the fixed DC bus voltage mode operation of the corresponding energy storage chopper and execute the judgment module; otherwise, the photovoltaic chopper is used to detect whether the photovoltaic power station has power, and when the photovoltaic power station has power, any energy storage is charged, and the voltage of the energy storage is continuously detected.

[0105] The judgment module is used for setting the operation mode of the output chopper and judging whether the grid-side voltage has power, and when the grid-side voltage has power, the operation grid-connected mode is opened, the grid-connected module is called to send the photovoltaic power to the grid side in the maximum output mode, otherwise, the off-grid mode is opened, and the off-grid module is called to send the photovoltaic power to the load side in the maximum output mode.

[0106] The grid-connected module is used for setting the grid-connected operation mode of the master and slave inverters, and determining whether the photovoltaic power station charges each energy storage based on the state of charge of each energy storage.

[0107] The off-grid module is used for setting the off-grid operation mode of the master and slave inverters, and determining the operation mode of the photovoltaic chopper and the operation state of each energy storage based on the relationship between the photovoltaic power and the load power and the state of charge of each energy storage.

[0108] In the embodiment, the judgment module comprises:

[0109] The grid-connected judgment unit is used for closing the grid-side grid-connected switch to open the operation grid-connected mode when the grid-side voltage has power, and executing the grid-connected module to send the photovoltaic power to the grid side in the maximum output mode.

[0110] The off-grid judgment unit is used for opening the off-grid mode by disconnecting the grid-side grid-connected switch when the grid-side voltage has no power, and executing the off-grid module to send the photovoltaic power to the load side in the maximum output mode.

[0111] In the embodiment, the grid-connected module comprises:

[0112] The first grid-connected unit is configured to change the grid-connected power given value when the state of charge of the energy storage in the fixed DC bus mode is lower than 90%, and the photovoltaic power station charges the energy storage until the state of charge reaches 90%, otherwise the photovoltaic power is fully grid-connected.

[0113] The second grid-connected unit is configured to change the power distribution coefficient according to the proportion of the state of charge of each energy storage when the state of charge of the energy storage not in the fixed DC bus mode is lower than 90%, and the photovoltaic power station charges each energy storage, and stops charging when the state of charge of each energy storage reaches 90%, and the photovoltaic power is fully grid-connected.

[0114] In the embodiment, the off-grid module comprises:

[0115] The first off-grid unit is configured to charge the energy storage with the state of charge lower than 90% with the remaining photovoltaic power in the photovoltaic chopper when the photovoltaic power is greater than the load power, and when the state of charge of the energy storage reaches 90%, the remaining photovoltaic power raises the DC bus voltage, and the photovoltaic chopper enters the limited power operation mode, and the given value of the limited power is equal to the load power.

[0116] The second off-grid unit is configured to operate the photovoltaic chopper at the maximum power and each energy storage enters the fixed DC bus mode when the photovoltaic power is less than the load power and the state of charge of each energy storage is greater than 30%, and each energy storage discharges according to the droop control.

[0117] The third off-grid unit is configured to standby the energy storage with the state of charge lower than 30% when the photovoltaic power is less than the load power and the state of charge of any energy storage is lower than 30%.

[0118] The fourth off-grid unit is configured to detect the voltage module when the photovoltaic power is less than the load power and the state of charge of each energy storage is lower than 30%.

[0119] In the embodiment, the control system is deployed on a control chip, and the control chip is connected with the photovoltaic chopper, each energy storage chopper, the output chopper, the master inverter and the slave inverter.

[0120] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system or a computer program product. Therefore, the present application can be in the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware aspects. Moreover, the present application can be in the form of a computer program product implemented on one or more computer usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer usable program code.

[0121] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks. Figure 1 one or more flow or blocks.

[0122] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the function specified in the flowchart block or blocks. Figure 1 one or more flow or blocks. Figure 1 one or more flow or blocks.

[0123] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks. Figure 1 one or more flow or blocks.

[0124] The above merely provides an embodiment of the present application, but is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall fall within the scope of the claims of the present application.

Claims

1. A method for controlling a multi-port intelligent microgrid energy exchange, the method comprising: Comprise: S1, detect the voltage of each energy storage through each energy storage chopper, when the voltage of any one energy storage is greater than the energy storage threshold, the energy storage chopper corresponding to the energy storage threshold greater than the energy storage voltage opens the fixed DC bus voltage mode operation and executes S2; otherwise, detect whether the photovoltaic power station has power through the photovoltaic chopper, when the photovoltaic power station has power, charge any one energy storage, continue to detect the voltage of the energy storage; S2, set the operation mode of the output chopper and judge whether the grid side voltage has power, when the grid side voltage has power, then start running and open the grid mode, execute S3 to send the photovoltaic power to the grid side in the maximum output mode, otherwise open the off-grid mode, execute S4 to send the photovoltaic power to the load side in the maximum output mode; S3, set the grid-connected operation mode of the master inverter and the slave inverter, and determine whether the photovoltaic power station charges each energy storage based on the state of charge of each energy storage; S4, set the off-grid operation mode of the master inverter and the slave inverter, and determine the operation mode of the photovoltaic chopper and the operation state of each energy storage based on the relationship between the photovoltaic power and the load power and the state of charge of each energy storage; Wherein, the multi-port intelligent microgrid energy exchanger comprises: a photovoltaic chopper, at least two energy storage choppers, an output chopper, a master inverter, a slave inverter and a control chip; One end of the photovoltaic chopper and one end of the master inverter are connected, one end of one energy storage chopper and one end of the slave inverter are connected, and one end of the other energy storage chopper and one end of the output chopper are connected; The other end of the master inverter and the other end of the slave inverter are connected to generate three AC ports and a first DC port, the other end of the output chopper generates a second DC port, the first AC port is connected with the grid, and the remaining AC ports and the first DC port and the second DC port are all connected with the load; The other end of the photovoltaic chopper is externally connected with a photovoltaic power station, and the other ends of the two energy storage choppers are respectively connected with an external energy storage; The first DC port is connected with a 48V DC load, and the second DC port is connected with a 400V DC load.

2. The control method according to claim 1, characterized by, The first AC port is connected with the grid in turn through an inverter side grid-connected switch and a grid side grid-connected switch.

3. The control method according to claim 1, characterized by, The energy storage chopper corresponding to the energy storage threshold greater than the energy storage voltage opens the fixed DC bus voltage mode operation and executes S2, comprising: When the energy storage chopper corresponding to the energy storage threshold greater than the energy storage voltage opens the fixed DC bus voltage mode operation, judge whether the DC bus side voltage reaches the control target value, if the DC bus voltage is greater than the control target value, close the inverter side grid-connected switch to execute S2, otherwise continue to detect the voltage of each energy storage.

4. The control method according to claim 1, characterized by, The setting of the operation mode of the output chopper comprises: Set the low voltage value of the output chopper running, and take the output chopper as a charging pile; The low voltage is 400V.

5. The control method according to claim 1, characterized by, When the grid side voltage has power, then start running and open the grid mode, execute S3 to send the photovoltaic power to the grid side in the maximum output mode, otherwise open the off-grid mode, execute S4 to send the photovoltaic power to the load side in the maximum output mode, comprising: When the grid voltage is on, the grid-side grid-connected switch is closed to start the grid-connected mode, and the photovoltaic power is sent to the grid side in the maximum output mode, otherwise the grid-side grid-connected switch is opened to start the off-grid mode, and the photovoltaic power is sent to the load side in the maximum output mode.

6. The control method according to claim 1, characterized by, The grid-connected operation mode of the master inverter and the slave inverter is set, and the grid-connected operation mode of the master inverter and the slave inverter comprises: The master inverter is set to operate in the PQ mode of a given grid-connected power, and the slave inverter automatically follows the master inverter.

7. The control method according to claim 1, characterized by, The photovoltaic power station is determined to charge each energy storage based on the state of charge of each energy storage, and the photovoltaic power station is determined to charge each energy storage based on the state of charge of each energy storage comprises: When the state of charge of the energy storage in the fixed DC bus mode is lower than 90%, the grid-connected power given value is changed, the photovoltaic power station charges the corresponding energy storage until it is charged to 90%, otherwise the photovoltaic power is all grid-connected; When the state of charge of the energy storage not in the fixed DC bus mode is lower than 90%, the power distribution coefficient is changed according to the proportion of the state of charge of each energy storage, the photovoltaic power station charges each energy storage, and when the state of charge of each energy storage is 90%, the charging is stopped and the photovoltaic power is all grid-connected.

8. The control method according to claim 1, characterized by, Before the off-grid mode is started, it comprises: The state of charge of each energy storage is determined, and when the state of charge of any energy storage is greater than 30%, the off-grid mode is started, otherwise the voltage of each energy storage is continuously detected.

9. The control method according to Claim 1, characterized by, The off-grid operation mode of the master inverter and the slave inverter is set, and the off-grid operation mode of the master inverter and the slave inverter comprises: The master inverter is set to operate in the VF mode under the condition of an AC voltage of 380V, and the slave inverter automatically follows the master inverter.

10. The control method according to claim 1, characterized by, The operation mode of the photovoltaic chopper and the operation state of each energy storage are determined based on the relationship between the photovoltaic power and the load power and the state of charge of each energy storage, and the operation mode of the photovoltaic chopper and the operation state of each energy storage are determined based on the relationship between the photovoltaic power and the load power and the state of charge of each energy storage comprises: When the photovoltaic power is greater than the load power, the remaining photovoltaic power in the photovoltaic chopper charges the energy storage with a state of charge lower than 90%, and when the state of charge of the energy storage reaches 90%, the remaining photovoltaic power raises the DC bus voltage, then the photovoltaic chopper enters the limited power operation mode, and the given value of the limited power is equal to the load power; When the photovoltaic power is less than the load power and the state of charge of each energy storage is greater than 30%, the photovoltaic chopper operates at the maximum power and each energy storage enters the fixed DC bus mode, and each energy storage discharges to the load according to the droop control; When the photovoltaic power is less than the load power and the state of charge of any energy storage is lower than 30%, the energy storage with a state of charge lower than 30% is on standby; When the photovoltaic power is less than the load power and the state of charge of each energy storage is lower than 30%, each energy storage is in standby and returns to S1.

11. The control method according to claim 1, wherein The grid-connected operation mode of the master inverter and the slave inverter further comprises: The multi-port intelligent micro-grid energy exchanger performs island detection in the grid-connected operation control, and if islanding occurs, it is transferred to the VF mode according to overvoltage or undervoltage or overfrequency or underfrequency.

12. The control method according to claim 1, characterized by, The off-grid operation mode of the master inverter and the slave inverter further comprises: The multi-port intelligent micro-grid energy exchanger is transferred to the grid-connected operation mode if the grid recovers to normal in the off-grid operation mode.

13. A control system for a control method of a multi-port smart microgrid energy exchanger according to any one of claims 1 to 12, characterized by, It comprises: The detection voltage module is configured to detect the voltage of each energy storage connected to each energy storage chopper, and when the voltage of any energy storage is greater than the energy storage threshold, the energy storage chopper corresponding to the energy storage threshold greater than the energy storage voltage is started to run in the direct current bus voltage mode and the judgment module is executed; otherwise, the photovoltaic chopper is used to detect whether the photovoltaic power station has power, and when the photovoltaic power station has power, any energy storage is charged, and the voltage of the energy storage is continuously detected; The judgment module is configured to set the operation mode of the output chopper and judge whether the grid-side voltage has power, and when the grid-side voltage has power, the grid-connected mode is started, the grid-connected module is called to send the photovoltaic power to the grid-side in the maximum output mode, otherwise, the off-grid mode is started, and the off-grid module is called to send the photovoltaic power to the load side in the maximum output mode; The grid-connected module is configured to set the grid-connected operation mode of the master inverter and the slave inverter, and determine whether the photovoltaic power station charges each energy storage based on the state of charge of each energy storage. The off-grid module is configured to set the off-grid operation mode of the master inverter and the slave inverter, and determine the operation mode of the photovoltaic chopper and the operation state of each energy storage based on the relationship between the photovoltaic power and the load power and the state of charge of each energy storage.

14. The control system of claim 13, wherein, The judgment module comprises: The grid-connected judgment unit is configured to close the grid-side grid-connected switch to start the grid-connected mode when the grid-side voltage has power, and execute the grid-connected module to send the photovoltaic power to the grid-side in the maximum output mode, The off-grid judgment unit is configured to disconnect the grid-side grid-connected switch to start the off-grid mode when the grid-side voltage has no power, and execute the off-grid module to send the photovoltaic power to the load side in the maximum output mode.

15. The control system of claim 13, wherein, The grid-connected module comprises: The first grid-connected unit is configured to change the grid-connected power given value when the state of charge of the energy storage already put into the direct current bus voltage mode is lower than 90%, the photovoltaic power station charges the corresponding energy storage until the state of charge reaches 90%, otherwise, the photovoltaic power is all grid-connected; The second grid-connected unit is configured to change the power distribution coefficient according to the proportion of the state of charge of each energy storage when the state of charge of the energy storage not put into the direct current bus voltage mode is lower than 90%, so that the photovoltaic power station charges each energy storage, and when the state of charge of each energy storage is 90%, the charging is stopped, and the photovoltaic power is all grid-connected.

16. The control system of claim 13, wherein, The off-grid module comprises: The first off-grid unit is configured to charge the energy storage with the state of charge lower than 90% with the remaining photovoltaic power in the photovoltaic chopper when the photovoltaic power is greater than the load power, and when the state of charge of the energy storage reaches 90%, the remaining photovoltaic power will raise the direct current bus voltage, so that the photovoltaic chopper enters the limited power operation mode, and the limited power given value is equal to the load power; The second off-grid unit is configured to run the photovoltaic chopper at the maximum power and each energy storage enters the direct current bus voltage mode when the photovoltaic power is less than the load power and the state of charge of each energy storage is greater than 30%, and each energy storage discharges to the load according to the droop control; The third off-grid unit is configured to standby the energy storage with the state of charge lower than 30% when the photovoltaic power is less than the load power and the state of charge of any energy storage is lower than 30%. The fourth off-grid unit is used for standby calling detection voltage module when photovoltaic power is less than load power and state of charge of each energy storage is less than 30%.

17. The control system of claim 13, wherein, The control system is arranged on a control chip, and the control chip is connected with the photovoltaic chopper, each energy storage chopper, the output chopper, the master inverter and the slave inverter.

Images