Energy storage system
By connecting the midpoint of the battery cluster to the midpoint of the bus, and using components such as protection circuits and slow-start circuits to stabilize the half-bus voltage, the problem of high cost in existing energy storage systems is solved, and the effect of reducing the bus capacitance capacity and system cost is achieved.
Patent Information
- Application Number
- CN202420817757.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-18
- Publication Date
- 2025-05-09
- Estimated Expiration
- 2034-04-18
AI Technical Summary
In existing energy storage systems, the capacity of the bus capacitor is relatively large, which makes the system cost high and difficult to reduce. Especially when PCS adopts three-level vector control, the capacitance value of the bus capacitor is more difficult.
By connecting the midpoint of the battery cluster to the midpoint of the bus and using components such as protection circuits and slow-start circuits to stabilize the half-bus voltage, thereby reducing the capacity of the bus capacitor.
It is realized that the capacity of the bus capacitor is reduced without affecting the stability of the bus voltage, thereby reducing the cost of the energy storage system.
Smart Images
Figure CN222852017U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of new energy technology, and specifically to an energy storage system. Background Art
[0002] The energy storage system includes a battery cluster, a bus capacitor and an energy storage converter (PCS, Power Conversion System). The battery cluster is connected to the DC side of the PCS. The battery cluster generally includes multiple battery cells connected in series or multiple battery cells connected in series and in parallel. The bus capacitor can also be set inside the PCS cabinet. The bus capacitor is used to stabilize the bus voltage. For the PCS, the bus includes the upper bus and the lower bus. The upper bus voltage requires the corresponding bus capacitor to be stable, and the lower bus voltage requires the corresponding bus capacitor to be stable. Generally, the bus capacitor has a relatively large capacitance. Therefore, the volume and cost of the bus capacitor in the energy storage system are both large. The capacitance of the bus capacitor is limited by multiple factors and cannot be reduced at will. For example, the three-level vector control adopted by the PCS will inject the third harmonic into the neutral point, which requires the bus capacitor to be stabilized, making it more difficult to reduce the capacitance of the bus capacitor. Utility Model Content
[0003] In view of this, the present application provides an energy storage system that can stabilize the voltage of half a bus and reduce the capacity of the bus capacitor, thereby reducing the cost of the energy storage system.
[0004] The present application provides an energy storage system, including: an energy storage inverter, a battery cluster and at least two bus capacitors: a first bus capacitor and a second bus capacitor; the positive electrode of the energy storage inverter is connected to the positive bus, the positive electrode of the battery cluster is connected to the positive bus, the negative electrode of the energy storage inverter is connected to the negative bus, the negative electrode of the battery cluster is connected to the negative bus, the two ends of the first bus capacitor are respectively connected to the positive bus and the bus midpoint, the two ends of the second bus capacitor are respectively connected to the bus midpoint and the negative bus; the midpoint of the battery cluster is connected to the bus midpoint.
[0005] A possible implementation manner further includes: a protection circuit; the midpoint of the busbar is connected to the midpoint of the battery cluster through the protection circuit; and the protection circuit includes: at least one of a switch and a fuse.
[0006] In a possible implementation, the protection circuit includes: a slow-start circuit and a semiconductor switch device connected in series.
[0007] A possible implementation also includes: a controller; the semiconductor switch device includes: a first controllable switch and a second controllable switch connected in series; the controller is used to control one of the first controllable switch and the second controllable switch to be turned off to disconnect the protection circuit.
[0008] In a possible implementation, the protection circuit further includes: an inductor; the inductor is connected in series with the switch, or the inductor is connected in series with the fuse.
[0009] In a possible implementation, there are multiple battery clusters; the midpoints of the multiple battery clusters are connected together to the midpoint of the bus; the positive poles of the multiple battery clusters are connected to the positive pole of the energy storage inverter, and the negative poles of the multiple battery clusters are connected to the negative pole of the energy storage inverter.
[0010] In a possible implementation, there are multiple protection circuits; the protection circuits also include: multiple bus capacitors; the multiple bus capacitors are connected in series between the positive bus and the negative bus, the series node of two adjacent bus capacitors connected in series is connected to the first end of the protection circuit, and the second end of the protection circuit is connected to a battery node of the corresponding voltage level in the battery cluster, and the battery node is two adjacent battery cell nodes connected in series.
[0011] In a possible implementation, the protection circuit includes a slow-start circuit and a fuse connected in series.
[0012] In a possible implementation, the slow-start circuit includes a slow-start switch and a slow-start resistor connected in series.
[0013] A possible implementation manner further includes: a slow-start circuit; the midpoint of the busbar is connected to the midpoint of the battery cluster through the slow-start circuit.
[0014] It can be seen that this application has the following beneficial effects:
[0015] In order to reduce the capacity of the bus capacitor and reduce costs, the embodiment of the present application uses a battery cluster to compensate for the capacity of the bus capacitor, because in the electrochemical energy storage scenario, the battery can be defined as a capacitor with a large capacitance. The energy storage system provided by the embodiment of the present application connects the midpoint of the battery cluster to the midpoint of the bus, thereby stabilizing the half-bus voltage. Since the battery cluster stabilizes the half-bus voltage as a capacitor in a certain sense, the capacity of the bus capacitor can be reduced, thereby reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 is a schematic diagram of an energy storage system;
[0017] Figure 2 A specific topological diagram of the energy storage system;
[0018] Figure 3 A voltage waveform diagram of a bus midpoint;
[0019] Figure 4 A schematic diagram of an energy storage system provided in an embodiment of the present application;
[0020] Figure 5A schematic diagram of another energy storage system provided in an embodiment of the present application;
[0021] Figure 6 A schematic diagram of a protection circuit provided in an embodiment of the present application;
[0022] Figure 7 A schematic diagram of another protection circuit provided in an embodiment of the present application;
[0023] Figure 8 A schematic diagram of another protection circuit provided in an embodiment of the present application;
[0024] Fig. 9 A schematic diagram of another protection circuit provided in an embodiment of the present application;
[0025] Fig.10 A schematic diagram of a slow-start circuit provided in an embodiment of the present application;
[0026] Fig.11 A schematic diagram of another protection circuit provided in an embodiment of the present application;
[0027] Fig.12 A schematic diagram of another protection circuit provided in an embodiment of the present application;
[0028] Fig.13 A schematic diagram of another protection circuit provided in an embodiment of the present application;
[0029] Fig.14 A schematic diagram of another protection circuit provided in an embodiment of the present application;
[0030] Fig.15 A schematic diagram of another energy storage system provided in an embodiment of the present application. DETAILED DESCRIPTION
[0031] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the embodiments of the present application are further described in detail below in conjunction with the accompanying drawings and specific implementation methods.
[0032] See also Figure 1 , which is a schematic diagram of an energy storage system.
[0033] The energy storage system generally includes: PCS100 and a battery cluster 200. PCS100 also includes a bus capacitor 300 and a filter circuit 400. The PCS100 in each embodiment of the present application only includes the main power circuit of the PCS. The positive pole of PCS100 is connected to the positive bus, the positive pole of the battery cluster 200 is connected to the positive bus, the negative pole of PCS100 is connected to the negative bus, the negative pole of the battery cluster 200 is connected to the negative bus, and the point N of PCS100 is connected to the bus midpoint O. In actual products, the point N of PCS100 and the bus midpoint O can be one point. The embodiments of the present application do not specifically limit the number of bus capacitors, and generally include at least two bus capacitors: a first bus capacitor and a second bus capacitor; the two ends of the first bus capacitor are respectively connected to the positive bus and the bus midpoint, and the two ends of the second bus capacitor are respectively connected to the bus midpoint and the negative bus; Figure 1 It is only an example that the first bus capacitor is connected to the positive bus through an inductor, and the second bus capacitor is connected to the negative bus through another inductor. It should be understood that the inductor may not be included, and the bus capacitor may be directly connected to the positive bus or the negative bus.
[0034] The AC side of the PCS 100 is connected to a first end of the filter circuit 400 , and a second end of the filter circuit 400 may be connected to a power grid or may be connected to the power grid via a transformer, which is not specifically limited here.
[0035] Figure 1 The battery cluster 200 shown may include a plurality of battery cells connected in series.
[0036] The embodiment of the present application does not specifically limit the specific topology of the PCS 100, nor the topology of the filter circuit 400. A possible implementation method can be found in Figure 2 , Figure 2 A specific topology of PCS100 is shown in FIG. 1 . PCS100 may adopt a three-level topology structure. Figure 2 A specific topology of the filter circuit 400 is also shown, including an inductor and a capacitor.
[0037] It should be understood that Figure 1 and Figure 2 The introduction is made by taking the three-phase AC side as an example. It should be understood that the AC side of the PCS can also be single-phase. The technical solution provided in the embodiment of the present application can be applied to both three-phase energy storage systems and single-phase energy storage systems.
[0038] Since the voltage level on the DC side of the energy storage system is relatively high, a bus capacitor with a larger capacity is required to stabilize the bus voltage. The larger the capacity of the bus capacitor, the more energy can be stored, the more stable the bus voltage is, and the smaller the impact of voltage fluctuations on the bus capacitor. However, the larger the capacity of the bus capacitor, the larger the volume and the higher the cost. In order to reduce the capacity of the bus capacitor and reduce costs, the embodiment of the present application uses a battery cluster to compensate for the capacity of the bus capacitor, because in the electrochemical energy storage scenario, the battery can be defined as a capacitor with a very large capacitance. Since the positive and negative poles of the battery cluster are respectively connected to the positive bus and the negative bus, the total bus voltage can obtain better stability, but the half-bus voltage still needs to rely on the bus capacitor to stabilize. For example, the three-level vector control of the PCS will inject the third harmonic into the neutral point. Since the N point of the PCS is connected to the bus midpoint O, the voltage fluctuation of the N point directly affects the voltage fluctuation of the bus midpoint O, and the voltage fluctuation of the bus midpoint O will affect the stability of the half-bus voltage. Figure 3 As shown, the voltage at the bus midpoint O will fluctuate. Therefore, the capacity of the bus capacitor cannot be reduced arbitrarily.
[0039] In order to utilize the battery cluster to stabilize the half-bus voltage, the embodiment of the present application connects the midpoint of the battery cluster to the midpoint of the bus, thereby stabilizing the half-bus voltage. Since the battery cluster stabilizes the half-bus voltage as a capacitor in a certain sense, the capacity of the bus capacitor can be reduced, thereby reducing costs.
[0040] The following is a detailed description with reference to the accompanying drawings.
[0041] See also Figure 4 , which is a schematic diagram of an energy storage system provided in an embodiment of the present application.
[0042] The energy storage system provided in the embodiment of the present application includes: a PCS 100 and a battery cluster 200;
[0043] The positive electrode of PCS100 is connected to the positive bus, the positive electrode of battery cluster 200 is connected to the positive bus, the negative electrode of PCS100 is connected to the negative bus, the negative electrode of battery cluster 200 is connected to the negative bus, point N of PCS100 is connected to the bus midpoint O, and the midpoint A of battery cluster 200 is connected to the bus midpoint O.
[0044] It should be understood that the midpoint A of the battery cluster is a node at half the voltage of the entire battery cluster. For example, if the battery cluster includes 100 cells connected in series, the midpoint A of the battery cluster is the series node between the 50th cell and the 51st cell. It should be understood that the battery cluster may also include multiple cells connected in series and parallel. In short, the midpoint A of the battery cluster refers to the connection position corresponding to half the voltage of the entire battery cluster. This connection position is led out and connected to the N point of the PCS through the protection battery.
[0045] Since the midpoint A of the battery cluster and the midpoint O of the bus are connected together, the equivalent capacitance characteristics of the battery cluster can be used to stabilize the voltage of the bus midpoint O, and the capacity of the battery cluster can be used to compensate for the capacity of the bus capacitor, so that a bus capacitor with smaller capacity can be used, thereby reducing the volume of the bus capacitor and reducing costs.
[0046] In addition, in order to protect the battery cluster and PCS when overcurrent occurs in the energy storage system, refer to Figure 5 , which is a schematic diagram of another energy storage system provided in an embodiment of the present application.
[0047] The energy storage system provided in the embodiment of the present application further includes: a protection circuit 500;
[0048] Point N of PCS 100 is connected to the midpoint A of battery cluster 200 through protection circuit 500;
[0049] The protection circuit 500 includes at least one of a switch and a fuse. For example, when the protection circuit 500 includes a switch, when it is detected that the current flowing through the protection circuit 500 is greater than or equal to a preset current, the switch is controlled to be disconnected, that is, the point N of the PCS 100 is disconnected from the midpoint A of the battery cluster 200.
[0050] For another implementation, see Figure 6 , which is a schematic diagram of a protection circuit provided in an embodiment of the present application.
[0051] When the protection circuit 500 includes a fuse FUSE, when the current flowing through the protection circuit 500 exceeds the limit value of the fuse FUSE, the fuse FUSE is automatically disconnected, and the point N of the PCS100 is disconnected from the midpoint A of the battery cluster 200, thereby preventing excessive current from entering the battery cluster 200 from the PCS100, or from entering the PCS100 from the battery cluster 200.
[0052] In another implementation, in order to prevent high-frequency components from entering the battery cluster and affecting the battery life, the protection circuit provided in the embodiment of the present application may further include an inductor.
[0053] See also Figure 7 , which is a schematic diagram of another protection circuit provided in an embodiment of the present application.
[0054] The protection circuit provided in the embodiment of the present application includes an inductor L and a fuse FUSE connected in series. The fuse FUSE can implement overcurrent protection, which has been introduced above and will not be repeated here.
[0055] See also Figure 8 , which is a schematic diagram of another protection circuit provided in an embodiment of the present application.
[0056] The protection circuit provided in the embodiment of the present application includes an inductor L, a first controllable switch Q1 and a second controllable switch Q2 connected in series. The function of Q1 and Q2 is to prevent overcurrent, and the series connection of Q1 and Q2 corresponds to the current control in two directions of inversion and rectification, respectively. In a possible implementation, Q1 and Q2 can be semiconductor switching devices, and in order to completely block the current on the protection circuit path, the body diode of Q1 and the body diode of Q2 are connected top to top.
[0057] It should be understood that the energy storage system provided in the embodiment of the present application may further include a controller; the controller is used to control the first controllable switch Q1 and the second controllable switch Q2 to be turned off to disconnect the protection circuit. For example, L is connected to the battery cluster and Q2 is connected to the PCS. When both Q1 and Q2 are turned off, due to the presence of the body diode of Q1, the current cannot flow from the PCS to the battery cluster, and due to the presence of the body diode of Q2, the current cannot flow from the battery cluster to the PCS.
[0058] In addition, in order to prevent the voltage difference between the midpoint of the battery cluster and the midpoint of the busbar from being too large, causing excessive impact at the moment of connection, the protection circuit may include a slow-start circuit, which is described in detail below in conjunction with the accompanying drawings.
[0059] See also Fig. 9 , which is a schematic diagram of another protection circuit provided in an embodiment of the present application.
[0060] The protection circuit provided in the embodiment of the present application may further include: a slow-start circuit 501 and a semiconductor switch device connected in series; the semiconductor switch device is further introduced as Q1 and Q2 connected in series.
[0061] See also Fig.10 , illustrates an implementation of a slow-start circuit, where the slow-start circuit 501 includes a relay RLY and a slow-start resistor R connected in parallel. It should be understood that the relay RLY can be replaced by other controllable switch devices.
[0062] When the protection circuit is used actively, when the half bus voltage fluctuates greatly, RLY is disconnected, and the bus midpoint is connected to the midpoint of the battery cluster through the slow-start resistor R. After waiting for a period of time, Q1 and Q2 can be turned on, and the bus midpoint is connected to the midpoint of the battery cluster through Q1 and Q2.
[0063] After the midpoint of the busbar is successfully connected to the midpoint of the battery cluster, the slow-start resistor R does not need to be connected to the circuit all the time. At this time, the control relay RLY is closed to bypass the slow-start resistor R to avoid the slow-start resistor R being connected to the circuit, which will continue to generate heat and increase power consumption.
[0064] For example, one possible implementation of a controller controlling Q1 and Q2 is as follows:
[0065] Get the positive half bus voltage VPbus With negative half bus voltage V Nbus The size of the positive and negative busbars is further calculated to obtain the difference ΔV=|V Pbus -V Nbus |.
[0066] 2. If ΔV is greater than the preset voltage, Q1 and Q2 are turned on;
[0067] 3. After waiting for the preset time t, turn on RLY.
[0068] 4. Detect the current flowing through Q1 or Q2. If it is greater than the preset current, turn off Q1 or Q2.
[0069] The energy storage system provided in the embodiment of the present application, the protection circuit may include at least one of the various devices described above, and may be a combination of multiple devices, for example, see Fig.11 , the protection circuit may include a slow-start circuit, an inductor L, Q1 and Q2 connected in series, and the slow-start circuit includes RLY and R connected in parallel. Fig.12 , the protection circuit may include a slow-start circuit, a fuse FUSE, and Q1 and Q2 connected in series, and the slow-start circuit includes RLY and R in parallel. Fig.13 The protection circuit may include a slow-start circuit, an inductor L, a fuse FUSE, and Q1 and Q2 connected in series, and the slow-start circuit includes RLY and R connected in parallel.
[0070] The energy storage system described above only connects the midpoint of the battery cluster to the midpoint of the bus to achieve the function of stabilizing half the bus voltage. In addition, the energy storage system provided in the embodiment of the present application can stabilize other proportions of bus voltage in addition to stabilizing half the bus voltage, for example, stabilizing 1 / N bus voltage, where N is an integer greater than or equal to 2, such as 1 / 4 bus voltage, 3 / 4 bus voltage, etc. For ease of understanding, a detailed description is given below in conjunction with the accompanying drawings.
[0071] In order to disconnect the slow-start resistor from the circuit after the slow-start, the slow-start circuit may further include a controllable switch connected in series with the slow-start resistor. Figures 10 to 13 The slow-start resistor in the circuit can be connected in series with the controllable switch and then in parallel with the relay. Fig.10 As an example, when a controllable switch tube is added, such as Fig.14 As shown, Fig.14 In the example, the controllable switch is also a relay, that is, the slow-start circuit includes a first relay RLY1, a second relay RLY2 and a slow-start resistor R. RLY2 and R are connected in series and then in parallel with RLY1. When the system is slow-started, RLY2 is closed and RLY1 is disconnected. The system is powered on through R to reduce the impact of the current. When the system is slow-started, RLY1 is closed and RLY2 is disconnected, and the slow-start resistor R is removed from the system to avoid excessive power consumption and heat.
[0072] See also Fig.15 , a schematic diagram of another energy storage system provided in an embodiment of the present application.
[0073] The energy storage system provided in the embodiment of the present application includes multiple protection circuits; and also includes: multiple bus capacitors; a first bus capacitor C1, a second bus capacitor C2, a third bus capacitor C3 and a fourth bus capacitor C4.
[0074] After being connected in series, multiple bus capacitors are connected between the positive bus and the negative bus. The series node of two adjacent bus capacitors connected in series is connected to the first end of the corresponding protection circuit. The second end of the protection circuit is connected to the battery node of the corresponding voltage level in the battery cluster. The battery node is two adjacent battery cell nodes connected in series. The voltage level means that the bus voltage and the battery cluster voltage are divided into N levels. The bus voltage node corresponds to the divided voltage node of the battery cluster. For example, the bus 1 / 2 voltage node is connected to the battery cluster 1 / 2 voltage node, the bus 1 / 3 voltage node is connected to the battery cluster 1 / 3 voltage node, etc.
[0075] For example, the common end of C1 and C2 is connected to the quarter node BAT_1 / 4 of the battery cluster through the corresponding protection circuit 500, the bus midpoint O is connected to the half node BAT_N of the battery cluster through the corresponding protection circuit 500, and the common end of C3 and C4 is connected to the three quarter node BAT_3 / 4 of the battery cluster through the corresponding protection circuit 500. Fig.15 The energy storage system provided can utilize battery clusters to achieve stability of 1 / 4 bus voltage, 1 / 2 bus voltage, and 3 / 4 bus voltage.
[0076] Fig.15 Only three protection circuits are used as an example to introduce the use of battery clusters to stabilize 1 / 4 bus voltage, 1 / 2 bus voltage and 3 / 4 bus voltage. It should be understood that other proportions of bus voltages can also be stabilized, which will not be repeated here.
[0077] The energy storage system described in the above embodiment further includes an inductor connected in series with the bus capacitor, and the inductor can suppress high frequencies.
[0078] The energy storage systems described in the above embodiments are all described using one battery cluster as an example. It should be understood that in order to expand the capacity of the energy storage system, the energy storage system may include multiple battery clusters, that is, the energy storage system provided in the embodiment of the present application has multiple battery clusters; the midpoints of the multiple battery clusters are connected together and connected to the bus point N of the energy storage inverter; the positive poles of the multiple battery clusters are connected to the positive pole of the energy storage inverter, and the negative poles of the multiple battery clusters are connected to the negative pole of the energy storage inverter.
[0079] The various methods for stabilizing the bus voltage described in the above embodiments are also applicable to the case of multiple battery clusters, and will not be described in detail here.
[0080] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. An energy storage system, characterized in that: include: An energy storage converter, a battery cluster, and at least two of the following bus capacitors: a first bus capacitor and a second bus capacitor; The positive electrode of the energy storage inverter is connected to the positive bus, the positive electrode of the battery cluster is connected to the positive bus, the negative electrode of the energy storage inverter is connected to the negative bus, the negative electrode of the battery cluster is connected to the negative bus, the two ends of the first bus capacitor are respectively connected to the positive bus and the bus midpoint, the two ends of the second bus capacitor are respectively connected to the bus midpoint and the negative bus; the midpoint of the battery cluster is connected to the bus midpoint.
2. The energy storage system according to claim 1, characterized in that: Also includes: Protection circuit; The midpoint of the busbar is connected to the midpoint of the battery cluster through the protection circuit; The protection circuit includes at least one of a switch and a fuse.
3. The energy storage system according to claim 2, characterized in that: The protection circuit comprises: a slow-start circuit and a semiconductor switch device connected in series.
4. The energy storage system according to claim 3, characterized in that: Also includes: Controller; The semiconductor switch device comprises: a first controllable switch and a second controllable switch connected in series; The controller is used to control one of the first controllable switch and the second controllable switch to be turned off to disconnect the protection circuit.
5. The energy storage system according to any one of claims 2 to 4, characterized in that: The protection circuit further includes: an inductor; The inductor is connected in series with the switch, or the inductor is connected in series with the fuse.
6. The energy storage system according to any one of claims 1 to 4, characterized in that: There are multiple battery clusters; The midpoints of the multiple battery clusters are connected together to connect the midpoint of the busbar; the positive electrodes of the multiple battery clusters are connected to the positive electrode of the energy storage inverter, and the negative electrodes of the multiple battery clusters are connected to the negative electrode of the energy storage inverter.
7. The energy storage system according to any one of claims 2 to 4, characterized in that: The protection circuit is multiple; and further includes: multiple bus capacitors; The multiple bus capacitors are connected in series between the positive bus and the negative bus, the series node of two adjacent bus capacitors connected in series is connected to the first end of the corresponding protection circuit, the second end of the protection circuit is connected to the battery node of the corresponding voltage level in the battery cluster, and the battery node is two adjacent battery cell nodes connected in series.
8. The energy storage system according to claim 2, characterized in that: The protection circuit comprises a slow-start circuit and a fuse connected in series.
9. The energy storage system according to claim 3 or 8, characterized in that: The slow-start circuit comprises a slow-start switch and a slow-start resistor connected in series.
10. The energy storage system according to claim 1, characterized in that: Also includes: Soft start circuit; The busbar midpoint is connected to the midpoint of the battery cluster through the slow-start circuit.