A hybrid switching modulation method and system

Abstract

The present invention provides a hybrid switching modulation method and system, the method comprising: obtaining an SPWM three-phase modulation wave generated by a sinusoidal pulse width modulation method; sampling the SPWM three-phase modulation wave to obtain a first sampling result; calculating a modulation ratio of the first sampling result, and determining whether the modulation ratio is greater than or equal to a preset modulation ratio, wherein the modulation ratio is a ratio of a spatial reference voltage vector amplitude to a DC bus voltage; and when the modulation ratio is greater than or equal to the preset modulation ratio, superimposing a zero-sequence component on the SPWM three-phase modulation wave to obtain a DPWMA three-phase modulation wave, for increasing the voltage utilization rate of the SPWM three-phase modulation wave.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic inverters, and in particular to a hybrid switching modulation method and system. Background Art

[0002] Sinusoidal pulse width modulation (PWM) is a relatively mature and widely used PWM method. It's based on the theory that narrow pulses of equal impulse but different shapes produce essentially the same effect when applied to a link with inertia. By using a sinusoidal variation in pulse width and a sine-wave-equivalent PWM waveform to control the on-off switching of the inverter circuit, the equivalent output voltage is changed. While PWM can produce three-phase sinusoidal voltages, this modulation method suffers from low DC voltage utilization and a high number of switching cycles for the circuit's switching elements, resulting in high switching losses.

[0003] In some modulation schemes, the problems of low voltage utilization and high switching losses can be solved by improving the sinusoidal pulse width modulation method. However, this will also introduce other problems such as electromagnetic interference. How to improve the problems of low voltage utilization and high switching losses in the modulation process based on the sinusoidal pulse width modulation method? The existing technology does not have a good technical solution. Summary of the Invention

[0004] The problem solved by the present invention is how to improve the voltage utilization rate in the modulation process of the sinusoidal pulse width modulation method.

[0005] To solve the above problems, in a first aspect, the present invention provides a hybrid switching modulation method, comprising:

[0006] Obtain the SPWM three-phase modulation wave generated by the sinusoidal pulse width modulation method;

[0007] Sampling the SPWM three-phase modulation wave to obtain a first sampling result;

[0008] Calculating a modulation ratio of the first sampling result, and determining whether the modulation ratio is greater than or equal to a preset modulation ratio, wherein the modulation ratio is a ratio of a spatial reference voltage vector amplitude to a DC bus voltage;

[0009] When the modulation ratio is greater than or equal to the preset modulation ratio, a zero-sequence component is superimposed on the SPWM three-phase modulation wave to obtain a DPWMA three-phase modulation wave.

[0010] Compared with the existing technology, the present invention combines the advantages of sinusoidal pulse width modulation and DPWMA modulation. By sampling the three-phase modulated wave, a sampling result is obtained, and it is judged whether the modulation ratio of the sampling result is greater than or equal to the preset modulation ratio. If the modulation ratio is too large, it means that at the sampling moment, the voltage utilization rate of the three-phase modulated wave obtained by the sinusoidal pulse width modulation method is low. Superimposing the zero-sequence component on the basis of the SPWM three-phase modulated wave can reduce the switching frequency of the switch tube in the three-phase inverter, reduce switching losses, and also improve the voltage utilization rate of the three-phase modulated wave.

[0011] Optionally, before superimposing a zero-sequence component on the SPWM three-phase modulation wave to obtain a DPWMA three-phase modulation wave when the modulation ratio is greater than or equal to the preset modulation ratio, the method further includes:

[0012] Determining a first distance and a second distance between the per-unit value of each phase electrical signal in the three-phase electrical signal and a modulation wave boundary according to the per-unit value of the three-phase sine wave in the SPWM three-phase modulation wave, wherein 1, 0, and -1 are used as the modulation wave boundary, when the per-unit value is between 0 and 1, the first distance is the distance between the per-unit value and 1, and the second distance is the distance between the per-unit value and 0; when the per-unit value is between -1 and 0, the first distance is the distance between the per-unit value and 0, and the second distance is the distance between the per-unit value and -1;

[0013] The zero-sequence component is determined according to the first distance and the second distance.

[0014] Optionally, determining the zero-sequence component according to the first distance and the second distance includes:

[0015] Selecting one of the three-phase electrical signals as the phase signal to be calculated;

[0016] Obtaining the first distance and the second distance corresponding to the phase signal to be calculated;

[0017] The zero-sequence component of the phase signal to be calculated is determined according to the minimum value of the first distance and the second distance.

[0018] Optionally, determining the zero-sequence component of the phase signal to be calculated according to the minimum value of the first distance and the second distance includes:

[0019] When the per-unit value of the phase signal to be calculated is greater than or equal to 0, directly superimposing the zero-sequence component into the SPWM three-phase modulation wave;

[0020] When the per-unit value of the phase signal to be calculated is less than 0, the value of the zero-sequence component is increased by 1, and then the zero-sequence component is superimposed on the SPWM three-phase modulation wave.

[0021] Optionally, sampling the SPWM three-phase modulation wave to obtain a first sampling result includes:

[0022] Sampling the SPWM three-phase modulation wave to obtain three-phase sampling data;

[0023] A coordinate system transformation is performed on the three-phase sampling data to obtain the first sampling result, wherein the first sampling result is represented by a dq coordinate system.

[0024] Optionally, after calculating the modulation ratio of the first sampling result and determining whether the modulation ratio is greater than or equal to a preset modulation ratio, the method further includes:

[0025] When the modulation ratio is less than the preset modulation ratio, a sinusoidal pulse width modulation driving signal is injected into the three-phase inverter.

[0026] Optionally, when the modulation ratio is greater than or equal to the preset modulation ratio, after superimposing a zero-sequence component on the SPWM three-phase modulation wave to obtain a DPWMA three-phase modulation wave, the method further includes:

[0027] Sampling the DPWMA three-phase modulation wave to obtain a second sampling result;

[0028] Calculating a modulation ratio of the second sampling result, and determining whether the modulation ratio of the second sampling result is greater than or equal to the preset modulation ratio;

[0029] When the modulation ratio of the second sampling result is less than the preset modulation ratio, a sinusoidal pulse width modulation driving signal is injected into the three-phase inverter.

[0030] Optionally, after calculating the modulation ratio of the second sampling result and determining whether the modulation ratio of the second sampling result is greater than or equal to the preset modulation ratio, the method further includes:

[0031] When the modulation ratio of the second sampling result is greater than or equal to the preset modulation ratio, the zero-sequence component is added to the SPWM three-phase modulation wave to obtain a DPWMA three-phase modulation wave.

[0032] Optionally, the preset modulation ratio value is 1.

[0033] In another aspect, the present invention further provides a hybrid switching modulation system, comprising a processor unit;

[0034] The processor unit is used to implement the hybrid switching modulation method described above.

[0035] The beneficial effects of the hybrid switching modulation system relative to the prior art are the same as those of the hybrid switching modulation method, and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the flow of a hybrid switching modulation method according to an embodiment of the present invention;

[0037] Figure 2 Schematic diagram of a hybrid switching modulation method according to an embodiment of the present invention;

[0038] Figure 3 Schematic diagram of the flow before step S400 of the hybrid switching modulation method according to an embodiment of the present invention;

[0039] Figure 4 1. This is a schematic diagram of a detailed flow chart of step S390 of the hybrid switching modulation method according to an embodiment of the present invention;

[0040] Figure 5 4 is a schematic diagram of a detailed flow chart of step S400 of the hybrid switching modulation method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described herein. Instead, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0042] It should be understood that the various steps described in the method embodiments of the present invention may be performed in different orders and / or in parallel. In addition, the method embodiments may include additional steps and / or omit the steps shown. The scope of the present invention is not limited in this respect.

[0043] The term "including" and its variations used in this document are open inclusions, that is, "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiments". The relevant definitions of other terms will be given in the following description. It should be noted that the concepts of "first", "second", etc. mentioned in the present invention are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0044] It should be noted that the modifications of "one" and "multiple" mentioned in the present invention are illustrative rather than restrictive. Those skilled in the art should understand that unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0045] like Figure 1 As shown, an embodiment of the present invention provides a hybrid switching modulation method, including:

[0046] Step S100: obtaining an SPWM three-phase modulation wave generated by a sinusoidal pulse width modulation method.

[0047] SPWM (Sinusoidal PWM) is a sinusoidal pulse width modulation method.

[0048] In one embodiment, SPWM modulation is used to generate a modulated waveform with a low common-mode voltage, thereby preventing severe electromagnetic interference caused by the high amplitude common-mode voltage of the photovoltaic inverter. In this embodiment, the circuit includes a photovoltaic panel and a three-phase inverter. The photovoltaic panel is used to input a DC bus voltage to the three-phase inverter. After receiving a PWM drive signal from a controller, the three-phase inverter performs PWM modulation based on the PWM drive signal to produce three AC currents with evenly separated phase angles. The initial PWM drive signal is an SPWM drive signal. In the initial state, the a-phase, b-phase, and c-phase sinusoidal modulated waves generated by SPWM modulation are obtained.

[0049] Step S200: sampling the SPWM three-phase modulation wave to obtain a first sampling result.

[0050] After obtaining the sinusoidal modulation wave in the initial state, the modulated sinusoidal wave is sampled and the sampling result is analyzed. It can be known from the sampling result whether the current modulated electrical signal has a qualified voltage utilization rate.

[0051] Specifically, the first sampling result includes a phase a sampling result, a phase b sampling result, and a phase c sampling result, and the sampling results of phases a, b, and c are analyzed separately to determine the voltage utilization rate of each phase electrical signal during modulation.

[0052] Step S300 , calculating a modulation ratio of the first sampling result, and determining whether the modulation ratio is greater than or equal to a preset modulation ratio, wherein the modulation ratio is a ratio of a spatial reference voltage vector amplitude to a DC bus voltage.

[0053] Optionally, the preset modulation ratio is 1.

[0054] In one embodiment, the ratio of the spatial reference voltage vector amplitude to the DC bus voltage (i.e., the output voltage of the photovoltaic panel to the three-phase inverter) is selected as the modulation ratio, which can determine the actual situation at the sampling moment and determine the specific modulation method based on the actual situation.

[0055] Step S400: When the modulation ratio is greater than or equal to the preset modulation ratio, a zero-sequence component is superimposed on the SPWM three-phase modulation wave to obtain a DPWMA three-phase modulation wave.

[0056] When the modulation ratio is greater than or equal to the preset modulation ratio, that is, the modulation ratio is too large, it means that at the modulation moment, the utilization rate of the DC bus voltage is low, and it is necessary to improve the voltage utilization rate on the basis of SPWM modulation, that is, to superimpose the zero-sequence component on the SPWM three-phase modulation wave to improve the voltage utilization rate through DPWMA modulation.

[0057] Optionally, after calculating the modulation ratio of the first sampling result and determining whether the modulation ratio is greater than or equal to a preset modulation ratio, the method further includes:

[0058] When the modulation ratio is less than the preset modulation ratio, a sinusoidal pulse width modulation driving signal is injected into the three-phase inverter.

[0059] In one embodiment, when the modulation ratio is less than a preset modulation ratio, that is, the modulation ratio is too small, it indicates that a large common-mode voltage may appear at the modulation moment. Regardless of the PWM drive signal injected into the three-phase inverter at the modulation moment, the PWM drive signal is changed to an SPWM drive signal. The common-mode voltage is suppressed as much as possible through SPWM modulation to prevent electromagnetic interference problems.

[0060] Alternatively, as Figure 2 and Figure 3 As shown, before superimposing a zero-sequence component on the SPWM three-phase modulation wave to obtain a DPWMA three-phase modulation wave when the modulation ratio is greater than or equal to the preset modulation ratio, the method further includes:

[0061] Step S380: determining a first distance and a second distance between the per-unit value of each phase electrical signal in the three-phase electrical signal and a modulation wave boundary based on the per-unit value of the three-phase sine wave in the SPWM three-phase modulation wave, wherein 1, 0, and -1 are used as the modulation wave boundary. When the per-unit value is between 0 and 1, the first distance is the distance between the per-unit value and 1, and the second distance is the distance between the per-unit value and 0; when the per-unit value is between -1 and 0, the first distance is the distance between the per-unit value and 0, and the second distance is the distance between the per-unit value and -1.

[0062] Step S390: Determine the zero-sequence component according to the first distance and the second distance.

[0063] In one embodiment, the SPWM three-phase modulation wave is expressed as:

[0064] ,

[0065] in, Represent the sine waves of phase a, phase b and phase c respectively, M represents the modulation ratio, represents angular velocity, and t represents time.

[0066] The modulation ratio M is defined as the spatial reference voltage vector amplitude and DC bus voltage The ratio of the spatial reference voltage vector magnitude include , respectively represent the reference voltage vector amplitude of phase a, the reference voltage vector amplitude of phase b and the reference voltage vector amplitude of phase c.

[0067] According to the principle of zero-sequence component injection, the three-phase modulation wave of DPWMA is expressed as:

[0068] ,

[0069] in, Represents the zero-sequence component.

[0070] The distance between the per-unit value of the sine wave of phase a, phase b and phase c and the boundary of the modulation wave is taken as the first distance and the second distance , expressed as:

[0071] ,

[0072] ,

[0073] By the first distance and the second distance It can be seen that when When it is greater than or equal to 0, the first distance is The distance from boundary 1, when When it is less than 0, the first distance is The distance from the boundary 0; when When it is greater than or equal to 0, the second distance is The distance from the boundary 0, when When it is less than 0, the second distance is Distance from border - 1.

[0074] Alternatively, as Figure 4 As shown, determining the zero-sequence component according to the first distance and the second distance includes:

[0075] Step S391, selecting one phase of the three-phase electrical signal as the phase signal to be calculated;

[0076] Step S392, obtaining the first distance and the second distance corresponding to the phase signal to be calculated;

[0077] Step S393: Determine the zero-sequence component of the phase signal to be calculated according to the minimum value of the first distance and the second distance.

[0078] In one embodiment, the zero-sequence component is expressed as:

[0079] ,

[0080] in, represents the absolute value of the first distance, Indicates the absolute value of the second distance.

[0081] Optionally, determining the zero-sequence component of the phase signal to be calculated according to the minimum value of the first distance and the second distance includes:

[0082] When the per-unit value of the phase signal to be calculated is greater than or equal to 0, directly superimposing the zero-sequence component into the SPWM three-phase modulation wave;

[0083] When the per-unit value of the phase signal to be calculated is less than 0, the value of the zero-sequence component is increased by 1, and then the zero-sequence component is superimposed on the SPWM three-phase modulation wave.

[0084] In one embodiment, the superposition of zero-sequence components can be expressed as:

[0085] ,

[0086] In one embodiment, DPWMA modulation can be formed by superimposing a zero-sequence component on the basis of SPWM modulation. The SPWM modulation interval is in the interval [0,1]. The modulation interval after superimposing the zero-sequence component can reach [0, ], therefore, the voltage utilization rate can be improved by superimposing the zero-sequence component at the moment when the SPWM modulation voltage utilization rate is low. This modulation process has a low computational complexity and is applicable to any level inverter.

[0087] Optionally, sampling the SPWM three-phase modulation wave to obtain a first sampling result includes:

[0088] Sampling the SPWM three-phase modulation wave to obtain three-phase sampling data;

[0089] A coordinate system transformation is performed on the three-phase sampling data to obtain the first sampling result, wherein the first sampling result is represented by a dq coordinate system.

[0090] In one embodiment, the SPWM three-phase modulated wave is sampled. To simplify calculation and obtain better modulation effect, the coordinate system of the modulated wave is transformed from the abc three-phase coordinate system to the dq coordinate system.

[0091] Alternatively, as Figure 5 As shown, when the modulation ratio is greater than or equal to the preset modulation ratio, after superimposing a zero-sequence component on the SPWM three-phase modulation wave to obtain a DPWMA three-phase modulation wave, the method further includes:

[0092] Step S410, sampling the DPWMA three-phase modulation wave to obtain a second sampling result;

[0093] Step S420, calculating the modulation ratio of the second sampling result, and determining whether the modulation ratio of the second sampling result is greater than or equal to the preset modulation ratio;

[0094] Step S430: When the modulation ratio of the second sampling result is less than the preset modulation ratio, injecting a sinusoidal pulse width modulation driving signal into the three-phase inverter.

[0095] Optionally, the preset modulation ratio value is 1.

[0096] In one embodiment, after the zero-sequence component is superimposed on the SPWM modulated wave for the first time, the superimposed DPWMA three-phase modulated wave is resampled to obtain a second sampling result. The three-phase modulated wave in the second sampling result is subjected to a coordinate system transformation and represented by a dq coordinate system. The modulation ratio of the signal is re-determined. When the modulation ratio is still greater than 1, the DPWMA drive signal is continuously injected into the inverter so that the zero-sequence component continues to be superimposed on the SPWM three-phase modulated wave.

[0097] In another embodiment, when the second sampling result shows that the modulation ratio is less than the preset modulation ratio, it means that the voltage utilization is in a higher range. At this time, the SPWM drive signal is injected into the three-phase inverter and the superposition of the zero-sequence component is stopped.

[0098] Another embodiment of the present invention provides a hybrid switching modulation system, including a processor unit;

[0099] The processor unit is used to implement the hybrid switching modulation method described above.

[0100] Another embodiment of the present invention provides an electronic device, comprising a memory and a processor; the memory is used to store a computer program; the processor is used to implement the hybrid switching modulation method described above when executing the computer program.

[0101] Yet another embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the hybrid switching modulation method described above is implemented.

[0102] An electronic device that can serve as a server or client of the present invention will now be described, which is an example of a hardware device that can be applied to various aspects of the present invention. Electronic devices are intended to represent various forms of digital electronic computer devices, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. Electronic devices can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present invention described and / or required herein.

[0103] Electronic devices include a computing unit that can perform various appropriate actions and processes based on computer programs stored in read-only memory (ROM) or loaded from a storage unit into random access memory (RAM). RAM can also store various programs and data required for device operation. The computing unit, ROM, and RAM are connected to each other via a bus. An input / output (I / O) interface is also connected to the bus.

[0104] Computer systems may include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The client and server relationship arises through computer programs running on the respective computers and having a client-server relationship to each other.

[0105] Those skilled in the art will appreciate that all or part of the processes in the above-described method embodiments can be implemented by instructing the relevant hardware through a computer program. The program can be stored in a computer-readable storage medium. When executed, the program can include the processes in the above-described method embodiments. The storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM). In this application, the units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, and may be located in a single location or distributed across multiple network elements. Some or all of these units can be selected based on actual needs to achieve the objectives of the embodiments of the present invention. Furthermore, the functional units in the various embodiments of the present invention can be integrated into a single processing unit, each unit can exist physically separately, or two or more units can be integrated into a single unit. These integrated units can be implemented in either hardware or software functional units.

[0106] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A hybrid switching modulation method, characterized in that: include: Obtain the SPWM three-phase modulation wave generated by the sinusoidal pulse width modulation method; Sampling the SPWM three-phase modulation wave to obtain a first sampling result; Calculating a modulation ratio of the first sampling result, and determining whether the modulation ratio is greater than or equal to a preset modulation ratio, wherein the modulation ratio is a ratio of a spatial reference voltage vector amplitude to a DC bus voltage; When the modulation ratio is greater than or equal to the preset modulation ratio, a zero-sequence component is superimposed on the SPWM three-phase modulation wave to obtain a DPWMA three-phase modulation wave; Sampling the DPWMA three-phase modulation wave to obtain a second sampling result; Calculating a modulation ratio of the second sampling result, and determining whether the modulation ratio of the second sampling result is greater than or equal to the preset modulation ratio; When the modulation ratio of the second sampling result is greater than or equal to the preset modulation ratio, adding the zero-sequence component to the SPWM three-phase modulation wave to obtain a DPWMA three-phase modulation wave; When the modulation ratio of the second sampling result is less than the preset modulation ratio, a sinusoidal pulse width modulation driving signal is injected into the three-phase inverter.

2. The hybrid switching modulation method according to claim 1, characterized in that: Before superimposing a zero-sequence component on the SPWM three-phase modulation wave to obtain a DPWMA three-phase modulation wave when the modulation ratio is greater than or equal to the preset modulation ratio, the method further includes: Determining a first distance and a second distance between the per-unit value of each phase electrical signal in the three-phase electrical signal and a modulation wave boundary according to the per-unit value of the three-phase sine wave in the SPWM three-phase modulation wave, wherein 1, 0, and -1 are used as the modulation wave boundary, when the per-unit value is between 0 and 1, the first distance is the distance between the per-unit value and 1, and the second distance is the distance between the per-unit value and 0; when the per-unit value is between -1 and 0, the first distance is the distance between the per-unit value and 0, and the second distance is the distance between the per-unit value and -1; The zero-sequence component is determined according to the first distance and the second distance.

3. The hybrid switching modulation method according to claim 2, characterized in that: Determining the zero-sequence component according to the first distance and the second distance includes: Selecting one of the three-phase electrical signals as the phase signal to be calculated; Obtaining the first distance and the second distance corresponding to the phase signal to be calculated; The zero-sequence component of the phase signal to be calculated is determined according to the minimum value of the first distance and the second distance.

4. The hybrid switching modulation method according to claim 3, characterized in that: The determining the zero-sequence component of the phase signal to be calculated according to the minimum value of the first distance and the second distance includes: When the per-unit value of the phase signal to be calculated is greater than or equal to 0, directly superimposing the zero-sequence component into the SPWM three-phase modulation wave; When the per-unit value of the phase signal to be calculated is less than 0, the value of the zero-sequence component is increased by 1, and then the zero-sequence component is superimposed on the SPWM three-phase modulation wave.

5. The hybrid switching modulation method according to claim 1, characterized in that: Sampling the SPWM three-phase modulation wave to obtain a first sampling result includes: Sampling the SPWM three-phase modulation wave to obtain three-phase sampling data; A coordinate system transformation is performed on the three-phase sampling data to obtain the first sampling result, wherein the first sampling result is represented by a dq coordinate system.

6. The hybrid switching modulation method according to claim 1, characterized in that: After calculating the modulation ratio of the first sampling result and determining whether the modulation ratio is greater than or equal to a preset modulation ratio, the method further includes: When the modulation ratio is less than the preset modulation ratio, a sinusoidal pulse width modulation driving signal is injected into the three-phase inverter.

7. The hybrid switching modulation method according to claim 1, characterized in that: The preset modulation ratio value is 1.

8. A hybrid switching modulation system, characterized in that: including a processor unit; The processor unit is used to implement the hybrid switching modulation method according to any one of claims 1 to 7.

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