Asymmetric state compensation system of photovoltaic inverter

Abstract

The utility model discloses an asymmetric state compensation system of a photovoltaic inverter, comprising a compensation control module, a state induction module, a PWM module and a photovoltaic inverter, the compensation control module is connected with the state induction module, the PWM module and a power grid, the state induction module is connected with the photovoltaic inverter, the PWM module is connected with the photovoltaic inverter, and the photovoltaic inverter is connected with the power grid; the compensation control module comprises a phase synchronization unit, a power control unit and a current control unit, the phase synchronization unit is connected with the power grid and the power control unit, the power control unit is connected with the current control unit, and the current control unit is connected with the PWM module. According to the utility model, the phase synchronization unit, the power control unit and the current control unit are arranged to compensate the asymmetric state of the photovoltaic inverter from three aspects of phase synchronization, power control and current control, thereby effectively optimizing the asymmetric fault prevention capability of the photovoltaic inverter and the quality of output electric energy, and improving the power generation efficiency.

Description

TECHNICAL FIELD

[0001] The utility model relates to photovoltaic inverter technical field especially relates to an asymmetric state compensation system of photovoltaic inverter. BACKGROUND

[0002] Photovoltaic grid-connected power generation is an important direction of solar energy application, and is also the main way of solar energy from supplementary energy to alternative energy. Among them, the inverter is an important core component of photovoltaic grid-connected power generation system, which can convert the direct current power output by the solar cell module into alternating current power, and apply it to the power grid in China. The performance directly determines the power generation level of the photovoltaic grid-connected power generation system.

[0003] The traditional photovoltaic inverter control strategy is to run under the condition of adapting to three-phase symmetrical power grid, but in actual application, due to the use of some high-power loads or the fault of power grid equipment itself, the power grid will appear three-phase asymmetric state, which will lead to the reduction of output power quality and the low power generation efficiency. UTILITY MODEL CONTENTS

[0004] The utility model discloses a photovoltaic inverter's asymmetric state compensation system, sets up phase synchronization unit, power control unit, current control unit, and respectively from phase synchronization, power control and current control three aspects to the asymmetric state of photovoltaic inverter compensation, effectively optimizes the anti-asymmetric fault ability of photovoltaic inverter and the quality of output electric energy, improves power generation efficiency.

[0005] The utility model provides a photovoltaic inverter's asymmetric state compensation system, the system includes compensation control module, state response module, PWM module, photovoltaic inverter, compensation control module connects state response module, PWM module and power grid, state response module connects photovoltaic inverter, PWM module connects photovoltaic inverter, photovoltaic inverter connects power grid;

[0006] The compensation control module includes phase synchronization unit, power control unit, current control unit, the input of phase synchronization unit is connected with power grid, the output of phase synchronization unit is connected with the input of power control unit, the output of power control unit is connected with the input of current control unit, the output of current control unit is connected with PWM module.

[0007] Further, the phase synchronization unit comprises a decomposition unit, a decoupling unit and a filter unit, an input end of the decomposition unit is connected with the power grid, an output end of the decomposition unit is connected with an input end of the decoupling unit, an output end of the decoupling unit is connected with an input end of the filter unit, and an output end of the filter unit is connected with an input end of the power control unit.

[0008] Further, the decoupling unit comprises a positive sequence decoupling unit and a negative sequence decoupling unit, and the positive sequence decoupling unit and the negative sequence decoupling unit are arranged in parallel.

[0009] Further, the photovoltaic inverter comprises an inverter unit, a direct current bus, a direct current processing module and an alternating current processing module, an output end of the direct current processing module is connected with an input end of the direct current bus, an output end of the direct current bus is connected with an input end of the inverter unit, an output end of the inverter unit is connected with an input end of the alternating current processing module, and an output end of the alternating current processing module is connected with an output end of the photovoltaic inverter.

[0010] Further, the system further comprises a switch module, and the switch module is arranged on a connecting line between the photovoltaic inverter and the power grid.

[0011] Further, a lightning protection device is arranged between the switch module and the photovoltaic inverter.

[0012] Further, the system further comprises an isolation module, and the isolation module is arranged on a connecting line between the compensation control module and the power grid.

[0013] Further, the system further comprises a leakage current detection module, and the leakage current detection module is arranged at an output end of the photovoltaic inverter.

[0014] Further, the system further comprises an insulation detection module, and the insulation detection module is arranged at an output end of the photovoltaic inverter.

[0015] Further, the system further comprises an anti-islanding effect module, and the anti-islanding effect module is arranged on a connecting line between the photovoltaic inverter and the power grid.

[0016] The utility model provides a kind of asymmetric state compensation system of photovoltaic inverter, setting by phase synchronization unit, power control unit and current control unit the compensation control module of composition, through the electric energy data that state sensing module real-time collection is analyzed, respectively from phase synchronization, power control and current control three aspects to the asymmetric state of photovoltaic inverter is compensated, effectively optimize the anti-asymmetric fault capability of photovoltaic inverter and the quality of output electric energy, improve power generation efficiency;In addition, there are switch module, lightning protection device, isolation module, leakage current detection module, insulation detection module and anti-islanding effect module, effectively improve the security and stability of system operation. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical scheme in the embodiments of the utility model or prior art, the drawings needed to be used in the following embodiment or prior art description will be briefly introduced, obviously, the drawings in the following description are only some embodiments of the utility model, and for those skilled in the art, other drawings can be obtained without creative labor on the premise.

[0018] Figure 1 It is the asymmetric state compensation system module architecture diagram of photovoltaic inverter in the embodiments of the utility model;

[0019] Figure 2 It is the asymmetric state compensation system circuit principle diagram of photovoltaic inverter in the embodiments of the utility model. DETAILED DESCRIPTION

[0020] The technical scheme in the embodiments of the utility model will be clearly and completely described in the following by combining with the drawings in the embodiments of the utility model, obviously, the described embodiments are only some embodiments of the utility model, not all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the utility model.

[0021] In the utility model, it should be understood that terms such as "include" or "have" are intended to indicate the existence of features, numbers, steps, acts, components, parts or combinations thereof disclosed in the specification, and not to exclude the possibility of existence or addition of one or more other features, numbers, steps, acts, components, parts or combinations thereof.

[0022] In addition, it also needs to be explained that the embodiments in the utility model and the features in the embodiments can be combined with each other without conflict. The utility model will be described in detail below with reference to the drawings and in combination with embodiments.

[0023] The utility model embodiment provides a kind of asymmetric state compensation system of photovoltaic inverter, the system includes compensation control module, state induction module, PWM module, photovoltaic inverter.

[0024] In one optional implementation of the embodiment, as shown in Figure 1 Figure 1 The utility model embodiment shows the asymmetric state compensation system module architecture diagram of photovoltaic inverter, the system includes compensation control module, state induction module, PWM module, photovoltaic inverter, wherein the compensation control module is connected the state induction module, PWM module and power grid, the state induction module is connected the photovoltaic inverter, the PWM module is connected the photovoltaic inverter, and the photovoltaic inverter is connected power grid.

[0025] In one optional implementation of the embodiment, the compensation control module is used to analyze the electric energy data collected by the state induction module, generates phase synchronization signal, power control signal and current control signal respectively based on the control strategy under static coordinate system, and sends the phase synchronization signal, power control signal and current control signal to the PWM module.

[0026] In one optional implementation of the embodiment, the phase synchronization unit includes decomposition unit, decoupling unit and filter unit, the input end of the decomposition unit is connected with power grid, the output end of the decomposition unit is connected with the input end of the decoupling unit, the output end of the decoupling unit is connected with the input end of the filter unit, and the output end of the filter unit is connected with the input end of the power control unit.

[0027] Specifically, the phase synchronization unit adopts the control strategy of three-phase frequency locked loop (Dual Second-Order General Integrator-based Frequency Locked Loop, DSOGL-FLL) based on double second-order generalized integrator, which mainly takes the grid voltage frequency as the direct control object under the static coordinate system, transforms the positive sequence component and the negative sequence component of the grid voltage frequency simultaneously by using the decomposition unit, decomposes them into the components of positive sequence and negative sequence under d, q coordinate system, and constructs the virtual orthogonal signal of voltage under the static coordinate system based on the decoupling unit composed of two second-order generalized integrators through decoupling operation, generates phase synchronization signal based on the frequency locked loop after filtering based on the filter unit, and then realizes the synchronous operation of three-phase grid.

[0028] ​Compared with the traditional control strategy of three-phase phase-locked loop based on rotating coordinate system (Direct Digital Synthesizer with Rotating Frame Phase-Locked Loop, DDRF-PLL), the structure is simpler, the frequency tracking response is faster, and the overall synchronization efficiency is higher.

[0029] In an optional implementation of the embodiment, the decoupling unit comprises a positive sequence decoupling unit and a negative sequence decoupling unit, and the positive sequence decoupling unit and the negative sequence decoupling unit are arranged in parallel.

[0030] Specifically, the positive sequence decoupling unit and the negative sequence decoupling unit are second-order generalized integrators (SOGI) arranged in parallel, the positive sequence decoupling unit is used for decoupling the positive sequence component, and the negative sequence decoupling unit is used for decoupling the negative sequence component.

[0031] In an optional implementation of the embodiment, the power control unit is used for stabilizing control of transient power when an asymmetric fault occurs in the power grid, to generate a power control signal.

[0032] Specifically, the power control unit sets one of an active power reference value and a reactive power reference value in the transient power of the power grid as a zero reference, generates the power control signal according to the relationship between the current value of the positive sequence component and the negative sequence component of the power grid voltage vector and the 90-degree lagging quadrature component value.

[0033] In an optional implementation of the embodiment, the current control unit is used for controlling the power grid current to generate a current control signal.

[0034] Specifically, the current control unit is provided with an alternating current proportional resonant controller (PR controller), which directly tracks the alternating current in the power grid, and compared with a direct current controller (PI controller), the control efficiency and control accuracy are higher in the application scenario of the alternating current power grid.

[0035] In an optional implementation of the embodiment, the state sensing module is used for collecting power data, including voltage data, current data, power data, etc., and transmitting the collected data to the compensation control module as data support.

[0036] In an optional implementation of the embodiment, the PWM module is a PWM power driving module (Pulse Width Modulation), configured to receive the phase synchronization signal, the power control signal and the current control signal sent by the compensation control module, and generate a driving signal to drive the photovoltaic inverter to implement control.

[0037] In an optional implementation of the embodiment, the photovoltaic inverter comprises an inverter unit, a DC bus, a DC power processing module and an AC power processing module, the output end of the DC power processing module is connected to the input end of the DC bus, the output end of the DC bus is connected to the input end of the inverter unit, the output end of the inverter unit is connected to the input end of the AC power processing module, and the output end of the AC power processing module is connected to the output end of the photovoltaic inverter.

[0038] Specifically, the DC power processing module is configured to process a DC input power, the inverter unit and the DC bus are configured to convert the DC power into AC power, and the AC power processing module is configured to process an AC output point.

[0039] In an optional implementation of the embodiment, the system further comprises a switch module, which is arranged on a connection line between the photovoltaic inverter and the power grid.

[0040] Specifically, the switch module is composed of a copper bar and a power distribution unit (PDU), and is configured to realize a system circuit switching function.

[0041] In an optional implementation of the embodiment, a lightning protection device is arranged between the switch module and the photovoltaic inverter.

[0042] In an optional implementation of the embodiment, the system further comprises an isolation module, which is arranged on a connection line between the compensation control module and the power grid.

[0043] Specifically, the isolation module is configured to isolate electrical connection between an electric energy transmission line and a signal transmission line.

[0044] In an optional implementation of the embodiment, the system further comprises a leakage current detection module, which is arranged at the output end of the photovoltaic inverter.

[0045] Specifically, the leakage current detection module is a SEL sensor, and is configured to detect a leakage current of the system.

[0046] In an optional implementation of the embodiment, the system further comprises an insulation detection module, which is arranged at an output end of the photovoltaic inverter.

[0047] Specifically, the insulation detection module comprises a reference resistance group, a resistance group to be measured, and an ISO power supply, the resistance value of the resistance group to be measured is calculated by the resistance value of the reference resistance group, the voltage value of the ISO power supply, and the voltage value of the three-phase power grid to ground, and whether insulation is present is determined based on a comparison between the resistance value of the resistance group to ground and a preset threshold.

[0048] In an optional implementation of the embodiment, the system further comprises an anti-islanding effect module, which is arranged on a connection line between the photovoltaic inverter and the power grid.

[0049] Specifically, the anti-islanding effect module is composed of an inductor, a capacitor, and a resistor connected in parallel and grounded, and a kind of active islanding detection algorithm and a kind of passive islanding detection algorithm are respectively preset, wherein the active islanding detection algorithm indirectly causes the power grid frequency to deviate by controlling the reactive current, and whether islanding effect occurs is determined by the deviation amount, and the passive islanding detection algorithm detects the voltage and frequency output by the inverter, and determines whether islanding effect occurs when the overvoltage and underfrequency thresholds are triggered.

[0050] In summary, the embodiment of the utility model provides an asymmetric state compensation system of photovoltaic inverter, sets up the compensation control module composed of phase synchronization unit, power control unit and current control unit, through the analysis of the electric energy data collected by the state sensing module in real time, the asymmetric state of photovoltaic inverter is compensated from three aspects of phase synchronization, power control and current control, effectively optimizes the anti-asymmetric fault capability of photovoltaic inverter and the quality of output electric energy, improves the power generation efficiency, in addition, the switch module, lightning protection device, isolation module, leakage current detection module, insulation detection module and anti-islanding effect module are arranged, effectively improve the safety and stability of system operation.

[0051] The asymmetric state compensation system of photovoltaic inverter provided by the embodiment of the utility model is introduced in detail, the principle and implementation mode of the utility model are described by using specific examples in this paper, the above embodiment is only used to help understand the method and core idea of the utility model; at the same time, for the general technical personnel in the field, according to the idea of the utility model, the specific implementation mode and application range will be changed, and the above description should not be understood as the limitation of the utility model.

Claims

1. An asymmetric state compensation system for a photovoltaic inverter, characterized by, The system comprises a compensation control module, a state sensing module, a PWM module, a photovoltaic inverter, the compensation control module is connected with the state sensing module, the PWM module and a power grid, the state sensing module is connected with the photovoltaic inverter, the PWM module is connected with the photovoltaic inverter, and the photovoltaic inverter is connected with the power grid. The compensation control module comprises a phase synchronization unit, a power control unit and a current control unit, an input end of the phase synchronization unit is connected with the power grid, an output end of the phase synchronization unit is connected with an input end of the power control unit, an output end of the power control unit is connected with an input end of the current control unit, and an output end of the current control unit is connected with the PWM module.

2. The asymmetrical state compensation system for a photovoltaic inverter of claim 1, wherein, The phase synchronization unit comprises a decomposition unit, a decoupling unit and a filter unit, an input end of the decomposition unit is connected with the power grid, an output end of the decomposition unit is connected with an input end of the decoupling unit, an output end of the decoupling unit is connected with an input end of the filter unit, and an output end of the filter unit is connected with an input end of the power control unit.

3. The asymmetrical state compensation system for a photovoltaic inverter of claim 2, wherein, The decoupling unit comprises a positive sequence decoupling unit and a negative sequence decoupling unit, and the positive sequence decoupling unit and the negative sequence decoupling unit are arranged in parallel.

4. The asymmetrical state compensation system for a photovoltaic inverter of claim 1, wherein, The photovoltaic inverter comprises an inverter unit, a direct current bus, a direct current processing module and an alternating current processing module, an output end of the direct current processing module is connected with an input end of the direct current bus, an output end of the direct current bus is connected with an input end of the inverter unit, an output end of the inverter unit is connected with an input end of the alternating current processing module, and an output end of the alternating current processing module is connected with an output end of the photovoltaic inverter.

5. The asymmetrical state compensation system of a photovoltaic inverter of claim 1, wherein, The system further comprises a switch module, and the switch module is arranged on a connecting line between the photovoltaic inverter and the power grid.

6. The asymmetrical state compensation system of a photovoltaic inverter of claim 5, wherein, A lightning protection device is arranged between the switch module and the photovoltaic inverter.

7. The asymmetrical state compensation system of a photovoltaic inverter of claim 1, wherein, The system further comprises an isolation module, and the isolation module is arranged on a connecting line between the compensation control module and the power grid.

8. The asymmetrical state compensation system of a photovoltaic inverter of claim 1, wherein, The system further comprises a leakage current detection module, and the leakage current detection module is arranged at an output end of the photovoltaic inverter.

9. The asymmetrical state compensation system of a photovoltaic inverter of claim 1, wherein, The system further comprises an insulation detection module, and the insulation detection module is arranged at the output end of the photovoltaic inverter.

10. The asymmetrical state compensation system of a photovoltaic inverter of claim 1, wherein, The system further comprises an anti-island effect module, and the anti-island effect module is arranged on a connecting line between the photovoltaic inverter and the power grid.

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