CN108768198A - A kind of redundancy structure Fault tolerant inverter and its control strategy applied to grid-connected microgrid - Google Patents

Abstract

The invention discloses a redundant structure fault-tolerant inverter applied to grid-connected microgrid and its control strategy. For the redundant fault-tolerant inverter with traditional three-phase bridge topology, only a trigger type bidirectional switch TR is added. _a , TR _b and TR _c and fast fuses F ₇ , F ₈ and F ₉ solve the problem of single switch open circuit, single switch short circuit, single bridge arm open circuit, The fault tolerance of the six fault modes of single bridge arm short circuit, two bridge arm open circuit, and two bridge arm short circuit faults are applied to the grid-connected microgrid, so that the inverter can still operate normally after the above six combined fault modes occur , without the need to cut off the microgrid from the main grid due to inverter failure, it can still operate normally, which improves the fault tolerance of traditional power switching tube redundant inverters by 60%.

Description

A fault-tolerant inverter with redundant structure and its control strategy for grid-connected microgrid

technical field

The invention relates to the technical field of electric power automation control, in particular to a redundant structure fault-tolerant inverter applied to a grid-connected microgrid and a control strategy thereof.

Background technique

Damage to the power switch tube will cause the power converter, especially the inverter, to work in an abnormal state. If it is not diagnosed and eliminated in time, it will cause secondary faults and eventually cause the system to shut down. In order to reduce the impact of power switch tube failure on the system, detection and protection circuits such as overvoltage, overcurrent, overheating and drive circuit undervoltage are applied to the inverter. These conventional protection circuits are installed in the Intelligent Power Module (Intelligent Power Module, IPM) has become a standard, which guarantees the safe operation of the inverter to a certain extent. However, since the inverter works in a complex environment, load disturbance, grid disturbance, abnormal use and electromagnetic interference may cause the failure of the protection circuit, while the traditional inverter adopts a three-phase bridge topology, which is not fault-tolerant ability. Therefore, it is particularly important to study the topology of the inverter with fault tolerance and the corresponding control strategy to improve the reliability of the system.

Redundant configuration refers to the repeated configuration of some components of the system. When the system fails, the redundantly configured components intervene and undertake the work of the failed component, thereby reducing the downtime of the system. It usually refers to increasing the reliability of the system through multiple backups. sex.

Fault tolerance refers to maintaining the original performance of the entire system in the event of certain failures or maintaining safe, reliable and continuous operation under the premise of reducing some performance indicators. The active fault-tolerant control system uses real-time online diagnosis technology to actively respond to failures (such as changing control parameters, performing fault-tolerant reconstruction, etc.), so as to ensure that the operating performance of the system is as close as possible to the original system.

The fault-tolerant control method is to connect an extra bridge arm in parallel beside the original bridge arm. Because the redundant bridge arm can replace the failed bridge arm, the power converter can still maintain normal working performance after the failure. In addition, the redundant bridge arm can also be connected in series with the original bridge arm to realize topology reconstruction after the failure. Since bridge arm level redundant control has gradually achieved a good balance between system performance and cost in recent years, it has become a research hotspot in the field of fault-tolerant control. However, when only one switching device in the inverter fails, the entire bridge arm is cut off, and only a single-phase fault is fault-tolerant, and the fault-tolerant space is small.

Contents of the invention

The present invention is a redundant structure fault-tolerant inverter aimed at the traditional three-phase bridge topology, which does not have single-tube open circuit, single-tube short circuit, single bridge arm open circuit, single bridge arm short circuit, two bridge arm open circuit, and two bridge arm short circuit. In order to solve the problem of insufficient fault tolerance of these six failure modes, an inverter topology and its control strategy with redundant power switch tubes are proposed and applied to grid-connected microgrids to solve the problem of traditional topology inverter power failure. The six combined failure modes that cannot be solved by the switch realize the fault tolerance of single-tube open circuit, single-tube short circuit, single-arm open circuit, single-arm short circuit, two-arm open circuit, and two-arm short-circuit faults of the power switch, making the inverter After the above six failure modes occur, the inverter can still operate normally. It does not need to cut off the microgrid from the main grid due to inverter failure, and it can still operate normally, which improves the percentage of traditional power switching tube redundant inverters. 60% fault tolerance.

In order to solve the above technical problems, the technical solution adopted by the present invention is a redundant structure fault-tolerant inverter and its control strategy applied to the grid-connected microgrid, which is characterized in that it includes a DC voltage source and a parallel capacitor and four parallel bridge arms, the four parallel bridge arms constitute an inverter with redundant power switching tubes.

The inverter system with redundant power switching tubes according to the present invention is characterized in that the four parallel bridge arms include the first bridge arm including sequentially series-connected power switching device T ₇ , trigger bidirectional switch TR ₇ , trigger Type bidirectional switch TR ₈ , power switching device T ₈ ; the second bridge arm includes power switching device T ₁ , fast fuse F ₁ , fast fuse F ₇ , fast fuse F ₂ , and power switching device T ₂ in series; The three bridge arms include power switching device T ₃ , fast fuse F ₃ , fast fuse F ₈ , fast fuse F ₄ , and power switching device T ₄ in series; the fourth bridge arm includes power switching device T ₅ , fast fuse Fuse F ₅ , fast blow fuse F ₉ , fast blow fuse F ₆ , power switching device T ₆ .

The midpoints of the trigger type bidirectional switch TR ₇ and the trigger type bidirectional switch TR ₈ of the first bridge arm of the present invention are connected to one end of the parallel connection of the trigger type bidirectional switches TR _a , TR _b and TR _c ; the trigger type bidirectional switch The other end of TR _a is connected between the fast fuse F ₇ of the second bridge arm and the fast fuse F ₂ ; the other end of the trigger type bidirectional switch TR _b is connected to the fast fuse F ₈ of the third bridge arm Between the fast fuse F ₄ and the trigger type bidirectional switch TR _c , the other end is connected between the fast fuse F ₅ and the fast fuse F ₉ of the fourth bridge arm; the trigger type bidirectional switch TR One end of _ab is connected between the fast fuse F ₁ and fast fuse F ₇ of the second bridge arm, and the trigger bidirectional switch TR _bc is connected to the fast fuse F ₅ and fast fuse F ₉ of the fourth bridge arm Between, the other end of the trigger type bidirectional switch TR _ab and the other end of the trigger type bidirectional switch TR _bc are connected in series between the fast fuse F ₃ and the fast fuse F ₈ of the third bridge arm; the trigger type bidirectional switch TR One end of _ac is connected between the fast fuse F ₇ and the fast fuse F ₂ of the second bridge arm, and the other end is connected between the fast fuse F ₉ and the fast fuse F ₆ of the fourth bridge arm;

Realize that the steps of the present invention are as follows:

If there is a short-circuit fault in T ₁ , fuse F ₁ and turn on the trigger type bidirectional switch TR _a & TR ₇ at the same time; if T ₁ has an open circuit fault, turn on the trigger type bidirectional switch TR _a & TR ₇

If there is a short-circuit fault in T ₂ , fuse F ₂ and turn on the trigger type bidirectional switch TR _a & TR ₈ at the same time; if T ₂ has an open circuit fault, turn on the trigger type bidirectional switch TR _a & TR ₈ ;

If a short-circuit fault occurs in T ₃ , fuse F ₃ and turn on the trigger type bidirectional switch TR _b & TR ₇ at the same time; if an open circuit fault occurs in T ₃ , turn on the trigger type bidirectional switch TR _b & TR ₇ ;

If a short-circuit fault occurs in T ₄ , fuse F ₄ and turn on the trigger type bidirectional switch TR _b & TR ₈ at the same time; if an open circuit fault occurs in T ₄ , turn on the trigger type bidirectional switch TR _b & TR ₈ ;

If there is a short-circuit fault in T ₅ , fuse F ₅ and turn on the trigger type bidirectional switch TR _c & TR ₇ at the same time; if there is an open circuit fault in T ₅ , turn on the trigger type bidirectional switch TR _b & TR ₈ ;

If there is a short-circuit fault in T ₆ , fuse F ₆ and turn on the trigger type bidirectional switch TR _c & TR ₈ at the same time; if T ₆ has an open circuit fault, turn on the trigger type bidirectional switch TR _b & TR ₈ ;

If a short-circuit fault occurs in T ₁ and an open-circuit fault occurs in T ₂ , then F ₁ is fused, and the trigger type bidirectional switch TR _a &TR ₇ &TR ₈ is turned on;

If there is an open-circuit fault in T ₁ and a short-circuit fault in T ₂ , then F ₂ will be blown, and the trigger type bidirectional switch TR _a & TR ₇ & TR ₈ will be turned on;

If a short-circuit fault occurs in T ₁ and a short-circuit fault occurs in T ₂ , F ₁ & F ₂ will be fused, and the trigger type bidirectional switch TR _a & TR ₇ & TR ₈ will be turned on;

If an open-circuit fault occurs in T ₁ and an open-circuit fault occurs in T ₂ , the trigger type bidirectional switches TR _a & TR ₇ & TR ₈ are turned on;

If there is a short-circuit fault in T ₃ and an open-circuit fault in T ₄ , then F ₃ will be blown, and then the trigger type bidirectional switch TR _b & TR ₇ & TR ₈ will be turned on;

If there is an open-circuit fault in T ₃ and a short-circuit fault in T ₄ , then fuse F ₄ , and turn on the trigger type bidirectional switch TR _b & TR ₇ & TR ₈ ;

If a short-circuit fault occurs in T ₃ and a short-circuit fault occurs in T ₄ , then fuse F ₃ & F ₄ , and turn on the trigger type bidirectional switch TR _b & TR ₇ & TR ₈ ;

If an open-circuit fault occurs in T ₃ and an open-circuit fault occurs in T ₄ , then conduction trigger type bidirectional switches TR _b & TR ₇ & TR ₈ ;

If there is a short-circuit fault in T ₅ and an open-circuit fault in T ₆ , then F ₅ will be blown, and then the trigger type bidirectional switch TR _c & TR ₇ & TR ₈ will be turned on;

If there is an open-circuit fault in T ₅ and a short-circuit fault in T ₆ , then F ₆ will be blown, and then the trigger type bidirectional switch TR _c & TR ₇ & TR ₈ will be turned on;

If a short-circuit fault occurs in T ₅ and a short-circuit fault occurs in T ₆ , F ₅ & F ₆ will be blown, and the trigger type bidirectional switch TR _c & TR ₇ & TR ₈ will be turned on;

If an open-circuit fault occurs in T ₅ and an open-circuit fault occurs in T ₆ , then conduction trigger type bidirectional switch TR _c & TR ₇ & TR ₈ ;

If a short-circuit fault occurs in T ₁ and an open-circuit fault occurs in T ₄ , F ₁ & F ₈ will be fused, and the trigger type bidirectional switch TR _b & TR _ab & TR ₇ & TR ₈ will be turned on;

If T ₁ has an open-circuit fault and T ₄ has a short-circuit fault, F ₄ & F ₈ will be fused, and the trigger type bidirectional switch TR _b & TR _ab & TR ₇ & TR ₈ will be turned on;

If a short-circuit fault occurs in T ₁ and a short-circuit fault occurs in T ₄ , F ₁ & F ₄ & F ₈ will be fused, and the trigger type bidirectional switch TR _b & TR _ab & TR ₇ & TR ₈ will be turned on;

If an open-circuit fault occurs in T ₁ and an open-circuit fault occurs in T ₄ , then the fuse F ₈ is turned on, and the trigger type bidirectional switch TR _b &TR _ab &TR ₇ &TR ₈ is turned on;

If there is a short-circuit fault in T ₂ and an open-circuit fault in T ₃ , then F ₂ & F ₇ will be blown, and the trigger type bidirectional switch TR _a & TR _ab & TR ₇ & TR ₈ will be turned on;

If T ₂ has an open-circuit fault and T ₃ has a short-circuit fault, F ₃ & F ₇ will be fused, and the trigger type bidirectional switch TR _a & TR _ab & TR ₇ & TR ₈ will be turned on;

If a short-circuit fault occurs in T ₂ and a short-circuit fault occurs in T ₃ , then F ₂ & F ₃ & F ₇ will be blown, and then the trigger type bidirectional switch TR _a & TR _ab & TR ₇ & TR ₈ will be turned on;

If an open-circuit fault occurs in T ₂ and an open-circuit fault occurs in T ₃ , the fuse F ₇ is blown, and the trigger type bidirectional switch TR _a & TR _ab & TR ₇ & TR ₈ is turned on;

If a short-circuit fault occurs in T ₁ and an open-circuit fault occurs in T ₆ , F ₁ & F ₉ will be fused, and the trigger type bidirectional switch TR _c & TR _ac & TR ₇ & TR ₈ will be turned on;

If T ₁ has an open-circuit fault and T ₆ has a short-circuit fault, F ₃ & F ₉ will be fused, and the trigger type bidirectional switch TR _c & TR _ac & TR ₇ & TR ₈ will be turned on;

If a short-circuit fault occurs in T ₁ and a short-circuit fault occurs in T ₆ , F ₁ & F ₆ & F ₉ will be fused, and the trigger type bidirectional switch TR _c & TR _ac & TR ₇ & TR ₈ will be turned on;

If an open-circuit fault occurs in T ₁ and an open-circuit fault occurs in T ₆ , the fuse F ₉ will be blown, and the trigger type bidirectional switch TR _c & TR _ac & TR ₇ & TR ₈ will be turned on;

If T ₂ has a short-circuit fault and T ₅ has an open-circuit fault, F ₂ & F ₇ will be fused, and the trigger type bidirectional switch TR _a & TR _ac & TR ₇ & TR ₈ will be turned on;

If there is an open-circuit fault in T ₂ and a short-circuit fault in T ₅ , F ₅ & F ₇ will be fused, and the trigger type bidirectional switch TR _a & TR _ac & TR ₇ & TR ₈ will be turned on;

If a short-circuit fault occurs in T ₂ and a short-circuit fault occurs in T ₅ , F ₂ & F ₅ & F ₇ will be fused, and the trigger type bidirectional switch TR _a & TR _ac & TR ₇ & TR ₈ will be turned on;

If an open-circuit fault occurs in T ₂ and an open-circuit fault occurs in 5, F ₇ will be blown, and the trigger type bidirectional switch TR _a & TR _ac & TR ₇ & TR ₈ will be turned on;

If there is a short-circuit fault in T ₃ and an open-circuit fault in T ₆ , then F ₃ & F ₉ will be blown, and the trigger type bidirectional switch TR _c & TR _bc & TR ₇ & TR ₈ will be turned on;

If T ₃ has an open-circuit fault and T ₆ has a short-circuit fault, F ₆ & F ₉ will be fused, and the trigger type bidirectional switch TR _c & TR _bc & TR ₇ & TR ₈ will be turned on;

If a short-circuit fault occurs in T ₃ and a short-circuit fault occurs in T ₆ , F ₃ & F ₆ & F ₉ will be blown, and the trigger type bidirectional switch TR _c & TR _bc & TR ₇ & TR ₈ will be turned on;

If an open-circuit fault occurs in T ₃ and an open-circuit fault occurs in T ₆ , the fuse F ₉ will be turned on, and the trigger type bidirectional switch TR _c & TR _bc & TR ₇ & TR ₈ will be turned on;

If a short-circuit fault occurs in T ₄ and an open-circuit fault occurs in T ₅ , F ₄ & F ₈ will be fused, and the trigger type bidirectional switch TR _b & TR _bc & TR ₇ & TR ₈ will be turned on;

If there is an open-circuit fault in T ₄ and a short-circuit fault in T ₅ , F ₅ & F ₈ will be fused, and the trigger type bidirectional switch TR _b & TR _bc & TR ₇ & TR ₈ will be turned on;

If a short-circuit fault occurs in T ₄ and a short-circuit fault occurs in T ₅ , F ₄ & F ₅ & F ₈ will be blown, and the trigger type bidirectional switch TR _b & TR _bc & TR ₇ & TR ₈ will be turned on;

If an open-circuit fault occurs in T ₄ and an open-circuit fault occurs in T ₅ , then F ₈ is blown, and the trigger type bidirectional switch TR _b &TR _bc &TR ₇ &TR ₈ is turned on.

Further, if the T1 or T3 or _T5 single tube _of the present invention has _a short circuit or open circuit fault, then use _T7 to _replace the pulse signal originally given to _T1 or _T3 or _T5 by _T1 or _T3 or T5 In turn, it is sent to the power switching device T ₇ , and the power switching device T ₇ and T ₂ or T ₄ or T ₆ form phase a, b or c of the three phases, so that the inverter can maintain normal operation.

Further, if the T1 or T4 or _T6 single tube of the present invention has _a short circuit or open circuit fault, then use _T8 to _replace the pulse signal originally given to _T2 or _T4 or _T6 by _T2 or _T4 or _T6 In turn, it is sent to the power switching device T ₈ , and the power switching device T ₈ and T ₁ or T ₃ or T ₅ constitute phase a, b or c of the three phases, so that the inverter can maintain normal operation.

Further, if the single bridge arm where T ₁ and T ₂ are located in the present invention has a short circuit or an open circuit fault, T ₇ and T ₈ are used to replace T ₁ and T ₂ , and the pulse signals originally given to T ₁ and T ₂ are changed to The power switching devices T 7 and T 8 are sent to the power switching devices T ₇ and T ₈ , and the power switching devices T ₇ and T ₈ constitute phase a of the three phases, so that the inverter can maintain normal operation.

Further, if the single bridge arm where T3 and T4 are located in the present invention has a short circuit or open circuit fault, _T7 and _T8 are used to replace _T3 and _T4 , and the _pulse signals originally given to _T3 and _T4 are _changed to The power switching devices T 7 and T 8 are sent to the power switching devices T ₇ and T ₈ , and the power switching devices T ₇ and T ₈ form phase b of the three phases, so that the inverter can maintain normal operation.

Further, if there is a short-circuit or open-circuit fault in the single bridge arm where T5 and _T6 are located in the present invention, _T7 and _T8 are used to replace _T5 and _T6 , and the pulse signals originally given to _T5 and _T6 are _changed to The power switching devices T 7 and T 8 are sent to the power switching devices T ₇ and T ₈ , and the power switching devices T ₇ and T ₈ form phase c in the three phases, so that the inverter can keep running normally.

Further, if there is a short-circuit or open-circuit fault in the two bridge arms where T ₁ and T ₄ are located in the present invention, T ₇ and T ₈ are used to replace T ₁ and T ₄ , and the pulse signals originally given to T ₁ and T ₄ are changed to The power switching devices T 7 and T 8 are sent to the power switching devices T ₇ and T ₈ , and the power switching devices T ₇ and T ₈ form phase b of the three phases, so that the inverter can maintain normal operation.

Further, if there is a short circuit or open circuit fault in the _two bridge arms where T2 and T3 are located in the present invention, _T7 and _T8 are used to replace _T2 and _T3 , and the pulse signals originally given to _T2 and _T3 are _changed to The power switching devices T 7 and T 8 are sent to the power switching devices T ₇ and T ₈ , and the power switching devices T ₇ and T ₈ constitute phase a of the three phases, so that the inverter can maintain normal operation.

Further, if the two bridge arms where T ₁ and T ₆ are located in the present invention have short-circuit or open-circuit faults, T ₇ and T ₈ are used to replace T ₁ and T ₆ , and the pulse signals originally given to T ₁ and T ₆ are changed to The power switching devices T 7 and T 8 are sent to the power switching devices T ₇ and T ₈ , and the power switching devices T ₇ and T ₈ form phase c in the three phases, so that the inverter can keep running normally.

Further, if there is a short circuit or open circuit fault in the _two bridge arms where T2 and T5 are located in the present invention, _T7 and _T8 are used to replace _T2 and _T5 , and the pulse signals originally given to _T2 and _T5 are _changed to The power switching devices T 7 and T 8 are sent to the power switching devices T ₇ and T ₈ , and the power switching devices T ₇ and T ₈ constitute phase a of the three phases, so that the inverter can maintain normal operation.

Further, if there is a short circuit or open circuit fault in the _two bridge arms where T3 and _T6 are located in the present invention, _T7 and _T8 are used to replace T3 and _T6 , and the pulse signals originally given to _T3 and _T6 are _changed to The power switching devices T 7 and T 8 are sent to the power switching devices T ₇ and T ₈ , and the power switching devices T ₇ and T ₈ form phase c in the three phases, so that the inverter can keep running normally.

Further, if there is a short-circuit or open _- circuit fault in the two bridge arms where T4 and T5 are located in the present invention, _T7 and _T8 are used to replace _T4 and _T5 , and the pulse signals originally given to _T4 and _T5 are _changed to The power switching devices T 7 and T 8 are sent to the power switching devices T ₇ and T ₈ , and the power switching devices T ₇ and T ₈ form phase b of the three phases, so that the inverter can maintain normal operation.

The present invention lies in that after the power switching device fails during operation, the redundant power switching devices T ₇ and T ₈ receive corresponding reset pulse signals, and the uninterrupted inverter operates normally.

Description of drawings

Figure 1 is based on the equivalent circuit diagram of the power tube redundant inverter topology;

Figure 2 The switch state table corresponding to the component failure of the power tube redundant inverter topology;

Fig. 3 The system structure and control strategy frame diagram of the power switching tube redundant inverter applied to the microgrid;

Figure 4 Power switch tube redundant inverter pulse signal reset table;

Figure 5 Test voltage of the common connection point of the power switch tube redundant inverter;

Fig. 6 The output current of the inverter when the phase a of the power switching tube redundant inverter fails;

Fig. 7 The output current of the inverter when the b-phase fault of the power switching tube redundant inverter is faulty;

Fig. 8 The output current of the inverter when the c-phase fault of the power switching tube redundant inverter is faulty;

Figure 9 Power switch tube redundant inverter (e) Output current of the inverter after reconfiguration.

Detailed ways

Figure 1 is an equivalent circuit diagram based on the topology of redundant power tube inverters. The power switching devices T ₁ ~ T ₆ are three-phase redundant inverter circuits in microgrid grid-connected, and T ₇ and T ₈ are redundant The rest of the power switching devices used for reconstruction when the inverter fails, F1-F9 are the power switching devices or bridge arms used to cut off the corresponding connection when the inverter power switching devices or bridge arms fail, TR _a , TR _b , TR _{c and} TR _ac , TR _ab , TR _bc and TR ₇ , and TR ₈ are trigger type bidirectional switches used for reconfiguration when the redundant inverter is running and fails. The grid voltage amplitude is 311V and the frequency is 50Hz. The DC side voltage of the inverter is 800V, the filter inductor on the output side of the inverter is 2mH, and the filter capacitor is 200uF.

Figure 2, the component failure corresponding switch state table of the power tube redundant inverter topology, lists the possible fault combination modes of T1~T6 and the corresponding action state table of fast fuses and trigger bidirectional switches.

Figure 3, the system structure and control strategy frame diagram of the power switch tube redundant inverter applied to the microgrid, the power switch tube in the inverter is replaced by T ₇ or (and) T ₈ after a failure, which is obtained by PQ control The effective power and reactive power of the inverter are calculated and fed back to the SPWM pulse modulation control system after calculating the reference value of the inner loop, and the corresponding pulse trigger signal is sent to the replacement power switch tube T ₇ or (and) T ₈ , so that the inverter After the inverter fails and is reconfigured, it can still operate normally without conversion algorithm, and there is no need to disconnect the microgrid from the main grid due to inverter failure.

Figure 4 After the power switch tube redundant inverter fails, the pulse signal resets the sending table for the replacement power switch tube T ₇ or (and) T ₈ .

The control steps of SPWM pulse signal combined with PQ control:

For example: u is the voltage of the three-phase AC power grid, i is the line current, and the three-phase u and i are respectively subjected to dq transformation in the two-phase rotating coordinate system to obtain ( u _d , u _q ) and ( i _d , i _q ) . Then the power expression in the two-phase rotating coordinate system dq,

(1)

Assuming that the three-phase system operates symmetrically, there is no zero-sequence component, and when t = 0, the initial phase angle of phase a voltage is 0, then u _q = 0, the formula (1) can be simplified as,

(2)

When using the PQ control method, the output P and Q are constant values; when running stably, u _d is a constant value. Therefore, the reference value of the current can be obtained:

(3)

After obtaining the current reference value, the active power and reactive power output by the inverter can be adjusted by adjusting the active current and the reactive current. When the inverter is a voltage type, the control signal that needs to convert the current is a voltage control signal. The voltage equation is obtained according to Figure 3,

(4)

v is the output voltage of the inverter, the dq transformation is performed on the three-phase v in the two-phase rotating coordinate system to obtain ( v _d , v _q ). Transform the formula (4) into the expression under the two-phase rotating coordinate system dq,

(5)

The model shown in (5) above has a strong coupling, which requires eliminating the coupling between the d-axis and the q-axis, so that the components of the two axes can be adjusted separately without mutual influence. The state feedback quantity of two currents is introduced to achieve decoupling, and the following control equation can be obtained,

(6)

The current control loop adopts the PI adjustment method. The purpose is to compare the current reference value with the actual current signal fed back to the controller, and quickly adjust the difference through the PI adjustment method to achieve the result of zero steady-state error. Here the value of K _p is 5.2, and the value of K _i is 0.8. When the steady-state error of the output current value is 0, the output current of the inverter can keep the given reference value of the current unchanged, so that the output voltage of the inverter can track the voltage of the large power grid.

Figures 5 to 9 are the simulation verification data and voltage and current waveforms of the redundant structure fault-tolerant inverter and its control method applied to the grid-connected microgrid. When the phase a, phase b, and phase c of the inverter microgrid When the power switch tubes of the bridge arms fail respectively, before the inverter is reconstructed, the three-phase output currents of a, b, and c appear in the waveforms shown in Figures 5-8, and the output currents with inconsistent amplitudes and non-sinusoidal waves are obtained. The main power grid is connected in parallel, so the electricity at the common connection point does not change as shown in Figure 5. The purpose of its PQ control is to maintain a constant output power of the microgrid, so the output current of the microgrid must be corrected through PQ control, so that the reconstructed The power switch tube effectively replaces the faulty power switch tube, as shown in Figure 9, and the same output current as before the fault is obtained, and the feasibility and effectiveness of the present invention are verified by simulation.

Claims (6)

1. A redundant structure fault-tolerant inverter and its control strategy applied to grid-connected microgrid, characterized in that it comprises a DC voltage source and a parallel capacitor and four parallel bridge arms, the four parallel The bridge arm constitutes an inverter with redundant power switching tubes. 2. The redundant structure fault-tolerant inverter and its control strategy applied to the grid-connected microgrid according to claim 1, characterized in that, the four parallel bridge arms include the first bridge arm including sequentially series-connected power switches Device T ₇ , trigger type bidirectional switch TR ₇ , trigger type bidirectional switch TR ₈ , power switching device T ₈ ; the second bridge arm includes sequentially series-connected power switching device T ₁ , fast fuse F ₁ , fast fuse F ₇ , fast fuse Fuse F ₂ , power switching device T ₂ ; the third bridge arm includes power switching device T ₃ , fast fuse F ₃ , fast fuse F ₈ , fast fuse F ₄ , and power switching device T ₄ in series; the fourth The bridge arm includes a power switching device T ₅ , a fast fuse F ₅ , a fast fuse F ₉ , a fast fuse F ₆ and a power switching device T ₆ in series in sequence. 3. The redundant structure fault-tolerant inverter and its control strategy applied to the grid-connected microgrid according to claim 2, characterized in that, the trigger type bidirectional switch TR ₇ of the first bridge arm and the trigger type bidirectional switch The midpoint of TR ₈ is connected to one end of the parallel connection of trigger type bidirectional switches TR _a , TR _b and TR _c ; the other end of the trigger type bidirectional switch TR _a is connected to the fast fuse F ₇ of the second bridge arm and the fast fuse Between F ₂ ; the other end of the trigger type bidirectional switch TR _b is connected between the fast fuse F ₈ and the fast fuse F ₄ of the third bridge arm; the other end of the trigger type bidirectional switch TR _c , connected between the fast fuse F ₅ and the fast fuse F ₉ of the fourth bridge arm; one end of the trigger type bidirectional switch TR _ab is connected to the fast fuse F ₁ and the fast fuse F of the second bridge arm Between ₇ , one end of the trigger type bidirectional switch TR _bc , connected between the fast fuse F ₅ and the fast fuse F ₉ of the fourth bridge arm, the other end of the trigger type bidirectional switch TR _ab and the other end of the trigger type bidirectional switch TR _bc Connect in series between the fast fuse F ₃ and the fast fuse F ₈ of the third bridge arm; one end of the trigger type bidirectional switch TR _ac is connected to the fast fuse F ₇ and the fast fuse F ₂ of the second bridge arm The other end is connected between the fast fuse F ₉ and the fast fuse F ₆ of the fourth bridge arm. 4. The redundant structure fault-tolerant inverter and its control strategy applied to the grid-connected microgrid according to any one of claims 1 to 3, characterized in that, the redundant inverter of the power switching tube with the topology described in the application The implementation steps of the converter system are as follows: If there is a short-circuit fault in T ₁ , fuse F ₁ and turn on the trigger type bidirectional switch TR _a & TR ₇ at the same time; if T ₁ has an open circuit fault, turn on the trigger type bidirectional switch TR _a & TR ₇ If there is a short-circuit fault in T ₂ , fuse F ₂ and turn on the trigger type bidirectional switch TR _a & TR ₈ at the same time; if T ₂ has an open circuit fault, turn on the trigger type bidirectional switch TR _a & TR ₈ ; If a short-circuit fault occurs in T ₃ , fuse F ₃ and turn on the trigger type bidirectional switch TR _b & TR ₇ at the same time; if an open circuit fault occurs in T ₃ , turn on the trigger type bidirectional switch TR _b & TR ₇ ; If a short-circuit fault occurs in T ₄ , fuse F ₄ and turn on the trigger type bidirectional switch TR _b & TR ₈ at the same time; if an open circuit fault occurs in T ₄ , turn on the trigger type bidirectional switch TR _b & TR ₈ ; If there is a short-circuit fault in T ₅ , fuse F ₅ and turn on the trigger type bidirectional switch TR _c & TR ₇ at the same time; if there is an open circuit fault in T ₅ , turn on the trigger type bidirectional switch TR _b & TR ₈ ; If there is a short-circuit fault in T ₆ , fuse F ₆ and turn on the trigger type bidirectional switch TR _c & TR ₈ at the same time; if T ₆ has an open circuit fault, turn on the trigger type bidirectional switch TR _b & TR ₈ ; If a short-circuit fault occurs in T ₁ and an open-circuit fault occurs in T ₂ , then F ₁ is fused, and the trigger type bidirectional switch TR _a &TR ₇ &TR ₈ is turned on; If there is an open-circuit fault in T ₁ and a short-circuit fault in T ₂ , then F ₂ will be blown, and the trigger type bidirectional switch TR _a & TR ₇ & TR ₈ will be turned on; If a short-circuit fault occurs in T ₁ and a short-circuit fault occurs in T ₂ , F ₁ & F ₂ will be fused, and the trigger type bidirectional switch TR _a & TR ₇ & TR ₈ will be turned on; If an open-circuit fault occurs in T ₁ and an open-circuit fault occurs in T ₂ , the trigger type bidirectional switches TR _a & TR ₇ & TR ₈ are turned on; If there is a short-circuit fault in T ₃ and an open-circuit fault in T ₄ , then F ₃ will be blown, and then the trigger type bidirectional switch TR _b & TR ₇ & TR ₈ will be turned on; If there is an open-circuit fault in T ₃ and a short-circuit fault in T ₄ , then fuse F ₄ , and turn on the trigger type bidirectional switch TR _b & TR ₇ & TR ₈ ; If a short-circuit fault occurs in T ₃ and a short-circuit fault occurs in T ₄ , then fuse F ₃ & F ₄ , and turn on the trigger type bidirectional switch TR _b & TR ₇ & TR ₈ ; If an open-circuit fault occurs in T ₃ and an open-circuit fault occurs in T ₄ , then conduction trigger type bidirectional switches TR _b & TR ₇ & TR ₈ ; If there is a short-circuit fault in T ₅ and an open-circuit fault in T ₆ , then F ₅ will be blown, and then the trigger type bidirectional switch TR _c & TR ₇ & TR ₈ will be turned on; If there is an open-circuit fault in T ₅ and a short-circuit fault in T ₆ , then F ₆ will be blown, and then the trigger type bidirectional switch TR _c & TR ₇ & TR ₈ will be turned on; If a short-circuit fault occurs in T ₅ and a short-circuit fault occurs in T ₆ , F ₅ & F ₆ will be blown, and the trigger type bidirectional switch TR _c & TR ₇ & TR ₈ will be turned on; If an open-circuit fault occurs in T ₅ and an open-circuit fault occurs in T ₆ , then conduction trigger type bidirectional switch TR _c & TR ₇ & TR ₈ ; If a short-circuit fault occurs in T ₁ and an open-circuit fault occurs in T ₄ , F ₁ & F ₈ will be fused, and the trigger type bidirectional switch TR _b & TR _ab & TR ₇ & TR ₈ will be turned on; If T ₁ has an open-circuit fault and T ₄ has a short-circuit fault, F ₄ & F ₈ will be fused, and the trigger type bidirectional switch TR _b & TR _ab & TR ₇ & TR ₈ will be turned on; If a short-circuit fault occurs in T ₁ and a short-circuit fault occurs in T ₄ , F ₁ & F ₄ & F ₈ will be fused, and the trigger type bidirectional switch TR _b & TR _ab & TR ₇ & TR ₈ will be turned on; If an open-circuit fault occurs in T ₁ and an open-circuit fault occurs in T ₄ , then the fuse F ₈ is turned on, and the trigger type bidirectional switch TR _b &TR _ab &TR ₇ &TR ₈ is turned on; If there is a short-circuit fault in T ₂ and an open-circuit fault in T ₃ , then F ₂ & F ₇ will be blown, and the trigger type bidirectional switch TR _a & TR _ab & TR ₇ & TR ₈ will be turned on; If T ₂ has an open-circuit fault and T ₃ has a short-circuit fault, F ₃ & F ₇ will be fused, and the trigger type bidirectional switch TR _a & TR _ab & TR ₇ & TR ₈ will be turned on; If a short-circuit fault occurs in T ₂ and a short-circuit fault occurs in T ₃ , then F ₂ & F ₃ & F ₇ will be blown, and then the trigger type bidirectional switch TR _a & TR _ab & TR ₇ & TR ₈ will be turned on; If an open-circuit fault occurs in T ₂ and an open-circuit fault occurs in T ₃ , the fuse F ₇ is blown, and the trigger type bidirectional switch TR _a & TR _ab & TR ₇ & TR ₈ is turned on; If a short-circuit fault occurs in T ₁ and an open-circuit fault occurs in T ₆ , F ₁ & F ₉ will be fused, and the trigger type bidirectional switch TR _c & TR _ac & TR ₇ & TR ₈ will be turned on; If T ₁ has an open-circuit fault and T ₆ has a short-circuit fault, F ₃ & F ₉ will be fused, and the trigger type bidirectional switch TR _c & TR _ac & TR ₇ & TR ₈ will be turned on; If a short-circuit fault occurs in T ₁ and a short-circuit fault occurs in T ₆ , F ₁ & F ₆ & F ₉ will be fused, and the trigger type bidirectional switch TR _c & TR _ac & TR ₇ & TR ₈ will be turned on; If an open-circuit fault occurs in T ₁ and an open-circuit fault occurs in T ₆ , the fuse F ₉ will be blown, and the trigger type bidirectional switch TR _c & TR _ac & TR ₇ & TR ₈ will be turned on; If T ₂ has a short-circuit fault and T ₅ has an open-circuit fault, F ₂ & F ₇ will be fused, and the trigger type bidirectional switch TR _a & TR _ac & TR ₇ & TR ₈ will be turned on; If there is an open-circuit fault in T ₂ and a short-circuit fault in T ₅ , F ₅ & F ₇ will be fused, and the trigger type bidirectional switch TR _a & TR _ac & TR ₇ & TR ₈ will be turned on; If a short-circuit fault occurs in T ₂ and a short-circuit fault occurs in T ₅ , F ₂ & F ₅ & F ₇ will be fused, and the trigger type bidirectional switch TR _a & TR _ac & TR ₇ & TR ₈ will be turned on; If an open-circuit fault occurs in T ₂ and an open-circuit fault occurs in 5, F ₇ will be blown, and the trigger type bidirectional switch TR _a & TR _ac & TR ₇ & TR ₈ will be turned on; If there is a short-circuit fault in T ₃ and an open-circuit fault in T ₆ , then F ₃ & F ₉ will be blown, and the trigger type bidirectional switch TR _c & TR _bc & TR ₇ & TR ₈ will be turned on; If T ₃ has an open-circuit fault and T ₆ has a short-circuit fault, F ₆ & F ₉ will be fused, and the trigger type bidirectional switch TR _c & TR _bc & TR ₇ & TR ₈ will be turned on; If a short-circuit fault occurs in T ₃ and a short-circuit fault occurs in T ₆ , F ₃ & F ₆ & F ₉ will be blown, and the trigger type bidirectional switch TR _c & TR _bc & TR ₇ & TR ₈ will be turned on; If an open-circuit fault occurs in T ₃ and an open-circuit fault occurs in T ₆ , the fuse F ₉ will be turned on, and the trigger type bidirectional switch TR _c & TR _bc & TR ₇ & TR ₈ will be turned on; If a short-circuit fault occurs in T ₄ and an open-circuit fault occurs in T ₅ , F ₄ & F ₈ will be fused, and the trigger type bidirectional switch TR _b & TR _bc & TR ₇ & TR ₈ will be turned on; If there is an open-circuit fault in T ₄ and a short-circuit fault in T ₅ , F ₅ & F ₈ will be fused, and the trigger type bidirectional switch TR _b & TR _bc & TR ₇ & TR ₈ will be turned on; If a short-circuit fault occurs in T ₄ and a short-circuit fault occurs in T ₅ , F ₄ & F ₅ & F ₈ will be blown, and the trigger type bidirectional switch TR _b & TR _bc & TR ₇ & TR ₈ will be turned on; If an open-circuit fault occurs in T ₄ and an open-circuit fault occurs in T ₅ , then F ₈ is blown, and the trigger type bidirectional switch TR _b &TR _bc &TR ₇ &TR ₈ is turned on. 5. The redundant structure fault-tolerant inverter and its control strategy applied to the grid-connected micro-grid according to claim 4, characterized in that, _a short-circuit or open _- circuit fault occurs in the single tube _of T1 or T3 or T5 , then use T ₇ to replace T ₁ or T ₃ or T _5. The pulse signal originally given to T ₁ or T ₃ or T ₅ is sent to the power switching device T ₇ , and the power switching device T ₇ and T ₂ or T ₄ or T ₆ constitutes phase a, b or c of the three phases to keep the inverter running normally; if the single tube of T ₁ or T ₄ or T ₆ has a short circuit or open circuit fault, then use T ₈ to replace T ₂ or T ₄ or _T6 originally gave the pulse signal to _T2 or _T4 or _T6 and then sent to the power switching device _T8 , the power switching device _T8 and T1 or T3 or _T5 form _a or b in the _three phases or phase c, to keep the inverter running normally; if the single bridge arm where T ₁ and T ₂ are located has a short circuit or open circuit fault, T ₇ and T ₈ are used to replace T ₁ and T ₂ , which were originally assigned to T _{1 The} pulse signal with T2 is sent to the power switching devices _T7 and _T8 in turn, and the power switching devices _T7 and _T8 constitute phase a of the _three phases to keep the inverter running normally; the T3 and T If there is a short-circuit or open-circuit fault in the single bridge arm where ₄ is located, T ₇ and T ₈ are used to replace T ₃ and T ₄ , and the pulse signals originally given to T ₃ and T ₄ are sent to power switching devices T ₇ and T ₈ instead. Power switching devices T ₇ and T ₈ form phase b of the three phases to keep the inverter running normally; if the single bridge arm where T ₅ and T ₆ are located has a short circuit or open circuit fault, then use T ₇ and T ₈ Instead of _T5 and _T6 , the pulse signals originally given to _T5 and _T6 are sent to the power switching devices _T7 and _T8 , and the power switching devices _T7 and _T8 constitute the c phase of the three phases, making the inverter If the two bridge arms where T ₁ and T ₄ are located are short-circuited or open-circuit faulted, then T ₇ and T ₈ are used to replace T ₁ and T ₄ , and the pulse signals originally given to T ₁ and T ₄ are transferred to And sent to the power switching devices T ₇ and T ₈ , the power switching devices T ₇ and T ₈ constitute phase b of the three phases, so that the inverter can maintain normal operation; the two bridge arms where T ₂ and T ₃ are located appear Short circuit or open circuit fault, replace T ₂ and T ₃ with T ₇ and T ₈ , the pulse signal originally assigned to T ₂ and T ₃ is sent to power switching devices T ₇ and T ₈ , power switching devices T ₇ and T ₈ constitutes phase a of the three phases to keep the inverter running normally; if the two bridge arms where T ₁ and T ₆ are located are short-circuited or open-circuit faulted, T ₇ and T ₈ are used to replace T ₁ and T ₆ , The pulse signals originally assigned to T ₁ and T ₆ are sent to power switching devices T ₇ and T ₈ in turn, and the power switching devices T ₇ and T ₈ form phase c of the three phases, so that the inverter can maintain normal operation; T ₂ and T ₅ If there is a short-circuit or open-circuit fault in the two bridge arms, T ₇ and T ₈ are used to replace T ₂ and T ₅ , and the pulse signals originally assigned to T ₂ and T ₅ are sent to power switching devices T ₇ and T ₈ , and the power The switching devices T ₇ and T ₈ form the a phase of the three phases to keep the inverter running normally; if the two bridge arms where T ₃ and T ₆ are located have a short circuit or open circuit fault, then use T ₇ and T ₈ instead T ₃ and T ₆ , the pulse signals originally given to T ₃ and T ₆ are sent to the power switching devices T ₇ and T ₈ , and the power switching devices T ₇ and T ₈ constitute phase c of the three phases, so that the inverter Keep normal operation; if the two bridge arms where T4 and T5 are located are short _- circuited or open _- circuited, _T7 and _T8 are used instead of _T4 and _T5 , and the pulse signals originally given to _T4 and T5 are _changed to The power switching devices T 7 and T 8 are sent to the power switching devices T ₇ and T ₈ , and the power switching devices T ₇ and T ₈ form phase b of the three phases, so that the inverter can maintain normal operation. 6. The redundant structure fault-tolerant inverter and its control strategy applied to the grid-connected microgrid according to any one of claims 5 to 15, characterized in that, after the power switching device fails during operation, the redundant power switching device T ₇ and T ₈ receive the corresponding reset pulse signal, and the uninterruptible inverter operates normally.