Where low-voltage transformers are installed and large-scale electrical equipment should be equipped with reactive power compensation devices, especially those with low power factor must be installed in industrial, mining, enterprises and residential areas. Large asynchronous motor, transformer, welding machine, punch, lathe group, air compressor, press, crane, smelting, steel rolling, aluminium rolling, large switch, electric irrigation equipment, electric locomotive and so on are particularly needed. Apart from incandescent lamp lighting in residential areas, air conditioning, refrigerators and other reactive power consumption objects can not be ignored. In rural areas, the power consumption is relatively poor, the power supply is insufficient in most areas, the voltage fluctuation is very large, and the power factor is especially low. The installation of static var generator is an effective measure to improve the power supply situation and improve the utilization rate of electric energy.
In solar inverters, there are parasitic inductances which are harmful to power switching devices. They are stray inductances. Stray inductance will increase with the increase of current, the size of connecting wire and the distance. In the process of IGBT switching off, voltage spikes will occur due to the sharp decrease of current. There are several risks: First, IGBT will be overvoltage. In the case of high current, it is necessary to use IGBT with higher voltage level, but the device with higher voltage level will lose more and cost more. Secondly, voltage spike will also bring additional switching loss, which will reduce system efficiency and increase cost.
Reasonable design of interconnected conductors of inverters to reduce the inductance and its influence is very important to improve the reliability and operation performance of inverters. Inverters generally adopt the following three methods to reduce stray inductance:
1.Using stacked bus
The positive and negative terminal directions of capacitors are consistent with the current directions, and the distance between capacitors and power devices is as short as possible, the distance between the positive and negative poles of the stacked bus is as short as possible. The distributed inductance of the line is reduced by the parallel distribution of the positive and negative electrodes, which reduces the reverse peak voltage at both ends of the power element, reduces the requirement of the power device for the voltage protection absorption circuit, improves the reliability and stability of the operation of the power device, and improves the integration of the circuit so as to facilitate maintenance.
2.Using high frequency absorption thin film capacitance
Absorbing capacitors play a similar role in the circuit to low-pass filters, which can absorb the peak voltage. Usually used in insulated gate bipolar transistor (IGBT), eliminating the peak voltage caused by busbar stray inductance, avoiding the damage of insulated gate bipolar transistor.
3.Using power module
The power module uses special technology to integrate and package multiple components together, which ensures the shortest distance between components and reduces the distributed inductance of the circuit. To reduce stray inductance, medium power group series inverters usually adopt the scheme of power module and centralized inverters, usually adopt the scheme of stacked bus and absorbing thin film capacitors.
1. PV and utility power take the load at same time ( can setting ). 2. Output power factor PF=1.0 3. On/Off grid with energy storage. 4. AC charging and AC output time setting. 5. Charging voltage and charging current timing. 6. External Wi-Fi device optional. 7. Connected with battery optional. 8. Wide PV input range 120-450VDC. 9. MAX PV Array Power 4500W.
Usually the harmonic current is proportional to the working current of the harmonic source equipment. Dynamic harmonic filter, which measures load harmonic current by controller, controls bi-directional thyristor zero-crossing trigger, realizes dynamic harmonic filtering and reactive power compensation for non-linear load, and has no impact, inrush and transition during switching process.
1.Automatically tracking the harmonic of compensating change has high controllability and fast responsiveness. Compensation performance is not affected by the frequency fluctuation of power grid, and filtering characteristics are not affected by system impedance, which can eliminate the risk of resonance with system impedance.
2.It can not only control harmonics, but also compensate reactive power, restrain flicker and improve power factor. It can independently compensate for a single harmonic source or centrally compensate for multiple harmonic sources. The specified sub-harmonics are eliminated when harmonics are eliminated, and no energy storage elements are needed when reactive power is compensated.
3.Full-bridge PWM converter is used to generate compensating current, and power devices are operated by the third generation IGBT with high frequency switching mode. IGBT devices and drive and protection circuits are equipped with success rate unit module, which makes the converter small in size, high in efficiency and high in reliability.
4.The current detection technology based on instantaneous reactive power is used to detect harmonic current. The dynamic compensation of harmonic current is realized by multiple instantaneous current tracking control. Because of the current control, the harmonic can be compensated to the maximum extent without overload.
5.TSF+TSC can form a dynamic harmonic and reactive power compensator. It is suitable for situations with high load harmonic content, low power factor and large load fluctuation. It has dual functions of TSF and TSC, and can effectively realize dynamic harmonic suppression and reactive power compensation.
6.The high-speed detection and operation of DSP ensures the accuracy and effectiveness of harmonic detection and compensation control; it also has intelligent monitoring function, flexible device operation, clear operation parameters and working status, automatic fault diagnosis; and it can expand communication excuse and monitor by PC.
Meeting users’ requirements: – PF=0.99 and THDi < 5% – Compensation for 2- to 50-order harmonics – Capacitive and inductive reactive power compensation – Three-phase unbalance co
The common structure of on grid solar power generation system includes centralized, series, multi-series and AC modules. In centralized, series and multi-series systems, there are series and parallel solar cell modules, so the maximum power point tracking of the system is aimed at the whole series-parallel solar cell array, which can not take into account each solar cell array in the system. The utilization of single solar cell array is low, the system has poor ability to resist local shadows, and the system expansion flexibility is not enough. The solar on grid micro-inverters are connected with a single solar cell module, which can directly convert the DC output of the solar cell module into AC and transmit it to the grid. They have the following advantages:
1.It ensures that each solar cell module runs at the maximum power point, and has a strong ability to resist local shadows.
2.By integrating micro-inverters with solar cell modules, can realize modular design, plug-and-play and hot plug-and-play, while the system expansion is simple and convenient.
3.Micro-inverters do not occupy installation space independently. Distributed installation is easy to configure. They can make full use of space and adapt to different installation directions and angles.
4.The system has high redundancy and reliability, and the failure of a single module will not affect the whole system.
1. Built-in MPPT solar controller 2. Pure sine wave output 3. The charging current is big up to 85 Amp 4. Output power factor:s 0.9-1 5. Well accept generator’s output 6. Full automatical and silent operation 7. Automatically transfer between battery and line modes 8. Microprocessor control guarantees high reliability 9. Remote control function 10. Four-steps intelligent charging control to recharging time 11. Bypass and bypass voltage regulation function 12. With AVR function (optional) 13. Mains/solar output priority level for the customer to choose . 14. Mains/solar/ mains & solar charging three mode of priorities for the customer to choose . 15. Battery type can choose from 0-9
A device used to filter one or more harmonics in power system; most of its structures are composed of inductors, capacitors and resistors, i.e. passive harmonic filters, which also serve as reactive power compensation; the emerging filtering technology also includes active harmonic filters.
It is used to filter harmonics in power system with voltage less than 1000 volts, such as harmonics generated by six-pulse rectifier, also known as harmonic generator.
Based on the principle of electromagnetic induction and reactor, a filter compensation system is composed of high performance filter capacitors connected in series with high linearity filter devices to compensate reactive power while absorbing the main harmonic components of the system. By integrating dynamic reactive power compensation and filtering functions, it can quickly follow the load changes, and has three main functions: restraining current fluctuation, absorbing harmonics of power grid and compensating reactive power.
