A reactive power control method and controller for single-phase inverter

Abstract

The present invention provides a reactive power control method and controller for a single-phase inverter, which is applied to the field of inverter technology. The grid voltage phase is obtained through a phase-locked loop (PLL), and the reactive angle β required at this time is calculated according to the grid connection requirement. The reactive angle β is combined with the grid voltage phase to obtain a sine value, and then a current with a reactive component is calculated through a reference current to achieve reactive power correction. By designing a multi-loop control strategy based on a quasi-proportional resonant regulator, efficient reactive power control of a single-phase inverter is achieved, the harmonic distortion rate of the grid-connected current is reduced, and the power factor accuracy is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of inverters, and in particular relates to a reactive power control method and a controller for a single-phase inverter. Background Art

[0002] With the increasing penetration of renewable energy in single-phase power grids, the power grid has put forward the requirement of flexible control of reactive power output and power factor for single-phase photovoltaic grid-connected inverters. When the non-isolated photovoltaic grid-connected inverter with unipolar modulation performs reactive power compensation, it will cause the grid-connected current to produce serious distortion at the zero-crossing point of the grid voltage, which greatly increases the total harmonic distortion rate of the grid-connected current and also causes the power factor to fail to meet the error range of ±0.01.

[0003] In the prior art, the actual AC quantity (such as output current) is usually ) Delay 90° to create an orthogonal component , and the virtual orthogonal components The virtual vector I in the two-phase stationary coordinate system ReIm is synthesized. After synchronous rotating coordinate transformation, the d-axis and q-axis components corresponding to the virtual vector I can be obtained. , By performing independent PI regulator control, independent regulation of VSR active and reactive power can be achieved.

[0004] When the reactive power has deviation, the above method cannot obtain the deviation amount and thus the calibration amount, so the accuracy is not high. In addition, the method has a large amount of calculation and a slow response. Summary of the invention

[0005] In view of the above problems in the prior art, the purpose of the present invention is to provide a reactive power control method for a single-phase inverter, by designing a multi-loop control strategy based on a quasi-proportional resonant regulator, to achieve efficient reactive power control of the single-phase inverter, reduce the harmonic distortion rate of the grid-connected current, and improve the power factor accuracy.

[0006] A reactive power control method for a single-phase inverter obtains the grid voltage phase through a phase-locked loop (PLL) And adjust the inverter output phase and grid voltage phase Synchronize, calculate the reactive angle β required at this time according to the grid connection requirements, and compare the reactive angle β with the grid voltage phase After combining, take the sine value and then pass the reference current The current reference with reactive component is calculated to achieve reactive power correction.

[0007] Preferably, the method specifically comprises the following steps:

[0008] Comparing DC voltage and DC bus voltage To generate an error signal, and output a reference current through a PI regulator according to the error signal ;

[0009] Obtaining the grid voltage phase through the phase-locked loop PLL , and then calculate the reactive angle β according to the reactive power requirements in the grid connection standard;

[0010] The grid voltage phase Add the reactive angle β and take the sine value and pass it through the reference current Limit the current to get the current given signal at this time , the current given signal Including active component current given signal and reactive component current given signal;

[0011] The quasi-proportional resonant controller QPR is based on the collected inductor current Given current signal After processing, the output signal of the quasi-proportional resonant controller QPR drives the switch tube after sinusoidal pulse width modulation to realize the grid-connected control of the inverter.

[0012] Preferably, the DC bus voltage .

[0013] Preferably, the power factor The reactive phase at this time is calculated , use a power meter or electric meter to measure the actual grid voltage phase , thus obtaining the reactive angle .

[0014] Preferably, the current given signal .

[0015] Preferably, the transfer function of the quasi-proportional resonant regulator QPR is .

[0016] Another object of the present invention is to provide a controller for reactive power control of a single-phase inverter, comprising:

[0017] Deviation calculation module: calculate DC voltage and DC bus voltage The error signal between

[0018] PI module: According to the DC voltage and DC bus voltage The error signal between the output and the corresponding reference current ;

[0019] Reactive power calculation module: obtain the grid voltage phase through the phase-locked loop PLL , and then calculate the reactive angle β according to the reactive power requirements in the grid connection standard; Add the reactive angle β and take the sine value and pass it through the reference current Limit the current to get the current given signal at this time ;

[0020] Control module: The quasi-proportional resonant controller QPR is used to control the inductor current according to the collected Given current signal After processing, the output signal of the quasi-proportional resonant controller QPR drives the switch tube after sinusoidal pulse width modulation to realize the grid-connected control of the inverter.

[0021] The beneficial effects of the present invention are as follows: the reactive power control method and controller of the single-phase inverter adopt a multi-loop control strategy based on a quasi-proportional resonant regulator QPR, realizes efficient reactive power control of the single-phase inverter, and can effectively reduce the harmonic distortion rate of the grid-connected current. The control accuracy of the power factor is improved, and the error range of ±0.01 can be met. Through the application of the multi-loop control strategy, the zero-static error control of the grid current is realized, and the stability and response speed of the system are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0023] Figure 1 It is a system block diagram of the present invention. DETAILED DESCRIPTION

[0024] Embodiment 1

[0025] like Figure 1 As shown, a reactive power control method for a single-phase inverter is used to obtain the grid voltage phase through a phase-locked loop (PLL). And adjust the inverter output phase and grid voltage phase Synchronize, calculate the reactive angle β required at this time according to the grid connection requirements, and compare the reactive angle β with the grid voltage phase After combining, take the sine value and then pass the reference current The current reference with reactive component is calculated to achieve reactive power correction.

[0026] The specific steps include:

[0027] Step 1: Compare DC Voltages and DC bus voltage To generate an error signal, and according to the error signal through the PI regulator to adjust, the output of the DC voltage outer loop regulator to obtain the reference current Among them, the DC bus voltage , DC bus voltage The set value is determined by external sampling, To measure the grid voltage, it is necessary to ensure that the DC bus voltage Stable, PI regulator output reference current Accurate and convenient for subsequent signal adjustment.

[0028] Step 2: Get the grid voltage phase through the phase-locked loop PLL And adjust the inverter output phase and grid voltage phase Synchronize. Make the inverter output phase consistent with the grid voltage Consistency can improve power transmission efficiency, reduce reactive power, smooth the grid connection process, reduce transient shocks and oscillations, and improve system stability.

[0029] Step 3: Calculate the reactive power angle β according to the reactive power requirements in the grid connection standard, that is, according to the power factor Calculate the reactive phase at this time , the actual grid voltage phase is measured by a power meter or electric meter , get the reactive angle required at this time , where k is the proportional coefficient, which is generally set according to the adjustment time, and the value range of K is 0.1-0.9.

[0030] Step 4: Change the grid voltage phase Add the sine value to the reactive angle β and pass it through the reference current Limit the current to get the current given signal at this time , the current given signal Including active component current given signal and reactive component current given signal, current given signal .

[0031] Step 5: Since the given signal is a sinusoidal quantity, in order to achieve zero static error control, the transfer function is The quasi-proportional resonant regulator QPR is based on the collected inductor current Given current signal After processing, the output signal of the quasi-proportional resonant controller QPR drives the switch tube after sinusoidal pulse width modulation to realize the grid-connected control of the inverter. is the proportionality coefficient; is the integration coefficient; is the cut-off frequency; is the resonant frequency, .

[0032] The integral link in the quasi-proportional resonant controller QPR is also called a generalized integrator, which can integrate the amplitude of the sinusoidal quantity of the resonant frequency, achieve infinite gain at the resonant frequency point, and have almost no attenuation outside this frequency point. The quasi-proportional resonant controller QPR and sinusoidal pulse width modulation work together to enable the inverter to be stably and efficiently connected to the grid.

[0033] Embodiment 2

[0034] The second aspect of the present invention is to provide a controller for reactive power control of a single-phase inverter, comprising a deviation calculation module, a PI module, a reactive power calculation module and a control module, wherein the deviation calculation module is used to calculate the DC voltage and DC bus voltage The PI module is used to generate an error signal based on the DC voltage. and DC bus voltage The error signal between the output and the corresponding reference current .

[0035] The reactive power calculation module is used to obtain the grid voltage phase through the phase-locked loop PLL , and then calculate the reactive angle β according to the reactive power requirements in the grid connection standard; Add the reactive angle β and take the sine value and pass it through the reference current Limit the current to get the current given signal at this time .

[0036] The control module is used to control the inductor current according to the collected inductor current through the quasi-proportional resonant controller QPR. Given current signal After processing, the output signal of the quasi-proportional resonant controller QPR drives the switch tube after sinusoidal pulse width modulation to realize the grid-connected control of the inverter.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A reactive power control method for a single-phase inverter, characterized in that: The grid voltage phase θ' is obtained through the phase-locked loop PLL and the inverter output phase is adjusted to be synchronized with the grid voltage phase θ'. The reactive angle β required at this time is calculated according to the grid connection requirements. The reactive angle β is combined with the grid voltage phase θ' to obtain the sine value, and then the reference current is used to calculate the reactive angle β. The current reference with reactive component is calculated to achieve reactive power correction; The specific steps include: Compare DC voltage V dc and DC bus voltage To generate an error signal, and output a reference current through a PI regulator according to the error signal The grid voltage phase θ' is obtained through the phase-locked loop PLL, and then the reactive angle β is calculated according to the reactive power requirements in the grid connection standard; The grid voltage phase θ' is added to the reactive angle β, and the sine value is taken and then passed through the reference current Limit the current to get the current given signal at this time The current given signal Including active component current given signal and reactive component current given signal; The quasi-proportional resonant controller QPR is based on the collected inductor current I L Given current signal After processing, the output signal of the quasi-proportional resonant controller QPR drives the switch tube after sinusoidal pulse width modulation to realize the grid-connected control of the inverter.

2. The reactive power control method of a single-phase inverter according to claim 1, characterized in that: The DC bus voltage V Grid is the measured grid voltage.

3. The reactive power control method of a single-phase inverter according to claim 1, characterized in that: By power factor The reactive phase θ at this time is calculated * =COS -1 PF, using a power meter or electric meter to measure the actual grid voltage phase θ', thus obtaining the reactive angle β = θ * ±k(θ * -θ'), where P is the active power and S is the apparent power.

4. The reactive power control method of a single-phase inverter according to claim 1, characterized in that: The current given signal 5. The reactive power control method of a single-phase inverter according to claim 1, characterized in that: The transfer function of the quasi-proportional resonant controller QPR is Where: K P is the proportionality coefficient; K R is the integral coefficient; ω C is the cut-off frequency; ω0 is the resonant frequency.

6. A controller for reactive power control of a single-phase inverter, characterized in that: A reactive power control method for a single-phase inverter according to any one of claims 1 to 5, comprising: Deviation calculation module: calculates DC voltage V dc and DC bus voltage The error signal between PI module: According to the DC voltage V dc and DC bus voltage The error signal between the output and the corresponding reference current Reactive power calculation module: The grid voltage phase θ' is obtained through the phase-locked loop PLL, and then the reactive angle β is calculated according to the reactive power requirements in the grid connection standard; the grid voltage phase θ' is added to the reactive angle β, and the sine value is taken and then passed through the reference current Limit the current to get the current given signal at this time Control module: The quasi-proportional resonant controller QPR is used to control the inductor current I L Given current signal After processing, the output signal of the quasi-proportional resonant controller QPR drives the switch tube after sinusoidal pulse width modulation to realize the grid-connected control of the inverter.

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