Energy storage high-voltage box, voltage adaptive control method and on-load switching method

Abstract

The invention provides an energy storage high-voltage box, a voltage adaptive control method and an on-load switching method. The high-voltage box comprises a controller, a PCS module, a DC / DC module and a lithium battery module. The PCS module is used for converting alternating current into direct current; the voltage of the AC side of the PCS module is recorded as a third voltage, and the voltage of the DC side of the PCS module is recorded as a second voltage; one side of the DC / DC module is connected with the PCS module in series to form a first loop, and the other side of the DC / DC module is connected with the lithium battery module in series to form a second series loop; wherein voltages at the two ends of the lithium battery module are recorded as first voltages; and the controller is connected with the DC / DC module and is used for collecting the first voltage and the second voltage. According to the invention, the arc discharge problems of high voltage ride through, inter-cluster balance and on-load switching are effectively solved.

Description

Technical Field

[0001] The present invention belongs to the field of energy storage systems, and in particular to the field of high-voltage boxes of energy storage systems. Background Art

[0002] As the global energy structure transformation accelerates, the importance of energy storage systems as a key technical means to improve energy utilization efficiency, ensure power supply stability, and promote large-scale access of renewable energy to the power grid is becoming increasingly prominent.

[0003] At present, energy storage systems mainly include battery energy storage, pumped storage, flywheel energy storage and other technical types. Among them, battery energy storage has become one of the most widely used energy storage methods due to its advantages such as high energy density, fast response speed and flexible installation. In particular, lithium-ion battery technology has made great progress in recent years and occupies an important position in the field of energy storage. However, despite the continuous progress of battery energy storage technology, it still faces many challenges.

[0004] On the one hand, battery performance is affected by many factors. For example, the battery state of charge (SOC) changes during the charging and discharging process. When the SOC is low, the battery cluster voltage decreases. At this time, if the grid voltage fluctuates, especially if it suddenly increases, it will cause a series of problems for the power storage converter (PCS). During the charging and discharging process, the PCS may experience overmodulation, control loop loss of control, and uncontrolled rectification due to sudden changes in grid voltage, which may lead to overcurrent faults, namely high voltage ride-through, which poses a serious threat to the safe and stable operation of the energy storage system.

[0005] On the other hand, the DC side characteristics of the energy storage system also bring technical difficulties. The DC side voltage is usually high, and the DC circuit has no zero crossing point, which makes it very easy for traditional mechanical switches (such as contactors) to produce arcing when opening and closing the circuit. The arc will not only damage the switch equipment and shorten its service life, but also interfere with the normal operation of the circuit and reduce the reliability of the energy storage system.

[0006] In addition, in an energy storage system with multiple clusters of lithium batteries connected in parallel, since the voltage of each cluster of batteries is difficult to be completely consistent and the internal resistance is small, direct parallel connection will lead to the generation of large circulating currents, which will not only cause energy loss, but also accelerate the aging of power circuit components and reduce the life and performance of the entire energy storage system.

[0007] In view of this, this application is proposed. Summary of the invention

[0008] Provided are a high-voltage box for an energy storage system, a voltage adaptive control method and a load switching method, which effectively solve the arcing problems of high voltage ride-through, inter-cluster balance and load switching.

[0009] The present invention is achieved through the following technical solutions:

[0010] A high-voltage box for an energy storage system, comprising:

[0011] Controller, PCS module, DC / DC module and lithium battery module;

[0012] A PCS module is used to convert AC power into DC power; the voltage on the AC side of the PCS module is recorded as the third voltage, and the voltage on the DC side of the PCS module is recorded as the second voltage;

[0013] A DC / DC module, one side of which is connected in series with the PCS module to form a first loop, and the other side of which is connected in series with the lithium battery module to form a second series loop; wherein the voltage across the lithium battery module is recorded as the first voltage;

[0014] A controller, connected to the DC / DC module, for collecting the first voltage and the second voltage;

[0015] Wherein, the third voltage=line voltage*(√2 / 2)*K, where K is the modulation ratio.

[0016] Furthermore, it also includes: a circuit breaker, a contactor, and a fuse;

[0017] The circuit breaker is set in the first circuit and connected in series with the PCS module and the DC / DC module;

[0018] The contactor and the fuse are arranged in the second series circuit, and the contactor, the fuse, the lithium battery module and the DC / DC module are connected in series.

[0019] Further, a bypass line is included;

[0020] One end of the bypass line is connected to the bypass unit in the DC / DC module, and the other end is connected to the lithium battery module.

[0021] On the other hand, the present application also provides a voltage adaptive control method based on the above energy storage system high voltage box, comprising the following steps:

[0022] Step 1, voltage acquisition: the controller acquires the first voltage, the second voltage and the third voltage;

[0023] Step 2, first difference calculation: the controller calculates the absolute value of the difference between the first voltage and the second voltage, which is recorded as the first difference;

[0024] Step 3, comparing the first difference with the first threshold: the controller determines whether the first difference is greater than the first threshold; if so, the first difference is used as the target value and the process jumps to step 6; if not, the process jumps to step 4;

[0025] Step 4, calculating the second difference: the controller calculates the absolute value of the difference between the third voltage and the second voltage, which is recorded as the second difference;

[0026] Step 5, comparing the second difference with the second threshold: the controller determines whether the second difference is greater than the second threshold; if so, the second difference is used as the target value and jumps to step 6; if not, conduction is performed through the bypass;

[0027] Step 6: DC / DC module adjustment: The controller adjusts the voltage of the DC / DC module to a target value.

[0028] On the other hand, the present application also provides a method for switching on and off a load based on the high-voltage box of the energy storage system, comprising:

[0029] Normal power on, normal power off, emergency power off and reclosing.

[0030] Furthermore, normal power-on includes:

[0031] Step A1, closing the circuit breaker;

[0032] Step A2, closing the contactor;

[0033] Step A3, closing the DC / DC module;

[0034] Step A4, soft start of the PCS module;

[0035] Step A5: Close the main circuit of the PCS module.

[0036] Furthermore, normal power off includes:

[0037] Step B1, the main circuit of the PCS module is opened;

[0038] Step B2, opening the DC / DC module;

[0039] Step B3, opening the contactor;

[0040] Step B3: Open the circuit breaker.

[0041] Furthermore, emergency power off includes:

[0042] Step C1, opening the DC / DC module;

[0043] Step C2: Open the contactor.

[0044] Furthermore, the reclosing includes:

[0045] Step D1, closing the contactor;

[0046] Step D2, the DC / DC module is switched on.

[0047] Compared with the prior art, the present invention has the following advantages:

[0048] 1) This application solves the high voltage ride-through and inter-cluster balance by adjusting the voltage of the DC / DC modules connected in series.

[0049] 2) This application uses a DC / DC module as a solid-state switch (soft switch). When performing load switching, the DC / DC module is operated first, and then the mechanical switch is operated, which effectively improves the load switching life and the operating reliability of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0051] Figure 1 This is the internal topology diagram of the high-voltage box of the energy storage system of this embodiment;

[0052] Figure 2 It is the battery cluster topology diagram;

[0053] Figure 3 FIG. 4 is a flow chart of the voltage adaptive control method of this embodiment. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] Figure 1 FIG. 2 shows the internal topology of the high voltage box of the energy storage system of this embodiment. Figure 1 As shown, the energy storage system high voltage box of this embodiment includes a PCS module 10 , a DC / DC module 20 , a controller 30 , a lithium battery module 40 , a circuit breaker 50 , a contactor 60 and a fuse 70 .

[0056] The PCS module 10 , the circuit breaker 50 and the DC / DC module 20 form a first loop; the DC / DC module 20 , the contactor 60 , the fuse 70 and the lithium battery module 40 form a second loop. The controller 30 is connected to the DC / DC module 20 .

[0057] Furthermore, the second circuit includes a bypass line 80 , one end of the bypass line 80 is connected to the bypass unit in the DC / DC module, and the other end of the bypass line 80 is connected to the lithium battery module 40 .

[0058] The PCS module 10 is used to convert alternating current into direct current, i.e., AC input and output DC+ and DC-;

[0059] Optionally, the DC / DC module 20 is a unidirectional DC / DC.

[0060] Figure 2 The figure shows the connection diagram of the battery cluster. Figure 2 As shown, multiple lithium batteries are connected to the DC bus (i.e. Figure 1 DC+ and DC-) connections.

[0061] See again Figure 1 , the voltage on the AC side of the PCS module 10 is recorded as the third voltage U3, the voltage on the DC side of the PCS module 10 (i.e., one side of the DC / DC module 20) is recorded as the second voltage U2, and the voltage on one side of the lithium battery module 40 (i.e., the other side of the DC / DC module 20) is recorded as the first voltage U1, wherein the third voltage U3 = line voltage*(√2 / 2)*K, where K is the modulation ratio.

[0062] On the other hand, this embodiment also provides a voltage adaptive control method based on the above-mentioned high-voltage box, comprising the following steps:

[0063] Step 1, voltage acquisition: the controller 30 acquires the first voltage U1, the second voltage U2 and the third voltage U3;

[0064] Step 2, first difference calculation: the controller 30 calculates the absolute value of the difference between the first voltage U1 and the second voltage U2, recorded as the first difference △U1;

[0065] Step 3, comparing the first difference △U1 with the first threshold value T1: the controller 30 determines whether the first difference △U1 is greater than the first threshold value T1; if so, the first difference △U1 is used as the target value and the process goes to step 6; if not, the process goes to step 4;

[0066] Step 4, calculation of the second difference △U2: the controller 30 calculates the absolute value of the difference between the third voltage U3 and the second voltage △U2, which is recorded as the second difference △U2;

[0067] Step 5, comparing the second difference △U2 with the second threshold value T2: the controller 30 determines whether the second difference △U2 is greater than the second threshold value T2; if so, the second difference △U2 is used as the target value and the process jumps to step 6; if not, conduction is performed through the bypass;

[0068] Step 6: DC / DC module 20 adjustment: the controller 30 adjusts the voltage of the DC / DC module 20 to a target value.

[0069] This embodiment can effectively solve the technical problems of high voltage ride-through and inter-cluster balance through the above voltage adaptive control method.

[0070] On the other hand, this embodiment also provides a method based on the above-mentioned high voltage box being normally powered on, comprising the following steps:

[0071] Step A1, closing the circuit breaker 50;

[0072] Step A2, closing the contactor 60;

[0073] Step A3, closing the DC / DC module 20;

[0074] Step A4, soft start of the PCS module 10;

[0075] Step A5: The main circuit of the PCS module 10 is closed.

[0076] A normal power-off process includes the following steps:

[0077] Step B1, the main circuit of the PCS module 10 is opened;

[0078] Step B2, the DC / DC module 20 is turned off;

[0079] Step B3, the contactor 60 is opened;

[0080] Step B3: Open the circuit breaker 50.

[0081] Emergency power off includes the following steps:

[0082] Step C1, the DC / DC module 20 is turned off;

[0083] Step C2: the contactor 60 is opened.

[0084] Reclosing includes the following steps:

[0085] Step D1, closing the contactor 60;

[0086] Step D2, the DC / DC module 20 is switched on.

[0087] The "equal" or "same" or "equal" disclosed in the present invention must take into account the distribution of engineering parameters, and the error distribution is within ±30%; the definition of "parallel" of two line segments or two straight lines is that the angle between the two line segments or two straight lines is less than or equal to 45 degrees; the definition of "perpendicular" of two line segments or two straight lines is that the angle between the two line segments or two straight lines is within the range of [60, 120] degrees; the definition of "phase mismatch" also needs to take into account the distribution of engineering parameters, and the error distribution of the degree of mismatch is within ±30%. In addition, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. Without more constraints, an element defined by the phrase "comprising a ..." does not exclude the existence of other identical elements in the process, method, article or apparatus comprising the element.

[0088] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0089] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one 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 invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-voltage box for an energy storage system, characterized in that: include: Controller, PCS module, DC / DC module and lithium battery module; A PCS module is used to convert AC power into DC power; the voltage on the AC side of the PCS module is recorded as the third voltage, and the voltage on the DC side of the PCS module is recorded as the second voltage; A DC / DC module, one side of which is connected in series with the PCS module to form a first loop, and the other side of which is connected in series with the lithium battery module to form a second series loop; wherein the voltage across the lithium battery module is recorded as the first voltage; A controller, connected to the DC / DC module, for collecting the first voltage and the second voltage; Wherein, the third voltage=line voltage*(√2 / 2)*K, where K is the modulation ratio.

2. The energy storage system high voltage box according to claim 1, characterized in that: Also includes: circuit breakers, contactors, fuses; The circuit breaker is set in the first circuit and connected in series with the PCS module and the DC / DC module; The contactor and the fuse are arranged in the second series circuit, and the contactor, the fuse, the lithium battery module and the DC / DC module are connected in series.

3. The energy storage system high voltage box according to claim 1, characterized in that: Also includes bypass lines; One end of the bypass line is connected to the bypass unit in the DC / DC module, and the other end is connected to the lithium battery module.

4. A voltage adaptive control method for a high voltage box of an energy storage system according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1, voltage acquisition: the controller acquires the first voltage, the second voltage and the third voltage; Step 2, first difference calculation: the controller calculates the absolute value of the difference between the first voltage and the second voltage, which is recorded as the first difference; Step 3, comparing the first difference with the first threshold: the controller determines whether the first difference is greater than the first threshold; If yes, the first difference is used as the target value and the process goes to step 6; if no, the process goes to step 4; Step 4, calculating the second difference: the controller calculates the absolute value of the difference between the third voltage and the second voltage, which is recorded as the second difference; Step 5, comparing the second difference with the second threshold: the controller determines whether the second difference is greater than the second threshold; if so, the second difference is used as the target value and jumps to step 6; if not, conduction is performed through the bypass; Step 6: DC / DC module adjustment: The controller adjusts the voltage of the DC / DC module to a target value.

5. A method for switching on and off a high-voltage box of an energy storage system according to any one of claims 1 to 3, characterized in that: include: Normal power on, normal power off, emergency power off and reclosing.

6. The on-load switching method according to claim 5, characterized in that: Normal power-on includes: Step A1, closing the circuit breaker; Step A2, closing the contactor; Step A3, closing the DC / DC module; Step A4, soft start of the PCS module; Step A5: Close the main circuit of the PCS module.

7. The on-load switching method according to claim 5, characterized in that: Normal power-off includes: Step B1, the main circuit of the PCS module is opened; Step B2, opening the DC / DC module; Step B3, opening the contactor; Step B3: Open the circuit breaker.

8. The on-load switching method according to claim 5, characterized in that: Emergency power outages include: Step C1, opening the DC / DC module; Step C2: Open the contactor.

9. The on-load switching method according to claim 5, characterized in that: Reclosing includes: Step D1, closing the contactor; Step D2, the DC / DC module is switched on.

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