A flexible shore-based variable-frequency power supply system based on a movable energy storage device

Abstract

The present invention provides a flexible shore-based variable-frequency power supply system based on a movable energy storage device, which includes a flexible shore-based variable-frequency power supply, a movable energy storage device, and a seamless switching interface; the output end of the movable energy storage device is connected to the seamless switching interface and is connected to the DC bus of the flexible shore-based variable-frequency power supply through the seamless switching interface. The seamless switching interface includes a DC switch K1 and a diode reverse protection circuit. The negative pole of the diode reverse protection circuit is connected to the positive pole of the DC bus of the variable-frequency power supply. Two contacts at the upper end of the DC switch K1, one is connected to the positive pole of the diode reverse protection circuit, and the other is directly connected to the negative pole of the DC bus of the variable-frequency power supply; the lower end of the DC switch K1 is connected to the movable energy storage device. The movable container energy storage device is connected to the DC bus of the flexible shore-based variable-frequency power supply through the designed seamless switching interface, and has the function of an online uninterruptible power supply, greatly improving the power supply continuity and reliability of the shore-based variable-frequency power supply.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible onshore variable-frequency power supply systems, and particularly relates to a flexible onshore variable-frequency power supply system based on a movable energy storage device. Background Art

[0002] During the period when a ship is berthed at a port, heavy oil and diesel are used for power generation to meet the electricity demand, discharging a large amount of sulfur oxides (SOX), nitrogen oxides (NOX) and particulate matter into the atmosphere, and accompanied by the noise of the generator diesel engine, which has a serious impact on the ecosystem, the surrounding environment and human health. In the context of port environmental protection, governments around the world are actively promoting the application and development of onshore power at ports, that is, during the period when a ship is berthed at a port, the ship generator is no longer used, but the onshore variable-frequency power supply system at the dock is used to provide energy.

[0003] Traditional onshore variable-frequency power supplies draw power from the port power grid, and after voltage and frequency conversion and isolation, they supply power to the incoming ships. However, the port power grid has many loads and is prone to abnormal interruptions. When the grid power supply is abnormally interrupted, the traditional onshore variable-frequency power supply will also interrupt its output, causing the ship to lose power and resulting in low power supply reliability. At large port terminals, the investment in building onshore power for each berth is huge, and a reliable power supply device is the guarantee for ship electricity consumption. Summary of the Invention

[0004] In order to solve the technical problems proposed in the background art, the present invention provides a flexible onshore variable-frequency power supply system based on a movable energy storage device. The movable container energy storage device is connected to the DC bus of the flexible onshore variable-frequency power supply through a designed seamless switching interface, forming an onshore variable-frequency power supply system that can flexibly access the energy storage device, and enabling it to have the function of an online uninterruptible power supply, greatly improving the power supply continuity and reliability of the onshore variable-frequency power supply.

[0005] To achieve the above purpose, the present invention is implemented by adopting the following technical solutions:

[0006] A flexible onshore variable-frequency power supply system based on a movable energy storage device, comprising a flexible onshore variable-frequency power supply, a movable energy storage device and a seamless switching interface; the output end of the movable energy storage device is connected to one end of the seamless switching interface, and the other end of the seamless switching interface is connected to the DC bus of the flexible onshore variable-frequency power supply.

[0007] The seamless switching interface includes a DC switch K1 and a diode reverse protection circuit. The negative pole of the diode reverse protection circuit is connected to the positive pole of the DC bus of the variable-frequency power supply. One of the two contacts at the upper end of the DC switch K1 is connected to the positive pole of the diode reverse protection circuit, and the other is directly connected to the negative pole of the DC bus of the variable-frequency power supply; the two contacts at the lower end of the DC switch K1 are connected to the two DC output ends of the movable energy storage device.

[0008] Further, the diode reverse protection circuit is composed of multiple diode circuits connected in parallel. Each of the diode circuits is composed of one or more diodes connected in series. Moreover, overcurrent protection devices are connected to both the upper and lower sides of the series-connected diodes. The positive and negative polarities of all the diodes are in the same direction. The positive direction of the diode is the positive direction of the diode reverse protection circuit, and the negative direction of the diode is the negative direction of the diode reverse protection circuit.

[0009] Further, the no-disturbance switching interface further includes a lightning arrester SPD. The upper end of the lightning arrester SPD is directly connected to the DC output terminal port of the mobile energy storage device at the lower end of the no-disturbance switching interface, and the lower end of the lightning arrester SPD is grounded.

[0010] Further, the mobile energy storage device is a containerized energy storage battery device.

[0011] The control method of a flexible shore-based variable-frequency power supply system based on a mobile energy storage device includes the following:

[0012] 1) The flexible shore-based variable-frequency power supply is based on PWM modulation technology and outputs a rated voltage that remains unchanged and a full-load output capacity that remains unchanged within a wide DC voltage operating range. The operating range of the DC bus voltage is from a minimum value U min to a maximum value U Max . When powered by the power frequency supply, the DC voltage range is U Mid to U Max ; when powered by the energy storage, the DC voltage range is U min to U Mid ;

[0013] 2) The no-disturbance switching interface between the energy storage power supply and the power frequency power supply uses high-power diodes for isolation and no-disturbance switching. When the power frequency power supply is normal, the DC bus voltage is relatively high and the diodes are cut off, and the energy storage power supply exits. When the power frequency grid power supply is abnormal and the flexible shore-based variable-frequency power supply cannot draw power from the grid, the high-power diodes of the no-disturbance switching interface conduct, and the output terminal of the mobile energy storage device supplies power to the flexible shore-based variable-frequency power supply, enabling the normal output of the flexible shore-based variable-frequency power supply to be maintained.

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

[0015] The uninterruptible power supply shore-based variable frequency power supply system based on a movable energy storage device of the present invention has a non-disturbing switching interface that differentiates from an active DCDC converter, with high reliability, small footprint, and low loss, enabling non-disturbing switching of a high-power energy storage device. During ship power supply, when the port power supply is interrupted, it can be non-disturbingly switched to the energy storage device for power supply, avoiding power interruption for the ship; during a power grid interruption, the energy storage device continuously supplies power to the ship through the shore-based variable frequency power supply; when the port power supply is restored, it can be non-disturbingly switched back to the power grid for power supply, and the energy storage device enters the standby state. Throughout the process, the ship continuously uses electricity, and the output characteristics, power capacity, and overload capacity of the shore-based variable frequency power supply system remain unchanged. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 FIG. is the overall structure diagram of a flexible shore-based variable frequency power supply system based on a movable energy storage device of the present invention;

[0017] Figure 2 FIG. is the specific circuit diagram of the non-disturbing switching interface of the present invention.

[0018] In the figure: 1 - input switch, 2 - rectifier transformer, 3 - variable frequency power supply input switch, 4 - rectifier unit of the variable frequency power supply, 5 - DC bus, 6 - inverter unit and output filter device, 7 - non-disturbing switching interface, 8 - isolation transformer, 9 - output switch, 10 - movable energy storage device, 11 - diode reverse stop protection circuit. SPECIFIC EMBODIMENTS

[0019] The following provides a detailed description of the specific embodiments provided by the present invention in conjunction with the accompanying drawings.

[0020] As Figure 1 shown, a flexible shore-based variable frequency power supply system based on a movable energy storage device includes a flexible shore-based variable frequency power supply, a movable energy storage device, and a non-disturbing switching interface.

[0021] The flexible shore-based variable frequency power supply is a prior art. As Figure 1 shown, it includes an input switch 1, a rectifier transformer 2, a variable frequency power supply input switch 3, a rectifier unit 4 of the variable frequency power supply, a DC bus 5, an inverter unit and output filter device 6, an isolation transformer 8, and an output switch 9 that are connected in sequence from the input end to the output end.

[0022] The movable energy storage device 10 adopts a containerized energy storage battery device, which is formed by installing energy storage batteries in a container. The output terminals B+ and B- of the movable energy storage device 10, that is, the battery, are connected to one end of the non-disturbing switching interface 7, and the other end of the non-disturbing switching interface 7 is connected to A+ and A- of the DC bus 5 of the flexible shore-based variable frequency power supply.

[0023] As Figure 2As shown, the non-interference switching interface 7 includes a DC switch K1 and a diode reverse protection circuit 11. The diode reverse protection circuit 11 is composed of multiple diode circuits connected in parallel. Each diode circuit is composed of more than one diode connected in series. Moreover, overcurrent protection devices are connected to both the upper and lower sides after the diodes are connected in series. The positive and negative polarities of all diodes are in the same direction. The positive direction of the diode is the positive direction of the diode reverse protection circuit 11, and the negative direction of the diode is the negative direction of the diode reverse protection circuit 11. Figure 2 In the figure, the fuse F1 and the fuse F2 (overcurrent protection devices) are connected before and after the diodes D1 and D2 are connected in series to form the first diode circuit. The fuse F3 and the fuse F4 are connected before and after the diodes D3 and D4 are connected in series to form the second diode circuit,..., the fuse Fn-1 and the fuse Fn are connected before and after the diodes Dn-1 and Dn are connected in series to form the last diode circuit. These diode circuits are connected in parallel to form the diode reverse protection circuit 11.

[0024] The negative pole of the diode reverse protection circuit 11 is connected to the positive pole A+ of the DC bus 5 of the variable-frequency power supply. One of the two contacts at the upper end of the DC switch K1 is connected to the positive pole of the diode reverse protection circuit 11, and the other is directly connected to the negative pole A- of the DC bus 5 of the variable-frequency power supply; the two contacts at the lower end of the DC switch K1 are connected to the two DC output terminals B+ and B- of the mobile energy storage device.

[0025] The non-interference switching interface 7 further includes a lightning arrester SPD. The upper end of the lightning arrester SPD is directly connected to the DC output terminal ports B+ and B- of the mobile energy storage device 10 at the lower end of the non-interference switching interface 7, and the lower end of the lightning arrester SPD is grounded.

[0026] The control method of a flexible shore-based variable-frequency power supply system based on a mobile energy storage device includes the following:

[0027] 1) The flexible shore-based variable-frequency power supply is based on PWM modulation technology, and outputs a rated voltage that remains unchanged and a full-load output capacity that remains unchanged within a wide DC voltage operating range. The operating range of the DC bus voltage is from the minimum value U min to the maximum value U Max . When powered by the power frequency, the DC voltage range is U Mid to U Max ; when powered by the energy storage, the DC voltage range is U min to U Mid , and U Mid is the intermediate value of the DC bus voltage operating range.

[0028] 2) The seamless switching interface between the energy storage power supply and the industrial frequency power supply uses high-power diodes for isolation and seamless switching. When the industrial frequency power supply is normal, the DC bus voltage is relatively high and the diodes are cut off, and the energy storage power supply exits. When the industrial frequency grid power supply is abnormal, the flexible onshore variable-frequency power supply cannot draw power from the grid. The high-power diodes at the seamless switching interface conduct, and the output end of the mobile energy storage device supplies power to the flexible onshore variable-frequency power supply, enabling the normal output of the flexible onshore variable-frequency power supply to be maintained.

[0029] The circuit principle of the seamless switching of the seamless switching interface 7 is explained as follows:

[0030] The diode reverse-stop protection circuit 11 plays a role of reverse cut-off. The DC switch K1 is the main switch of the device. When the mobile energy storage device 10 is installed and ready for use, the switch can be closed. When the DC switch K1 is closed, the mobile energy storage device 10 is connected to the DC bus 5 of the variable-frequency power supply through the diode reverse-stop protection circuit 11.

[0031] 1) When the port grid power supply is normal, the onshore variable-frequency power supply draws power from the grid. At this time, the voltage of the DC bus 5 of the variable-frequency power supply is higher than the output voltage of the mobile energy storage device 10. All the diodes in the diode reverse-stop protection circuit 11 are in the reverse cut-off state, the diode reverse-stop protection circuit 11 does not conduct, the mobile energy storage device 10 and the DC bus 5 of the variable-frequency power supply are in a disconnected state, isolating the mobile energy storage device 10, and the DC bus 5 of the variable-frequency power supply will not charge the mobile energy storage device 10 in reverse, without affecting the working state of the onshore variable-frequency power supply itself.

[0032] 2) When the port grid power supply is abnormal, the onshore variable-frequency power supply cannot draw power from the grid. At this time, the voltage of the DC bus 5 of the variable-frequency power supply is lower than the output voltage of the mobile energy storage device 10. All the diodes in the diode reverse-stop protection circuit 11 are in the forward conduction state, the diode reverse-stop protection circuit 11 conducts, the mobile energy storage device 10 and the DC bus 5 of the variable-frequency power supply are in a connected state, and the output end of the mobile energy storage device 10 supplies power to the DC bus 5 of the variable-frequency power supply, enabling the normal output of the onshore variable-frequency power supply to be maintained.

[0033] Regardless of whether the port grid power supply is normal or abnormal, the DC switch K1 does not need to be disconnected. Due to the reverse cut-off function of the diode reverse-stop protection circuit 11, when the mobile energy storage device 10 is not required to supply power to the onshore variable-frequency power supply, the diode reverse-stop protection circuit 11 does not conduct and can automatically disconnect the connection. When the port grid power supply is abnormal, since the voltage of the DC bus 5 of the variable-frequency power supply is lower than the output voltage of the mobile energy storage device 10, the diode reverse-stop protection circuit 11 can be automatically conducted. There is no switching-on or switching-off process in the whole process. Therefore, it can be seamlessly switched to the energy storage device to achieve uninterrupted continuous power supply of the onshore variable-frequency power supply.

[0034] The circuit principle of the diode reverse-stop protection circuit 11:

[0035] First, a diode circuit is formed by connecting multiple diodes in series. Then, the circuit structure principle of connecting multiple diode circuits in parallel is as follows: Connecting multiple diodes in series is considered for the voltage withstand performance of the diodes. After multiple diodes are connected in series, the overall voltage withstand level can be improved. Connecting multiple diode circuits in parallel is considered for the rated current of the diodes. Multiple parallel connections can increase the overall rated current. Since the voltage level of the DC bus 5 of the variable-frequency power supply is higher than the voltage withstand of a single diode, a structure of series-connected diodes is adopted. At the same time, in order to ensure the supply current between the mobile energy storage device 10 and the shore-based variable-frequency power supply, a structure of connecting multiple diode circuits in parallel can achieve a rated current of 3000 A DC. Two overcurrent protection devices (such as fuses F1, F2, etc.) are used to provide multiple overcurrent protection for a single diode circuit.

[0036] Function of the lightning arrester SPD

[0037] Since the container-type energy storage battery device is adopted in this solution, the external electrical ports of the container need lightning protection functions to prevent external spike currents from entering the interior and damaging the internal electrical components. The lightning arrester SPD plays the above role.

[0038] The above embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the above embodiments. The methods used in the above embodiments are all conventional methods unless otherwise specified.

Claims

1. A flexible shore-based variable-frequency power supply system based on a movable energy storage device, characterized in that, it includes a flexible shore-based variable-frequency power supply, a movable energy storage device, and a seamless switching interface; the output end of the movable energy storage device is connected to one end of the seamless switching interface, and the other end of the seamless switching interface is connected to the DC bus of the flexible shore-based variable-frequency power supply; the seamless switching interface includes a DC switch K1 and a diode reverse protection circuit. The negative pole of the diode reverse protection circuit is connected to the positive pole of the DC bus of the variable-frequency power supply. One of the two contacts at the upper end of the DC switch K1 is connected to the positive pole of the diode reverse protection circuit, and the other is directly connected to the negative pole of the DC bus of the variable-frequency power supply; the two contacts at the lower end of the DC switch K1 are connected to the two DC output ends of the movable energy storage device; The described flexible shore-based variable-frequency power supply is based on PWM modulation technology, and the DC voltage operating range is from the minimum value U min to the maximum value U Max . The intermediate voltage demarcation point between the power frequency power supply and the mobile energy storage device is U Mid . When powered by the power frequency, the DC voltage range is U Mid to U Max ; when powered by energy storage, the DC voltage range is U min to U Mid . The seamless switching interface between the energy storage power supply and the industrial-frequency power supply uses high-power diodes for isolation and seamless switching. When the industrial-frequency power supply is normal, the DC bus voltage is relatively high and the diodes are cut off, and the energy storage power supply exits. When the industrial-frequency grid power supply is abnormal, the flexible shore-based variable-frequency power supply cannot draw power from the grid, and the high-power diodes of the seamless switching interface are turned on, and the output end of the movable energy storage device supplies power to the flexible shore-based variable-frequency power supply, which can maintain the normal output of the flexible shore-based variable-frequency power supply; Regardless of whether the port grid power supply is normal or abnormal, the DC switch K1 does not need to be disconnected. Due to the reverse cut-off effect of the diode reverse protection circuit, when the movable energy storage device does not need to supply power to the shore-based variable-frequency power supply, the diode reverse protection circuit does not conduct and disconnects automatically. When the port grid power supply is abnormal, since the voltage of the DC bus of the variable-frequency power supply is lower than the output voltage of the movable energy storage device, the diode reverse protection circuit is automatically turned on. There is no switching process of the switch in the whole process. Therefore, it can be seamlessly switched to the energy storage device to realize the uninterrupted continuous power supply of the shore-based variable-frequency power supply.

2. A flexible shore-based variable-frequency power supply system based on a movable energy storage device according to claim 1, characterized in that, the diode reverse protection circuit is composed of multiple diode circuits connected in parallel, each of the diode circuits is composed of one or more diodes connected in series, and overcurrent protection devices are connected to the upper and lower sides after the diodes are connected in series, and the positive and negative polarities of all diodes are in the same direction.

3. A flexible shore-based variable-frequency power supply system based on a movable energy storage device according to claim 1, characterized in that, the seamless switching interface further includes a lightning arrester SPD. The upper end of the lightning arrester SPD is directly connected to the DC output terminal port of the movable energy storage device at the lower end of the seamless switching interface, and the lower end of the lightning arrester SPD is grounded.

4. A flexible shore-based variable-frequency power supply system based on a movable energy storage device according to claim 1, characterized in that, the movable energy storage device is a containerized energy storage battery device.

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