CN109742758B - APF compensation method based on Dyn11 transformer - Google Patents
APF compensation method based on Dyn11 transformer Download PDFInfo
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Abstract
The application particularly relates to an APF compensation method based on a Dyn11 transformer, which comprises the step of using a phase-locked loop to carry out phase locking on grid-connected point voltage to obtain phase angle information of high-voltage side terminal voltage. The phase angle information of the load current of the two pairs of high-voltage side currents and the voltage of the high-voltage side end adopts a DFT algorithm to extract reactive power and harmonic components of the currents and converts the reactive power and the harmonic components to the low-voltage side to obtain reactive power and harmonic components of the low-voltage side currents of the Dyn11 transformer; the difference of the three direct current side voltages is used as the input of the voltage control module to output delta i d ，△i d As the d-axis component of the dq coordinate system, the command current is obtained by dq-abc coordinate conversion. Fifthly, subtracting the instruction current from the APF equipment output current to obtain a difference value; the difference value is input to a current control module, and the current control module calculates an output control quantity according to the input difference value. Inputting the control quantity into an SVPWM module; the SVPWM module outputs a switch control signal to the corresponding IGB for control.
Description
Technical Field
The application belongs to the field of power electronics, and particularly relates to an APF compensation method based on a Dyn11 transformer.
Background
With the rapid development of power electronics technology, various power electronics devices and nonlinear loads bring about a great deal of harmonic pollution problems, so that the quality of a power grid is adversely affected, and in order to solve the increasingly serious harmonic problems of the power grid, an Active Power Filter (APF) can be adopted as a device for dynamically compensating the harmonic of the power grid. In the conventional use occasion, firstly, load current and grid voltage are detected, harmonic wave and reactive component in the load current are extracted through a harmonic decomposition algorithm, and then current tracking control is carried out. To achieve accurate harmonic compensation, it is a primary task to obtain accurate sampled values. The electrical quantities sampled by a common Active Power Filter (APF) are mainly: grid voltage at grid connection, load current, compensation current of APF and DC side voltage of APF. For some special occasions, such as a power system with a Dyn11 transformer, the grid connection point of the APF equipment needs to be selected at a low voltage side, the low voltage side cannot measure the load current, the sampled load current can only be the load current value at a high voltage side, the collected electric quantity changes, and a harmonic detection method needs to be adjusted. In summary, how to design a new harmonic detection method according to the working characteristics of the Dyn11 transformer is a key to solve the problem that the traditional harmonic decomposition is not applicable any more in the occasion of introducing the Dyn11 transformer.
Disclosure of Invention
1. The technical problems to be solved are as follows:
the application provides a harmonic detection method based on a Dyn11 transformer, which solves the problem that the traditional harmonic detection method cannot be used due to the change of the sampling amount after the Dyn11 transformer is introduced.
2. The technical scheme is as follows:
an APF compensation method based on a Dyn11 transformer, wherein a load is connected to the high-voltage side end of the Dyn11 transformer, and APF equipment is connected to the low-voltage side end of the Dyn11 transformer; the method is characterized in that: the APF equipment collects load current of a high-voltage side end of the Dyn11 transformer, grid-connected point voltage of a low-voltage side end of the Dyn11 transformer, output current of the APF equipment and direct-current side voltage of the APF equipment.
Wherein, the APF compensation method comprises the following steps:
step one: using a phase-locked loop PLL to phase-lock the grid-connected point voltage acquired by the APF equipment to obtain phase angle theta, sin theta and cos theta values of the grid-connected point voltage; thereby calculating the value of sin (theta-30 DEG) and cos (theta-30 DEG); the sin (theta-30 DEG) and cos (theta-30 DEG) values are phase angle information of the high-voltage side end voltage of the Dyn11 transformer.
Step two: APF equipment collects current load current i at high voltage side of Dyn11 transformer la 、i lb 、i lc The method comprises the steps of carrying out a first treatment on the surface of the Load current i at high-voltage side of Dyn11 transformer la 、i lb 、i lc And (3) adopting DFT algorithm to obtain the phase angle information of the Dyn11 transformer high-voltage side terminal voltage obtained in the step one la 、i lb 、i lc Harmonic decomposition is carried out, and reactive power and harmonic components in the harmonic decomposition are extractedQuantity i ha 、i hb 、i hc And will i ha 、i hb 、i hc Conversion to low-voltage side to obtain reactive power and harmonic component i of Dyn11 transformer low-voltage side current ha ’、i hb ’、i hc ’。
Step three: sampling value U of direct-current side voltage of APF equipment dc And set value U dc * Difference is made to obtain a difference DeltaU dc The method comprises the steps of carrying out a first treatment on the surface of the Will be DeltaU dc As input to the voltage control module; the output Deltai of the voltage control module d As the d-axis component of the dq coordinate system, the active component i of the instruction current is obtained through dq-abc coordinate conversion da 、i db 、i dc 。
Step four: obtaining the active component i of the instruction current in the third step da 、i db 、i dc And i ha 、i hb 、i hc Respectively adding to obtain instruction current i refa 、i refb 、i refc 。
Step five: will command current i refa 、i refb 、i refc Output current i from APF device sa 、i sb 、i sc Subtracting to obtain a difference Deltai sa 、△i sb 、△i sc The method comprises the steps of carrying out a first treatment on the surface of the The difference Deltai is calculated sa 、△i sb 、△i sc Input to a current control module, which is based on the input Δi sa 、△i sb 、△i sc By calculating the output control quantity U ma 、U mb 、U mc 。
Step six: and D, obtaining a control quantity U from the step five ma 、U mb 、U mc As input to the SVPWM module; the SVPWM module outputs corresponding switch control signals and transmits each switch control signal to the corresponding IGBT so as to control the working state of each IGBT.
Further, the voltage control module adopts a PI controller.
Further, the current control module adopts a PI+PR controller.
Further, the APF device is a parallel APF device; and the parallel APF equipment is connected with the grid at the low-voltage side end of the Dyn11 transformer.
3. The beneficial effects are that:
according to the method, calculation errors caused by overlarge transformation ratio of the Dyn11 transformer can be avoided, so that APF equipment can be arranged on a low-voltage side to effectively compensate reactive power and harmonic current of a high-voltage side in the occasion of using the Dyn11 transformer.
Drawings
FIG. 1 is a diagram showing the connection and sampling of a conventional APF;
FIG. 2 illustrates the wiring and sampling of APF in the case of Dyn11 transformers according to the present application;
fig. 3 is a control block diagram of a harmonic compensation method based on a Dyn11 transformer provided by the application;
fig. 4 is a control schematic block diagram of a voltage control module of the harmonic compensation method based on the Dyn11 transformer provided by the application;
fig. 5 is a control schematic block diagram of a current control module of the harmonic compensation method based on the Dyn11 transformer provided by the application.
Detailed Description
The present application will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram of a conventional APF connection and sampling scheme; it can be seen from the figure that the sampled electrical quantity is mainly composed of load current, grid-connected point voltage and equipment output current. In the case of introducing the Dyn11 transformer, as shown in fig. 2, the parallel APF device needs to be connected to the grid on the low voltage side of the Dyn11 transformer, and the collected electric quantity will be changed into the load current on the high voltage side of the Dyn11 transformer, the grid-connected point voltage on the low voltage side of the Dyn11 transformer, the output current of the APF device and the dc voltage on the APF device, so the control method should be changed accordingly.
As shown in fig. 3, the APF compensation method includes the following steps:
step one: using a phase-locked loop PLL to phase-lock the grid-connected point voltage acquired by the APF equipment to obtain phase angle theta, sin theta and cos theta values of the grid-connected point voltage; thereby calculating the value of sin (theta-30 DEG) and cos (theta-30 DEG); the sin (theta-30 DEG) and cos (theta-30 DEG) values are phase angle information of the high-voltage side end voltage of the Dyn11 transformer.
Step two: APF equipment collects current load current i at high voltage side of Dyn11 transformer la 、i lb 、i lc The method comprises the steps of carrying out a first treatment on the surface of the Load current i at high-voltage side of Dyn11 transformer la 、i lb 、i lc And (3) adopting DFT algorithm to obtain the phase angle information of the Dyn11 transformer high-voltage side terminal voltage obtained in the step one la 、i lb 、i lc Harmonic decomposition is carried out, and reactive and harmonic components i in the harmonic decomposition are extracted ha 、i hb 、i hc And will i ha 、i hb 、i hc Conversion to low-voltage side to obtain reactive power and harmonic component i of Dyn11 transformer low-voltage side current ha ’、i hb ’、i hc ’。
The specific process is as follows:
high side current load current i using Dyn11 transformer la 、i lb 、i lc DFT algorithm is adopted to the i for the high-voltage side phase angle information la 、i lb 、i lc Harmonic decomposition is carried out, and reactive and harmonic components i in the harmonic decomposition are extracted ha 、i hb 、i hc 。
Due to i ha 、i hb 、i hc Is the harmonic component of the high-voltage side current, which is converted to i at the low-voltage side ha ’、i hb ’、i hc ' the conversion process is shown in formula (1).
Step three: sampling value U of direct-current side voltage of APF equipment dc And set value U dc * Difference is made to obtain a difference DeltaU dc The method comprises the steps of carrying out a first treatment on the surface of the Will be DeltaU dc As input to the voltage control module; the output Deltai of the voltage control module d As the d-axis component of the dq coordinate system, the active component i of the instruction current is obtained through dq-abc coordinate conversion da 、i db 、i dc 。
Step four: obtaining the active component i of the instruction current in the third step da 、i db 、i dc And i ha 、i hb 、i hc Respectively adding to obtain instruction current i refa 、i refb 、i refc 。
Step five: will command current i refa 、i refb 、i refc Output current i from APF device sa 、i sb 、i sc Subtracting to obtain a difference Deltai sa 、△i sb 、△i sc The method comprises the steps of carrying out a first treatment on the surface of the The difference Deltai is calculated sa 、△i sb 、△i sc Input to a current control module, which is based on the input Δi sa 、△i sb 、△i sc By calculating the output control quantity U ma 、U mb 、U mc 。
Step six: and D, obtaining a control quantity U from the step five ma 、U mb 、U mc As input to the SVPWM module; the SVPWM module outputs corresponding switch control signals and transmits each switch control signal to the corresponding IGBT so as to control the working state of each IGBT.
Further, the voltage control module adopts a PI controller. FIG. 4 is a control schematic diagram of a voltage control module used in the present application, in which the DC side voltage of the APF device is sampled by a value U dc And set value U dc * Difference is made to obtain a difference DeltaU dc ；△U dc As input to the voltage control module, the output Δi of the voltage control module d The controller used in the voltage control module is a conventional PI controller, and its transfer function is:
wherein K is p 、K I Proportional and integral constants, respectively.
Further, the current control module adopts a PI+PR controller. Command current i refa 、i refb 、i refc And the output current i of the device sa 、i sb 、i sc Subtracting to obtain a difference Deltai sa 、△i sb 、△i sc . The current control module is used for controlling the current according to the input delta i sa 、△i sb 、△i sc Obtaining the output control quantity U through calculation ma 、U mb 、U mc . The current control module is added with a resonance controller to control the output control quantity U on the basis of adopting a conventional PI controller ma 、U mb 、U mc A plurality of resonant controllers are connected in parallel with a conventional PI controller. The transfer function of the PR controller is:
wherein K is P And K R The proportionality coefficient and the resonance coefficient omega of the resonance controller respectively 0 The fundamental frequency, h is the harmonic order. The resonance controller is added in the current control module, so that the resonance control effect can be maintained, the stability of the system is improved, the compensation of the appointed subharmonic current can be realized, the appointed subharmonic current is compensated according to different compensation requirements, and the control is flexible and the adaptability is strong.
While the application has been described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the application, and it is intended that the scope of the application shall be defined by the appended claims.
Claims (4)
1. An APF compensation method based on a Dyn11 transformer, wherein a load is connected to the high-voltage side end of the Dyn11 transformer, and APF equipment is connected to the low-voltage side end of the Dyn11 transformer; the method is characterized in that: the APF equipment collects load current at the high-voltage side of the Dyn11 transformer, grid-connected point voltage at the low-voltage side of the Dyn11 transformer, output current of the APF equipment and direct-current side voltage of the APF equipment;
the APF compensation method comprises the following steps:
step one: using a phase-locked loop PLL to phase-lock the grid-connected point voltage acquired by the APF equipment to obtain phase angle theta, sin theta and cos theta values of the grid-connected point voltage; thereby calculating the value of sin (theta-30 DEG) and cos (theta-30 DEG); the sin (theta-30 DEG) and cos (theta-30 DEG) values are phase angle information of the high-voltage side end voltage of the Dyn11 transformer;
step two: APF equipment collects current load current i at high voltage side of Dyn11 transformer la 、i lb 、i lc The method comprises the steps of carrying out a first treatment on the surface of the Load current i at high-voltage side of Dyn11 transformer la 、i lb 、i lc And (3) adopting DFT algorithm to obtain the phase angle information of the Dyn11 transformer high-voltage side terminal voltage obtained in the step one la 、i lb 、i lc Harmonic decomposition is carried out, and reactive and harmonic components i in the harmonic decomposition are extracted ha 、i hb 、i hc And will i ha 、i hb 、i hc Conversion to low-voltage side to obtain reactive power and harmonic component i of Dyn11 transformer low-voltage side current ha ’、i hb ’、i hc ’；
Step three: sampling value U of direct-current side voltage of APF equipment dc And set value U dc * Difference is made to obtain a difference DeltaU dc The method comprises the steps of carrying out a first treatment on the surface of the Will be DeltaU dc As input to the voltage control module; the output Deltai of the voltage control module d As the d-axis component of the dq coordinate system, the active component i of the instruction current is obtained through dq-abc coordinate conversion da 、i db 、i dc ；
Step four: obtaining the active component i of the instruction current in the third step da 、i db 、i dc And i ha 、i hb 、i hc Respectively adding to obtain instruction current i refa 、i refb 、i refc ；
Step five: will command current i refa 、i refb 、i refc Output current i from APF device sa 、i sb 、i sc Subtracting to obtain a difference Deltai sa 、△i sb 、△i sc The method comprises the steps of carrying out a first treatment on the surface of the The difference Deltai is calculated sa 、△i sb 、△i sc Input to a current control module, which generates a delta according to the inputi sa 、△i sb 、△i sc By calculating the output control quantity U ma 、U mb 、U mc ；
Step six: and D, obtaining a control quantity U from the step five ma 、U mb 、U mc As input to the SVPWM module; the SVPWM module outputs corresponding switch control signals and transmits each switch control signal to the corresponding IGBT so as to control the working state of each IGBT.
2. The Dyn11 transformer-based APF compensation method of claim 1, wherein: the voltage control module adopts a PI controller.
3. The Dyn11 transformer-based APF compensation method of claim 1, wherein: the current control module adopts a PI+PR controller.
4. The Dyn11 transformer-based APF compensation method of claim 1, wherein: the APF equipment is parallel APF equipment; and the parallel APF equipment is connected with the grid at the low-voltage side end of the Dyn11 transformer.
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