A bidirectional multi-mode hybrid energy storage circuit

Abstract

The invention relates to a bidirectional multi-mode hybrid energy storage circuit, comprising: an energy-type energy storage element BAT, a power-type energy storage element C, a switch group K1, K2, K3, K4, an inductor L, a bidirectional DC / DC converter D and a load R; one end of the positive electrode of the energy-type energy storage element is connected to the positive input end of the bidirectional DC / DC converter through a first switch K1; the other end is connected to the positive output end of the bidirectional DC / DC converter through the inductor L and a fourth switch K4 in sequence; one end of the positive electrode of the power-type energy storage element is connected to the positive input end of the bidirectional DC / DC converter through a second switch K2, and the other end is connected to the positive output end of the bidirectional DC / DC converter through a third switch K3; the negative electrodes of the energy-type and power-type energy storage elements are connected to the negative input end of the bidirectional DC / DC converter together; the invention realizes full utilization of the power-type energy storage element and prolongs the service life of the energy storage system.

Description

Technical Field

[0001] The present invention belongs to the technical field of power systems, and relates to an energy storage circuit in a power system, in particular to a bidirectional multi-mode hybrid energy storage circuit. Background Art

[0002] At present, in the power system, the energy storage system has the characteristics of real-time absorption and release of energy, improving the quality of electric energy, and can generally be divided into two categories: energy-type energy storage technology and power-type energy storage technology. Energy-type energy storage technology has the advantages of high energy density and long energy storage time, but low power density and short cycle life, and is not suitable for compensating short-term pulse power fluctuations, such as batteries, lithium batteries, pumped storage, compressed air energy storage, etc. Power-type energy storage elements have the advantages of high power density, fast response speed, and long cycle life, but low energy density and high self-discharge rate, such as supercapacitors, flywheel energy storage, superconducting magnetic energy storage, etc. Both can meet the needs of different application modes due to their respective advantages.

[0003] With the rapid development of the economy, the load has higher and higher requirements for energy storage systems. A single energy storage system is affected by its own performance and is difficult to meet the needs of the load. There is an urgent need to develop energy storage systems with both high power density and high power density. A single energy storage technology cannot have the advantages of both energy storage technologies at the same time. Its shortcomings are: 1. It cannot meet different application requirements; 2. The control method is single and not flexible enough to meet the corresponding control requirements; 3. If the energy storage element is destroyed, the energy storage system will be directly paralyzed, which is not conducive to the reliability of the system operation.

[0004] At present, common hybrid energy storage systems are mainly passive and active. The main feature of the passive hybrid energy storage system is that the energy storage element and the power storage element are directly connected in parallel and connected to the load. Therefore, the voltage between the two energy storage units must be synchronized in real time. This topology is simple, does not require the configuration of DC / DC converters, and does not require additional control. The cost is low, but the power storage element of this structure cannot be fully utilized, resulting in a large amount of waste of power storage element capacity. In addition, when the load has a high power demand, it is impossible to flexibly adjust the energy distribution between the energy storage element and the power storage element according to the demand. The main feature of the active hybrid energy storage system is that two DC / DC converters are used to supply power to the load. The structure is relatively comprehensive and can realize the power distribution of energy storage elements and power storage elements in any proportion. However, the configuration cost of the active energy storage system is high, and the structure and control are complex. The DC / DC converter is affected by the power demand and is configured larger, which is not conducive to the realization of high energy density and high power density.

[0005] Therefore, how to develop a hybrid energy storage system that is simple in structure, efficient and reliable, and has both high energy density and high power density is a technical problem that technicians in this field are eager to solve. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and to propose a bidirectional multi-mode hybrid energy storage circuit which has a reasonable design, a simple structure, high efficiency and reliability, and both high energy density and high power density.

[0007] The present invention solves the practical problem by adopting the following technical solutions:

[0008] A bidirectional multi-mode hybrid energy storage circuit, comprising: an energy type energy storage element BAT, a power type energy storage element C, a switch group K1, K2, K3, K4, an inductor L, a bidirectional DC / DC converter D and a load R;

[0009] One end of the positive electrode of the energy storage element is connected to the positive input end of the bidirectional DC / DC converter through the first switch K1; the other end of the positive electrode of the energy storage element is connected to the positive output end of the bidirectional DC / DC converter through the inductor L and the fourth switch K4 in sequence;

[0010] One end of the positive electrode of the power type energy storage element is connected to the positive input end of the bidirectional DC / DC converter through the second switch K2, and the other end of the positive electrode of the power type energy storage element is connected to the positive output end of the bidirectional DC / DC converter through the third switch K3;

[0011] The negative electrode of the energy type energy storage element and the negative electrode of the power type energy storage element are connected to the negative input terminal of the bidirectional DC / DC converter;

[0012] The load R is connected in parallel with the output end of the bidirectional DC / DC converter.

[0013] Moreover, the first switch K1 , the second switch K2 , the third switch K3 and the fourth switch K4 are all bidirectional thyristor switches.

[0014] Moreover, the load R is an electrical load, a DC bus or a DC grid.

[0015] Advantages and beneficial effects of the present invention:

[0016] 1. The present invention overcomes the shortcoming of the existing hybrid energy storage system that cannot take into account both high energy density and high power density by coordinating the control of energy storage elements and power storage elements. Compared with the existing hybrid energy storage system, the present invention has a simple structure, simple control and low cost. At the same time, the present invention realizes the effective management of energy storage elements and power storage elements, and fully utilizes power storage elements while meeting the load requirements, avoiding frequent charging and discharging of energy storage elements and extending the service life of the energy storage system.

[0017] 2. The bidirectional multi-mode hybrid energy storage circuit of the present invention is different from other hybrid energy storage systems in that it realizes efficient energy transmission; the hybrid energy storage of the present invention can work alone or in mixed operation, and the destruction of any energy storage element will not lead to the paralysis of the entire energy storage system, which effectively improves the reliability of the energy storage system; the present invention can provide eight operating modes, which meets the diversity of the system's energy storage needs and makes up for the shortcomings of the application of a single energy storage element; the present invention uses a combination of energy-type and power-type energy storage elements to improve the performance of the energy storage system, reduce internal losses, extend the battery charge and discharge cycle, and reduce the cost of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a circuit schematic diagram of a bidirectional multi-mode hybrid energy storage circuit of the present invention;

[0019] Figure 2 is a schematic diagram of working mode 1 of a bidirectional multi-mode hybrid energy storage circuit provided by an embodiment of the present invention;

[0020] Figure 3 is a schematic diagram of working mode 2 of a bidirectional multi-mode hybrid energy storage circuit provided by an embodiment of the present invention;

[0021] Figure 4 is a schematic diagram of working mode 3 of a bidirectional multi-mode hybrid energy storage circuit provided by an embodiment of the present invention;

[0022] Figure 5 is a schematic diagram of working mode 4 of a bidirectional multi-mode hybrid energy storage circuit provided by an embodiment of the present invention;

[0023] Figure 6 is a schematic diagram of working mode 5 of a bidirectional multi-mode hybrid energy storage circuit provided by an embodiment of the present invention;

[0024] Figure 7 is a schematic diagram of working mode 6 of a bidirectional multi-mode hybrid energy storage circuit provided by an embodiment of the present invention;

[0025] Figure 8 is a schematic diagram of working mode 7 of a bidirectional multi-mode hybrid energy storage circuit provided by an embodiment of the present invention;

[0026] Fig. 9 is a schematic diagram of working mode 8 of a bidirectional multi-mode hybrid energy storage circuit provided by an embodiment of the present invention;

[0027] Description of reference numerals:

[0028] BAT-energy type energy storage element; C-power type energy storage element; L-inductor; K1, K2, K3, K4-bidirectional controllable switches; D-bidirectional DC / DC converter; R-load. DETAILED DESCRIPTION

[0029] The embodiments of the present invention are further described in detail below with reference to the accompanying drawings:

[0030] A bidirectional multi-mode hybrid energy storage circuit, such as Figure 1 As shown, it includes: an energy storage element BAT, a power storage element C, a switch group K1, K2, K3, K4, an inductor L, a bidirectional DC / DC converter D and a load R;

[0031] One end of the positive electrode BAT+ of the energy storage element is connected to the positive input terminal Din+ of the bidirectional DC / DC converter through the first switch K1; the other end of the positive electrode BAT+ of the energy storage element is connected to the positive output terminal Dout+ of the bidirectional DC / DC converter through the inductor L and the fourth switch K4 in sequence;

[0032] One end of the positive electrode C+ of the power type energy storage element is connected to the positive input terminal Din+ of the bidirectional DC / DC converter through the second switch K2, and the other end of the positive electrode C+ of the power type energy storage element is connected to the positive output terminal Dout+ of the bidirectional DC / DC converter through the third switch K3;

[0033] The negative electrode BAT- of the energy type energy storage element and the negative electrode C- of the power type energy storage element are connected to the negative input terminal Din- of the bidirectional DC / DC converter;

[0034] The load R is connected in parallel with the output end of the bidirectional DC / DC converter (i.e., one end of the load R is connected to the positive output end Dout+ of the bidirectional DC / DC converter, and the other end of the load R is connected to the negative output end Dout- of the bidirectional DC / DC converter);

[0035] The inductor is used to suppress the impact current of the energy storage element; the bidirectional DC / DC converter is used for energy exchange between the energy storage element, the power storage element and the load.

[0036] The first switch K1, the second switch K2, the third switch K3 and the fourth switch K4 are all bidirectional thyristor switches;

[0037] The load R is an electrical load, a DC bus or a DC grid.

[0038] In this embodiment, the bidirectional thyristor switch is an integration of a pair of common thyristors connected in anti-parallel. Both positive and negative trigger pulses applied to the gate can trigger the tube to turn on. Therefore, there are four triggering modes, the control method is simple, and the operation is convenient.

[0039] In this embodiment, the bidirectional DC / DC converter is a DC / DC converter with wide voltage input, adjustable output voltage and power. The output and input of the hybrid energy storage element energy are adjusted by controlling the on and off of the power switch tube of the bidirectional DC / DC converter.

[0040] In this embodiment, according to the functional requirements of different application scenarios, the opening and closing of switches K1-K4 are controlled to achieve the following eight operating modes:

[0041] Embodiment 1:

[0042] Energy storage element directly supplies power to the load: disconnect controllable switches K1, K2, and K3, and close switch K4.

[0043] When the hybrid energy storage system is used in situations where energy recovery is required, the hybrid energy storage system should ensure that as much energy as possible is recovered to avoid waste. When the power-type energy storage element is fully charged and can no longer recover energy, power will be supplied to the energy-type energy storage element. The hybrid energy storage system works in working mode 1, such as Figure 2 As shown, in this mode, the controllable switches K1, K2, and K3 are disconnected, K4 is closed, and the bidirectional DC / DC converter stops working.

[0044] Embodiment 2:

[0045] The power storage element directly supplies power to the load: disconnect the controllable switches K1, K2, and K4, and close the switch K3.

[0046] When the hybrid energy storage system is used in situations where energy recovery is required, the hybrid energy storage system should ensure that as much energy as possible is recovered to avoid waste. When the SOC of the power storage element is high, the energy storage element does not need to be charged by the bidirectional DC / DC converter. The combined power supply works in working mode 2, such as Figure 3 As shown, in this mode, the controllable switches K1, K2, and K4 are disconnected, K3 is closed, and the bidirectional DC / DC converter stops working.

[0047] Embodiment 3:

[0048] The power type energy storage element supplies power to the load through the bidirectional DC / DC converter: disconnect the controllable switches K1, K3, and K4, and close the switch K2.

[0049] When the hybrid energy storage system is discharged, the working mode of the hybrid energy storage system is determined according to the typical characteristics of the load power demand. When the load power demand is small and changes dramatically, and the SOC of the power type energy storage element is at a high level, the energy storage system works in working mode 3, such as Figure 4 As shown. In this mode, the controllable switches K1, K3, and K4 are disconnected, and K2 is closed. In this mode, the power storage element is solely responsible for the power demand of the load through a bidirectional DC / DC converter. The power storage element has the ability to charge and discharge at high power in a short time, can be charged and discharged many times, and has a long cycle life. It is suitable for adjustment at the transient operation level. The power storage element can provide power support relatively quickly in a short period of time. For example, short-term high-power output on the power generation side and the grid side can compensate for reactive power, support voltage, and also play a role in frequency regulation. On the new energy side, small-capacity, high-power energy storage can smooth the output curve. Since there are many factors affecting photovoltaic energy, photovoltaic energy is basically changing dynamically. This causes the energy inside the photovoltaic power generation system to change dynamically, and the input and output are often not well matched. As an intermediate link, the power storage device can provide a transition unit for energy between each other in a short time.

[0050] Embodiment 4:

[0051] The energy storage element supplies power to the load through a bidirectional DC / DC converter: disconnect the controllable switches K2, K3, and K4, and close the switch K1.

[0052] When the hybrid energy storage system is discharged, the working mode of the hybrid energy storage system is determined according to the typical characteristics of the load power demand. When the load power demand is large and the change is relatively slow, the energy storage system works in working mode 4, such as Figure 5 As shown. In this mode, the controllable switches K2, K3, and K4 are disconnected, and K1 is closed. In this mode, the energy storage element is solely responsible for the power demand of the load through a bidirectional DC / DC converter. The energy storage has a large storage capacity and a slow charging and discharging speed. It is mainly suitable for peak shaving and valley filling, load regulation, or backup power supply at the steady-state operation level. For example, due to the randomness and volatility of new energy sources such as photovoltaics and wind power, the new energy grid-connected system often has insufficient output during peak power consumption and excess output during low power consumption. A large-capacity energy storage system is used to store energy. Storing excess energy in the energy storage device during low power consumption and supplying power during peak power consumption can greatly reduce the burden of grid dispatching, improve the stability of the grid, and significantly improve the quality of power.

[0053] Embodiment 5:

[0054] The energy storage element and the power storage element are connected in parallel to directly supply power to the load: the controllable switches K1 and K2 are disconnected, and the switches K3 and K4 are closed.

[0055] When the load power demand is small, in order to avoid energy loss caused by the bidirectional DC / DC converter, the hybrid energy storage system switches to working mode 5 to supply power to the load. Figure 6 As shown, in this mode, the controllable switches K1 and K2 are disconnected, K3 and K4 are closed, and the bidirectional DC / DC converter stops working. The energy storage element and the power storage element are connected in parallel to directly supply power to the load. The energy storage element is filtered by the inductor L1 to meet the low-frequency power demand of the load, and the power storage element meets the high-frequency power demand of the load.

[0056] Embodiment 6:

[0057] The energy storage element is connected in parallel with the power storage element to supply power to the load through a bidirectional DC / DC converter: the switches K2 and K4 are opened, and the switches K1 and K3 are closed.

[0058] When the hybrid energy storage system is discharged, the working mode of the hybrid energy storage system is determined according to the typical characteristics of the load power demand. When the load power demand is large and the SOC of the power type energy storage element is at a high level, the energy storage system works in working mode 6, such as Figure 7 As shown. In this mode, the controllable switches K2 and K4 are disconnected, and K1 and K3 are closed. In this mode, the energy storage element shares the power demand of the load with the power storage element through a bidirectional DC / DC converter, making full use of the high power density, long cycle life, and fast response speed of the power storage element to share the high-frequency part of the load power, and taking advantage of the high energy density of the energy storage element to share the low-frequency part of the load power, and the input and output characteristics of the energy storage element are optimized.

[0059] Embodiment 7:

[0060] The power type energy storage element is connected in parallel with the energy type energy storage element to supply power to the load through a bidirectional DC / DC converter: the switches K1 and K3 are opened, and the switches K2 and K4 are closed.

[0061] When the hybrid energy storage system is discharged, the working mode of the hybrid energy storage system is determined according to the typical characteristics of the load power demand. When the load power demand is not large and the SOC of the power type energy storage element is at a high level, the energy storage system works in working mode 7, such as Figure 8As shown. In this mode, the controllable switches K1 and K3 are disconnected, and K2 and K4 are closed. In this mode, the power storage element shares the power demand of the load with the energy storage element through a bidirectional DC / DC converter. At this time, the DC bus voltage connected to the energy storage element changes relatively little during the system charging and discharging process, and the energy storage element basically works in a constant current mode. The charging and discharging current of the energy storage element is optimized and the life is extended.

[0062] Embodiment 8:

[0063] The energy storage element is connected in parallel with the load through a bidirectional DC / DC converter and supplies power to the power storage element at the same time: the controllable switches K2 and K4 are disconnected, and the switches K1 and K3 are closed.

[0064] When the hybrid energy storage system is used in situations where energy recovery is required, the hybrid energy storage system should ensure that as much energy as possible is recovered to avoid waste. From the perspective of protecting energy storage elements, frequent charging and discharging operations of energy storage elements should be avoided as much as possible, so power storage elements are used for energy recovery first. When the SOC of the power storage element is small, in order to restore the power of the power storage element as soon as possible, in addition to load energy recovery, the energy storage element also supplies power to the power storage element through a bidirectional DC / DC converter. The hybrid energy storage system operates in working mode 8, such as Fig. 9 As shown, in this mode, the controllable switches K2 and K4 are disconnected, K1 and K3 are closed, and the bidirectional DC / DC converter works.

[0065] The present invention controls the state of the bidirectional controllable switch to put the energy-type energy storage element and the power-type energy storage element in different working modes, which not only combines the advantages of energy-type and power-type energy storage, but also better meets the load power demand. At the same time, the system is reliable, compact, small in size and low in cost.

[0066] It should be emphasized that the embodiments of the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific implementation modes. Any other implementation modes derived by those skilled in the art based on the technical solutions of the present invention also fall within the scope of protection of the present invention.

Claims

1. A bidirectional multi-mode hybrid energy storage circuit, characterized in that: include: Energy storage element BAT, power storage element C, switch group K1, K2, K3, K4, inductor L, bidirectional DC / DC converter D and load R; One end of the positive electrode of the energy storage element is connected to the positive input end of the bidirectional DC / DC converter through the first switch K1; the other end of the positive electrode of the energy storage element is connected to the positive output end of the bidirectional DC / DC converter through the inductor L and the fourth switch K4 in sequence; One end of the positive electrode of the power type energy storage element is connected to the positive input end of the bidirectional DC / DC converter through the second switch K2, and the other end of the positive electrode of the power type energy storage element is connected to the positive output end of the bidirectional DC / DC converter through the third switch K3; The negative electrode of the energy type energy storage element and the negative electrode of the power type energy storage element are connected to the negative input terminal of the bidirectional DC / DC converter; The load R is connected in parallel with the output end of the bidirectional DC / DC converter; The first switch K1, the second switch K2, the third switch K3 and the fourth switch K4 are all bidirectional thyristor switches; The load R is an electrical load, a DC bus or a DC grid; According to the functional requirements of different applications, the following eight operating modes can be realized by controlling the opening and closing of the K1-K4 switches: Energy storage element directly supplies power to the load: disconnect controllable switches K1, K2, and K3, and close switch K4; The power storage element directly supplies power to the load: disconnect the controllable switches K1, K2, and K4, and close the switch K3; The power type energy storage element supplies power to the load through the bidirectional DC / DC converter: disconnect the controllable switches K1, K3, and K4, and close the switch K2; The energy storage element supplies power to the load through a bidirectional DC / DC converter: disconnect the controllable switches K2, K3, and K4, and close the switch K1; The energy storage element and the power storage element are connected in parallel to directly supply power to the load: disconnect the controllable switches K1 and K2, and close the switches K3 and K4; The energy storage element is connected in parallel with the power storage element to supply power to the load through a bidirectional DC / DC converter: the switches K2 and K4 are opened, and the switches K1 and K3 are closed; The power type energy storage element is connected in parallel with the energy type energy storage element through a bidirectional DC / DC converter to supply power to the load: disconnect switches K1 and K3, and close switches K2 and K4; The energy storage element is connected in parallel with the load through a bidirectional DC / DC converter and supplies power to the power storage element at the same time: the controllable switches K2 and K4 are disconnected, and the switches K1 and K3 are closed.

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