Sensitivity-based photovoltaic inverter control parameter identification method

Abstract

The invention discloses a photovoltaic inverter control parameter identification method based on sensitivity, relates to the field of parameter identification, and aims at solving the problems that an existing control strategy is photovoltaic inverter control parameter identification based on a virtual synchronous machine technology, the identification mode is complex, and the identification effect is poor. The method comprises the following steps: step 1, collecting capacitor side output voltage and load side output current in a photovoltaic inverter, obtaining photovoltaic inverter active power and photovoltaic inverter reactive power, and inputting the active power and the reactive power to a control model; and step 2, according to the active current control target value and the reactive current control target value output by the control model, obtaining a proportionality coefficient and an integral coefficient in a PI controller in the control model. The method is used for identifying the control parameters.

Description

Technical Field

[0001] The invention relates to the field of parameter identification, and belongs to a parameter identification method. Background Art

[0002] The control of the photovoltaic inverter is composed of control links. Due to the different characteristics of each grid-connected control link, the frequency domain characteristics of the photovoltaic inverter are different. Therefore, in the photovoltaic inverter, the PI control parameters of the active and reactive power control links directly affect the frequency domain characteristics of the photovoltaic inverter and need to be identified to simulate the frequency domain characteristics of the real photovoltaic inverter for power analysis.

[0003] However, the existing control strategy is based on the identification of photovoltaic inverter control parameters using virtual synchronous machine technology, which has a complex identification method and poor identification effect. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that the existing control strategy is based on the identification of photovoltaic inverter control parameters of virtual synchronous machine technology, the identification method is complex, and the identification effect is poor. A method for identifying photovoltaic inverter control parameters based on sensitivity is proposed.

[0005] A photovoltaic inverter control parameter identification method based on sensitivity, characterized in that the method includes the following contents:

[0006] Step 1: Collect the capacitor side output voltage and load side output current of the photovoltaic inverter to obtain the active power and reactive power of the photovoltaic inverter, and input them into the control model;

[0007] Step 2: According to the active current control target value and the reactive current control target value output by the control model, the proportional coefficient and the integral coefficient in the PI controller in the control model are obtained.

[0008] Preferably, in step 1, the process of obtaining the active power of the photovoltaic inverter and the reactive power of the photovoltaic inverter is:

[0009] The output voltage on the capacitor side and the output current on the load side of the photovoltaic inverter are collected. The output voltage on the capacitor side of the photovoltaic inverter is transformed by a No. 1 Pike converter to obtain the component voltage on the d-axis and the component voltage on the q-axis. The output current on the load side is transformed by a No. 2 Pike converter to obtain the component current on the d-axis and the component current on the q-axis. The component voltage on the d-axis, the component voltage on the q-axis, the component current on the d-axis and the component current on the q-axis are sent to the power calculation module to obtain the active power P of the photovoltaic inverter and the reactive power Q of the photovoltaic inverter.

[0010] Preferably, the control model includes a delay link, a PI controller and a switching switch;

[0011] The delay link includes a No. 1 delay module, a No. 2 delay module, a No. 3 delay module, a No. 4 delay module and a No. 5 delay module; the PI controller includes a No. 1 PI controller and a No. 2 PI controller;

[0012] Given active power P m Input to the No. 1 delay module, output the given active power maximum value or the given active power minimum value; given active power instruction P ord The active power P of the photovoltaic inverter is input to the No. 3 delay module, which outputs the active power of the photovoltaic inverter after the delay.

[0013] The switch is used to switch the delayed active power command and the given active power maximum value or the given active power minimum value, and the difference between the switched value and the delayed photovoltaic inverter active power is sent to the No. 1 PI controller to output the active current control target value I p_cmd ;

[0014] Given reactive power command Q ord Input to the No. 4 delay module, output the delayed reactive power command; the photovoltaic inverter reactive power Q is input to the No. 5 delay module, output the delayed photovoltaic inverter reactive power; the delayed reactive power command is subtracted from the delayed photovoltaic inverter reactive power, and the difference is sent to the No. 2 PI controller to output the reactive current control target value I q_cmd .

[0015] Preferably, the control model further comprises a controller;

[0016] The controller is used to limit the active power instruction after delay by using the given active power maximum value or the given active power minimum value, so that the active power instruction after delay is less than the given active power maximum value or the given active power minimum value.

[0017] Preferably, the first delay module t 1 It is expressed as:

[0018]

[0019] In the formula, s is the differential operator, T mpp It is the output delay of the maximum power command.

[0020] Preferably, the third delay module and the fifth delay module t 2 All are expressed as:

[0021]

[0022] In the formula, s is the differential operator, T m Delay for actual power measurement.

[0023] Preferably, the first PI controller and the second PI controller k are both expressed as:

[0024]

[0025] In the formula, K p is the proportionality coefficient, s is the differential operator, T p is the integration coefficient.

[0026] The beneficial effects of the present invention are:

[0027] The present invention establishes a control model, sets an active current control target value and a reactive current control target value, and calculates control parameters, namely, a proportional coefficient and an integral coefficient, according to the active power and reactive power of the photovoltaic inverter collected from the photovoltaic inverter. According to the identified proportional coefficient and integral coefficient, the dynamic characteristics of the photovoltaic inverter can be obtained, and the state of the photovoltaic inverter can be observed in real time, so that each photovoltaic inverter site can be analyzed more accurately.

[0028] In addition, in the MPPT working mode, if the rate of change of the active power output by the photovoltaic inverter is too fast, the inverter may be damaged, and if it is too slow, the response speed will be affected, which is not conducive to the recovery of the system. The present invention can obtain the maximum value of a given active power or the minimum value of a given active power according to the control model, identify its maximum rate of change and minimum rate of change, and achieve real-time monitoring to avoid affecting the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a flow chart of a sensitivity-based photovoltaic inverter control parameter identification method;

[0030] Figure 2 This is a typical schematic diagram of a photovoltaic inverter;

[0031] Figure 3 This is the schematic diagram of the photovoltaic power generation unit control model. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0034] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0035] Example:

[0036] Combination Figures 1 to 3 This embodiment describes a photovoltaic inverter control parameter identification method based on sensitivity, the method comprising the following contents:

[0037] Step 1: Collect the capacitor side output voltage and load side output current of the photovoltaic inverter to obtain the active power and reactive power of the photovoltaic inverter, and input them into the control model;

[0038] Step 2: According to the active current control target value and the reactive current control target value output by the control model, the proportional coefficient and the integral coefficient in the PI controller in the control model are obtained.

[0039] Specifically, the sensitivity test shows that no matter in the case of changing the reference value or short circuit fault, the active power has a great influence on the parameter K. p , T p More sensitive, reactive power to parameter K q , T q Therefore, the output power of the distributed generation unit can be changed by setting the working conditions, and the measured data can be collected to identify the required parameters.

[0040] The following describes the process of obtaining the active power and reactive power of the photovoltaic inverter:

[0041] The output voltage on the capacitor side and the output current on the load side of the photovoltaic inverter are collected. The output voltage on the capacitor side of the photovoltaic inverter is transformed by a No. 1 Pike converter to obtain the component voltage on the d-axis and the component voltage on the q-axis. The output current on the load side is transformed by a No. 2 Pike converter to obtain the component current on the d-axis and the component current on the q-axis. The component voltage on the d-axis, the component voltage on the q-axis, the component current on the d-axis and the component current on the q-axis are sent to the power calculation module to obtain the active power P of the photovoltaic inverter and the reactive power Q of the photovoltaic inverter.

[0042] The control model structure is introduced below: The control model includes a delay link, a PI controller and a switching switch;

[0043] The delay link includes a No. 1 delay module, a No. 2 delay module, a No. 3 delay module, a No. 4 delay module and a No. 5 delay module; the PI controller includes a No. 1 PI controller and a No. 2 PI controller;

[0044] Given active power P m Input to the No. 1 delay module, output the given active power maximum value or the given active power minimum value; given active power instruction Pord The active power P of the photovoltaic inverter is input to the No. 3 delay module, which outputs the active power of the photovoltaic inverter after the delay.

[0045] The switch is used to switch the delayed active power command and the given active power maximum value or the given active power minimum value, and the difference between the switched value and the delayed photovoltaic inverter active power is sent to the No. 1 PI controller to output the active current control target value I p_cmd ;

[0046] Given reactive power command Q ord Input to the No. 4 delay module, output the delayed reactive power command; the photovoltaic inverter reactive power Q is input to the No. 5 delay module, output the delayed photovoltaic inverter reactive power; the delayed reactive power command is subtracted from the delayed photovoltaic inverter reactive power, and the difference is sent to the No. 2 PI controller to output the reactive current control target value I q_cmd .

[0047] The following further describes the components of the control model: the control model also includes a controller;

[0048] The controller is used to limit the active power instruction after delay by using the given active power maximum value or the given active power minimum value, so that the active power instruction after delay is less than the given active power maximum value or the given active power minimum value.

[0049] The following is an introduction to the delay module No. 1 1 It is expressed as:

[0050]

[0051] In the formula, s is the differential operator, T mpp It is the output delay of the maximum power command.

[0052] The following introduces the delay module No. 3 and the delay module No. 5. 2 All are expressed as:

[0053]

[0054] In the formula, s is the differential operator, T m Delay for actual power measurement.

[0055] The following introduces the No. 1 PI controller and the No. 2 PI controller k, both of which are expressed as:

[0056]

[0057] In the formula, K p is the proportionality coefficient, s is the differential operator, T pis the integration coefficient.

[0058] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. A photovoltaic inverter control parameter identification method based on sensitivity, characterized in that: The method comprises the following: Step 1: Collect the capacitor side output voltage and load side output current of the photovoltaic inverter to obtain the active power and reactive power of the photovoltaic inverter, and input them into the control model; Step 2: According to the active current control target value and the reactive current control target value output by the control model, the proportional coefficient and the integral coefficient in the PI controller in the control model are obtained.

2. A sensitivity-based photovoltaic inverter control parameter identification method according to claim 1, characterized in that: In step 1, the process of obtaining the active power and reactive power of the photovoltaic inverter is as follows: The output voltage on the capacitor side and the output current on the load side of the photovoltaic inverter are collected. The output voltage on the capacitor side of the photovoltaic inverter is transformed by a No. 1 Pike converter to obtain the component voltage on the d-axis and the component voltage on the q-axis. The output current on the load side is transformed by a No. 2 Pike converter to obtain the component current on the d-axis and the component current on the q-axis. The component voltage on the d-axis, the component voltage on the q-axis, the component current on the d-axis and the component current on the q-axis are sent to the power calculation module to obtain the active power P of the photovoltaic inverter and the reactive power Q of the photovoltaic inverter.

3. A photovoltaic inverter control parameter identification method based on sensitivity according to claim 1, characterized in that: The control model includes a delay link, a PI controller and a switching switch; The delay link includes a No. 1 delay module, a No. 2 delay module, a No. 3 delay module, a No. 4 delay module and a No. 5 delay module; the PI controller includes a No. 1 PI controller and a No. 2 PI controller; Given active power P m Input to the No. 1 delay module, output the given active power maximum value or the given active power minimum value; given active power instruction P ord The active power P of the photovoltaic inverter is input to the No. 3 delay module, which outputs the active power of the photovoltaic inverter after the delay. The switch is used to switch the delayed active power command and the given active power maximum value or the given active power minimum value, and the difference between the switched value and the delayed photovoltaic inverter active power is sent to the No. 1 PI controller to output the active current control target value I p_cmd ; Given reactive power command Q ord Input to the No. 4 delay module, output the delayed reactive power command; the photovoltaic inverter reactive power Q is input to the No. 5 delay module, output the delayed photovoltaic inverter reactive power; the delayed reactive power command is subtracted from the delayed photovoltaic inverter reactive power, and the difference is sent to the No. 2 PI controller to output the reactive current control target value I q_cmd .

4. The method for identifying photovoltaic inverter control parameters based on sensitivity according to claim 1, characterized in that: The control model also includes a controller; The controller is used to limit the active power instruction after delay by using the given active power maximum value or the given active power minimum value, so that the active power instruction after delay is less than the given active power maximum value or the given active power minimum value.

5. The method for identifying photovoltaic inverter control parameters based on sensitivity according to claim 3, characterized in that: The delay module No. 1 t1 is expressed as: In the formula, s is the differential operator, T mpp It is the output delay of the maximum power command.

6. A photovoltaic inverter control parameter identification method based on sensitivity according to claim 3, characterized in that: The delay module No. 3 and the delay module No. 5 t2 are both expressed as: In the formula, s is the differential operator, T m Delay for actual power measurement.

7. A photovoltaic inverter control parameter identification method based on sensitivity according to claim 3, characterized in that: The first PI controller and the second PI controller k are both expressed as: In the formula, K p is the proportionality coefficient, s is the differential operator, T p is the integration coefficient.

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