A method for controlling the phase loss of a Vienna rectifier circuit

Abstract

The present invention provides a method for controlling the phase loss of a Vienna rectifier circuit. The method for controlling the phase loss of the Vienna rectifier circuit simultaneously executes a three-phase conventional control strategy and a phase-loss control strategy. The phase-loss switching control unit selects the driving signals generated by executing the above two control strategies according to the phase-loss information detected by the phase-locked and phase-loss detection unit, and supplies them to the driving circuit, so as to enable the Vienna rectifier circuit to operate normally and stably under normal or phase-loss conditions. The present invention avoids the drawback that the conventional Vienna rectifier circuit shuts down for protection when a phase loss occurs, and uses the two control strategies for seamless switching to enable the Vienna rectifier circuit to operate normally, ensuring the continuity of the load power supply. The present invention enables the Vienna rectifier circuit to operate normally with both three-phase power supply and two-phase power supply, broadening the application range of the Vienna rectifier circuit and having certain application value.

Description

Technical Field

[0001] The present invention relates to a method for controlling phase loss of a Vienna rectifier circuit, belonging to the field of power electronics technology. Background Technique

[0002] A three-phase rectifier circuit converts three-phase alternating current into direct current and is widely used in various industrial occasions. The topological structures of three-phase rectifier circuits include three-phase uncontrolled rectifier circuits, three-phase phase-controlled rectifier circuits, PWM rectifier circuits, Vienna rectifier circuits, buck rectifier circuits, etc. The Vienna rectifier circuit has the advantages of fewer switching devices, the voltage stress borne by the switching tube being half of the DC-side bus voltage, and no need to consider the through conduction of the upper and lower bridge arms and the setting of the dead zone of the switching tube, and thus has been widely used.

[0003] The Vienna rectifier circuit is applicable to a three-phase power supply circuit. When a phase loss occurs, the existing conventional control method is to promptly identify the phase-loss fault and then stop for protection, which will inevitably affect the continuity of power supply to the load. In special industrial occasions, when any one of the three phases is missing, it is required that the Vienna rectifier circuit outputs normally. The three-phase conventional control strategy is difficult to meet the requirements, and a new control method needs to be studied to enable the Vienna rectifier circuit to work normally during phase loss. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the Vienna rectifier circuit cannot work normally when any one of the three phases is missing.

[0005] To solve the above technical problem, the technical solution of the present invention is to provide a method for controlling phase loss of a Vienna rectifier circuit. The Vienna rectifier circuit is a conventional circuit composed of a three-phase power supply, three-phase inductors, six rectifier diodes, three bidirectional switches each composed of two common-source MOS tubes, a series bus capacitor, and a load. The phase-loss control method is characterized by including the following steps:

[0006] Simultaneously execute the three-phase conventional control strategy and the three-phase phase-loss control strategy, and the phase-loss switching control unit selects one of the driving signals generated by the three-phase conventional control strategy or the three-phase phase-loss control strategy according to the phase-loss information detected by the phase-locked and phase-loss detection unit as the final driving signal to drive the driving circuit to drive the Vienna rectifier circuit, so as to realize that the Vienna rectifier circuit can work normally and stably under normal conditions or phase-loss conditions.

[0007] Preferably, the phase-loss switching control unit receives the phase-loss information generated by the phase-locked and phase-loss detection unit to switch between two operating states, namely the normal operating state and the phase-loss operating state;

[0008] When switching between the two operating states, the measure of blocking the three-phase PWM wave is adopted to make the output voltage not fluctuate violently during the operating state switching.

[0009] When the open - phase switching control unit switches to the normal operation state, the open - phase switching control unit selects the driving signal generated by the three - phase conventional control strategy as the final driving signal for the driving circuit; when the open - phase switching control unit switches to the open - phase operation state, the open - phase switching control unit selects the driving signal generated by the three - phase open - phase control strategy as the final driving signal for the driving circuit.

[0010] Preferably, the three - phase conventional control strategy is based on the double - loop control of voltage and current in the dq coordinate system, and the driving signals d a1 、d b1 、d c1 .

[0011] Preferably, the implementation of the three - phase conventional control strategy includes the following steps:

[0012] Step 1: Compare the given voltage U oref with the output voltage U o of the Vienna rectifier circuit collected. The error value between the given voltage U oref and the output voltage U o is calculated by the voltage controller to obtain the d - axis current given value

[0013] Step 2: Compare the d - axis current given value obtained in Step 1 with the d - axis current feedback value i d obtained by dq transformation of the three - phase current input to the Vienna rectifier circuit. The error value between the d - axis current given value and the d - axis current feedback value i d is calculated by the current controller to obtain the d - axis control value u d ; compare the q - axis current given value with the q - axis current feedback value i q obtained by dq transformation of the three - phase current input to the Vienna rectifier circuit. The error value between the q - axis current given value and the q - axis current feedback value i q is calculated by the current controller to obtain the q - axis control value u q ;

[0014] Step 3: The u d 、u q obtained in Step 2 are transformed from dq to αβ to obtain u α 、u β , and then the driving signals d a1 、db1 and d c1 and sent to the open - phase switching control unit.

[0015] Preferably, the open - phase control strategy is based on the double - loop control of voltage and current in the natural coordinate system, and the driving signals d a2 and d b2 and d c2 .

[0016] Preferably, the implementation of the open - phase control strategy includes the following steps:

[0017] Step 1: Compare the given voltage U oref with the output voltage U o of the Vienna rectifier circuit collected. The error value between the given voltage U oref and the output voltage U o is calculated by the voltage controller to obtain the d - axis current given value

[0018] Step 2: Multiply the d - axis current given value obtained in Step 1 by the absolute value of the phase sinβ of the two non - defective phases obtained by the phase - locked loop through the three - phase voltages input to the Vienna rectifier circuit to obtain the current - loop given i ref . Take the absolute value of any non - open - phase current as the current feedback |i ？ |. The difference between the current - loop given i ref and the current feedback |i ？ | is passed through the current controller to obtain the control command u;

[0019] Step 3: The control command u obtained in Step 2 is modulated by PWM to obtain the driving signals d a2 and d b2 and d c2 and sent to the open - phase switching control unit.

[0020] Preferably, the implementation of the open - phase switching control unit includes the following steps:

[0021] Step 1: Judge the current operating state. If it is in the normal operating state, execute the second step; if it is in the open - phase operating state, execute Step 5;

[0022] Step 2: Judge whether an open - phase occurs. If no open - phase occurs, execute the first step; if an open - phase occurs, identify which phase has an open - phase and execute Step 3;

[0023] Step 3: If phase A has an open - phase, to prevent the DC voltage from jumping due to the open - phase, block the PWM waves of the three phases and start the wave - blocking timer T a ; at the same time, take the current i bAssign to the feedback current i in the open-phase control strategy ？ ;

[0024] If phase B is open, to prevent the DC voltage from jumping due to the open phase, block the PWM waves of the three phases and start the wave-blocking timer T b ; At the same time, assign the current i of phase A a to the feedback current i in the open-phase control strategy ？ ;

[0025] If phase C is open, to prevent the DC voltage from jumping due to the open phase, block the PWM waves of the three phases and start the wave-blocking timer T c ; At the same time, assign the current i of phase A a to the feedback current i in the open-phase control strategy ？ ;

[0026] Step Four: The wave-blocking timer T a , the wave-blocking timer T b or the wave-blocking timer T c After the timing reaches 1 ms, use the drive signals d a2 , d b2 , d c2 generated by the open-phase control strategy as the final drive signals Among them, if phase A is open, the drive signal of phase A is 0, which means blocking the drive of phase A. If phase B is open, the drive signal of phase B is 0, which means blocking the drive of phase B. If phase C is open, the drive signal of phase C is 0, which means blocking the drive of phase C; switch the operating state to the open-phase operating state and execute Step Five;

[0027] Step Five: Determine whether the open phase has been restored. If the open phase has not been restored, execute Step Five. If the open phase has been restored, execute Step Six;

[0028] Step Six: To prevent the DC voltage from jumping due to the restoration of the open phase, block the PWM waves of the three phases and start the wave-blocking timer T a , the wave-blocking timer T b or the wave-blocking timer T c ;

[0029] Step Seven: The wave-blocking timer T a , the wave-blocking timer T b or the wave-blocking timer T c After the timing reaches 1 ms, use the drive signals generated by the three-phase conventional control strategy as the final drive signals Switch the operating state to the normal operating state and execute Step Two.

[0030] Preferably, the inductance, rectifier diodes, MOS transistors, and series bus capacitors in the Vienna rectifier circuit are selected according to the current during two-phase operation, which is 1.732 times larger than the device selection of the conventional Vienna rectifier circuit, so as to achieve full-load normal operation during a phase loss.

[0031] The beneficial effects of the present invention are as follows: The phase-loss control method for a Vienna rectifier circuit provided by the present invention overcomes the drawback that the conventional control method of the Vienna rectifier circuit protects and shuts down when a phase is lost. When a phase loss occurs in the Vienna circuit, the present invention smoothly switches the three-phase conventional control strategy to the phase-loss control strategy to maintain the stability of the output voltage. After the phase loss is restored, it smoothly switches back to the three-phase conventional control strategy, enabling the Vienna rectifier circuit to operate normally in both three-phase and two-phase conditions, broadening the application range of the Vienna rectifier circuit and having a certain practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a control block diagram of a phase-loss control method for a Vienna rectifier circuit according to the present invention;

[0033] Figure 2 It is a flowchart of the phase-loss switching control unit according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The following further elaborates the present invention in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0035] As Figure 1 shown, it is a control block diagram of a phase-loss control method for a Vienna rectifier circuit disclosed by the present invention. In the present invention, the Vienna rectifier circuit is a conventional circuit, which is composed of a three-phase power supply, three-phase inductors, six rectifier diodes, three bidirectional switches, two series bus capacitors, and a load. The three-phase inductors L a , L b , L c are respectively connected in series at both ends of the three-phase power supplies U a , U b , U c and the diodes D ap , D an , D bp , D bn , D cp , D cn . One end of the bidirectional switches S a , S b , S c is respectively connected to the A, B, and C terminals, and the other end is connected to the two series bus capacitors Cf1 , the N-terminal of C f2 , the load is connected in parallel between the positive and negative poles of the bus.

[0036] As Figure 1 shown in the control block diagram of the open-phase control method for a Vienna rectifier circuit, both the three-phase conventional control strategy and the open-phase control strategy are executed. The open-phase switching control unit selects one of the driving signals generated by the above two control strategies as the final driving signal according to the open-phase information detected by the phase-locked and open-phase detection unit to the driving circuit, so as to realize the normal and stable operation of the Vienna rectifier circuit under normal or open-phase conditions.

[0037] As Figure 1 shown in the control block diagram of the open-phase control method for a Vienna rectifier circuit, the three-phase conventional control strategy is a double-loop control of voltage and current loops based on dq coordinates, and the driving signal d is obtained through space vector modulation a1 , d b1 , d c1 ; the open-phase control strategy is a double-loop control of voltage and current loops in the natural coordinate system, and the driving signals d a2 , d b2 , d c2 are obtained through PWM modulation; the three-phase conventional control strategy and the open-phase control strategy share the voltage loop and the phase-locked and open-phase detection unit, saving digital processor resources.

[0038] As Figure 1 shown in the control block diagram of the open-phase control method for a Vienna rectifier circuit, the phase-locked and open-phase detection unit detects the phase signals sinα and cosα during normal operation for use in coordinate transformation. At the same time, the phase signal sinβ of the remaining two phases during open-phase is detected as the phase during open-phase, so as to achieve power factor correction and low input current THD under both control strategies.

[0039] As Figure 2 shown in the flowchart of the open-phase switching control unit, it receives the open-phase information generated by the phase-locked and open-phase detection unit to switch between the two operating states of normal operation and open-phase operation, and adopts the measure of blocking the three-phase PWM wave during switching to make the output voltage not fluctuate violently during state switching.

[0040] The following combines Figure 2 to illustrate the specific implementation process of the present invention by way of example.

[0041] Initially, the three-phase power supply is normal, and the Vienna rectifier circuit operates in the normal operation state. The open-phase switching control unit uses the driving signals d a1 , d b1 , d c1It is sent to the drive circuit as the final drive signal to enable the normal operation of the conventional Vienna circuit.

[0042] During operation, the A phase suddenly loses phase due to some reason. After the phase-locked and phase-loss detection unit detects the phase loss of the A phase, it notifies the phase-loss switching control unit and sends the phase sinβ between the B and C phases to the phase-loss control strategy. After receiving the phase-loss information of the A phase, the phase-loss switching control unit blocks the PWM waves of the three phases and starts the wave-blocking timing; at the same time, it assigns the B-phase current i b to the feedback current i in the phase-loss control strategy ？ .

[0043] After the wave-blocking timing reaches 1 ms, the drive signal generated by the phase-loss control strategy is used as the final drive signal. It should be noted that the drive signal of the A phase is 0, that is, the drive of the A phase is blocked, and the drive signals of the B and C phases are the same; the operating state switches to the phase-loss operating state.

[0044] During the phase-loss operation, the A phase recovers. After the phase-locked and phase-loss detection unit detects the recovery of the A phase, it notifies the phase-loss switching control unit and sends the phase information sinα and cosα of the three phases to the three-phase conventional control strategy. After receiving the phase-loss information of the A phase, the phase-loss switching control unit blocks the PWM waves of the three phases and starts the wave-blocking timing.

[0045] After the wave-blocking timing reaches 1 ms, the drive signal generated by the three-phase conventional control strategy is used as the final drive signal, and the operating state switches to the normal operating state.

[0046] The phase-loss conditions of the B and C phases are similar to those of the A phase. Those skilled in the art can refer to the above description and combine Figure 2 the relevant technical solutions, which will not be elaborated here.

Claims

1. A method for controlling the phase loss of a Vienna rectifier circuit, the Vienna rectifier circuit being a conventional circuit composed of a three-phase power supply, three-phase inductors, six rectifier diodes, three bidirectional switches each consisting of two common-source MOS transistors, a series bus capacitor, and a load, characterized in that, The open-phase control method includes the following steps: Execute the three-phase conventional control strategy and the three-phase open-phase control strategy simultaneously. The open-phase switching control unit selects one of the driving signals generated by the three-phase conventional control strategy or the three-phase open-phase control strategy according to the open-phase information detected by the phase-locked and open-phase detection unit as the final driving signal. Supply the driving circuit to drive the Vienna rectifier circuit, so as to realize the normal and stable operation of the Vienna rectifier circuit under normal conditions or open-phase conditions. The open-phase control strategy is based on the double-loop control of voltage and current loops in the natural coordinate system, and the driving signals d a2 , d b2 , d c2 are obtained through PWM modulation. Its implementation includes the following steps: Step 1: Apply the given voltage U oref and compare it with the output voltage U o of the collected Vienna rectifier circuit. The error value between the given voltage U oref and the output voltage U o is calculated by the voltage controller to obtain the d-axis current reference value Step 2, the d-axis current reference value obtained in Step 1 is multiplied by the absolute value of the phase sinβ of the two non-defective phases obtained by the phase-locked loop through the three-phase voltages input to the Vienna rectifier circuit to obtain the reference current i of the current loop ref , and the absolute value of any one of the non-phase-loss currents is used as the current feedback |i ？ |. The difference between the reference current i of the current loop ref and the current feedback |i ？ | passes through the current controller to obtain the control command u; Step 3: The control command u obtained in Step 2 is subjected to PWM modulation to obtain the drive signal d a2 , d b2 , d c2 , and sent to the open-phase switching control unit; The implementation of the open-phase switching control unit includes the following steps: Step 1, determine the current operating state. If it is in the normal operating state, execute Step 2. If it is in the open-phase operating state, execute Step 5; Step 2, determine whether an open phase occurs. If no open phase occurs, execute Step 1. If an open phase occurs, identify which phase has an open phase and execute Step 3; Step 3: If the A-phase is open-phase, to prevent the DC voltage from jumping due to the open-phase, block the PWM waves of the three phases and start the wave-blocking timer T a ; At the same time, assign the B-phase current i b to the feedback current i ？ in the open-phase control strategy; If phase B is open-phase, to prevent the DC voltage from jumping due to the open-phase, block the PWM waves of the three phases and start the wave-blocking timer T b ; At the same time, assign the current i a of phase A to the feedback current i ？ in the open-phase control strategy; If phase C is open-phase, to prevent the DC voltage from jumping due to open-phase, block the PWM waves of the three phases and start the wave-blocking timer T c ; At the same time, assign the current i a of phase A to the feedback current i ？ in the open-phase control strategy; Step Four: Wave-blocking Timer T a , Wave-blocking Timer T b or Wave-blocking Timer T c After the timing reaches 1 ms, use the driving signals d a2 , d b2 , d c2 generated by the open-phase control strategy as the final driving signals Among them, if phase A is open, the driving signal of phase A is 0, which means blocking the driving of phase A; if phase B is open, the driving signal of phase B is 0, which means blocking the driving of phase B; if phase C is open, the driving signal of phase C is 0, which means blocking the driving of phase C; switch the operating state to the open-phase operating state and execute Step Five; Step 5, determine whether the open phase is restored. If the open phase is not restored, execute Step 5. If the open phase is restored, execute Step 6; Step 6: To prevent the DC voltage from jumping during the restoration of a phase loss, block the PWM waves of the three phases and start the wave-blocking timer T a , wave-blocking timer T b or wave-blocking timer T c ; Step Seven: Wave-blocking Timer T a , Wave-blocking Timer T b or Wave-blocking Timer T c After the timing reaches 1 ms, use the drive signal generated by the three-phase conventional control strategy as the final drive signal Switch the operating state to the normal operating state and execute Step Two.

2. The phase loss control method of a Vienna rectifier circuit according to claim 1, characterized in that, The open-phase switching control unit receives the open-phase information generated by the phase-locked and open-phase detection unit to switch between two operating states: the normal operating state and the open-phase operating state; When switching between the two operating states, the measure of blocking the three-phase PWM wave is adopted to make the output voltage not fluctuate violently during the operating state switching; When the phase-loss switching control unit switches to the normal operation state, the phase-loss switching control unit selects the driving signal generated by the three-phase conventional control strategy as the final driving signal for the driving circuit; when the phase-loss switching control unit switches to the phase-loss operation state, the phase-loss switching control unit selects the driving signal generated by the three-phase phase-loss control strategy as the final driving signal for the driving circuit.

3. The phase-loss control method of a Vienna rectifier circuit according to claim 1, characterized in that The described three-phase conventional control strategy is based on the double-loop control of the voltage and current loops in the dq coordinate system, and the driving signals d a1 , d b1 , d c1 are obtained through space vector modulation.

4. The phase loss control method of a Vienna rectifier circuit according to claim 3, characterized in that The implementation of the three-phase conventional control strategy includes the following steps: Step 1: Apply the given voltage U oref Compare it with the output voltage U o of the Vienna rectifier circuit collected. The error value between the given voltage U oref and the output voltage U o is calculated by the voltage controller to obtain the d-axis current reference value Step 2, the d-axis current reference value obtained in Step 1 is compared with the d-axis current feedback value i obtained by dq transformation of the three-phase currents input to the Vienna rectifier circuit d . The error value between the d-axis current reference value and the d-axis current feedback value i d is calculated by the current controller to obtain the d-axis control value u d ; the q-axis current reference value is compared with the q-axis current feedback value i obtained by dq transformation of the three-phase currents input to the Vienna rectifier circuit q . The error value between the q-axis current reference value and the q-axis current feedback value i q is calculated by the current controller to obtain the q-axis control value u q ; Step 3: The u obtained in Step 2 d and u q are transformed from dq to αβ to obtain u α and u β , and then the drive signals d a1 , d b1 , and d c1 are obtained through space vector modulation and sent to the open-phase switching control unit.

5. The phase loss control method of a Vienna rectifier circuit according to claim 1, characterized in that, The inductance, rectifier diode, MOS transistor, and series bus capacitor in the Vienna rectifier circuit are selected according to the current when operating in two phases.

Images