CN105808901A - Method for determining on-state loss of modularized multilevel converter - Google Patents

Abstract

The invention relates to a method for determining on-state loss of a modularized multilevel converter. The method comprises the steps of determining IGBT (Insulated Gate Bipolar Transistor) on-state loss in single-phase upper and lower bridge arms of the modularized multilevel converter; determining diode on-state loss in the single-phase upper and lower bridge arms of the modularized multilevel converter; and determining three-phase on-state loss of the modularized multilevel converter. According to the method, an analytic expression of the on-state loss of the modularized multilevel converter is effectively solved based on instantaneous currents of an IGBT and a diode, thereby facilitating quantitative analysis of the on-state loss of the MMC (modularized multilevel converter) and bringing convenience for system optimization design.

Description

A kind of defining method of modularization multi-level converter on-state loss

Technical field

The present invention relates to the computational methods of a kind of Power Electronic Technique, in particular to the defining method of a kind of modularization multi-level converter on-state loss.

Background technology

From 2002, R.Marquart and the A.Lesnicar of the National Defence University of Munich, Germany federation proposes modularization multi-level converter (ModularMultilevelConverter jointly, MMC), MMC inverter obtains development widely and application due to its topological structure advantage in voltage-source type high voltage current changer field, and its topological structure is as shown in Figure 1.In based on the flexible direct current power transmission system of voltage source converter, Transbay Power System Interconnection engineering that Siemens Company in 2010 puts into operation in the U.S. and all adopt MMC inverter in the flexible DC power transmission demonstration project of Chinese Nanhui in 2011；In the high voltage DC transformers of direct current network, high pressure DC/DC changer (commutator transformer) based on MMC has become domestic and international study hotspot；In motor drag application, existing a large amount of scholar's research are based on the asynchronous machine frequency conversion control technique of MMC inverter.

In MMC inverter, main employing device for power switching is insulated gate bipolar transistor IGBT (InsulatedGateBipolarTransistor, IGBT).It is limited to the resistance to voltage levels of single IGBT, for meeting high voltage applications demand, its usage quantity is a lot, so what the loss of MMC inverter was mainly caused by device for power switching, and the operation stability of IGBT is also one of key factor of reliability service affecting whole system.The main cause of IGBT operational failure is that its junction temperature is too high, and therefore good Cooling Design and system optimization are the premises of system reliability service.Based in the flexible direct current power transmission system of MMC, system works in 50Hz, and the Loss Research of power device provides theory support for system Cooling Design, parameter type selecting etc.；Based in the high pressure DC/DC changer of MMC, system works in intermediate frequency operating mode (500Hz～1kHz), rising along with operating frequency, while in changer, the passive device such as electric capacity, inductance volume reduces, the loss of IGBT constant power device rises, and therefore to optimize the Loss Research of MMC in design essential for system loss and volume compromise；Based in the motor drag technology of MMC, system requires to work in frequency conversion operating mode according to speed governing, the loss calculation under need to studying the relation of MMC inverter loss and frequency and carrying out different frequency.

The appraisal procedure of power device loss can be divided into testing inspection, physical modeling and mathematical analysis three class.Method for testing and detecting is only applicable to low pressure small-power occasion, and the method for physical modeling will based on substantial amounts of device Fabrication parameter, it is difficult to obtain.Current MMC inverter Loss Research all adopts mathematical methods, according to some component characteristic parameters that manufacturer provides, the characterisitic function of fitting power device, and then carries out the loss evaluation based on power device average current and effective current or online loss calculation.Loss evaluation based on average current and effective current fails to provide the analytical expression of MMC loss, it is impossible to be simply obtained the quantitative relationship of MMC loss and inverter percentage modulation power factor, meritorious through-put power etc.；Online loss calculation needs to obtain the voltage in MMC inverter each moment, electric current and driving signal etc. and carries out computing, not strong in Optimized System Design stage utility, is difficult to and Optimized Program seamless connection.

Summary of the invention

For the deficiencies in the prior art, it is an object of the invention to provide the defining method of a kind of modularization multi-level converter on-state loss, the present invention is based on the transient current of IGBT and diode, effectively solve the analytical expression of modularization multi-level converter on-state loss, contribute to the quantitative analysis of MMC on-state loss, it is simple to the realization of Optimized System Design program.

It is an object of the invention to adopt following technical proposals to realize:

The present invention provides the defining method of a kind of modularization multi-level converter on-state loss, and described modular multilevel voltage source converter is made up of three-phase, is often made up of upper and lower two brachium pontis that the structure connected is identical；The exchange end of the midpoint connection mode massing multilevel converter of upper and lower two brachium pontis；

In described upper and lower two brachium pontis, each brachium pontis includes 1 reactor submodule identical with N number of structure；After the sub module cascade of each brachium pontis, one end is connected with the exchange end of modularization multi-level converter by reactor；After the sub module cascade of each brachium pontis, the other end is connected with submodule one end of the cascade of two other phase brachium pontis, forms the both positive and negative polarity bus of modular multilevel voltage source converter DC terminal；Described submodule is made up of the capacitor branches that half-bridge is connected in parallel, and described half-bridge is made up of upper brachium pontis and lower brachium pontis, and described upper brachium pontis and lower brachium pontis form by insulated gate bipolar transistor IGBT and fly-wheel diode FWD connected in parallel；

It thes improvement is that, described method comprises the steps:

Step 1: determine IGBT on-state loss in the single-phase upper and lower brachium pontis of modularization multi-level converter；

Step 2: determine diode on-state loss in the single-phase upper and lower brachium pontis of modularization multi-level converter；

Step 3: determine the three-phase on-state loss of modularization multi-level converter.

Further, described step 1 comprises the steps:

Step 1.1: the IGBT on-state voltage drop by under device relation curve matching and interpolation calculation normal operation junction temperature:

Utilize insulated gate bipolar transistor IGBT collection emitter voltage-collected current curve to carry out 25 ° and 125 ° of junction temperature matchings, draw the expression formula of IGBT collection emitter voltage and On current, as shown in following formula (1) and (2)；Recycling interpolation calculation obtains the relational expression of IGBT collection emitter voltage and On current under working junction temperature, as shown in following formula (3):

V_{ce_125}=U₁₂₅+R₁₂₅·i_T(1)；

V_{ce_25}=U₂₅+R₂₅·i_T(2)；

$V_{\mathrm{ce}\_\mathrm{Tj}}=(V_{\mathrm{ce}\_125}-V_{\mathrm{ce}\_25})\·\frac{T_j-25}{100}+V_{\mathrm{ce}25}=[(U_{125}-U_{25})\·\frac{T_j-25}{100}+U_{25}]+[(R_{125}-R_{25})\·\frac{T_j-25}{100}+R_{25}]\·i_T=U_{\mathrm{Tj}}+R_{\mathrm{Tj}}\·i_T---\left(3\right);$

Wherein: i_TOn current for IGBT；V_{ce_125}And V_{ce_25}Represent that IGBT junction temperature is the collection emitter voltage under 125 ° and 25 °, U₁₂₅And U₂₅Represent that IGBT junction temperature is the threshold voltage under 125 ° and 25 °, producer the relation curve matching of the collection emitter voltage-collected current provided；R₁₂₅And R₂₅For the forward conduction resistance under IGBT junction temperature 125 ° and 25 °, producer the relation curve matching of the collection emitter-base bandgap grading-collected current provided；T_jFor working junction temperature；V_{ce_Tj}Represent that IGBT junction temperature is T_jUnder collection emitter voltage；U_TjRepresent that IGBT junction temperature is T_jUnder threshold voltage；R_TjRepresent that IGBT junction temperature is T_jUnder forward conduction resistance；

Step 1.2: calculate the on-state loss in single half-bridge submodule；

Upper and lower bridge arm current is expressed as formula (4) and (5)；In submodule the condition of IGBTT1 conducting be IGBTT1 trigger signal for just and bridge arm current be negative, therefore the On current of IGBTT1 is expressed as formula (6)；The product of collection emitter voltage and the On current of IGBT turn-on instant exchanges to average in the primitive period at one and is achieved with the on-state loss of IGBT, and the on-state loss of IGBTT1 is expressed as following (7) formula:

i_T1=| i_arm|·G_T1·S_T1；(arm=up/down) (6)；

$P_{T1\mathrm{con}}=\frac{1}{T_s}\·{\∫}_t^{t+T_s}(V_{\mathrm{ce}\_\mathrm{Tj}}\·i_{T1})\mathrm{dt}=\frac{1}{T_s}\·{\∫}_t^{t+T_s}[(U_{\mathrm{Tj}}+R_{\mathrm{Tj}}\·i_{T1})\·i_{T1}]\mathrm{dt}---\left(7\right);$

Wherein: i_upFor upper bridge arm current；i_downFor lower bridge arm current；i_armFor bridge arm current；I_dElectric current for MMC Converter DC-side；I_mFor MMC inverter AC phase current peak value；θ is the phase angle of MMC inverter AC phase voltage；φ is the angle that MMC AC phase current lags behind phase voltage；i_T1For T1 On current；G_T1Driving signal for IGBTT1；S_T1For the conditional function of IGBTT1, when bridge arm current direction is for bearing, value is 1, and bridge arm current direction is timing value is 0；P_T1conIt is T for junction temperature_jThe on-state loss of lower IGBTT1；V_{ce_Tj}It is T for junction temperature_jThe collection emitter voltage of lower IGBTT1；Ts is the cycle of MMC inverter output AC voltage；

Step 1.3: the on-state loss of T1 in all submodules of brachium pontis in calculating:

If upper brachium pontis submodule number is n, and in each submodule, IGBT junction temperature is equal；Being added by the on-state loss of IGBT all in upper brachium pontis, obtaining the on-state loss of IGBTT1 in all submodules of upper brachium pontis is formula (8), and utilizes formula (6) to carry out abbreviation to obtain formula (9)；According to MMC operation mechanism, in each submodule of upper brachium pontis IGBTT1 drive signal and be expressed as formula (10):

$P_{\mathrm{up}{T}_{1-\mathrm{on}}}=\frac{1}{T_s}{\∫}_0^{T_s}{U}_{\mathrm{Tj}}\·(i_{T_{1-1}}+i_{T_{1-2}}+...+i_{T_{1-n}})+R_{\mathrm{Tj}}\·(i_{T_{1-1}}^2+...+i_{T_{1-n}}^2)\·\mathrm{dt}---\left(8\right);$

$P_{\mathrm{up}{T}_{1-\mathrm{on}}}=\frac{1}{T_s}{\∫}_0^{T_s}[(U_{\mathrm{Tj}}\·|i_{\mathrm{up}}|+R_{\mathrm{Tj}}\·{\left|i_{\mathrm{up}}\right|}^2)\·S_{T_1}(G_{T_{1-1}}+...+G_{T_{1-n}})]\·\mathrm{dt}---\left(9\right);$

$G_{T_{1-1}}+...+G_{T_{1-n}}=\frac{U_{d/2}-U_m\cos \mathrm{\θ}}{U_{d/n}}=\frac{n}{2}-n\frac{U_m}{U_d}\cos \mathrm{\θ}---\left(10\right);$

Wherein:For the on-state loss of IGBTT1 in all submodules of upper brachium pontis；The respectively On current of IGBTT1 in n upper brachium pontis submodule；The respectively driving signal of IGBTT1 in n upper brachium pontis submodule；U_dFor DC voltage；U_mPeak value for MMC inverter output single-phase alternating voltage；

Step 1.4: the on-state loss of IGBTT2 in all submodules of brachium pontis in calculating:

With reference to the computational methods of the on-state loss of T1 in all submodules in brachium pontis in step 1.2 and 1.3, the on-state loss of T2 in all submodules can be obtained in upper brachium pontis, as shown in following formula (11)；When being left out dead band, in submodule, the driving signal of IGBTT2 and IGBTT1 drive signal complementary, as shown in following formula (12)；That each submodule IGBTT2 of upper brachium pontis drives signal and be expressed as following formula (13):

$P_{\mathrm{up}{T}_{2-\mathrm{on}}}=\frac{1}{T_s}{\∫}_0^{T_s}[(U_{\mathrm{Tj}}\·|i_{\mathrm{up}}|+R_{\mathrm{Tj}}\·{\left|i_{\mathrm{up}}\right|}^2)\·S_{T_2}(G_{T_{2-1}}+...+G_{T_{2-n}})]\·\mathrm{dt}---\left(11\right);$

$G_{T_1}=~G_{T_2}---\left(12\right);$

$G_{T_{2-1}}+...+G_{T_{2-n}}=n-(\frac{n}{2}-n\frac{U_m}{U_d}\cos \mathrm{\θ})=\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ}---\left(13\right);$

Wherein:For the on-state loss of T2 in all submodules of upper brachium pontis；The respectively driving signal of T2 in n upper brachium pontis submodule；For the conditional function of T2, when bridge arm current direction is for being 0 time negative, bridge arm current direction is timing is 1；

Step 1.5: the on-state loss of all IGBT in brachium pontis in calculating:

The conduction loss of IGBTT1 and IGBTT2 all in upper brachium pontis is added, obtains the on-state loss of all IGBT in upper brachium pontis；According to upper bridge arm current zero crossing, it is three integration types by the on-state loss abbreviation of IGBT all in upper brachium pontis, as shown in formula (14):

$\begin{array}{c}{P}_{\mathrm{up}\_\mathrm{IGBTon}}=P_{\mathrm{up}{T}_{1-\mathrm{on}}}+P_{\mathrm{up}{T}_{2-\mathrm{on}}}=\frac{1}{2\mathrm{\π}}{\∫}_0^{{\mathrm{\θ}}_1}(U_{\mathrm{Tj}}\·i_{\mathrm{up}}+R_{\mathrm{Tj}}\·i_{\mathrm{up}}^2)\·(\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}+\\ \frac{1}{2\mathrm{\π}}{\∫}_{{\mathrm{\θ}}_1}^{{\mathrm{\θ}}_2}({-U}_{\mathrm{Tj}}\·i_{\mathrm{up}}+R_{\mathrm{Tj}}\·i_{\mathrm{up}}^2)\·(\frac{n}{2}-n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}+\frac{1}{2\mathrm{\π}}{\∫}_{{\mathrm{\θ}}_2}^{{\mathrm{\θ}}_1}(U_{\mathrm{Tj}}\·i_{\mathrm{up}}+R_{\mathrm{Tj}}\·i_{\mathrm{up}}^2)\·(\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}+\\ (\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}\end{array}---\left(14\right);$

Wherein, P_{up_IGBTon}On-state loss for IGBT all in upper brachium pontis；θ₁、θ₂Respectively go up angle corresponding during bridge arm current zero passage；

Step 1.6: calculate the on-state loss of the lower all IGBT of brachium pontis:

Calculate shown in the on-state loss such as following formula (15) of the lower all IGBT of brachium pontis:

$\begin{array}{c}{P}_{\mathrm{down}\_\mathrm{IGBTon}}=P_{\mathrm{down}{T}_{1-\mathrm{on}}}+P_{\mathrm{down}{T}_{2-\mathrm{on}}}=\frac{1}{T_s}{\∫}_0^{{\mathrm{\θ}}_{\′}^1}(-U_{\mathrm{Tj}}\·i_{\mathrm{down}}+R_{\mathrm{Tj}}\·i_{\mathrm{down}}^2)\·(\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}+\\ \frac{1}{T_s}{\∫}_{{\mathrm{\θ}}_{\′}^1}^{{\mathrm{\θ}}_{\′}^2}(U_{\mathrm{Tj}}\·i_{\mathrm{down}}+R_{\mathrm{Tj}}\·i_{\mathrm{down}}^2)\·(\frac{n}{2}-n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}\\ \frac{1}{T_s}{\∫}_{{\mathrm{\θ}}_2^{\′}}^{2\mathrm{\π}}({-U}_{\mathrm{Tj}}\·i_{\mathrm{down}}+R_{\mathrm{Tj}}\·i_{\mathrm{down}}^2)\·(\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}\end{array}---\left(15\right);$

Wherein: P_{down_IGBTon}On-state loss for all IGBT of lower brachium pontis；For the on-state loss sum of T1 in lower brachium pontis submodule；For the on-state loss sum of T2 in lower brachium pontis submodule；θ'₁、θ'₂Angle corresponding when respectively descending bridge arm current zero passage；

Step 1.7: calculate the on-state loss of all IGBT in upper and lower brachium pontis:

Step 1.5 and 1.6 gained on-state loss are added, obtain the on-state loss of all IGBT in upper and lower brachium pontis, and obtain formula (16) after upper and lower bridge arm current expression formula (4) and (5) are brought into abbreviation:

Further, described step 2 includes: in upper and lower brachium pontis shown in the on-state loss of all diodes such as following formula (17):

Wherein: P_DiodeonOn-state loss for diodes all in upper and lower brachium pontis；U_fFor the threshold voltage that diode junction temperature is under Tj；R_fFor the conducting resistance that diode junction temperature is under Tj.

Further, described step 3 comprises the steps:

Step 3.1: calculate the on-state loss of MMC inverter single-phase power device

The loss on the same stage of the IGBT on-state loss of step 1 and step 2 gained and diode is added, obtains the on-state loss of the single-phase all power devices of MMC inverter, as shown in following formula (18):

Wherein: P_{on_phase}On-state loss for MMC inverter single-phase power device；

Step 3.2: calculate the on-state loss of MMC inverter three phase power device:

Shown in the on-state loss such as following formula (19) of MMC inverter three phase power device:

P_{on_total}=3P_{on_phase}(19)；

Wherein: P_{on_total}On-state loss for MMC inverter three phase power device.

Compared with immediate prior art, the excellent effect that technical scheme provided by the invention has is:

1, MMC inverter on-state loss computational methods provided by the present invention be based on each power device conducting transient current push over, explicit physical meaning；

2, MMC inverter on-state loss computational methods provided by the present invention can calculate the on-state loss analytical expression obtaining each several part power device in MMC inverter, including the on-state loss of T1, T2, diode D1 and diode D2 in upper brachium pontis submodule, lower brachium pontis submodule and all submodules, contribute to realizing the relative analysis of each several part loss；

3, MMC inverter on-state loss calculation expression provided by the present invention can obtain the quantitative relationship of each several part on-state loss and inverter percentage modulation power factor, meritorious through-put power, it is simple to loss braking measure is studied；

4, MMC inverter on-state loss computational methods applied range provided by the present invention, it is possible to be applicable to the flexible direct current power transmission system based on MMC inverter, the isolated form DC/DC changer based on MMC and the motor drag equal loss based on MMC and analyze.

Accompanying drawing explanation

Fig. 1 is modularization multi-level converter circuit topology figure provided by the invention；

Fig. 2 is the topological diagram of modularization multi-level converter Neutron module provided by the invention；

Fig. 3 is the graph of relation of the IGBT collection emitter voltage-collected current provided for producer provided by the invention；

Fig. 4 is the graph of relation of diode turn-on voltage-forward current that producer provided by the invention provides；

Fig. 5 is MMC Inverter circuit oscillogram provided by the invention；Wherein (a) is bridge arm current waveform diagram on MMC inverter, and (b) is bridge arm current waveform diagram under MMC inverter.

Detailed description of the invention

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in further detail.

The present invention provides the defining method of a kind of modularization multi-level converter on-state loss, and wherein modular multilevel voltage source converter circuit topology figure is as it is shown in figure 1, be made up of three-phase, is often made up of upper and lower two brachium pontis that the structure connected is identical；The exchange end of the midpoint connection mode massing multilevel converter of upper and lower two brachium pontis；

In described upper and lower two brachium pontis, each brachium pontis includes 1 reactor submodule identical with N number of structure；After the sub module cascade of each brachium pontis, one end is connected with the exchange end of modularization multi-level converter by reactor；After the sub module cascade of each brachium pontis, the other end is connected with submodule one end of the cascade of two other phase brachium pontis, forms the both positive and negative polarity bus of modular multilevel voltage source converter DC terminal；Described submodule is made up of the capacitor branches that half-bridge is connected in parallel, and described half-bridge is made up of upper brachium pontis and lower brachium pontis, and described upper brachium pontis and lower brachium pontis form by insulated gate bipolar transistor IGBT and fly-wheel diode FWD connected in parallel；Comprise the steps:

Step 1: IGBT on-state loss in the single-phase upper and lower brachium pontis of computing module multilevel converter；

Step 2: diode on-state loss in the single-phase upper and lower brachium pontis of computing module multilevel converter；

Step 3: the three-phase on-state loss of computing module multilevel converter.

Described step 1 includes following sub-step:

Step 1.1: by the IGBT on-state voltage drop under device relation curve matching and interpolation calculation normal operation junction temperature；

The curve utilizing insulated gate bipolar transistor IGBT collection emitter voltage-collected current that production firm provides is fitted, and generally provides the curves under 25 ° and 125 ° two kinds test junction temperatures, as shown in Figure 3.Curve is fitted the relational expression that can draw 25 ° and 125 ° lower IGBT collection emitter voltages with On current, as shown in formula (1) and (2).Recycling interpolation calculation obtains the relational expression of IGBT collection emitter voltage and On current under working junction temperature, as shown in formula (3).

V_{ce_125}=U₁₂₅+R₁₂₅·i_T(1)；

V_{ce_25}=U₂₅+R₂₅·i_T(2)；

$V_{\mathrm{ce}\_\mathrm{Tj}}=(V_{\mathrm{ce}\_125}-V_{\mathrm{ce}\_25})\·\frac{T_j-25}{100}+V_{\mathrm{ce}25}=[(U_{125}-U_{25})\·\frac{T_j-25}{100}+U_{25}]+[(R_{125}-R_{25})\·\frac{T_j-25}{100}+R_{25}]\·i_T=U_{\mathrm{Tj}}+R_{\mathrm{Tj}}\·i_T---\left(3\right);$

Wherein: i_TOn current for IGBT；V_{ce_125}And V_{ce_25}Represent that IGBT junction temperature is the collection emitter voltage under 125 ° and 25 °, U₁₂₅And U₂₅Represent that IGBT junction temperature is the threshold voltage under 125 ° and 25 °, producer the relation curve matching of the collection emitter voltage-collected current provided；R₁₂₅And R₂₅For the forward conduction resistance under IGBT junction temperature 125 ° and 25 °, producer the relation curve matching of the collection emitter-base bandgap grading-collected current provided；T_jFor working junction temperature；V_{ce_Tj}Represent that IGBT junction temperature is T_jUnder collection emitter voltage；U_TjRepresent that IGBT junction temperature is T_jUnder threshold voltage；R_TjRepresent that IGBT junction temperature is T_jUnder forward conduction resistance.

Step 1.2: calculate the on-state loss of T1 in single half-bridge submodule:

For A phase, according to MMC operation mechanism, upper and lower bridge arm current is represented by formula (4) and (5), and it is substantially shown in waveform such as Fig. 5 (a) and (b).Obtained by half-bridge sub modular structure as shown in Figure 2, in submodule the condition of T1 conducting be T1 trigger signal for just and bridge arm current be negative, therefore the On current of T1 is expressed as formula (6)；The product of collection emitter voltage and the On current of IGBT turn-on instant exchanges to average in the primitive period at one and is achieved with the on-state loss of IGBT.Therefore, the on-state loss of T1 can be expressed as formula (7):

i_T1=| i_arm|·G_T1·S_T1；(arm=up/down) (6)；

$P_{T1\mathrm{con}}=\frac{1}{T_s}\·{\∫}_t^{t+T_s}(V_{\mathrm{ce}\_\mathrm{Tj}}\·i_{T1})\mathrm{dt}=\frac{1}{T_s}\·{\∫}_t^{t+T_s}[(U_{\mathrm{Tj}}+R_{\mathrm{Tj}}\·i_{T1})\·i_{T1}]\mathrm{dt}---\left(7\right);$

Wherein: i_upFor upper bridge arm current；i_downFor lower bridge arm current；Iarm is bridge arm current；I_dElectric current for MMC Converter DC-side；I_mFor MMC inverter AC phase current peak value；θ is the phase angle of MMC inverter AC phase voltage；φ is the angle that MMC AC phase current lags behind phase voltage；i_T1For T1 On current；G_T1Driving signal for T1；S_T1For the conditional function of T1, when bridge arm current direction is for bearing, value is 1, and bridge arm current direction is timing value is 0, and the positive direction of bridge arm current is as shown in Figure 1；P_T1conIt is T for junction temperature_jThe on-state loss of lower T1；V_{ce_Tj}It is T for junction temperature_jThe collection emitter voltage of lower T1；Ts is the cycle of MMC inverter output AC voltage.

Step 1.3: the on-state loss of T1 in all submodules of brachium pontis in calculating

Assume that upper brachium pontis submodule number is n, and in each submodule, IGBT junction temperature is equal.Being added by the on-state loss of upper IGBT all in upper brachium pontis, can go up the on-state loss of T1 in all submodules of brachium pontis is formula (8).And utilize formula (6) to carry out abbreviation to obtain formula (9).The submodule quantity used due to the modularization multi-level converter under high pressure applications is more, according to MMC operation mechanism, in each submodule of upper brachium pontis T1 drive signal and formula (10) can be expressed as.

$P_{\mathrm{up}{T}_{1-\mathrm{on}}}=\frac{1}{T_s}{\∫}_0^{T_s}{U}_{\mathrm{Tj}}\·(i_{T_{1-1}}+i_{T_{1-2}}+...+i_{T_{1-n}})+R_{\mathrm{Tj}}\·(i_{T_{1-1}}^2+...+i_{T_{1-n}}^2)\·\mathrm{dt}---\left(8\right);$

$P_{\mathrm{up}{T}_{1-\mathrm{on}}}=\frac{1}{T_s}{\∫}_0^{T_s}[(U_{\mathrm{Tj}}\·|i_{\mathrm{up}}|+R_{\mathrm{Tj}}\·{\left|i_{\mathrm{up}}\right|}^2)\·S_{T_1}(G_{T_{1-1}}+...+G_{T_{1-n}})]\·\mathrm{dt}---\left(9\right);$

$G_{T_{1-1}}+...+G_{T_{1-n}}=\frac{U_{d/2}-U_m\cos \mathrm{\θ}}{U_{d/n}}=\frac{n}{2}-n\frac{U_m}{U_d}\cos \mathrm{\θ}---\left(10\right);$

Wherein:For the on-state loss of T1 in all submodules of upper brachium pontis；The respectively On current of T1 in n upper brachium pontis submodule；The respectively driving signal of T1 in n upper brachium pontis submodule；U_dFor DC voltage；U_mPeak value for MMC inverter output single-phase alternating voltage.

Step 1.4: the on-state loss of T2 in all submodules of brachium pontis in calculating

With reference to the computational methods of the on-state loss of T1 in all submodules in brachium pontis in step 1.2 and 1.3, the on-state loss of T2 in all submodules can be obtained in upper brachium pontis, as shown in formula (11).When being left out dead band, in submodule, the driving signal of T2 and T1 drive signal complementary, are represented by formula (12).When group module number is more, that each submodule T2 of upper brachium pontis drives signal and formula (13) can be expressed as.

$P_{\mathrm{up}{T}_{2-\mathrm{on}}}=\frac{1}{T_s}{\∫}_0^{T_s}[(U_{\mathrm{Tj}}\·|i_{\mathrm{up}}|+R_{\mathrm{Tj}}\·{\left|i_{\mathrm{up}}\right|}^2)\·S_{T_2}(G_{T_{2-1}}+...+G_{T_{2-n}})]\·\mathrm{dt}---\left(11\right);$

$G_{T_1}=~G_{T_2}---\left(12\right);$

$G_{T_{2-1}}+...+G_{T_{2-n}}=n-(\frac{n}{2}-n\frac{U_m}{U_d}\cos \mathrm{\θ})=\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ}---\left(13\right);$

Wherein:For the on-state loss of T2 in all submodules of upper brachium pontis；The respectively driving signal of T2 in n upper brachium pontis submodule；For the conditional function of T2, when bridge arm current direction is for being 0 time negative, bridge arm current direction is timing is 1.

Step 1.5: the on-state loss of all IGBT in brachium pontis in calculating:

The conduction loss of T1 and T2 all in upper brachium pontis is added, the on-state loss of all IGBT in upper brachium pontis can be obtained.According to upper bridge arm current zero crossing, it is three integration types by the on-state loss abbreviation of IGBT all in upper brachium pontis, as shown in formula (14).

$\begin{array}{c}{P}_{\mathrm{up}\_\mathrm{IGBTon}}=P_{\mathrm{up}{T}_{1-\mathrm{on}}}+P_{\mathrm{up}{T}_{2-\mathrm{on}}}=\frac{1}{2\mathrm{\π}}{\∫}_0^{{\mathrm{\θ}}_1}(U_{\mathrm{Tj}}\·i_{\mathrm{up}}+R_{\mathrm{Tj}}\·i_{\mathrm{up}}^2)\·(\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}+\\ \frac{1}{2\mathrm{\π}}{\∫}_{{\mathrm{\θ}}_1}^{{\mathrm{\θ}}_2}({-U}_{\mathrm{Tj}}\·i_{\mathrm{up}}+R_{\mathrm{Tj}}\·i_{\mathrm{up}}^2)\·(\frac{n}{2}-n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}+\frac{1}{2\mathrm{\π}}{\∫}_{{\mathrm{\θ}}_2}^{{\mathrm{\θ}}_1}(U_{\mathrm{Tj}}\·i_{\mathrm{up}}+R_{\mathrm{Tj}}\·i_{\mathrm{up}}^2)\·(\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}+\\ (\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}\end{array}---\left(14\right);$

Wherein, P_{up_IGBTon}On-state loss for IGBT all in upper brachium pontis；_θ1、_θ2Respectively go up angle corresponding during bridge arm current zero passage, as shown in Fig. 5 (a).

Step 1.6: calculate the on-state loss of the lower all IGBT of brachium pontis:

Adopt and calculate same method with the on-state loss of all IGBT of upper brachium pontis, calculate shown in the on-state loss such as formula (15) of the lower all IGBT of brachium pontis.

$\begin{array}{c}{P}_{\mathrm{down}\_\mathrm{IGBTon}}=P_{\mathrm{down}{T}_{1-\mathrm{on}}}+P_{\mathrm{down}{T}_{2-\mathrm{on}}}=\frac{1}{T_s}{\∫}_0^{{\mathrm{\θ}}_{\′}^1}(-U_{\mathrm{Tj}}\·i_{\mathrm{down}}+R_{\mathrm{Tj}}\·i_{\mathrm{down}}^2)\·(\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}+\\ \frac{1}{T_s}{\∫}_{{\mathrm{\θ}}_{\′}^1}^{{\mathrm{\θ}}_{\′}^2}(U_{\mathrm{Tj}}\·i_{\mathrm{down}}+R_{\mathrm{Tj}}\·i_{\mathrm{down}}^2)\·(\frac{n}{2}-n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}\\ \frac{1}{T_s}{\∫}_{{\mathrm{\θ}}_2^{\′}}^{2\mathrm{\π}}({-U}_{\mathrm{Tj}}\·i_{\mathrm{down}}+R_{\mathrm{Tj}}\·i_{\mathrm{down}}^2)\·(\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}\end{array}---\left(15\right);$

Wherein: P_{down_IGBTon}On-state loss for all IGBT of lower brachium pontis；For the on-state loss sum of T1 in lower brachium pontis submodule；For the on-state loss sum of T2 in lower brachium pontis submodule；θ'₁、θ'₂Angle corresponding when respectively descending bridge arm current zero passage, as shown in Fig. 5 (b).

Step 1.7: calculate the on-state loss of all IGBT in upper and lower brachium pontis

Step 1.5 and 1.6 gained on-state loss are added, obtain the on-state loss of all IGBT in upper and lower brachium pontis, and obtain formula (16) after upper and lower bridge arm current expression formula (4) and (5) are brought into abbreviation

Step 2: calculate the on-state loss of all diodes in upper and lower brachium pontis

Adopt the computational methods same with step 1, it is possible to try to achieve the on-state loss of all diodes in upper and lower brachium pontis, as shown in formula (17).

Wherein: P_DiodeonOn-state loss for diodes all in upper and lower brachium pontis；U_fFor the threshold voltage that diode junction temperature is under Tj, producer relation curve matching the interpolated method of 125 ° and the 25 ° forward conduction voltage-On currents provided solve and obtain, and the relation curve of diode forward conducting voltage-On current is as shown in Figure 4；R_fFor the conducting resistance that diode junction temperature is under Tj, obtain after the interpolated computing of relation curve matching of 125 ° and 25 ° forward conduction voltage-On currents of the diode provided by producer equally.

Step 3: calculate the on-state loss of MMC inverter three phase power device:

Step 3.1: calculate the on-state loss of MMC inverter single-phase power device:

The loss of step 1 and step 2 gained is added, the on-state loss of the single-phase all power devices of MMC inverter can be obtained, as shown in formula (18).

Wherein: P_{on_phase}On-state loss for MMC inverter single-phase power device.

Step 3.2: calculate the on-state loss of MMC inverter three phase power device

Owing to MMC inverter three-phase symmetrical runs, the loss of threephase switch device is approximately the same, therefore the on-state loss of MMC inverter three phase power device is represented by formula (19):

P_{on_total}=3P_{on_phase}(19)；

Wherein: P_{on_total}On-state loss for MMC inverter three phase power device.

Finally should be noted that: above example is only in order to illustrate that technical scheme is not intended to limit; although the present invention being described in detail with reference to above-described embodiment; the specific embodiment of the present invention still can be modified or equivalent replacement by those of ordinary skill in the field; these are without departing from any amendment of spirit and scope of the invention or equivalent replace, within the claims of the present invention all awaited the reply in application.

Claims (4)

1. a defining method for modularization multi-level converter on-state loss, described modular multilevel voltage source converter is made up of three-phase, is often made up of upper and lower two brachium pontis that the structure connected is identical；The exchange end of the midpoint connection mode massing multilevel converter of upper and lower two brachium pontis；

In described upper and lower two brachium pontis, each brachium pontis includes 1 reactor submodule identical with N number of structure；After the sub module cascade of each brachium pontis, one end is connected with the exchange end of modularization multi-level converter by reactor；After the sub module cascade of each brachium pontis, the other end is connected with submodule one end of the cascade of two other phase brachium pontis, forms the both positive and negative polarity bus of modular multilevel voltage source converter DC terminal；Described submodule is made up of the capacitor branches that half-bridge is connected in parallel, and described half-bridge is made up of upper brachium pontis and lower brachium pontis, and described upper brachium pontis and lower brachium pontis form by insulated gate bipolar transistor IGBT and fly-wheel diode FWD connected in parallel；

It is characterized in that, described method comprises the steps:

Step 1: determine IGBT on-state loss in the single-phase upper and lower brachium pontis of modularization multi-level converter；

Step 2: determine diode on-state loss in the single-phase upper and lower brachium pontis of modularization multi-level converter；

Step 3: determine the three-phase on-state loss of modularization multi-level converter.

2. defining method as claimed in claim 1, it is characterised in that described step 1 comprises the steps:

Step 1.1: the IGBT on-state voltage drop by under device relation curve matching and interpolation calculation normal operation junction temperature:

Utilize insulated gate bipolar transistor IGBT collection emitter voltage-collected current curve to carry out 25 ° and 125 ° of junction temperature matchings, draw the expression formula of IGBT collection emitter voltage and On current, as shown in following formula (1) and (2)；Recycling interpolation calculation obtains the relational expression of IGBT collection emitter voltage and On current under working junction temperature, as shown in following formula (3):

V_{ce_125}=U₁₂₅+R₁₂₅·i_T(1)；

V_{ce_25}=U₂₅+R₂₅·i_T(2)；

$V_{\mathrm{ce}\_\mathrm{Tj}}=(V_{\mathrm{ce}\_125}-V_{\mathrm{ce}\_25})\·\frac{T_j-25}{100}+V_{\mathrm{ce}25}=[(U_{125}-U_{25})\·\frac{T_j-25}{100}+U_{25}]+[(R_{125}-R_{25})\·\frac{T_j-25}{100}+R_{25}]\·i_T=U_{\mathrm{Tj}}+R_{\mathrm{Tj}}\·i_T---\left(3\right);$

Wherein: i_TOn current for IGBT；V_{ce_125}And V_{ce_25}Represent that IGBT junction temperature is the collection emitter voltage under 125 ° and 25 °, U₁₂₅And U₂₅Represent that IGBT junction temperature is the threshold voltage under 125 ° and 25 °, producer the relation curve matching of the collection emitter voltage-collected current provided；R₁₂₅And R₂₅For the forward conduction resistance under IGBT junction temperature 125 ° and 25 °, producer the relation curve matching of the collection emitter-base bandgap grading-collected current provided；T_jFor working junction temperature；V_{ce_Tj}Represent that IGBT junction temperature is T_jUnder collection emitter voltage；U_TjRepresent that IGBT junction temperature is T_jUnder threshold voltage；R_TjRepresent that IGBT junction temperature is T_jUnder forward conduction resistance；

Step 1.2: calculate the on-state loss in single half-bridge submodule；

Upper and lower bridge arm current is expressed as formula (4) and (5)；In submodule the condition of IGBTT1 conducting be IGBTT1 trigger signal for just and bridge arm current be negative, therefore the On current of IGBTT1 is expressed as formula (6)；The product of collection emitter voltage and the On current of IGBT turn-on instant exchanges to average in the primitive period at one and is achieved with the on-state loss of IGBT, and the on-state loss of IGBTT1 is expressed as following (7) formula:

i_T1=| i_arm|·G_T1·S_T1；(arm=up/down) (6)；

$P_{T1\mathrm{con}}=\frac{1}{T_s}\·{\∫}_t^{t+T_s}(V_{\mathrm{ce}\_\mathrm{Tj}}\·i_{T1})\mathrm{dt}=\frac{1}{T_s}\·{\∫}_t^{t+T_s}[(U_{\mathrm{Tj}}+R_{\mathrm{Tj}}\·i_{T1})\·i_{T1}]\mathrm{dt}---\left(7\right);$

Wherein: i_upFor upper bridge arm current；i_downFor lower bridge arm current；i_armFor bridge arm current；I_dElectric current for MMC Converter DC-side；I_mFor MMC inverter AC phase current peak value；θ is the phase angle of MMC inverter AC phase voltage；φ is the angle that MMC AC phase current lags behind phase voltage；i_T1For T1 On current；G_T1Driving signal for IGBTT1；S_T1For the conditional function of IGBTT1, when bridge arm current direction is for bearing, value is 1, and bridge arm current direction is timing value is 0；P_T1conIt is T for junction temperature_jThe on-state loss of lower IGBTT1；V_{ce_Tj}It is T for junction temperature_jThe collection emitter voltage of lower IGBTT1；Ts is the cycle of MMC inverter output AC voltage；

Step 1.3: the on-state loss of T1 in all submodules of brachium pontis in calculating:

If upper brachium pontis submodule number is n, and in each submodule, IGBT junction temperature is equal；Being added by the on-state loss of IGBT all in upper brachium pontis, obtaining the on-state loss of IGBTT1 in all submodules of upper brachium pontis is formula (8), and utilizes formula (6) to carry out abbreviation to obtain formula (9)；According to MMC operation mechanism, in each submodule of upper brachium pontis IGBTT1 drive signal and be expressed as formula (10):

$P_{\mathrm{up}{T}_{1-\mathrm{on}}}=\frac{1}{T_s}{\∫}_0^{T_s}{U}_{\mathrm{Tj}}\·(i_{T_{1-1}}+i_{T_{1-2}}+...+i_{T_{1-n}})+R_{\mathrm{Tj}}\·(i_{T_{1-1}}^2+...+i_{t_{1-n}}^2)\·\mathrm{dt}---\left(8\right);$

$P_{\mathrm{up}{T}_{1-\mathrm{on}}}=\frac{1}{T_s}{\∫}_0^{T_s}[(U_{\mathrm{Tj}}\·|i_{\mathrm{up}}|+R_{\mathrm{Tj}}\·{\left|i_{\mathrm{up}}\right|}^2)\·S_{T_1}(G_{T_{1-1}}+...+G_{T_{1-n}})]\·\mathrm{dt}---\left(9\right);$

$G_{T_{1-1}}+...+G_{T_{1-n}}=\frac{U_{d/2}-U_m\cos \mathrm{\θ}}{U_{d/n}}=\frac{n}{2}-n\frac{U_m}{U_d}\cos \mathrm{\θ}---\left(10\right);$

Wherein:For the on-state loss of IGBTT1 in all submodules of upper brachium pontis；The respectively On current of IGBTT1 in n upper brachium pontis submodule；The respectively driving signal of IGBTT1 in n upper brachium pontis submodule；U_dFor DC voltage；U_mPeak value for MMC inverter output single-phase alternating voltage；

Step 1.4: the on-state loss of IGBTT2 in all submodules of brachium pontis in calculating:

With reference to the computational methods of the on-state loss of T1 in all submodules in brachium pontis in step 1.2 and 1.3, the on-state loss of T2 in all submodules can be obtained in upper brachium pontis, as shown in following formula (11)；When being left out dead band, in submodule, the driving signal of IGBTT2 and IGBTT1 drive signal complementary, as shown in following formula (12)；That each submodule IGBTT2 of upper brachium pontis drives signal and be expressed as following formula (13):

$P_{\mathrm{up}{T}_{2-\mathrm{on}}}=\frac{1}{T_s}{\∫}_0^{T_s}[(U_{\mathrm{Tj}}\·|i_{\mathrm{up}}|+R_{\mathrm{Tj}}\·{\left|i_{\mathrm{up}}\right|}^2)\·S_{T_{\text{2}}}(G_{T_{2-1}}+...+G_{T_{2-n}})]\·\mathrm{dt}---\left(11\right);$

$G_{T_1}=~G_{T_2}---\left(12\right);$

$G_{T_{2-1}}+...+G_{T_{2-n}}=n-(\frac{n}{2}-n\frac{U_m}{U_d}\cos \mathrm{\θ})=\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ}---\left(13\right);$

Wherein:For the on-state loss of T2 in all submodules of upper brachium pontis；The respectively driving signal of T2 in n upper brachium pontis submodule；For the conditional function of T2, when bridge arm current direction is for being 0 time negative, bridge arm current direction is timing is 1；

Step 1.5: the on-state loss of all IGBT in brachium pontis in calculating:

The conduction loss of IGBTT1 and IGBTT2 all in upper brachium pontis is added, obtains the on-state loss of all IGBT in upper brachium pontis；According to upper bridge arm current zero crossing, it is three integration types by the on-state loss abbreviation of IGBT all in upper brachium pontis, as shown in formula (14):

$\begin{array}{c}{P}_{\mathrm{up}\_\mathrm{IGBTon}}=P_{\mathrm{up}{T}_{1-\mathrm{on}}}+P_{\mathrm{up}{T}_{2-\mathrm{on}}}=\frac{1}{2\mathrm{\π}}{\∫}_0^{{\mathrm{\θ}}_1}(U_{\mathrm{Tj}}\·i_{\mathrm{up}}+R_{\mathrm{Tj}}\·i_{\mathrm{up}}^2)\·(\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}+\\ \frac{1}{2\mathrm{\π}}{\∫}_{{\mathrm{\θ}}_1}^{{\mathrm{\θ}}_2}(-U_{\mathrm{Tj}}\·i_{\mathrm{up}}+R_{\mathrm{Tj}}\·i_{\mathrm{up}}^2)\·(\frac{n}{2}-n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}+\frac{1}{2\mathrm{\π}}{\∫}_{{\mathrm{\θ}}_2}^{2\mathrm{\π}}(U_{\mathrm{Tj}}\·i_{\mathrm{up}}+R_{\mathrm{Tj}}\·i_{\mathrm{up}}^2).\\ (\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}\end{array}---\left(14\right);$

Wherein, P_{up_IGBTon}On-state loss for IGBT all in upper brachium pontis；θ₁、θ₂Respectively go up angle corresponding during bridge arm current zero passage；

Step 1.6: calculate the on-state loss of the lower all IGBT of brachium pontis:

Calculate shown in the on-state loss such as following formula (15) of the lower all IGBT of brachium pontis:

$\begin{array}{c}{P}_{\mathrm{down}\_\mathrm{IGBTon}}=P_{\mathrm{down}{T}_{1-\mathrm{on}}}+P_{\mathrm{down}{T}_{2-\mathrm{on}}}=\frac{1}{T_s}{\∫}_0^{{\mathrm{\θ}}_1^{\′}}(-U_{\mathrm{Tj}}\·i_{\mathrm{down}}+r_{\mathrm{Tj}}\·i_{\mathrm{down}}^2)\·(\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}+\\ \frac{1}{T_s}{\∫}_{{\mathrm{\θ}}_1^{\′}}^{{\mathrm{\θ}}_2^{\′}}(U_{\mathrm{Tj}}\·U_{\mathrm{Tj}}\·i_{\mathrm{down}}+R_{\mathrm{Tj}}\·i_{\mathrm{down}}^2)\·(\frac{n}{2}-n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}+\\ \frac{1}{T_s}{\∫}_{{\mathrm{\θ}}_2^{\′}}^{2\mathrm{\π}}(-U_{\mathrm{Tj}}\·i_{\mathrm{down}}+R_{\mathrm{Tj}}\·i_{\mathrm{down}}^2)\·(\frac{n}{2}+n\frac{U_m}{U_d}\cos \mathrm{\θ})\·\mathrm{d\θ}\end{array}---\left(15\right);$

Wherein: P_{down_IGBTon}On-state loss for all IGBT of lower brachium pontis；For the on-state loss sum of T1 in lower brachium pontis submodule；For the on-state loss sum of T2 in lower brachium pontis submodule；θ'₁、θ'₂Angle corresponding when respectively descending bridge arm current zero passage；

Step 1.7: calculate the on-state loss of all IGBT in upper and lower brachium pontis:

Step 1.5 and 1.6 gained on-state loss are added, obtain the on-state loss of all IGBT in upper and lower brachium pontis, and obtain formula (16) after upper and lower bridge arm current expression formula (4) and (5) are brought into abbreviation:

3. defining method as claimed in claim 1, it is characterised in that described step 2 includes: in upper and lower brachium pontis shown in the on-state loss of all diodes such as following formula (17):

Wherein: P_DiodeonOn-state loss for diodes all in upper and lower brachium pontis；U_fFor the threshold voltage that diode junction temperature is under Tj；R_fFor the conducting resistance that diode junction temperature is under Tj.

4. defining method as claimed in claim 1, it is characterised in that described step 3 comprises the steps:

Step 3.1: calculate the on-state loss of MMC inverter single-phase power device

The loss on the same stage of the IGBT on-state loss of step 1 and step 2 gained and diode is added, obtains the on-state loss of the single-phase all power devices of MMC inverter, as shown in following formula (18):

Wherein: P_{on_phase}On-state loss for MMC inverter single-phase power device；

Step 3.2: calculate the on-state loss of MMC inverter three phase power device:

Shown in the on-state loss such as following formula (19) of MMC inverter three phase power device:

P_{on_total}=3P_{on_phase}(19)；

Wherein: P_{on_total}On-state loss for MMC inverter three phase power device.