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Due to the nonuniform solar irradiance, unequal ambient temperatures, or inconsistent degradation of photovoltaic (PV) modules in three-phase cascaded H-bridge (CHB) PV inverter, the unbalanced output power among PV modules will lead to the imbalanced power between phases and bridges, resulting in unbalanced or even distorted grid current between three phases, which cannot meet the requirements of grid codes. Concerning this issue, this article proposes a novel power equalization method based on the combination of hybrid modulation strategy and zero-sequence injection methods, which deals with interbridge power imbalance by hybrid modulation and interphase power imbalance by zero-sequence injection methods. By utilizing the proposed method, three-phase-balanced grid currents with low total harmonic distortion are able to be achieved even when the interbridge and the interphase power are seriously unbalanced. In addition, each H-bridge cell in three-phase CHB inverter uses square-wave modulation, which maximizes the dc-side voltage utilization of each H-bridge cell, thus extending its power balance region. Experimental results achieved by a laboratory prototype of a three-phase seven-level CHB inverter demonstrate both feasibility and validity of the proposed method.

Due to different solar radiation, temperature, and other reasons of modules in the three-phase cascaded H-bridge (CHB) photovoltaic (PV) inverter, the output power among PV modules will be unequal and lead to unbalanced grid currents, which cannot meet the requirements of grid codes. On the other hand, the second-order voltage ripple is aroused in the dc-link capacitor since each phase-leg of the CHB inverter is made up of a single-phase inverter. Concerning these two issues, this paper proposes an optimized third harmonic injection method based on fundamental frequency zero sequence injection (FFZSI), which is a conventional method to handle the slight power imbalance problem. In this paper, the FFZSI is adopted to redistribute the power among three phases, and then the third harmonic is injected into the three-phase combined reference waveforms according to the two requirements: all modules are free from overmodulation and the dc-link voltage fluctuation is mostly reduced. Therefore, the proposed method can reduce the dc-link voltage fluctuation and extend the power balance range of FFZSI at the same time. The validity and effectiveness of the proposed method are verified by simulation and experimental results.

The development of Global Navigation Satellite System (GNSS) promotes multi-GNSS real-time precise point positioning (PPP) which raises a strong demand for real-time precise clock products. The increase of navigation systems and satellites leads to an extremely large number of observations, ambiguities and other unknowns, which makes the traditional undifferenced (UD) clock estimation method much time-consuming. We need processing of high computation efficiency for multi-GNSS real-time clock estimation. To satisfy the demand of multi-GNSS real-time clock estimation, we introduce a dual-thread parallel algorithm that consists of two threads with difference computation efficiency. The slow thread runs the traditional UD method and updates all the parameters of satellite and receiver clock, ZTD and ambiguity at a rather low rate. The fast thread runs a reduced UD method to update satellite clocks in real-time, in which the ZTDs and ambiguities are corrected with the latest estimates from the slow thread. Multi-GNSS observations of 75 stations are collected from DOY 200 to 230, 2015 to test the proposed algorithm. The dual-thread parallel method requires an average time of 2 s at each processing epoch, which is much faster than the traditional UD method. The multi-GNSS clock solutions of the introduced method exhibit good agreement with the WUM final products, with the RMS better than 0.2 ns, which is comparable to that of the UD method. Multi-GNSS kinematic PPP tests based on the clock solutions verify the introduced method further. The clock solution of the parallel method is precise enough to support real-time multi-GNSS PPP, which is comparable to the UD method and better than the ED method.

Precise orbit products are essential and a prerequisite for global navigation satellite system (GNSS) applications, which, however, are unavailable or unusable when satellites are undertaking maneuvers. We propose a clock-constrained reverse precise point positioning (RPPP) method to generate the rather precise orbits for GNSS maneuvering satellites. In this method, the precise clock estimates generated by the dynamic precise orbit determination (POD) processing before maneuvering are modeled and predicted to the maneuvering periods and they constrain the RPPP POD during maneuvering. The prediction model is developed according to different clock types, of which the 2-h prediction error is 0.31 ns and 1.07 ns for global positioning system (GPS) Rubidium (Rb) and Cesium (Cs) clocks, and 0.45 ns and 0.60 ns for the Beidou navigation satellite system (BDS) geostationary orbit (GEO) and inclined geosynchronous orbit (IGSO)/Median Earth orbit (MEO) satellite clocks, respectively. The performance of this proposed method is first evaluated using the normal observations without maneuvers. Experiment results show that, without clock-constraint, the average root mean square (RMS) of RPPP orbit solutions in the radial, cross-track and along-track directions is 69.3 cm, 5.4 cm and 5.7 cm for GPS satellites and 153.9 cm, 12.8 cm and 10.0 cm for BDS satellites. When the constraint of predicted satellite clocks is introduced, the average RMS is dramatically reduced in the radial direction by a factor of 7–11, with the value of 9.7 cm and 13.4 cm for GPS and BDS satellites. At last, the proposed method is further tested on the actual GPS and BDS maneuver events. The clock-constrained RPPP POD solution is compared to the forward and backward integration orbits of the dynamic POD solution. The resulting orbit differences are less than 20 cm in all three directions for GPS satellite, and less than 30 cm in the radial and cross-track directions and up to 100 cm in the along-track direction for BDS satellites. From the orbit differences, the maneuver start and end time is detected, which reveals that the maneuver duration of GPS satellites is less than 2 min, and the maneuver events last from 22.5 min to 107 min for different BDS satellites., Remote Sensing, 11 (16), ISSN:2072-4292

The uneven irradiation and temperature in photovoltaic (PV) modules of three-phase cascaded B-bridge (CHB) inverters will cause the unbalanced output power between solar panels, resulting in unbalanced grid current between three phases. In addition, since each phase can be regarded as a single-phase inverter, the second harmonic voltage pulsation of dc-side capacitors is a problem to be solved. To solve these two problems, a third harmonic injection optimization method on the basis of fundamental frequency zero sequence is proposed in this paper. The third harmonic with the same amplitude of fundamental modulated wave signal is injected into the modulated wave signal when the amplitude of synthesized wave signal is no greater than unity. Otherwise, the amplitude of third harmonic is decreased correspondingly to ensure the amplitude of synthesized wave signal being unity. With this method, the dc-side voltage pulsation is effectively restrained and the power balancing limit of CHB inverter is expanded. The feasibility and effectiveness of this method are verified by an experimental prototype of a three-phase seven-level CHB inverter.

Quadrature Demodulation IR-UWB radar is a new form of impulse-radio Ultrawide Band (IR-UWB) radar and it can improve the resolution of distance measurement. This paper focuses on a new method for vital sign – specifically breathing rate and heart rate – from the phase of recorded I/Q signals, using Quadrature Demodulation IR-UWB radar. The results of the experiment show that a better estimation of heart rate can be got from such a new method based on the phase difference.

Enhanced cholinergic activity contributes to the production of complex autonomic manifestations of motion sickness (MS). However, whether anti-cholinergics exert their anti-MS effects through central or peripheral actions remained unclarified. In the present study, we investigated the effects of mecamylamine (MEC) and scopolamine (SCOP) on rotation-induced gastrointestinal symptoms (conditioned gaping and defecation), locomotion disturbances (hypoactivity and impaired balance performance), hypothermia as well as Fos expression in vestibulo-autonomic regions in rats. We also observed the effects of hexamethonium (HEX) and methyl scopolamine (MSCP) on those MS behavioral responses. The efficacy of all these drugs on rotation-induced emesis and other MS symptoms in cats was also examined. We found that intragastric administration of MEC and SCOP inhibited rotation-induced gaping and defecation in rats, but only MEC showed a dose-dependent manner. MEC aggravated rotation-induced balance disorder and failed to attenuate rotation-induced hypothermia as the SCOP did. MEC was more effective for inhibiting Fos expression in the caudal vestibular nucleus and nucleus of solitary tract than SCOP. Intraperitoneal injection of HEX and MSCP also significantly alleviated rotation-induced gastrointestinal symptoms, and showed benefit to balance performance in rats. In cats, MEC, SCOP and HEX had prophylactic effects against rotation-induced emesis and salivation, and deceased non-retching/vomiting symptoms, but MSCP only attenuated emesis. It suggested that MEC and SCOP might alleviate gastrointestinal symptoms of MS via inhibiting peripheral autonomic nervous system and central vestibulo-autonomic pathways. The nicotinic acetylcholine receptor inhibitors like MEC might be new candidates against gastrointestinal symptoms induced by MS or other vestibular disorders.

A new water–sediment separation structure with a herringbone separation grid has been developed for debris flow defense. Previous model experiments showed that, compared to existing structures, this structure can continuously maintain its water–sediment separation function. However, in the structure design, the length of the separation grid is key to its success in separating water and sediment. This paper presents a theoretical formula for calculating the design length of the grid. The theoretical formula shows that the grid length relates to the debris flow velocity v x, the grid width B, and the grid incline angle θ. A series of model experiments were conducted in the laboratory to test the accuracy of the formula. The results show that the experimental value and the theoretical value for grid length form a linear relationship and the design length of the grid may be corrected by a coefficient. Further analysis indicates that the correction coefficient changes with the bulk density of debris flow. Finally, a formula for determining the grid design length is derived from the theoretical formula, corrected using a coefficient related to the bulk density of a debris flow.

When only data transmission signals with a bandwidth of 1 MHz exist in the rover, the position can be obtained using the differential group delay data of the same-beam very long baseline interferometry (VLBI). The relative position between a lunar rover and a lander can be determined with an error of several hundreds of meters. When the guidance information of the rover is used to determine relative position, the rover’s wheel skid behavior and integral movement may influence the accuracy of the determined position. This paper proposes a new method for accurately determining relative position. The differential group delay and biased differential phase delay are obtained from the same-beam VLBI observation, while the modified biased differential phase delay is obtained using the statistic mean value of the differential group delay and the biased phase delay as basis. The small bias in the modified biased phase delay is estimated together with other parameters when the relative position of the rover is calculated. The effectiveness of the proposed method is confirmed using the same-beam VLBI observation data of SELENE. The radio sources onboard the rover and the lander are designed for same-beam VLBI observations. The results of the simulations of the differential delay of the same-beam VLBI observation between the rover and the lander show that the differential delay is sensitive to relative position. An approach to solving the relative position and a strategy for tracking are also introduced. When the lunar topography data near the rover are used and the observations are scheduled properly, the determined relative position of the rover may be nearly as accurate as that solved using differential phase delay data.