A grid-connected system for electrical energy recovery

Abstract

The utility model belongs to the technical field of electric energy recovery, specifically relates to a kind of grid-connected system of electric energy recovery, including the engine, energy storage converter and energy storage discharge module that are electrically connected in turn, the energy storage discharge module is used to join into grid with electric energy;The energy storage discharge module includes energy storage energy management unit, discharge converter and energy storage unit, and the energy storage unit includes battery manager and battery pack that are electrically connected in turn, the energy storage energy management unit is separately connected with the battery manager and the discharge converter communication, the energy storage converter is electrically connected with the battery manager, and the output of discharge converter is connected grid.The utility model can solve the electric energy recovery problem in diesel generator aging test by optimizing grid-connected system structure, and help to improve energy utilization.

Description

Technical Field

[0001] This utility model belongs to the technical field of energy recovery, specifically relating to a grid-connected system for energy recovery. Background Technology

[0002] As a commonly used emergency and backup power source, diesel generators undergo aging tests during their production, maintenance, and performance testing. These tests are crucial for verifying their reliability and lifespan. During aging tests, diesel generators must operate continuously under different load conditions (such as idling, rated load, and overload), generating a significant amount of electrical energy.

[0003] Currently, the electrical energy generated during diesel generator aging tests is mostly consumed through energy-consuming devices such as water resistors and resistance boxes. This not only results in a serious waste of fuel energy (diesel generators have a power generation efficiency of about 30%-40%, and energy loss is significant), but also requires additional equipment to address heat dissipation issues, increasing testing costs.

[0004] In the process of realizing this utility model, the inventors discovered that the prior art has at least the following problems:

[0005] Existing diesel generators are affected by fluctuations in their speed and uneven fuel supply, resulting in high voltage fluctuation rate, poor frequency stability, and high harmonic content. Direct grid connection can easily cause impacts on the power grid, making it more difficult to recover energy. The inrush current at the moment of diesel generator start-up and the residual voltage during shutdown are difficult to recover effectively, further reducing energy utilization. Utility Model Content

[0006] The purpose of this invention is to provide a grid-connected system for energy recovery, addressing the shortcomings of existing technologies. By optimizing the grid-connected system structure, the problem of energy recovery during diesel generator aging tests can be solved, which helps to improve energy utilization efficiency.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A grid-connected system for energy recovery includes an engine, an energy storage converter, and an energy storage discharge module connected in sequence. The energy storage discharge module is used to connect electrical energy into the power grid. The energy storage discharge module includes an energy storage management unit, a discharge converter, and an energy storage unit. The energy storage unit includes a battery manager and a battery pack connected in sequence. The energy storage management unit is communicatively connected to the battery manager and the discharge converter, respectively. The energy storage converter is electrically connected to the battery manager, and the output terminal of the discharge converter is connected to the power grid.

[0009] In some possible implementations, an energy meter is installed at the output end of the engine, an anti-reverse current meter is installed at the power grid, and an energy storage meter is installed at the output end of the discharge converter. The energy meter, the anti-reverse current meter, and the energy storage meter are all connected to the energy storage management unit via communication lines.

[0010] In some possible implementations, the output of the engine is connected in parallel with multiple resistor boxes, and the output of the discharge converter is connected in parallel with multiple loads.

[0011] In some possible implementations, the energy storage converter is electrically connected to the discharge converter and the battery manager via DC lines, respectively, and the battery manager is electrically connected to the battery pack via DC lines.

[0012] In some possible implementations, the DC line is divided into a positive DC line and a negative DC line, and both the positive DC line and the negative DC line are connected in series with a circuit breaker.

[0013] In some possible implementations, the energy storage management unit is communicatively connected to the battery manager and the discharge converter via communication lines, and the battery manager is communicatively connected to the energy storage converter via a communication line.

[0014] In some possible implementations, the engine and the energy storage converter are connected by AC line power, and the output of the discharge converter is connected to the power grid by AC line power.

[0015] In some possible implementations, a protection device is provided between the battery manager and the battery pack. One end of the protection device is communicatively connected to the battery manager via a communication line, and the other end of the protection device is electrically connected to the battery pack via a DC line.

[0016] In some possible implementations, the engine is a diesel engine.

[0017] In some possible implementations, the battery pack is a lithium iron phosphate battery pack, and the battery pack is equipped with a liquid cooling heat sink.

[0018] One of the above technical solutions has the following beneficial effects:

[0019] This invention optimizes the grid-connected system structure and, considering the output characteristics of diesel generators, utilizes an energy storage converter in conjunction with an energy storage discharge module to recover electrical energy from the diesel engine. It features both off-grid and grid-connected capabilities, and is automatically controlled by an energy storage management unit without switching. This solves the problem of the energy storage system being unable to discharge to the grid while charging, improving the reliability of the testing system. Furthermore, the energy recovery via the energy storage converter allows for setting and controlling the diesel engine's output power, thus improving testing efficiency. The energy storage management unit communicates with both the energy storage converter and the discharge converter, enabling energy scheduling and allowing the energy storage system to simultaneously charge and discharge to the grid while the diesel generator is undergoing aging testing, thereby improving energy utilization and ensuring grid connection stability. Attached Figure Description

[0020] The features, advantages and technical effects of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings.

[0021] Figure 1 This is a circuit connection diagram of the present invention.

[0022] The reference numerals in the attached figures are explained as follows:

[0023] 1- Engine;

[0024] 2-Energy storage converter;

[0025] 3-Energy storage and discharge module;

[0026] 4-Energy Storage Management Unit;

[0027] 5-Discharge converter;

[0028] 61-Battery Manager; 62-Battery Pack; 63-Protection Device;

[0029] 7-Energy Table;

[0030] 8-Anti-backflow meter;

[0031] 9-Energy storage meter. Detailed Implementation

[0032] If certain terms are used in the specification and claims to refer to specific components, those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The term "comprising" as used throughout the specification and claims is an open-ended term and should be interpreted as "comprising but not limited to." "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error.

[0033] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be interpreted as indicating or implying relative importance.

[0034] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0035] The present invention will be further described in detail below with reference to the accompanying drawings, but this is not intended to limit the present invention.

[0036] Because the output power of existing diesel generators is affected by fluctuations in their speed and uneven fuel supply, they have characteristics such as high voltage fluctuation rate, poor frequency stability and high harmonic content. Direct grid connection can easily cause impact on the power grid, making it more difficult to recover energy and connect to the grid. The inrush current at the moment of diesel generator start-up and the residual voltage during shutdown are difficult to recover effectively, further reducing energy utilization.

[0037] like Figure 1As shown, the grid-connected power recovery system of this utility model includes an engine 1, an energy storage converter 2, and an energy storage discharge module 3 connected in sequence. The energy storage discharge module 3 is used to connect the power to the grid. The energy storage discharge module 3 includes an energy storage management unit 4, a discharge converter 5, and an energy storage unit. The energy storage unit includes a battery manager 61 and a battery pack 62 connected in sequence. The energy storage management unit 4 is communicatively connected to the battery manager 61 and the discharge converter 5, respectively. The energy storage converter 2 is electrically connected to the battery manager 61, and the output terminal of the discharge converter 5 is connected to the grid. This invention optimizes the grid-connected system structure and, considering the output characteristics of diesel generators, utilizes an energy storage converter 2 in conjunction with an energy storage discharge module 3 to recover electrical energy from the diesel engine. It possesses both off-grid and grid-connected capabilities, and is automatically controlled by an energy storage management unit 4 (EMS control unit), eliminating the need for switching. This solves the problem of the energy storage system being unable to discharge to the grid while charging, improving the reliability of the testing system. Furthermore, by recovering energy through the energy storage converter 2, the output power of the diesel engine can be set and controlled to a specific power level, contributing to improved testing efficiency. The energy storage management unit 4 (EMS control unit) is communicatively connected to the energy storage converter 2 and the discharge converter 5, enabling energy scheduling for both. This allows the energy storage system to simultaneously charge and discharge to the grid while the diesel generator is undergoing aging testing, improving energy utilization and ensuring grid connection stability.

[0038] It should be noted that: Engine 1 is a diesel engine, and the energy storage converter 2 (energy storage PCS) serves as the generator energy recovery and charging module. Its output power can be set in the system, supporting different power outputs from 0kW to 200kW, or it can be set to a constant power 200kW output mode. When the energy storage is fully charged and there is no load to absorb it, a resistive load can be started to continue the engine aging test. It is compatible with diesel generators of different power (50kW-500kW) and can meet different test standards through parameter configuration, demonstrating strong versatility. Energy storage converter 2 is a 250kW wideband AC / DC converter with an input of 400VAC and an output of 768VDC, capable of charging battery pack 62. The energy storage unit is designed as a 522kWh lithium iron phosphate battery pack (260S2P 3.2V), with a SOC operating range of 8%-92%. The energy storage discharge module 3 also features a 250kW grid-connected inverter with an adjustable power factor of 0.9-1.0 and an output voltage of 400VAC.

[0039] Taking a 200kW diesel generator as an example, with a rated voltage of 380VAC, a rated speed of 1500r / min, and an aging test cycle of 200 hours, the load conditions during the aging test of the diesel generator include, but are not limited to, idling, rated load step, and recovery during startup.

[0040] 1) Idle speed stage (20% load, 40kW):

[0041] The generator output is P1 = 45kW (including losses), the load is P2 = 40kW, and ΔP = 5kW.

[0042] The charging module is charged at a constant current of 5kW, and the three energy storage discharge modules are connected to the grid at the grid allowable value of 5kW, maintaining a state of charge (SOC) of 8%.

[0043] 2) Rated load step change (100% load, 200kW):

[0044] When the load suddenly increases from 40kW to 200kW (50ms step), the control unit predicts ΔP_pre = 15kW 30ms in advance, adjusts P_charge = 0 and P_discharge = 15kW to buffer the power surge. After stabilization, P1 = 210kW, P2 = 200kW, ΔP = 10kW, P_charge = 10kW, and P_discharge = 10kW.

[0045] 3) Recovery during the startup phase:

[0046] Within 0-15 seconds, the generator voltage rises from 80V to 380V, the charging module is activated in low-voltage mode, the energy storage converter 2 (PCS charging module) charges the energy storage battery, the PCS outputs 768V DC to charge the battery, recovering approximately 5kWh of energy, and the SOC rises from 8% to 11%.

[0047] 4) Implementation Results

[0048] The energy storage discharge efficiency is calculated as 0.87.

[0049] The cumulative energy recovered during the 200-hour test was 200kW × 200h × 0.87 = 34800kWh. The recovered energy was simultaneously fed into the grid and consumed by the grid-connected load. If the load consumption was insufficient, the energy storage system would store the energy and supply it to the load when the generator was no longer undergoing aging tests. The recovery rate reached 87%. The grid-connected current THD was 2.3%, and the voltage fluctuation rate was ±1.8%, both of which met the grid access standards.

[0050] This utility model targets the output characteristics of diesel generators and achieves effective recovery of high-fluctuation and high-harmonic electrical energy through the combination of energy storage converter 2 and energy storage discharge module 3. The energy recovery and utilization rate is increased to more than 85%, while the recovery and utilization rate of existing structures is less than 5%, which helps to reduce diesel consumption costs.

[0051] This utility model adopts an energy storage management unit 4 (EMS control unit) to realize dynamic energy distribution and early response control, which solves the grid connection problem caused by sudden load changes and speed fluctuations of diesel generators. The grid connection current harmonic distortion rate is ≤3%, and the voltage or frequency fluctuation rate is controlled within the allowable range of the power grid.

[0052] This invention covers the entire testing phase, including startup, steady state, and shutdown, and recovers startup residual voltage and coasting electrical energy that cannot be utilized by existing structures, thereby increasing energy recovery by an additional 10%-15%.

[0053] In the grid-connected system for energy recovery according to this utility model, an energy meter 7 is installed at the output end of the engine 1, an anti-reverse current meter 8 is installed on the power grid, and an energy storage meter 9 is installed at the output end of the discharge converter 5. The energy meter 7, the anti-reverse current meter 8, and the energy storage meter 9 are all connected to the energy storage management unit 4 via communication lines, which facilitates the energy storage management unit 4 (EMS control unit) to perform energy dispatching on the energy storage converter 2 (energy storage PCS) and the discharge converter 5 (energy storage discharge PCS). This enables the energy storage system to charge and discharge to the grid simultaneously while the diesel generator is undergoing aging testing, thereby improving energy utilization and ensuring grid connection stability. The energy meter 9, energy meter 7, anti-reverse current meter 8, and energy storage meter 9 are all commercially available models.

[0054] In the grid-connected energy recovery system according to this utility model, multiple resistor boxes are connected in parallel to the output terminal of the engine 1. This means that if the diesel generator generates excessive electrical energy during aging tests, it can be consumed through the resistor boxes. Multiple loads are connected in parallel to the output terminal of the discharge converter 5, meaning the electrical energy is absorbed by the grid-connected loads. If the load absorption is insufficient, the energy storage system stores the electrical energy and supplies it to the loads when the generator is not undergoing aging tests, thus improving the recovery rate. The number of resistor boxes and loads connected to the circuit can be controlled by switches.

[0055] In the grid-connected energy recovery system according to this utility model, the energy storage converter 2 is electrically connected to the discharge converter 5 and the battery manager 61 (BMS) via DC lines. The battery manager 61 is electrically connected to the battery pack 62 via DC lines. The DC lines are divided into positive DC lines and negative DC lines. Both the positive and negative DC lines are connected in series with circuit breakers to provide overload protection. When the circuit current exceeds the rated value, the power supply is cut off to prevent equipment damage. They also provide short-circuit protection by quickly disconnecting and eliminating short-circuit faults to avoid system collapse.

[0056] In the grid-connected system for energy recovery according to this utility model, the energy storage management unit 4 is connected to the battery manager 61 and the discharge converter 5 via communication lines, and the battery manager 61 is connected to the energy storage converter 2 via communication lines.

[0057] In the grid-connected system for energy recovery according to this utility model, the engine 1 and the energy storage converter 2 are connected by AC line to realize the recovery of electrical energy generated by the engine 1, and the output terminal of the discharge converter 5 is connected to the power grid by AC line to realize the integration of electrical energy into the power grid.

[0058] In the grid-connected energy recovery system according to this utility model, a protection device 63 is provided between the battery manager 61 and the battery pack 62. One end of the protection device 63 is communicatively connected to the battery manager 61 via a communication line, and the other end of the protection device 63 is electrically connected to the battery pack 62 via a DC line. Specifically, the protection device 63 can ensure battery safety and extend its service life. In other embodiments, the protection device 63 can also perform voltage protection, current protection, temperature control, and equalization management.

[0059] In the grid-connected system for energy recovery according to this utility model, a liquid-cooled heat sink is provided inside the battery pack 62. Specifically, the flow rate of the liquid coolant can be designed to be 20L / min, which helps to improve the heat dissipation effect of the battery pack 62 and extend the service life of the battery pack 62.

[0060] The working principle of this utility model is as follows:

[0061] This invention optimizes the grid-connected system structure and, considering the output characteristics of diesel generators, utilizes an energy storage converter 2 in conjunction with an energy storage discharge module 3 to recover electrical energy from the diesel engine. It possesses both off-grid and grid-connected capabilities, and is automatically controlled by an energy storage management unit 4 (EMS control unit), eliminating the need for switching. This solves the problem of the energy storage system being unable to discharge to the grid while charging, improving the reliability of the testing system. Furthermore, by recovering energy through the energy storage converter 2, the output power of the diesel engine can be set and controlled to a specific power level, contributing to improved testing efficiency. The energy storage management unit 4 communicates with the energy storage converter 2 and the discharge converter 5, enabling energy scheduling for both. This allows the energy storage system to simultaneously charge and discharge to the grid while the diesel generator is undergoing aging testing, improving energy utilization and ensuring grid connection stability.

[0062] Based on the disclosure and teachings of the above specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, this utility model is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on this utility model are within the protection scope of this utility model. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on this utility model.

Claims

1. A grid-connected system for electrical energy recovery, characterized in that, It includes an engine (1), an energy storage converter (2) and an energy storage discharge module (3) connected in sequence, wherein the energy storage discharge module (3) is used to connect electrical energy into the power grid; The energy storage discharge module (3) includes an energy storage management unit (4), a discharge converter (5), and an energy storage unit. The energy storage unit includes a battery manager (61) and a battery pack (62) connected in sequence. The energy storage management unit (4) is communicatively connected to the battery manager (61) and the discharge converter (5) respectively. The energy storage converter (2) is electrically connected to the battery manager (61). The output terminal of the discharge converter (5) is connected to the power grid.

2. A grid-connected system for electrical energy recovery as claimed in claim 1, wherein: An energy meter (7) is installed at the output end of the engine (1), an anti-reverse flow meter (8) is installed in the power grid, and an energy storage meter (9) is installed at the output end of the discharge converter (5). The energy meter (7), the anti-reverse flow meter (8), and the energy storage meter (9) are all connected to the energy storage energy management unit (4) via a communication line.

3. A grid-connected system for electrical energy recovery as claimed in claim 1, wherein: The output terminal of the engine (1) is connected in parallel with multiple resistor boxes, and the output terminal of the discharge converter (5) is connected in parallel with multiple loads.

4. The grid-connected system for energy recovery as described in claim 1, characterized in that: The energy storage converter (2) is electrically connected to the discharge converter (5) and the battery manager (61) via DC lines, and the battery manager (61) is electrically connected to the battery pack (62) via DC lines.

5. A grid-connected system for electrical energy recovery as claimed in claim 4, wherein: The DC line is divided into a positive DC line and a negative DC line, and both the positive DC line and the negative DC line are connected in series with a circuit breaker.

6. The grid-connected system for energy recovery as described in claim 1, characterized in that: The energy storage management unit (4) is connected to the battery manager (61) and the discharge converter (5) via communication lines, and the battery manager (61) is connected to the energy storage converter (2) via communication lines.

7. The grid-connected system for energy recovery as described in claim 1, characterized in that: The engine (1) and the energy storage converter (2) are connected by AC line, and the output terminal of the discharge converter (5) is connected to the power grid by AC line.

8. A grid-connected system for electrical energy recovery as claimed in claim 1, wherein: A protection device (63) is provided between the battery manager (61) and the battery pack (62). One end of the protection device (63) is connected to the battery manager (61) via a communication line, and the other end of the protection device (63) is connected to the battery pack (62) via a DC line.

9. The grid-connected system for energy recovery as described in claim 1, characterized in that: The engine (1) is a diesel engine.

10. The grid-connected system for energy recovery as described in claim 1, characterized in that: The battery pack (62) is a lithium iron phosphate battery pack, and a liquid cooling heat sink is provided inside the battery pack (62).

Images