A power plant auxiliary power security uninterrupted power supply system and a control method thereof

Abstract

The present application relates to the technical field of safe power supply, in particular to a power plant auxiliary power uninterrupted power supply system and a control method thereof, comprising a single diesel generator set, at least four security section busbars and at least one bridge type power inverter group, the bridge type power inverter group comprising a four-quadrant power inverter and a standby power module, when detecting an abnormal security section busbar with power failure or temporary drop, the bridge type power inverter group disconnects the working incoming line circuit breaker connected with the abnormal security section busbar, and controls the power inverter connected with the abnormal security section busbar to be in a variable current state, so as to supply power to the abnormal security section busbar through the power inverter in the variable current state. The present application realizes uninterrupted switching of the security power supply by adopting an online backup switching mode of the bridge type power inverter group, and can ensure effective power supply to the security section busbar load after the power failure of the power plant auxiliary power security section busbar, thereby improving the power supply reliability of the power plant security power supply.

Description

Technical Field

[0001] This invention relates to the field of safe power supply technology, and in particular to an uninterrupted power supply system for power plant auxiliary power and its control method. Background Technology

[0002] According to the "GB 500660 Technical Specification for Design of Thermal Power Plants", units with a capacity of 200MW and above are required to be equipped with AC backup power supplies. These backup power supplies should preferably be fast-starting diesel generator sets. Currently, the backup power supply wiring method involves configuring one diesel generator set per unit, with two backup busbars per unit. Backup loads are evenly connected to the two backup busbars according to the number of units. Figure 1 This diagram illustrates the wiring structure of a traditional single-unit emergency power supply. The advantage of this wiring method is that the emergency busbar section corresponds to the unit's auxiliary power busbar, resulting in strong unit integration. The diesel generator set serves as the emergency power supply after a power outage. When any emergency busbar section loses power, the diesel generator set can quickly start to supply power to the emergency PC section. However, based on long-term operating experience, this topology has two problems. First, because the diesel generator is in a cold standby state, there is a risk of starting failure during emergency starts, especially when the maintenance of the diesel generator itself is inadequate, which significantly increases the risk of starting failure. Second, power switching under this wiring method is a power outage switching, and the power outage time depends on the starting and switching time of the diesel generator, generally ranging from 8 to 15 seconds.

[0003] Furthermore, once the backup power supply is restored, the backup loads automatically engage according to their respective process interlocking requirements. Some loads engage with a delay or manually, thus ensuring the reliability of the backup power supply. However, critical loads may experience interruptions or startup failures, jeopardizing the safe shutdown of the main unit. Therefore, ensuring the reliability of the backup power supply for plant auxiliary power is particularly important. In recent years, although some power plants have improved their wiring methods by interconnecting the backup PC sections of two diesel generator sets to shorten the switching time of the backup power supply when a single unit loses its auxiliary power, Figure 2 This diagram illustrates the interconnection of the safety PC section between two diesel generator sets. However, this introduces another problem: when the safety busbar or load restarts or malfunctions due to power outage, the resulting voltage change will inevitably cause a temporary voltage drop in the normal safety busbar, thus affecting the normal operation of its safety load. In other words, after the safety interconnection of different units, equipment failure or load startup will affect the power supply of other busbar sections. Moreover, this improvement method still cannot fundamentally solve the problem of relying on the reliable and rapid startup of diesel generators when both units lose power at the same time. Summary of the Invention

[0004] This invention provides an uninterrupted power supply system and control method for power plant auxiliary power supply. The technical problem it solves is that the current interconnection method of the auxiliary power supply for power plants not only affects the power supply of other bus sections when equipment fails or load starts after the auxiliary power of different units is interconnected, but also still cannot solve the dependence on the reliable and rapid start-up of diesel generators when the auxiliary power of two units is lost at the same time.

[0005] To address the above technical problems, this invention provides an uninterrupted power supply system for power plant auxiliary power and its control method.

[0006] In a first aspect, the present invention provides an uninterrupted power supply system for backup power in a power plant. The power supply system includes: a single diesel generator set, at least four backup bus sections, and at least one bridge power inverter set. Each backup bus section is connected to the working power supply of the plant through a working incoming circuit breaker, and each backup bus section is connected to the diesel generator set in parallel after being connected to a standby incoming circuit breaker.

[0007] The bridge-type power inverter group includes a four-quadrant power inverter and a backup power module. The backup power module includes a backup power supply, a diode, and a power isolation switch connected in series. Each safety section bus is connected to the AC side of the four-quadrant power inverter through an inverter incoming circuit breaker. The DC side of the four-quadrant power inverter is connected to a DC side isolation switch and then connected in parallel to one end of the power isolation switch of the backup power module. The other end of the power isolation switch is connected to the backup power supply through a diode.

[0008] The bridge-type power inverter group is used to disconnect the working incoming circuit breaker connected to the abnormal safety section bus when an abnormal safety section bus is detected, and control the power inverter connected to the abnormal safety section bus in the four-quadrant power inverter to be in the converter state so as to supply power to the abnormal safety section bus through the power inverter in the converter state, while controlling the remaining power inverters to be in the rectification state.

[0009] The backup power module is used to supply power to the corresponding abnormal safety bus via a four-quadrant power inverter when all the safety bus sections are abnormal safety bus sections; the abnormal safety bus section is the safety bus section that experiences power loss or temporary descent.

[0010] In a further embodiment, the bridge power inverter group is internally equipped with a voltage detection and protection control circuit;

[0011] The voltage detection and protection control circuit is used to collect the voltage of each safety section bus and the current of the corresponding working incoming circuit breaker in real time, obtain the effective value of the corresponding safety section bus voltage and the effective value of the working incoming current, and determine the abnormal safety section bus and the normal safety section bus based on the difference in the effective value of the safety section bus voltage and the difference in the effective value of the working incoming current between the current cycle and the previous cycle.

[0012] Furthermore, based on the effective values ​​of the voltage and current of the protection section bus, the working incoming load and voltage per-unit value of the normal protection section bus are obtained. The power inverter connected to the normal protection section bus in the four-quadrant power inverter is taken as the power inverter to be allocated. Based on the working incoming load and voltage per-unit value of the normal protection section bus, the rectified active power allocation and rectified reactive power allocation of the power inverter to be allocated are dynamically adjusted so that the bridge power inverter group can operate in any one of the four quadrants of the active-reactive plane.

[0013] In a further implementation plan, determining the abnormal and normal safety busbars based on the difference in the effective value of the safety busbar voltage and the difference in the effective value of the working incoming current between the current and previous cycles specifically includes:

[0014] Based on the effective values ​​of the voltage and the working incoming current of the safety section busbar, calculate the difference in the effective value of the voltage of the safety section busbar between the current cycle and the previous cycle, and the difference in the effective value of the working incoming current of the safety section busbar between the current cycle and the previous cycle.

[0015] The effective value change difference of the safety section bus voltage is compared with a preset voltage difference threshold, and the effective value change difference of the working incoming current is compared with a preset current difference threshold. If it is detected that the effective value change difference of the safety section bus voltage is higher than the preset voltage difference threshold and the effective value change difference of the working incoming current is higher than the preset current difference threshold, then the corresponding safety section bus is determined to be an abnormal safety section bus; otherwise, the corresponding safety section bus is determined to be a normal safety section bus.

[0016] In a further implementation, the rectified active power of the inverter to be allocated is proportionally allocated based on the working incoming load of the normal safety section bus, with the direction being from the normal safety section bus to the abnormal safety section bus.

[0017] The rectified reactive power distribution of the inverter to be allocated is proportional to the voltage level of the normal safety bus, with the flow direction from the high-voltage safety bus to the low-voltage safety bus.

[0018] In a further implementation scheme, the formula for calculating the rectified active power allocation is:

[0019]

[0020]

[0021] In the formula, P 逆 P represents the rectified active power of the inverter to be allocated power; m P represents the active power requirement of the m-th abnormal safety section busbar; ∑ P represents the total working incoming load of all normal safety busbar sections; n P represents the working incoming load of the nth normal safety bus, excluding the abnormal safety bus and the normal safety bus connected to the inverter to be allocated power; N represents the total number of normal safety buses, excluding the abnormal safety bus and the normal safety bus connected to the inverter to be allocated power; S This represents the total working incoming load of all normal safety busbars except for the abnormal safety busbar and the normal safety busbar connected to the inverter to be allocated power.

[0022] In a further implementation scheme, the calculation formula for the rectified reactive power allocation is as follows:

[0023]

[0024] In the formula, Q 逆 This represents the rectified reactive power of the inverter to be allocated power; This represents the per-unit voltage value of the normal safety busbar connected to the inverter to be allocated power; Q represents the per-unit voltage value of the nth normal safety bus, excluding the abnormal safety bus and the normal safety bus connected to the inverter to be allocated power; N represents the total number of normal safety buses, excluding the abnormal safety bus and the normal safety bus connected to the inverter to be allocated power; ∑ This indicates the reactive power requirement for all abnormal safety bus sections.

[0025] In a further implementation, the bridge power inverter group is also used to control the output voltage frequency and phase of the four-quadrant power inverter to be consistent with the power supply of the diesel generator set when all the protection section busbars are abnormal protection section busbars, and if it is detected that the power supply of the diesel generator set on the line side of the inverter incoming circuit breaker is normal and the user inputs a diesel generator protection power supply parallel restoration command, and control all the inverter incoming circuit breakers and the standby incoming circuit breaker to close, so that the four-quadrant power inverter is restored to hot standby state, and all abnormal protection section loads are transferred to the diesel generator set for power supply;

[0026] Furthermore, when it is detected that the diesel generator set needs to be restored to the plant auxiliary power supply, or when the plant auxiliary power supply of the abnormal safety section bus is restored to normal, in response to the user-input parallel power supply restoration command, the output voltage frequency and phase of the four-quadrant power inverter are controlled to be consistent with the plant auxiliary power supply, and the working incoming circuit breaker connected to the abnormal safety section bus is controlled to close, so that the four-quadrant power inverter is restored to hot standby state, and the load of the abnormal safety section bus is transferred to the plant auxiliary power supply.

[0027] In a further implementation, when the abnormal safety section load is powered by a diesel generator set and it is detected that the diesel generator set power supply needs to be restored to the plant auxiliary power supply, before controlling the output voltage frequency and phase of the four-quadrant power inverter to be consistent with the plant auxiliary power supply, all the inverter incoming line circuit breakers are controlled to trip, so that the abnormal safety section bus load is powered by the four-quadrant power inverter.

[0028] In a further embodiment, the power supply system further includes a power supply control module;

[0029] The power supply control module is used to control all working incoming circuit breakers and inverter incoming circuit breakers to be in the closed state when the entire power supply system is running normally. All safety section busbars are normally powered by the power plant's auxiliary power system, and the four-quadrant power inverter is in a hot standby state. At this time, there is no power flow inside the bridge power inverter group, the standby incoming circuit breaker is in a hot standby state, and the diesel generator set is in a cold standby state.

[0030] Secondly, the present invention provides a control method for an uninterruptible power supply system for power plant auxiliary power, applying the aforementioned uninterruptible power supply system for power plant auxiliary power, the control method comprising the following steps:

[0031] The safety busbars are inspected, and those that experience power loss or temporary power drop are identified as abnormal safety busbars.

[0032] When an abnormal safety section bus is detected, the working incoming circuit breaker connected to the abnormal safety section bus is disconnected, and the power inverter connected to the abnormal safety section bus in the four-quadrant power inverter is controlled to be in the converter state so as to supply power to the abnormal safety section bus through the power inverter in the converter state, while the remaining power inverters are controlled to be in the rectification state.

[0033] When all the aforementioned security bus sections are abnormal security bus sections, the control backup power module supplies power to the corresponding abnormal security bus section through a four-quadrant power inverter.

[0034] This invention provides an uninterruptible power supply system and control method for backup power supply in power plants. The power supply system includes a single diesel generator set, at least four backup bus sections, and at least one bridge power inverter group. The bridge power inverter group includes a four-quadrant power inverter and a backup power module. When the bridge power inverter group detects an abnormal backup bus section experiencing power loss or temporary sag, it disconnects the working incoming circuit breaker connected to the abnormal backup bus section and controls the power inverter connected to the abnormal backup bus section in the four-quadrant power inverter to enter a converter state, so as to supply power to the abnormal backup bus section through the power inverter in the converter state. When all backup bus sections are abnormal backup bus sections, the backup power module supplies power to the corresponding abnormal backup bus section through the four-quadrant power inverter. Compared with existing technologies that use power failure switching for abnormal safety buses, this power supply system uses bridge power inverters to switch abnormal safety buses online as backup, achieving uninterrupted switching of safety power. It can ensure effective power supply to the load of the safety bus section after the power supply to the power plant's auxiliary power safety section is lost. At the same time, it reduces the dependence of the safety power supply on the success and time of diesel generator power restoration, improves the ability of the auxiliary power safety power supply system to cope with complex electrical faults, and has the advantages of safety and reliability. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the wiring structure of a conventional single-unit emergency power supply provided in an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the interconnection of the safety PC section between two conventional diesel generator sets provided in an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of the uninterruptible power supply system for power plant auxiliary power supply provided in an embodiment of the present invention;

[0038] Figure 4 This is a schematic diagram of the operation mode of a single-section security busbar (PC1A section) when it loses power, provided in an embodiment of the present invention;

[0039] Figure 5 This is a schematic diagram of the operation mode of the two security busbars (PC1A section and PC1B section) when power is lost, provided in an embodiment of the present invention;

[0040] Figure 6 This is a schematic diagram of the operation mode of the three-section safety busbar (PC1A section, PC1B section, PC2A section) when power is lost, provided in an embodiment of the present invention;

[0041] Figure 7 This is a schematic diagram of the operation mode when all four sections of the safety busbar lose power, as provided in an embodiment of the present invention.

[0042] Figure 8 This is a schematic diagram of the control method for an uninterrupted power supply system for power plant auxiliary power supply provided in an embodiment of the present invention. Detailed Implementation

[0043] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0044] This invention provides an uninterruptible power supply system for backup power in a power plant. The system includes a single diesel generator set, at least four backup bus sections, and at least one bridge-type power inverter set. Each backup bus section is connected to the working power supply of the plant via a working incoming circuit breaker. Each backup bus section is connected to the diesel generator set in parallel via a backup incoming circuit breaker. A diesel generator power circuit breaker KC is connected between the backup incoming circuit breaker and the diesel generator set. For ease of understanding, the power supply system provided in this embodiment is described below. Figure 3 As shown, the following will be a detailed description of a power supply system including a single diesel generator set, four safety bus sections, and a bridge power inverter set. The working incoming circuit breakers are labeled K1AA, K1BA, K2AA, and K2BA, the standby incoming circuit breakers are labeled K1AB, K1BB, K2AB, and K2BB, and the four safety bus sections are labeled PC1A, PC1B, PC2A, and PC2B.

[0045] The bridge-type power inverter group includes a four-quadrant power inverter and a backup power module. The backup power module includes a backup power supply, a diode D, and a power isolation switch K0 connected in series. Since the 220V battery has a large capacity, it can still support the stable operation of the plant's backup power supply for a sufficient period of time in the extreme case of a complete loss of power to the four safety bus sections, facilitating the restoration of the diesel generator power supply or the plant's working power supply. Therefore, this embodiment uses the power plant's original 220V battery as a backup power supply, and a diode D is connected in series on the output side of the 220V battery to avoid reverse charging of the battery by the DC side of the power inverter.

[0046] The four-quadrant power inverter includes four power inverters, labeled PA, PB, PC, and PD. Each power inverter has a DC-side isolating switch connected to its DC side, labeled K1, K2, K3, and K4. The DC side of each four-quadrant power inverter is connected to one end of the power isolation switch K0 of the backup power module after being connected to the DC-side isolating switch. The other end of the power isolation switch K0 is connected to the backup power supply through a diode D. Each safety section busbar is connected to the AC side of one of the four-quadrant power inverters through an inverter incoming circuit breaker, labeled K1AC, K1BC, K2AC, and K2BC, to allow for maintenance of the power inverters by controlling the inverter incoming circuit breakers.

[0047] This embodiment adds a four-quadrant power inverter to the power plant's auxiliary power security supply to form a bridge power inverter group. The bridge power inverter group can independently control active and reactive power, realize the bidirectional power flow function of active and reactive power, so that it can adapt to different application needs, improve the flexibility and efficiency of the power system, and at the same time, the power of the inverter can meet the requirements of islanded operation of the security PC section.

[0048] In this embodiment, the power supply system is equipped with a power supply control module. When the entire power supply system is operating normally, the power supply control module controls all working incoming circuit breakers K1AA, K1BA, K2AA, K2BA and inverter incoming circuit breakers K1AC, K1BC, K2AC, K2BC to be in the closed state. All safety bus sections PC1A, PC1B, PC2A and PC2B are normally powered by the power plant's auxiliary power system, so that the four-quadrant power inverter is in a hot standby state. At this time, there is no power flow inside the bridge power inverter group. The standby incoming circuit breakers K1AB, K1BB, K2AB, K2BB and diesel generator power circuit breaker KC are in a hot standby state, and the diesel generator set is in a cold standby state.

[0049] The bridge-type power inverter group is internally equipped with a voltage detection and protection control circuit. In this embodiment, the voltage of each safety bus section PC1A, PC1B, PC2A, and PC2B, as well as the current of the corresponding working incoming circuit breakers K1AA, K1BA, K2AA, and K2BA, are collected in real time by the voltage detection and protection control circuit. The effective values ​​of the corresponding safety bus voltage and the effective values ​​of the working incoming current are obtained. Based on the difference in the effective value of the safety bus voltage between the current cycle and the previous cycle, the effective values ​​of the safety bus voltage are calculated. The effective value variation of the working incoming current is used to determine whether each safety bus section has experienced power outages or temporary drops, thereby screening out abnormal and normal safety bus sections from all safety bus sections. Specifically, based on the effective value variation of the safety bus voltage and the effective value variation of the working incoming current between the current and previous cycles, it is determined whether each safety bus section has experienced power outages or temporary drops, thus screening out abnormal and normal safety bus sections from all safety bus sections.

[0050] Based on the effective values ​​of the voltage and current of the protection busbars, calculate the difference in effective voltage and current of each protection busbar between the current and previous cycles. Simultaneously, compare the difference in effective voltage and current of each protection busbar between the current and previous cycles with preset voltage and current difference thresholds. If a difference in effective voltage of a protection busbar is detected... If the voltage difference value is higher than a preset voltage difference threshold and the effective value change difference of the working incoming current is higher than a preset current difference threshold, then the corresponding single-section safety bus is considered to have experienced power outage or sag, and the corresponding safety bus is determined to be an abnormal safety bus; otherwise, the corresponding safety bus is determined to be a normal safety bus. In this embodiment, it can be preferentially set that when the current cycle effective value of the safety bus voltage decreases by 30% compared to the previous cycle effective value and the change of the current cycle effective value of the working incoming current is negative compared to the previous cycle effective value, that is, when the plant power outage or sag occurs, i.e.:

[0051]

[0052] In the formula, U * This represents the per-unit voltage value; k-1 represents the previous cycle; k represents the current cycle.

[0053] When any single safety bus section experiences power loss or sag, the bridge power inverter group treats all safety bus sections experiencing power loss or sag as abnormal safety bus sections. In this case, the bridge power inverter group responds quickly by disconnecting the working incoming circuit breaker connected to the abnormal safety bus section and controlling the power inverters connected to the abnormal safety bus section in the four-quadrant power inverters to be in converter mode, so as to supply power to the abnormal safety bus section through the power inverters in converter mode, while controlling the remaining power inverters to be in rectification mode.

[0054] Simultaneously, the voltage detection and protection control circuit obtains the working incoming load and per-unit voltage value of the normal safety section bus based on the effective value of the bus voltage and the effective value of the working incoming current. It then designates the power inverter connected to the normal safety section bus among the four-quadrant power inverters as the power inverter to be allocated. At this time, the power inverter to be allocated is in rectification mode. In this embodiment, based on the working incoming load and per-unit voltage value of the normal safety section bus, the active power distribution and reactive power distribution of the power inverter to be allocated in rectification mode are dynamically adjusted, so that the bridge power inverter group operates in any four quadrant of the active-reactive plane. The calculation formula for the rectified active power distribution is:

[0055]

[0056]

[0057] In the formula, P 逆 P represents the rectified active power of the inverter to be allocated power; m P represents the active power requirement of the m-th abnormal safety section busbar; ∑ P represents the total working incoming load of all normal safety busbar sections; n P represents the working incoming load of the nth normal safety bus, excluding the abnormal safety bus and the normal safety bus connected to the inverter to be allocated power; N represents the total number of normal safety buses, excluding the abnormal safety bus and the normal safety bus connected to the inverter to be allocated power; S This represents the total working incoming load of all normal safety busbars except for the abnormal safety busbar and the normal safety busbar connected to the inverter to be allocated power.

[0058] The formula for calculating the rectified reactive power distribution is as follows:

[0059]

[0060] In the formula, Q 逆 This represents the rectified reactive power of the inverter to be allocated power; This represents the per-unit voltage value of the normal safety busbar connected to the inverter to be allocated power; Q represents the per-unit voltage value of the nth normal safety bus, excluding the abnormal safety bus and the normal safety bus connected to the inverter to be allocated power; N represents the total number of normal safety buses, excluding the abnormal safety bus and the normal safety bus connected to the inverter to be allocated power; ∑ This indicates the reactive power requirement for all abnormal safety bus sections.

[0061] In this embodiment, the rectified active power of the inverter to be allocated is proportionally distributed based on the load size of the working incoming line of the normal safety section bus, with the flow direction from the normal safety section bus to the abnormal safety section bus; the rectified reactive power of the inverter to be allocated is proportionally distributed based on the voltage level of the normal safety section bus, with the flow direction from the high-voltage safety section bus to the low-voltage safety section bus. It should be noted that, compared to the existing dual-power converter topology where power can only flow from the normal power supply side to the power failure side, the active and reactive power allocation strategy adopted in this embodiment allows the entire bridge power... The bridge power converter group independently controls the output of active and reactive power, thereby making the flow direction of reactive power inconsistent with that of active power. This changes the flow direction of active and reactive power. Therefore, through appropriate control, the entire bridge power converter group can operate in any quadrant of the active-reactive power plane, giving it wider adaptability and higher flexibility. It can independently control active and reactive power according to system requirements, improving the stability and reliability of the power system, and has broad application prospects in power systems.

[0062] To facilitate understanding of the response control process of a bridge power inverter group when power is lost or a sag occurs on any single safety bus section, the following examples illustrate the control processes for power loss or sag on a single safety bus section, two safety bus sections, three safety bus sections, and all safety bus sections:

[0063] like Figure 4As shown, when only the PC1A section of the safety bus experiences a power outage or temporary drop, the PC1A section becomes an abnormal safety bus, while the remaining PC1B, PC2A, and PC2B sections remain normal safety buses. In this situation, the bridge power inverter group responds quickly, tripping the incoming circuit breaker K1AA. Simultaneously, the corresponding power converter PA enters the conversion state, while the other three power converters are in the rectification state. Power converter PA converts current to supply power to the PC1A section of the safety bus. The voltage detection and protection control circuit dynamically adjusts the active power distribution of the other three power converters PB, PC, and PD, which are in the rectification state, thereby achieving a reasonable distribution of active power. The bus section with less load undertakes more active power. The rectified active power allocated to power inverters PB, PC, and PD are as follows:

[0064]

[0065] at this time,

[0066] P ∑ =P2+P3+P4

[0067] In the formula, P B P C and P D P1 represents the rectified active power allocated by the power inverters PB, PC, and PD, respectively; P2 represents the active power required by the safety bus section PC1A; P3 represents the working incoming load of the safety bus section PC1B; P4 represents the working incoming load of the safety bus section PC2A; and P5 represents the working incoming load of the safety bus section PC2B.

[0068] Simultaneously, the voltage detection and protection control circuit dynamically adjusts the reactive power distribution of the other three power inverters PB, PC, and PD, which are in rectification mode, to achieve a reasonable distribution of reactive power. This allows the high-voltage safety bus to bear more reactive power. The rectified reactive power allocated to the power inverters PB, PC, and PD are as follows:

[0069]

[0070] In the formula, Q B Q C and Q D U1, U2, and U3 represent the rectified reactive power allocated by the power inverters PB, PC, and PD, respectively; U4 represents the per-unit voltage value of the safety bus section PC1B; U5 represents the per-unit voltage value of the safety bus section PC2A; U6 represents the per-unit voltage value of the safety bus section PC2B; Q represents the per-unit voltage value of the safety bus section PC2B; Q represents the per-unit voltage value of the safety bus section PC2B. ∑ This indicates the reactive power requirement of the abnormal safety section bus. Here, it refers to the reactive power requirement of the abnormal safety section bus PC1A.

[0071] After the working power supply of the abnormal safety section bus PC1A is restored, in this embodiment, after the bridge power inverter group detects that the working power supply of the line side of the working incoming circuit breaker K1AA is normal, if a working power supply parallel restoration command issued manually by the user is received at the same time, the inverter PA is controlled to adjust the output voltage frequency and phase to keep it consistent with the working power supply. Then, the inverter PA automatically outputs a closing command for the working incoming circuit breaker K1AA. The working incoming circuit breaker K1AA completes the closing, the power inverter group returns to the hot standby state, and the load of the abnormal safety section bus is transferred to the plant auxiliary power supply, thus realizing the working power supply restoration process of the abnormal safety section bus.

[0072] Similarly, when any two sections of the safety busbar experience power outages or temporary drops simultaneously or sequentially, for example: Figure 5 As shown, power outages or temporary drops occur on the safety bus sections PC1A and PC1B. Both PC1A and PC1B are considered abnormal safety bus sections, while the remaining safety bus sections PC2A and PC2B are considered normal. At this time, the bridge power inverter group responds quickly, tripping the incoming circuit breakers K1AA and K1BA. Simultaneously, the corresponding power converters PA and PB are in conversion mode, and power converters PC and PD are in rectification mode. Power converters PA and PB supply power to safety bus sections PC1A and PC1B. The voltage detection and protection control circuit dynamically adjusts the active power distribution of the power converters PC and PD in rectification mode, thereby achieving a reasonable distribution of active power from power converters PA and PB. The bus section with less load receives more active power. The rectified active power allocated to power inverters PC and PD is as follows:

[0073]

[0074] at this time,

[0075] P ∑ =P3+P4

[0076] Simultaneously, the voltage detection and protection control circuit dynamically adjusts the reactive power distribution of the power inverters PC and PD in rectification mode to achieve reasonable reactive power distribution, enabling the high-voltage protection bus to bear more reactive power. The rectified reactive power distributed by the power inverters PC and PD, and the power supply recovery process of the abnormal protection bus are the same as the power distribution method and power supply recovery process of the abnormal protection bus when only the protection bus PC1A section experiences power loss or temporary sag, as described above. Therefore, they will not be repeated here.

[0077] Similarly, when any three sections of the safety busbar experience power outages or temporary drops simultaneously or sequentially, for example: Figure 6As shown, when power outages or temporary drops occur in the safety bus sections PC1A, PC1B, and PC2A, these sections are considered abnormal safety bus sections, while the remaining safety bus section PC2B is a normal safety bus section. In this situation, the bridge power inverter group responds quickly, tripping the incoming circuit breakers K1AA, K1BA, and K2AA. Simultaneously, the corresponding power converters PA, PB, and PC are in converter mode, and the power converter PD is in rectification mode. Power converters PA, PB, and PC convert power to supply power to the safety bus sections PC1A, PC1B, and PC2A. The subsequent power distribution process and the restoration process of the abnormal safety bus power supply are the same as those described above when only the safety bus section PC1A experiences a power outage or temporary drop, and will not be repeated here.

[0078] When all four sections of the safety busbar experience power outages or temporary drops simultaneously or sequentially, such as Figure 7 As shown, the security bus sections PC1A, PC1B, PC2A, and PC2B are all abnormal security bus sections. In other words, all of the aforementioned security bus sections are abnormal. At this time, the bridge power inverter group responds quickly, tripping the working incoming circuit breakers K1AA, K1BA, K2AA, and K2BA. Simultaneously, the backup power module supplies power to the corresponding abnormal security bus sections through the four-quadrant power inverters. That is, the power inverters are powered by the 220V battery pack in the plant's backup power module. All four power inverters operate in converter mode, supplying power to the corresponding security bus sections respectively.

[0079] When all the aforementioned safety busbars are abnormal safety busbars, if the bridge power inverter group detects that the diesel generator set has completed startup, the KC circuit breaker is automatically closed under the control of the diesel generator set, and the diesel generator set power supply on the line side of the inverter incoming circuit breakers K1AC, K1BC, K2AC, and K2BC is normal and receives the user's input diesel generator safety power supply parallel restoration command, then the output voltage frequency and phase of the four-quadrant power inverter are controlled to be consistent with the diesel generator set power supply, and the closing commands of the inverter incoming circuit breakers K1AC, K1BC, K2AC, and K2BC are output sequentially, controlling all the aforementioned inverter incoming circuit breakers K1AC, K1BC, K2AC, and K2BC and the standby incoming circuit breaker to complete the closing, the four-quadrant power inverter is restored to hot standby state, and all abnormal safety section loads are transferred to the diesel generator set for power supply.

[0080] When it is necessary to restore the diesel generator set power supply to the plant auxiliary power supply, the power converter receives the parallel restoration command for the working power supply issued by the user. The power converter sequentially outputs trip commands for the inverter incoming circuit breakers K1AC, K1BC, K2AC, and K2BC, controlling the tripping of the inverter incoming circuit breakers K1AC, K1BC, K2AC, and K2BC. The abnormal safety section bus load is powered by the four-quadrant power inverter. The corresponding power inverter adjusts the output voltage frequency and phase to keep it consistent with the working power supply, and then sequentially outputs closing commands for the working incoming circuit breakers K1AA, K1BA, K2AA, and K2BA. The power converter returns to the hot standby state, and the safety section load is transferred to the working power supply.

[0081] Therefore, in this embodiment, when it is detected that the diesel generator set power supply needs to be restored to the plant auxiliary power supply, or when the plant auxiliary power supply of the abnormal safety section busbar returns to normal, in response to the user-input parallel power supply restoration command, the output voltage frequency and phase of the four-quadrant power inverter are controlled to be consistent with the plant auxiliary power supply, and the working incoming circuit breaker connected to the abnormal safety section busbar is controlled to close, so that the four-quadrant power inverter returns to hot standby state, and the load of the abnormal safety section busbar is transferred to the plant auxiliary power supply. Specifically, when the abnormal safety section load is powered by the diesel generator set and it is detected that the diesel generator set power supply needs to be restored to the plant auxiliary power supply, before controlling the output voltage frequency and phase of the four-quadrant power inverter to be consistent with the plant auxiliary power supply, all the inverter incoming circuit breakers are controlled to trip, so that the abnormal safety section busbar load is powered by the four-quadrant power inverter.

[0082] In summary, the voltage detection and protection control circuit configured in this embodiment can determine whether the voltage dip of the protection busbar is caused by a fault in the external power supply system or a fault within the power supply range of the protection busbar. When the effective value of the working current of the protection busbar at power frequency is greater than the current frequency set threshold, the current frequency set threshold is a set value that can be set based on the feedback current provided by the protection motor-type load that avoids external faults. If it is detected that the effective value change difference of the protection busbar voltage of a protection busbar is higher than the preset voltage difference threshold and the effective value change difference of the working current is higher than the preset current difference threshold, the circuit can detect voltage dips. If a fault occurs on the power supply bus of the safety section, it can be determined that a power outage or voltage drop has occurred within the power supply range. In this case, after the bridge power inverter group trips the corresponding working incoming circuit breaker of the safety section bus, it blocks the output of the corresponding power inverter to avoid damage to the power inverter. Similarly, when the power converter is running with the safety section bus, if a fault occurs within the power supply range of the safety section bus and causes the power converter to block the output, the corresponding standby incoming switch (K1AB, K1BB, K2AB and / or K2BB) is blocked from closing to prevent the diesel generator standby power supply from being manually connected to the faulty bus, which would cause the fault range to expand.

[0083] The uninterruptible power supply topology for power plant auxiliary power supply provided in this embodiment uses a four-quadrant power converter composed of power components, with a star connection on the DC side. This achieves reliable interconnection between the diesel generator set and the four sections of the emergency bus power supply, replacing the currently commonly used power failure switching method with online uninterrupted switching. This improves the reliability of the power plant's emergency power supply and solves the problem of the impact of equipment failure or load startup on the power quality of other bus sections after the interconnection of different units. In addition, this embodiment connects the plant's original 220V battery bank to the DC side of the power converter. In the event of a power failure in all four sections of the emergency bus, the 220V battery bank can be used as a temporary power source to provide temporary emergency power to the emergency bus load. This allows time for manual repair after the diesel generator fails to start, reducing the high requirements for the success rate of diesel engine self-starting and thus enhancing the stability and reliability of the plant auxiliary power supply system.

[0084] This invention provides an uninterruptible power supply system for power plant auxiliary power, comprising a single diesel generator set, at least four safety bus sections, and at least one bridge power inverter group. The bridge power inverter group includes a four-quadrant power inverter and a backup power module. When the bridge power inverter group detects an abnormal safety bus section experiencing power loss or temporary sag, it disconnects the working incoming circuit breaker connected to the abnormal safety bus section and controls the power inverter connected to the abnormal safety bus section in the four-quadrant power inverter to enter a converter state, so as to supply power to the abnormal safety bus section through the power inverter in the converter state. Unlike the commonly used power failure switching methods, this embodiment adopts online backup switching to achieve uninterrupted switching of the backup power supply in the event of a power failure in the backup section of the power plant's auxiliary power bus. This ensures effective power supply to the load of the backup section of the bus. This control method not only reduces the dependence on the success and time of diesel generator power restoration, but also improves the ability of the auxiliary power backup power system to cope with complex electrical faults. It has the advantages of safety and reliability and can provide a strong guarantee for the stable operation of the power plant.

[0085] In one embodiment, such as Figure 8 As shown, this embodiment of the invention provides a control method for an uninterruptible power supply system for power plant auxiliary power, applying the aforementioned uninterruptible power supply system for power plant auxiliary power. The control method includes the following steps:

[0086] S1. Inspect the safety busbars and identify any safety busbars that experience power loss or temporary slump as abnormal safety busbars;

[0087] S2. When an abnormal safety section bus is detected, the working incoming circuit breaker connected to the abnormal safety section bus is disconnected, and the power inverter connected to the abnormal safety section bus in the four-quadrant power inverter is controlled to be in the converter state so as to supply power to the abnormal safety section bus through the power inverter in the converter state, while controlling the remaining power inverters to be in the rectification state.

[0088] S3. When all the aforementioned security bus sections are abnormal security bus sections, the control backup power module supplies power to the corresponding abnormal security bus section through a four-quadrant power inverter.

[0089] It should be noted that the sequence number of each process does not 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 this application.

[0090] Specific limitations regarding the control method for an uninterruptible power supply system for power plant auxiliary power can be found in the above-described limitations for such a system, and will not be repeated here. Those skilled in the art will recognize that the various modules and steps described in conjunction with the embodiments disclosed in this application can be implemented in hardware, software, or a combination of both. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0091] This invention provides a control method for an uninterrupted power supply system for power plant auxiliary power backup. When an abnormal backup busbar experiences power loss or a temporary drop in power consumption, the method disconnects the working incoming circuit breaker connected to the abnormal backup busbar and controls the power inverter connected to the abnormal backup busbar in a four-quadrant power inverter to enter a converter state. This converter supplies power to the abnormal backup busbar. Simultaneously, when all backup busesbars are abnormal, the backup power module supplies power to the corresponding abnormal backup busbar through a four-quadrant power inverter. Compared to existing technologies that use power failure switching, this application uses online uninterrupted switching to solve the power supply problem when a backup busbar experiences power loss or a temporary drop. This ensures that the backup power supply can continuously and stably supply power in emergencies, significantly improving the reliability of the power plant's backup power supply. It also addresses the impact of equipment failure or load startup on the power supply quality of another busbar after interconnection of different generating units, thereby ensuring the stable operation of the entire power plant.

[0092] The embodiments described above are merely preferred embodiments of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various improvements and substitutions without departing from the technical principles of this invention, and these improvements and substitutions should also be considered within the scope of protection of this application. Therefore, the scope of protection of this patent application should be determined by the scope of the claims.

Claims

1. A power plant auxiliary power supply uninterruptible power supply system, characterized in that, The power supply system includes: a single diesel generator set, at least four safety bus sections, and at least one bridge power inverter set; each safety bus section is connected to the plant's working power supply through a working incoming circuit breaker, and each safety bus section is connected to the diesel generator set in parallel after being connected to a standby incoming circuit breaker. The bridge-type power inverter group includes a four-quadrant power inverter and a backup power module. The backup power module includes a backup power supply, a diode, and a power isolation switch connected in series. Each safety section bus is connected to the AC side of the four-quadrant power inverter through an inverter incoming circuit breaker. The DC side of the four-quadrant power inverter is connected to a DC side isolation switch and then connected in parallel to one end of the power isolation switch of the backup power module. The other end of the power isolation switch is connected to the backup power supply through a diode. The bridge-type power inverter group is used to disconnect the working incoming circuit breaker connected to the abnormal safety section bus when an abnormal safety section bus is detected, and control the power inverter connected to the abnormal safety section bus in the four-quadrant power inverter to be in the converter state so as to supply power to the abnormal safety section bus through the power inverter in the converter state, while controlling the remaining power inverters to be in the rectification state. The backup power module is used to supply power to the corresponding abnormal safety bus via a four-quadrant power inverter when all the safety bus sections are abnormal safety bus sections; the abnormal safety bus section is the safety bus section that experiences power loss or temporary descent. The bridge power inverter group is equipped with a voltage detection and protection control circuit. The voltage detection and protection control circuit is used to collect the voltage of each safety section bus and the current of the corresponding working incoming circuit breaker in real time, obtain the effective value of the corresponding safety section bus voltage and the effective value of the working incoming current, and determine the abnormal safety section bus and the normal safety section bus based on the difference in the effective value of the safety section bus voltage and the difference in the effective value of the working incoming current between the current cycle and the previous cycle. Furthermore, based on the effective value of the voltage of the safety section bus and the effective value of the working incoming current, the working incoming load and voltage per unit value of the normal safety section bus are obtained. The power inverter connected to the normal safety section bus in the four-quadrant power inverter is taken as the power inverter to be allocated. Based on the working incoming load and voltage per unit value of the normal safety section bus, the rectified active power allocation and rectified reactive power allocation of the power inverter to be allocated are dynamically adjusted so that the bridge power inverter group can operate in any one of the four quadrants of the active-reactive plane. The rectified active power of the inverter to be allocated is proportionally allocated based on the working incoming load of the normal safety section bus, with the direction being from the normal safety section bus to the abnormal safety section bus. The rectified reactive power distribution of the inverter to be allocated is proportional to the voltage level of the normal safety bus, with the flow direction from the high-voltage safety bus to the low-voltage safety bus.

2. The uninterruptible power supply system for power plant auxiliary power as described in claim 1, characterized in that, The method of determining abnormal and normal safety bus sections based on the difference in effective voltage and effective current of each safety bus section between the current and previous cycles includes: Based on the effective values ​​of the voltage and the working incoming current of the safety section busbar, calculate the difference in the effective value of the voltage of the safety section busbar between the current cycle and the previous cycle, and the difference in the effective value of the working incoming current of the safety section busbar between the current cycle and the previous cycle. The effective value change difference of the safety section bus voltage is compared with a preset voltage difference threshold, and the effective value change difference of the working incoming current is compared with a preset current difference threshold. If it is detected that the effective value change difference of the safety section bus voltage is higher than the preset voltage difference threshold and the effective value change difference of the working incoming current is higher than the preset current difference threshold, then the corresponding safety section bus is determined to be an abnormal safety section bus; otherwise, the corresponding safety section bus is determined to be a normal safety section bus.

3. The uninterruptible power supply system for power plant auxiliary power as described in claim 1, characterized in that, The formula for calculating the rectified active power distribution is: In the formula, This represents the rectified active power of the inverter to be allocated power; This represents the active power requirement of the m-th abnormal safety section busbar; This represents the total working incoming load of all normal safety busbar sections; This represents the working incoming load of the nth normal safety bus, excluding the abnormal safety bus and the normal safety bus connected to the inverter to be allocated power; N represents the total number of normal safety buses, excluding the abnormal safety bus and the normal safety bus connected to the inverter to be allocated power. This represents the total working incoming load of all normal safety busbars except for the abnormal safety busbar and the normal safety busbar connected to the inverter to be allocated power.

4. The uninterruptible power supply system for power plant auxiliary power as described in claim 1, characterized in that, The calculation formula for the rectified reactive power distribution is as follows: In the formula, This represents the rectified reactive power of the inverter to be allocated power; This represents the per-unit voltage value of the normal safety busbar connected to the inverter to be allocated power; This represents the per-unit voltage value of the nth normal safety bus, excluding the abnormal safety bus and the normal safety bus connected to the inverter to be allocated power; N represents the total number of normal safety buses, excluding the abnormal safety bus and the normal safety bus connected to the inverter to be allocated power. This indicates the reactive power requirement for all abnormal safety bus sections.

5. The uninterruptible power supply system for power plant auxiliary power as described in claim 1, characterized in that: The bridge-type power inverter group is also used to control the output voltage frequency and phase of the four-quadrant power inverter to be consistent with the power supply of the diesel generator set when all the protection section busbars are abnormal protection section busbars. If the power supply of the diesel generator set on the line side of the inverter incoming circuit breaker is detected to be normal and the user input diesel generator protection power supply parallel restoration command is received, the four-quadrant power inverter is controlled to close all the inverter incoming circuit breakers and the standby incoming circuit breaker, so that the four-quadrant power inverter is restored to hot standby state and all abnormal protection section loads are transferred to the diesel generator set for power supply. Furthermore, when it is detected that the diesel generator set needs to be restored to the plant auxiliary power supply, or when the plant auxiliary power supply of the abnormal safety section bus is restored to normal, in response to the user-input parallel power supply restoration command, the output voltage frequency and phase of the four-quadrant power inverter are controlled to be consistent with the plant auxiliary power supply, and the working incoming circuit breaker connected to the abnormal safety section bus is controlled to close, so that the four-quadrant power inverter is restored to hot standby state, and the load of the abnormal safety section bus is transferred to the plant auxiliary power supply.

6. The uninterruptible power supply system for power plant auxiliary power as described in claim 5, characterized in that: When the abnormal safety section load is powered by the diesel generator set and it is detected that the diesel generator set power supply needs to be restored to the plant auxiliary power supply, before controlling the output voltage frequency and phase of the four-quadrant power inverter to be consistent with the plant auxiliary power supply, control all the inverter incoming line circuit breakers to trip, so that the abnormal safety section bus load is powered by the four-quadrant power inverter.

7. The uninterruptible power supply system for power plant auxiliary power as described in claim 1, characterized in that: The power supply system also includes a power supply control module; The power supply control module is used to control all working incoming circuit breakers and inverter incoming circuit breakers to be in the closed state when the entire power supply system is running normally. All safety section busbars are normally powered by the power plant's auxiliary power system, and the four-quadrant power inverter is in a hot standby state. At this time, there is no power flow inside the bridge power inverter group, the standby incoming circuit breaker is in a hot standby state, and the diesel generator set is in a cold standby state.

8. A control method for an uninterrupted power supply system for backup power in a power plant, characterized in that, The control method for using the uninterruptible power supply system for power plant auxiliary power as described in any one of claims 1 to 7 includes the following steps: The safety busbars are inspected, and those that experience power loss or temporary power slump are identified as abnormal safety busbars. When an abnormal safety section bus is detected, the working incoming circuit breaker connected to the abnormal safety section bus is disconnected, and the power inverter connected to the abnormal safety section bus in the four-quadrant power inverter is controlled to be in the converter state so as to supply power to the abnormal safety section bus through the power inverter in the converter state, while the remaining power inverters are controlled to be in the rectification state. When all the aforementioned security bus sections are abnormal security bus sections, the control backup power module supplies power to the corresponding abnormal security bus section through a four-quadrant power inverter.

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