Multi-winding transformer containing energy storage unit and use method of multi-winding transformer

Abstract

The invention relates to a multi-winding transformer containing energy storage units and a use method of the multi-winding transformer. The transformer comprises a comprehensive control module, a first energy storage assembly and a second energy storage assembly. The first energy storage assembly is connected with the secondary winding and the control module, the second energy storage assembly is connected with the tertiary winding and the comprehensive control module, and the direct current side of the first energy storage assembly and the direct current side of the second energy storage assembly are connected through a direct current bus. The energy storage of the secondary winding and the energy storage of the tertiary winding are in a mutual standby state. On the basis that a group of energy storage devices are led out from the second winding of the transformer, an independent third winding is added to lead out the other group of energy storage devices, the two groups of energy storage devices are connected through a bus on the direct current side, output of the two groups of energy storage devices is flexibly allocated according to application scenes, and the output of the two groups of energy storage devices is adjusted under the condition that the primary side voltage and the secondary side voltage of the transformer are adjustable. Influences of common-mode current, high-frequency components, direct-current components and the like can be effectively avoided under short-time transient voltage fluctuation.

Description

Technical Field

[0001] This invention relates to the field of transformers, and more particularly to a multi-winding transformer containing an energy storage unit and its usage method. Background Technology

[0002] With the large-scale integration of distributed photovoltaic (PV) power, the problem of voltage exceeding the lower or upper limits is becoming increasingly prominent due to unstable PV output and increased impact loads, threatening the safe and stable operation of the power distribution system. Traditional transformers suffer from slow voltage regulation response and limited adjustable functions. Therefore, many energy storage devices are currently integrated into the power distribution system for high-quality voltage regulation. While directly connecting energy storage devices to the transformer load side can achieve faster voltage regulation, it still exposes the system to electromagnetic transients such as common-mode current, high-frequency components, and DC components, leading to unstable power quality. Furthermore, connecting energy storage devices only through a magnetically isolated third winding can avoid the influence of electromagnetic transients, but it cannot simultaneously regulate both the primary and secondary voltages. Therefore, how to achieve both high-quality and comprehensive voltage regulation when integrating energy storage devices is a key issue that needs to be addressed. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a multi-winding transformer with an energy storage unit and its usage method, thus solving the deficiencies of the prior art.

[0004] The objective of this invention is achieved through the following technical solution: a multi-winding transformer containing an energy storage unit, the transformer comprising an integrated control module, a first energy storage component, and a second energy storage component; the first energy storage component is connected to the secondary winding and the control module respectively, the second energy storage component is connected to the tertiary winding and the integrated control module respectively, and the DC sides of the first energy storage component and the second energy storage component are connected through a DC bus. The energy storage of the secondary and tertiary windings is in a backup state for each other. When a long-term steady-state voltage fluctuation occurs, the energy storage of the secondary winding will work to continuously output power to compensate for the voltage. When a short-term sharp voltage fluctuation occurs, and the electromagnetic transient component content is greater than the set value, the energy storage of the tertiary winding will work to continuously output power to compensate for the voltage. When the energy storage of one of them reaches the upper limit of charging or the lower limit of discharging, the other set of energy storage will be connected through the DC bus as a supplement.

[0005] The first energy storage component includes a first converter module, a first DC-DC step-up / step-down module, and a first energy storage device; the secondary winding is connected to the first converter module, the first converter module is connected to the first DC-DC step-up / step-down module, the first DC-DC step-up / step-down module is connected to the first energy storage device, and the integrated control module is connected to the first converter module and the first DC-DC step-up / step-down module.

[0006] The second energy storage component includes a second converter module, a second DC-DC step-up / step-down module, and a second energy storage device; the tertiary winding is connected to the second converter module, the second converter module is connected to the second DC-DC step-up / step-down module, the second DC-DC step-up / step-down module is connected to the second energy storage device, and the integrated control module is connected to the second converter module and the second DC-DC step-up / step-down module.

[0007] The secondary winding is also connected to the load.

[0008] A method of using a multi-winding transformer containing an energy storage unit, the method comprising: When the voltage of a certain winding of the transformer is detected to rise to the set upper limit, the corresponding converter module starts the rectification control mode to convert the AC power to DC power. At the same time, the corresponding DC step-up and step-down module starts the step-down control mode to reduce the voltage to the rated voltage of the corresponding energy storage device and charge the energy storage device. When the voltage of a certain winding of the transformer is detected to drop to the set lower limit, the corresponding DC step-up / step-down module starts the step-up control mode to increase the DC voltage of the corresponding energy storage device to the rated voltage of the winding. At the same time, the corresponding converter module starts the inverter control mode to convert the DC power to AC power. At this time, the energy storage device releases electrical energy to the transformer.

[0009] The present invention has the following advantages: a multi-winding transformer with energy storage unit and its usage method, on the basis that a set of energy storage devices has been led out from the second winding of the transformer, an independent third winding is added to lead out another set of energy storage devices. The two sets of energy storage devices are connected by a bus on the DC side. The output of the two sets of energy storage devices can be flexibly adjusted according to the application scenario. While ensuring that the voltage on both the primary and secondary sides of the transformer can be adjusted, it can effectively avoid the influence of common-mode current, high-frequency components, DC components and other factors under short-term transient voltage fluctuations. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a flowchart illustrating the method of the present invention. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of this application provided below with reference to the accompanying drawings is not intended to limit the scope of protection of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The present invention will be further described below with reference to the accompanying drawings.

[0012] One embodiment of the present invention relates to a multi-winding transformer containing an energy storage unit. Based on the fact that a set of energy storage devices has been led out from the second winding of the transformer, an independent third winding is added to lead out another set of energy storage devices. The two sets of energy storage devices are connected by a DC bus on their respective DC sides. The output of the two sets of energy storage devices can be flexibly adjusted according to the application scenario, which can avoid the influence of electromagnetic transient components and adjust the voltage at different positions of the transformer.

[0013] like Figure 1 As shown, it specifically includes the following: A 10kV / 0.4kV / 0.4kV core-type three-winding distribution transformer has its secondary winding connected in parallel to converter module 1, DC-DC step-up / step-down module 1, and energy storage device 1. Its tertiary winding is connected in parallel to converter module 2, DC-DC step-up / step-down module 2, and energy storage device 2. Two DC buses connect the DC sides of converter module 1 and converter module 2. The secondary winding is the one normally connected to the load. The converter module is a three-phase bridge circuit consisting of six IGBTs connected in anti-parallel with diodes and two capacitors. The DC-DC step-up / step-down module is a bidirectional DC-DC converter. The energy storage device is a battery bank with a rated DC voltage of 96V. A voltage measurement device and a power electronic device integrated control module are also included.

[0014] The energy storage in the secondary winding and the tertiary winding of the transformer are in a backup state for each other. When a long-term steady-state voltage fluctuation occurs, the energy storage in the secondary winding will work to continuously compensate for the voltage. When a short-term, sharp voltage fluctuation occurs, and the accompanying electromagnetic transient components such as common-mode current, high-frequency components, and DC components exceed the set value, the energy storage in the tertiary winding will work to continuously compensate for the voltage. When one of the energy storage devices reaches its upper limit for charging or its lower limit for discharging, the other energy storage device can be connected to the DC bus as a supplement.

[0015] like Figure 2As shown, during the operation of a distribution transformer, the voltage will fluctuate due to factors such as photovoltaic output and load fluctuations, and may even exceed the limit. Therefore, another embodiment of the present invention relates to a method of using a multi-winding transformer containing an energy storage unit, specifically including the following: Scenario 1: When the system's photovoltaic output is excessive or the load is significantly low, the transformer voltage rises to the set upper limit of 10.7kV. At this time, if the detected voltage waveform is stable and the electromagnetic transient component is small, converter module 1 rectifies the AC power into DC power, and converter module 1 reduces the DC voltage to the rated voltage of energy storage device 1, charging the battery bank in energy storage device 1. The state of charge (SOC) of the battery bank can be increased to 90% through charging, thereby fully storing the extra electrical energy and reducing the transformer voltage. However, if the initially detected electromagnetic transient component of the voltage is small, the modules involved in the above process are changed from module 1 to module 2. Specifically, if the SOC of battery bank 1 is greater than 90%, but the voltage is still higher than the set upper limit and further charging is required, converter module 1 will not start, battery bank 1 will stop charging, and converter module 2 will start. Electrical energy will continue to be transferred to battery bank 2 through the DC bus to charge battery bank 2. Similarly, the same applies to the handling of battery pack No. 2 when its SOC is greater than 90%.

[0016] Scenario 2: When the system's photovoltaic output suddenly decreases or the load significantly increases, the transformer voltage drops to the set lower limit of 9.3kV. In this case, if the detected voltage waveform is stable and the electromagnetic transient components are minimal, the battery bank in energy storage device 1 will discharge, the DC-DC step-up / step-down module 1 will increase the DC voltage, and the converter module 1 will rectify and invert the DC power into AC power, injecting energy into the transformer. The battery bank's SOC can be reduced to a maximum of 10% through discharge, thereby increasing the transformer voltage. If the detected voltage electromagnetic transient components are initially minimal, the modules involved in the above process will change from device 1 to device 2. Specifically, when the SOC of battery bank 1 is less than 10%, but the voltage is still below the set lower limit, and continued discharge is required, the DC-DC step-up / step-down module 1 will not start, battery bank 1 will stop discharging, and the DC-DC step-up / step-down module 2 will start, allowing battery bank 2 to discharge and continue transmitting energy to the AC side of the transformer via the DC bus. Similarly, the handling of battery bank 2 when its SOC is less than 10% is the same.

[0017] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and improvements, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A multi-winding transformer containing an energy storage unit, characterized in that: The transformer includes an integrated control module, a first energy storage component, and a second energy storage component; the first energy storage component is connected to the secondary winding and the control module respectively, the second energy storage component is connected to the tertiary winding and the integrated control module respectively, and the DC sides of the first energy storage component and the second energy storage component are connected through a DC bus. The energy storage of the secondary and tertiary windings is in a backup state for each other. When a long-term steady-state voltage fluctuation occurs, the energy storage of the secondary winding will work to continuously output power to compensate for the voltage. When a short-term sharp voltage fluctuation occurs, and the electromagnetic transient component content is greater than the set value, the energy storage of the tertiary winding will work to continuously output power to compensate for the voltage. When the energy storage of one of them reaches the upper limit of charging or the lower limit of discharging, the other set of energy storage will be connected through the DC bus as a supplement.

2. A multi-winding transformer with an energy storage unit according to claim 1, characterized in that: The first energy storage component includes a first converter module, a first DC-DC step-up / step-down module, and a first energy storage device; the secondary winding is connected to the first converter module, the first converter module is connected to the first DC-DC step-up / step-down module, the first DC-DC step-up / step-down module is connected to the first energy storage device, and the integrated control module is connected to the first converter module and the first DC-DC step-up / step-down module.

3. A multi-winding transformer with an energy storage unit according to claim 1, characterized in that: The second energy storage component includes a second converter module, a second DC-DC step-up / step-down module, and a second energy storage device; the tertiary winding is connected to the second converter module, the second converter module is connected to the second DC-DC step-up / step-down module, the second DC-DC step-up / step-down module is connected to the second energy storage device, and the integrated control module is connected to the second converter module and the second DC-DC step-up / step-down module.

4. A multi-winding transformer with an energy storage unit according to claim 1, characterized in that: The secondary winding is also connected to the load.

5. A method of using a multi-winding transformer containing an energy storage unit as described in any one of claims 1-4, characterized in that: The method of use includes: When the voltage of a certain winding of the transformer is detected to rise to the set upper limit, the corresponding converter module starts the rectification control mode to convert the AC power to DC power. At the same time, the corresponding DC step-up and step-down module starts the step-down control mode to reduce the voltage to the rated voltage of the corresponding energy storage device and charge the energy storage device. When the voltage of a certain winding of the transformer is detected to drop to the set lower limit, the corresponding DC step-up / step-down module starts the step-up control mode to increase the DC voltage of the corresponding energy storage device to the rated voltage of the winding. At the same time, the corresponding converter module starts the inverter control mode to convert the DC power to AC power. At this time, the energy storage device releases electrical energy to the transformer.

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