High fault-tolerant TNPC inverter
By introducing fault-tolerant bridge arms and monitoring modules into the TNPC inverter, rapid fault switching is achieved, solving the low reliability problem of traditional inverters and improving the operating stability and power supply reliability of the equipment.
Patent Information
- Application Number
- CN202510818157.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-18
- Publication Date
- 2025-09-26
AI Technical Summary
Traditional multi-level inverters have low reliability. Failure of any switching device may cause equipment paralysis, affect the stability of the power system, and pose a major risk of power accidents.
A high-fault-tolerant TNPC inverter is designed, which includes a fault-tolerant bridge arm, a DC bus capacitor module, a TNPC module, a control module, a monitoring module, an LCL filter and an AC relay. By detecting faults and switching to the fault-tolerant bridge arm, the normal operation of the equipment is ensured.
It improves the reliability of the inverter, reduces the failure rate, ensures the continuity and reliability of power supply, is suitable for the power supply needs of important loads, and reduces the economic losses caused by failures.
Smart Images
Figure CN120710345A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of power conversion, and in particular relates to a high fault-tolerant TNPC inverter. Background Art
[0002] Energy conservation, emission reduction, and green energy are the new roadmaps for the power system and the entire energy industry. The booming development of renewable energy has made multilevel inverter technology a hot research topic. Multilevel inverter technology has been around since the 1980s and has evolved into a wide range of topologies. Compared to traditional two-level topologies, multilevel topologies offer significant advantages, including lower output harmonics, higher power quality, and reduced switch voltage stress. However, multilevel topologies require more switching devices, which not only increases cost and control complexity in practical applications, but also reduces overall reliability. A single failure in a single switch could potentially disable the entire inverter and even impact the stable operation of other equipment in the power system, causing cascading failures and leading to major power outages and immeasurable economic losses.
[0003] Therefore, it is necessary to propose a high fault-tolerant TNPC inverter to solve the above problems. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a highly fault-tolerant TNPC inverter, which is used to improve the reliability of traditional TNPC inverters and reduce the failure rate. When any one of the three-phase bridge arms of ABC fails, the equipment can continue to operate normally and ensure power supply reliability.
[0005] In order to achieve the above technical effects, the technical solution adopted by the present invention is: A high fault-tolerant TNPC inverter, comprising: Fault-tolerant bridge arm, DC bus capacitor module, TNPC module, control module, monitoring module, LCL filter and AC relay; The TNPC module comprises three-phase ABC bridge arms, each phase bridge arm consisting of two vertical pipes and two horizontal pipes; The hardware structure of the fault-tolerant bridge arm is consistent with the single-phase bridge arm of the TNPC module, and does not work when the circuit is normal; The control module is used for: Detect input / output voltage and current signals to generate switch tube drive signals. Detect the voltage signal of each bridge arm switch tube to make fault judgment. When any phase of the TNPC module fails, the driving signal of the faulty phase is switched to the fault-tolerant bridge arm; The monitoring module receives the signal from the control module and issues a graded alarm based on the fault type.
[0006] Preferably, the fault-tolerant bridge arm replaces the faulty phase when any phase of the TNPC module fails, and the control module does not issue a load reduction or shutdown instruction during the replacement.
[0007] Preferably, the control module executes a fault judgment algorithm, specifically including: Establish a standard coding table for voltage stress of switching tubes and convert the voltage stress value into a four-bit binary code; the first two digits represent the phase sequence, and the last two digits represent the stress level; Collect the voltage value of each switch tube in real time and convert it into the measured code; Compare the measured code with the standard code table. If they are inconsistent, the corresponding switch tube is determined to be faulty.
[0008] Preferably, the voltage stress level coding rule is: 00 means 0 voltage stress, 01 means Vdc / 2 voltage stress, and 10 means Vdc voltage stress; The phase sequence coding rule is: 00 represents phase A, 01 represents phase B, and 10 represents phase C.
[0009] Preferably, the control module is further used to stabilize the DC bus midpoint voltage, ie, the N-point voltage.
[0010] Preferably, the monitoring module specifically alarms for bridge arm faults, and the alarm method includes fault light signal graded indication; when there is no bridge arm fault, the control module triggers load reduction or shutdown operation; when there is a bridge arm fault, only the alarm is triggered without performing load reduction or shutdown.
[0011] Preferably, the switch tubes of the TNPC module and the fault-tolerant bridge arm are composed of IGBT single tubes or IGBT bridge arm modules.
[0012] Preferably, the control module uses SPWM modulation or SVPWM modulation to generate PWM drive pulses.
[0013] Preferably, the fault-tolerant bridge arm is a detachable backup module, which will not affect the basic inversion function of the TNPC module after removal.
[0014] Preferably, the DC bus capacitor module is used to support the bus voltage and filter out voltage fluctuations; the LCL filter is used to output high-quality electric energy; and the AC relay is used to switch between on-grid and off-grid modes.
[0015] The beneficial effects of the present invention are as follows: A fault-tolerant bridge arm is added to the traditional TNPC inverter. The hardware structure of this bridge arm is exactly the same as that of the bridge arm in the TNPC inverter, and there is no need to design the hardware structure of this bridge arm separately. If a bridge arm module is used, only one module position needs to be reserved for a safe fault-tolerant bridge arm. If a single-tube solution is adopted, four IGBT single-tube positions need to be reserved. When the power level remains unchanged, the overall volume and weight of the device will not change much, and the power density of the device will not be reduced. At the same time, since this bridge arm is used as a replacement bridge arm in the event of a sudden fault, its control method is exactly the same as the fault phase, and no additional control strategy is required. Only a fault judgment algorithm needs to be added.
[0016] Therefore, the high-fault-tolerant TNPC inverter device of the present invention can improve the reliability of traditional TNPC inverters and reduce the device's failure rate. The added monitoring module can help operation and maintenance personnel easily identify the fault type, accelerating the fault location and resolution cycle. The high-fault-tolerant TNPC inverter of the present invention can effectively cope with the application scenarios of large-scale converters connected to the power grid, reducing the failure rate of converter equipment and the probability of cascading failures, providing strong protection for the reliability of power grid power supply, and providing strong technical support for the continuous power supply requirements of important loads such as data centers and network rooms. It is very suitable for the safe and reliable operation of new power systems. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 This is a schematic diagram of the high fault-tolerant TNPC inverter of the present invention; Figure 2 A schematic diagram of a current flow path in a working state according to an embodiment of the present invention; Figure 3 A schematic diagram of a current flow path in a working state according to an embodiment of the present invention; Figure 4 Schematic diagram of the current flow path in the freewheeling state in an embodiment of the present invention; Figure 5 This is a flow chart of fault judgment in an embodiment of the present invention. DETAILED DESCRIPTION
[0018] Example 1: like Figure 1 As shown, a high fault-tolerant TNPC inverter includes: Fault-tolerant bridge arm, DC bus capacitor module, TNPC module, control module, monitoring module, LCL filter and AC relay; The TNPC module comprises three-phase ABC bridge arms, each phase bridge arm consisting of two vertical pipes and two horizontal pipes; The hardware structure of the fault-tolerant bridge arm is consistent with the single-phase bridge arm of the TNPC module, and does not work when the circuit is normal; The control module is used for: Detect input / output voltage and current signals to generate switch tube drive signals. Detect the voltage signal of each bridge arm switch tube to make fault judgment. When any phase of the TNPC module fails, the driving signal of the faulty phase is switched to the fault-tolerant bridge arm; The monitoring module receives the signal from the control module and issues a graded alarm based on the fault type.
[0019] Preferably, the fault-tolerant bridge arm replaces the faulty phase when any phase of the TNPC module fails, and the control module does not issue a load reduction or shutdown instruction during the replacement.
[0020] Preferably, the control module executes a fault judgment algorithm, specifically including: Establish a standard coding table for voltage stress of switching tubes and convert the voltage stress value into a four-bit binary code; the first two digits represent the phase sequence, and the last two digits represent the stress level; Collect the voltage value of each switch tube in real time and convert it into the measured code; Compare the measured code with the standard code table. If they are inconsistent, the corresponding switch tube is determined to be faulty.
[0021] Preferably, the voltage stress level coding rule is: 00 means 0 voltage stress, 01 means Vdc / 2 voltage stress, and 10 means Vdc voltage stress; The phase sequence coding rule is: 00 represents phase A, 01 represents phase B, and 10 represents phase C.
[0022] Preferably, the control module is further used to stabilize the DC bus midpoint voltage, ie, the N-point voltage.
[0023] Preferably, the monitoring module specifically alarms for bridge arm faults, and the alarm method includes fault light signal graded indication; when there is no bridge arm fault, the control module triggers load reduction or shutdown operation; when there is a bridge arm fault, only the alarm is triggered without performing load reduction or shutdown.
[0024] Preferably, the switch tubes of the TNPC module and the fault-tolerant bridge arm are composed of IGBT single tubes or IGBT bridge arm modules.
[0025] Preferably, the control module uses SPWM modulation or SVPWM modulation to generate PWM drive pulses.
[0026] Preferably, the fault-tolerant bridge arm is a detachable backup module, which will not affect the basic inversion function of the TNPC module after removal.
[0027] Preferably, the DC bus capacitor module is used to support the bus voltage and filter out voltage fluctuations; the LCL filter is used to output high-quality electric energy; and the AC relay is used to switch between on-grid and off-grid modes.
[0028] Example 2: A high fault-tolerant TNPC inverter consists of a fault-tolerant bridge arm, a DC bus capacitor module, a TNPC module, a control module, a monitoring module, an LCL filter, and an AC relay. Figure 1 As shown in the figure, the TNPC module is the most fundamental module for implementing the inverter function. Based on its current capacity and voltage level requirements, it is best to use IGBTs as switching transistors. This can be constructed using a single IGBT or IGBT bridge arm modules. The fault-tolerant bridge arm is an additional bridge arm added to the TNPC inverter, and its switching transistors are the same as those in the TNPC module. During normal circuit operation, the fault-tolerant bridge arm is inoperative. If any phase in the TNPC module fails, the fault-tolerant bridge arm replaces the faulty phase, ensuring continued circuit operation. The control module detects input and output voltage and current signals to generate drive signals for the switching transistors. It also detects the voltage signals of each transistor in the bridge arm to determine arm faults. The monitoring module provides alarms for various inverter faults, including a dedicated fault warning when a bridge arm fails, accelerating fault location. The DC bus capacitor module supports voltage and filters bus voltage fluctuations. The LCL filter ensures high-quality power output. The AC relay module switches the inverter to and from off-grid mode.
[0029] More specifically, the control module includes control of the TNPC's three-phase bridge arm and a fault diagnosis algorithm. The three-phase bridge arm can be controlled using either SPWM or SVPWM modulation. The former is simple to implement and offers low output harmonics, but it reduces DC voltage utilization. The latter addresses the former's low DC voltage utilization but is more complex and requires processing larger amounts of data. Therefore, the choice depends on actual application requirements.
[0030] Example 3: Both SPWM modulation and SVPWM modulation are relatively mature control strategies, so this embodiment focuses on the fault judgment algorithm: When the TNPC topology works normally, its output voltage has three states: high level, zero level and negative level. The output three-phase voltage waveform is as follows: Figure 2 As shown, the current flow path in its working state during one cycle is as follows Figure 3 As shown, the current flow path during freewheeling is as follows Figure 4 The red-marked switch indicates that it is in the triggered on state, but whether current flows depends on the circuit's operating conditions. The dashed line in the figure represents the current flow path in this state. Based on the operating and freewheeling states of the TNPC inverter, the voltage stress table for each switch is shown in Table 1.
[0031] Table 1: Voltage stress of each switch tube of TNPC inverter;
[0032] According to the voltage stress table for each switching transistor, taking phase A as an example, during the positive half-cycle of the voltage, the voltage stress of the upper vertical transistor Sa1 switches back and forth between 0 and Vdc / 2, while the voltage stress of the lower vertical transistor Sa4 switches back and forth between Vdc / 2 and Vdc. The voltage stress of the horizontal vertical transistor Sa2 switches back and forth between 0 and Vdc / 2, and the voltage stress of the horizontal horizontal transistor Sa3 remains at 0. To facilitate algorithm implementation, 00 represents a voltage stress of 0, 01 represents a voltage stress of Vdc / 2, and 10 represents a voltage stress of Vdc. Furthermore, to distinguish between phases A, B, and C, a two-digit phase identification code is added: 00 represents phase A, 01 represents phase B, and 10 represents phase C. This yields a standard coding table for the voltage stress of each switching transistor within a cycle, as shown in Table 2. The voltage stress code consists of a four-bit binary number, with the first two digits representing one of the three phases A, B, and C, and the last two digits representing the voltage stress.
[0033] Table 2: Standard coding table for voltage stress of each switching tube in one cycle;
[0034] By collecting the voltage signals of each switch tube and converting them into digital codes according to the same coding method in the coding table, and comparing them with the codes in the standard coding table, if the two do not match, it indicates that a switch tube has failed. At this time, the drive of the faulty phase is turned off, and the drive signal of the faulty phase is used to control the fault-tolerant bridge arm. Because the hardware structure of the fault-tolerant bridge arm is exactly the same as that of any of the three phases ABC, as long as the same control pulse is applied, the fault-tolerant bridge arm can completely replace the faulty bridge arm to work; Figure 5 This is a flow chart of fault diagnosis performed when the device is working.
[0035] In summary, the present invention significantly improves the reliability of the inverter and reduces the failure rate of the device by adding a fault-tolerant bridge arm to the traditional TNPC inverter topology. By converting the periodic changes in the voltage stress of each switch tube during operation of the TNPC inverter into a digital code and comparing it with a standard coding table, it is possible to accurately determine whether a particular switch tube has failed. When a fault occurs, the control module quickly shuts off the drive pulse of the faulty phase and transmits the drive signal of the faulty phase to the fault-tolerant bridge arm, allowing the inverter to continue normal operation without affecting power supply continuity. This provides reliable power supply for the safe and reliable operation of the power system and for critical loads such as data centers and network rooms, thus avoiding economic losses caused by converter failures.
Claims
1. A high fault-tolerant TNPC inverter, characterized in that: Including fault-tolerant bridge arm, DC bus capacitor module, TNPC module, control module, monitoring module, LCL filter and AC relay; The TNPC module comprises three-phase ABC bridge arms, each phase bridge arm consisting of two vertical pipes and two horizontal pipes; The hardware structure of the fault-tolerant bridge arm is consistent with the single-phase bridge arm of the TNPC module, and does not work when the circuit is normal; The control module is used for: Detect input / output voltage and current signals to generate switch tube drive signals. Detect the voltage signal of each bridge arm switch tube to make fault judgment. When any phase of the TNPC module fails, the driving signal of the faulty phase is switched to the fault-tolerant bridge arm; The monitoring module receives the signal from the control module and issues a graded alarm based on the fault type.
2. The high fault-tolerant TNPC inverter according to claim 1, characterized in that: The fault-tolerant bridge arm replaces the faulty phase when any phase of the TNPC module fails, and the control module does not issue a load reduction or shutdown instruction during the replacement.
3. The high fault-tolerant TNPC inverter according to claim 1, characterized in that: The control module executes a fault judgment algorithm, specifically including: Establish a standard coding table for voltage stress of switching tubes and convert the voltage stress value into a four-bit binary code; the first two digits represent the phase sequence, and the last two digits represent the stress level; Collect the voltage value of each switch tube in real time and convert it into the measured code; Compare the measured code with the standard code table. If they are inconsistent, the corresponding switch tube is determined to be faulty.
4. The high fault-tolerant TNPC inverter according to claim 3, characterized in that: The voltage stress level coding rules are as follows: 00 means 0 voltage stress, 01 means Vdc / 2 voltage stress, and 10 means Vdc voltage stress; The phase sequence coding rule is: 00 represents phase A, 01 represents phase B, and 10 represents phase C.
5. The high fault-tolerant TNPC inverter according to claim 1, characterized in that: The control module is also used to stabilize the DC bus midpoint voltage, ie, the N-point voltage.
6. The high fault-tolerant TNPC inverter according to claim 1, characterized in that: The monitoring module issues a special alarm for bridge arm faults, and the alarm mode includes fault light signal graded indication; when there is no bridge arm fault, the control module triggers load reduction or shutdown operation; when there is a bridge arm fault, only the alarm is triggered without performing load reduction or shutdown.
7. The high fault-tolerant TNPC inverter according to claim 1, characterized in that: The switch tubes of the TNPC module and the fault-tolerant bridge arm are composed of IGBT single tubes or IGBT bridge arm modules.
8. The high fault-tolerant TNPC inverter according to claim 1, characterized in that: The control module uses SPWM modulation or SVPWM modulation to generate PWM driving pulses.
9. The high fault-tolerant TNPC inverter according to claim 1, characterized in that: The fault-tolerant bridge arm is a detachable backup module, and its removal does not affect the basic inversion function of the TNPC module.
10. The high fault-tolerant TNPC inverter according to claim 1, characterized in that: The DC bus capacitor module is used to support the bus voltage and filter out voltage fluctuations; the LCL filter is used to output high-quality electric energy; and the AC relay is used for switching between on-grid and off-grid modes.