Low voltage ride through device

Abstract

The utility model relates to the field of power electronics, especially low voltage crossing device, it includes voltage monitoring unit, compensation voltage generating system and overhauling isolation device. In the utility model, the device is in series between power supply and protected load, carries out real -time power grid voltage monitoring through bridge circuit, and carries out difference calculation, and the required compensation voltage is accurately generated on this basis, once finds that power supply voltage deviates from rated voltage level, generates a suitable compensation voltage injection system through energy storage device and IGBT inverter system, and the purpose of this compensation voltage is to offset the drop of power grid voltage, thereby realizes the effective management of voltage sag, guarantees load side voltage stability, ensures that sensitive load still can be unaffectedly operated when power grid voltage is abnormal.

Description

Technical Field

[0001] This utility model relates to the field of power electronics and power system stability, and in particular to low voltage ride-through devices. Background Technology

[0002] With the rapid development of industrialization and informatization, the power system, as the infrastructure of modern society, is crucial for ensuring the stability and reliability of production and daily life. However, voltage sags in power systems are becoming increasingly prominent, severely impacting continuous production industries. Voltage sags not only lead to direct economic losses, such as product and material losses, but can also cause indirect losses, including reduced yield, equipment start-up time losses, delayed delivery, and damage to customer reputation. Therefore, improving the power quality of power systems, especially addressing voltage sags, has become a primary concern for the international power supply community.

[0003] In existing technologies, one approach to address voltage sags is to install solid-state circuit breakers (SSCBs) in power systems. By utilizing the fast operating speed and contactless nature of thyristors, SSCBs enable rapid, arc-free switching of combined switches, effectively suppressing the dangerous consequences of voltage sags and fault currents. During steady-state conduction, they also fully leverage the low contact resistance of electrical contacts, improving efficiency and eliminating the need for complex heat dissipation devices.

[0004] Currently, solid-state circuit breakers generally employ power electronic components such as GTOs (Gated Turn-Off Thyristors), IGBTs (Insulated Gate Bipolar Transistors), or IGCTs (Intelligent Gated Converters) to improve system response speed and control accuracy. However, their economic efficiency in handling high-current faults is poor, and they usually need to be deployed in conjunction with traditional mechanical circuit breakers, which undoubtedly adds complexity and cost to system configuration. Utility Model Content

[0005] This invention provides a low voltage ride-through device that solves the problem of voltage sag through a novel topology. It also features a modular design, simple structure, low operating cost, easy expansion, and uninterrupted maintenance.

[0006] This utility model provides the following technical solution: a low-voltage ride-through device, comprising a voltage monitoring unit, a compensation voltage generation system, and a maintenance isolation device, wherein:

[0007] The compensation voltage generation system includes a rectifier, an energy storage device, an IGBT inverter, and a control processing unit. The input terminal of the rectifier is connected to an input circuit breaker, and the output terminal of the rectifier is connected to the input terminal of the IGBT inverter. A capacitor and an energy storage device are connected in parallel between the rectifier and the IGBT inverter. The IGBT inverter is connected to the control processing unit, and the output terminal of the IGBT inverter is connected to an output circuit breaker.

[0008] As a further improvement to this technical solution, the input terminal of the voltage monitoring unit is connected to the output terminal of the distribution transformer, the input terminal of the distribution transformer is connected to the three-phase input power supply, and the output terminal of the distribution transformer is connected to the input circuit breaker and the maintenance isolation device.

[0009] As a further improvement to this technical solution, the maintenance isolation device includes two thyristors and two air switches. The anode of thyristor 1 is connected to the output terminal of the voltage detection unit, the cathode of thyristor 1 is connected to the load input terminal, the cathode of thyristor 2 is connected to the output terminal of the voltage detection unit, and the anode of thyristor 2 is connected to the load input terminal.

[0010] As a further improvement to this technical solution, the thyristor 1 and thyristor 2 are connected in reverse parallel, and the air switch 1 and air switch 2 are connected in parallel with both thyristors.

[0011] Compared with the prior art, the beneficial effects of this utility model are:

[0012] 1. A brand-new topology is adopted to detect voltage fluctuations and calculate the difference. When the supply voltage deviates from the rated voltage level, a suitable compensation voltage injection system is generated through the IGBT inverter system. This can effectively manage various types of single-phase, two-phase, and three-phase voltage drops and interruptions. This means that it can provide users with a more stable and reliable power supply environment and reduce equipment damage or operation interruptions caused by grid anomalies.

[0013] 2. The compensation voltage generation system has a built-in energy storage device, which can immediately provide 100% of the rated voltage output even in the event of a complete power outage. This feature ensures that critical loads such as medical equipment and safety systems can continue to operate stably even in the event of extreme grid failures, avoiding data loss and risks to life and property.

[0014] 3. The modular design allows for flexible expansion based on actual needs. The device is also equipped with maintenance isolation devices, which can support uninterrupted maintenance, greatly reducing long-term operation and maintenance costs and improving system availability and economy. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the topological structure of this utility model. Detailed Implementation

[0016] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0017] To illustrate the technical content, structural features, objectives, and effects of this invention in detail, the following description is provided in conjunction with the embodiments.

[0018] The accompanying diagrams provide a detailed explanation.

[0019] Please see Figure 1 One embodiment provided by this utility model:

[0020] The low-voltage ride-through device includes a voltage monitoring unit, a compensation voltage generation system, and a maintenance isolation device, wherein:

[0021] The compensation voltage generation system includes a rectifier, energy storage device, IGBT inverter, and control processing unit. The rectifier input is connected to an input circuit breaker, and the rectifier output is connected to the IGBT inverter input. A capacitor and an energy storage device (a supercapacitor) are connected in parallel between the rectifier and the IGBT inverter. The IGBT inverter is connected to the control processing unit, which uses a TMS320F28335 DSP chip. This chip has a built-in 12-bit AD converter with a sampling frequency of 10kHz, enabling real-time acquisition of the difference signal output from the voltage monitoring unit. The DSP chip connects to the signal output of the voltage monitoring unit via an SPI interface with a communication baud rate of 1Mbps to ensure real-time data transmission. Simultaneously, the DSP chip's PWM output port is directly connected to the IGBT inverter's drive circuit, with a PWM carrier frequency set to 15kHz and a dead time configured to 2μs to prevent shoot-through of the IGBT upper and lower bridge arms. The IGBT inverter output is connected to the output circuit breaker. As the core component, the IGBT inverter rapidly adjusts the amplitude and phase of the output voltage based on instructions from the control processing unit, generating a voltage that precisely matches the required compensation amount. The high-efficiency conversion capability of the IGBT inverter ensures that the compensation voltage can be generated in a very short time to cope with various voltage drop situations. The energy storage device is a supercapacitor bank with a rated voltage of DC 450V and a capacity of 10F. It is connected in parallel with the rectifier output through a bidirectional DC / DC converter. When the system voltage is normal, it is charged by the DC voltage output by the rectifier. The charging cut-off voltage is 420V, and the discharging cut-off voltage is 300V. When the system voltage drops, it releases the stored energy to provide the necessary power to the IGBT inverter to generate the compensation voltage, ensuring that the compensation process is not interrupted due to momentary energy shortages.

[0022] The voltage monitoring unit's input terminal is connected to the distribution transformer's output terminal, which in turn is connected to a three-phase power supply. The output terminal is connected to an input circuit breaker and a maintenance isolation device. The integrated bridge circuit within the voltage monitoring unit uses a high-precision operational amplifier OP07 to form a differential amplifier circuit, with a voltage measurement range of 0-500VAC and a measurement accuracy of ±0.5%. The reference voltage is provided by a high-precision voltage reference chip LM4040, with a stability of ±0.1%. The difference signal is converted into a digital signal by an AD7705 converter (16-bit precision) and sent to the control processing unit to guide the compensation voltage generation system in generating the corresponding compensation voltage to maintain voltage stability on the load side.

[0023] The maintenance isolation device includes two thyristors and two air switches. Thyristor 1's anode is connected to the output of the voltage detection unit, and its cathode is connected to the load input. Thyristor 2's cathode is also connected to the output of the voltage detection unit, and its anode is connected to the load input. Thyristors 1 and 2 are connected in anti-parallel, using model KP500A / 1600V. Their trigger circuit is directly driven by the I / O port of the control processing unit, with a trigger pulse width of 10μs and a trigger current of 500mA. Air switches 1 and 2 are connected in parallel with both thyristors. The air switches are MCB type circuit breakers with auxiliary contacts, rated current of 250A, and breaking capacity of 10kA. This device internally configures two thyristors (SCRs) and two air switches, with thyristors 1 and 2 connected in anti-parallel. This design allows the load to be switched to another power supply path by opening and closing the air switches without interrupting the load power supply. In this way, the system can perform routine checks or component replacements without interrupting the power supply to the load, which greatly improves the maintainability and availability of the system, reduces downtime, and lowers maintenance costs.

[0024] Working principle:

[0025] This device is connected in series between the power supply and the protected load. It monitors the grid voltage in real time via a voltage monitoring unit and uses an internal bridge circuit to monitor and calculate the voltage difference. If the supply voltage deviates from the rated voltage level, the control processing unit controls the IGBT inverter system to generate a suitable compensation voltage injection system, ensuring stable output voltage and preventing the protected load from being affected by voltage fluctuations. The specific control flow is as follows:

[0026] 1. The voltage monitoring unit compares the collected grid voltage with the reference voltage and generates a difference signal ΔU. When the absolute value of ΔU exceeds 5% of the rated voltage (i.e. ±19V), the compensation mechanism is triggered.

[0027] 2. After receiving the difference signal ΔU, the control processing unit uses a PI control algorithm to process it, with the proportional coefficient Kp set to 0.5 and the integral time Ti set to 0.01s, to calculate the required voltage compensation amount.

[0028] 3. Based on the compensation amount, the control processing unit generates the corresponding PWM waveform through SPWM modulation technology, and adjusts the output voltage amplitude and phase of the IGBT inverter to make the compensation voltage equal in magnitude and opposite in direction to the grid voltage gap, thereby ensuring that the load side voltage is stable within the rated value ±2%.

[0029] 4. When the system voltage drops, the energy storage device absorbs the required energy to compensate for the lost voltage. In the event of a complete power outage, when the control processing unit detects that the grid voltage is 0V for more than 10ms through the voltage monitoring unit, it immediately switches to constant voltage output mode. At this time, the energy storage device directly supplies power to the IGBT inverter. Closed-loop control ensures that the load end outputs 100% of the rated voltage, with a response time of ≤5ms.

[0030] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A low voltage ride through device, characterized by, It includes a voltage monitoring unit, a compensation voltage generation system, and a maintenance isolation device, wherein: The compensation voltage generation system includes a rectifier, an energy storage device, an IGBT inverter, and a control processing unit. The input terminal of the rectifier is connected to an input circuit breaker, and the output terminal of the rectifier is connected to the input terminal of the IGBT inverter. A capacitor and an energy storage device are connected in parallel between the rectifier and the IGBT inverter. The IGBT inverter is connected to the control processing unit, and the output terminal of the IGBT inverter is connected to an output circuit breaker.

2. The low voltage ride through device of claim 1, wherein: The input terminal of the voltage monitoring unit is connected to the output terminal of the distribution transformer, the input terminal of the distribution transformer is connected to the three-phase input power supply, and the output terminal of the distribution transformer is connected to the input circuit breaker and the maintenance isolation device.

3. The low voltage ride through device of claim 2, wherein: The maintenance isolation device includes two thyristors and two air switches. The anode of thyristor 1 is connected to the output terminal of the voltage detection unit, and the cathode of thyristor 1 is connected to the load input terminal. The cathode of thyristor 2 is connected to the output terminal of the voltage detection unit, and the anode of thyristor 2 is connected to the load input terminal.

4. The low voltage ride through device of claim 3, wherein: The thyristor 1 and thyristor 2 are connected in reverse parallel, and the air switch 1 and air switch 2 are connected in parallel with both thyristors.

Images