True bipolar direct-current online uninterruptible power supply device

Abstract

The utility model provides a true bipolar direct-current online uninterruptible power supply device, and relates to the technical field of direct-current uninterruptible power supply devices. The direct current uninterruptible power supply comprises an input circuit breaker, a first input switch, a first Buck-Boost converter, a first output switch, a first bidirectional DC-DC converter, a second input switch, a second Buck-Boost converter, a second output switch, a second bidirectional DC-DC converter, an energy storage device, a static bypass switch and a manual bypass switch. On the other hand, the current rigid load can be changed into the flexible load in an optical storage direct-current flexible system, so that the reliability of direct-current true bipolar power supply is improved, and power peak regulation and consumption of renewable energy sources are realized.

Description

Technical Field

[0001] The utility model relates to the technical field of DC uninterruptible power supply devices, in particular to a true bipolar DC online uninterruptible power supply device. Background Technique

[0002] In recent years, with the gradual deterioration of the environment and the increasing scarcity of fossil energy, renewable energy has developed rapidly in recent years. The penetration of distributed generation is of great significance for reducing environmental protection pressure, saving investment in power transmission and transformation, and improving power supply reliability. DC power transmission and DC distribution technologies are one of the effective technical means to solve the grid connection of distributed power sources.

[0003] At present, there are two mainstream DC distribution architectures, namely the single-pole system and the bipolar system. In GB / T 16895.1, the single-pole system is called a two-wire structure, and the bipolar system is called a three-wire structure. The single-pole system consists of a positive pole (L+) and a negative pole (L-), providing a single DC voltage level between the two wires. Its structure is simple and easier to control, but its reliability is worse than that of the bipolar system. When a fault occurs in the DC bus, all loads will face the risk of power loss. The bipolar system consists of a positive pole (L+), a negative pole (L-), and an intermediate stage (M) (T / CABEE 030-2022 Design Standard for DC Distribution in Civil Buildings). Two DC voltage levels are provided between the three-wire structures, namely the voltage between the positive / negative poles and the intermediate stage and the voltage between the positive and negative poles. Among them, the pseudo-bipolar structure works in a similar way to the unipolar structure. When a fault occurs in the positive or negative pole, both the positive and negative poles need to be powered off; while the true bipolar DC network can still operate under a single-pole fault, and because it has two different levels, it can provide more choices for loads and distributed power sources. In addition, the true bipolar network has certain similarities with the traditional three-phase four-wire AC system, that is, the voltage between the positive and negative poles is analogous to the line voltage in the three-phase four-wire system, and the voltage of each pole is analogous to the phase voltage. This similarity with the AC system is conducive to system operation, improvement, and control scheme design. The true bipolar structure has a wider applicability. Combining with the dual-bus power supply structure, it can ensure the high power supply reliability of the DC distribution network and the flexibility of DC load access.

[0004] Uninterruptible power supply equipment (UPS): A power supply equipment composed of a converter, a switch, and an energy storage device (such as a battery), which maintains the power continuity of the load when the input power supply fails.

[0005] The DC true bipolar online uninterruptible power supply supplies power to relatively important loads (such as first-class loads and second-class loads) in true bipolar DC power supply. When a power interruption occurs due to a failure of the input power supply, the energy storage device (such as a storage battery) can continuously supply power to the load through an inverter and a switch. When the true bipolar DC network is powered by only one pole under a unipolar fault, the single-pole power supply is converted into a bipolar power supply through a converter, and the electric energy in the energy storage device is not required. When the input power is insufficient or power transfer is required, the energy storage device and the input DC can also supply power simultaneously to increase the power supply continuous time, improve the energy storage utilization rate, and participate in the flexible regulation of the load. Summary of the Invention

[0006] The purpose of the present invention is to solve the technical problems raised in the above-mentioned background technology.

[0007] The present invention adopts the following technical solution: A true bipolar DC online uninterruptible power supply device includes an input circuit breaker, a first input switch, a first Buck-Boost converter, a first output switch, a first bidirectional DC-DC converter, a second input switch, a second Buck-Boost converter, a second output switch, a second bidirectional DC-DC converter, an energy storage device, a static bypass switch, and a manual bypass switch.

[0008] Input L+, input M, and input L- are connected to the input end of the input circuit breaker through input terminals. The outputs of the input circuit breaker respectively connect L+ to the input of the first input switch and L- to the input of the second input switch. M is the neutral point of the converter and also the output neutral line of the converter, which is connected to the output M terminal. The output end of the first input switch is connected to the input end of the first Buck-Boost converter. The input L+ is connected to the input end of the first output switch after being regulated by the first Buck-Boost converter. The output end of the first output switch is connected to the output L+ terminal. The output end of the second input switch is connected to the input end of the second Buck-Boost converter. The input L+ is connected to the input end of the second output switch after being regulated by the second Buck-Boost converter. The output end of the second output switch is connected to the output L+ terminal.

[0009] The positive and negative of one group of energy storage devices are respectively connected to the input of the first bidirectional DC-DC converter, which is connected to the input of the first output switch and the output of the first Buck-Boost converter. In the discharge mode, the energy storage device is converted into a stable DC voltage by the first bidirectional DC-DC converter and output to the load, or is then fed to the input L+ through the first Buck-Boost converter. The positive and negative of another group of energy storage devices are respectively connected to the input of the second bidirectional DC-DC converter, which is connected to the input of the second output switch and the output of the second Buck-Boost converter. In the discharge mode, the energy storage device is converted into a stable DC voltage by the second bidirectional DC-DC converter and output to the load, or is then fed to the input L- through the second Buck-Boost converter.

[0010] The input L+ of the static bypass switch is connected to the output L+ of the input circuit breaker and the input of the first input switch, and the input L- of the static bypass switch is connected to the output L- of the input circuit breaker and the input of the second input switch. The output L+ of the static bypass switch is connected to the output of the first output switch and the L+ of the output terminal, and the output L- of the static bypass switch is connected to the output of the second output switch and the L- of the output terminal.

[0011] The manual bypass switch is also called the maintenance bypass switch. The input end is connected to the input end L+, input M, input L- and the input end of the input circuit breaker. The output of the manual bypass switch is connected to the output end L+, output M, output L- and the output end of the first output switch, the neutral line M, and the output end of the second output switch. When a system failure occurs, the load is directly powered through the manual bypass switch.

[0012] The Buck-Boost converter is a bidirectional DC-DC converter, which has the following functions: on the one hand, when working in the DC-UPS function, when the input DC voltage is greater than the rated output voltage, the Buck-Boost circuit works in the buck mode, and when the input DC voltage is less than the rated output voltage, the Buck-Boost circuit works in the boost mode, thereby stabilizing the output voltage and improving the output power quality. On the other hand, during flexible load regulation, when the power consumption is less than the power generation of new energy or during the power consumption valley, the Buck-Boost converter is linked with the bidirectional DC-DC converter, and the charging power of the bidirectional DC-DC converter is increased by the Buck-Boost converter; when the power consumption is greater than the power generation of new energy or during the power consumption peak period, the energy storage device discharges through the bidirectional DC-DC converter, and the Buck-Boost reduces the conversion power or reversely supplies power to the input DC, thereby achieving the effect of peak shaving and valley filling and transferring the power load.

[0013] The function of the bidirectional DC-DC converter is as follows: when charging is required, the bidirectional DC-DC operates in the charging mode, taking power from the input DC to charge the energy storage device; when discharging is required, the electrical energy stored in the energy storage device is released to the load or fed back to the input DC power grid in reverse.

[0014] On the one hand, the embodiment of the present application provides a DC true bipolar online uninterruptible power supply (DC-UPS) function, and the DC-UPS function mainly has the following working modes:

[0015] Mains online mode: when the input DC is within the normal input range, the DC-UPS operates in the mains online mode. In the mains online mode, the input DC passes through the input circuit breaker, the first input switch, and the second input switch to the first Buck-Boost converter and the second Buck-Boost converter. After passing through the first Buck-Boost converter and the second Buck-Boost converter, the input DC voltage becomes a stable DC power, and then passes through the first output switch and the second output switch to supply power to the load. As Figure 2 shown, the pointed arrow method marked in the figure is the power flow direction, and the thick line is the main working current path.

[0016] When the energy storage device needs to be charged in the DC online UPS mode, the first bidirectional DC-DC converter obtains electrical energy from the positive bus to charge the energy storage device, and the second bidirectional DC-DC converter obtains electrical energy from the negative bus to charge the energy storage device. As Figure 3 shown, the pointed arrow method marked in the figure is the power flow direction, and the thick line is the main working current path.

[0017] Battery discharge mode: when the input DC is abnormal, the DC-UPS operates in the battery discharge mode. In the battery discharge mode, the power supply path of the positive DC bus is that the energy storage device discharges through the first bidirectional DC-DC converter. The positive output of the first bidirectional DC-DC converter is connected to the input of the first output switch, the negative output of the first bidirectional DC-DC converter is connected to the neutral line M, and the output of the first output switch is connected to the output L+; the power supply path of the negative DC bus is that the energy storage device discharges through the second bidirectional DC-DC converter. The positive output of the second bidirectional DC-DC converter is connected to the neutral line M, the negative output of the second bidirectional DC-DC converter is connected to the input of the second input switch, and the output of the second input switch is connected to the output L-. As Figure 4 shown, the pointed arrow method marked in the figure is the power flow direction, and the thick line is the main working current path.

[0018] Static Bypass Mode: When a fault occurs in the internal converter of the DC-UPS, the DC-UPS automatically switches to the bypass mode. When operating in the static bypass mode, the input circuit breaker is closed, the input mains power is connected to the input circuit breaker, and the static switch conducts, bypassing the input DC to the output through the static switch. When the input is a true bipolar DC power supply and a fault occurs in one of the input poles, only the L+ or L- pole of the static bypass switch can be opened. When the DC-UPS is in the economic operation mode and the input DC is within the nominal range, the DC-UPS is in the static bypass state. When the input DC is outside the nominal range, the DC-UPS operates in the DC online mode or the battery discharge mode. As Figure 5 shown, the arrowhead method marked in the figure indicates the power flow direction, and the thick line is the main working current path.

[0019] Manual Bypass Mode: When there is an internal fault or maintenance in the DC-UPS, the manual bypass switch can be manually closed. To avoid electric shock during maintenance, after the manual bypass switch is closed, the input circuit breaker is disconnected. At this time, the input DC is connected to the input terminal of the manual bypass switch, and the input terminal of the manual bypass switch is connected to the output terminal. As Figure 6 shown, the arrowhead method marked in the figure indicates the power flow direction, and the thick line is the main working current path.

[0020] Input L- Phase Loss Operation Mode: When a fault occurs in the L- of the true bipolar DC power supply, the input L+ can still supply power normally. The input L+ passes through the input circuit breaker, the first input switch to the input terminal of the first Buck-Boost converter. The first Buck-Boost converter converts the unstable input DC into a stable positive DC power. The output of the first Buck-Boost converter is connected to the output L+ through the first output switch. The first bidirectional DC-DC converter operates in the charging mode, and the second bidirectional DC-DC converter operates in the discharging mode. The first bidirectional DC-DC converter and the second bidirectional DC-DC converter cooperate to convert the positive DC output from the first Buck-Boost converter into a stable negative DC after transformation, which is connected to the output L- through the second output DC switch. The conversion from input L+ to output L+ and L- is completed. As Figure 7 shown, the arrowhead method marked in the figure indicates the power flow direction, and the thick line is the main working current path.

[0021] Input L+ open-phase operation mode: When a fault occurs in L+ of the true bipolar DC power supply, the input L- can still supply power normally. The input L- passes through the input circuit breaker, the second input switch to the input terminal of the second Buck-Boost converter. The second Buck-Boost converter converts the unstable input DC into a stable negative DC power. The output of the second Buck-Boost converter is connected to the output L- through the second output switch. The second bidirectional DC-DC converter operates in the charging mode, and the first bidirectional DC-DC converter operates in the discharging mode. The first bidirectional DC-DC converter and the first bidirectional DC-DC converter cooperate to convert the negative DC output from the first Buck-Boost converter into a stable positive DC after transformation, and connect it to the output L+ through the first output DC switch. The transformation from input L+ to output L+ and L- is completed. As Figure 8 shown, the arrowhead method marked in the figure is the power flow direction, and the thick line is the main working current path.

[0022] When a fault occurs in L- of the input true bipolar DC power supply resulting in a power outage and at the same time a fault occurs in the output L+ and it must be disconnected, the DC-UPS can operate with the input DC positive and the output DC negative, as Figure 9 shown, the arrowhead method marked in the figure is the power flow direction, and the thick line is the main working current path.

[0023] When a fault occurs in L- of the input true bipolar DC power supply resulting in a power outage and at the same time a fault occurs in the output L- and it must be disconnected, the DC-UPS can operate with the input DC positive and the output DC positive, as Figure 10 shown, the arrowhead method marked in the figure is the power flow direction, and the thick line is the main working current path.

[0024] When a fault occurs in L+ of the input true bipolar DC power supply resulting in a power outage and at the same time a fault occurs in the output L- and it must be disconnected, the DC-UPS can operate with the input DC negative and the output DC positive, as Figure 11 shown, the arrowhead method marked in the figure is the power flow direction, and the thick line is the main working current path.

[0025] When a fault occurs in L+ of the input true bipolar DC power supply resulting in a power outage and at the same time a fault occurs in the output L+ and it must be disconnected, the DC-UPS can operate with the input DC negative and the output DC negative, as Figure 12 shown, the arrowhead method marked in the figure is the power flow direction, and the thick line is the main working current path.

[0026] When a fault occurs in the output L+, the DC-UPS only shuts down the output L+; when a fault occurs in the output L-, the DC-UPS only shuts down the output L-; as Figure 13 、 Figure 14 shown, the arrowhead method marked in the figure is the power flow direction, and the thick line is the main working current path.

[0027] On the other hand, the embodiments of the present application provide a flexible load function for realizing the operation of a virtual power plant in a photovoltaic energy storage DC-AC flexible system. The flexible power supply mainly has the following working modes:

[0028] Peak shaving and valley filling: During the peak electricity consumption period, the electric energy stored in the energy storage device is supplied to the input DC output power through the first bidirectional DC-DC converter, the second bidirectional DC-DC converter, the first Buck-Boost converter, the second Buck-Boost converter, the first input switch, and the second input switch. During the valley electricity consumption period, the input direct current passes through the first input switch, the second input switch, the first Buck-Boost converter, the second Buck-Boost converter, the first bidirectional DC-DC converter, and the second bidirectional DC-DC converter to charge the energy storage device, and store the electric energy of the power grid in the energy storage device.

[0029] Maximizing the utilization of new energy: In the photovoltaic energy storage DC-AC flexible system, when the electricity generated by new energy is greater than the current load demand, the excess electric energy passes through the first input switch, the second input switch, the first Buck-Boost converter, the second Buck-Boost converter, the first bidirectional DC-DC converter, and the second bidirectional DC-DC converter to charge the energy storage device, and store the excess electric energy of the power grid in the energy storage device. When the electricity generated by new energy is less than the electric energy provided by the load and the DC power grid, the electric energy stored in the energy storage device passes through the first bidirectional DC-DC converter, the second bidirectional DC-DC converter, the first Buck-Boost converter, the second Buck-Boost converter, the first input switch, and the second input switch to supply power to the input DC, or the electric energy stored in the energy storage device passes through the first bidirectional DC-DC converter, the second bidirectional DC-DC converter, the first output switch, and the second output switch to supply power to the load, reducing the power consumption from the power grid.

[0030] Constant power operation: Constant power supply may be the most efficient operation mode of the power grid. When the electricity consumption of the load is less than the supply of the DC power grid, the electric energy provided by the power grid minus the electric energy consumed by the load passes through the input direct current through the first input switch, the second input switch, the first Buck-Boost converter, the second Buck-Boost converter, the first bidirectional DC-DC converter, and the second bidirectional DC-DC converter to charge the energy storage device. When the load is greater than the supply of the DC power grid, the electric energy stored in the energy storage device passes through the first bidirectional DC-DC converter, the second bidirectional DC-DC converter, and together with the electric energy provided by the power grid, passes through the first output switch and the second output switch to supply power to the load.

[0031] Off-grid operation mode: When the DC power grid is powered off, the electric energy stored in the energy storage device is supplied to the load through the first bidirectional DC-DC converter, the second bidirectional DC-DC converter, the first output switch, and the second output switch. At the same time, it is supplied to the DC power grid after passing through the first Buck-Boost converter, the second Buck-Boost converter, the first input switch, and the second input switch.

[0032] The bidirectional DC-DC converter adopts an asymmetric CLLC soft-switching circuit to improve efficiency and reduce electromagnetic interference.

[0033] Compared with the prior art, the advantages and positive effects of the present utility model are as follows:

[0034] 1. In the present utility model, in the case of a single-pole fault, the device can convert the remaining single-pole power supply into a bipolar power supply through the internal DC-DC converter and Buck-Boost converter, ensuring that the system can still provide a stable bipolar output during a single-pole fault, improving the reliability of the power supply system, reducing the frequency of using the energy storage device, and thus extending the service life of the battery.

[0035] Through the true bipolar DC power supply system, when one pole of the input DC power supply fails, the other pole can still continue to supply power, avoiding the single-point fault of the system and improving the continuity and stability of power supply.

[0036] 2. In the present utility model, the DC-UPS device can flexibly switch between the battery charging mode and the discharging mode, using the energy storage device to supply power to the load when the power grid supply is insufficient, or charging the energy storage device when the power grid supply is sufficient, realizing peak shaving and valley filling of electric energy and optimizing the electric energy utilization efficiency.

[0037] The addition of the energy storage device enables the system to reduce its dependence on the power grid during peak electricity consumption periods, and at the same time store excess electric energy during low electricity consumption periods, improving the energy utilization rate and the peak shaving capacity of the power system.

[0038] 3. In the present utility model, through the voltage conversion and stable output functions of the Buck-Boost converter, the stability of the output voltage is ensured, providing high-quality DC electric energy, which is suitable for loads with high requirements for power quality.

[0039] The soft-switching design of the bidirectional DC-DC converter reduces electromagnetic interference, improves the electric energy conversion efficiency of the system, and ensures the efficient transmission of electric energy.

[0040] 4. In the present utility model, by combining with the photovoltaic-energy storage-direct-current flexible system, renewable energy such as photovoltaic power generation can be effectively utilized, reducing the dependence on traditional fossil energy.

[0041] This device supports the combination of photovoltaic power generation, energy storage, and DC power supply systems, achieving flexible power scheduling and distribution, promoting the consumption of renewable energy, and improving the comprehensive utilization efficiency of energy. Description of the Drawings

[0042] Figure 1 It is the DC online uninterruptible power supply for the DC bipolar power supply mode in the present utility model;

[0043] Figure 2 It is the DC-UPS in the utility model with the mains online working mode + battery, not charging;

[0044] Figure 3 It is the DC-UPS in the utility model with the mains online working mode + battery charging;

[0045] Figure 4 It is the DC-UPS in the utility model with the battery discharge working mode;

[0046] Figure 5 It is the DC-UPS in the utility model with the static bypass working mode;

[0047] Figure 6 It is the DC-UPS in the utility model with the manual bypass working mode;

[0048] Figure 7 It is the DC-UPS in the utility model with the input L-phase loss operation mode;

[0049] Figure 8 It is the DC-UPS in the utility model with the input L+ phase loss operation mode;

[0050] Figure 9 It is the DC-UPS in the utility model with the input L-phase loss + output L+ protection disconnection;

[0051] Figure 10 It is the DC-UPS in the utility model with the input L-phase loss + output L- protection disconnection;

[0052] Figure 11 It is the DC-UPS in the utility model with the input L+ phase loss + output L- protection disconnection;

[0053] Figure 12 It is the DC-UPS in the utility model with the input L+ phase loss + output L- protection disconnection;

[0054] Figure 13 It is the DC-UPS in the utility model with the input normal + output L+ protection disconnection;

[0055] Figure 14 It is the DC-UPS in the utility model with the input normal + output L- protection disconnection;

[0056] Figure 15 This is the schematic diagram of the DC-UPS embodiment in the present utility model. Specific embodiments

[0057] In order to more clearly understand the above objects, features, and advantages of the present utility model, the following further describes the present utility model with reference to the accompanying drawings and embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0058] In the following description, many specific details are set forth in order to fully understand the present utility model. However, the present utility model can also be implemented in other ways different from those described herein. Therefore, the present utility model is not limited by the specific embodiments disclosed in the following specification.

[0059] Embodiment

[0060] A true bipolar DC online uninterruptible power supply device (UPS), as Figure 1 shown, includes the following components:

[0061] Input circuit breaker: used to connect the input terminals L+, input M, and input L- and provide overload and short-circuit protection. A 3P DC circuit breaker is selected.

[0062] The first input switch and the second input switch: used to control the input connection of the DC power supply. DC relays are selected.

[0063] The first Buck-Boost converter and the second Buck-Boost converter: used for voltage conversion and stable output, including components such as input capacitors, Buck-Boost inductors, MOSFETs Q1, Q2, and output filter inductors.

[0064] The first output switch and the second output switch: used to control the output connection of the DC power supply. DC relays are selected.

[0065] The first bidirectional DC-DC converter and the second bidirectional DC-DC converter: used for charge and discharge control of the energy storage device, including components such as energy storage side filter capacitors, full-bridge circuit power tubes, isolation transformers, excitation inductors, resonant inductors, and resonant capacitors.

[0066] Energy storage device: includes a storage battery or other energy storage devices, used to provide power support when the input power supply fails.

[0067] Static bypass switch: used to automatically switch to the bypass mode when a fault occurs in the internal converter of the DC-UPS. A bidirectional switch composed of two series-connected MOSFETs in common emitter configuration is selected.

[0068] Manual bypass switch: Used to manually switch the power path, and a manual rotary switch is selected.

[0069] In one embodiment, in the utility-on mode, the DC power input passes through the input circuit breaker, the first input switch, and the second input switch, and then through the first Buck-Boost converter and the second Buck-Boost converter for voltage conversion and stable output respectively. The stabilized DC power supplies the load through the first output switch and the second output switch.

[0070] When the energy storage device needs to be charged, the first bidirectional DC-DC converter obtains electrical energy from the positive bus to charge the energy storage device, and the second bidirectional DC-DC converter obtains electrical energy from the negative bus to charge the energy storage device. As Figure 3 shown, the pointed arrow method marked in the figure is the power flow direction, and the thick line is the main working current path.

[0071] In one embodiment, in the battery discharge mode, the energy storage device discharges through the first bidirectional DC-DC converter and the second bidirectional DC-DC converter, and the stabilized DC power output by the converter supplies the load through the first output switch and the second output switch respectively. As Figure 4 shown, the pointed arrow method marked in the figure is the power flow direction, and the thick line is the main working current path.

[0072] In one embodiment, when a fault occurs in the internal converter of the DC-UPS, the system automatically switches to the static bypass mode. The input DC power supplies the load directly through the static bypass switch. As Figure 5 shown, the pointed arrow method marked in the figure is the power flow direction, and the thick line is the main working current path.

[0073] In one embodiment, in the manual bypass mode, when a fault occurs inside the DC-UPS or maintenance is required, the manual bypass switch can be manually closed to supply power to the load directly through the manual bypass switch, and the input circuit breaker is disconnected to ensure safety. As Figure 6 shown, the pointed arrow method marked in the figure is the power flow direction, and the thick line is the main working current path.

[0074] In one embodiment, in the input L-phase-loss operation mode, the input L+ passes through the input circuit breaker and the first input switch to the first Buck-Boost converter for voltage conversion, and the stabilized DC power supplies the output L+ through the first output switch. At the same time, the first bidirectional DC-DC converter operates in the charging mode, and the second bidirectional DC-DC converter operates in the discharging mode to convert the positive-polarity DC power output by the first Buck-Boost converter into negative-polarity DC power to supply the output L-. As Figure 7 shown, the pointed arrow method marked in the figure is the power flow direction, and the thick line is the main working current path.

[0075] In one embodiment, in the input L+ open-phase operation mode, the input L- undergoes voltage conversion through the input circuit breaker, the second input switch to the second Buck-Boost converter, and the stabilized DC power supply supplies power to the output L- through the second output switch. At the same time, the second bidirectional DC-DC converter operates in the charging mode, and the first bidirectional DC-DC converter operates in the discharging mode to convert the negative-polarity direct current output by the second Buck-Boost converter into positive-polarity direct current to supply power to the output L+. As Figure 8 shown, the pointed manner marked in the figure is the power flow direction, and the thick line is the main working current path.

[0076] In one embodiment, when a fault occurs in the input DC bipolar power supply of L- and the output L+ must be disconnected, the DC-UPS can operate in the input DC positive and output DC negative mode. As Figure 9 shown, the pointed manner marked in the figure is the power flow direction, and the thick line is the main working current path. And in the virtual power plant mode, through intelligent scheduling and management of energy storage devices, distributed energy sources and loads, the optimal allocation and management of electric energy are realized; in the off-grid mode, the energy storage device supplies power independently to ensure the normal operation of the equipment. The overall design improves the energy utilization efficiency and system reliability, making it have wide applications and importance in modern power systems.

[0077] The bidirectional DC-DC converter adopts an asymmetric CLLC soft-switching circuit to improve efficiency and reduce electromagnetic interference.

[0078] In the above embodiments, the true bipolar DC online uninterruptible power supply device can achieve reliable power supply in various operation modes, improve power supply reliability and power quality, and has the function of flexible load regulation, which is suitable for the "photovoltaic energy storage DC flexibility" system to realize power peak shaving and consumption of renewable energy.

[0079] The above is only a preferred embodiment of the present invention, and it is not intended to limit the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes and apply them to other fields. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims

1. A true bipolar DC online uninterruptible power supply device, characterized in that, Including: Input circuit breaker; First input switch and second input switch; First Buck-Boost converter and second Buck-Boost converter; First output switch and second output switch; First bidirectional DC-DC converter and second bidirectional DC-DC converter; Energy storage device; Static bypass switch and manual bypass switch Wherein, the input L+, input M, and input L- are connected to the input terminal of the input circuit breaker through input terminals. The output of the input circuit breaker is respectively connected to the input terminals of the first input switch and the second input switch. The output terminal of the first input switch is connected to the input terminal of the first Buck-Boost converter. The output terminal of the second input switch is connected to the input terminal of the second Buck-Boost converter. The output terminal of the first Buck-Boost converter is connected to the input terminal of the first output switch. The output terminal of the second Buck-Boost converter is connected to the input terminal of the second output switch. The output terminal of the first output switch is connected to the output L+ terminal. The output terminal of the second output switch is connected to the output L- terminal.

2. The true bipolar DC online uninterruptible power supply device according to claim 1, characterized in that: The positive electrode and negative electrode of the energy storage device are respectively connected to the input terminals of the first bidirectional DC-DC converter and the second bidirectional DC-DC converter. The output terminal of the first bidirectional DC-DC converter is connected to the input terminal of the first output switch and the output terminal of the first Buck-Boost converter. The output terminal of the second bidirectional DC-DC converter is connected to the input terminal of the second output switch and the output terminal of the second Buck-Boost converter.

3. The true bipolar DC online uninterruptible power supply device according to claim 1, characterized in that: The input terminals of the static bypass switch are respectively connected to the input terminals of the first input switch and the second input switch. The output terminals of the static bypass switch are respectively connected to the output terminals of the first output switch and the second output switch.

4. The true bipolar DC online uninterruptible power supply device according to claim 1, characterized in that: The input terminals of the manual bypass switch are respectively connected to input L+, input M, and input L-. The output terminals of the manual bypass switch are respectively connected to output L+, output M, and output L-.

5. The true bipolar DC online uninterruptible power supply device according to claim 1, characterized in that: The first Buck-Boost converter and the second Buck-Boost converter have a buck mode and a boost mode for stabilizing the output voltage.

6. The true bipolar DC online uninterruptible power supply device according to claim 1, wherein: The first bidirectional DC-DC converter and the second bidirectional DC-DC converter respectively have a charging mode and a discharging mode. In the discharging mode, the energy storage device supplies power to the load through the bidirectional DC-DC converter.

7. The true bipolar DC online uninterruptible power supply device according to claim 1, characterized in that: The energy storage device cooperates with the first Buck-Boost converter through the first bidirectional DC-DC converter to convert unstable direct current into a stable output voltage.

8. The true bipolar DC online uninterruptible power supply device according to claim 1, characterized in that: The bidirectional DC-DC converter adopts an asymmetric CLLC soft-switching circuit to improve efficiency and reduce electromagnetic interference.

9. The true bipolar DC online uninterruptible power supply device according to claim 1, wherein: The output switch can automatically close the corresponding output terminal in case of a load fault to ensure the stable operation of the system.

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