Power grid simulator system

Abstract

The utility model relates to a power grid simulator system, which comprises a phase-shifting transformer, a plurality of power units and a control unit, and also comprises four-quadrant rectification reactors and an LC filter device, the power units are three-phase input and single-phase output, the three-phase input ends of the power units are respectively connected with one four-quadrant rectification reactor, and the LC filter device is connected with the control unit. The input ends of the four-quadrant rectification reactors are connected in parallel and then are connected to a secondary side winding of the phase-shifting transformer, the single-phase output ends of the plurality of power units are connected in series to form a cascade structure, the output end of the cascade structure is connected to the LC filtering device, the LC filtering device is connected to a tested system, and the tested system is connected to the phase-shifting transformer. The primary side of the phase-shifting transformer is connected to an alternating-current power grid; according to the utility model, current abrupt change is limited, and variable-voltage and variable-frequency high-voltage direct output is realized, so that the operation efficiency of an electric power system can be effectively improved, the reliability and the stability of a power grid are improved, the energy loss and the production cost are reduced, and energy conservation and emission reduction of the electric power system are realized.

Description

Technical Field

[0001] The utility model relates to the technical field of power grids, in particular to a power grid simulator system. Background Art

[0002] Grid simulators have different grid standards in different countries around the world. Most manufacturers of exported electrical products require power supplies to simulate the grids of different countries to provide services such as design and development engineers, production line testing, product quality assurance testing, life testing, and over-high / low voltage simulation testing. This requires the equipment power supply to provide pure and reliable, low-harmonic distortion, highly stable frequency and voltage regulation rate sinusoidal power output. Imported electrical equipment also requires voltage and frequency conversion experiments and quality testing to ensure that the products are suitable for my country's grid standards, thereby ensuring the normal operation of the imported electrical equipment.

[0003] A power grid simulator is a digital representation of the grid's operational status, based on power grid operational theories and mathematical models. It can predict dynamic changes in the grid under varying operating conditions, such as fluctuations in parameters like voltage, current, power, and frequency, providing important guidance for the design, operation, and maintenance of power systems. A power grid simulator is a crucial tool in power system design, operation, and maintenance, used in a variety of areas, including power system fault diagnosis, new equipment evaluation, protection system testing and performance verification, and simulated power market operations and transactions. As power systems increase in complexity and diversity, the application value of power grid simulators is also growing. However, existing power grid simulators exhibit various grid anomalies, harmonics, and three-phase imbalances, all of which can cause sudden current fluctuations in the simulator, potentially damaging equipment and leading to various accidents. Summary of the Invention

[0004] The utility model provides a power grid simulator system, which limits current mutations and realizes high-voltage direct output with voltage and frequency conversion, thereby effectively improving the operating efficiency of the power system, improving the reliability and stability of the power grid, while reducing energy losses and production costs, and realizing energy conservation and emission reduction of the power system.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A power grid simulator system includes a phase-shifting transformer, multiple power units, and a control system, and also includes a four-quadrant rectifier reactor and an LC filter device. The power unit has a three-phase input and a single-phase output. The three-phase input ends of the power unit are respectively connected to a four-quadrant rectifier reactor. The input ends of the four-quadrant rectifier reactors are connected in parallel to the secondary winding of the phase-shifting transformer. The single-phase output ends of the multiple power units are connected in series to form a cascade structure. The output end of the cascade structure is connected to the LC filter device. The LC filter device is connected to the system under test. The primary side of the phase-shifting transformer is connected to an AC power grid.

[0007] The power unit includes a three-phase bridge IGBT conversion module, a DC capacitor and an H-bridge IGBT conversion module connected in sequence from the input end to the output end;

[0008] The LC filter device includes a three-phase inductor, a filter resistor, a capacitor, a Hall current sensor H1, a Hall current sensor H2 and a voltage sensor. The filter resistor, the capacitor and the Hall current sensor H2 are connected in series to form a series circuit. The series circuit is connected in parallel with the voltage sensor and the system under test and then in series with the output end of the three-phase inductor. The input end of the three-phase inductor is connected in series to the output end of the cascade structure. The ground end of the cascade structure is connected to the Hall current sensor H1 and then grounded.

[0009] Furthermore, the control system includes a bus module, a CPU, a PWM module, a digital module, an analog module, a communication module and a display module, the analog module is connected to the PWM module, the PWM module is connected to the digital module, the digital module is connected to the CPU digital interface, the communication port of the CPU is respectively connected to the bus module and the communication module, and the bus interface is connected to the display module.

[0010] Furthermore, it also includes a fuse, which is connected in series to the three-phase input terminals U and W of the power unit.

[0011] Compared with the prior art, the beneficial effects of the present invention are:

[0012] 1) Use multiple power units in series to achieve high-voltage direct output with variable voltage and frequency to supply three-phase loads;

[0013] 2) After the grid voltage is phase-shifted and stepped down by the phase-shifting transformer, it is sent to the four-quadrant rectifier reactor on each branch, which further limits the current mutation and makes the system highly reliable and safe;

[0014] 3) Suppress the output harmonics through the LC filter device, improve the output high-frequency characteristic impedance, and damp the filter oscillation;

[0015] 4) Realize remote monitoring and network control through the control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural diagram of the present utility model.

[0017] Figure 2 It is a schematic diagram of the connection structure between a phase group on the secondary side of the phase-shifting transformer and a power unit according to the present invention. DETAILED DESCRIPTION

[0018] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0019] See Figure 1 , is a schematic diagram of the structure of the present invention. The present invention provides a power grid simulator system, comprising a phase-shifting transformer, 9 power units, a control system, 27 four-quadrant rectifier reactors, fuses, and an LC filter device. The power units have three-phase input and single-phase output. The three-phase input terminals of the power units are respectively connected to a four-quadrant rectifier reactor. The fuses are connected in series to the three-phase input terminals U and W of the power units. The input terminals of the four-quadrant rectifier reactors are connected in parallel to the secondary winding of the phase-shifting transformer. The single-phase output terminals of the multiple power units are connected in series to form a cascade structure. The output terminal of the cascade structure is connected to the LC filter device, which is connected to the system under test. The primary side of the phase-shifting transformer is connected to the AC power grid.

[0020] The power unit comprises a three-phase bridge IGBT conversion module, a DC capacitor and an H-bridge IGBT conversion module which are sequentially connected from an input end to an output end.

[0021] The LC filter device includes a three-phase inductor L, a filter resistor R, a capacitor C, a Hall current sensor H1, a Hall current sensor H2 and a voltage sensor PT. The filter resistor R, the capacitor C and the Hall current sensor H2 are connected in series to form a series circuit. The series circuit is connected in parallel with the voltage sensor PT and the system under test and then in series with the output end of the three-phase reactor L. The input end of the three-phase reactor L is connected in series to the output end of the cascade structure. The ground end of the cascade structure is connected to the Hall current sensor H1 and then grounded.

[0022] The primary winding of the phase-shifting transformer is connected to the input terminal of the power grid, the input voltage of the power grid is 0.4KV, and the secondary side has 27 secondary windings, which are connected in a triangle and divided into 9 different phase groups. Figure 2 , a structural diagram of a phase group of the secondary winding of the phase-shifting transformer connected to the power unit to form an IGBT controlled rectifier circuit structure, the phase-shifting transformer is made of NOMEX insulation material and has an insulation grade of H class dry-type transformer.

[0023] The control system includes a bus module, a CPU, a PWM module, a digital module, an analog module, a communication module and a display module. The analog module is connected to the PWM module, the PWM module is connected to the digital module, the digital module is connected to the CPU digital interface, the communication port of the CPU is respectively connected to the bus module and the communication module, and the bus interface is connected to the display module.

[0024] Working principle: After the grid voltage is phase-shifted and stepped down by the multiple isolation transformers on the secondary side of the phase-shifting transformer, it is sent to the four-quadrant rectifier reactor on each branch, which can further limit the current mutation. Finally, the power unit is connected. The power unit is an AC-DC-AC PWM power supply inverter structure with three-phase input and single-phase output. The output ends of adjacent power units are connected in series to form a cascade structure to achieve high-voltage direct output with variable voltage and frequency to supply three-phase loads. Each power unit is powered by a set of secondary windings of the input transformer, and the power units and the secondary windings of the transformer are insulated from each other.

[0025] Each phase has 9 power units connected in series, and the rated voltage of each power unit is 690V, achieving continuous output of line voltage 0-10kV and frequency 0-50Hz.

[0026] The phase-shifting transformer adopts a multiple design to achieve the purpose of reducing input harmonics. After the multiple sets of secondary windings of the transformer are phase-shifted and supply power to the power unit, they can form a multi-level phase-shift superposition rectification method. This can greatly improve the current waveform on the grid side, eliminate grid-side harmonics below 59, and improve the power factor on the grid side. The power factor on the grid side can be increased to above 0.95 without any power factor compensation or harmonic suppression devices. Due to the mutual independence of the secondary windings of the transformer, the main circuit of each power unit is relatively independent, with extremely high reliability and safety. The four-quadrant power unit adopts an AC-DC-AC conversion structure, with three-phase controlled rectification and single-phase inversion, and energy can be bidirectionally circulated, which facilitates forward feeding and energy feedback, saving energy and environmental protection.

[0027] The function of the three-phase reactor L in the LC filter device is to suppress the derived harmonics and improve the derived high-frequency characteristic impedance; the function of the filter resistor R is to act as an impedance, mainly damping the filter oscillation; the function of the capacitor C is to filter the clutter or ripple in the circuit, so that the circuit can achieve a smooth and stable working state; the Hall current sensors H1, H2 and the voltage sensor PT are used as detection elements, and play a display and protection role for the overall output side of the power grid simulator.

[0028] The control system is a fully digital signal control device. After the control program that meets the user's on-site working conditions is downloaded to the control system through the programmer, the control system generates multi-level PWM control waveforms, realizes control functions such as fast protection and network communication, and meets the user's special requirements; the display screen on the display module provides a friendly monitoring and operation interface, and displays the working status of each component of the power grid simulator system in real time, so that the user can understand the working status of the system intuitively and accurately, and can realize remote monitoring and network control.

[0029] The above embodiments are implemented under the premise of the technical solution of the present utility model, and detailed implementation methods and specific operation processes are given, but the protection scope of the present utility model is not limited to the above embodiments. The methods used in the above embodiments are conventional methods unless otherwise specified.

Claims

1. A power grid simulator system comprising a phase-shifting transformer, a plurality of power units and a control system, characterized in that: It also includes a four-quadrant rectifier reactor and an LC filter device. The power unit has a three-phase input and a single-phase output. The three-phase input ends of the power unit are respectively connected to a four-quadrant rectifier reactor. The input ends of the four-quadrant rectifier reactors are connected in parallel to the secondary winding of the phase-shifting transformer. The single-phase output ends of the multiple power units are connected in series to form a cascade structure. The output end of the cascade structure is connected to the LC filter device. The LC filter device is connected to the system under test. The primary side of the phase-shifting transformer is connected to the AC power grid. The power unit includes a three-phase bridge IGBT conversion module, a DC capacitor and an H-bridge IGBT conversion module connected in sequence from the input end to the output end; The LC filter device includes a three-phase inductor, a filter resistor, a capacitor, a Hall current sensor H1, a Hall current sensor H2 and a voltage sensor. The filter resistor, the capacitor and the Hall current sensor H2 are connected in series to form a series circuit. The series circuit is connected in parallel with the voltage sensor and the system under test and then in series with the output end of the three-phase inductor. The input end of the three-phase inductor is connected in series to the output end of the cascade structure. The ground end of the cascade structure is connected to the Hall current sensor H1 and then grounded.

2. A power grid simulator system according to claim 1, characterized in that: The control system includes a bus module, a CPU, a PWM module, a digital module, an analog module, a communication module and a display module. The analog module is connected to the PWM module, the PWM module is connected to the digital module, the digital module is connected to the CPU digital interface, the communication port of the CPU is respectively connected to the bus module and the communication module, and the bus module is connected to the display module.

3. A power grid simulator system according to claim 1, characterized in that: The invention also includes a fuse, which is connected in series to the three-phase input terminals U and W of the power unit.

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