Hybrid energy storage isolation inversion system and control method thereof

Abstract

The invention discloses a hybrid energy storage isolation inversion system and a control method thereof.The hybrid energy storage isolation inversion system comprises a dual-power-supply change-over switch, a rectifying circuit, an inversion circuit, a direct-current conversion circuit, a battery pack, a photovoltaic module, an EMS, a display interface, a generator, a power grid and a load, the input end of the dual-power-supply change-over switch is connected into the power grid and the generator, and the output end of the dual-power-supply change-over switch is connected with the rectifying circuit; the switching of the dual-power change-over switch is controlled by the EMS, and the rectification circuit is set to be a three-phase rectification circuit. The hybrid energy storage isolation inversion system can be stable under the condition that the power grid is abnormal but still has power supply, meanwhile, energy of the hybrid energy storage isolation inversion system is optimized, the working states of the battery pack and the generator can be switched according to the state of the power grid, and therefore stable operation of the load is guaranteed, and meanwhile the power supply efficiency of the hybrid energy storage isolation inversion system is improved. A power grid can be utilized to supply power to the maximum extent, the requirement for electricity storage capacity is lowered, and use cost is reduced.

Description

Technical Field

[0001] The present invention specifically relates to a hybrid energy storage isolation inverter system and a control method thereof. Background Art

[0002] A hybrid energy storage isolated inverter system is a system that combines multiple energy storage technologies, aiming to improve the performance and efficiency of the overall system through the complementary characteristics of different energy storage technologies. This system usually includes different types of energy storage devices such as battery packs, supercapacitors, photovoltaic modules, etc., and performs energy conversion and management through inverters;

[0003] In the power supply networks of some regions at home and abroad, the problem of unstable power supply quality is relatively common, which manifests itself in three-phase imbalance, phase loss, voltage fluctuation and power outage. These problems lead to the load equipment being unable to obtain continuous and stable power supply, which in turn has an adverse effect on its normal operation and may even cause damage to the electrical equipment. In order to ensure that the load equipment can operate continuously and stably, a hybrid energy storage isolation inverter system is usually equipped at the load end to ensure the normal use of electricity.

[0004] However, the traditional hybrid energy storage isolation inverter system cannot be connected to the grid normally when the grid has abnormal conditions such as phase loss, voltage fluctuation or three-phase imbalance. That is, when the grid still has power supply but there is an abnormality, the traditional hybrid energy storage isolation inverter system can only operate off-grid, resulting in the load being unable to fully utilize the power supply of the grid. Only a higher energy storage capacity can be configured to ensure the stable operation of the load at all times, which increases the cost of use.

[0005] Therefore, it is necessary to invent a hybrid energy storage isolation inverter system and a control method thereof to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to provide a hybrid energy storage isolation inverter system and a control method thereof, wherein the hybrid energy storage isolation inverter system can be stable when the power grid is abnormal but there is still power supply, and at the same time, the energy of the hybrid energy storage isolation inverter system is optimized, and the working status of the battery pack and the generator can be switched according to the power grid status, thereby ensuring stable operation of the load while maximizing the use of power supply from the power grid, reducing the demand for storage capacity, and reducing the cost of use, so as to solve the above-mentioned deficiencies in the technology.

[0007] In order to achieve the above-mentioned object, the present invention provides the following technical solutions: a hybrid energy storage isolation inverter system, comprising a dual power supply switch, a rectifier circuit, an inverter circuit, a DC conversion circuit, a battery pack, a photovoltaic module, an EMS, a display interface, a generator, a power grid, and a load;

[0008] The input end of the dual power switch is connected to the power grid and the generator, the output end is connected to the rectifier circuit, and the dual power switch is switched under the control of the EMS;

[0009] The rectifier circuit is configured as a three-phase rectifier circuit, and the input end of the rectifier circuit is connected to the power grid, and supports phase loss, overvoltage, undervoltage, and three-phase unbalanced operation;

[0010] The inverter circuit is an off-grid inverter, which is used to take power from the DC bus and invert it to output to the load;

[0011] The input sources of the DC conversion circuit are photovoltaic modules and rectifier circuits. The photovoltaic modules are preferably used as the input source. When the power of the DC conversion circuit cannot support the inverter circuit, the rectifier circuit is used as power supplement.

[0012] The battery pack is connected to the DC bus and is charged and discharged according to the power on the DC bus;

[0013] The EMS is used to coordinate and dispatch the operation of the entire hybrid energy storage isolation inverter system;

[0014] The display interface is a human-computer interaction interface for reading the working conditions of the hybrid energy storage isolation inverter system, including working status, alarm information, parameter settings

[0015] In the aforementioned hybrid energy storage isolation inverter system, the battery pack is connected to the DC bus and is charged and discharged according to the power on the DC bus, specifically:

[0016] Discharging includes discharge mode and low power discharge mode, and charging includes charge mode and floating charge mode;

[0017] Among them, discharge mode: as the load of the inverter circuit fluctuates, when the power delivered to the DC bus by the rectifier circuit and the DC conversion circuit connected to the photovoltaic module cannot meet the load, the battery pack enters the discharge mode;

[0018] Low-power discharge mode: When the battery pack SOC is greater than or equal to the upper charge limit setting threshold, the output power of the rectifier circuit and the DC conversion circuit is controlled to be equal to 95% of the input power of the inverter circuit. The battery pack enters the low-power discharge mode, and the discharge power is 5% of the input power of the inverter circuit.

[0019] Charging mode: read the allowable charging current of the battery pack in real time. When the power of the rectifier circuit and the DC conversion circuit connected to the photovoltaic module meets the inverter circuit load and has a margin, the power greater than the inverter circuit load is transmitted to the DC bus, and the battery pack enters the charging mode. The charging current is less than or equal to the allowable charging current of the battery pack. When the battery pack issues a prohibition charging command, charging stops;

[0020] Floating charge mode: When the battery pack SOC is determined to be equal to the floating charge setting threshold, the output power of the rectifier circuit and the DC conversion circuit is controlled to be equal to the input power of the inverter circuit. The battery pack enters the floating charge mode and is in a micro-charge and micro-discharge state.

[0021] The aforementioned hybrid energy storage isolation inverter system, wherein the dual power switch input end is connected to the power grid and the generator output end via a connecting line, and the dual power switch output end is connected to the rectifier circuit input end via a connecting line;

[0022] The output end of the photovoltaic module is connected to the input end of the DC conversion circuit through a connecting line;

[0023] The EMS output terminal is connected to the display interface input terminal via a connecting line

[0024] The output end of the inverter circuit is connected to the input end of the load through a connecting line;

[0025] The battery pack is connected to the DC bus via a connecting wire;

[0026] The output end of the rectifier circuit and the output end of the DC conversion circuit are both connected to the DC bus through a connecting line;

[0027] The input end of the inverter circuit is connected to the DC bus through a connecting line;

[0028] The generator, the DC conversion circuit, the dual power supply switch, the battery pack and the inverter circuit are connected to the EMS via a communication bus to realize the EMS information reading and control functions.

[0029] A control method for a hybrid energy storage isolation inverter system comprises the following steps:

[0030] Step 1: Click Start on the display interface, and the hybrid energy storage isolation inverter system enters the startup state. The rectifier circuit, inverter circuit, and DC conversion circuit obtain the input source state and perform self-test, waiting for the EMS command to enter the corresponding working mode;

[0031] Step 2: After the system enters the running state, the EMS controls the inverter circuit to start, the inverter circuit draws power from the DC bus, and the output power fluctuates with the load;

[0032] Step 3: When the system is in operation, the EMS makes a judgment based on the battery pack SOC and dynamically adjusts the output power of the rectifier circuit and the DC conversion circuit;

[0033] Step 4: When an abnormality occurs in the power grid, the rectifier circuit enters a two-phase or single-phase working mode, limits the power according to the input voltage, and controls the rectifier circuit to output the maximum power according to the current state of the power grid;

[0034] Step 5: When the output power of the rectifier circuit and the DC conversion circuit cannot meet the input power of the inverter circuit, the battery pack supplements the power to support the inverter circuit, and the battery enters the discharge mode;

[0035] Step 6: When the battery pack is discharged to an SOC less than or equal to the generator start setting threshold, the generator operation mode is entered, and the EMS reads the grid status in real time and switches the operation mode.

[0036] In the aforementioned control method of the hybrid energy storage isolation inverter system, in step 1, the circuit includes a rectifier circuit, an inverter circuit, and a DC conversion circuit;

[0037] The input source of the rectifier circuit is the power grid or generator, the input source of the DC conversion circuit is the photovoltaic module, and the input source of the inverter circuit is the DC bus;

[0038] The self-test of the rectifier circuit, inverter circuit, and DC conversion circuit is as follows: the EMS reads the status of each circuit and the battery pack through the communication bus, detects the voltage of the input source, the power allowed to be output, and whether the circuit is faulty, and sends the detection information to the communication bus, which is judged and processed by the EMS. That is, the EMS reads from the communication bus, and each circuit waits for the EMS instruction to enter the corresponding working mode;

[0039] When a serious fault occurs in each circuit, the fault circuit stops working; when a minor fault occurs, the circuit runs at a reduced load. The specific fault content is reported to the EMS through the communication bus, and the EMS displays the fault information on the display screen;

[0040] If the battery pack has a serious fault, the system will be prohibited from working. If it has a minor fault, it will operate normally and report the specific fault content to the EMS through the communication bus. The EMS will display the fault information on the display screen.

[0041] When there is no fault in the circuit, the EMS controls the startup and operation of each circuit through the communication bus;

[0042] Among them, the status of the battery pack includes: SOC, temperature, voltage, current, allowed charge and discharge current, working status, and fault information;

[0043] Among them, SOC is the state of charge of the battery pack, that is, the available state of the remaining power in the battery pack.

[0044] In the control method of the hybrid energy storage isolation inverter system described above, in step 2, the inverter circuit draws power from the DC bus, and the output power fluctuates with the load, specifically:

[0045] The output power of the inverter circuit is equal to the power required by the load. When the load exceeds the output capacity of the inverter circuit, the inverter circuit reports an overload fault and stops working.

[0046] In the control method of the hybrid energy storage isolated inverter system described above, in step 3, when the system is in operation, the EMS makes a judgment based on the battery pack SOC and dynamically adjusts the output power of the rectifier circuit and the DC conversion circuit, specifically:

[0047] When the battery pack SOC is greater than or equal to the floating charge setting threshold, the battery pack enters the floating charge mode. The EMS controls the output power of the rectifier circuit and the DC conversion circuit to be equal to the input power of the inverter circuit. The battery pack fluctuates in the micro-charge and micro-discharge state as the inverter power fluctuates.

[0048] When the battery pack SOC is equal to the upper charge limit setting threshold, the battery pack enters the low-power discharge mode, controls the output power of the rectifier circuit and the DC conversion circuit to be equal to 95% of the input power of the inverter circuit, and the battery pack output power is 5% of the input power of the inverter circuit, until the battery pack SOC is discharged to equal to the floating charge setting threshold, and then enters the floating charge mode;

[0049] When the battery pack SOC is equal to 100% or the battery pack issues a charge prohibition command, the battery pack enters the discharge mode, controls the rectifier circuit and the DC conversion circuit to shut down, and the battery pack alone supplies power to the inverter circuit until the battery pack SOC is discharged to equal the float charge setting threshold, then enters the float charge mode;

[0050] When the battery pack SOC is less than the floating charge setting threshold + 5, the battery pack enters the charging mode, controlling the output power sum of the rectifier circuit and the DC conversion circuit to be greater than the inverter circuit input power, and the value greater than is less than or equal to the allowable charging power of the battery pack.

[0051] In the control method of the hybrid energy storage isolated inverter system described above, in step 5, when the output power of the rectifier circuit and the DC conversion circuit cannot meet the input power of the inverter circuit, the battery pack supplements the power to support the operation of the inverter circuit. At this time, the battery enters the discharge mode, specifically:

[0052] When the battery pack is discharged to a SOC less than or equal to the generator start setting threshold, it enters the generator working mode, and the EMS controls the dual power supply switch to switch from grid input to generator input. The EMS sends a start signal to the generator, and the generator will provide power to the rectifier circuit and output power to the DC bus for battery pack charging and inverter circuit input;

[0053] When the battery pack is discharged to an SOC less than or equal to the discharge lower limit setting threshold, the EMS controls the inverter circuit to stop working, and the EMS controls the rectifier circuit and the DC conversion circuit to charge the battery pack first, until the battery pack is charged to an SOC greater than the discharge lower limit setting threshold + 5, the EMS controls the inverter circuit to start working.

[0054] In the control method of the hybrid energy storage isolation inverter system described above, in step 6, when the battery pack is discharged to an SOC less than or equal to the generator start setting threshold, the generator operation mode is entered, and the EMS reads the grid status in real time and switches the operation mode, specifically:

[0055] When it is identified that the number of stable input phases of the power grid is greater than or equal to 2 within a certain period of time, it switches to the power grid working mode, otherwise it continues to work in the generator mode;

[0056] In generator mode, when the battery pack SOC is greater than or equal to the generator charging upper limit threshold, the generator stops working and judges the grid status. When the input phase number is greater than or equal to 1, the EMS controls the dual power supply switch to switch to grid input, uses the grid to support the inverter circuit, and the battery pack is used as a supplement. The battery pack SOC status is read and judged in real time, and the judgment of the discharge lower limit setting threshold continues.

[0057] The beneficial effects of the present invention are:

[0058] The present invention controls the inverter circuit through EMS. When taking power from the DC bus, the output power follows the load fluctuation, thereby providing the load with stable and reliable power isolated from the power grid, ensuring the stable operation of the load, and judging the SOC state of the battery pack, dynamically adjusting the output power of the rectifier circuit and the DC conversion circuit, ensuring that the battery pack can store sufficient electricity and support the operation of the inverter circuit, and when the power grid is abnormal, the rectifier circuit enters a two-phase or single-phase working mode to maximize the use of the power grid. At the same time, when the battery pack is discharged to an SOC less than or equal to the generator start setting threshold, it enters the generator working mode to ensure that the load has reliable, continuous and stable power supply, and can maximize the use of the power grid power supply, reducing the use cost of the generator. Compared with the prior art, the hybrid energy storage isolation inverter system can be stable when the power grid is abnormal but still has power supply. At the same time, the energy of the hybrid energy storage isolation inverter system is optimized, and the working state of the battery pack and the generator can be switched according to the power grid state, thereby ensuring the stable operation of the load while maximizing the use of the power grid power supply, reducing the demand for storage power and reducing the use cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0060] Figure 1 It is a control flow chart of the hybrid energy storage isolation inverter system of the present invention. DETAILED DESCRIPTION

[0061] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0062] The present invention provides a hybrid energy storage isolation inverter system, including a dual power supply switch, a rectifier circuit, an inverter circuit, a DC conversion circuit, a battery pack, a photovoltaic module, an EMS, a display interface, a generator, a power grid, and a load;

[0063] The input end of the dual power switch is connected to the power grid and the generator, the output end is connected to the rectifier circuit, and the dual power switch is switched under the control of the EMS;

[0064] The rectifier circuit is configured as a three-phase rectifier circuit, and the input end of the rectifier circuit is connected to the power grid, and supports phase loss, overvoltage, undervoltage, and three-phase unbalanced operation;

[0065] The inverter circuit is an off-grid inverter, which is used to take power from the DC bus and invert it to output to the load;

[0066] The input sources of the DC conversion circuit are photovoltaic modules and rectifier circuits, with photovoltaic modules being preferred as the input source. When the power of the DC conversion circuit cannot support the inverter circuit, the rectifier circuit is used as power supplement;

[0067] The battery pack is connected to the DC bus and is charged and discharged according to the power on the DC bus. Specifically:

[0068] Discharging includes discharge mode and low power discharge mode, and charging includes charge mode and floating charge mode;

[0069] Among them, discharge mode: as the load of the inverter circuit fluctuates, when the power delivered to the DC bus by the rectifier circuit and the DC conversion circuit connected to the photovoltaic module cannot meet the load, the battery pack enters the discharge mode;

[0070] Low-power discharge mode: When the battery pack SOC is greater than or equal to the upper charge limit setting threshold, the output power of the rectifier circuit and the DC conversion circuit is controlled to be equal to 95% of the input power of the inverter circuit. At this time, the battery pack enters the low-power discharge mode, and the power discharged by the battery pack is 5% of the input power of the inverter circuit.

[0071] Charging mode: read the allowable charging current of the battery pack in real time. When the power of the DC conversion circuit connected to the rectifier circuit and the photovoltaic module meets the inverter circuit load and has a margin, the power greater than the inverter circuit load is transmitted to the DC bus. At this time, the battery pack enters the charging mode, and the charging current is less than or equal to the allowable charging current of the battery pack. When the battery pack issues a prohibition charging command, charging stops;

[0072] Floating charge mode: When the battery pack SOC is equal to the floating charge setting threshold, the output power of the rectifier circuit and the DC conversion circuit is controlled to be equal to the input power of the inverter circuit. At this time, the battery pack enters the floating charge mode, and the battery pack is in a state of micro-charge and micro-discharge, which is similar to static.

[0073] The EMS is used to coordinate and dispatch the operation of the entire hybrid energy storage isolation inverter system;

[0074] The display interface is a human-computer interaction interface, which is used to read the working conditions of the hybrid energy storage isolation inverter system, including working status, alarm information, and parameter settings;

[0075] Further, in the above technical solution, the input end of the dual power switch is connected to the power grid and the output end of the generator through a connecting line, and the output end of the dual power switch is connected to the input end of the rectifier circuit through a connecting line;

[0076] The output end of the photovoltaic module is connected to the input end of the DC conversion circuit through a connecting line;

[0077] The EMS output terminal is connected to the display interface input terminal via a connecting line;

[0078] The output end of the inverter circuit is connected to the input end of the load through a connecting line;

[0079] The battery pack is connected to the DC bus via a connecting wire;

[0080] The output end of the rectifier circuit and the output end of the DC conversion circuit are both connected to the DC bus through a connecting line;

[0081] The input end of the inverter circuit is connected to the DC bus through a connecting line;

[0082] The generator, the DC conversion circuit, the dual power supply switch, the battery pack and the inverter circuit are connected to the EMS via a communication bus to realize the EMS information reading and control functions.

[0083] The present invention provides Figure 1 A control method for a hybrid energy storage isolation inverter system is shown, comprising the following steps:

[0084] Step 1: Click Start on the display interface, and the hybrid energy storage isolation inverter system enters the startup state. The rectifier circuit, inverter circuit, and DC conversion circuit obtain the input source state and perform self-test, waiting for the EMS command to enter the corresponding working mode;

[0085] Wherein, the circuit includes a rectifier circuit, an inverter circuit, and a DC conversion circuit;

[0086] Among them, the input source of the rectifier circuit is the power grid or generator, the input source of the DC conversion circuit is the photovoltaic module, and the input source of the inverter circuit is the DC bus;

[0087] Among them, the self-test of the rectifier circuit, inverter circuit, and DC conversion circuit is specifically as follows: the EMS reads the status of each circuit and the battery pack through the communication bus, detects the voltage of the input source, the power allowed to be output, and whether the circuit is faulty, and sends the detection information to the communication bus, which is judged and processed by the EMS, that is, the EMS reads from the communication bus, and each circuit waits for the EMS instruction to enter the corresponding working mode;

[0088] When a serious fault occurs in each circuit, the fault circuit stops working; when a minor fault occurs, the circuit runs at a reduced load. The specific fault content is reported to the EMS through the communication bus, and the EMS displays the fault information on the display screen;

[0089] Among them, the faulty circuit stops working, and the fault of each circuit does not affect the normal operation of other circuits;

[0090] If the battery pack has a serious fault, the system will be prohibited from working. If it has a minor fault, it will operate normally and report the specific fault content to the EMS through the communication bus. The EMS will display the fault information on the display screen.

[0091] When there is no fault in the circuit, the EMS controls the startup and operation of each circuit through the communication bus.

[0092] Among them, a serious fault means that this fault will cause the device to fail to operate normally, or continued operation will cause damage to the device, pose a safety hazard, etc. This fault will execute a protection action to stop operation.

[0093] A minor fault means that the device temperature, power supply, communication, etc. are abnormal, but it does not affect the normal operation of the device. The device will run at a reduced load or normally, which serves as an early warning.

[0094] Among them, the status of the battery pack includes: SOC, temperature, voltage, current, allowed charge and discharge current, working status, and fault information;

[0095] Among them, SOC is the state of charge of the battery pack, that is, the available state of the remaining power in the battery pack;

[0096] In this step, by identifying the status of each circuit, each circuit is controlled to enter an appropriate working state, and corresponding information is displayed through a display interface, so that the staff can clearly identify the working conditions and abnormal conditions of the system.

[0097] Step 2: After the system enters the running state, the EMS controls the inverter circuit to start, the inverter circuit draws power from the DC bus, and the output power fluctuates with the load;

[0098] The inverter circuit draws power from the DC bus, and the output power fluctuates with the load. Specifically, the output power of the inverter circuit is equal to the power required by the load. When the load exceeds the output capacity of the inverter circuit, the inverter circuit reports an overload fault and stops working.

[0099] In this step, by controlling the inverter circuit, stable and reliable power isolated from the power grid is provided to the load, which not only ensures the stable operation of the load, but also avoids damage to electrical equipment caused by power grid anomalies.

[0100] Step 3: When the system is in operation, the EMS makes a judgment based on the battery pack SOC and dynamically adjusts the output power of the rectifier circuit and the DC conversion circuit. Specifically:

[0101] When the battery pack SOC is greater than or equal to the floating charge setting threshold, the battery pack enters the floating charge mode. The EMS controls the output power of the rectifier circuit and the DC conversion circuit to be equal to the input power of the inverter circuit. The battery pack fluctuates in the micro-charge and micro-discharge state as the inverter power fluctuates, which is close to being static.

[0102] When the battery pack SOC is equal to the upper charge limit setting threshold, the battery pack enters the low-power discharge mode, controls the output power of the rectifier circuit and the DC conversion circuit to be equal to 95% of the input power of the inverter circuit, and the battery pack output power is 5% of the input power of the inverter circuit, until the battery pack SOC is discharged to equal to the floating charge setting threshold, and then enters the floating charge mode;

[0103] When the battery pack SOC is equal to 100% or the battery pack issues a charge prohibition command, the battery pack enters the discharge mode, controls the rectifier circuit and the DC conversion circuit to shut down, and the battery pack alone supplies power to the inverter circuit until the battery pack SOC is discharged to equal the float charge setting threshold, then enters the float charge mode;

[0104] When the battery pack SOC is less than the floating charge setting threshold + 5, the battery pack enters the charging mode, and controls the output power sum of the rectifier circuit and the DC conversion circuit to be greater than the input power of the inverter circuit, and the greater value is less than or equal to the allowed charging power of the battery pack;

[0105] Among them, the floating charge setting threshold is generally set to 90%. When the battery pack SOC reaches the threshold, it will enter the floating charge mode, which can effectively extend the service life of the battery pack. It can also be adjusted according to site conditions and subjective needs;

[0106] In this step, through the control algorithm based on the battery pack SOC, the operation of each circuit is intelligently and dynamically regulated, which can not only ensure that the battery pack stores sufficient electricity, but also effectively extend the battery life and avoid overcharging and over-discharging of the battery pack.

[0107] Step 4: When an abnormality occurs in the power grid, the rectifier circuit enters a two-phase or single-phase working mode, limits the power according to the input voltage, and controls the rectifier circuit to output the maximum power according to the current state of the power grid;

[0108] In this step, the rectifier circuit is controlled to output the maximum power according to the current state of the power grid, thereby making the most of the power grid.

[0109] Step 5: When the output power of the rectifier circuit and the DC conversion circuit cannot meet the input power of the inverter circuit, the battery pack supplements the power to support the operation of the inverter circuit. At this time, the battery enters the discharge mode, specifically:

[0110] When the battery pack is discharged to a SOC less than or equal to the generator start setting threshold, it enters the generator working mode, and the EMS controls the dual power supply switch to switch from grid input to generator input. The EMS sends a start signal to the generator, and the generator will provide power to the rectifier circuit and output power to the DC bus for battery pack charging and inverter circuit input;

[0111] When the battery pack is discharged to the point where the SOC is less than or equal to the lower discharge limit setting threshold, the EMS controls the inverter circuit to stop working, and the EMS controls the rectifier circuit and the DC conversion circuit to charge the battery pack first, until the battery pack is charged to the point where the SOC is greater than the lower discharge limit setting threshold + 5, the EMS controls the inverter circuit to start working;

[0112] In this step, by identifying the battery pack SOC, when the battery pack is low on power and the rectifier circuit and DC conversion circuit are underpowered, the dual power switch is controlled to switch the input source of the rectifier circuit to the generator, and the generator is started, thereby ensuring that the load has a reliable, continuous and stable power supply.

[0113] Step 6: When the battery pack is discharged to an SOC less than or equal to the generator start setting threshold, the generator operation mode is entered, and the EMS reads the grid status in real time and switches the operation mode. Specifically:

[0114] When it is identified that the number of stable input phases of the power grid is greater than or equal to 2 within a certain period of time, it switches to the power grid working mode, otherwise it continues to work in the generator mode;

[0115] In generator mode, when the battery pack SOC is greater than or equal to the generator charging upper limit threshold, the generator stops working and judges the grid status. When the input phase number is greater than or equal to 1, the EMS controls the dual power supply switch to switch to grid input, making maximum use of the grid to support the inverter circuit, and the battery pack is used as a supplement. The battery pack SOC status is read and judged in real time, and then the discharge lower limit setting threshold is judged;

[0116] In this step, by identifying the grid status and controlling the generator and dual power switching switch, in the case of grid abnormalities and low battery of the battery pack, it can not only ensure that the load has a reliable, continuous and stable power supply, but also maximize the use of grid power supply and reduce the cost of generator use.

[0117] In summary, the present invention controls the inverter circuit through EMS. When taking power from the DC bus, the output power follows the load fluctuation, thereby providing the load with stable and reliable power isolated from the power grid, ensuring the stable operation of the load, and judging the SOC state of the battery pack, dynamically adjusting the output power of the rectifier circuit and the DC conversion circuit, ensuring that the battery pack can store sufficient electricity and support the operation of the inverter circuit, and when the power grid is abnormal, the rectifier circuit enters a two-phase or single-phase working mode to maximize the use of the power grid. At the same time, when the battery pack is discharged to an SOC less than or equal to the generator start setting threshold, it enters the generator working mode to ensure that the load has reliable, continuous and stable power supply, and can maximize the use of the power grid power supply, reducing the use cost of the generator. The hybrid energy storage isolation inverter system can be stable when the power grid is abnormal but still has power supply. At the same time, the energy of the hybrid energy storage isolation inverter system is optimized, and the working state of the battery pack and the generator can be switched according to the power grid state, thereby ensuring the stable operation of the load while maximizing the use of the power grid power supply, reducing the demand for storage power and reducing the use cost;

[0118] At the same time, the hybrid energy storage isolation inverter system is an isolated power supply system, which realizes the isolated operation of the power grid and the load, avoids the equipment from being affected by the fluctuation of the power grid, avoids unnecessary damage, and can adjust the capacity of each circuit according to the changes in power demand, flexibly expand the power supply capacity, and has an intermediate bridge of the DC bus. It can accept various input sources through the rectifier circuit and DC conversion circuit, including but not limited to wind energy, solar energy, AC power, generators, etc. It is not only highly adaptable, but also can effectively improve the stability and efficiency of the power supply, providing more reliable and efficient power services for the load.

[0119] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A hybrid energy storage isolation inverter system, characterized in that: Including dual power switch, rectifier circuit, inverter circuit, DC conversion circuit, battery pack, photovoltaic module, EMS, display interface, generator, power grid, and load; The input end of the dual power switch is connected to the power grid and the generator, the output end is connected to the rectifier circuit, and the dual power switch is switched under the control of the EMS; The rectifier circuit is configured as a three-phase rectifier circuit, and the input end of the rectifier circuit is connected to the power grid, and supports phase loss, overvoltage, undervoltage, and three-phase unbalanced operation; The inverter circuit is an off-grid inverter, which is used to take power from the DC bus and invert it to output to the load; The input sources of the DC conversion circuit are photovoltaic modules and rectifier circuits. The photovoltaic modules are preferably used as the input source. When the power of the DC conversion circuit cannot support the inverter circuit, the rectifier circuit is used as power supplement. The battery pack is connected to the DC bus and is charged and discharged according to the power on the DC bus; The EMS is used to coordinate and dispatch the operation of the entire hybrid energy storage isolation inverter system; The display interface is a human-computer interaction interface, which is used to read the working conditions of the hybrid energy storage isolation inverter system, including working status, alarm information, and parameter settings.

2. A hybrid energy storage isolation inverter system according to claim 1, characterized in that: The battery pack is connected to the DC bus and is charged and discharged according to the power on the DC bus, specifically: Discharging includes discharge mode and low power discharge mode, and charging includes charge mode and floating charge mode; Among them, discharge mode: as the load of the inverter circuit fluctuates, when the power delivered to the DC bus by the rectifier circuit and the DC conversion circuit connected to the photovoltaic module cannot meet the load, the battery pack enters the discharge mode; Low-power discharge mode: When the battery pack SOC is greater than or equal to the upper charge limit setting threshold, the output power of the rectifier circuit and the DC conversion circuit is controlled to be equal to 95% of the input power of the inverter circuit. The battery pack enters the low-power discharge mode, and the discharge power is 5% of the input power of the inverter circuit. Charging mode: read the allowable charging current of the battery pack in real time. When the power of the rectifier circuit and the DC conversion circuit connected to the photovoltaic module meets the inverter circuit load and has a margin, the power greater than the inverter circuit load is transmitted to the DC bus, and the battery pack enters the charging mode. The charging current is less than or equal to the allowable charging current of the battery pack. When the battery pack issues a prohibition charging command, charging stops; Floating charge mode: When the battery pack SOC is determined to be equal to the floating charge setting threshold, the output power of the rectifier circuit and the DC conversion circuit is controlled to be equal to the input power of the inverter circuit. The battery pack enters the floating charge mode and is in a micro-charge and micro-discharge state.

3. A hybrid energy storage isolation inverter system according to claim 1, characterized in that: The input end of the dual power switch is connected to the power grid and the output end of the generator through a connecting line, and the output end of the dual power switch is connected to the input end of the rectifier circuit through a connecting line; The output end of the photovoltaic module is connected to the input end of the DC conversion circuit through a connecting line; The EMS output terminal is connected to the display interface input terminal via a connecting line The output end of the inverter circuit is connected to the input end of the load through a connecting line; The battery pack is connected to the DC bus via a connecting wire; The output end of the rectifier circuit and the output end of the DC conversion circuit are both connected to the DC bus through a connecting line; The input end of the inverter circuit is connected to the DC bus through a connecting line; The generator, the DC conversion circuit, the dual power supply switch, the battery pack and the inverter circuit are connected to the EMS via a communication bus to realize the EMS information reading and control functions.

4. A control method for a hybrid energy storage isolation inverter system according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: Click Start on the display interface, and the hybrid energy storage isolation inverter system enters the startup state. The rectifier circuit, inverter circuit, and DC conversion circuit obtain the input source state and perform self-test, waiting for the EMS command to enter the corresponding working mode; Step 2: After the system enters the running state, the EMS controls the inverter circuit to start, the inverter circuit draws power from the DC bus, and the output power fluctuates with the load; Step 3: When the system is in operation, the EMS makes a judgment based on the battery pack SOC and dynamically adjusts the output power of the rectifier circuit and the DC conversion circuit; Step 4: When an abnormality occurs in the power grid, the rectifier circuit enters a two-phase or single-phase working mode, limits the power according to the input voltage, and controls the rectifier circuit to output the maximum power according to the current state of the power grid; Step 5: When the output power of the rectifier circuit and the DC conversion circuit cannot meet the input power of the inverter circuit, the battery pack supplements the power to support the inverter circuit, and the battery enters the discharge mode; Step 6: When the battery pack is discharged to an SOC less than or equal to the generator start setting threshold, the generator operation mode is entered, and the EMS reads the grid status in real time and switches the operation mode.

5. The control method of a hybrid energy storage isolation inverter system according to claim 4 is characterized in that: In step 1, the circuit includes a rectifier circuit, an inverter circuit, and a DC conversion circuit; The input source of the rectifier circuit is the power grid or generator, the input source of the DC conversion circuit is the photovoltaic module, and the input source of the inverter circuit is the DC bus; The self-test of the rectifier circuit, inverter circuit, and DC conversion circuit is as follows: the EMS reads the status of each circuit and the battery pack through the communication bus, detects the voltage of the input source, the power allowed to be output, and whether the circuit is faulty, and sends the detection information to the communication bus, which is judged and processed by the EMS. That is, the EMS reads from the communication bus, and each circuit waits for the EMS instruction to enter the corresponding working mode; When a serious fault occurs in each circuit, the fault circuit stops working; when a minor fault occurs, the circuit runs at a reduced load. The specific fault content is reported to the EMS through the communication bus, and the EMS displays the fault information on the display screen; If the battery pack has a serious fault, the system will be prohibited from working. If it has a minor fault, it will operate normally and report the specific fault content to the EMS through the communication bus. The EMS will display the fault information on the display screen. When there is no fault in the circuit, the EMS controls the startup and operation of each circuit through the communication bus; Among them, the status of the battery pack includes: SOC, temperature, voltage, current, allowed charge and discharge current, working status, and fault information; Among them, SOC is the state of charge of the battery pack, that is, the available state of the remaining power in the battery pack.

6. The control method of a hybrid energy storage isolation inverter system according to claim 4, characterized in that: In step 2, the inverter circuit draws power from the DC bus, and the output power fluctuates with the load, specifically: The output power of the inverter circuit is equal to the power required by the load. When the load exceeds the output capacity of the inverter circuit, the inverter circuit reports an overload fault and stops working.

7. The control method of a hybrid energy storage isolation inverter system according to claim 4, characterized in that: In step 3, when the system is in operation, the EMS makes a judgment based on the battery pack SOC and dynamically adjusts the output power of the rectifier circuit and the DC conversion circuit, specifically: When the battery pack SOC is greater than or equal to the floating charge setting threshold, the battery pack enters the floating charge mode. The EMS controls the output power of the rectifier circuit and the DC conversion circuit to be equal to the input power of the inverter circuit. The battery pack fluctuates in the micro-charge and micro-discharge state as the inverter power fluctuates. When the battery pack SOC is equal to the upper charge limit setting threshold, the battery pack enters the low-power discharge mode, controls the output power of the rectifier circuit and the DC conversion circuit to be equal to 95% of the input power of the inverter circuit, and the battery pack output power is 5% of the input power of the inverter circuit, until the battery pack SOC is discharged to equal to the floating charge setting threshold, and then enters the floating charge mode; When the battery pack SOC is equal to 100% or the battery pack issues a charge prohibition command, the battery pack enters the discharge mode, controls the rectifier circuit and the DC conversion circuit to shut down, and the battery pack alone supplies power to the inverter circuit until the battery pack SOC is discharged to equal the float charge setting threshold, then enters the float charge mode; When the battery pack SOC is less than the floating charge setting threshold + 5, the battery pack enters the charging mode, controlling the output power sum of the rectifier circuit and the DC conversion circuit to be greater than the inverter circuit input power, and the value greater than is less than or equal to the allowable charging power of the battery pack.

8. The control method of a hybrid energy storage isolation inverter system according to claim 4, characterized in that: In step 5, when the output power of the rectifier circuit and the DC conversion circuit cannot meet the input power of the inverter circuit, the battery pack supplements the power to support the operation of the inverter circuit. At this time, the battery enters the discharge mode, specifically: When the battery pack is discharged to a SOC less than or equal to the generator start setting threshold, it enters the generator working mode, and the EMS controls the dual power supply switch to switch from grid input to generator input. The EMS sends a start signal to the generator, and the generator will provide power to the rectifier circuit and output power to the DC bus for battery pack charging and inverter circuit input; When the battery pack is discharged to an SOC less than or equal to the discharge lower limit setting threshold, the EMS controls the inverter circuit to stop working, and the EMS controls the rectifier circuit and the DC conversion circuit to charge the battery pack first, until the battery pack is charged to an SOC greater than the discharge lower limit setting threshold + 5, the EMS controls the inverter circuit to start working.

9. The control method of a hybrid energy storage isolation inverter system according to claim 4, characterized in that: In step 6, when the battery pack is discharged to an SOC less than or equal to the generator start setting threshold, the generator operation mode is entered, and the EMS reads the grid status in real time and switches the operation mode, specifically: When it is identified that the number of stable input phases of the power grid is greater than or equal to 2 within a certain period of time, it switches to the power grid working mode, otherwise it continues to work in the generator mode; In generator mode, when the battery pack SOC is greater than or equal to the generator charging upper limit threshold, the generator stops working and judges the grid status. When the input phase number is greater than or equal to 1, the EMS controls the dual power supply switch to switch to grid input, uses the grid to support the inverter circuit, and the battery pack is used as a supplement. The battery pack SOC status is read and judged in real time, and the judgment of the discharge lower limit setting threshold continues.

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