Inverter system, control method of inverter system, and related device

Abstract

The application provides an inverter system, a control method and a control device of the inverter system. The inverter system comprises an inverter, a PID module and a controller. The DC side of the inverter is used for connecting a DC bus, the PID module is connected to the negative pole or the positive pole of the DC bus, and the controller is connected with the PID module. The controller is configured to control the PID module to adjust its output voltage at least once according to a preset period when the PID module adjusts the ground voltage of the DC bus to a target ground voltage through an output target voltage, and the adjusted output voltage fluctuates within a preset amplitude relative to the target voltage. The current voltage output by the PID module after the PID module adjusts the output voltage, the current ground voltage of the DC bus and the current bus voltage are obtained. The ground impedance of the DC side is determined according to the voltage values. The application can perform real-time insulation detection without affecting the PID function.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, specifically to an inverter system, a control method and device for the inverter system, and a photovoltaic system. Background Technology

[0002] In the field of photovoltaic power generation technology, photovoltaic inverter systems need to simultaneously possess the functions of suppressing or repairing potential potential-induced degradation and real-time detection of insulation impedance to ground. The former aims to ensure the long-term power generation efficiency of photovoltaic modules, while the latter is an important measure to ensure the electrical safety of the system and compliance with safety regulations.

[0003] In related technologies, a common approach to achieve the above two functions is to configure the system with an independent Potential Induced Degradation (PID) module (hereinafter referred to as the PID module) and an Insulation State Observation (ISO) module (hereinafter referred to as the ISO module). The controller then controls the PID module and the ISO module to work alternately in a time-sharing manner.

[0004] However, in existing photovoltaic inverter systems, the operating conditions of the PID module and the ISO module conflict, requiring them to work alternately at different times. As a result, they cannot operate simultaneously, making it impossible to monitor the insulation impedance to ground in real time during the continuous adjustment of the PID module, which affects the safety and stability of the system. Summary of the Invention

[0005] In view of this, embodiments of the present invention aim to provide a control method, device, storage medium and electronic device for an inverter system, so as to solve the problem in the related art that the inverter system cannot simultaneously complete the real-time monitoring of the ground insulation status during continuous PID voltage regulation.

[0006] The present invention provides an inverter system, comprising: an inverter, a PID module, and a controller; the DC side of the inverter is used to connect to a DC bus; the PID module is connected to the negative or positive terminal of the DC bus; and the controller is connected to the PID module. The controller is configured as follows: When the PID module adjusts the DC bus voltage to ground to the target voltage by outputting the target voltage, the PID module is controlled to adjust its output voltage at least once according to a preset cycle, and the adjusted output voltage fluctuates within a preset range relative to the target voltage. The current voltage output by the PID module after the PID module adjusts its output voltage, the current voltage to ground of the DC bus, and the current bus voltage are obtained. The impedance value of the DC side to ground is determined based on the current voltage, the current voltage to ground, and the current bus voltage.

[0007] Determining the impedance value of the DC side to ground based on the current voltage, the current voltage to ground, and the current bus voltage includes: In one embodiment, based on the circuit topology of the PID module, the impedance value of the DC side to ground is determined according to the current voltage, the current voltage to ground, and the current bus voltage.

[0008] In one embodiment, determining the impedance value of the DC side to ground based on the circuit topology of the PID module, according to the current voltage, the current voltage to ground, and the current bus voltage, includes: Obtain the target equation, which is an equation constructed based on the circuit topology of the PID module with the impedance to ground as the unknown; The impedance value of the DC side to ground is determined based on the target equation, the current voltage, the current voltage to ground, and the current bus voltage.

[0009] In one embodiment, obtaining the current voltage output by the PID module after the PID module adjusts its output voltage, the current voltage to ground of the DC bus, and the current bus voltage includes: The first current voltage output by the PID module after the PID module adjusts its output voltage once, the first current voltage to ground of the DC bus, and the first current bus voltage are obtained. The step of determining the impedance value of the DC side to ground impedance based on the target equation, the current voltage, the current voltage to ground, and the current bus voltage includes: Obtain the target bus voltage of the DC bus when the PID module outputs the target voltage; The impedance value of the DC side to ground is determined based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the target voltage, the target voltage to ground, and the target bus voltage.

[0010] In one embodiment, determining the impedance value of the DC-side ground impedance based on the target equation, the first current voltage, the first current ground voltage, the first current bus voltage, the target voltage, the target ground voltage, and the target bus voltage includes: Substituting the first current voltage, the first current voltage to ground, and the first current bus voltage into the target equation, we obtain the first equation; Substituting the target voltage, the target voltage to ground, and the target bus voltage into the target equation yields the second equation; Solve the first and second equations simultaneously to obtain the positive and negative ground impedances of the DC side; The impedance value of the DC side to ground is determined based on the positive impedance to ground and the negative impedance to ground.

[0011] In one embodiment, the PID module includes a current-limiting impedance and an adjustable power supply; the DC bus voltage to ground includes the negative terminal voltage of the DC bus to ground. The negative terminal of the DC bus is grounded through the negative ground impedance, and the current limiting impedance is connected in series with the adjustable power supply and then in parallel with the negative ground impedance. The positive terminal of the DC bus is grounded through the grounding impedance; The expression for the objective equation is: V0=Upv- (R1+R3) R2+R1 R3] / R2 R3+Vbus R1 / R3; Wherein, V0 is the output voltage of the PID module, Upv- is the negative voltage to ground of the DC bus, R1 is the impedance value of the current limiting impedance, R2 is the impedance value of the positive impedance to ground, R3 is the impedance value of the negative impedance to ground, and Vbus is the bus voltage of the DC bus.

[0012] In one embodiment, the controller is further configured to: Calculate the absolute value of the difference between the first current voltage and the target voltage to obtain the first absolute value; Calculate the absolute value of the difference between the first current ground voltage and the target ground voltage to obtain the second absolute value; If the first absolute value is greater than the first threshold, and / or the second absolute value is greater than the second threshold, then the step of determining the impedance value of the DC side to ground impedance based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the target voltage, the target voltage to ground, and the target bus voltage is executed.

[0013] In one embodiment, obtaining the current voltage output by the PID module after the PID module adjusts its output voltage, the current voltage to ground of the DC bus, and the current bus voltage includes: The first current voltage output by the PID module after the PID module adjusts its output voltage once, the first current voltage to ground of the DC bus, and the first current bus voltage are obtained. The second current voltage output by the PID module after another adjustment of its output voltage, the second current voltage to ground of the DC bus and the second current bus voltage are obtained. The step of determining the impedance value of the DC side to ground impedance based on the target equation, the current voltage, the current voltage to ground, and the current bus voltage includes: The impedance value of the DC side to ground is determined based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the second current voltage, the second current voltage to ground, and the second current bus voltage.

[0014] In one embodiment, determining the impedance value of the DC-side impedance to ground based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the second current voltage, the second current voltage to ground, and the second current bus voltage includes: Substituting the first current voltage, the first current voltage to ground, and the first current bus voltage into the target equation, we obtain the first equation; Substituting the second current voltage, the second current voltage to ground, and the second current bus voltage into the target equation yields the third equation; Solve by combining the first equation and the third equation to obtain the positive and negative impedances to ground on the DC side; The impedance value of the DC side to ground is determined based on the positive impedance to ground and the negative impedance to ground.

[0015] In one embodiment, the number of inverters is multiple, and the number of PID modules is one; The DC sides of multiple inverters are connected in parallel. The DC side of any one of the multiple inverters is connected to the PID module.

[0016] In one embodiment, the number of inverters is multiple, and the number of PID modules is less than or equal to the number of inverters; The DC sides of the multiple inverters are isolated from each other, and the AC sides of the multiple inverters are connected in parallel. Each of the PID modules is connected to the DC side of one of the plurality of inverters, and at most one of the PID modules is connected to the DC side of each inverter.

[0017] Another aspect of the present invention provides a control method for an inverter system, the inverter system comprising: an inverter, a PID module, and a controller; the DC side of the inverter is used to connect to a DC bus; the PID module is connected to the negative or positive terminal of the DC bus; the controller is connected to the PID module; the control method includes: When the PID module adjusts the DC bus voltage to ground to the target voltage by outputting the target voltage, the PID module is controlled to adjust its output voltage at least once according to a preset cycle, and the adjusted output voltage fluctuates within a preset range relative to the target voltage. The current voltage output by the PID module after the PID module adjusts its output voltage, the current voltage to ground of the DC bus, and the current bus voltage are obtained. The impedance value of the DC side to ground is determined based on the current voltage, the current voltage to ground, and the current bus voltage.

[0018] In another aspect, the present invention provides a control device for an inverter system, the inverter system comprising: an inverter, a PID module, and a controller; the DC side of the inverter is used to connect to a DC bus; the PID module is connected to the negative or positive terminal of the DC bus; the controller is connected to the PID module; the control device comprises: The control unit is configured to, when the PID module adjusts the DC bus voltage to ground to the target voltage by outputting the target voltage, control the PID module to adjust its output voltage at least once according to a preset cycle, and the adjusted output voltage fluctuates within a preset range relative to the target voltage. The acquisition unit is used to acquire the current voltage output by the PID module after the PID module adjusts its output voltage, the current voltage to ground of the DC bus, and the current bus voltage. The determining unit is used to determine the impedance value of the DC side to ground impedance based on the current voltage, the current voltage to ground, and the current bus voltage.

[0019] In another aspect, the present invention provides a photovoltaic system, which includes the inverter system described in any of the above embodiments. Compared with related technologies, the inverter system provided by the present invention has the following advantages: The inverter system provided by this invention includes an inverter, a PID module, and a controller. The DC side of the inverter is connected to a DC bus. The PID module is connected to the negative or positive terminal of the DC bus. The controller is connected to the PID module. The controller is configured to: when the PID module adjusts the DC bus voltage to ground to the target voltage by outputting a target voltage, control the PID module to adjust its output voltage at least once according to a preset period. The adjusted output voltage fluctuates within a preset range relative to the target voltage, thereby actively introducing a periodic voltage disturbance into the output voltage of the PID module during the period of maintaining the PID regulation function. The adjusted output voltage is limited by the preset range, so that the PID regulation function of the PID module can be normally realized. Then, the current voltage output by the PID module, the current DC bus voltage to ground, and the current bus voltage during the disturbance process are acquired. Then, based on these current voltages, current voltages to ground, and current bus voltages, the impedance value of the DC side to ground is directly determined. This allows for the introduction of voltage disturbances to induce changes in the electrical parameters of the inverter system, yielding the changed electrical parameters. Since there is a fixed mapping relationship between the electrical parameters and the DC-side impedance to ground when the inverter system structure remains unchanged, the changed electrical parameters can be used to accurately calculate the DC-side impedance to ground value. This enables real-time detection of the inverter's DC-side impedance to ground in the inverter system without affecting the PID suppression or repair function, improving the safety and reliability of the inverter system operation. Furthermore, it eliminates the need for additional dedicated insulation detection hardware modules, reducing the system's cost and complexity. Attached Figure Description

[0020] Figure 1 The diagram shown is a structural schematic of an inverter system in some related technologies provided by an embodiment of the present invention.

[0021] Figure 2 The diagram shown is a structural schematic of an inverter system in some related technologies provided by an embodiment of the present invention.

[0022] Figure 3 The diagram shown is a structural schematic of an inverter system provided in an embodiment of the present invention.

[0023] Figure 4 The diagram shown is a schematic representation of the operation of an inverter system according to an embodiment of the present invention.

[0024] Figure 5 The diagram shown is a schematic diagram of the circuit topology of a PID module provided in an embodiment of the present invention.

[0025] Figure 6 The diagram shown is a schematic diagram of the circuit topology of another PID module provided in an embodiment of the present invention.

[0026] Figure 7 The diagram shown is a topology diagram of a multi-inverter parallel system provided in an embodiment of the present invention.

[0027] Figure 8 The diagram shown is a schematic diagram of another multi-inverter parallel system topology provided by an embodiment of the present invention.

[0028] Figure 9 The diagram shown is a topology diagram of another multi-inverter parallel system provided by an embodiment of the present invention.

[0029] Figure 10 The diagram shown is a flowchart illustrating a control method for an inverter system according to an embodiment of the present invention.

[0030] Figure 11 The diagram shown is a schematic block diagram of the control device for an inverter system provided in an embodiment of the present invention.

[0031] Figure 12 The diagram shown is a block diagram of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] In the field of photovoltaic power generation technology, to suppress or repair the potential-induced degradation effect of photovoltaic modules, a DC PID module is usually configured in the inverter system (hereinafter referred to as the inverter system). The core function of this PID module is to actively control and maintain the DC bus voltage to ground at a preset target value by outputting a precisely adjustable voltage. Specifically, this scheme connects the PID module as a controlled voltage source to the system. Changes in its output voltage directly affect the DC bus voltage to ground, thereby stabilizing the DC bus voltage to ground within the range required to suppress the PID effect and ensuring the long-term power generation efficiency of the photovoltaic power plant.

[0034] In addition, to ensure the electrical safety of the inverter system, an ISO module is typically configured within it. The core function of this module is to detect the DC-side insulation resistance to ground in real time by injecting detection signals and acquiring relevant electrical quantities, thereby determining whether the insulation condition has deteriorated. Specifically, this is achieved by setting up independent insulation detection hardware circuitry or a dedicated detection mode. A signal of a specific frequency or waveform is injected into the DC or AC side, and the resulting voltage and current changes are measured. The insulation resistance to ground is then calculated based on a circuit model, enabling timely alarms in the event of insulation faults and ensuring the safety of personnel and equipment.

[0035] like Figure 1 As shown, in some related technologies, the PID module and ISO module are integrated on the AC side of the inverter to form a PID&ISO module. The PID&ISO module can independently implement the PID function or the ISO function. Specifically, the inverter system can switch the PID&ISO module to execute the PID function or the ISO function through internal switching devices (such as controllers), but it is not possible to execute the PID function and the ISO function at the same time.

[0036] like Figure 2 As shown, in some other related technologies, the PID module is connected to the DC side of the inverter, and the ISO module is connected to the AC side of the inverter. The controller can control the PID module or the ISO module to be put into use, and can also independently implement the PID or ISO function, but it cannot implement the PID function and the ISO function to be executed at the same time.

[0037] In summary, currently, when an inverter system needs to perform insulation testing in PID mode, it must first exit PID mode and switch to ISO mode. After the insulation testing is completed, it must re-enter PID mode and restore the target voltage.

[0038] However, in some special scenarios, such as nighttime repair scenarios where the PID function needs to operate continuously or scenarios requiring continuous suppression in high humidity environments, the above operating mode will cause the PID function to be periodically interrupted. Specifically, this manifests as a reduction in the PID treatment effect and a loss of real-time insulation monitoring. The system cannot achieve real-time monitoring of the insulation status without affecting the PID function, thus the stability and safety of the inverter system cannot be guaranteed.

[0039] Therefore, as the requirements for operational safety and reliability of photovoltaic systems continue to increase, how to simultaneously monitor the real-time insulation status to ground during continuous PID voltage regulation has become an urgent problem to be solved.

[0040] In view of the above problems, one embodiment of the present invention provides an inverter system, such as... Figure 3As shown, the inverter system may include an inverter, a PID module, and a controller. The DC side of the inverter is connected to the DC bus; the PID module is connected to either the negative or positive terminal of the DC bus; and the controller is connected to the PID module.

[0041] As an example, please refer again. Figure 3 Taking the application of the inverter system 100 in a photovoltaic power generation scenario as an example, the photovoltaic power generation scenario may include a photovoltaic array, an inverter 110, a PID module 120, and a controller 130. The photovoltaic array is composed of multiple photovoltaic modules connected in series or parallel, used to convert solar energy into DC power. The DC side of the inverter 110 is connected to the photovoltaic array through a DC bus, used to convert the DC power generated by the photovoltaic array into AC power and feed it into the grid or supply local loads. The PID module 120 is connected to the negative or positive terminal of the DC bus; in this embodiment, it is described as being connected to the negative terminal of the DC bus. The PID module 120 draws power from the AC or DC side of the inverter system 100, and its core is a power supply with adjustable output voltage, used to inject or draw current from the DC bus, thereby regulating the DC bus voltage to ground. The controller 130 is connected to the PID module 120, used to send control commands to the PID module 120, and receive sampled values ​​from the voltage sampling circuit in the inverter system 100.

[0042] Alternatively, the controller 130 may be a standalone control unit or part of the main controller 130 of the inverter 110.

[0043] Optionally, the voltage sampling circuit may include multiple voltage sensors, such as a first voltage sensor for sampling the output voltage of the PID module 120, a second voltage sensor for sampling the DC bus voltage to ground, and a third voltage sensor for sampling the DC bus voltage, etc.

[0044] The controller 130 can be configured as follows: When the PID module 120 adjusts the DC bus voltage to ground to the target voltage by outputting the target voltage, the PID module 120 adjusts its output voltage at least once according to a preset cycle, and the adjusted output voltage fluctuates within a preset range relative to the target voltage.

[0045] The current voltage output by PID module 120 after adjusting its output voltage, the current ground voltage of DC bus, and the current bus voltage are obtained.

[0046] Determine the impedance value of the DC side to ground based on the current voltage, the current voltage to ground, and the current bus voltage.

[0047] The DC-to-ground impedance of inverter 110 refers to the equivalent insulation resistance between the DC-to-ground side of inverter 110 and the ground. Specifically, its impedance value is typically the parallel value of the positive-to-ground impedance of the positive terminal of inverter 110's DC-to-ground and the negative-to-ground impedance of the negative terminal of inverter 110's DC-to-ground. This impedance value reflects the insulation condition of the DC-to-ground side of inverter 110; a higher value indicates better insulation.

[0048] In some implementations, after determining the impedance value of the DC side to ground, the impedance value can be output through a human-machine interface module (such as a display, touch screen, etc.) to prompt the staff on the current insulation status of the inverter system 100.

[0049] For example, as one specific implementation, the controller 130 may internally include a periodic timer and a disturbance amplitude setting module. The operation of the inverter system 100 can be as follows: Figure 4 As shown: The controller 130 can start the PID power supply to work in order to repair or suppress the voltage to ground of the negative terminal of the DC bus.

[0050] Once the PID module 120 has stabilized the negative voltage to ground of the DC bus at the target value (i.e., the target voltage to ground) through its internal closed-loop control (e.g., sampling the negative voltage to ground and comparing it with an internal target value, and adjusting its output voltage through proportional-integral control), the controller 130 determines that the PID module 120 has entered the steady-state maintenance phase. At this time, a set of data (V1, V2, V3) can be collected when the PID module 120 is in the target voltage steady state, where V1 is the specific voltage value of the target voltage, V2 is the specific voltage value of the target voltage to ground, and V3 is the target bus voltage of the DC bus collected when the PID module 120 outputs the target voltage V1.

[0051] At this time, the controller 130 can start the aforementioned periodic timer. Whenever the timer reaches a preset period T, the controller 130 generates a disturbance command. This disturbance command instructs the PID module 120 to adjust its output voltage from the currently stable target voltage V_target to a disturbance voltage V_disturb (i.e., the adjusted output voltage). The difference ΔV between the disturbance voltage V_disturb and the target voltage V_target is limited to a preset amplitude ΔV_max, i.e., |V_disturb - V_target| ≤ ΔV_max. The adjusted output voltage fluctuates within the preset amplitude relative to the target voltage without affecting the PID control effect of the PID module 120.

[0052] During the process of PID module 120 adjusting its output voltage according to a preset cycle to generate a disturbance voltage, controller 130 can sample the output voltage of PID module 120 (i.e., output voltage) through a first voltage sensor, sample the voltage between the negative terminal of the DC bus and ground (i.e., ground voltage) through a second voltage sensor, and sample the voltage between the positive and negative terminals of the DC bus (i.e., bus voltage Vbus) through a third voltage sensor. Specifically, after PID module 120 outputs the disturbance voltage V_disturb, the electrical state of the system will undergo a dynamic adjustment process and eventually reach a new steady state. Controller 130 can synchronously trigger sampling of the above three voltage quantities at one or more specific moments after the disturbance is applied. For example, as an implementation, controller 130 can perform a set of samples at the moment t1 when it is determined that the system has re-entered a steady state after the disturbance (e.g., the change in negative ground voltage after several consecutive samplings is less than a threshold), to obtain the first current voltage V1 at time t1. First current voltage to ground V2 and the first current bus voltage V3 .

[0053] The voltage sensors mentioned above can be independent voltage sensors, or they can be multiplexed voltage detection circuits existing inside the inverter 110 and connected to the analog-to-digital conversion interface of the controller 130 through a multiplexer. No limitation is made here.

[0054] Next, the controller 130 obtains the voltage data obtained above (such as the first current voltage V1 at time t1). First current voltage to ground V2 and the first current bus voltage V3 After that, it can be combined with, for example Figure 5 Based on the circuit topology of the PID module 120, the positive and negative ground impedances R3 and R2 on the DC side are calculated. Specifically, the controller 130 internally stores or has a target equation based on the PID module 120 and the DC-side ground circuit topology. This equation establishes the mathematical relationship between the output voltage V0 of the PID module 120, the negative ground voltage Upv- of the DC bus, the DC bus voltage Vbus, the known current-limiting impedance R1, and the ground impedances R2 and R3 to be determined.

[0055] The controller 130 can substitute one or more sets of voltage data obtained above into the target equation to solve for the unknown ground impedances R2 and R3. For example, if a set of data (V1, V2, V3) of the PID module 120 in the target voltage steady state and a set of data (V1, V2, V3) in the steady state after disturbance are obtained... V2 V3 Then, substituting these equations into the target equation yields two equations. Solving these two equations simultaneously solves for the two unknowns, R2 and R3. Specifically, to ensure that the target voltage V1 is equal to the first current voltage V1... If they are not equal, you can make |V1-V1 |>M or|V2-V2 When |>N, the disturbance voltage is collected, where neither M nor N is 0.

[0056] The above-mentioned solution process can be implemented by the central processing unit of the controller 130 executing a pre-stored algorithm program.

[0057] Then, the controller 130 can calculate the parallel value of the positive ground impedance R3 and the negative ground impedance R2, and determine the parallel value as the ground impedance value of the DC side of the inverter 110.

[0058] After the calculation is completed, the controller 130 can output the impedance value through a communication interface (such as CAN, RS485), or connect to a local display for local display, and can also trigger an alarm signal when the impedance value is lower than the safety threshold.

[0059] The preset period T can refer to the time interval between two adjacent disturbances applied to the output voltage by the PID module 120 controlled by the controller 130.

[0060] Understandably, the preset period T needs to simultaneously meet real-time monitoring requirements and safety and system stability requirements. On the one hand, to ensure the system can monitor changes in impedance to ground in a timely manner, the preset period T should not be too large. If T is too large, the system may not be able to detect impedance anomalies in time when insulation performance deteriorates rapidly, posing a safety hazard. Therefore, for scenarios with high safety requirements, T can be set to a smaller value (e.g., 5 to 10 seconds); for scenarios with stable insulation conditions, T can be appropriately increased (e.g., 30 to 60 seconds).

[0061] On the other hand, to ensure the safe and stable operation of the system, the preset period T should not be too small. If T is too small, frequent voltage disturbances may cause the DC bus voltage to ground to exceed the allowable range of safety regulations, or affect the normal operation of the PID function, or even cause control loop instability. In addition, there is a coupling relationship between the disturbance amplitude and the preset period T: when the disturbance amplitude is large, T should be increased appropriately to give the system sufficient recovery time; when the disturbance amplitude is small, T can be decreased appropriately to improve the real-time detection performance.

[0062] As an optional implementation, the preset period T ranges from 5 seconds to 60 seconds. In one embodiment, the preset period T is set to 10 seconds to achieve a good balance between real-time detection and system stability. Furthermore, the controller 130 can also dynamically adjust the preset period T according to the system operating status: when an abnormal downward trend in the impedance to ground is detected, T is automatically shortened to enhance monitoring; when the insulation condition is good and stable, T is appropriately increased to reduce the impact on the PID function.

[0063] The preset amplitude fluctuation refers to the fact that the change in the disturbance voltage relative to the target voltage is limited to a preset safety and functionally permissible range, such as the absolute value of the change not exceeding 50V. In one embodiment, the absolute value of the change is 10-30V, so as to avoid having a substantial impact on the function or exceeding the system safety regulations.

[0064] It is understood that the various specific values ​​described in this embodiment (e.g., the preset period T is 5 seconds, 10 seconds, 30 seconds, 60 seconds, the preset amplitude is 50V, etc.) are exemplary parameters provided to facilitate a clear explanation of the technical solution of this invention, and do not constitute any limitation on the scope of protection of this invention. In different application scenarios (e.g., different photovoltaic system capacities, different safety standards, different environmental conditions, etc.), the above values ​​can be reasonably adjusted and optimized according to actual needs. As long as the technical concept of synchronously detecting insulation impedance by periodically perturbing the output voltage during PID function operation proposed in this invention is adopted, regardless of the specific parameters selected, it falls within the scope of protection of this invention. Any parameter adjustments or adaptive modifications based on the concept of this invention are not considered substantial changes to the technical solution of this invention.

[0065] As can be seen, in this embodiment, the inverter system 100 includes an inverter 110, a PID module 120, and a controller 130. The DC side of the inverter 110 is connected to the DC bus. The PID module 120 is connected to the negative or positive terminal of the DC bus. The controller 130 is connected to the PID module 120. The controller 130 is configured to: when the PID module 120 adjusts the DC bus voltage to ground to the target voltage by outputting the target voltage, control the PID module 120 to adjust its output voltage at least once according to a preset period. The adjusted output voltage fluctuates within a preset range relative to the target voltage, thereby actively introducing a periodic voltage disturbance into the output voltage of the PID module 120 during the period of maintaining the PID regulation function. The output voltage is limited by a preset amplitude, allowing the PID module 120's PID regulation function to be implemented normally. Next, the current voltage output by the PID module 120, the current DC bus voltage to ground, and the current bus voltage are acquired during the disturbance. Then, based on these current voltages, current voltages to ground, and current bus voltages, the impedance value of the DC side to ground is directly determined. This allows for accurate calculation of the impedance value to ground based on the changes in electrical parameters caused by the voltage disturbance. This achieves real-time detection of the inverter system 100's insulation status to ground without affecting the PID suppression or repair function, improving the safety and reliability of the inverter system 100's operation. Furthermore, it eliminates the need for additional dedicated insulation detection hardware modules, reducing system cost and complexity.

[0066] In some implementations, the impedance value of the DC side to ground is determined based on the current voltage, the current voltage to ground, and the current bus voltage, including: Based on the circuit topology of the PID module, the impedance value of the DC side to ground is determined according to the current voltage, the current voltage to ground, and the current bus voltage.

[0067] For example, the mapping relationship between the output voltage of the PID module, the DC bus voltage to ground, and the DC bus voltage and the DC side impedance to ground can be determined based on the circuit topology of the PID module; then, the impedance value of the DC side impedance to ground can be determined according to the mapping relationship and the obtained current voltage, current voltage to ground, and current bus voltage.

[0068] The mapping relationship can be represented by a mathematical model, a functional relationship, or a lookup table, etc., and no limitation is made here.

[0069] As an example, during the periodic adjustment of the PID module's output voltage, the controller collects the current voltage, current voltage to ground, and current bus voltage at at least one moment. Different moments within this at least one period correspond to different adjustment periods. For example, at least one moment may include moments t1 and t2. The PID module adjusts its output voltage once in period T1 and once in period T2 according to a preset period. Periods T1 and T2 can be two adjacent periods. Moment t1 corresponds to adjustment period T1, meaning moment t1 is a moment within adjustment period T1, and moment t2 corresponds to adjustment period T2, meaning moment t2 is a moment within adjustment period T2. Then, the controller substitutes these collected electrical parameters into the mapping relationship and calculates the DC-side impedance to ground by solving or looking up a table.

[0070] In some implementations, based on the circuit topology of the PID module, the impedance value of the DC side to ground is determined according to the current voltage, the current voltage to ground, and the current bus voltage, including: Obtain the target equation, which is an equation constructed based on the circuit topology of the PID module with the impedance to ground as the unknown.

[0071] Determine the impedance value of the DC side to ground based on the target equation, current voltage, current voltage to ground, and current bus voltage.

[0072] In some implementations, the PID module includes a current-limiting impedance and an adjustable power supply, and the DC bus voltage to ground includes the negative terminal voltage to ground.

[0073] The negative terminal of the DC bus is grounded through the negative impedance to ground, and the current limiting impedance is connected in series with the adjustable power supply and then in parallel with the negative impedance to ground.

[0074] The positive terminal of the DC bus is grounded through a ground impedance; The objective equation is expressed as follows: V0=Upv- (R1+R3) R2+R1 R3] / R2 R3+Vbus R1 / R3 (1) Where V0 is the output voltage of the PID module, Upv- is the negative voltage of the DC bus to ground, R1 is the impedance value of the current limiting impedance, R2 is the impedance value of the positive impedance to ground, R3 is the impedance value of the negative impedance to ground, and Vbus is the bus voltage of the DC bus.

[0075] Continuing with the example above, let's take... Figure 5The circuit topology of the PID module is explained below. The PID module specifically includes a current-limiting impedance R1 with a known resistance value and an adjustable power supply. The adjustable power supply is connected in series with the current-limiting impedance R1 and then connected between the negative terminal of the DC bus and ground. The negative terminal of the DC bus is grounded through the positive ground impedance R2, and the positive terminal of the DC bus is grounded through the negative ground impedance R3. According to the circuit principle, the objective equation describing the steady-state relationship of this circuit can be derived. Its expression is shown in the above expression (1), where Upv- specifically represents the voltage of the negative terminal of the DC bus to ground. This objective equation accurately describes Figure 5 The constraint relationships between various electrical quantities. As long as a sufficient number of (V0, Upv-, Vbus) data sets satisfying the equation at different operating points are obtained, the unknowns R2 and R3 can be solved. Then, by calculating the parallel value of R2 and R3, the impedance value of the DC side to ground can be obtained.

[0076] As can be seen, in this embodiment, the pre-constructed objective equation is used, which makes the calculation process of insulation impedance reliable and the results accurate and reliable, avoiding the errors caused by estimation based on experience or fuzzy relationships.

[0077] It is understandable that the specific form of the objective equation depends on the specific circuit topology of the PID module. For example, if the PID module uses other forms of output circuits or connection methods, or if the system-to-ground model considers more parasitic parameters, its objective equation will also change accordingly. However, regardless of the form, its core is an equation established based on circuit network theory, with the impedance to be determined as the variable. By adopting the above-described specifically defined objective equation, this preferred solution provides a directly implementable and physically clear mathematical model for the quantitative calculation of insulation impedance, thereby enhancing the feasibility of the core concept of this invention and the accuracy of the results. As an example, for instance in... Figure 6 In the circuit topology shown, the PID module can be connected to the positive terminal of the DC bus. In this case, the expression for the objective equation is as follows: V0=-Upv+ [(R1+R2)] R3+R1 R2] / R3 R2+Vbus R1 / R2 (2) Where Upv+ is the positive terminal voltage to ground of the DC bus.

[0078] In some implementations, obtaining the current voltage output by the PID module after the PID module adjusts its output voltage, the current DC bus voltage to ground, and the current bus voltage includes: The first current voltage output by the PID module after one adjustment of its output voltage, the first current voltage to ground of the DC bus, and the first current bus voltage are obtained. Based on the target equation, current voltage, current voltage to ground, and current bus voltage, determine the impedance value of the DC side to ground, including: Obtain the target bus voltage of the DC bus when the PID module outputs the target voltage; Based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the target voltage, the target voltage to ground, and the target bus voltage, determine the impedance value of the DC side to ground impedance.

[0079] In some implementations, the impedance value of the DC side to ground impedance is determined based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the target voltage, the target voltage to ground, and the target bus voltage, including: Substituting the first current voltage, the first current voltage to ground, and the first current bus voltage into the objective equation, we obtain the first equation.

[0080] Substituting the target voltage, target voltage to ground, and target bus voltage into the target equation yields the second equation.

[0081] Solve the first and second equations simultaneously to obtain the positive and negative ground impedances of the DC side.

[0082] The impedance value of the DC side to ground is determined based on the positive impedance to ground and the negative impedance to ground.

[0083] For example, after adjusting its output voltage once, the PID module can collect the first current voltage output by the PID module, the first current DC bus voltage to ground, and the first current bus voltage at the first time t1. Furthermore, after the PID module adjusts the negative voltage to ground to the target value and stabilizes, the system is at a known steady-state operating point A. At this time, the controller can sample and record three sets of voltages at this operating point: the PID module output voltage (i.e., target voltage V1), the negative voltage to ground (i.e., target voltage to ground V2), and the bus voltage (target bus voltage V3). Subsequently, after applying a disturbance and the system stabilizes again (as at the first time t1), another set of data (V1) is sampled. V2 V3 ), where V1 V2 is the first current voltage at time t1. V3 is the first current voltage to ground at time t1. Let be the first current bus voltage at time t1. Since the data (V1, V2, V3) at operating point A also satisfy the objective equation (1), therefore, (V1, V2, V3) and (V1 V2 V3 Substituting these equations into the objective equation (1), we obtain two independent equations. These two equations form a system of two equations in R2 and R3. Where V1 and V1 Substitute these terms into the V0 term of the objective equation (1). V2 and V2 Substitute these terms into the Upv-term in objective equation (1). V3 and V3 Substitute the Vbus term into the objective equation (1) respectively.

[0084] Following the example above, (V1) V2 V3 Substituting (V1, V2, V3) into equation (1), we get the first equation F1(R2, R3) = 0; substituting (V1, V2, V3) into equation (1), we get the second equation F2(R2, R3) = 0; then we solve the first and second equations simultaneously to find the values ​​of R2 and R3.

[0085] Finally, the parallel value of R2 and R3 can be calculated, and this parallel value can be used as the impedance value of the DC side to ground.

[0086] As can be seen, in this embodiment, the existing steady-state operating point data (i.e., the target voltage V1, target ground voltage V2, and target bus voltage V3) of the inverter system, which must be generated and recorded to maintain the function, are used as one of the calculation benchmarks. This reduces the requirement for the number of additional active disturbance sampling times, simplifies the data acquisition logic in some cases, and may improve the robustness of the final impedance calculation results by using more stable initial steady-state data.

[0087] In some implementations, the controller is also configured to: Calculate the absolute value of the difference between the first current voltage and the target voltage to obtain the first absolute value.

[0088] Calculate the absolute value of the difference between the first current voltage to ground and the target voltage to ground to obtain the second absolute value.

[0089] If the first absolute value is greater than the first threshold, and / or the second absolute value is greater than the second threshold, then the step of determining the impedance value of the DC side to ground impedance based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the target voltage, the target voltage to ground, and the target bus voltage is executed.

[0090] For example, the controller is also configured to perform a validity check before executing the step "determine the impedance value of the DC side to ground impedance based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the target voltage, the target voltage to ground, and the target bus voltage". Specifically, this includes calculating the first current voltage V1. The absolute value of the difference between the voltage and the target voltage V1 (as described above |V1-V1) |), obtain the first absolute value |ΔV1|; calculate the first current ground voltage V2. The absolute value of the difference between the target voltage and the ground voltage V2 (e.g., |V2-V2) The first absolute value |ΔV1| is obtained. If the first absolute value |ΔV1| is greater than the first threshold M, and / or the second absolute value |ΔV2| is greater than the second threshold N, then the step "determine the impedance value of the DC side to ground based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the target voltage, the target voltage to ground, and the target bus voltage" is executed to calculate the impedance; otherwise, the sampling data of this disturbance is discarded, and the process waits for the next disturbance cycle. For example, both the first threshold M and the second threshold N can be set to 10V. This design ensures that the data is used for calculation only when the voltage change caused by the disturbance is sufficiently significant.

[0091] Considering that if the perturbation is too small, the two sets of data before and after the perturbation will be too close, and the two equations established will be close to linearly correlated. During the solution process, numerical calculation errors may easily lead to inaccurate results or even solution failure. In this embodiment, by introducing a threshold judgment mechanism, invalid data caused by insufficient perturbation amplitude or external noise interference can be automatically filtered out, thereby ensuring that the two sets of data used for solving the simultaneous equations have sufficient independence, effectively improving the effectiveness and reliability of impedance calculation results.

[0092] In other embodiments, obtaining the current voltage output by the PID module after the PID module adjusts its output voltage, the current DC bus voltage to ground, and the current bus voltage includes: The first current voltage output by the PID module, the first current voltage to ground of the DC bus, and the first current bus voltage are obtained after the PID module adjusts its output voltage once.

[0093] The second current voltage output by the PID module after another adjustment of its output voltage, the second current voltage to ground of the DC bus, and the second current bus voltage are obtained.

[0094] Based on the target equation, current voltage, current voltage to ground, and current bus voltage, determine the impedance value of the DC side to ground impedance, including...

[0095] Based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the second current voltage, the second current voltage to ground, and the second current bus voltage, determine the impedance value of the DC side to ground impedance.

[0096] In some implementations, the impedance value of the DC side to ground impedance is determined based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the second current voltage, the second current voltage to ground, and the second current bus voltage, including: Substituting the first current voltage, the first current voltage to ground, and the first current bus voltage into the objective equation, we obtain the first equation.

[0097] Substituting the second current voltage, the second current voltage to ground, and the second current bus voltage into the objective equation yields the third equation.

[0098] Solve the first and third equations simultaneously to obtain the positive and negative ground impedances of the DC side.

[0099] The impedance value of the DC side to ground is determined based on the positive impedance to ground and the negative impedance to ground.

[0100] For example, after adjusting its output voltage once, the PID module can acquire the first current voltage output by the PID module, the first current voltage to ground of the DC bus, and the first current bus voltage at a first time t1. After adjusting its output voltage again, the PID module can acquire the second current voltage output by the PID module, the second current voltage to ground of the DC bus, and the second current bus voltage at a second time t2. Accordingly, the step "acquiring the current voltage output by the PID module, the current voltage to ground of the DC bus, and the current bus voltage after the PID module adjusts its output voltage" may include: acquiring the first current voltage V1 at the first time. First current voltage to ground V2 First current bus voltage V3 ; and obtain the second current voltage V1 at the second time t2. Second current ground voltage V2 Second current bus voltage V3 .

[0101] The first moment and the second moment can correspond to the moment when the output voltage of the PID module is disturbed to two different voltage values.

[0102] The step "Determine the impedance value of the DC side to ground based on the target equation, current voltage, current voltage to ground, and current bus voltage" can specifically include: Based on the objective equation and the first current voltage V1 First current voltage to ground V2 First current bus voltage V3 Second current voltage V1 The second current ground voltage V2 and the second current bus voltage V3 are used to determine the ground impedance.

[0103] Specifically, the calculation process can be: (V1) V2 V3 Substituting (V1) into the objective equation (1), we obtain the first equation; V2 V3 Substituting into the objective equation (1), we obtain the third-party equation.

[0104] Then, the first and third equations are solved simultaneously to obtain the ground impedances R2 and R3. Next, the parallel value of R2 and R3 can be calculated and used as the ground impedance value of the DC side.

[0105] In this embodiment, the impedance to ground is calculated using voltage information collected during voltage disturbances. This allows insulation impedance detection to be performed independently, even when the PID module is in a dynamic adjustment phase or when the target voltage value itself may change, without relying on a fixed target steady-state data as a reference. This makes the detection of impedance to ground more flexible and broadens the applicable scenarios of this solution.

[0106] Furthermore, in some implementations, the dual perturbation point calculation method in this embodiment can be combined with the validity threshold judgment in the aforementioned embodiments to simultaneously achieve the dual effects of computational flexibility and result reliability.

[0107] The foregoing embodiments mainly illustrate the core method in a single inverter application scenario. To clarify the specific application of this core inventive concept in complex photovoltaic system architectures and enhance the engineering practical value of the method, this application also provides specific embodiments for various system topologies.

[0108] In some implementations, there are multiple inverters and one PID module.

[0109] Multiple inverters are connected in parallel on their DC sides.

[0110] The DC side of any one of the multiple inverters is connected to the PID module.

[0111] For example, such as Figure 7 As shown, Figure 7The diagram illustrates a multi-inverter parallel system topology (Scenario 1) according to an embodiment of this application. In this embodiment, there are multiple inverters and one PID module. The DC sides of the multiple inverters are connected in parallel and share the same DC bus. A single PID module is connected to this DC bus. Among the multiple inverters, any controller within one inverter can be designated to perform the aforementioned calculation of the ground impedance, or a single master controller can be responsible for it. Since all inverters are connected in parallel on their DC sides, they share the same DC bus and ground impedance. In practical applications, when the inverters in this embodiment are in grid-connected mode, voltage perturbation can be applied and sampled using the single PID module to obtain the system ground impedance of the entire inverter system. When the inverters in this embodiment are in shutdown mode, voltage perturbation can be applied and sampled using the single PID module to obtain the ground impedance of the parallel DC sides of the multiple inverters. The specific implementation method for obtaining the DC side ground impedance value by applying voltage perturbation and sampling using the PID module can be found in the above embodiment and will not be repeated here.

[0112] As can be seen, this embodiment can achieve system-level insulation monitoring with the lowest hardware cost, and is suitable for centralized or string inverter systems connected in parallel on the DC side.

[0113] In some implementations, there are multiple inverters and multiple PID modules.

[0114] The AC sides of multiple inverters are isolated from each other, and the AC sides of multiple inverters are connected in parallel. Each inverter has a PID module connected to its DC side.

[0115] For example, such as Figure 8 As shown, Figure 8 The diagram illustrates a multi-inverter parallel system topology (Scenario 2) according to another embodiment of this application. In this embodiment, there are multiple inverters and multiple PID modules. The DC sides of the multiple inverters are isolated from each other (i.e., each inverter is connected to an independent photovoltaic string), while their AC sides are connected in parallel. Each inverter's DC side is connected to an independent PID module. At this time, each inverter can independently execute the aforementioned concurrency and insulation detection methods. When the inverters are shut down (not connected to the grid), each inverter unit can independently detect its own DC input side's impedance to ground. This enables independent insulation health status monitoring for each inverter unit.

[0116] In some implementations, there are multiple inverters and one PID module.

[0117] The AC sides of multiple inverters are isolated from each other, and the AC sides of multiple inverters are connected in parallel.

[0118] The DC side of any one of the multiple inverters is connected to the PID module.

[0119] For example, such as Figure 9 As shown, Figure 9 The diagram shows a multi-inverter parallel system topology (Scenario 3) according to yet another embodiment of this application. In this embodiment, there are multiple inverters and one PID module.

[0120] Multiple inverters have their DC sides isolated from each other, while their AC sides are connected in parallel. A PID module is connected to the DC side of any one of the inverters. This inverter with the PID module can execute the concurrent detection method of this scheme. When the inverter is in a shutdown state, it can detect the ground impedance of its DC side connected to the inverter. During grid-connected operation, the voltage disturbance applied by the PID module is used to obtain the system ground impedance of the entire inverter system, realizing system-level insulation detection under grid-connected conditions. This allows the scheme of this implementation to achieve a balance between hardware cost and system-level detection capability.

[0121] In other implementations, there are multiple inverters and multiple PID modules, with the number of PID modules being less than the number of inverters. The AC sides of the multiple inverters are isolated from each other and connected in parallel. Each PID module is connected to the DC side of one of the multiple inverters, and at most one PID module is connected to the DC side of each inverter.

[0122] For example, in practical applications, when the inverter is in a shutdown state, each PID module can detect the DC-side impedance to ground of the inverter to which the PID module is connected by applying a voltage disturbance, thereby obtaining a portion of the DC-side impedance to ground of the inverter.

[0123] In summary, the inverter system provided in this embodiment achieves parallel operation of the PID function and insulation detection by applying periodic, small-amplitude perturbations to the output voltage of the PID module during normal operation and solving for the ground impedance based on the electrical parameters before and after the perturbation. Furthermore, this inverter system requires no additional hardware, reducing system costs. In addition, it can achieve near 24-hour continuous insulation monitoring, improving system safety. Moreover, it is compatible with various system topologies, offering strong applicability; and its detection accuracy is controllable, does not affect the normal function of the PID module, and is easy to implement in engineering.

[0124] An embodiment of the present invention provides a control method for an inverter system. This control method can be applied to the inverter system in any of the above embodiments, specifically to the controller in the inverter system. For example... Figure 10 As shown, the method may include: 410. When the PID module adjusts the DC bus voltage to ground to the target voltage by outputting the target voltage, the PID module is controlled to adjust its output voltage at least once according to a preset cycle, and the adjusted output voltage fluctuates within a preset range relative to the target voltage.

[0125] 420. Obtain the current voltage output by the PID module after adjusting its output voltage, the current ground voltage of the DC bus, and the current bus voltage.

[0126] 440. Determine the impedance value of the DC side to ground based on the current voltage, the current voltage to ground, and the current bus voltage.

[0127] For details on the specific implementation of the control method of the above inverter system, please refer to the implementation process of the working principle of the inverter system in the above embodiments, which will not be repeated here.

[0128] Figure 11 The diagram shown is a block diagram of a control device for an inverter system according to an embodiment of the present invention. The inverter system includes an inverter, a PID module, and a controller; the DC side of the inverter is connected to the DC bus; the PID module is connected to the negative or positive terminal of the DC bus; the controller is connected to the PID module; as shown... Figure 11 As shown, the control device 500 of the inverter system may include: The control unit 510 is used to control the PID module to adjust its output voltage at least once according to a preset cycle when the PID module adjusts the DC bus voltage to the target voltage by outputting the target voltage, and the adjusted output voltage fluctuates within a preset range relative to the target voltage. The acquisition unit 520 is used to acquire the current voltage output by the PID module after the PID module adjusts its output voltage, the current ground voltage of the DC bus, and the current bus voltage. The determining unit 530 is used to determine the impedance value of the DC side to ground impedance based on the current voltage, the current voltage to ground, and the current bus voltage.

[0129] For example, in practical applications, the control unit can specifically employ a microcontroller, digital signal processor, field-programmable gate array (FPGA), or application-specific integrated circuit (ASIC). It generates periodic voltage regulation signals through its internal timer and PWM output module, which then control the PID module via a drive circuit. The acquisition unit can specifically employ a resistor divider network, an isolation amplifier, and an analog-to-digital converter (ADC) (integrated within the microcontroller or FPGA, or as a separate chip) to acquire the voltage signal. The determination unit can specifically employ the computational core within a microcontroller, FPGA, or ASIC to solve for the impedance value by running a calculation program or using embedded logic.

[0130] The specific implementation process of the functions and roles of each module in the above device can be found in the implementation process of the corresponding steps of the control method of the inverter system in the above embodiments, and will not be repeated here.

[0131] An embodiment of the present invention also provides a photovoltaic system, which includes the inverter system in the above embodiment. The inverter system can be connected to a DC source and a load respectively. Specifically, the DC source can be a photovoltaic energy storage battery, a photovoltaic panel or other photovoltaic module, and the load can be the power grid.

[0132] Figure 12 The diagram shown is a block diagram of an electronic device 600 provided in an embodiment of the present invention.

[0133] Reference Figure 12 The electronic device 600 includes a processing component 610, which further includes one or more processors, and memory resources represented by memory 620 for storing instructions, such as application programs, that can be executed by the processing component 610. The application programs stored in memory 620 may include one or more modules, each corresponding to a set of instructions. Furthermore, the processing component 610 is configured to execute instructions to perform the control methods of the inverter system described above.

[0134] Electronic device 600 may also include a power supply component configured to perform power management of electronic device 600, a wired or wireless network interface configured to connect electronic device 600 to a network, and an input / output (I / O) interface. Electronic device 600 may operate on an operating system stored in memory 620, such as Windows Server™, Mac OSX™, Unix™, Linux™, FreeBSD™, or similar.

[0135] A non-transitory computer-readable storage medium, wherein when the instructions in the storage medium are executed by the processor of the aforementioned electronic device 600, the aforementioned electronic device 600 is able to execute the control method of the aforementioned inverter system.

[0136] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0137] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0138] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0139] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0140] In addition, each PID module in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0141] If the aforementioned function is implemented as a software PID module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program checksums, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0142] Furthermore, it should be noted that the combination of the various technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0143] It should be noted that the above examples are merely specific embodiments of the present invention, and the present invention is obviously not limited to the above embodiments, with many similar variations. All modifications that can be directly derived or conceived by those skilled in the art from the content disclosed in this invention should fall within the protection scope of this invention.

[0144] It should be understood that the terms "first," "second," etc., mentioned in the embodiments of the present invention are merely for the purpose of more clearly describing the use of the technical solutions in the embodiments of the present invention, and are not intended to limit the scope of protection of the present invention.

[0145] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications or equivalent substitutions made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An inverter system, characterized in that, include: The system includes an inverter, a PID module, and a controller; the DC side of the inverter is connected to a DC bus; the PID module is connected to the negative or positive terminal of the DC bus; and the controller is connected to the PID module. The controller is configured as follows: When the PID module adjusts the DC bus voltage to ground to the target voltage by outputting the target voltage, the PID module is controlled to adjust its output voltage at least once according to a preset cycle, and the adjusted output voltage fluctuates within a preset range relative to the target voltage. The current voltage output by the PID module after the PID module adjusts its output voltage, the current voltage to ground of the DC bus, and the current bus voltage are obtained. The impedance value of the DC side to ground is determined based on the current voltage, the current voltage to ground, and the current bus voltage.

2. The inverter system according to claim 1, characterized in that, Determining the impedance value of the DC side to ground based on the current voltage, the current voltage to ground, and the current bus voltage includes: Based on the circuit topology of the PID module, the impedance value of the DC side to ground is determined according to the current voltage, the current voltage to ground, and the current bus voltage.

3. The inverter system according to claim 2, characterized in that, The circuit topology based on the PID module determines the impedance value of the DC side to ground based on the current voltage, the current voltage to ground, and the current bus voltage, including: Obtain the target equation, which is an equation constructed based on the circuit topology of the PID module with the impedance to ground as the unknown; The impedance value of the DC side to ground is determined based on the target equation, the current voltage, the current voltage to ground, and the current bus voltage.

4. The inverter system according to claim 3, characterized in that, The process of obtaining the current voltage output by the PID module after the PID module adjusts its output voltage, the current voltage to ground of the DC bus, and the current bus voltage includes: The first current voltage output by the PID module after the PID module adjusts its output voltage once, the first current voltage to ground of the DC bus, and the first current bus voltage are obtained. The step of determining the impedance value of the DC side to ground impedance based on the target equation, the current voltage, the current voltage to ground, and the current bus voltage includes: Obtain the target bus voltage of the DC bus when the PID module outputs the target voltage; The impedance value of the DC side to ground is determined based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the target voltage, the target voltage to ground, and the target bus voltage.

5. The inverter system according to claim 4, characterized in that, The step of determining the impedance value of the DC side to ground impedance based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the target voltage, the target voltage to ground, and the target bus voltage includes: Substituting the first current voltage, the first current voltage to ground, and the first current bus voltage into the target equation, we obtain the first equation; Substituting the target voltage, the target voltage to ground, and the target bus voltage into the target equation yields the second equation; Solve the first and second equations simultaneously to obtain the positive and negative ground impedances of the DC side; The impedance value of the DC side to ground is determined based on the positive impedance to ground and the negative impedance to ground.

6. The inverter system according to claim 5, characterized in that, The PID module includes a current-limiting impedance and an adjustable power supply, and the DC bus voltage to ground includes the negative terminal voltage of the DC bus to ground. The negative terminal of the DC bus is grounded through the negative ground impedance, and the current limiting impedance is connected in series with the adjustable power supply and then in parallel with the negative ground impedance. The positive terminal of the DC bus is grounded through the grounding impedance; The expression for the objective equation is: V0=Upv- [(R1+R3) R2+R1 R3] / R2 R3+Vbus R1 / R3; Wherein, V0 is the output voltage of the PID module, Upv- is the negative voltage to ground of the DC bus, R1 is the impedance value of the current limiting impedance, R2 is the impedance value of the positive impedance to ground, R3 is the impedance value of the negative impedance to ground, and Vbus is the bus voltage of the DC bus.

7. The inverter system according to claim 4, characterized in that, The controller is also configured to: Calculate the absolute value of the difference between the first current voltage and the target voltage to obtain the first absolute value; Calculate the absolute value of the difference between the first current ground voltage and the target ground voltage to obtain the second absolute value; If the first absolute value is greater than the first threshold, and / or the second absolute value is greater than the second threshold, then the step of determining the impedance value of the DC side to ground impedance based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the target voltage, the target voltage to ground, and the target bus voltage is executed.

8. The inverter system according to claim 3, characterized in that, The process of obtaining the current voltage output by the PID module after the PID module adjusts its output voltage, the current voltage to ground of the DC bus, and the current bus voltage includes: The first current voltage output by the PID module after the PID module adjusts its output voltage once, the first current voltage to ground of the DC bus, and the first current bus voltage are obtained. The second current voltage output by the PID module after another adjustment of its output voltage, the second current voltage to ground of the DC bus and the second current bus voltage are obtained. The step of determining the impedance value of the DC side to ground impedance based on the target equation, the current voltage, the current voltage to ground, and the current bus voltage includes: The impedance value of the DC side to ground is determined based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the second current voltage, the second current voltage to ground, and the second current bus voltage.

9. The inverter system according to claim 8, characterized in that, The step of determining the impedance value of the DC side to ground impedance based on the target equation, the first current voltage, the first current voltage to ground, the first current bus voltage, the second current voltage, the second current voltage to ground, and the second current bus voltage includes: Substituting the first current voltage, the first current voltage to ground, and the first current bus voltage into the target equation, we obtain the first equation; Substituting the second current voltage, the second current voltage to ground, and the second current bus voltage into the target equation yields the third equation; Solve by combining the first equation and the third equation to obtain the positive and negative impedances to ground on the DC side; The impedance value of the DC side to ground is determined based on the positive impedance to ground and the negative impedance to ground.

10. The inverter system according to any one of claims 1 to 9, characterized in that, The number of inverters is multiple, and the number of PID modules is one; The DC sides of multiple inverters are connected in parallel. The DC side of any one of the multiple inverters is connected to the PID module.

11. The inverter system according to any one of claims 1 to 9, characterized in that, The number of inverters is multiple, and the number of PID modules is less than or equal to the number of inverters; The DC sides of the multiple inverters are isolated from each other, and the AC sides of the multiple inverters are connected in parallel. Each of the PID modules is connected to the DC side of one of the plurality of inverters, and at most one of the PID modules is connected to the DC side of each inverter.

12. A control method for an inverter system, characterized in that, The inverter system includes: an inverter, a PID module, and a controller; the DC side of the inverter is connected to a DC bus; the PID module is connected to the negative or positive terminal of the DC bus; the controller is connected to the PID module; the control method includes: When the PID module adjusts the DC bus voltage to ground to the target voltage by outputting the target voltage, the PID module is controlled to adjust its output voltage at least once according to a preset cycle, and the adjusted output voltage fluctuates within a preset range relative to the target voltage. The current voltage output by the PID module after the PID module adjusts its output voltage, the current voltage to ground of the DC bus, and the current bus voltage are obtained. The impedance value of the DC side to ground is determined based on the current voltage, the current voltage to ground, and the current bus voltage.

13. A control device for an inverter system, characterized in that, The inverter system includes: an inverter, a PID module, and a controller; the DC side of the inverter is used to connect to a DC bus; the PID module is connected to the negative or positive terminal of the DC bus; the controller is connected to the PID module; the control device includes: The control unit is configured to, when the PID module adjusts the DC bus voltage to ground to the target voltage by outputting the target voltage, control the PID module to adjust its output voltage at least once according to a preset cycle, and the adjusted output voltage fluctuates within a preset range relative to the target voltage. The acquisition unit is used to acquire the current voltage output by the PID module after the PID module adjusts its output voltage, the current voltage to ground of the DC bus, and the current bus voltage. The determining unit is used to determine the impedance value of the DC side to ground impedance based on the current voltage, the current voltage to ground, and the current bus voltage.

14. A photovoltaic system, characterized in that, The photovoltaic system includes the inverter system as described in any one of claims 1 to 11.

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