CN112187083A - Power loss calculation method of three-level wind power converter - Google Patents

Abstract

The invention provides a power loss calculation method of a three-level wind power converter, which comprises the following steps: determining the relation between the conduction angle and the duty ratio of the switching tubes T1, T2 and T5 and the diodes D1, D2 and D5 under a modulation strategy; calculating the turn-on loss, the turn-off loss and the on-state loss of the switching tubes T1, T2 and T5 according to the turn-on angle and the duty ratio; and calculating the turn-off loss and the turn-on loss of the diodes D1, D2 and D5 according to the turn-on angle and the duty ratio. The invention provides a method for calculating the turn-on loss, the turn-off loss and the on-state loss of a switching tube and a method for calculating the turn-off loss and the on-state loss of a diode, starts from a model of the turn-on loss, the turn-off loss and the turn-on loss of a power device, and comprehensively considers the influence of a modulation strategy on the loss calculation of a wind power converter.

Description

A method for calculating the power loss of a three-level wind power converter

technical field

The invention belongs to the field of power devices, and in particular relates to a power loss calculation method of a three-level wind power converter.

Background technique

The power loss of switching devices is a major source of heat generation in the main circuit of the converter. Excessive switching device losses will lead to device temperature rise, system performance degradation and even inverter failure. Therefore, the estimation of switching device losses is very important, and it is extremely necessary for the design of the converter circuit, mechanical structure and cooling system. However, the estimation is also very complicated, and it has a certain relationship with the switching device characteristics of the converter, circuit topology, PWM (pulse width modulation) method, absorption circuit and circuit stray inductance. In conventional techniques, switching device losses are calculated by averaging the effects over a longer period of time. For the average value calculated according to the average effect, there are only a few simple ways to ensure the temperature rise of the switching device, such as turning on and off the absorption circuit at the same time, and designing the main parameters of the absorption circuit to be large enough. This scheme converts the power loss of the switching device into the loss of the absorption circuit at a relatively high cost. Alternatively, the cooling effect of the cooling system of the converter can be enhanced, and some air-cooled converters can be designed as water-cooled converters, but such measures increase the cost of the converter to a certain extent and reduce the cost of the converter. s efficiency. It is the inaccurate estimation of the power loss of the switching device that brings difficulties to the design and optimization of the entire system of the converter.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention provides a method for calculating the power loss of a three-level wind power converter.

The method for calculating the power loss of a three-level wind power converter provided by the present invention, wherein, the single-phase bridge arm in the three-level wind power converter includes switching transistors T1-T6, diodes D1-D6 and capacitors Cd1 and Cd2, Each of the switch transistors T1-T6 is in anti-parallel with the corresponding diode Di, i is an integer and 1≤i≤6, that is, the collector or anode of the switch transistor Ti is connected to the corresponding diode Di. The cathode of the diode Di, and the emitter or cathode of the switch tube Ti is connected to the anode of the corresponding diode Di, the switch tubes T1-T4 are connected in series in sequence, that is, the emitter or cathode of the previous switch tube is connected to The collector or anode of the latter switch tube; the positive pole of the capacitor Cd1 is connected to the collector or anode of the switch tube T1, and the negative pole of the capacitor Cd1 is connected to the positive pole of the capacitor Cd2 and the switch tube T5. Emitter or cathode; the cathode of the capacitor Cd2 is connected to the emitter or cathode of the switch tube T4; the collector or anode of the switch tube T5 is connected to the emitter or cathode of the switch tube T1, the switch The emitter or cathode of the tube T5 is connected to the collector or anode of the switch tube T6; the emitter or cathode of the switch tube T6 is connected to the collector or anode of the switch tube T4,

The power device loss calculation method includes:

Determine the relationship between the conduction angle of the switches T1, T2, T5 and the diodes D1, D2, D5 and the duty cycle;

Calculate the turn-on loss, turn-off loss, and on-state loss of the switch transistors T1, T2, and T5 according to the conduction angle and the duty cycle;

The turn-off loss and on-state loss of the diodes D1 , D2 and D5 are calculated according to the conduction angle and the duty cycle.

further,

Let α represent the power factor angle and M the modulation degree, then

When the conduction angle of the switch tube T1 is in the interval [0, π-α], the duty cycle is Msin(wt+α);

When the conduction angle of the diode D1 is in the interval [2π-α, 2π], the duty cycle is Msin(wt+α);

When the conduction angle of the switch tube T2 is in the interval [0, π], the duty cycle is (1+Msin(wt+α))/2;

When the conduction angle of the diode D2 is in the interval [π, 2π-α], the duty cycle is (1+Msin(wt+α))/2;

When the conduction angle of the diode D2 is in the interval [2π-α, 2π], the duty cycle is (1+Msin(wt+α))/2;

When the conduction angle of the switch tube T5 is in the interval [π, 2π-α], the duty ratio is (1+Msin(wt+α))/2;

When the conduction angle of the switch tube T5 is in the interval [2π-α, 2π], the duty ratio is (1-Msin(wt+α))/2;

When the conduction angle of the diode D5 is in the interval [0, π-α], the duty cycle is (1-Msin(wt+α))/2;

When the conduction angle of the diode D5 is in the interval [π-α, π], the duty ratio is (1+Msin(wt+α))/2.

further,

The turn-on losses of the switches T1, T2, and T5 are

in,

k₁是根据IGCT开通时开关条件与标准测试条件关系引入的修正系数，Q_on0是单脉冲开通能量，V_d0和i_L0是数据手册中的标准测试条件；I _p and U _m are the amplitudes of the single-phase bridge arm current I and voltage U, respectively, w is the frequency of the current I and voltage U, t represents time, f _sw is the switching frequency of the device,

k ₁ is the correction coefficient introduced according to the relationship between the switching conditions and the standard test conditions when the IGCT is turned on, Q _on0 is the single-pulse turn-on energy, and V _d0 and i _L0 are the standard test conditions in the data sheet;

The turn-off losses of the switches T1, T2, and T5 are

in,

k₂是根据所述开关管关断时开关条件与标准测试条件关系引入的修正系数，Q_off0为单脉冲关断能量；

k ₂ is a correction coefficient introduced according to the relationship between the switching condition and the standard test condition when the switch tube is turned off, and Q _off0 is the single-pulse turn-off energy;

The on-state losses of the switches T1, T2, and T5 are:

in,

V _T0 is the threshold voltage, and r _T is the slope resistance.

further,

The turn-off losses of the diodes D1, D2, D5 are

k₃是根据所述二极管关断时开关条件与标准测试条件关系引入的修正系数；in,

k ₃ is a correction coefficient introduced according to the relationship between the switching condition and the standard test condition when the diode is turned off;

The on-state losses of the diodes D1, D2, D5 are

further,

The loss of the switch tube T1 includes:

switching loss

On-state loss

further,

The loss of the switch tube T2 includes:

switching loss

On-state loss

further,

The loss of switch tube T5 includes:

switching loss

On-state loss

further,

The losses of the diode D1 include:

switching loss

On-state loss

further,

The losses of the diode D2 include:

switching loss

On-state loss

further,

The losses of the diode D5 include:

switching loss

On-state loss

The power loss calculation method of the three-level wind power converter of the present invention proposes a calculation method for the turn-on loss, turn-off loss and on-state loss of a switch tube and a calculation method for the turn-off loss and on-state loss of a diode. , turn-off and turn-on loss models, and comprehensively consider the influence of the modulation strategy on the loss calculation. The calculation method is more accurate than the traditional method, which can provide a theoretical and technical basis for the heat dissipation design and operation status evaluation of wind power converters.

Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure pointed out in the description, claims and drawings.

Description of drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are For some embodiments of the present invention, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

FIG. 1 shows an ANPC (Active-neutral-point-clamped) three-level single-phase bridge arm structure using the power loss calculation method of the present invention;

FIG. 2 shows a schematic diagram of the relationship between voltage and current in a modulation period according to an embodiment of the present invention.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Figure 1 shows the structure diagram of the ANPC three-level single-phase bridge arm of the three-level wind power converter. It can be seen from FIG. 1 that the single-phase bridge arm includes switch transistors T1-T6, diodes D1-D6, and capacitors Cd1 and Cd2. Among them, the switch tubes T1-T6 are all fully controlled power electronic devices such as IGCT (Integrated Gate Commutated Thyristor). Assuming that each switch tube Ti (i is an integer and 1≤i≤6) is an IGCT, in the ANPC three-level single-phase bridge arm, each of the switch tubes Ti is in antiparallel with the corresponding diode Di, That is, the anode of the switch tube Ti is connected to the cathode of the diode Di, and the cathode of the switch tube Ti is connected to the anode of the diode Di. The switch tubes T1-T4 are connected in series in sequence, that is, the cathode of the previous switch tube is connected to the anode of the latter switch tube; the positive pole of the capacitor Cd1 is connected to the anode of the switch tube T1, and the negative pole of the capacitor Cd1 is connected to the positive pole of the capacitor Cd2 and the switch tube. The cathode of T5; the cathode of the capacitor Cd2 is connected to the cathode of the switch tube T4; the anode of the switch tube T5 is connected to the cathode of the switch tube T1, the cathode of the switch tube T5 is connected to the anode of the switch tube T6; the cathode of the switch tube T6 is connected to the switch tube Anode of tube T4. Wherein, the fully controlled power electronic device may also be IGBT (Insulated Gate Bipolar Transistor) or IEGT (Injection Enhanced Gate Transistor). When the switch tube is an IGBT or an IEGT, the anode of the switch tube in FIG. For the collector, the cathode of the switch tube in the aforementioned Figure 1 should be the emitter. Among them, the switches T5 and T6 are clamp switches. When T5 and T6 are always turned off and only use their anti-parallel diodes, the single-phase bridge arm is a neutral point clamped NPC (Neutral point clamped, neutral point clamped). Bit) mode; when T5 and T6 also participate in modulation, the single-phase bridge arm is in active neutral point clamp ANPC mode.

The invention takes the power loss of the IGCT, the anti-parallel diode and the clamping diode in the ANPC three-level single-phase bridge arm as the object, and provides a calculation method of the power loss under different switching states according to the characteristics of the switching device.

The calculation of the loss needs to consider the operation status of each power device in one modulation cycle, as shown in Figure 2, where α represents the power factor angle. According to the situation of the single-phase bridge arm current and voltage zero-crossing point, one modulation period can be divided into four regions. Taking the single-phase bridge arm current as a sinusoidal waveform, the voltage sinusoidal waveform has a power factor angle, and the single-phase bridge arm current I and voltage U are expressed as the following equations (1) and (2).

I=I _p sin(wt) (1)

U=U _m sin(wt+α) (2)

Among them, I _p and U _m are the amplitudes of the current I and the voltage U, respectively, w is the frequency of the current I and the voltage U, and t represents the time.

According to the symmetry of the upper and lower bridge arms of the ANPC converter, taking the power device of the upper bridge arm as an example, it can be seen that the relationship between the conduction angle and the duty cycle of each switching device in the ANPC converter is shown in Table 1, where M Indicates modulation.

Table 1 Conduction angle and duty cycle of each switching device in the ANPC converter

switching device conduction angle duty cycle T1 [0, π-α] Msin(wt+α) D1 [2π-α, 2π] Msin(wt+α) T2 [0, π] (1+Msin(wt+α))/2 D2 [π, 2π-α] (1+Msin(wt+α))/2 D2 [2π-α, 2π] (1+Msin(wt+α))/2 T5 [π, 2π-α] (1+Msin(wt+α))/2 T5 [2π-α, 2π] (1-Msin(wt+α))/2 D5 [0, π-α] (1-Msin(wt+α))/2 D5 [π-α,π] (1+Msin(wt+α))/2

The switching and conduction losses of each power device of the upper bridge arm (including switching transistors T1, T2, T5 and diodes D1, D2, and D5) are calculated below.

(1) IGCT turn-on loss

The turn-on loss of the IGCT device is

k₁是根据IGCT开通时开关条件与标准测试条件关系引入的修正系数，Q_on0是单脉冲开通能量，可设为1.8J，V_d0和i_L0是数据手册中的标准测试条件。where f _sw is the switching frequency of the device,

k ₁ is the correction factor introduced according to the relationship between the switching conditions and the standard test conditions when the IGCT is turned on, Q _on0 is the single-pulse turn-on energy, which can be set to 1.8J, and V _d0 and i _L0 are the standard test conditions in the data sheet.

(2) IGCT turn-off loss

The turn-off loss of the IGCT device is

k₂是根据IGCT关断时开关条件与标准测试条件关系引入的修正系数，Q_off0为单脉冲关断能量。in,

k ₂ is a correction coefficient introduced according to the relationship between the switching conditions and the standard test conditions when the IGCT is turned off, and Q _off0 is the single-pulse turn-off energy.

(3) Diode turn-off loss

The diode only considers the turn-off loss, and the turn-off loss of the diode is

k₃是根据二极管关断时开关条件与标准测试条件关系引入的修正系数。in,

k ₃ is the correction factor introduced according to the relationship between the switching conditions and the standard test conditions when the diode is turned off.

(4) IGCT conduction loss

The IGCT on-state loss is

Wherein, V _T0 is the threshold voltage, r _T is the slope resistance, and the threshold voltage and slope resistance satisfy the on-state peak voltage V _T =V _T0 +i·r _T of the IGCT obtained by fitting the VI curve of the IGCT.

(5) Diode on-state loss

The diode conduction loss is

The system switching loss of the three-level single-phase bridge arm of the ANPC is calculated below.

The system switching loss of the ANPC three-level converter is related to the modulation strategy of the converter, and the present application calculates the system switching loss for the carrier phase-shift modulation strategy.

In the carrier phase-shift PWM, the switching frequencies of the three switching devices T1, T2, and T5 are completely equal. The phase difference between the two carriers is 180 degrees, respectively corresponding to the fundamental frequency modulation of the inner tube and the fundamental frequency modulation of the outer tube. The relationship between the conduction angle and the duty cycle of each power electronic device in the ANPC converter in the carrier phase-shift mode is shown in Table 2, where M represents the modulation degree.

(11) Loss of switch tube T1

The losses of the switch tube T1 include:

switching loss

On-state loss

(22) Loss of diode D1

The losses of diode D1 include:

switching loss

On-state loss

(33) Loss of switch tube T2

The loss of switch tube T2 includes:

switching loss

On-state loss

(44) Loss of diode D2

Diode D2 losses include:

switching loss

On-state loss

(55) Loss of switch tube T5

The loss of switch tube T5 includes:

switching loss

On-state loss

(66) Loss of diode D5

Diode D5 losses include:

switching loss

On-state loss

The switch tube in the above embodiment can also be an IGBT or an IEGT. According to the symmetry of the upper and lower bridge arms of the ANPC converter, the switching and conduction losses of the switches T3, T4, T6 and the diodes D3, D4, and D6 can be obtained.

To sum up, the power loss calculation method of the three-level wind power converter of the present invention proposes a calculation method for the turn-on loss, turn-off loss, and on-state loss of a switch tube, and a calculation method for the turn-off loss and on-state loss of a diode. The turn-on, turn-off, and conduction loss models of power devices are started, and the influence of the modulation strategy on the loss calculation is comprehensively considered. technical foundation.

Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements to some of the technical features; and these Modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. A power loss calculation method of a three-level wind power converter is characterized in that a single-phase bridge arm of the three-level wind power converter comprises switching tubes T1-T6, diodes D1-D6 and capacitors Cd1 and Cd2, each switching tube Ti in the switching tubes T1-T6 is connected with a corresponding diode Di in an anti-parallel mode, i is an integer and is not less than 1 and not more than 6, namely a collector or an anode of each switching tube Ti is connected to a cathode of the corresponding diode Di, an emitter or a cathode of each switching tube Ti is connected to an anode of the corresponding diode Di, and the switching tubes T1-T4 are sequentially connected in series, namely an emitter or a cathode of a previous switching tube is connected to a collector or an anode of a next switching tube; the positive electrode of the capacitor Cd1 is connected to the collector or anode of the switch tube T1, and the negative electrode of the capacitor Cd1 is connected to the positive electrode of the capacitor Cd2 and the emitter or cathode of the switch tube T5; the negative electrode of the capacitor Cd2 is connected to the emitter or the cathode of the switch tube T4; the collector or anode of the switch tube T5 is connected to the emitter or cathode of the switch tube T1, the emitter or cathode of the switch tube T5 is connected to the collector or anode of the switch tube T6; the emitter or cathode of the switch tube T6 is connected to the collector or anode of the switch tube T4,

the power device loss calculation method is characterized by comprising the following steps:

determining the relation between the conduction angles and the duty ratios of the switching tubes T1, T2 and T5 and the diodes D1, D2 and D5;

calculating the turn-on loss, the turn-off loss and the on-state loss of the switching tubes T1, T2 and T5 according to the turn-on angle and the duty ratio;

and calculating the turn-off loss and the turn-on loss of the diodes D1, D2 and D5 according to the turn-on angle and the duty ratio.

2. The method of claim 1, wherein the method of calculating the power loss of a three-level wind power converter,

let alpha denote the power factor angle, M be the modulation degree, then

When the conduction angle of the switch tube T1 is in an interval [0, pi-alpha ], the duty ratio is M sin (wt + alpha);

when the conduction angle of the diode D1 is in an interval [2 pi-alpha, 2 pi ], the duty ratio is M sin (wt + alpha);

when the conduction angle of the switching tube T2 is in an interval [0, pi ], the duty ratio is (1+ M sin (wt + alpha))/2;

when the conduction angle of the diode D2 is in an interval [ pi, 2 pi-alpha ], the duty ratio is (1+ M sin (wt + alpha))/2;

when the conduction angle of the diode D2 is in an interval [2 pi-alpha, 2 pi ], the duty ratio is (1+ M sin (wt + alpha))/2;

when the conduction angle of the switching tube T5 is in an interval [ pi, 2 pi-alpha ], the duty ratio is (1+ M sin (wt + alpha))/2;

when the conduction angle of the switching tube T5 is in an interval [2 pi-alpha, 2 pi ], the duty ratio is (1-M sin (wt + alpha))/2;

when the conduction angle of the diode D5 is in an interval [0, pi-alpha ], the duty ratio is (1-M sin (wt + alpha))/2;

when the conduction angle of the diode D5 is in an interval [ pi-alpha, pi ], the duty ratio is (1+ M sin (wt + alpha))/2.

3. The method of claim 2, wherein the power loss of the three-level wind power converter is calculated,

the switching tubes T1, T2 and T5 have switching losses of

Wherein,

I_pand U_mThe amplitudes of the current I and the voltage U of the single-phase bridge arm respectively, w is the frequency of the current I and the voltage U, t represents time, f_swFor the switching frequency of the device to be,

k₁is a correction coefficient, Q, introduced according to the relationship between the switching condition and the standard test condition when the IGCT is switched on_on0Is a single pulse of switching-on energy, V_d0And i_L0Is a standard test condition in data manuals;

the turn-off losses of the switching tubes T1, T2 and T5 are

Wherein,

k₂is a correction coefficient, Q, introduced according to the relation between the switching condition and the standard test condition when the switching tube is turned off_off0The energy is turned off for a single pulse;

the on-state losses of the switching tubes T1, T2 and T5 are

Wherein,

V_T0is a threshold voltage r_TIs a slope resistance.

4. The method of claim 3, wherein the power loss of the three-level wind power converter is calculated,

the diodes D1, D2 and D5 have turn-off losses of

Wherein,

k₃the correction coefficient is introduced according to the relation between the switching condition and the standard test condition when the diode is turned off;

the on-state losses of the diodes D1, D2 and D5 are

5. The method of claim 3, wherein the power loss of the three-level wind power converter is calculated,

the loss of the switching tube T1 includes:

switching losses

Loss of on state

6. The method for calculating the power loss of a three-level wind power converter according to claim 3 or 5,

the loss of the switching tube T2 includes:

switching losses

Loss of on state

7. The method for calculating the power loss of a three-level wind power converter according to claim 3 or 5,

the losses of the switching tube T5 include:

switching losses

Loss of on state

8. The method of claim 4, wherein the power loss of the three-level wind power converter is calculated,

the losses of the diode D1 include:

switching losses

Loss of on state

9. The method for calculating the power loss of a three-level wind power converter according to claim 4 or 8,

the losses of the diode D2 include:

switching losses

Loss of on state

10. The method for calculating the power loss of a three-level wind power converter according to claim 4 or 8,

the losses of the diode D5 include:

switching losses

Loss of on state

Images