CN108183508B - Control method of photovoltaic inverter under two-way MPPT input condition - Google Patents
Control method of photovoltaic inverter under two-way MPPT input condition Download PDFInfo
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Abstract
The invention discloses a control method of a photovoltaic inverter under two-way MPPT input conditions, which is characterized in that the magnitude of two-way input PV voltage is compared, one way with higher voltage is started to carry out MPPT tracking, and the other way is started to carry out MPPT tracking after the bus reference voltage is stably set, namely the way works stably, so that the two ways of MPPT started by the photovoltaic inverter work sequentially without mutual influence, and the conventional working state of a solar power generation system can be maintained. Therefore, the invention can stably set the bus reference voltage, so that the tracking loading of the maximum power point is more stable, the normal work of the solar power generation system is ensured, the maximum power point is not required to be repeatedly tracked, and the overall efficiency is higher.
Description
Technical Field
The invention relates to a photovoltaic inverter, in particular to a control method of the photovoltaic inverter under the condition of two-path MPPT input.
Background
In a photovoltaic grid-connected power generation system, a photovoltaic inverter converts direct current output by a photovoltaic array or a photovoltaic combiner box into alternating current and outputs the alternating current. The existing photovoltaic inverter is started under the condition of two-way MPPT input, two-way MPPT is started and tracked simultaneously, tracking loading is unstable due to the change of bus reference voltage, the photovoltaic inverter needs to repeatedly track a maximum power point for many times until tracking is successful, and a solar power generation system cannot normally work easily in the process.
Disclosure of Invention
In order to solve the above problems, an object of the present invention is to provide a control method for a photovoltaic inverter under two MPPT input conditions, which can stably set a bus reference voltage without repeatedly tracking a maximum power point, so that tracking and loading of the maximum power point are more stable.
In order to make up for the defects of the prior art, the invention adopts the technical scheme that:
the control method of the photovoltaic inverter under the condition of two-path MPPT input comprises the following steps:
A. after the photovoltaic inverter is initialized, acquiring PV voltages of the photovoltaic inverter in a power-on self-detection stage under the condition of two paths of MPPT input, namely a first path of solar panel open-circuit voltage PV1 and a second path of solar panel open-circuit voltage PV 2;
B. obtaining rated bus voltage BV2 of the photovoltaic inverter, and comparing PV1, PV2 and BV2 to determine the working state of bus initial reference voltage BV1 and a BOOST converter;
C. the method comprises the steps that a photovoltaic inverter enters a grid-connected state, MPPT tracking is carried out on one path of input with higher voltage in PV1 and PV2, and meanwhile, a first path of solar panel reference voltage PV10 and a second path of solar panel reference voltage PV20 of the photovoltaic inverter are obtained, so that the working state of a BOOST converter and bus reference voltage BV3 of the input path are dynamically adjusted;
D. MPPT tracking is carried out on one path of input with lower voltage in PV1 and PV2, the BOOST converters with the input path are started, and the sizes among PV10, PV20 and BV2 are compared, so that the working states of the two paths of BOOST converters and the bus reference voltage BV3 are dynamically adjusted, and a stable bus reference voltage BV3 is obtained.
Further, step B includes:
if PV1> PV2 and PV1> BV2, then BV1 is PV1, and the BOOST converter of the first path is not started;
if PV1> PV2 and (BV2-30V) < PV1< BV2, then BV1 ═ BV2+30V, start the BOOST converter of the first way;
if PV1 is greater than PV2 and PV1< (BV2-30V), BV1 is BV2, and the BOOST converter of the first path is started.
Further, step C includes:
if PV1> PV2 and PV10> BV2, then BV3 is PV10, and the BOOST converter of the first path is not started;
if PV1> PV2 and (BV2-30V) < PV10< BV2, then BV3 ═ BV2+30V, start the BOOST converter of the first way;
if PV1 is greater than PV2 and PV10< (BV2-30V), BV3 is BV2, and the BOOST converter of the first path is started.
Further, step D includes:
if PV10 is more than PV20, (PV10-PV20) <25V, PV10< (BV2-25V), starting two BOOST converters, BV3 is BV 2;
if PV10> PV20 and (PV10-PV20) <25V, PV10> (BV2-25V), two-way BOOST converter is started, BV3 ═ PV10+ 25V.
Further, step D includes:
if PV10> PV20 and (PV10-PV20) >25V, PV10> (BV2+5V), the BOOST converter of the second path is started, BV3 ═ PV 10;
if PV10 is greater than PV20, (PV10-PV20) >25V, PV10< (BV 2-8V), two-way BOOST converter is started, BV3 is BV 2.
The invention has the beneficial effects that: the invention provides a control method of a photovoltaic inverter under two-way MPPT input conditions, which is characterized in that one way with higher voltage is started for MPPT tracking by comparing the magnitude of two-way input PV voltage, and the other way is started for MPPT tracking after the bus reference voltage is stably set, namely the way works stably, so that the two ways of MPPT started by the photovoltaic inverter work sequentially without mutual influence, and the conventional working state of a solar power generation system can be maintained. Therefore, the invention can stably set the bus reference voltage, so that the tracking loading of the maximum power point is more stable, the normal work of the solar power generation system is ensured, the maximum power point is not required to be repeatedly tracked, and the overall efficiency is higher.
Drawings
The following description of the preferred embodiments of the present invention will be made in conjunction with the accompanying drawings.
Fig. 1 is a schematic circuit diagram of a photovoltaic inverter of the present invention under two MPPT input conditions;
FIG. 2 is a flow chart of the steps of the present invention.
Detailed Description
Referring to fig. 1 and 2, the control method of the photovoltaic inverter under the condition of two-way MPPT input includes the following steps:
A. after the photovoltaic inverter is initialized, acquiring PV voltages of the photovoltaic inverter in a power-on self-detection stage under the condition of two paths of MPPT input, namely a first path of solar panel open-circuit voltage PV1 and a second path of solar panel open-circuit voltage PV 2;
B. obtaining rated bus voltage BV2 of the photovoltaic inverter, and comparing PV1, PV2 and BV2 to determine the working state of bus initial reference voltage BV1 and a BOOST converter;
C. the method comprises the steps that a photovoltaic inverter enters a grid-connected state, MPPT tracking is carried out on one path of input with higher voltage in PV1 and PV2, and meanwhile, a first path of solar panel reference voltage PV10 and a second path of solar panel reference voltage PV20 of the photovoltaic inverter are obtained, so that the working state of a BOOST converter and bus reference voltage BV3 of the input path are dynamically adjusted;
D. MPPT tracking is carried out on one path of input with lower voltage in PV1 and PV2, the BOOST converters with the input path are started, and the sizes among PV10, PV20 and BV2 are compared, so that the working states of the two paths of BOOST converters and the bus reference voltage BV3 are dynamically adjusted, and a stable bus reference voltage BV3 is obtained.
Specifically, the values of the first path of solar panel open-circuit voltage PV1 and the second path of solar panel open-circuit voltage PV2 can be obtained through external collection and detection, the rated bus voltage BV2 is a fixed parameter, once the grid voltage is determined, the first path of solar panel open-circuit voltage PV 6324 and the second path of solar panel open-circuit voltage PV2 are also determined accordingly, and can be generally obtained through the product specifications thereof, in addition, the first path of solar panel reference voltage PV10 and the second path of solar panel reference voltage PV20 are parameters which change in real time in the MPPT tracking process, after the MPPT tracking reaches the maximum working point, the parameter values thereof do not change, and the initial bus reference voltage BV1 and the bus reference voltage BV3 can be determined by the above-mentioned voltages, so except that PV1 and PV2 are marked in fig. 1, other related voltages are not marked in fig. 1; the BOOST converter is also called a parallel switch converter, and is a commonly used conversion device in the solar technology, the working state of the BOOST converter in the embodiment refers to whether the BOOST converter works, and the BOOST converter can be set by a worker according to a voltage relationship, and a preferred implementation circuit of the BOOST converter can refer to fig. 1; the number of the photovoltaic inverters is not limited, and the photovoltaic inverters are connected to the bus and are driven and controlled by the bus; the PV voltage is the open-circuit voltage of the solar panel, the setting of the step B is to prepare for the path with higher PV voltage to enter a grid-connected state, and meanwhile, if the BOOST converter needs to work, the voltage on the bus needs to be softly started in the power-on self-test stage of the photovoltaic inverter so as to stably control the grid-connected operation, meanwhile, the maximum power point does not need to be repeatedly tracked, and the overall efficiency is higher; by comparing the magnitude of the two paths of input PV voltages, one path with higher voltage is started firstly to carry out MPPT tracking, and when the bus reference voltage is stably set, namely the path works stably, the other path is started to carry out MPPT tracking, so that the two paths of MPPT started by the photovoltaic inverter work successively without influencing each other, and the conventional working state of the solar power generation system can be maintained. Therefore, the invention can stably set the bus reference voltage, so that the tracking loading of the maximum power point is more stable, the normal work of the solar power generation system is ensured, the maximum power point is not required to be repeatedly tracked, and the overall efficiency is higher. In addition, in the embodiment, the two paths of related parameters are distinguished only for better illustrating the basic principle of the present invention, and should not be construed as a limitation on themselves.
Wherein, step B includes:
if PV1> PV2 and PV1> BV2, then BV1 is PV1, and the BOOST converter of the first path is not started;
if PV1> PV2 and (BV2-30V) < PV1< BV2, then BV1 ═ BV2+30V, start the BOOST converter of the first way;
if PV1 is greater than PV2 and PV1< (BV2-30V), BV1 is BV2, and the BOOST converter of the first path is started.
Similarly, since the input of each path is not specific, the above control method is also applicable to the case when PV1< PV2, for example, if PV1< PV2 and PV2> BV2, BV1 is PV2, and the BOOST converter of the second path is not started, which is not described herein.
The initial reference voltage of the bus is determined through the step B, so that the grid connection can be stably carried out, and a good foundation is laid for MPPT tracking later.
Wherein, step C includes:
if PV1> PV2 and PV10> BV2, then BV3 is PV10, and the BOOST converter of the first path is not started;
if PV1> PV2 and (BV2-30V) < PV10< BV2, then BV3 ═ BV2+30V, start the BOOST converter of the first way;
if PV1 is greater than PV2 and PV10< (BV2-30V), BV3 is BV2, and the BOOST converter of the first path is started.
Similarly, since the input of each path is not specific, the above control method is also applicable to the case when PV1< PV2, for example, if PV1< PV2 and PV20> BV2, BV3 is PV20, and the BOOST converter of the second path is not started, which is not described herein.
And C, determining the bus reference voltage in the working state of the path with higher PV voltage, which is beneficial to stabilizing the grid-connected working state of the path and ensuring that the path is stably tracked to the maximum working point.
Wherein, step D includes:
if PV10 is more than PV20, (PV10-PV20) <25V, PV10< (BV2-25V), starting two BOOST converters, BV3 is BV 2;
if PV10> PV20 and (PV10-PV20) <25V, PV10> (BV2-25V), two-way BOOST converter is started, BV3 ═ PV10+ 25V.
Similarly, since the input of each path is not specific, the above control method is also applicable to the case when PV10< PV20, for example, if PV10< PV20 and (PV20-PV10) <25V, PV20< (BV2-25V), two paths of BOOST converters are activated, BV3 equals BV2, which is not described herein again.
Wherein, step D includes:
if PV10> PV20 and (PV10-PV20) >25V, PV10> (BV2+5V), the BOOST converter of the second path is started, BV3 ═ PV 10;
if PV10 is greater than PV20, (PV10-PV20) >25V, PV10< (BV 2-8V), two-way BOOST converter is started, BV3 is BV 2.
Similarly, since the input of each path is not specific, the above control method is also applicable to the case when PV10< PV20, for example, if PV10< PV20 and (PV20-PV10) >25V, PV20> (BV2+5V), the BOOST converter of the second path is started, BV3 is PV10, which is not described herein again.
Step D, determining the bus reference voltage based on the fluctuation range of the rated bus voltage, wherein according to the experience of the applicant, the selection of the fluctuation range is more suitable by taking 25V and 8V as base points; stable bus reference voltage is obtained through the step D, a worker can stably track the maximum power point loaded to one path with lower voltage only by setting correspondingly, the maximum power points of two paths of MPPT can be easily tracked by matching with the previous steps, repeated tracking is not needed, and the efficiency is higher.
While the preferred embodiments and basic principles of the present invention have been described in detail, it will be understood by those skilled in the art that the invention is not limited to the embodiments, but is intended to cover various modifications, equivalents and alternatives falling within the scope of the invention as claimed.
Claims (1)
1. The control method of the photovoltaic inverter under the condition of two-path MPPT input is characterized by comprising the following steps of:
A. after the photovoltaic inverter is initialized, acquiring PV voltages of the photovoltaic inverter in a power-on self-detection stage under the condition of two paths of MPPT input, namely a first path of solar panel open-circuit voltage PV1 and a second path of solar panel open-circuit voltage PV 2;
B. obtaining a rated bus voltage BV2 of the photovoltaic inverter, if PV1> PV2 and PV1> BV2, then the bus initial reference voltage BV1 is PV1, and the BOOST converter of the first path is not started; if PV1> PV2 and (BV2-30V) < PV1< BV2, then BV1 ═ BV2+30V, start the BOOST converter of the first way;
if PV1 is greater than PV2 and PV1< (BV2-30V), BV1 is BV2, and a BOOST converter of the first path is started;
C. the photovoltaic inverter enters a grid-connected state, MPPT tracking is carried out on one path of input with higher voltage in PV1 and PV2, meanwhile, a first path of solar panel reference voltage PV10 and a second path of solar panel reference voltage PV20 of the photovoltaic inverter are obtained, if PV1 is larger than PV2 and PV10 is larger than BV2, a bus reference voltage BV3 is equal to PV10, and a BOOST converter of the first path is not started;
if PV1> PV2 and (BV2-30V) < PV10< BV2, then BV3 ═ BV2+30V, start the BOOST converter of the first way;
if PV1 is greater than PV2 and PV10< (BV2-30V), BV3 is BV2, and a BOOST converter of the first path is started;
D. MPPT tracking is carried out on one input of PV1 and PV2, which is lower in voltage, a BOOST converter of the input is started, sizes among PV10, PV20 and BV2 are compared, if PV10 is larger than PV20 and (PV10-PV20) <25V, PV10< (BV2-25V), two BOOST converters are started, and BV3 is BV 2;
if PV10> PV20 and (PV10-PV20) <25V, PV10> (BV2-25V), two-way BOOST converter is started, BV3 ═ PV10+ 25V;
if PV10> PV20 and (PV10-PV20) >25V, PV10> (BV2+5V), the BOOST converter of the second path is started, BV3 ═ PV 10;
if PV10 is greater than PV20, (PV10-PV20) >25V, PV10< (BV 2-8V), two-way BOOST converter is started, BV3 is BV 2.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2012137830A (en) * | 2010-12-24 | 2012-07-19 | Ntt Facilities Inc | Solar power generation system |
| CN102854912A (en) * | 2012-09-27 | 2013-01-02 | 北京京仪绿能电力***工程有限公司 | Double-line MPPT (Maximum Power Point Tracking) tracking device and method |
| CN108183508A (en) * | 2018-01-18 | 2018-06-19 | 珠海联合电能技术有限公司 | Control method of the photovoltaic DC-to-AC converter under two-way MPPT input conditions |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2012137830A (en) * | 2010-12-24 | 2012-07-19 | Ntt Facilities Inc | Solar power generation system |
| CN102854912A (en) * | 2012-09-27 | 2013-01-02 | 北京京仪绿能电力***工程有限公司 | Double-line MPPT (Maximum Power Point Tracking) tracking device and method |
| CN108183508A (en) * | 2018-01-18 | 2018-06-19 | 珠海联合电能技术有限公司 | Control method of the photovoltaic DC-to-AC converter under two-way MPPT input conditions |
Non-Patent Citations (1)
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| 基于改进粒子群算法的多路光伏MPPT控制;张海宁等;《电力电子技术》;20170520;第51卷(第5期);第39-41页 * |
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