Hybrid space vector modulation method for current source type hydrogen generation converter

Abstract

The application discloses a kind of mixed space vector modulation methods of current source type hydrogen production converter, belong to power electronic conversion control technical field.The method includes: constructing two kinds of current vector sequence mode, and combining adaptive threshold judging mechanism, whether according to line voltage exceeds set threshold dynamically switches vector sequence mode;According to the action sequence of the current vector of the selected vector sequence mode reconstruction traditional space vector modulation, realize partial switching device natural shutdown in combination with alternating current side voltage polarity relationship;According to the selected vector sequence mode and the action time of each current vector, through carrier comparison and switch selection logic generation pulse width modulation driving signal, complete the space vector modulation control to current source rectifier.The application can effectively eliminate the effect of superimposed current, reduce the switching times of switching device, reduce switching loss, significantly improve the operating performance of current source rectifier in hydrogen production converter, effectively guarantee the current stability and power quality of hydrogen production power supply system.

Description

Technical Field

[0001] This invention relates to the field of power electronic conversion and power conversion control technology, and in particular to a hybrid space vector modulation method for a current source type hydrogen production converter. It belongs to the modulation and control technology of current source type power converters in hydrogen production systems and is applicable to the power conversion stage of renewable energy electrolysis water hydrogen production systems. Background Technology

[0002] As the core power conversion device in the water electrolysis hydrogen production system, the hydrogen converter undertakes the critical task of converting the AC power from the power grid into the large current, low voltage, and stable DC power required by the electrolyzer. Its operating efficiency, current stability, and power quality directly determine the hydrogen production efficiency, service life, and grid compatibility of the electrolyzer.

[0003] Currently, the preferred topology for high-power hydrogen production converters is the current source rectifier (CSR) based on pulse width modulation (PWM) control, which has advantages such as continuous DC-side current and strong short-circuit resistance. However, the traditional space vector modulation (SVM) method of CSR suffers from problems such as current distortion caused by commutation overlap time, high losses due to numerous switching cycles, and system fluctuations caused by current sharing. These issues make it difficult to meet the application requirements of stable power supply for high current electrolyzers and power quality adaptation to renewable energy grids, becoming a key technological bottleneck that urgently needs to be overcome in the field of green hydrogen production. Summary of the Invention

[0004] In view of this, the present invention proposes a hybrid space vector modulation method for a current source type hydrogen production converter. By reconstructing the current vector sequence in traditional space vector modulation and combining two current vector sequence modes and an adaptive threshold judgment mechanism, the method aims to reduce the number of switching operations, reduce switching losses, and avoid current sharing. This ensures the continuity of the DC current and the stability of the output of the hydrogen production converter, improves its operating efficiency, power quality, and operational stability in water electrolysis hydrogen production systems, and adapts to the application scenarios of renewable energy green hydrogen production.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a hybrid space vector modulation method for a current-source hydrogen generator converter, wherein the hydrogen generator converter is a current-source rectifier based on pulse width modulation control; the method includes: Collect the three-phase current signal and three-phase voltage signal on the AC side of the current source rectifier, and establish a space vector model of the current source rectifier; Based on the space vector model, the reference current vector is determined according to the three-phase current signal, and the duration of each reference current vector within one switching cycle is calculated. Based on the instantaneous values ​​of the three-phase voltage signals, the three-phase voltages are divided into maximum voltage, intermediate voltage, and minimum voltage, and the phase current vectors corresponding to the maximum voltage, intermediate voltage, and minimum voltage are defined as the maximum current vector, intermediate current vector, and minimum current vector, respectively. Two current vector sequence modes are constructed. Each current vector sequence mode includes: determining the action order of the maximum current vector, the intermediate current vector, and the minimum current vector, as well as the corresponding switching path, based on the parity of the sector where the reference current vector is located. Calculate the line voltage and set a voltage threshold; compare the line voltage with the set voltage threshold, and dynamically select one from two current vector sequence modes; Based on the selected current vector sequence mode and the duration of action, the current vector action sequence and action time within a switching cycle are determined, a modulation signal is generated and compared with the carrier signal to obtain a PWM drive signal, which drives the power switching device of the current source rectifier.

[0007] Furthermore, the first current vector sequence mode includes: When the reference current vector When in an odd sector, the current vector sequence is defined as follows: The switch corresponding to high voltage is reverse-blocked by the switch corresponding to low voltage. The off and on signals and A constant on signal is set between the off and on signals; when When in an even sector, the order in which the current vector is defined is as follows: The switch corresponding to low voltage will be reverse-blocked by the switch corresponding to high voltage. The off and on signals and A constant on signal is set between the off and on signals; The second type of current vector sequence mode includes: when When in an odd sector, the current vector sequence is defined as follows: The switch corresponding to high voltage is reverse-blocked by the switch corresponding to low voltage. A constant on signal is set between the off and on signals, and respectively at... Add slack current time at the signal turn-on and turn-off points ;when When in an even sector, the switch corresponding to the low voltage will be reverse-blocked by the switch corresponding to the high voltage, thus defining the order of the current vectors as follows: ,exist A constant on signal is set between the off and on signals, and respectively at... Add slack current time at the signal turn-on and turn-off points ; in, , and These represent the maximum current vector, the intermediate current vector, and the minimum current vector, respectively. , , These represent the switches corresponding to the maximum current vector, intermediate current vector, and minimum current vector, respectively.

[0008] Furthermore, the three-phase current signal and three-phase voltage signal of the AC side of the current source rectifier are collected, including: obtaining the three-phase input voltage and input current information of the current source rectifier through voltage sensors and current sensors.

[0009] Furthermore, the duration of each reference current vector within a switching cycle is calculated, including: The acquired signal is subjected to switching cycle averaging filtering; The current quantities in the three-phase stationary coordinate system are converted into two-dimensional coordinates using the Clarke coordinate transformation. αβ The current space vector in the stationary coordinate system; the current source rectifier includes nine switching states, corresponding to nine space current vectors, and based on the nine space current vectors, a regular hexagon including six space vector sectors is constructed; The spatial vector sector in which the reference current vector is located is determined based on the position angle of the current spatial vector, and the composition relationship between the reference current vector and the two adjacent effective current vectors in the spatial vector sector is calculated. Based on the position angle of the reference current vector and the switching period, calculate the duration of action of two adjacent effective current vectors and the zero vector.

[0010] Furthermore, one switching cycle Internal effective current vector The duration of action are respectively Zero vector The duration of action is The reference current vector The following conditions must be met: ; Based on the position angle of the reference current vector and the switching period, calculate the duration of action of the two adjacent effective current vectors and the zero vector: ; in The modulation coefficient, , Represents a vector angle; if If located in other sectors, then , ,in This indicates the modified angle. express Convert the sector it is located to a sector. The vector in the vector is used to calculate the corresponding action time.

[0011] Furthermore, the line voltage is compared with the set threshold, and one of two current vector sequence modes is dynamically selected, including: when the line voltage exceeds the threshold, the first current vector sequence mode is used; when the line voltage is within the threshold, the second current vector sequence mode is used.

[0012] Furthermore, voltage threshold The calculation method is as follows: ; in, h This represents the height of the triangular high-frequency ripple voltage envelope; v represents each The height variation of the ideal line voltage; This represents the maximum value of the envelope height of the triangular high-frequency ripple voltage; , f The power grid frequency; U This represents the amplitude of the ideal line voltage of the grid-side capacitor. This represents one switching cycle.

[0013] Furthermore, the calculation of line voltage includes: The reference line current and the PWM line current are defined as follows: ; Subscript ref Indicates the reference current value. p=0,n,n+ 1 indicates PWM current vector The corresponding phase current; The relationship between PWM line current and DC side current is as follows: ; in n Represents the reference current vector The sector number; Voltage ripple of grid-side capacitors Represented as: ; The integral sum of the difference between the reference current and the pulse width modulation line current over the switching cycle remains close to zero. ; The envelope expression for the high-frequency ripple of the capacitor line voltage is: ; in, Indicates the AC side capacitance; a , b , c This indicates the number of the three phases.

[0014] Further, determining the current vector action sequence within a switching cycle based on the selected current vector sequence mode and the said action duration includes: Assuming the height of the triangular wave is ,in It is the duration of action corresponding to the current vector; The modulation signal is calculated based on the current vector order in the selected vector sequence mode. : Sequence Mode 1: In odd sectors, the current vector order is defined as follows: ; ; In the even sector, the current vector order is defined as follows: ; ; Sequence Mode 2: In odd sectors, the current vector order is defined as follows: ; ; In the even sector, the current vector order is defined as follows: ; .

[0015] Furthermore, based on the instantaneous values ​​of the three-phase voltage signals, the three-phase voltages are divided into maximum voltage, intermediate voltage, and minimum voltage, and the phase current vectors corresponding to the maximum voltage, intermediate voltage, and minimum voltage are defined as the maximum current vector, intermediate current vector, and minimum current vector, respectively, including: The collected three-phase input voltage information is processed using a switching cycle averaging filtering method, and the maximum phase voltage is determined based on the magnitude relationship of the instantaneous values ​​of the three-phase voltages on the AC side. Intermediate phase voltage and minimum phase voltage ; Based on the phase voltage relationship of the corresponding switches, the current vector is divided into... , and Three types; among them for The corresponding phase current vector, correspond , correspond The corresponding switches are respectively used , , express; ; in x , y , z They represent a , b , c one of the, , , This represents the current vector corresponding to the phase. , , They represent a , b , c Three-phase AC voltage.

[0016] Compared with the prior art, the present invention has the following advantages: In the above technical solution, the action sequence of the current vector is reconstructed by utilizing the principle that the switch corresponding to high voltage is reverse-blocked by the switch corresponding to low voltage. A constant conduction signal is set in different sequence modes, reducing the number of switching operations to four to six, significantly less than the eight operations of the traditional SVM5, thereby reducing switching losses. Simultaneously, this reconstruction method ensures the continuity of the DC-side current of the current source rectifier without introducing superposition time, improving the current waveform quality and enhancing the grid-side current quality under any power factor condition. Furthermore, this method obtains symmetrical switching drive signals by directly comparing the carrier wave and the modulation wave, making it easy to implement in a digital processor. Moreover, by constructing two current vector sequence modes and combining them with an adaptive threshold judgment method for dynamic selection, the phenomenon of current sharing is effectively avoided. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the topology of a three-phase current source rectifier in an embodiment of the present invention; Figure 2 This is a flowchart of the hybrid space vector modulation method in an embodiment of the present invention; Figure 3 This is a schematic diagram of the spatial current vector distribution of the current source rectifier in an embodiment of the present invention; Figure 4This is a schematic diagram of the current vector action sequence of a traditional SVM5. Figure 5 This is a schematic diagram of the first current vector sequence mode in an embodiment of the present invention, where (a) is the base sector (sector I) and (b) is the even sector (sector II). Figure 6 This is a schematic diagram of the second current vector sequence mode in an embodiment of the present invention, (a) odd-numbered sectors (sector I), and (b) even-numbered sectors (sector II). Figure 7 The diagram shows the adaptive threshold and line voltage ripple envelope in an embodiment of the present invention. (a) is the line voltage ripple envelope, (b) is the positive threshold, and (c) is the negative threshold. Figure 8 The diagram shows a comparison of grid current quality under different power factor angles and modulation indices in simulation between the traditional method and the method of the present invention. (a) Traditional method with time superposition, (b) Method of the present invention with time superposition. Figure 9 The following is a comparison of FFT analysis of the conventional method and the method of the present invention under unity power factor in the experiment: (a) the method of the present invention, (b) the conventional method. Figure 10 The image shows a comparison of FFT analysis of the conventional method and the method of the present invention under the lead power factor in the experiment. (a) The method of the present invention, (b) The conventional method. Figure 11 The figures show a comparison of FFT analysis of the conventional method and the method of the present invention under the lag power factor in the experiment. (a) The method of the present invention, (b) The conventional method. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] To maintain continuous DC current during power switch switching, the drive signal is delayed and turned off; this delayed turn-off time is called the overlap time (OT). However, the introduction of OT leads to harmonics in the grid-side current, reducing the utilization rate of the DC current. Space Vector Modulation (SVM) improves the output waveform of the CSR by frequently switching the switching state during modulation. While this reduces harmonic distortion, the overlap time effect (OTE) becomes more pronounced due to the increased number of switching operations. Therefore, to eliminate OTE and optimize SVM modulation with minimal switching operations, this invention proposes a hybrid space vector modulation (HSVM) method to optimize the modulation of the current source rectifier. By changing the current vector action sequence in the traditional five-segment SVM method (SVM5), two different current vector sequence modes are proposed, reducing the number of switching operations, thereby reducing OT and improving the utilization rate of the DC current.

[0022] The hybrid space vector modulation method proposed in this invention is applicable to three-phase current source rectifier systems in hydrogen production systems, such as... Figure 1 As shown, the main power section uses IGBTs as switching transistors. Six basic switching units ( S 1- S 6) The basic switching unit of the system is composed of IGBTs and diodes connected in series to ensure single-phase current flow. This is the grid voltage. , and It is the current flowing through the power grid. L and C are the inductance and capacitance on the AC side, respectively. Together, they form an LC filter, which can suppress high-frequency current harmonics. , and It is the three-phase AC voltage of the converter. , and It is the filtered line current. For DC-side energy storage inductor, This represents the DC current, and the rightmost side of the circuit is the load.

[0023] like Figure 2 As shown, a hybrid space vector modulation method for a current source type hydrogen generator includes the following steps: Step S1: Collect the AC side voltage and current signals of the three-phase current source rectifier, establish a spatial vector model of the current source rectifier based on the collected voltage and current signals, and convert the three-phase current into a current space vector in a two-dimensional stationary coordinate system; In practice, the three-phase input voltage and current information of the current source rectifier can be obtained through voltage and current sensors, and the acquired signals can be averaged and filtered during the switching cycle to reduce the impact of noise. The current space vector is obtained by performing coordinate transformation on the three-phase current, converting the current quantity in the three-phase stationary coordinate system into a two-dimensional vector. αβ The space vector of current in a stationary coordinate system.

[0024] The Clarke transform can be used to transform a three-phase stationary phase. Coordinate system transformation to αβ Coordinate system: ; Recorded as: ; in This is called the Clark transform with constant amplitude.

[0025] Step S2: Based on the space vector model, determine the reference current vector according to the three-phase current signal, and calculate the duration of each reference current vector within one switching cycle; like Figure 3 The diagram shows the spatial current vector distribution of a current source rectifier. A three-phase current source rectifier has nine switching states, resulting in nine corresponding spatial current vectors. , , , , , It is an active vector. , , These are zero vectors. Based on these nine current vectors, a regular hexagon divided into six sectors can be constructed, and these six sectors are further divided into odd sectors. ) and even sectors ( According to the ampere-second balance principle, the reference current vector... Similar active vectors can be used. and a zero vector Synthesis. Synthesis in different sectors. The phase current vectors are as follows: Sector Switching transistor Keep it in the on state, while the switching transistor Alternating on / off states correspond to the following current vector: , and ; sector Switching transistor Keep it in the on state, while the switching transistor Alternating on / off states correspond to the following current vector: , and ; sector Switching transistor Keep it in the on state, while the switching transistor Alternating on / off states correspond to the following current vector: , and ; sector Switching transistor Keep it in the on state, while the switching transistor Alternating on / off states correspond to the following current vector: , and ; sector Switching transistor Keep it in the on state, while the switching transistor Alternating on / off states correspond to the following current vector: , and ; sector Switching transistor Keep it in the on state, while the switching transistor Alternating on / off states correspond to the following current vector: , and .

[0026] The duration of each reference current vector depends on its position angle within the sector. and modulation coefficient The calculation is obtained, and it satisfies one switching cycle. The sum of the durations of action of all spatial vectors within the space equals the switching cycle. One switching cycle... Inner vector The duration of action are respectively Zero vector The duration of action is It can be calculated as follows: ; We can conclude that: ; in Modulation coefficient , Indicates a vector angle. If If it is located in another sector, then it can be expressed by the following formula: ; Convert it to a sector The vector in the vector is used to calculate the corresponding action time. This indicates the modified angle. express The sector in which it is located.

[0027] Step S3: Based on the instantaneous values ​​of the three-phase voltage signals, divide the three-phase voltage into maximum voltage, intermediate voltage, and minimum voltage, and define the phase current vectors corresponding to the maximum voltage, intermediate voltage, and minimum voltage as the maximum current vector, intermediate current vector, and minimum current vector, respectively. In this step, the collected three-phase input voltage information is processed using a switching cycle averaging filtering method. Then, by comparing the filtered three-phase voltage information, the corresponding voltage relationships are determined. First, the maximum phase voltage is determined based on the magnitude relationship of the instantaneous values ​​of the three-phase voltages on the AC side. Intermediate phase voltage and minimum phase voltage Based on the phase voltage relationship of the corresponding switches, the current vector is divided into... , and Three types. Among them... for The corresponding phase current vector, correspond , correspond The switches corresponding to these phase current vectors are respectively... , , express.

[0028]

[0029] in , , They represent a , b , c Three-phase AC voltage; x , y , z They represent a ,b , c One of the three phases, , , This represents the current vector corresponding to the phase.

[0030] Step S4: Construct two current vector sequence modes. Each current vector sequence mode includes: determining the action order of the maximum current vector, the intermediate current vector, and the minimum current vector, as well as the corresponding switch switching path, based on the parity of the sector where the reference current vector is located. The first type of current vector sequence mode includes: when When in an odd sector, the current vector sequence is defined as follows: The switch corresponding to high voltage will be reverse-blocked by the switch corresponding to low voltage. The off and on signals and A constant on signal is set between the off and on signals; when When in an even sector, the order in which the current vector is defined is as follows: The switch corresponding to low voltage will be reverse-blocked by the switch corresponding to high voltage. The off and on signals and A constant on signal is set between the off and on signals; The second type of current vector sequence mode includes: when When in an odd sector, the current vector sequence is defined as follows: The switch corresponding to high voltage will be reverse-blocked by the switch corresponding to low voltage. A constant on signal is set between the off and on signals, and respectively at... Add slack current time at the signal turn-on and turn-off points ;when When in an even sector, the switch corresponding to the low voltage will be reverse-blocked by the switch corresponding to the high voltage, thus defining the order of the current vectors as follows: ,exist A constant on signal is set between the off and on signals, and respectively at... Add slack current time at the signal turn-on and turn-off points .

[0031] Step S5: Calculate the line voltage and set a voltage threshold; compare the line voltage with the set threshold and dynamically select one from two current vector sequence modes; Specifically, a voltage threshold is set, and an adaptive threshold judgment method is established. By detecting the system operating status parameters, two current vector sequence modes are dynamically selected. When the line voltage exceeds the threshold, the first current vector sequence mode is used; when the line voltage is within the threshold, the second current vector sequence mode is used, thereby effectively avoiding the current sharing phenomenon.

[0032] Among them, voltage threshold The calculation method is as follows: ; in, h This represents the height of the triangular high-frequency ripple voltage envelope; v represents each The height variation of the ideal line voltage; This represents the maximum value of the envelope height of the triangular high-frequency ripple voltage; , f The power grid frequency; U This represents the amplitude of the ideal line voltage of the grid-side capacitor. This represents one switching cycle.

[0033] The line voltage is calculated as follows: The reference line current and the PWM line current are defined as follows: ; Subscript ref Indicates the reference current value. p=0,n,n+ 1 represents the pulse width modulation current vector. The corresponding phase current; The relationship between the pulse width modulation line current and the DC side current is as follows: ; in n Represents the reference current vector The sector number; Voltage ripple of grid-side capacitors Represented as: ; The integral sum of the difference between the reference current and the PWM line current over the switching cycle remains close to zero. ; The envelope expression for the high-frequency ripple of the capacitor line voltage is: .

[0034] Step S6: Determine the current vector action sequence and action time within a switching cycle according to the selected current vector sequence mode and action duration, generate a modulation signal and compare it with the carrier signal to obtain a PWM drive signal to drive the power switching device of the current source rectifier.

[0035] Specifically, assuming the height of the triangular wave is ,in This refers to the duration of action of the current vector. Based on the reconstructed current vector sequence, the new modulation signal is recalculated. : Sequence Mode 1: In odd sectors, the current vector order is defined as follows: .

[0036]

[0037] In the even sector, the current vector order is defined as follows: .

[0038]

[0039] Sequence Mode 2: In odd sectors, the current vector order is defined as follows: .

[0040]

[0041] In the even sector, the current vector order is defined as follows: .

[0042]

[0043] New modulation signal The three-phase drive signal is obtained by comparing it with the carrier signal. Based on logical operations, drive signals are distributed to the corresponding switches. .

[0044] In the above embodiments, the action sequence of the current vector is reconstructed by utilizing the principle that the switch corresponding to high voltage is reverse-blocked by the switch corresponding to low voltage. A constant conduction signal is set in different sequence modes, reducing the number of switching operations to four to six, which is significantly reduced compared to the eight operations of the traditional SVM5, thereby reducing switching losses. At the same time, this reconstruction method ensures the continuity of the DC side current of the current source rectifier without introducing superposition time, improves the current waveform quality, and can improve the grid-side current quality under any power factor conditions. In addition, this method can obtain symmetrical switching drive signals by directly comparing the carrier wave and the modulation wave, which is easy to implement in a digital processor. Furthermore, by constructing two current vector sequence modes and combining them with an adaptive threshold judgment method for dynamic selection, the occurrence of current sharing phenomenon is effectively avoided.

[0045] Figure 4 This is a schematic diagram of the current vector action sequence of a traditional SVM5, with the shaded area representing the superposition time. This shows a deviation from the ideal current condition. Figure 4As can be seen, in an ideal traditional SVM5, the current changes simultaneously with the switching, without overlap. The vector sequence of a traditional SVM5 is... , , , , Taking the first sector as an example, the vector sequence of traditional SVM5 is: , , , , . The corresponding switch is turned on. , ; The corresponding switch is turned on. , ; The corresponding switch is turned on. , Within a single switching cycle: Normally open; After one activation and one shutdown; It was opened twice and shut down twice; After one turn-on and one turn-off, a total of 8 switching operations are performed. Using the traditional SVM5 combined with the overlay time (OT) method, taking sector I as an example, when... In sector I, the three-phase line voltage relationship > ≥ At that time, the current vector sequence is .exist arrive During the transition, due to ≥ ,exist period, quilt Reverse blocking, current still flows. Similarly, from arrive During the transition, During this period, the current still flows. Compared to the ideal traditional SVM5, the action time of the current vector changes, leading to a change in the ideal SVM5. OT combined with SVM5 There is a discrepancy between them. It can be seen that there is a necessary switching time when the current vector is switched. Therefore, there are 8 switching operations.

[0046] Figure 5 This is a schematic diagram of the first current vector sequence mode proposed in this invention. When When in an odd sector, the switch corresponding to high voltage is reverse-blocked by the switch corresponding to low voltage, and the current vector sequence is defined as follows: ,exist The off and on signals and A constant on signal is set between the off and on signals; when When in an even sector, the switch corresponding to the low voltage will be reverse-blocked by the switch corresponding to the high voltage, thus defining the order of the current vectors as follows: ,exist The off and on signals and A constant on signal is set between the turn-off and turn-on signals. When using the first current vector sequence mode, the number of switching operations is reduced to four. More specifically, in odd-numbered sectors, taking the first sector as an example, the three-phase voltage relationship is: > ≥ , for ( correspond ); for ( correspond ); for ( correspond The current vector sequence used at this time is: ,Right now . The corresponding switch is turned on. , ; The corresponding switch is turned on. , ; The corresponding switch is turned on. , The switch corresponding to the high voltage is reverse-blocked by the switch corresponding to the low voltage, and... and A constant on signal is set between the on and off signals, therefore , Normally open; After one activation and one shutdown; After one turn-on and one turn-off, there are a total of 4 switching operations. The analysis for other sectors is similar. In even-numbered sectors, taking the second sector as an example, the three-phase voltage relationship is as follows: > ≥ , for ( correspond ); for ( correspond ); for ( correspond The current vector sequence used at this time ,Right now . The corresponding switch is turned on. , ; The corresponding switch is turned on. , ; The corresponding switch is turned on. , The switch corresponding to the low voltage is reverse-blocked by the switch corresponding to the high voltage, and... and A constant on signal is set between the on and off signals, therefore , Normally open; After one activation and one shutdown; After one on and one off cycle, a total of 4 on / off cycles were performed. Analysis of other sectors is similar.

[0047] Figure 6 This is a schematic diagram of the second current vector sequence mode proposed in this invention. When When in an odd sector, the current vector sequence is defined as follows: ,exist A constant on signal is set between the off and on signals, and respectively at... Add slack current time at the signal turn-on and turn-off points ;when When in an even sector, the switch corresponding to the low voltage will be reverse-blocked by the switch corresponding to the high voltage, thus defining the order of the current vectors as follows: ,exist A constant on signal is set between the off and on signals, and respectively at... Add slack current time at the signal turn-on and turn-off points When using the second current vector sequence mode, the number of switching operations is reduced to six. More specifically, in odd-numbered sectors, taking the first sector as an example, the three-phase voltage relationship is as follows: > > , for ( correspond ); for ( correspond ); for ( correspond The current vector sequence used at this time ,Right now . The corresponding switch is turned on. , ; The corresponding switch is turned on. , ; The corresponding switch is turned on. , .exist A constant on signal is set between the on and off signals, and... Add overlap time at the start and end of the signal Therefore Normally open; After one activation and one shutdown; After one activation and one shutdown; After one turn-on and one turn-off, a total of 6 switching operations are performed. The analysis for other sectors is similar. In even-numbered sectors, taking the second sector as an example, the three-phase voltage relationship is as follows: > > , for ( correspond ); for ( correspond ); for ( correspond The current vector sequence used at this time ,Right now . The corresponding switch is turned on. , ; The corresponding switch is turned on. , The switch corresponding to I3 is turned on. , .exist A constant on signal is set between the on and off signals, and... Add overlap time at the start and end of the signal Therefore Normally open; After one activation and one shutdown; After one activation and one shutdown; After one on and one off cycle, a total of 6 on / off cycles were performed. Analysis of other sectors is similar.

[0048] Therefore, during the entire modulation process, the number of switches is 4 in the first current vector sequence mode and 6 in the second current vector sequence mode. The average number of switches in one switching cycle (both the first and second current vector sequence modes are used) is less than 6, which is less than the number of switches (8) of the traditional SVM5.

[0049] like Figure 7 The diagram shows the adaptive threshold and line voltage ripple envelope. The actual line voltage is obtained by superimposing the voltage ripple and the ideal line voltage. This diagram illustrates two cases where the actual line voltage waveform precisely touches the zero boundary at the minimum (maximum) point in the second half of the modulation period. Geometric relationships show that the high-frequency ripple voltage... h Height and ideal line voltage variation during each switching cycle The sum of the heights of v is always greater than the threshold.

[0050] Figure 8 The diagram shows a comparison of grid current quality under different power factor angles and modulation indices using the traditional SVM5 method and the proposed HSVM method in MATLAB / Simulink simulations. FFT analyses were performed using the traditional SVM5 method combined with the OT method and the proposed HSVM method combined with the overlap time OT method at different power factor angles and modulation indices. It can be seen that regardless of changes in the power factor angle and modulation indices, the total harmonic distortion (THD) of the HSVM method is lower than that of the traditional method. Especially at low modulation indices, the THD of the traditional method increases significantly, while the HSVM method maintains a stable low THD. Simulation results verify the superiority of this method under different power factor angles and modulation indices.

[0051] like Figure 9 The image shows a comparison of FFT analysis of the present invention (HSVM method) and the conventional method on a CSR experimental platform at unity power factor. Conventional method The THD value of the HSVM method is 4.68%, while the THD value of the HSVM method is 3.65%.

[0052] like Figure 10 The image shows a comparison of FFT analysis of the present invention (HSVM method) and the conventional method on a CSR experimental platform, under the condition of a leading power factor. Conventional method The THD value of the HSVM method is 4.56%, while the THD value of the HSVM method is 3.44%.

[0053] like Figure 11 The image shows a comparison of FFT analysis of the present invention (HSVM method) and the conventional method on a CSR experimental platform, under the condition of lag power factor. Conventional method i ra The THD value of the HSVM method is 5.39%, while the THD value of the HSVM method is 3.66%.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hybrid space vector modulation method for a current source type hydrogen generation converter, the hydrogen generation converter being a current source rectifier based on pulse width modulation control; characterized in that, The method includes: Collect the three-phase current signal and three-phase voltage signal on the AC side of the current source rectifier, and establish a space vector model of the current source rectifier; Based on the space vector model, the reference current vector is determined according to the three-phase current signal, and the duration of each reference current vector within one switching cycle is calculated. Based on the instantaneous values ​​of the three-phase voltage signals, the three-phase voltages are divided into maximum voltage, intermediate voltage, and minimum voltage, and the phase current vectors corresponding to the maximum voltage, intermediate voltage, and minimum voltage are defined as the maximum current vector, intermediate current vector, and minimum current vector, respectively. Two current vector sequence modes are constructed. Each current vector sequence mode includes: determining the action order of the maximum current vector, the intermediate current vector, and the minimum current vector, as well as the corresponding switching path, based on the parity of the sector where the reference current vector is located. Calculate the line voltage and set a voltage threshold; compare the line voltage with the set voltage threshold, and dynamically select one from two current vector sequence modes; Based on the selected current vector sequence mode and the duration of action, the current vector action sequence and action time within a switching cycle are determined, a modulation signal is generated and compared with the carrier signal to obtain a pulse width modulation drive signal, so as to drive the power switching device of the current source rectifier.

2. The hybrid space vector modulation method of a current source type hydrogen generator converter according to claim 1, characterized by, The first type of current vector sequence mode includes: When the reference current vector When in an odd sector, the current vector sequence is defined as follows: The switch corresponding to high voltage is reverse-blocked by the switch corresponding to low voltage. The off and on signals and A constant on signal is set between the off and on signals; when When in an even sector, the switch corresponding to the low voltage will be reverse-blocked by the switch corresponding to the high voltage. The order of defining the current vector is as follows: ,exist The off and on signals and A constant on signal is set between the off and on signals; The second type of current vector sequence mode includes: when When in an odd sector, the current vector sequence is defined as follows: The switch corresponding to high voltage is reverse-blocked by the switch corresponding to low voltage. A constant on signal is set between the off and on signals, and respectively at... Add slack current time at the signal turn-on and turn-off points ;when When in an even sector, the switch corresponding to the low voltage will be reverse-blocked by the switch corresponding to the high voltage, thus defining the order of the current vectors as follows: ,exist A constant on signal is set between the off and on signals, and respectively at... Add slack current time at the signal turn-on and turn-off points ; in, , and These represent the maximum current vector, the intermediate current vector, and the minimum current vector, respectively. , , These represent the switches corresponding to the maximum current vector, intermediate current vector, and minimum current vector, respectively.

3. The hybrid space vector modulation method of a current source type hydrogen generator converter according to claim 1, characterized by, Acquiring the three-phase current signal and three-phase voltage signal on the AC side of the current source rectifier includes: obtaining the three-phase input voltage and input current information of the current source rectifier through voltage sensors and current sensors.

4. The hybrid space vector modulation method for a current source type hydrogen generator according to claim 3, characterized in that, Calculate the duration of each reference current vector within a switching cycle, including: The acquired signal is subjected to switching cycle averaging filtering; The current in the three-phase stationary coordinate system is converted into a two-dimensional current space vector by Clarke coordinate transformation αβ a current source rectifier comprising nine switching states, corresponding to nine space current vectors, based on which a regular hexagon comprising six space vector sectors is constructed; The spatial vector sector in which the reference current vector is located is determined based on the position angle of the current spatial vector, and the composition relationship between the reference current vector and the two adjacent effective current vectors in the spatial vector sector is calculated. Based on the position angle of the reference current vector and the switching period, calculate the duration of action of two adjacent effective current vectors and the zero vector.

5. The hybrid space vector modulation method for a current source type hydrogen generator according to claim 4, characterized in that, One switching cycle Internal effective current vector The duration of action are respectively Zero vector The duration of action is The reference current vector The following conditions must be met: ； Based on the position angle of the reference current vector and the switching period, calculate the duration of action of the two adjacent effective current vectors and the zero vector: ； in The modulation coefficient, , Represents a vector angle; if If located in other sectors, then , ,in This indicates the modified angle. express Convert the sector it is located to a sector. The vector in the vector is used to calculate the corresponding action time.

6. The hybrid space vector modulation method of a current-source-type hydrogen generator converter according to claim 2, wherein The line voltage is compared with the set threshold, and one of two current vector sequence modes is dynamically selected, including: when the line voltage exceeds the threshold, the first current vector sequence mode is used; when the line voltage is within the threshold, the second current vector sequence mode is used.

7. The hybrid space vector modulation method of a current-source-type hydrogen generator converter according to claim 1 or 6, characterized by, voltage threshold is calculated as follows: ； in, h This represents the height of the triangular high-frequency ripple voltage envelope; v represents the height change of the ideal line voltage during each switching cycle; This represents the maximum value of the envelope height of the triangular high-frequency ripple voltage; , f The power grid frequency; U This represents the amplitude of the ideal line voltage of the grid-side capacitor. This represents one switching cycle.

8. The hybrid space vector modulation method of a current-source-type hydrogen generator converter according to claim 7, wherein The calculation of line voltage includes: The reference line current and the pulse width modulation line current are defined as follows: ； subscript ref denotes a reference current value, p=0,n,n+ 1 denotes a pulse width modulated current vector a corresponding phase current; The relationship between the pulse width modulation line current and the DC side current is as follows: ； wherein n denotes a reference current vector the number of the sector in which the mobile station is located; Voltage ripple of a grid-side capacitor is expressed as: ； The integral sum of the difference between the reference current and the pulse width modulation line current over the switching cycle remains close to zero. ； The envelope expression for the high-frequency ripple of the capacitor line voltage is: ； wherein represents an AC side capacitor; a , b , c represents the number of three phases.

9. The hybrid space vector modulation method of a current-source-type hydrogen generator converter according to claim 5, wherein Determining the current vector action sequence within a switching cycle based on the selected current vector sequence mode and the duration of action includes: Assume the height of the triangle wave is where is the time of action corresponding to the current vector; calculating a modulation signal in accordance with the order of the current vectors in the selected vector sequence pattern : Sequence Mode 1: In odd sectors, the current vector order is defined as follows: ; ； In the even sector, the current vector order is defined as ; ； Sequence pattern 2: In odd sectors, the current vector order is defined as ; ； In the even sector, the current vector order is defined as ; 。 10. The hybrid space vector modulation method for a current source type hydrogen converter according to claim 1, characterized in that, Based on the instantaneous values ​​of the three-phase voltage signals, the three-phase voltages are divided into maximum voltage, intermediate voltage, and minimum voltage. The phase current vectors corresponding to the maximum, intermediate, and minimum voltages are defined as the maximum current vector, intermediate current vector, and minimum current vector, respectively, including: The collected three-phase input voltage information is processed using a switching cycle averaging filtering method, and the maximum phase voltage is determined based on the magnitude relationship of the instantaneous values ​​of the three-phase voltages on the AC side. Intermediate phase voltage and minimum phase voltage ; Based on the phase voltage relationship of the corresponding switches, the current vector is divided into... , and Three types; among them for The corresponding phase current vector, correspond , correspond The corresponding switches are respectively used , , express; ； in x , y , z They represent a , b , c One of the three phases, , , This represents the current vector corresponding to the phase. , , They represent a , b , c Three-phase AC voltage.

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