Utilization of renewable energy resources, such as solar and wind, has seen rapid growth on the power grid worldwide. To mitigate the adverse impact of these volatile generation on the reliability of the power grid, fast balancing services are increasingly procured by system operators from various resources, such as flexible air-conditioning and space heating loads. Recent work of the authors has demonstrated technical feasibility and various benefits of using variable-speed vapor compression equipment for two fast load balancing services, namely frequency regulation and solar photovoltaic power smoothing. A major control issue was also identified in prior experimental tests: the drastic changes of the compressor speed for fast load balancing have caused severe superheat regulation issues including oscillations and even wet compression. To this end, a gain-scheduled feedforward and proportional integral (PI) controller is proposed and presented in this paper, which uses the real-time compressor speed in determining compensating control actuation of the expansion valve to mitigate the disturbance effect. Both simulation and experimental validations of the proposed control strategy were carried out with a 3-ton variable-speed heat pump. Test results have shown that the proposed controller is effective in improving the superheat regulation performance for three load balancing scenarios, i.e., compressor speed step changes, frequency regulation and photovoltaic smoothing. The demonstrated performance gains include fast post-disturbance recovery of the superheat with the settling time shortened by 63% to 83%, complete avoidance of wet compression and enhanced transient energy efficiency.

太阳能和风能等可再生能源的利用在全球电网中快速增长。为了减轻这些不稳定发电对电网可靠性的不利影响，系统运营商越来越多地从各种资源（例如灵活的空调和空间供暖负载）中采购快速平衡服务。作者最近的工作证明了使用变速蒸汽压缩设备进行两种快速负载平衡服务的技术可行性和各种好处，即频率调节和太阳能光伏功率平滑。在之前的实验测试中还发现了一个主要的控制问题：用于快速负载平衡的压缩机速度的剧烈变化导致了严重的过热调节问题，包括振荡甚至湿压缩。为此，本文提出并提出了一种增益调度前馈和比例积分 (PI) 控制器，该控制器使用实时压缩机速度来确定膨胀阀的补偿控制驱动，以减轻干扰影响。所提出的控制策略的模拟和实验验证均使用 3 吨变速热泵进行。测试结果表明，所提出的控制器可有效提高三种负载平衡场景的过热调节性能，即压缩机速度阶跃变化、频率调节和光伏平滑。所展示的性能提升包括过热的快速扰动后恢复，稳定时间缩短了 63% 至 83%，