Distributed photovoltaic district flexible control method based on 380V low-voltage grid connection

Abstract

The invention relates to a 380V low-voltage grid-connected-based distributed photovoltaic area flexible control method, which comprises the following operations: starting a service App, reading configuration, determining a data acquisition source, monitoring the load and voltage of an area after a platform starts flexible control, delaying for 10 seconds for retesting if the three-phase voltage exceeds the limit, regulating and controlling a photovoltaic inverter if the three-phase voltage still exceeds the limit, reducing the power by 20%, and controlling the power of the photovoltaic inverter by 20% if the three-phase voltage still exceeds the limit. After that, retesting is carried out every 15 minutes, if the power exceeds the limit continuously, the power is reduced continuously until the power is reduced to 20% of the normal value, and after the voltage is recovered, the power is adjusted according to the load rate gt; the content is reduced by 20% when the content is 80%; the content is reduced by 5% when the content is 70%-80%; lt; and the process is circulated until the voltage and the load are reasonable, and if the platform closes the flexible control, the App immediately adjusts the power of the inverter to 100%. According to the method, the problem of stability of the power grid of the photovoltaic transformer area is solved, including the problems of voltage out-of-limit, line loss increase, substandard power factor and the like.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a distributed photovoltaic area flexible control method based on 380V low-voltage grid connection. Background Art

[0002] With the rapid growth of distributed photovoltaics, the power quality of photovoltaic areas has become particularly important. The access of distributed photovoltaics will cause voltage limit exceeding, reverse overload exceeding the standard, power reduction, and line loss increase in the area.

[0003] Most existing solutions are to affect the operating status of the inverter by adding a protocol converter next to the inverter. When the protocol converter finds an abnormality, some will shut down the inverter or adjust the inverter active power to stabilize the power grid in the substation area. Some will control the inverter by controlling micro-breaks. This solution has the following disadvantages:

[0004] 1. Only the current inverter is regulated, without any optimization adjustment based on the whole area.

[0005] 2. Directly shutting off a user's power generation will affect the user's revenue and be directly perceived by the user, causing conflicts between the user and the system.

[0006] 3. Generally, the protocol converter will decide the adjustment strategy based on whether the voltage in the substation exceeds the limit at that time. Because it is only for a certain user, when the power generation of some users is turned off, if the power grid reaches a reasonable stable state, other protocol converters will no longer be adjusted. This method is unfair to users.

[0007] 4. This solution only regulates the devices that are monitored first, regardless of the current power usage status of the user, which exacerbates the occurrence of unfairness.

[0008] 5. Currently, the inverter data collected on the distribution side is collected by the fusion terminal directly through the carrier on the protocol converter, which will conflict with the data collection on the marketing side. In order not to affect the marketing data collection, when encountering problems, it is priority to stop the data collection on the distribution side or dismantle the equipment.

[0009] Therefore, it is necessary to design a new technical solution. Summary of the invention

[0010] The purpose of the present invention is to provide a distributed photovoltaic area flexible control method based on 380V low-voltage grid connection, which solves the problems raised in the background technology.

[0011] To achieve the above object, the present invention provides the following technical solution: a distributed photovoltaic area flexible control method based on 380V low-voltage grid connection, comprising the following method steps:

[0012] Step 1: After the service app is started, read the configuration information and decide whether to obtain the voltage and load data from the converged terminal or the concentrator according to the method of obtaining the area voltage and load in the configuration information;

[0013] Step 2: Wait for the platform to issue a flexible control start instruction; after the flexible control function is turned on, start obtaining the load and voltage values ​​of the substation;

[0014] Step 3: Determine the voltage and load conditions of the substation. When any of the three-phase voltages exceeds 235V, if it is the first time that the voltage exceeds the limit, wait for 10 seconds and obtain the substation voltage and load conditions again. If it still exceeds the limit, send a control instruction to the photovoltaic inverter under the substation to reduce the active power percentage by 20%;

[0015] Step 4: Wait for 15 minutes and then re-evaluate the voltage and load conditions of the substation. If the voltage is still over the limit, continue to drop by 20% until it drops to 20% of the normal level and stops falling.

[0016] Step 5: If the voltage returns to normal in step 3, determine whether the reverse load of the substation exceeds the limit. If the load rate is greater than 80%, send a control instruction to the inverter under the substation to reduce the active power percentage by 20%;

[0017] Step 6: If the load rate is between 70% and 80%, a control instruction is sent to the inverter under the substation to reduce the active power percentage by 5%;

[0018] Step 7: If the load rate is less than 70%, a control instruction is sent to the inverter under the substation to increase the active power percentage by 20%;

[0019] Step 8: Repeat steps 3-7 until the voltage and load of the station area reach a reasonable range;

[0020] Step 9: If the platform issues a command to close the flexible control, after receiving the control command, the business App sends a control command to the inverter in the substation to adjust the active power percentage to 100%.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention performs regulation on the entire station area, avoiding the drawbacks of regulating a single inverter;

[0023] Instead of directly disconnecting the user's inverter, a relatively gentle regulation strategy is adopted;

[0024] The data collection and control of the protocol converter is realized through the concentrator without affecting the meter reading of the concentrator;

[0025] The control strategy adopts a step-by-step control strategy, which makes the control more precise;

[0026] The grid stability issues in photovoltaic areas have been resolved, including voltage exceeding the limit, increased line loss, and power factor not meeting the standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0028] Figure 1 A method flow chart of a distributed photovoltaic area flexible control method based on 380V low-voltage grid connection of the present invention;

[0029] Figure 2 The topological diagram is a distributed photovoltaic area flexible control method based on 380V low-voltage grid connection of the present invention. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0031] The present invention provides a distributed photovoltaic area flexible control method based on 380V low-voltage grid connection.

[0032] A complete solution for flexible control of photovoltaic power stations, including flexible control software algorithms and acquisition control inverter methods, is designed to solve the stability problems of photovoltaic power grids, including voltage over-limit, increased line loss, and substandard power factor.

[0033] Specific installation and debugging operations Figure 2 As shown:

[0034] 1. Install a protocol converter between the inverter and the concentrator, close to the inverter side. The protocol converter and the inverter are directly linked through 485, and the concentrator and the protocol converter communicate directly through the carrier;

[0035] 2. According to the inverter protocol, configure the relevant point information of the protocol converter and read the data from the inverter;

[0036] 3. The protocol converter's file information is sent to the concentrator through the marketing master station, and the concentrator can read the data of the protocol converter;

[0037] 4. Connect the fusion terminal to the 485-II port of the concentrator through the 485 line;

[0038] 5. Install the photovoltaic flexible control App (QCWGet698) on the fusion terminal and configure the APP related parameters ( / data / app / QCWGet698 / configFile / config.xml). The serial port parameter related configuration must be configured accurately;

[0039] 6. After configuration, restart the business App (containerrestartc_QCWGet698) to read the protocol converter related data;

[0040] 7. To enable the flexible control function, you need to issue an enable command through the platform. After enabling it, the business App will monitor the voltage and load conditions in the substation. If the voltage and load in the substation are out of limit, it will regulate all photovoltaic users in the substation. According to the regulation strategy, the substation voltage and reverse load will be gradually adjusted to a reasonable range, and callback will be made when the voltage and load are lower than the limit value, so that users cannot perceive the regulation of the inverter.

[0041] The specific control operations are as follows:

[0042] The photovoltaic flexible control App (QCWGet698) on the fusion terminal monitors the substation voltage (line voltage under the transformer) and reverse load (line load of the reverse power transmission after the photovoltaic substation is connected to the grid). The substation voltage and load conditions can be obtained in two ways: one is through the fusion terminal's own exchange data, and the other is to obtain the voltage and load values ​​by reading the exchange data of the concentrator, such as Figure 1 As shown;

[0043] Step 1: After the service app is started, read the configuration information and decide whether to obtain the voltage and load data from the converged terminal or the concentrator according to the method of obtaining the area voltage and load in the configuration information;

[0044] Step 2: Wait for the platform to issue a flexible control start instruction; after the flexible control function is turned on, start obtaining the load and voltage values ​​of the substation;

[0045] Step 3: Determine the voltage and load conditions of the substation. When any of the three-phase voltages exceeds 235V, if it is the first time that the voltage exceeds the limit, wait for 10 seconds and obtain the substation voltage and load conditions again. If it still exceeds the limit, send a control instruction to the photovoltaic inverter under the substation to reduce the active power percentage by 20%;

[0046] Step 4: Wait for 15 minutes and then re-evaluate the voltage and load conditions of the substation. If the voltage is still over the limit, continue to drop by 20% until it drops to 20% of the normal level and stops falling.

[0047] Step 5: If the voltage returns to normal in step 3, determine whether the reverse load of the substation exceeds the limit. If the load rate is greater than 80%, send a control instruction to the inverter under the substation to reduce the active power percentage by 20%;

[0048] Step 6: If the load rate is between 70% and 80%, a control instruction is sent to the inverter under the substation to reduce the active power percentage by 5%;

[0049] Step 7: If the load rate is less than 70%, a control instruction is sent to the inverter under the substation to increase the active power percentage by 20%;

[0050] Step 8: Repeat steps 3-7 until the voltage and load of the station area reach a reasonable range;

[0051] Step 9: If the platform issues a command to close the flexible control, after receiving the control command, the business App sends a control command to the inverter in the substation to adjust the active power percentage to 100%.

[0052] In summary: the present invention regulates the entire substation, avoiding the drawbacks of regulating a single inverter; does not directly disconnect the user's inverter, and adopts a relatively gentle regulation strategy; realizes data collection and regulation of the protocol converter through the concentrator, which does not affect the meter reading of the concentrator; the regulation strategy adopts a step-by-step regulation strategy, and the regulation is more precise; solves the stability problems of the photovoltaic substation power grid, including voltage exceeding the limit, increased line loss, power factor not meeting the standard and other problems.

Claims

1. A distributed photovoltaic area flexible control method based on 380V low voltage grid connection, characterized in that: The method comprises the following steps: Step 1: After the service app is started, read the configuration information and decide whether to obtain the voltage and load data from the converged terminal or the concentrator according to the method of obtaining the area voltage and load in the configuration information; Step 2: Wait for the platform to issue a flexible control start instruction; after the flexible control function is turned on, start obtaining the load and voltage values ​​of the substation; Step 3: Determine the voltage and load conditions of the substation. When any of the three-phase voltages exceeds 235V, if it is the first time that the voltage exceeds the limit, wait for 10 seconds and obtain the substation voltage and load conditions again. If it still exceeds the limit, send a control instruction to the photovoltaic inverter under the substation to reduce the active power percentage by 20%; Step 4: Wait for 15 minutes and then re-evaluate the voltage and load conditions of the substation. If the voltage is still over the limit, continue to drop by 20% until it drops to 20% of the normal level and stops falling. Step 5: If the voltage returns to normal in step 3, determine whether the reverse load of the substation exceeds the limit. If the load rate is greater than 80%, send a control instruction to the inverter under the substation to reduce the active power percentage by 20%; Step 6: If the load rate is between 70% and 80%, a control instruction is sent to the inverter under the substation to reduce the active power percentage by 5%; Step 7: If the load rate is less than 70%, a control instruction is sent to the inverter under the substation to increase the active power percentage by 20%; Step 8: Repeat steps 3-7 until the voltage and load of the station area reach a reasonable range; Step 9: If the platform issues a command to close the flexible control, after receiving the control command, the business App sends a control command to the inverter in the substation to adjust the active power percentage to 100%.

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