Based on the photovoltaic module energy output method of measurement of volt-ampere characteristic
Technical field
The present invention relates to photovoltaic field tests, be specially a kind of photovoltaic module energy output method of measurement based on volt-ampere characteristic.
Background technology
Volt-ampere characteristic test is the method for testing of test light photovoltaic assembly various performance parameters, and the energy output test of photovoltaic module is normally under outdoor natural light shines, the real-time energy output monitoring under utilizing the test circuit of inverter self or other electric current and voltage meter apparatus additional to carry out photovoltaic module operating state.We illustrate the method for testing of generation current amount for inverter.At the positive and negative electrode of the input access photovoltaic module of inverter, inverter changes the electric current and voltage output characteristic of photovoltaic module by maximal power tracing algorithm, makes photovoltaic module remain at maximum power output state.Then by photovoltaic module voltage, the current parameters of built-in electric current and voltage test circuit test input, thus calculate current realtime power, then sampled by certain time interval, thus accumulation obtains the energy output summation of assembly within a period of time.The energy output test being carried out photovoltaic module by inverter is the effective way extensively adopted at present, but the method is by the impact of different manufacturers inverter maximal power tracing algorithm, the maximum power point of assembly there will be larger skew, truly can not reflect assembly energy output under practical circumstances.
In addition the at present measurement of assembly property be mostly standard STC environment (25 DEG C, 1000W/m
2irradiance, AM1.5 spectroscopic light source) under maximum power value Pmax, but assembly is when outside work, and the condition such as ambient temperature and irradiance is different, needs a kind of more scientific method to weigh the characteristic of assembly.The test of assembly energy output is weighed mark as assembly property and is accepted by more people at present, also needs better method more accurately and carries out reliably, repeatable test.
Summary of the invention
The object of this invention is to provide a kind of photovoltaic module energy output method of measurement based on volt-ampere characteristic, descend the energy output of test light photovoltaic assembly can be subject to load and the impact of maximum power control strategy, the problem that the reliability of test result is a greater impact in working order to solve prior art.
In order to achieve the above object, the technical solution adopted in the present invention is:
Based on the photovoltaic module energy output method of measurement of volt-ampere characteristic, it is characterized in that: utilize photovoltaic module Testing Instrument for Volt-ampere Characteristic, the volt-ampere characteristic of photovoltaic module to be measured is measured in multiple identical continuous time interval fixedly reached, and the measuring condition setting of test next time is carried out according to current test curve, comprise maximum current test specification and the setting of sampling point position, improve test accuracy.Find out photovoltaic module maximum power to be measured corresponding in each time interval according to volt-ampere characteristic after each test, and draw out the time dependent curve of photovoltaic module maximum power to be measured.Again photovoltaic module maximum power to be measured in each time interval was multiplied with the time interval and obtains the energy output of photovoltaic module to be measured in each time interval, then accumulation computing is carried out to the energy output of photovoltaic module to be measured in continuous time interval, obtain the accumulated generation amount of photovoltaic module to be measured in continuous time interval, finally show the accumulated generation value in a period of time.
The described photovoltaic module energy output method of measurement based on volt-ampere characteristic, is characterized in that: the described time interval can according to the adjustment from 1 second to 30 points of measuring accuracy needs.
The present invention is by measuring continuous volt-ampere characteristic in Fixed Time Interval, obtain the comparatively accurately maximum power value of photovoltaic module under outdoor different conditions, by obtaining obtainable more accurately the generate electricity value of photovoltaic module under outside work condition with time integral mode, because the time interval is selected, to little of as far as possible level second, can improve the accuracy index of follow-on test.
The invention has the beneficial effects as follows, provide novel assembly energy output method of testing, and improve the accuracy of test, the examination criteria that can be photovoltaic as standard method of measurement is formulated and is provided foundation.
Accompanying drawing explanation
Fig. 1 is volt-ampere characteristic schematic diagram in the present invention.
Fig. 2 is energy output test schematic diagram.
Embodiment
Tested photovoltaic module is placed on outdoor unscreened position, positive and negative binding post is connected to respectively the test input of photovoltaic module Testing Instrument for Volt-ampere Characteristic.Utilize photovoltaic module Testing Instrument for Volt-ampere Characteristic, the volt-ampere characteristic of photovoltaic module to be measured is measured in multiple identical continuous time interval fixedly reached, and the measuring condition setting of test next time is carried out according to current test curve, comprise maximum current test specification and the setting of sampling point position, improve test accuracy.Find out photovoltaic module maximum power to be measured corresponding in each time interval according to volt-ampere characteristic after each test, and draw out the time dependent curve of photovoltaic module maximum power to be measured.Again photovoltaic module maximum power to be measured in each time interval was multiplied with the time interval and obtains the energy output of photovoltaic module to be measured in each time interval, then accumulation computing is carried out to the energy output of photovoltaic module to be measured in continuous time interval, obtain the accumulated generation amount of photovoltaic module to be measured in continuous time interval, finally show the accumulated generation value in a period of time.
As shown in Figure 1, utilization tests out the photovoltaic module volt-ampere characteristic as figure from Testing Instrument for Volt-ampere Characteristic, software is utilized to find out maximum power point Pmax wherein, and obtain short circuit current Isc, as the maximum current test specification of test next time, and current sampling interval setting is on average set according to testing current scope.As shown in Figure 2, abscissa is the testing time, and Δ t just sets when testing and starting, and can not change in test process.Ordinate is the maximum power point Pmax found on curve after each voltage-current characteristic test curve generates.After the time interval of Δ t1, two test point Pmax.0 and Pmax.1 can be produced.Consider that the time interval is enough little, and the change of power curve meets normal distribution feature, the average power content in Δ t1 directly adopts Pmax.1, the energy output E1=Pmax.1* Δ t as shown in FIG. in Δ t1.Accumulated generation amount in the whole testing time just can be designated as E=Pmax.1* Δ t+Pmax.2* Δ t+ ... + Pmax.N* Δ t.