Direct current side coupling type super capacitor-battery hybrid energy storage system

Abstract

The invention relates to a direct current side coupling type super capacitor-battery hybrid energy storage system. According to the energy storage system, a super-capacitor module and a battery module are directly connected on the direct current side through a bidirectional DC / DC converter, the super-capacitor module is connected with a power grid through a current source type converter, the battery module is connected with the power grid through a voltage source type converter, and a modularized and extensible topological structure is formed. The system has multiple differentiated working modes, cooperative efficient operation of the super-capacitor and the battery can be achieved according to working conditions, high-frequency / short-time power is preferentially borne by the super-capacitor, and the battery is responsible for steady-state energy adjustment. And meanwhile, by virtue of the boosting capability of the current source type converter, the super capacitor can support the power grid in a short time and strong manner in a deep discharging manner. And the battery module charges the super capacitor module through the bidirectional DC / DC converter, so that the influence of frequent charging of the super capacitor on the grid-side electric energy quality is reduced. The method can effectively reduce the aging loss of the battery, improves the energy storage utilization efficiency and the power grid friendliness, assists the new energy consumption and the safe and stable operation of the power grid, and has economic and social benefits.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and in particular to a DC-coupled supercapacitor-battery hybrid energy storage system. Background Technology

[0002] With the rapid growth of new energy power generation and the increasing proportion of power electronic equipment, the inertia level of the power system is decreasing, the primary frequency regulation capability is weakening, and frequency disturbances are more likely to occur and change more rapidly. To meet the grid's requirements for frequency stability, frequency regulation power stations are gradually transforming from traditional rotating units to fast-regulating resources centered on energy storage. Energy storage frequency regulation power stations typically need to respond to frequency regulation commands in seconds or even less and continuously provide available regulation capacity over a longer time scale, thus placing higher demands on the dynamic response capability, energy management capability, and lifespan economy of energy storage systems.

[0003] In existing energy storage frequency regulation power stations, battery energy storage systems are widely used due to their high energy density and flexible configuration. However, grid frequency regulation commands are characterized by significant randomness and high-frequency fluctuations, with frequent positive and negative switching of power commands, high ramp rates, and rapid instantaneous power changes. Under these conditions, batteries need to withstand high-frequency charging and discharging as well as large current pulsations, which can easily lead to increased internal resistance, capacity decay, and accelerated temperature rise, thereby shortening lifespan and increasing operation and maintenance costs. At the same time, to meet dynamic performance and lifespan constraints, battery systems often need to increase redundancy or reduce available power utilization, affecting the economic efficiency and sustainable operation of the frequency regulation power station.

[0004] To improve frequency regulation response speed and reduce battery impact, some frequency regulation power plants have introduced high-power-density energy storage units such as supercapacitors to form hybrid energy storage systems with batteries. Supercapacitors have advantages such as high power, fast response, and long cycle life, making them suitable for handling high-frequency power disturbances and short-term support; batteries are suitable for providing relatively stable power support and energy balance. However, existing hybrid energy storage still has shortcomings in topology and energy flow methods: on the one hand, if supercapacitors are frequently charged directly from the grid side through grid-connected converters, it may introduce additional grid-side power fluctuations and power quality disturbances; on the other hand, if the energy coupling method between different energy storage units is not flexible enough or the isolation capability is insufficient, it can easily lead to DC-side mutual interference and unclear power distribution boundaries, affecting the stability and grid-friendliness during frequency regulation.

[0005] Furthermore, frequency regulation power plants need to consider various operating conditions in actual operation, such as high-frequency small-amplitude regulation, continuous steady-state support, and short-term high-power support. Different operating conditions place significant differences on the power response speed, energy continuity, and charge / discharge path requirements of energy storage units. Existing systems often struggle to simultaneously meet the comprehensive needs of fast response, stable support, and strong support in terms of multi-mode switching, energy replenishment paths, and power support paths. Therefore, there is an urgent need for a hybrid energy storage system structure for frequency regulation power plant applications that can achieve a clear division of labor between high-frequency disturbances and steady-state support, and controllable energy flow paths. Summary of the Invention

[0006] In view of this, the present invention aims to provide a DC-coupled supercapacitor-battery hybrid energy storage system for grid-connected applications such as frequency regulation power plants that require rapid power regulation and continuous stable support. By implementing differentiated division of labor between the supercapacitor circuit and the battery circuit at the system structure level, the supercapacitor prioritizes handling the high-frequency pulsating power and short-term rapid power change demands of the grid side, while the battery undertakes relatively stable power support and energy storage needs. Furthermore, through DC-side energy coupling and recharge path design, the energy recharging of the supercapacitor is mainly completed by the battery side. This reduces the impact of frequent grid-side charging of the supercapacitor on power quality while meeting frequency regulation performance requirements, thereby improving the system's grid-friendly nature, scalability, and operational economy.

[0007] To achieve the above objectives, the present invention provides a DC-coupled supercapacitor-battery hybrid energy storage system, comprising the following: This invention provides a DC-coupled supercapacitor-battery hybrid energy storage system, including a supercapacitor module, a battery module, a bidirectional isolated DC / DC converter, a current source converter, and a voltage source converter. The first port of the bidirectional isolated DC / DC converter is electrically connected to the supercapacitor module, and the second port is electrically connected to the battery module, enabling bidirectional energy exchange between the supercapacitor module and the battery module on the DC side, and facilitating energy recharge of the supercapacitor module. The current source converter is connected to the supercapacitor module on its DC side and to the power grid on its AC side, allowing the supercapacitor module to provide high-frequency pulsating power support to the power grid via the current source converter. The voltage source converter is connected to the battery module on its DC side and to the power grid on its AC side, enabling bidirectional power interaction between the battery module and the power grid via the voltage source converter, thus forming a supercapacitor-battery hybrid energy storage topology with DC-coupled and AC-branched grid connection.

[0008] Based on the aforementioned supercapacitor-battery hybrid energy storage topology with DC-side coupling and AC-side branch grid connection, this invention proposes and supports the following four operating modes and their energy flow paths to meet the typical operational needs of power systems, thereby achieving coordinated frequency regulation capabilities of "fast response of supercapacitors and stable support of batteries".

[0009] High-frequency regulation mode: When the grid experiences high-frequency pulsating power demand or short-term rapid power change demand, the system enters the high-frequency regulation mode. In this mode, the supercapacitor circuit prioritizes rapid power support. The energy output from the supercapacitor module forms a current source characteristic through a DC inductor and outputs high-frequency pulsating power to the grid through a current source converter, providing timely support for rapid frequency fluctuations and high-frequency disturbances. Simultaneously, the battery circuit primarily handles relatively stable power support needs. The battery module interacts with the grid via a voltage source converter, providing continuous and stable energy support and power floor for the frequency regulation process, thus sharing the grid's frequency regulation demands at different time scales.

[0010] Low-frequency energy replenishment / release mode: When the frequency regulation command has a persistent bias over a long timescale, requiring energy balancing, or when the supercapacitor module's energy decreases and needs to restore its rapid support capability, the system enters the low-frequency energy replenishment / release mode. In this mode, the battery module, as the main energy regulation unit, continuously or steadily outputs / absorbs power from the grid via a voltage source converter to meet the low-frequency, steady-state energy release or absorption requirements. Simultaneously, the supercapacitor module's energy replenishment is completed through the DC side, i.e., the battery module transfers energy to the supercapacitor module via a bidirectional isolated DC / DC converter, realizing supercapacitor replenishment and energy recovery. This eliminates the need for frequent direct charging of the supercapacitor from the grid side, reducing the impact on grid-side power fluctuations and power quality, and maintaining its energy reserves readily available for rapid frequency regulation support.

[0011] Deep Discharge Co-protection Mode: When the grid requires short-term high-power support, power deficit is significant, or frequency deviation develops rapidly, the system enters the deep discharge co-protection mode. In this mode, the supercapacitor module provides short-term high-power output to the grid through deep discharge. Its energy is rapidly released to the grid via DC inductors and current source converters to achieve short-term strong support. Simultaneously, the battery module maintains its steady-state support capability, outputting relatively stable power to the grid via voltage source converters, achieving coordinated support and continuous support for the supercapacitor's strong support process. Furthermore, when the supercapacitor energy approaches its lower limit or the strong support ends, the system completes a protective transition through battery-side steady-state support and DC-side regenerative braking mechanisms, preventing over-discharge of the supercapacitor from affecting subsequent support capabilities and system operational safety.

[0012] Collaborative Backup Operation Mode: When the grid frequency regulation demand is weak or the system is in standby mode, the system enters the collaborative backup operation mode. In this mode, the battery modules maintain bidirectional power interaction with the grid via voltage source converters to maintain the overall energy state and state of charge window of the energy storage station; the supercapacitor modules maintain a rapid support ready state, and their energy is mainly maintained and replenished on the DC side by the battery modules through bidirectional isolated DC / DC converters to ensure that the supercapacitors are in the energy range that can be rapidly discharged. When there is a high-frequency pulsating power demand or a short-term rapid power change on the grid side, the system can quickly switch from standby mode to high-frequency regulation operation mode; when there is a short-term high-power support demand, the system can quickly enter the deep discharge collaborative protection mode, thereby realizing rapid response and stable support of the frequency regulation power station under multiple operating conditions.

[0013] By adopting the above technical solution, the beneficial effects of the present invention are as follows: 1. The energy management strategy proposed in this invention for a DC-coupled supercapacitor-battery hybrid energy storage system enables the allocation of high-frequency components of frequency modulation commands and load disturbances to the supercapacitor module, and low-frequency components to the battery module, thereby decoupling the battery from high-frequency regulation, reducing battery aging and loss, and improving the lifespan of the battery module.

[0014] 2. The present invention proposes a DC-coupled supercapacitor-battery hybrid energy storage system, which realizes energy interaction and power buffering between the supercapacitor module and the battery module on the DC side through an independent bidirectional isolated DC / DC converter. This allows the energy recharging of the supercapacitor module to be mainly completed by the battery side, avoiding grid-side power fluctuations and power quality disturbances caused by the supercapacitor frequently charging directly from the grid side.

[0015] 3. This invention further provides operating modes such as short-term strong support and deep discharge: When the power grid experiences a short-term large power shortage or requires strong support, the supercapacitor module can achieve short-term high power output through deep discharge, quickly improving the frequency regulation response amplitude and ramp-up capability; in terms of energy utilization, the two types of energy storage units operate under their respective advantageous conditions, reducing conservative limiting and redundancy reserves, thereby improving the energy storage capacity utilization rate and the frequency regulation available power utilization rate, enhancing the continuous regulation capability and comprehensive benefits of the power system under multiple operating conditions. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1This is a schematic diagram of a DC-coupled supercapacitor-battery hybrid energy storage system provided in an embodiment of the present invention; Figure 2 These are four operating modes of a DC-coupled supercapacitor-battery hybrid energy storage system provided in this embodiment of the invention. Specific implementation methods

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0019] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0020] like Figure 1 , Figure 2 As shown, this invention addresses the problems of short battery life, low energy utilization, and poor operational reliability in traditional battery energy storage systems applied to power systems. It establishes a DC-side coupled supercapacitor-battery hybrid energy storage system, the structural schematic of which is shown below. Figure 1 As shown. The core energy storage module of this DC-coupled supercapacitor-battery hybrid energy storage system includes a supercapacitor module and a battery module. The power conversion module includes a current source converter, a bidirectional isolated DC / DC converter, and a voltage source converter. The DC side of the current source converter is connected to the supercapacitor unit, and the output side is connected to the power grid. It has a three-phase full-bridge structure, and each phase arm contains two switches. It has bidirectional voltage withstand capability and unidirectional current capability, for example... Each component consists of an IGBT in reverse series with a diode. The DC side of the voltage source converter is connected to the battery cell, and the output side is connected to the power grid. It has a three-phase full-bridge structure, with each phase arm containing two switches, and possesses unidirectional voltage withstand capability and bidirectional current capability. For example... Each is an IGBT reverse parallel diode structure.

[0021] like Figure 2 As shown, the DC-coupled supercapacitor-battery hybrid energy storage system of the present invention mainly has four operating modes, including the following: (1) High-frequency modulation working mode: When there is a high-frequency pulsating power demand or a short-term rapid power change demand on the grid side, the system enters the high-frequency modulation working mode. At this time, the supercapacitor circuit takes the lead in undertaking the task of rapid power support. The energy output by the supercapacitor module forms a current source characteristic through the DC inductor and outputs high-frequency pulsating power to the grid through the current source converter, so as to realize timely support for rapid frequency fluctuations and high-frequency disturbances. At the same time, the battery circuit mainly undertakes the relatively stable power support demand. The battery module interacts with the grid through the voltage source converter, providing continuous and stable energy support and power backing for the frequency modulation process, thereby completing the sharing of the grid frequency modulation demand at different time scales.

[0022] (2) Low-frequency energy replenishment / release mode: When the frequency regulation command has a continuous bias over a long time scale and energy balancing is required, or when the supercapacitor module's energy decreases and its rapid support capability needs to be restored, the system enters the low-frequency energy replenishment / release mode. In this mode, the battery module, as the main energy regulation unit, continuously or steadily outputs / absorbs power to the grid via a voltage source converter to meet the low-frequency, steady-state energy release or absorption requirements; at the same time, the energy replenishment of the supercapacitor module is completed through the DC side, that is, the battery module transfers energy to the supercapacitor module through a bidirectional isolated DC / DC converter, realizing supercapacitor replenishment and energy recovery, so that the supercapacitor does not need to be frequently charged directly from the grid side, reducing the impact on grid-side power fluctuations and power quality, and maintaining its energy reserves that can be used for rapid frequency regulation support at any time.

[0023] (3) Deep Discharge Co-protection Mode: When the power grid requires short-term high power support, the power deficit is significant, or the frequency deviation develops rapidly, the system enters the deep discharge co-protection mode. In this mode, the supercapacitor module provides short-term high power output to the power grid through deep discharge. Its energy is quickly released to the power grid through DC inductors and current source converters to achieve short-term strong support. At the same time, the battery module maintains its steady-state support capability and outputs relatively stable power to the power grid through voltage source converters, achieving coordinated support and continuous support for the strong support process of the supercapacitor. Furthermore, when the supercapacitor energy approaches the lower limit or the strong support ends, the system completes a protective transition through the battery-side steady-state support and DC-side compensation mechanism to avoid the supercapacitor over-discharge affecting the subsequent support capability and system operation safety.

[0024] (4) Collaborative Backup Working Mode: When the grid frequency regulation demand is weak or the system is in standby mode, the system enters the collaborative backup working mode. In this mode, the battery module maintains bidirectional power interaction capability with the grid through a voltage source converter to maintain the overall energy state and state of charge window of the energy storage station; the supercapacitor module maintains a rapid support ready state, and its energy is mainly maintained and replenished by the battery module on the DC side through a bidirectional isolated DC / DC converter to ensure that the supercapacitor is in the energy range that can be rapidly discharged. When there is a high-frequency pulsating power demand or a short-term rapid power change on the grid side, the system can quickly switch from the standby state to the high-frequency regulation working mode; when there is a short-term high-power support demand, the system can quickly enter the deep discharge collaborative protection mode, thereby realizing the rapid response and stable support of the frequency regulation power station under multiple operating conditions.

[0025] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0026] The embodiments of this invention are intended to cover all such substitutions, modifications, and variations falling within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A DC-coupled supercapacitor-battery hybrid energy storage system, characterized in that, The system includes a supercapacitor module, a battery module, a bidirectional isolated DC / DC converter, a current source converter, and a voltage source converter. The first port of the bidirectional isolated DC / DC converter is electrically connected to the supercapacitor module, and the second port is electrically connected to the battery module, enabling bidirectional energy exchange between the supercapacitor module and the battery module on the DC side, and facilitating energy recharge of the supercapacitor module. The DC side of the current source converter is connected to the supercapacitor module, and the AC side is connected to the power grid, allowing the supercapacitor module to provide high-frequency pulsating power support to the power grid via the current source converter. The DC side of the voltage source converter is connected to the battery module, and the AC side is connected to the power grid, enabling bidirectional power interaction between the battery module and the power grid via the voltage source converter, thus forming a supercapacitor-battery hybrid energy storage topology with DC-side coupling and AC-side branch grid connection.

2. The DC-coupled supercapacitor-battery hybrid energy storage system according to claim 1, characterized in that, The system employs differentiated power support methods using supercapacitor circuits and battery circuits. The supercapacitor circuit primarily addresses the high-frequency pulsating power and short-term rapid power change requirements of the grid side, providing rapid power support to the grid via a current source converter from the supercapacitor module. The battery circuit primarily addresses relatively stable power support requirements, providing continuous or stable power support to the grid via a voltage source converter from the battery module, and enabling bidirectional power interaction with the grid when needed.

3. The system according to claim 1, characterized in that, The system has a short-time strong support working mode. When the grid needs short-term high power support, the supercapacitor module provides short-time high power output to the grid in a deep discharge mode. Its energy flow path is that the supercapacitor module outputs power to the grid through the DC inductor, DC coupling node and current source inverter. At the same time, the battery module maintains its steady-state support capability. Its energy flow path is that the battery module outputs power to the grid through the voltage source inverter.

4. The system according to claim 1, characterized in that, The system has an energy recovery mode. When the supercapacitor module's energy decreases or it needs to restore its rapid support capability, the battery module charges the supercapacitor module through the bidirectional isolated DC-DC converter. The energy flow path is that the battery module transfers energy to the supercapacitor module via the bidirectional isolated DC-DC converter, so that the supercapacitor module's recovery is completed on the DC side, thereby avoiding the impact on the grid power quality caused by the supercapacitor module frequently charging from the grid side.

5. The system according to claim 1, characterized in that, The system has a power surplus absorption mode. When there is regenerative energy or power surplus on the grid side that needs to be absorbed, the battery module undertakes the absorption and energy storage. The energy flow path is that the grid transmits power to the DC coupling node through the voltage source inverter and enters the battery module. The supercapacitor module does not participate in the charging process of absorbing energy from the grid side.

6. The system according to claim 1, characterized in that, The system has a modular and scalable structure. At least one of the supercapacitor module and / or the battery module can be configured as multiple groups in parallel or multiple units combined. Multiple groups of supercapacitor modules are connected to the same DC coupling node through corresponding bidirectional isolated DC-DC converters. The battery module is connected to the grid through a voltage source inverter, and the supercapacitor module is connected to the grid through a current source inverter, so as to realize capacity expansion and redundancy configuration.

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