CN109406854B - Harmonic instruction current obtaining method, device and equipment of single-phase active filter - Google Patents
Harmonic instruction current obtaining method, device and equipment of single-phase active filter Download PDFInfo
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Abstract
The invention discloses a method, a device and equipment for obtaining harmonic instruction current of a single-phase active filter, wherein the method comprises the following steps: acquiring load current, power grid voltage and direct-current side voltage at the current moment; acquiring an angular frequency value and a phase value of an alternating current power grid at the current moment corresponding to the voltage of the power grid by using a phase-locked loop of a single-phase active filter; obtaining harmonic command current at the current moment according to the load current, the active component, the direct current side voltage feedback and the phase value; acquiring direct-current side voltage feedback at the current moment according to the direct-current side voltage; obtaining harmonic command current at the current moment according to the load current, the active component and the phase value; therefore, the harmonic instruction current is obtained by utilizing the integral link, the influence of the low-pass filter in the process of obtaining the harmonic instruction current is eliminated, the algorithm for obtaining the harmonic instruction current is simpler, and the precision and the compensation effect of the obtained harmonic instruction current are improved.
Description
Technical Field
The invention relates to the technical field of active filtering, in particular to a method, a device and equipment for obtaining harmonic instruction current of a single-phase active filter.
Background
With the wide use of single-phase power electronic equipment, a large amount of generated harmonic waves seriously affect the power quality of a single-phase power grid. Therefore, the use of single-phase active power filters is an important means for harmonic suppression and reactive compensation. The main principle is shown in fig. 1, a harmonic command current module (command current calculation) can calculate the harmonic command current required for compensation as the given of a control module, and the control module controls VT1～VT4The on and off of the APF (Active Power Filter) circuit enables the APF main circuit to generate a current which is equal to the instruction current in magnitude and opposite in phase to achieve the purpose of Active filtering. Therefore, the accuracy of the harmonic command current directly affects the compensation effect of the whole single-phase APF system.
In the prior art, the detection method using the most widely harmonic command current is a detection method based on the instantaneous power theory, the method acquires the harmonic command current by dq conversion, and a schematic diagram is shown in fig. 2 and is obtained by low-pass filteringFilter (Low Pass Filter: LPF) for load current iLD-axis component after dq conversion
Processing to obtain d-axis direct current
And then dq inverse transformation is carried out to obtain the active component i of the fundamental currentf. Load current iLRe-sum the active component i of the fundamental currentfObtaining the sum i of the harmonic current and the reactive current by differencehAnd the harmonic wave command current can be obtained by adding the direct current side feedback current
It is apparent from fig. 2 that the LPF becomes a critical part of the overall detection system, and the performance of the LPF determines the accuracy of the final harmonic command current. However, differences in the type, cutoff frequency, and order of the LPFs, for example, can cause differences in the resulting harmonic command current, including amplitude attenuation, phase delay, and the like.
Therefore, how to obtain the harmonic command current more simply and conveniently, avoid the influence of a low-pass filter in the traditional algorithm on the harmonic command current, and improve the precision of the obtained harmonic command current is a problem which needs to be solved urgently at present.
Disclosure of Invention
The invention aims to provide a method, a device and equipment for obtaining harmonic instruction current of a single-phase active filter, so that the harmonic instruction current can be obtained by utilizing a simple and feasible integration link, and the precision of the obtained harmonic instruction current is improved.
In order to solve the above technical problem, the present invention provides a method for obtaining a harmonic command current of a single-phase active filter, including:
acquiring load current, power grid voltage and direct-current side voltage at the current moment;
acquiring an angular frequency value and a phase value of the alternating current power grid at the current moment corresponding to the power grid voltage by using a phase-locked loop of the single-phase active filter;
calculating an active component of the load current according to the load current, the grid voltage and the angular frequency value;
acquiring the direct current side voltage feedback of the current moment according to the direct current side voltage;
and obtaining the harmonic command current at the current moment according to the load current, the active component, the direct-current side voltage feedback and the phase value.
Optionally, the obtaining the dc side voltage feedback of the current time according to the dc side voltage includes:
and inputting the difference between the direct current side voltage and a preset voltage value into a PI controller, and taking the output of the PI controller as the direct current side voltage feedback.
Optionally, the calculating an active component of the load current according to the load current, the grid voltage and the angular frequency value includes:
by using
Calculating an effective value of active power of a preset period in which the current moment is located; wherein the content of the first and second substances,
in the period of the voltage of the power grid, ω (k) is the angular frequency value, i is the number of samples in the preset period, k is the current time, VSFor the grid voltage iLIs the load current;
by using
Calculating the voltage effective value of the preset period; wherein, | | VSThe | is the effective value of the voltage;
by using
Calculating the equivalent conductance of the preset period; wherein the content of the first and second substances,g is the equivalent conductance;
using ia(k)＝G·vs(k) Calculating the active component; wherein v iss(k) For the grid voltage ia(k) Is the active component.
Optionally, when the preset period is one period,
wherein f is the rated frequency of the single-phase power grid, fsThe sampling frequency of the load current, the grid voltage and the direct-current side voltage is used.
Optionally, the obtaining the harmonic command current at the current moment according to the load current, the active component, and the phase value includes:
using ih(k)＝iL(k)-ia(k) Calculating the harmonic current of the current moment; wherein ih(k) Is the harmonic current;
by using
Calculating the harmonic command current; wherein idc(k) For the DC side voltage feedback, θ (k) is the phase value,
the harmonic command current.
Optionally, the obtaining of the load current, the grid voltage, and the dc side voltage at the current moment includes:
and acquiring the load current, the grid voltage and the direct-current side voltage through a sampling circuit.
Optionally, after obtaining the harmonic command current at the current time according to the load current, the active component, and the phase value, the method further includes:
and outputting the difference between the harmonic command current and the compensation current at the current moment to a hysteresis comparison controller, and acquiring PWM (pulse width modulation) modulation pulses output by the hysteresis comparison controller so as to perform current tracking compensation.
Optionally, the obtaining the load current, the grid voltage, and the dc-side voltage by using a sampling circuit includes:
and acquiring the load current, the grid voltage, the direct-current side voltage and the compensation current through a sampling circuit.
The invention also provides a harmonic instruction current acquisition device of the single-phase active filter, which comprises:
the sampling acquisition module is used for acquiring the load current, the power grid voltage and the direct current side voltage at the current moment;
the calculation module is used for acquiring an angular frequency value and a phase value of the alternating current power grid at the current moment corresponding to the power grid voltage by using a phase-locked loop of the single-phase active filter;
the active component calculation module is used for calculating the active component of the load current according to the load current, the grid voltage and the angular frequency value;
the direct current side voltage feedback calculation module is used for acquiring direct current side voltage feedback at the current moment according to the direct current side voltage;
and the harmonic instruction current calculation module is used for acquiring the harmonic instruction current at the current moment according to the load current, the active component and the phase value.
In addition, the present invention also provides a harmonic instruction current obtaining apparatus of a single-phase active filter, including:
a memory for storing a computer program;
a processor for implementing the steps of the harmonic command current acquisition method of a single-phase active filter according to any one of the preceding claims when executing said computer program.
The invention provides a harmonic instruction current obtaining method of a single-phase active filter, which comprises the following steps: acquiring load current, power grid voltage and direct-current side voltage at the current moment; acquiring an angular frequency value and a phase value of an alternating current power grid at the current moment corresponding to the voltage of the power grid by using a phase-locked loop of a single-phase active filter; calculating the active component of the load current according to the load current, the grid voltage and the angular frequency value; acquiring direct-current side voltage feedback at the current moment according to the direct-current side voltage; obtaining harmonic command current at the current moment according to the load current, the active component, the direct current side voltage feedback and the phase value;
therefore, the harmonic instruction current is obtained by utilizing the integral link, the influence of the low-pass filter in the process of obtaining the harmonic instruction current is eliminated, the algorithm for obtaining the harmonic instruction current is simpler, the precision of the obtained harmonic instruction current is improved, the compensation effect is better compared with a single-phase active filter of the traditional algorithm, and the user experience is improved; in addition, the invention also provides a harmonic instruction current acquisition device and equipment of the single-phase active filter, and the harmonic instruction current acquisition device and equipment also have the beneficial effects.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic diagram of a topology structure of a single-phase active filter and a system control thereof according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a harmonic command current acquisition method of a single-phase active filter in the prior art;
fig. 3 is a flowchart of a method for obtaining a harmonic command current of a single-phase active filter according to an embodiment of the present invention;
fig. 4 is a schematic flowchart of another harmonic command current obtaining method for a single-phase active filter according to an embodiment of the present invention;
FIG. 5 is a diagram showing the post-compensation effect of the harmonic command current acquisition method of a single-phase active filter in the prior art;
FIG. 6 is a diagram showing the effect of the harmonic command current obtaining method of the single-phase active filter according to another embodiment of the present invention after compensation;
fig. 7 is a structural diagram of a harmonic command current obtaining apparatus of a single-phase active filter according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 3, fig. 3 is a flowchart illustrating a harmonic command current obtaining method of a single-phase active filter according to an embodiment of the present invention. The method can comprise the following steps:
step 101: and acquiring the load current, the power grid voltage and the direct current side voltage at the current moment.
The purpose of this step may be to obtain a load current (non-linear load side current), a grid voltage (single-phase grid voltage) and a dc side voltage, such as a load current i in fig. 4, required for calculating a harmonic command current at the present moment by a processor such as a DSP (Digital Signal Processing) chipLVoltage V of the power gridSAnd controlling the current output value idcCorresponding DC side voltage Vdc。
Specifically, the specific way of acquiring the load current, the grid voltage and the direct-current side voltage at the current moment by a processor such as a DSP chip can be set by a designer according to a practical scene and user requirements, for example, the load current, the grid voltage and the direct-current side voltage at the current moment can be directly acquired by the DSP chip; in consideration of the sampling rate and the calculation capability of the existing DSP chip, the sampling circuit may also be configured to provide the DSP chip with sampling signals corresponding to the load current, the grid voltage, and the dc-side voltage at the present time, such as the sampling frequency of the sampling circuitThe rate may be set to fsAnd 10kHz, namely, the DSP chip acquires the load current, the power grid voltage and the direct current side voltage at the current moment through a sampling circuit. The present embodiment does not limit the load current, the grid voltage, and the dc-side voltage at the present moment as long as the processor can obtain the load current, the grid voltage, and the dc-side voltage.
Step 102: and acquiring the angular frequency value and the phase value of the alternating current power grid at the current moment corresponding to the power grid voltage by using the phase-locked loop of the single-phase active filter.
The purpose of this step is to calculate the sampled grid voltage at the current time by using a Phase Locked Loop (PLL) in the single-Phase active filter, and obtain an angular frequency value and a Phase value of the corresponding ac grid, for example, the Phase Locked Loop (PLL) of the single-Phase parallel active filter in fig. 1 is implemented as a digital PLL, and the soft PLL is implemented as a digital PLL for the sampled grid voltage V at the current timeSThe angular frequency value ω (k) and the phase value θ (k) at this time are calculated.
Specifically, the circuit of fig. 1 includes a main circuit including an H-bridge composed of 4 fully-controlled power switches, an external ac inductor, and an energy storage capacitor on the dc side, in addition to the non-linear load simulated by connecting the uncontrollable diode bridge to the RC load.
It can be understood that, the specific process of calculating the grid voltage at the current time by the phase-locked loop of the single-phase active filter in this step and acquiring the angular frequency value and the phase value of the ac grid at the current time can be implemented in a manner the same as or similar to that in the prior art, as long as the processor such as the DSP chip can acquire the angular frequency value and the phase value of the ac grid at the current time corresponding to the grid voltage at the current time by using the phase-locked loop of the single-phase active filter. The present embodiment does not set any limit to this.
Step 103: and calculating the active component of the load current according to the load current, the grid voltage and the angular frequency value.
The purpose of this step may be to calculate, by a processor such as a DSP chip, an active component of the load current at the present time by using the load current, the grid voltage, and the angular frequency value at the present time.
Specifically, the step may include:
step 201: by using
Calculating an active power effective value of a preset period in which the current moment is located; wherein the content of the first and second substances,
and in the period of the voltage of the power grid, omega (k) is an angular frequency value, i is the sampling number of a preset period, and k is the current moment.
It can be understood that the preset period of the current time k in this step may be set by a designer or a user, for example, the rated frequency f of the single-phase power grid is 50Hz, and the sampling frequency f of the sampling circuit is set by the designer or the usersWhen 10kHz is the frequency at which the processor obtains the load current, the grid voltage and the dc-side voltage, the preset period may be one period, that is, the preset period is 10kHz
That is, the preset period is a period consisting of every 200 sampling points.
Step 202: by using
Calculating the voltage effective value of a preset period; wherein, | | VSAnd | is a voltage effective value.
Step 203: by using
Calculating the equivalent conductance of a preset period; wherein G is the equivalent conductance.
It is understood that the purpose of this step may be to utilize the active power effective value P and the voltage effective value V of the preset periodSAnd | l, calculating to obtain the equivalent conductance G of the preset period.
Step 204: using ia(k)＝G·vs(k) Calculating an active component; wherein v iss(k) Is the load current ia(k) Is the active component.
It can be understood that the purpose of this step may be to utilize the equivalent conductance G of the preset period in which the present time k is located and the grid voltage v obtained at the present time ks(k) Calculating the load current i obtained at the current moment kL(k) Active component i ofa(k)。
Specifically, the rated frequency f of the single-phase power grid is 50Hz, and the sampling frequency f of the sampling circuitsFor example, 10kHz, the network voltage v at the present time is assumeds(k)＝Vmsin θ (k), load current
Wherein, VmIs the voltage amplitude, INIn order to be the magnitude of the current,
for the current N times of component phase, the preset period can be one period, and the number of samples in one period can be obtained from the grid frequency and the sampling frequency
The effective value of active power of one period can be obtained:
the voltage effective value of one period can be obtained:
correspondingly, one cycle of equivalent conductance can be derived:
by using the equivalent conductance of one cycle, the active component of the load current can be obtained:
it should be noted that, in steps 201 to 204, the active component of the load current may be obtained by calculating the equivalent conductance of the preset period at the present time. The specific manner of calculating the active component of the load current in step 103 according to the load current, the grid voltage, and the angular frequency value may be set by a designer, and the embodiment does not limit the present invention as long as the processor, such as a DSP chip, can calculate and obtain the active component of the load current at the present moment.
Step 104: and obtaining the direct current side voltage feedback at the current moment according to the direct current side voltage.
It can be understood that, in the process of controlling the compensation current of the active power filter, the change of the system active power demand caused by the influence of the line impedance and the switching loss and the change of the load current can cause the fluctuation of the dc side capacitor voltage, so that the dc side capacitor undervoltage or even overvoltage affects the compensation effect on the harmonic current, and in severe cases, the reliable operation of the filter can be endangered. The dc side voltage must be kept substantially constant while controlling the compensation current. The DC side voltage can be controlled by PID regulation control method as shown in FIG. 1, and the step can be the DC side voltage V at the present momentdc(k) The difference between the current value and a preset voltage value (preset reference voltage value) is input into the PI controller, and the output of the PI controller is used as the direct current side voltage feedback i at the current momentdc(k)。
Specifically, the specific manner of obtaining the dc side voltage feedback at the current time according to the dc side voltage at the current time in this step may be set by a designer according to a practical scene and a user requirement, and when the dc side voltage is controlled by using the PID adjustment control method shown in fig. 1, the dc side voltage feedback at the current time may be obtained by using the PI controller; when the dc-side voltage is controlled by other methods, the obtaining method of the dc-side voltage feedback at the current time may also be changed correspondingly, and this embodiment does not limit this.
It should be noted that, in this embodiment, no limitation is imposed on the sequence of this step and steps 102 and 103, as long as it is ensured that the step is executed to obtain the dc-side voltage feedback at the current time before the harmonic command current at the current time is obtained by using the dc-side voltage feedback at the current time, which is not limited in this embodiment.
Step 105: and obtaining the harmonic command current at the current moment according to the load current, the active component, the direct current side voltage feedback and the phase value.
It is understood that, as shown in fig. 4, the step may be performed according to the load current (i) at the present momentL) And the active component (i) of the load currenta) Calculating the harmonic current (i) at the current momenth) E.g. using ih(k)＝iL(k)-ia(k) Calculating the harmonic current i at the current momenth(k) (ii) a Then according to the harmonic current (i) at the current momenth) DC side voltage feedback (i)dc) And phase value (theta) to calculate harmonic command current at the present time, e.g. using
Calculating a harmonic command current, wherein idc(k) Is the direct current side voltage feedback of the current moment, theta (k) is the phase value of the current moment,
the harmonic command current at the current moment.
Specifically, the specific manner of obtaining the harmonic instruction current at the current time in this step may be set by a designer, and if the above manner is adopted, as long as the processor such as the DSP chip can obtain the harmonic instruction current at the current time according to the load current, the active component, the dc-side voltage feedback and the phase value at the current time, this embodiment does not limit this.
It should be noted that, because the current is followedWhen tracking compensation control is carried out, the active filter can generate a current which is in a large reverse direction with harmonic current and the like to offset the harmonic current and the harmonic current so as to achieve the aim of compensating harmonic waves, and the tracking condition of the compensation current to the expected current is directly related to the compensation effect of the harmonic waves. As shown in fig. 1, the harmonic command current at the present moment obtained by the calculation in this step needs to be compared and controlled by using the current hysteresis comparison control method
And the actual compensation current value i at the present momentCAnd performing difference calculation, and sending the obtained difference value to a hysteresis comparison controller to obtain a corresponding PWM modulation pulse. Due to the existence of current feedback in hysteresis comparison control, the dynamic response speed is increased, the capability of suppressing intra-loop disturbance is enhanced, the control precision is higher, and the adaptability to loads is strong. However, the switching frequency, the switching loss and the control precision are all affected by the width of the hysteresis band, the narrower the hysteresis band is, the higher the control precision is, and the higher the switching frequency is, so that the switching loss is increased. Conversely, the wider the hysteresis band, the lower the control accuracy, but the lower the switching frequency, thereby reducing the switching loss.
That is, the present step may further include a step of outputting a difference between the harmonic command current at the present time and the compensation current at the present time to the hysteresis comparison controller, and obtaining the PWM modulation pulse output by the hysteresis comparison controller to perform the current tracking compensation. Correspondingly, in the step 101, not only the load current, the grid voltage and the direct-current side voltage at the current moment can be obtained, but also the compensation current at the current moment can be obtained; for example, the processor may obtain the load current, the grid voltage, the dc-side voltage, and the compensation current at the present moment through the sampling circuit.
Specifically, the rated frequency f of the single-phase power grid is 50Hz, and the sampling frequency f of the sampling circuitsFor example, 10kHz, the network voltage v at the present time is assumeds(k)＝Vmsin θ (k), load current
And the preset period may be one periodMeanwhile, a simulation model for comparing the method provided by the embodiment with the traditional method is established under MATLAB/Simulink, and on the premise of ensuring the consistency of other parts, the traditional algorithm and the method provided by the patent are respectively used for simulation in a current calculation module. The results show that both methods can enable the single-phase APF to work normally and can effectively compensate. Network current i compensated for by two methodsSPerforming FFT (fast algorithm of discrete Fourier transform) analysis, and respectively performing compensation on the two methods in the fifth and sixth graphsSTHD (total harmonic distortion), which is 3.44% in the conventional algorithm, and 1.27% in the method provided in this embodiment. Obviously, the method provided by the embodiment is simpler in algorithm compared with the traditional method, and the compensation effect is greatly improved.
In the embodiment of the invention, the harmonic instruction current is obtained by utilizing the integral link, the influence of the low-pass filter in the process of obtaining the harmonic instruction current is eliminated, the algorithm for obtaining the harmonic instruction current is simpler, the precision of the obtained harmonic instruction current is improved, the compensation effect is better compared with a single-phase active filter of a traditional algorithm, and the user experience is improved.
Referring to fig. 7, fig. 7 is a structural diagram of a harmonic command current obtaining apparatus of a single-phase active filter according to an embodiment of the present invention. The apparatus may include:
the sampling acquisition module 100 is configured to acquire a load current, a grid voltage, and a dc side voltage at a current moment;
the calculation module 200 is configured to obtain an angular frequency value and a phase value of the ac power grid at a current moment corresponding to the grid voltage by using a phase-locked loop of the single-phase active filter;
an active component calculating module 300, configured to calculate an active component of the load current according to the load current, the grid voltage, and the angular frequency value;
a dc-side voltage feedback calculation module 400, configured to obtain a dc-side voltage feedback at a current time according to the dc-side voltage;
and a harmonic command current calculating module 500, configured to obtain a harmonic command current at the current moment according to the load current, the active component, and the phase value.
Optionally, the dc-side voltage feedback calculating module 400 may include:
and the direct current side voltage feedback calculation submodule is used for inputting the difference between the direct current side voltage and a preset voltage value into the PI controller and taking the output of the PI controller as direct current side voltage feedback.
Optionally, the active component calculating module 300 may include:
sub-computation sub-module of active power for utilizing
Calculating an active power effective value of a preset period in which the current moment is located; wherein the content of the first and second substances,
in the period of the grid voltage, omega (k) is an angular frequency value, i is the sampling number of a preset period, k is the current moment, and VSFor the mains voltage, iLIs the load current;
an operator module for effective voltage value calculation for utilizing
Calculating the voltage effective value of a preset period; wherein, | | VSThe | is a voltage effective value;
equivalent conductance calculation submodule for utilizing
Calculating the equivalent conductance of a preset period; wherein G is the equivalent conductance;
an active component calculation submodule for utilizing ia(k)＝G·vs(k) Calculating an active component; wherein v iss(k) For the mains voltage, ia(k) Is the active component.
Optionally, the harmonic command current calculating module 500 may include:
harmonic current calculation submodule for utilizing ih(k)＝iL(k)-ia(k) Calculating the harmonic current at the current moment; wherein ih(k) Is a harmonic current;
harmonic command current calculation submodule for utilizing
Calculating harmonic command current; wherein idc(k) For DC side voltage feedback, θ (k) is a phase value,
is a harmonic command current.
Optionally, the sample acquiring module 100 may include:
and the sampling acquisition submodule is used for acquiring the load current, the power grid voltage and the direct current side voltage through the sampling circuit.
Optionally, the apparatus may further include:
and the current tracking compensation module is used for outputting the difference between the harmonic instruction current and the compensation current at the current moment to the hysteresis comparison controller, and acquiring the PWM modulation pulse output by the hysteresis comparison controller so as to perform current tracking compensation.
Optionally, the sampling acquisition submodule may be specifically configured to acquire the load current, the grid voltage, the dc side voltage, and the compensation current through the sampling circuit.
In the embodiment of the invention, the harmonic instruction current is obtained by utilizing the integral link, the influence of the low-pass filter in the process of obtaining the harmonic instruction current is eliminated, the algorithm for obtaining the harmonic instruction current is simpler, the precision of the obtained harmonic instruction current is improved, the compensation effect is better compared with a single-phase active filter of a traditional algorithm, and the user experience is improved.
In addition, the present invention also provides a harmonic instruction current obtaining apparatus of a single-phase active filter, including: a memory for storing a computer program; a processor for implementing the steps of the harmonic command current obtaining method of the single-phase active filter as provided in the above embodiments when executing the computer program.
The embodiments are described in a progressive manner in the specification, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the device and the equipment disclosed by the embodiment, the description is relatively simple because the device and the equipment correspond to the method disclosed by the embodiment, and the relevant parts can be referred to the method part for description.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
The method, the device and the equipment for obtaining the harmonic command current of the single-phase active filter provided by the invention are described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (9)
1. A harmonic command current obtaining method of a single-phase active filter is characterized by comprising the following steps:
acquiring load current, power grid voltage and direct-current side voltage at the current moment;
acquiring an angular frequency value and a phase value of the alternating current power grid at the current moment corresponding to the power grid voltage by using a phase-locked loop of the single-phase active filter;
calculating an active component of the load current according to the load current, the grid voltage and the angular frequency value;
acquiring the direct current side voltage feedback of the current moment according to the direct current side voltage;
obtaining the harmonic instruction current at the current moment according to the load current, the active component, the direct-current side voltage feedback and the phase value;
wherein said calculating an active component of said load current from said load current, said grid voltage and said angular frequency value comprises:
by using
Calculating an effective value of active power of a preset period in which the current moment is located; wherein the content of the first and second substances,
in the period of the voltage of the power grid, ω (k) is the angular frequency value, i is the number of samples in the preset period, k is the current time, VSFor the grid voltage iLIs the load current;
by using
Calculating the voltage effective value of the preset period; wherein, | | VSThe | is the effective value of the voltage;
by using
Calculating the equivalent conductance of the preset period; wherein G is the equivalent conductance;
using ia(k)＝G·vs(k) Calculating the active component; wherein v iss(k) For the grid voltage ia(k) Is the active component.
2. The method for obtaining harmonic command current of a single-phase active filter according to claim 1, wherein the obtaining the dc-side voltage feedback of the current time according to the dc-side voltage comprises:
and inputting the difference between the direct current side voltage and a preset voltage value into a PI controller, and taking the output of the PI controller as the direct current side voltage feedback.
3. The method according to claim 1, wherein when the predetermined period is one period,
wherein f is the rated frequency of the single-phase power grid, fsThe sampling frequency of the load current, the grid voltage and the direct-current side voltage is used.
4. The method according to claim 1, wherein the obtaining the harmonic command current at the current time according to the load current, the active component and the phase value comprises:
using ih(k)＝iL(k)-ia(k) Calculating the harmonic current of the current moment; wherein ih(k) Is the harmonic current;
by using
Calculating the harmonic command current; wherein idc(k) For the DC side voltage feedback, θ (k) is the phase value,
the harmonic command current.
5. The method for obtaining harmonic command current of a single-phase active filter according to any one of claims 1 to 4, wherein the obtaining of the load current, the grid voltage and the DC side voltage at the present time comprises:
and acquiring the load current, the grid voltage and the direct-current side voltage through a sampling circuit.
6. The method according to claim 5, further comprising, after obtaining the harmonic command current at the current time based on the load current, the active component, and the phase value, the step of obtaining the harmonic command current at the current time:
and outputting the difference between the harmonic command current and the compensation current at the current moment to a hysteresis comparator, and acquiring a PWM (pulse width modulation) modulation pulse output by the hysteresis comparator to perform current tracking compensation.
7. The method according to claim 6, wherein the obtaining the load current, the grid voltage, and the DC-side voltage by a sampling circuit comprises:
and acquiring the load current, the grid voltage, the direct-current side voltage and the compensation current through a sampling circuit.
8. A harmonic command current obtaining apparatus of a single-phase active filter, comprising:
the sampling acquisition module is used for acquiring the load current, the power grid voltage and the direct current side voltage at the current moment;
the calculation module is used for acquiring an angular frequency value and a phase value of the alternating current power grid at the current moment corresponding to the power grid voltage by using a phase-locked loop of the single-phase active filter;
the active component calculation module is used for calculating the active component of the load current according to the load current, the grid voltage and the angular frequency value;
the direct current side voltage feedback calculation module is used for acquiring direct current side voltage feedback at the current moment according to the direct current side voltage;
the harmonic instruction current calculation module is used for acquiring the harmonic instruction current at the current moment according to the load current, the active component and the phase value;
wherein the active component calculation module includes:
sub-computation sub-module of active power for utilizing
Calculating an effective value of active power of a preset period in which the current moment is located; wherein the content of the first and second substances,
in the period of the grid voltage, omega (k) is an angular frequency value, i is the sampling number of a preset period, k is the current moment, and VSFor the mains voltage, iLIs the load current;
an operator module for effective voltage value calculation for utilizing
Calculating the voltage effective value of the preset period; wherein, | | VSThe | is a voltage effective value;
equivalent conductance calculation submodule for utilizing
Calculating the equivalent conductance of the preset period; wherein G is the equivalent conductance;
an active component calculation submodule for utilizing ia(k)＝G·vs(k) Computing stationThe active component; wherein v iss(k) For the mains voltage, ia(k) Is the active component.
9. A harmonic command current obtaining apparatus of a single-phase active filter, comprising:
a memory for storing a computer program;
a processor for implementing the steps of the harmonic command current acquisition method of a single-phase active filter according to any one of claims 1 to 7 when executing said computer program.
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