具有完全集成电流检测IC的智能电网应用中提高智能电网应用的效率雷竞技最新网址

具有完全集成电流检测IC的智能电网应用中提高智能电网应用的效率雷竞技最新网址

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By Shaun Milano Allegro MicroSystems, LLC, and
Andreas P. Friedrich 雷竞技竞猜下载Allegro Microsystems欧洲

Focus on the Photovoltaic System

随着对全球能源和环境意识需求的越来越多，电力电子应用受到提高效率的压力。雷竞技最新网址智能电网的出现，插入式混合动力电动车（PHEV）和全电池电动车（BEV）以及电网绑定光伏（PV）和其他网格捆绑的可再生能源系统，所有这些都将需要开发效率的发展逆变器。特别地，光伏逆变器设计的新发展是在最小化每瓦的成本和增加从太阳系中利用的最大功率来实现最佳投资回报。Allegro™Microsystems LLC开发了独特的高性能集成电流传感器IC系列，旨在用于智能电网逆变器和电机控制应用。雷竞技最新网址

PV Systems

The rising cost of fossil fuels, combined with a growing awareness of the need for low carbon emissions, have triggered intense research and development activities in technologies that use renewable resources. Renewable energy contributes 19% of global final consumption and has grown at double-digit rates annually for many technologies over the last five years [1]. In particular, windmills and photovoltaic (PV) solar technologies have been experiencing significant development, with grid-connected solar PV technology growing the fastest at annual rates of greater than 60% [1].

The major challenge associated with solar energy production is the conversion of the DC currents generated by the PV panel to the sinusoidal AC current of the power grid. Figure1 illustrates a simple block diagram of the PV system and is comprised of a solar panel array and an inverter in a grid-connected configuration with switching control as well as maximum power point tracking (MPPT). MPPT modules are often employed on each PV string for larger arrays because the maximum power point can change continually from one solar string to another depending on variances in solar radiation. Current sensors are essential in tracking these DC current levels and a microcontroller is then used to adjust the system’s operating point to deliver the maximum power available from each PV string. A comparison of these current measurements is also useful in detecting deficient PV strings. The vast number of low power PV systems for residential use can also employ current sensors to control MPPT and improve inverter efficiency. MPPT and inverter control both require accurate current sensing.

A Revolution in Hall-Effect Current Sensing

这些行业领先的Allegro电流传感器IC的功能和优势包括：

• The highest current resolution, lowest-noise spectral density Hall sensor ICs in the marketplace
• Precise factory programming of sensor IC gain and offset
• Signal processing and package design innovations enable greater than 120 kHz output bandwidth and fast output response time
• Proprietary, small footprint sensor IC packages, with galvanic isolation
• 降低功率损耗：符合孔的通孔和低电阻综合导体包

By employing advanced BiCMOS process technology and innovative packaging techniques, it is possible to provide a fully integrated solution with enhanced accuracy and resolution even at high bandwidth. Figure 2 shows the evolution of output peak to peak noise and bandwidth of Allegro Hall current sensor linear ICs. The noise level has seen a reduction of 10X while the bandwidth has more than doubled.

我nverter Sensing

An inverter includes three major parts: a DC-to-DC converter that amplifies the voltage from solar panels to the high voltage required by the grid; a DC-to-AC inverter that converts the DC current into the AC sinusoidal shape of the grid; and various electrical control components to control the system and optimize efficiency as well as ensuring compliance with the requirements of the power regulations and safety standards.

The high efficiency DC-to-AC inverter generates an alternating current signal for direct connection to the AC power grid. As a result, the signal must be compliant with the utility system requirements. It must be synchronized to the grid and have low total harmonic distortion (THD). Electrical current sensors are needed here in a control loop in order to ensure proper connection to the grid. They must accurately measure both AC and DC currents and have high dynamic performances. Very fast response time is required to react quickly to any change in the grid and shut off or disconnect the system before damage occurs. The high output bandwidth feature enables the system to measure highfrequency AC currents and harmonics.

For inverters without a transformer or with a high-frequency transformer, low offset temperature drift (high accuracy) sensors make it possible to control the DC component in the AC current fed to the grid. Regulations differ from country to country for this electrical DC current limit, but generally it is small and of the
order of tens to hundreds of milliamperes. Furthermore, failure functions such as short-circuit protection and overload protection make it easy for the current sensors to detect these conditions and quickly report them to the microcontroller.

Advanced Hall Current Sensor IC Solutions

One drawback of conventional Hall-effect sensors, when used in current sensing applications, has been a general limitation in accuracy of the zero ampere output voltage and Hall amplifier sensitivity over changes in temperature as well as the output signal bandwidth and output noise. Allegro MicroSystems has developed a family of innovative, fully integrated, current sensor packages that are ideally suited for inverter applications that drastically improve the offset, sensitivity and bandwidth operation of Hall based current sensor IC’s. In each of the sensor packages, the IC itself is the most important component and contains a precision Hall-effect element that is coupled to a low-offset, high-accuracy amplifier.

BICMOS工艺允许具有数字电路的精确放大器设计，用于出厂编程增益和偏移温度。Hall元件和放大器都是加强的，以提高精度和偏移漂移性能。Allegro开发了专有的斩波稳定和过滤技术，导致业界领先的展台，低噪声性能，如图2所示。模拟输出响应时间小于4μs允许更高频率的开关逆变器的感测。在在较雷竞技最新网址低频率下工作的应用中，可以进一步过滤输出以降低输出上的噪声并提高分辨率。Allegro Hall电流传感器的输出分辨率通过这些改进的放大器和过滤技术彻底改变。

图3显示了独特有效的专利包aging technique for Hall-effect current sensor IC that provides a small form factor, especially useful where space is limited. The current to be sensed flows through the conductive copper path between the four pins at the lower left corner of the package and the four pins at the lower right corner of the package. The Hall-effect IC is assembled into the package using standard flip chip assembly techniques. Three major advantages result:

• The Hall-effect sensing element is in close proximity to the current-carrying conductor, thereby maximizing magnetic coupling and signal to noise ratio that improves device accuracy.
• The Hall-effect IC is not in contact with the integrated conductor, thereby maintaining voltage isolation and enabling working voltages as high as 500 VRMS needed on the DC side of the PV inverter and the DC-to-DC converter. Solder bumps attached to the low-voltage input/output pads on the Hall IC make contact
  利用图3的上部示出的引线指示。
• Since the Hall-effect current sensor linear IC is fully integrated it allows Allegro to factory program the device to compensate for zero amp and sensitivity variation over temperature.
  
  
  

图3中的框图显示了先进的功能可以集成到设备中以减少整体材料成本;例如，具有用户可编程跳点的<2μs响应的过电流故障输出。在过流情况下，快速数字故障输出可用于保护IGBT器件。内部导体电阻仅为1MΩ，并提供低功耗损耗，使封装能够在85°C环境温度下支撑最多40℃的连续电流。该设备采用模拟输出，Allegro部件号具有不同的敏感性，用于低功率逆变器。

The Allegro CB package current sensor IC family (figure 4) provides users with an integrated current sensing solution that offers a series conductor resistance of 100 μΩ for ultra-low power loss. These current sensor ICs are designed for sensing currents from 50 to 200 A and can be used in high power PV inverters.

在CB封装配置中，高精度高带宽线性霍尔IC放置在浓缩的铁磁芯的间隙中，该芯缠绕在主要导体周围。这些集成传感器提供大约450 VRMS的工作电压。

For applications that require sensing currents above 200 A, as in HEV inverters or high power PV systems, designers can use an Allegro family of current sensor linear Hall sensor ICs in the gap of a simple steel ‘C’ core concentrator as in figure 5. These sensors come with analog or a digital PWM output.

Conclusion

Allegro MicroSystems has developed a line of fully integrated Hall-effect current sensor ICs that provide highly accurate output voltage signals proportional to the applied current. Advanced IC and packaging techniques enable bandwidth improvements above 120 kHz as well as low noise amplifier designs that improve device accuracy throughout the entire operating temperature range. The proprietary packaging techniques also provide small form factor devices with galvanic isolation and Allegro factory programming for stable zero ampere and full scale output over temperature. These advances allow design engineers to use Hall-effect based current sensor ICs in new applications where increased energy efficiency or new operating features are required.

参考

[1] REN21 Renewable Energy Policy Network for the 21st Century – Renewables 2010, Global Status Report – p.15
[2] IMS Research - 2010年年度报告的光伏逆变器

This paper originally appeared at the Smart Grid Forum in October 2011.