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Application of Digital Signal Controller in Solar Inverter ​

Mar 01, 2021

Application of Digital Signal Controller in Solar Inverter

1. The digital signal controller (DSC) is the core of the digital control system. The digital signal controller (DSC) platform is capable of combining the control peripherals of the microcontroller (MCU) and the processing capabilities of stream DSP (digital signal processing) technology. Combined with economy, it is characterized by simplicity and ease of use. Today, TI, Microchip and other companies provide the high performance of DSP and the integration and ease of use of microcontrollers. The unique combination of excellent processing capabilities, interrupt processing functions, control specific peripheral integration capabilities and economy provides substantial control systems. The benefits. Through these advantages, such as improved system efficiency and increased innovative performance, fewer external components can be used, lower costs, and miniaturized packaging products for space-constrained applications can be introduced. Now that we grasp the current concept of green environmental protection at home and abroad, develop and produce solar photovoltaic modules and solar photovoltaic systems, and continue to develop a series of application products suitable for international and domestic market needs, which are in line with "making solar power, the earth cleaner, and benefiting mankind." "The purpose. As a digital signal controller (DSC), it can be described as appropriate and versatile in its development and application, such as green energy, digital power, lighting, household appliances, industrial control, automotive products, medical and metering, etc. Based on the advantages of digital controller technology in industrial applications, this article will analyze and explain the application of DSC technology in solar inverters. Since it is applied in solar inverters, the concepts related to solar energy should be introduced first.

 2. Concepts related to solar energy. Solar photovoltaic modules and solar photovoltaic systems. Its product production ranges from monocrystalline silicon rods, silicon wafers, cells to modules. The design and integration of system engineering has achieved rapid development and is used in new energy power generation and power generation. , Communications, firefighting, aviation, vehicles and ships and other fields have been widely used.

2.1 Solar photovoltaic technology. Solar energy is the most important basic energy source among various renewable energy sources. The conversion of solar radiation energy into electrical energy through conversion devices belongs to solar photovoltaic power generation technology. Photoelectric conversion devices usually use the principle of photovoltaic effect of semiconductor devices for photoelectricity. Converted, so it is also called solar photovoltaic technology. The basic characteristics of photovoltaic cells are: when light irradiates the surface of the solar cell, a part of the photons are absorbed by the silicon material, and the energy of the photons is transferred to the silicon atoms, which makes the electrons transition into free electrons, which are concentrated on both sides of the PN junction to form a potential difference. When the circuit is connected externally, under the action of this voltage, a current will flow through the external circuit to produce a certain output power. The essence of this process is: the process of converting photon energy into electrical energy.

2.2 Composition and type of photovoltaic power generation system A basic solar photovoltaic power generation system is composed of solar panels, controllers, inverters and batteries. There are two types of photovoltaic power generation systems: grid-connected power generation and independent power generation. Grid-connected power generation system means that the electricity generated by the solar cell array is directly transmitted to the AC grid through the grid-connected inverter, or the electricity generated by the solar energy is directly supplied to the AC load through the grid-connected inverter; the independent power generation system is solar energy The electric energy generated by the battery array is charged by the battery and converted from direct current to alternating current through an inverter. It should be said that solar photovoltaic systems can be widely used in a variety of green energy sources such as solar wind power generation controllers, inverter power supplies, and grid-connected inverter power supplies. On this occasion, we will focus on analyzing the application of DSC technology in solar inverters.

3. Application scheme of solar inverter system

3.1 The question is raised The future acquisition of energy on a global scale is an emerging focus issue. Several alternative solutions for fossil fuels have been studied and will enter the industrialized production process in various regions of the world. Photovoltaic grid-connected power generation converts the direct current generated by the solar cell array into alternating current to feed the grid. It is the only way for solar power generation to achieve sustainable development. Solar energy is one of the most widespread alternative energy sources, and its focus is on the delivery of photovoltaic (PV) systems, which include high-performance solar inverters used in electric utilities, commercial buildings, and personal residences. The inverter is a key component of the entire solar system. It can convert the variable DC voltage output of the PV battery into a clean 50Hz or 60Hz sinusoidal current, which is suitable for commercial power grids or local power grids. As a photovoltaic grid-connected power generation system (such as a combined type), the entire system consists of two parts: the control system and the power main circuit. The power main circuit uses high-power intelligent power module IPM. The control system uses DSP as the core to detect the power signal on the DC side and the grid side. Through maximum power optimization, voltage and current adjustment, and space vector PWM waveform generation control, it is driven to power The loop sends out control commands to convert the DC power output by the solar DC conversion unit into AC power and feed it back to the grid. The solar grid-connected inverter is the core part of the grid-connected power generation system. Its main function is to invert the direct current from solar panels into single-phase alternating current and send it to the grid. For this reason, it is necessary to explain the technical characteristics of the inverter power supply.

 3.2 What is an inverter power supply? An inverter power supply is a device that converts direct current into alternating current, and is the core component of solar and wind power generation systems. According to the product design, it is divided into four categories: solar and wind power special sine wave inverter power; economical solar and wind power control and inverter integrated machine; solar grid-connected inverter power supply and wind power grid-connected inverter power supply. Its special sine wave inverter power supply for solar and wind power generation is the core component of solar and wind power generation systems. The power supply is designed and manufactured according to the characteristics of new energy power generation systems. It is mainly used in solar power stations, wind power stations, wind, light, and oil. , Storage complementary power generation system and household solar power supply system. Its performance characteristics are: DSP chip control, intelligent power module assembly, pure sine wave output, output voltage stabilization, frequency stabilization, and various protection functions such as overvoltage, undervoltage, overload, short circuit, and reverse input polarity. Variable efficiency ≥85%, with AC bypass function, excellent input and output EMI/EMC indicators, can be equipped with RS232/485 interface, with high reliability and high efficiency.

3.3 Solar grid-connected inverter power supply

Design scheme of solar grid-connected inverter power supply with TMS320C2000 DSP as the control system

The performance characteristics of this design scheme are: DSC chip control, intelligent power module assembly; MPPT (residential operation near the maximum power point, that is, MPPT working mode) control, timely tracking of the maximum output power of solar panels; pure sine wave output, Automatic synchronization and grid connection, low current harmonic content, no pollution to the grid, no impact; disturbance detection technology to realize operation control; LCD and LED display functions, complete protection and alarm functions; RS232/485 communication to achieve remote Data acquisition and monitoring; with grid-connected/independent operation function. Technical indicators: power (for example, 1kW-50kW): input DC voltage (200V-400V), output harmonic distortion rate ≤5%, overload capacity 150%, 10 seconds, inverter efficiency>92%, operating environment temperature -25℃ ~ +55℃.

3.2 DSC is a solar grid-connected inverter power supply design scheme for the control system. Since the DSP chip is the core component of DSC, the solar grid-connected inverter power supply design scheme is based on DSP technology. It is time to take TMS320C2000TM DSP as a typical application for analysis. Because the platform based on TMS320C2000TM DSP can best respond to the real-time challenges of multiple implementation lines of solar inverters. So take TMS320C2000TM DSP as a typical application for analysis. The TMS320028xTM, the core 32-bit CPU running at the highest frequency of 150MHz, can efficiently execute the high-precision algorithms required to operate the panel at the maximum power point, ensuring the highest power conversion efficiency, even under the most demanding and changing conditions is also like this. The driving of the main bridge of the DC/AC converter is executed by the highly flexible PWM module of the TMS320C 2000 device and used in conjunction with the on-chip high-speed 12-bit ADC to adjust the required current and voltage to obtain the most common sinusoidal waveform. The design scheme of solar grid-connected inverter power supply consists of two parts: control system and power main circuit. The on-chip high-speed 12-bit ADC on C2000 can perform A/D conversion on battery voltage, battery temperature, ambient temperature, and analog quantities of metering counters. The DC/DC conversion link adjusts the working point of the photovoltaic array to make it track the maximum power point. Therefore, a Boost boost chopper is connected after the solar panel to increase the voltage to 400V. This design is beneficial to improve the efficiency of the system and is also convenient for the grid-connected control of the rear-stage full-bridge inverter. The DC/AC inverter link mainly makes the output current and the grid voltage in phase, and obtains unit power factor at the same time. For the control system, when the control circuit is powered on, it first detects the grid parameters and the voltage of the photovoltaic cell. When the grid voltage is normal, the full-bridge inverter works in the PWM rectifier state, and the intermediate voltage is about 400V. During the operation of the inverter, the control chip DSP detects the intermediate voltage and grid-connected current. If the intermediate voltage is too high or the grid-connected current exceeds the maximum current, the control chip will block the full-bridge inverter and the boost chopper. The switch tube controls the pulse and disconnects the relay at the same time. After a delay, try to restart again. If the fault still exists, disconnect the inverter and the DSP can quickly respond to commands. The maximum power output of the solar cell changes with the change of light intensity and temperature, and the maximum power tracking of the system is controlled by the pre-stage Boost boost chopper. In order to realize the grid-connected current with the same frequency and phase as the grid voltage, it is controlled by the rear-stage full-bridge inverter. Their control is coordinated by the DSP chip TMS320C2000 to complete the inverter design. In addition to the solar grid-connected inverter power supply for the control system mentioned above with DSC, this article will also introduce technologies and applications such as solar wind power generation system applications, solar and wind power controllers and wind turbine grid-connected inverter power supplies.

4. Application of solar wind power generation system Solar wind power generation system utilizes natural energy, which is inexhaustible and inexhaustible. Its use not only solves the electricity problem of the current 80 million residents without electricity in our country, but also improves the current global environmental pollution problem. In addition, its use brings huge economic benefits to users. According to statistics, the electricity investment for erecting 5 kilometers of wires and beyond is far greater than the one-time investment in the solar wind power generation system. Due to the strong complementarity between solar and wind energy, the wind-solar hybrid power generation system makes up for the resource shortcomings of wind power and photovoltaic independent systems. At the same time, wind power and photovoltaic systems can be used universally in battery packs and inverter links, so the cost of wind and solar hybrid power generation systems can be reduced, and the system costs tend to be reasonable.

5. The controller for solar and wind power generation. The controller is a device that effectively controls the power generated by solar energy or wind turbines to charge the battery, and the battery discharges to the load, so that the battery works within the safe working voltage and current range. Its control performance directly affects the battery life and system efficiency.

5.1 All-digital solar intelligent controller All-digital solar intelligent controller adopts microcomputer and non-contact control technology, and has various protection functions. It is widely used in post and telecommunications, microwave, optical cable transmission, railway communication and signal, and can also be remote Electricity is provided in regions, islands and mobile places. Since the life of solar cells is generally more than 20 years, the system has a high reliability of life and can replace diesel engines to achieve unattended operation. Performance characteristics: The control circuit is completely isolated from the main circuit and can be grounded positively or negatively; LED and LCD display functions can display the current battery voltage, solar cell array output current, load current and battery charging current, daily power generation, and cumulative power generation Multi-channel (6 channels/12 channels/18 channels, etc.) solar energy can be connected at the same time; the stepped control method can maximize the electric energy generated by the solar cell to charge the battery, and the efficiency is greatly improved; the charging voltage detection of each channel has " The "backlash" control function can prevent the static switch from entering the oscillation state; a series of alarm and protection functions such as overcharge, overdischarge, overload, short circuit, reverse connection, overheating, etc.; Hall current transformer detection current; temperature compensation adjustment voltage; recent 30 days of power data collection, power can be stored when power is lacking; solar cumulative power generation per day, solar historical cumulative power generation, power failure data is not lost; with RTC function, you can check the current time, at any time abnormalities (overcharge, Overdischarge, overload, short circuit, etc.), the time of different faults will be recorded separately and sent to the host computer for display; provide standard RS232/RS485 interface; according to the different needs of customers, different levels of lightning protection devices can be installed; according to the needs of the system, you can Provides functions such as light control, oil engine, and backup power supply.

 5.2 All-digital wind power intelligent controller The all-digital wind power intelligent controller is a device that controls the wind generator to convert wind energy into electric energy and store it in the storage battery. The controller all adopts microcomputer and non-contact control technology, and has various protection functions. , It is widely used in post and telecommunications, microwave, optical cable transmission, railway communication and signal, and can also provide electricity for remote areas, islands and mobile places. Its performance characteristics are similar to the full digital solar intelligent controller, but the differences are as follows: multiple fans can be connected at the same time; the stepped control method can maximize the power generated by the fan to charge the battery, and the charging efficiency is greatly improved; Built-in high-power fan unloading resistance, stepless adjustment, step-by-step input, so that the battery will not undergo sudden high current charging, greatly improving the battery life; the fan slows down steadily, effectively preventing the fan from flying; the power data collection of the last 30 days, The battery can be stored when there is no electricity.

5.3 Principles and characteristics of tailless fan controller

5.3. The characteristics of the tailless fan controller adopts Microchip's special micro-processing chip; special anemometer and high-performance wind direction sensor; real-time display of wind speed, wind direction, power, voltage, current, hand/auto brake, yaw, pitch and other information ;Excellent EMI/EMC indicators, equipped with RS232/RS485 and host computer monitoring software; with under/overvoltage automatic switching, three-level electric brakes can be realized, automatic shut-off of the propellers; automatic protection functions against lightning, overload, short-circuit and other faults And fault alarm; the best cut-in wind speed and cut-out wind speed can be set, and intelligent control can be carried out during operation, and the pitch and yaw direction can be changed automatically according to the changes of wind speed and wind direction to achieve maximum power output; working temperature -20℃~+ 70℃, can be equipped with micro printer. Its scope of application is suitable for the control of various tailless wind turbines.

 5.4 Wind-solar hybrid intelligent controller Wind-solar hybrid intelligent controller is a device that controls solar cells and wind generators to convert solar energy and wind energy into electric energy and stores it in storage batteries. Because wind resources and sunlight resources are distributed differently in different regions, seasons, and weather conditions , With a certain degree of complementarity. At the same time, the one-time investment in making full use of wind resources for power generation is low, while the maintenance of new energy power generation systems is low, and the wind-solar complementary system is adopted, which is cost-effective. It has the characteristics of solar controller and wind power controller.

 5.5 Street lamp controller Solar street lamp is an independent lighting system, street lamp controller is a device that converts solar energy into electric energy and stores it in a battery to provide lighting for the road, It adopts microcomputer chip and non-contact control technology, and has various protection functions. The performance characteristics are: automatic lighting on/off control (light control, timing can be set); time control has 1 hour, 3 hours, 4 hours, 5 hours, 6 hours, 8 hours free choice; battery charge/discharge, under Automatic control of voltage/overvoltage/reverse connection protection and temperature compensation; automatic load open/short circuit protection, and self-reset protection.

 6 Wind turbine grid-connected inverter power wind turbine grid-connected power generation is to convert the alternating current generated by the wind generator into alternating current and feed it to the grid. Like solar power generation, wind power generation is the only way for new energy power generation to move towards sustainable development. Its performance characteristics are similar to those of solar grid-connected inverter power supplies.

 7 Special host computer software for photovoltaic wind power generation system. This software provides users with an online system for remote monitoring of power supply and electrical equipment. It cooperates with multi-function off-grid and grid-connected inverter power supplies to display and process real-time data and analyze system functions. , System accident recall, various document backups, user level selection, realization of remote specific function control, new user power usage learning, online help and other functions. The specific functions are as follows: ① Real-time data display and processing: For non-real-time data such as system power and accident records, according to the power system collection cycle, do regular collection and packaging. Process and backup within the set time period of the system's corresponding collection cycle. ②Accident recall: detailed accident records (accurate to the second, displayed in time period, and record all operating parameters of the system for future reference); multiple query methods (by site, time, date and combination); report generation and printing; Data software and data hardware backup. ③Alarm function: with alarm parameter setting, alarm parameter display and maintenance. Provide sound (content can be selected by oneself to meet individual needs, while providing PC internal buzzer alarm to save power for users), light, SMS, email, telephone and other alarm methods. ④Safe mode: Provide users with authority management, password login, error-free operation design, upgrade the power supply knowledge database, and new power users to learn image data; real-time control of power equipment, comprehensive and specific parameters, and prevent misoperation. ⑤Additional functions and humanized design: diversified data display; design to avoid repeated operation; wireless monitoring can also be realized.

8 Concluding remarks It should be said that many domestic and foreign manufacturers have many series of solar and wind power generation systems and products. The application features introduced above are only from the perspective of commonality. Therefore, when selecting, the parameters and indicators should be determined according to actual needs to obtain higher levels. The price/performance ratio.