Modular uninterruptible power supply based on partial power converters and control method thereof

Abstract

This invention discloses a modular uninterruptible power supply (UPS) based on a partial power converter and its control method, aiming to solve the problems of insufficient modularity, high power handling capacity, and high losses in existing DC UPS based on full power converters. The UPS is implemented as a three-port partial power converter consisting of dual active full-bridge DC / DC converters connected in a special configuration. This partial power converter compactly integrates the DC bus connected to the main power supply, the backup battery, and the DC load into a modular UPS. The UPS control method, comprised of three parts—constant current charging control for the backup battery, constant voltage control for the load, and switching commands for these two controls—ensures that the converter's transmitted power is always a portion of the sum of the backup battery power and the DC load power in four different modes: grid-connected mode, islanded mode, battery-out mode, and load-out mode. This reduces converter transmission losses and improves system energy efficiency and economy.

Description

Technical Field

[0001] This invention relates to the field of uninterruptible power supplies, specifically a modular uninterruptible power supply based on a partial power converter and its control method. Background Technology

[0002] In recent years, technologies such as big data, cloud computing, artificial intelligence, and 5G have developed rapidly, leading to an explosive growth in the scale of global data computing and processing. Data centers, as the core infrastructure for data storage and computing, have also experienced rapid growth in scale and number. By 2021, the total electricity consumption of global data centers approached 320 TWh, accounting for 1.3% of global total electricity consumption; it is projected that by 2030, the total electricity consumption of global data centers will account for 8% of global total electricity consumption. Against this backdrop, energy conservation and efficiency improvement in data centers have become issues of close concern to countries worldwide.

[0003] In data centers, power supply and distribution systems account for approximately 12% of total power consumption, ranking third. Uninterruptible power supplies (UPS) constitute the majority of this power consumption, therefore improving UPS efficiency will contribute to overall data center energy efficiency. Traditional UPS systems typically use AC / DC converters and DC / AC converters to connect the main power supply, backup batteries, and loads, resulting in a complex structure, high energy conversion losses, and low efficiency due to multiple stages. To address these issues, a modular UPS solution containing only AC / DC converters is proposed, reducing energy conversion stages, improving system efficiency, and enhancing UPS reliability. With the rapid development of DC power grids and DC energy storage technologies, DC UPS systems based on DC / DC converters have also emerged. However, existing DC / DC converter-based uninterruptible power supplies (UPS) typically consist of a backup battery and a DC / DC converter, which are relatively independent of the DC load and lack a distributed, modular structure suitable for data centers. In addition, existing DC / DC converter-based UPSs all use traditional full-power converters, meaning the converter handles all the power that needs to be processed. UPSs based on full-power converters still have relatively high losses and poor economic efficiency, which is one of the important factors hindering further improvement in energy efficiency of data centers. Summary of the Invention

[0004] To address the problems of insufficient modularity, high power handling capacity, and large losses in existing DC uninterruptible power supplies based on full-power converters, this invention proposes a modular uninterruptible power supply based on a partial-power converter and its control method.

[0005] This invention is achieved using the following technical solution:

[0006] A modular uninterruptible power supply based on a partial power converter is characterized by: a partial power converter, a backup battery, a DC bus connected to the main power supply, and a DC load connected in a compact manner, wherein the partial power converter consists of a dual active full-bridge DC / DC converter and an inductor L. m1 and inductor L m2 Through a special connection, a dual active full-bridge DC / DC converter with three ports can be configured using a full-bridge FB. m1 , full bridge FB m2 It consists of a high-frequency isolation transformer. First, the positive terminal of the DC bus passes through inductor L. m1 Connect the positive terminal of the DC load, and connect the negative terminal of the DC load to the positive terminal of the backup battery (the connection point between the negative terminal of the DC load and the positive terminal of the backup battery is denoted as node T). Connect the negative terminal of the backup battery to the negative terminal of the DC bus, thus forming the DC bus and inductor L. m1 A series branch consisting of a DC load and a backup battery. Secondly, the positive terminal of the DC bus passes through inductor L. m1 Connect the entire bridge FB m1 Positive pole, full bridge FB m1 The negative terminal passes through inductor L m2 Connect to node T to form a DC bus and inductor L. m1 , full bridge FB m1 Inductor L m2 The branch connected in series with the backup battery, and at the same time the full bridge FB m1 It also forms a parallel connection with the DC load. Full-bridge FB m2 The positive terminal passes through inductor L m2 Connected to node T, its negative terminal is connected to the negative terminal of the backup battery, which is the full-bridge FB. m2 After inductor L m2 It is connected in parallel with the backup battery to form a feedback branch. The DC bus of the main power supply, the backup battery and the DC load are compactly connected to form an uninterruptible power supply module through a partial power converter. When the main power supply is running normally, the partial power converter simultaneously charges the backup battery and supplies power to the load. When the main power supply fails to operate, the backup battery provides uninterrupted power to the load through the partial power converter.

[0007] A modular uninterruptible power supply (UPS) control method based on a partial power converter is implemented based on the aforementioned modular UPS based on a partial power converter. This method comprises the following three parts:

[0008] (1) Backup battery constant current charging control: Its control objective is to achieve constant current charging of the backup battery while the main power supply is operating normally. In a modular uninterruptible power supply based on a partial power converter, the DC load current I... mload and backup battery current I mbatAt node T, coupling occurs with a portion of the power converter current. Let the transverse branch current at node T (i.e., the current flowing through inductor L) be denoted as... m2 The current is I dif The coupling current relationship is I dif =I mbat -I mload Therefore, by controlling the transverse branch current I at node T... dif This indirectly controls the backup battery charging current. Specifically, the backup battery charging current reference value is set to I. mbat,ref Collect the actual DC load current I mload Then, the reference value of the transverse branch current at node T is calculated as I. dif-ref =I mbat-ref -I mload Then, the actual value I of the transverse branch current at node T is collected. dif The reference value I of the transverse branch current at node T. dif-ref and actual value I dif The difference is calculated and input into the proportional-integral controller (PI) for constant current charging control of the backup battery. mc In the middle, the phase shift duty cycle reference value D of the dual active full-bridge DC / DC converter is output. mc-ref This enables the control of constant current charging of the backup battery.

[0009] (2) Constant load voltage control: Its control objective is to ensure that the backup battery can discharge to the DC load and maintain a stable DC load voltage when the main power supply fails to operate normally. The DC load voltage reference value is set to V. mload-ref Collect the actual value of DC load voltage V mload The difference between the two is calculated, and this difference is input to the proportional-integral controller (PI) for constant load voltage control. mv In the middle, the phase shift duty cycle reference value D of the dual active full-bridge DC / DC converter is output. mv-ref This ensures that the DC load voltage remains stable when the backup battery discharges.

[0010] (3) Switching command for constant current charging control of backup battery and constant voltage control of load: Used to switch between constant current charging control of backup battery and constant voltage control of load. The selection of constant current charging control of backup battery and constant voltage control of load depends on the operation / exit status of the main power supply, DC load and backup battery (main power supply status is S1, DC load status is S2, backup battery status is S3, normal operation is 1, and exit operation is 0). According to the different operation status of the three, the modular uninterruptible power supply based on the partial power converter is mainly divided into four types: grid-connected mode, islanded mode, battery exit operation mode and load exit operation mode. ① Grid-connected mode: The main power supply, DC load and backup battery are all operating normally. The corresponding switch status of these three is S1=1, S2=1 and S3=1. At this time, constant current charging control of backup battery needs to be enabled. ② Islanded mode: The main power supply exits operation due to failure. The DC load and backup battery are both operating normally. The corresponding switch status of these three is S1=0, S2=1 and S3=1. At this time, constant voltage control of load needs to be enabled. ③ Battery Outage Mode: Both the main power supply and the DC load are operating normally, but the backup battery is out of service due to a fault or planned shutdown. The corresponding switch states are S1=1, S2=1, and S3=0. In this mode, constant voltage load control needs to be activated to maintain stable operation of the DC load. ④ Load Outage Mode: Both the main power supply and the backup battery are operating normally, but the DC load is out of service due to a fault or planned shutdown. The corresponding switch states are S1=1, S2=0, and S3=1. In this mode, constant current charging control for the backup battery can be activated to allow the DC load to be put back into operation at any time. In summary, the choice between constant current charging control for the backup battery and constant voltage load control is mainly related to S1 and S3. Therefore, the switching command for these two controls is S... c-v =S1&&S3. When S c-v When D = 1, the backup battery constant current charging control is activated and the load constant voltage control is disabled. mc-ref As a control signal, it is fed into the dual active full-bridge DC / DC converter; when S c-v When = 0, the backup battery constant current charging control is disabled, and the load constant voltage control is activated. mv-ref This signal is fed into the dual active full-bridge DC / DC converter as a control signal. Finally, according to S... c-v The final determined phase shift duty cycle reference value is input to the single phase shift control module to generate the switching signal that drives the dual active full-bridge DC / DC converter.

[0011] Regardless of whether the backup battery is under constant current charging control or load is under constant voltage control, the power processed by some power converters in the uninterruptible power supply is always a portion of the sum of the DC load power and the backup battery power, specifically:

[0012]

[0013] Among them, Fm P is the partial power factor, used to measure the partial power handling capability of a partial power converter; m1 and P m2 FB flows across the entire bridge respectively m1 and FB m2 Power; P mdc P represents the power flowing through the DC bus. mbat and P mload These are the power ratings of the backup battery and the DC load, respectively; h mv =V mbat / V mdc Backup battery voltage V mbat and bus voltage V mdc The ratio; h mc =I mload / I mbat DC load current I mload and backup battery current I mbat The ratio.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] (1) By designing a new special connection method, this invention improves the traditional dual active DC / DC converter with only two ports into a partial power converter that can provide three ports. Compared with the traditional uninterruptible power supply that requires two DC / DC converters to connect the DC bus, backup battery and DC load, this invention can achieve a compact connection of the DC bus, backup battery and DC load by using only one designed partial power converter. This not only simplifies the structure of the uninterruptible power supply, but also realizes the modularity of the uninterruptible power supply, which is conducive to improving the reliability of the uninterruptible power supply and the flexibility of distributed layout and expansion.

[0016] (2) In traditional DC uninterruptible power supplies, the load and power supply are relatively independent, that is, they are both directly connected to the DC bus, which is not conducive to expansion connections. This invention integrates the main power supply, backup battery and DC load into a module through a partial power converter, which makes the structure more compact. This modular structure is more conducive to distributed applications. As many as you want to connect, you can directly connect them in units of modules, which can achieve plug and play.

[0017] (3) In the uninterruptible power supply of the present invention, since the converter only handles part of the power rather than the full power of the module, it can reduce the loss of the uninterruptible power supply and improve the operating efficiency of the uninterruptible power supply, which is conducive to improving the overall energy efficiency of the data center. Since the converter only handles part of the power rather than the full power of the module, it can reduce the requirements for the rated parameters of the converter components, save equipment costs, and improve the economy of the uninterruptible power supply.

[0018] (4) This invention comprises three parts: constant current charging control of the backup battery, constant voltage control of the load, and switching commands for these two controls. This uninterruptible power supply (UPS) control method ensures that the converter's transmission power is always a portion of the sum of the backup battery power and the DC load power in four different operating modes: grid-connected mode, islanded mode, battery-out mode, and load-out mode. In other words, by reducing the converter's transmission power, transmission losses are reduced, thus improving the UPS system's energy efficiency. The flexible switching between the four operating modes not only simplifies UPS control but also enhances the UPS's operational flexibility and adaptability to different operating conditions.

[0019] (5) The partial power converter of this invention is mainly proposed for uninterruptible power supplies. It is applicable to uninterruptible power supply scenarios and has special and novel characteristics. At present, there are no related technologies based on partial power converters in the field of uninterruptible power supplies. Attached Figure Description

[0020] Figure 1 This is a topology diagram of a modular uninterruptible power supply based on a partial power converter according to the present invention.

[0021] Figure 2 This is a schematic diagram of a modular uninterruptible power supply control method based on a partial power converter according to the present invention.

[0022] Figure 3 This is a schematic diagram of the power flow of a modular uninterruptible power supply based on a partial power converter in grid-connected mode.

[0023] Figure 4 This is a schematic diagram of the power flow of a modular uninterruptible power supply based on a partial power converter in islanded mode.

[0024] Figure 5 This is a schematic diagram of the power flow of a modular uninterruptible power supply based on a partial power converter in the battery-out operation mode.

[0025] Figure 6 This is a schematic diagram of the power flow of a modular uninterruptible power supply based on a partial power converter in the load-out operation mode.

[0026] Figure 7 This is a partial power coefficient curve.

[0027] Figure 8The experimental waveforms show the flexible switching between grid-connected and islanded modes of a modular uninterruptible power supply based on a partial power converter. Among them, (a) is the change graph of DC bus, load, and backup battery voltage during the switching experiment; (b) is the change graph of DC bus, load, and backup battery current during the switching experiment; (c) is the change graph of partial power converter current during the switching experiment; (d) is the change graph of DC bus, load, and backup battery power during the switching experiment; (e) is the change graph of partial power converter transmitted power during the switching experiment; and (f) is the change graph of partial power factor during the switching experiment.

[0028] Figure 9 The experimental waveforms show the flexible switching between grid-connected mode and battery-out operation mode of a modular uninterruptible power supply based on a partial power converter. Among them, (a) is the change graph of DC bus, load, and backup battery voltage during the switching experiment; (b) is the change graph of DC bus, load, and backup battery current during the switching experiment; (c) is the change graph of partial power converter current during the switching experiment; (d) is the change graph of DC bus, load, and backup battery power during the switching experiment; (e) is the change graph of partial power converter transmitted power during the switching experiment; and (f) is the change graph of partial power coefficient during the switching experiment.

[0029] Figure 10 The experimental waveforms show the flexible switching between grid-connected mode and load-out operation mode of a modular uninterruptible power supply based on a partial power converter. Among them, (a) is the change graph of DC bus, load, and backup battery voltage during the switching experiment; (b) is the change graph of DC bus, load, and backup battery current during the switching experiment; (c) is the change graph of partial power converter current during the switching experiment; (d) is the change graph of DC bus, load, and backup battery power during the switching experiment; (e) is the change graph of partial power converter transmitted power during the switching experiment; and (f) is the change graph of partial power coefficient during the switching experiment. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0031] A modular uninterruptible power supply based on a partial power converter, such as Figure 1 As shown, it consists of a partial power converter, a backup battery, a DC bus connected to the main power supply, and a DC load, all connected in a compact manner and can provide three ports. The partial power converter comprises a dual active full-bridge DC / DC converter and an inductor L... m1 and inductor L m2 Through a special connection configuration, the dual active full-bridge DC / DC converter consists of a full-bridge FB...m1 , full bridge FB m2 It consists of a high-frequency isolation transformer. The special connection is as follows: First, the positive terminal of the DC bus passes through inductor L... m1 Connect the positive terminal of the DC load to the positive terminal of the backup battery, and connect the negative terminal of the DC load to the positive terminal of the backup battery. The connection point between the negative terminal of the DC load and the positive terminal of the backup battery is denoted as node T. The negative terminal of the backup battery is connected to the negative terminal of the DC bus, thus forming the DC bus and inductor L. m1 A series branch consisting of a DC load and a backup battery. Secondly, the positive terminal of the DC bus passes through inductor L. m1 Connect the entire bridge FB m1 Positive pole, full bridge FB m1 The negative terminal passes through inductor L m2 Connect to node T to form a DC bus and inductor L. m1 , full bridge FB m1 Inductor L m2 The branch connected in series with the backup battery, and at the same time the full bridge FB m1 It also forms a parallel connection with the DC load. Full-bridge FB m2 The positive terminal passes through inductor L m2 Connected to node T, its negative terminal is connected to the negative terminal of the backup battery, which is the full-bridge FB. m2 After inductor L m2 It is connected in parallel with the backup battery to form a feedback branch.

[0032] The DC bus connected to the main power supply, the backup battery, and the DC load are compactly configured into an uninterruptible power supply module through a partial power converter. When the main power supply is running normally, the partial power converter simultaneously charges the backup battery and supplies power to the load. When the main power supply fails to operate, the backup battery provides uninterrupted power to the load through the partial power converter.

[0033] A control method for a modular uninterruptible power supply based on a partial power converter, such as Figure 2 As shown, this is a modular uninterruptible power supply based on a partial power converter, which includes the following three parts:

[0034] (1) Backup battery constant current charging control: Its control objective is to achieve constant current charging of the backup battery while the main power supply is operating normally. In a modular uninterruptible power supply based on a partial power converter, the DC load current I... mload and backup battery current I mbat At node T, coupling occurs with a portion of the power converter current. Let the transverse branch current at node T (i.e., the current flowing through inductor L) be denoted as... m2 The current is I dif The coupling current relationship is I dif =I mbat -I mloadTherefore, by controlling the transverse branch current I at node T... dif This indirectly controls the backup battery charging current. Specifically, the backup battery charging current reference value is set to I. mbat,ref Collect the actual DC load current I mload Then, the reference value of the transverse branch current at node T is calculated as I. dif-ref =I mbat-ref -I mload Then, the actual value I of the transverse branch current at node T is collected. dif The reference value I of the transverse branch current at node T. dif-ref and actual value I dif The difference is calculated and input into the proportional-integral controller (PI) for constant current charging control of the backup battery. mc In the middle, the phase shift duty cycle reference value D of the dual active full-bridge DC / DC converter is output. mc-ref This enables the control of constant current charging of the backup battery.

[0035] (2) Constant load voltage control: Its control objective is to ensure that the backup battery can discharge to the DC load and maintain a stable DC load voltage when the main power supply fails to operate normally. The DC load voltage reference value is set to V. mload-ref Collect the actual value of DC load voltage V mload The difference between the two is calculated, and this difference is input to the proportional-integral controller (PI) for constant load voltage control. mv In the middle, the phase shift duty cycle reference value D of the dual active full-bridge DC / DC converter is output. mv-ref This ensures that the DC load voltage remains stable when the backup battery discharges.

[0036] (3) Switching command for backup battery constant current charging control and load constant voltage control: Used to switch between the above-mentioned backup battery constant current charging control and load constant voltage control. The selection of backup battery constant current charging control and load constant voltage control depends on the operating / exit status of the main power supply, DC load and backup battery (main power supply status is S1, DC load status is S2, backup battery status is S3, normal operation is 1, and exit operation is 0). According to the different operating statuses of the three, modular uninterruptible power supplies based on partial power converters are mainly divided into four types: grid-connected mode, islanded mode, battery exit operation mode and load exit operation mode. ① Grid-connected mode: such as Figure 3 As shown, the main power supply, DC load, and backup battery are all operating normally, and their corresponding switch states are S1=1, S2=1, and S3=1. At this time, the backup battery constant current charging control needs to be enabled; ② Island mode: as shown... Figure 4As shown, the main power supply has stopped operating due to a fault, while the DC load and backup battery are operating normally. The corresponding switch states for these three are S1=0, S2=1, and S3=1. At this time, constant voltage load control needs to be activated. ③ Battery exits operating mode: (e.g., ...) Figure 5 As shown, the main power supply and DC load are operating normally, but the backup battery is out of service due to a fault or planned shutdown. The corresponding switch states for these three are S1=1, S2=1, and S3=0. In this case, constant voltage load control needs to be activated to maintain stable operation of the DC load. ④ Load shutdown mode: (e.g., ...) Figure 6 As shown, the main power supply and backup battery are both operating normally. The DC load is either out of service due to a fault or planned shutdown. The corresponding switch states for these three are S1=1, S2=0, and S3=1. In this case, the backup battery constant current charging control can be activated to allow the DC load to be put back into operation at any time. In summary, the choice between backup battery constant current charging control and load constant voltage control is mainly related to S1 and S3. Therefore, the switching command for these two controls is S... c-v =S1&&S3. When S c-v When D = 1, the backup battery constant current charging control is activated and the load constant voltage control is disabled. mc-ref As a control signal, it is fed into the dual active full-bridge DC / DC converter; when S c-v When = 0, the backup battery constant current charging control is disabled, and the load constant voltage control is activated. mv-ref This signal is fed into the dual active full-bridge DC / DC converter as a control signal. Finally, according to S... c-v The final determined phase shift duty cycle reference value is input to the single phase shift control module to generate the switching signal that drives the dual active full-bridge DC / DC converter.

[0037] Regardless of whether it's under constant current charging control of the backup battery or constant voltage control of the load, the power processed by some power converters in an uninterruptible power supply is always a portion of the sum of the DC load power and the backup battery power, such as... Figure 7 As shown, specifically:

[0038]

[0039] Among them, F m P is the partial power factor, used to measure the partial power handling capability of a partial power converter; m1 and P m2 FB flows across the entire bridge respectively m1 and FB m2 Power; P mdc P represents the power flowing through the DC bus. mbat and P mload These are the power ratings of the backup battery and the DC load, respectively; h mv =V mbat / V mdc Backup battery voltage Vmbat and bus voltage V mdc The ratio; h mc =I mload / I mbat DC load current I mload and backup battery current I mbat The ratio.

[0040] In this invention, the smaller the partial power coefficient, the better. When the DC load current I mload and backup battery current I mbat When any one of them is 0, its partial power coefficient is only related to the backup battery voltage V. mbat Bus voltage V mdc The ratio is related; when the DC load current I mload and backup battery current I mbat When none of the values ​​are 0, its regulation is affected by the backup battery voltage V. mbat Bus voltage V mdc DC load current I mload and backup battery current I mbat The influence of these four factors is addressed through system control and the selection and adjustment of components to keep the partial power coefficient of the uninterruptible power supply (UPS) at a low level.

[0041] like Figure 8 The figure shows the experimental waveforms of a modular uninterruptible power supply (UPS) based on a partial power converter, flexibly switching between grid-connected and islanded modes. ① Phase 1 (t = 0~1s): All components are in operation, and the UPS operates in grid-connected mode. DC bus voltage V mdc =750V, backup battery voltage V mbat =370V, load voltage V mload =380V. Load current I mload =13A, backup battery current I mbat =20A, therefore the transverse branch current I at node T is dif =I mbat -I mload =7A, full bridge FB m1 and FB m2 The current is I m1 ≈I m2 =3.5A, partial power factor F m Approximately 10.5%. ② Phase Two (t = 1~2s): A short-term power outage occurs in the main power supply (S1 disconnects and becomes 0). The uninterruptible power supply automatically switches from grid-connected mode to islanded mode to provide uninterrupted power to the DC load. When the main power supply disconnects at t = 1s, S1 abruptly changes from 1 to 0, causing the control switching command S... c-vWhen the value changes from 1 to 0, the backup battery constant current charging control in grid-connected mode automatically switches to load constant voltage control in islanded mode. Under load constant voltage control, the backup battery discharges to the DC load to maintain uninterrupted power supply and maintains the load voltage V. mload =380V. After switching to islanded mode, the main power supply was cut off, causing I... mdc =0A, while the backup battery switches to discharge mode, with a discharge current of I. mbat = -13.5A, full bridge FB m1 and FB m2 Current shares I dif =I mbat -I mload , that is I m1 ≈I m2 = -13.3A, partial power factor F m Approximately 50%. ③ Stage Three (t = 2-3s): The main power supply resumes operation, and all system states quickly return to the initial grid-connected mode, such as... Figure 8 As shown in the figure, t = 2 to 3 s.

[0042] like Figure 9 The figure shows the experimental waveforms of a modular uninterruptible power supply (UPS) based on a partial power converter flexibly switching between grid-connected mode and battery-out operation mode. ① Stage 1 (t = 0~1s): In the initial state, the UPS operates in grid-connected mode, and... Figure 8 Phase 1 is similar and will not be described further. ② Phase 2 (t = 1~2s): Switch S3 is opened, the backup battery briefly exits operation, and the uninterruptible power supply automatically switches from grid-connected mode to battery-off operation mode. When the backup battery is disconnected at t = 1s, S3 abruptly changes from 1 to 0, causing the control switching command S... c-v When the value changes from 1 to 0, the backup battery constant current charging control automatically switches to load constant voltage control, ensuring that the load voltage is stably maintained at V. mload =380V, backup battery out of service, therefore I mbat =0A. The transverse branch current at node T is I. dif =-I mload =-13A,I dif By the whole bridge FB m1 and FB m2 Current is regulated together, and I m1 ≈I m2 = -6.5A, the partial power converter transmission power is 2.47kW, significantly less than the DC load power of 4.94kW. In the backup battery off-line mode, the partial power factor F... m Approximately 50%. ③ Phase 3 (t = 2-3s): The backup battery is reconnected, and all system states quickly return to the initial grid-connected mode, which will not be described in detail here.

[0043] like Figure 10 The figure shows the experimental waveforms of a modular uninterruptible power supply (UPS) based on a partial power converter flexibly switching between grid-connected mode and load-out operation mode. ① Stage 1 (t = 0–1s): Initially, the UPS operates in grid-connected mode, which will not be described further. ② Stage 2 (t = 1–2s): Switch S2 is opened, the DC load briefly exits operation, and the UPS automatically switches from grid-connected mode to load-out operation mode. At t = 1s when the DC load stops operating, S2 abruptly changes from 1 to 0, but the control switching command S... c-v =S1 &&S3 will not change, therefore constant current charging control for the backup battery will continue to be used to replenish the backup battery's charge. Although the DC load is disconnected, the full-bridge FB used to connect the DC load remains operational. m1 The DC-side voltage can still be maintained at 380V to facilitate the reconnection of DC loads to the uninterruptible power supply system at any time. (DC load out of operation, therefore I...) mload =0A, while the backup battery charging current is I. mbat =20A. The transverse branch current at node T is I. dif =I mbat =20A, I dif By the whole bridge FB m1 and FB m2 Current regulation, i.e., I m1 ≈I m2 =10A. The partial power converter transmission power is 3.7kW, significantly less than the backup battery charging power of 7.4kW. In the load off-line operation mode, the partial power factor F m Approximately 50%. ③ Stage 3 (t = 2~3s): The DC load is reconnected, and all states of the system quickly return to the initial grid-connected mode, which will not be described in detail here.

[0044] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A modular uninterruptible power supply based on a partial power converter, characterized in that: It includes a power converter, a backup battery, a DC bus connected to the main power supply, and a DC load. The power converter includes a dual active full-bridge DC / DC converter and an inductor. L m1 and inductor L m2 The dual active full-bridge DC / DC converter consists of a full-bridge FB m1 , full bridge FB m2 It consists of a high-frequency isolation transformer; The positive terminal of the DC bus is connected to an inductor. L m1 Connect the positive terminal of the DC load to the positive terminal of the backup battery, and connect the negative terminal of the DC load to the positive terminal of the backup battery. The connection point between the negative terminal of the DC load and the positive terminal of the backup battery is denoted as node T. The negative terminal of the backup battery is connected to the negative terminal of the DC bus, thus forming the DC bus and inductor. L m1 A series branch consisting of a DC load and a backup battery; DC bus positive terminal passes through an inductor L m1 Connect the entire bridge FB m1 Positive pole, full bridge FB m1 The negative terminal passes through the inductor L m2 Connected to node T, thus forming a DC bus and inductor L m1 , full bridge FB m1 ,inductance L m2 The branch connected in series with the backup battery, and at the same time the full bridge FB m1 It also forms a parallel connection with the DC load; Full Bridge FB m2 The positive terminal passes through the inductor L m2 Connected to node T, its negative terminal is connected to the negative terminal of the backup battery, which is the full-bridge FB. m2 After inductance L m2 It is connected in parallel with the backup battery to form a feedback branch; The DC bus connected to the main power supply, the backup battery, and the DC load are compactly configured into an uninterruptible power supply module through a partial power converter. When the main power supply is running normally, the partial power converter simultaneously charges the backup battery and supplies power to the load. When the main power supply fails to operate, the backup battery provides uninterrupted power to the load through the partial power converter.

2. A control method for a modular uninterruptible power supply based on a partial power converter as described in claim 1, characterized in that, The control method It includes the following three parts: (1) Backup battery constant current charging control: Its control objective is to achieve constant current charging of the backup battery when the main power supply is running normally; In a modular uninterruptible power supply based on a partial power converter, the DC load current... I mload and backup battery current I mbat At node T, coupling occurs with a portion of the power converter current. Let the transverse branch current at node T be... I dif The coupling current relationship is as follows: I dif = I mbat – I mload By controlling the transverse branch current at node T I dif This indirectly controls the backup battery charging current; specifically, a reference value for the backup battery charging current is set. I mbat-ref Collect the actual current of the DC load I mload Then, the reference value of the transverse branch current at node T is calculated. I dif-ref = I mbat-ref – I mload Then, the actual value of the transverse branch current at node T is collected. I dif The reference value of the transverse branch current at node T. I dif-ref and actual value I dif The difference is calculated and input into the proportional-integral controller (PI) for constant current charging control of the backup battery. mc In the middle, the phase shift duty cycle reference value of the dual active full-bridge DC / DC converter is output. D mc-ref This enables constant current charging control of the backup battery; (2) Constant load voltage control: Its control objective is to control the backup battery to discharge to the DC load and maintain the stability of the DC load voltage when the main power supply is abnormally disconnected. Set the DC load voltage reference value to V mload-ref Collect the actual value of DC load voltage V mload The difference between the two is calculated, and this difference is input to the proportional-integral controller (PI) for constant load voltage control. mv In the middle, the phase shift duty cycle reference value of the dual active full-bridge DC / DC converter is output. D mv-ref This ensures that the DC load voltage remains stable when the backup battery discharges; (3) Switching instruction for backup battery constant current charging control and load constant voltage control: used to switch between the above-mentioned backup battery constant current charging control and load constant voltage control; the switching instruction for backup battery constant current charging control and load constant voltage control is as follows: S c-v = S 1&& S 3, when S c-v When =1, the backup battery constant current charging control is activated, and the load constant voltage control is disabled. D mc-ref As a control signal, it is sent to the dual active full-bridge DC / DC converter; when S c-v When the value is 0, the backup battery constant current charging control is disabled, and the load constant voltage control is activated. D mv-ref As a control signal, it is fed into the dual active full-bridge DC / DC converter; finally, according to S c-v The final determined phase-shift duty cycle reference value is input to the single-phase-shift control module, generating a switching signal to drive the dual active full-bridge DC / DC converter; where the main power supply state is denoted as... S 1. The DC load status is denoted as S 2. The status of the backup battery is recorded as follows: S 3. Normal operation is 1, and exiting operation is 0.

3. The control method according to claim 2, characterized in that, Based on the different operating states of the main power supply, DC load, and backup battery, modular uninterruptible power supplies (UPS) based on partial power converters are mainly divided into four types: grid-connected mode, islanded mode, battery-out mode, and load-out mode. ① Grid-connected mode: The main power supply, DC load, and backup battery are all operating normally, and the corresponding switch states of these three are as follows: S 1=1、 S 2=1、 S 3=1, at this time the backup battery constant current charging control needs to be enabled; ② Island mode: the main power supply is shut down due to a fault, but the DC load and backup battery are operating normally. The corresponding switch states of these three are: S 1=0、 S 2=1、 S 3=1, at this time the constant voltage load control needs to be enabled; ③ Battery exit operation mode: the main power supply and DC load are operating normally, and the backup battery is out of operation due to fault or planned exit. The corresponding switch states for these three are: S 1=1、 S 2=1、 S 3=0, at this time, constant voltage load control needs to be enabled to maintain stable operation of the DC load; ④ Load exit operation mode: both the main power supply and the backup battery are operating normally, and the DC load is exiting operation due to a fault or planned shutdown. The corresponding switch states for these three are: S 1=1、 S 2=0、 S 3=1, at this time the backup battery constant current charging control is activated so that the DC load can be put back into operation at any time.

4. The control method according to claim 2, characterized in that, Regardless of whether the backup battery is under constant current charging control or load is under constant voltage control, the power processed by some power converters in the uninterruptible power supply is always a portion of the sum of the DC load power and the backup battery power, specifically: ， in, F m The partial power factor is used to measure the partial power handling capability of a partial power converter. P m1 and P m2 FB flows across the entire bridge respectively m1 and FB m2 The power; P mdc This refers to the power flowing through the DC bus; P mbat and P mload These are the power ratings for the backup battery and the DC load, respectively. h mv = V mbat / V mdc Backup battery voltage V mbat and bus voltage V mdc The ratio; h mc = I mload / I mbat DC load current I mload and backup battery current I mbat The ratio.

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