Quasi-hot standby fault-tolerant control method and system of bridge arm alternating current converter

Abstract

The application provides a kind of bridge arm alternate current converter's quasi-hot spare fault-tolerant control method and system, belongs to the field of power system flexible HVDC converter fault-tolerant control technology, the method includes generating the modulation wave signal of each normal operation module on each bridge arm;For bridge arm alternate current converter normal operation, based on the modulation wave signal, the switch signal of each module of shaping circuit is generated, according to the zero point of network side ac voltage, the switch signal of each controllable device of switch circuit is generated;For bridge arm alternate current converter after fault occurs, the operation of original fault module is replaced by pre-charged spare H bridge module, the fault-tolerant control operation of bridge arm alternate current converter is realized.The application reduces the impact on control system and power switch device when spare module is put into by pre-charging spare H bridge submodule to rated voltage, has better transient recovery performance and fault-tolerant performance, realizes the rapid recovery after the failure of bridge arm alternate current converter submodule.

Description

Technical Field

[0001] This invention belongs to the field of fault-tolerant control technology for flexible DC transmission converters in power systems, and particularly relates to a quasi-hot standby fault-tolerant control method and system for bridge arm alternating converters. Background Technology

[0002] The proportion of new energy sources in the energy internet will become increasingly important, and intelligent and modular power electronic equipment has attracted widespread attention. Flexible DC transmission technology has solved the regional mismatch problem between new energy bases and load centers, becoming a research hotspot in recent years. Among them, the converter, as the core equipment of high-voltage DC transmission technology, has laid the foundation for the rapid development and engineering application of flexible DC transmission technology due to its reliability and economy. Modular multilevel converters (MMCs) have advantages such as modular structure, simple control, easy expansion, good harmonic characteristics, and high efficiency, and have become the preferred solution for AC / DC power interconnection. Each phase arm of an MMC consists of many submodules (SMs) connected in series. Among them, the half-bridge submodule (HBSM) is widely used due to its simple structure and low cost. However, since the half-bridge submodule (MMC) cannot completely block the fault current path under DC fault conditions, it requires the use of AC or DC circuit breakers to achieve fault isolation, which also increases the complexity of the system and construction costs.

[0003] The alternate arm converter (AAC) has received widespread attention since its inception. While possessing the advantages of traditional MMCs, it also features low complexity and high economy, achieving DC fault ride-through capability. The topology of an AAC is as follows: Figure 1 As shown, each phase consists of an upper bridge arm and a lower bridge arm. Each bridge arm comprises a series-connected full-bridge module and a fully controlled device. The series-connected full-bridge module and the fully controlled device are respectively called the shaping circuit section and the switching circuit section. The former outputs a low-harmonic distortion sine wave through the stacked module capacitor voltage, while the latter alternately conducts the upper and lower bridge arms of one phase every half sine cycle. Compared with MMC, the AAC-based converter station can save approximately 40% of the number of modules and 50% of the module capacitor size.

[0004] Since the shaping circuitry on the six arms of the AAC (Automatic Anchored Circuit) consists of cascaded H-bridge modules, the number of H-bridge modules increases with the increase in DC or AC voltage levels, thus increasing the likelihood of failure. Due to application limitations, immediate shutdown is often not possible upon failure, and abnormal operation reduces equipment lifespan and, in severe cases, impacts the safe operation of the power grid. Therefore, the AAC should possess a certain degree of fault tolerance, making research into fault-tolerant control strategies for the failure of a single AAC module particularly important.

[0005] An AAC (Automatic Converter) should possess the capabilities of fault detection, fault location, and fault clearing after a fault occurs, and should restore the converter to normal operation through fault-tolerant control strategies. The novel quasi-hot standby fault-tolerant control strategy proposed in this invention primarily addresses the process of restoring the converter to normal operation after fault clearing. Existing fault-tolerant control methods are generally divided into hardware fault-tolerant methods and software fault-tolerant methods. The former obtains fault tolerance by inserting additional components into the converter, while the latter ensures continuous system operation under fault conditions by switching or modifying the control strategy. In practice, software fault-tolerant methods mostly sacrifice some performance to maintain continuous equipment operation, but they are usually difficult to restore to their rated power.

[0006] In comparison, hardware fault-tolerant methods have a clear advantage in fully restoring the normal operation of the converter after a fault through redundant components. Most existing fault-tolerant control research focuses on implementing fault-tolerant functions for traditional two-level and three-level converters, without paying attention to the recovery speed of the bridge arm alternating converter topology and its fault-tolerant methods. Furthermore, some fault-tolerant control schemes sacrifice some performance to maintain the short-term operation of the equipment. Therefore, research on fault-tolerant control strategies for AAC and the rapid restoration of normal operation after a fault is particularly important. Summary of the Invention

[0007] To address the aforementioned shortcomings in the prior art, this invention provides a quasi-hot standby fault-tolerant control method and system for bridge arm alternating converters. By pre-charging the standby H-bridge module to its rated voltage, this invention reduces the impact on the control system and topology when the standby module is put into operation, resulting in better transient recovery performance and fault tolerance, and enabling rapid recovery after AAC submodule failure.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] This solution provides a quasi-hot standby fault-tolerant control method for bridge arm alternating converters, including the following steps:

[0010] S1. Generate the modulation wave signal of each normally operating module on each bridge arm;

[0011] S2. When the bridge arm alternating converter is running normally, based on the modulation wave signal, the switching signals of each module of the shaping circuit and the switching signal of the pre-charged backup H-bridge module are generated. When the bridge arm alternating converter fails, the switching signals of each faulty module in the shaping circuit are cut off, and the operation of the original faulty module is replaced by the pre-charged backup H-bridge module, so as to realize the fault-tolerant control operation of the bridge arm alternating converter.

[0012] S3. Based on the zero-crossing point detected by the grid-side AC voltage, generate switching signals for each fully controlled device in the switching circuit of the bridge arm alternator, and control the switching action of the bridge arm alternator during normal operation and after a fault.

[0013] The beneficial effects of this invention are: by charging the backup H-bridge module to the rated voltage in advance, this invention reduces the impact on the control system and topology when the backup module is put into operation, and has better transient recovery performance and fault tolerance.

[0014] Further, step S1 includes the following steps:

[0015] S101. Based on the set active power reference value P ref and reactive power reference value Q ref Combined with measured active power P and reactive power Q The active power reference value of the inner loop current is obtained through the PI controller. i d_ref and reactive power reference value i q_ref ;

[0016] S102. Obtain the active component of the measured phase current by Parker transformation of the grid-side phase current. i d and reactive components i q In conjunction with active power reference values i d_ref and reactive power reference value i q_ref The active component of the modulated wave signal is obtained through a PI controller. u rd and reactive components u rq ;

[0017] S103, Based on the active power component u rd and reactive components u rq Combined with the grid angular frequency output by the phase-locked loop (PLL) ωt The modulation wave signals of each normally operating module are obtained through inverse Parker transformation.u ref .

[0018] The beneficial effects of the above-mentioned further solutions are: the present invention can generate modulation wave signals of each module through the above design, accurately control the active power and reactive power output of the converter, and at the same time control the power factor of the grid-connected current, and has a fast tracking speed for control quantity transformation.

[0019] Furthermore, in step S2, the generation of switching signals for each module of the shaping circuit and the switching signal for the pre-charged spare H-bridge module specifically involves:

[0020] A1. When the bridge arm alternator is operating normally, the modulation wave signal obtained in step S1 is... u ref Send to carrier phase-shift modulation;

[0021] A2. A compensation voltage is generated using several capacitor voltage regulators, and the compensation voltage is added to the original modulation wave of different modules;

[0022] A3. Using the original modulation waves of each module after the addition of compensation voltage, generate the switching signals of each module of the shaping circuit;

[0023] A4. Generate the modulation wave signal of the pre-charged standby H-bridge module in the quasi-hot standby system;

[0024] A5. Send the modulated wave signal generated in step A4 to the carrier phase shift modulation to generate the pre-charged standby H-bridge module switching signal.

[0025] The beneficial effects of the above-mentioned further solution are: by using multiple capacitor voltage regulators, the capacitor voltage of each module can be precisely controlled, the voltage balance of each module can be maintained, the average service life of the capacitor can be improved, and the generated modulated wave signal of the backup H-bridge module precharged can enable the backup module to operate stably at the rated voltage, and can complete fault-tolerant operation as soon as possible after a fault occurs, achieving rapid recovery.

[0026] Furthermore, in step S2, after a failure occurs in the bridge arm alternating converter, the switching signals of each faulty module in the shaping circuit are cut off, and the operation of the original faulty module is replaced by a pre-charged backup H-bridge module, thereby realizing the fault-tolerant control operation of the bridge arm alternating converter. Specifically, this is as follows:

[0027] B1. When the bridge arm alternator fails, the fault-tolerant instruction module is used to issue a fault-tolerant operation signal;

[0028] B2. Bypass the faulty module, and disconnect the switching signal input of the faulty module in the shaping circuit and disconnect the modulation wave signal. u p ;

[0029] B3. Control the fault-tolerant switch group to operate according to the fault-tolerant operation signal, put the pre-charged backup H-bridge module into operation, and switch the switch signal of the pre-charged backup H-bridge module to the switch signal of the original faulty module, so as to realize the fault-tolerant control operation of the bridge arm alternator.

[0030] The beneficial effects of the above-mentioned further solutions are: the present invention completes the rapid location and removal of faults after the fault is detected through the above design, and realizes the commissioning of the backup sub-module. The converter can enter the fault-tolerant operation state and resume normal operation in a short time, which greatly improves the reliability and service life of the equipment.

[0031] Furthermore, step S3 specifically includes:

[0032] Based on the AC voltage signal of each phase, switching signals are switched at the voltage zero-crossing point to generate switching signals for the upper and lower bridge arm switching circuits of each phase in the bridge arm alternating converter. G DSjp and G DSjn The switching action of the bridge arm alternating converter during normal operation and after a fault occurs, i.e. j When the phase voltage on the phase grid side is positive, the upper bridge arm switching circuit is turned on, and the lower bridge arm switching circuit is turned off. j When the phase voltage on the phase grid side is negative, the lower bridge arm switching circuit is turned on, and the upper bridge arm switching circuit is turned off.

[0033] The beneficial effects of the above-mentioned further solutions are: the correct conduction and cutoff of the switching circuit ensures the normal current path and power flow of the converter, enabling the converter to operate normally and to operate fault-tolerantly after a fault.

[0034] This invention provides a quasi-hot standby fault-tolerant control system for a bridge arm alternating converter, comprising:

[0035] A dual closed-loop control subsystem is used to generate modulation wave signals for each normally operating module on each bridge arm;

[0036] The fault-tolerant switch control subsystem is used to generate switching signals for each module of the shaping circuit and a pre-charged backup H-bridge module based on the modulation wave signal when the bridge arm alternating converter is running normally. When the bridge arm alternating converter fails, the switching signals of each faulty module in the shaping circuit are cut off, and the pre-charged backup H-bridge module is used to replace the operation of the original faulty module, so as to realize the fault-tolerant control operation of the bridge arm alternating converter.

[0037] The switching circuit control subsystem is used to detect the zero-crossing point of the grid-side AC voltage, generate switching signals for each fully controlled device in the switching circuit of the bridge arm alternating converter, and control the switching action of the bridge arm alternating converter during normal operation and after a fault.

[0038] The beneficial effects of this invention are: by pre-charging the backup H-bridge sub-module to the rated voltage, this invention reduces the impact on the control system and topology when the backup module is put into operation, and has better transient recovery performance and fault tolerance, thus achieving rapid recovery after AAC module failure. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the topology of the bridge arm alternating converter.

[0040] Figure 2 This is a schematic diagram of the bridge arm alternating converter topology under the traditional cold standby fault-tolerant method.

[0041] Figure 3 This is a diagram of the AAC topology under the novel quasi-hot standby fault-tolerant control strategy proposed in this invention.

[0042] Figure 4 This is a schematic diagram of the AAC control system under the quasi-hot standby fault-tolerant control mode of the present invention. Detailed Implementation

[0043] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0044] Example 1

[0045] In this embodiment, the topology of AAC is as follows: Figure 1 As shown, each phase consists of an upper bridge arm and a lower bridge arm, with each bridge arm consisting of series-connected... N SM Each full-bridge module and N DS It consists of a series of fully controlled devices, with the series-connected full-bridge module and the fully controlled devices referred to as the shaping circuit section and the switching circuit section, respectively. u sj and i sj ( j = a, b, c) represents the voltage and current on the AC side, where a, b, c represent three phases. v jp and v jn ( j = a, b, c) represent the output voltages of the upper and lower bridge arms, i jp andi jn ( j = a,b,c) represents the current flowing through the upper and lower bridge arms, DS jp and DS jn ( j = a, b, c) represents the on / off switch of the upper and lower bridge arms. L s This refers to the reactor connecting the AC-side converter to the power grid. C dc This indicates the supporting capacitor on the DC side. L dc Indicates the DC-side filter inductor. V dc This represents the DC-side voltage. The positive direction of the current is defined as follows: Figure 1 As shown.

[0046] Unlike traditional modular multilevel converters where both upper and lower arms conduct simultaneously, the AAC converter operates with complementary switching on and off of the upper and lower arms during normal operation. By controlling the number of modules in the shaping circuit, the multilevel voltage output from both arms can approximate the modulated wave. Let the AC side voltage of the converter... u sj and current i sj for:

[0047] (1)

[0048] In the formula: V m , I m Indicates the magnitude of the grid voltage and current; ω Indicates the angular frequency of the power grid; φ Represents the power factor angle, and φ ∈(- π / 2, π / 2); β j express j Initial phase of phase voltage t Indicates time.

[0049] Traditional cold standby fault-tolerant control methods enable AAC (Automatic Anchored Circuit) to operate with fault tolerance by using additional spare components. These methods include redundant switches, redundant bridge arms, redundant H-bridge modules, and redundant systems to achieve fault-tolerant control. Since the shaping and switching circuits of all six bridge arms of the AAC are identical, the following analysis focuses on the upper bridge arm of phase a as an example. Figure 2 This is a diagram of the AAC topology using redundant H-bridge modules. (The diagram is from...) Figure 2 It can be seen that the switching circuit has the following when the AAC is working normally: NEach operating H-bridge module, including redundant H-bridge modules, is cascaded within the AAC. However, these redundant H-bridge modules are in bypass mode during normal AAC operation. Upon fault detection, the faulty module is immediately disconnected, and the redundant H-bridge modules are put into operation, restoring the AAC to normal operation within a certain timeframe. The number of redundant H-bridge modules determines the fault tolerance capability of the fault-tolerant AAC; more redundant H-bridge modules allow for more simultaneous failures. The cold standby fault-tolerant control strategy maintains the rectifier's output power unchanged before and after a fault, ensuring that the rectifier's grid-side operating state remains unchanged before and after fault-tolerant operation. It is worth noting that each H-bridge module in this configuration is a bypass module. When the bypass switch... P Next m When the port is connected, the H-bridge module is put into operation. n When the port is open, the H-bridge module is bypassed. Therefore, the connection and disconnection of the H-bridge module can be achieved by using a bypass switch.

[0050] Traditional three-phase converters employ software fault-tolerant control strategies such as bypassing the normal phase non-faulty unit method, fundamental phase shift compensation method, and bus voltage reconstruction method. Applying the bus voltage reconstruction method to AACs yields a traditional hot-standby fault-tolerant control strategy. The basic idea is to increase the output voltage of the non-faulty H-bridge modules after a fault occurs to restore the total DC-side voltage of the shaping circuit. When using hot-standby fault-tolerant control, the normally operating H-bridge modules need to increase the DC-side output capacitor voltage; the increase value needs to be determined based on the voltage value missing from the faulty H-bridge module. When there is a switch circuit on the AAC bridge arm... k When one H-bridge module fails, the DC-side capacitor voltage of each normally operating H-bridge module needs to be increased by the following voltage value Δ. U The calculation method is as follows:

[0051] (2)

[0052] in, Indicates the rated voltage of the faulty module. N This indicates the total number of modules in the shaping circuit on the bridge arm when it is operating normally.

[0053] In the hot standby fault-tolerant control strategy, to maintain the total output voltage unchanged before and after a fault, the DC-side capacitor voltage of each H-bridge needs to be adjusted during fault-tolerant operation. for:

[0054] (3)

[0055] in, This indicates the rated reference voltage of the shaping circuit module on the bridge arm.

[0056] That is, after a fault occurs, the capacitor voltage output on the DC side of each normally operating H-bridge unit should be increased by Δ from the original reference voltage. U .

[0057] like Figure 3 As shown, the present invention provides a quasi-hot standby fault-tolerant control method for a bridge arm alternating converter, the implementation method of which is as follows:

[0058] S1. Generate the modulation wave signal for each normally operating module on each bridge arm. The implementation method is as follows:

[0059] S101. Based on the set active power reference value P ref and reactive power reference value Q ref Combined with measured active power P and reactive power Q The active power reference value of the inner loop current is obtained through the PI controller. i d_ref and reactive power reference value i q_ref ;

[0060] S102. Obtain the active component of the measured phase current by Parker transformation of the grid-side phase current. i d and reactive components i q In conjunction with active power reference values i d_ref and reactive power reference value i q_ref The active component of the modulated wave signal is obtained through a PI controller. u rd and reactive components u rq ;

[0061] S103, Based on the active power component u rd and reactive components u rq Combined with the grid angular frequency output by the phase-locked loop (PLL) ωt The modulation wave signals of each normally operating module are obtained through inverse Parker transformation. u ref ;

[0062] S2. When the bridge arm alternating converter is running normally, based on the modulation wave signal, the switching signals of each module of the shaping circuit and the switching signal of the pre-charged backup H-bridge module are generated. When the bridge arm alternating converter fails, the switching signals of each faulty module in the shaping circuit are cut off, and the operation of the original faulty module is replaced by the pre-charged backup H-bridge module, so as to realize the fault-tolerant control operation of the bridge arm alternating converter.

[0063] In step S2, the switching signals for each module of the shaping circuit and the switching signals for the pre-charged spare H-bridge module are generated, specifically as follows:

[0064] A1. When the bridge arm alternator is operating normally, the modulation wave signal obtained in step S1 is... u ref Send to carrier phase-shift modulation;

[0065] A2. A compensation voltage is generated using several capacitor voltage regulators, and the compensation voltage is added to the original modulation wave of different modules;

[0066] A3. Using the original modulation waves of each module after the addition of compensation voltage, generate the switching signals of each module of the shaping circuit;

[0067] A4. Generate the modulation wave signal of the pre-charged standby H-bridge module in the quasi-hot standby system;

[0068] A5. Send the modulated wave signal generated in step A4 to the carrier phase shift modulation to generate the pre-charged standby H-bridge module switching signal;

[0069] In step S2, after a fault occurs in the bridge arm alternating converter, the switching signals of each faulty module in the shaping circuit are cut off, and the operation of the original faulty module is replaced by a pre-charged backup H-bridge module, thereby realizing the fault-tolerant control operation of the bridge arm alternating converter. Specifically, it is as follows:

[0070] B1. When the bridge arm alternator fails, the fault-tolerant instruction module is used to issue a fault-tolerant operation signal;

[0071] B2. Bypass the faulty module, and disconnect the switching signal input of the faulty module in the shaping circuit and disconnect the modulation wave signal. u p ;

[0072] B3. Control the fault-tolerant switch group to operate according to the fault-tolerant operation signal, put the pre-charged backup H-bridge module into operation, and switch the switch signal of the pre-charged backup H-bridge module to the switch signal of the original faulty module, so as to realize the fault-tolerant control operation of the bridge arm alternator.

[0073] S3. Based on the zero-crossing point detected by the grid-side AC voltage, generate the switching signals for each fully controlled device in the switching circuit of the bridge arm alternator, specifically as follows:

[0074] Based on the AC voltage signal of each phase, switching signals are switched at the voltage zero-crossing point to generate switching signals for the upper and lower bridge arm switching circuits of each phase in the bridge arm alternating converter. G DSjp and G DSjnThe switching action of the bridge arm alternating converter during normal operation and after a fault occurs, i.e. j When the phase voltage on the phase grid side is positive, the upper bridge arm switching circuit is turned on, and the lower bridge arm switching circuit is turned off. j When the phase voltage on the phase grid side is negative, the lower bridge arm switching circuit is turned on, and the upper bridge arm switching circuit is turned off.

[0075] In this embodiment, the cold standby fault-tolerant control strategy maintains the same output power of the AAC before and after fault-tolerant control. However, because the newly added H-bridge module needs to charge the capacitor, the DC voltage will oscillate and converge before reaching steady-state operation, resulting in a longer transient recovery time under cold standby fault-tolerant control. The hot standby fault-tolerant control strategy does not require a backup redundant H-bridge module, but it experiences a voltage drop for a certain period during the initial fault-tolerant operation. Furthermore, when the redundant capacitor voltage margin is insufficient, the hot standby fault-tolerant control strategy cannot restore the AAC to normal operation. Combining the advantages of the two traditional redundancy fault-tolerant methods, this invention proposes a novel quasi-hot standby fault-tolerant control strategy, which pre-charges the backup H-bridge module, achieving rapid recovery after an AAC failure compared to traditional fault-tolerant strategies.

[0076] In this embodiment, Figure 3 This is the AAC topology diagram under the novel quasi-hot standby fault-tolerant control strategy proposed in this invention, which is... Figure 3 It can be seen that the overall structure includes a main circuit section and a quasi-thermal standby section, wherein the main circuit section is... Figure 1 The structure shown includes a grid-side AC power supply, a grid-side equivalent inductance, a DC-side power supply, a DC-side supporting capacitor, a DC-side equivalent inductance, and three-phase bridge arms (a, b, c). Each phase bridge arm includes upper and lower arms, and each arm consists of cascaded full-bridge modules (shaping circuits) and fully controlled devices (switching circuits). This main circuit section maintains the normal operation of the bridge arm AC converter; the quasi-hot standby section is as follows... Figure 3 As shown, it includes a quasi-hot standby system grid-side power supply, equivalent inductance, full-bridge module, and fault-tolerant switch group. The function of the fault-tolerant switch group is to control whether the quasi-hot standby subsystem is put into operation in the main circuit. This quasi-hot standby part can realize the fault-tolerant control operation of the bridge arm alternating converter after a fault, that is, the pre-charge module of the quasi-hot standby system is put into the main circuit system to replace the original faulty module.

[0077] In this embodiment, as Figure 3 As shown, fault-tolerant switch group S a , S b1 , S b2 , S c1 and S c2The AAC's operating state is controlled based on the received fault-tolerant operation command signal. This operating state includes normal operation and fault-tolerant operation. When the AAC is in normal operation, the main circuit and the quasi-hot standby section do not affect each other. When switching to fault-tolerant operation, the pre-charged standby H-bridge module will be put into operation in the main circuit immediately after the fault is cleared, thus enabling the AAC to resume normal operation in a short time. Because the DC-side capacitor voltage of the quasi-hot standby H-bridge module has been pre-charged to near the normal operating H-bridge capacitor voltage value, its fault-tolerant operation can greatly improve the equipment recovery speed.

[0078] In this embodiment, the present invention reduces the impact on the control system and topology when the backup H-bridge submodule is put into operation by charging the backup H-bridge submodule to the rated voltage in advance, thus achieving better transient recovery performance and fault tolerance, and realizing rapid recovery after AAC module failure.

[0079] Example 2

[0080] like Figure 4 As shown, the present invention provides a quasi-hot standby fault-tolerant control system for a bridge arm alternating converter, comprising:

[0081] A dual closed-loop control subsystem is used to generate modulation wave signals for each normally operating module on each bridge arm;

[0082] The fault-tolerant switch control subsystem is used to generate switching signals for each module of the shaping circuit and a pre-charged backup H-bridge module based on the modulation wave signal when the bridge arm alternating converter is running normally. When the bridge arm alternating converter fails, the switching signals of each faulty module in the shaping circuit are cut off, and the pre-charged backup H-bridge module is used to replace the operation of the original faulty module, so as to realize the fault-tolerant control operation of the bridge arm alternating converter.

[0083] The switching circuit control subsystem is used to detect the zero-crossing point of the grid-side AC voltage, generate switching signals for each fully controlled device in the switching circuit of the bridge arm alternating converter, and control the switching action of the bridge arm alternating converter during normal operation and after a fault.

[0084] In this embodiment, as Figure 4 As shown, Figure 4 This is a schematic diagram of the AAC control system under the quasi-hot standby fault-tolerant control mode of the present invention. It is divided into three control parts: a dual closed-loop control subsystem, a fault-tolerant switch signal control subsystem, and a switch circuit control subsystem. (See diagram.) u p The modulated wave signal of the pre-charged backup H-bridge module in the quasi-hot standby subsystem before a fault; S p The switching signal of the pre-charged backup H-bridge module before the failure; Si This is the switching signal for a normal H-bridge module on the bridge arm; S m This is the switching signal for the faulty H-bridge module. The dual-loop control subsystem can generate modulation wave signals for each normally operating module on each bridge arm. Specifically, the generation process is as follows: the power outer loop control section of the dual-loop control subsystem uses the set active power reference value... P ref and reactive power reference value Q ref Combined with measured active power P and reactive power Q The active power reference value of the inner loop current is obtained through the PI controller. i d_ref and reactive power reference value i q_ref The inner current loop control section converts the grid-side phase current into the active component of the measured phase current through Parker transformation. i d and reactive components i q The active power reference value is combined with the inner loop current generated by the outer power loop. i d_ref and reactive power reference value i q_ref The active component of the modulated signal is obtained after passing through a PI controller. u rd and reactive components u rq The active and reactive components of the modulation signal output from the inner loop current PI controller are combined with the grid angular frequency output from the phase-locked loop (PLL). ω t The modulation signal is obtained after inverse Parker transformation. u ref .

[0085] In this embodiment, as Figure 4 As shown, the function of the fault-tolerant switch control subsystem is to generate the switching signals for each module during normal operation. After a fault occurs in the AAC module, the faulty module is bypassed, and its switching signal input is disconnected, thus disconnecting the module modulation signal of the quasi-hot standby system. u p By controlling the fault-tolerant switch group to operate via fault-tolerant command signals, the pre-charged backup H-bridge module in the quasi-hot standby subsystem is put into operation in the main circuit, and the switching signals of the original faulty module are switched off. S mThe pre-charged standby module is connected to the main circuit section. During normal operation, the modulation wave signal is sent to carrier phase-shifted switching pulse width modulation (CPS-PWM). Multiple capacitor voltage regulators (CVRs) can be used to generate compensation voltages to achieve capacitor voltage balance among modules. These compensation voltages are added to the original modulation waves of different modules, thus achieving good inter-module capacitor voltage balance. The compensated modulation wave signals of each module after CVR are then processed by CPS-PWM to generate switching signals for each module in the shaping circuit. The dual closed-loop control subsystem for quasi-hot standby generates the modulation wave signal for the pre-charged standby H-bridge module in the quasi-hot standby system. This signal is then sent to CPS-PWM to generate the switching signals for the pre-charged standby H-bridge module in the quasi-hot standby subsystem. Upon a fault, the fault-tolerant switch subsystem will first issue a fault-tolerant operation signal via the fault-tolerant command module. The faulty module will be bypassed immediately, and its switching signal will be cut off. The fault-tolerant switch group will then activate, putting the pre-charged backup H-bridge module from the quasi-hot standby subsystem into operation in the main circuit. The switching signal of the pre-charged backup H-bridge module in the quasi-hot standby subsystem will be switched to the original switching signal of the faulty module, ensuring the rectifier can quickly resume normal operation after a fault. The backup H-bridge module under the quasi-hot standby fault-tolerant control strategy has an independent control system, thus maintaining the capacitor's rated voltage during charging. Furthermore, because the backup H-bridge module is pre-charged, it has a faster recovery speed when connected to the main circuit system.

[0086] In this embodiment, as Figure 4 As shown, the function of the switching circuit control subsystem is to generate control signals (i.e., switching signals) for each fully controlled device in the switching circuit. Based on the working principle of the bridge arm alternating converter, the upper and lower bridge arms will alternately conduct for half a sine cycle in each sinusoidal period and remain closed for the next half cycle. Therefore, the switching signals can be switched at the zero-crossing point of the voltage by detecting the AC voltage signal of each phase. That is, the switching circuit of the upper bridge arm of phase a will conduct when the voltage on the grid side of phase a is positive and turn off when it is negative; the lower bridge arm will conduct when the voltage on the grid side of phase a is negative and turn off when it is positive. The other two are similarly controlled, and alternating conduction generates the switching signals for the upper and lower bridge arm switching circuits of each phase. G DSjp and G DSjn .

[0087] This invention reduces the impact on the control system and topology when the backup H-bridge module is put into operation by pre-charging the backup H-bridge module to the rated voltage, resulting in better transient recovery performance and fault tolerance.

Claims

1. A quasi-hot standby fault-tolerant control method for a bridge arm alternating converter, characterized in that, Includes the following steps: S1. Generate the modulation wave signal for each normally operating module on each bridge arm; step S1 includes the following steps: S101. Based on the set active power reference value P ref and reactive power reference value Q ref Combined with measured active power P and reactive power Q The active power reference value of the inner loop current is obtained through the PI controller. i d_ref and reactive power reference value i q_ref ; S102. Obtain the active component of the measured phase current by Parker transformation of the grid-side phase current. i d and reactive components i q In conjunction with active power reference values i d_ref and reactive power reference value i q_ref The active component of the modulated wave signal is obtained through a PI controller. u rd and reactive components u rq ; S103, Based on the active power component u rd and reactive components u rq Combined with the grid angular frequency output by the phase-locked loop (PLL) ωt The modulation wave signals of each normally operating module are obtained through inverse Parker transformation. u ref ; S2. When the bridge arm alternating converter is running normally, based on the modulation wave signal, the switching signals of each module of the shaping circuit and the switching signal of the pre-charged backup H-bridge module are generated. When the bridge arm alternating converter fails, the switching signals of each faulty module in the shaping circuit are cut off, and the operation of the original faulty module is replaced by the pre-charged backup H-bridge module, so as to realize the fault-tolerant control operation of the bridge arm alternating converter. In step S2, the switching signals for each module of the shaping circuit and the switching signals for the pre-charged spare H-bridge module are generated, specifically as follows: A1. When the bridge arm alternator is operating normally, the modulation wave signal obtained in step S1 is... u ref Send to carrier phase-shift modulation; A2. A compensation voltage is generated using several capacitor voltage regulators, and the compensation voltage is added to the original modulation wave of different modules; A3. Using the original modulation waves of each module after the addition of compensation voltage, generate the switching signals of each module of the shaping circuit; A4. Generate the modulation wave signal of the pre-charged standby H-bridge module in the quasi-hot standby system; A5. Send the modulated wave signal generated in step A4 to the carrier phase shift modulation to generate the pre-charged standby H-bridge module switching signal; In step S2, after a fault occurs in the bridge arm alternating converter, the switching signals of each faulty module in the shaping circuit are cut off, and the operation of the original faulty module is replaced by a pre-charged backup H-bridge module, thereby realizing the fault-tolerant control operation of the bridge arm alternating converter. Specifically, it is as follows: B1. When the bridge arm alternator fails, the fault-tolerant instruction module is used to issue a fault-tolerant operation signal; B2. Bypass the faulty module, and disconnect the switching signal input of the faulty module in the shaping circuit and disconnect the modulation wave signal. u p ; B3. Control the fault-tolerant switch group to operate according to the fault-tolerant operation signal, put the pre-charged backup H-bridge module into operation, and switch the switch signal of the pre-charged backup H-bridge module to the switch signal of the original faulty module, so as to realize the fault-tolerant control operation of the bridge arm alternator. S3. Based on the zero-crossing point detected by the grid-side AC voltage, generate switching signals for each fully controlled device in the switching circuit of the bridge arm alternator, and control the switching action of the bridge arm alternator during normal operation and after a fault.

2. The quasi-hot standby fault-tolerant control method for bridge arm alternating converters according to claim 1, characterized in that, Step S3 specifically involves: Based on the AC voltage signal of each phase, switching signals are switched at the voltage zero-crossing point to generate switching signals for the upper and lower bridge arm switching circuits of each phase in the bridge arm alternating converter. G DSjp and G DSjn The switching action of the bridge arm alternating converter during normal operation and after a fault occurs, i.e. j When the phase voltage on the phase grid side is positive, the upper bridge arm switching circuit is turned on, and the lower bridge arm switching circuit is turned off. j When the phase voltage on the phase grid side is negative, the lower bridge arm switching circuit is turned on, and the upper bridge arm switching circuit is turned off.

3. A quasi-hot standby fault-tolerant control system for a bridge arm alternating converter, used to execute the quasi-hot standby fault-tolerant control method according to any one of claims 1-2, characterized in that, include: A dual closed-loop control subsystem is used to generate modulation wave signals for each normally operating module on each bridge arm; The fault-tolerant switch control subsystem is used to generate switching signals for each module of the shaping circuit and a pre-charged backup H-bridge module based on the modulation wave signal when the bridge arm alternating converter is running normally. When the bridge arm alternating converter fails, the switching signals of each faulty module in the shaping circuit are cut off, and the pre-charged backup H-bridge module is used to replace the operation of the original faulty module, so as to realize the fault-tolerant control operation of the bridge arm alternating converter. The switching circuit control subsystem is used to detect the zero-crossing point of the grid-side AC voltage, generate switching signals for each fully controlled device in the switching circuit of the bridge arm alternating converter, and control the switching action of the bridge arm alternating converter during normal operation and after a fault.

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