Industrial and commercial energy storage grid-connected and off-grid system

Abstract

The invention belongs to the technical field of energy storage electric control, and particularly relates to an industrial and commercial energy storage grid-connected and off-grid system, which comprises a photovoltaic module, an energy management module and an intelligent change-over switch, and is characterized in that the photovoltaic module is connected to an off-grid load and a grid-connected load through a photovoltaic inverter, and the energy management module is connected to the photovoltaic inverter through an energy storage converter; the off-grid load and the grid-connected load are respectively connected to the energy storage converter, the grid-connected load is connected to the energy management module, and the intelligent change-over switch is respectively connected to the photovoltaic inverter and the energy storage converter. According to the invention, the problem of grid-connected and off-grid switching impact can be solved, and the operation safety of the load is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage electronic control, and in particular relates to an industrial and commercial energy storage and off-grid system. Background Art

[0002] The on-grid and off-grid system is a photovoltaic power generation system that combines on-grid and off-grid functions. It can be connected to the grid when the grid is operating normally to provide power to the load. At present, the difficulty of industrial and commercial energy storage on-grid and off-grid switching technology is that the switch state switching and control strategy switching must be completed within microseconds. The response speed of traditional mechanical switches (milliseconds) is difficult to meet and cannot meet the requirements of uninterruptible power supply. When the switching moment impact occurs, oscillation or system crash may occur. Therefore, the present invention aims to improve the operational stability of industrial and commercial energy storage on-grid and off-grid systems. Summary of the Invention

[0003] The purpose of the present invention is to provide an industrial and commercial energy storage on-grid and off-grid system to address the shortcomings of the existing technology and solve the problem of on-grid and off-grid switching impact.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] An industrial and commercial energy storage and off-grid system includes a photovoltaic module connected to an off-grid load and a grid-connected load via a photovoltaic inverter;

[0006] An energy management module is connected to the photovoltaic inverter via an energy storage converter, the off-grid load and the grid-connected load are respectively connected to the energy storage converter, and the grid-connected load is connected to the energy management module;

[0007] The intelligent transfer switch is connected to the photovoltaic inverter and the energy storage converter respectively.

[0008] Furthermore, the on-grid and off-grid system further includes a first metering unit, and the energy management module is connected to the three-phase mains power unit through the first metering unit.

[0009] Furthermore, the on-grid and off-grid system further includes a second metering unit, and the energy storage converter is connected to the energy management module via the second metering unit.

[0010] Furthermore, the grid-connected and off-grid system further includes a closing and opening control unit, and the energy management module is respectively connected to the grid-connected load, the photovoltaic inverter and the energy storage converter through the closing and opening control unit.

[0011] Furthermore, the grid-connected and off-grid system also includes a main control circuit breaker and an auxiliary control circuit breaker, the intelligent transfer switch, the grid-connected load, the energy storage converter and the energy management module are respectively connected to the main control circuit breaker, and the intelligent transfer switch, the grid-connected load and the energy management module are respectively connected to the auxiliary control circuit breaker.

[0012] Furthermore, the on-grid and off-grid system further includes a battery pack, and the energy storage converter and the energy management module are respectively connected to the battery pack.

[0013] Furthermore, the energy storage converter includes a grid-connected mode unit and an off-grid mode unit, the intelligent conversion switch, the energy management module and the battery pack are respectively connected to the grid-connected mode unit, the energy conversion switch, the energy management module and the battery pack are respectively connected to the off-grid mode unit, and the energy storage converter can realize bidirectional energy conversion between AC and DC, realizing bidirectional current conversion or bidirectional energy storage inversion.

[0014] Furthermore, the intelligent transfer switch includes a first conversion unit and a second conversion unit, the grid-connected mode unit and the grid-connected load are respectively connected to the first conversion unit, and the off-grid mode unit and the off-grid load are respectively connected to the second conversion unit.

[0015] Furthermore, the first conversion unit has a normal power circuit switch and a backup power circuit switch.

[0016] Furthermore, the second conversion unit has a normal power circuit conversion switch and a backup power circuit conversion switch.

[0017] Furthermore, the grid-connected and off-grid system further includes a voltage judgment unit, and the off-grid load and the grid-connected load are respectively connected to the voltage judgment unit.

[0018] Furthermore, the photovoltaic inverter is an MPPT inverter capable of converting direct current into alternating current, and current transformers are connected between the off-grid load and the grid-connected load and the photovoltaic inverter, respectively.

[0019] The beneficial effects of the present invention are: 1) the present invention connects an intelligent transfer switch between the photovoltaic inverter and the energy storage converter, which solves the problem of grid-connected and off-grid switching impact, can achieve mutual coordination between grid-connected and off-grid, and makes the system more stable; 2) the present invention can operate normally during a power outage in the power grid, can meet the requirements of uninterruptible power supply, and ensure the normal use and operation safety of the load. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a block diagram of the components of the present invention.

[0021] Figure 2 Schematic diagram of the circuit of the present invention. DETAILED DESCRIPTION

[0022] If certain words are used in the specification and claims to refer to specific components, those skilled in the art should understand that manufacturers may use different terms to refer to the same component. This specification and claims do not use differences in name as a way to distinguish components, but rather use differences in the functions of the components as the criteria for distinction. For example, the term "including" mentioned throughout the specification and claims is an open-ended term and should be interpreted as "including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve technical problems within a certain error range and basically achieve technical effects.

[0023] The inventors discovered that existing on-grid and off-grid systems operate poorly and are unable to adapt to the operational demands of various loads. Therefore, they proposed a new hybrid on-grid and off-grid application circuit and control system for industrial and commercial energy storage. This circuit and control system addresses peak-valley arbitrage, allowing businesses to reduce electricity costs through "valley charging and peak discharging." It also addresses backup power needs, allowing users with high reliability requirements, such as data centers and hospitals, to mitigate the risk of power outages through energy storage. It also addresses green power consumption needs and, combined with distributed photovoltaics, increases self-generation and self-consumption rates.

[0024] The following is combined with Figures 1-2 The present invention is further described in detail with reference to the accompanying drawings and specific examples, but is not intended to limit the present invention.

[0025] An industrial and commercial energy storage and off-grid system includes a photovoltaic module, an energy management module and an intelligent transfer switch. The photovoltaic module is connected to an off-grid load and a grid-connected load through a photovoltaic inverter. The energy management module is connected to the photovoltaic inverter through an energy storage converter. The off-grid load and the grid-connected load are respectively connected to the energy storage converter. The grid-connected load is connected to the energy management module. The intelligent transfer switch is respectively connected to the photovoltaic inverter and the energy storage converter.

[0026] Among them, the on-grid and off-grid system also includes a first metering unit, a second metering unit and a battery pack. The energy management module is connected to the three-phase mains unit through the first metering unit. The three-phase mains unit is a 380V power grid. The energy storage converter is connected to the energy management module through the second metering unit. The energy storage converter and the energy management module are respectively connected to the battery pack.

[0027] In order to better cope with power outages in the power grid, the grid-connected and off-grid system also includes a closing and opening control unit. The energy management module is connected to the grid-connected load, photovoltaic inverter and energy storage converter respectively through the closing and opening control unit.

[0028] Among them, the energy storage converter includes a grid-connected mode unit and an off-grid mode unit. The intelligent conversion switch, energy management module and battery pack are respectively connected to the grid-connected mode unit, and the energy conversion switch, energy management module and battery pack are respectively connected to the off-grid mode unit. The energy storage converter can realize bidirectional energy conversion between AC and DC, and realize bidirectional current conversion or bidirectional energy storage inversion.

[0029] In addition, the intelligent transfer switch includes a first conversion unit and a second conversion unit, the grid-connected mode unit and the grid-connected load are respectively connected to the first conversion unit, the first conversion unit has a normal power circuit switch and a backup power circuit switch, the off-grid mode unit and the off-grid load are respectively connected to the second conversion unit, the second conversion unit has a normal power circuit switch and a backup power circuit switch.

[0030] In addition, the on-grid and off-grid system also includes a main control circuit breaker K13 and an auxiliary control circuit breaker K2. The intelligent transfer switch, grid-connected load, energy storage converter and energy management module are respectively connected to the main control circuit breaker K13. The main control circuit breaker K13 is used when the grid-connected load is off-grid. The intelligent transfer switch, grid-connected load and energy management module are respectively connected to the auxiliary control circuit breaker K2. The auxiliary control circuit breaker K2 is used when the grid-connected load is connected to the grid.

[0031] The specific control circuit connections in the on-grid and off-grid hybrid system are as follows:

[0032] 1. The positive and negative outputs of the battery pack are connected to the grid-connected mode unit PCS1 through the circuit breaker K12. The circuit breaker K12 realizes electrical connection and isolation with the DC side of the grid-connected mode unit PCS1.

[0033] Connected to the off-grid mode unit PCS2 through the circuit breaker K11, the circuit breaker K11 realizes electrical connection and isolation with the DC side of the off-grid mode unit PCS2;

[0034] The grid-connected mode unit PCS1 and the off-grid mode unit PCS2 share a battery pack, which can be charged by the grid-connected mode unit PCS1 to prevent the off-grid mode unit PCS2 from draining the battery pack and causing a power outage. Each PCS is a bidirectional converter. The grid-connected mode unit PCS1 can charge or discharge the battery pack during peak and off-peak periods. The off-grid mode unit PCS2 can supply power to off-grid loads and charge the battery pack when sufficient photovoltaic energy is available.

[0035] 2. The AC output of the grid-connected mode unit PCS1 is connected to the first conversion unit through the circuit breaker K6. The first conversion unit is an integrated automatic transfer switch. The circuit breaker K6 realizes the electrical connection and isolation between the grid-connected mode unit PCS1 and the power grid;

[0036] The AC output of the off-grid mode unit PCS2 is connected to the load through the circuit breaker K7. The circuit breaker K7 realizes the electrical connection and isolation between the AC output of the off-grid mode unit PCS2 and the load.

[0037] The common power circuit switch of the first conversion unit is connected to the grid-connected circuit breaker K1, and the backup power circuit switch of the first conversion unit is connected to the circuit breaker K7, the common power circuit switch of the second conversion unit, and the circuit breaker K9 respectively;

[0038] The function of the first conversion unit is to automatically disconnect the switch of the common power circuit and close the switch of the backup power circuit when the power grid is cut off. When the power grid is restored, it automatically switches from the backup power to the common power circuit, realizing automatic switching between grid connection and off-grid connection.

[0039] Circuit breaker K1 is the main circuit breaker at the grid connection point, which realizes the electrical connection and isolation between the grid and all loads;

[0040] The second conversion unit is an integrated automatic transfer switch. When the off-grid mode unit PCS2 fails or the battery pack loses power and disconnects the AC output, the second conversion unit automatically disconnects the normal power circuit transfer switch and simultaneously closes the backup power circuit transfer switch, realizing automatic switching between off-grid power supply and grid-connected power supply to ensure power supply to important loads.

[0041] Circuit breaker K9 can realize electrical connection and isolation between photovoltaic output and load;

[0042] 3. The off-grid load is connected to the second conversion unit through the circuit breaker K8. The circuit breaker K8 realizes the electrical connection and isolation between the power supply side and the load;

[0043] 4. The PV inverter MPPT is connected to the PV panels through circuit breaker K10 and to the load through circuit breaker K9. The PV inverter's AC output supplies power to the off-grid load. If the off-grid load cannot fully consume the power, the battery pack can be charged through the off-grid mode unit PCS2.

[0044] 5. Auxiliary control circuit breaker K2 is the main circuit breaker for grid-connected loads, and main control circuit breaker K13 is the main circuit breaker for off-grid use. The grid-connected load is decomposed into several branches based on the power capacity of the off-grid mode unit PCS2, and each branch is isolated by a circuit breaker. K2 and K13 are mutually exclusive. When K2 is closed, K13 is open, and when K13 is closed, K2 is open. The purpose is to close K13 when the grid-connected load is used off-grid. Without K2 isolation, the common power circuit of the first conversion unit will be energized, automatically restoring the common power circuit, and then disconnecting the off-grid backup power circuit, causing the switch to toggle repeatedly.

[0045] 6. The EMS energy management module communicates with the battery pack, grid-connected mode unit PCS1, off-grid mode unit PCS2, the first metering unit, and the second metering unit through the COM port to achieve communication interaction; the EMS energy management module is electrically connected with K1, K2, K3, K4, K5, K9, and K13 through the DO port to achieve automatic control of opening and closing in the system.

[0046] The specific implementation of the control circuit of the above-mentioned on-grid and off-grid hybrid system is as follows:

[0047] Grid-connected mode:

[0048] 1. The EMS energy management module detects that the grid voltage is normal through the first metering unit, controls K1, K2, K3, K4, and K5 to close, and K13 to open. At this time, the grid-connected load is working normally, and the first conversion unit is in the state of connecting to the common power circuit;

[0049] 2. Manually close K6 and K12, and the grid-connected mode unit PCS1 is connected to the grid. At this time, PCS1 can charge or discharge according to the EMS off-peak scheduling strategy. The EMS energy management module uses the current collected by the first metering unit to determine the current load in real time and adjust the charge and discharge power of PCS1 in real time to ensure that the energy storage charging does not exceed the design load of the total distribution. When discharging, the energy storage is only used by the load and does not flow back to the grid;

[0050] 3. Manually close K11, K7, and K8. The off-grid mode unit PCS2 outputs power, the second conversion unit is in the state of connecting to the common power circuit, and the off-grid load works normally. At this time, PCS2 acts as an uninterruptible power supply to achieve uninterrupted power supply to the load;

[0051] 4. Manually close K10 to connect to the PV module. When the EMS energy management module determines that the off-grid mode unit PCS2 is outputting normally, it controls K9 to close. At this time, the PV inverter MPPT is connected to the off-grid load. If the PV power is less than the load, the PV and energy storage will supply power to the load at the same time. If the PV power is 0, the load will be supplied by the energy storage. If the PV power is greater than the load, the PV module will supply power to the load and charge the energy storage at the same time. When the EMS energy management module determines that the off-grid mode unit PCS2 has a fault, it controls K9 to disconnect to prevent the PV module output from affecting the second conversion unit from switching to the backup power supply.

[0052] Off-grid mode:

[0053] 1. When the power grid is out of power, the first conversion unit automatically switches to the backup power supply circuit. At this time, the grid-connected mode unit PCS1 follows the off-grid mode unit PCS2 to adjust the phase and frequency. The EMS energy management module obtains the current load through the current collection and calculation of the off-grid load by the second metering unit, and then sends the dispatching power to the grid-connected mode unit PCS1. At this time, the off-grid load is mainly powered by the grid-connected mode unit PCS1, and the off-grid mode unit PCS2 reserves capacity for the grid-connected load to prepare for off-grid startup;

[0054] 2. When the EMS energy management module detects a power outage in the grid through the first metering unit, it controls K1, K2, K3, K4, and K5 to open. When the grid-connected mode unit PCS1 starts to supply power to the off-grid load, the EMS energy management module controls K13 to close, and the first branch of the grid-connected load K3 to close. At this time, the first branch load is supplied by the off-grid mode unit PCS2. The EMS energy management module adjusts the dispatching power of the grid-connected mode unit PCS1 in real time based on the current load calculated by the second metering unit. At this time, the off-grid load and the first branch of the grid-connected load are mainly supplied by the grid-connected load. Mode unit PCS1 supplies power, and off-grid mode unit PCS2 reserves capacity for off-grid startup of grid-connected loads in other branches. Similarly, grid-connected loads in other branches are closed in sequence. This meets the demand for off-grid use of grid-connected loads. After the loads are decomposed through branches, excessive startup impact is avoided, and the PCS configuration does not require excessive redundancy. In addition, the PCS does not need to switch between on-grid and off-grid modes. The grid-connected PCS only performs grid-connected scheduling, and the off-grid PCS is fixed in off-grid mode. The system stability can be improved by the mutual cooperation of the grid-connected PCS and the off-grid PCS.

[0055] Off-grid restoration and grid connection:

[0056] When the EMS energy management module detects power coming from the grid through the first metering unit, it controls K13 to open and K1 and K2 to close. At this time, the grid-connected load is switched to the grid for power supply, and the off-grid load continues to be powered by the off-grid mode unit PCS2. The first conversion unit automatically switches from the backup power supply back to the normal power supply circuit. At this time, the grid-connected mode unit PCS1 follows the grid to adjust the phase and frequency to achieve switching from off-grid to grid-connected.

[0057] The hybrid on-grid and off-grid application circuit and control method of this invention effectively addresses the impact of on-grid and off-grid switching. The PCS capacity configuration does not require excessive redundancy, and a standard modular PCS can be used, resulting in low cost. Furthermore, this solution independently connects the user's critical loads and other loads. The critical loads are connected to an independent off-grid mode PCS, while the other loads are connected to the grid-connected PCS. This allows the critical loads to meet the requirements of uninterruptible power supply, while other loads can also be used off-grid. Furthermore, the grid-connected mode can meet peak-valley arbitrage needs and can also be connected to distributed photovoltaics to meet the needs of green power consumption.

[0058] Based on the disclosure and teachings of the above description, those skilled in the art will be able to make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the above specific embodiments. Any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention fall within the scope of protection of the present invention. In addition, although certain specific terms are used in this description, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. An industrial and commercial energy storage and off-grid system, characterized in that: include: Photovoltaic modules are connected to off-grid loads and grid-connected loads through photovoltaic inverters; An energy management module is connected to the photovoltaic inverter via an energy storage converter, the off-grid load and the grid-connected load are respectively connected to the energy storage converter, and the grid-connected load is connected to the energy management module; The intelligent transfer switch is connected to the photovoltaic inverter and the energy storage converter respectively.

2. The industrial and commercial energy storage and off-grid system according to claim 1, characterized in that: It also includes a first metering unit, and the energy management module is connected to the three-phase mains power unit through the first metering unit.

3. The industrial and commercial energy storage and off-grid system according to claim 1, characterized in that: It also includes a second metering unit, and the energy storage converter is connected to the energy management module through the second metering unit.

4. The industrial and commercial energy storage and off-grid system according to claim 1, characterized in that: It also includes a closing and opening control unit, and the energy management module is connected to the grid-connected load, the photovoltaic inverter and the energy storage converter respectively through the closing and opening control unit.

5. The industrial and commercial energy storage and off-grid system according to claim 1, characterized in that: It also includes a main control circuit breaker and an auxiliary control circuit breaker. The intelligent transfer switch, the grid-connected load, the energy storage converter and the energy management module are respectively connected to the main control circuit breaker, and the intelligent transfer switch, the grid-connected load and the energy management module are respectively connected to the auxiliary control circuit breaker.

6. The industrial and commercial energy storage and off-grid system according to any one of claims 1 to 5, characterized in that: It also includes a battery pack, and the energy storage converter and the energy management module are respectively connected to the battery pack.

7. The industrial and commercial energy storage and off-grid system according to claim 6, characterized in that: The energy storage converter includes a grid-connected mode unit and an off-grid mode unit. The intelligent transfer switch, the energy management module and the battery pack are respectively connected to the grid-connected mode unit. The energy transfer switch, the energy management module and the battery pack are respectively connected to the off-grid mode unit.

8. The industrial and commercial energy storage and off-grid system according to claim 7, characterized in that: The intelligent transfer switch includes a first conversion unit and a second conversion unit. The grid-connected mode unit and the grid-connected load are respectively connected to the first conversion unit, and the off-grid mode unit and the off-grid load are respectively connected to the second conversion unit.

9. The industrial and commercial energy storage and off-grid system according to claim 8, characterized in that: The first conversion unit has a common power circuit switch and a backup power circuit switch.

10. The industrial and commercial energy storage and off-grid system according to claim 8, characterized in that: The second conversion unit has a common power circuit conversion switch and a standby power circuit conversion switch.

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