Auxiliary power supply energy taking method for full-direct-current system equipment

Abstract

The invention discloses an auxiliary power supply energy taking method for full-direct-current system equipment, belongs to the technical field of direct-current power transmission, and aims to replace a one-way blocking element of a grid-connected point of a new energy station with a direct-current circuit breaker and replace a one-way direct-current converter on a station side with a two-way power converter at the same time. Through the transformation, the direct current line is always kept in an electrified state under various working conditions, so that electric energy can be directly obtained from the low-voltage side of the bidirectional power converter, and power is supplied to auxiliary equipment in a new energy station. The problems that an auxiliary power supply in a full-direct-current system depends on external long-distance power supply and is high in cost and poor in reliability are effectively solved, on-site efficient energy taking of the auxiliary power supply is achieved, and the economical efficiency and the self-sustaining capacity of the system are improved.

Description

Technical Field

[0001] This application relates to the field of DC power transmission technology, and more specifically, to a method for harvesting auxiliary power for all-DC system equipment. Background Technology

[0002] With the continuous expansion of renewable energy generation scale such as wind power and photovoltaics and their increasing proportion in the power structure, all-DC collection and transmission systems for new energy sources have become an ideal solution for achieving efficient power transmission due to their significant technological advantages. Compared with traditional AC power generation modes, all-DC systems overcome limitations such as reactive power, frequency stability, and power angle stability, possessing higher transmission efficiency and longer transmission distances. They can significantly improve the collection and transmission capabilities of large-scale new energy generation, and are therefore regarded as an important technological path to meet future clean energy consumption needs.

[0003] In traditional photovoltaic (PV) power plants, the auxiliary power supply for the power generation units is typically drawn from the AC output of the inverter, the PV modules themselves, or external AC power sources to supply loads such as control systems, monitoring equipment, cooling devices, fire protection systems, and lighting. This model, under an AC aggregation architecture, can reliably meet the energy consumption requirements of auxiliary equipment. Figure 1 The diagram shows the topology of an existing high-voltage direct-connected energy storage system. In this topology, a unidirectional blocking diode is installed at the grid connection point. While this effectively isolates DC-side faults, it also completely blocks the possibility of current flowing back into the power station from the DC bus. This means that when the power station stops generating electricity, the auxiliary power supply cannot obtain power from the DC line and must rely entirely on external power sources. This results in inherent drawbacks such as low reliability, high cost, and complex operation and maintenance.

[0004] However, in all-DC convergence systems, the high manufacturing cost of key equipment such as bidirectional DC transformers and DC circuit breakers makes it difficult to achieve rapid, economical, and reliable isolation when line faults occur, especially facing the challenge of selective isolation after multiple renewable energy sources are fed in. Common designs typically configure unidirectional blocking diodes at the grid connection point to enhance system reliability, but this measure also introduces new problems: limited by the electrical characteristics of unidirectional DC / DC converters and blocking diodes, auxiliary power cannot be directly obtained from the DC line, often requiring reliance on a booster station or nearby AC system to draw external power, increasing system complexity and construction costs.

[0005] In all-DC power generation systems, medium-voltage DC transmission lines may extend for tens of kilometers, with large voltage drops and high difficulty in power extraction, making traditional auxiliary power supply methods unsuitable. Therefore, how to provide a stable, reliable, and economical power supply for auxiliary equipment in photovoltaic power generation units under such conditions has become a key issue that urgently needs to be addressed in the development of current all-DC collection technology. Summary of the Invention

[0006] The purpose of this application is to overcome the shortcomings of existing technologies and provide a method for harvesting auxiliary power for all-DC system equipment. This method effectively solves the problems of auxiliary power supply relying on external long-distance power supply, high cost, and poor reliability in all-DC systems, and realizes efficient local power harvesting for auxiliary power supply.

[0007] The objective of this application is achieved through the following technical solution: In a first aspect, this application proposes a method for auxiliary power extraction in a full DC system. The method is applied to a DC grid-connected system, wherein a unidirectional blocking diode is installed at the grid connection point of the renewable energy power plant, and a unidirectional DC / DC transformer is installed on the power plant side. The method includes: Replace the unidirectional blocking diode at at least one DC line grid connection point with a DC circuit breaker; Replace the unidirectional DC converter on the DC line station side with a bidirectional power converter; Electrical energy is drawn from the low-voltage side of the bidirectional power converter to serve as auxiliary power for auxiliary equipment in the new energy power station.

[0008] In one possible implementation, the bidirectional power converter is a bidirectional DC / DC converter, and power is drawn from the low-voltage DC side of the bidirectional DC / DC converter to supply power to auxiliary equipment. In one possible implementation, the method further includes filtering the extracted electrical energy and providing overvoltage protection. In one possible implementation, the bidirectional power converter is a bidirectional AC / DC converter, and power is drawn from the low-voltage side of the bidirectional AC / DC converter to supply power to auxiliary equipment. In one possible implementation, the method further includes an intelligent switching step: prioritizing the use of DC power to power auxiliary equipment, and automatically switching to AC power when DC power is insufficient.

[0009] In one possible implementation, the method further includes harmonic suppression processing of the extracted electrical energy. Secondly, this application proposes an auxiliary power supply system for implementing the first aspect of an all-DC system, comprising: DC circuit breakers are installed at the grid connection point of new energy power plants; A bidirectional power converter is installed on the side of the new energy power station, and its low-voltage side is connected to the auxiliary power equipment of the station. A DC circuit breaker, in conjunction with a bidirectional power converter, enables the DC line to be continuously energized, providing power to auxiliary equipment.

[0010] In one possible implementation, the bidirectional power converter is a bidirectional DC / DC converter, with a filter module and an overvoltage protection module connected to its low-voltage side output. In one possible implementation, the bidirectional power converter is a bidirectional AC / DC converter, with an intelligent switching module connected to its low-voltage side output terminal for distributing electrical energy to DC or AC auxiliary equipment. In one possible implementation, an energy storage unit is also included, connected to the low-voltage side of the bidirectional power converter as a backup power source.

[0011] The main solution and its various further alternatives described above can be freely combined to form multiple solutions, all of which are solutions that can be adopted and are claimed in this application; furthermore, the (non-conflicting alternatives) can also be freely combined with each other and with other alternatives. Those skilled in the art, after understanding the solution of this application, will realize from the prior art and common general knowledge that there are many combinations, all of which are technical solutions to be protected in this application, and will not be exhaustively listed here.

[0012] This application discloses a method for harvesting auxiliary power for equipment in a full DC system, belonging to the field of DC transmission technology. It replaces the unidirectional blocking element at the grid connection point of a new energy power plant with a DC circuit breaker, and simultaneously replaces the unidirectional DC converter on the power plant side with a bidirectional power converter. Through these modifications, the DC line remains energized under various operating conditions, enabling direct energy harvesting from the low-voltage side of the bidirectional power converter to power auxiliary equipment within the new energy power plant. This effectively solves the problems of reliance on external long-distance power supply, high cost, and poor reliability in full DC systems, achieving efficient local energy harvesting for auxiliary power and improving the system's economy and self-sufficiency. Attached Figure Description

[0013] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a topology diagram of an existing high-voltage direct-connected energy storage system.

[0015] Figure 2 A schematic flowchart of an auxiliary power supply harvesting method for an all-DC system device according to an embodiment of this application is shown.

[0016] Figure 3 A schematic diagram of a system topology and energy flow implementation method is shown.

[0017] Figure 4 A schematic diagram of another system topology and energy flow implementation method is shown. Detailed Implementation

[0018] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0019] Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] Please refer to Figure 2 , Figure 2 This paper presents a flowchart illustrating an auxiliary power supply method for a fully DC system according to an embodiment of this application. The method is applied to a DC grid-connected system, wherein a unidirectional blocking diode is installed at the grid connection point of the renewable energy power station, and a unidirectional DC / DC transformer is installed on the power station side. The method includes: Step S1: Replace the unidirectional blocking diode at at least one DC line grid connection point with a DC circuit breaker.

[0021] Step S2: Replace the unidirectional DC converter on the DC line station side with a bidirectional power converter.

[0022] Step S3: Extract electrical energy from the low-voltage side of the bidirectional power converter to serve as auxiliary power for auxiliary electrical equipment in the new energy power station.

[0023] This invention relates to a method for auxiliary power extraction in a fully DC system, primarily applied to DC collection and grid-connected systems using renewable energy plants such as photovoltaic and wind power plants as power sources. In a typical initial configuration of such systems, the grid connection point of the renewable energy plant is usually equipped with a unidirectional blocking diode for fault isolation; simultaneously, a unidirectional DC / DC transformer is installed on the plant side to boost the DC voltage for grid connection. The power supply for various auxiliary electrical equipment within the plant typically relies on external power sources or additional generators, introducing additional construction and operation costs into the DC collection system.

[0024] In step S1, at least one DC line in the system is selected, and the original unidirectional blocking diode at its grid connection point is replaced with a DC circuit breaker. This replacement is crucial because the DC circuit breaker has both the ability to quickly disconnect faults and the ability to ensure the electrical continuity of the line under normal and non-fault abnormal conditions, overcoming the difficulty of power supply caused by the unidirectional conduction of the diode.

[0025] In step S2, the existing unidirectional DC-DC converter on the selected line station side is replaced with a bidirectional power converter. Here, "bidirectional" means that the converter allows energy to flow in both directions, not only boosting the electrical energy generated by the new energy station and transmitting it to the DC grid, but also having the ability to extract energy from the DC grid and step it down for output.

[0026] In step S3, electrical energy is directly drawn from the low-voltage side of the bidirectional power converter and used as an auxiliary power source for all auxiliary electrical equipment in the new energy power station. Thus, by replacing the two key components mentioned above, the modified DC line can remain energized under any operating condition, becoming a reliable local power source. This completely eliminates dependence on remote external power sources, significantly reduces system costs, and greatly improves the reliability and self-sufficiency of the entire DC power supply system.

[0027] In one possible embodiment, Figure 3 A schematic diagram of a system topology and energy flow implementation is shown. Grid connection point device replacement: The unidirectional blocking diode originally located at the grid connection point of the DC collection line is replaced with a DC circuit breaker. Power station side device replacement: The unidirectional DC / DC converter originally located at the renewable energy power station side is replaced with a bidirectional DC / DC converter.

[0028] After the above modifications, the electrical characteristics of the DC line have undergone a fundamental change: regardless of whether the source-side renewable energy power station is generating electricity (daytime) or not generating electricity (nighttime), and regardless of whether it is in normal operation or fault isolation, due to the conduction characteristics of the DC circuit breaker and the bidirectional power throughput capability of the bidirectional DC / DC converter, the line always constitutes a "permanently energized line".

[0029] At this point, electrical energy can be continuously transmitted through this line to the bidirectional DC / DC converter. Therefore, power can be directly drawn from the low-voltage side interface of this bidirectional DC / DC converter. After appropriate voltage transformation and voltage regulation filtering, the obtained electrical energy can provide a stable and reliable power supply for all auxiliary system equipment in the site, such as control, monitoring, cooling, and fire protection, achieving efficient "local energy extraction" and completely eliminating dependence on remote external power sources.

[0030] In another possible embodiment, Figure 4 A schematic diagram of another system topology and energy flow implementation method is shown. Grid connection point device replacement: The unidirectional blocking diode originally located at the grid connection point of the DC collection line is replaced with a DC circuit breaker. Station-side device replacement: The unidirectional DC / DC converter originally located at the renewable energy station side is replaced with a bidirectional AC / DC converter.

[0031] After the aforementioned modifications, similar to the previous ones, this DC line also transforms into a "permanently energized line": regardless of the power generation status (day / night) or operating status of the renewable energy power station on the source side, the line remains continuously energized due to the conduction of the DC circuit breaker and the energy exchange capability of the bidirectional AC / DC converter. At this time, electrical energy can be stably delivered to the bidirectional AC / DC converter. Its key advantage lies in the ability to simultaneously obtain both alternating current (AC) and direct current (DC) power output from the low-voltage side of this bidirectional AC / DC converter. This provides a direct and flexible power supply option for different types of auxiliary equipment within the power station (such as pumps, fans, and lighting requiring AC power, and control and communication systems requiring DC power), eliminating the need for additional conversion equipment, further improving the economy and power supply efficiency of system integration, and providing a comprehensive and reliable power solution for the entire power station's auxiliary systems.

[0032] The bidirectional power converter is a bidirectional DC / DC converter that draws power from the low-voltage DC side of the bidirectional DC / DC converter to supply power to auxiliary equipment.

[0033] The bidirectional DC / DC converter, through pulse-width modulation control of its semiconductor switching devices, possesses bidirectional energy transfer capabilities. It can both step down and convert medium-to-high voltage DC power from the DC collector line to low-voltage DC power, and also achieve reverse energy transfer in specific modes. Power is directly drawn from the low-voltage DC side of the aforementioned bidirectional DC / DC converter. This low-voltage DC output, after filtering and protection circuitry, is directly connected to the DC bus of the station's auxiliary equipment, thus providing a stable and reliable DC power supply for critical auxiliary loads such as control systems, communication equipment, and cooling fans. This design eliminates the need for additional AC / DC conversion stages, significantly improving energy extraction efficiency.

[0034] The method also includes filtering the extracted electrical energy and overvoltage protection.

[0035] By configuring an LC filter circuit in the front stage, high-frequency ripple and electromagnetic interference in the power supply are effectively suppressed, ensuring a smooth and stable output waveform. At the same time, a multi-stage overvoltage protection module consisting of transient voltage suppression diodes and varistors (MOVs) is set in the output circuit. When the line encounters abnormal conditions such as lightning strikes or operational overvoltages, it can quickly clamp and absorb surge energy to prevent high voltage impacts from damaging sensitive auxiliary equipment in the downstream stage.

[0036] The bidirectional power converter is a bidirectional AC / DC converter, which draws power from the low-voltage side of the bidirectional AC / DC converter to supply power to auxiliary equipment.

[0037] This bidirectional AC / DC converter achieves efficient bidirectional conversion between DC bus voltage and AC power through fully controlled switching devices and a PWM control strategy. Innovatively, this invention draws power from the low-voltage side of the bidirectional AC / DC converter—its low-voltage output, after rectification, filtering, and voltage regulation, can simultaneously provide both AC and DC power outputs: the AC output can directly power AC auxiliary equipment such as fans and pumps; the DC output powers DC loads such as control systems and communication modules via a dedicated DC bus.

[0038] The method also includes an intelligent switching step: prioritizing the use of DC power to power auxiliary equipment, and automatically switching to AC power when DC power is insufficient.

[0039] The intelligent control unit monitors the voltage and power quality parameters of the DC power supply circuit in real time, prioritizing the use of power from the DC bus to power auxiliary equipment. When an abnormal DC voltage or insufficient power output is detected, the control unit immediately drives a solid-state switching switch to automatically switch to the AC power supply circuit. This intelligent switching mechanism, through a dual-circuit redundancy design, fully leverages the high efficiency and stability of DC power supply while ensuring the continuity and reliability of the auxiliary power supply system under extreme conditions, effectively enhancing the system's adaptability to different operating states.

[0040] The method also includes harmonic suppression processing of the extracted electrical energy.

[0041] By configuring an IGBT-based power bridge arm and a digital signal processor in the active filter unit, the load-side current waveform is detected in real time, and a reverse harmonic compensation current is generated. When characteristic harmonics or non-characteristic harmonics are generated during the operation of the bidirectional AC / DC converter, the active filter system can achieve dynamic compensation of harmonic components within 10ms. At the same time, a tuned passive filter is installed in parallel to provide an impedance-type absorption path for specific harmonics.

[0042] The following is a possible implementation of an auxiliary power harvesting system for an all-DC system, which is used to perform the various execution steps and corresponding technical effects of the auxiliary power harvesting method for all-DC system equipment shown in the above embodiments and possible implementations, including: DC circuit breakers are installed at the grid connection point of new energy power plants; A bidirectional power converter is installed on the side of the new energy power station, and its low-voltage side is connected to the auxiliary power equipment of the station. A DC circuit breaker, in conjunction with a bidirectional power converter, enables the DC line to be continuously energized, providing power to auxiliary equipment.

[0043] In one possible embodiment, the bidirectional power converter is a bidirectional DC / DC converter, and its low-voltage side output is connected to a filter module and an overvoltage protection module.

[0044] In one possible embodiment, the bidirectional power converter is a bidirectional AC / DC converter, and its low-voltage side output is connected to an intelligent switching module for distributing electrical energy to DC or AC auxiliary equipment.

[0045] In one possible embodiment, an energy storage unit is also included, connected to the low-voltage side of the bidirectional power converter as a backup power source.

[0046] Compared with the prior art, the embodiments of this application have the following beneficial effects: First, by modifying the system to form a permanent power line, auxiliary power can be obtained directly from the DC system, saving the expensive cable laying costs of long-distance external power supply.

[0047] Secondly, regardless of whether the new energy power station itself generates electricity, it can ensure uninterrupted power supply to auxiliary equipment, thus guaranteeing the stable operation of the core control system under any operating conditions.

[0048] Third, by using a bidirectional converter and prioritizing DC power supply, the number of AC-DC conversion steps is reduced, significantly lowering the losses during the power conversion process.

[0049] Fourth, it provides multiple output modes including AC and DC, which can directly adapt to different types of electrical equipment in the site, simplifying system design and reducing integration complexity.

[0050] Fifth, by integrating filtering, overvoltage protection and harmonic suppression functions, the purity and stability of the auxiliary power supply are ensured, effectively protecting sensitive equipment from power grid disturbances.

[0051] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for harvesting auxiliary power from equipment in a fully DC system, characterized in that, The method is applied to a DC collection grid-connected system, wherein the system has a unidirectional blocking diode at the grid connection point of the renewable energy power station and a unidirectional DC / DC transformer on the power station side, and the method includes: Replace the unidirectional blocking diode at at least one DC line grid connection point with a DC circuit breaker; Replace the unidirectional DC converter on the DC line station side with a bidirectional power converter; Electrical energy is drawn from the low-voltage side of the bidirectional power converter to serve as auxiliary power for auxiliary equipment in the new energy power station.

2. The auxiliary power supply method for all-DC system equipment as described in claim 1, characterized in that, The bidirectional power converter is a bidirectional DC / DC converter that draws power from the low-voltage DC side of the bidirectional DC / DC converter to supply power to auxiliary equipment.

3. The auxiliary power supply method for all-DC system equipment as described in claim 2, characterized in that, The method also includes filtering the extracted electrical energy and providing overvoltage protection.

4. The auxiliary power supply method for all-DC system equipment as described in claim 1, characterized in that, The bidirectional power converter is a bidirectional AC / DC converter, which draws power from the low-voltage side of the bidirectional AC / DC converter to supply power to auxiliary equipment.

5. The auxiliary power supply method for all-DC system equipment as described in claim 4, characterized in that, The method also includes an intelligent switching step: prioritizing the use of DC power to power auxiliary equipment, and automatically switching to AC power when DC power is insufficient.

6. The auxiliary power supply method for all-DC system equipment as described in claim 4 or 5, characterized in that, The method also includes harmonic suppression processing of the extracted electrical energy.

7. An auxiliary power supply harvesting system for implementing the method of any one of claims 1 to 6 in an all-DC system, characterized in that, include: DC circuit breakers are installed at the grid connection point of new energy power plants; A bidirectional power converter is installed on the side of the new energy power station, and its low-voltage side is connected to the auxiliary power equipment of the station. A DC circuit breaker, in conjunction with a bidirectional power converter, enables the DC line to be continuously energized, providing power to auxiliary equipment.

8. The auxiliary power supply system for all-DC system equipment as described in claim 7, characterized in that, The bidirectional power converter is a bidirectional DC / DC converter, and its low-voltage side output is connected to a filter module and an overvoltage protection module.

9. The auxiliary power supply system for a fully DC system as described in claim 7, characterized in that, The bidirectional power converter is a bidirectional AC / DC converter with an intelligent switching module connected to its low-voltage output terminal, which is used to distribute electrical energy to DC or AC auxiliary equipment.

10. The auxiliary power harvesting system for all-DC system equipment as described in claim 7, characterized in that, It also includes an energy storage unit, which is connected to the low-voltage side of the bidirectional power converter as a backup power source.

Images