阅读说明：本技术 一种模块化多电平变换器旋转非连续控制方法 (Rotation discontinuous control method for modular multilevel converter ) 是由 郭小强 王凡 王晓明 卢志刚 华长春 马瑞斯·马利诺夫斯基 乔瑟夫·格莱罗 于 2021-08-30 设计创作，主要内容包括：本发明公开了一种模块化多电平变换器旋转非连续控制方法,包括如下步骤：S1、确定级联H桥个数N,电路的开关频率k,根据级联H桥个数N,确定三角载波V-(c)的移相角θ和所需要的三角载波V-(c)个数N；S2、确定电路直流侧电压V-(in),电路中阻感负载R和L；S3、确定调制度m和钳位角度α,得到旋转DPWM调制波,在旋转DPWM调制波调制下生成相应电路拓扑的左侧桥臂调制波和右侧桥臂调制波,左侧桥臂调制波和右侧桥臂调制波均包括钳位部分和调制部分并分别与三角载波相比较产生驱动信号,进而驱动电路,从而完成相应调制过程。在钳位时间内,开关保持常通或者关断状态,在正常调制时间内,开关高频动作。(The invention discloses a discontinuous control method for rotation of a modular multilevel converter, which comprises the following steps: s1, determining the number N of cascaded H bridges, the switching frequency k of the circuit, and determining the triangular carrier V according to the number N of the cascaded H bridges c Phase shift angle theta of and the required triangular carrier wave V c The number N; s2, determining the DC side voltage V of the circuit in Resistance-inductance loads R and L in the circuit; and S3, determining the modulation degree m and the clamping angle alpha to obtain a rotary DPWM (digital pulse width modulation) wave, generating a left bridge arm modulation wave and a right bridge arm modulation wave of a corresponding circuit topology under the modulation of the rotary DPWM modulation wave, wherein the left bridge arm modulation wave and the right bridge arm modulation wave both comprise a clamping part and a modulation part and are respectively compared with a triangular carrier to generate a driving signal, and then driving the circuit, thereby completing the corresponding modulation process. During the clamping time, the switchKeeping a normally-on or off state, and in normal modulation time, the switch acts at high frequency.)

1. A rotation discontinuous control method of a modular multilevel converter is characterized by comprising the following steps: the method comprises the following steps:

s1, determining the number N of cascaded H bridges, the switching frequency k of the circuit, and determining the triangular carrier V according to the number N of the cascaded H bridges_cPhase shift angle theta of and the required triangular carrier wave V_cThe number N;

s2, determining the DC side voltage V of the circuit_inResistance-inductance loads R and L in the circuit;

s3, determining a modulation degree m and a clamping angle alpha to obtain a rotary DPWM (digital pulse width modulation) modulation wave, generating a left bridge arm modulation wave and a right bridge arm modulation wave of a corresponding circuit topology under the modulation of the rotary DPWM modulation wave, wherein the left bridge arm modulation wave and the right bridge arm modulation wave both comprise a clamping part and a modulation part and are respectively compared with a triangular carrier wave, and when the left bridge arm modulation wave or the right bridge arm modulation wave is larger than the triangular carrier wave, generating a high driving signal; when the left bridge arm modulation wave or the right bridge arm modulation wave is smaller than the triangular carrier wave, the generated driving signal is low, the switch keeps a normally-on or off state within the clamping time, and the switch acts at a high frequency within the normal modulation time to drive the circuit, so that the corresponding modulation process is completed.

2. The discontinuous control method for rotation of the modular multilevel converter according to claim 1, wherein the discontinuous control method comprises the following steps: the expression of the triangular carrier phase shift angle θ in step S1 is:

3. the discontinuous control method for rotation of the modular multilevel converter according to claim 2, wherein: in step S3, the clamping angle α is any one of 30 °, 60 °, and 120 °.

4. The discontinuous control method for rotation of the modular multilevel converter according to claim 3, wherein the discontinuous control method comprises the following steps: in step S3, the expression of the rotating DPWM modulation wave is:

wherein, V_DrefIs a modulated wave, V, modified from a conventional DPWM modulated wave_dclampThe representation is a clamp type modulation wave, the positive and negative half cycle amplitudes are the same, and are positiveThe amplitude value in the negative half period is kept constant and is used for clamping the switch to enable the switch to keep a certain state;

V_Drefexpression:

V_dclampexpression:

5. the discontinuous control method for rotation of the modular multilevel converter according to claim 4, wherein the discontinuous control method comprises the following steps: in step S3, the circuits of the left arm modulated wave and the right arm modulated wave are sequentially divided into eight stages in one cycle, the first stage: the switch on the upper side of the left bridge arm is normally on, the switch on the lower side of the left bridge arm is turned off, the switch on the right bridge arm acts at high frequency, and the second stage is started after the first stage is finished; the second stage is as follows: the upper side switch of the left bridge arm and the lower side switch of the right bridge arm are in a normally-on state, the lower side switch of the left bridge arm and the upper side switch of the right bridge arm are in an off state, and a third stage is started after the second stage is finished; the third stage: the upper side switch of the left bridge arm and the lower side switch of the right bridge arm are in a normally-on state, the lower side switch of the left bridge arm and the upper side switch of the right bridge arm are in an off state, and the fourth stage is started after the third stage is finished; the fourth stage: the switch at the lower side of the right bridge arm is always kept in a normally-on state, the switch at the upper side of the right bridge arm is always kept in an off state, the switch at the left bridge arm acts in a high frequency mode, and the fifth stage is started after the fourth stage is finished; the fifth stage: the switch on the lower side of the left bridge arm is normally on, the switch on the upper side of the left bridge arm is switched off, the switch on the right bridge arm is switched on and switched off in a high frequency mode, and the sixth stage is started after the fifth stage is finished; the sixth stage: the upper side switch of the left bridge arm and the lower side switch of the right bridge arm are in an off state, the lower side switch of the left bridge arm and the upper side switch of the right bridge arm are in a normally-on state, and the seventh stage is started after the sixth stage is finished; a seventh stage: the upper side switch of the left bridge arm and the lower side switch of the right bridge arm are in an off state, the lower side switch of the left bridge arm and the upper side switch of the right bridge arm are in a normally-on state, and the eighth stage is started after the seventh stage is finished; the eighth stage: and the upper side switch of the right bridge arm is normally on, the lower side switch of the right bridge arm is turned off, the left bridge arm switch is turned on and turned off at high frequency, and after the eighth stage is finished, the periodic cycle is started.

6. The discontinuous control method for rotation of the modular multilevel converter according to claim 5, wherein: the specific circuit state process in the first stage is as follows: the modulation wave of the left bridge arm is at the clamping part, and the modulation wave V of the left bridge arm_dLIs always greater than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In a normally-on state, the lower side switch S of the left bridge arm₁₂In an off state; modulated wave V of right bridge arm_dRIn the modulation part, the right bridge arm switch is switched on and off in high frequency, and when the right bridge arm modulates the wave V_dRGreater than a triangular carrier V_cTime, the lower side switch S of the right side bridge arm₁₄On while the upper switch S of the right bridge arm₁₃Turning off; when the right bridge arm modulates the wave V_dRLess than the triangular carrier V_cTime, right side bridge arm upper side switch S₁₃Conducting while the lower side switch S of the right side bridge arm₁₄Turning off, wherein the first stage is finished;

the specific circuit state process of the second stage is as follows: the modulation wave of the left bridge arm and the modulation wave of the right bridge arm are both in the clamping part, and the modulation wave V of the left bridge arm_dLAnd the modulated wave V of the right bridge arm_dRIs always greater than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In a normally-on state, the lower side switch S of the left bridge arm₁₂In an off state; lower switch S of right bridge arm₁₄On while the upper switch S of the right bridge arm₁₃Turning off, wherein the second stage is finished;

the third stage specifically comprises the following circuit state processes: the modulation wave of the left bridge arm and the modulation wave of the right bridge arm are all positionedIn the clamping part, the left bridge arm modulates the wave V_dLAnd the modulated wave V of the right bridge arm_dRIs always greater than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In a normally-on state, the lower side switch S of the left bridge arm₁₂In an off state; lower switch S of right bridge arm₁₄Normally on state, with switch S on the right arm₁₃An off state, at which point the third stage ends;

the fourth stage specifically comprises the following circuit state processes: the modulated wave of the right bridge arm is in the clamping part, and the modulated wave V of the right bridge arm_dRIs always greater than the triangular carrier V_cRight side bridge arm lower side switch S₁₄In a normally-on state, and simultaneously, the upper side switch S of the right bridge arm₁₃Keeping the off state, the left bridge arm modulates the wave V_dLIn the modulation part, the left bridge arm switch is switched on and off in high frequency, and when the left bridge arm modulates the wave V_dLGreater than a triangular carrier V_cTime, left side bridge arm upper side switch S₁₁On, left side bridge arm lower side switch S₁₂Turning off; when the left bridge arm modulates the wave V_dLLess than the triangular carrier V_cTime, left side bridge arm upper side switch S₁₁Off, left arm lower switch S₁₂Conducting, and ending the fourth stage;

the specific circuit state process of the fifth stage is as follows: the modulation wave of the left bridge arm is at the clamping part, and the modulation wave V of the left bridge arm_dLIs always less than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In an off state, the switch S is arranged at the lower side of the left bridge arm₁₂In a normally on state; modulated wave V of right bridge arm_dRIn the modulation part, the right bridge arm switch is switched on and off in high frequency, and when the right bridge arm modulates the wave V_dRGreater than a triangular carrier V_cTime, the lower side switch S of the right side bridge arm₁₄On while the upper switch S of the right bridge arm₁₃Turning off; when the right bridge arm modulates the wave V_dRLess than the triangular carrier V_cTime, right side bridge arm upper side switch S₁₃Conducting while the lower side switch S of the right side bridge arm₁₄Turning off, wherein the fifth stage is finished;

the sixth oneThe specific circuit state process of the stage is as follows: the modulation wave of the left bridge arm and the modulation wave of the right bridge arm are both in the clamping part, and the modulation wave V of the left bridge arm_dLAnd the modulated wave V of the right bridge arm_dRIs always less than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In an off state, the switch S is arranged at the lower side of the left bridge arm₁₂In a normally on state; lower switch S of right bridge arm₁₄Is in an off state, and simultaneously the upper side switch S of the right bridge arm₁₃In the normal on state, the sixth stage is finished;

the specific circuit state process in the seventh stage is as follows: the modulation wave of the left bridge arm and the modulation wave of the right bridge arm are both in the clamping part, and the modulation wave V of the left bridge arm_dLAnd the modulated wave V of the right bridge arm_dRIs always less than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In an off state, the switch S is arranged at the lower side of the left bridge arm₁₂In a normally on state; lower switch S of right bridge arm₁₄Is in an off state, and simultaneously the upper side switch S of the right bridge arm₁₃In the normal on state, the seventh stage is finished;

the specific circuit state process of the eighth stage is as follows: the modulated wave of the right bridge arm is in the clamping part, and the modulated wave V of the right bridge arm_dRIs always less than the triangular carrier V_cRight side bridge arm lower side switch S₁₄In the off state, the upper side switch S of the right bridge arm₁₃Keeping a normal open state; at the moment, the left bridge arm modulates the wave V_dLIn the modulation part, the left bridge arm switch acts in high frequency, when the left bridge arm modulates the wave V_dLGreater than a triangular carrier V_cTime, left side bridge arm upper side switch S₁₁On, left side bridge arm lower side switch S₁₂Turning off; when the left bridge arm modulates the wave V_dLLess than the triangular carrier V_cTime, left side bridge arm upper side switch S₁₁Off, left arm lower switch S₁₂And conducting, and finishing the eighth stage at the moment.

Technical Field

The invention relates to the technical field of multi-level inverters, in particular to a rotation discontinuous control method of a modular multi-level converter.

Background

In recent years, multilevel inverters have been widely used in high voltage and high power systems. The multi-level inverter has the advantages of high voltage system capability, low harmonic distortion, easiness in expansion, high fault-tolerant capability and the like. Therefore, the multi-level inverter is widely applied to a high-voltage direct-current power transmission system and a renewable energy system. There are many topologies for multilevel inverters, with cascaded H-bridges being one of the most widely used topologies. There are many modulation modes of the cascaded H-bridge, including carrier phase shift, carrier stacking, discontinuous modulation, etc. The carrier phase shift modulation technology has great performance advantages, can ensure the power balance among modules and the quality of output waveforms, and is widely applied to the industrial field. However, carrier phase shift modulation has limitations such as high switching frequency, large circuit loss, and low circuit efficiency. Due to the high efficiency of the discontinuous modulation circuit and the small number of switching times, the application occasions are gradually increased.

It is easy to observe that the DPWM is only switched in the clamped part and the switch is still in high frequency operation for the rest of the time. Due to the appearance of a novel rotary type modulation wave, the heating and the loss balance of the switch can be greatly reduced and guaranteed. Therefore, the patent combines the rotary modulating wave and the DPWM to provide a rotary DPWM modulating method.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a discontinuous control method for rotation of a modular multilevel converter, which has fewer switching times, low switching loss, improved circuit efficiency and balanced heating among modules compared with the traditional DPWM modulation, thereby prolonging the service life of a switch and improving the reliability of a circuit.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a rotation discontinuous control method of a modular multilevel converter comprises the following steps:

s1, determining the number N of cascaded H bridges, the switching frequency k of the circuit, and determining the triangular carrier V according to the number N of the cascaded H bridges_cPhase shift angle theta of and the required triangular carrier wave V_cThe number N;

s2, determining the DC side voltage V of the circuit_inResistance-inductance loads R and L in the circuit;

s3, determining a modulation degree m and a clamping angle alpha to obtain a rotary DPWM (digital pulse width modulation) wave, generating a left bridge arm modulation wave and a right bridge arm modulation wave of a corresponding circuit topology under the modulation of the rotary DPWM modulation wave, wherein the left bridge arm modulation wave and the right bridge arm modulation wave both comprise a clamping part and a modulation part and are respectively compared with a triangular carrier wave, and when the left bridge arm modulation wave or the right bridge arm modulation wave is larger than the triangular carrier wave, a generated driving signal is high; when the left bridge arm modulation wave or the right bridge arm modulation wave is smaller than the triangular carrier wave, the generated driving signal is low, the switch keeps a normally-on or off state within the clamping time, and the switch acts at a high frequency within the normal modulation time to drive the circuit, so that the corresponding modulation process is completed.

The technical scheme of the invention is further improved as follows: the expression of the triangular carrier phase shift angle θ in step S1 is:

the technical scheme of the invention is further improved as follows: in step S3, the clamping angle α is any one of 30 °, 60 °, and 120 °.

The technical scheme of the invention is further improved as follows: in step S3, the DPWM modulation wave expression of rotation is:

wherein, V_DrefIs a modulated wave, V, modified from a conventional DPWM modulated wave_dclampThe clamp type modulation wave is represented, the positive half cycle amplitude and the negative half cycle amplitude are the same, and the amplitude in the positive half cycle and the negative half cycle is kept constant and is used for clamping the switch to enable the switch to keep a certain state;

V_Drefexpression:

V_dclampexpression:

the technical scheme of the invention is further improved as follows: in step S3, the circuits of the left arm modulated wave and the right arm modulated wave are sequentially divided into eight stages in one cycle, the first stage: the upper switch of the left bridge arm is normally on, the lower switch of the left bridge arm is turned off, the switch of the right bridge arm acts at high frequency, and the second stage is started after the first stage is finished; the second stage is as follows: the upper side switch of the left bridge arm and the lower side switch of the right bridge arm are in a normal on state, the lower side switch of the left bridge arm and the upper side switch of the right bridge arm are in an off state, and a third stage is started after the second stage is finished; the third stage: the upper side switch of the left bridge arm and the lower side switch of the right bridge arm are in a normally-on state, the lower side switch of the left bridge arm and the upper side switch of the right bridge arm are in an off state, and a fourth stage is started after the third stage is finished; the fourth stage: the switch at the lower side of the right bridge arm is always kept in a normally-on state, the switch at the upper side of the right bridge arm is always kept in an off state, the switch at the left bridge arm acts in a high frequency mode, and the fifth stage is started after the fourth stage is finished; the fifth stage: the switch on the lower side of the left bridge arm is normally on, the switch on the upper side of the left bridge arm is switched off, the switch on and off of the right bridge arm are conducted in high frequency, and the sixth stage is started after the fifth stage is finished; a sixth stage: the upper side switch of the left bridge arm and the lower side switch of the right bridge arm are in an off state, the lower side switch of the left bridge arm and the upper side switch of the right bridge arm are in a normally-on state, and the seventh stage is started after the sixth stage is finished; the seventh stage: the upper side switch of the left bridge arm and the lower side switch of the right bridge arm are in an off state, the lower side switch of the left bridge arm and the upper side switch of the right bridge arm are in a normally-on state, and the eighth stage is started after the seventh stage is finished; the eighth stage: and the upper side switch of the right bridge arm is normally on, the lower side switch of the right bridge arm is turned off, the left bridge arm switch is turned on and turned off at high frequency, and after the eighth stage is finished, the periodic cycle is started.

The technical scheme of the invention is further improved as follows: the specific circuit state process in the first stage is as follows: the modulation wave of the left bridge arm is at the clamping part, and the modulation wave V of the left bridge arm_dLIs always greater than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In a normally-on state, the lower side switch S of the left bridge arm₁₂In an off state; modulated wave V of right bridge arm_dRIn the modulation part, the right bridge arm switch is switched on and off in high frequency, and when the right bridge arm modulates the wave V_dRGreater than a triangular carrier V_cTime, the lower side switch S of the right side bridge arm₁₄On while the upper switch S of the right bridge arm₁₃Turning off; when the right bridge arm modulates the wave V_dRLess than the triangular carrier V_cTime, the upper switch S of the right bridge arm₁₃Conducting while the lower side switch S of the right side bridge arm₁₄Turning off, wherein the first stage is finished;

the specific circuit state process of the second stage is as follows: the modulation wave of the left bridge arm and the modulation wave of the right bridge arm are both in the clamping part, and the modulation wave V of the left bridge arm_dLAnd the modulated wave V of the right bridge arm_dRIs always greater than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In a normally-on state, the lower side switch S of the left bridge arm₁₂In an off state; lower switch S of right bridge arm₁₄On while the upper switch S of the right bridge arm₁₃Turning off, wherein the second stage is finished;

the third stage specifically comprises the following circuit state processes: the modulation wave of the left bridge arm and the modulation wave of the right bridge arm are both in the clamping part, and the modulation wave V of the left bridge arm_dLAnd the modulated wave V of the right bridge arm_dRIs always greater than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In a normally-on state, the lower side switch S of the left bridge arm₁₂In an off state; lower switch S of right bridge arm₁₄Normally on state, with switch S on the right arm₁₃An off state, at which point the third stage ends;

the fourth stage specifically comprises the following circuit state processes: the modulation wave of the right bridge arm is at the clamping part, and the modulation wave V of the right bridge arm_dRIs always greater than the triangular carrier V_cRight side bridge arm lower side switch S₁₄In a normally-on state, and simultaneously, the upper side switch S of the right bridge arm₁₃Keeping the off state, the left bridge arm modulates the wave V_dLIn the modulation part, the left bridge arm switch is switched on and off in high frequency, and when the left bridge arm modulates the wave V_dLGreater than a triangular carrier V_cTime, left side bridge arm upper side switch S₁₁On, left side bridge arm lower side switch S₁₂Turning off; when the left bridge arm modulates the wave V_dLLess than the triangular carrier V_cTime, left side bridge arm upper side switch S₁₁Off, left arm lower switch S₁₂Conducting, and ending the fourth stage;

the specific circuit state process of the fifth stage is as follows: the modulation wave of the left bridge arm is at the clamping part, and the modulation wave V of the left bridge arm_dLIs always less than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In an off state, the switch S is arranged at the lower side of the left bridge arm₁₂In a normally on state; modulated wave V of right bridge arm_dRIn the modulation part, the right bridge arm switch is switched on and off in high frequency, and when the right bridge arm modulates the wave V_dRGreater than a triangular carrier V_cTime, the lower side switch S of the right side bridge arm₁₄On while the upper switch S of the right bridge arm₁₃Turning off; when it is on the rightSide bridge arm modulated wave V_dRLess than the triangular carrier V_cTime, right side bridge arm upper side switch S₁₃Conducting while the lower side switch S of the right side bridge arm₁₄Turning off, wherein the fifth stage is finished;

the specific circuit state process of the sixth stage is as follows: the modulation wave of the left bridge arm and the modulation wave of the right bridge arm are both in the clamping part, and the modulation wave V of the left bridge arm_dLAnd the modulated wave V of the right bridge arm_dRIs always less than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In an off state, the switch S is arranged at the lower side of the left bridge arm₁₂In a normally on state; lower switch S of right bridge arm₁₄Is in an off state, and simultaneously the upper side switch S of the right bridge arm₁₃In the normal state, the sixth stage is finished;

the specific circuit state process in the seventh stage is as follows: the modulation wave of the left bridge arm and the modulation wave of the right bridge arm are both in the clamping part, and the modulation wave V of the left bridge arm_dLAnd the modulated wave V of the right bridge arm_dRIs always less than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In an off state, the switch S is arranged at the lower side of the left bridge arm₁₂In a normally on state; lower switch S of right bridge arm₁₄Is in an off state, and simultaneously the upper side switch S of the right bridge arm₁₃In the normal state, the seventh stage is finished;

the specific circuit state process of the eighth stage is as follows: the modulated wave of the right bridge arm is in the clamping part, and the modulated wave V of the right bridge arm_dRIs always less than the triangular carrier V_cRight side bridge arm lower side switch S₁₄In the off state, the upper side switch S of the right bridge arm₁₃Keeping a normal open state; at the moment, the left bridge arm modulates the wave V_dLIn the modulation part, the left bridge arm switch acts in high frequency, when the left bridge arm modulates the wave V_dLGreater than a triangular carrier V_cAt the time, the left side bridge arm upper switch S₁₁On, left side bridge arm lower side switch S₁₂Turning off; when the left bridge arm modulates the wave V_dLLess than triangular carrier V_cTime, left side bridge arm upper side switch S₁₁Off, left arm lower switch S₁₂And conducting, and finishing the eighth stage.

Due to the adoption of the technical scheme, the invention has the technical progress that:

the modulation method is different from the traditional modulation method, switches in the circuit are not always in high-frequency action, but are switched between high frequency and low frequency, a left bridge arm modulation wave and a right bridge arm modulation wave of a circuit topology are generated under the modulation of a rotary DPWM modulation wave, the left bridge arm modulation wave and the right bridge arm modulation wave both comprise a clamping part and a modulation part, the switching frequency can be effectively reduced, the circuit efficiency is improved, the left bridge arm modulation wave and the right bridge arm modulation wave are sequentially divided into eight stages in one period, the switches are switched on and off in an ordered mode, and the output waveform quality can be ensured while the switching frequency is reduced; under the prerequisite of guaranteeing output waveform quality, rotatory DPWM modulation has less switching frequency than traditional DPWM modulation, and switching loss is low, and circuit efficiency obtains promoting, and the intermodule is heated the equilibrium, and then can prolong switch life, promotes the circuit reliability.

Drawings

FIG. 1 is a single-phase cascaded H-bridge multilevel inverter topology;

FIG. 2 is a schematic diagram of a triangular carrier wave in the present invention;

FIG. 3 is a schematic diagram of the novel modulation wave generation process of the present invention;

FIG. 4 is a schematic diagram of the present invention of the rotating DPWM modulation principle;

FIG. 5 is a schematic diagram of the rotary DPWM modulation operation of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following examples:

as shown in fig. 1, there are N cascaded H-bridge cascades in the graph, and when the method for controlling the rotation discontinuity of the modular multilevel converter provided by the present invention is applied to an H-bridge topology, compared with a conventional modulation method, there are fewer switching times, switches in the circuit are not always in high-frequency action, but are switched between high frequency and low frequency, and a left bridge arm modulation wave and a right bridge arm modulation wave of the circuit topology are generated under the modulation of a rotating DPWM modulation wave, and both the left bridge arm modulation wave and the right bridge arm modulation wave include a clamping part and a modulation part, so that the switching times can be effectively reduced, the circuit efficiency can be improved, the side bridge arm modulation wave and the right bridge arm modulation wave are sequentially divided into eight stages in one cycle, switches are turned on and off in an ordered manner, and the switching times can be reduced while the output waveform quality can be guaranteed; under the prerequisite of guaranteeing output waveform quality, rotatory DPWM modulation has less switching frequency than traditional DPWM modulation, and switching loss is low, and circuit efficiency obtains promoting, and the intermodule is heated the equilibrium, and then can prolong switch life, promotes circuit reliability.

The method specifically comprises the following steps:

s1, as shown in figure 2, determining the number N of cascaded H bridges, the switching frequency k of the circuit, and determining the triangular carrier V according to the number N of the cascaded H bridges_cPhase shift angle theta of and the required triangular carrier wave V_cThe number N; the expression of the triangular carrier phase shift angle theta is as follows:

s2, determining the DC side voltage V of the circuit_inResistance-inductance loads R and L in the circuit;

s3, determining a modulation degree m and a clamping angle α, where the clamping angle α is any one of 30 °, 60 ° and 120 °, and the clamping angle α adopted by the present invention is 60 °, to obtain a rotating DPWM modulated wave, and as shown in fig. 3 (c), the rotating DPWM modulated wave expression is:

wherein, V_DrefIs a modulated wave modified from a conventional DPWM modulated wave, as shown in fig. 3 (a); v_dclampThe representation is a clamp-type modulated wave, as shown in FIG. 3(b)The positive and negative half cycle amplitudes are the same, and the amplitudes in the positive and negative half cycles are kept constant, so that the positive and negative half cycle amplitudes are used for clamping the switch to enable the switch to keep a certain state;

V_Drefexpression:

V_dclampexpression:

generating a left bridge arm modulation wave and a right bridge arm modulation wave of a corresponding circuit topology under the modulation of a rotary DPWM modulation wave, wherein the left bridge arm modulation wave and the right bridge arm modulation wave both comprise a clamping part and a modulation part and are respectively compared with a triangular carrier wave, and when the left bridge arm modulation wave or the right bridge arm modulation wave is larger than the triangular carrier wave, the generated driving signal is high; when the left bridge arm modulation wave or the right bridge arm modulation wave is smaller than the triangular carrier, the generated driving signal is low, the switch keeps a normally-on or off state within the clamping time, and the switch acts at a high frequency within the normal modulation time to drive the circuit, so that the corresponding modulation process is completed.

The specific modulation process is as follows, fig. 4 is a schematic diagram of the principle of DPWM modulation of the single-phase cascaded H-bridge multi-level inverter provided by the invention, and since the upper and lower switching tubes of the same bridge arm are in complementary conduction, the left bridge arm in fig. 4 only displays the upper side switch S of the left bridge arm₁₁Drive signal g of₁₁The left bridge arm only displays the driving signal g of the right bridge arm side switch₁₄In the figure, V_oThe output voltage of the H bridge AC side is shown, and the input voltage of the DC side is shown as E.

The left arm modulated wave and the right arm modulated wave are sequentially divided into eight stages in one cycle as shown in fig. 3 (c):

the first stage (t)₀-t₁) And a second stage (t)₁-t₂) Corresponding concrete circuitThe state process is shown in FIG. 5(1), the first stage (t)₀-t₁): the upper side switch of the left side bridge arm is normally on, the lower side switch of the left side bridge arm is turned off, the right side bridge arm switch acts at high frequency, and the specific circuit state process is as follows: the modulation wave of the left bridge arm is in the clamping part, and the modulation wave V of the left bridge arm_dLIs always greater than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In a normally-on state, the lower side switch S of the left bridge arm₁₂In an off state; modulated wave V of right bridge arm_dRIn the modulation part, the right bridge arm switch is switched on and off in high frequency, and when the right bridge arm modulates the wave V_dRGreater than a triangular carrier V_cTime, the lower side switch S of the right side bridge arm₁₄On while the upper switch S of the right bridge arm₁₃Turning off; when the right bridge arm modulates the wave V_dRLess than the triangular carrier V_cTime, right side bridge arm upper side switch S₁₃Conducting while the right side bridge lower side switch S₁₄And turning off, wherein the first stage is finished, and the second stage is turned on after the first stage is finished.

The second stage (t)₁-t₂): the left side bridge arm upper side switch and the right side bridge arm lower side switch are in a normally-on state, the left side bridge arm lower side switch and the right side bridge arm upper side switch are in an off state, and the specific circuit state process is as follows: the modulation wave of the left bridge arm and the modulation wave of the right bridge arm are both in the clamping part, and the modulation wave V of the left bridge arm_dLAnd the modulated wave V of the right bridge arm_dRIs always greater than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In a normally-on state, the lower side switch S of the left bridge arm₁₂In an off state; lower switch S of right bridge arm₁₄On while the right side bridge arm upper side switch S₁₃And turning off, finishing the second stage at the moment, and turning on the third stage after finishing the second stage.

The third stage (t)₂-t₃) And a fourth phase (t)₃-t₄) The corresponding specific circuit state process is shown in FIG. 5(2), and the third stage (t)₂-t₃): the upper switch of the left bridge arm and the lower switch of the right bridge arm are in a normal on state, and the lower side of the left bridge armThe switch and the switch on the upper side of the right bridge arm are in an off state, and the specific circuit state process is as follows: the modulation wave of the left bridge arm and the modulation wave of the right bridge arm are both in the clamping part, and the modulation wave V of the left bridge arm_dLAnd the modulated wave V of the right bridge arm_dRIs always greater than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In a normally-on state, a switch S is arranged on the lower side of the left bridge arm₁₂In an off state; lower switch S of right bridge arm₁₄Normally on state, with switch S on the right arm₁₃And (4) a shutdown state, wherein the third stage is finished, and the fourth stage is started after the third stage is finished.

The fourth stage (t)₃-t₄): the lower side switch of the right side bridge arm always keeps a normally-on state, the upper side switch of the right side bridge arm always keeps an off state, the left side bridge arm switch acts at high frequency, and the specific circuit state process is as follows: the modulated wave of the right bridge arm is in the clamping part, and the modulated wave V of the right bridge arm_dRIs always greater than the triangular carrier V_cRight side bridge arm lower side switch S₁₄In a normally-on state, and simultaneously, the upper side switch S of the right bridge arm₁₃Keeping the off state, the left bridge arm modulates the wave V_dLIn the modulation part, the left bridge arm switch is switched on and off in high frequency, and when the left bridge arm modulates the wave V_dLGreater than a triangular carrier V_cTime, left side bridge arm upper side switch S₁₁On, left side bridge arm lower side switch S₁₂Turning off; when the left bridge arm modulates the wave V_dLLess than the triangular carrier V_cTime, left side bridge arm upper side switch S₁₁Off, left arm lower switch S₁₂And conducting, finishing the fourth stage at the moment, and starting the fifth stage after finishing the fourth stage.

The fifth stage (t)₄-t₅) And a sixth phase (t)₅-t₆) The corresponding specific circuit state process is shown in FIG. 5(3), the fifth stage (t)₄-t₅): the switch on the lower side of the left bridge arm is normally on, the switch on the upper side of the left bridge arm is turned off, the switch on the right bridge arm is turned on and turned off at high frequency, and the specific circuit state process is as follows: the modulation wave of the left bridge arm is in the clamping part, and the modulation wave V of the left bridge arm_dLIs always smaller than the triangleCarrier wave V_cAt this time, the left side bridge arm upper side switch S₁₁In the off state, the switch S is arranged at the lower side of the left bridge arm₁₂In a normally on state; modulated wave V of right bridge arm_dRIn the modulation part, the right bridge arm switch is switched on and off in high frequency, and when the right bridge arm modulates the wave V_dRGreater than triangular carrier wave V_cTime, the lower side switch S of the right side bridge arm₁₄On while the upper switch S of the right bridge arm₁₃Turning off; when the right bridge arm modulates the wave V_dRLess than the triangular carrier V_cTime, right side bridge arm upper side switch S₁₃Conducting while the lower side switch S of the right side bridge arm₁₄And turning off, finishing the fifth stage at the moment, and turning on the sixth stage after the fifth stage is finished.

The sixth stage (t)₅-t₆): the left side bridge arm upper side switch and the right side bridge arm lower side switch are in an off state, the left side bridge arm lower side switch and the right side bridge arm upper side switch are in a normally-on state, and the specific circuit state process is as follows: the modulation wave of the left bridge arm and the modulation wave of the right bridge arm are both in the clamping part, and the modulation wave V of the left bridge arm_dLAnd the modulated wave V of the right bridge arm_dRIs always less than the triangular carrier V_cAt this time, the left side bridge arm upper side switch S₁₁In an off state, the switch S is arranged at the lower side of the left bridge arm₁₂In a normally on state; lower switch S of right bridge arm₁₄In an off state, and simultaneously the upper side switch S of the right bridge arm₁₃And (4) in a normally-on state, wherein the sixth stage is ended, and the seventh stage is started after the sixth stage is ended.

Seventh stage (t)₆-t₇) And an eighth stage (t)₇-t₈) The corresponding specific circuit state process is shown in FIG. 5(4), and the seventh stage (t)₆-t₇): the left side bridge arm upper side switch and the right side bridge arm lower side switch are in an off state, the left side bridge arm lower side switch and the right side bridge arm upper side switch are in a normally-on state, and the specific circuit state process is as follows: the modulation wave of the left bridge arm and the modulation wave of the right bridge arm are both in the clamping part, and the modulation wave V of the left bridge arm_dLAnd the modulated wave V of the right bridge arm_dRIs always less than the triangular carrier V_cAt this time, the left side bridgeArm upside switch S₁₁In the off state, the switch S is arranged at the lower side of the left bridge arm₁₂In a normally on state; lower switch S of right bridge arm₁₄Is in an off state, and simultaneously the upper side switch S of the right bridge arm₁₃And (4) in a normal on state, wherein the seventh stage is ended, and the eighth stage is started after the seventh stage is ended.

The eighth stage (t)₇-t₈): the upper side switch of the right side bridge arm is normally on, the lower side switch is turned off, the left side bridge arm switch is in high-frequency on and off, and the specific circuit state process is as follows: the modulated wave of the right bridge arm is in the clamping part, and the modulated wave V of the right bridge arm_dRIs always less than the triangular carrier V_cRight side bridge arm lower side switch S₁₄In the off state, the upper side switch S of the right bridge arm₁₃Keeping a normal open state; at the moment, the left bridge arm modulates the wave V_dLIn the modulation part, the left bridge arm switch acts in high frequency, when the left bridge arm modulates the wave V_dLGreater than a triangular carrier V_cTime, left side bridge arm upper side switch S₁₁On, left side bridge arm lower side switch S₁₂Turning off; when the left bridge arm modulates the wave V_dLLess than triangular carrier V_cTime, left side bridge arm upper side switch S₁₁Off, left arm lower switch S₁₂And conducting, finishing the eighth stage at the moment, and starting the periodic cycle after finishing the eighth stage.