An energy storage pcs dc bus overvoltage suppression and protection system and method

Abstract

The application relates to the technical field of converters, in particular to an energy storage PCS DC bus overvoltage suppression and protection system and method; 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 input into the IGBT of the inverter unit of the energy storage PCS module through the control module and the PWM modulation module in sequence; 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 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 realized through switching of the three target loops. The application realizes rapid response and effective suppression of the DC bus overvoltage problem in the energy storage system, ensures stable operation of the system according to the predetermined power, and improves the overall operation stability and safety of the energy storage system.

Description

Technical Field

[0001] This invention relates to the field of converter technology, specifically to an energy storage PCS DC bus overvoltage suppression and protection system and method. Background Technology

[0002] As a key device in power conversion, the power storage converter (PCS) mainly consists of an AC inverter side and a DC bus side. The DC bus side is connected in parallel with the batteries. Two common parallel configurations for PCS are the common DC bus type and the single-cluster direct connection type. To ensure DC voltage stability, the DC bus is usually equipped with a capacitor of appropriate capacity. However, due to limitations in the withstand voltage stress of key components such as the bus capacitor and IGBTs, DC overvoltage protection is one of the important safeguards for PCS operation. Traditional DC overvoltage protection mechanisms rely on real-time monitoring of the DC voltage by the control unit. Once the DC voltage value exceeds a preset protection threshold, the control unit immediately blocks the IGBT drive pulses and disconnects the AC / DC switch to protect the PCS devices from damage.

[0003] However, in practical applications, especially when the PCS is fully charged, if the battery system malfunctions and suddenly disconnects, the DC-side capacitance will decrease sharply. In this situation, the DC bus capacitor voltage will rise rapidly, and the larger the output capacity before the fault, the faster the voltage rises. Since there is a time delay between the controller detecting the overvoltage fault signal and executing the latching pulse operation, this increases the risk of damage to the bus capacitor or IGBTs due to overvoltage during this period.

[0004] To address this issue, the traditional solution is to increase the withstand voltage of DC-side components during selection. While this approach can ensure component safety to some extent, it significantly increases device cost and size. Especially in scenarios where PCS operate on a common bus, if each PCS triggers overvoltage protection sequentially and shuts down one by one, the total capacitance of the DC-side capacitors will continuously decrease. In this case, the PCS that shuts down later will face a higher risk of overvoltage damage. Summary of the Invention

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

[0006] The present invention achieves the above objectives through the following technical solutions:

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

[0008] The output of the energy storage PCS module is modulated sequentially by the control module and the PWM modulation module before being input to 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 overvoltage suppression and protection function of the DC bus of the energy storage PCS is realized by switching the three target loops.

[0011] Furthermore, 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 IGBTs; and the AC side is connected to the power grid via an AC circuit breaker.

[0013] Furthermore, the first target loop is used to track the upper-level power command 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 in the inner loop.

[0016] A method for overvoltage suppression and protection of a DC bus in an energy storage PCS, employing any of the above-described energy storage PCS DC bus overvoltage suppression and protection systems, the method comprising 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 this happens, the control module will be 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 less than the overvoltage protection threshold U dcovThr2 When this happens, the control module is switched from the second target loop to the third target loop;

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

[0021] When the DC voltage U dc Exceeding the overvoltage protection threshold U dcovThr2 When the interlock pulse is applied, the switch action for protection deactivation is initiated.

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

[0023] The second target loop is a DC voltage suppression constant current loop, which outputs the maximum allowable discharge command for active power and zero reactive power.

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

[0025] Furthermore, the overvoltage suppression threshold U dcovThr1 The lowest value required to determine if an abnormality has occurred on the DC side;

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

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

[0028] Furthermore, the overvoltage suppression threshold U dcovThr1 Below the overvoltage protection threshold U dcovThr2 And it is higher than the battery's rated operating voltage.

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

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

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

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

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

[0034] Wherein, Gdc2(s) is the open-loop transfer function of the system using the second target loop; Gdc(s) is the open-loop transfer function of the system using the third target loop; Gvpi(s) is the transfer function of the PI control loop; Gd(s) is the transfer function of the PCS controller delay element; C0 is the bus capacitance value; G K The coefficient is the equivalent current inner loop inertial element; 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 includes a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the computer program, when executed by the processor, implements the overvoltage suppression and protection method for the DC bus of the energy storage PCS as described above.

[0036] The beneficial effects of this invention are as follows:

[0037] By introducing a DC voltage suppression loop, compared with the traditional overvoltage protection mechanism, this invention can flexibly adjust the current command before the DC bus voltage rises abnormally to trigger the overvoltage blocking protection, significantly slowing down the rate of rise of DC voltage (dv / dt), thereby effectively avoiding overvoltage damage to key components on the DC side and greatly improving the safety performance and operational reliability of the energy storage PCS system. Attached Figure Description

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

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

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

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

[0042] Figure 5 A flowchart of an energy storage PCS DC bus overvoltage suppression and protection method according to one embodiment of the present invention;

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

[0044] Wherein, ①—first target loop, ②—second target loop, ③—third target loop. Detailed Implementation

[0045] The invention will now be discussed with reference to exemplary embodiments. It should be understood that the described embodiments are merely intended to enable those skilled in the art to better understand and thus implement the invention, and are not intended to imply any limitation on the scope of the invention.

[0046] As used herein, the term "comprising" and its variations are to be interpreted as open-ended terms meaning "including but not limited to". The term "based on" is to be interpreted as "at least partially based on". The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment".

[0047] Example 1

[0048] Figure 1 This is a typical topology block diagram of an energy storage PCS; Figure 2 This is a control block diagram of an energy storage PCS DC bus overvoltage suppression and protection system according to one 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 sequentially by the control module and the PWM modulation module before being input to 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 overvoltage suppression and protection functions of the energy storage PCS DC bus are 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 a DC circuit breaker; the inverter unit includes IGBTs; the AC side is connected to the power grid via an AC circuit breaker.

[0054] Preferably, the first target loop ① is used to track the upper-level power command in real time to obtain the current of the inner loop;

[0055] The second target loop ② is used to perform constant current discharge conversion on the busbar to obtain the current of the inner loop;

[0056] The third target loop ③ is used to control the bus voltage at a constant voltage to obtain the current in the inner loop.

[0057] This embodiment proposes an energy storage PCS DC bus overvoltage suppression and protection system, including an energy 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. The constant power tracking outer loop is a first target loop ①, which is used to track the upper-level power command 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, which 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, which 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 modulated wave by controlling the target output, and then outputs PWM pulses through the PWM modulation module to drive the IGBTs of the inverter unit in the energy storage PCS module, thereby realizing 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 address potential DC bus overvoltage issues in energy storage systems. 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 a DC circuit breaker to ensure stable energy storage and transmission; the inverter unit uses power electronic devices such as IGBTs to convert and regulate electrical energy; and the AC side is connected to the grid via an AC circuit breaker to achieve grid connection and output of electrical energy. Regarding the control module, the system cleverly designs three target loops: a constant power tracking outer loop (first target loop ①), a DC voltage suppression constant current loop (second target loop ②), and a DC voltage suppression constant voltage loop (third target loop ③). The constant power tracking outer loop tracks the power commands from the upper level in real time, ensuring stable operation of the system at the predetermined power. The DC voltage suppression loop flexibly switches between constant current discharge and constant voltage control modes based on the DC bus voltage status, enabling rapid response and effective suppression of DC bus overvoltage. In actual operation, the PCS controller in the control module intelligently selects and switches to the appropriate target loop based on the real-time monitored DC bus voltage and preset threshold conditions. By adjusting the target output modulation wave and processing it through the PWM modulation module, a precise PWM pulse signal is generated to drive the IGBTs 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 an energy storage PCS module, a control module, and a PWM modulation module, and cleverly designs a constant power tracking outer loop and a DC voltage suppression loop (including constant current and constant voltage control modes). This achieves rapid response and effective suppression of DC bus overvoltage problems in the energy storage system, ensuring that the system operates stably at the predetermined power, while precisely controlling the energy flow of the energy storage converter, thereby improving the overall operational stability and safety of the energy storage system.

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

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

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

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

[0064] Wherein, Gdc2(s) is the open-loop transfer function of the system using the second target loop ②; Gdc(s) is the open-loop transfer function of the system 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 PCS controller delay element; C0 is the bus capacitance value; G K The coefficient of the equivalent current inner loop inertial element; 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 embodiment, Gdc(s) is the open-loop transfer function of the system using a DC voltage suppression loop, Gvpi(s) is the transfer function of the PI control loop, and Gdc(s) is the open-loop transfer function of the system using a DC voltage suppression loop ②. Considering the timeliness of protection during design, 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 PCS controller delay element; C0 is the bus capacitance value; G K This is the coefficient of the equivalent current inner loop inertial element, which is related to the current inner loop control parameters.

[0066] This invention improves the control bandwidth of the DC voltage suppression loop to 1 / 5 to 1 / 4 of the control bandwidth of the current inner loop 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] Example 2

[0068] like Figure 1-3 As shown, according to one embodiment of the present invention, an energy storage PCS DC bus overvoltage suppression and protection system is provided. 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, thereby realizing 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, and a DC circuit breaker. The AC side is connected to the power grid via an AC circuit breaker. The inverter unit consists of IGBTs.

[0070] The input terminal of the control module is connected to the output terminal of the energy storage PCS module. The control module includes a PCS controller, which controls the target output modulated wave.

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

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

[0073] First target loop ①: Constant power tracking outer loop, which tracks the upper-level power command in real time to obtain the inner loop current I. dref I qref , among which, I dref For positive sequence active power command, I qref This is a positive-sequence reactive power command.

[0074] Second target loop ②: DC voltage suppression constant current loop, which performs constant current discharge conversion on the bus, serving as the inner loop command (i.e., the inner loop current) I. dref I qref .

[0075] Third target loop ③: DC voltage suppression constant voltage loop, which performs constant voltage control on the bus voltage, as the inner loop command I. dref I qref .

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

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

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

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

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

[0081] In the overvoltage suppression and protection system of the DC bus of the energy storage PCS, when the second target loop ② is used, the open-loop given current inner loop command is used. When the third target loop ③ is used, the 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 This is a logic diagram of an energy storage PCS DC bus overvoltage suppression and protection system according to one embodiment of the present invention. Figure 4 As shown, the system's working logic 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 Furthermore, the AC network voltage is normal and there are no other faults, so the second target loop ② is started;

[0084] If currently operating under the second target loop ②, the DC voltage U dc Less than the overvoltage protection threshold U dcovThr2 And DC voltage U dc Below the constant pressure control target value U dcref Start the third target loop ③;

[0085] If currently operating 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 With 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 If the interlock pulse is triggered, the protection will be deactivated.

[0086] The preset threshold U in this embodiment dtThr With undervoltage protection threshold U dcuvThr The threshold is a pre-set threshold, determined based on the actual state of the system.

[0087] This invention employs a triple-loop design of constant power tracking, constant current discharge, and constant voltage control to achieve precise suppression and protection of DC bus voltage. This ensures 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] Example 3

[0089] Figure 5 This is a flowchart illustrating an embodiment of the overvoltage suppression and protection method for a DC bus in an energy storage PCS according to the present invention. Figure 5 As shown, according to one embodiment of the present invention, a method for suppressing and protecting overvoltage on a DC bus of an energy storage PCS, employing any of the energy storage PCS DC bus overvoltage suppression and protection systems of the present invention, includes the following steps:

[0090] Step S102, monitor 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 At that time, the control module will be 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 At that time, the control module will be switched from the second target loop ② to the third target loop ③;

[0093] Step S108, when the DC voltage U dc Controlled approach to constant pressure control target value U dcref When the preset duration is reached, the interlock pulse is activated, 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 interlock pulse is applied, the switch action for protection deactivation is initiated.

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

[0096] The second target loop ② is a DC voltage suppression constant current loop, which outputs the maximum allowable discharge command for active power and zero reactive power.

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

[0098] Preferably, the switching action includes the tripping of AC or DC circuit breakers.

[0099] In this embodiment, when the controller detects the DC side voltage (DC voltage U) dc The voltage suddenly rises to the DC voltage suppression loop activation threshold (overvoltage suppression threshold U). dcovThr1 When the DC voltage suppression loop is activated, the DC voltage reference value (constant voltage control target value U) is set. dcref Set below the battery's rated operating voltage; when the DC voltage U dc When the DC voltage stabilizes to the reference target value (DC voltage reference value), the blocking pulse triggers an overvoltage fault, tripping 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 decrease dv / dt until it triggers the overvoltage protection threshold U. dcovThr2 After the blocking pulse, the AC and DC side switches will be opened.

[0100] The DC voltage suppression loop is based on the outer loop of the inner current loop. Since it is necessary to suppress the rise of DC voltage, a constant current mode must be used first, and then switched to a constant voltage mode. The output current command I also needs to be adjusted. dref Directional restrictions are implemented. Using constant current mode first can accelerate the response time of the DC voltage suppression loop and quickly reduce dv / dt. Then, constant voltage mode is used to ensure the stability of the control system before lockout, preventing AC current oscillations caused by voltage drops below the rated operating range, which could expand the fault range.

[0101] First, continuously monitor the DC bus voltage U. dc Once U is discovered dc Exceeding the preset overvoltage suppression threshold U dcovThr1 However, it has not yet reached a higher overvoltage protection threshold U. dcovThr2 Upon this, 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 rapidly slow down the voltage rise rate (dv / dt). If the DC voltage subsequently drops to less than or equal to the constant voltage control target value U... dcrefAnd the overvoltage protection threshold U was not triggered. dcovThr2 Then 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. When the DC voltage approaches the target threshold (constant voltage control target value U), dcref After maintaining this state for a certain period, the system will execute a protection deactivation switching action, including the tripping of AC and DC circuit breakers. If the DC voltage U at any stage... dc Exceeding the overvoltage protection threshold U dcovThr2 If the pulse is blocked immediately and a switching action is performed to prevent equipment damage, the advantage of this method is that by introducing a DC voltage suppression loop, the current command is dynamically adjusted before triggering overvoltage protection, effectively reducing the rate of rise of DC voltage, thereby ensuring the safety of DC-side equipment and avoiding damage caused by overvoltage. Compared with traditional overvoltage protection strategies, this provides higher system stability and safety.

[0102] Compared to traditional overvoltage protection strategies, this invention significantly improves the overvoltage suppression and protection capabilities of the DC bus in energy storage PCS. By introducing a DC voltage suppression loop and dynamically adjusting the current command before triggering overvoltage protection, this invention effectively slows down the rate of rise of 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 DC-side devices but also improves the stability and reliability of the entire system. When faced with severe dv / dt overvoltage faults, this 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 one embodiment of the present invention, the overvoltage suppression threshold U dcovThr1 The lowest value required to determine if an abnormality has occurred on the DC side;

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

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

[0106] Preferably, the overvoltage suppression threshold U dcovThr1 Below the overvoltage protection threshold U dcovThr2 And it is higher than the battery's rated operating voltage.

[0107] In this embodiment, three key thresholds are specified: overvoltage suppression threshold U. dcovThr1 Constant pressure control target value U dcref and overvoltage protection threshold U dcovThr2 Detailed limitations were imposed. Among them, U dcovThr1As the minimum threshold for detecting DC-side anomalies, it is set slightly higher than the battery's rated operating voltage but lower than the bus safety threshold (overvoltage protection threshold U). dcovThr2 This ensures that overvoltage suppression measures can be initiated at the initial stage of an abnormal voltage rise. The constant voltage control target value U... dcref The voltage is then set within the battery's rated operating voltage range as the target value for voltage stability control. When the DC voltage exceeds U... dcovThr1 But it did not touch U dcovThr2 When this happens, the system switches to a DC voltage suppression constant current loop to rapidly reduce the voltage rise rate; if the voltage can be reduced to U... dcref Below and less than U dcovThr2 Then it switches to a constant voltage loop to stabilize the voltage. Once the voltage exceeds U... dcovThr2 At this bus safety threshold, the system will immediately execute protective actions, blocking the pulse and tripping the AC / DC circuit breaker to prevent equipment damage.

[0108] This invention effectively improves the overvoltage protection capability and operational safety of energy storage systems by precisely setting thresholds and dynamically adjusting control strategies.

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

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

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

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

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

[0114] In this embodiment, the open-loop transfer function of the system 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 to the system using the second objective loop ②, the system using the third objective loop ③ adds the transfer function Gvpi(s) of the PI control loop to the numerator of its open-loop transfer function. The PI control loop is a commonly used feedback control strategy that achieves precise control of the controlled object through both proportional (P) and integral (I) control actions.

[0116] Control bandwidth refers to the frequency range within which a control system can respond; it determines the system's sensitivity to changes in input signals and its response speed. 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 both a fast response to changes in DC bus voltage and avoids system instability caused by excessively high control bandwidth.

[0117] This invention achieves optimized control of the DC bus overvoltage suppression and protection system of the energy storage PCS through precise mathematical modeling 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 DC-side devices.

[0118] Example 4

[0119] Figure 6 This is a flowchart of another embodiment of the energy storage PCS DC bus overvoltage suppression and protection method of the present invention, as shown below. Figure 6 As shown, according to one embodiment of the present invention, a method for suppressing and protecting overvoltage on a DC bus of an energy storage PCS includes the following steps:

[0120] Step S202: When the DC voltage U dc Greater than the overvoltage suppression threshold U dcovThr1 And less than the overvoltage protection threshold U dcovThr2 At that time, 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 but does not trigger the overvoltage protection threshold U dcovThr2 In this case, the DC current after the fault is quickly switched to discharge the DC side quickly, reducing the rate of rise of the bus voltage.

[0122] Step S204: When the DC voltage U dc Below the constant pressure control target value U dcref It did not exceed the overvoltage protection threshold U. dcovThr2 When switching from DC voltage suppression loop ② to 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), dcrefWhen this occurs, the system should be quickly switched to DC voltage tracking to avoid triggering undervoltage protection due to a continuous decrease in the bus capacitor voltage.

[0124] Step S206: When the DC voltage U dc Controlled approach to the target threshold (constant pressure control target value U) dcref After a certain period of time, the blocking pulse will be activated, and the protection exit switch will be activated.

[0125] Step S208: If the DC voltage exceeds the overvoltage protection threshold U during the entire process... dcovThr2 When this occurs, the suppression loop control must be terminated immediately, the lockout pulse must be blocked, and the protection exit switch action must be performed.

[0126] This invention utilizes an intelligent switching control loop to quickly intervene when the DC voltage is abnormal. First, a DC voltage suppression loop rapidly reduces the rate of increase in bus voltage. Then, it switches to a DC voltage tracking loop in a timely manner to avoid undervoltage. Finally, it safely exits control when the voltage is under control and close to the target. If the voltage exceeds the limit during the entire process, it immediately provides protection, effectively reducing the dv / dt of the DC voltage rise and ensuring the safety of DC-side devices. Compared with traditional overvoltage protection methods, it has higher flexibility and protection efficiency.

[0127] Example 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, it implements any of the energy storage PCS DC bus overvoltage suppression and protection methods of the present invention.

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

[0130] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the equipment and media described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0131] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

[0132] It should be understood that the sequence number of each step in the invention and embodiments of the present invention does not absolutely imply 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. A method for overvoltage suppression and protection of a DC bus in an energy storage PCS, comprising an energy storage PCS DC bus overvoltage suppression and protection system, characterized in that, The system includes: Energy storage PCS module, control module, PWM modulation module; The output of the energy storage PCS module is modulated sequentially by the control module and the PWM modulation module before being input to 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. Switching between these three target loops enables overvoltage suppression and protection of the energy storage PCS DC bus. The method includes 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 this happens, the control module will be 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 less than the overvoltage protection threshold U dcovThr2 When this happens, the control module is switched from the second target loop to the third target loop; When the DC voltage U dc Controlled approach to the constant pressure control target value U dcref When the preset duration is reached, the interlock pulse is activated, and the protection exit switch action is performed. When the DC voltage U dc Exceeding the overvoltage protection threshold U dcovThr2 When the interlock pulse is applied, the switch action for protection deactivation is initiated.

2. The method for overvoltage suppression and protection of the DC bus of the energy storage PCS according to claim 1, 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 IGBTs; and the AC side is connected to the power grid via an AC circuit breaker.

3. The method for overvoltage suppression and protection of the DC bus of the energy storage PCS according to claim 1, characterized in that: The first target loop is used to track the power command from the upper level 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 in the inner loop.

4. The method for overvoltage suppression and protection of the DC bus of the energy storage PCS according to claim 1, characterized in that: The first target loop is a constant power tracking outer loop, with the power target value as input and the current command value as output; The second target loop is a DC voltage suppression constant current loop, which outputs the maximum allowable discharge command for active power and zero reactive power. The third target loop is a DC voltage suppression constant voltage loop, with active power input being the DC voltage reference value, output being the active current command, and reactive power setpoint being zero.

5. The method for overvoltage suppression and protection of the DC bus of the energy storage PCS according to claim 1, characterized in that: The overvoltage suppression threshold U dcovThr1 The lowest value required to determine if an abnormality has occurred on the DC side; The constant pressure control target value U dcref Set within the battery's rated operating voltage range; The overvoltage protection threshold U dcovThr2 This is the busbar safety threshold.

6. The method for overvoltage suppression and protection of the DC bus of the energy storage PCS according to claim 5, characterized in that: The overvoltage suppression threshold U dcovThr1 Below the overvoltage protection threshold U dcovThr2 And it is higher than the battery's rated operating voltage.

7. The method for overvoltage suppression and protection of the DC bus of an energy storage PCS according to claim 1, characterized in that: The switching action includes the tripping of AC and DC circuit breakers.

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

9. 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 the computer program, when executed by the processor, implements the overvoltage suppression and protection method for the DC bus of the energy storage PCS as described in any one of claims 1-8.

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