Distributed photovoltaic group control and group adjustment method and system based on flexible adjustment

Abstract

The invention relates to a distributed photovoltaic group control and group adjustment method and system based on flexible adjustment. The method comprises the following steps: obtaining the total power and voltage of a transformer area; whether reverse heavy overload occurs or not is judged based on the total power of the transformer area, and peak regulation control is carried out according to the judgment result; whether overvoltage out-of-limit occurs or not and the out-of-limit grade when overvoltage out-of-limit occurs are judged based on the transformer area voltage, the output of the adjustable photovoltaic inverter is flexibly adjusted according to the judgment result, and meanwhile, a switching signal is generated according to the output proportion of the adjustable photovoltaic inverter to control the on and off of the non-adjustable photovoltaic inverter. Therefore, the output of the non-adjustable photovoltaic inverter can be flexibly adjusted synchronously. According to the invention, the adjustable photovoltaic inverter and the non-adjustable photovoltaic inverter in the transformer area can be synchronously and flexibly adjusted, so that the adjusting efficiency is improved, the adjusting effect is improved, and the stability of a power grid is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of distributed photovoltaic power generation, and in particular to a distributed photovoltaic group control and group regulation method and system based on flexible regulation. Background Art

[0002] The grid connection of distributed photovoltaics increases the uncertainty on the "source" side, exposing the distribution network to problems such as harmonics and low power quality. Distributed photovoltaics are mostly used on a large scale in rural areas, where the grid structure is relatively weak and the equipment level is relatively backward. During peak hours, the photovoltaic output exceeds the rated capacity of the access line or distribution transformer, causing the distribution line and distribution transformer to be reversely overloaded, and even burning equipment; distributed photovoltaics are connected to the end of the distribution network in large quantities. Due to the mismatch between the load characteristics and the photovoltaic output characteristics, and the weak active support capability of power electronic equipment for the dynamic reactive power of the power grid, the system voltage support and regulation capabilities drop sharply, resulting in serious voltage over-limit of the medium and low voltage distribution network.

[0003] When reverse heavy overload and voltage over-limit occur, it is necessary to adjust the output of the photovoltaic inverter under the substation, that is, to adjust the output power, voltage, frequency and other parameters of the inverter in real time through intelligent control technology to adapt to changes in the operation status of the power grid, optimize the power quality, and improve the absorption capacity of distributed photovoltaic power generation. There are two types of existing photovoltaic inverters: one is an adjustable photovoltaic inverter, which can flexibly adjust the active and reactive power of the inverter to increase or decrease the output of the inverter; the other is a non-adjustable photovoltaic inverter, which can only perform rigid closing operations and cannot be flexibly adjusted. Therefore, when the substation contains both adjustable photovoltaic inverters and non-adjustable photovoltaic inverters, the adjustment strength of different types of inverters will be different, which affects the fairness of the adjustment, and then affects the efficiency and effect of the flexible adjustment. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a distributed photovoltaic group control and modulation method and system based on flexible regulation, which can realize group control and modulation of photovoltaic inverters according to real-time operation data of the distribution system.

[0005] The technical solution adopted by the present invention to solve the technical problem is: to provide a distributed photovoltaic group control and group adjustment method based on flexible adjustment, which is applied to the intelligent fusion terminal of each substation, including the following steps: Acquire collected data of the substation area, wherein the data of the substation area includes total power and voltage of the substation area; Determine whether reverse overload occurs based on the total power of the substation, and perform peak load control according to the judgment result; Based on the voltage in the substation, it is judged whether overvoltage exceeds the limit and the level of overvoltage when it occurs. According to the judgment result, the output of the adjustable photovoltaic inverter is flexibly adjusted. At the same time, a switching signal is generated according to the output ratio of the adjustable photovoltaic inverter to control the conduction and shutdown of the non-adjustable photovoltaic inverter, so as to flexibly adjust the output of the non-adjustable photovoltaic inverter synchronously.

[0006] Furthermore, the duty cycle of the switch signal of the non-adjustable photovoltaic inverter is equal to the output ratio of the adjustable photovoltaic inverter.

[0007] Further, judging whether an over-voltage limit occurs and the over-voltage level based on the station area voltage includes: When the station area voltage is greater than or equal to the first voltage setting value and less than the second voltage setting value in at least the first set time period, it is determined that an overvoltage limit has occurred and the overvoltage level is level I; When the station area voltage is greater than or equal to the second voltage setting value and less than the third voltage setting value in at least the second setting time period, it is determined that an overvoltage limit has occurred and the overvoltage level is level II; When the station area voltage is greater than or equal to the third voltage setting value and less than the fourth voltage setting value in at least the third setting time period, it is determined that an overvoltage limit has occurred and the overvoltage level is level III; When the station voltage is greater than or equal to the fourth voltage setting value in at least a fourth setting time period, it is determined that an over-voltage limit has occurred and the over-voltage level is level IV.

[0008] Furthermore, the flexibly adjusting the output of the adjustable photovoltaic inverter according to the judgment result includes: When an overvoltage exceeds the limit and the overvoltage level is level I, level II or level III, the reactive power factor of all adjustable photovoltaic inverters under the substation is adjusted to the set value, and the substation voltage in the next substation operation data collection cycle after reactive power adjustment is compared with the fifth voltage setting value. If it is less than or equal to the fifth voltage setting value, the adjustment is stopped, otherwise the active power of each adjustable photovoltaic inverter under the substation is adjusted; When an overvoltage exceeds the limit and the overvoltage level is IV, all photovoltaic inverters in the control console area will be in standby mode.

[0009] Furthermore, the active power of each adjustable photovoltaic inverter under the substation is adjusted, including: According to the rated power of each adjustable photovoltaic inverter in the substation, the active power is reduced to keep the output ratio of all adjustable photovoltaic inverters unchanged; Report overvoltage event information.

[0010] Furthermore, it also includes: When the station voltage is less than or equal to the fifth voltage setting value in at least a fifth setting time period, the adjustable photovoltaic inverter is adjusted to output the maximum power, and the non-adjustable photovoltaic inverter is controlled to open.

[0011] Furthermore, the first set time period is 24 times the collection cycle, the second set time period is 12 times the collection cycle, the third set time period is 6 times the collection cycle, the fourth set time period is 0.1 times the collection cycle, and the fifth set time period is 12 times the collection cycle.

[0012] Furthermore, judging whether a reverse heavy overload occurs based on the total power of the substation area, and performing peak load regulation control according to the judgment result, includes: Determine whether the total power of the substation area is negative in at least a sixth set time period and its absolute value is greater than the power upper limit threshold, and if so, perform peak load control; It is determined whether the total power of the area is negative in at least the seventh set time period and its absolute value is less than the power lower limit threshold. If so, all inverters in the area are set to generate power at full output.

[0013] Furthermore, the sixth set time period is 1 times the collection period, and the seventh set time period is 4 times the collection period.

[0014] Furthermore, the method also includes the step of adjusting the limited power of each photovoltaic inverter in the substation according to the received master station instruction.

[0015] The present invention also provides a distributed photovoltaic group control and group adjustment system based on flexible adjustment, comprising: The power system master station is used to issue master station instructions; The property management platform is used to receive the main station's instructions and convert them into a set format and then store them in the corresponding instruction topic; A fusion terminal, used to execute any of the methods described above; Low-voltage intelligent equipment is used to collect substation data and send it to the fusion terminal, and execute photovoltaic regulation instructions on the master station side or local side.

[0016] Furthermore, the power system master station includes a distribution automation system zone I master station and a distribution automation system zone IV master station, wherein the distribution automation system zone I master station sends photovoltaic control instructions to the distribution automation system zone IV master station in the form of E files from time to time, and the distribution automation system zone IV master station parses the received E files, obtains the control substation information and control content, and then associates the substation fusion terminal coding information to generate the master station instructions and issue them.

[0017] Furthermore, the master station instruction is issued by calling the property management northbound issuing interface.

[0018] Furthermore, the fusion terminal obtains the main station instructions by subscribing to the instruction topic of the property management platform.

[0019] Beneficial Effects Due to the adoption of the above technical scheme, the present invention has the following advantages and positive effects compared with the prior art: the present invention adjusts the duty cycle of the switch signal of the non-adjustable photovoltaic inverter by referring to the output ratio of the adjustable photovoltaic inverter in the same substation, and utilizes the structural characteristics of the non-adjustable photovoltaic inverter itself to close through the power electronic switch, thereby realizing synchronous flexible regulation of the output of the non-adjustable inverter; the present invention deploys the photovoltaic flexible regulation strategy in the substation intelligent fusion terminal in the same area, and can issue group management and group control instructions to all substations that need to respond, and issue them to the downstream intelligent devices for response, thereby improving the efficiency of batch substations to quickly adjust the photovoltaic power generation output; the fusion terminal can obtain line and photovoltaic operation data from the downstream intelligent devices, including but not limited to photovoltaic inverters, smart meters, smart switches and other equipment, to obtain complete substation operation data, thereby solving the problem that the uncontrollable photovoltaic inverter line cannot obtain photovoltaic power generation data; the present invention removes the installation of the intermediate protocol conversion module by adopting the smart inverter directly connected to the fusion terminal, thereby reducing the types of equipment and reducing the maintenance cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flow chart of a first embodiment of the present invention; Figure 2 Schematic diagram of a system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0022] The first embodiment of the present invention relates to a distributed photovoltaic group control and group adjustment method based on flexible regulation, which is applied to the intelligent fusion terminal of each substation, such as Figure 1 As shown, the following steps are included: Receive instructions from the master station; If the received master station command includes a power adjustment command, the power limit of each photovoltaic inverter in the substation is adjusted according to the power adjustment command, otherwise: Obtain the collected substation operation data, which includes the total power and voltage of the substation; Determine whether reverse overload occurs based on the total power of the substation, and perform peak load control according to the judgment result; Based on the voltage in the substation area, it is judged whether an overvoltage limit has occurred and the level of the overvoltage limit when the overvoltage limit has occurred. According to the judgment result, the output of the adjustable photovoltaic inverter is flexibly adjusted. At the same time, a switch signal is generated according to the output ratio of the adjustable photovoltaic inverter to control the conduction and shutdown of the non-adjustable photovoltaic inverter, so as to flexibly adjust the output of the non-adjustable photovoltaic inverter synchronously; wherein: When the station area voltage is greater than or equal to the first voltage setting value and less than the second voltage setting value in at least the first set time period, it is determined that an overvoltage limit has occurred and the overvoltage level is level I; When the station area voltage is greater than or equal to the second voltage setting value and less than the third voltage setting value in at least the second setting time period, it is determined that an overvoltage limit has occurred and the overvoltage level is level II; When the station area voltage is greater than or equal to the third voltage setting value and less than the fourth voltage setting value in at least the third setting time period, it is determined that an overvoltage limit has occurred and the overvoltage level is level III; When the station area voltage is greater than or equal to the fourth voltage setting value in at least a fourth setting time period, it is determined that an overvoltage limit has occurred and the overvoltage level is level IV; When an overvoltage exceeds the limit and the overvoltage level is level I, level II or level III, the reactive power factor of all adjustable photovoltaic inverters in the substation is adjusted to the set value, and the substation voltage in the next acquisition cycle after the reactive power adjustment is compared with the fifth voltage setting value. If it is less than or equal to the fifth voltage setting value, the adjustment is stopped, otherwise the active power of each adjustable photovoltaic inverter in the substation is adjusted; When an overvoltage exceeds the limit and the overvoltage level is IV, all photovoltaic inverters in the control console area will be in standby mode; When the station voltage is less than or equal to the fifth voltage setting value within at least the fifth set time period, the adjustable photovoltaic inverter is adjusted to output maximum power, and the non-adjustable photovoltaic inverter is controlled to open.

[0023] The present implementation is further described below in conjunction with a specific power system.

[0024] like Figure 2 As shown, it includes a distribution automation system zone I master station ①, a distribution automation system zone IV master station ②, a property management platform ③, a fusion terminal ④, and a low-voltage intelligent device ⑤, wherein the low-voltage intelligent device ⑤ includes an intelligent circuit breaker 1, a photovoltaic inverter unit 2 communicating with the fusion terminal ④, a direct-type photovoltaic inverter 3, and a smart meter 4, wherein the photovoltaic inverter unit 2 includes two parts: a protocol converter 21 and a photovoltaic inverter 22.

[0025] Photovoltaic control instructions are issued from top to bottom along the red arrow in the figure: (1) From the master station in zone 1 to the master station in zone 4: The PV control instructions are transmitted in the form of E files. The master station in zone 1 transmits E files to the master station server in zone 4 from time to time. The master station in zone 4 parses the E files in real time, obtains the control area information and control content, and associates the area fusion terminal coding information. The command instruction is issued by calling the property management northbound interface to issue the interface; (2) From the master station of the fourth district to the property management platform: The master station of the fourth district (distribution network cloud master station) sends instructions according to the northbound interface of the property management platform. After receiving the instructions, the IoT management platform converts the commands into JSON format and stores them in the corresponding topic command, waiting for the fusion terminal to read the data; (3) From the property management platform to the fusion terminal: The fusion terminal subscribes to the topic command of the property management platform. After receiving the command, the fusion terminal returns a successful receipt to the property management platform. (4) Fusion terminal to low-voltage intelligent device: The fusion terminal controls the operation of the photovoltaic inverter according to the parsed instructions.

[0026] Photovoltaic telemetering data is uploaded from bottom to top along the green arrow in the figure: (1) Low-voltage smart devices to fusion terminals: Low-voltage smart devices send photovoltaic-related data to fusion terminals through HPLC, 485, or power line carrier; (2) Integration terminal to property management platform: The integration terminal pushes photovoltaic remote signaling and telemetry data to the property management platform in JSON format through the MQTT protocol. The remote signaling data is pushed in real time, and the telemetry data is pushed every 15 minutes. (3) From the property management platform to the master station in District 4: The master station in District 4 establishes a photovoltaic telesignal and telemetry data point table, and analyzes and displays the data through the telemetry service interface provided by the measurement center.

[0027] The photovoltaic control scheme is deployed remotely or locally in the form of an APP in the intelligent fusion terminal of each substation. The control strategy is mainly for reverse heavy overload control and overvoltage regulation. When reverse heavy overload or overvoltage occurs, the fusion terminal will control the photovoltaic inverter or grid-connected box intelligent switch according to the corresponding control threshold, and can also parse the master station command to execute the corresponding control strategy.

[0028] Reverse heavy overload control The photovoltaic control APP continuously monitors the power value of the substation. It can set the upper and lower limits of reverse active power locally or receive the upper and lower limit thresholds set by the master station. When the reverse power exceeds the limit, it is proportionally distributed to the power output of the N inverters that need to be adjusted to achieve the overall peak control power control target of the substation.

[0029] Table 1 Reverse heavy overload judgment conditions condition parameter Condition 1 The reverse power of the substation is greater than the upper limit setting value, and the duration is 5 minutes Condition 2 The reverse power of the substation is less than the lower limit setting value and the total power is negative for 5 consecutive times, and the duration is 20 minutes. Control Target The reverse power of the substation area does not exceed the limit, and the reverse load rate is normal When the reverse power in the substation reaches regulation condition 1, peak regulation control is performed.

[0030] When the reverse power in the substation reaches recovery condition 2, all inverters in the substation are restored to 100% output.

[0031] If the master station instructs power limit, the master station instruction adjustment will be given priority. The photovoltaic control APP receives the master station instruction and adjusts the power limit according to the proportion that each inverter in the substation needs to adjust. If the master station needs to generate power at full output, the master station instruction will be executed to restore full output power generation.

[0032] Overvoltage limit regulation The local judgment conditions and adjustment principles for voltage over-limit should be implemented in accordance with Table 2. The over-limit voltage Ux and duration Tx can be set on the master station side.

[0033] Table 2 Judgment conditions a) The photovoltaic control APP obtains the voltage of the photovoltaic inverter based on the exchange, and if the voltage exceeds the limit, the overvoltage regulation strategy is activated; b) Comprehensively determine whether conditions 1-3 are met. If so, adjust the cosφ of the reactive power of the N inverters in the substation to 0.9; c) After executing a reactive power regulation command, monitor the inverter voltage value within the acquisition period (5 minutes). If the voltage limit U5 is met, the regulation is stopped. If the voltage limit is still exceeded, the active power regulation is continued. d) When the inverter voltage is continuously monitored, if conditions 1-3 are met, the active power adjustment command will continue to be executed, the active power output command will be adjusted down in the same proportion according to the rated power of all inverters in the substation, and the overvoltage event information will be reported. Generally, 3-4 adjustment gears can be set; e) If the voltage monitoring value meets condition 4, the inverter is controlled to standby.

[0034] f) If the voltage monitoring value meets condition 5, the flexible adjustment restores the maximum power output of the photovoltaic inverter, synchronously completes the inverter startup, and continuously monitors the grid-connected voltage.

[0035] If the master station issues a control instruction, the adjustment will be based on the master station instruction first.

[0036] The above two strategies correspond to the flexible adjustment of two types of low-voltage equipment. One is the adjustable photovoltaic inverter, which is divided into a pass-through inverter with communication function that can be directly connected to the fusion terminal and a traditional inverter that must go through a protocol conversion unit to connect to the fusion terminal. The other is a non-adjustable photovoltaic inverter.

[0037] In this embodiment, the adjustable photovoltaic inverter under the substation increases or decreases the output of the inverter by flexibly adjusting the active and reactive power of the inverter. In order to achieve synchronous flexible regulation of the non-adjustable photovoltaic inverter, a PWM-like pulse control method is used to control the closing of the non-adjustable photovoltaic inverter. When a reverse heavy overload or overvoltage occurs, the photovoltaic flexible control APP will set a repeated time period. During this time period, the output ratio of the adjustable photovoltaic inverter under the same substation is referred to, and the duty cycle of the PWM-like pulse signal is set according to the output ratio. This signal is used to drive the opening or closing of the non-adjustable photovoltaic inverter, thereby achieving synchronous flexible regulation of the output of the non-adjustable photovoltaic inverter. In this way, when the adjustable photovoltaic inverter changes the output ratio, the non-adjustable photovoltaic inverter can simultaneously change the proportion of the output time in equal proportion, thereby changing the output mean.

[0038] If the master station has a control command for the above operations, the master station command will be responded to first.

[0039] For example, if the transformer capacity of a certain area is 500,000W, the master station sends the transformer capacity of 500,000, the upper and lower thresholds of reverse power of 60% and 30%, and the collection control cycle is 5 minutes to the control APP.

[0040] When the reverse power exceeds the upper threshold of the substation, peak load control is performed.

[0041] When the acquisition control cycle (5 minutes) is reached, the control APP collects and analyzes the cross-collection data, extracts the real-time power N of the substation, for example, N = -350000W, which means that the reverse power of the substation is 350KW. The control APP calculates the maximum reverse power of the substation Y = 500000 * 60%, Y = 300000 W according to the upper limit of the reverse overload threshold (for example, 60%). The calculation shows that the photovoltaic output reduction required in the substation is M = 350000-300000, M = 50000.

[0042] The control APP calculates the current total photovoltaic output of the substation as P based on the cumulative real-time power generation of all inverters at this time, for example, P=450KW (the active power of all inverters in the substation is added together), and calculates the target photovoltaic output P0=PM based on the calculated photovoltaic output derating of the substation, that is, P0 = 450kw-50kw=400KW.

[0043] The control APP calculates the upper limit of the power generation of each inverter according to the current power of all inverters in the area. If the current power generation of each inverter is P1 P2 P3…PN, then the target power of each inverter is For example, if the current power of the first inverter is P1 = 50KW, the control power of the first inverter is =44.4KW, and use this to calculate the control power of other inverters, and send the power upper limit value to each inverter in turn to achieve the peak regulation purpose.

[0044] When the reverse power in the substation area is less than the lower threshold of the substation area or there is no reverse power, peak load recovery is performed.

[0045] When the acquisition control cycle (5 minutes) is reached, the control APP collects and analyzes the cross-acquisition data, extracts the real-time power N of the substation, for example, N = -100000W, which means that the reverse power of the substation is 100KW. The control APP calculates the maximum reverse power of the substation Y = 500000 * 30%, Y = 150000 W according to the lower limit of the reverse overload threshold (for example, 30%). The actual reverse power of the substation is at the lower limit of the reverse power threshold of the substation.

[0046] After five consecutive detections (five cycles), all inverters in the substation will be restored to 100% output.

[0047] The second embodiment of the present invention relates to a distributed photovoltaic group control and group adjustment system based on flexible regulation, such as Figure 2 As shown, it includes a distribution automation system zone I master station ①, a distribution automation system zone IV master station ②, a property management platform ③, a fusion terminal ④, and a low-voltage intelligent device ⑤, wherein the low-voltage intelligent device ⑤ includes an intelligent circuit breaker 1, a photovoltaic inverter unit 2 communicating with the fusion terminal ④, a direct-type photovoltaic inverter 3, and a smart meter 4, wherein the photovoltaic inverter unit 2 includes two parts: a protocol converter 21 and a photovoltaic inverter 22.

[0048] Photovoltaic control instructions are issued from top to bottom along the red arrow in the figure: (1) From the master station in zone 1 to the master station in zone 4: The PV control instructions are transmitted in the form of E files. The master station in zone 1 transmits E files to the master station server in zone 4 from time to time. The master station in zone 4 parses the E files in real time, obtains the control area information and control content, and associates the area fusion terminal coding information. The command instruction is issued by calling the property management northbound interface to issue the interface; (2) From the master station of the fourth district to the property management platform: The master station of the fourth district (distribution network cloud master station) sends instructions according to the northbound interface of the property management platform. After receiving the instructions, the IoT management platform converts the commands into JSON format and stores them in the corresponding topic command, waiting for the fusion terminal to read the data; (3) From the property management platform to the fusion terminal: The fusion terminal subscribes to the topic command of the property management platform. After receiving the command, the fusion terminal returns a successful receipt to the property management platform. (4) Fusion terminal to low-voltage intelligent device: The fusion terminal controls the operation of the photovoltaic inverter according to the parsed instructions.

[0049] Photovoltaic telemetering data is uploaded from bottom to top along the green arrow in the figure: (1) Low-voltage smart devices to fusion terminals: Low-voltage smart devices send photovoltaic-related data to fusion terminals through HPLC, 485, or power line carrier; (2) Integration terminal to property management platform: The integration terminal pushes photovoltaic remote signaling and telemetry data to the property management platform in JSON format through the MQTT protocol. The remote signaling data is pushed in real time, and the telemetry data is pushed every 15 minutes. (3) From the property management platform to the master station in District 4: The master station in District 4 establishes a photovoltaic telesignal and telemetry data point table, and analyzes and displays the data through the telemetry service interface provided by the measurement center.

[0050] The photovoltaic control scheme is deployed remotely or locally in the form of an APP in the intelligent fusion terminal of each substation. The control strategy is mainly for reverse heavy overload control and overvoltage regulation. When reverse heavy overload or overvoltage occurs, the fusion terminal will control the photovoltaic inverter or grid-connected box intelligent switch according to the corresponding control threshold, and can also parse the master station command to execute the corresponding control strategy.

[0051] Reverse heavy overload control The photovoltaic control APP continuously monitors the power value of the substation. It can set the upper and lower limits of reverse active power locally or receive the upper and lower limit thresholds set by the master station. When the reverse power exceeds the limit, it is proportionally distributed to the power output of the N inverters that need to be adjusted to achieve the overall peak control power control target of the substation.

[0052] Table 1 Reverse heavy overload judgment conditions condition parameter Condition 1 The reverse power of the substation is greater than the upper limit setting value, and the duration is 5 minutes Condition 2 The reverse power of the substation is less than the lower limit setting value and the total power is negative for 5 consecutive times, and the duration is 20 minutes. Control Target The reverse power of the substation area does not exceed the limit, and the reverse load rate is normal When the reverse power in the substation reaches regulation condition 1, peak regulation control is performed.

[0053] When the reverse power in the substation reaches recovery condition 2, all inverters in the substation are restored to 100% output.

[0054] If the master station instructs power limit, the master station instruction adjustment will be given priority. The photovoltaic control APP receives the master station instruction and adjusts the power limit according to the proportion that each inverter in the substation needs to adjust. If the master station needs to generate power at full output, the master station instruction will be executed to restore full output power generation.

[0055] Overvoltage limit regulation The local judgment conditions and adjustment principles for voltage over-limit should be implemented in accordance with Table 2. The over-limit voltage Ux and duration Tx can be set on the master station side.

[0056] Table 2 Judgment conditions a) The photovoltaic control APP obtains the voltage of the photovoltaic inverter based on the exchange, and if the voltage exceeds the limit, the overvoltage regulation strategy is activated; b) Comprehensively determine whether conditions 1-3 are met. If so, adjust the cosφ of the reactive power of the N inverters in the substation to 0.9; c) After executing a reactive power regulation command, monitor the inverter voltage value within the acquisition period (5 minutes). If the voltage limit U5 is met, the regulation is stopped. If the voltage limit is still exceeded, the active power regulation is continued. d) When the inverter voltage is continuously monitored, if conditions 1-3 are met, the active power adjustment command will continue to be executed, the active power output command will be adjusted down in the same proportion according to the rated power of all inverters in the substation, and the overvoltage event information will be reported. Generally, 3-4 adjustment gears can be set; e) If the voltage monitoring value meets condition 4, the inverter is controlled to standby.

[0057] f) If the voltage monitoring value meets condition 5, the flexible adjustment restores the maximum power output of the photovoltaic inverter, synchronously completes the inverter startup, and continuously monitors the grid-connected voltage.

[0058] If the master station issues a control instruction, the adjustment will be based on the master station instruction first.

[0059] For the above two strategies, there are two types of flexible adjustment of low-voltage equipment. One is the adjustable photovoltaic inverter, which is divided into a pass-through inverter with communication function that can be directly connected to the fusion terminal and a traditional inverter that must go through a protocol conversion unit to connect to the fusion terminal. The other is a non-adjustable photovoltaic inverter.

[0060] In this embodiment, the adjustable photovoltaic inverter under the substation increases or decreases the output of the inverter by flexibly adjusting the active and reactive power of the inverter. In order to achieve synchronous flexible regulation of the non-adjustable photovoltaic inverter, a PWM-like pulse control method is used to control the closing of the non-adjustable photovoltaic inverter. When a reverse heavy overload or overvoltage occurs, the photovoltaic flexible control APP will set a repeated time period. During this time period, the output ratio of the adjustable photovoltaic inverter under the same substation is referred to, and the duty cycle of the PWM-like pulse signal is set according to the output ratio. This signal is used to drive the opening or closing of the non-adjustable photovoltaic inverter, thereby achieving synchronous flexible regulation of the output of the non-adjustable photovoltaic inverter. In this way, when the adjustable photovoltaic inverter changes the output ratio, the non-adjustable photovoltaic inverter can simultaneously change the proportion of the output time in equal proportion, thereby changing the output mean.

[0061] If the master station has a control command for the above operations, the master station command will be responded to first.

Claims

1. A distributed photovoltaic group control and group adjustment method based on flexible regulation, characterized in that: The intelligent fusion terminal applied to each area includes the following steps: Acquire the collected substation operation data, wherein the substation operation data includes the total power and voltage of the substation; Determine whether reverse overload occurs based on the total power of the substation, and perform peak load control according to the judgment result; Based on the voltage in the substation, it is judged whether overvoltage exceeds the limit and the level of overvoltage when it occurs. According to the judgment result, the output of the adjustable photovoltaic inverter is flexibly adjusted. At the same time, a switching signal is generated according to the output ratio of the adjustable photovoltaic inverter to control the conduction and shutdown of the non-adjustable photovoltaic inverter, so as to flexibly adjust the output of the non-adjustable photovoltaic inverter synchronously.

2. The method according to claim 1, characterized in that The duty cycle of the switch signal of the non-adjustable photovoltaic inverter is equal to the output ratio of the adjustable photovoltaic inverter.

3. The method according to claim 1, characterized in that The method of judging whether an overvoltage limit occurs and the overvoltage level based on the photovoltaic inverter voltage includes: When the station area voltage is greater than or equal to the first voltage setting value and less than the second voltage setting value in at least the first set time period, it is determined that an overvoltage limit has occurred and the overvoltage level is level I; When the station area voltage is greater than or equal to the second voltage setting value and less than the third voltage setting value in at least the second setting time period, it is determined that an overvoltage limit has occurred and the overvoltage level is level II; When the station area voltage is greater than or equal to the third voltage setting value and less than the fourth voltage setting value in at least the third setting time period, it is determined that an overvoltage limit has occurred and the overvoltage level is level III; When the station voltage is greater than or equal to the fourth voltage setting value in at least a fourth setting time period, it is determined that an over-voltage limit has occurred and the over-voltage level is level IV.

4. The method according to claim 3, characterized in that The flexibly adjusting the output of the adjustable photovoltaic inverter according to the judgment result includes: When an overvoltage exceeds the limit and the overvoltage level is level I, level II or level III, the reactive power factor of all adjustable photovoltaic inverters under the substation is adjusted to the set value, and the substation voltage in the next substation operation data collection cycle after reactive power adjustment is compared with the fifth voltage setting value. If it is less than or equal to the fifth voltage setting value, the adjustment is stopped, otherwise the active power of each adjustable photovoltaic inverter under the substation is adjusted; When an overvoltage exceeds the limit and the overvoltage level is IV, all photovoltaic inverters in the control console area will be in standby mode.

5. The method according to claim 4, characterized in that The active power of each adjustable photovoltaic inverter under the station area is adjusted, including: According to the rated power of each adjustable photovoltaic inverter in the substation, the active power is reduced to keep the output ratio of all adjustable photovoltaic inverters unchanged; Report overvoltage event information.

6. The method according to claim 4, characterized in that Also includes: When the station voltage is less than or equal to the fifth voltage setting value in at least a fifth setting time period, the adjustable photovoltaic inverter is adjusted to output the maximum power, and the non-adjustable photovoltaic inverter is controlled to open.

7. The method according to claim 1, characterized in that The method of judging whether a reverse heavy overload occurs based on the total power of the substation area and performing peak load regulation control according to the judgment result includes: Determine whether the total power of the substation area is negative in at least a sixth set time period and its absolute value is greater than the power upper limit threshold, and if so, perform peak load control; It is determined whether the total power of the area is negative in at least the seventh set time period and its absolute value is less than the power lower limit threshold. If so, all inverters in the area are set to generate power at full output.

8. The method according to claim 1, characterized in that The method also includes the step of adjusting the limited power of each photovoltaic inverter in the substation according to the received master station instruction.

9. A distributed photovoltaic group control and group adjustment system based on flexible regulation, characterized in that: include: The power system master station is used to issue master station instructions; The property management platform is used to receive the main station's instructions and convert them into a set format and then store them in the corresponding instruction topic; A fusion terminal, configured to execute any one of the methods described in claims 1 to 8; Low-voltage intelligent equipment is used to collect substation operation data and send it to the fusion terminal, and execute photovoltaic regulation instructions on the master station side or local side.

10. The system according to claim 9, characterized in that The power system master station includes the distribution automation system zone I master station and the distribution automation system zone IV master station, wherein the distribution automation system zone I master station sends photovoltaic control instructions to the distribution automation system zone IV master station in the form of E files from time to time, and the distribution automation system zone IV master station parses the received E files, obtains the control substation information and control content, and then associates the substation fusion terminal coding information to generate the master station instructions and issue them.

Images