Three-level uninterruptible power supply mode control system and method based on DC power supply system

Abstract

The present invention discloses a three-level uninterruptible power supply mode control system based on a DC power supply system, including: an AC / DC rectifier module, a parallel power supply component, a DC load, and a freewheeling circuit, wherein the freewheeling circuit is composed of a DC bus, a freewheeling diode and a plurality of parallel power supply components in series, and is used to switch the power supply mode by replacing the topological wiring. Also disclosed is a three-level uninterruptible power supply mode control method based on a DC power supply system, including the following steps: S1: extracting key state quantities of a three-level uninterruptible power supply; S2: judging the working condition of the power supply circuit; S3: switching the power supply mode of the three-level uninterruptible power supply system according to the current power supply working condition. The present invention is based on a flexible switching method of a three-level uninterruptible power supply mode with an improved topology, and designs an improved parallel DC power supply topology structure, so that the power supply can be normally and reliably supplied under normal, abnormal and extreme working conditions, thereby improving the reliability of the power supply scheme under the condition of variable power supply scenarios.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current power supply system control, and in particular to a three-level uninterruptible power supply mode control system and method based on a direct current power supply system. Background Art

[0002] DC power supply systems are widely used in scenarios with high power supply reliability requirements. The battery group formed by multiple batteries in series is the key to the reliable power supply of the DC power supply system, while the performance degradation of a single battery often becomes a shortcoming that restricts the reliable power supply of the entire battery group and even the DC power supply system. The three-level uninterruptible power supply technology is a technical upgrade of the traditional series-type DC power supply system and is a unique technology under the battery parallel-type DC power supply system. The battery parallel-type DC power supply system is a device system that connects multiple batteries (power sources) in parallel to provide a higher output voltage or current. Taking the parallel-type DC power supply system based on power electronic modules and intelligent control technology as an example, the basic idea is that a single battery is directly boosted by a power electronic module to obtain the rated voltage, and a single battery and its charge and discharge control module form a power supply component (branch), and a reasonable number of power supply components (branches) are connected in parallel to meet the total capacity requirements of the DC power supply system. This type of device is widely used in various fields, such as substations, power plants, renewable energy fields (stations), rail transit, data centers, etc.

[0003] In the prior art, since the conventional series-type DC power supply system can only ensure reliable power supply under normal power supply conditions when each cell in the entire battery group is operating healthily, it is impossible to ensure reliable power supply under abnormal or extreme fault conditions such as single cell battery failure. Therefore, it is necessary to improve the circuit structure to ensure power supply reliability under abnormal or extreme fault conditions. Summary of the invention

[0004] The present invention provides a three-level uninterruptible power supply mode control system and method based on a DC power supply system that can flexibly cope with three different operating conditions: normal operating conditions, abnormal operating conditions and extreme operating conditions, and reliably supply electric energy, which can solve at least one of the above-mentioned technical problems.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A three-level uninterruptible power supply mode control system based on a DC power supply system, comprising:

[0007] AC / DC rectifier module, used to provide DC power supply energy to the DC bus and provide charging energy to the parallel power supply components;

[0008] A parallel power supply assembly, which has a plurality of components, each of which is connected in parallel to the DC bus via a bidirectional DC-DC group management module and is used as a backup power supply when the AC unit is in an abnormal state;

[0009] There are multiple DC loads, which are connected in parallel to the DC bus through air switches respectively;

[0010] It also includes a freewheeling circuit, which is composed of a DC bus, a freewheeling diode and a plurality of parallel power supply components in series, and is used to switch the power supply mode by replacing the topological wiring.

[0011] Furthermore, there are two freewheeling diodes, which are respectively connected in series on both sides of the plurality of parallel power supply components and are respectively connected in series to the DC bus.

[0012] Furthermore, the parallel power supply assembly includes a plurality of parallel battery packs.

[0013] Furthermore, the AC / DC rectifier module is connected to a remote AC power source.

[0014] Furthermore, under normal operating conditions, the direction of electric energy flow is: the AC power supply passes through the AC / DC rectifier module to provide DC power supply energy for the DC bus and provide charging energy for the parallel power supply component, and the freewheeling circuit does not flow current.

[0015] Furthermore, under abnormal working conditions, the direction of electric energy flow is: the AC power supply stops supplying power, the parallel power supply component supplies power to the DC bus through the bidirectional DC / DC grouping management module, and the freewheeling circuit does not flow current.

[0016] Furthermore, under extreme working conditions, the direction of electric energy flow is: when the AC power supply stops supplying power, the bidirectional DC / DC grouping management module no longer circulates current, and the freewheeling circuit transmits current to the DC bus and supplies power to the DC load.

[0017] A three-level uninterruptible power supply mode control method based on a DC power supply system is implemented using the three-level uninterruptible power supply mode control system based on a DC power supply system, and further includes the following steps:

[0018] S1: Extract the key state quantities of the three-level uninterruptible power supply:

[0019] S11: Voltage stability:

[0020]

[0021] Uw is the voltage stability, Ui is the voltage at time i, is the average voltage at multiple moments;

[0022] This state quantity reflects the voltage fluctuation of the power supply system. When the fluctuation is large, it means that the power supply reliability is poor and it is necessary to consider switching the power supply.

[0023] S12: Current stability:

[0024]

[0025] Iw is the current stability, Ii is the current at time i, is the average current at multiple moments;

[0026] This state quantity reflects the current fluctuation of the power supply system. When the fluctuation is large, it means that there is a large change in the load, which may lead to a decrease in power supply reliability;

[0027] S13: Power fluctuation:

[0028]

[0029] Pw is the power stability, Pi is the power at time i, is the average power at multiple moments;

[0030] This state quantity reflects the power fluctuation of the power supply system. When the fluctuation is large, it means that there is a large change in the load, which may lead to a decrease in power supply reliability;

[0031] S14: Power supply capacity adequacy:

[0032]

[0033] Cw is the capacity stability, Ci is the capacity at time i, is the average capacity at multiple moments;

[0034] This state quantity reflects the capacity adequacy of the power supply system. When the fluctuation is large, it means that the capacity of the power supply itself has changed, which may lead to reduced power supply reliability.

[0035] S2: Determine the working condition of the power supply circuit:

[0036] S21: Based on the correlation between the historical working data of the power supply and the above-mentioned state quantities, the weight coefficients corresponding to different parameters are set to obtain the corresponding function f of the multi-parameter fusion analysis:

[0037] f=ω1Uw+ω2Iw+ω3Pw+ω4Cw

[0038] ω1~ω4 are weight coefficients corresponding to multiple parameters, which are set in sequence according to the correlation between Uw, Iw, Pw, Cw and the power supply status. The correlation is arranged according to Uw>Cw>Iw>Pw, so that the values ​​of ω1~ω4 are set to 0.4, 0.2, 0.1, and 0.3 respectively;

[0039] S22: Calculate the value of function f and make interval judgment:

[0040] f is in the interval (0, 0.3), and the corresponding power supply condition is normal;

[0041] f is in the interval of (0.3, 0.6), and the corresponding power supply condition is abnormal;

[0042] f is in the interval (0.6, 1), and the corresponding power supply condition is extreme.

[0043] S3: Switch the power supply mode of the three-level uninterruptible power supply system according to the current power supply conditions.

[0044] The beneficial effects of the present invention are embodied in:

[0045] 1. The present invention is based on a power supply condition classification method based on multi-parameter fusion. By extracting the key state quantities of the three-level uninterruptible power supply system, a fusion judgment method is proposed according to the correlation between the state quantities and the power supply scheme, thereby realizing intelligent judgment of the power supply condition, providing a basis for switching the three-level power supply mode, and solving the problem that the power supply mode is difficult to switch in time.

[0046] 2. The present invention is based on a flexible switching method for the three-level uninterruptible power supply mode with an improved topology. According to different power supply conditions, an improved parallel DC power supply topology structure is designed. By dynamically switching different topologies, the power supply can be able to supply power normally and reliably under normal, abnormal and extreme conditions, thereby improving the reliability of the power supply solution under changing power supply scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a circuit diagram of a parallel DC power supply system.

[0048] Figure 2 It is a circuit diagram of a parallel DC power supply system in a three-level uninterruptible power supply mode according to an embodiment of the present invention.

[0049] Figure 3 It is a schematic diagram of the flow of electric energy under normal operating conditions of the three-level uninterruptible power supply system of an embodiment of the present invention.

[0050] Figure 4 It is a schematic diagram of the flow of electric energy under abnormal conditions of the three-level uninterruptible power supply system of an embodiment of the present invention.

[0051] Figure 5It is a schematic diagram of the flow of electric energy under extreme working conditions of the three-level uninterruptible power supply system of an embodiment of the present invention.

[0052] Figure 6 It is a flow chart of a method for controlling a three-level uninterruptible power supply mode according to an embodiment of the present invention. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. It should be noted that if the meaning of "and / or" appears in the full text, including three parallel solutions, taking "A and / or B" as an example, it includes solution A, or solution B, or solutions that A and B meet at the same time. In addition, "multiple" refers to more than two.

[0054] See also Figure 1 The embodiment of the present invention provides a three-level uninterruptible power supply mode control system based on a DC power supply system, comprising:

[0055] AC / DC rectifier module, used to provide DC power supply energy to the DC bus and provide charging energy to the parallel power supply components;

[0056] A parallel power supply assembly, which has a plurality of components, each of which is connected in parallel to the DC bus via a bidirectional DC-DC group management module and is used as a backup power supply when the AC unit is in an abnormal state;

[0057] There are multiple DC loads, which are connected in parallel to the DC bus through air switches respectively;

[0058] It also includes a freewheeling circuit, which is composed of a DC bus, a freewheeling diode and a plurality of parallel power supply components in series, and is used to switch the power supply mode by replacing the topological wiring.

[0059] The present invention is based on a flexible switching method for three-level uninterruptible power supply modes with an improved topology. According to different power supply conditions, an improved parallel DC power supply topology structure is designed. By dynamically switching different topologies, the power supply can be normally and reliably supplied under normal, abnormal and extreme conditions, thereby improving the reliability of the power supply solution under changing power supply scenarios.

[0060] In this embodiment, the parallel power supply assembly includes multiple parallel battery groups and a bidirectional DC / DC grouping management module matched with each battery group. The bidirectional DC / DC grouping management module is used to realize group management of the battery groups and bidirectional feedback of electric energy, providing a more flexible battery charging and discharging management mode for the DC power supply system.

[0061] In this embodiment, there are two freewheeling diodes, which are respectively connected in series on both sides of the plurality of parallel power supply components and are respectively connected in series to the DC bus, so as to provide a spare electrical circuit connected to the DC bus for the parallel power supply components.

[0062] In this embodiment, the AC / DC rectifier module adopts a high-frequency rectifier module for electric power, which is connected to the AC side power supply in the substation to convert AC power into DC power and provide normal power supply for the DC power supply system.

[0063] In this embodiment, under normal operating conditions, the direction of electric energy flow is: the AC power supply passes through the AC / DC rectifier module to provide DC power supply energy for the DC bus and provide charging energy for the parallel power supply component, and the freewheeling circuit does not flow current.

[0064] In this embodiment, under abnormal working conditions, the direction of electric energy flow is: the AC power supply stops supplying power, the parallel power supply component supplies power to the DC bus through the bidirectional DC / DC grouping management module, and the freewheeling circuit does not flow current.

[0065] In this embodiment, under extreme working conditions, the direction of electric energy flow is: the AC power supply stops supplying power, the bidirectional DC / DC grouping management module no longer circulates current, the freewheeling circuit transmits current to the DC bus and supplies power to the DC load.

[0066] See also Figure 2 The embodiment of the present invention further provides a three-level uninterruptible power supply mode control method based on a DC power supply system, which is implemented by using the three-level uninterruptible power supply mode control system based on a DC power supply system, and further includes the following steps:

[0067] S1: Extract the key state quantities of the three-level uninterruptible power supply:

[0068] S11: Voltage stability:

[0069]

[0070] Uw is the voltage stability, Ui is the voltage at time i, is the average voltage at multiple moments;

[0071] This state quantity reflects the voltage fluctuation of the power supply system. When the fluctuation is large, it means that the power supply reliability is poor and it is necessary to consider switching the power supply.

[0072] S12: Current stability:

[0073]

[0074] Iw is the current stability, Ii is the current at time i, is the average current at multiple moments;

[0075] This state quantity reflects the current fluctuation of the power supply system. When the fluctuation is large, it means that there is a large change in the load, which may lead to a decrease in power supply reliability;

[0076] S13: Power fluctuation:

[0077]

[0078] Pw is the power stability, Pi is the power at time i, is the average power at multiple moments;

[0079] This state quantity reflects the power fluctuation of the power supply system. When the fluctuation is large, it means that there is a large change in the load, which may lead to a decrease in power supply reliability;

[0080] S14: Power supply capacity adequacy:

[0081]

[0082] Cw is the capacity stability, Ci is the capacity at time i, is the average capacity at multiple moments;

[0083] This state quantity reflects the capacity adequacy of the power supply system. When the fluctuation is large, it means that the capacity of the power supply itself has changed, which may lead to reduced power supply reliability.

[0084] The three-level uninterruptible power supply is output by three high-voltage AC power sources, one for the main power supply, the second for the backup power supply, and the third for the diesel generator set or other emergency power supply output. Among them, the main (backup) power supply can be realized by selecting distribution transformers of different specifications to convert the power grid voltage into a three-phase low-voltage power supply input. Diesel generator sets can select generator sets of different specifications and models (different power supply capacities) according to the actual needs of the corresponding work;

[0085] By extracting the key status quantities of the above three-level uninterruptible power supply, it helps to provide data support and decision-making basis for subsequent power supply plan decisions.

[0086] S2: Determine the working condition of the power supply circuit:

[0087] S21: Based on the correlation between the historical working data of the power supply and the above-mentioned state quantities, the weight coefficients corresponding to different parameters are set to obtain the corresponding function f of the multi-parameter fusion analysis:

[0088] f=ω1Uw+ω2Iw+ω3Pw+ω4Cw

[0089] ω1~ω4 are weight coefficients corresponding to multiple parameters, which are set in sequence according to the correlation between Uw, Iw, Pw, Cw and the power supply status. The correlation is arranged according to Uw>Cw>Iw>Pw, so that the values ​​of ω1~ω4 are set to 0.4, 0.2, 0.1, and 0.3 respectively;

[0090] S22: Calculate the value of function f and make interval judgment:

[0091] f is in the interval (0, 0.3), and the corresponding power supply condition is normal;

[0092] f is in the interval of (0.3, 0.6), and the corresponding power supply condition is abnormal;

[0093] f is in the interval (0.6, 1), and the corresponding power supply condition is extreme.

[0094] S3: Switch the power supply mode of the three-level uninterruptible power supply system according to the current power supply conditions.

[0095] The present invention is based on a power supply condition classification method based on multi-parameter fusion. By extracting the key state quantities of a three-level uninterruptible power supply system, a fusion judgment method is proposed according to the correlation between the state quantities and the power supply scheme, thereby realizing intelligent judgment of the power supply condition, providing a basis for switching the three-level power supply mode, and solving the problem that the power supply mode is difficult to switch in time.

[0096] It should be understood that the examples and implementation modes described herein are for illustrative purposes only and are not intended to limit the present invention. Those skilled in the art may make various modifications or changes based on the examples and implementation modes. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A three-level uninterruptible power supply mode control system based on a DC power supply system, comprising: AC / DC rectifier module, used to provide DC power supply energy to the DC bus and provide charging energy to the parallel power supply components; A parallel power supply assembly, which has a plurality of components, which are connected in parallel to the DC busbar via the bidirectional DC / DC group management module and are used as a backup power supply when the AC unit is in an abnormal state; There are multiple DC loads, which are connected in parallel to the DC bus through air switches respectively; It is characterized in that it also includes a freewheeling circuit, which is composed of a DC bus, a freewheeling diode and a plurality of parallel power supply components in series, and is used to switch the power supply mode by replacing the topological wiring; The following steps are also included: S1: Extract the key state quantities of the three-level uninterruptible power supply: S11: Voltage stability: U w is the voltage stability, U i is the voltage at time i, is the average voltage at multiple moments; This state quantity reflects the voltage fluctuation of the power supply system. When the fluctuation is large, it means that the power supply reliability is poor and it is necessary to consider switching the power supply. S12: Current stability: I w is the current stability, I i is the current at time i, is the average current at multiple moments; This state quantity reflects the current fluctuation of the power supply system. When the fluctuation is large, it means that there is a large change in the load, which may lead to a decrease in power supply reliability; S13: Power fluctuation: P w is the power stability, P i is the power at time i, is the average power at multiple moments; This state quantity reflects the power fluctuation of the power supply system. When the fluctuation is large, it means that there is a large change in the load, which may lead to a decrease in power supply reliability; S14: Power supply capacity adequacy: C w is the capacity stability, C i is the capacity at time i, is the average capacity at multiple moments; This state quantity reflects the adequacy of the power supply system's capacity. When the fluctuation is large, it means that the capacity of the power supply itself has changed, which may lead to reduced power supply reliability. S2: Determine the working condition of the power supply circuit: S21: Based on the correlation between the historical working data of the power supply and the above-mentioned state quantities, the weight coefficients corresponding to different parameters are set to obtain the corresponding function f of the multi-parameter fusion analysis: ω1~ω4 are weight coefficients corresponding to multiple parameters, respectively, and U w ,I w , P w , C w The correlation with the power supply status is set in sequence, and the correlation size is set according to U w >C w >I w >P w Arrange them so that the values ​​of ω1~ω4 are set to 0.4, 0.2, 0.1, and 0.3 respectively; S22: Calculate the value of function f and make interval judgment: f is in the interval (0, 0.3), and the corresponding power supply condition is normal; f is in the interval of (0.3, 0.6), and the corresponding power supply condition is abnormal; f is in the interval (0.6, 1), and the corresponding power supply condition is extreme; S3: Switch the power supply mode of the three-level uninterruptible power supply system according to the current power supply conditions.

2. The three-level uninterruptible power supply mode control system based on the DC power supply system according to claim 1, characterized in that: There are two freewheeling diodes, which are respectively connected in series on both sides of the plurality of parallel power supply components and are respectively connected in series to the DC bus.

3. The three-level uninterruptible power supply mode control system based on the DC power supply system according to claim 1, characterized in that: The parallel power supply assembly includes a plurality of parallel-connected storage battery groups.

4. The three-level uninterruptible power supply mode control system based on the DC power supply system according to claim 1, characterized in that: The AC / DC rectifier module is connected to a remote AC power source.

5. The three-level uninterruptible power supply mode control system based on the DC power supply system according to claim 1, characterized in that: Under normal working conditions, the direction of electric energy flow is: the AC power supply passes through the AC / DC rectifier module to provide DC power supply energy for the DC bus and provide charging energy for the parallel power supply component, and the freewheeling circuit does not flow current.

6. The three-level uninterruptible power supply mode control system based on a DC power supply system as claimed in claim 1, characterized in that: Under abnormal working conditions, the direction of electric energy flow is: the AC power supply stops supplying power, the parallel power supply component supplies power to the DC bus through the bidirectional DC / DC grouping management module, and the freewheeling circuit does not flow current.

7. The three-level uninterruptible power supply mode control system based on a DC power supply system as claimed in claim 1, characterized in that: Under extreme working conditions, the direction of electric energy flow is: when the AC power supply stops supplying power, the bidirectional DC / DC group management module no longer circulates current, and the freewheeling circuit transmits current to the DC bus and supplies power to the DC load.

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