CN105785281A - Photovoltaic grid-connected inverter MPPT (maximum power point tracking) efficiency test method and device - Google Patents

Abstract

The invention provides a method and device for testing the MPPT efficiency of a photovoltaic grid-connected inverter, and relates to the technical field of photovoltaic power generation. The method includes: determining a voltage and current output strategy of a programmable DC power supply according to a preset irradiance change strategy; controlling the programmable DC power supply to the photovoltaic grid-connected inverter to be tested Output voltage and current, and determine the theoretical maximum output power value of the photovoltaic array at each time sampling point; monitor the input voltage of the photovoltaic grid-connected inverter and the input current of the photovoltaic grid-connected inverter at each time sampling point; The theoretical maximum output power value of the photovoltaic array at the sampling point, the input voltage and input current of the photovoltaic grid-connected inverter at each sampling point determine the maximum power point tracking efficiency of the photovoltaic grid-connected inverter. The invention can solve the problems in the prior art that the test process is lengthy and it is difficult to synthesize static and dynamic maximum power point tracking efficiency tests.

Description

Method and device for testing MPPT efficiency of photovoltaic grid-connected inverter

technical field

The invention relates to the technical field of photovoltaic power generation, in particular to a method and device for testing MPPT efficiency of a photovoltaic grid-connected inverter.

Background technique

At present, as the global climate problem is getting worse and the contradiction between energy supply and demand is intensifying, countries around the world are adjusting energy policies from the perspective of sustainable development and ensuring energy supply security, and incorporating new energy development into national development strategies. Solar energy has become a renewable energy power generation method because of its abundant resources, inexhaustibility, cleanness and safety. At present, large-scale and distributed grid-connected photovoltaic power plants have been widely used.

In a photovoltaic power station, the photovoltaic grid-connected inverter is an important device that converts the direct current generated by the solar cell into alternating current and then feeds it into the grid. Photovoltaic grid-connected inverters rarely operate in a stable environment, because the sun's irradiance changes due to the weather, and it is also different in different time periods of the day, so the maximum power point tracking of photovoltaic grid-connected inverters ( MaximumPowerPointTracking, referred to as MPPT) efficiency is more difficult. The maximum power point tracking of the photovoltaic grid-connected inverter is to track and control the changes of the output voltage and current due to the changes of the surface temperature of the photovoltaic modules and the change of the solar irradiance, so that the solar cell array can always maintain the working state of the maximum output , to obtain automatic tuning behavior for maximum power output. The maximum power point tracking efficiency of a photovoltaic grid-connected inverter is the difference between the DC power obtained by the tested inverter and the theoretical solar array simulator working at the maximum power point within the specified period of time. power ratio.

At present, when testing the maximum power point tracking efficiency of photovoltaic grid-connected inverters, most of them need to manually adjust the voltage and current input to the grid-connected inverter, and artificially adjust the time of the simulated voltage and current, resulting in a lengthy test process. Moreover, the current maximum power point tracking efficiency test for grid-connected inverters is only for the static maximum power point tracking efficiency test, and it is difficult to integrate static and dynamic maximum power point tracking efficiency tests.

Contents of the invention

Embodiments of the present invention provide a method and device for testing the MPPT efficiency of photovoltaic grid-connected inverters, so as to solve the tedious test process in the prior art, and the maximum power point tracking efficiency test of grid-connected inverters is only for static maximum power Point tracking efficiency test, it is difficult to synthesize static and dynamic maximum power point tracking efficiency test problems.

In order to achieve the above object, the present invention adopts following technical scheme:

A method for testing the MPPT efficiency of a photovoltaic grid-connected inverter, comprising:

Determine a voltage and current output strategy of a programmable DC power supply according to a preset irradiance change strategy;

Controlling the programmable DC power supply to output voltage and current to the photovoltaic grid-connected inverter to be tested according to the output strategy of the voltage and current;

Determine the theoretical maximum output power value of the photovoltaic array at each time sampling point according to the voltage and current output strategy of the programmable DC power supply;

Monitor the input voltage of the photovoltaic grid-connected inverter and the input current of the photovoltaic grid-connected inverter at each time sampling point;

According to the theoretical maximum output power value of the photovoltaic array at each time sampling point, the input voltage and input current of the photovoltaic grid-connected inverter at each time sampling point determine the maximum power point tracking efficiency of the photovoltaic grid-connected inverter .

Specifically, according to the theoretical maximum output power value of the photovoltaic array at each time sampling point, the input voltage and input current of the photovoltaic grid-connected inverter at each time sampling point determine the photovoltaic grid-connected inverter Maximum power point tracking efficiency, including:

The maximum power point tracking efficiency η _MPPT of the photovoltaic grid-connected inverter is determined by the following formula:

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; MPPT</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; PV</span>}\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span>$

Among them, U _DC,i is the input voltage of the photovoltaic grid-connected inverter at each time sampling point; I _DC,i is the input current of the photovoltaic grid-connected inverter at each time sampling point; ΔT _i is the input current of each time sampling point Time interval; P _pvmax,i is the theoretical maximum output power value of the photovoltaic array at each time sampling point.

In addition, the controlling the programmable DC power supply to output voltage and current to the photovoltaic grid-connected inverter to be tested according to the output strategy of the voltage and current includes:

The output voltage of the programmable DC power supply is controlled to be constant, and the output current of the programmable DC power supply is controlled in real time according to the irradiance change strategy.

In addition, the controlling the programmable DC power supply to output voltage and current to the photovoltaic grid-connected inverter to be tested according to the voltage and current output strategy includes:

The output current of the programmable DC power supply is controlled to be constant, and the output voltage of the programmable DC power supply is controlled in real time according to the irradiance change strategy.

In addition, the controlling the programmable DC power supply to output voltage and current to the photovoltaic grid-connected inverter to be tested according to the voltage and current output strategy includes:

The output power of the programmable DC power supply is controlled to be constant, and the output voltage and output current of the programmable DC power supply are controlled in real time according to the irradiance change strategy.

Specifically, the irradiance change strategy includes multiple test time periods, the test irradiance corresponding to each test time period, and the change rate of irradiance between adjacent test time periods.

In addition, the test irradiance includes: 1000W/m ² , 500W/m ² , 300W/m ² , 200W/m ² and 100W/m ² ;

The change rate of the irradiance includes: 100W/m ² s and 10W/m ² s.

A test device for MPPT efficiency of a photovoltaic grid-connected inverter, comprising:

A voltage and current output strategy determining unit, configured to determine a voltage and current output strategy of a programmable DC power supply according to a preset irradiance change strategy;

A programmable DC power supply control unit, configured to control the programmable DC power supply to output voltage and current to the photovoltaic grid-connected inverter to be tested according to the output strategy of the voltage and current;

The theoretical maximum output power value determination unit is used to determine the theoretical maximum output power value of the photovoltaic array at each time sampling point according to the output strategy of the voltage and current of the programmable DC power supply;

The monitoring unit is used to monitor the input voltage of the photovoltaic grid-connected inverter and the input current of the photovoltaic grid-connected inverter at each time sampling point;

The maximum power point tracking efficiency determination unit is used to determine the photovoltaic grid-connected inverter input voltage and input current according to the theoretical maximum output power value of the photovoltaic array at each sampling point at each time and the input current of the photovoltaic grid-connected inverter at each sampling point at each time. Grid-connected inverter maximum power point tracking efficiency.

In addition, the maximum power point tracking efficiency determination unit is specifically used for:

The maximum power point tracking efficiency η _MPPT of the photovoltaic grid-connected inverter is determined by the following formula:

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; MPPT</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; PV</span>}\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span>$

Among them, U _DC,i is the input voltage of the photovoltaic grid-connected inverter at each time sampling point; I _DC,i is the input current of the photovoltaic grid-connected inverter at each time sampling point; ΔT _i is the input current of each time sampling point Time interval; P _pvmax,i is the theoretical maximum output power value of the photovoltaic array at each time sampling point.

In addition, the programmable DC power supply control unit is specifically used for:

The output voltage of the programmable DC power supply is controlled to be constant, and the output current of the programmable DC power supply is controlled in real time according to the irradiance change strategy.

Alternatively, the programmable DC power supply control unit is specifically used for:

The output current of the programmable DC power supply is controlled to be constant, and the output voltage of the programmable DC power supply is controlled in real time according to the irradiance change strategy.

Alternatively, the programmable DC power supply control unit is specifically used for:

The output power of the programmable DC power supply is controlled to be constant, and the output voltage and output current of the programmable DC power supply are controlled in real time according to the irradiance change strategy.

In addition, the irradiance change strategy includes a plurality of test time periods, test irradiance corresponding to each test time period, and a change rate of irradiance between adjacent test time periods.

Specifically, the test irradiance includes: 1000W/m ² , 500W/m ² , 300W/m ² , 200W/m ² and 100W/m ² ;

The change rate of the irradiance includes: 100W/m ² s and 10W/m ² s.

The method and device for testing the MPPT efficiency of a photovoltaic grid-connected inverter provided by the embodiments of the present invention can determine a voltage and current output strategy of a programmable DC power supply according to a preset irradiance change strategy, and control the The programmable DC power supply outputs voltage and current to the photovoltaic grid-connected inverter to be tested according to the output strategy of the voltage and current; the photovoltaic square at each time sampling point is determined according to the output strategy of the voltage and current of the programmable DC power supply The theoretical maximum output power value of the photovoltaic array; monitor the input voltage of the photovoltaic grid-connected inverter and the input current of the photovoltaic grid-connected inverter at each time sampling point; according to the theoretical maximum output power value of the photovoltaic square array at each time sampling point, The input voltage and input current of the photovoltaic grid-connected inverter at each time sampling point determine the maximum power point tracking efficiency of the photovoltaic grid-connected inverter. In this way, the present invention can complete the test of the MPPT efficiency of the photovoltaic grid-connected inverter without manual adjustment. The test of static and dynamic maximum power point tracking efficiency avoids the problem that the current test of maximum power point tracking efficiency of grid-connected inverters is only for static maximum power point tracking efficiency, and the test results are not accurate.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained according to these drawings without any creative effort.

Fig. 1 is the flow chart of the testing method of MPPT efficiency of photovoltaic grid-connected inverter provided by the embodiment of the present invention;

Fig. 2 is a schematic curve diagram of an irradiance change strategy in an embodiment of the present invention;

Fig. 3 is the comprehensive static and dynamic MPPT efficiency test curve for the first time of the OELMAIERPAC55kW grid-connected inverter in the embodiment of the present invention;

Fig. 4 is the comprehensive static and dynamic MPPT efficiency test curve for the second time of OELMAIERPAC55kW grid-connected inverter in the embodiment of the present invention;

Fig. 5 is the comprehensive static and dynamic MPPT voltage and current test curve for the first time of the OELMAIERPAC55kW grid-connected inverter in the embodiment of the present invention;

Fig. 6 is the comprehensive static and dynamic MPPT voltage and electric current second test curve of OELMAIERPAC55kW grid-connected inverter in the embodiment of the present invention;

Fig. 7 is the comprehensive static and dynamic MPPT efficiency first test curve of the EHE-N5KS5kW grid-connected inverter in the embodiment of the present invention;

Fig. 8 is the comprehensive static and dynamic MPPT efficiency second test curve of the EHE-N5KS5kW grid-connected inverter in the embodiment of the present invention;

Fig. 9 is the comprehensive static and dynamic MPPT voltage and current first test curve of the EHE-N5KS5kW grid-connected inverter in the embodiment of the present invention;

Figure 10 is the second test curve of the comprehensive static and dynamic MPPT voltage and current of the EHE-N5KS5kW grid-connected inverter in the embodiment of the present invention;

11 is a schematic structural diagram of a test system for the MPPT efficiency of a photovoltaic grid-connected inverter in an embodiment of the present invention;

Fig. 12 is a schematic structural diagram of a test device for MPPT efficiency of a photovoltaic grid-connected inverter provided by an embodiment of the present invention.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

As shown in Figure 1, a method for testing MPPT efficiency of a photovoltaic grid-connected inverter provided by an embodiment of the present invention includes:

Step 101. Determine a voltage and current output strategy of a programmable DC power supply according to a preset irradiance change strategy.

Step 102, controlling the programmable DC power supply to output voltage and current to the photovoltaic grid-connected inverter to be tested according to the output strategy of voltage and current.

Step 103: Determine the theoretical maximum output power value of the photovoltaic array at each time sampling point according to the voltage and current output strategy of the programmable DC power supply.

Step 104, monitoring the input voltage of the photovoltaic grid-connected inverter and the input current of the photovoltaic grid-connected inverter at each time sampling point.

Step 105. Determine the maximum power point tracking efficiency of the photovoltaic grid-connected inverter according to the theoretical maximum output power value of the photovoltaic array at each time sampling point, and the input voltage and input current of the photovoltaic grid-connected inverter at each time sampling point.

The method for testing the efficiency of the photovoltaic grid-connected inverter MPPT provided by the embodiment of the present invention can determine the output strategy of the voltage and current of a programmable DC power supply according to a preset irradiance change strategy, and control the programmable DC power supply Output voltage and current to the photovoltaic grid-connected inverter to be tested according to the output strategy of voltage and current; determine the theoretical maximum output power value of the photovoltaic array at each time sampling point according to the output strategy of programmable DC power supply voltage and current; monitor The input voltage of the photovoltaic grid-connected inverter and the input current of the photovoltaic grid-connected inverter at each time sampling point; according to the theoretical maximum output power value of the photovoltaic square array at each time sampling point, the photovoltaic grid-connected inverter at each time sampling point The input voltage and input current of the inverter determine the maximum power point tracking efficiency of the photovoltaic grid-connected inverter. In this way, the present invention can complete the test of the MPPT efficiency of the photovoltaic grid-connected inverter without manual adjustment. The test of static and dynamic maximum power point tracking efficiency avoids the problem that the current test of maximum power point tracking efficiency of grid-connected inverters is only for static maximum power point tracking efficiency, and the test results are not accurate.

In the above step 105, the maximum power point tracking efficiency of the photovoltaic grid-connected inverter is determined according to the theoretical maximum output power value of the photovoltaic square array at each time sampling point, and the input voltage and input current of the photovoltaic grid-connected inverter at each time sampling point, The maximum power point tracking efficiency η _MPPT of the photovoltaic grid-connected inverter can be determined by the following formula:

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; MPPT</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; PV</span>}\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span>$

Among them, U _DC,i is the input voltage of the photovoltaic grid-connected inverter at each time sampling point; I _DC,i is the input current of the photovoltaic grid-connected inverter at each time sampling point; ΔT _i is the input current of each time sampling point The time interval is generally 1 second; P _pvmax,i is the theoretical maximum output power value of the photovoltaic array at each time sampling point.

The control programmable DC power supply in the above step 102 outputs voltage and current to the photovoltaic grid-connected inverter to be tested according to the output strategy of voltage and current. Change strategy to control the output current of programmable DC power supply in real time.

Alternatively, the output current of the programmable DC power supply can be controlled to be constant, and the output voltage of the programmable DC power supply can be controlled in real time according to the irradiance change strategy.

Alternatively, the output power of the programmable DC power supply can be controlled to be constant, and the output voltage and output current of the programmable DC power supply can be controlled in real time according to the irradiance change strategy.

In addition, the above-mentioned irradiance change strategy may include multiple test time periods, the test irradiance corresponding to each test time period, and the change rate of irradiance between adjacent test time periods.

For example, the above test irradiance may include: 1000W/m ² , 500W/m ² , 300W/m ² , 200W/m ² and 100W/m ² .

The aforementioned rate of change of irradiance may include: 100W/m ² s and 10W/m ² s.

For example, the irradiance change strategy can be shown in Figure 2 and Table 1 below:

Table 1:

It can be seen that, as shown in Table 1 and Figure 2, the irradiance change strategy is that the grid-connected inverter starts up and enters steady-state operation. The irradiance within 300 seconds is 100W/m ² , and then the irradiance is 10W/m ² s The rate of change of the irradiance slowly rises to 1000W/m ² within 90 seconds, and continues to run for 180 seconds... In this way, until the above 19 steps of serial numbers are completed, the accumulation lasts for 4282 seconds. Among them, in step 18, the key steps in Table 1 can be repeatedly tested, so that the accuracy and stability of subsequent test results are higher. For example, continuously run for 300s under the condition of 100W/ ^m2 irradiance, after the grid-connected inverter enters a stable operation state, changing the irradiance to test the MPPT tracking performance of the inverter can ensure the stability of the test, and select 1000W /m ² , 500W/m ² , 300W/m ² , 200W/m ² and 100W/m ² typical high, medium and low typical irradiance working conditions, and a repeated test, combined with grid-connected inverter The usual MPPT response time of the inverter, using the remote control and monitoring system, pre-edited and set the simulated irradiance change rate, so that the programmable DC power supply can be 100W/m ² s and 10W/m ² s with the specified irradiance Two kinds of change rate mutations to ensure the accuracy of the data.

Through the above steps 101-105, the following two grid-connected inverters can be tested:

The first is the test of OELMAIERPAC 55kW grid-connected inverter in Germany:

Figures 3 to 6 are the MPPT efficiency curves, DC input voltage and current variation curves of the grid-connected inverter corresponding to different irradiances.

According to the corresponding formula in the above step 105, taking into account the recorded inverter DC input voltage, current value and sampling time, and the theoretical maximum output power value of the photovoltaic array at the corresponding time, and averaging two consecutive MPPT efficiency test results, it can be obtained MPPT efficiency values of the OELMAIERPAC5 inverter.

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; MPPT</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; PV</span>}\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 98.18</span>}<span\; class="notranslate">\; \%</span>$

In addition, the test of China's EHE-N5KS5kW grid-connected inverter:

According to the formula in the above step 105, the MPPT efficiency of the EHE-N5KS5kW inverter can be obtained by including the recorded inverter DC input voltage, current value and sampling time, and the theoretical maximum power point power value of the photovoltaic array at the corresponding time The value is 96.31% as shown in the following formula. The test results of the static and dynamic comprehensive MPPT efficiency of the grid-connected inverter twice are shown in Figure 7 to Figure 10. The average value of the static and dynamic comprehensive MPPT efficiency value repeated twice is EHE- Static and dynamic combined MPPT efficiency test results for N5KS 5kW inverter.

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; MPPT</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; PV</span>}\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 96.31</span>}<span\; class="notranslate">\; \%</span>$

It is worth noting that the method for testing the MPPT efficiency of a photovoltaic grid-connected inverter according to the embodiment of the present invention can be realized by a testing system for the MPPT efficiency of a photovoltaic grid-connected inverter as shown in FIG. 11 :

The MPPT efficiency test system of the photovoltaic grid-connected inverter includes a programmable DC power supply 21 , a power analyzer 22 , a switch cabinet 23 , an oscilloscope 24 , and a test platform remote control system 25 . Among them, the test platform remote control system 25 communicates with the programmable DC power supply 21 and the switch cabinet 23. The programmable DC power supply 21 is connected to the photovoltaic grid-connected inverter 26 to be tested. The other end of 26 is connected in series with power analyzer 22, switch cabinet 23 and oscilloscope 24. In addition, the switch cabinet 23 may also be connected with an AC analog grid 27 for power supply.

The programmable DC power supply 21 in this embodiment can simulate irradiance changes under various weather conditions, such as complex and changeable weather conditions such as sunny days, rainy days, and cloudy, and environmental conditions such as shadows, dust, and snow. Irradiance change, the function of simulating the I/V output characteristics of the solar cell square array through the change of irradiance, can realize the operation mode of constant voltage, constant current and constant power, and can change according to the preset irradiance strategies to implement voltage, current, and power control and regulation. Through the above-mentioned test platform remote control system 25, within the allowable voltage and current limit range of the inverter, the parameter command can be transmitted in real time, and the current output electrical parameters can be adjusted to carry out the whole test process.

The power analyzer 22 can monitor and analyze the output power of the photovoltaic grid-connected inverter 26 . The switchgear 23 can control the circuit on-off of the MPPT efficiency test system of the entire photovoltaic grid-connected inverter. The oscilloscope 24 can display the current and voltage parameters output by the photovoltaic grid-connected inverter 26 for presentation.

Corresponding to the above-mentioned method embodiment in FIG. 1 , the embodiment of the present invention provides a test device for MPPT efficiency of a photovoltaic grid-connected inverter, as shown in FIG. 12 , including:

The voltage and current output strategy determining unit 31 can determine a voltage and current output strategy of a programmable DC power supply according to a preset irradiance change strategy.

The programmable DC power supply control unit 32 can control the programmable DC power supply to output voltage and current to the photovoltaic grid-connected inverter to be tested according to the output strategy of voltage and current.

The theoretical maximum output power value determination unit 33 can determine the theoretical maximum output power value of the photovoltaic array at each time sampling point according to the voltage and current output strategy of the programmable DC power supply.

The monitoring unit 34 can monitor the input voltage of the photovoltaic grid-connected inverter and the input current of the photovoltaic grid-connected inverter at each time sampling point.

The maximum power point tracking efficiency determination unit 35 can determine the maximum value of the photovoltaic grid-connected inverter according to the theoretical maximum output power value of the photovoltaic square array at each time sampling point, and the input voltage and input current of the photovoltaic grid-connected inverter at each time sampling point. Power point tracking efficiency.

In addition, the maximum power point tracking efficiency determination unit 35 can specifically determine the maximum power point tracking efficiency η _MPPT of the photovoltaic grid-connected inverter through the following formula:

${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; MPPT</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; PV</span>}\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span>$

Among them, U _DC,i is the input voltage of the photovoltaic grid-connected inverter at each time sampling point; I _DC,i is the input current of the photovoltaic grid-connected inverter at each time sampling point; ΔT _i is the input current of each time sampling point Time interval; P _pvmax,i is the theoretical maximum output power value of the photovoltaic array at each time sampling point.

In addition, the programmable DC power supply control unit 32 can control the output voltage of the programmable DC power supply to be constant, and control the output current of the programmable DC power supply in real time according to the irradiance change strategy. Or control the output current of the programmable DC power supply to be constant, and control the output voltage of the programmable DC power supply in real time according to the irradiance change strategy. Or control the output power of the programmable DC power supply to be constant, and control the output voltage and output current of the programmable DC power supply in real time according to the irradiance change strategy.

In addition, the irradiance change strategy includes multiple test time periods, the test irradiance corresponding to each test time period, and the change rate of irradiance between adjacent test time periods.

Specifically, the test irradiance includes: 1000W/m ² , 500W/m ² , 300W/m ² , 200W/m ² and 100W/m ² . The rate of change of the irradiance includes: 100W/m ² s and 10W/m ² s.

It is worth noting that, the specific implementation manner of the test device for the MPPT efficiency of the photovoltaic grid-connected inverter provided by the embodiment of the present invention may refer to the method embodiment shown in FIG. 1 above, and will not be repeated here.

The test device for the MPPT efficiency of the photovoltaic grid-connected inverter provided by the embodiment of the present invention can determine the output strategy of the voltage and current of a programmable DC power supply according to a preset irradiance change strategy, and control the programmable DC power supply Output voltage and current to the photovoltaic grid-connected inverter to be tested according to the output strategy of voltage and current; determine the theoretical maximum output power value of the photovoltaic array at each time sampling point according to the output strategy of programmable DC power supply voltage and current; monitor The input voltage of the photovoltaic grid-connected inverter and the input current of the photovoltaic grid-connected inverter at each time sampling point; according to the theoretical maximum output power value of the photovoltaic square array at each time sampling point, the photovoltaic grid-connected inverter at each time sampling point The input voltage and input current of the inverter determine the maximum power point tracking efficiency of the photovoltaic grid-connected inverter. In this way, the present invention can complete the test of the MPPT efficiency of the photovoltaic grid-connected inverter without manual adjustment. The test of static and dynamic maximum power point tracking efficiency avoids the problem that the current test of maximum power point tracking efficiency of grid-connected inverters is only for static maximum power point tracking efficiency, and the test results are not accurate.

Those skilled in the art should understand that the embodiments of the present invention may be provided as methods, systems, or computer program products. Accordingly, the present invention can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general purpose computer, special purpose computer, embedded processor, or processor of other programmable data processing equipment to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing equipment produce a An apparatus for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions The device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions can also be loaded onto a computer or other programmable data processing device, causing a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process, thereby The instructions provide steps for implementing the functions specified in the flow chart or blocks of the flowchart and/or the block or blocks of the block diagrams.

In the present invention, specific examples have been applied to explain the principles and implementation methods of the present invention, and the descriptions of the above examples are only used to help understand the method of the present invention and its core idea; meanwhile, for those of ordinary skill in the art, according to this The idea of the invention will have changes in the specific implementation and scope of application. To sum up, the contents of this specification should not be construed as limiting the present invention.

Claims (14)

1. A method for testing the MPPT efficiency of a photovoltaic grid-connected inverter, characterized in that it comprises: Determine a voltage and current output strategy of a programmable DC power supply according to a preset irradiance change strategy; Controlling the programmable DC power supply to output voltage and current to the photovoltaic grid-connected inverter to be tested according to the output strategy of the voltage and current; Determine the theoretical maximum output power value of the photovoltaic array at each time sampling point according to the voltage and current output strategy of the programmable DC power supply; Monitor the input voltage of the photovoltaic grid-connected inverter and the input current of the photovoltaic grid-connected inverter at each time sampling point; According to the theoretical maximum output power value of the photovoltaic array at each time sampling point, the input voltage and input current of the photovoltaic grid-connected inverter at each time sampling point determine the maximum power point tracking efficiency of the photovoltaic grid-connected inverter . 2. the method for testing the efficiency of photovoltaic grid-connected inverter MPPT according to claim 1, is characterized in that, described according to the theoretical maximum output power value of the photovoltaic array at each time sampling point, each time sampling point The input voltage and input current of the photovoltaic grid-connected inverter determine the maximum power point tracking efficiency of the photovoltaic grid-connected inverter, including: The maximum power point tracking efficiency η _MPPT of the photovoltaic grid-connected inverter is determined by the following formula: ${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; MPPT</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; PV</span>}\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span>$ Among them, U _DC,i is the input voltage of the photovoltaic grid-connected inverter at each time sampling point; I _DC,i is the input current of the photovoltaic grid-connected inverter at each time sampling point; ΔT _i is the input current of each time sampling point Time interval; P _pvmax,i is the theoretical maximum output power value of the photovoltaic array at each time sampling point. 3. The method for testing the MPPT efficiency of a photovoltaic grid-connected inverter according to claim 2, wherein the control of the programmable DC power supply to the photovoltaic grid-connected power supply to be tested is performed according to the output strategy of the voltage and current. Inverter output voltage and current, including: The output voltage of the programmable DC power supply is controlled to be constant, and the output current of the programmable DC power supply is controlled in real time according to the irradiance change strategy. 4. The method for testing the MPPT efficiency of a photovoltaic grid-connected inverter according to claim 2, wherein the control of the programmable DC power supply to the photovoltaic grid-connected power supply to be tested is based on the output strategy of the voltage and current. Inverter output voltage and current, including: The output current of the programmable DC power supply is controlled to be constant, and the output voltage of the programmable DC power supply is controlled in real time according to the irradiance change strategy. 5. The method for testing the MPPT efficiency of a photovoltaic grid-connected inverter according to claim 2, wherein the control of the programmable DC power supply to the photovoltaic grid-connected power supply to be tested according to the output strategy of the voltage and current Inverter output voltage and current, including: The output power of the programmable DC power supply is controlled to be constant, and the output voltage and output current of the programmable DC power supply are controlled in real time according to the irradiance change strategy. 6. The method for testing the MPPT efficiency of a photovoltaic grid-connected inverter according to any one of claims 1-5, wherein the irradiance variation strategy includes a plurality of test time periods, each test time period corresponds to The test irradiance and the rate of change of irradiance between adjacent test periods. 7. The method for testing MPPT efficiency of photovoltaic grid-connected inverters according to claim 6, wherein the test irradiance includes: 1000W/m ² , 500W/m ² , 300W/m ² , 200W/m 2 m ² and 100W/m ² ; The change rate of the irradiance includes: 100W/m ² s and 10W/m ² s. 8. A test device for MPPT efficiency of a photovoltaic grid-connected inverter, characterized in that it includes: A voltage and current output strategy determining unit, configured to determine a voltage and current output strategy of a programmable DC power supply according to a preset irradiance change strategy; A programmable DC power supply control unit, configured to control the programmable DC power supply to output voltage and current to the photovoltaic grid-connected inverter to be tested according to the output strategy of the voltage and current; The theoretical maximum output power value determination unit is used to determine the theoretical maximum output power value of the photovoltaic array at each time sampling point according to the output strategy of the voltage and current of the programmable DC power supply; The monitoring unit is used to monitor the input voltage of the photovoltaic grid-connected inverter and the input current of the photovoltaic grid-connected inverter at each time sampling point; The maximum power point tracking efficiency determination unit is used to determine the photovoltaic grid-connected inverter input voltage and input current according to the theoretical maximum output power value of the photovoltaic array at each sampling point at each time and the input current of the photovoltaic grid-connected inverter at each sampling point at each time. Grid-connected inverter maximum power point tracking efficiency. 9. The test device for the MPPT efficiency of the photovoltaic grid-connected inverter according to claim 8, wherein the maximum power point tracking efficiency determination unit is specifically used for: The maximum power point tracking efficiency η _MPPT of the photovoltaic grid-connected inverter is determined by the following formula: ${\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{\mathrm{<span\; class="notranslate">\; MPPT</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; PV</span>}\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span>$ Among them, U _DC,i is the input voltage of the photovoltaic grid-connected inverter at each time sampling point; I _DC,i is the input current of the photovoltaic grid-connected inverter at each time sampling point; ΔT _i is the input current of each time sampling point Time interval; P _pvmax,i is the theoretical maximum output power value of the photovoltaic array at each time sampling point. 10. The test device for MPPT efficiency of a photovoltaic grid-connected inverter according to claim 9, wherein the programmable DC power supply control unit is specifically used for: The output voltage of the programmable DC power supply is controlled to be constant, and the output current of the programmable DC power supply is controlled in real time according to the irradiance change strategy. 11. The photovoltaic grid-connected inverter MPPT efficiency test device according to claim 9, wherein the programmable DC power supply control unit is specifically used for: The output current of the programmable DC power supply is controlled to be constant, and the output voltage of the programmable DC power supply is controlled in real time according to the irradiance change strategy. 12. The photovoltaic grid-connected inverter MPPT efficiency test device according to claim 9, wherein the programmable DC power supply control unit is specifically used for: The output power of the programmable DC power supply is controlled to be constant, and the output voltage and output current of the programmable DC power supply are controlled in real time according to the irradiance change strategy. 13. The test device for the MPPT efficiency of a photovoltaic grid-connected inverter according to any one of claims 8-12, wherein the irradiance change strategy includes a plurality of test time periods, each test time period corresponds to The test irradiance and the rate of change of irradiance between adjacent test periods. 14. The photovoltaic grid-connected inverter MPPT efficiency test device according to claim 13, wherein the test irradiance includes: 1000W/m ² , 500W/m ² , 300W/m ² , 200W/m 2 m ² and 100W/m ² ; The change rate of the irradiance includes: 100W/m ² s and 10W/m ² s.