Power Analysis: New Levels of Accuracy and Flexibility Meet the Challenges of Evolving Technology and Standards


Anoop Gangadharan at Yokogawa Europe

In rapidly evolving industry sectors like renewable energy, electric vehicles, and energy-efficient technologies, the need for reliability in testing to enhance safety, efficiency, and performance has never been greater. Changing application needs and evolving industry standards call for custom measurements and consistent accuracy, meaning that engineers need a test and analysis platform that not only delivers reliable measurements today but is also ready for the challenges of tomorrow. 

 

Consumer Demands in the Automotive Sector

In the automotive sector, meeting consumer demands for greater charging capacity, shorter charging times, and greater traveling range requires thorough positive and negative cycle evaluations of battery charge and discharge characteristics. 

Similarly, the evaluation of inverter signals needs to account for the harmonic superimpositions from switching circuits. Minimizing the interference from this switching noise requires isolated inputs, high-speed sample rates, and longtime observation (Figure 1).

 

Measuring power-train efficiency in an electric vehicle, showing four DC measurements (1 to 4) with the corresponding mechanical power measurements (M1 to M4).

Figure 1. Measuring power-train efficiency in an electric vehicle, showing four DC measurements (1 to 4) with the corresponding mechanical power measurements (M1 to M4).

 

With the forthcoming advent of contactless charging, such evaluations will need to be done at lower power factors, while motor-drive technologies are using higher switching frequencies. Not every measurement solution in the market has the ability to guarantee high accuracies in such conditions.

 

Energy Demands in Power Networks

Similarly, in the area of power transmission and distribution, new developments such as renewable energy stations, energy-positive buildings, and infrastructures mean that electricity no longer has a unidirectional flow from the power station to the consumer since solar as part of renewable energy able to supply power (Figure 2).

A multitude of renewable and non-renewable power stations feeding the grid need robust testing and accurate measurements by engineers that in charge of ensuring a balanced grid, to reduce the impact of noise, distortions, and harmonics from multiple sources.

 

A precision power analyser helps engineers in renewable energy grids to improve conversion efficiency by offering precision insights in charging, discharging, storage and overall efficiency.

Figure 2. A precision power analyzer helps engineers in renewable energy grids to improve conversion efficiency by offering precision insights in charging, discharging, storage and overall efficiency.

 

Power generation stations and large consumers also need to evaluate the effects of their power outputs and power usage levels on the grid and on other users.

 

Reliability and Versatility

These developments require a versatile test platform that not only delivers reliable measurements today but is also ready for the challenges of tomorrow. Hence, power measurement solutions now need to achieve accuracies that stay relevant for years to come.

High-accuracy measuring instruments also need to include the ability to carry out high-frequency measurements. 

With mean voltages increasingly differing greatly from the fundamental voltage waveform, harmonic measurements are needed to establish the values of derived measurements such as active power. Similarly, addressing the challenges of measuring parameters such as energy efficiency, harmonic content, and power factor will require both progressively greater accuracy and consistency in measurement over the specified ranges and conditions.

Again, the use of brushless DC motors and PWM (pulse-width-modulated) waveforms demands the simultaneous measurement of normal values with harmonics for overmodulation analysis of PWM waveforms and the high-speed measurement of power fluctuations.

 

Addressing the Challenges

These challenges are now being addressed in the Yokogawa WT5000 (Figure 3): the first of a new generation of Precision Power Analysers that offers exceptional measurement accuracy of 0.03% combined with stability, noise immunity, and plug-in modular flexibility.

 

Figure 3. The Yokogawa WT5000 combines measurement accuracy of 0.03% with modular flexibility. Here, a WT5000 is configured for simultaneous synchronized measurements from four torque and rotation sensors to determine the overall efficiency of four motors.

 

Versatility is provided by seven built-in slots for user-swappable power input modules (Figure 4) and diverse mainframe options that enable users to expand or reconfigure the WT5000 as their applications and their requirements change. In addition to measurements on power parameters, the torque and speed from four separate motors can be measured.

Other key features include 

  • the ability to use 5 A or 30 A input modules in conjunction with the split-screen touch display to compare multichannel measurements and custom measurements for added flexibility, 
  • with user-defined triggers and computations as well as functions like dual-motor evaluation. 

The WT5000 also performs harmonic measurements including comparisons of two simultaneous measurements up to the 500th order.

Simplicity of operation results from the full touchscreen interface, supported by hardware hotkeys and powerful software for remote measurements, interconnection, and configuration.

 

The WT5000 has seven built-in slots for user-swappable power input modules and mainframe options that enable users to expand or reconfigure the WT5000 as their requirements change.

Figure 4. The WT5000 has seven built-in slots for user-swappable power input modules and mainframe options that enable users to expand or reconfigure the WT5000 as their requirements change.

 

High-Speed A/D Converter

The WT5000 achieves the world’s highest measuring accuracy: ±0.03% of the total at 50/60Hz - by using an 18-bit analog/digital converter with a sampling frequency of 10 MS/s. This makes it possible to accurately capture waveforms from the latest high-speed inverter devices.

Very high-speed power devices using semiconductor materials such as silicon carbide and gallium nitride are increasingly being used in the latest power-conversion products such as inverter and drives. 

As a result, common-mode voltage effects can create noise problems that can affect the performance of measurement systems. The design of the WT5000 minimizes the effects of high-frequency common-mode voltage, resulting in an excellent CMRR (common-mode rejection ratio) characteristic.

The WT5000 incorporates internal memory of up to 32 Gbyte (/ M1 option) for storing large quantities of measurement data in field applications. This is achieved without the need for any external storage media, while at the same time speeding up the measurement process.

The availability of up to seven input channels allows the instrument to support applications that previously could only have been measured by synchronizing several separate instruments. As a result, it offers considerable savings in installation space, communications overheads and cost-effectiveness. Further space-saving benefits result from the use of the plug-in input modules.

The 30A and 5A modules, for example, can be switched for applications involving electric vehicles or fuel-cell vehicles, where developers are increasingly required to evaluate a number of different motors. Using the /MTR1 and /MTR2 options, it is possible to evaluate up to four motors simultaneously with one unit.

The dual harmonic measurement function makes it possible to measure the carrier frequency component from the rotational speed of the motor in an inverter drive, while checking the influence of the carrier frequency on the motor drive.

 

High-Current Measurements

An increasing number of applications require the evaluation of larger-current devices, typical examples being electric vehicles and large-scale solar installations. Since an external current sensor input function is fitted as standard in both the 30 A and 5 A input modules of the WT5000, the instrument can measure up to 30 A or 5 A with direct input. For much higher currents dedicated high-current sensors are available.

 

Conclusion

The unmatched 0.03% accuracy and modular architecture of the WT5000 helps engineers to innovate their power testing and analysis with precision, flexibility, and confidence. Whether it is for the development of energy-efficient devices and appliances, plug-in hybrid/ electric vehicles or renewable energy technologies, the WT5000 helps engineers to solve design challenges, improve productivity and ensure quality through reliable power measurements.

The accuracy and precision of the WT5000 is backed up by calibrations carried out at Yokogawa’s European standards laboratory at its European headquarters in The Netherlands. This facility offers ISO17025 accredited power calibration, to national and international standards, at frequencies up to 100 kHz: a requirement for higher harmonic measurements specified in quality standards such as ISO9000.

 

About the Author

Anoop Gangadharan is product marketing manager at Yokogawa Europe. He holds a BSc in electronics and telecommunications from Rajagiri School of Engineering and Technology and an MSc in business administration and marketing from RSM Erasmus Universiteit.

 

More information: Yokogawa Europe    Source: Bodo's Power Systems, October 2018