Power grid simulation device considering simulation test precision

Abstract

A power grid simulation device considering simulation test precision mainly comprises a switch module, a voltage reduction and transformation module, a converter assembly and an electronic load, and the converter assembly comprises a rectification part, an inversion part and a conversion part; wherein the inversion part adopts a three-phase four-bridge-arm type structure and performs positive and negative zero-sequence closed-loop control on output voltage and / or output current, and the converter part preferably adopts a CLLC type resonant converter structure and can realize high-precision voltage / current simulation.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of power grid simulation test, especially relates to a power grid simulation device considering simulation test accuracy. BACKGROUND

[0002] The power grid simulator is widely applied grid-connected equipment and grid connection test device, can simulate the output of alternating current or direct current voltage under different conditions, simulates the power consumption environment of different kinds of equipment to carry out relevant tests, such as photovoltaic inverter, energy storage converter, etc. But most of the converters may appear voltage change frequently and persistently, and dramatic change at a specific time during operation, which is mainly due to load fluctuation, external environment and other factors.

[0003] Due to the characteristics of large voltage variation range and low energy density of the power grid simulator, high precision of output voltage variation needs to be ensured during simulation test to ensure the accuracy of grid-connected device simulation test results. SUMMARY

[0004] In view of the above situation, the power grid simulation device considering simulation test accuracy is provided, the topology structure and control mode of the inverter part of the power grid simulator are optimized and improved, three-phase four-bridge arm topology and positive and negative zero sequence closed-loop feedback control are adopted, the extraction precision of output voltage and output current positive and negative sequence components is improved, compared with the existing power grid simulator product, the simulation accuracy of the power grid simulator can be effectively improved.

[0005] The power grid simulation device considering simulation test accuracy provided by the present disclosure mainly comprises: a switch module, a step-down transformer module, a converter assembly and an electronic load, wherein:

[0006] The switch module is used to control the connection and disconnection of the power grid simulation device and the power supply grid.

[0007] The step-down transformer module is used to reduce the high voltage of the power grid to a suitable voltage for power supply or feedback of the converter.

[0008] The converter assembly comprises a rectifier part, an inverter part and a conversion part, wherein:

[0009] The rectifier part is used to output stable direct current voltage to the subsequent inverter part and conversion part.

[0010] The inverter part is used to output controllable alternating current voltage.

[0011] The converter part is used to output controllable direct current voltage.

[0012] The electronic load is used to simulate resistive load, capacitive load and inductive load.

[0013] The inverter part adopts a three-phase four-bridge arm structure, and is used for positive, negative and zero sequence closed-loop control of output voltage and / or output current.

[0014] Further, the inverter part comprises a DDSRF-PLL three-phase phase-locked loop circuit, a PR proportional resonance regulation module and a 3D-SVPWM three-dimensional space vector pulse width modulation module, wherein: the DDSRF-PLL three-phase phase-locked loop circuit is used to extract positive, negative and zero sequence components of the output voltage and the output current, and is used for calculating a target voltage reference value; and the PR proportional resonance regulation module and the 3D-SVPWM three-dimensional space vector pulse width modulation module are used to obtain control signals of the four-bridge arm, so as to realize high-precision voltage simulation.

[0015] Further, the conversion part adopts a CLLC resonant converter structure, so as to realize zero-voltage turn-on of the switch and reduce the switching loss.

[0016] Further, the switch module adopts a 10kV switch cabinet, and the switch cabinet is provided with a high-speed circuit breaker, which is used for controlling connection and disconnection of the power grid simulation device and the power supply grid.

[0017] Further, the device further comprises a test wiring cabinet, which is used for connection with a test product, provides an extended interface, prevents simultaneous failure of the power grid simulation device and the test product, and plays a buffering role.

[0018] Compared with the prior art, the power grid simulation device has the following beneficial effects: ① the inverter part adopts a three-phase four-bridge arm structure, which can control zero sequence components compared with a three-bridge arm structure; ② the converter part adopts a CLLC resonant converter structure, which can realize zero-voltage turn-on of the switch and reduce the switching loss; ③ the DDSRF-PLL circuit structure reduces the reaction time and has high extraction accuracy of target components; and ④ the wiring cabinet is provided, which facilitates subsequent expansion of parallel connection of the system. BRIEF DESCRIPTION OF DRAWINGS

[0019] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout the figures, and in which:

[0020] Figure 1 FIG. 1 is a circuit structure schematic diagram of an exemplary power grid simulation device according to the present disclosure;

[0021] Figure 2 FIG. 1 is a circuit structure schematic diagram of an exemplary power grid simulation device according to the present disclosure; DETAILED DESCRIPTION

[0022] Preferred embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0023] This disclosure provides a power grid simulation apparatus that considers the accuracy of simulation testing, for improving the simulation accuracy of a power grid simulator. An exemplary embodiment of this disclosure is attached. Figure 1 and attached Figure 2 As shown, this power grid simulator system consists of a 10kV switchgear, a step-down transformer, a converter, electronic loads, and a test wiring cabinet. Among these components:

[0024] (1) The switch cabinet is equipped with a high-speed circuit breaker for controlling the connection and disconnection between the power grid simulator and the power supply network.

[0025] (2) A step-down transformer reduces the high voltage of the power grid to a suitable voltage to supply power to the converter or provide feedback.

[0026] (3) The converter assembly is divided into: rectifier section (AC / DC), inverter section (DC / AC), and converter section (DC / DC), among which,

[0027] The rectifier is used to output a stable DC voltage to the subsequent inverter and converter, while the output power factor is as close to 1 as possible to ensure that the grid simulator can work efficiently.

[0028] The inverter section is used to output a controllable AC voltage. The target output voltage value is achieved by changing the reference voltage of the inverter's control strategy.

[0029] The converter section is used to output a controllable DC voltage, and the magnitude of the output DC voltage value is adjusted by controlling the converter switch.

[0030] (4) The RLC electronic load is mainly used to test the characteristics of the test object when it is in islanded operation. It can simulate the characteristics of resistive load, capacitive load and inductive load. It can operate in single phase, three phase and unbalanced mode. The front-end configuration and isolation transformer are isolated from the test object. This part and the converter assembly combine the output voltage through the transformer, so that pure AC output, pure DC output or AC-DC hybrid output can be adopted according to the situation.

[0031] (5) Preferably, it also includes: a test wiring cabinet for connecting to the test object, which can be expanded to add interfaces, and at the same time prevents the power grid simulator and the test object from failing at the same time, thus playing a buffer role.

[0032] Appendix Figure 2For the specific topology of the converter section, the inverter section of this structure adopts a three-phase four-bridge-arm structure, and the converter section adopts a CLLC type resonant converter structure. Compared with the conventional three-phase three-bridge-arm inverter, the former adds an inductor-loaded bridge arm, creating an additional loop for zero-sequence current to flow in, which can precisely control the zero-sequence current and voltage. At the same time, due to the presence of neutral inductance, the size and weight of the inverter system filter are reduced accordingly, and the THD of the output inductor current and neutral current can be effectively reduced. The latter, due to the limiting effect of inductance and capacitance at the transformer, enables the converter switch to achieve zero-voltage turn-on, ensuring the accuracy of the output voltage.

[0033] The working principle of this embodiment is as follows: The inverter part of the power grid simulator adopts a positive and negative zero sequence control scheme. It quickly extracts the positive and negative zero sequence components of the output voltage and output current through DDSRF-PLL (three-phase phase-locked loop), calculates the target voltage reference value, and then obtains the control signal of the four bridge arms through PR (proportional resonance) regulation and 3D-SVPWM modulation (three-dimensional space vector pulse width modulation) to achieve high-precision voltage simulation.

[0034] In this embodiment, the three-phase four-bridge arm structure and CLLC structure design are combined to effectively improve the output voltage accuracy.

[0035] The system also includes host computer control software, through which all equipment, instruments, and data acquisition are uniformly managed and controlled.

[0036] The equipment communicates via Ethernet, and standard tests such as high and low voltage ride-through and IEC harmonic flicker can be performed using the accompanying software.

[0037] The above technical solutions are merely exemplary embodiments of this utility model. For those skilled in the art, based on the application methods and principles disclosed in this utility model, it is easy to make various types of improvements or modifications, and not limited to the solutions described in the specific embodiments of this utility model. Therefore, the methods described above are only preferred and not restrictive.

Claims

1. A power grid simulation device considering the accuracy of simulation testing, characterized in that, include: Switching modules, step-down transformer modules, converter components, and electronic loads, including: The switch module is used to control the connection and disconnection between the power grid simulation device and the power grid; Step-down transformer modules are used to reduce the high voltage of the power grid to a suitable voltage to power the converter or provide feedback. The converter assembly includes: a rectifier section, an inverter section, and a converter section, wherein: The rectifier section is used to output a stable DC voltage to the subsequent inverter and conversion sections; The inverter section is used to output a controllable AC voltage; The converter section is used to output a controllable DC voltage; Electronic loads are used to simulate resistive, capacitive, and inductive loads. The inverter section adopts a three-phase four-bridge arm structure for positive, negative, and zero-sequence closed-loop control of the output voltage and / or output current.

2. The apparatus according to claim 1, characterized in that, The inverter section includes: a DDSRF-PLL three-phase phase-locked loop circuit, a PR proportional resonant modulation module, and a 3D-SVPWM three-dimensional space vector pulse width modulation module. Specifically, the DDSRF-PLL three-phase phase-locked loop circuit is used to extract the positive, negative, and zero-sequence components of the output voltage and output current to calculate the target voltage reference value. Then, the PR proportional resonant modulation module and the 3D-SVPWM three-dimensional space vector pulse width modulation module are used to obtain the control signals of the four bridge arms, thereby achieving high-precision voltage simulation.

3. The apparatus according to claim 1 or 2, characterized in that, The conversion section adopts a CLLC type resonant converter structure to achieve zero-voltage switching and reduce switching losses.

4. The apparatus according to claim 1, characterized in that, The switch module adopts a 10kV switch cabinet, which contains a high-speed circuit breaker for controlling the connection and disconnection of the power grid simulation device with the power grid.

5. The apparatus according to claim 1, characterized in that, Also includes: The test junction box is used to connect to the test object, provides an expansion interface, and acts as a buffer in case the power grid simulation device and the test object fail simultaneously.

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