Energy storage PCS DC bus overvoltage suppression and protection system and method

Abstract

The invention relates to the technical field of converters, in particular to an overvoltage suppression and protection system and method for a direct-current bus of an energy storage PCS. The system comprises an energy storage PCS module, a control module and a PWM modulation module. The output of the energy storage PCS module is modulated by the control module and the PWM modulation module in sequence and then is input into an IGBT of an inversion unit of the energy storage PCS module; the control module comprises a first target loop, a second target loop and a third target loop; the first target loop is a constant-power tracking outer loop, the second target loop is a direct-current voltage suppression constant-current loop, the third target loop is a direct-current voltage suppression constant-voltage loop, and the over-voltage suppression and protection functions of the direct-current bus of the energy storage PCS are achieved by switching the three target loops. According to the invention, rapid response and effective suppression of the DC bus overvoltage problem in the energy storage system are realized, stable operation of the system according to the predetermined power is ensured, and the overall operation stability and safety of the energy storage system are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of converters, and in particular to an energy storage PCS DC bus overvoltage suppression and protection system and method. Background Art

[0002] As a key device for power conversion, the power storage converter (PCS) has a topological structure mainly divided into the AC inverter side and the DC bus side. Among them, the DC bus side is connected in parallel with the battery. In the parallel connection mode of PCS, the common DC bus type and the single cluster direct connection type are two common configurations. To ensure the stability of the DC voltage, the DC bus is usually equipped with capacitors of appropriate capacity. However, due to the limitations of the withstand voltage stress of key components such as bus capacitors and IGBTs, DC overvoltage protection is one of the important protections for the safe operation of PCS. The traditional DC overvoltage protection mechanism relies on the real-time monitoring of the DC voltage by the control unit. Once the DC voltage value exceeds the preset protection threshold, the control unit will immediately lock the drive pulse of the IGBT and disconnect the AC / DC switch to protect the PCS devices from damage.

[0003] However, in actual applications, especially when the PCS is in a fully loaded charging state, if the battery system is abnormal and suddenly disconnected, this will cause the capacitance value on the DC side to decrease sharply. In this case, the voltage of the DC bus capacitor will rise rapidly, and the larger the output capacity before the fault, the faster the voltage rises. Since there is a certain time delay from the controller detecting the overvoltage fault signal to executing the latching pulse operation, this increases the risk of damage to devices such as bus capacitors or IGBTs due to overvoltage during this period.

[0004] To address this problem, the traditional solution is to increase the withstand voltage of DC side devices when selecting them. Although this approach can ensure the safety of devices to a certain extent, it will also lead to a significant increase in device cost and volume. Especially in the scenario where PCSs share the busbar, if each PCS triggers the overvoltage protection one by one and exits operation one by one, the total capacity of the DC side capacitor will continue to decrease. At this time, the PCS that exits later will face a higher risk of overvoltage damage. Summary of the invention

[0005] The purpose of the present invention is to provide an energy storage PCS DC bus overvoltage suppression and protection system and method in order to solve at least one of the above technical problems.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] An energy storage PCS DC bus overvoltage suppression and protection system, comprising: an energy storage PCS module, a control module, and a PWM modulation module;

[0008] The output of the energy storage PCS module is modulated by the control module and the PWM modulation module in turn and then input into the IGBT of the inverter unit of the energy storage PCS module;

[0009] The control module includes a first target loop, a second target loop and a third target loop;

[0010] The first target loop is a constant power tracking outer loop, the second target loop is a DC voltage suppression constant current loop, and the third target loop is a DC voltage suppression constant voltage loop. The energy storage PCS DC bus overvoltage suppression and protection function is achieved by switching the three target loops.

[0011] Further, the energy storage PCS module includes: a DC side, an inverter unit, and an AC side;

[0012] The DC side includes a battery system, a bus capacitor, and a DC circuit breaker; the inverter unit includes an IGBT; and the AC side is connected to the power grid through an AC circuit breaker.

[0013] Furthermore, the first target loop is used to track the upper power instruction in real time to obtain the current of the inner loop;

[0014] The second target loop is used to perform constant current discharge conversion on the bus to obtain the current of the inner loop;

[0015] The third target loop is used to perform constant voltage control on the bus voltage to obtain the current of the inner loop.

[0016] A method for suppressing and protecting a DC bus overvoltage of an energy storage PCS is provided, using any of the above-described systems for suppressing and protecting a DC bus overvoltage of an energy storage PCS. The method comprises the following steps:

[0017] Monitoring DC voltage U dc ;

[0018] When the DC voltage U dc Greater than the overvoltage suppression threshold U dcovThr1 And not greater than the overvoltage protection threshold U dcovThr2 When the control module is switched from the first target loop to the second target loop;

[0019] When the DC voltage U dc Not greater than the constant pressure control target value U dcref And is less than the overvoltage protection threshold U dcovThr2 When the control module is switched from the second target loop to the third target loop;

[0020] When the DC voltage U dc Controlled to approach the constant pressure control target value U dcrefWhen the preset duration is reached, the pulse is locked and the protection exit switch action is performed;

[0021] When the DC voltage U dc Exceeding the overvoltage protection threshold U dcovThr2 When the pulse is locked, the protection exit switch action is performed.

[0022] Furthermore, the first target loop is a constant power tracking outer loop, the input of which is a power target value, and the output of which is a current command value;

[0023] The second target loop is a DC voltage suppression constant current loop, the output active power is directly given the maximum allowable discharge instruction, and the reactive power is given as zero;

[0024] The third target loop is a DC voltage suppression constant voltage loop, the active input is a DC voltage reference value, the output is an active current instruction, and the reactive power reference is zero.

[0025] Furthermore, the overvoltage suppression threshold U dcovThr1 It is the minimum value for judging whether there is abnormality on the DC side;

[0026] The constant pressure control target value U dcref Set within the rated operating voltage range of the battery;

[0027] The overvoltage protection threshold U dcovThr2 is the busbar safety threshold.

[0028] Furthermore, the overvoltage suppression threshold U dcovThr1 Below the overvoltage protection threshold U dcovThr2 And higher than the rated working voltage of the battery.

[0029] Furthermore, the switching action includes opening of AC and DC circuit breakers.

[0030] Furthermore, the system open-loop transfer function using the second target loop is:

[0031] Gdc2(s)=Gd(s) / (s·C0·(G K +s))

[0032] The system open-loop transfer function using the third target loop is:

[0033] Gdc(s)=(Gvpi(s)·Gd(s)) / (s·C0·(G K +s))

[0034] Wherein, Gdc2(s) is the system open-loop transfer function using the second target loop; Gdc(s) is the system open-loop transfer function using the third target loop; Gvpi(s) is the transfer function of the PI control loop; Gd(s) is the transfer function of the delay link of the PCS controller; C0 is the bus capacitance value; G K is the coefficient of the equivalent current inner loop inertia link; the control bandwidth of the second target loop and the third target loop is 1 / 5 to 1 / 4 of the current inner loop control bandwidth.

[0035] An electronic device comprises a processor, a memory and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, the energy storage PCS DC bus overvoltage suppression and protection method described above is implemented.

[0036] The beneficial effects of the present invention are:

[0037] By introducing a DC voltage suppression loop, compared with the traditional overvoltage protection mechanism, the present invention can flexibly adjust the current command before the DC bus voltage abnormally rises to trigger the overvoltage lockout protection, significantly slowing down the DC voltage rise rate (dv / dt), thereby effectively preventing key components on the DC side from suffering overvoltage damage, greatly improving the safety performance and operational reliability of the energy storage PCS system. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a typical topology block diagram of an energy storage PCS;

[0039] Figure 2 A control block diagram of an energy storage PCS DC bus overvoltage suppression and protection system according to an embodiment of the present invention;

[0040] Figure 3 A control block diagram of a DC voltage suppression loop according to an embodiment of the present invention;

[0041] Figure 4 A logic diagram of an energy storage PCS DC bus overvoltage suppression and protection system according to an embodiment of the present invention;

[0042] Figure 5 A flow chart of a method for suppressing and protecting a DC bus overvoltage of an energy storage PCS according to an embodiment of the present invention;

[0043] Figure 6 The present invention is a flowchart of a method for overvoltage suppression and protection of a DC bus of an energy storage PCS according to another embodiment of the present invention.

[0044] Among them, ① is the first target loop, ② is the second target loop, and ③ is the third target loop. DETAILED DESCRIPTION

[0045] The content of the present invention will now be discussed with reference to exemplary embodiments. It should be understood that the embodiments discussed are only to enable those skilled in the art to better understand and thus implement the content of the present invention, rather than implying any limitation on the scope of the present invention.

[0046] As used herein, the term “including” and variations thereof are to be interpreted as open-ended terms meaning “including, but not limited to.” The term “based on” is to be interpreted as “based, at least in part, on.” The terms “one embodiment” and “an embodiment” are to be interpreted as “at least one embodiment.”

[0047] Embodiment 1

[0048] Figure 1 This is a typical topology block diagram of an energy storage PCS; Figure 2 FIG. 1 is a control block diagram of an energy storage PCS DC bus overvoltage suppression and protection system according to an embodiment of the present invention. Figure 1-2 As shown, according to one embodiment of the present invention, an energy storage PCS DC bus overvoltage suppression and protection system includes: an energy storage PCS module, a control module, and a PWM modulation module;

[0049] The output of the energy storage PCS module is modulated by the control module and the PWM modulation module in turn and then input into the IGBT of the inverter unit of the energy storage PCS module;

[0050] The control module includes a first target loop ①, a second target loop ② and a third target loop ③;

[0051] The first target loop ① is a constant power tracking outer loop, the second target loop ② is a DC voltage suppression constant current loop, and the third target loop ③ is a DC voltage suppression constant voltage loop. By switching the three target loops, the energy storage PCS DC bus overvoltage suppression and protection function is realized.

[0052] like Figure 1 As shown, preferably, the energy storage PCS module includes: a DC side, an inverter unit, and an AC side;

[0053] The DC side includes a battery system, bus capacitors, and DC circuit breakers; the inverter unit includes IGBTs; and the AC side is connected to the grid via an AC circuit breaker.

[0054] Preferably, the first target loop is used to track the upper power instruction in real time to obtain the current of the inner loop;

[0055] The second target loop ② is used to convert the busbar into a constant current discharge to obtain the current of the inner loop;

[0056] The third target loop ③ is used to perform constant voltage control on the bus voltage to obtain the current of the inner loop.

[0057] In this embodiment, a storage PCS DC bus overvoltage suppression and protection system is proposed, including a storage PCS module, a control module and a PWM modulation module; the control module includes a constant power tracking outer loop and a DC voltage suppression loop; wherein the constant power tracking outer loop is the first target loop ①, the first target loop ① is used to track the upper power instruction in real time to obtain the current of the inner loop; the DC voltage suppression loop includes a second target loop ② and a third target loop ③, the second target loop ② is a DC voltage suppression constant current loop, the second target loop ② is used to perform constant current discharge conversion on the bus to obtain the current of the inner loop; the third target loop ③ is a DC voltage suppression constant voltage loop, the third target loop ③ is used to perform constant voltage control on the bus voltage to obtain the current of the inner loop. The PCS controller in the control module outputs a modulation wave by controlling the target, and then outputs a PWM pulse through the PWM modulation module to drive the IGBT of the inverter unit in the storage PCS module to realize the DC / AC or AC / DC energy flow of the energy storage converter.

[0058] The energy storage PCS DC bus overvoltage suppression and protection system integrates the energy storage PCS module, control module and PWM modulation module, aiming to effectively deal with the DC bus overvoltage problem that may occur in the energy storage system. Specifically, the energy storage PCS module consists of a DC side, an inverter unit and an AC side. The DC side is equipped with a battery system, bus capacitors and DC circuit breakers to ensure the stable storage and transmission of electric energy; the inverter unit uses power electronic devices such as IGBT to achieve the conversion and regulation of electric energy; the AC side is connected to the power grid through an AC circuit breaker to achieve grid connection and output of electric energy. In terms of the control module, the system cleverly designs three target loops, namely the constant power tracking outer loop (the first target loop ①), the DC voltage suppression constant current loop (the second target loop ②) and the DC voltage suppression constant voltage loop (the third target loop ③). Among them, the constant power tracking outer loop is responsible for real-time tracking of the superior power command to ensure that the system can operate stably according to the predetermined power; and the DC voltage suppression loop flexibly switches to constant current discharge or constant voltage control mode according to the voltage state of the DC bus to achieve rapid response and effective suppression of DC bus overvoltage. In actual operation, the PCS controller in the control module will intelligently select and switch to the appropriate target loop based on the real-time monitored DC bus voltage and the preset threshold conditions. By adjusting the target output modulation wave and processing it through the PWM modulation module, an accurate PWM pulse signal is generated to drive the IGBT of the inverter unit to switch, thereby achieving precise control of the DC / AC or AC / DC energy flow of the energy storage converter.

[0059] The energy storage PCS DC bus overvoltage suppression and protection system of the present invention integrates the energy storage PCS module, the control module and the PWM modulation module, and cleverly designs the constant power tracking outer loop and the DC voltage suppression loop (including constant current and constant voltage control modes), thereby achieving rapid response and effective suppression of the DC bus overvoltage problem in the energy storage system, ensuring that the system operates stably according to the predetermined power, while accurately controlling the energy flow of the energy storage inverter, and improving the overall operation stability and safety of the energy storage system.

[0060] Figure 3 FIG. 1 is a control block diagram of a DC voltage suppression loop according to an embodiment of the present invention. Figure 3 As shown, according to one embodiment of the present invention, the system open-loop transfer function using the second target loop ② is:

[0061] Gdc2(s)=Gd(s) / (s·C0·(G K +s))

[0062] The system open-loop transfer function using the third target loop ③ is:

[0063] Gdc(s)=(Gvpi(s)·Gd(s)) / (s·C0·(G K +s))

[0064] Among them, Gdc2(s) is the system open-loop transfer function using the second target loop ②; Gdc(s) is the system open-loop transfer function using the third target loop ③; Gvpi(s) is the transfer function of the PI control loop; Gd(s) is the transfer function of the delay link of the PCS controller; C0 is the bus capacitance value; G K is the coefficient of the equivalent current inner loop inertia link; the control bandwidth of the second target loop ② and the third target loop ③ is 1 / 5 to 1 / 4 of the current inner loop control bandwidth.

[0065] In this implementation, Gdc(s) is the system open-loop transfer function using a DC voltage suppression loop, Gvpi(s) is the transfer function of the PI control loop, Gdc(s) is removed and Gvpi(s) is the system open-loop transfer function using a DC voltage suppression loop ②. When designing, the timeliness of protection is taken into consideration, and the control bandwidth can be increased to 1 / 5 to 1 / 4 of the current inner loop control bandwidth; Gd(s) is the transfer function of the delay link of the PCS controller; C0 is the bus capacitance value; G K is the coefficient of the equivalent inner current loop inertia link, which is related to the inner current loop control parameters.

[0066] The present invention improves the control bandwidth of the DC voltage suppression loop to 1 / 5 to 1 / 4 of the current inner loop control bandwidth by designing a specific open-loop transfer function, thereby enhancing the timeliness of protection and optimizing the performance of the DC voltage suppression loop.

[0067] Embodiment 2

[0068] like Figure 1-3 As shown, according to an embodiment of the present invention, a storage PCS DC bus overvoltage suppression and protection system, the PCS controller controls the target output modulation wave, and then outputs PWM pulses through the PWM modulation module to drive the IGBT of the inverter unit to achieve the DC / AC or AC / DC energy flow of the energy storage converter; the system includes: an energy storage PCS module, a control module, and a PWM modulation module;

[0069] The energy storage PCS module consists of a DC side, an inverter unit, and an AC side. The DC side includes a battery system, bus capacitors, DC circuit breakers, etc. The AC side is connected to the grid via an AC circuit breaker; and the inverter unit consists of IGBTs.

[0070] The input end of the control module is connected to the output end of the energy storage PCS module, and the control module includes a PCS controller, and the target output modulation wave is controlled by the PCS controller;

[0071] The input end of the PWM modulation module is connected to the output end of the control module. The PWM modulation module performs PWM modulation on the output of the energy storage PCS, outputs PWM pulses, and drives the IGBT of the inverter unit.

[0072] The control module includes three loops: the first target loop ①, the second target loop ②, and the third target loop ③;

[0073] First target loop ①: Constant power tracking outer loop, real-time tracking of the upper power command to obtain the current I of the inner loop dref ,I qref , where I dref is the current positive sequence active power instruction, I qref It is the current positive sequence reactive power instruction.

[0074] Second target loop ②: DC voltage suppresses constant current loop, performs constant current discharge conversion on the bus, and serves as the inner loop instruction (i.e., the inner loop current) I dref ,I qref .

[0075] The third target loop ③: DC voltage suppression constant voltage loop, which controls the bus voltage at a constant voltage as the inner loop instruction I dref ,I qref .

[0076] like Figure 3 As shown, Gi(s)=1 / (G K +s) is the current inner loop, which can be equivalent to the first-order inertia link, where G KRelated to the inner loop control parameters; Gvpi(s) is the transfer function of the PI controller in series with the DC voltage loop, that is, the transfer function of the PI control loop; 1 / C0 is the controlled object, C0 is the bus capacitance value, considering the controller delay link Gd(s), the system open-loop transfer function is as follows,

[0077] The system open-loop transfer function using the second target loop is:

[0078] Gdc2(s)=Gd(s) / (s·C0·(G K +s))

[0079] The system open-loop transfer function using the third target loop is:

[0080] Gdc(s)=(Gvpi(s)·Gd(s)) / (s·C0·(G K +s))

[0081] In the energy storage PCS DC bus overvoltage suppression and protection system, when the second target loop ② is used, an open-loop given current inner loop instruction is used. When the third target loop ③ is used, a constant voltage outer loop is introduced, that is, Gvpi(s)*Gdc2(s) is its open-loop transfer function. Since the DC voltage suppression loop is used for suppression and protection, the loop bandwidth needs to be set as high as possible. Here, 1 / 5 to 1 / 4 of the current inner loop control bandwidth is taken.

[0082] Figure 4 FIG. 1 is a logic diagram of an energy storage PCS DC bus overvoltage suppression and protection system according to an embodiment of the present invention. Figure 4 As shown, the working logic of the system includes:

[0083] If the real-time collected DC voltage U dc Greater than the overvoltage suppression threshold U dcovThr1 , less than the overvoltage protection threshold U dcovThr2 , and the AC grid voltage is normal without other faults, start the second target loop ②;

[0084] If it is currently working in the second target loop ②, the DC voltage U dc Less than the overvoltage protection threshold U dcovThr2 , and the DC voltage U dc Lower than the constant pressure control target value U dcref , start the third target loop ③;

[0085] If it is currently working under the third target loop ③, the DC voltage U dc Greater than the undervoltage protection threshold U dcuvThr , and the DC voltage is stable at the constant voltage control target value U dcref Nearby, actual value U dc and constant pressure control target value Udcref The absolute value of the difference is less than the preset threshold U dtThr ; or the current DC voltage U dc Greater than the overvoltage protection threshold U dcovThr2 , the pulse is locked and the protection is exited.

[0086] The preset threshold U in this embodiment dtThr and undervoltage protection threshold U dcuvThr It is a preset threshold value, which is determined according to the actual status of the system.

[0087] The present invention realizes precise suppression and protection of the DC bus voltage by adopting a triple loop design of constant power tracking, constant current discharge and constant voltage control, ensuring that the system can operate stably and take timely measures when the voltage is abnormal, effectively improving the safety and reliability of the energy storage system.

[0088] Embodiment 3

[0089] Figure 5 FIG. 1 is a flow chart of a method for suppressing and protecting an overvoltage of a DC bus of an energy storage PCS according to an embodiment of the present invention. Figure 5 As shown, according to an embodiment of the present invention, a method for suppressing and protecting an overvoltage of a DC bus of an energy storage PCS is provided, using any one of the overvoltage suppression and protection systems for the DC bus of an energy storage PCS of the present invention, and the method comprises the following steps:

[0090] Step S102, monitoring the DC voltage U dc ;

[0091] Step S104, when the DC voltage U dc Greater than the overvoltage suppression threshold U dcovThr1 And not greater than the overvoltage protection threshold U dcovThr2 When the control module is switched from the first target loop ① to the second target loop ②;

[0092] Step S106, when the DC voltage U dc Not greater than the constant pressure control target value U dcref And less than the overvoltage protection threshold U dcovThr2 When the control module is switched from the second target loop ② to the third target loop ③;

[0093] Step S108, when the DC voltage U dc Controlled close to the constant pressure control target value U dcref When the preset duration is reached, the pulse is locked and the protection exit switch action is performed;

[0094] Step S110, when the DC voltage U dc Exceeding the overvoltage protection threshold U dcovThr2 When the pulse is locked, the protection exit switch action is performed.

[0095] Preferably, the first target loop ① is a constant power tracking outer loop, the input is the power target value, and the output is the current command value;

[0096] The second target loop ② is a DC voltage suppression constant current loop, in which the output active power is directly given the maximum allowable discharge instruction, and the reactive power is given as zero;

[0097] The third target loop ③ is a DC voltage suppression constant voltage loop, the active input is a DC voltage reference value, the output is an active current command, and the reactive reference is zero.

[0098] Preferably, the switching action includes opening of an AC or DC circuit breaker.

[0099] In this embodiment, when the controller detects the DC side voltage (DC voltage U dc ) suddenly rises to the DC voltage suppression loop startup threshold (overvoltage suppression threshold U dcovThr1 ), the DC voltage suppression loop is activated and the DC voltage reference value (constant voltage control target value U dcref ) is set to below the rated operating voltage of the battery; when the DC voltage U dc When the DC voltage stabilizes to the reference target value (DC voltage reference value), the latching pulse triggers an overvoltage fault and trips the AC and DC side switches; when the DC voltage cannot stabilize to the reference target value (DC voltage reference value), the DC voltage will slow down the dv / dt until the overvoltage protection threshold U is triggered. dcovThr2 , after the locking pulse, the AC and DC side switches are opened.

[0100] The DC voltage suppression loop is an outer loop based on the current inner loop. Since the DC voltage rise needs to be suppressed, the constant current mode should be used first and then switched to the constant voltage mode. The output current command I dref Directional restriction. Firstly, the constant current mode can speed up the response time of the DC voltage suppression loop and quickly reduce dv / dt. Then the constant voltage mode is used to ensure the stability of the control system before locking. The voltage will not drop below the rated working range, causing AC current oscillation and expanding the fault range.

[0101] First, the DC bus voltage U is continuously monitored dc Once you find U dc Exceeds the preset overvoltage suppression threshold U dcovThr1 However, the higher overvoltage protection threshold U has not yet been reached. dcovThr2 , the system immediately switches the control strategy from the constant power tracking outer loop (first target loop ①) to the DC voltage suppression constant current loop (second target loop ②). At this time, the system operates with the maximum allowable discharge current command to quickly slow down the voltage rise rate (dv / dt). If the DC voltage subsequently decreases to less than or equal to the constant voltage control target value U dcrefAnd the overvoltage protection threshold U is not triggered dcovThr2 , the control strategy will further switch to the DC voltage suppression constant voltage loop (third target loop ③) to stabilize the voltage to the reference value. dcref ) and maintain for a certain period of time, the system will execute the protection exit switch action, including the opening of AC and DC circuit breakers. dc Exceeding the overvoltage protection threshold U dcovThr2 , the pulse is immediately locked and the switching action is performed to prevent damage to the equipment. The advantage of this method is that by introducing a DC voltage suppression loop, the current command is dynamically adjusted before the overvoltage protection is triggered, effectively reducing the rise rate of the DC voltage, thereby ensuring the safety of the DC side equipment and avoiding damage caused by overvoltage. Compared with the traditional overvoltage protection strategy, it provides higher system stability and safety.

[0102] Compared with traditional overvoltage protection strategies, the present invention significantly improves the ability of energy storage PCS DC bus overvoltage suppression and protection. By introducing a DC voltage suppression loop and dynamically adjusting the current command before triggering the overvoltage protection, the present invention effectively slows down the rate of rise of the DC voltage (dv / dt), thereby greatly reducing the risk of damage to DC side equipment due to overvoltage. This invention not only ensures the safe operation of related devices on the DC side, but also improves the stability and reliability of the entire system. When faced with severe dv / dt overvoltage faults, the present invention can respond quickly and effectively execute protection strategies, providing a solid guarantee for the long-term stable operation of the energy storage system.

[0103] According to an embodiment of the present invention, the overvoltage suppression threshold U dcovThr1 It is the minimum value for judging whether there is abnormality on the DC side;

[0104] Constant pressure control target value U dcref Set within the rated operating voltage range of the battery;

[0105] Overvoltage protection threshold U dcovThr2 is the busbar safety threshold.

[0106] Preferably, the overvoltage suppression threshold U dcovThr1 Lower than the overvoltage protection threshold U dcovThr2 And higher than the rated working voltage of the battery.

[0107] In this embodiment, there are three key thresholds: overvoltage suppression threshold U dcovThr1 , constant pressure control target value U dcref and overvoltage protection threshold U dcovThr2 The following are the detailed definitions. dcovThr1As the minimum judgment value for abnormal conditions on the DC side, it is set to be slightly higher than the rated operating voltage of the battery but lower than the bus safety threshold (overvoltage protection threshold U dcovThr2 ) to ensure that overvoltage suppression measures can be initiated at the early stage of abnormal voltage rise. Constant voltage control target value U dcref The voltage is set within the rated operating voltage range of the battery as the target value for voltage stability control. dcovThr1 But it did not touch U dcovThr2 When the voltage is reduced to U dcref Below and less than U dcovThr2 , then switch to the constant voltage loop to stabilize the voltage. Once the voltage exceeds U dcovThr2 When the busbar reaches the safety threshold, the system will immediately perform protection actions, blocking pulses and tripping AC and DC circuit breakers to prevent equipment damage.

[0108] The present invention effectively improves the overvoltage protection capability and operational safety of the energy storage system by accurately setting thresholds and dynamically adjusting control strategies.

[0109] According to one embodiment of the present invention, the system open-loop transfer function using the second target loop ② is:

[0110] Gdc2(s)=Gd(s) / (s·C0·(G K +s))

[0111] The system open-loop transfer function using the third target loop ③ is:

[0112] Gdc(s)=(Gvpi(s)·Gd(s)) / (s·C0·(G K +s))

[0113] Among them, Gdc2(s) is the system open-loop transfer function using the second target loop; Gdc(s) is the system open-loop transfer function using the third target loop; Gvpi(s) is the transfer function of the PI control loop; Gd(s) is the transfer function of the delay link of the PCS controller; C0 is the bus capacitance value; G K is the coefficient of the equivalent current inner loop inertia link; the control bandwidth of the second target loop and the third target loop is 1 / 5 to 1 / 4 of the current inner loop control bandwidth.

[0114] In this implementation, the system open-loop transfer function when using the second target loop ② (DC voltage suppression constant current loop) and the third target loop ③ (DC voltage suppression constant voltage loop) is defined in detail, and the design principle of the control bandwidth is clarified.

[0115] Compared with the second target loop ②, the system open-loop transfer function using the third target loop ③ adds the transfer function Gvpi(s) of the PI control loop in the numerator. The PI control loop is a commonly used feedback control strategy that achieves precise control of the controlled object through two control actions: proportional (P) and integral (I).

[0116] The control bandwidth refers to the frequency range that the control system can respond to, which determines the system's sensitivity and response speed to changes in the input signal. In this embodiment, the control bandwidth of the second target loop ② and the third target loop ③ is designed to be 1 / 5 to 1 / 4 of the current inner loop control bandwidth. This design principle ensures that the system responds quickly to changes in the DC bus voltage and avoids system instability caused by excessively high control bandwidth.

[0117] The present invention realizes the optimized control of the energy storage PCS DC bus overvoltage suppression and protection system through precise mathematical models and control bandwidth design principles; this not only improves the stability and response speed of the system, but also effectively reduces the DC bus voltage rise rate (dv / dt), thereby protecting the safe operation of related devices on the DC side.

[0118] Embodiment 4

[0119] Figure 6 FIG. 1 is a flow chart of a method for overvoltage suppression and protection of a DC bus of an energy storage PCS according to another embodiment of the present invention. Figure 6 As shown, according to one embodiment of the present invention, a method for suppressing and protecting an overvoltage of a DC bus of an energy storage PCS comprises the following steps:

[0120] Step S202: When the DC voltage U dc Greater than the overvoltage suppression threshold U dcovThr1 , and is less than the overvoltage protection threshold U dcovThr2 When the constant power outer loop ① is quickly switched to the DC voltage suppression loop ②;

[0121] Specifically, when the DC voltage is too high and does not trigger the overvoltage protection threshold U dcovThr2 When the fault occurs, the DC current after the fault is quickly switched to discharge the DC side quickly, reducing the bus voltage increase rate;

[0122] Step S204: When the DC voltage U dc Lower than the constant pressure control target value U dcref , does not exceed the overvoltage protection threshold U dcovThr2 When , the DC voltage suppression loop ② is switched to the DC voltage suppression loop ③;

[0123] Specifically, when the voltage is lower than the reference voltage target value (i.e., the constant voltage control target value U dcref), it should quickly switch to DC voltage tracking to avoid the continuous decrease of bus capacitor voltage triggering undervoltage protection;

[0124] Step S206: When the DC voltage U dc Controlled approach target threshold (constant pressure control target value U dcref ) for a certain period of time, the pulse is locked and the protection exit switch is activated;

[0125] Step S208: During the whole process, if the DC voltage exceeds the overvoltage protection threshold U dcovThr2 When the protection is turned off, the suppression loop control must be terminated immediately, the pulse must be locked, and the protection exit switch action must be performed.

[0126] The present invention uses an intelligent switching control loop to quickly intervene when the DC voltage is abnormal. It first uses the DC voltage suppression loop to quickly reduce the bus voltage increase rate, then switches to the DC voltage tracking loop in time to avoid undervoltage, and safely exits control when the voltage is controlled to be close to the target. If the voltage exceeds the limit during the whole process, protection is immediately performed, which effectively reduces the dv / dt of the DC voltage rise and ensures the safety of DC-side devices. Compared with traditional overvoltage protection methods, it has higher flexibility and protection efficiency.

[0127] Embodiment 5

[0128] According to one embodiment of the present invention, an electronic device includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, any energy storage PCS DC bus overvoltage suppression and protection method of the present invention is implemented.

[0129] According to one embodiment of the present invention, a computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, any energy storage PCS DC bus overvoltage suppression and protection method of the present invention is implemented.

[0130] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described devices and media can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0131] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present application.

[0132] It should be understood that the size of the serial numbers of each step in the content of the invention and the embodiments of the present invention does not absolutely mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

Claims

1. An energy storage PCS DC bus overvoltage suppression and protection system, characterized in that: include: Energy storage PCS module, control module, PWM modulation module; The output of the energy storage PCS module is modulated by the control module and the PWM modulation module in turn and then input into the IGBT of the inverter unit of the energy storage PCS module; The control module includes a first target loop, a second target loop and a third target loop; The first target loop is a constant power tracking outer loop, the second target loop is a DC voltage suppression constant current loop, and the third target loop is a DC voltage suppression constant voltage loop. The energy storage PCS DC bus overvoltage suppression and protection function is achieved by switching the three target loops.

2. The energy storage PCS DC bus overvoltage suppression and protection system according to claim 1 is characterized in that: The energy storage PCS module includes: a DC side, an inverter unit, and an AC side; The DC side includes a battery system, a bus capacitor, and a DC circuit breaker; the inverter unit includes an IGBT; and the AC side is connected to the power grid through an AC circuit breaker.

3. The energy storage PCS DC bus overvoltage suppression and protection system according to claim 1 is characterized in that: The first target loop is used to track the upper power instruction in real time to obtain the current of the inner loop; The second target loop is used to perform constant current discharge conversion on the bus to obtain the current of the inner loop; The third target loop is used to perform constant voltage control on the bus voltage to obtain the current of the inner loop.

4. A method for suppressing and protecting an energy storage PCS DC bus overvoltage, using the energy storage PCS DC bus overvoltage suppression and protection system as described in any one of claims 1 to 3, characterized in that: The method comprises the following steps: Monitoring DC voltage U dc ; When the DC voltage U dc Greater than the overvoltage suppression threshold U dcovThr1 And not greater than the overvoltage protection threshold U dcovThr2 When the control module is switched from the first target loop to the second target loop; When the DC voltage U dc Not greater than the constant pressure control target value U dcref And is less than the overvoltage protection threshold U dcovThr2 When the control module is switched from the second target loop to the third target loop; When the DC voltage U dc Controlled to approach the constant pressure control target value U dcref When the preset duration is reached, the pulse is locked and the protection exit switch action is performed; When the DC voltage U dc Exceeding the overvoltage protection threshold U dcovThr2 When the pulse is locked, the protection exit switch action is performed.

5. The method for overvoltage suppression and protection of a DC bus of an energy storage PCS according to claim 4 is characterized in that: The first target loop is a constant power tracking outer loop, the input of which is a power target value, and the output of which is a current command value; The second target loop is a DC voltage suppression constant current loop, the output active power is directly given the maximum allowable discharge instruction, and the reactive power is given as zero; The third target loop is a DC voltage suppression constant voltage loop, the active input is a DC voltage reference value, the output is an active current instruction, and the reactive power reference is zero.

6. The method for overvoltage suppression and protection of a DC bus of an energy storage PCS according to claim 4 is characterized in that: The overvoltage suppression threshold U dcovThr1 It is the minimum value for judging whether there is abnormality on the DC side; The constant pressure control target value U dcref Set within the rated operating voltage range of the battery; The overvoltage protection threshold U dcovThr2 is the busbar safety threshold.

7. The method for overvoltage suppression and protection of a DC bus of an energy storage PCS according to claim 6 is characterized in that: The overvoltage suppression threshold U dcovThr1 Below the overvoltage protection threshold U dcovThr2 And higher than the rated working voltage of the battery.

8. The method for overvoltage suppression and protection of a DC bus of an energy storage PCS according to claim 4 is characterized in that: The switching action includes opening of AC and DC circuit breakers.

9. The method for overvoltage suppression and protection of a DC bus of an energy storage PCS according to claim 4 is characterized in that: The system open-loop transfer function using the second target loop is: Gdc2(s)=Gd(s) / (s·C0·(G K +s)) The system open-loop transfer function using the third target loop is: Gdc(s)=(Gvpi(s)·Gd(s)) / (s·C0·(G K +s)) Wherein, Gdc2(s) is the system open-loop transfer function using the second target loop; Gdc(s) is the system open-loop transfer function using the third target loop; Gvpi(s) is the transfer function of the PI control loop; Gd(s) is the transfer function of the delay link of the PCS controller; C0 is the bus capacitance value; G K is the coefficient of the equivalent current inner loop inertia link; the control bandwidth of the second target loop and the third target loop is 1 / 5 to 1 / 4 of the current inner loop control bandwidth.

10. An electronic device, characterized in that: It includes a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, the energy storage PCS DC bus overvoltage suppression and protection method as described in any one of claims 4 to 9 is implemented.

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