CN102075097A - Method for controlling n+1 fault redundancy of cascade type converter - Google Patents

Abstract

The invention discloses a method for controlling the n+1 fault redundancy of a cascade type converter, which comprises the following steps of: firstly, carrying out balancing control based on the direct current voltage and capacitance of an H-bridge rectifier in UPF (Unity Power Factor) four quadrants; secondly, controlling the n+1 fault redundancy; and thirdly, adjusting a CPS-SPWM (Carrier Phase Shift- Sinusoidal Pulse Width Modulation) switch after a bypass has faults, i.e. correspondingly adjusting the modulation of the CPS-SPWM switch of residual n non-fault units and generating trigger pulse according the number of n-cascade units. According to the invention, the utilization rate of direct current side voltage of each power unit can be effectively improved and the switch loss, duldt and the fault rate of a power device can be reduced.

Description

A kind of cascade converter n+1 fault redundance control method

Technical field

The present invention relates to a kind of cascade converter n+1 fault redundance control method.

Background technology

The present many level current transformers of Cascade H bridge type are along with the increase of concatenated power element number, the failure rate of device increases greatly, thereby reduced the security reliability of operation, mainly exist at present the fault tolerant technique of three kinds of cascade connection type convertor assemblys: first kind is three symmetrical bypass modes, promptly after device the trouble unit of some occurs in mutually, three-phase all bypasses the unit of equal number, this method has been avoided the imbalance of three-phase voltage, but when bypassing trouble unit, also bypass the normal cell of non-fault in mutually, the device output capacity also decreases; Second method is a n+1 Redundant Control mode, promptly do not increase a standby redundancy unit mutually, when power cell fault of certain middle mutually appearance, with this trouble unit bypass, and do not influence the operate as normal of other non-fault phases, this fault-tolerant control technology realizes simple, reliable, but has reduced the voltage utilization of device operate as normal; The third method is the neutral point excursion technology, this method bypass trouble unit, the basic principle formula is by the phase place adjustment to the device three-phase output voltage, reach the target of output three-phase symmetric voltage, this method does not only consider at the controlled target of three-phase line voltage symmetry that the capacity of phase voltage exerts oneself, thereby mainly be applicable to the failure tolerant control of high voltage converter, and for the failure tolerant control of the convertor assemblys such as DSTATCOM that require three-phase phase-splitting control and inapplicable.

Summary of the invention

The invention provides a kind of cascade converter n+1 fault redundance control method, it can improve the dc voltage utilance of each power cell effectively, reduces switching loss, duldt and the failure rate of power device.

The present invention has adopted following technical scheme: step 1, at first the direct voltage electric capacity based on UPF four-quadrant H bridge rectifier carries out equilibrium control: each unit H bridge rectifier is by isolating transformer T _iConnect the AC power bus, wherein AC side filter inductance L _RiBe used for satisfying rectification of rectifier unity power factor and filter function requirement, i=1,2 ..., n, when capacitance voltage rises, control H bridge four-quadrant rectifier is in the UPF inverter mode, with the quick feedback communication electrical network of capacitive energy, capacitor discharge is when capacitance voltage descends, the control rectifier is in the UPF rectification state, absorbs the AC network energy and electric capacity is charged;

Step 2, the n+1 fault redundance is controlled: the voltage of DC side is U when establishing the operation of power cell quota _Dc, when normal operation, each unit n/ (n+1) rated capacity work, the voltage reference value of corresponding DC side is nU _Dc/ (n+1), when detect certain mutually in a certain power cell when breaking down, control system is sent this trouble unit of control command bypass, simultaneously, regulate this mutually in other n non-trouble unit DC reference voltage values, by UPF rectification control dc voltage is stabilized in U _Dc

Step 3, after the bypass fault to the adjustment of CPS-SPWM switch: at first, the CPS-SPWM pulse of Cascade H bridge type DSTATCOM generates sequential, gets cascade unit N=5, I _X1, I _X2, I _X3, I _X4Be respectively the upper and lower IGBT switching device of each a power cell left side upper and lower and right brachium pontis of brachium pontis, X=1......5; U _DcRepresent each unit dc voltage, each power cell carrier wave V _Rx, the time that x=1......5 staggers mutually is T _s=T _c/ 2N, wherein T _cBe carrier cycle, carrier wave V _RxPhase place and V _{Rx '}Differ 180 °, be used for forming the I of power cell x respectively _X1And I _X4Trigger impulse, u _sBe the SPWM modulating wave; At t _nConstantly, n=1......10, t _K+1=T _sBe one-period sample modulation ripple u _s, generate SPWM trigger impulse P _X1And P _X4, the corresponding respectively I that triggers _X1And I _X4, I _X2And I _X3Trigger impulse P _X2, P _X3Respectively with P _X1And P _X4On the contrary, add dead band time-delay in practice, x=1......5 establishes the carrier frequency 1/T of n+1 cascade unit _c, the sampling period is T _s, T then _s=T _c/ 2 (n+1), when certain mutually in a certain power cell break down and after by bypass, if still generate trigger impulse according to n+1 cascade unit number before the fault, then install output voltage owing to only be formed by stacking by n unit output voltage, harmonic content will increase, therefore, the CPS-SPWM switch modulation of n non-trouble unit of residue is made corresponding adjustment, promptly generate trigger impulse according to n cascade unit number.

Described rectifier adopts distributed autonomous control system, and on the one hand, the rectification control system of each unit operates in the UPF rectification state independently of one another, and on the other hand, the rectification control system of each unit is independent of master control system.

Described CPS-SPWM switch modulation to n non-trouble unit of residue is made corresponding adjustment and is adopted following method: T _cConstant, T _sChange, select the preceding cascade unit number n+1=5 of fault, then the sampling period T of each power cell _s=T _c/ 10, generate sequential in the CPS-SPWM pulse, at 0/5T _s, T _s/ 6T _s, 2T _s/ 7T _s, 3T _s/ 8T _s, 4T _s/ 9T _sConstantly, the sample modulation ripple generates power cell A successively ₁, A ₂, A ₃, A ₄, A ₅Trigger impulse, when a certain power cell broke down, it was constant to establish carrier cycle, was T _c, with the sampling period at T _cInterior redistribution is put, thereby owing to the sampling period after the cascade unit number n=4. modulation after the fault is T _s=T _c/ 8, generate sequential by 4 concatenated power unit CPS-SPWM pulses like this and trigger 4 non-trouble units of residue, will produce complete CPS-SPWM output voltage.

Described CPS-SPWM switch modulation to n non-trouble unit of residue is made corresponding adjustment and is adopted following method: T _cChange T _sIt is constant,, select the preceding cascade unit number n+1=5 of fault, then the sampling period T of each power cell _s=T _c/ 10, generate sequential in the CPS-SPWM pulse, at 0/5T _s, T _s/ 6T _s, 2T _s/ 7T _s, 3T _s/ 8T _s, 4T _s/ 9T _sConstantly, the sample modulation ripple generates power cell A successively ₁, A ₂, A ₃, A ₄, A ₅Trigger impulse, work as A ₂Break down, keep sampling period T _cConstant, the carrier cycle of fault phase is adjusted, establish adjusted carrier cycle T _{C '}', and the carrier cycle of other non-fault phases keeps T _cConstant, the carrier cycle T of adjusted fault phase _s' and adjust preceding T _{C '}Exist following relation:

It is 0/4T that adjusted CPS-SPWM pulse generates sequential _s, T _s/ 5T _s, 2T _s/ 6T _s, 3T _s/ 7T _s, the sample modulation ripple generates power cell A successively constantly ₁, A ₃, A ₄, A ₅Trigger impulse, therefore this method, still can guarantee the synchronism of three-phase current sampling because sampling period of fault phase does not change after the fault before and after fault.

The present invention has following beneficial effect: the present invention is when device is working properly, can improve the dc voltage utilance of each power cell effectively, reduce switching loss, duldt and the failure rate of power device, and when device occurs redundancy with interior power cell fault, device can in time be adjusted fault phase power output, and the compensation performance to device does not exert an influence, and in addition, the device output voltage remains good harmonic characterisitic before and after fault.Rectifier of the present invention adopts distributed autonomous control system, has like this that response speed is fast, AC power bus bar side output harmonic wave content is little, simple and reliable

Description of drawings

Fig. 1 is that the direct voltage electric capacity that the present invention is based on UPF four-quadrant H bridge rectifier carries out the balanced schematic diagram of controlling

Fig. 2 is the single-phase main circuit structure schematic diagram of Cascade H bridge type DSTATCOM of the present invention

Fig. 3 generates sequential chart for the SPWM pulse of concatenated power of the present invention unit

Fig. 4 for before the fault of the present invention, fault post-sampling period T _sAdjust forward and backward CPS-SPWM pulse and generate sequential chart

Fig. 5 is carrier cycle T of the present invention _cCPS-SPWM pulse before and after adjusting generates sequential chart

Embodiment

Embodiment one, the invention discloses a kind of cascade converter modified model n+1 fault redundance control method, it may further comprise the steps: step 1, at first the direct voltage electric capacity based on UPF four-quadrant H bridge rectifier carries out equilibrium control: in Fig. 1, each unit H bridge rectifier is by isolating transformer T _iConnect the AC power bus, wherein AC side filter inductance L _RiBe used for satisfying rectification of rectifier unity power factor and filter function requirement, i=1,2, ..., n, when capacitance voltage rises, control H bridge four-quadrant rectifier is in the UPF inverter mode, with the quick feedback communication electrical network of capacitive energy, capacitor discharge, when capacitance voltage descends, the control rectifier is in the UPF rectification state, absorbs the AC network energy and to the electric capacity charging, rectifier adopts distributed autonomous control system, on the one hand, the rectification control system of each unit operates in the UPF rectification state independently of one another, and on the other hand, the rectification control system of each unit is independent of master control system;

Step 2, the n+1 fault redundance is controlled: the voltage of DC side is U when establishing the operation of power cell quota _Dc, when normal operation, each unit n/ (n+1) rated capacity work, the voltage reference value of corresponding DC side is nU _Dc/ (n+1), when detect certain mutually in a certain power cell when breaking down, control system is sent this trouble unit of control command bypass, simultaneously, regulate this mutually in other n non-trouble unit DC reference voltage values, by UPF rectification control dc voltage is stabilized in U _Dc

Step 3, after the bypass fault to the adjustment of CPS-SPWM switch: in Fig. 2, at first, the CPS-SPWM pulse of Cascade H bridge type DSTATCOM generates sequential, gets cascade unit N=5, I _X1, I _X2, I _X3, I _X4Be respectively the upper and lower IGBT switching device of each a power cell left side upper and lower and right brachium pontis of brachium pontis, X=1......5; U _DcRepresent each unit dc voltage, each power cell carrier wave V _Rx, the time that x=1......5 staggers mutually is T _s=T _c/ 2N, wherein T _cBe carrier cycle, the SPWM pulse of each power cell generates sequential and sees Fig. 3, carrier wave V _RxPhase place and V _{Rx '}Differ 180 °, be used for forming the I of power cell x respectively _X1And I _X4Trigger impulse, u _sBe the SPWM modulating wave;

At t _nConstantly, n=1......10, t _K+1=T _sBe one-period sample modulation ripple u _s, generate SPWM trigger impulse P _X1And P _X4, the corresponding respectively I that triggers _X1And I _X4, I _X2And I _X3Trigger impulse P _X2, P _X3Respectively with P _X1And P _X4On the contrary, add dead band time-delay in practice, x=1......5 establishes the carrier frequency 1/T of n+1 cascade unit _c, the sampling period is T _s, T then _s=T _c/ 2 (n+1), when certain mutually in a certain power cell break down and after by bypass, if still generate trigger impulse according to n+1 cascade unit number before the fault, then install output voltage owing to only be formed by stacking by n unit output voltage, harmonic content will increase, therefore, CPS-SPWM switch modulation to n non-trouble unit of residue is made corresponding adjustment, promptly generate trigger impulse according to n cascade unit number, in Fig. 4, the CPS-SPWM switch modulation of n non-trouble unit of residue is made corresponding adjustment adopt following method: T _cConstant, T _sChange, select the preceding cascade unit number n+1=5 of fault, then the sampling period T of each power cell _s=T _c/ 10, generate sequential in the CPS-SPWM pulse, at 0/5T _s, T _s/ 6T _s, 2T _s/ 7T _s, 3T _s/ 8T _S, 4T _s/ 9T _sConstantly, the sample modulation ripple generates power cell A successively ₁, A ₂, A ₃, A ₄, A ₅Trigger impulse, when a certain power cell broke down, it was constant to establish carrier cycle, was T _c, with the sampling period at T _cInterior redistribution is put, thereby owing to the sampling period after the cascade unit number n=4. modulation after the fault is T _s=T _c/ 8, generate sequential by 4 concatenated power unit CPS-SPWM pulses like this and trigger 4 non-trouble units of residue, will produce complete CPS-SPWM output voltage.

Embodiment two, the invention discloses a kind of cascade converter modified model n+1 fault redundance control method, and it may further comprise the steps: step 1, and at first the direct voltage electric capacity based on UPF four-quadrant H bridge rectifier carries out equilibrium control:

In Fig. 1, each unit H bridge rectifier connects AC power bus, wherein AC side filter inductance L by isolating transformer Ti _RiBe used for satisfying rectification of rectifier unity power factor and filter function requirement, i=1,2, ..., n, when capacitance voltage rises, control H bridge four-quadrant rectifier is in the UPF inverter mode, with the quick feedback communication electrical network of capacitive energy, capacitor discharge, when capacitance voltage descends, the control rectifier is in the UPF rectification state, absorbs the AC network energy and to the electric capacity charging, rectifier adopts distributed autonomous control system, on the one hand, the rectification control system of each unit operates in the UPF rectification state independently of one another, and on the other hand, the rectification control system of each unit is independent of master control system;

Step 2, the n+1 fault redundance is controlled: the voltage of DC side is U when establishing the operation of power cell quota _Dc, when normal operation, each unit n/ (n+1) rated capacity work, the voltage reference value of corresponding DC side is nU _Dc/ (n+1), when detect certain mutually in a certain power cell when breaking down, control system is sent this trouble unit of control command bypass, simultaneously, regulate this mutually in other n non-trouble unit DC reference voltage values, by UPF rectification control dc voltage is stabilized in U _Dc

Step 3, after the bypass fault to the adjustment of CPS-SPWM switch: in Fig. 2, at first, the CPS-SPWM pulse of Cascade H bridge type DSTATCOM generates sequential, gets cascade unit N=5, I _X1, I _X2, I _X3, I _X4Be respectively the upper and lower IGBT switching device of each a power cell left side upper and lower and right brachium pontis of brachium pontis, X=1......5; U _DcRepresent each unit dc voltage, each power cell carrier wave V _Rx, the time that x=1......5 staggers mutually is T _s=T _c/ 2N, wherein T _cBe carrier cycle, the SPWM pulse of each power cell generates sequential and sees Fig. 3, carrier wave V _RxPhase place and V _{Rx '}Differ 180 °, be used for forming the I of power cell x respectively _X1And I _X4Trigger impulse, u _sBe the SPWM modulating wave;

At t _nConstantly, n=1......10, t _K+1=T _sBe one-period sample modulation ripple u _s, generate SPWM trigger impulse P _X1And P _X4, the corresponding respectively I that triggers _X1And I _X4, I _X2And I _X3Trigger impulse P _X2, P _X3Respectively with P _X1And P _X4On the contrary, add dead band time-delay in practice, x=1......5 establishes the carrier frequency 1/T of n+1 cascade unit _c, the sampling period is T _s, T then _s=T _c/ 2 (n+1), when certain mutually in a certain power cell break down and after by bypass, if still generate trigger impulse according to n+1 cascade unit number before the fault, then install output voltage owing to only be formed by stacking by n unit output voltage, harmonic content will increase, therefore, CPS-SPWM switch modulation to n non-trouble unit of residue is made corresponding adjustment, promptly generate trigger impulse according to n cascade unit number, in Fig. 5, the CPS-SPWM switch modulation of n non-trouble unit of residue is made corresponding adjustment also can adopt following method: T _cChange T _sIt is constant,, select the preceding cascade unit number n+1=5 of fault, then the sampling period T of each power cell _s=T _c/ 10, generate sequential in the CPS-SPWM pulse, at 0/5T _s, T _s/ 6T _s, 2T _s/ 7T _s, 3T _s/ 8T _s, 4T _s/ 9T _sConstantly, the sample modulation ripple generates power cell A successively ₁, A ₂, A ₃, A ₄, A ₅Trigger impulse, work as A ₂Break down, keep sampling period T _cConstant, the carrier cycle of fault phase is adjusted, establish adjusted carrier cycle T _{C '}', and the carrier cycle of other non-fault phases keeps T _cConstant, the carrier cycle T of adjusted fault phase _{C '}' and adjust preceding T _{C '}Exist following relation: It is 0/4T that adjusted CPS-SPWM pulse generates sequential _s, T _s/ 5T _s, 2T _s/ 6T _s, 3T _s/ 7T _s, the sample modulation ripple generates power cell A successively constantly ₁, A ₃, A ₄, A ₅Trigger impulse, therefore this method, still can guarantee the synchronism of three-phase current sampling because sampling period of fault phase does not change after the fault before and after fault.

Claims (4)

1. cascade converter n+1 fault redundance control method, it may further comprise the steps:

Step 1, at first the direct voltage electric capacity based on UPF four-quadrant H bridge rectifier carries out equilibrium control: each unit H bridge rectifier is by isolating transformer T _iConnect the AC power bus, wherein AC side filter inductance L _RiBe used for satisfying rectification of rectifier unity power factor and filter function requirement, i=1,2 ..., n, when capacitance voltage rises, control H bridge four-quadrant rectifier is in the UPF inverter mode, with the quick feedback communication electrical network of capacitive energy, capacitor discharge is when capacitance voltage descends, the control rectifier is in the UPF rectification state, absorbs the AC network energy and electric capacity is charged;

Step 2, the n+1 fault redundance is controlled: the voltage of DC side is U when establishing the operation of power cell quota _Dc, when normal operation, each unit n/ (n+1) rated capacity work, the voltage reference value of corresponding DC side is nU _Dc/ (n+1), when detect certain mutually in a certain power cell when breaking down, control system is sent this trouble unit of control command bypass, simultaneously, regulate this mutually in other n non-trouble unit DC reference voltage values, by UPF rectification control dc voltage is stabilized in U _Dc

Step 3, after the bypass fault to the adjustment of CPS-SPWM switch: at first, the CPS-SPWM pulse of Cascade H bridge type DSTATCOM generates sequential, gets cascade unit N=5, I _X1, I _X2, I _X3, I _X4Be respectively the upper and lower IGBT switching device of each a power cell left side upper and lower and right brachium pontis of brachium pontis, X=1......5; U _DcRepresent each unit dc voltage, each power cell carrier wave V _Rx, the time that x=1......5 staggers mutually is T _s=T _c/ 2N, wherein T _cBe carrier cycle, carrier wave V _RxPhase place and V _{Rx '}Differ 180 °, be used for forming the I of power cell x respectively _X1And I _X4Trigger impulse, u _sBe the SPWM modulating wave; At t _nConstantly, n=1......10, t _K+1=T _sBe one-period sample modulation ripple u _s, generate SPWM trigger impulse P _X1And P _X4, the corresponding respectively I that triggers _X1And I _X4, I _X2And I _X3Trigger impulse P _X2, P _X3Respectively with P _X1And P _X4On the contrary, add dead band time-delay in practice, x=1......5 establishes the carrier frequency 1/T of n+1 cascade unit _c, the sampling period is T _s, T then _s=T _c/ 2 (n+1), when certain mutually in a certain power cell break down and after by bypass, if still generate trigger impulse according to n+1 cascade unit number before the fault, then install output voltage owing to only be formed by stacking by n unit output voltage, harmonic content will increase, therefore, the CPS-SPWM switch modulation of n non-trouble unit of residue is made corresponding adjustment, promptly generate trigger impulse according to n cascade unit number.

2. cascade converter n+1 fault redundance control method according to claim 1, it is characterized in that described rectifier adopts distributed autonomous control system, on the one hand, the rectification control system of each unit operates in the UPF rectification state independently of one another, on the other hand, the rectification control system of each unit is independent of master control system.

3. cascade converter n+1 fault redundance control method according to claim 1 is characterized in that described CPS-SPWM switch modulation to residue n non-trouble unit makes corresponding adjustment and adopt following method: T _cConstant, T _sChange, select the preceding cascade unit number n+1=5 of fault, then the sampling period T of each power cell _s=T _c/ 10, generate sequential in the CPS-SPWM pulse, at 0/5T _s, T _s/ 6T _s, 2T _s/ 7T _s, 3T _s/ 8T _s, 4T _s/ 9T _sConstantly, the sample modulation ripple generates power cell A successively ₁, A ₂, A ₃, A ₄, A ₅Trigger impulse, when a certain power cell broke down, it was constant to establish carrier cycle, was T _c, with the sampling period at T _cInterior redistribution is put, thereby owing to the sampling period after the cascade unit number n=4. modulation after the fault is T _s=T _c/ 8, generate sequential by 4 concatenated power unit CPS-SPWM pulses like this and trigger 4 non-trouble units of residue, will produce complete CPS-SPWM output voltage.

4. cascade converter n+1 fault redundance control method according to claim 1 is characterized in that described CPS-SPWM switch modulation to residue n non-trouble unit makes corresponding adjustment and adopt following method: T _cChange T _sIt is constant,, select the preceding cascade unit number n+1=5 of fault, then the sampling period T of each power cell _s=T _c/ 10, generate sequential in the CPS-SPWM pulse, at 0/5T _s, T _s/ 6T _s, 2T _s/ 7T _s, 3T _s/ 8T _s, 4T _s/ 9T _sConstantly, the sample modulation ripple generates power cell A successively ₁, A ₂, A ₃, A ₄, A ₅Trigger impulse, work as A ₂Break down, keep sampling period T _cConstant, the carrier cycle of fault phase is adjusted, establish adjusted carrier cycle T _{C '}', and the carrier cycle of other non-fault phases keeps T _cConstant, the carrier cycle T of adjusted fault phase _{C '}' and adjust preceding T _{C '}Exist following relation:

It is 0/4T that adjusted CPS-SPWM pulse generates sequential _s, T _s/ 5T _s, 2T _s/ 6T _s, 3T _s/ 7T _s, the sample modulation ripple generates power cell A successively constantly ₁, A ₃, A ₄, A ₅Trigger impulse, therefore this method, still can guarantee the synchronism of three-phase current sampling because sampling period of fault phase does not change after the fault before and after fault.

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