A dead-time compensation method and terminal applied to H6 bridge inverter output reactive power
By calculating the phase shift angles of voltage and current, the dead-zone compensation period is determined, and the duty cycle of the PWM signal is adjusted in the H6 bridge inverter. This solves the problems of large current harmonics and poor waveform quality caused by the dead zone, and achieves higher waveform quality and reactive power control accuracy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 弘正储能(上海)能源科技有限公司
- Filing Date
- 2023-02-13
- Publication Date
- 2026-07-14
Smart Images
Figure CN116317526B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of new energy grid connection technology, and in particular to a dead zone compensation method and terminal for H6 bridge inverters when the output is reactive. Background Technology
[0002] The H6 bridge inverter, as an integrated photovoltaic and energy storage inverter, has both grid-connected and off-grid operation capabilities.
[0003] H6 bridge inverter circuit, such as Figure 1 As shown, when the modulation wave is positive, the control waveforms of each switching transistor are as follows: Figure 2 As shown, each switching transistor is controlled using PWM control. The voltage and current waveforms at the grid terminal are as follows: Figure 3 As shown, there is a time difference between voltage and current, which causes the directions of voltage and current to be inconsistent in time period T1 and time period T3, resulting in reactive power output.
[0004] When operating in grid-connected mode, there is a need to output reactive power to the grid. However, in actual PWM drive modulation, in order to prevent the upper bridge arm switch from being directly connected to the lower upper bridge arm switch, a dead zone is usually added between the conduction of the upper bridge arm switch and the conduction of the lower upper bridge arm switch. The existence of the dead zone in each conduction gap will cause distortion of the modulation wave, resulting in large current harmonics and poor waveform quality when outputting reactive power.
[0005] How to reduce current harmonics and improve waveform quality is an urgent problem to be solved. Summary of the Invention
[0006] The purpose of this invention is to provide a dead-zone compensation method and terminal for reactive power output of an H6 bridge inverter. By calculating the phase shift angle of voltage and current, in one cycle, during the first time period between the voltage zero crossing point and the phase shift angle, reverse compensation is performed on the modulation wave to reduce the duty cycle of the PWM. During the third time period other than the first time period, forward compensation is performed on the modulation wave to increase the duty cycle of the PWM. The power absorbed due to the dead zone is compensated to the modulation wave, thereby improving waveform quality and reactive power control accuracy.
[0007] Firstly, the above-mentioned objective of this invention is achieved through the following technical solution:
[0008] A dead-zone compensation method for H6 bridge inverters when outputting reactive power includes obtaining the active current setpoint and reactive current setpoint of the H6 bridge inverter output according to the scheduling and control objectives, calculating the phase shift angle of voltage and current, and determining the dead-zone compensation period and compensation form according to the sign of the phase shift angle.
[0009] The present invention is further configured such that the phase shift angle x of voltage and current is calculated by the following formula: x = arctan(Iqref / Idref), where Idref is the active current setting value and Iqref represents the reactive current setting value.
[0010] The present invention is further configured such that: when the phase shift angle is positive, during the first time period before the grid voltage crosses zero, corresponding compensation is performed according to the sign of the modulation wave; when the phase shift angle is negative, during the second time period after the grid voltage crosses zero, corresponding compensation is performed according to the sign of the modulation wave, and the compensation value is equal to the dead zone consumption value.
[0011] The present invention is further configured to: perform reverse compensation on the modulation wave during the first time period and / or the second time period; and perform forward compensation on the modulation wave during the third time period other than the first time period and / or the second time period within the voltage sine wave period.
[0012] The present invention is further configured to: perform reverse compensation on the modulation wave by subtracting the dead zone compensation value downward when the modulation wave is positive, and subtracting the dead zone compensation value upward when the modulation wave is negative, thereby reducing the duty cycle of the PWM signal; and perform positive compensation on the modulation wave by increasing the dead zone compensation value upward when the modulation wave is positive, and increasing the dead zone compensation value downward when the modulation wave is negative, thereby increasing the duty cycle of the PWM signal.
[0013] The present invention is further configured as follows: based on the voltage sampling frequency, after the period counter is cleared to zero at the voltage zero-crossing point, counting begins; based on the phase shift angle, the current phase angle zero-crossing sequence number is calculated, and the phase shift angle is mapped to the current phase angle zero-crossing sequence number.
[0014] The present invention is further configured to: determine the compensation time node based on the real-time count value and the zero-crossing sequence number of the current phase angle, and perform dead zone forward or reverse compensation in different time periods.
[0015] The present invention is further configured such that: if the current phase angle zero-crossing sequence number is positive, the duty cycle of the PWM signal is reduced when the real-time count value is less than the negative current phase angle zero-crossing sequence number; and the duty cycle of the PWM signal is increased when the real-time count value is greater than or equal to the negative current phase angle zero-crossing sequence number.
[0016] The present invention is further configured as follows: if the zero-crossing sequence number of the current phase angle is negative, the sum of the number of sampling points of the voltage cycle and the zero-crossing sequence number of the current phase angle is calculated. When the real-time count value is greater than or equal to the difference, the duty cycle of the PWM signal is reduced; when the real-time count value is less than the difference, the duty cycle of the PWM signal is increased.
[0017] Secondly, the above-mentioned objective of this invention is achieved through the following technical solution:
[0018] A dead-zone compensation terminal for H6 bridge inverters when outputting reactive power includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the method described in this application.
[0019] Compared with the prior art, the beneficial technical effects of this application are as follows:
[0020] 1. This application calculates the phase shift angle and determines the time intervals for dead zone reverse compensation and forward compensation based on the sign of the phase shift angle, thereby compensating the modulated wave and improving the output waveform quality;
[0021] 2. Furthermore, this application uses sampling and counting to correspond the phase shift angle to the zero-crossing sequence number of the current phase angle. Based on the sign of the zero-crossing sequence number of the current phase angle, the time periods of dead zone reverse compensation and forward compensation are determined, thus simplifying the phase angle compensation.
[0022] 3. Furthermore, this application compares the real-time count value with the zero-crossing sequence number of the current phase angle to determine the time period of dead zone reverse compensation and forward compensation, and uses the method of increasing or decreasing the PWM duty cycle in different time periods to achieve dead zone compensation. The compensation method is simple and easy to implement. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the H6 bridge inverter structure in the existing technology;
[0024] Figure 2 This is a schematic diagram of the PWM signal and modulation wave driven by the H6 bridge inverter in the existing technology;
[0025] Figure 3 This is a schematic diagram of the grid-connected voltage and current timing of the H6 bridge inverter in the existing technology;
[0026] Figure 4 This is a schematic diagram of the dead time of an H6 bridge inverter in the existing technology;
[0027] Figure 5 This is a schematic diagram of the dead zone positive compensation of the positive half-cycle of the modulation wave according to a specific embodiment of this application;
[0028] Figure 6 This is a schematic diagram of positive compensation for the zero-crossing dead zone of a modulation wave according to a specific embodiment of this application;
[0029] Figure 7 This is a schematic flowchart of a dead zone compensation method according to a specific embodiment of this application. Detailed Implementation
[0030] The present invention will be further described in detail below with reference to the accompanying drawings.
[0031] This application discloses a dead-zone compensation method for H6 bridge inverters when outputting reactive power. The method includes calculating the phase shift angle of the grid voltage and current, determining the compensation time period based on the sign of the phase shift angle, and performing dead-zone reverse compensation within one cycle from the voltage zero-crossing point to the time point corresponding to the phase shift angle. In the remaining time periods within the cycle, dead-zone forward compensation is performed. That is, between the voltage zero-crossing point and the time point corresponding to the phase shift angle, the modulated wave is subtracted from the dead-zone compensation value, and in the remaining time periods within the cycle, the modulated wave is increased by the dead-zone compensation value.
[0032] To accurately position the phase shift angle, sampling is performed within one cycle, and the phase shift angle is mapped to the zero-crossing sequence number of the current phase angle. When the voltage crosses zero, the counter is reset to zero and then counts again. Within the time point from the voltage zero-crossing point to the time point corresponding to the zero-crossing sequence number of the current phase angle, the dead-zone compensation value is subtracted from the modulated wave. For other sampling values, the dead-zone compensation value is added to the modulated wave.
[0033] In this application, the given value of the inner current loop, i.e. the given value of the active current Idref of the grid voltage, is obtained according to the scheduling and control objectives. It is obtained by the output of the outer loop PI controller of the DC bus voltage. The reactive current Iqref is obtained according to the reactive current demand.
[0034] The phase shift angle X of voltage and current is:
[0035] x=arctan(Iqref / Idref) (1);
[0036] If the phase shift angle is positive, within one cycle, before the grid voltage crosses zero, dead zone reverse compensation is performed within the time period corresponding to the phase shift angle, and dead zone forward compensation is performed during the remaining time periods. If the phase shift angle is negative, within one cycle, after the grid voltage crosses zero, dead zone reverse compensation is performed within the time period corresponding to the phase shift angle, and dead zone forward compensation is performed during the remaining time periods.
[0037] The modulated wave moves along the Y-axis away from the X-axis, increasing the duty cycle of the PWM signal and performing positive dead-time compensation; conversely, the modulated wave moves along the Y-axis towards the X-axis, decreasing the duty cycle of the PWM signal and performing reverse dead-time compensation.
[0038] The H6 bridge incorporates a dead time between the lower bridge arm's cutoff and the upper bridge arm's conduction to prevent simultaneous conduction of both arms, which could damage the switching transistors. Figure 4 As shown. Depending on the performance of the switching transistor, the dead time has a minimum value, but the actual dead time is greater than the minimum value.
[0039] The modulated wave is shifted along the Y-axis away from the X-axis, such as... Figure 5As shown, the positive compensation scenario is illustrated. The solid modulated wave is the initial waveform, and the dashed modulated wave is the waveform after the shift. It can be seen that after the shift, the conduction time changes from t1 to t2, the duty cycle of the PWM signal increases, the conduction time of the switching transistor increases, and the output power increases accordingly to compensate for the power lost due to the dead time.
[0040] In the case of negative compensation, the opposite is not shown. After the shift, the duty cycle of the PWM signal decreases, the on-time of the switching transistor decreases, and the output power decreases accordingly to compensate for the power lost due to the dead time. And so on.
[0041] Figure 6 The diagram illustrates the compensation method at the voltage zero-crossing point. The solid line modulated wave represents the initial waveform, and the dashed line modulated wave represents the shifted waveform. The phase shift angle is negative, and point a1 is the point corresponding to the phase shift angle. During the time interval between the current voltage zero-crossing point and point a1, negative compensation is performed on the modulated wave, subtracting dead zone compensation downwards. During the time interval between the previous voltage zero-crossing point and point a1, positive compensation is performed on the modulated wave, adding dead zone compensation upwards.
[0042] The same logic applies to the case where the phase shift angle is positive.
[0043] By sampling and counting the voltage cycle and quantizing the phase shift angle, the accuracy of the timing of compensation can be improved.
[0044] If the sampling frequency of the voltage period is f, then the number of sampling points n within one period T is... T for:
[0045] n T =T / f (2);
[0046] Then the zero-crossing ordinal number n of the current phase angle cnt for:
[0047] n cnt =n T ×π×x / 2 (3);
[0048] In the formula, x represents the phase shift angle, which is the phase shift angle quantized.
[0049] In one specific embodiment of this application, assuming the sampling frequency is 50µs and the period of a 50Hz sine wave is 20ms, then the number of sampling points n T =20ms / 50us=400;
[0050] Current phase angle zero-crossing ordinal number: n cnt = 400 × π × x / 2.
[0051] Record the number of real-time samples, compare the number of real-time samples with the zero-crossing sequence number of the current phase angle, and determine the time node for compensation and the compensation method for the corresponding time period.
[0052] When the phase shift angle is positive, n cnt >0, the real-time sampling count value n P With n T -n cnt Values are compared, in n P >n T -n cnt At this time, the modulation wave is shifted downwards, reducing the duty cycle of the PWM signal, thereby reducing the on-time of the switching transistor. P ≤n T -n cnt At this time, the modulation wave is shifted upward, increasing the duty cycle of the PWM signal, thereby increasing the on-time of the switching transistor.
[0053] When the phase shift angle is negative, n cnt <0, the real-time sampling count value n P With -n cnt Values are compared, in n P <-n cnt At this time, the modulation wave is shifted downwards, reducing the duty cycle of the PWM signal, thereby reducing the on-time of the switching transistor. P >-n cnt At this time, the modulation wave is shifted upward, increasing the duty cycle of the PWM signal, thereby increasing the on-time of the switching transistor.
[0054] After one cycle ends, the counter is reset to zero, and the above operation is repeated in the next cycle.
[0055] In one specific embodiment of this application, a dead-zone compensation method is provided for H6 bridge inverters when the output is reactive power, such as... Figure 7 As shown, it includes the following steps:
[0056] S1, Begin;
[0057] S2. Based on the scheduling or control objectives, obtain the active current Idref and reactive current Iqref;
[0058] S3. Calculate the phase shift angle X based on the active and reactive currents, and convert the phase shift angle into the zero-crossing sequence number n of the current phase angle. cnt ;
[0059] S4. Determine if the grid voltage is at a zero crossing point. If yes, proceed to the next step; otherwise, go to S6.
[0060] S5. Set the real-time sampling count to zero and start recording the sampling count;
[0061] S6. Determine if the zero-crossing sequence number of the current phase angle is positive. If yes, proceed to the next step. If no, go to S8.
[0062] S7. Determine if the number of real-time sampling times is greater than the number of sampling points n. T If the difference between the phase angle and the zero-crossing sequence number of the current is true, proceed to S10; otherwise, proceed to S9.
[0063] S8. Determine if the number of real-time samplings is less than the negative current phase angle zero-crossing sequence number. If not, proceed to the next step. If yes, go to S10.
[0064] S9. Perform positive compensation, increase the dead zone compensation of the modulated wave upward, increase the conduction time of the modulated wave, and then go to S11.
[0065] S10. Perform reverse compensation by subtracting the dead zone compensation from the modulated wave downwards to reduce the conduction time of the modulated wave.
[0066] S11, the counter enters the next counting cycle, then proceeds to S2.
[0067] A positive phase shift angle indicates capacitive reactive power, while a negative phase shift angle indicates inductive reactive power.
[0068] In one specific embodiment of this application, dead zone compensation is performed at a rate of 1% of the cycle.
[0069] This application discloses a dead-zone compensation terminal device for H6 bridge inverters when outputting reactive power. The terminal device of this embodiment includes: a processor, a memory, and a computer program stored in the memory and executable on the processor, such as a phase shift angle calculation and judgment program. When the processor executes the computer program, it implements the method of this application.
[0070] For example, the computer program can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules / units can be a series of computer program instruction segments capable of performing specific functions, which describe the execution process of the computer program in the dead-zone compensation terminal device applied when the H6 bridge inverter outputs reactive power. For example, the computer program can be divided into multiple modules, each with the following specific functions:
[0071] 1. Phase shift angle calculation module, used to calculate the phase shift angle;
[0072] 2. Judgment module, used to determine the compensation method.
[0073] The dead-zone compensation terminal device applied to the H6 bridge inverter when outputting reactive power can be a computing device such as a desktop computer, laptop, handheld computer, or cloud server. This terminal device may include, but is not limited to, a processor and memory. Those skilled in the art will understand that the above examples are merely illustrations of the dead-zone compensation terminal device applied to the H6 bridge inverter when outputting reactive power, and do not constitute a limitation on the device. It may include more or fewer components than illustrated, or combine certain components, or use different components. For example, the dead-zone compensation terminal device may also include input / output devices, network access devices, buses, etc.
[0074] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor. This processor is the control center of the dead-zone compensation terminal device applied when the H6 bridge inverter outputs reactive power, and it connects all parts of the dead-zone compensation terminal device using various interfaces and lines.
[0075] The memory can be used to store the computer program and / or modules. The processor, by running or executing the computer program and / or modules stored in the memory, and by calling the data stored in the memory, implements various functions of the dead-zone compensation terminal device applied to the H6 bridge inverter when the output is reactive. The memory may mainly include a program storage area and a data storage area. The program storage area may store the operating system, at least one application program required for a function (such as sound playback function, image playback function, etc.), etc.; the data storage area may store data created according to the use of the mobile phone (such as audio data, phonebook, etc.). In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as hard disk, memory, plug-in hard disk, smart media card (SMC), secure digital card (SD) card, flash card, at least one disk storage device, flash memory device, or other volatile solid-state storage device.
[0076] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.
Claims
1. A dead-zone compensation method applied to H6 bridge inverters when outputting reactive power, characterized in that: This includes obtaining the active current setpoint and reactive current setpoint of the H6 bridge inverter output based on the scheduling and control objectives, calculating the phase shift angle of voltage and current, and determining the dead zone compensation period and compensation form based on the sign of the phase shift angle. When the phase shift angle is positive, compensation is made according to the sign of the modulation wave during the first time period before the grid voltage crosses zero; when the phase shift angle is negative, compensation is made according to the sign of the modulation wave during the second time period after the grid voltage crosses zero, and the compensation value is equal to the dead zone consumption value. Based on the voltage sampling frequency, the period counter is reset to zero at the voltage zero-crossing point and counting begins. Based on the phase shift angle, the current phase angle zero-crossing sequence number is calculated, and the phase shift angle is mapped to the current phase angle zero-crossing sequence number. Based on the real-time count value and the current phase angle zero-crossing sequence number, the compensation time node is determined, and dead zone forward or reverse compensation is performed in different time periods.
2. The dead-zone compensation method for H6 bridge inverters when outputting reactive power as described in claim 1, characterized in that: The phase shift angle x of voltage and current is calculated by the following formula: x = arctan(Iqref / Idref), where Idref is the active current setting value and Iqref represents the reactive current setting value.
3. The dead-zone compensation method for H6 bridge inverters when outputting reactive power as described in claim 1, characterized in that: In the first time period and / or the second time period, reverse compensation is performed on the modulated wave; in the third time period, excluding the first time period and / or the second time period, positive compensation is performed on the modulated wave within the voltage sine wave period.
4. The dead-zone compensation method for H6 bridge inverters when outputting reactive power as described in claim 3, characterized in that: Reverse compensation of the modulation wave involves subtracting the dead-time compensation value downwards when the modulation wave is positive, and subtracting the dead-time compensation value upwards when the modulation wave is negative, thereby reducing the duty cycle of the PWM signal. Positive compensation of the modulation wave involves increasing the dead-time compensation value upwards when the modulation wave is positive, and increasing the dead-time compensation value downwards when the modulation wave is negative, thereby increasing the duty cycle of the PWM signal.
5. The dead-zone compensation method for H6 bridge inverters when outputting reactive power as described in claim 1, characterized in that: If the current phase angle zero-crossing sequence number is positive, decrease the duty cycle of the PWM signal when the real-time count value is less than the negative current phase angle zero-crossing sequence number, and increase the duty cycle of the PWM signal when the real-time count value is greater than or equal to the negative current phase angle zero-crossing sequence number.
6. The dead-zone compensation method for H6 bridge inverters when outputting reactive power as described in claim 1, characterized in that: If the zero-crossing sequence number of the current phase angle is negative, calculate the sum of the number of sampling points of the voltage cycle and the zero-crossing sequence number of the current phase angle. When the real-time count value is greater than or equal to the difference, decrease the duty cycle of the PWM signal; when the real-time count value is less than the difference, increase the duty cycle of the PWM signal.
7. A dead-zone compensation terminal for H6 bridge inverters when outputting reactive power, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, it implements the method as described in any one of claims 1-6.