Primary circuit of fuel cell multi-unit parallel power generation system

Abstract

The utility model discloses a primary circuit of a fuel cell multi-unit parallel power generation system, which comprises a multi-split boosting transformer and a plurality of power generation modules, each power generation module comprises a plurality of power generation units, a convergence device and a direct current-alternating current converter, and each power generation unit comprises a fuel cell stack and a direct current-direct current converter; the output of the fuel cell stack is converted by the direct current-direct current converter and then is connected to the confluence device through a cable, the output of the confluence device is connected to the direct current-alternating current converter through a cable, and the direct current-alternating current converter converts direct current into alternating current and is connected to the multi-split boosting transformer; and the multi-split boosting transformer boosts the voltage and outputs the boosted voltage to a power grid. According to the utility model, electrical isolation between the power generation units is realized, and insulation resistance reduction caused by too many galvanic piles connected in parallel is prevented.

Description

Technical Field

[0001] The utility model relates to the technical field of fuel cells and the field of distributed power generation, and in particular to a primary circuit of a fuel cell multi-unit parallel power generation system. Background Art

[0002] A fuel cell is a device that converts the chemical energy in hydrogen fuel into electrical energy through an electrochemical reaction. Due to its advantages such as high energy conversion rate, clean and pollution-free reaction products and strong adaptability, fuel cell systems have begun to be promoted and applied in the field of distributed power generation.

[0003] Due to the power limitation of fuel cell stacks, when designing a high-power fuel cell power station with a power of more than 2 megawatts, multiple stacks can only be connected in parallel. However, the parallel connection of stacks reduces the insulation resistance of the system. For IT systems, the reduced insulation resistance cannot meet the electrical safety requirements.

[0004] In order to improve the insulation resistance of the system, the battery stack can be divided into multiple power generation units, and each power generation unit can be equipped with an isolation transformer to achieve electrical isolation, thereby improving the overall insulation resistance of the system. However, adding an isolation transformer will reduce the efficiency of the system and increase the system cost. Figure 1 shown.

[0005] In summary, the primary circuit design of a high-power fuel cell power generation system needs to meet the insulation resistance requirements of the system while improving the power generation efficiency and economy of the system as much as possible. Utility Model Content

[0006] In order to solve the following technical problems:

[0007] 1) Low efficiency. The efficiency of the current mainstream isolation transformer is about 99%. The isolation transformer added to improve the insulation resistance adds electrical equipment to the primary circuit, reducing the system efficiency.

[0008] 2) Low insulation resistance. The circuit with multiple battery stacks in parallel results in low overall insulation resistance of the system and high electrical safety risk.

[0009] 3) High cost. Isolation transformers are expensive. The greater the total power of the system, the more isolation transformers are required, and the higher the overall cost of the system.

[0010] The utility model provides a primary circuit of a fuel cell multi-unit parallel power generation system, which realizes electrical isolation between power generation units and prevents a reduction in insulation resistance due to too many parallel-connected fuel cell stacks.

[0011] The technical solution adopted by the utility model is as follows:

[0012] A primary circuit of a fuel cell multi-unit parallel power generation system comprises a multi-split step-up transformer and a plurality of power generation modules, wherein the power generation modules comprise a plurality of power generation units, a confluence device and a DC-AC converter, and the power generation units comprise a fuel cell stack and a DC-DC converter; the output of the fuel cell stack is converted by a DC-DC converter and then connected to the confluence device via a cable, the output of the confluence device is connected to the DC-AC converter via a cable, the DC-AC converter converts DC power into AC power and is connected to a multi-split step-up transformer, and the multi-split step-up transformer steps up the voltage and then outputs it to a power grid.

[0013] Furthermore, the output end of the fuel cell stack is connected to the input end of a DC-DC converter, and the DC-DC converter increases or decreases the stack voltage to a voltage required by the input end of the DC-AC converter.

[0014] Furthermore, the output ends of the plurality of DC-DC converters are connected to the input end of the merging device to realize parallel connection of the power generation units.

[0015] Furthermore, the number of the power generation units connected in parallel depends on the insulation resistance of the power generation units. The lower the insulation resistance, the greater the number of the power generation units connected in parallel; and the higher the insulation resistance, the smaller the number of the power generation units connected in parallel.

[0016] Furthermore, the merging device is provided with a circuit breaker for short-circuit protection.

[0017] Furthermore, the output end of the merging device is connected to the input end of a DC-AC converter, and the DC-AC converter converts the DC power output by the merging device into low-voltage three-phase AC power.

[0018] Furthermore, a plurality of windings are provided on the low voltage side of the multi-split step-up transformer, and each winding is electrically isolated from each other.

[0019] Furthermore, only one winding is provided on the high voltage side of the multi-split step-up transformer.

[0020] Furthermore, the multi-split step-up transformer realizes electrical isolation between multiple power generation units.

[0021] Furthermore, the multi-split step-up transformer can increase the AC voltage to a voltage level of 10KV, 35KV or higher.

[0022] The beneficial effects of the utility model are:

[0023] 1) The electrical isolation between power generation units is realized to prevent the reduction of insulation resistance due to too many parallel battery stacks;

[0024] 2) The entire circuit has no isolation transformer, only a first-stage step-up transformer, which improves the power conversion efficiency and thus improves the power generation efficiency of the entire system.

[0025] 3) The entire system has only one multi-split transformer and no isolation transformer, which significantly reduces costs and improves the economic benefits of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the primary circuit schematic of a conventional high-power fuel cell system.

[0027] Figure 2 It is a primary circuit principle diagram of a fuel cell multi-unit parallel power generation system according to an embodiment of the utility model.

[0028] Figure numerals: 1-power generation unit, 2-fuel cell stack, 3-DC-DC converter, 4-collecting device, 5-DC-AC converter, 6-multi-split step-up transformer, 7-grid. DETAILED DESCRIPTION

[0029] In order to have a clearer understanding of the technical features, purposes and effects of the utility model, the specific implementation methods of the utility model are now described. It should be understood that the specific embodiments described herein are only used to explain the utility model, and are not used to limit the utility model, that is, the embodiments described are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the utility model.

[0030] like Figure 2 As shown, this embodiment provides a primary circuit of a fuel cell multi-unit parallel power generation system, including a multi-split boost transformer 6 and a plurality of power generation modules, the power generation module including a plurality of power generation units 1, a confluence device 4 and a DC-AC converter 5, the power generation unit 1 including a fuel cell stack 2 and a DC-DC converter 3. The output of each fuel cell stack 2 is converted by the DC-DC converter 3 and then connected to the confluence device 4 through a cable, the output of the confluence device 4 is connected to the DC-AC converter 5 through a cable, the DC-AC converter 5 converts DC power into AC power and connects to the multi-split boost transformer 6, the multi-split boost transformer 6 realizes electrical isolation of the plurality of power generation units 1, and boosts low voltage power to medium voltage or high voltage power output to the power grid 7.

[0031] In this embodiment, the fuel cell stack 2 converts the chemical energy in the hydrogen fuel into electrical energy through an electrochemical reaction. The output end of the fuel cell stack 2 is connected to the input end of the DC-DC converter 3. The DC-DC converter 3 increases or decreases the stack voltage to the voltage required by the input end of the DC-AC converter 5.

[0032] The output ends of multiple DC-DC converters 3 are connected to the input ends of the confluence device 4 to achieve parallel connection. The number of parallel connections can be determined according to the insulation resistance of the power generation unit 1. The more parallel connections there are, the lower the insulation resistance is, and the fewer parallel connections there are, the higher the insulation resistance is.

[0033] Preferably, the merging device 4 may be a merging cabinet, and the merging device 4 is provided with a circuit breaker for short-circuit protection.

[0034] Preferably, the output end of the converging device 4 is connected to the input end of the DC-AC converter 5, and the DC-AC converter 5 converts the DC power output by the converging device 4 into low-voltage three-phase AC power.

[0035] Preferably, the low-voltage side of the multi-split step-up transformer 6 is provided with a plurality of windings, each of which is electrically isolated from the other; and the high-voltage side of the multi-split step-up transformer 6 is provided with only one winding. The multi-split step-up transformer 6 not only realizes the electrical isolation between the plurality of power generation units 1, but also realizes the function of increasing the AC voltage to a voltage level of 10KV, 35KV or higher.

[0036] The above is only a preferred embodiment of the utility model. It should be understood that the utility model is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the utility model, and should be within the scope of protection of the claims attached to the utility model.

Claims

1. A primary circuit of a multi-unit parallel power generation system of a fuel cell, characterized in that: It includes a multi-split step-up transformer and multiple power generation modules, the power generation modules include multiple power generation units, a confluence device and a DC-AC converter, the power generation unit includes a fuel cell stack and a DC-DC converter; the output of the fuel cell stack is converted by the DC-DC converter and then connected to the confluence device through a cable, the output of the confluence device is connected to the DC-AC converter through a cable, the DC-AC converter converts DC power into AC power and is connected to the multi-split step-up transformer, the multi-split step-up transformer boosts the voltage and outputs it to the power grid.

2. The primary circuit of a fuel cell multi-unit parallel power generation system according to claim 1, characterized in that: The output end of the fuel cell stack is connected to the input end of the DC-DC converter, and the DC-DC converter increases or decreases the stack voltage to the voltage required by the input end of the DC-AC converter.

3. The primary circuit of a fuel cell multi-unit parallel power generation system according to claim 1, characterized in that: The output ends of the plurality of DC-DC converters are connected to the input end of the converging device to realize the parallel connection of the power generation units.

4. The primary circuit of a fuel cell multi-unit parallel power generation system according to claim 3, characterized in that: The number of the power generation units connected in parallel depends on the insulation resistance of the power generation units. The lower the insulation resistance, the greater the number of the power generation units connected in parallel; and the higher the insulation resistance, the smaller the number of the power generation units connected in parallel.

5. The primary circuit of a fuel cell multi-unit parallel power generation system according to claim 1, characterized in that: The confluence device is provided with a circuit breaker for short circuit protection.

6. The primary circuit of a fuel cell multi-unit parallel power generation system according to claim 1, characterized in that: The output end of the converging device is connected to the input end of the DC-AC converter, and the DC-AC converter converts the DC power output by the converging device into low-voltage three-phase AC power.

7. The primary circuit of a fuel cell multi-unit parallel power generation system according to claim 1, characterized in that: The low voltage side of the multi-split step-up transformer is provided with a plurality of windings, and each winding is electrically isolated from each other.

8. The primary circuit of a fuel cell multi-unit parallel power generation system according to claim 1, characterized in that: The high voltage side of the multi-split step-up transformer is provided with only one winding.

9. The primary circuit of a fuel cell multi-unit parallel power generation system according to claim 1, characterized in that: The multi-split step-up transformer achieves electrical isolation between multiple power generation units.

10. The primary circuit of a fuel cell multi-unit parallel power generation system according to claim 1, characterized in that: The multi-split step-up transformer can step up the AC voltage to a voltage level of 10KV, 35KV or higher.

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