CN103269172A - Modular multi-level inverter bridge arm asymmetric control method - Google Patents

Abstract

The invention discloses a modular multi-level inverter bridge arm asymmetric control method which achieves good control over three-phase circulation flow asymmetry and direct current fluctuation caused by asymmetry of modular multi-level inverter bridge arms. The method includes a first step of determining the number of bridge arm rated submodules, rated capacitance voltage instruction values and rated average energy according to system capacity and voltage classes, a second step of detecting the number of the submodules, normally working actually, of each bridge arm and calculating an actual instruction value of capacitance voltage of each bridge arm according to the relation that the average energy of the bridge arms is equal to the rated average energy, and a third step of enabling the instruction value of the voltage of each bridge arm to divide the actual instruction value of the capacitance voltage of each bridge arm, and obtaining the number of the submodules, needing to be inputted actually, of each bridge arm. The modular multi-level inverter bridge arm asymmetric control method effectively restrains the three-phase circulation flow asymmetry and direct current fluctuation caused by asymmetry of the bridge arms.

Description

The asymmetric control method of a kind of modularization multi-level converter brachium pontis

Technical field

The present invention relates to power electronics and direct current transportation field, relate in particular to the control method under the asymmetric situation of a kind of modularization multi-level converter brachium pontis.

Technical background

Along with the development of regenerative resources such as wind-powered electricity generation, solar energy, it is also more and more deep that these distributed energies insert the research of electrical networks, these generation modes have randomness strong, away from characteristics such as trunk electrical networks.The flexible DC power transmission system has advantages such as the ability, AC system short circuit current limitation capability of meritorious idle quick decoupling zero control, is a kind of good regenerative resource and net mode.

Modularization multi-level converter is the converter that is applicable to flexible DC power transmission of a kind of novelty of occurring in recent years.Modularization multi-level converter is made up of 6 brachium pontis, each brachium pontis is composed in series by submodule and the brachium pontis reactor of some, by controlling the number that each brachium pontis drops into, excises submodule, make the output voltage that exchanges side approach AC sinusoidal voltage, the output voltage of DC side approaches direct voltage, realizes the stable operation of system.

6 brachium pontis submodule numbers equated that be called the brachium pontis symmetry status, 6 brachium pontis submodule numbers are not exclusively equal, are called the brachium pontis asymmetrical state when modularization multi-level converter normally moved.The brachium pontis asymmetrical state generally is owing to certain (a bit) brachium pontis has the parton module failure to be bypassed, and causes its submodule number to be less than other brachium pontis.The asymmetric of brachium pontis will cause the asymmetric and direct current fluctuation of modularization multi-level converter three phase circulations.

Summary of the invention

Purpose of the present invention is intended at the deficiencies in the prior art, has proposed the asymmetric control method of a kind of modularization multi-level converter brachium pontis,

The asymmetric control method of a kind of modularization multi-level converter brachium pontis, described modularization multi-level converter is made up of 6 brachium pontis, each brachium pontis is composed in series by submodule and brachium pontis reactor, by controlling the number that each brachium pontis drops into, excises submodule, make the output voltage that exchanges side approach AC sinusoidal voltage, the output voltage of DC side approaches direct voltage; When 6 brachium pontis submodule numbers not exclusively equated, the control step was as follows:

1) arbitrary brachium pontis submodule capacitor's capacity of establishing in 6 brachium pontis is C, and the specified submodule number of brachium pontis is N _Rated, the specified command value U of brachium pontis submodule capacitance voltage _Crated, the specified average energy of brachium pontis is W _Rated: $W_{\mathrm{rated}}={0.5\mathrm{CN}}_{\mathrm{rated}}{\mathrm{<figure-callout\; id="2"\; label="U\; Crated"\; filenames="130506163148.png"\; state="\{\{state\}\}">U</figure-callout>}}_{\mathrm{Crated}}^{};$

2) the actual submodule of establishing in 6 brachium pontis of arbitrary brachium pontis is counted N, capacitance voltage actual instruction value U _C, brachium pontis actual average energy is W:

3) equal specified average energy according to brachium pontis actual average energy, capacitance voltage actual instruction value U _CCalculating can get: $U_C=\sqrt{\frac{N_{\mathrm{rated}}}{N}}{U}_{\mathrm{Crated}};$

4) establishing the bridge arm voltage command value is U _Arm, then the brachium pontis actual submodule that need drop into is counted N _Arm: N _Arm=U _ArmU _C

4) the bridge arm voltage command value U described in _ArmBridge arm voltage command value for DSP or the generation of NI Compactrio controller; 4) N described in _ArmThe submodule number that the brachium pontis actual needs that produces for DSP or NI Compactrio controller drops into.

Beneficial effect of the present invention:

Comprise a large amount of submodules in the modularization multi-level converter, the probability of submodule fault is very high, so the asymmetric phenomenon of brachium pontis (be some or the submodule number of several brachium pontis and other brachium pontis unequal) appears in modularization multi-level converter easily.When brachium pontis is asymmetric, the direct current of modularization multi-level converter fails to be convened for lack of a quorum and produces a wave component, cause DC side loss and harmonic wave to increase, patent of the present invention can effectively suppress the asymmetric direct current fluctuation that brings of modularization multi-level converter brachium pontis, has lowered loss and harmonic wave.

Description of drawings

Fig. 1 is the structural representation of modularization multi-level converter.

Fig. 2 is the structural representation of brachium pontis submodule.

Fig. 3 is the control block diagram of the asymmetric control method of modularization multi-level converter brachium pontis.

Fig. 4 is the effect schematic diagram of the asymmetric control method of modularization multi-level converter brachium pontis.

Embodiment

Describe the present invention below with reference to the accompanying drawings in detail, it is more obvious that purpose of the present invention and effect will become.

The asymmetric control method of a kind of modularization multi-level converter brachium pontis, described modularization multi-level converter is made up of 6 brachium pontis, and each brachium pontis is composed in series by submodule and brachium pontis reactor, as shown in Figure 1.Figure 2 shows that the structure of brachium pontis submodule, submodule is formed in parallel with dc capacitor by the IGBT series connection of two band inverse parallel diodes again, and the tie point of two IGBT and dc capacitor negative pole are the output of submodule.By controlling the number that each brachium pontis drops into, excises submodule, make the output voltage that exchanges side approach AC sinusoidal voltage, the output voltage of DC side approaches direct voltage; When 6 brachium pontis submodule numbers not exclusively equate, control step following (as shown in Figure 3):

1) arbitrary brachium pontis submodule capacitor's capacity of establishing in 6 brachium pontis is C, and the specified submodule number of brachium pontis is N _Rated, the specified command value of brachium pontis submodule capacitance voltage is U _Crated, the specified average energy of brachium pontis is W _Rated:

Wherein, the capacitor's capacity C 1) is the appearance value of submodule electric capacity shown in Figure 2; 1) the specified submodule described in is counted N _RatedNumber for the specified submodule of each brachium pontis shown in Figure 1; 1) the rated capacity voltage U described in _CratedBe submodule rated capacity voltage shown in Figure 2; 1) the specified average energy W described in _RatedAverage energy for the specified submodule of brachium pontis shown in Figure 1.

2) the actual submodule of establishing in 6 brachium pontis of arbitrary brachium pontis is counted N, capacitance voltage actual instruction value U _C, brachium pontis actual average energy is W:

2) the actual submodule of the brachium pontis described in is counted the number that N is the actual submodule of each brachium pontis shown in Figure 1; 2) the capacitance voltage actual instruction value U described in _CActual capacitance voltage instruction value for submodule shown in Figure 2; 2) the brachium pontis actual average energy W described in is each brachium pontis submodule actual average energy shown in Figure 1.

3) equal specified average energy according to brachium pontis actual average energy, capacitance voltage actual instruction value U _CCalculating can get: $U_C=\sqrt{\frac{N_{\mathrm{rated}}}{N}}{U}_{\mathrm{Crated}};$

4) establishing the bridge arm voltage command value is U _Arm, then the brachium pontis actual submodule that need drop into is counted N _Arm: N _Arm=U _ArmU _C

4) the bridge arm voltage command value U described in _ArmBridge arm voltage command value for DSP or the generation of NI Compactrio controller; 4) N described in _ArmThe submodule number that the brachium pontis actual needs that produces for DSP or NI Compactrio controller drops into.

Embodiment

Modularization multi-level converter is as inverter work, and dc voltage is ± 30kV, and exchanging the side line voltage effective value is 35kV, and the specified submodule of brachium pontis is counted N _RatedBe 70, brachium pontis submodule rated capacity voltage instruction value U _CratedBe 1kV, submodule capacitor's capacity C is 8000uF, and during modularization multi-level converter brachium pontis symmetry, it is 70 that the actual submodule of brachium pontis is counted N.0s to 0.3s, modularization multi-level converter brachium pontis symmetry; 0.3s after, A goes up the actual submodule number of brachium pontis mutually and becomes 62, and all the other 5 brachium pontis submodule numbers are 70 still, during 0.3s to 0.5s, do not use method of the present invention, use method of the present invention behind the 0.5s.The design sketch that produces as shown in Figure 4.Be the direct current among the embodiment shown in Fig. 4, before the 0.3s, modularization multi-level converter brachium pontis symmetry, direct current is the Constant Direct Current amount; 0.3s during 0.5s, the modular multilevel brachium pontis is asymmetric, but does not use control method of the present invention, still uses conventional control method, fluctuation appears in direct current; 0.5s after, the control method of using the present invention to propose, the direct current fluctuation is suppressed well.

The above only is a specific embodiment of the present invention, does not constitute any limitation of the invention.All any modifications of doing within the spirit and principles in the present invention, be equal to and replace and improvement etc., all should be included within protection scope of the present invention.

Claims (2)

1. asymmetric control method of modularization multi-level converter brachium pontis, it is characterized in that, described modularization multi-level converter is made up of 6 brachium pontis, each brachium pontis is composed in series by submodule and brachium pontis reactor, by controlling the number that each brachium pontis drops into, excises submodule, make the output voltage that exchanges side approach AC sinusoidal voltage, the output voltage of DC side approaches direct voltage; When 6 brachium pontis submodule numbers not exclusively equated, the control step was as follows:

1) arbitrary brachium pontis submodule capacitor's capacity of establishing in 6 brachium pontis is C, and the specified submodule number of brachium pontis is N _Rated, the specified command value of brachium pontis submodule capacitance voltage is U _Crated, the specified average energy of brachium pontis is W _Rated: $W_{\mathrm{rated}}={0.5\mathrm{CN}}_{\mathrm{rated}}{U}_{\mathrm{Crated}}^2;$

2) the actual submodule of establishing in 6 brachium pontis of arbitrary brachium pontis is counted N, capacitance voltage actual instruction value U _C, brachium pontis actual average energy is W:

3) equal specified average energy according to brachium pontis actual average energy, capacitance voltage actual instruction value U _CCalculating can get: $U_C=\sqrt{\frac{N_{\mathrm{rated}}}{N}}{U}_{\mathrm{Crated}};$

4) establishing the bridge arm voltage command value is U _Arm, then the brachium pontis actual submodule that need drop into is counted N _Arm: N _Arm=U _ArmU _C

2. the asymmetric control method of modularization multi-level converter brachium pontis according to claim 1 is characterized in that 4) described in bridge arm voltage command value U _ArmBridge arm voltage command value for DSP or the generation of NI Compactrio controller; 4) N described in _ArmThe submodule number that the brachium pontis actual needs that produces for DSP or NI Compactrio controller drops into.

Images