Photovoltaic inverter control device, method and control system

Abstract

The present invention provides a photovoltaic inverter control device, method, and control system. The device includes a controller and a switching module. The switching module includes three phase branches, each phase branch including at least one of a resistance module, a capacitance module, and an inductance module. The controller is configured to receive instructions from an intelligent fusion terminal and generate corresponding control signals based on the instructions, wherein the instructions are issued by the intelligent fusion terminal when the operating state of the photovoltaic inverter needs to be adjusted. The switching module is configured to connect the modules indicated by the control signals in each phase branch between the substation-side node and the user-side grid-connected node in accordance with the control signals, thereby changing the voltage value of the user-side grid-connected node. The photovoltaic inverter is configured to adjust the household photovoltaic output based on the voltage value of the user-side grid-connected node. The present invention enables indirect flexible control of household photovoltaic output.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic power generation, and more specifically, relates to a photovoltaic inverter control device, method and control system. Background Art

[0002] The grid-connected inverter can automatically adjust the photovoltaic output according to the grid-connected node voltage. It has strong adaptive capabilities and can play a good role in stabilizing the voltage under the microgrid operation state. It is very beneficial to improving the power supply reliability and accommodating distributed power sources.

[0003] However, with the increasing number of distributed power sources, excessive reverse transmission capacity often occurs, threatening the stable operation of the power grid. At this time, the node voltage at the substation does not change accordingly, resulting in the inability to automatically adjust the photovoltaic output. The only way to adjust the photovoltaic output is to control the inverter. However, the inverter is a user device, which is difficult to adjust. Frequent adjustment can easily damage the user device, making it impossible to implement in practical applications.

[0004] Existing technologies typically use a power outage to directly cut off power to prevent it from threatening the stable operation of the grid. While this method is quick to take effect, it is slow to recover and can severely impact photovoltaic power consumption. Summary of the Invention

[0005] The object of the present invention is to provide a photovoltaic inverter control device, method and control system to solve the technical problem in the prior art that photovoltaic output cannot be indirectly controlled.

[0006] To achieve the above-mentioned object, the technical solution adopted by the present invention is to provide a photovoltaic inverter control device, the device comprising a controller and a switching module; the switching module comprises three-phase branches, each phase branch comprising at least one of a resistance module, a capacitance module, and an inductance module;

[0007] The controller is configured to receive instructions from the intelligent fusion terminal and generate corresponding control signals according to the instructions, wherein the instructions are issued by the intelligent fusion terminal when the operating state of the photovoltaic inverter needs to be adjusted;

[0008] The switching module is used to connect the modules indicated by the control signal in each phase branch between the substation side node and the user side grid-connected node according to the control signal, so as to change the voltage value of the user side grid-connected node; wherein, the photovoltaic inverter is used to adjust the household photovoltaic output according to the voltage value of the user side grid-connected node.

[0009] In a possible implementation, each phase branch in the switching module includes:

[0010] The resistive module includes a resistor module and a first switch connected in parallel with the resistor module;

[0011] A capacitive module, comprising a capacitor module and a second switch connected in parallel with the capacitor module;

[0012] The inductive module includes an inductive module and a third switch connected in parallel with the inductive module;

[0013] The resistive module, the capacitive module and the inductive module are connected in series.

[0014] In a possible implementation, the three-phase branch includes: an A-phase branch, a B-phase branch, and a C-phase branch;

[0015] The output node of the A-phase branch is connected to the output node of the B-phase branch via a fourth switch, and the output node of the B-phase branch is connected to the output node of the C-phase branch via a fifth switch.

[0016] In a possible implementation, the switching module is installed inside the circuit breaker and connected in series to the main power supply circuit of the circuit breaker;

[0017] Alternatively, the switching module is installed outside the circuit breaker and connected in series between the load end of the circuit breaker and the user-side grid-connected node, and the circuit breaker is set in series between the substation-side node and the user-side grid-connected node.

[0018] In a possible implementation, the controller is configured to receive a first instruction from the intelligent convergence terminal and generate a first control signal according to the first instruction;

[0019] The switching module is configured to connect the resistance module and the capacitance module in each phase branch in series between the substation side node and the user side grid-connected node according to the first control signal;

[0020] The first instruction is issued when the intelligent fusion terminal detects that the power grid is in the first operating state, or is issued when the intelligent fusion terminal receives a first command, and the first command is used to indicate that the power grid is in the first operating state;

[0021] The first operating state indicates that the reactive output value of the household photovoltaic needs to be increased, and the increased reactive output value is less than the first set value; when the power grid is in the first operating state, the power factor value of the substation transformer is less than the first threshold and greater than the second threshold, and / or the voltage value of the user-side grid connection point is less than the first voltage value and greater than the second voltage value.

[0022] In a possible implementation, the controller is configured to receive a second instruction from the intelligent convergence terminal and generate a second control signal according to the second instruction;

[0023] The switching module is configured to connect the resistance modules in each phase branch in series between the substation side node and the user side grid-connected node according to the second control signal;

[0024] The second instruction is issued when the intelligent fusion terminal detects that the power grid is in the second operating state, or is issued when the intelligent fusion terminal receives a second command, and the second command is used to indicate that the power grid is in the second operating state;

[0025] The second operating state indicates that the reactive output value of the household photovoltaic needs to be increased, and the increased reactive output value is greater than or equal to the first set value; when the power grid is in the second operating state, the power factor value of the substation transformer is less than or equal to the second threshold, and / or the voltage value of the user-side grid connection point is less than or equal to the second voltage value.

[0026] In a possible implementation, the controller is configured to receive a third instruction from the intelligent convergence terminal and generate a third control signal according to the third instruction;

[0027] The switching module is configured to connect the resistance module and the inductance module in each phase branch in series between the substation side node and the user side grid-connected node according to the third control signal;

[0028] The third instruction is issued when the intelligent fusion terminal detects that the power grid is in a third operating state, or is issued when receiving a third command, and the third command is used to indicate that the power grid is in the third operating state;

[0029] The third operating state refers to a reverse heavy load state. When the power grid is in the third operating state, the voltage value of the user-side grid connection point is greater than a preset upper limit value;

[0030] The controller is further configured to receive a fourth instruction from the intelligent fusion terminal and generate a fourth control signal according to the fourth instruction;

[0031] The switching module is further configured to remove the resistance module, the capacitance module, and the inductance module in each phase branch from between the substation side node and the user side grid-connected node according to the fourth control signal;

[0032] The fourth instruction is issued when the intelligent fusion terminal detects that the power grid is in a normal operating state, or is issued when the intelligent fusion terminal receives a fourth command, and the fourth command is used to indicate that the power grid is in a normal operating state.

[0033] In a possible implementation, the controller is configured to receive a fifth instruction from the intelligent converged terminal and generate a fifth control signal according to the fifth instruction;

[0034] The switching module is configured to connect the capacitor modules in each phase branch in series between the substation side node and the user side grid-connected node according to the fifth control signal;

[0035] The switching module is further configured to close the fourth switch and the fifth switch;

[0036] The fifth instruction is issued when the intelligent fusion terminal detects that the power grid is in a fifth operating state, or is issued when the intelligent fusion terminal receives a fifth command, and the fifth command is used to indicate that the power grid is in the fifth operating state;

[0037] When the power grid is in the fifth operating state, the household photovoltaic output value is zero.

[0038] Another aspect of the present invention further provides a control system, comprising: a photovoltaic inverter control device and the intelligent fusion terminal.

[0039] Another aspect of the present invention further provides a photovoltaic inverter control method, comprising:

[0040] receiving an instruction from the intelligent fusion terminal and generating a corresponding control signal according to the instruction, wherein the instruction is issued by the intelligent fusion terminal when the operating state of the photovoltaic inverter needs to be adjusted;

[0041] According to the control signal, the modules indicated by the control signal in each phase branch are respectively connected between the substation side node and the user side grid-connected node to change the voltage value of the user side grid-connected node; wherein, the photovoltaic inverter is used to adjust the household photovoltaic output according to the voltage value of the user side grid-connected node.

[0042] The photovoltaic inverter control device, method and control system provided by the present invention include a controller and a switching module; the controller is used to receive instructions from an intelligent fusion terminal and generate corresponding control signals according to the instructions, wherein the instructions are issued by the intelligent fusion terminal when the operating state of the photovoltaic inverter needs to be adjusted; the switching module is used to connect the modules indicated by the control signals in each phase branch between the substation side node and the user side grid-connected node according to the control signals, so as to change the voltage value of the user side grid-connected node; wherein the photovoltaic inverter is used to adjust the household photovoltaic output according to the voltage value of the user side grid-connected node. Different control instructions are generated according to different grid operating states, so as to facilitate connecting different functional modules between the substation side node and the user side grid-connected node to change the voltage value of the user side grid-connected node, thereby achieving the technical effect of indirect flexible control of household photovoltaic output. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 A schematic structural diagram of a photovoltaic inverter control device provided in one embodiment of the present invention;

[0045] Figure 2 A schematic structural diagram of a switching module provided in one embodiment of the present invention;

[0046] Figure 3 A schematic diagram of an installation node of a switching module provided in one embodiment of the present invention;

[0047] Figure 4 A schematic diagram of installation nodes of a switching module provided in yet another embodiment of the present invention;

[0048] Figure 5 A schematic flow chart of a photovoltaic inverter control method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0049] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0050] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a photovoltaic inverter control device provided by an embodiment of the present invention. The photovoltaic inverter control device 1 includes a controller 11 and a switching module 12. The switching module 12 includes three phase branches, each of which includes at least one of a resistance module, a capacitance module, and an inductance module.

[0052] The controller 11 is configured to receive instructions from the intelligent fusion terminal and generate corresponding control signals according to the instructions. The instructions are issued by the intelligent fusion terminal when the operating state of the photovoltaic inverter needs to be adjusted.

[0053] Switching module 12 is configured to connect the modules indicated by the control signals in each phase branch between the substation-side node and the user-side grid-connected node in accordance with the control signals, thereby changing the voltage value of the user-side grid-connected node. The photovoltaic inverter is configured to adjust the household photovoltaic output based on the voltage value of the user-side grid-connected node.

[0054] For example, refer to Figure 2 , Figure 2 This is a structural diagram of a switching module provided in an embodiment of the present invention, wherein the switching module 12 includes an A-phase branch, a B-phase branch, and a C-phase branch.

[0055] Each phase branch contains:

[0056] The resistive module 121 includes a resistor module 1211 and a first switch 1212 connected in parallel with the resistor module;

[0057] The capacitive module 122 includes a capacitor module 1221 and a second switch 1222 connected in parallel with the capacitor module;

[0058] The inductive module 123 includes an inductive module 1231 and a third switch 1232 connected in parallel with the inductive module;

[0059] The resistive module 121 , the capacitive module 122 and the inductive module 123 are connected in series.

[0060] Optionally, the output node of the A-phase branch is connected to the output node of the B-phase branch via a fourth switch 124 , and the output node of the B-phase branch is connected to the output node of the C-phase branch via a fifth switch 125 .

[0061] It should be noted that Figure 2 The structure of the switching module 12 shown is merely exemplary and is not intended to be a specific limitation on the switching module 12 .

[0062] Optional, see Figure 3 and Figure 4 , the switching module 12 can be installed inside the circuit breaker and connected in series to the main power supply circuit of the circuit breaker;

[0063] Alternatively, the switching module 12 is installed outside the circuit breaker and connected in series between the load end of the circuit breaker and the user-side grid-connected node. The circuit breaker is set in series between the substation-side node X1 and the user-side grid-connected node X2.

[0064] In actual application, users can integrate the controller 11 and the switching module 12 into a whole according to their own needs and set them in Figure 3 or Figure 4 Alternatively, only the switching module 12 is set to Figure 3 or Figure 4In the position shown, the controller 11 is set at the far end.

[0065] In a possible implementation, the controller 11 is configured to receive a first instruction from the intelligent convergence terminal and generate a first control signal according to the first instruction.

[0066] The switching module 12 is configured to connect the resistance module 1211 and the capacitance module 1221 in each phase branch in series between the substation-side node X1 and the user-side grid-connected node X2 according to the first control signal.

[0067] The first instruction is issued when the intelligent fusion terminal detects that the power grid is in the first operating state, or is issued when the intelligent fusion terminal receives the first command, and the first command is used to indicate that the power grid is in the first operating state.

[0068] The first operating state indicates that the reactive output of the household photovoltaic system needs to be increased, and the increased reactive output is less than a first set value. For example, when the power grid is in the first operating state, the power factor of the substation transformer is less than a first threshold value and greater than a second threshold value, and / or the voltage at the user-side grid connection point is less than a first voltage value and greater than a second voltage value.

[0069] That is to say, the intelligent fusion terminal can monitor the operation status of the power grid by itself, and when it is monitored that the power factor value of the transformer in the substation is less than the first threshold value and greater than the second threshold value, and / or the voltage value of the user-side grid connection point is less than the first voltage value and greater than the second voltage value, it is determined that the power grid is currently in the first operation state;

[0070] Alternatively, the intelligent fusion terminal only receives the first command, where the first command is used to indicate that the power grid is currently in the first operating state.

[0071] At this time, the reactive output value of the household photovoltaic system needs to be increased, and the increased reactive output value is less than the first set value. The intelligent fusion terminal sends a first instruction to the controller 11 based on the current situation. According to the first instruction, the controller 11 controls the first switch 1212 and the third switch 1232 in each phase branch of the switching module to be opened, the second switch 1222 to be closed, and the fourth switch 124 and the fifth switch 125 to be opened, thereby achieving the effect of connecting the resistance module 1211 and the capacitance module 1221 in each phase branch in series between the substation-side node X1 and the user-side grid-connected node X2.

[0072] More specifically, the above actions can be accomplished by issuing a control code sequence. For example, the intelligent fusion terminal issues a first instruction D =

[0100] . Upon receiving this instruction, the photovoltaic inverter control device controls the switching module to open the first switch 1212 and the third switch 1232 in each phase branch, close the switch 1222 KL, and open the fourth switch 124 and the fifth switch 125.

[0073] It should be noted that the control code sequence D here is [DKR DKL DKC DKD], where DKR is used to indicate the switch state of the first switch 1212 (DKR=1, indicating that the first switch 1212 is closed; DKR=0, indicating that the first switch 1212 is open), DKL is used to indicate the switch state of the second switch 1222 (DKL=1, indicating that the second switch 1222 is closed; DKL=0, indicating that the second switch 1222 is open), DKC is used to indicate the switch state of the third switch 1232 (DKC=1, indicating that the third switch 1232 is closed; DKC=0, indicating that the third switch 1232 is open), and DKD is used to indicate the switch states of the fourth switch 124 and the fifth switch 125 (DKD=1, indicating that the fourth switch 124 and the fifth switch 125 are closed; DKD=0, indicating that the fourth switch 124 and the fifth switch 125 are open).

[0074] The voltage difference formula between the substation side node X1 and the user side grid connection point X2 is: Among them, ΔU represents the voltage difference between the substation-side node X1 and the user-side grid-connected node X2, P represents the active power output value of the household photovoltaic system, R represents the resistance value, Q represents the reactive power output value of the household photovoltaic system, X represents the reactance value, and U1 represents the voltage value of the substation-side node X1.

[0075] Under normal grid operation, the reactive output of household PV systems is low. According to the voltage difference formula above, after resistor module 1211 and capacitor module 1221 are added, resistance R increases; reactance X also increases, but due to the addition of capacitor module 1221, reactance X is negative. The reactive output Q of the household PV system is approximately 0, while active output remains normal. Consequently, voltage difference ΔU increases, and the voltage U2 at the user-side grid-connected node increases.

[0076] When the PV inverter detects that the voltage value U2 of the user-side grid-connected node is greater than the PV rated grid-connected voltage value U ref When , the household photovoltaic system is controlled to increase reactive power output and reduce active power output, the total apparent power remains unchanged, and no curtailment occurs. Due to the increase in reactive power output and the negative reactance value X, the voltage difference ΔU will decrease rapidly until U2=U ref , household photovoltaic enters a stable state. Compared with the normal state, this state has an increase in reactive power output, a decrease in active power output, and an unchanged total apparent power.

[0077] In a possible implementation, the controller 11 is configured to receive a second instruction from the intelligent convergence terminal and generate a second control signal according to the second instruction;

[0078] The switching module 12 is used to connect the resistance module 1211 in each phase branch in series between the substation side node X1 and the user side grid-connected node X2 according to the second control signal.

[0079] The second instruction is issued when the intelligent fusion terminal detects that the power grid is in the second operating state, or is issued when the intelligent fusion terminal receives the second command, and the second command is used to indicate that the power grid is in the second operating state;

[0080] The second operating state indicates that the reactive output of the household photovoltaic system needs to be increased, and the increased reactive output is greater than or equal to the first set value. For example, when the power grid is in the second operating state, the power factor of the substation transformer is less than or equal to a second threshold value, and / or the voltage of the user-side grid connection point is less than or equal to a second voltage value.

[0081] That is to say, the intelligent fusion terminal can monitor the operation status of the power grid by itself, and when it is monitored that the power factor value of the transformer in the substation is less than or equal to the second threshold value, and / or the voltage value of the user-side grid connection point is less than or equal to the second voltage value, it is determined that the power grid is currently in the second operation state;

[0082] Alternatively, the intelligent fusion terminal only receives the second command, where the second command is used to indicate that the power grid is currently in the second operating state.

[0083] At this time, the reactive output value of the household photovoltaic system needs to be increased, and the increased reactive output value must be greater than or equal to the first set value. Based on the current situation, the intelligent fusion terminal sends a second instruction to the controller 11. Based on the second instruction, the controller 11 controls the first switch 1212 in each phase branch of the switching module 12 to open, the second switch 1222 and the third switch 1232 to close, and the fourth switch 124 and the fifth switch 125 to open, thereby achieving the effect of connecting the resistance module 1211 in each phase branch in series between the substation-side node X1 and the user-side grid-connected node X2.

[0084] More specifically, the above actions can be accomplished by issuing a control code sequence. For example, the intelligent fusion terminal issues a second instruction D=

[0110] . After receiving the instruction, the photovoltaic inverter control device controls the switching module 12 to open the first switch 1212 in each phase branch, close the second switch 1222 and the third switch 1232, and open the fourth switch 124 and the fifth switch 125.

[0085] After resistor module 1211 is added, according to the voltage difference formula above, the resistance value R increases; the reactive power output value Q of the household photovoltaic system is approximately 0; and the active power output is normal. Therefore, the voltage difference value ΔU increases, and the voltage value U2 of the user-side grid-connected node increases.

[0086] When the PV inverter detects that the voltage value U2 of the user-side grid-connected node is greater than the PV rated grid-connected voltage value U refWhen the household photovoltaic system is controlled to increase reactive power output and reduce active power output, the total apparent power remains unchanged and no solar curtailment occurs. Due to the reduction in active power output, the voltage difference ΔU begins to decrease until U2=U ref , household photovoltaic enters a stable state. Compared with the normal state, this state has an increase in reactive power output, a decrease in active power output, and an unchanged total apparent power.

[0087] Compared to the case where both resistor module 1211 and capacitor module 1221 are simultaneously engaged, in this state, only resistor module 1211 is engaged, resulting in a slower reduction in the voltage difference. Therefore, the increased reactive power output in this state is greater than the reactive power output required to be increased in the first operating state (i.e., the first set value). The specific value of the first set value is determined by the values ​​of the resistor and capacitor and is not specifically limited here.

[0088] In a possible implementation, the controller 11 is configured to receive a third instruction from the intelligent convergence terminal and generate a third control signal according to the third instruction;

[0089] The switching module 12 is configured to connect the resistance module 1211 and the inductance module 1231 in each phase branch in series between the substation-side node X1 and the user-side grid-connected node X2 according to the third control signal;

[0090] The third instruction is issued when the intelligent fusion terminal detects that the power grid is in the third operating state, or is issued when receiving the third command, and the third command is used to indicate that the power grid is in the third operating state;

[0091] The third operating state refers to a reverse overload state. When the power grid is in the third operating state, the voltage value of the user-side grid-connected node is greater than a preset upper limit value.

[0092] In other words, the intelligent fusion terminal can monitor the operation status of the power grid by itself. When it detects that the voltage value of the user-side grid-connected node is greater than the preset upper limit, it determines that the power grid is currently in a reverse overload state;

[0093] Alternatively, the intelligent fusion terminal only receives the third command, where the third command is used to indicate that the power grid is currently in a reverse overload state.

[0094] At this time, it is necessary to limit the power output of the household photovoltaic system. Based on the current situation, the intelligent fusion terminal sends a third instruction to the controller 11. Based on the third instruction, the controller 11 controls the first switch 1212 and the second switch 1222 in each phase branch of the switching module 12 to be open, the third switch 1232 to be closed, and the fourth switch 124 and the fifth switch 125 to be open. This achieves the effect of connecting the resistance module 1211 and the inductance module 1231 in each phase branch in series between the substation-side node X1 and the user-side grid-connected node X2.

[0095] More specifically, the above actions can be accomplished by issuing a control code sequence. For example, the intelligent fusion terminal issues a third instruction D=

[0010] . Upon receiving the instruction, the photovoltaic inverter control device controls the switching module 12 to open the first switch 1212 and the second switch 1222 in each phase branch, close the third switch 1232, and open the fourth switch 124 and the fifth switch 125.

[0096] After the resistor module 1211 and the inductor module 1231 are put into operation, according to the above voltage difference formula, the resistance value R increases; the reactance value X increases. Since the inductor module 1231 is put into operation, X is a positive value; the reactive output value Q of the household photovoltaic is approximately 0; the active output is output normally, so the voltage difference ΔU increases, and the voltage value U2 of the user-side grid-connected node increases.

[0097] When the PV inverter detects that the voltage value U2 of the user-side grid-connected node is greater than the PV rated grid-connected voltage value U ref When the household photovoltaic system is controlled to increase reactive power output and reduce active power output. At this time, in the voltage difference formula, the product of active power output value P and resistance value R decreases, and the product of reactive power output value Q and reactance value X increases. The change of ΔU depends on the specific values ​​of the connected resistance value R and reactance value X. ΔU may decrease first and then increase or continue to increase. However, in either case, if the minimum value of U2 cannot satisfy U2=U ref , it will cause the photovoltaic inverter to abandon light and reduce the apparent power of household photovoltaics, that is, reduce the active output and reactive output until U2=U ref , the photovoltaic power enters a stable state, which has the effect of limiting the photovoltaic output. Compared with the normal state, this state increases reactive power output, decreases active power output, and reduces total apparent power.

[0098] In a possible implementation, the controller 11 is further configured to receive a fourth instruction from the intelligent fusion terminal and generate a fourth control signal according to the fourth instruction;

[0099] The switching module 12 is further configured to remove the resistance module 1211, the capacitance module 1221, and the inductance module 1231 in each phase branch from between the substation-side node X1 and the user-side grid-connected node X2 according to the fourth control signal;

[0100] The fourth instruction is issued when the intelligent fusion terminal detects that the power grid is in normal operation, or is issued when the intelligent fusion terminal receives the fourth command, and the fourth command is used to indicate that the power grid is in normal operation.

[0101] In other words, the intelligent fusion terminal can monitor the operation status of the power grid by itself. When it detects that the voltage value of the user-side grid-connected node and the power factor of the transformer in the substation are both within the preset standard range, it determines that the power grid is currently in normal operation.

[0102] Alternatively, the intelligent fusion terminal only receives the fourth command, where the fourth command is used to indicate that the power grid is currently in a normal operating state.

[0103] At this point, there is no need to adjust the operating state of the photovoltaic inverter. The intelligent fusion terminal sends a fourth instruction to the controller 11 based on the current situation. Based on the fourth instruction, the controller 11 controls the first switch 1212, the second switch 1222, and the third switch 1232 in each phase branch of the switching module 12 to close, and the fourth switch 124 and the fifth switch 125 to open, thereby eliminating the resistance module 1211, the capacitance module 1221, and the inductance module 1231 in each phase branch from between the substation-side node X1 and the user-side grid-connected node X2.

[0104] More specifically, the above actions can be accomplished by issuing a control code sequence. For example, the intelligent fusion terminal issues a first instruction D=

[1110] . After receiving the instruction, the photovoltaic inverter control device controls the first switch 1212, the second switch 1222, and the third switch 1232 in each phase branch of the switching module 12 to close, and the fourth switch 124 and the fifth switch 125 to open.

[0105] When the grid is operating normally, according to the voltage difference formula above, the resistance value R is zero; the reactance value X is zero; the reactive power output value Q of the household photovoltaic system is approximately 0; and the active power output is normal. Therefore, the voltage difference value ΔU is zero, and the voltage value U1 at the substation-side node is equal to the voltage value U2 at the user-side grid-connected node.

[0106] In a possible implementation, the controller 11 is configured to receive a fifth instruction from the intelligent convergence terminal and generate a fifth control signal according to the fifth instruction;

[0107] The switching module 12 is configured to connect the capacitor modules 1231 in each phase branch in series between the substation-side node X1 and the user-side grid-connected node X2 according to the fifth control signal;

[0108] The switching module 12 is further configured to close the fourth switch 124 and the fifth switch 125;

[0109] Among them, the fifth instruction is issued when the intelligent fusion terminal detects that the power grid is in the fifth operating state, or is issued when the fifth command is received. The fifth command is used to indicate that the power grid is in the fifth operating state; when the power grid is in the fifth operating state, the household photovoltaic output value is zero.

[0110] In other words, the intelligent fusion terminal can monitor the grid operation status by itself, and when it detects that the household photovoltaic output value is zero, it determines the current fifth operation status of the grid;

[0111] Alternatively, the intelligent fusion terminal only receives the fifth command, where the fifth command is used to indicate that the power grid is currently in the fifth operating state.

[0112] When the household photovoltaic output is zero (i.e., at night), the voltage U2 at the user-side grid-connected node decreases. At this point, capacitive current compensation is required. The intelligent fusion terminal sends a fifth instruction to controller 11 based on the current situation. Controller 11 controls switching module 12 to close first switch 1212 and second switch 1222 in each phase branch, disconnect third switch 1232, and close fourth switch 124 and fifth switch 125, thereby connecting the capacitor modules 1221 in each phase branch in parallel to form a whole, which is then connected in series between substation-side node X1 and user-side grid-connected node X2.

[0113] More specifically, the above actions can be accomplished by issuing a control code sequence. For example, the intelligent fusion terminal issues the fifth instruction D=

[1101] . After receiving the instruction, the photovoltaic inverter control device controls the switching module 12 to close the first switch 1212 and the second switch 1222 in each phase branch, open the third switch 1232, and close the fourth switch 124 and the fifth switch 125.

[0114] When the capacitor module 1221 is used alone, the voltage difference ΔU is zero. The capacitor module 1221 generates a capacitive component that is injected into the grid system, which not only increases the reactive component in the grid system but also raises the voltage value of the user-side network point, improving the power quality.

[0115] An embodiment of the present invention provides a photovoltaic inverter control device comprising a controller and a switching module. The controller is configured to receive instructions from an intelligent fusion terminal and generate corresponding control signals based on the instructions. The switching module is configured to connect the modules indicated by the control signals in each phase branch between the substation-side node and the user-side grid-connected node, in accordance with the control signals, to change the voltage value of the user-side grid-connected node, thereby regulating the household photovoltaic output. The resistance module can increase the voltage value of the user-side grid-connected node, activate the photovoltaic inverter regulation mode, and change the active and reactive output of the household photovoltaic system. The capacitance module can control the regulation range of the household photovoltaic active and reactive outputs and control the regulation amplitude per unit time; it is used to compensate for the system's reactive power. The inductance module can control the total apparent power of the household photovoltaic system. Different control instructions are generated according to different operating states of the power grid, so that modules with different functions can be connected between the substation-side node and the user-side grid-connected node to change the voltage value of the user-side grid-connected node, thereby achieving the technical effect of indirect flexible control of the household photovoltaic output.

[0116] Another aspect of the present invention provides a control system, including: a photovoltaic inverter control device and an intelligent fusion terminal.

[0117] An intelligent fusion terminal is used to monitor the operation status of the power grid and issue instructions based on the operation status of the power grid; or, an intelligent fusion terminal is used to receive commands and issue instructions based on the commands;

[0118] The photovoltaic inverter control device is used to receive instructions and control the designated module to access the node on the substation side and the grid-connected node on the user side according to the instructions.

[0119] An embodiment of the present invention provides a control system comprising: a photovoltaic inverter control device and an intelligent fusion terminal. The intelligent fusion terminal is configured to autonomously monitor the operating status of the power grid and issue instructions based on the grid operating status; alternatively, the intelligent fusion terminal is configured to receive commands and issue them accordingly. The photovoltaic inverter control device is configured to receive the commands and, in accordance with the commands, control the connection of a specified module between a substation-side node and a user-side grid-connected node. By connecting different modules between the substation-side node and the user-side grid-connected node, the voltage value of the user-side grid-connected node can be changed, forcing the photovoltaic inverter to adjust the household photovoltaic output.

[0120] Please refer to Figure 5 In another aspect of the present invention, a photovoltaic inverter control method is provided, comprising:

[0121] Step 501: receiving an instruction from the intelligent fusion terminal and generating a corresponding control signal according to the instruction, wherein the instruction is issued by the intelligent fusion terminal when the operating state of the photovoltaic inverter needs to be adjusted;

[0122] Step 502: According to the control signal, the modules indicated by the control signal in each phase branch are connected between the substation side node and the user side grid-connected node to change the voltage value of the user side grid-connected node; wherein the photovoltaic inverter is used to adjust the household photovoltaic output according to the voltage value of the user side grid-connected node.

[0123] An embodiment of the present invention provides a photovoltaic inverter control method, comprising: receiving instructions from an intelligent fusion terminal and generating corresponding control signals based on the instructions; and, in accordance with the control signals, connecting the modules indicated by the control signals in each phase branch between the substation-side node and the user-side grid-connected node to change the voltage value of the user-side grid-connected node. By connecting different modules between the substation-side node and the user-side grid-connected node, the voltage value of the user-side grid-connected node can be changed, forcing the photovoltaic inverter to adjust the household photovoltaic output.

[0124] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A photovoltaic inverter control device, characterized in that: The device includes a controller and a switching module; the switching module includes three-phase branches, and each phase branch includes at least one of a resistance module, a capacitance module, and an inductance module; The controller is configured to receive instructions from the intelligent fusion terminal and generate corresponding control signals according to the instructions, wherein the instructions are issued by the intelligent fusion terminal when the operating state of the photovoltaic inverter needs to be adjusted; The switching module is used to connect the module indicated by the control signal in each phase branch between the substation side node and the user side grid-connected node according to the control signal, so as to change the voltage value of the user side grid-connected node; wherein the photovoltaic inverter is used to adjust the household photovoltaic output according to the voltage value of the user side grid-connected node; Each phase branch in the switching module includes: The resistive module includes a resistor module and a first switch connected in parallel with the resistor module; A capacitive module, comprising a capacitor module and a second switch connected in parallel with the capacitor module; The inductive module includes an inductive module and a third switch connected in parallel with the inductive module; The resistive module, the capacitive module and the inductive module are connected in series.

2. The photovoltaic inverter control device according to claim 1, wherein: The three-phase branch includes: phase A branch, phase B branch and phase C branch; The output node of the A-phase branch is connected to the output node of the B-phase branch via a fourth switch, and the output node of the B-phase branch is connected to the output node of the C-phase branch via a fifth switch.

3. The photovoltaic inverter control device according to claim 1, wherein: The switching module is installed inside the circuit breaker and connected in series to the main power supply circuit of the circuit breaker; Alternatively, the switching module is installed outside the circuit breaker and connected in series between the load end of the circuit breaker and the user-side grid-connected node, and the circuit breaker is set in series between the substation-side node and the user-side grid-connected node.

4. The photovoltaic inverter control device according to claim 1, wherein: The controller is configured to receive a first instruction from the intelligent fusion terminal and generate a first control signal according to the first instruction; The switching module is configured to connect the resistance module and the capacitance module in each phase branch in series between the substation side node and the user side grid-connected node according to the first control signal; The first instruction is issued when the intelligent fusion terminal detects that the power grid is in the first operating state, or is issued when the intelligent fusion terminal receives a first command, and the first command is used to indicate that the power grid is in the first operating state; The first operating state indicates that the reactive output value of the household photovoltaic needs to be increased, and the increased reactive output value is less than the first set value; when the power grid is in the first operating state, the power factor value of the substation transformer is less than the first threshold and greater than the second threshold, and / or the voltage value of the user-side grid connection point is less than the first voltage value and greater than the second voltage value.

5. The photovoltaic inverter control device according to claim 1, wherein: The controller is configured to receive a second instruction from the intelligent fusion terminal and generate a second control signal according to the second instruction; The switching module is configured to connect the resistance modules in each phase branch in series between the substation side node and the user side grid-connected node according to the second control signal; The second instruction is issued when the intelligent fusion terminal detects that the power grid is in the second operating state, or is issued when the intelligent fusion terminal receives a second command, and the second command is used to indicate that the power grid is in the second operating state; The second operating state indicates that the reactive output value of the household photovoltaic system needs to be increased, and the increased reactive output value is greater than or equal to the first set value; when the power grid is in the second operating state, the power factor value of the substation transformer is less than or equal to the second threshold value, and / or the voltage value of the user-side grid connection point is less than or equal to the second voltage value.

6. The photovoltaic inverter control device according to claim 1, wherein: The controller is configured to receive a third instruction from the intelligent fusion terminal and generate a third control signal according to the third instruction; The switching module is configured to connect the resistance module and the inductance module in each phase branch in series between the substation side node and the user side grid-connected node according to the third control signal; The third instruction is issued when the intelligent fusion terminal detects that the power grid is in a third operating state, or is issued when receiving a third command, and the third command is used to indicate that the power grid is in the third operating state; The third operating state refers to a reverse heavy load state. When the power grid is in the third operating state, the voltage value of the user-side grid connection point is greater than a preset upper limit value; The controller is further configured to receive a fourth instruction from the intelligent fusion terminal and generate a fourth control signal according to the fourth instruction; The switching module is further configured to remove the resistance module, the capacitance module, and the inductance module in each phase branch from between the substation side node and the user side grid-connected node according to the fourth control signal; The fourth instruction is issued when the intelligent fusion terminal detects that the power grid is in a normal operating state, or is issued when the intelligent fusion terminal receives a fourth command, and the fourth command is used to indicate that the power grid is in a normal operating state.

7. The photovoltaic inverter control device according to claim 2, wherein: The controller is configured to receive a fifth instruction from the intelligent fusion terminal and generate a fifth control signal according to the fifth instruction; The switching module is configured to connect the capacitor modules in each phase branch in series between the substation side node and the user side grid-connected node according to the fifth control signal; The switching module is further configured to close the fourth switch and the fifth switch; The fifth instruction is issued when the intelligent fusion terminal detects that the power grid is in a fifth operating state, or is issued when the intelligent fusion terminal receives a fifth command, and the fifth command is used to indicate that the power grid is in the fifth operating state; When the power grid is in the fifth operating state, the household photovoltaic output value is zero.

8. A control system comprising: The photovoltaic inverter control device and the intelligent fusion terminal according to claim 1.

9. A photovoltaic inverter control method, characterized in that: Applied to the photovoltaic inverter control device according to claim 1, the method comprises: receiving an instruction from the intelligent fusion terminal and generating a corresponding control signal according to the instruction, wherein the instruction is issued by the intelligent fusion terminal when the operating state of the photovoltaic inverter needs to be adjusted; According to the control signal, the modules indicated by the control signal in each phase branch are respectively connected between the substation side node and the user side grid-connected node to change the voltage value of the user side grid-connected node; wherein, the photovoltaic inverter is used to adjust the household photovoltaic output according to the voltage value of the user side grid-connected node.

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